Low-friction machinable fluorine-containing composite material as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of high polymer materials, and particularly relates to a low-friction machinable fluorine-containing composite material as well as a preparation method and application thereof. The middle-low friction machinable fluorine-containing composite material is prepared from the following raw materials in percentage by mass: 80-95% of fusible polytetrafluoroethylene and 5-20% of filler, the filler comprises any one or more of graphite, carbon fiber and polytetrafluoroethylene (PTFE). The low-friction machinable fluorine-containing composite material provided by the invention has low friction coefficient and high compression strength at the same time.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to a low-friction processable fluorine-containing composite material, its preparation method, and its application. Background Technology

[0002] Fluoropolymers (such as polytetrafluoroethylene (PTFE), perfluoroethylene-propylene copolymer (FEP), and polyvinylidene fluoride (PVDF)) are widely used in the automotive, electronics, machinery manufacturing, medical, and aerospace industries due to their excellent chemical stability, low coefficient of friction, and low dielectric constant, earning them the nickname "King of Plastics." PTFE is a polymer compound containing fluorine atoms in its main chain. The high dissociation energy of the CF bonds in its molecule, along with the high electronegativity and shielding effect of fluorine atoms, gives it excellent high and low temperature resistance and chemical stability. It also possesses good dielectric properties, low friction, non-adhesion, non-flammability, and lubricity, making it a high-performance polymer material. However, the high melt viscosity of PTFE makes it difficult to process PTFE through extrusion and injection molding. Furthermore, the high melt viscosity results in insufficient resin flow to fully wet the filler, making it difficult to establish a tight interfacial bond with the filler at the physical level, thus affecting its application.

[0003] Meltable fluoropolymers, such as meltable polytetrafluoroethylene (PFA) and fluorinated ethylene propylene copolymer (FEP), are widely used in extremely demanding fields such as semiconductor manufacturing, chemical corrosion protection, high-frequency communication, and high-end cables due to their excellent chemical inertness, extremely low surface energy, excellent high and low temperature resistance, outstanding dielectric properties, and weather resistance. With the increasingly widespread application of fluoropolymers, the requirements for materials are also becoming more stringent. Developing highly filled and reinforced fluoropolymer composites has become an urgent technical problem to be solved. PFA resin is a relatively new fluoroplastic. Similar to PTFE and FEP, PFA has comparable chemical resistance to PTFE, and its melting point is approximately 300℃. Compared to PTFE, which is difficult to melt process, PFA's advantage lies in its melt processability. It possesses advantages such as relatively high strength, high-temperature stability, chemical stability, and electrical insulation compared to other plastics, broadening its application range. PFA resin also has characteristics such as a low coefficient of friction, non-stickiness, and corrosion resistance. However, PFA also has some inherent defects, including poor wear resistance, weak load-bearing capacity, and susceptibility to cracking under high stress.

[0004] Therefore, it is particularly important to develop a composite material that maintains the low coefficient of friction of PFA while having high compressive strength, so that it can better meet the application requirements in fields such as chemical engineering, electronics, aerospace, and automotive manufacturing. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a low-friction processable fluorine-containing composite material, its preparation method and application, wherein the low-friction processable fluorine-containing composite material provided by the present invention has both a low coefficient of friction and high compressive strength.

[0006] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a low-friction, processable fluorine-containing composite material, wherein the raw materials for preparation, by weight percentage, include: 80-95% fusible polytetrafluoroethylene and 5-20% filler; The filler includes any one or more of graphite, carbon fiber, and polytetrafluoroethylene.

[0007] Preferably, the fusible polytetrafluoroethylene is a tetrafluoroethylene-perfluoroalkoxy vinyl ether copolymer; the melt index of the fusible polytetrafluoroethylene is 10~60g / 10min; and the particle size of the fusible polytetrafluoroethylene is 38~75μm.

[0008] Preferably, the graphite has a size of 1~5μm.

[0009] Preferably, the carbon fiber has a length of 0.3~0.6mm and a diameter of 7~10μm.

[0010] Preferably, the particle size of the polytetrafluoroethylene is 25~75μm.

[0011] This invention also provides a method for preparing the low-friction, processable fluorine-containing composite material described above, comprising the following steps: Meltable polytetrafluoroethylene and fillers are mixed and then melt-extruded and granulated in sequence to obtain granules; The granules are injection molded and compressed into a mold to obtain a low-friction, processable fluorine-containing composite material.

[0012] Preferably, the temperature of the melt extrusion is 360~380℃.

[0013] Preferably, the screw speed is set to 35~45 rpm and the torque is set to 15~25 N·m during the melt extrusion process.

[0014] Preferably, the injection compression temperature is 360~375℃, the time is 15~25s, and the pressure is 0.5~0.7MPa.

[0015] The present invention also provides the application of the low-friction processable fluorinated composite material described in the above technical solution or the low-friction processable fluorinated composite material prepared by the preparation method described in the above technical solution in chemical, electronic and electrical, aerospace or automobile manufacturing.

[0016] This invention provides a low-friction, processable fluorine-containing composite material, wherein the raw materials for preparation, by weight percentage, include: 80-95% fusible polytetrafluoroethylene and 5-20% filler; The filler includes any one or more of graphite, carbon fiber, and polytetrafluoroethylene.

[0017] Compared with the prior art, the present invention, employing the above technical solution, has the following technical effects: 1. Firstly, the matrix resin PFA possesses excellent corrosion resistance and high-temperature resistance (long-term operating temperature 260℃). However, due to the relatively weak van der Waals forces between molecular chain segments, slippage easily occurs under external forces, resulting in low compressive strength and poor dimensional stability. This invention introduces reinforcing fillers such as carbon fibers and graphite, forming a reinforcing network within the PFA matrix. This restricts the movement of PFA chain segments, improves the material's compressive properties, and inhibits creep. Therefore, the composite material prepared by this invention, while maintaining the matrix resin's effective resistance to corrosion from high-temperature corrosive solutions and significantly extending the material's service life and heat resistance, also exhibits significantly improved compressive strength and creep resistance.

[0018] 2. By modifying carbon fiber and graphite composites, this invention can significantly improve the mechanical strength of composite materials while reducing the coefficient of friction, making it suitable for both civilian and military applications and meeting the oil-free lubrication needs of various industries. Attached Figure Description

[0019] Figure 1 The yield strength diagrams are for the low-friction processable fluorine-containing composite materials prepared in Examples 1-3 of the present invention, wherein PFA-CF 90-10 is Example 1, PFA-CF 80-20 is Example 2, and PFA-CF-graphite 80-10-10 is Example 3. Figure 2 The figures show the compressive strength of the low-friction processable fluorinated composite materials prepared in Examples 4-8 of this invention at 25% strain. Among them, PFA-graphite 95-5 is Example 4, PFA-graphite 90-10 is Example 5, PFA-graphite 85-15 is Example 6, PFA-PTFE 95-5 is Example 7, and PFA-PTFE 90-10 is Example 8. Detailed Implementation

[0020] This invention provides a low-friction, processable fluorine-containing composite material, wherein the raw materials for preparation, by weight percentage, include: 80-95% fusible polytetrafluoroethylene (PFA) and 5-20% filler; The filler includes any one or more of graphite, carbon fiber, and polytetrafluoroethylene (PTFE).

[0021] Unless otherwise specified, the present invention does not have special requirements on the source of raw materials used, and commercially available products well known to those skilled in the art can be used.

[0022] In one embodiment, the filler includes any one or more of graphite, carbon fiber, and polytetrafluoroethylene (PTFE), with specific embodiments including graphite, carbon fiber, or PTFE, or carbon fiber and graphite. Carbon fiber serves as a reinforcing filler, while graphite and PTFE serve as lubricating fillers. When the filler is carbon fiber and graphite, the mass ratio of carbon fiber to graphite is 1:1.

[0023] As one embodiment, the raw materials for preparing the low-friction processable fluorine-containing composite material include: 80-95% fusible polytetrafluoroethylene (PTFE), specifically 80%, 85%, 90%, or 95% in the embodiments, and 5-20% filler, specifically 5%, 10%, 15%, or 20% in the embodiments; the raw materials for preparing the low-friction processable fluorine-containing composite material include 5-20% graphite, or 10-20% carbon fiber, or 10-20% polytetrafluoroethylene (PTFE).

[0024] In one embodiment, the fusible polytetrafluoroethylene (PFA) is a tetrafluoroethylene-perfluoroalkoxy vinyl ether copolymer; the melt index of the fusible polytetrafluoroethylene (PFA) is 10~60 g / 10 min, and in a specific embodiment it is 25~30 g / 10 min; the test temperature for the melt index is 370℃, and the sample used is a 5 kg weight; the melting point of the fusible polytetrafluoroethylene (PFA) is 297℃.

[0025] In one embodiment, the carbon fiber is T700 carbon fiber.

[0026] In one embodiment, the particle size of the fusible polytetrafluoroethylene (PFA) is 38~75μm, and in a specific embodiment it is 60μm; the size of the graphite is 1~5μm, and in another embodiment it is 1.67~2.5μm (6000~9000 mesh), and in a specific embodiment it is 1.875μm (8000 mesh); the length of the carbon fiber is 0.3~0.6mm, and in a specific embodiment it is 0.5mm, and the diameter is 7~10μm, and in a specific embodiment it is 8μm; the particle size of the polytetrafluoroethylene (PTFE) is 25~75μm, and in a specific embodiment it is 40~55μm, and the melting point is 330℃.

[0027] This invention also provides a method for preparing the low-friction, processable fluorine-containing composite material described above, comprising the following steps: Meltable polytetrafluoroethylene and fillers are mixed and then melt-extruded and granulated in sequence to obtain granules; The granules are injection molded and compressed into a mold to obtain a low-friction, processable fluorine-containing composite material.

[0028] In one embodiment, the mixing equipment is a pulverizer; the mixing is carried out under stirring conditions; the stirring speed is 5000~10000 rpm, and in a specific embodiment it is 7500 rpm; the mixing time is 30~60 min, and in a specific embodiment it is 40 min.

[0029] In one embodiment, the equipment used for melt extrusion is a twin-screw extruder; the temperature of melt extrusion is 360~380℃, and in a specific embodiment it is 370℃; the screw speed during melt extrusion is set to 35~45rpm, and in a specific embodiment it is 40rpm, and the torque is set to 15~25N·m, and in a specific embodiment it is 20N·m or 25N·m.

[0030] In one embodiment, the injection compression temperature is 360~375℃, specifically 375℃, the time is 15~25s, specifically 15s, and the pressure is 0.5~0.7MPa, specifically 0.6~0.7MPa; the mold temperature is 210~230℃, specifically 215℃.

[0031] This invention does not impose any special limitations on the shape of the mold. As needed, the shape of the mold can be adjusted to produce the desired product shape, such as a square.

[0032] As one implementation method, after molding, the composite material is further subjected to cutting, grinding, and surface treatment for subsequent use.

[0033] As one implementation method, the surface treatment involves rinsing with ultrapure water once, rinsing with ethanol once, and then drying in an oven at 110°C for 6 hours.

[0034] The present invention also provides the application of the low-friction processable fluorinated composite material described in the above technical solution or the low-friction processable fluorinated composite material prepared by the preparation method described in the above technical solution in chemical, electronic and electrical, aerospace or automobile manufacturing.

[0035] This invention does not impose any particular limitation on the application of the low-friction processable fluorinated composite material in chemical, electronic and electrical, aerospace and automobile manufacturing industries; any application method known in the art can be used.

[0036] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, but they should not be construed as limiting the scope of protection of the present invention.

[0037] Example 1 A mixture of 90 wt% meltable polytetrafluoroethylene (PFA) (melt index 25 g / 10 min, melting point 297 °C, particle size 60 μm) and 10 wt% carbon fiber (T700, length 0.5 mm, diameter 8 μm) was prepared by blending in a pulverizer at 7500 rpm for 40 min. The mixture was then melt-extruded in a twin-screw extruder (extrusion temperature: 370 °C, screw speed: 40 rpm, torque: 20 N·m), granulated, and injection-molded at 0.7 MPa and 375 °C into a mold at 215 °C to obtain friction strips (injection molded dimensions: length × width × thickness 45 × 20 × 2 mm).

[0038] Example 2 A mixture of 80 wt% PFA (melt index 25 g / 10 min, melting point 297 °C, particle size 60 μm) and 20 wt% carbon fiber (T700, length 0.5 mm, diameter 8 μm) was prepared by blending in a pulverizer at 7500 rpm for 40 min. The mixture was then melt-extruded in a twin-screw extruder (extrusion temperature: 370 °C, screw speed: 40 rpm, torque: 20 N·m), granulated, and injection-molded at 0.7 MPa and 375 °C in a mold at 215 °C to obtain friction strips (injection molded dimensions: length × width × thickness 45 × 20 × 2 mm).

[0039] Example 3 A mixture of 80 wt% PFA (melt index 25 g / 10 min, melting point 297 °C, particle size 60 μm), 10 wt% graphite (size 1.875 μm), and 10 wt% carbon fiber (T700, length 0.5 mm, diameter 8 μm) was prepared by blending at 7500 rpm for 40 min in a pulverizer. The mixture was then melt-extruded in a twin-screw extruder (extrusion temperature: 370 °C, screw speed: 40 rpm, torque: 20 N·m), granulated, and injection-molded at 0.7 MPa and 375 °C in a mold at 215 °C to obtain friction strips (injection molded dimensions: length × width × thickness 45 × 20 × 2 mm).

[0040] Example 4 A mixture of 95wt% PFA (melt index 25g / 10min, melting point 297℃, particle size 60μm) and 5wt% graphite (size 1.875μm) was prepared by blending in a pulverizer at 7500rpm for 40min. The mixture was then melt-extruded in a twin-screw extruder (extrusion temperature: 370℃, screw speed: 40rpm, torque: 20N·m), granulated, and injection-molded at 0.7MPa and 375℃ in a mold at 215℃ to obtain friction strips (injection molded dimensions: 45×20×2mm).

[0041] Example 5 A mixture of 90wt% PFA (melt index 25g / 10min, melting point 297℃, particle size 60μm) and 10wt% graphite (size 1.875μm) was prepared by blending in a pulverizer at 7500rpm for 40min. The mixture was then melt-extruded in a twin-screw extruder (extrusion temperature: 370℃, screw speed: 40rpm, torque: 20N·m), granulated, and injection-molded at 0.7MPa and 375℃ in a mold at 215℃ to obtain friction strips (injection molded dimensions: 45×20×2mm).

[0042] Example 6 A mixture of 85 wt% PFA (melt index 25 g / 10 min, melting point 297 °C, particle size 60 μm) and 15 wt% graphite (size 1.875 μm) was prepared by blending in a pulverizer at 7500 rpm for 40 min. The mixture was then melt-extruded in a twin-screw extruder (extrusion temperature: 370 °C, screw speed: 40 rpm, torque: 20 N·m), granulated, and injection-molded at 0.7 MPa and 375 °C into a mold at 215 °C to form friction specimens.

[0043] Example 7 A mixture of 95wt% PFA (melt index 25g / 10min, melting point 297℃, particle size 60μm) and 5wt% PTFE powder (particle size 45μm, melting point 330℃) was prepared by blending in a pulverizer at 7500rpm for 40min. The mixture was then melt-extruded in a twin-screw extruder (extrusion temperature: 370℃, screw speed: 40rpm, torque: 25N·m), granulated, and injection-molded at 0.7MPa and 375℃ into a mold at 215℃ to obtain friction strips (injection molded dimensions: 45×20×2mm).

[0044] Example 8 A mixture of 90wt% PFA (melt index 25 g / 10 min, melting point 297℃, particle size 60 μm) and 10wt% PTFE powder (particle size 45 μm, melting point 330℃) was prepared by blending in a pulverizer at 7500 rpm for 40 min. The mixture was then melt-extruded in a twin-screw extruder (extrusion temperature: 370℃, screw speed: 40 rpm, torque: 25 N·m), granulated, and injection-molded at 0.7 MPa and 375℃ into a mold at 215℃ to obtain friction strips (injection molded dimensions: 45 × 20 × 2 mm).

[0045] Comparative Example 1 100wt% PFA (melt index 25g / 10min, melting point 297℃, particle size 60μm) was melt-extruded in a twin-screw extruder (extrusion temperature: 370℃, screw speed: 40rpm, torque: 20N·m), granulated, and then injection-molded at 0.7MPa and 375℃ into a mold at 215℃ to obtain friction strips (injection molded dimensions: 45×20×2mm).

[0046] Comparative Example 2 100wt% fluorinated ethylene propylene copolymer (FEP) was melt-extruded in a twin-screw extruder (extrusion temperature: 370℃, screw speed: 40rpm, torque: 20N·m), granulated, and then injection-molded at 0.7MPa and 375℃ into a mold at 215℃ to obtain friction strips (injection molded dimensions: 45×20×2mm).

[0047] Performance testing The specimens prepared in Examples 1-8 and Comparative Examples 1-2 were subjected to mechanical property tests and steel ball grinding tests using a friction testing machine. The specimens were subjected to compression tests using a universal testing machine at a speed of 5 mm / min, and the coefficient of friction was tested using a friction and wear testing machine at a load of 20 N and a speed of 15 mm / s.

[0048] (1) Compression performance Sample dimensions and testing methods were performed in accordance with GB / T 1041-2008. If the yield strength was not observed in the sample, the compressive strength at 25% strain was used for comparison; the data are listed in Tables 1-2. Figures 1-2 .

[0049] (2) Friction coefficient performance test The friction coefficient behavior of PFA composites was evaluated using a linear reciprocating mode. The friction coefficient was measured on a tribological testing machine according to GB / T 3960-2016. The selected friction load was 20 N, the sliding speed was 15 mm / s, and the test time was 30 min. The data are listed in Tables 1-2. Figures 1-2 .

[0050] Table 1. Yield strength and coefficient of friction of Examples 1-3

[0051] Table 2. Compressive strength and coefficient of friction of Examples 4-8 and Comparative Examples 1-2 at 25% strain.

[0052] From Table 1 and Figure 1It can be seen that the yield strength of the PFA composite materials prepared in Examples 1-3 of this invention is 38.9-46.8 MPa, and the coefficient of friction is 0.268-0.298. The compressive strength of the PFA composite materials prepared in Examples 4-8 at 25% strain is 22.1-38.1 MPa, and the coefficient of friction is 0.226-0.318. Therefore, the PFA composite materials developed in this invention have good yield strength. By comparing Examples 1-3 with Comparative Example 1, it can be found that adding carbon fiber increases the mechanical properties of the material, especially the yield strength. By comparing Examples 4-8 with Comparative Example 1 (Table 2 and...), it can be seen that... Figure 2 It can be found that adding only lubricant (graphite, PTFE) can increase the compressive strength under strain by 25%, but it is still different from that in Examples 1-3. At the same time, the coefficient of friction also decreases significantly.

[0053] The carbon fibers and lubricating phases (polytetrafluoroethylene and graphite) from Examples 1 to 8 were added to the matrix. Compared with Comparative Examples 1 and 2, the phases at the interface were more uniformly distributed, the fiber-matrix interface was formed and participated in melting, and the compressive strength was significantly improved, thus achieving the purpose of wear resistance and friction reduction.

[0054] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A low-friction, processable fluorine-containing composite material, characterized in that, The raw materials for preparation, by mass percentage, include: 80-95% fusible polytetrafluoroethylene and 5-20% filler; The filler includes any one or more of graphite, carbon fiber, and polytetrafluoroethylene.

2. The low-friction, processable fluorine-containing composite material according to claim 1, characterized in that, The fusible polytetrafluoroethylene is a tetrafluoroethylene-perfluoroalkoxy vinyl ether copolymer; the melt index of the fusible polytetrafluoroethylene is 10~60g / 10min; the particle size of the fusible polytetrafluoroethylene is 38~75μm.

3. The low-friction, processable fluorine-containing composite material according to claim 1, characterized in that, The graphite has a size of 1~5μm.

4. The low-friction processable fluorine-containing composite material according to claim 1, characterized in that, The carbon fiber has a length of 0.3~0.6mm and a diameter of 7~10μm.

5. The low-friction processable fluorine-containing composite material according to claim 1, characterized in that, The particle size of the polytetrafluoroethylene is 25~75μm.

6. The method for preparing the low-friction processable fluorine-containing composite material according to any one of claims 1 to 5, characterized in that, Includes the following steps: Meltable polytetrafluoroethylene and fillers are mixed and then melt-extruded and granulated in sequence to obtain granules; The granules are injection molded and compressed into a mold to obtain a low-friction, processable fluorine-containing composite material.

7. The preparation method according to claim 6, characterized in that, The temperature of the melt extrusion is 360~380℃.

8. The preparation method according to claim 6 or 7, characterized in that, During the melt extrusion process, the screw speed is set to 35~45 rpm and the torque is set to 15~25 N·m.

9. The preparation method according to claim 6, characterized in that, The injection compression temperature is 360~375℃, the time is 15~25s, and the pressure is 0.5~0.7MPa.

10. The application of the low-friction processable fluorinated composite material according to any one of claims 1 to 5 or the low-friction processable fluorinated composite material prepared by the preparation method according to any one of claims 6 to 9 in chemical, electronic and electrical, aerospace or automotive manufacturing.

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