Articles formed from fluorine-containing elastomeric compositions using additive manufacturing methods, and additive manufacturing methods for thermoset elastomeric compositions

Abstract

Apparatus suitable for extruding curable polymers to form elastomeric articles using additive manufacturing, and curable fluorine-containing polymer compositions suitable for use in such apparatus, are disclosed, along with an additive manufacturing method for forming fluorine-containing elastomers. The additive manufacturing method includes providing a curable fluoropolymer composition, providing an additive manufacturing printer apparatus including a ram material extruder, the ram material extruder including a ram device and a printer nozzle, introducing the curable fluoropolymer composition into the ram material extruder, applying heat to the ram device, applying pressure to the ram device to extrude the curable fluoropolymer composition, and printing at least one layer of the extruded curable fluoropolymer composition exiting an outlet of the printer nozzle onto a substrate to form a fluorine-containing elastomeric article.

Description

[Technical Field]

[0001] Articles formed from fluorine-containing elastomeric compositions using additive manufacturing methods, and additive manufacturing methods for thermoset elastomeric compositions.

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS This U.S. non-provisional patent application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Patent Application No. 63 / 383,666, filed November 14, 2022, and entitled "Articles Formed from Fluorine-Containing Elastomer Compositions Using an Additive Manufacturing Method and Additive Manufacturing Methods for Thermoset Elastomer Compositions," and this U.S. non-provisional patent application also claims the benefit under 35 U.S.C. §120 of U.S. Provisional Patent Application No. 63 / 383,666, filed March 31, 2021, and entitled "Articles Formed from Fluorine-Containing Elastomer Compositions Using an Additive Manufacturing Method and Additive Manufacturing Methods for Thermoset Elastomer Compositions." This application claims priority as a nonprovisional continuation-in-part of U.S. patent application Ser. No. 17 / 219,249, entitled "Additive Manufacturing Methods for Thermoset Elastomer Compositions," which in turn claims the benefit under 35 U.S.C. § 119(e) of U.S. Provisional Patent Application No. 63 / 003,149, entitled "Articles Formed From Fluorine-Containing Elastomer Compositions Using an Additive Manufacturing Method and Additive Manufacturing Methods for Thermoset Elastomer Compositions," filed March 31, 2020, the entire disclosure of each of the above-referenced applications being incorporated herein by reference.

[0003] Background of the Invention FIELD OF THE INVENTION The present invention relates to the field of additive manufacturing, in particular additive manufacturing of thermoset elastomers, including fluorine-containing elastomers, through fused filament fabrication and deposition. [Background technology]

[0004] 2. Description of Related Art Additive manufacturing, also commonly referred to as three-dimensional ("3D") printing, is gaining popularity for rapid prototyping and commercial production of articles. Various types of additive manufacturing processes are known, including, among others, liquid bath photopolymerization methods such as stereolithography ("SLA"), material or binder jetting methods, powder bed fusion methods such as selective laser sintering ("SLS"), and material extrusion methods such as fused deposition modeling ("FDM"), fused filament fabrication ("FFF"), and direct pellet extrusion.

[0005] In the vat photopolymerization method, a liquid photopolymer resin is stored in a vat in which a build platform is positioned. An article can be formed based on a computer model of the article, in which the article is represented as a series of layers or cross sections. Based on the computer model, a first layer of the article is formed using UV light to selectively cure the liquid photopolymer resin. Once the first layer is formed, the build platform is lowered and UV light is used to cure the liquid photopolymer resin so that subsequent layers of the article are formed on top of the first layer. This process is repeated until a printed article is formed.

[0006] In material jetting methods, an article is prepared in a layer-by-layer manner by depositing droplets of a liquid material, such as a thermosetting photopolymer, to form the first layer of the article based on a computer model of the article. The deposited layer of liquid material is cured or hardened, such as by application of UV light. Subsequent layers are deposited in the same manner to produce a printed article. In binder jetting, an article is formed by depositing layers of powdered material onto a build platform and selectively depositing a liquid binder to bond the powder. Subsequent layers of powder and binder are deposited in the same manner, with the binder acting as an adhesive between the powder layers.

[0007] In powder bed fusion processes, specifically SLS, an article is formed by generating a computer model of the article to be printed, where the article is represented as a series of layers or cross sections. To prepare the article, layers of powder are deposited on a build platform, and the powder is sintered using a laser to form layers of the article based on the computer model. Once a layer is sintered, additional layers of powder are deposited and sintered. This process is repeated as necessary to form an article having the desired configuration.

[0008] In material extrusion methods such as FDM or FFF, a computer model of an article is generated, where the article is represented as a series of layers. The article is produced by feeding a filament of material into an extrusion head, which heats the filament and deposits it onto a substrate to form a layer of the article. Once a layer is formed, the extrusion head proceeds to deposit the next layer of the article based on the computer model of the article. This process is repeated in a layer-by-layer manner until the printed article is fully formed. Similarly, in direct pellet extrusion, pellets, rather than filaments, are used as the feed material; the pellets are fed into the extrusion head, heated, and deposited onto a substrate.

[0009] Various polymeric materials are known for use in additive manufacturing processes. Common polymeric materials used in additive manufacturing include acrylonitrile butadiene styrene (ABS), polyurethane, polyamide, polystyrene, and polylactic acid (PLA). More recently, high-performance engineering thermoplastics have been used to produce printed articles with improved mechanical and chemical properties relative to common polymeric materials. Such high-performance thermoplastics include polyaryletherketone, polyphenylsulfone, polycarbonate, and polyetherimide.

[0010] Additive manufacturing methods can be used to rapidly form articles having any of a variety of shapes and configurations, however, articles formed by additive manufacturing processes can suffer from poor interlayer adhesion in the z-direction of the printed article.

[0011] Currently, additive manufacturing using material extrusion three-dimensional printing (ME3DP), based on FFF and FDM, is considered a highly flexible and efficient additive manufacturing technique. In this process, a thermoplastic filament is heated and then "extruded" and fused to an underlying layer. This technique is seen as potentially useful in the art for developing manufactured components with more complex geometries using computer-aided design.

[0012] In addition to using the materials used as mentioned above, further attempts are being made to develop techniques using FFF to print soft thermoplastic elastomers such as ethylene vinyl acetate (EVA), ethylene propylene diene monomer in a polypropylene matrix (EPDM+PP), acrylonitrile-butadiene-styrene (ABS), and styrene-ethylene-butadiene-styrene (SEBS). However, such materials present challenges in processing and forming articles using FFF. N. Kumar et al., “3D Printing of Flexible Parts Using EVA Material,” Materials Physics and Mechanics 37, pp. 124-132 (2018), N. Kumar et al., “Additive Manufacturing of Flexible Electrically Conductive Polymer Compositions Using CNC-Assisted Fused Layer Modeling Process,” Journal of the Brazilian Society of Mechanical Sciences and Engineering, 40:175 (2018), and K. Elkins et al., “Soft Elastomers for Fused Deposition Modeling,” Virginia Polytechnic Institute and State University, presented in the International Solid Freeform Fabrication Symposium (1997).

[0013] Because such materials are soft, they tend to lack adequate compression set and heat resistance for many applications. To provide better performance, they are generally prepared for use in the form of compounded elastomers (i.e., curable elastomer compositions for vulcanization containing a curable polymer, one or more fillers, and generally also a cure system). When such materials are processed, they form network structures within the crosslinked rubber system, which can adversely affect the ability to fabricate objects using layered FFF techniques. There is a need in the art for the development of techniques where such networked structures provide the potential for the finished product to include strong interfacial bonds, assuming the ability to successfully form them exists using FFF or another additive technique.

[0014] A further problem in the art with regard to the development of additively processable formulations in the elastomeric area is that the processing characteristics of fully formulated curable elastomeric compositions are very different from those of thermoplastics (such as those typically used in FFF processing). When attempting to incorporate elastomers into additive manufacturing processes, particularly in the case of thermoset elastomers, care must be taken to keep the material below its cure temperature in the curable formulation before curing, for the purposes of processing the material. Such materials present additional challenges with regard to processing, as they have high viscosity when unheated (a problem usually addressed by the application of heat) and the need to prevent and inhibit the formation of crosslinks during processing and prior to intentional curing.

[0015] Feeding flexible filaments using currently available 3D printing equipment also presents challenges due to their viscosity and the need to prevent hardening, including preventing problems caused by filament buckling. Recent attempts to produce printed nitrile rubber using additive ram material extrusion (ARME) have been attempted using carbon-filled nitrile rubber, but material shrinkage occurred on the printing floor, even considering the use of various patterning techniques intended to mitigate the overall impact of shrinkage in the printing process. See D. Kazmer et al., “Additive Ram Material Extrusion and Diddling of Fully Compounded Thermoset Nitrile Rubber,” Polymer Composites, (July 2021) pp. 1-12.

[0016] Fluorine-containing elastomers, including both fluoroelastomers (FKM) and perfluoroelastomers (FFKM), are chemically and plasma resistant and can be used in certain compositions suitable for high-temperature and high-pressure applications. They are employed in a variety of end uses, particularly as seal and gasket components for use in pharmaceutical and semiconductor manufacturing, where chemical and / or plasma resistance and material purity are desirable attributes, and in oilfield and fluid handling applications due to their ability to withstand harsh chemicals, high temperatures, and high pressures. However, fluorine-containing elastomers are known in the art to be difficult to process and generally require careful formulation to ensure they are sufficiently blended in the formulation and do not prematurely cure. They are also quite expensive to manufacture, in some cases requiring cleanroom facilities and extrusion followed by compression molding.

[0017] There is a need in the art for methods of processing soft elastomeric materials, thermoset elastomers, and other elastomeric materials that have not previously been considered suitable for additive manufacturing, such as by FFF or FDM, and in particular for enabling articles to be more inexpensively formed from fluorine-containing elastomers, which are known to be difficult and / or expensive to process, and which have properties and processing challenges that otherwise support the currently accepted view in the art that such materials cannot be successfully processed using additive manufacturing, and there is a need for methods to eliminate problems with buckling and premature hardening of the material. There is also a need in the art for a method that can provide sufficient repeatability for use in product development and / or for specialized applications with high performance specifications and various end uses when attempting to additively print articles from FKM, FFKM, and similar soft elastomers, to provide uniform parts with good interlayer adhesion, such as seals, gaskets, and other small and large size components. Such specialized parts can be difficult to produce using conventional manufacturing techniques. Furthermore, there is a benefit and need in the art for a method that can provide sufficient yields, is simpler in operation and use, and also reduces waste, requires fewer raw materials, and lowers manufacturing costs associated with increased yields. [Prior art documents] [Non-patent literature]

[0018] [Non-Patent Document 1] N Kumar et al.,”3D Printing of Flexible Parts Using EVA Material,”Materials Physics and Mechanics 37,pp.124-132(2018) [Non-patent document 2] N. Kumar et al., “Additive Manufacturing of Flexible Electrically Conductive Polymer Compositions Using CNC-Assisted Fused Layer Modeling Process,” Journal of the Brazilian Society of Mechanical Sciences and Engineering, 40:175 (2018) [Non-patent document 3] K. Elkins et al., “Soft Elastomers for Fused Deposition Modeling,” Virginia Polytechnic Institute and State University, presented in the International Solid Freeform Fabrication Symposium (1997) [Non-patent document 4] D. Kazmer et al., “Additive Ram Material Extrusion and Diddling of Fully Compounded Thermoset Nitrile Rubber,” Polymer Composites, (July 2021) pp.1-12 Summary of the Invention [Means for solving the problem]

[0019] Brief Summary of the Invention The invention herein includes an additive manufacturing method for forming a fluorine-containing elastomeric article, the method comprising: providing a curable fluoropolymer composition comprising at least one curable fluoropolymer; providing an additive manufacturing printer apparatus comprising a ram material extruder, the ram material extruder comprising a ram device and a printer nozzle operable for extrusion under pressure; introducing the curable fluoropolymer composition into the ram material extruder; applying heat to the ram device comprising the printer nozzle of the Ram device; applying pressure to the ram device to extrude the curable fluoropolymer composition; and using the additive manufacturing printer apparatus to print at least one layer of the extruded curable fluoropolymer composition exiting an outlet of the printer nozzle onto a substrate to form a fluorine-containing elastomeric article.

[0020] In one embodiment of the method herein, the ram material extruder may further include a drive mechanism, such that the method may further include operating the drive mechanism to apply pressure to the ram device. The drive mechanism may include a drive motor operatively connected to a timing belt.

[0021] In another embodiment of the method, the step of applying pressure may include actuating a ram extruder to apply pressure by moving a platen on at least one lead screw in operative communication with a timing belt and rotating the at least one lead screw on a drive motor using the timing belt. In one embodiment, there are at least two lead screws. The ram device may include a piston having an exterior surface and a barrel having a first end, a second end, and an interior surface defining an interior space, the barrel configured to receive the piston after passing through a first opening in the first end of the barrel, the second end of the barrel being positioned to communicate with the printer nozzle, and the method further includes passing the piston into the interior space of the barrel such that the exterior surface of the piston faces the interior surface of the barrel while applying pressure to the ram device.

[0022] In the method, the step of introducing the curable fluoropolymer composition may include loading the curable fluoropolymer composition into the barrel between the printer nozzle and the first end of the barrel. Furthermore, in the method, the step of applying heat to the ram device may further include generating heat using a heating mechanism with a ram material extruder, or may further include heating the curable fluoropolymer composition to a temperature sufficient to initiate flow of the curable fluoropolymer composition within the ram device and below the temperature at which significant curing of the curable fluoropolymer composition occurs. Furthermore, the method may further include heating the curable fluoropolymer composition to a temperature below the temperature corresponding to the time T2 associated with the curable fluoropolymer composition as determined with a Rubber Process Analyzer using the ASTM D2084 test method. The curable fluoropolymer composition may be heated to a temperature below the temperature at which significant curing occurs.

[0023] In the method, the curable fluoropolymer composition comprises at least one curable fluoropolymer. At least one curable fluoropolymer can be partially fluorinated. At least one curable fluoropolymer in the curable fluoropolymer composition can be a curable perfluoropolymer. At least one curable fluoropolymer can be a perfluoropolymer, and the onset of curing of the perfluoropolymer can be indicated by thermal analysis using a differential scanning calorimeter.

[0024] In embodiments herein, the curable fluoropolymer composition may be heated to a temperature of from about 20°C to about 250°C, or from about 70°C to about 250°C, or from about 100°C to about 250°C, or from about 105°C to about 200°C, or from about 115°C to about 160°C.

[0025] In one embodiment of the method herein, the printer nozzle may include a nozzle body and a nozzle tip, the nozzle body defining a tapered internal chamber having an inlet for receiving the curable fluoropolymer composition extruded through the ram device and an outlet communicating with the inlet to the nozzle tip, the nozzle tip having an interior surface extending from the inlet of the nozzle tip to an outlet of the printer nozzle. In such an embodiment, the method may further include printing the extruded curable fluoropolymer composition by applying heat and pressure to extrude the curable fluoropolymer composition through the inlet of the nozzle body, the outlet of the nozzle body, the inlet of the nozzle tip, and the outlet of the printer nozzle. In the method, the nozzle tip may have a reduced diameter area at the outlet end of the nozzle tip to direct the extruded curable fluoropolymer composition through the outlet of the printer nozzle.

[0026] In one embodiment herein, the fluorine-containing elastomeric article can be a seal, and the inner diameter of the printer nozzle can be approximately the same as the outer diameter of the seal in a longitudinal cross section. The inner diameter of the printer nozzle outlet, measured laterally across the printer nozzle outlet, can be at least about 0.2 mm. In another embodiment, the inner diameter of the printer nozzle outlet, measured laterally across the printer nozzle outlet, can be from about 0.2 mm to about 3.3 mm, or from about 0.4 mm to about 1.6 mm.

[0027] The ram material extruder may further include a drive mechanism having a drive motor, which may provide sufficient pressure to extrude the material through the ram device and out the outlet of the printer nozzle while providing sufficient torque to overcome friction between the curable fluoropolymer composition within the ram device.

[0028] The drive motor may be a stepper motor with a geared transmission.

[0029] The method may further comprise analyzing the curable fluoropolymer composition and estimating the storage modulus to determine printing parameters for printing the curable fluoropolymer composition. The storage modulus is preferably estimated by, for example, using a rubber process analyzer or parallel plate rheometry or other suitable method to optimize the printing parameters for the curable fluoropolymer composition.

[0030] In embodiments herein, the additive manufacturing printer device may further include a pre-cooler, although this is not required when using a ram material extruder. If a pre-cooler is used, the method may further include cooling the curable fluoropolymer composition before introducing it into the ram device. In further embodiments herein, the substrate may optionally include a friction surface. The method may optionally further include coating the substrate with an adhesive. The substrate may be the base plate of a seal, for example, the base plate of a bonded seal or bonded gasket. In such cases, the method may further include printing the extruded curable fluoroelastomer composition onto the base plate. The seal may be selected from any gasket or seal. The base plate in embodiments herein may be a mold having an upper mold plate surface having an upper surface defining a cavity and / or a lower mold plate having an upper surface defining a cavity, and the method may further include printing the extruded curable fluoropolymer composition as a preform into one or both of the cavities on the upper mold plate surface and / or the upper surface of the lower mold plate of the mold.

[0031] In another embodiment herein, a support structure may be positioned on the base plate to assist in shape retention of the extruded curable fluoropolymer composition, and the method may further include printing the extruded curable fluoropolymer using the support structure. The support structure may be a permanent support or a removable fixture-like support. The support structure may be formed from a variety of materials, including thermoplastic materials, metals, or metal alloys. The support structure itself may also be formed by additive manufacturing and / or made from a dissolvable material.

[0032] In other embodiments herein, the additive manufacturing apparatus is capable of printing at temperatures below about 250° C., preferably below about 200° C., and more preferably below about 160° C. The additive manufacturing apparatus is also capable of printing at temperatures of at least about 20° C. in each of these cases.

[0033] The present invention also includes a fluorine-containing elastomer article formed by the method described hereinabove, wherein the article comprises an at least partially cured fluoroelastomer. Such article(s) may comprise an at least partially cured perfluoroelastomer. The curable fluoropolymer composition used in the method for forming the article may comprise at least one curable fluoropolymer having functional groups for reacting with a curing agent and at least one curing agent capable of reacting with the functional groups. The curable fluoropolymer composition may further comprise at least one filler. The curable fluoropolymer composition used to form the article is preferably sufficiently viscous to self-adhere to the substrate, but preferably still be removable from the substrate while substantially retaining its structural integrity. The curable fluoropolymer composition may be processed without curing during printing, or may be at least partially cured to a degree greater than 0% but less than about 25%. The curable fluoropolymer composition used to form the article in embodiments herein may comprise one or more additional curable fluoropolymers or one or more additional curable perfluoropolymers. In such cases, the curable fluoropolymer composition may also include one or more additional curing agents for curing the one or more additional curable fluoropolymers or one or more additional perfluoropolymers.

[0034] The present invention also includes a system for forming a three-dimensional additively manufactured fluorine-containing elastomeric article, the system comprising: (i) a curable fluoropolymer composition; and (ii) an additive manufacturing printer apparatus capable of forming a three-dimensional printed article, the apparatus comprising: a programmable additive manufacturing printer; a ram material extruder comprising: a ram device operable to receive the curable fluoropolymer composition and extrude the curable fluoropolymer composition under pressure; a printer nozzle having an inlet and an outlet; and a drive mechanism for applying pressure to the ram device, wherein the ram device is operated according to commands from the programmable additive manufacturing printer; and a heating device for applying heat to the ram device including the printer nozzle of the ram device, the printer nozzle configured to receive the curable fluoropolymer composition under pressure through the printer nozzle inlet and to enable heated extrusion of the fluoropolymer composition through the printer nozzle outlet to print a fluorine-containing elastomeric article.

[0035] In the system, the drive mechanism may include a drive motor operatively connected to the timing belt. The drive motor may be a stepper motor having a geared transmission. The ram material extruder may further include at least one lead screw and a movable platen movable on the at least one lead screw, the at least one lead screw being in operative communication with the timing belt. In one embodiment herein, there are two lead screws.

[0036] In embodiments of the systems herein, the ram device may further include a piston having an exterior surface and a barrel having a first end, a second end, and an interior surface defining an interior space, the barrel configured to receive the piston after passing through a first opening in the first end of the barrel, the second end of the barrel positioned to communicate with the printer nozzle. The piston may be within the interior space of the barrel such that the exterior surface of the piston faces the interior surface of the barrel.

[0037] The heating device of the system is preferably capable of heating the curable fluoropolymer composition to a temperature sufficient to initiate flow of the curable fluoropolymer composition within the ram device and below the temperature at which significant curing of the curable fluoropolymer composition occurs. The heating device may be capable of heating the curable fluoropolymer composition to a temperature below the temperature corresponding to the time T2 associated with the curable fluoropolymer composition, as determined by a Rubber Process Analyzer using the test method of ASTM D2084.

[0038] The additive manufacturing printer device is preferably capable of forming a three-dimensionally printed article comprising an at least partially fluorinated fluoroelastomer. The additive manufacturing printer device is preferably capable of forming a three-dimensionally printed article comprising a perfluoroelastomer. The additive manufacturing device is preferably capable of forming an article selected from a gasket and a seal. The article can be printed on a base plate. In one embodiment, the base plate is a mold having an upper mold plate having an upper surface and / or a lower mold plate having an upper surface, each upper surface defining a cavity, and the article can be printed on the cavity in the upper surface of the upper mold plate and / or the upper surface of the lower mold plate of the mold.

[0039] In another embodiment herein, a support structure is positioned on the base plate to help the extruded curable fluoropolymer composition retain its shape. The support structure can be a removable or permanent fixture, or a fixture-like support. The support structure can include one or more of a thermoplastic material, a metal, or a metal alloy. The support structure itself can be made by an additive manufacturing method and / or can include a dissolvable material.

[0040] The ram devices in the system may further include load cells that act as sensors to monitor the pressure within the ram devices.

[0041] The heating device in the system may be capable of heating the curable fluoropolymer composition to a temperature of from about 20°C to about 260°C, or from about 70°C to about 250°C, or from about 100°C to about 250°C, or from about 105°C to about 200°C, or from about 115°C to about 160°C.

[0042] The heating device may be positioned on the ram device of the system. The printer nozzle of the system may include a nozzle body and a nozzle tip, the nozzle body defining a tapered internal chamber having an inlet for receiving the curable fluoropolymer composition extruded through the ram device and an outlet communicating with the inlet to the nozzle tip, the nozzle tip having an interior surface extending from the inlet to the outlet of the printer nozzle. The nozzle tip may have a reduced diameter area at the nozzle outlet end of the nozzle tip for directing the extruded curable fluoropolymer composition through the outlet of the printer nozzle. The length of the printer nozzle, measured longitudinally along the printer nozzle from the inlet to the nozzle body to the printer nozzle outlet, may be about 1 to about 5 times the inner diameter of the nozzle outlet, preferably about 2 times the inner diameter of the nozzle outlet. The inner diameter of the nozzle outlet may be about 0.4 mm to about 1.6 mm, preferably about 0.8 mm.

[0043] The drive mechanism of the system may be capable of providing sufficient pressure to force the curable fluoropolymer composition through the ram device and out the outlet of the printer nozzle, while optionally providing sufficient torque to overcome friction between the curable fluoropolymer composition within the ram device if this becomes an issue. Optionally, but not required, the system may include a pre-cooler to cool the curable fluoropolymer composition before introducing it into the ram device, if desired.

[0044] The additive manufacturing printer device in one embodiment of the present invention is capable of printing at temperatures below about 250° C., preferably below about 200° C., and more preferably below about 160° C. In each case, the additive manufacturing printer device may also be capable of printing at temperatures of at least about 20° C.

[0045] The invention herein may also include an additive manufacturing method for forming a fluorine-containing elastomeric article based on fused filament fabrication, the method including: providing a filament formed from a curable fluoropolymer composition; providing an additive manufacturing printer having a drive mechanism and a printer nozzle; feeding the filament into the additive manufacturing printer through the drive mechanism and through a longitudinal passage defined by an inner wall of a support tube extending from a first end to a second end, the second end of the support tube being positioned so as to be in fluid communication with an inlet to the printer nozzle; applying heat to the filament; and printing successive layers of the filament exiting an outlet of the nozzle onto a substrate using the additive manufacturing printer to form a fluorine-containing elastomeric article.

[0046] In this embodiment of the method described above, the filament may be fed from a feed roller. The filament is preferably formed by extruding a curable fluoropolymer composition. The filament may be cooled prior to introducing the filament into the support tube. A cooling method may be applied prior to introducing the filament into the tube to stiffen the filament and reduce possible buckling. The filament may be cooled upon entering the drive mechanism.

[0047] In one embodiment of the method, a filament containing a curable fluoropolymer composition can be heated to a temperature sufficient for flow of the curable fluoropolymer composition within a printer apparatus, but below the temperature at which significant curing occurs. For example, the filament can be heated to a temperature below the temperature corresponding to the time T2 associated with the curable fluoropolymer composition, as determined on a Rubber Process Analyzer (RPA) using ASTM D2084, a test method known in the art. Suitable RPAs are commercially available. One suitable RPA is available, for example, from Alpha Technologies Company as the RPA Model 2000. Such a temperature allows the filament to be deposited on the previous layer within a time below T2, preventing or avoiding curing until curing is desired, for example, during a post-cure heating step.

[0048] The curable fluoropolymer can be partially fluorinated or a curable perfluoropolymer. When the fluoropolymer is a perfluoropolymer and filament feeding is used, in such a method, the filament can be heated to a temperature that allows the curable perfluoropolymer to flow and below the temperature at which significant curing occurs. For example, the onset of cure for perfluoropolymers can be indicated by thermal analysis using a differential scanning calorimeter (DSC). Cure characteristics will vary substantially depending on the curable FKM(s) and / or FFKM(s) selected to form the filament, particularly due to the cure system employed. Therefore, the DSC curve of the selected compound can be examined to determine the desired heating temperature.

[0049] In an exemplary embodiment, for certain types of materials, curable fluoropolymers that are partially, substantially, or fully fluorinated may be heated to a temperature of from about 100°C to about 250°C, preferably from about 105°C to about 200°C, and more preferably from about 115°C to 160°C, with the understanding that such temperatures will be adjusted depending on the compound and its cure system.

[0050] In this embodiment of the method, the heat is preferably generated by a heating mechanism within the additive manufacturing printer, preferably within the print head. The drive mechanism in this embodiment of the additive manufacturing printer preferably includes a drive wheel and a support wheel, and the method may further include threading the filament through the drive wheel and support wheel prior to entering the first end of the support tube. In an alternative embodiment, the first end of the support tube extends upward through the drive mechanism between the support wheel and the drive wheel, supporting the filament as it leaves the feed roller. The support tube wall may optionally define a side opening extending laterally therethrough, and the wall around the opening may be contoured to match the shape of the drive wheel, and the method may then further include feeding the filament such that it contacts the drive wheel within the area of ​​the side opening as it passes through the drive mechanism.

[0051] In further embodiments of the method, the drive mechanism may include a geared drive roller, and the method may further include feeding the filament through the geared drive roller. The support tube may extend from below the geared drive roller. A portion of the support tube may further extend above the geared drive roller, such that the method may further include feeding the filament through a portion of the support tube, above and into the geared drive roller. The method may further include cooling the portion of the support tube extending above the geared drive roller.

[0052] In this embodiment of the method using filament feeding, the nozzle outlet may define an opening, preferably wider than the outer diameter of the heated filament measured laterally before heating, measured laterally across the opening. The nozzle outlet opening may have a width, measured laterally across the outlet opening at its widest dimension, that is, in one embodiment, from about 10% to about 200% of the outer diameter of the filament measured laterally before heating.

[0053] Also in this embodiment, a portion of the nozzle extending from the printer's print head can have a length, measured longitudinally along the nozzle portion, from an entrance to the portion of the nozzle to an exit of the nozzle, the length being about 5 to about 20 times the diameter of the filament prior to heating. In another embodiment, the nozzle can have a length, measured longitudinally along the heated portion of the nozzle, within its heated portion that is about 1 to about 10 times the outer diameter of the heated filament. In such an embodiment, the nozzle filament formed from the curable fluoropolymer composition can preferably have an outer diameter of about 0.2 mm to about 20 mm, more preferably about 1.0 mm to about 3.0 mm, prior to heating.

[0054] The additive manufacturing printer in this embodiment of the method using filament feeding may include a drive motor for operating a drive mechanism that provides sufficient pressure to force material through the additive manufacturing printer and out the nozzle while providing sufficient torque to overcome friction between the filament and the additive manufacturing drive printer. In one embodiment herein, the drive motor may be a stepper motor with a geared transmission that may include at least one planetary gear for increasing the torque of the stepper motor.

[0055] The present invention further includes an article formed by a heated filament comprising a curable fluoropolymer composition using an additive manufacturing device, wherein the article comprises a fluoroelastomer. In one embodiment, the additive manufacturing device can be a fused filament fabrication device. The curable fluoropolymer composition can comprise a curable fluoropolymer, and in one embodiment, the curable fluoropolymer is perfluorinated such that it is a curable perfluoropolymer and the article comprises a perfluoroelastomer. The curable composition can comprise at least one curable fluoropolymer and at least one curing agent. In one embodiment herein using a melt-filament fabrication device as described above, the filament can have a diameter of about 0.2 mm to about 3.0 mm, preferably about 1.0 mm to about 2.0 mm.

[0056] In another embodiment of the method using a fused filament fabrication type apparatus, the method may further include analyzing the curable fluoropolymer formulation to estimate the storage modulus and determine, e.g., optimize, printing parameters, for example, using DMA, parallel plate rheometry, or other methods. In embodiments such as those described above, the curable fluoropolymer formulation may also be analyzed using a ram material extruder as described above, including estimating the storage modulus, using a rubber process analyzer, parallel plate rheometry, or other methods suitable for determining properties to optimize printing parameters.

[0057] The present invention also includes a curable fluorine-containing composition for use in an additive manufacturing composition, comprising a curable fluoropolymer having functional groups for reacting with a curing agent, and a curing agent capable of reacting with the functional groups. In the above-described embodiment using a fused filament fabrication type device, the fluorine-containing composition can have a torque of about 0.78 dNm when about 10% cured to about 28.01 dNm when about 90% cured. Such torque can be measured by RPA according to ASTM D2084 test methodology.

[0058] In embodiments herein, the curable fluorine-containing composition can be sufficiently viscous to self-adhere on a substrate, yet still be removable from the substrate while substantially retaining the structural integrity of the fluorine-containing material deposited on the substrate. In such embodiments, the curable composition can preferably be processed during printing using an additive manufacturing device without curing or with partial curing to an extent greater than 0% but less than about 25%.

[0059] The fluorine-containing composition of the present specification can comprise curable fluoropolymer, which is curable perfluoropolymer.It can comprise one or more additional curable fluoropolymers or one or more additional perfluoropolymers.The composition can then further comprise one or more additional curing agents to cure one or more additional curable fluoropolymers or one or more additional perfluoropolymers.

[0060] The present invention further includes an additive manufacturing apparatus capable of forming three-dimensional printed articles comprising an elastomer. This apparatus is useful when a filament-fed elastomer composition is used. This embodiment of the apparatus includes a printer drive mechanism configured to facilitate passage of a curable polymer filament through the printer drive mechanism, a drive motor in operative communication with the printer drive mechanism, the drive motor including a geared transmission mechanism that may include one or more planetary drive wheels, and a print head including a nozzle having an inlet for receiving the polymer filament and an outlet for heated extrusion of the curable polymer filament onto a substrate.

[0061] In this embodiment, the printer drive mechanism of the device may include a drive roller and a support roller, and the device may further include a support tube mounted to extend below the printer drive mechanism, the drive roller preferably positioned to contact a filament fed into the tube within the printer drive mechanism. The support tube may extend from a lower surface of the printer drive mechanism for communication between the printer drive mechanism and the nozzle inlet. The support tube preferably has a first end positioned above the printer drive mechanism and a second end preferably proximate the nozzle inlet, and the support tube is preferably configured to support a filament passing through the first end of the support tube and exiting through the second end of the support tube. The support tube preferably has a longitudinally extending wall with an interior surface defining a longitudinal passage from the first end of the tube to the second end of the tube, and an opening extending laterally through the wall of the tube from the interior surface to the exterior surface of the tube to promote direct contact between the drive roller and the filament passing through the longitudinal passage of the support tube. The first end of the support tube can be positioned to receive the curable polymer filament leaving the feed roller while avoiding buckling of the filament.

[0062] This embodiment of the apparatus may further include a pre-cooler for cooling the filament before it enters the printer drive mechanism.

[0063] The printer drive mechanism of this embodiment of the apparatus can be configured to facilitate passage of a curable fluoropolymer filament therethrough, and thus the article can include a fluoroelastomer. The printer drive mechanism can also be configured to facilitate passage of a curable perfluoropolymer filament therethrough, and thus the article can include a perfluoroelastomer.

[0064] The drive motor in this embodiment of the apparatus may be a stepper motor, and the geared transmission mechanism may include planetary gears configured to preferably provide a torque of from about 0.2 to about 4. However, it should be understood that the torque may be adjusted for different printing conditions and nozzle configurations.

[0065] The nozzle outlet in such embodiments may be from about 0.2 mm to about 20 mm, preferably from about 1.0 mm to about 3.0 mm.

[0066] In this embodiment of the device, the substrate may further comprise a friction surface to improve adhesion of the non-viscous extruded curable polymer onto the substrate. Such a friction surface may comprise, for example, an adhesive.

[0067] The additive manufacturing apparatus in this embodiment is preferably capable of printing at temperatures below about 250°C, more preferably below about 200°C, and most preferably below about 160°C.

[0068] In a further embodiment, the present invention also includes an additive manufacturing apparatus capable of forming three-dimensional printed articles comprising an elastomer composition, preferably provided as a filament feed material in the apparatus. In this embodiment, the apparatus includes a printer drive mechanism configured to facilitate passage of a curable polymer filament through the printer drive mechanism and including a geared drive roller, a drive motor in operative communication with the printer drive mechanism, a print head including a nozzle having an inlet for receiving the polymer filament and an outlet for heated extrusion of the curable polymer filament onto a substrate, and a pre-cooler for cooling the filament before entering the printer drive mechanism.

[0069] In such an embodiment, the apparatus may further include a support tube mounted to extend below the printer drive mechanism. The support tube may extend from below the geared drive roller for communication through the support tube between the geared roller of the printer drive mechanism and the nozzle inlet. The support tube may have a first end and a first portion positioned above the printer drive mechanism and a second portion extending from below the geared drive roller to a second end proximate the nozzle inlet. The first portion of the support tube may be mounted within or part of the precooler.

[0070] The first end of the support tube can be positioned to receive the curable polymer filament leaving the feed roller while avoiding buckling of the filament. The precooler can have a wall defining a cavity for receiving a coolant. The precooler wall can also define a bore for allowing passage of the filament to cool it before passing through the geared drive roller. The printer drive mechanism can be configured to facilitate passage of the curable fluoropolymer filament through the printer drive mechanism, and the article includes a fluoroelastomer. The printer drive mechanism can further be configured to facilitate passage of the curable perfluoropolymer filament through the printer drive mechanism, and the article includes a perfluoroelastomer. A brief description of some views of the drawing

[0071] The foregoing summary and the following detailed description of preferred embodiments of the invention will be better understood when read in conjunction with the accompanying drawings. For the purpose of illustrating the invention, there are shown in the drawings embodiments which are presently preferred. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. [Brief explanation of the drawings]

[0072] [Figure 1] FIG. 1 is a schematic flow chart representation of an apparatus according to one embodiment of the present invention.

[0073] [Figure 1A] FIG. 1A is a schematic flow chart representation of a preferred embodiment of the apparatus of FIG.

[0074] [Figure 2] FIG. 2 is a perspective view of an apparatus according to a preferred embodiment of the invention herein.

[0075] [Figure 2A] FIG. 2A is a longitudinal cross-sectional view of a portion of the device of FIG. 2 taken along line 2A-2A.

[0076] [Figure 3] FIG. 3 is a side elevational view of a support tube between a drive wheel and a support wheel with a polymer filament extending through the support tube for use in the apparatus of FIG.

[0077] FIG. 3A is a side elevational view of the support tube of FIG. 3 without the drive and support wheels.

[0078] [Figure 4] FIG. 4 is a bottom elevation view of a nozzle outlet of a prior art additive manufacturing printer.

[0079] [Figure 4A] FIG. 4A is a bottom elevational view of a nozzle outlet for use in an apparatus according to a preferred embodiment of the present invention.

[0080] [Figure 5] FIG. 5 is a schematic flow chart representation of steps for use in the invention herein.

[0081] [Figure 6] FIG. 6 is a graphical representation of filament length in mm with respect to applied temperature for extruded perfluoropolymer filaments.

[0082] [Figure 7] FIG. 7 is an example of a geared transmission mechanism for use in the embodiments herein.

[0083] FIG. 7a is an example of a planetary gear for use in the geared transmission of FIG.

[0084] [Figure 8] FIG. 8 is a differential scanning calorimeter graphical representation of the thermal behavior of the material in Sample 1.

[0085] [Figure 9]FIG. 9 is a differential scanning calorimeter graphical representation of the thermal behavior of the material in Sample 2.

[0086] [Figure 10] FIG. 10 is a differential scanning calorimeter graphical representation of the thermal behavior of the material in Sample 3.

[0087] [Figure 11] FIG. 11 is a cross-sectional view of a cooling device such as in FIG. 11A taken along line 11-11 for use with an apparatus according to one embodiment of a printer drive mechanism in a printing apparatus herein.

[0088] [Figure 11A] 11A is a top elevation view of the cooling device of FIG. 11. FIG.

[0089] [Figure 12] FIG. 12 is a graphical representation of storage modulus (G') in Pa versus temperature (° C.) for exemplary embodiments herein.

[0090] [Figure 13] FIG. 13 is a schematic flow chart representation of a further system according to another embodiment of the present invention including an additive manufacturing printer apparatus having a ram material extruder.

[0091] [Figure 14] FIG. 14 is a schematic flow chart representation of steps in a method of the invention herein using an apparatus such as that of FIG.

[0092] [Figure 15] 15 is a front bottom perspective view of a ram material extruder that may be used in the system of FIG. 13 and the method of FIG. 14.

[0093] [Figure 16] FIG. 16 is a top elevational view of the ram material extruder of FIG.

[0094] [Figure 17] FIG. 17 is a longitudinal cross-sectional view of the ram material extruder of FIG. 16 taken along line 17-17.

[0095] [Figure 18] FIG. 18 is a longitudinal cross-sectional view of the ram material extruder of FIG. 17 taken along line 18-18.

[0096] [Figure 19] FIG. 19 is an enlarged view of a portion of FIG. 17 showing the nozzle area of ​​the ram material extruder.

[0097] [Figure 20] FIG. 20 is a photographic image of a base plate for a gasket.

[0098] [Figure 21] FIG. 21 is a photographic image of the base plate for the seal.

[0099] [Figure 22] FIG. 22A is a photographic image of a printed gasket incorporating a fluoroelastomer printed seal on the base plate of FIG.

[0100] FIG. 22B is a photographic image of a printed gasket incorporating a perfluoroelastomer printed seal on the base plate of FIG.

[0101] [Figure 23] FIG. 23A is a photographic image of a seal incorporating a fluoroelastomer seal printed onto the base plate of FIG.

[0102] FIG. 23B is a photographic image of a seal incorporating a perfluoroelastomer seal printed onto the base plate of FIG.

[0103] [Figure 24]FIG. 24 is a perspective view of an embodiment of a ram material extruder for use in the apparatus and methods herein.

[0104] [Figure 25] FIG. 25 is a transverse cross-sectional view of a sample support structure for use in the methods herein.

[0105] [Figure 26] FIG. 26 is a perspective view of the support structure of FIG.

[0106] [Figure 27] FIG. 27 is a top elevation view of an assembly of a support structure according to claim 25, with a printed preform positioned thereon.

[0107] [Figure 28] FIG. 28 is a perspective view of the assembly of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0108] Detailed Description of the Invention The inventions herein include additive manufacturing methods for forming fluorine-containing elastomeric articles, articles formed from a method of extruding a curable fluoropolymer composition for printing using an additive manufacturing device, where the curable fluoropolymer composition may be provided, for example, in some embodiments herein in the form of a filament, or in other embodiments in small pieces, curable fluorine-containing compositions for use in additive manufacturing compositions, comprising a curable fluoropolymer having functional groups for reacting with a curing agent, and a curing agent capable of reacting with the functional groups, and additive manufacturing systems comprising a ram extruder and a curable fluoropolymer composition, and methods of forming articles using the system and method steps described.

[0109] As used herein, "additive manufacturing" can include a variety of manufacturing techniques and apparatus suitable for preparing an article by depositing heated material as layers onto a substrate in a layer-by-layer manner to form the article. The methods, articles, and compositions herein can be used in any of a variety of additive manufacturing processes, including, but not limited to, three-dimensional printing and material extrusion methods such as fused deposition modeling ("FDM"), fused filament fabrication ("FFF"), and direct pellet extrusion, among others, and the use of an additive ram material extruder (ARME). Preferably, the additive manufacturing process in some embodiments herein is a material extrusion method such as FFF or FDM, or a printing method employing an ARME or other ram extrusion printing device.

[0110] In an FDM or FFF process, for example, the curable polymer composition herein is preferably provided in the form of an extruded filament. In embodiments using a ram material extruder herein, it is not necessary to prepare a filament, but the filament can be used as the feed material.

[0111] A computer model of the article to be printed can be provided, as is known in additive manufacturing, and the computer model will represent the article as multiple layers or cross sections. The article is then formed in a layer-by-layer manner as the filament is fed into an extrusion nozzle at the outlet of a typical additive manufacturing device, which provides heat to the filament and extrudes the heated filament in an FKM or FFF process to deposit it on a build platform or substrate to form a layer of the article based on the computer model of the article. In the ram material extrusion method herein, if a curable fluoropolymer composition is present in a ram device that includes a nozzle end, heat is also applied to the nozzle. The heated filament, or extruded curable fluoropolymer composition exiting the nozzle, hardens as it is deposited to form a layer of the article. Subsequent layers of filament or extruded curable polymer are deposited on the first layer of filament to form subsequent layers of the article based on the computer model of the article. This process is repeated until all layers of the article have been deposited to form a printed article. Once the article is completed, various finishing processes may be performed, such as heat setting the article or surface treatments such as sanding to remove excess material.

[0112] When used in an additive manufacturing process to form printed articles as described herein, the curable fluoropolymer composition after printing is preferably crosslinked using a cure system and the application of heat, such as by heating the composition to a temperature sufficient to induce an initial cure of the curable fluoropolymer that produces crosslinking of some of the material, and / or by heating the composition to a temperature sufficient to substantially or completely crosslink the composition at an elevated temperature upon layer formation and / or during a post-cure step.

[0113] During processing through the apparatus and prior to passing through the nozzle, the filament or other curable fluoropolymer composition feed material is preferably heated only to a temperature sufficient to allow the curable fluoropolymer to flow through the apparatus and to avoid or minimize curing of the fluoropolymer until one or more layers are printed. During processing, the temperature is preferably kept below a temperature that allows flow but below which curing occurs or is initiated to a less substantial extent. The curable fluoropolymer composition as provided for use in the additive manufacturing processes herein is flowable through the apparatus but is not crosslinked, or is crosslinked only to a certain extent, while entering the heated nozzle in an FFF or FDM additive manufacturing apparatus, or in other embodiments herein, when entering the heated ram device or nozzle of a ram material extruder.

[0114] Curing will continue during the formation of individual layers in an additive manufacturing process, even after the layers have been deposited. In FFF or FDM machines, an extrusion head or nozzle may provide heat and allow the extruded filament to exit; in machines including ram material extruders, the barrel and / or nozzle end of the ram device may be heated to provide the heat necessary to induce crosslinking as the material exits, deposits, and hardens within the deposited layers. It is believed that such crosslinking during the additive manufacturing process helps strengthen the finished article by improving interlayer adhesion within the article.

[0115] Once the printed article is fully formed by the additive manufacturing process, a final heat curing step may also be performed, in which the printed article may undergo further crosslinking or post-cure. The desired temperature and time may vary depending on the curable fluoropolymer selected for the composition, as well as the desired degree of crosslinking and the presence or absence of any curing agents, co-curing agents, and / or cure accelerators, and, if applicable in some embodiments herein, the degree of crosslinking that already occurred while the filament was passing through the additive manufacturing device during the initial article formation step. Preferably, the majority of the curing of the curable fluoropolymer composition occurs through the sustained application of a level of heat during the final cure of the printed article or during post-cure on the formed article.

[0116] Curing the curable fluoropolymer is believed to provide increased adhesion between layers of the printed article, which provides the printed article with improved and more uniform mechanical properties, such as tensile strength and modulus, while still providing the article with the benefits of elastomeric materials, including compressive ability, strength, and resistance to chemicals, plasma, and high temperature and / or pressure conditions that may be encountered with the printed article during use.

[0117] Other benefits of using additive manufacturing to print elastomeric articles include improvements in manufacturing efficiency. Most elastomeric articles, such as O-rings and gaskets, experience low yields from compression molding, especially when attempting to create articles with more complex geometries. There are some cases where traditional compression molding limits the level of complex geometries achievable using such processes. Furthermore, for most fluoroelastomer and perfluoroelastomer articles, there is high material cost for the initial curing fluoro- or perfluoropolymer, as lost pieces due to washout and other issues during molding contribute to higher manufacturing costs. Using the precision of additive manufacturing 3D printing can reduce such process waste and save costs.

[0118] Furthermore, the modifications introduced to the additive manufacturing processes herein enable various commercially developed additive manufacturing devices to overcome challenges previously encountered in the art while attempting to form articles using thermoset and other softer and more viscous elastomers due to lack of strength combined with high viscosity in the extruded material.

[0119] Such improvements allow for solutions in preventing buckling of the extruded filament, printing in a controlled manner without unnecessary curing of material from the device nozzle, and problems resulting from friction within the device and adhesion of the extruded filament onto the receiving substrate surface that interfere with the ability to extrude material through the device print head or nozzle.

[0120] In additive manufacturing processes using conventional polymers or certain thermoplastic elastomers as previously demonstrated, the layers of a printed article are primarily bonded by mixing or melting the layers into each other by polymer diffusion. The curable fluoropolymer compositions of the present invention, when delivered to form a printed article, can be extruded without premature curing, allowing the layers to bond both by conventional interlayer adhesion and strengthening through sustained curing and crosslinking as the article is printed layer by layer.

[0121] The curable fluoropolymer compositions herein can be used to form prototypes, parts, and replacement parts for use in a variety of industries and various end uses, including, inter alia, oil and gas drilling and recovery, semiconductor processing, aerospace applications, seals and gaskets such as gaskets, seals, bonded gaskets, bonded seals, structural brackets, automotive applications, medical devices, prosthetics and implants, construction materials, and consumer products. For example, the curable fluoropolymer compositions can be formed into three-dimensional articles used to form sealing assemblies such as packaging, O-rings, V-rings, U-cups, gaskets, bonded gaskets, seals, bonded seals, bearings, valve seats, adapters, angled backup rings, and other products.

[0122] The resulting articles, because they are formed from fluorinated or perfluorinated materials, will also be solvent, chemical, and plasma resistant, enjoy good physical properties (e.g., tensile strength and modulus) and elastomeric properties, thermal properties, and compression set, and will be manufactured at a lower cost due to the elimination of waste in the material.

[0123] In one embodiment of the method herein, filaments formed to include a curable fluoropolymer composition are provided. In other embodiments herein, such as those using a ram material extruder, no filament feedstock is required and the curable fluoropolymer composition may be provided in gum form, such as pieces, pellets, sections, etc. Each such curable fluoropolymer composition for use herein includes one or more curable fluorine-containing polymers, also generally referred to herein as curable fluoropolymers.

[0124] The curable fluorine-containing polymer for use herein can be any suitable curable fluorine-containing polymer formed from one or more curable fluorine-containing monomers, one of which has functional groups to allow curing by reacting with one or more curing chemicals in the curing system.The curable fluorine-containing polymer can be a partially fluorinated curable fluoropolymer that forms a partially fluorinated elastomer (also referred to herein as a fluoroelastomer) upon curing, or can be a substantially or fully fluorinated (i.e., perfluorinated) curable perfluoropolymer that forms a perfluoroelastomer upon curing.

[0125] For the final application that will be used in high purity or clean environments, or for underground applications that encounter harsh chemicals and high temperatures and pressures, in order to make parts intended for, at least one curable fluoropolymer is preferably a curable perfluoropolymer that can be used to form perfluoroelastomers.The composition herein, whether it is a partially fluorinated curable fluoropolymer composition or a substantially or completely fluorinated curable perfluoropolymer composition, can contain only one fluoro- or perfluoropolymer, or can contain two or more such fluoro- or perfluoropolymers in the composition, which, when used and / or cured, will either form an elastomer article with only a single fluoro- or perfluoroelastomer, or when two or more are used, will form an article with a hybrid perfluoroelastomer.Furthermore, the curable fluoropolymer can be hybridized with the curable perfluoropolymer to make a partially fluorinated hybrid fluoroelastomer.

[0126] As used herein, "perfluoroelastomer" or "cured perfluoroelastomer," unless otherwise indicated, includes any cured elastomeric material or composition formed by curing a curable perfluoropolymer(s), such as the preferred curable perfluoropolymers in the curable compositions described herein.

[0127] "Curable perfluoropolymers" (sometimes also referred to in the art as "perfluoroelastomers" or more appropriately "perfluoroelastomer gums") suitable for use in forming cured perfluoroelastomers are polymers that are substantially fully fluorinated, preferably completely perfluorinated, on their polymer backbones. Based on this disclosure, it will be understood that due to the use of hydrogen as part of the functional crosslinking groups, some residual hydrogen may be present in some perfluoroelastomers within the crosslinks of those materials. Cured materials such as perfluoroelastomers are crosslinked polymer structures.

[0128] The curable perfluoropolymer used in the preferred perfluoroelastomer compositions herein for forming articles by additive manufacturing containing the cured perfluoroelastomer upon curing is formed by polymerizing one or more perfluorinated monomers, one of which is preferably a cure site as described above, i.e., a perfluorinated cure site monomer having a functional group to enable curing. The functional group can either be or contain a reactive group that may not be perfluorinated. Two or more curable fluoro- or perfluoropolymers, preferably at least one optional curing agent (curing agent), can be preferably incorporated into the composition herein, which is then cured to form the resulting crosslinked and cured fluoroelastomer composition, preferably a perfluoroelastomer composition as described herein.

[0129] As used herein, a curable fluorine-containing elastomer composition may be a curable perfluoropolymer composition, which may comprise only one curable perfluoropolymer or a blend of two or more such curable polymers, each of which (if perfluorinated) is formed by polymerizing two or more perfluorinated monomers, including at least one perfluorinated cure site monomer, with at least one functional group (cure site) for enabling curing. Such curable perfluoropolymer materials are generally also referred to as FFKM in accordance with the standardized rubber definition of the American Standard Test Method (ASTM) and as described herein above in ASTM standard D1418-17, the relevant portions of which are incorporated herein by reference.

[0130] As used herein, "compression set" refers to the tendency of an elastomer material to remain distorted and not return to its original shape after the compressive load is removed. The compression set value is expressed as the percentage of the original strain that the material cannot recover. For example, a compression set value of 0% indicates that the material completely returns to its original shape after the compressive load is removed. Conversely, a compression set value of 100% indicates that the material does not recover at all from the applied compressive load. A compression set value of 30% indicates that 70% of the original strain has been recovered. Higher compression set values ​​generally indicate the potential for seal leakage. When fully cured, articles formed using three-dimensional additive manufacturing and layer-by-layer forming processes can achieve elastomeric properties such as compression set, physical properties such as tensile strength and tensile modulus, and chemical and plasma resistance properties that are suitable for use in at least the same end use and environment in which perfluoroelastomers are currently used in the art.

[0131] As described herein, the present invention can include curable fluorine-containing elastomeric compositions, including curable perfluoroelastomer or curable fluoroelastomer compositions, and molded articles formed from such curable fluorine-containing elastomeric compositions.

[0132] Such perfluoroelastomer compositions preferably comprise at least one, more preferably two or more curable perfluoropolymers, preferably perfluorocopolymers, at least one of which has a high content of tetrafluoroethylene (TFE). Other suitable comonomers can include other ethylenically unsaturated fluoromonomers. When two such perfluoropolymers are used in a blend, both of them preferably contain TFE or another similar perfluorinated olefin monomer. Each curable perfluoropolymer can also preferably contain one or more perfluoroalkyl vinyl ethers (PAVEs), which contain alkyl or alkoxy groups that can be linear or branched, and can also contain ether linkages. Preferred PAVEs for use herein include, for example, perfluoromethyl vinyl ether (PMVE), perfluoroethyl vinyl ether (PEVE), perfluoropropyl vinyl ether (PPVE), perfluoromethoxy vinyl ether, and other similar compounds, and particularly preferred PAVEs are PMVE, PEVE, and PPVE. PAVEs may be used alone or in combination with the above PAVE types in the curable perfluoropolymer and final curable composition, so long as their use is consistent with the present invention as described herein.

[0133] The perfluoropolymer is preferably a copolymer of TFE, at least one PAVE, and at least one perfluorinated cure site monomer incorporating a cure site or functional group to enable crosslinking of the curable polymer. The cure site monomer can be of various types, with the preferred cure sites described herein. Preferred cure sites include those with nitrogen-containing groups; however, other cure site groups, such as carboxyl groups, alkylcarbonyl groups, or halogenated groups with iodine or bromine, and other cure sites known in the art can also be used, particularly since additional curable fluoropolymers or perfluoropolymers other than the first and / or second curable perfluoropolymers can be provided in the composition. The present disclosure herein also includes the use of radiation curing or the use of various preferred curing agents (also referred to herein as crosslinking agents or curing chemicals), and if other cure sites known in the art are used, other curing agents capable of curing such alternative cure sites can also be used. For example, peroxide cure systems, such as those based on organic peroxides and related peroxide co-curatives, can be used with halogenated functional cure site groups.

[0134] Exemplary cure site monomers are listed below and can be used in the curable fluoropolymer(s) or curable perfluoropolymer(s) described herein for use in the curable compositions, most of which are PAVE-based structures and have reactive sites. The polymers can vary, but preferred structures are those having the following structure (A): CF2=CFO(CF2CF(CF3)O) m (CF2) n -X 1 (A) In the formula, m is 0 or an integer of 1 to 5, n is an integer of 1 to 5, and X 1 is a nitrogen-containing group such as nitrile or cyano. However, carboxyl groups, alkoxycarbonyl groups, or halogenated end groups may also be present in X. 1 It can be used as:

[0135] a cure site or functional group X as described herein 1 For example, the nitrogen-containing group contains a reactive site for crosslinking when reacted with a curing agent. The compounds according to formula (A) can be used alone or in various optional combinations thereof. From the viewpoint of crosslinking, it is preferred that the crosslinking functional group is a nitrogen-containing group, preferably a nitrile group.

[0136] Further examples of cure site monomers according to formula (A) include those of formulas (1)-(17) below:

[0137] CY2=CY(CF2) n -X 2 (1) In the formula, Y is H or F, and n is an integer from 1 to about 8.

[0138] CF2=CFCF2R f2 -X 2 (2) In the formula, R f2 is (-CF2) n - and -(OCF2) n - and n is 0 or an integer from 1 to about 5.

[0139] CF2=CFCF2(OCF(CF3)CF2) m (OCH2CF2CF2) n OCH2CF2-X 2 (3) In the formula, m is 0 or an integer of 1 to about 5, and n is 0 or an integer of 1 to about 5.

[0140] CF2=CFCF2(OCH2CF2CF2) m (OCF(CF3)CF2) n OCF(CF2)-X 2 (4) In the formula, m is 0 or an integer of 1 to about 5, and n is 0 or an integer of 1 to about 5.

[0141] CF2=CF(OCF2CF(CF3)) m O(CF2) n -X 2 (5) In the formula, m is 0 or an integer of 1 to about 5, and n is an integer of 1 to about 8.

[0142] CF2=CF(OCF2CF(CF3)) m -X 2 (6) In the formula, m is an integer of 1 to about 5.

[0143] CF2=CFOCF2(CF(CF3)OCF2) n CF(-X 2 )CF3 (7) In the formula, n is an integer of 1 to about 4.

[0144] CF2=CFO(CF2) n OCF(CF3)-X 2 (8) In the formula, n is an integer of 2 to about 5.

[0145] CF2=CFO(CF2) n -(C6H4)-X 2 (9) In the formula, n is an integer from 1 to about 6.

[0146] CF2=CF(OCF2CF(CF3)) n OCF2CF(CF3)-X 2 (10) In the formula, n is an integer of 1 to about 2.

[0147] CH2=CFCF2O(CF(CF3)CF2O) n CF(CF3)-X 2 (11) In the formula, n is 0 or an integer of 1 to about 5.

[0148] CF2=CFO(CF2CF(CF3)O) m (CF2) n =X 2 (12) In the formula, m is 0 or an integer of 1 to about 4, and n is an integer of 1 to about 5.

[0149] CH2=CFCF2OCF(CF3)OCF(CF3)-X 2 (13)

[0150] CH2=CFCF2OCH2CF2-X 2 (14)

[0151] CF2=CFO(CF2CF(CF3)O)mCF2CF(CF3)-X 2 (15) where m is an integer greater than 0.

[0152] CF2=CFOCF(CF3)CF2O(CF2)nX 2 (16) wherein n is an integer that is at least 1.

[0153] CF2=CFOCF2OCF2CF(CF3))OCF2-X 2 (17) In the formula, X 2 can be a monomer reactive site such as a halogen or alkylated halogen group (I or Br, CH2I and similar alkylated or alkoxylated reactive halogen groups and the like). Such cure site monomers can be at least partially fluorinated for use with curable fluoropolymers, but preferably are perfluorinated along the portion of the cure site monomer's backbone that is within the polymer backbone when polymerized for use in curable perfluoropolymers.

[0154] Curable fluoropolymers that are not perfluorinated fluoropolymers can also be used in the present invention for use in making articles by additive manufacturing from fluoroelastomers. Such fluoropolymers (FKM) are materials classified by the standard rubber nomenclature definition provided by ASTM International in ASTM D1418-10a. Standard FKM polymers according to such elastomer nomenclature typically contain at least two monomers, one of which is fluorinated, preferably all of which are fluorinated to some extent, and at least one cure site monomer for use in vulcanization. The at least two monomers preferably include vinylidene fluoride and hexafluoropropene or similar fluorinated olefins, but may include various other monomers as well. The fluoroelastomer composition may also contain at least one curative agent capable of undergoing a crosslinking reaction with functional groups in the cure site monomer(s) of the fluoroelastomer.

[0155] Such cure site monomer(s) may include cure site monomers that are peroxide curable and may contain functional groups with halogenated materials such as Br or I within the cure site functional group. Such cure site monomers have reactive functional groups to enable crosslinking. At least two of the monomers in the FKM are preferably hexafluoropropene (HFP) and vinylidene fluoride (VF2), although other typical monomers may be used in addition to these two to form various fluoropolymers known in the art.

[0156] The curable fluoropolymer may be radiation crosslinkable, but is preferably crosslinkable (curable) through a cure system in which curing chemical(s) are added that are capable of reacting with functional groups in the cure site monomer to form an elastomeric material. For some cure systems, a co-curing chemical, or second curing chemical, that works in conjunction with the curing chemical may be used. Optionally, cure accelerator(s) may be employed as well. Compositions suitable for use in additive manufacturing herein may have a single curable fluoropolymer, or a combination of at least two curable fluoropolymers in the form of, for example, a polymer hybrid, a graft composition, or an alloy, depending on the desired final properties.

[0157] The terms "uncured" or "curable" refer to fluorine-containing polymers for use in the compositions herein that have not yet been subjected to crosslinking reactions to a significant extent such that the material is not yet sufficiently cured for its intended use.

[0158] The curable fluoropolymer for the compositions herein may optionally include additional such polymers in hybrid compositions or graft and / or copolymer compositions, as described above. Additionally, the polymer backbone may include various cure site monomer(s) along the chain to provide one or more different functional groups for crosslinking. The compositions may also include curative and co-curative agents and / or accelerators to assist the crosslinking reaction.

[0159] One or more curable fluoropolymers and / or one or more curable perfluoropolymers can be present in such compositions. Such polymers themselves are formed by polymerizing or copolymerizing one or more fluorinated monomers. Various techniques known in the art (direct polymerization, emulsion polymerization, and / or free radical initiated polymerization, latex polymerization, etc.) can be used to form such polymers.

[0160] FKM fluoropolymers can be formed by polymerizing two or more monomers, preferably one of which is at least partially fluorinated. For example, HFP and VF2 can be combined with tetrafluoroethylene (TFE), or one or more perfluoroalkyl vinyl ethers (PAVE), or similar monomers, along with at least one monomer that is a cure site monomer to enable curing, i.e., at least one fluoropolymer cure site monomer. The fluoroelastomer compositions as described herein can include any suitable standard curable fluoroelastomer fluoropolymer(s) (FKM) that can be cured to form a fluoroelastomer, and one or more other curing agents as described herein.

[0161] Examples of suitable curable FKM fluoropolymers include those sold under the trade names Tecnoflon® PL958 and Tecnoflon® 959, available from Solvay Solexis, SpA (Italy), or other similar fluoropolymers. Preferably, the curable fluoropolymers used herein have suitable physical properties, but also have a rheology and viscosity that, when employed in the applications herein and introduced into additive manufacturing processes, allow them to be extruded as filaments, for example, for use in FFF or FDM, or fed in pieces as a gum-form composition to a ram material extruder in a ram device. Other suppliers of such materials include, among others, Daikin Industries (Japan), Asahi Glass Company (Japan), 3M Corporation (Minnesota), SV Lebedev Synthetic Rubber Research Institute (Russia) (VNIISK), and EI DuPont de Nemours & Company, Inc. (Delaware). Such FKM polymers are not fully fluorinated on the polymer backbone.

[0162] According to the present invention, one or more curing chemicals (also referred to herein as curing agents) within a cure system are used. Suitable curing agents include bisphenyl-based curing agents, nitrile curing agents, and peroxide curing agents and co-curing agents, such as organic peroxides and co-curing agents. In a preferred embodiment herein for an FKM, the bisphenyl-based curing agent cures through the VF2 monomer group, preferably the adjacent HFP monomer, and the peroxide-based cure system cures through reaction with functional groups on the cure site monomer in the curable fluoropolymer. Suitable nitrile cure systems, such as those described above for FFKM, may also be used.

[0163] Preferred functional groups in cure site monomers for reaction with peroxide cure systems include those with halogenated reactive groups, e.g., iodine or bromine, however, those that may enhance the cure of, e.g., bisphenyl-based Similarly, additional cure sites, such as those having nitrile groups, i.e., nitrogen-containing reactive groups, can be provided in the same or different cure site monomers.

[0164] In still further embodiments, exemplary cure site monomers include those listed above, which have PAVE-based structures and reactive sites, such as those described as structure (A) and variations (1) through (17) above.

[0165] Fluoropolymers for use in the compositions herein can be synthesized using any known or later developed polymerization technique for forming fluorine-containing curable fluoropolymers by polymerization (including, for example, emulsion polymerization, latex polymerization, chain-initiated polymerization, batch polymerization, and others). Preferably, the polymerization is carried out so that reactive cure sites are located on at least one end of the polymer backbone and / or pendant from the main polymer backbone.

[0166] One possible method for preparing the polymer involves radical polymerization using initiators such as those known in the art for the polymerization of fluorine-containing elastomers (organic or inorganic peroxides and azo compounds). Typical initiators are persulfates, percarbonates, peresters, etc. Preferred initiators include salts of persulfates, oxycarbonates and esters, and ammonium persulfate, with ammonium persulfate (APS) being the most preferred. These initiators can be used alone or together with reducing agents such as sulfites and sulfites.

[0167] Standard polymerization procedures known in the art can be used. Cure site monomers can be added and copolymerized when preparing fluorine-containing elastomers. In their uncured or curable state, useful fluoroelastomer compositions can include dual-cure systems, such as those having two cure site monomers with active functional groups in combination with more than one type of curing agent, e.g., at least one bisphenyl-based curing agent, and an organic peroxide cure system, where the two cure systems are capable of undergoing crosslinking reactions with one of the functional groups of the cure site monomers present on the fluoropolymer(s). In addition, additional curing chemicals or combinations of curing chemicals and co-curing chemicals can be employed as desired, especially when additional cure site monomers are provided. Cure accelerators can also be used as desired. The halogen-containing functional groups mentioned can react with the organic peroxide curing chemicals and / or co-curing chemicals in a peroxide cure system.

[0168] When using peroxide cure systems in FKM fluoropolymers, suitable curable fluoropolymers include polymers of VF2, HFP, and cure site monomers, as discussed above, that have fluorinated structures with peroxide-curable functional groups, such as alkyl halides and other derivatives, and partially or fully halogenated hydrocarbon groups.

[0169] The curing chemical for peroxide-based cure systems can be any organic peroxide curing chemical and / or co-curing chemical known or hereafter developed in the art, such as organic and dialkyl peroxides or other peroxides capable of generating radicals by heating and engaging in a crosslinking reaction with the functional group(s) of the cure site monomer on the fluoropolymer chain. Exemplary dialkyl peroxides include di-tert-butyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, dicumyl peroxide, dibenzoyl peroxide, ditert-butyl perbenzoate, and di-[1,3-dimethyl-3-(tert-butylperoxy)butyl]carbonate. Other peroxide systems are described, for example, in U.S. Patent Nos. 4,530,971 and 5,153,272, the relevant portions of which regarding such curing chemicals are incorporated by reference.

[0170] Co-curing agents for such peroxide-curing chemistries typically include allylic compounds such as isocyanuric acid and similar compounds that are polyunsaturated and work in conjunction with the peroxide-curing chemistries to provide useful cures, such as triallyl cyanurate (TAC), triallyl isocyanurate (TAIC), tri(methylallyl) isocyanurate (TMAIC), tris(diallylamine)-s-triazine, triallyl phosphite, N,N-diallylacrylamide, hexaallylphosphoramide, N,N,N',N'-tetraalkyltetraphthalamide, N,N,N',N'-tetraallylmalonamide, trivinyl isocyanurate, 2,4,6-trivinylmethyltrisiloxane, and tri(5-norbornene-2-methylene) cyanurate. The most preferred, well known in the art, is triallyl cyanurate (TAIC), which is sold under trade names such as DIAK®, e.g., DIAK® #7, and TAIC®, including TAIC® DLC.

[0171] As the bisphenyl-based curing agent, bisphenyl-based materials and their derivatives can be used, but preferably, curing agents such as bisphenol A, BOAP, bisaminothiophenol, bisamidoxime, and / or bisamidrazone are used. However, curing agents containing amino groups such as monoamidines and monoamidoximes, triazines, cyano group-containing nitrile curing agents, organometallic compounds and their hydroxides, diamines and diamine carbamates, for example, N,N'-dicinnamylidene-1,6-hexanediamine, trimethylenediamine, cinnamylidene, trimethylenediamine, cinnamylideneethylenediamine, and cinnamylidenehexamethylenediamine, hexamethylenediamine carbamate, bis(4-aminocyclohexyl)methane carbamate, 1,3-diamine monocarbamate, etc. are also used. Additional curing agents such as cyclohexylpropane, ethylenediamine carbamate, trimethylenediamine carbamate, and those described in U.S. Pat. Nos. 7,521,510 B2, 7,247,749 B2, and 7,514,506 B2 (the relevant portions of each of which relating to listings of various curing agents for cyano-group-containing fluoropolymers and the like are incorporated herein) may also be used in addition to the bisphenyl-based curing agents and peroxide-based cure systems, if desired, and / or if additional cure site monomers curable by such agents are provided.

[0172] Bisphenyl-based curing agents and derivatives thereof, including BOAP, bisphenol A, bisphenol AF, and their salts and derivatives, bisaminothiophenol, and parabenzoquinone dioxime (PBQD), can also be used in combination with peroxide cure systems, if desired. In addition to these curing agents, other bisphenyl-based curing agents and derivatives thereof, such as those described in U.S. Pat. Nos. 7,247,749 and 7,521,510 (the relevant portions relating to such compounds are incorporated herein), can also be used. Regardless of the type of bisphenyl-based curing agent used, it is most preferred that the compound have at least one, and preferably two, hydroxyl-containing functional reactive cure sites for reaction with cure site monomers, as discussed above.

[0173] Each of the at least one cure site monomer in each of the curable fluoropolymers or perfluoropolymers herein is preferably present in an amount of from about 0.01 to about 10 mole percent of the curable fluoropolymer. The ratio of the other monomer(s) in the fluoropolymer can be varied within the skill in the art to achieve different properties in the final fluoropolymer or perfluoropolymer.

[0174] The total amount of curing agent used in compositions with curable fluoropolymers or perfluoropolymers is preferably from about 0.01 to about 10 parts by weight per 100 parts by weight of the curable fluoropolymer(s) in the composition.

[0175] Such curable fluoropolymer and perfluoropolymer compositions may contain various additives and fillers as are known for use in compounding fluorine-containing elastomers, or new additives to be developed in the future. Depending on the desired final properties, the fillers and additives in the composition, excluding the curing agent, may optionally be added in an amount of about 0.5 parts to about 100 parts by weight, based on the combined weight of the curable fluorine-containing polymers in the composition, preferably about 10 parts to about 50 parts by weight, based on the combined weight of the curable fluorine-containing polymers.

[0176] Optionally, but not necessarily, additives (other than the curatives described above) may be incorporated into the composition during compounding and prior to forming the extruded filaments, such as by mixing or blending. Additives are optional, not required, and may modify viscosity characteristics such that in some cases conditions will need to be adjusted. However, if desired, cure accelerators, curative co-agents, processing aids, plasticizers, fillers, and modifiers, such as silica, fluoropolymers (TFE and its melt-processible copolymers in micropowder form, pellets, fibers, and nanopowder form), fluorographite, silica, barium sulfate, carbon, carbon black, fluorocarbons, clay, talc, metal fillers (titanium oxide, aluminum oxide, yttrium oxide, silicon oxide, zirconium oxide), metal carbides (silicon carbide, aluminum carbide), metal nitrides (silicon nitride, aluminum nitride), and the like may be added to achieve certain elastomeric performance properties. ), other inorganic fillers (aluminum fluoride, fluorocarbons), colorants, organic dyes, and / or pigments such as azo, isoindoline, quinacridone, diketopyrrolopyrrole, anthraquinone, etc., imide fillers (such as polyimides, polyamideimides, and polyetherimides), ketone plastics (such as polyarylene ketones like PEEK, PEK, and PEKK), polyarylates, polysulfones, polyethersulfones, polyphenylene sulfides, polyoxybenzoates, etc., may be used in amounts known in the art and / or varied for different properties. All fillers herein may be used alone or in combination with two or more such fillers and additives.

[0177] Preferably, any optional filler is used in the amount described above, and the amount is less than about 100 parts by weight of the combined curable fluoro- or perfluoropolymer in the composition. The desired cure time and temperature, which can be used to evaluate the heating curve for additive manufacturing, can be developed based on the polymer composition being prepared, which should guide the selection of printing properties that allow the polymer to be at the desired position D on the filament heating curve, as discussed further below.

[0178] In preferred embodiments herein, the curable fluoropolymers and perfluoropolymers used herein preferably have a Mooney viscosity (ML1+10@121°C) of about 10 to about 160. These polymers may include various plasticizers known in the art or to be developed suitable for use in such polymers to adjust the Mooney viscosity of the curable fluoropolymer or perfluoropolymer, or blend(s) thereof, used in printing. It is also acceptable to select curable fluoropolymers and / or curable perfluoropolymers having somewhat lower Mooney viscosities (ML1+10@121°C) of about 20 to about 45, preferably about 20 to about 40, or about 20 to about 30, with or without optional plasticizers. The use of curable fluorine-containing elastomer(s) or elastomer formulation(s) having Mooney viscosities in the ranges described herein, alone and / or in combination with suitable plasticizer(s), can improve the ability to print such materials in the apparatus and methods herein in terms of providing easier printability, reducing shrinkage, shortening overall printing time while providing sufficient available printing time to avoid scorching or blistering, and increasing interlayer adhesion. Blends of curable fluoropolymer(s) and / or perfluoropolymer(s) having various Mooney viscosities, with or without the use of plasticizer(s), can also be used, and such blends can be tailored to the desired printing properties of a given curable fluoropolymer and / or perfluoropolymer material or formulation using the methods and apparatus herein.

[0179] The present invention further claims, in embodiments herein, to provide an additive manufacturing printer having a drive mechanism and a printer nozzle. Such additive manufacturing printers are commercially available for purchase, including, for example, those under the names Ultimaker, available from Ultimaker BV (The Netherlands), Monoprice Maker, available from Monoprice (Brea, California), and Creality3D Ender-5 Pro 3D Printer, available from Creality3d.shop. However, it should be understood that any such additive manufacturing printer capable of printing elastomeric articles based on the present disclosure herein may be used. Preferably, such a printer may have one or more of the preferred features of the device, including the improvements described herein, or may be directly fabricated by a manufacturer with alternative features (provided that the printer is capable of extruding a fluorine-containing curable fluoropolymer that is partially, substantially, or fully fluorinated, such that the three-dimensional article comprises a fluoroelastomer or perfluoroelastomer).

[0180] In one embodiment of the method for additively printing fluorine-containing elastomeric articles herein, a filament having a curable fluoropolymer composition is fed into the device, preferably after the filament enters a heated print head including a printing nozzle, and more preferably, heat is applied to the filament as it exits the nozzle to form a heated filament. In other embodiments of the method herein that use a ram material extruder, the curable perfluoropolymer enters the ram device directly and does not need to be in the form of a filament. However, it can be heated in the ram device, either in the barrel of the device and / or in the nozzle end of the device. Heat can be applied at any step in the process (for example, the curable polymer composition feedstock can be heated prior to introduction into the ram material extruder ram device, including the printer nozzle of the ram material extruder ram device, or the heated filament can be preheated when it enters the print drive mechanism, when it is in the print drive mechanism, when it is in the nozzle in the print head, or when it is in the nozzle portion extending from the print head to the nozzle outlet, so that the heated filament is hot enough to extrude the filament through the nozzle outlet), but it is preferred that the curable fluoropolymer composition feedstock or filament is flowable but not hot enough to initiate curing, or is heated only to minimize any curing to avoid substantial curing prior to printing one or more layers. Preferably, the curable fluoropolymer composition feedstock is heated in the ram material extruder ram device, including the nozzle of the ram material extruder ram device, or the filament is heated in the print head, enters the nozzle, advances through it, and exits from the nozzle outlet as a heated filament.

[0181] In one embodiment of the present specification, in a preferred example, the filament at the roller is cooled prior to entering the path through the printer to the nozzle, which helps to stiffen the filament and prevent possible buckling. Any suitable deep-chilling or cooling method and device can be used for this purpose, and such mechanisms are known in the art, and deep-chilling or cooling devices can be incorporated into any embodiment described herein, as described in more detail below. Furthermore, when using a device in which the curable fluoropolymer composition is fed directly to the ram material extruder, no pre-cooling or cooling is required. However, if desired, the fluoropolymer can be pre-cooled.

[0182] Referring to FIG. 6 , which shows a representative thermal curve, the effect on filament width is shown as temperature increases for a representative curable perfluoropolymer. As heat increases, filament thickness changes, becoming wider (thicker) as the filament moves from near ambient temperature (position A) to a level where the curing (i.e., cross-linking) reaction begins (position B). As curing progresses and temperature increases, the filament becomes thinner and smaller in diameter, reaching its thinnest level at position C, where substantial curing has occurred. Based on applicant's experiments, it was determined that for processing in various embodiments of the additive manufacturing device herein, curing of the material should be either avoided or less than about 25% cured to provide the material with sufficient strength, but not so much that curing would inhibit the ability to flow the curable material, extrude it through a nozzle, and allow for sustained curing during layer-by-layer deposition of the elastomeric article. Position D was identified as the ideal range for extruding the curable perfluoropolymer through a nozzle. It has also been determined that the majority of commercial printers designed for high temperature melting are completely unsuitable for use in additive manufacturing to form fluoro- or perfluoroelastomeric articles. Therefore, it is preferable to use additive manufacturing equipment that is capable of operating below 200°C, more preferably below about 250°C, more preferably below about 200°C, and even more preferably at or below 160°C.

[0183] In using such additive printer devices with perfluoropolymer filaments, it is further preferred that the curable perfluoropolymer be heated as the extruded filament is processed to a temperature prior to the onset of curing or to a temperature at which some curing occurs (which is minimized to a degree of greater than 0% to about 25% curing during printing). Similarly, when introducing a curable composition comprising a fluoropolymer or perfluoropolymer into a printing device that includes a ram material extruder, it is preferred that the extruded composition leaving the nozzle also be extruded to a temperature prior to the onset of curing or to a temperature at which some curing occurs (which is minimized to a degree of greater than 0% to about 25% curing).

[0184] Evaluation of the cure characteristics of curable fluoro- or perfluoropolymers can be performed by RPA using test method ASTM D2084, where the temperature of the heated filament or extruded curable fluoropolymer composition is preferably held below the temperature associated with time T2 on the curve using the RPA. Any suitable RPA can be used for this purpose, including commercial examples such as those mentioned above. In some embodiments, depending on the curable polymer used, the filament can be heated to a temperature of about 20°C to about 250°C, or about 70°C to about 250°C. In other embodiments, the filament can be heated to a temperature of about 100°C to about 250°C, preferably about 105°C to about 200°C, and most preferably about 110°C to about 160°C.

[0185] 1, a schematic flow chart is provided depicting a generic additive manufacturing apparatus for use in one embodiment herein, generally referred to as embodiment 100, in which an extruded filament 10 can be delivered in roll form from a feed roller 12. The feed roller can be any standard feed roller used for delivery of extruded polymer filaments.

[0186] The filament, which may be cooled upon initial introduction, is fed into the additive manufacturing printer 14 through a printer drive mechanism 16, which is preferably operated by a motor 18. In the preferred embodiment shown, a support tube 20 extends between the printer mechanism between the drive rollers and an inlet 42 of the nozzle 36 in the print head 34.

[0187] The support tube 20 can have a variety of shapes in transverse cross-section, such as circular, elliptical, oval, oval, square, triangular, polygonal, etc. Preferably, the support tube has several internal curved surfaces from its cross-sectional shape, such as a circular cross-sectional shape, for ease of filament advancement within the tube. The tube is formed from a longitudinally extending tubular wall 22 having an exterior surface and an interior surface 24 defining a longitudinally extending passageway 26. The support tube extends from a first end 28 to a second end 30. The filament exits the additive manufacturing printer 14 and enters a print head 32, which includes a nozzle 34. On leaving the nozzle 34, the extruded filament is consistently extruded through a nozzle outlet 40, which deposits the extruded filament 10 onto a substrate 36, and standard additive manufacturing computer-aided control (not shown), as known in the art, continues to move the print head, forming a layer-by-layer application of material to form an elastomeric article 38.

[0188] The second end 30 of the support tube is preferably positioned in close proximity (herein intended to mean within, near, adjacent to, in the general area of, juxtaposed to, or touching) to the inlet to the printer nozzle to allow fluid communication between the support tube and the print head at its second end. The closer the tube is, from a practical standpoint, the more support the tube can provide to the filament without encountering filament buckling. However, the actual proximity of the second end of the support tube to the inlet of the print head and nozzle will depend on the design of the specific apparatus used, and will influence the proximity that the second end of the support tube can reach.

[0189] Successive layers of heated filament exiting outlet 40 of nozzle 32 are printed onto substrate 36 using additive manufacturing printer 14 to form fluorine-containing elastomeric article 38.

[0190] The curable fluoropolymer and perfluoropolymer filaments provided to additive manufacturing printers are preferably formed by extruding a curable fluoropolymer composition. Such extruders are known in the art and are used to form fluoropolymer "ropes" for use in forming objects such as O-rings by compression molding. Such extruders can be used to prepare extruded filaments for use in additive manufacturing processes and are well known in the art.

[0191] Heat may be applied to some extent at any time during the process (including prior to introducing the filament into the tube) for controlled curing and flow, avoiding over- or premature curing while allowing the filament to flow through the process and out the nozzle. Preferably, however, the application of heat occurs within the print head as the filament enters the nozzle, allowing extruded flow through the nozzle and its outlet. The filament may have a range of viscosities, as discussed above, provided that it flows through the nozzle and curing is controlled.

[0192] The diagram illustrates this, as discussed above, with point D being the ideal processing temperature range for extrusion through the nozzle. For various polymers that may vary in temperature for curing, the temperature can be adjusted to accommodate the cure cycle of that polymer, as shown in the preferred area of ​​the cure curve within the representative curve in Figure 6 and the exemplary curves shown in Figures 8-10 associated with the examples herein. The curable fluoro- or perfluoropolymer, or blend thereof, is preferably cured within the nozzle exit and thereafter to an extent of about 10% to about 90% as the article is formed and finished (including any post-cure thereof).

[0193] The filament may be heated through any suitable heating mechanism 17 or heating device, including an external heater, a heated fan, or an optional heating device within the additive manufacturing printer, preferably the heating element is located within the printer drive mechanism and / or print head.

[0194] An apparatus in one embodiment herein is described in schematic flow chart form with reference to FIG. 1A. This embodiment is generally referred to herein as embodiment 200, with like numbers indicating common elements throughout all embodiments. As shown, a curable fluorine-containing polymer filament is fed into a three-dimensional additive manufacturing apparatus 214 from a feed roller 212 to a printer drive mechanism 216 within the apparatus 214, which includes a drive wheel (roller) 244 and a support wheel (roller) 246. As used herein, "wheel" and "roller" may be used interchangeably to refer to a feed device shaped in a generally circular, elliptical, or arcuate manner to drive the printing function and move the filament through the print drive mechanism. The two wheels 244, 246 move consistently through the printer drive mechanism 216, driven by the drive motor 218, to support and provide friction for the curable fluorine-containing filament as it passes through a space 248 (defined by the desired contact gap for the filament thickness) between the drive wheel 244 and the support wheel 246 prior to entering the first end 228 of the support tube 220.

[0195] In this embodiment, the apparatus may further include an optional feature having a first end 228 of the support tube 220 extending upwardly through the printer drive mechanism 216 between the support wheel 244 and the drive wheel 246, whereby the support tube may support the filament as it leaves the feed roller 212 and enters the printer drive mechanism, and may avoid buckling of the filament at this point, especially if some heat has already been applied (or from heat of frictional contact between the filament and the apparatus after it leaves the feed roller).

[0196] The support tube that may be used in such an embodiment differs from the support tube of embodiment 100 only with respect to the additional lateral openings shown in Figures 3 and 3A and discussed herein, and therefore the overall tube is otherwise the same.

[0197] The tube 220 is formed as a tubular wall 222 having a longitudinally extending passageway 226 defined by an interior surface 224 of the support tube wall 222. In an effort to control when curing begins as the fluorine-containing curable polymer that forms the elastomer is delivered, the tube is preferably formed from a material that does not introduce unnecessary frictional contact along the entire path of the tube's interior wall. Thus, the tube is also preferably formed from a smooth material, preferably a low-friction material such as polytetrafluoroethylene (PTFE) or a moldable copolymer of tetrafluoroethylene.

[0198] The support tube wall 222 also defines a side opening 250 extending laterally through the support tube wall 222 from an interior surface 224 of the support tube wall 222 to an exterior surface 252 of the wall. The wall defining and surrounding the opening 250 is contoured to match the shape of the drive wheel 224. The filament 210 can be fed through the support tube, preferably formed from a material that reduces friction during the process, as discussed above, so as to avoid unnecessarily engaging in curing too early in the process while passing through the support tube. As the filament 210 passes through the passage 226 of the support tube 220, the laterally extending side opening 250 allows for controlled contact of the filament with the drive wheel 244 in the area of ​​the side opening as it passes through the drive mechanism, keeping the filament moving consistently and at a desired speed while minimizing frictional impacts and maintaining smooth filament introduction into the support tube from above the printer drive mechanism (and close enough that the first end 228 of the support tube 220 can reach the feed roller 212) to support the filament, thereby enabling smooth and controllable passage of difficult-to-process elastomers, such as fluorine-containing elastomers, through an additive manufacturing printer without sacrificing the important role of the printer drive rollers in the printer drive mechanism in controlling the column height of the filament above the print drive mechanism and above the nozzle, directing the filament into the print head, and controlling the speed of its approach.

[0199] When forming a fluorine-containing elastomeric article such as a seal, the inner diameter of the printer nozzle outlet 240 (e.g., w2 in FIG. 6 ) can be sized to be approximately the same size as the outer longitudinal cross-sectional diameter of the seal intended to be formed. In one embodiment herein, due to the filament temperature profile, as shown in illustrative form in FIG. 6 , an improvement includes noting that when processing curable fluorine-containing polymers in an additive manufacturing apparatus, elastomeric materials of this nature (and other similarly viscous thermoset elastomers) require more pressure to leave the nozzle outlet than standard printing thermoplastic filaments. As shown in FIG. 4 , prior art printing nozzles can be somewhat smaller than those required to accommodate filaments formed from extruded curable fluorine-containing polymer(s) or other similarly elastomeric-based polymers. Most standard additive manufacturing equipment is not designed to handle the degree of pressure required to allow more viscous materials to pass easily (especially as they begin to cure to some degree from the application of heat). The standard approach to increasing the pressure on viscous thermoplastics is to heat them. However, too much heat on the curable fluorine-containing polymer(s) or similar uncured elastomer-based polymer(s) can cause curing to begin, which can restrict or weaken the filament at the wrong moment and / or cause buckling at the inlet 242 of the nozzle 234 or clogging of the nozzle.

[0200] 1 or 1A, as shown with reference to FIGS. 4 and 4A, the outlet 240 of the nozzle 234 (or outlet 40 in the nozzle 34) in the preferred embodiments herein may be modified to be wider than the standard inner diameter (ID) of the outlet O of the nozzle Q of a standard prior art additive printer device nozzle. The preferred outlet has an expanded inner diameter or width w2 (measured laterally at the widest dimension of the outlet) and a corresponding wider outer diameter or width w1 to accommodate the maximum outer diameter of the heated fluorine-containing fluoropolymer filament at a certain stage of the heat curve (see, for example, FIG. 6) where the fluoropolymer enters the preferred location D and the heat is controlled in the printer by the heating mechanism 217 in the same manner as in embodiment 100. By using an exit size that is approximately the same as the filament thickness based on its thermal curve at the preferred processing temperature, or within a range of ± about 0.1 mm to about 0.5 mm, the filament can be properly extruded through the nozzle, allowing for uninterrupted extrusion, avoiding clogging at the print head inlet, and preventing buckling. In embodiments described herein, the inner diameter can be at least about 0.2 mm, or from about 0.2 to about 3.3 mm. In another embodiment, the inner diameter can be from about 0.4 mm to about 1.6 mm.

[0201] For example, as shown in Figure 6, the filaments formed from the curable perfluoropolymer composition at preferred heating zone location D have an outer diameter of about 0.2 mm to about 20 mm. Accordingly, the nozzle may be sized appropriately, for example, the nozzle may be about 0.2 mm to about 20 mm, and preferably, in this particular example, about 1.0 mm to about 3.0 mm.

[0202] In preferred embodiments of embodiments 100 and 200, as used herein, the additive manufacturing printer 14, 214 preferably includes a drive motor 18, 218, preferably a stepper motor, for operating the drive mechanism. The motor preferably provides sufficient torque to overcome any friction between the filament and the additive manufacturing drive printer and its components, while providing sufficient pressure to push the material through the additive manufacturing printer and out the nozzle outlet without losing constant velocity and avoiding clogging or filament buckling.

[0203] Most standard additive printers have stepper motors designed for less viscous materials that are easily extrudable. Therefore, even when a stepper motor is used, the drive motor likely has insufficient torque for smooth filament movement and requires additional power for operation. Therefore, when printing elastomeric materials that are more viscous and / or need to be maintained at a constant speed and thickness to achieve a printed elastomeric article, additive manufacturing printers should have larger-capacity stepper motors and / or be modified to achieve the required torque and power requirements for operation. One preferred modification herein is to provide a geared transmission 257 to the stepper motor of the additive printer drive mechanism to increase the torque of the stepper motor. An example of a geared transmission mechanism may include one or more planetary gears 254. Such a geared transmission mechanism 257 including a planetary gear 254 is shown in FIGS. 7 and 7A. In FIG. 7A, a single planetary gear 254 is shown, attached to the drive shaft 256 of the stepper motor 218 as the geared transmission 257. A series of connecting smaller gears 258 having edge teeth 260 are rotatably positioned and interact with internally meshing teeth 262. A series of such planetary gears 254 can be used in series, in an interconnected fashion, to adjust and improve the standard drive motor torque of a commercial additive manufacturing printer. Table 1 below shows the increase in torque and other characteristics for a stepper motor modified using the configuration of Figure 7 compared to the same motor prior to modification. [Table 1]

[0204] The present invention further includes articles formed by heated filaments comprising a curable fluoropolymer composition extruded through the nozzle of an additive manufacturing apparatus. The apparatus may include features as described above and shown in assembled form in Figure 2. The additive manufacturing apparatus 14, 214 in this embodiment may be a fused filament fabrication or fused deposition apparatus for an FFF or FDM device in preferred embodiments.

[0205] Various curable fluorine-containing compositions can be used as additive manufacturing compositions herein and formed into three-dimensional articles, including one or more curable fluorine-containing polymers, including partially fluorinated fluoropolymers (FKMs) and substantially or fully fluorinated perfluoropolymers (FFKMs), each having functional groups for reaction with a curing agent, and may further include one or more curing agents suitable for curing the selected polymers, which are capable of reacting with the respective functional group or groups on the cure site monomer(s) of the selected fluoropolymer, as described above. Preferred fluoropolymers and perfluoropolymers for additive manufacturing in devices such as those described above have an uncured Mooney viscosity of about 10 to about 160 ML1+10 at 121°C.

[0206] The present invention further includes additive manufacturing apparatuses, as described above, capable of forming three-dimensionally printed elastomeric articles. The printer drive mechanism of the apparatus herein, in a preferred embodiment, may include a drive roller and a support roller, as described above, and the apparatus may further include a support tube, as described herein, mounted to extend below the printer drive mechanism such that the drive roller is preferably positioned to contact the extruded filament fed into the tube within the printer drive mechanism. The support tube may thus extend through the print head 232 from a lower surface, such as lower surface 264, of the printer drive mechanism to an area Y proximate the inlet 242 of the nozzle 234, as shown in FIGS. 2 and 2A .

[0207] The support tube may preferably have its first end 228 positioned above the printer drive mechanism 216, and its second end 230 preferably proximate the inlet of the nozzle 234. As described more fully above, the support tube 220 is preferably configured to support a curable fluorine-containing polymer filament passing through the support tube's first end 228 and exiting through the support tube's second end 230, and may also include a side opening, as described above, extending laterally through the tube wall from the tube's inner surface to its outer surface to promote direct contact between the drive roller and the filament passing through the support tube's longitudinal path. As also mentioned above, in one preferred embodiment, the support tube's first end 228 may be positioned closer to the feed roller to receive the curable polymer filament leaving the feed roller and reduce the column height to avoid buckling of the filament.

[0208] In further embodiments, the substrate 236 may include a friction surface to improve adhesion of the non-tacky extruded curable polymer onto the substrate. Because curable fluoropolymers contain tetrafluoroethylene and are highly inert, creating a tacky or frictional finish or upper surface, such as friction surface 266, on the substrate 236 may improve results in forming the finished article. While interlayer adhesion may be improved by the curing process, initial adhesion to the substrate 236 is important for building a stable article and laying down a strong first layer that will receive subsequent layers. Such friction surfaces may include, for example, adhesives, roughened surfaces, treatments that attract or have a minimal amount of adhesive, or PTFE-containing surfaces that may interact somewhat with the first printed layer. Such substrates with frictional surfaces or surface treatments may be used in any of the embodiments herein.

[0209] In another embodiment herein, support structures, such as removable or permanent fixtures, may be used to form articles of various shapes. Such structures are discussed in detail below.

[0210] As shown in FIG. 2 , the support tube has a length l1 measured vertically above the print drive mechanism, a length l4 from the bottom surface 264 of the print drive mechanism to an upper area Y adjacent the print head 232 containing the nozzle inlet 242, and also extends below the print drive mechanism. The distance from the substrate to the bottom of the feed roller 212 represents the total length of the filament path from the roller to the extrudate contacting the substrate and is represented as l5. The distance from the first end of the support tube to the location in the print head where the filament enters the nozzle is l2, and the length measured from the top of the support tube to the nozzle outlet is l3. The difference between l3 and l2 represents the nozzle height. The difference between l3 and the combined lengths of l1 and l4 is the height of the print drive mechanism. The height of the upwardly extending tube is preferably selected to approximately match the distance from the drive gear in the geared transmission to the heat break, i.e., the area where the filament enters the heated print head. The specific distance is selected based on the sizing of the drive gear within the geared transmission, motor, and associated transmission packaging. While shorter distances are preferred, the use of an upwardly extending tube provides sufficient support for the filament to function within and move normally through the 3D printing device.

[0211] As noted above, in various described embodiments, a cooling or deep-chilling device can be provided at the beginning of the process to achieve various benefits in the additive manufacturing of curable fluorine-containing polymer materials. For example, a deep-chilling or deep-chilling device E in the form of a pre-chiller, as shown in FIG. 11 , can be provided. Pre-chiller E is shown as a multi-layer container J mounted above a printer according to embodiment 200, but with a somewhat modified drive mechanism 216′ for use in an additive printer, such as printer 214′ according to embodiment 200′ herein. Such a drive mechanism can similarly be part of a filament extruder. The filament 210′ ​​shown in FIG. 11 is provided to a support tube 220′ through a bore Q defined by the multi-layer container J. As shown, bore Q is preferably of rounded transverse cross-section, but the shape can be modified for operational or design purposes. The bore allows for a smooth passage to the support tube while also allowing the filament 220′ to pass through the cooled walls and bore Q within the pre-chiller E. As the filament passes through, the filament temperature approaches the temperature of the coolant, such as the coolant in the cooling chamber EA (which is also defined by and within the structure of the multi-layer vessel J). A removable cover EB may be provided for cleaning, filling, and / or replacing the coolant T, as desired. While a pre-cooler is shown with device-attached printers such as embodiments 200, 200′ herein, a pre-cooler may be used with any of the embodiments herein.

[0212] The coolant used can vary, including a mixture of calcium chloride hexahydrate and ice to achieve a temperature of about -40°C. However, dry ice, regular ice, and others can be used depending on the temperature reduction and desired end conditions. The precooler E can be filled intermittently, such as with an optional cover EB, or can be filled continuously, such as by introducing a coolant, such as a coolant flowing through an exchanger designed for cooling, through a continuous exchange feed. Preferably, with fluorinated materials as described herein, the precooler is continuously filled and maintained at a preferred low temperature of about -40°C, although the temperature can be varied according to the materials selected.

[0213] Cooling and nozzle extrusion temperatures can be derived and selected using material properties as described herein, as measured using analytical tools such as dynamic mechanical analysis (DMA). Referring to FIG. 12, storage modulus can be measured over a range of temperatures, for example, from the coolant temperature to the cure temperature of the curable fluoropolymer or perfluoropolymer composition used and / or in the filament. In some cases, multiple DMA tests and analyses can be performed, with the final results normalized by matching DMA data at variable samples and overlapping temperatures. FIG. 12 is an example profile showing the range of storage modulus values ​​derived from two DMA tests, the first of which spanned from -80°C to 20°C and the second of which spanned from 20°C to 140°C. The storage modulus data at 20°C was used to "match" or scale the two data sets so that the relative storage modulus as a function of temperature was fully characterized for use.

[0214] The cooling temperature and nozzle extrusion temperature can be selected to determine the relative storage modulus during the additive manufacturing printing process. For example, point 1 shown on exemplary FIG. 12 corresponds to a −40° C. temperature and a 50 MPa storage modulus for the filament evaluated at the point (at corresponding point 1 in FIG. 11 ) where the filament is being driven through drive and support wheels 244′, 246′, such as the drive gears shown in FIG. 11 . The temperature at point 2 on FIG. 11 at the hot end of the drive mechanism as it enters the nozzle for printing is then selected to be 60° C. at point 2, where the storage modulus is 2 MPa, as shown by corresponding point 2 in FIG. 12 .

[0215] Other advantages of the apparatus and process when incorporating a precooler E can be identified with reference to the "free column length" of the support tube, which is generally defined herein as the distance from the centerline point within the drive roller or gear to the entrance below the roller / gear and into the lower portion of the support tube extending below the drive mechanism. In the exemplary apparatus shown in FIG. 11 , prepared using a commercial Hemera® extruder available from E3D Online (Oxfordshire, UK) equipped with dual drive gears and controlled minimum clearance, the free column length is 5 mm and the filament diameter is 1.75 mm. The extruder with the drive mechanism as described was mounted on a mounting bracket for printing applications. With respect to the free column length, if the driven filament is considered simply as a supported column, the critical buckling force (F) of the filament is cr ) is estimated as follows: F cr =μ EIπ 2 (I) L 2 where μ is the constraint coefficient, E is Young's modulus, I is the moment of inertia of the cross-sectional area, and L is the free column length. By using a precooler such as precooler E in FIG. 11, the critical buckling force F cr is increased from 0.36 N to 9.1 N in this exemplary embodiment, and the critical buckling pressure, P cr This corresponds to an increase in the maximum pressure, which is calculated as follows: F cr / A (II) In the formula, A is the cross-sectional area of ​​the filament between 0.15 MPa and 3.8 MPa.

[0216] Increasing the maximum pressure as described above significantly increases the achievable draw of the filament in the process and within the apparatus, thereby enabling the use of reduced nozzle orifice diameters. The achievable draw (meaning the reduction in filament diameter from the inlet into the nozzle and through the nozzle's exit) can be estimated by considering the filament extrusion as a solid material undergoing elastic-plastic deformation. The maximum draw ratio B is then estimated as Euler's number e, which is approximately 2.71828, increased by the ratio k of the maximum pressure to the storage modulus of the material being extruded, i.e., B=e Pcr / k (III)

[0217] For the material properties and filaments described, the use of a precooler for the curable fluoro- and perfluoropolymer compositions printed herein in this exemplary embodiment can increase the maximum draw ratio from 1.1 without a precooler to 6.6 with a precooler. The minimum orifice diameter can then be estimated as the filament diameter divided by the square of the draw ratio. Analysis suggests that the use of a precooler herein allows the nozzle orifice to be reduced from 1.69 mm to 0.68 mm. This principle and design can be employed with curable fluoropolymer compositions and curable perfluoropolymer compositions and other materials where such benefits would be advantageous in additive manufacturing printing.

[0218] In one process herein, in exemplary embodiment 300 as depicted in FIG. 5 , the method includes step 302 providing a curable polymer, such as the fluoropolymer or perfluoropolymer compositions described above, in extruded form (i.e., they may be pre-compounded and extruded into an initial rope or filament). The method includes providing 304 an additive manufacturing printer according to any embodiment herein, the printer preferably including a drive mechanism, a print head, and a nozzle. Heat is applied to the filament in step 306, which may be performed in the additive manufacturing printer drive mechanism or in the print head and / or nozzle at various stages of the process, including the feeding stage. A further step 308 includes feeding the filament through a support tube and through the additive manufacturing printer to exit as extrudate from an outlet of the print head nozzle and onto a substrate. Successive layers may then be applied onto the initially extruded layer onto the substrate in step 310 to form a three-dimensional, printed article on the substrate.

[0219] In a further embodiment herein, a method for forming a fluorine-containing elastomeric article is provided. The article is generally represented as embodiment 400 in FIG. 14. In the method, in step 402, a curable fluoropolymer composition is provided. The curable fluoropolymer composition can be any of the compositions described above with respect to the previous embodiment and can include one or more fluoropolymers that are at least partially fluorinated or fully fluorinated, i.e., perfluoropolymers, or combinations and hybrids thereof. As described above in the previous embodiment, curative(s), additives, and additional fluoropolymers or perfluoropolymers can be included. In step 403, an additive manufacturing printer apparatus is provided that includes a ram material extruder. The ram material extruder includes a ram device operable for extrusion under pressure and a printer nozzle. The additive manufacturing printer can be any of those described previously or suitable for being configured to support and / or be operatively connected to the ram material extruder. Suitable such printers include, for example, the Creality3D Ender-5 Pro 3D Printer, available online at Creality3D.shop. The ram material extruder can be any suitable such device, including various ARME-type printers, including the ARME1, ARME2, and ARME3 designs, or any variations or modifications thereof. The additive manufacturing printer apparatus should be capable of forming three-dimensionally printed articles including fluoroelastomers that are at least partially fluorinated, and fluoroelastomers that may be fully fluorinated in the form of perfluoroelastomers, as well as various combinations, alloys, and hybrids thereof. The apparatus should also be capable of printing articles such as component parts, including the various types of articles discussed above, including gaskets and seals.

[0220] In step 404, the method includes introducing the curable fluoropolymer composition for printing into a ram material extruder. The curable fluoropolymer composition can be provided in a compounded gum form, or in a preformed form such as a filament or other shape, or can simply be cut into gum pieces. In such embodiments, the composition can be introduced directly into the ram device of the ram material extruder, so that feeding the composition through a long processing path through a support tube and drive wheel can be avoided.

[0221] The method may include, similar to previous embodiments herein, analyzing the selected curable fluoropolymer composition prior to operation, estimating its storage modulus using DMA or parallel plate rheometry, optimizing printing parameters for the curable fluoropolymer composition, evaluating the applied flow temperature and pressure, and evaluating the desired nozzle tip.

[0222] In step 405, heat is applied to the ram device of the ram material extruder, including the printer nozzle of the ram material extruder. Heat may also be applied to the composition prior to introducing the composition into the ram device. Although not necessary when using a ram material extruder, if desired, the composition may be cooled using a cooler as shown above in the previous embodiment prior to introducing the composition into the device. However, such pre-cooling (while useful in the previously described filament embodiment) is entirely optional in this apparatus.

[0223] In embodiments herein, the additive manufacturing apparatus is capable of printing at temperatures lower than those required for thermoplastic materials, for example, less than about 250°C, or less than about 200°C, or even more preferably less than about 160°C, or less than about 100°C, or less than about 70°C, but in any case preferably also capable of printing at temperatures of at least about 20°C.

[0224] In step 406, pressure is applied to the ram device for the purpose of extruding the curable fluoropolymer composition through the ram device and out the printer nozzle outlet, preferably onto a substrate. The application of heat and pressure can occur sequentially or wholly or partially simultaneously. Applying pre-pressure without the application of heat can facilitate proper loading of the curable fluoropolymer composition into the ram device prior to printing. In step 407, an additive manufacturing device is used to print at least one layer of the extruded curable fluoropolymer composition. Printing of the composition occurs when the composition exits the printer nozzle outlet onto the substrate to form a printed article 538 having a fluorine-containing elastomer. Upon completion of printing, a fluorine-containing elastomer article 538 is formed in step 408, as shown with reference to FIGS. 13 and 14.

[0225] The present invention also includes a system, referred to herein as embodiment 500, that includes a curable fluoropolymer composition 510 and an additive manufacturing printer apparatus 514 capable of performing method 400. Such a system is shown schematically in Figure 13. The additive manufacturing printer apparatus 514 may be used in the method 400 described above and is therefore described herein.

[0226] The additive manufacturing printer apparatus 514 may be any suitable printer, such as described above with respect to step 403 of method 400. The curable fluoropolymer composition 510 may be any suitable curable fluoropolymer composition, as described above for use in the additive manufacturing embodiments herein. The additive manufacturing printer apparatus 514 preferably includes a programmable additive manufacturing printer 515 incorporating a controller 517 and associated software for printing an article using software code, as described above. The additive manufacturing printer apparatus 514 also includes a ram material extruder 519, which includes a ram device 521 and a printer nozzle 534, as best shown in FIGS. 15-19 . The ram material extruder 519 may be mounted to an associated apparatus of the additive manufacturing printer apparatus 514 on a gantry or other similar mechanism known in the art using a mounting plate.

[0227] The ram material extruder may be any currently available or later developed commercially or custom ram material extruder apparatus capable of performing the extrusion step using the materials herein in accordance with the present disclosure. Suitable ram material extruder devices may be obtained commercially or custom-built. A suitable source of such devices may be obtained from the SHAP3D™ Industry University Cooperative Research Center through the University of Massachusetts Lowell, One University Avenue, Lowell, MA, by requesting instructions and a parts list for constructing an ARME1, ARME2, or ARME3 device, or by requesting a pre-assembled ARME1, ARME2, or ARME3 device. The ARME1 device is as shown in Figures 15-19, and the ARME2 device is similar in configuration in that the timing belt and wheels are located in the upper portion of the assembly and have two lead screws. The ARME2 device is indicated when additional extrusion force is required. It is preferred that the ram material extruder incorporate at least one lead screw, although two such lead screws may also be used.

[0228] In one embodiment of the present invention, the printer apparatus 514 has a ram material extruder 519, and a lower platen 579 supports the operable apparatus of the extruder 519. Mounted to the rear of the lower platen 579 is a printer drive mechanism 516. In the preferred embodiment shown, the drive mechanism 516 may include a drive motor 518 and a timing belt 525 operable on two timing belt wheels 527. More wheels may be used, or a gear mechanism may be used, as desired. However, in the embodiment of the apparatus shown, the drive mechanism incorporates a timing belt and wheels, as shown. The drive mechanism may be used in the methods of the present invention and operated to apply pressure to a ram device 521.

[0229] The drive mechanism motor operates a timing belt, which rotates in conjunction with a lead screw 529 that passes through a lower platen 579, extends upward through the ram material extruder 519, passes through an opening in a middle platen 580, and terminates in an upper platen 578. The middle platen is movable up and down in the z-direction (generally vertically) to apply pressure to the ram device 521. As the lead screw 529 is rotated by movement of the drive mechanism's timing belt, a nut 577 facilitates the rotation and supports the lead screw, allowing the platen 580 to move up or down. As the middle platen moves downward, it presses down on the top of the ram device 521 at a load cell 561 that is in contact with a piston 531, as described below.

[0230] Thus, the method may include operating a drive mechanism to apply pressure to the ram device. Suitable pressures to be applied to the ram device may range from about 0.5 MPa (72 psi) to about 20 MPa (2,900 psi). The drive motor is operatively connected to a timing belt as shown. A lead screw 529 is operatively connected to a timing belt 525, and the lead screw 529 is rotated using the timing belt and drive motor 518. The drive motor 518 may be any suitable drive motor, but is preferably a stepper motor as described and exemplified above. A gear transmission mechanism may also be provided as needed. In a preferred embodiment herein, the drive motor provides sufficient torque to overcome friction between the curable fluoropolymer composition within the ram device 521 while providing sufficient pressure to extrude the curable fluoropolymer composition material through the ram device 521 and out the printer nozzle outlet 540.

[0231] The ram device 521 as shown further incorporates a piston and barrel arrangement as shown. The ram device 521 may further include a surrounding support structure that may also act as a heat sink or heat dissipation source. As shown in the embodiment of Figures 15-19, the support structure is a standoff 590. The piston 531 is connected to a load cell 561 that acts as a sensor for monitoring the load pressure on the ram device. The piston is movable upward and downward by a middle platen 580, which is a movable platen that can move on a lead screw 529. As the piston is drawn upward out of the barrel 541, a curable fluoropolymer composition in the form of a feedstock may be introduced into the barrel. The piston 531 has an exterior surface 533. In one embodiment to reduce weight and cost and / or control heat retention, the piston 531 may be hollow such that the piston 531 has an interior surface 593 that defines an interior space 535.

[0232] The barrel 537 has a first end 539 and a second end 541. The first end 539 of the barrel 537 is positioned at the upper end to receive the piston 531 through a first opening 547 formed in the first end 539 of the barrel. When the piston is within the barrel's interior space, the piston's exterior surface faces the barrel's interior surface. The two surfaces should be in face-to-face engagement, but with sufficient tolerance to allow sliding movement while preventing the possibility of back-pushing between the surfaces during application of heat and pressure. The barrel's second end 541 also preferably includes a second opening 549. The barrel's second end is configured to communicate with the printer nozzle 534. The barrel 537 has an exterior surface and an interior surface 543 that defines an interior space 545 within the barrel. Prior to passing the piston through the barrel, a curable fluoropolymer composition can be loaded into the open barrel 537. The barrel is configured to receive the piston after the piston passes through a first opening 547 at a first end 539 of the barrel. Similar to embodiment 400, the method herein can include applying pressure to the ram device while pressure is applied to position the piston within the interior space 545 of the barrel such that the exterior surface 533 faces the interior surface 543 of the barrel. The curable fluoropolymer composition 510 of system 500 can preferably be loaded into the barrel between the printer nozzle 534 and the first end 539 of the barrel 537.

[0233] To apply heat when and where desired in the method 400 herein, the equipment 514 in the system may include or be in communication with a heating device 523, which may be a heater such as a band or wrap heater, a heating element, an external heater, or a heater in communication with the piston and / or barrel of a ram device for heating the curable fluoropolymer composition. Preferably, the heating device is capable of heating the curable fluoropolymer composition to a temperature of at least about 20°C and up to at least about 250°C. The device is capable of heating the curable fluoropolymer composition to a temperature of less than about 250°C, less than about 200°C, or less than about 160°C. Preferred temperatures for heating the curable fluoropolymer are from about 20°C to about 250°C, or from about 70°C to about 250°C, or from about 100°C to about 250°C, or from about 105°C to about 200°C, or from about 115°C to about 160°C. As noted above, the polymer may be preheated as needed prior to loading or printing, according to the parameters described above to control the degree of crosslinking. When applying heat to the ram device, heat may be applied in a manner as described in the previous embodiment, such that the composition is heated to a temperature sufficient to initiate flow of the curable fluoropolymer composition within the ram device, but below the temperature at which significant curing of the curable fluoropolymer composition occurs. Furthermore, the composition may be heated to a temperature below the temperature corresponding to the time T2 associated with the curable fluoropolymer composition, as determined with a Rubber Process Analyzer using the ASTM D2084 test method, as described in the previous embodiment herein. The heating device 523 may be positioned on or around the ram device at various locations, such as around the barrel, around the nozzle, or both, or may be configured to heat the entire ram device. In one embodiment, the heating device 523 is positioned on the heated portion 596 of the nozzle.

[0234] The curable fluoropolymer composition is preferably heated to a temperature below the temperature at which significant curing occurs. Examples of preferred temperatures are provided above and also with respect to embodiments 200, 200'.

[0235] Regarding the curable fluoropolymer composition 510, similar to the compositions described above, it may be at least partially fluorinated or fully fluorinated. For such polymers, particularly perfluoropolymers, the onset of cure may be indicated by thermal analysis using a differential scanning calorimeter (DSC).

[0236] In the ram device 521, the printer nozzle 534 is shown in enlarged form in FIG. 19. The printer nozzle has a nozzle body 565 and a nozzle tip 567. In addition, the printer nozzle 534 has a printer nozzle inlet 542 and a printer nozzle outlet 540. As shown, these are separate pieces connected to each other for operation and cleaning. However, it should be understood that such parts may also be one piece.

[0237] As shown in FIG. 19 , the printer nozzle 534 may be removably attached to the barrel 537, such as by use of threads 551 on a portion of the barrel's interior surface 543 in the barrel's interior space 545 near the barrel's second end 541. Removable attachment facilitates cleaning and facilitates easy replacement of the printer nozzle with a different type of printer nozzle. An optional end cap 591 may also be provided to secure the ram device within the ram material extruder. The nozzle body 565 is configured to allow for smooth internal transition of the curable fluoropolymer composition as it leaves the barrel 537 and moves toward the printer nozzle outlet 540. Thus, the nozzle body may be provided with mating threads 553 on its exterior for engaging with the threads 551 on the interior surface 543 of the barrel 537. While threads are employed in this embodiment, other connection devices or methods, such as snap-fit ​​connectors, adhesives, press-fit connectors, screws, or rivets, may also be used, and although not preferred in the embodiment shown, the nozzle may be integral with the barrel.

[0238] As shown, to promote flow, nozzle body 565 has a tapered internal chamber 569 defined by the nozzle body, formed with an inlet 571 for receiving the composition extruded through ram device 521 as the composition is forced through barrel 537 by piston 531, and an outlet 572 in communication with nozzle tip 567. The taper as shown provides an inverted frustum configuration for good flowability, although the chamber may be formed to be non-tapered or sloped without using a circular cross-sectional configuration with a decreasing diameter as shown. Additionally, the chamber may be made so that the diameter or width, measured laterally across the nozzle body, decreases in a stepped or segmented manner toward the nozzle tip.

[0239] Nozzle body outlet 572 is located where nozzle tip 567 meets nozzle body 565. While nozzle body 565 and nozzle tip 567 may be removably attachable in preferred embodiments, as shown, to allow for interchangeability of different types of nozzle tips for different sizes of extrusion or different printing effects, and for ease of cleaning, the entire printer nozzle may also be formed such that the nozzle body and nozzle tip are one integral piece. As shown, to assemble the removable nozzle body 565 and nozzle tip 567, the nozzle tip is provided with mating threads 594 on the exterior that fit within a receiving opening in nozzle body 565. Where the top of nozzle tip 567 meets outlet 572 of nozzle body 565, a continuous and uninterrupted pathway is preferably formed, transitioning from the narrowest portion of nozzle body chamber 569 at nozzle body outlet 572 to a passageway 575 within nozzle tip 567 that extends from nozzle tip inlet 573 to printer nozzle outlet 540. The passageway is defined by an interior surface 574 that extends from a nozzle tip inlet 573 to a printer nozzle outlet 540. As the passageway approaches the printer nozzle outlet 540 of the nozzle tip 567, a reduced diameter area 576 is preferably provided in the nozzle outlet end 595 to direct the extruded curable fluoropolymer composition through the printer nozzle outlet 540 as it is heated under the application of pressure and passes through the printer nozzle outlet 540. In the method herein, printing the extruded curable fluoropolymer composition by the application of pressure and heat extrudes the curable fluoropolymer composition through the inlet 571 of the nozzle body 565, the outlet 572 of the nozzle body 565, the inlet 573 of the nozzle tip 567, and the printer nozzle outlet 540, which is also the outlet of the nozzle tip.

[0240] The printer nozzle 534 can be configured in various sizes and shapes for printing. The opening of the nozzle tip 567 can be shaped as described above to account for various end effects and various pressures, as well as the different viscosities of different curable fluoropolymer compositions as described in the previous embodiment. For example, the printer nozzle can have a length measured longitudinally along the nozzle from the nozzle body inlet to the printer nozzle outlet 540, which is about 1 to about 5 times the inner diameter (ID) of the printer nozzle outlet 540, preferably about 2 times the ID of the outlet 540. The ID of the printer nozzle outlet 540, measured laterally across the opening, is preferably sized to approximately the same size as the longitudinal cross-sectional outer diameter of the seal or other article to be formed. Preferably, it is at least about 0.2 mm, and can be about 0.2 to about 3.3 mm. In another embodiment, it can be about 0.4 to about 1.6 mm, or about 0.8 mm. Such dimensions can vary depending on the desired nozzle end effect. Additionally, the printer nozzle 534 may be fitted with an external heating device 523, which may optionally be a heated external cuff or sleeve on the nozzle and / or barrel portion of the ram device 521. The efficiency of the ram device operation allows for a wide variety of nozzle tip and nozzle length configurations, which may be adjusted based on the operating pressure, temperature, and flow characteristics, such as viscosity, of the curable fluoropolymer composition provided.

[0241] As the extruded fluoropolymer composition exits the nozzle tip, it is printed onto a substrate 536. As with previous embodiments herein, the substrate 536 may be provided with a friction surface 566 that is roughened or pre-coated with an adhesive or other treatment. The substrate may be a part or component onto which the extruded composition is applied in a pattern or within specific zones or areas. For example, the substrate may be a base plate 559 for a seal 555 or gasket 557. If the substrate is a molded component, it may be printed, for example, onto the upper surface of an upper mold plate surface and / or the upper surface of a lower mold plate, such upper surfaces may define cavities for forming such molded articles. The extruded fluoropolymer composition may be printed into cavities in such upper surfaces of the upper and / or lower mold plates, such cavities being configured to receive the printed curable fluoropolymer extrudate in the shape of the article to be formed as a preform. In one preferred embodiment herein, the substrate can be, for example, a mold base plate for a seal 555 or gasket 557, which can be in the form of a pre-sized mold for a seal or gasket (either an upper or lower mold plate) with cavities defined therein for receiving the extruded printing material and filling the cavities as a preform. The preform printed parts in the mold plates can be post-cured or otherwise more easily handled, and / or the base plates can be assembled with the printed article mounted between the plates, and the plates or assembly can then undergo curing and / or post-curing. Mold base plates with cavities on their surfaces, with and without molded seals as components, are shown in Figures 20 through 23B.

[0242] In other embodiments herein, the base plate may further include the use of a support structure SS, as shown in the example of FIGS. 25 and 26 . The support structure may be positioned on the base plate 536 or other substrate to assist in shape retention of the extruded curable fluoropolymer, as shown in one example of a support / preform assembly SA in FIGS. 26 and 27 . As shown in FIGS. 25 and 26 , the support structure includes two elements: a forming frame in the form of a frame body FB and optional guide pieces FG. The illustrated guide pieces are for forming a specific shape. The main support structure body and any associated guide pieces may be changed in shape and size, and any optional guide pieces may be moved internally or externally to the frame body. The illustrated frame guide pieces FG are for helping to enable shape retention around curved or arc-shaped areas. The frame body FB allows for support of the general shape of the layer(s) of the extruded article during printing and before any curing and / or post-cure steps, helping to support shape retention and reducing potential shrinkage after printing and curing and / or post-cure steps. In Figures 26 and 27, a support structure SS is shown with a printed article 538 in the form of a sample preform PF within a support structure / preform assembly SA. As shown, the preform PF is between a frame guide piece FG and a frame body FB of the support structure SS. Accordingly, the method of the present invention may further include using such a support structure to print extruded curable fluoropolymer(s) and / or perfluoropolymer(s) in the composition of the present invention in their uncured or partially cured state from an extrusion nozzle outlet as described above. It will be understood that the shape of the support structure can be varied depending on the intended shape of the printed article. The support structures herein help improve the quality of additively manufactured printed seals formed in accordance with the invention herein by preventing the curable fluorine-containing polymer from shrinking after deposition from the nozzle of the various additive printing mechanisms described in the embodiments herein.

[0243] The support structure herein can comprise a variety of materials, such as thermoplastics, metals, and / or metal alloys. The support structure can incorporate one or more of these types of materials; for example, the support structure can be fabricated with a metal layer or frame around a portion of the structure that includes a thermoplastic material, or with a different material used, for example, as a frame guide piece. When using a printable thermoplastic material, the support structure itself can also be formed using additive manufacturing techniques or can be a pre-formed shape designed to act as a support structure in the methods herein. Preferred materials for use in fabricating the support structure used in the present invention include those that can withstand the intended cure temperature of the fluorine-containing elastomer; i.e., the material should have a heat deflection temperature higher than the cure temperature of the elastomer to be printed. Thus, in the FKM / FFKM printing methods and apparatus herein, it is preferred that the support structure be capable of withstanding temperatures of at least about 130°C, at least 150°C, or at least 165°C, and in some cases even higher, depending on the selected curable fluorine-containing polymer, its curing process, and the specified processing, curing, and post-cure temperatures.

[0244] For example, for FKM / FFKM materials and formulations that cure at about 130°C, the support may be made using thermoplastics such as polycarbonate (e.g., 3DXMAX® polycarbonate with a deflection temperature of 135°C), polyvinylidene fluoride (e.g., FluorX™ PVDF with a deflection temperature of 158°C), polyetherimide (e.g., ThermaX™ PEI with a deflection temperature of 160°C), high temperature polylactic acid (e.g., Protopasta™ HTPLA with a deflection temperature of 150°C), polyetheretherketone (e.g., 3D4Makers™ PEEK with a deflection temperature of 156°C), polyphenylsulfone (e.g., ThermaX™ PPSU 3D with a deflection temperature of 190°C), or other suitable materials. For higher cure temperature FKM / FFKMs with cure temperatures of about 150°C, FluorX™ PVDF, ThermaX™ PEI, 3d4Makers™ PEEK, or ThermaX™ PPSU 3D material, or other suitable materials, may be used. For cure temperatures above 165°C, ThermaX™ PPSU 3D or other suitable materials may be used. For FKM / FFKM cure temperatures of about 160°C and above, metals and metal alloys with melting points above 160°C may also be utilized as the permanent support structure, including, for example, aluminum, stainless steel, brass, etc.

[0245] The support structure is preferably removable from the substrate, for example from the base plate, but may be formed as part of or in addition to the substrate, base plate.

[0246] When the extruded composition leaves the nozzle tip to form the fluorine-containing elastomeric article 538, the extruded composition may initially be at least partially cured, so that further curing can be carried out by post-curing or additional heating after removing the article from the substrate, as described in the previous embodiment, or on base plates, such as upper and / or lower mold base plates, which may be assembled to form a mold that can be cured in an oven or similar heating device. The curable fluoropolymer composition may be selected so that it is sufficiently viscous so that it can self-adhere to the substrate 536, yet still be removable from the substrate while substantially retaining its structural integrity. During processing of the fluoropolymer composition through the ram device, the fluoropolymer composition may be processed without curing, or, if it is at least partially cured but processable and flexible for printing, it may be processed by evaluating the polymer viscosity and rheological properties to maintain a temperature below a temperature corresponding to a time T2 associated with the curable fluoropolymer composition, as determined, for example, using the test method of ASTM D2084 on a Rubber Process Analyzer, as described elsewhere herein. Thus, the degree of cure permitted during printing will vary somewhat depending on the particular curable fluoropolymer composition and curable fluoropolymer(s) selected, which, in certain embodiments, may be cured to a degree greater than 0%, but preferably less than about 25%, during printing, taking the above into consideration.

[0247] In a further embodiment of the present invention, a variation of the ram material extruder 519 described above in embodiment 500 is shown in FIG. 24 as ram material extruder 519′. In all commonalities and in their use in printing, the parts are similar, and all parts have similar reference numbers unless otherwise specified. Devices 519 and 519′ differ with respect to the location of the timing belt wheel and timing belt placement area, as well as the number of lead screws used. Device 519′ is available from the above-mentioned suppliers or can be constructed thereby under the identifier ARME2. Device 519′ includes a lower platen 579′ that supports the operable components of extruder 519′. In the illustrated embodiment, drive mechanism 516′ may include a drive motor 518′ and a timing belt of the type shown as belt 525 in FIG. 15. Although no belt is shown in FIG. 24 , a belt of the same type as 545 could be made larger and run on three timing belt wheels 527′, routed along the path shown by curve P′ using tensioners or similar drive pins, such as pin 597′. Additionally, more than three wheels could be used as desired, or one or more gear mechanisms could be employed. However, in the apparatus embodiment 519′ shown, drive mechanism 516′ incorporates a timing belt, such as belt 525, and three wheels 527′ as shown, one associated with drive motor 518′ and one associated with each lead screw or lead screw 529′. In this embodiment, two lead screws 529′ are incorporated. Drive mechanism 516′ could be used in the methods of the present invention and operated to apply pressure to ram device 521′.

[0248] The drive mechanism motor 518' operates a timing belt that moves along a path P', rotating a wheel 527' in communication with a lead screw 529', which is shown passing through a lower platen 579', extending upward through the ram material extruder 519', passing through an opening in the middle platen 580', and terminating in the upper platen 578'. The middle platen is movable up and down in the Z direction (generally vertically) to apply pressure to the ram device 521'. As the lead screw 529' is rotated by movement of the drive mechanism and timing belt, the nut 577' facilitates the rotation and supports the lead screw, allowing the middle platen 580' to move upward or downward. As the middle platen 580' moves downward, it presses down on the top of the ram device 521' at the load cell 561, which is in contact with the piston 531' as described above. 15 and 24, it can be seen that the upper platens 578, 578' are configured differently, with the upper platen 578' being larger to allow the printer drive mechanism 516' to be mounted to the rear of the upper platen 578'. In FIG. 15, the drive mechanism 516 is mounted on the lower platen 579, which is therefore enlarged in device 519 to accommodate the drive mechanism 516.

[0249] When using a ram material extruder 519', the method can include operating a drive mechanism 516' to apply pressure to the ram device. Suitable pressures to be applied to the ram device can range from about 0.5 MPa (72 psi) to about 20.7 MPa (3,000 psi) for this device, which is higher than the ram material extruder 519 to allow for increased pressure and accommodate larger extrusion volumes. A drive motor 518' is operatively connected to the timing belt in the same manner as the motor operates with the timing belt in the ram material extruder 519, but operates along path P'. A lead screw 529' is operatively connected to the timing belt, and rotation of the lead screw 529', rotated by the timing belt and drive motor 518', drives the platen and actuates the piston. The drive motor 518' can be any suitable drive motor, but in the case of the ram material extruder 519, the drive motor is also preferably a stepper motor as described and illustrated above. Optional gear transmission mechanisms may also be provided, as described above with respect to the previous embodiment. The drive motor 518' also provides sufficient torque to overcome friction between the curable fluoropolymer composition within the ram device 521' while providing sufficient pressure to force the curable fluoropolymer composition material through the ram device 521' and out the printer nozzle outlet 540'.

[0250] The ram device 521' as shown incorporates the same piston and barrel arrangement as that of the ram device 521, as shown, and may further include a surrounding support structure that may also act as a heat sink or heat dissipation source in the same manner. The support structure is a standoff 590' similar to that of the ram material extruder 519. The piston 531' is connected to a load cell 561' that acts as a sensor for monitoring the load pressure on the ram device. The piston is movable upward and downward by an intermediate platen 580', which is a movable platen that can move on a lead screw 529'. As the piston is withdrawn upward out of the barrel 541', a curable fluoropolymer composition in the form of a feedstock may be introduced into the barrel. The piston 531' has an exterior surface 533'. In one embodiment to reduce weight and cost and / or control heat retention, the piston 531' may be hollow and configured in the same manner as shown for the piston 531 in FIGS. 16-19 associated with the ram material extruder 519. In all other respects the operation of the nozzle, piston and barrel is the same in ram material extruders 519, 519', the main difference being the location of the drive mechanism 516' in ram material extruder 519' and the use of two lead screws 529' and three wheels 527' to create a different timing belt path P' using pin 597' and wheels 527' to allow for additional extruder pressure on the piston.

[0251] The invention will now be described with reference to the following non-limiting examples. [Example]

[0252] Example 1 Three curable fluoropolymers were evaluated for additive manufacturing using an apparatus such as that shown in Figure 2 herein: a first curable fluoropolymer compound (Sample 1) that was an FKM commercially available from Solvay as Tecnoflon® 959; a second compound (Sample 2) that included an FKM available from Greene, Tweed (Kulpsville, PA) as Chemraz® G20; and a third compound (Sample 3) that included an FKM based on Tecnoflon® VPL75545.

[0253] The FFKM in Sample 2 included a curable perfluoropolymer and a bisphenyl-based curing agent, the bisphenyl-based curing agent being added at 1.3 parts by weight relative to the base perfluoropolymer. No additional additives were incorporated into the composition.

[0254] The FKM in Sample 1 was compounded with a peroxide cure system, constituting 5 percent of the FKM polymer; silica filler was incorporated into the FKM polymer at 13 percent; and colorants and processing aids were also included. The FFKM in Sample 2 and the FKM in Sample 1 were selected based on stiffness, which correlates with the more tacky nature of the compounded FFKM and FKM formulations, as well as their respective glass transition temperatures, filament extrusion capabilities, and moving die rheology (MDR) properties of the materials. The FKM in Sample 3 included carbon black filler and 2 percent of a peroxide curative polymer and 3 percent of a co-curative polymer. This formulation was also selected for its tack and variable cure and thermal analysis curves compared to the other samples.

[0255] Filaments were extruded in two outer diameter sizes, namely, 1.7 mm and 2.7 mm. Experimental tests were conducted both with and without a curing agent to assess the performance and properties of the materials as filaments. DSC profiles were run and are shown for Samples 1, 2, and 3 in Figures 8, 9, and 10, respectively, to provide best ranges and guidelines for printing the sample materials.

[0256] The material was introduced for printing in both the Ultimaker and the Monoprice Maker Select Plus, the latter being the most suitable for printing the material and was used for further testing.

[0257] The apparatus included an upwardly and downwardly extending support tube formed of PTFE to support the extruded filament. Side holes were provided in the tube as described above. The stepper motor was modified by including a series of planetary gears as shown in Figure 7A, and the nozzle opening was 2 mm. The temperature within the apparatus was maintained at 115 °C for printing and within an acceptable range (approximately 90 °C to approximately 120 °C) for printing FKM and FFKM.

[0258] The print head was set for a layer height of 1 mm, a line width of 1.75 mm, a packing density of 100%, a print temperature of 200° C., a build plate temperature of 25° C., and a print speed of 4 mm / sec. This layer height and line width were increased from the standard print level to match the increased nozzle width.

[0259] The temperature was maximized to reduce the viscosity sufficiently for easier extrusion from the nozzle and to promote adhesion to a friction surface formed from the adhesive tape material positioned on the substrate surface. Tensile specimens per ASTM D412-C were successfully printed from the material. Example 2

[0260] A formulation was prepared based on a perfluoropolymer commercially available as Tecnoflon® LT, a semi-viscous elastomeric material. The formulation (Sample 4) included a curable perfluoropolymer and a bisphenyl-based curing agent added to the base perfluoropolymer at 1.3 parts by weight. No additional additives were incorporated into the composition, and the printing was performed using a printing apparatus such as that shown in Figures 11 and 11A, with a precooler mounted on a movable Hemera® extruder as the driving mechanism. The sample was run using a nozzle opening of 1.5 mm and a nozzle temperature of 80°C.

[0261] Prior to printing, DMA analysis data was collected for both Sample 4 and Sample 3 (used in Example 1). For Sample 4, DMA analysis was performed at low temperatures from -80°C to 20°C, at a heating rate of 3°C / min and 50 gm force / load. Cooling was achieved using liquid nitrogen. Formulation samples were prepared as O-rings with a diameter of 139 in. using the uncured material. DMA analysis was tensile DMA. High-temperature DMA analysis was collected on samples at temperatures from 25°C to 150°C, at the same heating rate, using both 500 gm force / load and 50 gm force / load and the same formulation sample dimensions, but using compression DMA analysis. The same test was performed with Sample 3, but only at 50 gm force / load. This data was used to select the printing temperature and estimate the storage modulus G' (in Pa). The estimated graph shown for Sample 4 appears in Figure 12.

[0262] The estimated storage modulus was used as the modulus to estimate the maximum buckling force, maximum printing pressure, and maximum stretch ratio. The estimated modulus and calculated buckling force F cr The calculated maximum pressure (MPa), maximum draw ratio, and the calculated maximum draw ratio are shown in Table 2 below. Based on this data, the minimum nozzle diameter (mm) was determined for the equipment employed. [Table 2]

[0263] From this data, samples were printed into test plates on metal in the form of seals using the apparatus of Figures 11 and 11A using filaments of 1.75 mm diameter and 0.005 m free column length. Example 3

[0264] In this example, additive printing was prepared as three-dimensional additively manufactured articles of electrostatic chuck (ESC) seals and bonded gaskets using an additive manufacturing printer device with an additive ram material extruder (ARME).

[0265] The additive manufacturing printer device included a Creality3D Ender-5 Pro 3D Printer and controller, as well as a ram material extruder mounted on the printer. The ram material extruder conformed to the drawings shown in Figures 13-19 herein. The printer device was turned on, and the load cell indicator was plugged into a standard power source in a wall outlet. The load cell sensor / indicator was calibrated at the time the device was turned on, as required for each use, according to the ram material extruder's manufacturer's instructions. As described below, approximately 10-15 grams of a curable fluoropolymer composition, including partially fluorinated or fully fluorinated compounds in compounded gum form, was cut into pieces approximately 1 cubic centimeter or smaller, and the pieces were loaded into the barrel of the ram device on the ram material extruder. The additive manufacturing printer was interfaced with control software on a computer that communicated with the printer and controller. The computer provided a process plan with a series of commands and had a processor and software for additive printing. The computer can be built-in or a separate computer connected to the printer via USB, HDMI, or other similar connection. In the particular printer used, the computer includes the open-source Pronterface software, particularly Pronterface Printrun software, although any acceptable 3D printing software that works with ram material extruders and additive manufacturing printing devices can be utilized in accordance with the present invention. Pronterface connects to the printer and provides a graphical user interface that allows for monitoring and control of the additive manufacturing printer device. The software can be configured to operate the controller, or as a controller to operate the drive mechanism, including its motor, and to control the heating device to regulate its temperature. It is also possible to send G-code commands directly via a terminal, console window, or other typical G-code operations.

[0266] After loading the curable fluoropolymer composition into the ram material extruder, the printer was instructed by the computer to start and, using the control software, to send the cold extrusion command "M302P1." The printer was instructed to extrude until the calibrated load cell indicator indicated a 100 lb load. The cold extrusion step allowed for priming of the curable fluoropolymer composition to undergo the preprinting step. Once the curable fluoropolymer composition was primed in the barrel, the G-code for printing the Wolf gasket and seal produced in this example was loaded for operation using the control software; however, the G-code can also be loaded onto the SD card of the additive manufacturing printing device. The G-code for printing the desired seal was prepared using a MATLAB® script to modify the printing parameters and settings. Instructions for using the MATLAB® code are provided below. If no modifications are required when producing different articles, the provided G-code can be loaded directly and operated using the printer's control software or by using the printer's SD card inserted into the printer's direct control. The Wolf Gasket Seal base plate was placed on the printing platform of a Creality3D Ender-5 Pro 3D Printer in a position that matched the coordinates selected in the selected G-code and / or MATLAB script.

[0267] The printer was instructed to print a dry run without the application of heat from a heating device so that the printer could locate the seal base plate used as the printing substrate through the associated movements required by the seal printing g-code. The positioning of the base plate in the dry run allowed for accurate printing. Once the base plate was in the proper position, it was coated with a thin layer of Elmer's® spray adhesive to promote adhesion of the printed material to the base plate. After the dry run, a heating band, used as a heating device, was connected to a power source, turned on, and set to the desired printing temperature for the selected curable fluoropolymer composition.

[0268] Based on Applicant's testing, it has been determined that when printing compositions incorporating partially fluorinated curable fluoropolymers (FKM), operation of the ram material extruder functions at temperatures below 200° C., preferably about 100° C. Printing FKM at 100° C. has allowed for print times of about 60 to about 70 minutes.

[0269] Compositions comprising perfluorinated curable fluoropolymers (FFKM) are also preferably printed at temperatures below 200°C, preferably 140°C, allowing for a printing time of about 15 minutes before the onset of curing, which can make it difficult to complete the print.

[0270] Once the desired printing temperature was achieved through the use of the heating device, operation was held for an additional 5 minutes to allow the temperature throughout the filled curable fluoropolymer composition and the barrel to stabilize. The printer was then commanded to extrude material until sufficient pressure was achieved within the barrel, as indicated by the load cell indicator. The pressure range used in the printing test was approximately 300-400 lb. After approximately 300 lb. of pressure was achieved within the barrel, the operator commanded the printer to initiate a print cycle based on the loaded G-code.

[0271] The MATLAB® instructions for modifying the sticker printing G-code used were as follows:

[0272] In MATLAB®, open "DoubleLayer_WolfGasket.m" for the bonded gasket (WolfGasket in this case) or "FourPoint_Seal.m" for printing the seal. These scripts were prepared to create the G-code for the printer to print each seal and gasket.

[0273] These scripts included labeled parameters for adjusting the print speed and print height of the extruded curable fluoropolymer composition during printing according to the desired printing parameters.

[0274] Depending on the material being printed, the extrusion coefficient, a parameter within the MATLAB® script that controls the flow rate of the printing process based on the formulation used, is adjusted for optimal results. For FFKM formulations, a 30-fold adjustment may be used, For FKM formulations, a 20x adjustment may be used.

[0275] The printer software and G-code were also programmed with the desired print start position, which determines where the seal plate will be placed on the printer platform for accurate printing.

[0276] Upon inputting the desired printing parameters, the resulting output G-code file may be renamed to a desired name for later use.

[0277] Once the script is run and completed such that the printer's G-code has the desired parameters, including the start location of the seal to be printed, given as input to the script, the seal plate will be placed in its specified position that matches the start point parameter(s).

[0278] After the seal was in place, the seal plate was coated with the spray adhesive described above to promote adhesion between the deposited material and the seal plate.

[0279] The resulting printed sticker is shown in Figures 20-23B.

[0280] The curable fluoropolymer compositions used to print the bonded gaskets and seals are provided in Table 3 below, with components expressed in hundredths of parts by weight based on 100 parts by weight of the curable fluoropolymer in the composition. The FKM compositions were prepared in two different compositions, Sample A and Sample B, both of which contained Tecnoflon® VPL75545 FKM fluoropolymer, publicly available as a peroxide-curable polymer from Solvay®. Diak7 triallyl isocyanurate co-curing agent was used with Varox® DBPH peroxide curing agent or Varox® 130XL peroxide curing agent. The compositions of Samples A and B also contained the addition of silica filler and a low molecular weight polytetrafluoroethylene (PTFE) lubricating filler commercially available from Daikin Industries as Polyflon®. An additional Sample C was formed using a curable fluoropolymer available from Greene, Tweed® of Kulpsville, PA, namely, Tecnoflon® PFR X1055D (which uses the polymer of Tecnoflon® PFR X1055B but contains N990 carbon black), which is fully fluorinated (perfluoropolymer), and a bisaminophenol (BOAP) curative. [Table 3]

[0281] Sample A was extruded at a print speed of 0.75 mm / s using a nozzle exit diameter of 0.8 mm, and the ram device was heated to a barrel temperature of 100°C. The substrate for printing was a 3D printed Wolf gasket base plate as in FIG. 20 treated with Elmer's® spray glue. The resulting printed bonded gasket (Wolf gasket) is shown in FIG. 22A. Sample C was extruded at a print speed of 1 mm / s using a nozzle exit diameter of 1.4 mm. The ram device was heated to a barrel temperature of 140°C. The same base plate as shown in FIG. 20 was used and treated with Elmer's® spray glue. The resulting 3D printed Wolf gasket is shown in FIG. 22B.

[0282] ESC seals were printed using a base plate as in FIG. 21 as a receiving substrate for printing the seal. The base plate was treated with Elmer's spray glue for each printed seal. 3D printed ESC seals were printed using Sample A as shown in FIG. 23A. The seals were printed using a nozzle diameter of 0.8 mm, a barrel temperature of 100° C., and a printer speed of 1 mm / s. An additional ESC seal using the same base plate as FIG. 21 was printed using Sample C perfluoropolymer with a nozzle diameter of 1.4 mm, a barrel temperature of 140° C., and a printer speed of 1 mm / s. The resulting seal is shown in FIG. 23B.

[0283] The examples herein demonstrate that the systems herein, using a curable fluoropolymer composition with an additive manufacturing printing device, can be incorporated into methods using systems with ram material extruders to improve the repeatability of successfully formed parts with good precision. The parts produced involve complex geometries, and the ability to repeatably produce such parts reduces manufacturing costs by reducing waste and provides the ability to produce specialized parts and / or parts that are difficult to produce by compression molding.

[0284] It will be understood by those skilled in the art that changes may be made to the embodiments described above without departing from the broad inventive concept thereof. It is therefore to be understood that the invention is not limited to the particular embodiments disclosed, but that it is intended to cover modifications within the spirit and scope of the invention as defined by the appended claims.

Claims

1. 1. An additive manufacturing method for forming a fluorine-containing elastomeric article, comprising: providing a curable fluoropolymer composition comprising at least one curable fluoropolymer; providing an additive manufacturing printer apparatus comprising a ram material extruder, the ram material extruder comprising a ram device operable for extrusion under pressure and a printer nozzle; introducing said curable fluoropolymer composition into said ram material extruder; applying heat to the ram device including the printer nozzle of the ram device; applying pressure to the ram device to extrude the curable fluoropolymer composition; using the additive manufacturing printer device to print at least one layer of the extruded curable fluoropolymer composition exiting an outlet of the printer nozzle onto a substrate to form the fluorine-containing elastomeric article; A method comprising:

2. The method of claim 1 , wherein the ram material extruder further comprises a drive mechanism, the method further comprising operating the drive mechanism to apply pressure to the ram device.

3. 3. The method of claim 2, wherein the drive mechanism comprises a drive motor operatively connected to a timing belt.

4. 4. The method of claim 3, wherein the step of applying pressure includes actuating the ram extruder to apply pressure by movement of a platen on at least one lead screw in operative communication with the timing belt, and rotating the at least one lead screw using the timing belt on the drive motor.

5. The method of claim 4 wherein there are two lead screws.

6. 10. The method of claim 1, wherein the ram device comprises a piston having an exterior surface and a barrel having a first end, a second end, and an interior surface defining an interior space, the barrel configured to receive the piston after passing through a first opening in the first end of the barrel, the second end of the barrel positioned to communicate with the printer nozzle, the method further comprising passing the piston into the interior space of the barrel while applying pressure to the ram device, with the exterior surface of the piston facing the interior surface of the barrel.

7. 7. The method of claim 6, wherein introducing the curable fluoropolymer composition comprises loading the curable fluoropolymer composition into the barrel between the printer nozzle and the first end of the barrel.

8. The method of claim 1 , wherein applying heat to the ram device further comprises generating heat using a heating mechanism comprising the ram material extruder.

9. 10. The method of claim 1, wherein applying heat to the ram device further comprises heating the curable fluoropolymer composition to a temperature sufficient to initiate flow of the curable fluoropolymer composition within the ram device, but below a temperature at which significant curing of the curable fluoropolymer composition occurs.

10. 10. The method of claim 9, wherein the curable fluoropolymer composition is heated to a temperature below a temperature corresponding to a time T2 associated with the curable fluoropolymer composition as determined with a Rubber Process Analyzer using the test method of ASTM D2084.

11. 10. The method of claim 9, wherein the curable fluoropolymer composition is heated to a temperature below the temperature at which significant curing occurs.

12. 12. The method of claim 11, wherein the at least one curable fluoropolymer in the curable fluoropolymer composition is a perfluoropolymer, and the onset of cure of the perfluoropolymer is indicated by thermal analysis using a differential scanning calorimeter.

13. The method of claim 1, wherein the curable fluoropolymer composition is heated to a temperature of from about 20°C to about 250°C.

14. The method of claim 13, wherein the curable fluoropolymer composition is heated to a temperature of from about 70°C to about 250°C.

15. The method of claim 14, wherein the curable fluoropolymer composition is heated to a temperature of from about 100°C to about 250°C.

16. The method of claim 15, wherein the curable fluoropolymer composition is heated to a temperature of from about 105°C to about 200°C.

17. The method of claim 16, wherein the curable fluoropolymer composition is heated to a temperature of from about 115°C to about 160°C.

18. The method of claim 1 , wherein the at least one curable fluoropolymer in the curable fluoropolymer composition is partially fluorinated.

19. 10. The method of claim 1, wherein the at least one curable fluoropolymer in the curable fluoropolymer composition is a curable perfluoropolymer.

20. 10. The method of claim 1, wherein the printer nozzle comprises a nozzle body and a nozzle tip, the nozzle body defining a tapered internal chamber having an inlet for receiving the curable fluoropolymer composition extruded through the ram device and an outlet communicating with the inlet to the nozzle tip, the nozzle tip having an interior surface extending from the inlet in the nozzle tip to the outlet in the printer nozzle, the method further comprising printing the extruded curable fluoropolymer composition by applying heat and pressure to extrude the curable fluoropolymer composition through the inlet in the nozzle body, the outlet in the nozzle body, the inlet in the nozzle tip, and the outlet in the printer nozzle.

21. 21. The method of claim 20, wherein the nozzle tip has a reduced diameter area at an outlet end of the nozzle tip for directing the extruded curable fluoropolymer composition through the outlet of the printer nozzle.

22. 2. The method of claim 1, wherein the fluorine-containing elastomeric article is a seal, and the inner diameter of the printer nozzle outlet is approximately the same as the outer longitudinal cross-sectional diameter of the seal.

23. 23. The method of claim 22, wherein the inner diameter of the printer nozzle outlet is at least about 0.2 mm.

24. 10. The method of claim 1, wherein the printer nozzle outlet has an inner diameter of from about 0.2 mm to about 3.3 mm.

25. 25. The method of claim 24, wherein the inner diameter of the printer nozzle, measured across the printer nozzle outlet, is from about 0.4 to about 1.6 mm.

26. The method of claim 1 , wherein the ram material extruder further comprises a drive mechanism having a drive motor.

27. 27. The method of claim 26, wherein the drive motor is a stepper motor having a geared transmission.

28. 10. The method of claim 1, further comprising analyzing the curable fluoropolymer composition and estimating a storage modulus for determining printing parameters for printing the curable fluoropolymer composition.

29. 30. The method of claim 28, wherein the storage modulus is estimated using a rubber process analyzer or parallel plate rheometry to optimize the printing parameters for the curable fluoropolymer composition.

30. The method of claim 1 , wherein the substrate comprises a friction surface.

31. The method of claim 1 further comprising coating the substrate with an adhesive.

32. 10. The method of claim 1, wherein the elastomeric article is a bonded seal or a bonded gasket, the substrate is a base plate of the bonded seal or the bonded gasket, and the method further comprises printing the extruded curable fluoropolymer composition onto the base plate.

33. 33. The method of claim 32, wherein the base plate is an upper molded base plate having an upper surface defining a cavity and / or a lower molded base plate having an upper surface defining a cavity, the method further comprising printing the extruded curable fluoropolymer composition as a preform into at least one of the cavities of the upper molded base plate and / or the lower molded base plate.

34. 33. The method of claim 32, wherein a support structure is positioned on the base plate to assist in shape retention of the extruded curable fluoropolymer composition, the method further comprising printing the extruded curable fluoropolymer using the support structure.

35. 35. The method of claim 34, wherein the support structure is a removable fixture.

36. 33. The method of claim 32, wherein the support structure comprises one or more of a thermoplastic material, a metal, or a metal alloy.

37. 33. The method of claim 32, wherein the support structure is fabricated by additive manufacturing.

38. The method of claim 1 , wherein the elastomeric article is a seal or gasket.

39. 10. The method of claim 1 , wherein the additive manufacturing device is capable of printing at a temperature of less than about 250°C.

40. 40. The method of claim 39, wherein the additive manufacturing device is capable of printing at a temperature of less than about 200°C.

41. 41. The method of claim 40, wherein the additive manufacturing device is capable of printing at a temperature of less than about 160°C.

42. 40. The method of claim 39, wherein the additive manufacturing device is capable of printing at a temperature of at least 20°C.

43. 10. A fluorine-containing elastomeric article formed by the method of claim 1, said article comprising an at least partially cured fluoroelastomer.

44. 44. The fluorine-containing elastomeric article of claim 43, wherein said article comprises an at least partially cured perfluoroelastomer.

45. 44. The fluorine-containing elastomeric article of claim 43, wherein said curable fluoropolymer composition comprises at least one curable fluoropolymer having functional groups for reacting with a curing agent, and at least one curing agent capable of reacting with said functional groups.

46. 44. The fluorine-containing elastomeric article of claim 43, wherein said curable fluoropolymer composition further comprises at least one filler.

47. 44. The fluorine-containing elastomer of claim 43, wherein the curable fluoropolymer composition is sufficiently viscous to self-adhere to the substrate, yet can be removable from the substrate while still substantially retaining its structural integrity.

48. 44. The fluorine-containing elastomeric article of claim 43, wherein the curable fluoropolymer composition can be processed without curing during printing or at least partially cured to an extent greater than 0% but less than about 25%.

49. 44. The fluorine-containing elastomeric article of claim 43, wherein said curable fluoropolymer composition comprises one or more additional curable fluoropolymers or one or more additional curable perfluoropolymers.

50. 50. The fluorine-containing elastomeric article of claim 49, wherein said curable fluoropolymer composition comprises one or more additional curing agents for curing said one or more additional curable fluoropolymers or said one or more additional perfluoropolymers.

51. 1. A system for forming a three-dimensional additively manufactured fluorine-containing elastomeric article, comprising: (i) a curable fluoropolymer composition; (ii) an additive manufacturing printer device capable of forming a three-dimensional printed article; and The device comprises: a programmable additive manufacturing printer; a ram device operable to receive the curable fluoropolymer composition and extrude the curable fluoropolymer composition under pressure; a printer nozzle having an inlet and an outlet; a drive mechanism for applying pressure to the ram device, the ram device being operated according to commands from the programmable additive manufacturing printer; a ram material extruder comprising: a heating device for applying heat to the ram device, including the printer nozzle of the ram device; Equipped with the printer nozzle is configured to receive the curable fluoropolymer composition under pressure through the inlet of the printer nozzle and to enable heated extrusion of the fluoropolymer composition through the printer nozzle outlet to print a fluorine-containing elastomeric article.

52. 42. The system of claim 41, wherein the drive mechanism comprises a drive motor operatively connected to a timing belt.

53. 53. The system of claim 52, wherein the drive motor is a stepper motor having a geared transmission.

54. 53. The system of claim 52, wherein the ram material extruder further comprises at least one lead screw and a movable platen movable on the at least one lead screw, the at least one lead screw in operative communication with the timing belt.

55. 55. The system of claim 54, wherein there are two lead screws.

56. 52. The system of claim 51 , wherein the ram device comprises a piston having an exterior surface and a barrel having a first end, a second end, and an interior surface defining an interior space, the barrel configured to receive the piston after passing through a first opening in the first end of the barrel, the second end of the barrel positioned to communicate with the printer nozzle.

57. 57. The system of claim 56, wherein the exterior surface of the piston faces the interior surface of the barrel when the piston is within the interior space of the barrel.

58. 52. The system of claim 51, wherein the heating device is capable of heating the curable fluoropolymer composition to a temperature sufficient to initiate flow of the curable fluoropolymer composition within the ram device and below a temperature at which significant curing of the curable fluoropolymer composition occurs.

59. 52. The system of claim 51, wherein the heating device is capable of heating the curable fluoropolymer composition to a temperature below a temperature corresponding to a time T2 associated with the curable fluoropolymer composition as determined with a Rubber Process Analyzer using the test method of ASTM D2084.

60. 52. The system of claim 51, wherein the additive manufacturing printer device is capable of forming three dimensional printed articles comprising an at least partially fluorinated fluoroelastomer.

61. 52. The system of claim 51 , wherein the additive manufacturing printer device is capable of forming three-dimensional printed articles comprising a perfluoroelastomer.

62. 52. The system of claim 51 , wherein the additive manufacturing device is capable of forming an article selected from a gasket and a seal.

63. 63. The system of claim 62, wherein the article is printed on a base plate, and the article is a bonded gasket or a bonded seal.

64. 64. The system of claim 63, wherein the base plate is an upper molded base plate having an upper surface defining a cavity and / or a lower molded base plate having an upper surface defining a cavity, and the article is printed within the cavity on the upper surface of the upper molded base plate and / or within the cavity on the upper surface of the lower molded base plate.

65. 64. The system of claim 63, wherein a support structure is positioned on the base plate to assist in retaining the shape of the extruded curable fluoropolymer composition.

66. 66. The system of claim 65, wherein the support structure is a removable fixture.

67. 66. The system of claim 65, wherein the support structure comprises one or more of a thermoplastic material, a metal, or a metal alloy.

68. 66. The system of claim 65, wherein the support structure is fabricated by additive manufacturing.

69. 52. The system of claim 51, wherein the ram device further comprises a load cell acting as a sensor for monitoring pressure within the ram device.

70. 52. The system of claim 51, wherein the heating device is capable of heating the curable fluoropolymer composition to a temperature of from about 20°C to about 250°C.

71. 71. The system of claim 70, wherein the heating device is capable of heating the curable fluoropolymer composition to a temperature of from about 70°C to about 250°C.

72. 72. The system of claim 71, wherein the heating device is capable of heating the curable fluoropolymer composition to a temperature of from about 100°C to about 250°C.

73. 73. The system of claim 72, wherein the heating device is capable of heating the heated curable fluoropolymer composition to a temperature of from about 105°C to about 200°C.

74. 74. The system of claim 73, wherein the heating device is capable of heating the curable fluoropolymer composition to a temperature of from about 115°C to about 160°C.

75. 52. The system of claim 51, wherein the heating device is positioned on the ram device.

76. 52. The system of claim 51 , wherein the printer nozzle comprises a nozzle body and a nozzle tip, the nozzle body defining a tapered internal chamber having an inlet for receiving the curable fluoropolymer composition extruded through the ram device and an outlet communicating with the inlet to the nozzle tip, the nozzle tip having an interior surface extending from the inlet of the nozzle tip to the outlet of the printer nozzle.

77. 77. The system of claim 76, wherein the nozzle tip has a reduced diameter area at a nozzle outlet end of the nozzle tip to direct the extruded curable fluoropolymer composition through the outlet of the printer nozzle.

78. 52. The system of claim 51, wherein the inner diameter of the printer nozzle outlet is between about 0.4 mm and about 1.6 mm when measured laterally across the printer nozzle outlet.

79. 52. The system of claim 51 , wherein the additive manufacturing printer device is capable of printing at a temperature of less than about 250° C.

80. 80. The system of claim 79, wherein the additive manufacturing printer device is capable of printing at a temperature of less than about 200°C.

81. 81. The system of claim 80, wherein the additive manufacturing printer device is capable of printing at a temperature of less than about 160°C.

82. 80. The system of claim 79, wherein the additive manufacturing printer device is capable of printing at a temperature of at least 20°C.

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