Methods for polymer materials

Abstract

A method for preparing a polymer composition comprising a combination of silozane, crosslinked silozane, organic monomer and photoinitiator for enabling 3D printing, preferably stereolithography, of polysilozane structures using UV exposure times similar to those of conventional UV-curable resins, wherein the polymer composition enables the rapid production of article parts with complex shapes, depending on the mechanical properties of the polymer composition that retain fine features. Composites, articles and complex structures prepared by this method are also provided.

Description

[Technical Field]

[0001] This invention relates to methods and compositions for processing polymers for use in ceramics technology, as well as products thereof. More specifically, this invention relates to Si-CN ceramics and improved products prepared therefrom. [Background technology]

[0002] Existing methods for preparing Si-CN ceramics include U.S. Patent No. 10,385,234, which discloses a method of crosslinking polysilazane material using a fluoride-containing catalyst in tetrahydrofuran (THF), and O. Flores et al, J. Mat. Chem. A., 2013, 1, 15406. Improved processes are needed so that polymer-derived ceramic (PDC) materials can be easily fabricated and processed into novel, large, or complex shapes with improved properties such as improved strength and high-temperature resistance. More specifically, improved manufacturing methods are needed to prepare complex part shapes from high-performance materials and to accommodate further methods such as additive manufacturing. Problems with existing processes and materials include the inability to manufacture certain composite materials, and more specifically, the high cost of machining materials from blocks. Conventional methods and post-processing steps for achieving complex shapes using complex manufacturing are also costly. There is also a need to provide improved technologies that enable the manufacture of finer features and improve the strength of preforms. [Overview of the Initiative]

[0003] The present invention provides a method according to the appended claims. In the process of the present invention, a combination of silozane (preferably Durazane), crosslinked silozane (preferably crosslinked Durazane), an organic monomer, and a photoinitiator enables 3D printing of polysilozane structures using the same UV exposure time as conventional UV-curable resins. In one embodiment, the polymer composition provides a scaffold, and depending on the mechanical properties of the polymer scaffold that retain fine features, it becomes possible to produce parts with complex shapes. The advantages of this invention include a faster process and finer product characteristics. In a preferred embodiment, the silozane can be further crosslinked to full crosslink density through subsequent additional heat treatment. In one embodiment, during ceramicization, the polymer scaffold is decomposed, leaving behind a SiCN ceramic with good mechanical properties. In one embodiment, the combination and composition may include fillers such as silicon carbide, boron carbide, crushed carbon fiber, alumina silicate fiber, glass fiber, silicon carbide fiber, shredded silicon carbide fiber, shredded glass fiber, shredded alumina silicate fiber, metal fillers (stainless steel, cobalt, nickel), sialon particles, magnetic oxide fillers, and stabilizing fillers. In one embodiment, the high-temperature resistance is above 800°C, above 1500°C, or up to approximately 2000°C. In a further embodiment, the present invention provides a composite material prepared by the method of the present invention having a highly uniform microstructure or reduced porosity which is approximately 75% of the theoretical maximum density measured using the Archimedes method. In a further embodiment, the present invention provides for the use of polymers or composites prepared by any of the methods described above in the aerospace, automotive, oil and gas industries.

[0004] The advantages of the method of the present invention include the ability to produce improved parts using any crosslinked polysilazane with little deviation from existing manufacturing techniques, and thus dramatically reduce costs compared to standard ceramic matrix composites, and in particular produce improved articles for use in the automotive, energy, and aerospace industries.

[0005] If a catalyst is used, the catalyst may be a source of fluoride ions. The catalyst may be selected from tetraethylammonium fluoride or tetrabutylammonium fluoride. Preferably, the catalyst is tetrabutylammonium fluoride (TBAF). The solvent may be tetrahydrofuran. The solvent may further be toluene. The solvent may also be 2-methyltetrahydrofuran. The solvent may also be dibutyl ether. The solvent may be a mixture of tetrahydrofuran or toluene in any particular ratio, with or without an additional solvent selected from 2-methyltetrahydrofuran and dibutyl ether. The solvent may further be any other solvent known in the art that dissolves any of the oligosilazane, catalyst, and quenching agent. The oligomer:solvent mass ratio may be 8:1 to 1:8. More specifically, the oligomer:solvent mass ratio may be in the range of 8:1 to 1:1, and even more specifically, in the range of 8:1 to 3:1, and even more specifically, in the range of 8:1 to 5:1. The oligomer:solvent mass ratio may be in the range of 1:1 to 1:8, more specifically, in the range of 1:3 to 1:8, and even more specifically, in the range of 1:5 to 1:8. The oligomer:solvent mass ratio may preferably be in the range of 1:3 to 3:1. More preferably, the oligomer:solvent mass ratio may be 1:2 to 2:1. Even more preferably, the mass ratio may be 1:1.5 to 1:1. Most preferably, the mass ratio is 1:1.

[0006] The molar ratio of catalyst to oligomer repeating unit is 1 × 10⁻⁶ -4 ~10×10 -4 This is possible. More preferably, the molar ratio is 2 × 10 -4~10×10 -4 It may be. More preferably, the molar ratio is 2×10 -4 ~7×10 -4 It may be. Most preferably, the molar ratio is 2×10 -4 ~6×10 -4 It may be. The addition rate of the catalyst can be 10 to 100 (% of the total catalyst) / hour -1 It may be. Preferably, the addition rate can be 15 to 35 (% of the total catalyst) / hour -1 It may be. In one aspect, the present invention uses a reaction that can be carried out in a container having a height / width dimension ratio >1. The container can have an injection opening with a width / bottom surface dimension of ≦0.5. The resulting crosslinked polymer can produce a ceramic material without a significantly and homogeneously oxygen content upon pyrolysis at temperatures above 1200°C in an inert atmosphere. The catalyst is added dropwise, and the inhibitor can be selectively added throughout the reaction.

[0007] In a further aspect, the present invention provides polymers prepared by the method of the present invention and composites containing the polymers, and their use in energy including the aerospace, automotive, oil, and gas industries. Preferably, the polymers and composites have a low oxygen content, such as less than 10% by mass on average throughout the specimen. In a specific embodiment of the present invention, the solvent is THF, the catalyst is TBAF, the mass ratio of oligomer: solvent is 1:1.5 to 1:1, the molar ratio of catalyst: oligomer repeating unit is 2×10 -4 ~4×10 -4 and the catalyst is added on average at approximately 17 (% of the total catalyst) / hour -1 [[ID=3२]]It is added. In a specific embodiment, the solvent is THF, the catalyst is TBAF, the mass ratio of oligomer: solvent is 1:1, the molar ratio of catalyst: oligomer repeating unit is 3.6×10 -4 and the catalyst is added on average at approximately 17 (% of the total catalyst) / hour -1 It is added.

[0008] In other embodiments of the present invention, the solvent is toluene, the catalyst is TBAF, the mass ratio of oligomer: solvent is 1:1.5 to 1:1, and the molar ratio of catalyst: oligomer repeating unit is 2×10 -4 ~6×10 -4 and the catalyst is added on average for approximately 33 (total catalyst %) hours -1 . In a specific embodiment, the solvent is toluene, the catalyst is TBAF, the mass ratio of oligomer: solvent is 1:1, and the molar ratio of catalyst: oligomer repeating unit is 2.6×10 -4 and the catalyst is added on average for approximately 33 (total catalyst %) hours -1 .

[0009] In a further embodiment, the solvent is toluene, the mass ratio of oligomer: solvent is 1:1.1, and the molar ratio of catalyst: oligomer repeating unit is 5.2×10 -4 and the catalyst is added on average for approximately 33 (total catalyst %) hours -1 . In one embodiment, the present invention provides a method for chemically crosslinking a specific polysilazane (Durazane(TM) 1800, Merck) using a catalyst containing reactive F - ions (tetrabutylammonium fluoride, TBAF), which causes many reactions to result in a higher molecular weight polymer material. In one embodiment, the method of the present invention is not carried out under a dry inert gas, and is configured such that sufficient hydrogen gas is generated during the reaction, and as a result, by expelling the atmosphere above the reaction solution, an atmosphere that is "inert" (as far as moisture is concerned) is provided in situ. The actual degree of hydrolysis in the method of the present invention is also considered not to produce particularly high concentrations of siloxanes (and thus oxygen) in the final ceramic material produced. High concentrations of oxygen can be defined as a recognizable amount of the final ceramic containing oxides - for example, 15 mol% or the like.

[0010] By not including a protection step, significant additional advantages regarding expandability are provided. In one embodiment, a crosslinked material produced from Durazane™ 1800 and TBAF in THF is subsequently reacted and quenched with Ca(BH4) 2.2 THF to produce by-products CaF2 and tetrabutylammonium borohydride, which are then filtered and dried under vacuum to produce a ceramic precursor. The preparation of crosslinked materials by crosslinking polysilazanes under ambient conditions is particularly advantageous. In one embodiment, this technology uses the original atmosphere created by the synthesis as shielding and controls the synthesis time to ensure that enough H2 is generated to displace H2O from the reaction vessel atmosphere.

[0011] The special advantages stem from the elimination of the need for complex gas supply to the reaction vessel and facility requirements for gas and solvent purification or drying procedures. Any form of modification or addition can be made to the reaction without the need for complex air-sensitive techniques, which are essentially small-scale solutions in synthesis. Therefore, this synthesis is more adaptable and scalable. Possible applications for the improved PDC precursor according to the present invention include: • High-temperature ceramics for aerospace applications: foremost edges, exhaust ducts • High-temperature resistant materials - energy materials, automotive, aerospace ·Hard materials - polishing tools, supporting tools, cutting / processing tools • Chemical engineering - catalyst supports, food - and biotechnology • Functional materials - Electrical engineering, Micro / nano electronics Includes. Therefore, the method and products of the present invention have applications in a variety of industries, including automotive, aerospace, oil and gas, and the like. The method of the present invention can also be used in combination with other methods as appropriate. Features of any aspect or embodiment of the present invention may be used alone or in any combination with other aspects and embodiments as appropriate. The present invention is described in more detail hereby with reference to the following schematic diagram, which is only an example. [Brief explanation of the drawing]

[0012] [Figure 1] This figure shows EDS (elemental analysis) data for ceramic composites prepared from precursor materials of the method of the present invention. [Figure 2] This is a diagram showing the experimental setup using a round-bottom flask. [Figure 3] This is a diagram showing the experimental setup for a wide-rimmed container. [Figure 4] This is a schematic diagram showing the physical configuration for the fabrication of composite materials using polysilazane prepregs via conventional vacuum bag molding. [Figure 5] This figure shows the oxidation resistance of various polymer-derived ceramic matrix composite (PDCMC) samples. [Modes for carrying out the invention]

[0013] The present invention is more fully described herein with reference to the appended examples and drawings illustrating embodiments of the invention. The present invention should not be construed as being limited to the embodiments expressed herein. [Examples]

[0014] (Example 1) 400 g of oligosilazane, Durazane™ 1800 (Merck Life Sciences, India), was added to tetrahydrofuran THF (Sigma-Aldrich, Gillingham, UK) in a 1:1 mass ratio in a 3 L round-bottom flask at room temperature under magnetic stirring. The vessel was 24.3 cm high and 18.8 cm wide, with high curvature and a neck opening diameter of 2.5 cm. No reflux condenser or gas pathway was provided. After homogenization, 1 M tetrabutylammonium fluoride (TBAF) in THF (Sigma Aldrich, Gillingham, UK) was added dropwise. The addition rate was defined as the point at which the entire surface was covered with bubbles without significant surface damage due to large bubbles, and was controlled to prevent excessive release of H2 gas. The total amount of TBAF solution added, including the time when no addition was made due to the appearance of bubbles on the entire surface, was approximately 2.3 cm over a total of 6 hours. 3 The addition of a catalyst to the top of such bubbles leads to excessive polymerization of the thin bubble film, resulting in the formation of an insoluble film. This occurs at 0.00038 mol. -1 This addition rate corresponds to a final TBAF concentration of 0.00282 M. The final molar ratio of TBAF to oligosilazane repeating units was 0.000356. This mixture was stirred continuously until the gas release was complete. 0.1 cm 3 Finally, the TBAF solution was added to confirm that no further gas release occurred. Ca(BH4)2.2THF (Sigma Aldrich, Gillingham, UK), F - Add to the suspension in THF at a molar ratio of 1.5:1 (approximately 5 cm). 3 The suspension was stirred for 10 minutes, then filtered to remove aggregates, and the filtrate was collected and used as the synthesized solution for the compound application.

[0015] (Example 2) 300g of oligosilazan, Durazane™ 1800, was prepared as described in Example 1, using THF (1.7cm³). 3 The solution was treated with 1M TBAF and Ca(BH4)2.2THF in ) (at 0.00028 mol). -1 The addition rate corresponded to a final TBAF concentration of 0.00278 M. The final molar ratio of TBAF to oligosilazane repeating units was 0.000351. Subsequently, this solution was concentrated in a rotary evaporator at 85°C and a pressure of 800–300 mBar to obtain a pale yellow oily substance. This solidified as a pale glassy solid upon cooling to room temperature.

[0016] (Example 3) 400 g of oligosilazane, Durazane™ 1800, was treated with TBAF and Ca(BH4) 2.2 THF as described in Example 1. This was done at 0.00038 mol. -1 This addition rate corresponds to a final TBAF concentration of 0.00282 M. The final molar ratio of TBAF to oligosilazane repeating units was 0.000351. Next, the suspension was filtered to remove aggregates, and the filtrate was collected. This solution was then concentrated in a rotary evaporator at 85°C and a pressure of 850–700 mBar for a total of 15 minutes to obtain a pale yellow liquid. This liquid contained 22% by mass of residual THF solvent. This liquid was used as a viscous oil for compound applications.

[0017] (Example 4) 30 g of oligosilazane, Durazane™ 1800 (Merck Life Sciences, India), was added to toluene (Sigma-Aldrich, Gillingham, UK) in a 1:1 mass ratio in a 0.4 L round-bottom flask with a height of 13.5 cm, a width of 10 cm, and a neck opening diameter of 2.5 cm, and the mixture was stirred magnetically at room temperature. No reflux condenser or gas pathway was provided. After homogenization, 1M tetrabutylammonium fluoride (TBAF) in THF (Sigma Aldrich, Gillingham, UK) was added dropwise after being diluted 2-fold with toluene. The addition rate was controlled to prevent excessive release of H2 gas. The total volume of TBAF solution added was 0.25 cm³. 3 This mixture was stirred continuously until the gas release was complete. 0.05 cm 3 The TBAF solution was added last to confirm that no further gas release occurred. This was 2.08 × 10⁻⁶. -5 mol hour -1 This addition rate corresponds to a final TBAF concentration of 0.00202 M. The final molar ratio of TBAF to oligosilazane repeating units was 0.000258. Ca(BH4)2.2THF (Sigma Aldrich, Gillingham, UK), F - Add to the suspension in THF at a molar ratio of 1.5:1 (approximately 5 cm). 3 The suspension was stirred for 10 minutes, then filtered to remove aggregates, and the filtrate was collected and concentrated in a rotary evaporator at 85°C and 80 mBar. A pale yellow gel was obtained at room temperature.

[0018] (Example 5) 30 g of oligosilazane, Durazane™ 1800 (Merck Life Sciences, India), was added to toluene (Sigma-Aldrich, Gillingham, UK) in a 1:1 mass ratio in a 1 L round-bottom flask at room temperature under magnetic stirring. No reflux condenser or gas pathway was provided. After homogenization, 1 M tetrabutylammonium fluoride (TBAF) in THF (Sigma Aldrich, Gillingham, UK) was added dropwise. The addition rate was controlled to prevent excessive release of H2 gas. The total volume of TBAF solution added was 0.15 cm³. 3 This mixture was stirred continuously until the gas release was complete. 0.05 cm 3 The TBAF solution was added last to confirm that no further gas release occurred. This was 8.33 × 10⁻⁶. -5 mol hour -1 This addition rate corresponds to a final TBAF concentration of 0.00403 M. The final molar ratio of TBAF to oligosilazane repeating units was 0.000516. Ca(BH4)2.2THF (Sigma Aldrich, Gillingham, UK), F - Add to the suspension in THF at a molar ratio of 1.5:1 (approximately 5 cm). 3 The suspension was stirred for 10 minutes, then filtered to remove aggregates, and the filtrate was collected and concentrated in a rotary evaporator at 85°C and 80 mBar for 3 minutes. The product was collected as a viscous, pale liquid at room temperature.

[0019] (Example 6) The oily layer from Example 3 was extruded and spread evenly onto a plastic release film layer. A layer of Torayca COR8112 fibers was placed on top of this oily layer. A coating was applied using an extruder and rolling device. Subsequently, further layers of fibers and oil were applied until a total of 25 fiber plies were laminated. A further release film layer was placed on top of this stack, and the stack was placed between two steel plates spaced 4.6 mm apart. The resulting stack width was 5 mm. The pile was dried in a furnace at 160°C under ambient conditions, and then thermally decomposed in Ar(g) at 1280°C for 1 hour. Next, the sample was subjected to a bending test in accordance with ASTM C1341, and subsequently, energy-dispersive spectroscopy (Oxford Instruments, Oxford, UK) was performed on the matrix of the crushed ceramic composite using a scanning electron microscope (SEM). Figure 1: Atomic percentages of the major constituent elements—Si, C, N, and O—from numerous test sites. O was introduced as various impurities during synthesis or thermal decomposition. The box plots overlaid with experimental data points show the median and interquartile ranges of the atomic percentage distribution for data collected from all test sites.

[0020] Figure 1 clearly shows that all elements are observed in large quantities depending on their position. However, statistically speaking, a negligible amount of oxygen is widely present throughout the composite material. Compared to the extremely large amount of silicon, the matrix is ​​Si 1±0.48 C 1.58±0.61 N 0.68±0.57 O 0.11±0.11 The average stoichiometric content indicates that this ceramic is primarily Si-C glass and has a statistically negligible oxygen content, along with some nitrogen. High oxygen levels in a few locations are thought to be due to localized regions of oxygen concentration formed during strength testing or thermal decomposition, resulting from insufficient drying with inert gas supply. Extensive hydrolysis of the precursor material manifests as a significant increase in the average oxygen content compared to what is observed here. Therefore, it can be seen that the method of the present invention makes it possible to produce Si-CN ceramics with a minimum oxygen content without the many procedural inefficiencies and large-scale inhibitory complexities associated with the handling of air-sensitive chemicals.

[0021] (Example 7) Six further composite material samples were produced according to the method described in Example 6. The masses of these composite materials and their components are shown in Table 1. [Table 1] The average ceramic yield relative to the precursor material was calculated to be 74 ± 4%. The variability is thought to be due to a lack of consistency in the gas flow and temperature across the entire heat treatment furnace.

[0022] (Example 8) Resin-based and initiators The resin system may be prepared from a blend of polysilazane polymer and silazane oligomer, the oligomer acting as a reactive diluent to adjust the viscosity of the resin system to the desired level for use as a prepreg. The system allows for the processing of polysilazane into ceramic matrix composite components using suitable manufacturing techniques that enable the processing of standard polymer composites and the production of high-temperature resistant composite components. The reactive diluent includes any oligomer with a viscosity lower than that of the polysilazane, which can react with the polysilazane to form a crosslinked polymer network. A resin system of crosslinked durazane: durazane oligomer: organic monomer (methyl methacrylate): UV initiator was prepared. The following figures illustrate the advantages of a preferred embodiment. The schematic diagram in Figure 4 shows a method in which a polysilazane prepreg can be used in a vacuum bag molding process to produce polymer-derived ceramic matrix composite (PDCMC) parts. Since the properties of the polysilazane-based resin are similar to those of existing polymer resins used in prepregs for the production of PMC components, this process requires little to no modification to existing techniques.

[0023] Figure 5 shows that oxidation resistance was demonstrated through heat treatment at 1000°C for many test specimens, as shown in Figure 4. After heat treatment, the test specimens were tested using four-point bending, and the residual strength of the specimens was measured compared to samples that were not exposed to the heating conditions after thermal decomposition.

[0024] Polymer chemicals based on acrylate-based resins (1,6-hexanediol diacrylate) were tested using many common photoinitiators (4-dimethylaminobenzophenone and diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide) and combined with both polysilozane oligomers and crosslinked BB resins.

[0025] A wide range of common photopolymers can be used. The use of photopolymers provides polysilozane molded articles with improved mechanical strength and interlayer adhesion. This improved mechanical strength makes it possible to successfully print parts with fine features without the fraying that occurs due to delamination from the 3D printer's FEP film, both during and after printing.

Claims

1. A method for preparing a polymer composition comprising a combination of silozane, crosslinked silozane, organic monomer and photoinitiator for enabling 3D printing, preferably stereolithography, of a polysilozane structure using a UV exposure time similar to that of conventional UV-curable resins, wherein the polymer composition enables the rapid production of article parts with complex shapes, depending on the mechanical properties of the polymer composition that retain fine features.

2. The method according to claim 1, wherein the photoinitiator is selected from 4-dimethylaminobenzophenone and diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide.

3. The method according to claim 1 or 2, wherein the organic monomer is 1,6-hexanediol diacrylate.

4. The polysilazane composition comprises a resin system comprising a blend of a polysilazane polymer and a silazane oligomer, wherein the oligomer acts as a reactive diluent to adjust the viscosity of the resin system to a desired level for use as a prepreg, and may also contain fillers, and the system enables the processing of the polysilazane into ceramic matrix composite parts using a suitable manufacturing technique that enables the processing of standard polymer composites and the production of composite parts with high temperature resistance. The method according to any one of claims 1 to 3, wherein the reactive diluent comprises any oligomer having a viscosity lower than that of the polysilazane and can react with the polysilazane to form a crosslinked polymer network.

5. The method according to any one of claims 1 to 4, wherein the silozane can subsequently be subjected to additional heat treatment to reach a complete crosslink density.

6. The method according to any one of claims 1 to 5, wherein the polymer composition is decomposed during ceramicization, leaving behind a SiCN ceramic having good mechanical properties.

7. The method according to claim 1, wherein the crosslinked polymer is prepared by crosslinking under ambient conditions.

8. The method according to any one of claims 1 to 7, wherein the filler includes silicon carbide, boron carbide, crushed carbon fiber, alumina silicate fiber, glass fiber, silicon carbide fiber, shredded silicon carbide fiber, shredded glass fiber, shredded alumina silicate fiber, metal filler (stainless steel, cobalt, nickel), sialon particles, magnetic oxide filler, and stabilizing filler.

9. The method according to any one of claims 1 to 8, wherein the high temperature resistance is greater than 800°C, greater than 1500°C, or up to about 2000°C.

10. A composite material prepared by any one of claims 1 to 9, having a uniform microstructure or reduced porosity.

11. An article or complex structure prepared using the method described in any one of claims 1 to 10.

12. Use in the aerospace, automotive, energy, oil and gas industries of polymers or composites prepared by the method of any one of claims 1 to 11.

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