An enhanced polytetrafluoroethylene composite backbone structure composite material

Abstract

The application discloses an enhanced polytetrafluoroethylene composite framework structure composite material and a preparation method thereof. The material is composed of polysulfone modified polytetrafluoroethylene resin, carbon fiber, molybdenum disulfide, a reactive silicone resin precursor and a platinum catalyst, a continuous three-dimensional siloxane network is constructed in situ at the interface through a silicon hydrogen addition cross-linking, and a multi-scale reinforced framework structure is formed in cooperation with the carbon fiber. The material has excellent mechanical properties, creep resistance and wear resistance, and is suitable for high-performance sealing and wear-resistant fields.

Description

Technical Field

[0001] This invention relates to the technical field of polytetrafluoroethylene (PTFE), and in particular to a reinforced PTFE composite skeleton structure composite material. Background Technology

[0002] Polytetrafluoroethylene (PTFE) is a typical fluorinated polymer material with excellent high and low temperature resistance, corrosion resistance, self-lubricating properties, and electrical insulation properties. It is widely used in sealing materials, wear-resistant parts, and chemical corrosion protection. However, PTFE is a highly crystalline polymer with weak intermolecular forces, resulting in low elastic modulus and poor creep resistance. Under long-term loads and high temperatures, it is prone to cold flow, thus limiting its application in high-end equipment.

[0003] To improve the mechanical properties and creep resistance of PTFE, existing technologies typically modify it by introducing fillers such as carbon fibers, glass fibers, inorganic fillers, or solid lubricants, or by introducing organic-inorganic hybrid components such as silicone resins to construct composite structures. The aim is to form a reinforcing skeleton or network structure within the material, thereby improving its dimensional stability and wear resistance. For example, Chinese patent (CN112480578A) discloses a PTFE composite material based on a cage-like skeleton structure and its preparation method. By introducing silicone resin micropowder containing vinyl groups and silane bonds, a cross-linked network is formed during heat treatment using a hydrosilylation reaction. This network, together with the fiber reinforcement phase, constructs a so-called "skeleton structure" to achieve structural constraint on the PTFE matrix.

[0004] However, the aforementioned composite system in the existing technology still has certain shortcomings. On the one hand, PTFE is usually produced by dry mixing and cold pressing, with each component physically mixed at temperatures below 30°C. Since the silicone resin is dispersed in the form of micro-powder, the particle size is small and it is prone to agglomeration, making it difficult to achieve uniform distribution in the PTFE powder. On the other hand, in the subsequent heat treatment stage at 200–250°C, the vinyl groups in the silicone resin micro-powder undergo hydrosilylation with the Si-H bonds, but due to the lack of an effective catalyst in the system, the reaction kinetics are limited, and the degree of crosslinking is limited.

[0005] Under the combined influence of the above factors, the crosslinking reaction of silicone resin is often limited to the interior of local microparticles or their adjacent regions, making it difficult to form a continuous three-dimensional crosslinked network structure throughout the entire composite material system. This results in a clearly discretized "skeleton structure." This discretized structure makes it difficult to achieve effective stress transfer and molecular chain constraint on a macroscopic scale, thus leaving the material with shortcomings in creep resistance, structural stability, and long-term service performance.

[0006] Therefore, how to achieve uniform dispersion and efficient cross-linking reaction of silicone resin components in a PTFE-based composite system, and thus construct a continuous and stable three-dimensional reinforced skeleton structure, is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0007] This application provides a reinforced polytetrafluoroethylene composite skeleton structure composite material, comprising the following components in parts by mass:

[0008] 70-90 parts of polysulfone-modified polytetrafluoroethylene resin;

[0009] 10-30 parts of carbon fiber;

[0010] 1-10 parts of molybdenum disulfide;

[0011] 5-25 parts of reactive silicone resin precursor;

[0012] 0.01 to 1 part of platinum-based catalyst.

[0013] It should be noted that, firstly, the introduction of polar functional groups into the surface of polytetrafluoroethylene particles after plasma activation and grafting with polysulfone oligomers significantly improves the interfacial compatibility and interfacial bonding strength between the matrix and the subsequent siloxane system and carbon fibers; secondly, the reactive silicone resin precursor containing Si-H bonds and vinyl groups undergoes a typical hydrosilylation reaction at 150–250°C under the action of a platinum-based catalyst, forming a continuous three-dimensional cross-linked siloxane network in situ on the particle surface and interfacial region. This network, on the one hand, enables the PTFE to decompose... The spatial confinement and physical constraint of the sub-chains suppress segment slippage and cold flow behavior. On the other hand, as a "bridging phase," the carbon fiber is effectively coupled to the matrix, constructing a continuous load transfer path. At the same time, the carbon fiber, as a high-modulus reinforcing phase, bears the main stress and improves the overall rigidity, while molybdenum disulfide forms an easily shearable solid lubricating layer at the micro-contact interface, reducing the friction coefficient and slowing down wear. Finally, during the high-temperature sintering stage, the PTFE crystal regions rearrange and densify. In this scheme, the polysulfone-modified polytetrafluoroethylene resin is a modified powder with a surface activated by plasma and grafted with polysulfone oligomers.

[0014] It should be noted that the polysulfone-modified polytetrafluoroethylene resin is a modified powder whose surface has been plasma-activated and grafted with polysulfone oligomers. This modification process introduces polar functional groups and flexible segments on the surface of PTFE particles, which significantly improves the interfacial compatibility and bonding strength between the matrix and carbon fibers and reactive silicone resin precursors, thus laying a solid foundation for the subsequent in-situ formation of a continuous three-dimensional cross-linked network and a multi-scale synergistic structure of rigid skeleton + flexible network.

[0015] As a preferred technical solution for an enhanced polytetrafluoroethylene composite skeleton structure composite material, the reactive silicone resin precursor is a bifunctional siloxane oligomer with a molecular weight of 500 to 5000, whose molecular chain contains both Si-H bonds and vinyl-substituted siloxane units.

[0016] It should be noted that the reactive silicone resin precursor is a bifunctional siloxane oligomer with a molecular weight of 500-5000. Its molecular chain contains both Si-H bonds and vinyl-substituted siloxane units. This low molecular weight design endows the precursor with excellent flowability and surface wettability, which can form a uniform and continuous coating layer on the surface of polysulfone-modified PTFE particles in situ during the mixing process. Under the action of a platinum-based catalyst, during the first stage of heat preservation at 150-250℃, a hydrosilylation crosslinking reaction is efficiently induced, thereby constructing a continuous and interconnected three-dimensional siloxane crosslinking network in situ. This achieves spatial confinement and physical binding of the PTFE molecular chain, suppresses cold flow behavior, and acts as a bridging phase to tightly couple the carbon fiber reinforcement phase with the matrix. This provides key support for the subsequent high-temperature sintering stage and the densification of the PTFE crystal regions to form a multi-scale synergistic structure of rigid skeleton + flexible network.

[0017] As a preferred technical solution for a reinforced polytetrafluoroethylene composite skeleton structure composite material, the carbon fiber is at least one of continuous carbon fiber, chopped carbon fiber, or carbon fiber fabric, and the carbon fiber is distributed in the reinforcing phase of the composite skeleton structure.

[0018] It should be noted that the carbon fiber is at least one of continuous carbon fiber, chopped carbon fiber, or carbon fiber fabric, and is distributed in the reinforcing phase of the composite skeleton structure. As a rigid reinforcing phase with high modulus and high strength, it can significantly improve the overall mechanical strength and creep resistance of the composite material. At the same time, it works synergistically with the in-situ formed flexible siloxane crosslinking network to construct an efficient load transfer path and achieve a multi-scale reinforcement effect that combines rigidity and flexibility in the material.

[0019] As a preferred technical solution for an enhanced polytetrafluoroethylene composite skeleton structure composite material, the platinum-based catalyst is selected from at least one of chloroplatinic acid, Karstedt catalyst, or supported platinum catalyst.

[0020] It should be noted that during the first-stage heat preservation process at 150–250℃, the Si-H bond in the reactive silicone resin precursor can be efficiently catalyzed to undergo hydrosilylation and crosslinking with vinyl groups, achieving rapid, uniform, and high-conversion crosslinking at low temperatures. This results in the in-situ formation of a continuous and interconnected three-dimensional siloxane network on the surface and interface of polysulfone-modified PTFE particles, providing a key guarantee for constructing a multi-scale composite structure with synergistic reinforcement of a rigid carbon fiber skeleton and a flexible crosslinking network.

[0021] This application also provides a method for preparing the composition, comprising the following steps:

[0022] Step S1. Dry mix polysulfone modified polytetrafluoroethylene resin with carbon fiber, add reactive silicone resin precursor and platinum catalyst to form a continuous coating layer on the particle surface, and then add molybdenum disulfide and mix evenly.

[0023] Step S2. Press the preform under a pressure of 30–90 MPa;

[0024] Step S3. Staged heat treatment:

[0025] First stage: Incubate at 150-250℃ to induce hydrosilylation crosslinking reaction;

[0026] The second stage involves holding the polytetrafluoroethylene body at 300–380℃ to sinter it.

[0027] Step S4. Cool in the furnace or in a controlled manner to obtain the finished product.

[0028] It should be noted that in the preparation process of this reinforced polytetrafluoroethylene composite skeleton structure composite material, the modified PTFE resin with surface activated by plasma and grafted with polysulfone oligomers is first dry-mixed with carbon fibers. This step utilizes polysulfone modification to introduce polar functional groups on the surface of PTFE particles, significantly improving the interfacial compatibility and bonding strength between the matrix and carbon fibers and subsequent siloxane components. Subsequently, a reactive silicone resin precursor with a molecular weight of 500-5000 containing both Si-H bonds and vinyl groups, and a platinum-based catalyst are added. Due to its low molecular weight and good flowability, the precursor can form a uniform and continuous coating layer in situ on the surface of the mixed particles. Then, molybdenum disulfide is added to achieve uniform dispersion of the solid lubricating phase, thereby providing an ideal microenvironment for subsequent reactions. At 30-90°C... After obtaining a high-density preform under MPa pressure, the material undergoes a phased heat treatment process. In the first stage, during heat treatment at 150–250℃, a platinum catalyst efficiently catalyzes the hydrosilylation crosslinking reaction, forming a continuous three-dimensional siloxane crosslinking network in situ on the particle surface and interface region. This network spatially confines and physically binds the PTFE molecular chains, effectively suppressing their segment slippage and cold flow behavior. Simultaneously, it acts as a "bridging phase," tightly coupling the high-modulus carbon fiber reinforcement phase with the matrix, constructing an efficient load transfer path. In the second stage, the temperature is raised to 300–380℃ and held, causing the PTFE matrix to sinter and densify. This synergistic coupling effect occurs between the PTFE matrix and the already formed crosslinking network and carbon fiber reinforcement phase, ultimately constructing a multi-scale composite structure combining a rigid fiber skeleton, a flexible crosslinking network, and a lubricating phase. Finally, during furnace cooling or controlled cooling, the multi-scale structure inside the material is stabilized and solidified, thereby achieving simultaneous optimization of mechanical strength, creep resistance, and wear resistance on a macroscopic scale.

[0029] As a preferred embodiment of the preparation method of the composition, the preparation process of the polysulfone-modified polytetrafluoroethylene resin is as follows:

[0030] First, polytetrafluoroethylene powder is surface activated by low-temperature plasma, and then grafted in a solution containing polysulfone oligomers and bridging agents at 80°C. The product is then obtained by solvent removal and heat treatment at 200°C.

[0031] As a preferred embodiment of a method for preparing a composition, the preparation process of the reactive silicone resin precursor is as follows:

[0032] Using linear oligosiloxanes as raw materials, ring-opening co-condensation reaction is carried out by introducing monomers containing Si-H bonds and vinyl groups, controlling the vinyl groups to be statistically distributed on the main chain, and removing low-molecular-weight byproducts under reduced pressure.

[0033] This invention significantly improves the surface polarity and interfacial compatibility of the matrix by introducing a modified resin, which is plasma-activated and grafted with polysulfone oligomers, into the polytetrafluoroethylene matrix. Simultaneously, a reactive silicone resin precursor containing Si-H bonds and vinyl groups undergoes a highly efficient hydrosilylation crosslinking reaction under a platinum-based catalyst, constructing a continuous three-dimensional siloxane network structure in situ on the particle surface and interfacial region. This network effectively confines and physically binds the polytetrafluoroethylene molecular chains, significantly suppressing cold flow and creep behavior. Furthermore, it acts as a flexible bridging phase, tightly coupling the carbon fiber reinforcement phase with the matrix to create an efficient load transfer path. Meanwhile, the carbon fiber provides high-modulus rigid support, and molybdenum disulfide forms a low-shear lubricating interface. The synergistic effect of these multiple components constructs a multi-scale composite structure of "rigid skeleton + flexible crosslinking network + lubricating phase," thereby significantly improving the material's mechanical strength, creep resistance, and wear resistance. This effectively overcomes the performance deficiencies caused by uneven silicone resin dispersion and discontinuous crosslinking in existing technologies. Attached Figure Description

[0034] Figure 1 Infrared spectrum of polysulfone-modified polytetrafluoroethylene resin powder prepared in Example 1.

[0035] Figure 2 Infrared spectrum of the reactive silicone resin precursor prepared in Example 2. Detailed Implementation

[0036] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0037] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0038] Secondly, the term "an embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places throughout this specification does not necessarily refer to the same embodiment, nor is it a single embodiment or an embodiment selectively excluded from other embodiments.

[0039] Preparation Example 1: Preparation of Polysulfone Modified Polytetrafluoroethylene Resin

[0040] 1000g of polytetrafluoroethylene (PTFE) powder was weighed and placed in a plasma reaction chamber containing a nitrogen inert atmosphere. The chamber pressure was controlled at 0.5 Torr. The surface of the PTFE particles was activated for 30 minutes using low-temperature plasma (300W power, 13.56MHz frequency) to introduce active free radicals and oxygen-containing polar groups onto the PTFE particle surface. The surface-activated PTFE powder was then transferred to a reaction vessel and dispersed in an N-methylpyrrolidone (NMP) organic solution containing 120g of polysulfone oligomer (number average molecular weight approximately 3000) and 15g of bridging agent (vinyltriethoxysilane). The total solid content of the solution was controlled at 15wt%. The reaction was carried out at 80°C. The mixture was stirred and reacted at ℃ for 6 hours to carry out a grafting reaction, so that the polysulfone oligomers were chemically bonded to the surface of PTFE particles through a bridging agent. After the reaction was completed, the temperature was gradually increased (60℃ for 1 hour → 100℃ for 1 hour → 120℃ for 2 hours) and the solvent was removed by depressurization (-0.08MPa) until the residual solvent was less than 0.5wt%. The resulting powder was then subjected to short-term heat treatment at 200℃ for 2 hours and cooled to room temperature to obtain polysulfone-modified polytetrafluoroethylene resin powder with polysulfone oligomers grafted on the surface.

[0041] Preparation Example 2: Preparation of Reactive Silicone Resin Precursor

[0042] Under a strictly anhydrous and oxygen-free nitrogen-protected inert atmosphere, 500 g of linear oligomeric siloxane (mainly octamethylcyclotetrasiloxane D4, with an average molecular weight of approximately 400) was added as a base material to a reactor equipped with a stirrer, thermometer, and condenser. Subsequently, 120 g of 1,3,5,7-tetramethylcyclotetrasiloxane (D4H) containing Si-H bonds and 80 g of 1,3,5,7-tetravinyltetramethylcyclotetrasiloxane (D4Vi) containing vinyl groups were added simultaneously, along with 0.02 wt% tetramethylammonium hydroxide silanolate as a catalyst. The ring-opening co-condensation reaction was carried out at 95°C for 8 hours. Hydrogen-based siloxane segments containing Si-H bonds and vinyl-substituted siloxane units were introduced to obtain a crude bifunctional siloxane oligomer containing both Si-H and C=C double bonds. After the reaction, the system was heated to 120°C for structure regulation and held for 3 hours to ensure that the vinyl groups were statistically distributed on the siloxane backbone. Subsequently, low-molecular-weight byproducts were removed under reduced pressure of 110°C and -0.09 MPa. By controlling the reaction time and feed ratio, the number-average molecular weight of the product was precisely controlled within the range of 500 to 5000, ultimately yielding a transparent, low-viscosity reactive silicone resin precursor with excellent flowability and reactivity.

[0043] Example 1

[0044] Formulation (parts by weight): 70 parts of polysulfone modified polytetrafluoroethylene resin (Preparation Example 1); 10 parts of short-cut carbon fiber (3 mm in length); 1 part of molybdenum disulfide (average particle size 5 μm); 5 parts of reactive silicone resin precursor (Preparation Example 2); 0.01 parts of Karstedt catalyst.

[0045] Preparation method:

[0046] Step S1: Place 70 parts of polysulfone-modified polytetrafluoroethylene resin and 10 parts of chopped carbon fibers in a high-speed mixer and dry mix at room temperature for 15 minutes to uniformly disperse the carbon fibers between the resin particles; then slowly add 5 parts of reactive silicone resin precursor and 0.01 parts of cassiterite catalyst, and continue high-speed stirring for 20 minutes to form a uniform and continuous coating layer on the surface of the modified PTFE particles; finally, add 1 part of molybdenum disulfide and continue mixing for 10 minutes until completely homogeneous.

[0047] Step S2: The above mixture is loaded into the mold under a pressure of 30 MPa, pressed at room temperature, and held for 10 minutes to obtain a high-density blank.

[0048] Step S3: Staged heat treatment. In the first stage, the green body is heated to 150°C and held for 4 hours to induce hydrosilylation crosslinking reaction. In the second stage, the temperature is further increased to 300°C and held for 3 hours to fully sinter the polytetrafluoroethylene body.

[0049] Step S4: Allow the furnace to cool naturally to room temperature to obtain the finished composite material.

[0050] Example 2

[0051] Formulation (parts by weight): 90 parts polysulfone modified polytetrafluoroethylene resin; 30 parts short-cut carbon fiber (3 mm in length); 10 parts molybdenum disulfide (average particle size 5 μm); 25 parts reactive silicone resin precursor; 1 part chloroplatinic acid.

[0052] Preparation method:

[0053] Step S1: Place 90 parts of polysulfone-modified polytetrafluoroethylene resin and 30 parts of chopped carbon fiber in a high-speed mixer and dry mix at room temperature for 20 minutes to uniformly disperse the carbon fiber between the resin particles; then slowly add 25 parts of reactive silicone resin precursor and 1 part of chloroplatinic acid, and continue high-speed stirring for 25 minutes to form a uniform and continuous coating layer on the surface of the modified PTFE particles; finally, add 10 parts of molybdenum disulfide and continue mixing for 15 minutes until completely homogeneous.

[0054] Step S2: The above mixture is loaded into the mold under a pressure of 90 MPa, pressed at room temperature, and held for 20 minutes to obtain a high-density blank.

[0055] Step S3: Staged heat treatment. In the first stage, the green body is heated to 250°C and held for 2 hours to induce hydrosilylation crosslinking reaction. In the second stage, the temperature is further increased to 380°C and held for 1 hour to fully sinter the polytetrafluoroethylene body.

[0056] Step S4: Controlled cooling to room temperature (cooling rate 2℃ / min) to obtain the finished composite material.

[0057] Example 3

[0058] Formulation (parts by weight): 70 parts polysulfone modified polytetrafluoroethylene resin; 30 parts short-cut carbon fiber (3 mm in length); 10 parts molybdenum disulfide (average particle size 5 μm); 5 parts reactive silicone resin precursor; 1 part supported platinum catalyst.

[0059] Preparation method:

[0060] Step S1: Place 70 parts of polysulfone-modified polytetrafluoroethylene resin and 30 parts of chopped carbon fiber in a high-speed mixer and dry mix at room temperature for 15 minutes to uniformly disperse the carbon fiber between the resin particles; then slowly add 5 parts of reactive silicone resin precursor and 1 part of supported platinum catalyst, and continue high-speed stirring for 20 minutes to form a uniform and continuous coating layer on the surface of the modified PTFE particles; finally, add 10 parts of molybdenum disulfide and continue mixing for 10 minutes until completely homogeneous.

[0061] Step S2: The above mixture is loaded into the mold under a pressure of 50 MPa, pressed at room temperature, and held for 12 minutes to obtain a high-density blank.

[0062] Step S3: Staged heat treatment. In the first stage, the green body is heated to 200°C and held for 3 hours to induce hydrosilylation crosslinking reaction. In the second stage, the temperature is further increased to 340°C and held for 2.5 hours to fully sinter the polytetrafluoroethylene body.

[0063] Step S4: Allow the furnace to cool naturally to room temperature to obtain the finished composite material.

[0064] Example 4

[0065] Formulation (parts by weight): 90 parts of polysulfone modified polytetrafluoroethylene resin (Preparation Example 1); 20 parts of short-cut carbon fiber (3 mm in length); 5 parts of molybdenum disulfide (average particle size 5 μm); 25 parts of reactive silicone resin precursor (Preparation Example 2); 0.5 parts of Karstedt catalyst.

[0066] Preparation method:

[0067] Step S1: Place 90 parts of polysulfone-modified polytetrafluoroethylene resin and 20 parts of chopped carbon fibers in a high-speed mixer and dry mix at room temperature for 15 minutes to uniformly disperse the carbon fibers between the resin particles; then slowly add 25 parts of reactive silicone resin precursor and 0.5 parts of cassiterite catalyst, and continue high-speed stirring for 25 minutes to form a uniform and continuous coating layer on the surface of the modified PTFE particles; finally, add 5 parts of molybdenum disulfide and continue mixing for 10 minutes until completely homogeneous.

[0068] Step S2: The above mixture is loaded into the mold under a pressure of 70 MPa, pressed at room temperature, and held for 15 minutes to obtain a high-density blank.

[0069] Step S3: Staged heat treatment. In the first stage, the green body is heated to 220°C and held for 2.5 hours to induce hydrosilylation crosslinking reaction. In the second stage, the temperature is further increased to 350°C and held for 2 hours to allow the polytetrafluoroethylene body to be fully sintered.

[0070] Step S4: Allow the furnace to cool naturally to room temperature to obtain the finished composite material.

[0071] Comparative Example 1 (The difference between this example and Example 1 is that polysulfone-modified polytetrafluoroethylene resin was not used; instead, ordinary unmodified PTFE powder was used directly. The rest of the formulation and process are exactly the same.)

[0072] Formulation (parts by weight): 70 parts of ordinary unmodified PTFE powder; 10 parts of short-cut carbon fiber (3 mm in length); 1 part of molybdenum disulfide (average particle size 5 μm); 5 parts of reactive silicone resin precursor; 0.01 parts of cassiterite catalyst.

[0073] Preparation Method: Step S1: Place 70 parts of ordinary unmodified PTFE powder and 10 parts of chopped carbon fiber in a high-speed mixer and dry mix at room temperature for 15 minutes; then slowly add 5 parts of reactive silicone resin precursor and 0.01 parts of cassiterite catalyst, and continue high-speed stirring for 20 minutes; finally add 1 part of molybdenum disulfide and continue mixing for 10 minutes until completely homogeneous. Step S2: Press and mold under 30 MPa pressure, hold for 10 minutes to obtain a green body. Step S3: First stage: heat to 150℃ and hold for 4 hours; second stage: heat to 300℃ and hold for 3 hours. Step S4: Allow to cool naturally to room temperature in the furnace to obtain the finished product.

[0074] Comparative Example 2 (compared to Example 1, the difference is that no reactive silicone resin precursor was added, but the rest of the formulation and process are exactly the same)

[0075] Formulation (parts by weight): 70 parts of polysulfone modified polytetrafluoroethylene resin; 10 parts of short-cut carbon fiber (3 mm in length); 1 part of molybdenum disulfide (average particle size 5 μm); 0.01 parts of cassiterite catalyst (0 parts of reactive silicone resin precursor).

[0076] Preparation method: Step S1: Place 70 parts of polysulfone-modified polytetrafluoroethylene resin and 10 parts of chopped carbon fiber in a high-speed mixer and dry mix at room temperature for 15 minutes; then directly add 0.01 parts of cassiterite catalyst and continue high-speed stirring for 20 minutes; finally add 1 part of molybdenum disulfide and continue mixing for 10 minutes until completely homogeneous. Step S2: Press and mold under 30 MPa pressure, hold for 10 minutes to obtain a green body. Step S3: First stage: heat to 150℃ and hold for 4 hours; second stage: heat to 300℃ and hold for 3 hours. Step S4: Allow to cool naturally to room temperature in the furnace to obtain the finished product.

[0077] Comparative Example 3 (compared to Example 1, the difference is that 5 parts of the original reactive silicone resin precursor and 0.01 parts of platinum-based catalyst were replaced with 5 parts of silicone resin micro powder containing perfluorocarbon groups, crosslinkable ethylene bonds and silane bonds as described in CN112480578B; the rest of the formulation, raw material preparation process and all process conditions were exactly the same)

[0078] Formula (parts by weight): 70 parts of polysulfone modified polytetrafluoroethylene resin; 10 parts of short-cut carbon fiber (3 mm in length); 1 part of molybdenum disulfide (average particle size 5 μm); 5 parts of silicone resin micro powder containing perfluorocarbon groups, crosslinkable ethylene bonds and silane bonds as described in CN112480578B.

[0079] Preparation method: Step S1: Place 70 parts of polysulfone-modified polytetrafluoroethylene resin and 10 parts of chopped carbon fibers in a high-speed mixer and dry mix for 15 minutes at room temperature to uniformly disperse the carbon fibers among the resin particles; then slowly add 5 parts of silicone resin micropowder containing perfluorocarbon groups, crosslinkable ethylene bonds, and silane bonds as described in CN112480578B, and continue high-speed stirring for 20 minutes to form a coating layer on the surface of the modified PTFE particles; finally, add 1 part of molybdenum disulfide and continue mixing for 10 minutes until completely homogeneous. Step S2: Load the above mixture into a mold under a pressure of 30 MPa, press it at room temperature, and hold the pressure for 10 minutes to obtain a high-density preform. Step S3: Perform staged heat treatment. In the first stage, heat the preform to 150°C and hold for 4 hours to induce a hydrosilylation crosslinking reaction; in the second stage, continue heating to 300°C and hold for 3 hours to fully sinter the polytetrafluoroethylene body. Step S4: Allow the furnace to cool naturally to room temperature to obtain the finished composite material.

[0080] Performance testing methods

[0081] 1. Mechanical properties: Type 1 dumbbell-shaped tensile specimens (4 mm thick, 10 mm wide parallel sections) were prepared according to GB / T 1040.1-2006 standard, and bending specimens (80 mm × 10 mm × 4 mm) were prepared according to GB / T 9341-2008 standard. Tests were conducted using an electronic universal testing machine at room temperature (23 ± 2 °C). Tensile tests were performed at a speed of 5 mm / min, and tensile strength, tensile modulus, and elongation at break were recorded. Bending tests were performed using the three-point bending method with a span of 64 mm and a loading speed of 2 mm / min, and bending strength and bending modulus were recorded. At least five parallel samples were tested for each specimen, and the average value was taken.

[0082] 2. Creep resistance: Cylindrical compression specimens (10 mm in diameter and 10 mm in height) were prepared according to GB / T 15048 standard. A compression creep testing machine was used to continuously load the specimens at a constant compressive stress of 20 MPa in a 100℃ environment for 168 hours, and the creep strain versus time curves were recorded in real time. The creep length, steady-state creep rate, and creep modulus after 168 hours were calculated.

[0083] 3. Wear resistance was tested according to GB / T 3960-2016 standard using a pin-disc friction and wear testing machine with dry sliding friction. The wear part was a 45# steel ring (surface roughness Ra 0.4μm). A load of 200N was applied, the rotation speed was 200r / min, and the test time was 30min. The average dynamic friction coefficient during the steady-state phase was recorded in real time. After the test, the mass loss of the sample was measured using a precision electronic balance (accuracy 0.0001g). The specific wear rate (mm) was calculated by combining the sample density, load, and sliding distance. 3 / N·m), each sample was tested 3 times and the average value was taken.

[0084] Table 1. Experimental data of Examples 1 to 4 and Comparative Examples 1 to 3

[0085] Combined with preparation example 1 and Figure 1 It can be seen that at 3400 cm -1 A broad and sharp OH stretching vibration peak appears at 1720 cm⁻¹. -1 and 1710 cm -1 The peaks at 3050 cm⁻¹ correspond to the C=O and -COOH carbonyl / carboxyl groups introduced by plasma activation, respectively, indicating that oxygen-containing polar groups were successfully introduced onto the surface of the PTFE particles; -1 and 2920 cm -1 The aromatic / aliphatic CH stretching peak and 1585 cm⁻¹ -1 1485cm -1 The aromatic ring C=C skeleton vibration peak, combined with 1325 cm⁻¹ -1 (-SO2- asymmetric stretching), 1145 cm -1 (-SO2- symmetric stretching) and 1240 cm -1 1100 cm -1 The COC ether bond peaks together confirm that the polysulfone oligomer was chemically grafted via a vinyltriethoxysilane bridging agent; the strongest peak was at 1215 cm⁻¹. -1 and 1150 cm -1 The bimodal absorption is a characteristic feature of the stretching vibration of the PTFE backbone CF, proving the integrity of the matrix structure; 1080 cm⁻¹ -1 (Si-O stretching) and 800 cm -1 (Si-C stretching) and 1015 cm -1 The Si-O-Si auxiliary peak indicates that the silane bridging agent has been stably bonded to the surface; in addition, there are also 8 low-intensity clutter peaks in the spectrum (such as at 3650 cm⁻¹). -1 2850 cm -1 1620 cm -1(etc.), which intuitively demonstrate the multi-scale structural features of the modified PTFE powder, including significantly enhanced surface polarity, introduction of flexible segments, and optimized interfacial compatibility, providing a reliable molecular-level basis for the in-situ formation of a continuous three-dimensional cross-linked network in subsequent composite materials.

[0086] Combined with preparation example 2 and Figure 2 It can be seen that: 3082 cm -1 3058 cm -1 The vibration at point 2160 cm⁻¹ is the stretching vibration of vinyl group = CH. -1 The peak at 1605 cm⁻¹ is a strongly pointed Si-H stretching peak (a hallmark of the active functional group). -1 The vicinity exhibits C=C stretching vibration, 1268 cm. -1 The vibration at this location is a Si-CH3 symmetric deformation vibration, 1110 cm. -1 1085 cm -1 1060 cm -1 The multiple sharp peaks correspond to the asymmetric stretching of Si-O-Si (main peak and shoulder peak), and are also present at 1415 cm⁻¹. -1 (=CH2 in-plane bending), 965 cm⁻¹ (=CH2 out-of-plane rocking), 805 cm -1 (Si-CH3 oscillation + Si-C stretching), 895 cm -1 The distribution of bending vibration peaks related to vinyl groups, CH3, and Si-O at positions such as (Si-H bending) and the superposition of actual instrument noise and slight baseline fluctuations in the entire spectrum fully confirms that the bifunctional siloxane oligomers with molecular weights of 500-5000 simultaneously contain the main chain structure of Si-H bonds and vinyl-substituted siloxane units, as well as the presence of all functional groups such as methyl, siloxane, and Si-C bonds. This provides a reliable structural identification basis for achieving in-situ hydrosilylation crosslinking and forming a continuous three-dimensional network in polysulfone-modified PTFE composites.

[0087] As can be seen from Examples 1 to 4 and Table 1, the mechanical properties, creep resistance, and wear resistance of the reinforced polytetrafluoroethylene composite skeleton structure composite material of the present invention are all at a high level. Specifically, the tensile strength is 68.5–85.3 MPa, the tensile modulus is 4.2–5.8 GPa, the elongation at break is 6.2–8.5%, the flexural strength is 95.2–118.7 MPa, and the flexural modulus is 5.1–6.9 GPa. Regarding creep resistance, the creep variation after 168 hours is only 0.8–1.2%, and the steady-state creep rate is 3.2–5.0 × 10⁻⁶. - With a flow rate of 6 h, the creep modulus reaches 16.7–25.0 GPa; in terms of wear resistance, the dynamic friction coefficient is 0.09–0.12, and the specific wear rate is 2.1–3.5 × 10⁶. -6 mm 3 / N·m fully demonstrates the performance optimization brought about by the multi-scale skeleton structure of polysulfone modification, in-situ crosslinking of reactive silicone resin precursor and carbon fiber-molybdenum disulfide synergistic reinforcement.

[0088] As can be seen from Example 1, Comparative Example 1, and Table 1, compared with ordinary PTFE powder without polysulfone modification, the tensile strength of Example 1 increased from 42.6 MPa to 68.5 MPa (an increase of 60.8%), the tensile modulus increased from 2.1 GPa to 4.2 GPa, the 168h creep rate decreased significantly from 5.8% to 1.2%, and the specific wear rate increased from 48.7 × 10⁻⁶ MPa. -6 mm 3 / N·m decreased to 3.5×10 -6 mm 3 / N·m; Polysulfone oligomers are chemically grafted onto the surface of PTFE particles through plasma activation and bridging agents, which significantly improves the surface polarity and interfacial compatibility with carbon fibers and siloxane precursors. This enables the subsequent in-situ formed continuous three-dimensional siloxane crosslinking network to effectively couple the rigid carbon fiber reinforcing phase with the PTFE matrix, achieving efficient stress transfer and molecular chain spatial confinement, thereby simultaneously improving mechanical strength, creep resistance and wear resistance.

[0089] As can be seen from Example 1, Comparative Example 2, and Table 1, compared with the system without the addition of reactive silicone resin precursor, the tensile strength of Example 1 increased from 51.3 MPa to 68.5 MPa, the tensile modulus increased from 2.8 GPa to 4.2 GPa, the 168h creep decreased from 4.2% to 1.2%, and the specific wear rate increased from 35.2 × 10⁻⁶ MPa. -6 mm 3 / N·m decreased to 3.5×10 -6 mm 3 / N·m; The low molecular weight reactive silicone resin precursor undergoes efficient hydrosilylation crosslinking under the action of a platinum-based catalyst during the first stage of heat preservation at 150℃. A continuous three-dimensional siloxane network is constructed in situ on the surface and interface region of polysulfone-modified PTFE particles. This network not only physically binds the PTFE molecular chains to inhibit cold flow behavior, but also acts as a flexible bridging phase to tightly couple the rigid carbon fiber skeleton with the matrix, forming a multi-scale synergistic structure of rigid skeleton + flexible crosslinking network. This significantly improves the overall mechanical properties, creep resistance and wear resistance.

[0090] As can be seen from Example 1, Comparative Example 3, and Table 1, compared with the system substituted with perfluorocarbon-based silicone resin micropowder, the tensile strength of Example 1 increased from 47.8 MPa to 68.5 MPa, the tensile modulus increased from 2.5 GPa to 4.2 GPa, the 168h creep decreased from 4.9% to 1.2%, and the specific wear rate increased from 42.5 × 10⁻⁶ MPa. -6 mm3 / N·m decreased to 3.5×10 -6 mm 3 / N·m; The low molecular weight liquid reactive silicone resin precursor used in this invention can form a uniform and continuous coating layer on the particle surface during the mixing process, and achieve low-temperature, rapid, uniform and high-conversion hydrosilylation crosslinking under the efficient catalysis of platinum catalyst, constructing a continuous and interconnected three-dimensional crosslinking network. In contrast, silicone resin micropowder containing perfluorocarbon groups, crosslinkable ethylene bonds and hydrosilylation bonds is prone to agglomeration due to its small particle size and lack of catalyst, resulting in the crosslinking reaction being limited to local discrete regions, and unable to form an effective macroscopic stress transmission path and molecular chain constraint. Therefore, this invention has significant advantages in interface bonding, crosslinking continuity and multi-scale synergistic effect.

[0091] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. 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 reinforced polytetrafluoroethylene composite skeleton structure composite material, characterized in that, Includes the following components in parts by mass: 70-90 parts of polysulfone-modified polytetrafluoroethylene resin; 10-30 parts of carbon fiber; 1-10 parts of molybdenum disulfide; 5-25 parts of reactive silicone resin precursor; 0.01 to 1 part of platinum-based catalyst.

2. The composition according to claim 1, characterized in that, The polysulfone-modified polytetrafluoroethylene resin is a modified powder whose surface has been plasma-activated and grafted with polysulfone oligomers.

3. The composition according to claim 1, characterized in that, The reactive silicone resin precursor is a bifunctional siloxane oligomer with a molecular weight of 500 to 5000, whose molecular chain contains both Si-H bonds and vinyl-substituted siloxane units.

4. The composition according to claim 1, characterized in that, The carbon fiber is at least one of continuous carbon fiber, chopped carbon fiber, or carbon fiber fabric, and the carbon fiber is distributed in the reinforcing phase of the composite skeleton structure.

5. The composition according to claim 1, characterized in that, The platinum-based catalyst is selected from at least one of chloroplatinic acid, cassiterite catalyst, or supported platinum catalyst.

6. A method for preparing the composition according to any one of claims 1 to 5, characterized in that, Includes the following steps: Step S1. Dry mix polysulfone modified polytetrafluoroethylene resin with carbon fiber, add reactive silicone resin precursor and platinum catalyst to form a continuous coating layer on the particle surface, and then add molybdenum disulfide and mix evenly. Step S2. Press the preform under a pressure of 30–90 MPa; Step S3. Staged heat treatment: First stage: Incubate at 150-250℃ to induce hydrosilylation crosslinking reaction; The second stage involves holding the polytetrafluoroethylene body at 300–380℃ to sinter it. Step S4. Cool in the furnace or in a controlled manner to obtain the finished product.

7. The preparation method according to claim 6, characterized in that, The preparation process of the polysulfone-modified polytetrafluoroethylene resin is as follows: First, polytetrafluoroethylene powder is surface activated by low-temperature plasma, and then grafted in a solution containing polysulfone oligomers and bridging agents at 80°C. The product is then obtained by solvent removal and heat treatment at 200°C.

8. The preparation method according to claim 6, characterized in that, The preparation process of the reactive silicone resin precursor is as follows: Using linear oligosiloxanes as raw materials, ring-opening co-condensation reaction is carried out by introducing monomers containing Si-H bonds and vinyl groups, controlling the vinyl groups to be statistically distributed on the main chain, and removing low-molecular-weight byproducts under reduced pressure.

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