High-strength compression-resistant polytetrafluoroethylene material and method for producing the same

Abstract

The application relates to the technical field of polytetrafluoroethylene materials, in particular to a high-strength compression-resistant polytetrafluoroethylene material and a preparation method thereof, which comprises the following components in proportion by weight: 80-90 parts of polytetrafluoroethylene, 8-12 parts of modified fiber filler, 0.5-1 part of antioxidant, 2-4 parts of composite toughening agent and 1-2 parts of compatilizer. Through the synergistic effect of the modified fiber filler, the composite toughening agent and the antioxidant and other components, the stability of the material during high-temperature processing and long-term use is ensured, the mechanical performance of the polytetrafluoroethylene material is obviously improved, and the compression resistance and the tensile strength of the polytetrafluoroethylene material are synergistically improved.

Description

Technical Field

[0001] This invention relates to the technical field of polytetrafluoroethylene (PTFE) materials, and more particularly to a high-strength, compression-resistant PTFE material and its preparation method. Background Technology

[0002] Polytetrafluoroethylene (PTFE), a fluoropolymer with excellent chemical inertness and thermal stability, exhibits extremely low surface energy, excellent insulation properties, outstanding corrosion resistance, and a wide operating temperature range due to its unique molecular structure, leading to its widespread application in high-tech fields such as aerospace, chemical engineering, electronics, and medical applications. However, pure PTFE materials possess inherent defects such as low mechanical strength, poor creep resistance, and a large coefficient of linear expansion, limiting their application in load-bearing structural components and high-stress environments. Furthermore, in aerospace and chemical equipment, materials not only bear mechanical loads but may also face complex environments such as high-temperature airflow, chemical corrosion, and electric arc discharge. Under these conditions, even "flame-retardant" materials like PTFE may undergo thermal decomposition or even combustion. To overcome these shortcomings, researchers commonly employ composite modification methods by adding various fillers to PTFE, aiming to significantly improve its mechanical properties while maintaining its excellent chemical properties.

[0003] In the prior art, for example, Chinese patent CN202210972932.7 discloses a high-temperature resistant polytetrafluoroethylene (PTFE) composite material. This material improves the performance of PTFE by adding fiber-reinforced filler, cobalt dimethylimidazolium, and ceramic powder. Cobalt dimethylimidazolium and ceramic powder are mainly used to synergistically improve the high-temperature stability of the composite material. Although this technology has achieved some improvement in high-temperature resistance, it still has significant technical defects: First, the fiber-reinforced filler lacks an effective interfacial bonding mechanism with the PTFE matrix, resulting in insufficient interfacial bonding force. Under high stress, interfacial debonding easily occurs, limiting further improvement in the compressive strength of the composite material. Second, this technical solution lacks targeted toughening measures, making the material prone to brittle fracture under high stress conditions. This results in limited improvement in the mechanical properties of the composite material, making it difficult to meet the stringent requirements of high-strength compressive applications. Summary of the Invention

[0004] In view of this, the present invention proposes a high-strength compressive-resistant polytetrafluoroethylene material and its preparation method to solve the problem that the existing polytetrafluoroethylene materials have insufficient mechanical properties such as compressive strength, making it difficult to meet the requirements of high-strength compressive-resistant applications.

[0005] The technical solution of the present invention is achieved as follows: The present invention provides a high-strength, compression-resistant polytetrafluoroethylene material, which, by weight, comprises 80-90 parts of polytetrafluoroethylene, 8-12 parts of modified fiber filler, 0.5-1 parts of antioxidant, 2-4 parts of composite toughening agent, and 1-2 parts of compatibilizer.

[0006] Specifically, this invention achieves a significant improvement in the mechanical properties of polytetrafluoroethylene (PTFE) materials through the aforementioned components and synergistic effects. Specifically, the modified fiber filler, as the core reinforcing component, forms a strong interfacial bond with the PTFE matrix, efficiently transferring stress under compressive loads and significantly improving the material's compressive strength. The introduction of the composite toughening agent effectively improves the inherent brittleness of PTFE, significantly enhancing the material's impact toughness and elongation at break by absorbing crack propagation energy and inducing stress dispersion. The synergistic effect of the compatibilizer further optimizes the interfacial compatibility between the components, ensuring uniform dispersion of the filler in the matrix and effective load transfer. The addition of antioxidants ensures the stability of the material during high-temperature processing and long-term use.

[0007] Based on the above technical solutions, a preferred method for preparing modified fiber fillers includes the following steps:

[0008] S1. After acid treatment, basalt fibers are dispersed in DMF, zirconium tetrachloride and terephthalic acid are added, ultrasonically dispersed evenly, transferred to a reaction vessel, heated to 100-130℃ and reacted for 22-24 hours to obtain composite fibers;

[0009] S2. Mix p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, 3,5-dihydroxybenzoic acid and acetic anhydride, and heat to 140-160℃ for acetylation reaction for 1-2 hours; then remove acetic anhydride, add catalyst, and gradually heat to 280-320℃ under nitrogen protection for 4-6 hours to obtain liquid crystal polymer.

[0010] S3. Dissolve the liquid crystal polymer in NMP, add 3-isocyanate-propyltriethoxysilane and dibutyltin dilaurate at 80-100℃, and react for 2-4 hours to obtain the modifier;

[0011] S4. Disperse the composite fibers in toluene, add a modifier, heat to 80-100℃, and stir for 5-7 hours to obtain the modified fiber filler.

[0012] Specifically, in step S1, the acid-treated basalt fiber surface is rich in active sites such as hydroxyl and silanol groups. Zirconium tetrachloride serves as a metal node providing coordination centers, and terephthalic acid, as an organic ligand, binds to zirconium ions through coordination bonds. A UiO-66 type MOF crystal structure is slowly grown on the basalt fiber surface via a solvothermal method. The UiO-66 type MOF crystal structure exhibits good chemical stability, mechanical stability, and thermal stability. Upon heating, this MOF structure undergoes thermal decomposition, forming a dense inorganic flame-retardant barrier layer on the material surface, thus improving the flame-retardant rating of the composite material. Furthermore, the porous structure and coordination bonding mechanism of the UiO-66 type MOF can significantly influence the mechanical properties of the material. On one hand, it binds to the silanol groups on the basalt fiber surface through coordination bonds, forming a "molecular anchoring" effect that significantly improves the interfacial bonding strength between the fiber and the matrix. On the other hand, when the material is subjected to external forces, its rigid structure can share the stress transmission and dispersion functions with the siloxane structure. In step S2, a liquid crystal polymer with active side chains is prepared through a two-stage reaction involving acetylation protection and melt polycondensation. p-Hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid, as main-chain monomers, impart a rigid rod-like molecular conformation and liquid crystal phase behavior to the polymer. The introduction of 3,5-dihydroxybenzoic acid retains active hydroxyl groups on the polymer side chains that did not participate in the main-chain reaction, providing reaction sites for subsequent silanization. This liquid crystal polymer possesses intrinsic properties of high modulus and high strength, and can function as a molecular-level reinforcing agent. In step S3, triethoxysilane groups are introduced through the reaction of isocyanate groups with the hydroxyl groups on the side chains of the liquid crystal polymer. This maintains the rigid segmental structure of the liquid crystal polymer while endowing it with the ability to bond to inorganic surfaces. In step S4, covalent bonding between the modifier and the composite fiber is achieved through a silane coupling mechanism, realizing chemical bonding at the organic-inorganic interface.

[0013] Based on the above technical solutions, preferably, in step S1, the mass ratio of basalt fiber, zirconium tetrachloride, and terephthalic acid is 100 : (15-25) : (10-20).

[0014] Based on the above technical solutions, preferably, in step S2, the mass ratio of p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, 3,5-dihydroxybenzoic acid and acetic anhydride is 100 : (40-60) : (5-15) : (120-150), and the amount of catalyst added is 0.1-0.2% of the total mass of p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid and 3,5-dihydroxybenzoic acid.

[0015] Based on the above technical solutions, preferably, in step S2, the catalyst is potassium acetate, sodium acetate, or magnesium acetate.

[0016] Based on the above technical solutions, preferably, in step S3, the mass ratio of the liquid crystal polymer, 3-isocyanate-propyltriethoxysilane and dibutyltin dilaurate is 100 : (15-25): 0.1-0.2.

[0017] Based on the above technical solutions, preferably, in step S4, the mass ratio of composite fiber to modifier is 100:(15-25).

[0018] Based on the above technical solutions, preferably, the composite toughening agent includes fluororubber and polytetrafluoroethylene-perfluoropropylene copolymer, and the mass ratio of fluororubber to polytetrafluoroethylene-perfluoropropylene copolymer is 70-85:15-30.

[0019] The synergistic effect of fluororubber and polytetrafluoroethylene-perfluoropropylene copolymer effectively improves the brittle characteristics of PTFE-based composites, significantly enhancing the material's impact toughness and elongation at break. Fluororubber, as the main toughening component, absorbs a large amount of impact energy under impact loads through rapid rearrangement and conformational changes of its molecular chains. Simultaneously, it undergoes localized plastic deformation at the crack tip, effectively blunting stress concentration and preventing rapid crack propagation. FEP, as an auxiliary toughening component, has a molecular structure highly similar to the PTFE matrix, acting as a "molecular bridge" to significantly improve the interfacial compatibility between fluororubber and the PTFE matrix, promoting uniform stress transfer between different phases and avoiding stress concentration at the interface.

[0020] Based on the above technical solutions, preferably, the antioxidant is any one of antioxidant 1010, antioxidant 3114, antioxidant 703 and antioxidant DSTDP, and the compatibilizer is maleic anhydride-grafted polypropylene.

[0021] This invention also provides a method for preparing a high-strength, compression-resistant polytetrafluoroethylene material, the method comprising the following steps:

[0022] Polytetrafluoroethylene (PTFE), modified fiber filler, antioxidant, composite toughening agent, and compatibilizer are mixed to obtain a uniformly mixed powder. The powder is placed in a mold at room temperature and cold-pressed under a pressure of 20-30 MPa to obtain a preform. The preform is then placed in a sintering furnace and heated to 330-340℃ at a rate of 45-50℃ / h, and held at that temperature for 2-4 hours. Finally, the powder is cooled to room temperature in the furnace to obtain the PTFE material.

[0023] The high-strength, compression-resistant polytetrafluoroethylene material and its preparation method of the present invention have the following advantages over the prior art:

[0024] (1) The technical solution of the present invention significantly improves the overall performance of polytetrafluoroethylene (PTFE) materials. Among them, the modified fiber filler, as the main reinforcing phase, achieves excellent flame retardant performance while providing mechanical reinforcement through the dual effects of the MOF flame retardant layer and the liquid crystal polymer molecular reinforcement layer constructed on its surface; the composite toughening agent effectively improves the brittle fracture tendency of the material through the elastic deformation energy absorption mechanism of fluororubber and the interfacial compatibility regulation effect of FEP; the compatibilizer and antioxidant ensure the long-term reliability of the composite system from the perspectives of interfacial bonding and thermal stability, respectively.

[0025] (2) The modified fiber filler components form a multifunctional synergistic system integrating flame retardancy and reinforcement, ensuring that the material maintains excellent mechanical strength and compressive strength while possessing excellent flame retardant properties. Among them, basalt fiber, as a natural inorganic material, has non-combustible properties, providing a stable inorganic skeleton for the entire flame retardant system; the MOF layer constructed on the surface not only plays a core flame retardant role, but more importantly, it produces a synergistic enhancement effect on the mechanical properties of the material. The MOF structure combines with the silanol groups on the surface of the basalt fiber through coordination bonds to form a "molecular anchoring" effect, which significantly improves the interfacial bonding strength between the fiber and the matrix. At the same time, its rigid skeleton structure can effectively disperse stress concentration and delay crack propagation when the material is subjected to external forces, and together with the siloxane structure, it undertakes the stress transfer function. The zirconium metal nodes of the MOF are transformed into zirconium oxide ceramic phase at high temperature, and together with the basalt fiber, the MOF structure forms a synergistic effect with the basalt fiber. Wuyan fiber synergistically constructs a dual inorganic flame-retardant barrier, forming a flame-retardant protection system that is both internal and external. The liquid crystal polymer modifier, with its rigid rod-shaped molecular conformation, not only acts as a "molecular steel bar" to provide mechanical reinforcement, but its aromatic ring structure can also form a stable char layer during combustion. Together with the ceramic layer produced by MOF decomposition, it constructs a composite flame-retardant barrier. Through π-π stacking, it interacts strongly with the MOF aromatic ring skeleton, ensuring the stable dispersion and effective performance of the flame-retardant components. The introduction of silane coupling agent realizes the chemical bridging of the organic-inorganic interface. Its siloxane structure can also promote the densification of the inorganic flame-retardant layer at high temperatures, enhancing the integrity of the flame-retardant barrier.

[0026] (3) The composite toughening agent adopts a compound system of fluororubber and polytetrafluoroethylene-perfluoropropylene copolymer. Through the synergistic toughening mechanism of the two, the brittle characteristics of PTFE-based composite materials are effectively improved. Fluororubber is the main toughening phase, and FEP is the compatibility modifier, which significantly improves the interfacial bonding state between fluororubber and matrix, and promotes the uniform distribution and effective transmission of stress between different phases. Detailed Implementation

[0027] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0028] It should be noted that the basalt fiber was purchased from Taian Songze Composite Materials Co., Ltd., with a specification of 6mm; the polytetrafluoroethylene-perfluoropropylene copolymer was purchased from Dongguan Ruixing New Materials Technology Co., Ltd., with the grade HX-201; and the polytetrafluoroethylene was purchased from Dongguan Ruixing New Materials Technology Co., Ltd., with the grade 7AX. Example 1

[0029] This embodiment provides a high-strength, compression-resistant polytetrafluoroethylene (PTFE) material, comprising, by weight, 85 parts PTFE, 10 parts modified fiber filler, 0.8 parts antioxidant 3114, 3 parts composite toughening agent, and 1.5 parts maleic anhydride-grafted polypropylene. The composite toughening agent is a fluororubber and PTFE-perfluoropropylene copolymer with a mass ratio of 80:20. The preparation method is as follows:

[0030] Polytetrafluoroethylene (PTFE), modified fiber filler, antioxidant, composite toughening agent, and compatibilizer were sequentially added to a high-speed mixer. The mixture was first premixed at low speed for 10 minutes, and then mixed at high speed for 20 minutes to obtain a uniformly mixed powder. The mixed powder was placed in a mold at room temperature and cold-pressed at a pressure of 25 MPa for 30 minutes to obtain a preform. The preform was placed in a sintering furnace and heated to 335°C at a rate of 48°C / h under a nitrogen protective atmosphere, and held at that temperature for 3 hours. Then, it was cooled to room temperature with the furnace to obtain the PTFE material.

[0031] The preparation method of modified fiber filler includes the following steps:

[0032] S1. Treat 100g of basalt fiber with a 10% hydrochloric acid solution at 60℃ for 2h to remove surface impurities, wash with deionized water until neutral, and dry at 110℃ for 4h to obtain pretreated basalt fiber; disperse the pretreated basalt fiber in 500ml of DMF, add 20g of zirconium tetrachloride and 15g of terephthalic acid, ultrasonically disperse evenly, transfer the mixture to a high-pressure reactor lined with polytetrafluoroethylene, heat to 115℃ and react for 23h, after the reaction is completed, cool to room temperature, filter, wash and dry to obtain composite fiber;

[0033] S2. Mix 100g of p-hydroxybenzoic acid, 50g of 6-hydroxy-2-naphtholic acid, 10g of 3,5-dihydroxybenzoic acid and 135g of acetic anhydride, and carry out acetylation reaction at 150℃ for 1.5h under nitrogen protection; then remove the acetic anhydride, add 0.24g of sodium acetate, and gradually raise the temperature to 300℃ under nitrogen protection for 5h to obtain liquid crystal polymer; cool the product to room temperature, pulverize and sieve for later use.

[0034] S3. Dissolve 100g of liquid crystal polymer in 400ml of NMP, add 20g of 3-isocyanate-propyltriethoxysilane and 0.15g of dibutyltin dilaurate, and react at 90℃ for 3h under nitrogen protection. After the reaction is complete, add a large amount of methanol to precipitate the product, filter, wash, and vacuum dry to obtain the modifier.

[0035] S4. Disperse 100g of composite fiber in 500ml of toluene, ultrasonically disperse until uniform, add 20g of modifier, heat to 90℃, stir for 6h, filter and separate after reaction, wash and dry to obtain modified fiber filler. Example 2

[0036] This embodiment provides a high-strength, compression-resistant polytetrafluoroethylene (PTFE) material, comprising, by weight, 80 parts PTFE, 8 parts modified fiber filler, 0.5 parts antioxidant 3114, 2 parts composite toughening agent, and 1 part maleic anhydride-grafted polypropylene. The composite toughening agent is a fluororubber and PTFE-perfluoropropylene copolymer with a mass ratio of 70:30. The preparation method is as follows:

[0037] Polytetrafluoroethylene (PTFE), modified fiber filler, antioxidant, composite toughening agent, and compatibilizer were sequentially added to a high-speed mixer. The mixture was first premixed at low speed for 10 minutes, and then mixed at high speed for 20 minutes to obtain a uniformly mixed powder. The mixed powder was placed in a mold at room temperature and cold-pressed at a pressure of 20 MPa for 30 minutes to obtain a preform. The preform was placed in a sintering furnace and heated to 330°C at a rate of 45°C / h under a nitrogen protective atmosphere, and held at that temperature for 4 hours. Then, it was cooled to room temperature with the furnace to obtain the PTFE material.

[0038] The preparation method of modified fiber filler includes the following steps:

[0039] S1. Treat 100g of basalt fiber with a 10% hydrochloric acid solution at 60℃ for 2h to remove surface impurities, wash with deionized water until neutral, and dry at 110℃ for 4h to obtain pretreated basalt fiber; disperse the pretreated basalt fiber in 500ml of DMF, add 15g of zirconium tetrachloride and 10g of terephthalic acid, ultrasonically disperse evenly, transfer the mixture to a high-pressure reactor lined with polytetrafluoroethylene, heat to 100℃ and react for 24h, after the reaction is completed, cool to room temperature, filter, wash and dry to obtain composite fiber;

[0040] S2. Mix 100g of p-hydroxybenzoic acid, 40g of 6-hydroxy-2-naphtholic acid, 5g of 3,5-dihydroxybenzoic acid and 120g of acetic anhydride, and carry out acetylation reaction at 140℃ for 2h under nitrogen protection; then remove the acetic anhydride, add 0.145g of sodium acetate, and gradually raise the temperature to 280℃ under nitrogen protection for 6h to obtain liquid crystal polymer; cool the product to room temperature, pulverize and sieve for later use.

[0041] S3. Dissolve 100g of liquid crystal polymer in 400ml of NMP, add 15g of 3-isocyanate-propyltriethoxysilane and 0.1g of dibutyltin dilaurate, and react at 80℃ for 4h under nitrogen protection. After the reaction is complete, add a large amount of methanol to precipitate the product, filter, wash, and vacuum dry to obtain the modifier.

[0042] S4. Disperse 100g of composite fiber in 500ml of toluene, ultrasonically disperse until uniform, add 15g of modifier, heat to 80℃, stir for 7h, filter and separate after reaction, wash and dry to obtain modified fiber filler. Example 3

[0043] This embodiment provides a high-strength, compression-resistant polytetrafluoroethylene (PTFE) material, comprising, by weight, 90 parts PTFE, 12 parts modified fiber filler, 1 part antioxidant 3114, 4 parts composite toughening agent, and 2 parts maleic anhydride-grafted polypropylene. The composite toughening agent is a fluororubber and PTFE-perfluoropropylene copolymer in a mass ratio of 85:15. The preparation method is as follows:

[0044] Polytetrafluoroethylene (PTFE), modified fiber filler, antioxidant, composite toughening agent, and compatibilizer were sequentially added to a high-speed mixer. The mixture was first premixed at low speed for 10 minutes, and then mixed at high speed for 20 minutes to obtain a uniformly mixed powder. The mixed powder was placed in a mold at room temperature and cold-pressed at a pressure of 30 MPa for 30 minutes to obtain a preform. The preform was placed in a sintering furnace and heated to 340°C at a rate of 50°C / h under a nitrogen protective atmosphere, and held at that temperature for 2 hours. Then, it was cooled to room temperature with the furnace to obtain the PTFE material.

[0045] The preparation method of modified fiber filler includes the following steps:

[0046] S1. Treat 100g of basalt fiber with a 10% hydrochloric acid solution at 60℃ for 2h to remove surface impurities, wash with deionized water until neutral, and dry at 110℃ for 4h to obtain pretreated basalt fiber; disperse the pretreated basalt fiber in 500ml of DMF, add 25g of zirconium tetrachloride and 20g of terephthalic acid, ultrasonically disperse evenly, transfer the mixture to a high-pressure reactor lined with polytetrafluoroethylene, heat to 130℃ and react for 22h, after the reaction is completed, cool to room temperature, filter, wash and dry to obtain composite fiber;

[0047] S2. Mix 100g of p-hydroxybenzoic acid, 60g of 6-hydroxy-2-naphtholic acid, 15g of 3,5-dihydroxybenzoic acid and 150g of acetic anhydride, and react at 160℃ for 1 hour under nitrogen protection. Then remove the acetic anhydride, add 0.35g of sodium acetate, and gradually raise the temperature to 320℃ for 4 hours under nitrogen protection to obtain the liquid crystal polymer. Cool the product to room temperature, pulverize and sieve for later use.

[0048] S3. Dissolve 100g of liquid crystal polymer in 400ml of NMP, add 25g of 3-isocyanate-propyltriethoxysilane and 0.2g of dibutyltin dilaurate, and react at 100℃ for 2h under nitrogen protection. After the reaction is complete, add a large amount of methanol to precipitate the product, filter, wash, and vacuum dry to obtain the modifier.

[0049] S4. Disperse 100g of composite fiber in 500ml of toluene, ultrasonically disperse until uniform, add 25g of modifier, heat to 100℃, stir for 5h, filter and separate after reaction, wash and dry to obtain modified fiber filler.

[0050] Comparative Example 1

[0051] This comparative example provides a high-strength, compression-resistant polytetrafluoroethylene material, which, by weight, comprises 85 parts of polytetrafluoroethylene, 10 parts of modified fiber filler, 0.8 parts of antioxidant 3114, 3 parts of composite toughening agent, and 1.5 parts of maleic anhydride-grafted polypropylene. The composite toughening agent is fluororubber, and the preparation method is the same as in Example 1.

[0052] Comparative Example 2

[0053] This comparative example provides a high-strength, compression-resistant polytetrafluoroethylene (PTFE) material, comprising, by weight, 85 parts PTFE, 10 parts modified fiber filler, 0.8 parts antioxidant 3114, 3 parts composite toughening agent, and 1.5 parts maleic anhydride-grafted polypropylene. The composite toughening agent is a fluororubber and PTFE-perfluoropropylene copolymer in a mass ratio of 80:20. The preparation method is the same as in Example 1, except that:

[0054] The preparation method of modified fiber filler includes the following steps:

[0055] S1. Treat 100g of basalt fiber with a 10% hydrochloric acid solution at 60℃ for 2h to remove surface impurities, wash with deionized water until neutral, and dry at 110℃ for 4h to obtain pretreated basalt fiber.

[0056] S2. Mix 100g of p-hydroxybenzoic acid, 50g of 6-hydroxy-2-naphtholic acid, 10g of 3,5-dihydroxybenzoic acid and 135g of acetic anhydride, and carry out acetylation reaction at 150℃ for 1.5h under nitrogen protection; then remove the acetic anhydride, add 0.24g of sodium acetate, and gradually raise the temperature to 300℃ under nitrogen protection for 5h to obtain liquid crystal polymer; cool the product to room temperature, pulverize and sieve for later use.

[0057] S3. Dissolve 100g of liquid crystal polymer in 400ml of NMP, add 20g of 3-isocyanate-propyltriethoxysilane and 0.15g of dibutyltin dilaurate, and react at 90℃ for 3h under nitrogen protection. After the reaction is complete, add a large amount of methanol to precipitate the product, filter, wash, and vacuum dry to obtain the modifier.

[0058] S4. Disperse 100g of pretreated basalt fiber in 500ml of toluene, ultrasonically disperse until uniform, add 20g of modifier, heat to 90℃, stir for 6h, filter and separate after reaction, wash and dry to obtain modified fiber filler.

[0059] Comparative Example 3

[0060] This comparative example provides a high-strength, compression-resistant polytetrafluoroethylene (PTFE) material, comprising, by weight, 85 parts PTFE, 10 parts modified fiber filler, 0.8 parts antioxidant 3114, 3 parts composite toughening agent, and 1.5 parts maleic anhydride-grafted polypropylene. The composite toughening agent is a fluororubber and PTFE-perfluoropropylene copolymer in a mass ratio of 80:20. The preparation method is the same as in Example 1, except that:

[0061] The preparation method of modified fiber filler includes the following steps:

[0062] S1. Treat 100g of basalt fiber with a 10% hydrochloric acid solution at 60℃ for 2h to remove surface impurities, wash with deionized water until neutral, and dry at 110℃ for 4h to obtain pretreated basalt fiber; disperse the pretreated basalt fiber in 500ml of DMF, add 20g of zirconium tetrachloride and 15g of terephthalic acid, ultrasonically disperse evenly, transfer the mixture to a high-pressure reactor lined with polytetrafluoroethylene, heat to 115℃ and react for 23h, after the reaction is completed, cool to room temperature, filter, wash and dry to obtain composite fiber;

[0063] S2. Mix 100g of p-hydroxybenzoic acid, 50g of 6-hydroxy-2-naphtholic acid, 10g of 3,5-dihydroxybenzoic acid and 135g of acetic anhydride, and carry out acetylation reaction at 150℃ for 1.5h under nitrogen protection; then remove the acetic anhydride, add 0.24g of sodium acetate, and gradually raise the temperature to 300℃ under nitrogen protection for 5h to obtain liquid crystal polymer; cool the product to room temperature, pulverize and sieve for later use.

[0064] S3. Disperse 100g of composite fiber in 500ml of toluene, ultrasonically disperse until uniform, add 20g of liquid crystal polymer, heat to 90℃, stir for 6h, filter and separate after reaction, wash and dry to obtain modified fiber filler.

[0065] Comparative Example 4

[0066] This comparative example provides a high-strength, compression-resistant polytetrafluoroethylene (PTFE) material, comprising, by weight, 85 parts PTFE, 10 parts modified fiber filler, 0.8 parts antioxidant 3114, 3 parts composite toughening agent, and 1.5 parts maleic anhydride-grafted polypropylene. The composite toughening agent is a fluororubber and PTFE-perfluoropropylene copolymer in a mass ratio of 80:20. The preparation method is the same as in Example 1, except that:

[0067] The preparation method of modified fiber filler includes the following steps:

[0068] S1. Treat 100g of basalt fiber with a 10% hydrochloric acid solution at 60℃ for 2h to remove surface impurities, wash with deionized water until neutral, and dry at 110℃ for 4h to obtain pretreated basalt fiber.

[0069] S2. Add 20g zirconium tetrachloride and 15g terephthalic acid and disperse them in 500ml DMF. Disperse them evenly by ultrasonication. Transfer the mixture to a high-pressure reactor with a polytetrafluoroethylene liner. Heat the mixture to 115℃ and react for 23h. After the reaction is completed, cool it to room temperature. After filtration, washing and drying, obtain UiO-66 type MOF powder.

[0070] S3. Mix 100g of p-hydroxybenzoic acid, 50g of 6-hydroxy-2-naphtholic acid, 10g of 3,5-dihydroxybenzoic acid and 135g of acetic anhydride, and carry out acetylation reaction at 150℃ for 1.5h under nitrogen protection; then remove the acetic anhydride, add 0.24g of sodium acetate, and gradually raise the temperature to 300℃ under nitrogen protection for 5h to obtain liquid crystal polymer; cool the product to room temperature, pulverize and sieve for later use.

[0071] S4. Disperse 100g of pretreated basalt fiber in 500ml of toluene, ultrasonically disperse it evenly, add 20g of UiO-66 type MOF powder and 20g of liquid crystal polymer, use acetone as the dispersion medium, ball mill at 200rpm for 2h; then filter to remove acetone, vacuum dry at 60℃ for 8h to obtain modified fiber filler.

[0072] Performance testing

[0073] The polytetrafluoroethylene (PTFE) materials prepared in the examples and comparative examples were subjected to performance testing. The test indicators included tensile strength, elongation at break, and compressive creep. Tensile strength and elongation at break were tested according to GB / T 1040-1992. The compressive creep test method used a compression creep tester with cylindrical specimens of 20mm × 20mm. The test temperatures were room temperature and 150℃, the compressive load was 15MPa, and the test time was 60 hours. The compressive deformation value measured after 60 hours was calculated as (sample volume before test - sample volume after test) / sample volume after test × 100%. The test results are shown in Table 1.

[0074] Table 1 Performance Testing

[0075]

[0076] As shown in Table 1, the polytetrafluoroethylene material prepared by the technical solution of this invention has good comprehensive performance, achieving a synergistic improvement in tensile strength and compressive strength. The performance of Comparative Examples 1-4 is significantly lower than that of the Examples. The reasons for this are as follows: in Comparative Example 1, the lack of polytetrafluoroethylene-perfluoropropylene copolymer leads to a decrease in its mechanical properties; in Comparative Example 2, the lack of UiO-66 type MOF crystal structure leads to a certain decrease in its toughness and compressive strength. In Comparative Example 3, the toughness and compressive strength are worse, but the elongation at break is better than that of Comparative Example 2. This is because Comparative Example 3 uses a physical blending method of liquid crystal polymer and composite fiber, which lacks the chemical bond formed by the reaction of isocyanate groups and hydroxyl groups in step S3 and the covalent bond established by the silane coupling mechanism in step S4. This results in only weak interactions such as van der Waals forces at the interface between the liquid crystal polymer and the fiber. However, it is precisely this "free state" without chemical bond constraints that makes the liquid crystal polymer molecular chain more free, allowing the molecular chain to undergo plastic deformation under stress, thus exhibiting a better elongation at break than Comparative Example 2. In Comparative Example 4, physical blending was used, but the interfacial bonding strength was low, which still affected its mechanical properties.

[0077] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-strength, compression-resistant polytetrafluoroethylene material, characterized in that, By weight, it includes 80-90 parts of polytetrafluoroethylene, 8-12 parts of modified fiber filler, 0.5-1 part of antioxidant, 2-4 parts of composite toughening agent, and 1-2 parts of compatibilizer; the composite toughening agent includes fluororubber and polytetrafluoroethylene-perfluoropropylene copolymer, and the mass ratio of fluororubber to polytetrafluoroethylene-perfluoropropylene copolymer is 70-85:15-30; The preparation method of modified fiber filler includes the following steps: S1. After acid treatment, basalt fibers are dispersed in DMF, zirconium tetrachloride and terephthalic acid are added, ultrasonically dispersed evenly, transferred to a reaction vessel, heated to 100-130℃ and reacted for 22-24 hours to obtain composite fibers; S2. Mix p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, 3,5-dihydroxybenzoic acid and acetic anhydride, and heat to 140-160℃ for acetylation reaction for 1-2 hours; then remove acetic anhydride, add catalyst, and gradually heat to 280-320℃ under nitrogen protection for 4-6 hours to obtain liquid crystal polymer. S3. Dissolve the liquid crystal polymer in NMP, add 3-isocyanate-propyltriethoxysilane and dibutyltin dilaurate at 80-100℃, and react for 2-4 hours to obtain the modifier. S4. Disperse the composite fibers in toluene, add a modifier, heat to 80-100℃, and stir for 5-7 hours to obtain the modified fiber filler.

2. The high-strength, compression-resistant polytetrafluoroethylene material as described in claim 1, characterized in that: In step S1, the mass ratio of basalt fiber, zirconium tetrachloride, and terephthalic acid is 100 : (15-25) : (10-20).

3. The high-strength, compression-resistant polytetrafluoroethylene material as described in claim 1, characterized in that: In step S2, the mass ratio of p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, 3,5-dihydroxybenzoic acid and acetic anhydride is 100 : (40-60) : (5-15) : (120-150), and the amount of catalyst added is 0.1-0.2% of the total mass of p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid and 3,5-dihydroxybenzoic acid.

4. The high-strength, compression-resistant polytetrafluoroethylene material as described in claim 1, characterized in that: In step S2, the catalyst is potassium acetate, sodium acetate, or magnesium acetate.

5. The high-strength, compression-resistant polytetrafluoroethylene material as described in claim 1, characterized in that: In step S3, the mass ratio of the liquid crystal polymer, 3-isocyanate-propyltriethoxysilane and dibutyltin dilaurate is 100 : (15-25): 0.1-0.

2.

6. The high-strength, compression-resistant polytetrafluoroethylene material as described in claim 1, characterized in that: In step S4, the mass ratio of composite fiber to modifier is 100 : (15-25).

7. The high-strength, compression-resistant polytetrafluoroethylene material as described in claim 1, characterized in that: The antioxidant is any one of antioxidant 1010, antioxidant 3114, antioxidant 703 and antioxidant DSTDP, and the compatibilizer is maleic anhydride-grafted polypropylene.

8. A method for preparing a high-strength, compression-resistant polytetrafluoroethylene material as described in any one of claims 1-7, characterized in that: The preparation method includes the following steps: Polytetrafluoroethylene (PTFE), modified fiber filler, antioxidant, composite toughening agent, and compatibilizer are mixed to obtain a uniformly mixed powder. The powder is placed in a mold at room temperature and cold-pressed under a pressure of 20-30 MPa to obtain a preform. The preform is then placed in a sintering furnace and heated to 330-340℃ at a rate of 45-50℃ / h, and held at that temperature for 2-4 hours. Finally, the powder is cooled to room temperature in the furnace to obtain the PTFE material.

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