Method for post-treating a thermoplastic component

Abstract

In accordance with the present disclosure, there is provided a method for treating a thermoplastic part using a carboxylic acid ester solvent. Advantageously, it has been found that the carboxylic acid esters provide an effective and more environmentally friendly alternative to conventional alcohol-based solvents for treating thermoplastic parts, in particular for smoothing surfaces.

Description

Technical Field

[0001] The invention relates to a method for post-treating thermoplastic parts and to the use of carboxylic acid esters for carrying out the method. Background Art

[0002] Additive manufacturing techniques are becoming increasingly common in modern industry. However, a potential drawback of current additive manufacturing methods is that parts manufactured using such methods may exhibit a rough and castellated surface finish due to the layer-by-layer processing approach. It has also been found that parts manufactured by other manufacturing techniques may also exhibit suboptimal surface texture and appearance.

[0003] To address this problem, technologies aimed at improving the surface finish of thermoplastic parts have advanced significantly in recent years.

[0004] Current methods for smoothing such parts generally involve dissolving the rough surface of the part with an alcohol-based solvent to allow the surface to reflow, thereby achieving a smoothing effect. However, it has been found that many existing alcohol-based solvents are halogenated and / or derived from benzene derivatives.

[0005] Halogenated compounds are not found in nature and are therefore very difficult to break down. This means that they tend to be extremely persistent in the environment, which can lead to contamination of local ecosystems and wider environmental problems, such as depletion of the ozone layer. As a result, halogenated solvents need to be disposed of in large quantities and at great expense to avoid contaminating the environment.

[0006] At the same time, benzene derivatives are known carcinogens and may be harmful to animal and plant life. Therefore, the use of such derivatives is generally strictly regulated and may be prohibited in some applications / jurisdictions.

[0007] It is therefore an object of the present disclosure to provide an alternative range of solvents capable of processing thermoplastic parts. Summary of the invention

[0008] According to a first aspect of the present disclosure, there is provided a method for processing a thermoplastic part, comprising the steps of:

[0009] a) providing thermoplastic parts;

[0010] b) providing a fluid for post-treating a thermoplastic part to improve the surface finish of the thermoplastic part, wherein the fluid comprises at least one carboxylic acid ester;

[0011] c) a heating step, wherein the fluid is heated; and

[0012] d) An applying step, wherein the heated fluid is applied to the surface of the thermoplastic part.

[0013] Advantageously, carboxylic acid esters have been found to provide an effective and more environmentally friendly alternative to conventional alcohol-based solvents for processing thermoplastic parts.

[0014] In an exemplary embodiment, the carboxylate is a cyclic carboxylate (lactone).

[0015] Advantageously, cyclic carboxylic acid esters have been found to be particularly effective alternatives to conventional alcohol-based solvents for processing thermoplastic parts.

[0016] In an exemplary embodiment, the cyclic carboxylate has the following structure:

[0017]

[0018] wherein n is 2 to 10, each CH2 group may be optionally independently substituted with one or two substituents selected from alkyl, alkenyl, alkynyl, alkoxy, hydroxyl and carboxyl.

[0019] In an exemplary embodiment, the cyclic carboxylate comprises a 4-membered ring.

[0020] Advantageously, cyclic carboxylates having a 4-membered ring structure exhibit improved stability when compared to cyclic carboxylates having a ring structure with fewer than 4 members.

[0021] In exemplary embodiments, the cyclic carboxylic acid ester comprises a four (β-lactone) membered ring, a five (γ-lactone) membered ring, a six (δ-lactone) membered ring, or a seven (ε-lactone) membered ring.

[0022] Advantageously, cyclic carboxylates having a four-membered, five-membered, six-membered, or seven-membered ring structure tend to be more stable and easier to synthesize when compared to cyclic carboxylates having a ring structure of different members.

[0023] In an exemplary embodiment, the cyclic carboxylic acid ester comprises a 5-membered ring structure (γ-lactone).

[0024] Advantageously, cyclic carboxylic acid esters having a 5-membered ring structure have been found to be the most stable lactones for this application.

[0025] In an exemplary embodiment, the cyclic carboxylic acid ester is γ-valerolactone.

[0026] Advantageously, gamma-valerolactone is plant-based and can be produced from cellulosic biomass.Thus, unlike benzene derivatives, gamma-valerolactone is biodegradable and its production does not require the use of crude oil.

[0027] Furthermore, γ-valerolactone is non-halogenated and exhibits low acute toxicity to aquatic organisms. Thus, when compared to conventional solvents used to smooth thermoplastic materials, γ-valerolactone offers a more sustainable and environmentally friendly alternative.

[0028] In an exemplary embodiment, the cyclic carboxylic acid ester is gamma-butyrolactone.

[0029] In an exemplary embodiment, the cyclic carboxylic acid ester is ethylated γ-butyrolactone.

[0030] In an exemplary embodiment, the cyclic carboxylic acid ester is propylated γ-butyrolactone.

[0031] In an exemplary embodiment, the cyclic carboxylic acid ester is gamma-caprolactone.

[0032] In an exemplary embodiment, the cyclic carboxylic acid ester is selected from one of the following: β-propiolactone, δ-valerolactone, γ-hexalactone, γ-valerolactone, ε-caprolactone, or γ-caprolactone.

[0033] In an exemplary embodiment, the thermoplastic component may include a polar polymer.

[0034] In an exemplary embodiment, the thermoplastic component can include poly(vinyl chloride), poly(methyl methacrylate), polyamide, polyurethane, and / or combinations thereof.

[0035] In an exemplary embodiment, the thermoplastic material may include one or more of the following thermoplastics: polyamide (PA); polylactic acid (PLA); polysulfone (PSU); polyphenylsulfone (PPSU); polyetherimide (PEI); thermoplastic polyurethane (TPU); acrylonitrile butadiene styrene (ABS); polymethyl methacrylate (PMMA); polycarbonate (PC) and / or polyethylene terephthalate (PET).

[0036] In an exemplary embodiment, the component may comprise a polyamide.

[0037] In an exemplary embodiment, the component may include polyamide 12.

[0038] In an exemplary embodiment, the component may include polyamide 66.

[0039] In an exemplary embodiment, the component may include polyamide 46.

[0040] In an exemplary embodiment, the component may include polyamide 11.

[0041] In an exemplary embodiment, the component may include a thermoplastic elastomer.

[0042] In an exemplary embodiment, the component may include thermoplastic polyurethane (TPU).

[0043] In an exemplary embodiment, the component may comprise polylactic acid (PLA).

[0044] In an exemplary embodiment, the component may comprise polysulfone (PSU).

[0045] In an exemplary embodiment, the component may comprise polyphenylsulfone (PPSU).

[0046] In an exemplary embodiment, the component may comprise polyetherimide (PEI).

[0047] In an exemplary embodiment, the component may comprise acrylonitrile butadiene styrene (ABS).

[0048] In an exemplary embodiment, the component may include polymethyl methacrylate (PMMA).

[0049] In an exemplary embodiment, the component may include polycarbonate (PC).

[0050] In an exemplary embodiment, the component may comprise polyethylene terephthalate (PET).

[0051] In an exemplary embodiment, the thermoplastic part may be an additively manufactured part.

[0052] In an exemplary embodiment, the thermoplastic part may be a powder-based additively manufactured part.

[0053] In an exemplary embodiment, the additively manufactured part may be a filament-based additively manufactured part.

[0054] In an exemplary embodiment, the heating step includes heating the fluid to a temperature in a range of about 100°C to about 300°C.

[0055] Advantageously, it has been found that heating the fluid to a temperature in the range of 100°C to 300°C provides optimal conditions for processing thermoplastic parts without causing damage to the parts due to overheating.

[0056] In an exemplary embodiment, the heated fluid is applied to the surface of the thermoplastic part for an immersion time in a range from about 10 seconds to about 1 hour.

[0057] Advantageously, immersion times in the range of 10 seconds to 1 hour have been found to be optimal for processing thermoplastic parts without causing damage to the parts due to excessive exposure to the solvent.

[0058] In an exemplary embodiment, the heated fluid is applied to the surface of the thermoplastic part for an immersion time in a range from about 10 seconds to about 5 minutes.

[0059] Advantageously, it has been found that immersion times in the range of 10 seconds to 5 minutes are even better for processing thermoplastic parts without damaging the parts due to excessive exposure to the solvent.

[0060] In an exemplary embodiment, the fluid is provided as a liquid.

[0061] In an exemplary embodiment, the applying step includes immersing the thermoplastic part in the liquid.

[0062] In an exemplary embodiment, the heating step includes heating the liquid to a temperature in the range of about 140°C to about 200°C.

[0063] Advantageously, it has been found that when a liquid solvent is used, treatment at a temperature in the range of 160°C to 200°C is particularly effective.

[0064] In an exemplary embodiment, step a) comprises placing a thermoplastic part into a processing chamber, step c) comprises heating a fluid so as to cause the fluid to evaporate, and step d) comprises introducing the evaporated fluid into the processing chamber and causing the evaporated fluid to condense onto a surface of the thermoplastic part contained therein.

[0065] Advantageously, vapor treatment methods such as those described above provide a more controllable and more easily automated alternative to conventional liquid-based treatment methods.

[0066] In an exemplary embodiment, the method includes heating the vaporized fluid to a temperature in a range of about 120°C to about 180°C.

[0067] Advantageously, it has been found that when a steam treatment method is used, treatment at a temperature in the range of 150°C to 180°C is particularly effective.

[0068] In an exemplary embodiment, the interior of the processing chamber is maintained at a pressure of less than 100 kPa (1 bar).

[0069] Advantageously, maintaining the interior of the processing chamber at a pressure of less than 1 bar allows the solvent to evaporate at a lower temperature than would be possible if the process were carried out at atmospheric pressure. This helps to reduce the likelihood of thermal damage to the thermoplastic part during processing.

[0070] In an exemplary embodiment, the interior of the process chamber is maintained at a pressure in a range of about 1 kPa to about 50 kPa (about 10 mbar to about 500 mbar).

[0071] Advantageously, pressures in the range of 10 mbar to 500 mbar have been found to be particularly effective when using a steam treatment method.

[0072] In an exemplary embodiment, the interior of the process chamber is maintained at a pressure in a range of about 5 kPa to about 30 kPa (about 50 mbar to about 300 mbar).

[0073] Advantageously, it has been found that when using a steam treatment method, a pressure in the range of 50 mbar to 300 mbar is even more effective.

[0074] In an exemplary embodiment, the method further comprises, after step d):

[0075] e) applying negative pressure to the interior of the processing chamber so as to evaporate the condensed fluid from the surface of the thermoplastic part.

[0076] Advantageously, applying negative pressure to the interior of the processing chamber provides a readily controllable and automated method for removing excess solvent from the surface of the component while also reducing the likelihood of damage to the component due to excessive temperatures during the drying step.

[0077] In an exemplary embodiment, the method further comprises, after step d):

[0078] f) removing the heated fluid from the surface of the thermoplastic part; and

[0079] g) applying the heated fluid or heated fluid to the surface of the thermoplastic part.

[0080] Advantageously, it has been found that the surface finish of the thermoplastic part can be further improved by repeating the process.

[0081] In an exemplary embodiment, the material of the thermoplastic component comprises functional groups having a dipole moment greater than 0 Debye.

[0082] In an exemplary embodiment, the material of the thermoplastic component comprises functional groups having a dipole moment greater than 0.5 Debye.

[0083] In an exemplary embodiment, at least one carboxylic acid ester is a biodegradable carboxylic acid ester.

[0084] In an exemplary embodiment, the at least one carboxylic acid ester is a biosolvent.

[0085] According to a second aspect of the present disclosure, there is provided a use of a carboxylic acid ester for smoothing a thermoplastic part.

[0086] In an exemplary embodiment, the carboxylate is a cyclic carboxylate (lactone).

[0087] Advantageously, cyclic carboxylic acid esters have been found to be particularly effective alternatives to conventional alcohol-based solvents for processing thermoplastic parts.

[0088] In an exemplary embodiment, the cyclic carboxylate has the following structure:

[0089]

[0090] wherein n is 2 to 10, each CH2 group may be optionally independently substituted with one or two substituents selected from alkyl, alkenyl, alkynyl, alkoxy, hydroxyl and carboxyl.

[0091] In an exemplary embodiment, the cyclic carboxylate comprises a 4-membered ring.

[0092] Advantageously, cyclic carboxylates having a 4-membered ring structure exhibit improved stability when compared to cyclic carboxylates having a ring structure with fewer than 4 members.

[0093] In exemplary embodiments, the cyclic carboxylic acid ester may comprise a four-membered (β-lactone), a five-membered (γ-lactone), a six-membered (δ-lactone), or a seven-membered (ε-lactone) ring.

[0094] Advantageously, cyclic carboxylates having a four-membered, five-membered, six-membered, or seven-membered ring structure tend to be more stable and easier to synthesize when compared to cyclic carboxylates having a ring structure of different members.

[0095] In an exemplary embodiment, the cyclic carboxylic acid ester comprises a 5-membered ring structure (γ-lactone).

[0096] Advantageously, cyclic carboxylic acid esters having a five-membered ring structure have been found to be the most stable lactones for this application.

[0097] In an exemplary embodiment, the cyclic carboxylic acid ester is γ-valerolactone.

[0098] Advantageously, gamma-valerolactone is plant-based and can be produced from cellulosic biomass.Thus, unlike benzene derivatives, gamma-valerolactone is biodegradable and its production does not require the use of crude oil.

[0099] Furthermore, γ-valerolactone is non-halogenated and exhibits low acute toxicity to aquatic organisms. Thus, when compared to conventional solvents used to smooth thermoplastic materials, γ-valerolactone offers a more sustainable and environmentally friendly alternative.

[0100] In an exemplary embodiment, the cyclic carboxylic acid ester is gamma-butyrolactone.

[0101] In an exemplary embodiment, the cyclic carboxylic acid ester is ethylated γ-butyrolactone.

[0102] In an exemplary embodiment, the cyclic carboxylic acid ester is propylated γ-butyrolactone.

[0103] In an exemplary embodiment, the cyclic carboxylic acid ester is gamma-caprolactone.

[0104] In an exemplary embodiment, the cyclic carboxylic acid ester is selected from one of the following: β-propiolactone, δ-valerolactone, γ-caprolactone, γ-valerolactone, ε-caprolactone, or γ-caprolactone.

[0105] In an exemplary embodiment, the thermoplastic component may include a polar polymer.

[0106] In an exemplary embodiment, the thermoplastic component can include poly(vinyl chloride), poly(methyl methacrylate), polyamide, polyurethane, and / or combinations thereof.

[0107] In an exemplary embodiment, the thermoplastic material may include one or more of the following thermoplastics: polyamide (PA); polylactic acid (PLA); polysulfone (PSU); polyphenylsulfone (PPSU); polyetherimide (PEI); thermoplastic polyurethane (TPU); acrylonitrile butadiene styrene (ABS); polymethyl methacrylate (PMMA); polycarbonate (PC) and / or polyethylene terephthalate (PET).

[0108] In an exemplary embodiment, the component may comprise a polyamide.

[0109] In an exemplary embodiment, the component may include polyamide 12.

[0110] In an exemplary embodiment, the component may include polyamide 66.

[0111] In an exemplary embodiment, the component may include polyamide 46.

[0112] In an exemplary embodiment, the component may include polyamide 11.

[0113] In an exemplary embodiment, the component may include a thermoplastic elastomer.

[0114] In an exemplary embodiment, the component may include thermoplastic polyurethane (TPU).

[0115] In an exemplary embodiment, the component may comprise polylactic acid (PLA).

[0116] In an exemplary embodiment, the component may comprise polysulfone (PSU).

[0117] In an exemplary embodiment, the component may comprise polyphenylsulfone (PPSU).

[0118] In an exemplary embodiment, the component may comprise polyetherimide (PEI).

[0119] In an exemplary embodiment, the component may comprise acrylonitrile butadiene styrene (ABS).

[0120] In an exemplary embodiment, the component may include polymethyl methacrylate (PMMA).

[0121] In an exemplary embodiment, the component may include polycarbonate (PC).

[0122] In an exemplary embodiment, the component may comprise polyethylene terephthalate (PET).

[0123] In an exemplary embodiment, the material of the thermoplastic component comprises functional groups having a dipole moment greater than 0 Debye.

[0124] In an exemplary embodiment, the material of the thermoplastic component comprises functional groups having a dipole moment greater than 0.5 Debye.

[0125] In an exemplary embodiment, at least one carboxylate is a biodegradable carboxylate.

[0126] In an exemplary embodiment, the at least one carboxylic acid ester is a biosolvent.

[0127] In an exemplary embodiment, the thermoplastic part may be an additively manufactured part.

[0128] In an exemplary embodiment, the additively manufactured part may be a powder-based additively manufactured part.

[0129] In an exemplary embodiment, the additively manufactured part may be a filament-based additively manufactured part.

[0130] We consider the term "alpha lactone" to be defined as a cyclic carboxylic acid ester having a 3-membered ring structure (ie, there is one carbon atom between the C=O group and the -O- group).

[0131] We consider the term "beta-lactone" to be defined as a cyclic carboxylic acid ester having a 4-membered ring structure (ie, there are two carbon atoms between the C=O group and the -O- group).

[0132] We consider the term "gamma lactone" to be defined as a cyclic carboxylic acid ester having a 5-membered ring structure (ie, there are three carbon atoms between the C=O group and the -O- group).

[0133] We consider the term "delta lactone" to be defined as a cyclic carboxylic acid ester having a 6-membered ring structure (ie, there are four carbon atoms between the C=O group and the -O- group).

[0134] We consider the term "heating" to be defined as increasing the temperature to a level significantly above (eg, more than 5°C to 10°C) the ambient (eg, room) temperature.

[0135] We consider the term "fluid" to cover both liquids and gases.

[0136] We consider the term "post-processing" to be defined as processing a component after it has been built, wherein the post-processing is for the purpose of changing at least one physical property (eg, surface roughness) of the component after it has been built.

[0137] We consider the term "polar material" to be defined as a material or compound containing one or more functional groups having a dipole moment greater than 0 Debye (D), optionally greater than 0.5 D. In other words, a polar material contains functional groups having different areas of positive and negative charge. One Debye is defined as a material or compound having an absolute magnitude of 10 10 The electric dipole moment produced by two equal but opposite charges separated by 1 angstrom in electrostatic coulombs. The dipole moment can be calculated or measured using methods known in the art. BRIEF DESCRIPTION OF THE DRAWINGS

[0138] Embodiments of the present disclosure will now be described with reference to the accompanying drawings, in which:

[0139] Figure 1 is an apparatus for smoothing a thermoplastic part according to the method of the present disclosure;

[0140] Figure 2 is a flow chart describing a method of smoothing a thermoplastic part according to one aspect of the present disclosure;

[0141] Figure 3a are images showing a powder-based sample of polyamide 12 before and after a smoothing process using a γ-valerolactone solvent according to the method of the present disclosure;

[0142] Figure 3b are images showing a powder-based sample of polyamide 12 before and after a smoothing process using a γ-butyrolactone solvent according to the method of the present disclosure;

[0143] Figure 3c are images showing a powder-based sample of thermoplastic polyurethane before and after a smoothing process using a γ-valerolactone solvent according to the method of the present disclosure;

[0144] Figure 3d are images showing a powder-based sample of thermoplastic polyurethane before and after a smoothing process using a γ-butyrolactone solvent according to the method of the present disclosure;

[0145] Figure 3eare images showing a powder-based sample of thermoplastic polyurethane before and after a smoothing process using a γ-caprolactone solvent according to the method of the present disclosure;

[0146] Figure 3f are images showing a powder-based sample of polyamide 12 before and after a smoothing process using methyl 5-(dimethylamino)-2-methyl-5-oxopentanoate solvent according to the method of the present disclosure;

[0147] Figure 3g are images showing a powder-based sample of thermoplastic polyurethane before and after a smoothing process using methyl 5-(dimethylamino)-2-methyl-5-oxopentanoate solvent according to the method of the present disclosure;

[0148] Figure 3h are images showing polyphenylene sulfide based filament samples before and after a smoothing process using methyl 5-(dimethylamino)-2-methyl-5-oxopentanoate solvent according to the method of the present disclosure;

[0149] Figure 3i are images showing an injection molded (non-AM) sample of polyphenylsulfone (PPSU) before and after a smoothing process using a γ-valerolactone solvent according to the method of the present disclosure;

[0150] Figure 4 is an alternative apparatus for smoothing thermoplastic parts according to the method of the present disclosure; and

[0151] Figure 5 is a flow chart describing an alternative method of smoothing a thermoplastic part according to one aspect of the present disclosure. DETAILED DESCRIPTION

[0152] Figure 1 An apparatus 100 for post-processing a thermoplastic part is shown according to one embodiment of the present disclosure.

[0153] Figure 1 The apparatus 100 shown in is configured to treat a component 110 using a solvent vapor 108 and is composed of an airtight process chamber 102 , a reservoir 104 , and a vapor distribution system 106 .

[0154] The airtight process chamber 102 is sized to receive a component 110 therein and is fluidly connected to a reservoir 104 via a vapor distribution system 106 .

[0155] The vapor distribution system 106 is provided in the form of a tube having a first end at the outlet of the reservoir 104 and having a second end at the inlet of the process chamber 102. In use, the vapor distribution system 106 is configured to deliver solvent vapor 108 from the reservoir 104 to the process chamber 102.

[0156] The vapor distribution system 106 also includes a valve 105 to enable controlled introduction of solvent vapor 108 into the process chamber 102 .

[0157] The apparatus 100 also includes a vacuum pump 107 in fluid communication with the interior of the process chamber 102. The vacuum pump 107 is in operative communication with a controller 140 so that, in use, the vacuum pump 107 can be controlled to adjust the pressure applied to the interior of the process chamber 102 as may be required during processing.

[0158] The apparatus 100 also includes a pair of heating elements 109a, 109b. The heating elements 109a, 109b are in operative communication with the controller 140 or the controller 140 so that, in use, the heating elements 109a, 109b can be controlled to heat the solvent as may be required during processing.

[0159] The first heating element 109a forms part of a wall of the process chamber 102 and is configured to heat the solvent vapor within the process chamber 102 to a desired temperature, as will be described in more detail below. The second heating element 109b is associated with the reservoir 104 and is configured to evaporate the solvent contained in the reservoir before introducing the solvent into the process chamber 102.

[0160] In an exemplary embodiment, the apparatus 100 may form part of an additive manufacturing system, which may also include an additive manufacturing apparatus 120 configured to build the additive manufactured part 110 before the part 110 is post-processed by the apparatus 100. In some embodiments, the additive manufacturing apparatus 120 may be a powder-based additive manufacturing apparatus, such as a laser sintering apparatus or a multi-jet fusion apparatus, or may be a filament-based additive manufacturing apparatus, such as a fused filament apparatus.

[0161] It should also be understood that in alternative embodiments, the apparatus 100 may be provided as a separate and discrete system, and thus the apparatus 100 need not be associated with an additive manufacturing apparatus.

[0162] Now refer to Figure 1 and Figure 2 A method of post-processing an additively manufactured part according to one embodiment of the present disclosure is described.

[0163] In some embodiments, the additively manufactured part can be a powder-based additively manufactured part. In other words, the additively manufactured part can be obtained from a powder-based additive manufacturing technology, such as selective laser sintering or multi-jet fusion.

[0164] It is important to note that during a powder-based additive manufacturing process such as selective laser sintering or multi-jet fusion, a first layer of powdered build material is laid down on a build bed. The first layer of powdered build material is then sintered to form a first sintered layer of the additively manufactured part. A second layer of powdered build material is then laid down on the first sintered layer. The second layer of powdered build material is subsequently sintered to form a second sintered layer of the additively manufactured part. Subsequent layers are then applied and thereafter sintered in the same manner until a part having a desired shape is built up from multiple sintered layers.

[0165] Alternatively, in some embodiments, the additively manufactured component can be a filament-based additively manufactured component. In other words, the additively manufactured component can be obtained from a filament-based additive manufacturing technology, such as a fused filament process.

[0166] During the fused filament process, the filament material is heated and extruded through a nozzle, which selectively deposits the material on a build platform. After the first layer is deposited, the platform is lowered, or the nozzle is raised to extrude successive layers until the desired shape is constructed.

[0167] It has been found that the material on any surface of an additively manufactured part may often exhibit a different, less favorable structure than the material beneath the surface. Thus, the presence of less favorable structure on the surface of a given part may result in an additively manufactured part having a rough surface finish. The material on the surface of a part may exhibit a looser structure / morphology that is typically much weaker than the material beneath the surface of the additively manufactured part. It has been found that the less favorable material on the surface of a part may be treated with one or more carboxylic acid esters and an improved surface finish may subsequently be obtained.

[0168] It should also be understood that while the methods described below are described as being performed on additively manufactured parts, it should also be understood that the methods and apparatus described in the present application are also applicable to processing thermoplastic parts obtained by other types of manufacturing methods, including but not limited to injection molding, compression molding, thermoforming, extrusion, and computer numerically controlled (CNC) machining methods, such as milling, single-point and multi-point cutting, and grinding.

[0169] It will also be appreciated that parts obtained according to the post-processing methods described herein may be used in a variety of different applications, including but not limited to use in the medical, automotive, aerospace, construction, transportation, and consumer products fields.

[0170] In a first step 201 of the method, an additively manufactured component 110 is provided in a raw state (ie in a state immediately after a building operation).

[0171] exist Figure 1 and Figure 2 In the embodiment shown, the additively manufactured component 110 is a thermoplastic component obtained from a powder-based additive manufacturing method such as selective laser sintering or multi-shot spray fusion as described above. However, it should be understood that in other embodiments, other suitable powder-based or filament-based additive manufacturing methods may be used.

[0172] It has been found that the aforementioned method can also be used to treat polar materials. Polar materials are materials that contain polar polymers. Polar polymers contain polar functional groups with different positive and negative charge areas. That is, they contain functional groups with polar moments greater than 0D, optionally greater than 0.5D, such as polyamides. Advantageously, when paired with polar polymers, the polar solvents described herein have excellent solubility because the polar solvents can form hydrogen bonds with the polar polymers.

[0173] In the illustrated embodiment, the additively manufactured component comprises polyamide 12. However, it should be understood that in other embodiments, other suitable materials may be processed using the foregoing method.

[0174] For example, in some embodiments, the additively manufactured parts may include different grades of polyamide, including but not limited to polyamide 66, polyamide 46, and / or polyamide 11.

[0175] The foregoing method also finds application in the treatment of other thermoplastic materials, such as thermoplastic elastomers. Thermoplastic elastomers are a class of copolymers consisting of materials that possess both thermoplastic and elastomeric properties.

[0176] Thus, in some embodiments, the additively manufactured parts may include thermoplastic polyurethanes (TPUs), polyvinyl chloride-based thermoplastics, poly(methyl methacrylate), polyamides, and polyurethanes. However, it should also be understood that in other embodiments, other suitable thermoplastic elastomers may be processed using the aforementioned methods.

[0177] For example, in some embodiments, the additively manufactured parts may include styrenic block copolymers (e.g., polystyrene and polybutadiene), polyolefins (e.g., polyethylene and polypropylene), thermoplastic copolyesters (e.g., polyethylene terephthalate), rubbers, and / or elastomeric alloys.

[0178] Examples of materials that the additively manufactured part 110 may include include, but are not limited to, thermoplastic polyurethane (TPU) and various derivatives such as Quadrathane TM ARC, polyamide 12, 61 11 and other derivatives, such as glass, graphite or carbon reinforced polyamide, polycarbonate (PC), polyphenylene sulfide (PPS) and its derivatives, such as carbon fiber reinforced PPS (or PPSCF), polypropylene (PP), polyvinylidene fluoride (PVDF), polyetheretherketone (PEEK), polyetherketoneketone (PEKK) and other derivatives such as polyaryletherketone (PAEK), ethylene propylene rubber (EDPM), nitrile rubber (NBR), thermoplastic elastomer (TPE), polyetherimide (PEI), such as ULTEM TM 9085、ULTEM TM 1010, polylactic acid (PLA), polysulfone (PSU), polyphenylsulfone (PPSU), acrylonitrile butadiene styrene (ABS), polymethyl methacrylate (PMMA), polyethylene terephthalate (PET), etc.

[0179] At step 202 of the method, a fluid 108 comprising a carboxylic acid ester or a mixture of carboxylic acid esters is provided. In the embodiment shown, the carboxylic acid ester is a cyclic carboxylic acid ester (sometimes referred to as a lactone), namely, γ-valerolactone (e.g., γ-valerolactone 99%, which is available from Sigma-Aldrich). However, it should be understood that in other embodiments, other suitable carboxylates may be used.

[0180] The lactone comprises a 1-oxacycloalkane-2-one structure (-C(=O)-O-). Exemplary lactones for use in the present disclosure have the following structure:

[0181]

[0182] Wherein n is 2 to 10.Each CH2 group can be optionally substituted with one or more substituents.Exemplary substituents include alkyl, alkenyl, alkynyl, alkoxy, hydroxyl, carboxylic acid, nitro, etc.The ring can be saturated or unsaturated.One or more heteroatoms can replace one or more carbon atoms in the ring.

[0183] Cyclic carboxylates having at least a four-membered ring structure tend to exhibit improved stability when compared to cyclic carboxylates having a ring structure of less than four members, and thus carboxylates having a ring structure of at least four members tend to be preferred when performing the aforementioned method. Exemplary lactones having at least four members include β-propiolactone, γ-butyrolactone, δ-valerolactone (also known as valerolactone), γ-caprolactone, ethylated γ-butyrolactone, propylated γ-butyrolactone, and ε-caprolactone (also known as caprolactone), each of which may be optionally substituted with one or more substituents as described above and combinations thereof.

[0184] In some embodiments, the alkyl substituent is a straight chain or branched lower C1-15 lower alkyl, such as methyl, ethyl, propyl, butyl, hexyl, heptyl, octyl, decyl, dodecyl, pentadecyl, etc. In some embodiments, the alkenyl substituent is a straight chain or branched lower C1-15 lower alkenyl, such as vinyl, propenyl, butenyl, hexenyl, heptenyl, octenyl, decenyl, dodecenyl, pentadecenyl, etc. In some embodiments, the alkynyl substituent is a straight chain or branched lower C1-15 lower alkynyl, such as propynyl, butynyl, hexynyl, heptynyl, octynyl, decynyl, dodecynyl, pentadecynyl, etc. In some embodiments, the alkoxy substituent is a straight chain or branched lower C1-15 alkoxy, such as methoxy, ethoxy, propoxy, butoxy, hexyl, heptyl, octyl, decyl, dodecyloxy, pentadecyloxy, etc. In some embodiments, the carboxylic acid substituent is a straight or branched C1-15 monocarboxylic acid, dicarboxylic acid or tricarboxylic acid, such as formic acid, acetic acid, propionic acid, butyric acid. In some embodiments, the halogen is a fluorine, chlorine, bromine, iodine or astatine group. Preferred substituents include methyl and ethyl.

[0185] In particular, cyclic carboxylates containing five (γ-lactone) and six (δ-lactone) membered rings have been found to be most preferred. However, it should also be understood that in some embodiments, the method can be carried out using non-cyclic carboxylates.

[0186] Examples of suitable non-cyclic carboxylates may include, but are not limited to, compounds of the formula R2-C=OO-R3, wherein R2 and R3 are each independently selected from a linear or branched alkyl or alkoxy group having 1 to 6 carbons. Particularly preferred examples of non-cyclic carboxylates include methyl acetate, methyl lactate, ethyl lactate, dimethyl glutarate, ethyl acetate, 2-ethoxyethyl acetate, ethyl 3-ethoxypropionate, 2-ethylhexyl acetate, 2-ethoxyethyl isobutyrate, isopropyl acetate, propyl acetate, 2-methoxyethyl acetate, butyl acetate, 5-(dimethylamino)-2-methyl-5-oxopentanoic acid methyl ester, and combinations thereof.

[0187] In some embodiments, the fluid used in the present invention comprises a biodegradable "green" solvent. A green solvent is an environmentally friendly solvent or a biosolvent that can be derived from the processing of crops. Green solvents are developed as a more environmentally friendly substitute for petrochemical solvents. Green solvents are biodegradable, non-carcinogenic and nontoxic. Examples of suitable green solvents include above-mentioned cyclic esters and non-cyclic esters.

[0188] In the case of the illustrated embodiment of gamma-valerolactone, fluid 108 is initially provided within reservoir 104 of apparatus 100. In some embodiments, fluid 108 may be supplied to the reservoir in liquid form, and then may subsequently be heated by a dedicated heating device (e.g., heating element 109b) associated with reservoir 104 to vaporize fluid 108 prior to introduction into processing chamber 102. In alternative embodiments, fluid 108 may be supplied to the reservoir in an already vaporized form.

[0189] After at least some of the fluid 108 provided within the reservoir is in vapor form, solvent vapor 108 is delivered from reservoir 104 to process chamber 102 by opening valve 105 of vapor distribution system 106 and allowing solvent vapor 108 to flow into process chamber 102 .

[0190] After the solvent vapor 108 has been introduced into the process chamber 102, the solvent 108 can be further heated by the heating element 109a to a temperature suitable for overcoming the bonding between the material particles at the surface of the additively manufactured part. The exact temperature to which the solvent 108 is heated varies based on the flash point of the material being processed and the solvent used, but it is typically in the range of 100°C to 300°C, with optimal results typically obtained at temperatures in the range of 120°C to 180°C.

[0191] For example, it has been found that best results are obtained when additively manufactured parts comprising polyamide 12 are treated with gamma-valerolactone by heating the solvent to a temperature of about 150°C.

[0192] However, it should be understood that for some materials with higher melting points, such as PPS, and for some solvents with higher boiling points, such as methyl 5-(dimethylamino)-2-methyl-5-oxopentanoate, optimal results can be obtained at higher temperature ranges, such as temperatures in the range of 120°C to 280°C.

[0193] Additionally, it should be understood that in some embodiments, the solvent 108 may be heated to a temperature suitable for overcoming bonding between material particles at the surface of the additively manufactured part within the reservoir (prior to introduction into the processing chamber 102), and thus further heating of the solvent vapor within the processing chamber may not be required.

[0194] In some embodiments, the vacuum pump 107 may also be operated during processing to apply a negative pressure to the interior of the processing chamber 102. Typically, the pressure within the processing chamber 102 is maintained below 100 kPa (1 bar). It has been found that by creating a negative pressure environment within the processing chamber 102, the solvent can be evaporated at a lower temperature than that achievable under atmospheric conditions. This helps reduce the possibility of damage to components due to temperature during processing.

[0195] Additionally, applying negative pressure to process chamber 102 also helps draw vapor 108 from reservoir 104 and into process chamber 102 when valve 105 is opened in step 202 .

[0196] The precise pressure applied to the interior of the process chamber 102 tends to vary based on the thermodynamic properties of the solvent used for a given process and based on the temperature conditions within the process chamber 102. However, during processing, the pressure within the process chamber will generally be maintained in the range of 1 kPa to 50 kPa (10 mbar to 500 mbar), with best results generally being obtained at pressures in the range of 5 kPa to 30 kPa (50 mbar to 300 mbar).

[0197] For example, it has been found that best results are obtained when additively manufactured parts comprising polyamide 12 are treated with gamma-valerolactone by maintaining the pressure in the process chamber at about 20 kPa (200 mbar).

[0198] However, as described in the Experimental Examples section below, it was also discovered that the thermoplastic polyurethane samples could be treated with gamma-valerolactone vapor at atmospheric pressure. Thus, it should be understood that in some embodiments, the vapor treatment process can be performed at atmospheric pressure.

[0199] It should be appreciated that the temperature of the surface of the component 110 is initially below the condensation temperature of the solvent vapor 108 within the processing chamber 102. Therefore, any solvent vapor 108 that comes into contact with the surface of the component 110 will subsequently be cooled, which will cause it to condense onto the surface of the component 110. In this manner, the evaporated solvent 108 may be applied to the surface of the component 110.

[0200] In an exemplary embodiment, the component 110 may also be cooled, such as using a blast cooler, before being placed in the process chamber 102. This achieves a greater temperature difference between the component 110 and the solvent vapor 108, which allows the solvent vapor 108 to condense (and thus be applied) onto the surface of the component 110 more efficiently.

[0201] Furthermore, as increasing amounts of evaporated solvent 108 are introduced into process chamber 102 via vapor distribution system 106, the pressure within process chamber 102 will increase, causing more solvent to condense onto the surface of component 110 (since higher temperatures are required to evaporate a given solvent at higher pressures).

[0202] After the solvent vapor 108 is applied to the surface of the component 110 at step 204, the component 110 is then left to rest for a period of time. A period of 10 seconds to 1 hour has been found to be an optimal time to allow post-processing of the component 110.

[0203] For example, a treatment time of about 20 seconds has been found to be optimal when treating additively manufactured parts comprising polyamide 12 using gamma-valerolactone, however it will be appreciated that treatment times may vary depending on the materials and solvents used for a given treatment.

[0204] After the desired processing time has elapsed, the component 110 is dried during step 205 to remove the solvent from the surface of the component 110 and thereby prevent any further processing that could adversely affect the quality of the component.

[0205] In the embodiment shown, step 205 is performed by reapplying negative pressure, in this case, by reactivating vacuum pump 107 to a pressure of about 20 kPa (200 mbar) to the interior of the process chamber, so that any solvent present on the surface of the component is re-evaporated. The evaporated solvent 108 can then be passed through a filter, such as Figure 1 Activated carbon filter 103 is shown venting from processing chamber 102 to the outside atmosphere. However, it should be understood that in some embodiments, other suitable drying methods (eg, heating) may be used.

[0206] The dried part 110 is then removed from the processing chamber 102, thereby concluding the process.

[0207] As a result of the foregoing process, improved surface finish was observed in a variety of different parts treated with various different solvents, e.g. Figures 3a to 3h shown.

[0208] exist Figure 3a In the micrographs shown, the surface roughness of a powder-based AM part comprising polyamide 12 was reduced using γ-valerolactone solvent from an initial (as-treated) average surface roughness of 18.87 microns (left) to a smooth (final) average surface roughness of 3.54 microns (right).

[0209] Similarly, in Figure 3bIn the micrographs shown, the surface roughness of a powder-based AM part comprising polyamide 12 was reduced using a γ-butyrolactone solvent from an initial (as-treated) average surface roughness of 18.87 microns (left) to a smooth (final) average surface roughness of 0.97 microns (right).

[0210] exist Figure 3c In the micrographs shown, the surface roughness of a powder-based additively manufactured part comprising thermoplastic polyurethane (TPU) was reduced from an initial (as-treated) average surface roughness of 16.871 microns (left) to a smooth (final) average surface roughness of 0.992 microns (right) using γ-valerolactone solvent.

[0211] exist Figure 3d In the micrographs shown, the surface roughness of a powder-based additively manufactured part comprising thermoplastic polyurethane was reduced using a gamma-butyrolactone solvent from an initial (as-treated) average surface roughness of 16.871 microns (left) to a smooth (final) average surface roughness of 5.204 microns (right).

[0212] exist Figure 3e In the micrographs shown, the surface roughness of a powder-based additively manufactured part comprising thermoplastic polyurethane was reduced using a γ-caprolactone solvent from an initial (as-treated) average surface roughness of 16.871 microns (left) to a smooth (final) average surface roughness of 1.347 microns (right).

[0213] exist Figure 3f In the micrographs shown, the surface roughness of a powder-based additively manufactured part comprising polyamide 12 was reduced from an initial (as-treated) average surface roughness of 18.87 microns (left) to a smooth (final) average surface roughness of 1.37 microns (right) using a non-cyclic 5-(dimethylamino)-2-methyl-5-oxopentanoate solvent (CAS No. 1174627-68-9).

[0214] exist Figure 3g In the micrographs shown, the surface roughness of a powder-based additively manufactured part comprising a thermoplastic polyamide was reduced from an initial (as-treated) average surface roughness of 16.871 microns (left) to a smooth (final) average surface roughness of 1.25 microns (right) using a non-cyclic 5-(dimethylamino)-2-methyl-5-oxopentanoate solvent (CAS No. 1174627-68-9).

[0215] exist Figure 3hIn the micrographs shown, the surface roughness of a filament-based additively manufactured part containing polyphenylene sulfide (or "PPS") was reduced from an initial (as-treated) average surface roughness of 15.6 microns (left) to a smooth (final) average surface roughness of 2.5 microns (right) using a non-cyclic methyl 5-(dimethylamino)-2-methyl-5-oxopentanoate solvent.

[0216] exist Figure 3i In the micrographs shown, the surface roughness of an injection molded (non-AM) part comprising polyphenylsulfone (PPSU) was reduced using γ-valerolactone solvent from an initial (as-treated) average surface roughness of 2.797 μm (left) to a smooth (final) average surface roughness of 0.346 μm (right).

[0217] The precise conditions for obtaining these results are shown in the Experimental Examples section.

[0218] Figure 4 An apparatus 300 for post-processing a thermoplastic additively manufactured part is shown according to an alternative embodiment.

[0219] The apparatus 300 consists of a reservoir in the form of a solvent bath 302 and a heating element 304 .

[0220] Solvent bath 302 is configured to store solvent 306 to be used during post-processing operations, as will be described in more detail below. Solvent bath 302 has a size and configuration such that additively manufactured part 310 can be completely submerged in solvent 306 during post-processing operations.

[0221] The heating element 304 is positioned adjacent to the solvent bath 302 and is operably coupled to a controller 340 that is configured to control the heating element 304 in order to heat the solvent 306 to a desired temperature during post-processing operations.

[0222] and Figure 1 Like the apparatus described in , in an exemplary embodiment, apparatus 300 may form part of an additive manufacturing system prior to post-processing using apparatus 300, including additive manufacturing apparatus 320 configured for additively manufacturing part 310, or may be provided as a separate and independent system.

[0223] Now refer to Figure 4 and Figure 5 A method of post-processing an additively manufactured part according to another embodiment of the present disclosure is described.

[0224] In a first step 401, an additively manufactured component 310 is provided. The method for providing the component 310 in step 401 is substantially the same as for Figure 2The method described in step 201 of the described method is the same, so for the sake of brevity, it will not be described again in this part of the application.

[0225] and Figure 1 and Figure 2 As in the embodiment described in Figure 4 and Figure 5 In the illustrated embodiment, the additively manufactured component comprises polyamide 12. However, it should be understood that in other embodiments, other suitable materials may be processed using the foregoing method.

[0226] In step 402 of the method, a fluid 306 comprising a carboxylic acid ester is provided. Figure 1 and Figure 2 As in the embodiment shown, Figure 4 and Figure 5 In the embodiment shown, the carboxylic acid ester is a cyclic carboxylic acid ester, i.e., γ-valerolactone (e.g., γ-valerolactone 99%, which is available from Sigma-Aldrich). However, it should be understood that in other embodiments, other suitable carboxylates may be used.

[0227] and Figure 1 and Figure 2 The embodiments shown are different. Figure 4 The fluid 306 in the solvent bath 302 is provided as a liquid. After the liquid solvent 306 is provided in the solvent bath 302, in step 403, the solvent 306 is heated by the heating element 304 at atmospheric pressure.

[0228] In the embodiment shown, in which the additively manufactured part comprises polyamide 12, the fluid 306 provided within the solvent bath is heated to a temperature of about 150° C. However, it should also be understood that the temperature to which the solvent is heated may vary when the process is performed using different materials and / or solvents. For most materials and solvent types, the temperature to which the solvent bath is heated will be in the range of 100° C. to 300° C., with optimal results typically being obtained at a temperature in the range of 160° C. to 200° C.

[0229] However, it should be understood that for some materials with higher melting points, such as PPS, and for some solvents with higher boiling points, such as methyl 5-(dimethylamino)-2-methyl-5-oxopentanoate, optimal results can be obtained at higher temperature ranges, such as temperatures in the range of 120°C to 280°C.

[0230] As shown in step 404, after the liquid solvent is heated to the desired temperature, the component 310 is immersed in the solvent bath 302 to apply the liquid solvent 306 to the surface of the component 310. However, it should be understood that in alternative embodiments, the component 310 can be immersed in the solvent bath 302 before the liquid solvent 306 is heated.

[0231] After component 310 has been immersed and liquid solvent 306 is at the desired temperature, component 310 is allowed to sit within solvent bath 302 for a period of time (ie, immersion time), typically in the range of 10 seconds to 1 hour, to allow for post-processing of component 310 .

[0232] For example, a treatment time of about 20 seconds has been found to be optimal when treating additively manufactured parts comprising polyamide 12 using gamma-valerolactone, however it will be appreciated that treatment times may vary depending on the materials and solvents used for a given treatment.

[0233] After component 310 has been processed, component 310 is removed from solvent bath 302 and then washed at step 405 .

[0234] exist Figure 4 and Figure 5 In the illustrated embodiment, component 310 is washed by rinsing with water to remove any excess solvent 306 from component 110. However, in other embodiments, another suitable liquid, such as alcohol or acetone, may be used, or in other embodiments, the washing step may be omitted.

[0235] The component 310 is then dried at step 406. Figure 4 and Figure 5 In the illustrated embodiment, the part 310 is dried by removing the part from the processing chamber 302 and placing the part in a vacuum oven 330, which heats the part to a temperature above the boiling point of the carboxylate solvent. This helps remove any unwanted solvent from the part after processing, which helps avoid any unwanted removal of material from the part or other adverse effects that may be caused by excessive exposure to the solvent. However, in alternative embodiments, it should be understood that different drying processes may be used.

[0236] according to Figure 1 and Figure 2 as well as Figure 4 and Figure 5 By the method described, it has been found that the surface finish of additively manufactured thermoplastic parts can be greatly improved (e.g. Figure 3a to Figure 3h ) without using halogenated compounds or benzene derivatives.

[0237] It has also been discovered that in some embodiments, if further improvement is desired after a first processing run, steps 204 and 404 may be applied repeatedly to further improve the surface finish of the additively manufactured part.

[0238] Although the invention has been described above with reference to one or more preferred embodiments, it will be appreciated that various changes or modifications may be made without departing from the scope of the invention as defined in the appended claims.

[0239] Experimental example

[0240] GVL Steam PA12

[0241] In one embodiment, using Figure 2 The vapor smoothing method shown was successful for a sample of polyamide 12 under the following conditions:

[0242] Solvent - γ-valerolactone, ≥99%, FCC (Food Chemical Codex), FG (food grade), available from Sigma-Aldrich

[0243] Material - Polyamide 12 - 3D High Reusability PA 12, available from Hewlett Packard (HP)

[0244] Solvent temperature -150℃

[0245] Chamber pressure - 200 mbar

[0246] Processing time - 20 seconds

[0247] The following gamma-valerolactone solvent grades were also tested and found to give comparable results under the same conditions (all available from Sigma-Aldrich):

[0248] γ-Valerolactone, ≥99%, FCC (Food Chemical Codex), FG (Food Grade)

[0249] γ-Valerolactone 99%

[0250] γ-Valerolactone, biorenewable, ≥99%,

[0251] ·γ-Valerolactone, natural, 95%, FG (food grade)

[0252] γ-Valerolactone, analytical standard

[0253] GBL Steam PA12

[0254] In another embodiment, using Figure 2The vapor smoothing method shown was successful for a sample of polyamide 12 under the following conditions:

[0255] Solvent-γ-butyrolactone, (solvent grade), ≥99%, which can be obtained from Sigma Aldrich

[0256] Material - Polyamide 12 - 3D High Reusability PA 12, available from Hewlett Packard (HP)

[0257] Solvent temperature -150℃

[0258] Chamber pressure - 100 mbar

[0259] Processing time - 30 seconds

[0260] GBL impregnated PA12

[0261] In another embodiment, using Figure 5 The dip-smoothing method shown was successful for treating samples of polyamide 12 under the following conditions:

[0262] Solvent-γ-butyrolactone, (solvent grade), ≥99%, which can be obtained from Sigma Aldrich

[0263] Material - Polyamide 12 - 3D High Reusability PA12, available from Hewlett Packard (HP)

[0264] Solvent temperature -150℃

[0265] Chamber pressure - 1 atmosphere (atmosphere)

[0266] Dipping time - 1 minute

[0267] GVL Steam TPU

[0268] In another embodiment, using Figure 2 The vapor smoothing method shown successfully treated samples of thermoplastic polyurethane (TPU) under the following conditions:

[0269] Solvent - γ-valerolactone, ≥99%, FCC (Food Chemical Codex), FG (food grade), available from Sigma-Aldrich

[0270] Material - Thermoplastic Polyurethane - Ultrasint 88A (melting temperature 120°C to 150°C), which is available from BASF

[0271] Solvent temperature -150℃

[0272] Chamber pressure - 100 mbar

[0273] Processing time - 30 seconds

[0274] GVL impregnated with TPU

[0275] In another embodiment, using Figure 5 The dip-smoothing method shown successfully processed samples of thermoplastic polyurethane (TPU) under the following conditions:

[0276] Solvent - γ-valerolactone, ≥99%, FCC (Food Chemical Codex), FG (food grade), available from Sigma-Aldrich

[0277] Material - Thermoplastic Polyurethane - Ultrasint 88A (melting temperature 120°C to 150°C), which is available from BASF

[0278] Solvent temperature -150℃

[0279] Chamber pressure - 1 atmosphere (atmosphere)

[0280] Dipping time - 1 minute

[0281] GBL-Steam TPU

[0282] In another embodiment, using Figure 2 The vapor smoothing method shown successfully treated samples of thermoplastic polyurethane (TPU) under the following conditions:

[0283] Solvent-γ-butyrolactone- (solvent grade), ≥99%, which can be obtained from Sigma Aldrich

[0284] Material - Thermoplastic Polyurethane - Ultrasint 88A (melting temperature 120°C to 150°C), which is available from BASF

[0285] Solvent temperature -150℃

[0286] Chamber pressure - 100 mbar

[0287] Processing time - 30 seconds

[0288] GBL impregnated with TPU

[0289] In another embodiment, using Figure 5 The dip-smoothing method shown successfully processed samples of thermoplastic polyurethane (TPU) under the following conditions:

[0290] Solvent-γ-butyrolactone- (solvent grade), ≥99%, which can be obtained from Sigma Aldrich

[0291] Material - Thermoplastic Polyurethane - Ultrasint 88A (melting temperature 120°C to 150°C), which is available from BASF

[0292] Solvent temperature -150℃

[0293] Chamber pressure - 1 atmosphere (atmosphere)

[0294] Dipping time - 1 minute

[0295] GCL Steam TPU

[0296] In another embodiment, using Figure 2 The vapor smoothing method shown successfully treated samples of thermoplastic polyurethane (TPU) under the following conditions:

[0297] Solvent - γ-caprolactone, ≥ 98%, which can be obtained from Sigma Aldrich

[0298] Material - Thermoplastic Polyurethane - Ultrasint 88A (melting temperature 120°C to 150°C), which is available from BASF

[0299] Solvent temperature -150℃

[0300] Chamber pressure - 100 mbar

[0301] Processing time - 30 seconds

[0302] GCL impregnated with TPU

[0303] In another embodiment, using Figure 5 The dip-smoothing method shown successfully processed samples of thermoplastic polyurethane (TPU) under the following conditions:

[0304] Solvent - γ-caprolactone, ≥ 98%, which can be obtained from Sigma Aldrich

[0305] Material - Thermoplastic Polyurethane - Ultrasint 88A (melting temperature 120°C to 150°C), which is available from BASF

[0306] Solvent temperature -150℃

[0307] Chamber pressure - 1 atmosphere (atmosphere)

[0308] Dipping time - 1 minute

[0309] Non-annular steam PA12

[0310] In another embodiment, by Figure 2 The vapor smoothing method shown successfully treated a sample of polyamide 12 using a non-cyclic carboxylic acid ester under the following conditions:

[0311] Solvent-5-(dimethylamino)-2-methyl-5-oxopentanoic acid methyl ester (boiling point 280℃+-2℃)

[0312] Material - Polyamide 12 - 3D High Reusability PA12, available from Hewlett Packard (HP)

[0313] Solvent temperature -120℃ to 160℃

[0314] Chamber pressure -10 mbar to 200 mbar

[0315] Processing time – up to 1 hour.

[0316] Non-ring impregnated PA12

[0317] In another embodiment, by Figure 5 The dip-smoothing method shown successfully treated a sample of polyamide 12 using a non-cyclic carboxylic acid ester under the following conditions:

[0318] Solvent-5-(dimethylamino)-2-methyl-5-oxopentanoic acid methyl ester (boiling point 280℃+-2℃)

[0319] Material - Polyamide 12 - 3D High Reusability PA12, available from Hewlett Packard (HP)

[0320] Solvent temperature -140℃ to 300℃

[0321] Chamber pressure - 1 atmosphere (atmosphere)

[0322] Maceration time - up to 1 hour

[0323] Non-annular steam TPU

[0324] In another embodiment, by Figure 2 The vapor smoothing method shown successfully treated a sample of thermoplastic polyurethane using a non-cyclic carboxylic acid ester under the following conditions:

[0325] Solvent-5-(dimethylamino)-2-methyl-5-oxopentanoic acid methyl ester (boiling point 280℃+-2℃)

[0326] Material - Thermoplastic Polyurethane - Ultrasint 88A (melting temperature 120°C to 150°C), which is available from BASF

[0327] Solvent temperature -120℃ to 160℃

[0328] Chamber pressure -10 mbar to 200 mbar

[0329] Processing time – up to 1 hour.

[0330] Non-ring impregnated TPU

[0331] In another embodiment, by Figure 5 The dip-smoothing method shown successfully treated a sample of thermoplastic polyurethane using a non-cyclic carboxylic acid ester under the following conditions:

[0332] Solvent-5-(dimethylamino)-2-methyl-5-oxopentanoic acid methyl ester (boiling point 280℃+-2℃)

[0333] Material - Thermoplastic Polyurethane - Ultrasint 88A (melting temperature 120°C to 150°C), which is available from BASF

[0334] Solvent temperature -140℃ to 300℃

[0335] Chamber pressure - 1 atmosphere (atmosphere)

[0336] Maceration time - up to 1 hour

[0337] Non-annular steam PPS

[0338] In another embodiment, by Figure 2 The vapor smoothing method shown successfully treated a sample of carbon reinforced polyphenylene sulfide (PPS) using a non-cyclic carboxylic acid ester under the following conditions:

[0339] Solvent-5-(dimethylamino)-2-methyl-5-oxopentanoic acid methyl ester (boiling point 280℃+-2℃)

[0340] Material - Carbon reinforced polyphenylene sulfide (PPSCF) (15% carbon fiber)

[0341] Solvent temperature -180℃ to 240℃

[0342] Chamber pressure -1 mbar to 50 mbar

[0343] Processing time – up to 1 hour.

[0344] Non-ring impregnated PPS

[0345] In another embodiment, by Figure 5The dip-smoothing method shown successfully treated a sample of carbon-reinforced polyphenylene sulfide (PPS) using a non-cyclic carboxylic acid ester under the following conditions:

[0346] Solvent-5-(dimethylamino)-2-methyl-5-oxopentanoic acid methyl ester (boiling point 280℃+-2℃)

[0347] Material - Carbon reinforced polyphenylene sulfide (PPSCF) (15% carbon fiber)

[0348] Solvent temperature -180℃ to 300℃

[0349] Chamber pressure - 1 atmosphere (atmosphere)

[0350] Maceration time - up to 1 hour

[0351] GVL Steam TPU (Atmosphere)

[0352] In another example, a sample of thermoplastic polyurethane (TPU) was successfully treated under atmospheric conditions using the vapor smoothing method:

[0353] Solvent - γ-valerolactone, ≥99%, FCC (Food Chemical Codex), FG (food grade), available from Sigma-Aldrich

[0354] Material - Thermoplastic Polyurethane - Ultrasint 88A (melting temperature 120°C to 150°C), which is available from BASF

[0355] Solvent temperature -160℃

[0356] Processing pressure - 1 atmosphere

[0357] Dipping time - 2 seconds

[0358] GVL Steam PPSU (non-AM)

[0359] In another embodiment, by Figure 2 The vapor smoothing method shown was successful for treating a sample of polyphenylsulfone (PPSU) using γ-valerolactone under the following conditions:

[0360] Solvent - γ-valerolactone, ≥99%, FCC (Food Chemical Codex), FG (food grade), available from Sigma-Aldrich

[0361] Material-Polyphenylsulfone (PPSU)

[0362] Solvent temperature -150℃

[0363] Chamber pressure - 150 mbar

[0364] Processing time – 30 seconds.

Claims

1. A method for post-processing a thermoplastic part, comprising the following steps: a) provide thermoplastic parts, b) providing a fluid for treating the thermoplastic part to improve the surface finish of the thermoplastic part, wherein the fluid comprises at least one carboxylic acid ester; c) a heating step, wherein the fluid is heated; and d) An applying step, wherein a heated fluid is applied to the surface of the thermoplastic part.

2. The method according to claim 1, wherein the carboxylic acid ester is a cyclic carboxylic acid ester (lactone).

3. The method according to claim 2, wherein the cyclic carboxylic acid ester has the following structure: wherein n is 2 to 10, each CH2 group may be optionally substituted independently with one or two substituents selected from alkyl, alkenyl, alkynyl, alkoxy, hydroxyl and carboxyl.

4. The method of claim 2 or 3, wherein the cyclic carboxylic acid ester comprises a four-membered ring.

5. The method of claim 4, wherein the cyclic carboxylic acid ester comprises a four (β-lactone) membered ring, a five (γ-lactone) membered ring, a six (δ-lactone) membered ring, or a seven (ε-lactone) membered ring.

6. The method according to any one of claims 2 to 5, wherein the cyclic carboxylic acid ester is selected from one of the following: β-propiolactone, δ-valerolactone, γ-caprolactone, γ-valerolactone, ε-caprolactone or γ-caprolactone.

7. The method of claim 5, wherein the cyclic carboxylic acid ester comprises a five (γ-lactone) membered ring or a six (δ-lactone) membered ring.

8. The method of claim 7, wherein the cyclic carboxylic acid ester comprises a five (γ-lactone) membered ring.

9. The method according to claim 8, wherein the cyclic carboxylic acid ester is γ-valerolactone.

10. The method of any preceding claim, wherein the thermoplastic component comprises a polar polymer, optionally poly(vinyl chloride), poly(methyl methacrylate), polyamide, polyurethane, and combinations thereof.

11. A method according to any preceding claim, wherein the heating step comprises heating the fluid to a temperature in the range of about 100°C to about 300°C.

12. The method of any preceding claim, wherein the heated fluid is applied to the surface of the thermoplastic part for an immersion time in the range of about 10 seconds to about 1 hour, and optionally for an immersion time in the range of about 10 seconds to about 5 minutes.

13. A method according to any preceding claim, wherein the fluid is provided as a liquid, and wherein the applying step comprises immersing the thermoplastic part in the liquid, and optionally wherein the heating step comprises heating the liquid to a temperature in the range of about 140°C to about 200°C.

14. The method according to any one of claims 1 to 12, wherein step a) comprises placing the thermoplastic part into a processing chamber, wherein step c) comprises heating the fluid so as to cause evaporation of the fluid, and wherein step d) comprises introducing the evaporated fluid into the processing chamber and causing the evaporated fluid to condense onto a surface of the thermoplastic part contained therein.

15. The method of claim 14, wherein the method comprises heating the vaporized fluid to a temperature in the range of about 120°C to about 180°C.

16. The method of claim 14 or 15, wherein the interior of the process chamber is maintained at a pressure of less than 100 kPa (1 bar), optionally wherein the interior of the process chamber is maintained at a pressure in the range of about 1 kPa to about 50 kPa (about 10 mbar to about 500 mbar), and further optionally wherein the interior of the process chamber is maintained at a pressure in the range of about 5 kPa to about 30 kPa (about 50 mbar to about 300 mbar).

17. The method according to claim 16, wherein the method further comprises, after step d): e) applying negative pressure to the interior of the processing chamber to evaporate the condensed fluid from the surface of the thermoplastic part.

18. The method according to any preceding claim, wherein the method further comprises, after step d): f) removing the heated fluid from the surface of the thermoplastic part; and g) applying the heated fluid or heated fluid to the surface of the thermoplastic part.

19. A method according to any preceding claim, wherein the thermoplastic component comprises functional groups having a dipole moment greater than 0 Debye, and optionally a dipole moment greater than 0.5 Debye.

20. A method according to any preceding claim, wherein the thermoplastic part is an additively manufactured part, and optionally wherein the thermoplastic part is a powder-based additively manufactured part.

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