A polytetrafluoroethylene material, a method for preparing the same, and an application thereof

Abstract

This invention discloses a polytetrafluoroethylene (PTFE) material, its preparation method, and its applications. The preparation method of the PTFE material includes the following steps: S1. Pre-sintering PTFE resin to obtain a pre-sintered material; S2. Sintering a mixture comprising the pre-sintered material and a perfluoroalkoxy polymer resin to obtain the PTFE material. The resulting PTFE material possesses both excellent air permeability and high mechanical properties.

Description

Technical Field

[0001] This invention specifically relates to a polytetrafluoroethylene material, its preparation method, and its application. Background Technology

[0002] Porous polytetrafluoroethylene (PTFE) materials are widely used in pressure regulation, gas separation, waterproofing and breathability, and filtration materials due to their excellent high-temperature resistance, chemical stability, low surface energy, and good gas permeability. In battery systems, porous PTFE membranes are often used as explosion-proof valves or pressure regulating components to achieve a balance between internal gas release and liquid barrier. However, in practical applications, there is often a performance constraint between "high permeability" and "high mechanical strength" in porous PTFE materials: when the porosity is increased to enhance permeability, the structural strength often decreases; when the sintering density is increased to enhance strength, the permeability decreases significantly. Therefore, how to significantly improve mechanical properties and structural stability while maintaining stable permeability is a technical problem that urgently needs to be solved in this field.

[0003] CN106832695A discloses a PTFE film for explosion-proof valves and its preparation method. The main molding method includes: pre-treating PTFE resin, calcium oxide, polyurethane, and polystyrene by sieving, and then weighing them according to a specific weight ratio; mixing the PTFE resin and calcium oxide, followed by heating and drying; adding dry ice and polyurethane, and melting at 310±10℃; cooling the melt and cutting it into 5 mm × 5 mm particles; finally, extruding the particles through a die at the rear end of an extrusion device to form a film, and then performing subsequent processes such as molding, traction, spraying liquid ethylene glycol, and winding to obtain the final product. This product optimizes the performance of the PTFE film: using PTFE resin as the matrix, the addition of dry ice improves the film's brittleness, enabling it to meet the burst requirements of explosion-proof valves; simultaneously, the addition of polyurethane and polystyrene enhances the film's resistance to compression creep, dimensional stability, and high-temperature resistance. Test data shows that the obtained film has excellent waterproof performance and good tensile strength, while maintaining the basic properties of PTFE material. A PTFE film produced by adding dry ice has been provided. However, because dry ice sublimates rapidly at high temperatures, its behavior is difficult to control precisely, leading to uncertainties in structural uniformity and stability. Furthermore, the structure is formed by the removal of the additives, and there is a risk of structural loosening during long-term use, affecting the material's mechanical stability.

[0004] CN111864152A relates to a breathable explosion-proof membrane for power battery explosion-proof valves and its preparation method. The main molding process is based on micron-sized polytetrafluoroethylene (PTFE) suspension resin. After mixing with a pore-forming agent, the mixture is molded, sintered, and cooled, and finally wound up using a turning process to form a porous film. The main achievement is the successful preparation of a porous PTFE membrane with a unique microstructure, formed by the accumulation of surface-fused and interconnected resin microspheres, creating interconnected multi-channel air permeability. This membrane exhibits excellent comprehensive performance: the pore size is controllable within the range of 0.3-20 μm, the porosity is over 90%, achieving a balance between high air permeability and good water pressure resistance, while also possessing excellent flame retardant properties with a UL94 V-0 rating. This method utilizes the surface melting and interconnection of PTFE particles during sintering to form a connected channel structure. Although this method achieves high porosity and good air permeability, its system mainly relies on the self-fusion of PTFE particles, resulting in limited particle node bonding interfaces and a lack of independent binding reinforcing phases. Under long-term thermal stress or pressure cycling, materials may undergo creep or structural relaxation, thereby affecting dimensional stability.

[0005] CN113088018A discloses a polytetrafluoroethylene (PTFE) breathable membrane and its preparation method. This method involves using a pre-prepared PTFE membrane containing specific fillers and D... 50 PTFE sintered material with a particle size controlled between 50-150 μm is mixed with a second PTFE resin in specific weight proportions. The mixture is then subjected to molding, precisely controlled step-by-step sintering, and turning processes to finally produce a breathable membrane. While this method can control the membrane pore size and porosity to a certain extent, and give the breathable membrane certain air permeability, water pressure resistance, and mechanical strength, with low thermal shrinkage and relatively stable dimensions, meeting some of the requirements for battery explosion-proof valves, it still has significant drawbacks: this scheme only relies on adjusting the degree of sintering to improve the microstructure, without effectively strengthening the particle interface through melt flow bonding, and cannot synergistically improve air permeability and mechanical properties from a structural perspective, making it difficult to achieve simultaneous and significant optimization of both. Furthermore, its process is cumbersome, requiring precise step-by-step control of the sintering temperature, resulting in harsh process conditions and poor controllability, which is not conducive to continuous and stable industrial production.

[0006] Therefore, developing a thin film material that combines excellent air permeability and mechanical properties to meet the application requirements of explosion-proof valves for batteries is an urgent problem to be solved in this field. Summary of the Invention

[0007] This invention aims to overcome the shortcomings of existing polytetrafluoroethylene (PTFE) materials, which struggle to simultaneously possess both air permeability and mechanical properties, thus failing to meet application requirements. Instead, it provides a PTFE material, its preparation method, and its applications. The PTFE material provided by this invention exhibits both excellent air permeability and high mechanical properties.

[0008] The existing polytetrafluoroethylene (PTFE) materials have the following defects, making it difficult to simultaneously possess good air permeability and mechanical properties: (1) The single PTFE self-melting system has limited particle node bonding strength, and the preparation process relies on the addition of pore-forming agents, resulting in insufficient pore structure stability; (2) The preparation process is complex or requires high control precision. This invention introduces perfluoroalkoxy polymer resin (PFA) as a synergistic reinforcing phase to construct a "rigid skeleton-tough bonding phase" two-phase structure system, forming a stable and controllable porous network structure without the need for the addition of pore-forming agents, thereby achieving simultaneous improvement in air permeability and mechanical properties. In addition, regarding the selection of the pre-sintered material particle size range in the preparation of PTFE materials: From the perspective of particle packing theory, solid particles with a particle size of 100-180μm have good fluidity, can achieve uniform filling during molding, and also have a high packing density, which ensures moderate densification and avoids excessive shrinkage. When blended with a binder phase, solid particles with a diameter of 100-180 μm can form an ideal skeletal bonding structure, achieving sufficient interfacial bonding while retaining necessary interconnected pores. Whether the particle size is too small or too large, this balance will be disrupted, leading to deviations in material properties.

[0009] The present invention solves the above-mentioned technical problems through the following technical solution:

[0010] This invention provides a polytetrafluoroethylene (PTFE) material having a porous structure comprising PTFE resin and perfluoroalkoxy polymer resin, the two being fused together on their surfaces; the mass ratio of the PTFE resin to the perfluoroalkoxy polymer resin is 1:(0.05-0.4).

[0011] In this invention, the polytetrafluoroethylene material can be a microporous membrane with multiple permeable channels. After the perfluoroalkoxy polymer resin is melted, it is attached to the main structure of the polytetrafluoroethylene resin to improve the mechanical properties of the material.

[0012] In this invention, the perfluoroalkoxy polymer resin is attached to the skeleton structure of polytetrafluoroethylene resin, which plays a role in bonding and filling pores, thereby significantly improving air permeability without excessive loss of mechanical properties.

[0013] In this invention, the thickness of the polytetrafluoroethylene material is 0.1-0.8 mm, for example, 0.5 mm.

[0014] In this invention, the pore size of the polytetrafluoroethylene material is 1-5 μm.

[0015] In this invention, the mass ratio of the polytetrafluoroethylene resin to the perfluoroalkoxy polymer resin is 1:(0.1-0.4), preferably 1:0.05, 1:0.11 or 1:0.25.

[0016] This invention provides a method for preparing polytetrafluoroethylene (PTFE) material, the method comprising the following steps:

[0017] S1. Pre-sinter the polytetrafluoroethylene resin raw material to obtain a pre-sintered material;

[0018] S2. The mixture comprising the pre-sintered material and the perfluoroalkoxy polymer resin raw material is sintered to obtain the polytetrafluoroethylene material; the mass ratio of the pre-sintered material to the perfluoroalkoxy polymer resin raw material is 1:(0.05-0.4).

[0019] In step S1, the polytetrafluoroethylene resin raw material is a high molecular weight powdered resin prepared by suspension polymerization of tetrafluoroethylene as the main monomer in an aqueous medium.

[0020] In step S1, the pre-sintering temperature can be 350-360℃, for example, 360℃.

[0021] In step S1, the pre-sintering time can be 120-240 min, for example, 240 min.

[0022] In step S1, the pre-sintering process may further include crushing and / or sieving the pre-sintered material; wherein, the crushing method is preferably dry grinding; the sieving method is sieving through a sieve, which may specifically include the following steps: sieving the pre-sintered product through an 80-mesh sieve and a 150-mesh sieve in sequence, and selecting sieve groups between 80 and 150 mesh for subsequent steps.

[0023] In step S1, the pre-sintered material is the portion that can pass through an 80-mesh sieve but not through a 150-mesh sieve.

[0024] In step S2, the particle size of the pre-sintered material is 100-180 μm.

[0025] In step S2, the perfluoroalkoxy polymer resin raw material is a perfluoro thermoplastic fluorinated copolymer prepared by free radical copolymerization of tetrafluoroethylene and perfluoroalkyl vinyl ether.

[0026] In step S2, the perfluoroalkoxy polymer resin raw material is added to the reaction system in the form of an emulsion; wherein, the solid content of the emulsion is preferably 30 wt%-60 wt%, for example, 50 wt%.

[0027] In step S2, the mass ratio of the pre-sintered material to the perfluoroalkoxy polymer resin raw material is preferably 1:(0.05-0.4), more preferably 1:0.25.

[0028] In step S2, the method for preparing the mixture can be a method conventionally used in the art, for example, stirring the pre-sintered material with the perfluoroalkoxy polymer resin raw material;

[0029] The stirring speed can be a conventional stirring speed in the art, for example, 2000-6000 rpm, or for example, 4000 rpm;

[0030] The stirring time can be a conventional stirring time in the art, for example, 5-30 min, or for example, 10 min.

[0031] In step S2, before sintering, the mixture may be subjected to molding treatment; wherein, the molding pressure is preferably 10-30 MPa, more preferably 20-25 MPa, for example 20 MPa; the molding time is preferably 1-10 min, more preferably 2-5 min, for example 3 min; the mold shape used for molding may optionally be a hollow cylinder.

[0032] In some specific implementations, the blank obtained by the molding process is a hollow cylinder with an outer diameter of 20cm, an inner diameter of 6cm, and a height of 3cm.

[0033] In step S2, the sintering temperature can be 300-400℃, preferably 330-360℃, for example 340℃ or 350℃.

[0034] In step S2, the sintering time can be 1-5 hours, preferably 2-4 hours, for example 2 hours.

[0035] In this invention, the polytetrafluoroethylene material can be a thin film. Optionally, the polytetrafluoroethylene material can be subjected to a film-forming treatment, such as machining.

[0036] In this invention, the thickness of the polytetrafluoroethylene material can be 0.1-0.8 mm, for example, 0.5 mm.

[0037] In this invention, the pore size of the polytetrafluoroethylene material can be 1-5 μm.

[0038] In the preparation method of the polytetrafluoroethylene material of the present invention, the mass ratio of the pre-sintered material to the perfluoroalkoxy polymer resin raw material is 1:(0.1-0.4), preferably 1:0.05, 1:0.11 or 1:0.25.

[0039] In this invention, the preparation method of the polytetrafluoroethylene material includes, by weight, 70-90 parts of the pre-sintered material and 10-30 parts of the perfluoroalkoxy polymer resin raw material.

[0040] In this invention, the polytetrafluoroethylene material is prepared by suspension polymerization of the polytetrafluoroethylene resin raw material.

[0041] In this invention, in the method for preparing the polytetrafluoroethylene material, the D of the polytetrafluoroethylene resin raw material... v 50 represents 100-260μm.

[0042] In this invention, the D v 50 is the median particle size.

[0043] In this invention, the polytetrafluoroethylene material is prepared by suspension polymerization of the perfluoroalkoxy polymer resin raw material.

[0044] In this invention, in the method for preparing the polytetrafluoroethylene material, the D of the perfluoroalkoxy polymer resin raw material... v 50 is 0.12-0.16μm.

[0045] In this invention, the D v 50 was determined using laser diffraction scattering method.

[0046] The present invention also provides a polytetrafluoroethylene material, which is prepared by the polytetrafluoroethylene material preparation method described above.

[0047] The present invention also provides the application of the polytetrafluoroethylene material as described above in breathable components.

[0048] In this invention, the breathable component can be applied to power battery explosion-proof valves, energy storage battery pressure balancing components, waterproof and breathable structures for electronic devices, chemical corrosion-resistant breathable components, or high-temperature gas filter materials.

[0049] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.

[0050] The reagents and raw materials used in this invention are all commercially available.

[0051] The positive and progressive effects of this invention are as follows:

[0052] (1) The polytetrafluoroethylene material provided by the present invention forms a porous structure with uniform distribution and highly controllable size and porosity at the microscopic level, thus possessing both high air permeability and good mechanical strength. It also has low thermal shrinkage and excellent dimensional stability, which can fully meet its use in components with air permeability requirements, such as the stringent requirements of battery pack explosion-proof valves for the reliability and safety of air permeable materials during long-term use.

[0053] (2) This invention uses the synergistic compounding of polytetrafluoroethylene pre-sintered material with specific particle size and perfluoroalkoxy polymer resin raw material and process design to eliminate the need to add pore-forming agents during the preparation process. The process is simple, efficient, environmentally friendly, and suitable for large-scale continuous production. It has significant industrial application potential and market prospects. Attached Figure Description

[0054] Figure 1 This is a SEM image of the cross-sectional microstructure of the polytetrafluoroethylene material in Example 2.

[0055] Figure 2 This is a SEM image of the cross-sectional microstructure of the polytetrafluoroethylene material in Example 4. Detailed Implementation

[0056] The present invention will be further illustrated by way of embodiments below, but the present invention is not limited to the scope of the embodiments described herein.

[0057] Example 1

[0058] S1. Weigh a certain amount of polytetrafluoroethylene resin raw material (purchased from Zhejiang Gerui New Material Co., Ltd., product model GD-180, corresponding to Juhua Group's product model JF-GD180) and put it into a muffle furnace for pre-sintering. The pre-sintering temperature is 360℃ and the pre-sintering time is 240 min to obtain pre-sintered material. Then, the pre-sintered material is crushed and sieved. The portion with a particle size of 100-180μm is sieved for subsequent steps. The crushing is carried out in a crusher at a speed of 1000 rpm for 3 min.

[0059] S2. The pre-sintered material with a particle size of 100-180μm and the emulsion of perfluoroalkoxy polymer resin raw material (50wt%, commercial model D450G, purchased from Wuhan Hengfulong New Material Co., Ltd.) were mixed, pressed, sintered and film-forming were carried out at a solid mass ratio of 1:0.11 to obtain a polytetrafluoroethylene film.

[0060] The screening method involves screening through a sieve, retaining the portion that can pass through an 80-mesh sieve but not through a 150-mesh sieve.

[0061] The mixing process conditions are as follows: the mixing speed is 4000 rpm, the mixing time is 10 min, and then the mixture is dried at a temperature of 70℃ for 24 h.

[0062] The blanking process is a compression molding process. The compression molding pressure is 20 MPa and the compression molding time is 3 min, resulting in a cylindrical blank with an outer diameter of 20 cm, an inner diameter of 6 cm, and a height of 3 cm.

[0063] The sintering process conditions are as follows: sintering temperature is 340℃, and sintering time is 2 h.

[0064] The film-forming process involves turning, where the sintered blank is placed on a lathe for turning, resulting in a polytetrafluoroethylene film with a thickness of 0.5 mm.

[0065] Example 2

[0066] S1. Weigh a certain amount of polytetrafluoroethylene resin raw material (purchased from Zhejiang Gerui New Material Co., Ltd., product model GD-180, corresponding to Juhua Group's product model JF-GD180) and put it into a muffle furnace for pre-sintering. The pre-sintering temperature is 360℃ and the pre-sintering time is 240 min to obtain pre-sintered material. Then, the pre-sintered material is crushed and sieved. The portion with a particle size of 100-180μm is sieved for subsequent steps. The crushing is carried out in a crusher at a speed of 1000 rpm for 3 min.

[0067] S2. The pre-sintered material with a particle size of 100-180μm and the emulsion of perfluoroalkoxy polymer resin raw material (50wt%, commercial model D450G, purchased from Wuhan Hengfulong New Material Co., Ltd.) were mixed, pressed, sintered and film-forming were carried out at a solid mass ratio of 1:0.11 to obtain a polytetrafluoroethylene film.

[0068] The screening method involves screening through a sieve, retaining the portion that can pass through an 80-mesh sieve but not through a 150-mesh sieve.

[0069] The mixing process conditions are as follows: the mixing speed is 4000 rpm, the mixing time is 10 min, and then the mixture is dried at a temperature of 70℃ for 24 h.

[0070] The blanking process is a compression molding process. The compression molding pressure is 20 MPa and the compression molding time is 3 min, resulting in a cylindrical blank with an outer diameter of 20 cm, an inner diameter of 6 cm, and a height of 3 cm.

[0071] The sintering process conditions are as follows: sintering temperature is 350℃, and sintering time is 2 h.

[0072] The film-forming process involves turning, where the sintered blank is placed on a lathe for turning, resulting in a polytetrafluoroethylene film with a thickness of 0.5 mm.

[0073] Example 3

[0074] S1. Weigh a certain amount of polytetrafluoroethylene resin raw material (purchased from Zhejiang Gerui New Material Co., Ltd., product model GD-180, corresponding to Juhua Group's product model JF-GD180) and put it into a muffle furnace for pre-sintering. The pre-sintering temperature is 360℃ and the pre-sintering time is 240 min to obtain pre-sintered material. Then, the pre-sintered material is crushed and sieved. The portion with a particle size of 100-180μm is sieved for subsequent steps. The crushing is carried out in a crusher at a speed of 1000 rpm for 3 min.

[0075] S2. The pre-sintered material with a particle size of 100-180μm and the emulsion of perfluoroalkoxy polymer resin raw material (50wt%, commercial model D450G, purchased from Wuhan Hengfulong New Material Co., Ltd.) were mixed, pressed, sintered and film-forming at a solid mass ratio of 1:0.25 to obtain a polytetrafluoroethylene film.

[0076] The screening method involves screening through a sieve, retaining the portion that can pass through an 80-mesh sieve but not through a 150-mesh sieve.

[0077] The mixing process conditions are as follows: the mixing speed is 4000 rpm, the mixing time is 10 min, and then the mixture is dried at a temperature of 70℃ for 24 h.

[0078] The blanking process is a compression molding process. The compression molding pressure is 20 MPa and the compression molding time is 3 min, resulting in a cylindrical blank with an outer diameter of 20 cm, an inner diameter of 6 cm, and a height of 3 cm.

[0079] The sintering process conditions are as follows: sintering temperature is 340℃, and sintering time is 2 h.

[0080] The film-forming process involves turning, where the sintered blank is placed on a lathe for turning, resulting in a polytetrafluoroethylene film with a thickness of 0.5 mm.

[0081] Example 4

[0082] S1. Weigh a certain amount of polytetrafluoroethylene resin raw material (purchased from Zhejiang Gerui New Material Co., Ltd., product model GD-180, corresponding to Juhua Group's product model JF-GD180) and put it into a muffle furnace for pre-sintering. The pre-sintering temperature is 360℃ and the pre-sintering time is 240 min to obtain pre-sintered material. Then, the pre-sintered material is crushed and sieved. The portion with a particle size of 100-180μm is sieved for subsequent steps. The crushing is carried out in a crusher at a speed of 1000 rpm for 3 min.

[0083] S2. The pre-sintered material with a particle size of 100-180μm and the emulsion of perfluoroalkoxy polymer resin raw material (50wt%, commercial model D450G, purchased from Wuhan Hengfulong New Material Co., Ltd.) were mixed, pressed, sintered and film-forming at a solid mass ratio of 1:0.25 to obtain a polytetrafluoroethylene film.

[0084] The screening method involves screening through a sieve, retaining the portion that can pass through an 80-mesh sieve but not through a 150-mesh sieve.

[0085] The mixing process conditions are as follows: the mixing speed is 4000 rpm, the mixing time is 10 min, and then the mixture is dried at a temperature of 70℃ for 24 h.

[0086] The blanking process is a compression molding process. The compression molding pressure is 20 MPa and the compression molding time is 3 min, resulting in a cylindrical blank with an outer diameter of 20 cm, an inner diameter of 6 cm, and a height of 3 cm.

[0087] The sintering process conditions are as follows: sintering temperature is 350℃, and sintering time is 2 h.

[0088] The film-forming process involves turning, where the sintered blank is placed on a lathe for turning, resulting in a polytetrafluoroethylene film with a thickness of 0.5 mm.

[0089] Example 5

[0090] S1. Weigh a certain amount of polytetrafluoroethylene resin raw material (purchased from Zhejiang Gerui New Material Co., Ltd., product model GD-180, corresponding to Juhua Group's product model JF-GD180) and put it into a muffle furnace for pre-sintering. The pre-sintering temperature is 360℃ and the pre-sintering time is 240 min to obtain pre-sintered material. Then, the pre-sintered material is crushed and sieved. The portion with a particle size of 100-180μm is sieved for subsequent steps. The crushing is carried out in a crusher at a speed of 1000 rpm for 3 min.

[0091] S2. The pre-sintered material with a particle size of 100-180μm and the emulsion of perfluoroalkoxy polymer resin raw material (50wt%, commercial model D450G, purchased from Wuhan Hengfulong New Material Co., Ltd.) were mixed, pressed, sintered and film-forming at a solid mass ratio of 1:0.05 to obtain a polytetrafluoroethylene film.

[0092] The screening method involves screening through a sieve, retaining the portion that can pass through an 80-mesh sieve but not through a 150-mesh sieve.

[0093] The mixing process conditions are as follows: the mixing speed is 4000 rpm, the mixing time is 10 min, and then the mixture is dried at a temperature of 70℃ for 24 h.

[0094] The blanking process is a compression molding process. The compression molding pressure is 20 MPa and the compression molding time is 3 min, resulting in a cylindrical blank with an outer diameter of 20 cm, an inner diameter of 6 cm, and a height of 3 cm.

[0095] The sintering process conditions are as follows: sintering temperature is 340℃, and sintering time is 2 h.

[0096] The film-forming process involves turning, where the sintered blank is placed on a lathe for turning, resulting in a polytetrafluoroethylene film with a thickness of 0.5 mm.

[0097] Comparative Example 1

[0098] S1. Weigh a certain amount of polytetrafluoroethylene resin raw material (purchased from Zhejiang Gerui New Material Co., Ltd., product model GD-180, corresponding to Juhua Group's product model JF-GD180) and put it into a muffle furnace for pre-sintering. The pre-sintering temperature is 360℃ and the pre-sintering time is 240 min to obtain pre-sintered material. Then, the pre-sintered material is crushed and sieved. The portion with a particle size of 100-180μm is sieved for subsequent steps. The crushing is carried out in a crusher at a speed of 1000 rpm for 3 min.

[0099] S2. The pre-sintered material with a particle size of 100-180μm is pressed, sintered and film-forming to obtain a polytetrafluoroethylene film;

[0100] The screening method involves screening through a sieve, retaining the portion that can pass through an 80-mesh sieve but not through a 150-mesh sieve.

[0101] The mixing process conditions are as follows: the mixing speed is 4000 rpm, the mixing time is 10 min, and then the mixture is dried at a temperature of 70℃ for 24 h.

[0102] The blanking process is a compression molding process. The compression molding pressure is 20 MPa and the compression molding time is 3 min, resulting in a cylindrical blank with an outer diameter of 20 cm, an inner diameter of 6 cm, and a height of 3 cm.

[0103] The sintering process conditions are as follows: sintering temperature is 350℃, and sintering time is 2 h.

[0104] The film-forming process involves turning, where the sintered blank is placed on a lathe for turning, resulting in a polytetrafluoroethylene film with a thickness of 0.5 mm.

[0105] Comparative Example 2

[0106] S1. Weigh a certain amount of polytetrafluoroethylene resin raw material (purchased from Zhejiang Gerui New Material Co., Ltd., product model GD-180, corresponding to Juhua Group's product model JF-GD180) and an emulsion of perfluoroalkoxy polymer resin raw material (50wt%, product model D450G, purchased from Wuhan Hengfulong New Material Co., Ltd.) at a solid mass ratio of 1:0.25 and stir to mix. Place the mixture in a muffle furnace for pre-sintering at a pre-sintering temperature of 360℃ for 240 min to obtain a pre-sintered material. Then, pulverize and sieve the pre-sintered material to separate the particles with a particle size of 100-180μm for subsequent steps. Pulverization is carried out in a pulverizer at a speed of 1000 rpm for 3 min.

[0107] S2. A pre-sintered material with a particle size of 100-180μm is pressed, sintered, and film-forming to obtain a polytetrafluoroethylene (PTFE) film;

[0108] The screening method involves screening through a sieve, retaining the portion that can pass through an 80-mesh sieve but not through a 150-mesh sieve.

[0109] The mixing process conditions are as follows: the mixing speed is 4000 rpm, the mixing time is 10 min, and then the mixture is dried at a temperature of 70℃ for 24 h.

[0110] The blanking process is a compression molding process. The compression molding pressure is 20 MPa and the compression molding time is 3 min, resulting in a cylindrical blank with an outer diameter of 20 cm, an inner diameter of 6 cm, and a height of 3 cm.

[0111] The sintering process conditions are as follows: sintering temperature is 340℃, and sintering time is 2 h.

[0112] The film-forming process involves turning, where the sintered blank is placed on a lathe for turning, resulting in a polytetrafluoroethylene film with a thickness of 0.5 mm.

[0113] Comparative Example 3

[0114] S1. Weigh a certain amount of polytetrafluoroethylene resin raw material (purchased from Zhejiang Gerui New Material Co., Ltd., product model GD-180, corresponding to Juhua Group's product model JF-GD180) and put it into a muffle furnace for pre-sintering. The pre-sintering temperature is 360℃ and the pre-sintering time is 240 min to obtain pre-sintered material. Then, the pre-sintered material is crushed and sieved. The portion with a particle size of 100-180μm is sieved for subsequent steps. The crushing is carried out in a crusher at a speed of 1000 rpm for 3 min.

[0115] S2. The pre-sintered material with a particle size of 100-180μm and the emulsion of perfluoroalkoxy polymer resin raw material (50wt%, commercial model D450G, purchased from Wuhan Hengfulong New Material Co., Ltd.) were mixed, pressed, sintered and film-forming were carried out at a solid mass ratio of 1:0.5 to obtain a polytetrafluoroethylene film.

[0116] The screening method involves screening through a sieve, retaining the portion that can pass through an 80-mesh sieve but not through a 150-mesh sieve.

[0117] The mixing process conditions are as follows: the mixing speed is 4000 rpm, the mixing time is 10 min, and then the mixture is dried at a temperature of 70℃ for 24 h.

[0118] The blanking process is a compression molding process. The compression molding pressure is 20 MPa and the compression molding time is 3 min, resulting in a cylindrical blank with an outer diameter of 20 cm, an inner diameter of 6 cm, and a height of 3 cm.

[0119] The sintering process conditions are as follows: sintering temperature is 340℃, and sintering time is 2 h.

[0120] The film-forming process involves turning, where the sintered blank is placed on a lathe for turning, resulting in a polytetrafluoroethylene film with a thickness of 0.5 mm.

[0121] Example 1

[0122] (1) Microstructure testing

[0123] The cross-sectional morphology of the polytetrafluoroethylene films prepared in Examples 2 and 4 was observed and characterized using a scanning electron microscope (S-4800). Before testing, the samples were sputter-coated with gold for 60 s to improve surface conductivity; the accelerating voltage was set to 15 kV during testing. The cross-sectional micromorphology of Example 2 was obtained, as shown below. Figure 1 The cross-sectional microstructure of Example 4, such as... Figure 2 .

[0124] The cross-sectional microstructure of the polytetrafluoroethylene membrane prepared in Example 2 is as follows: Figure 1 It can be seen that the PTFE membrane obtained has a pore size of 1-5 μm, and the cross-section of the PTFE membrane exhibits a wrinkled, layered microstructure with uniformly distributed micron-sized spherical particles on the surface. These particles are tightly bonded to the substrate, forming continuous microporous channels, resulting in a relatively dense structure and uniform pore distribution. This is because, at 350℃, PTFE fully melts, and although the melt viscosity is high, it still exhibits significant viscous flow. PTFE resin particles fuse together, and the original particle interfaces gradually blur, thus forming a more continuous PTFE matrix, significantly improving the cohesive strength of the PTFE phase itself. Simultaneously, the high temperature promotes the interdiffusion and entanglement of molecular chains between PFA and PTFE at the phase interface, forming a stronger physical and chemical bond, resulting in high mechanical strength.

[0125] In addition, it contains a large number of interconnected micron-sized folds and micropores, with uniformly distributed and interconnected channels, providing a continuous pathway for gas diffusion and achieving high-efficiency air permeability while ensuring structural integrity.

[0126] The cross-sectional microstructure of the polytetrafluoroethylene membrane in Example 4 is as follows: Figure 2 The PTFE membrane obtained has a pore size of 1-5μm. The cross-section of the PTFE membrane exhibits a scale-like stacked morphology, with sharp edges and a continuous and complete structure. A large number of irregular angular particles are attached to the surface. Although there are certain gaps and pores between the layers, the overall connection is tight and there are no signs of loosening or breakage.

[0127] This is because a high PFA content imparts excellent initial bonding and filling properties to the material. High temperatures simultaneously trigger the self-fusion behavior of the PTFE matrix and the high flow characteristics of PFA. PTFE completely melts and undergoes significant viscous flow, while the low-viscosity, high-flow-rate PFA fully penetrates and fills the residual micropores within the system, resulting in a stronger interlayer bond. Deep interdiffusion occurs between the PTFE and PFA molecular chains at the phase interface, causing the phase interface to become blurred or even disappear, forming a macroscopically uniform and microscopically compatible "alloyed" structure. This structure can efficiently transfer and disperse stress, suppress localized failure behavior, significantly improve the material's tensile and tear resistance, and exhibit excellent mechanical strength.

[0128] Furthermore, the appropriate gaps and interconnected pores between the layers provide a continuous and unobstructed pathway for gas transport, achieving high-efficiency air permeability while ensuring structural density and mechanical stability. PTFE provides rigidity, heat resistance, and skeletal support, while PFA imparts toughness, adhesion, and processing fluidity. The synergistic effect of these two components allows the material to achieve a density close to theoretical density and controllable porosity, while simultaneously possessing excellent mechanical strength and air permeability.

[0129] Example 2

[0130] Air permeability test:

[0131] The gas permeability of the polytetrafluoroethylene membranes prepared in Examples 1-5 and Comparative Examples 1-3 was determined using a gas permeameter according to the ASTM E1449-23 standard method. Nitrogen was used as the test gas. The gas volume (ΔV) passing through a unit area (A) per unit time was recorded by adjusting the pressure difference across the membrane (1-20 kPa). The ambient temperature was controlled at 25 ± 1 °C, and the humidity at 50 ± 5%.

[0132] The test results are shown in Table 1.

[0133] Table 1

[0134]

[0135] Example 3

[0136] Mechanical property testing:

[0137] The mechanical properties of the polytetrafluoroethylene (PTFE) films prepared in Examples 1-5 and Comparative Examples 1-3 were characterized using stress-strain tensile testing. The tests were conducted according to ASTM D638 standard, with a tensile rate of 50 mm / min. Each sample was tested five times, and the average value was taken as the final result. The test results are shown in Table 2.

[0138] Table 2

[0139]

[0140] The polytetrafluoroethylene (PTFE) material provided by this invention significantly improves air permeability while ensuring that the mechanical properties meet application requirements. Specifically, it maintains a tensile strength of ≥5.38 MPa and an elongation at break of ≥54.24%. Simultaneously, with a pressure difference of 1 kPa across the material, the air permeability reaches 27.63 mL·min. -1 ·cm -2 Above; when the pressure difference across the material is 3 kPa, the air permeability reaches 40.56 mL·min. -1 ·cm -2 Above; when the pressure difference across the material is 5 kPa, the air permeability reaches 81.28 mL·min. -1 ·cm -2 Above; when the pressure difference across the material is 7 kPa, the air permeability reaches 110.58 mL·min. -1 ·cm -2 Above; when the pressure difference across the material is 10 kPa, the air permeability reaches 179.67 mL·min. -1 ·cm -2Above; when the pressure difference across the material is 15 kPa, the air permeability reaches 287.49 mL·min. -1 ·cm -2 Above; when the pressure difference across the material is 20 kPa, the air permeability reaches 373.98 mL·min. -1 ·cm -2 above.

[0141] Compared with Example 1, the main difference in Comparative Example 1 is the absence of perfluoroalkoxy polymer resin. As shown in Table 2, the polytetrafluoroethylene material prepared in Comparative Example 1 exhibits lower tensile strength and elongation at break, indicating weaker mechanical properties. This is because PFA provides excellent initial bonding and filling capabilities for the polytetrafluoroethylene material: PFA has high fluidity at high temperatures and can form a macroscopically uniform and microscopically compatible "alloyed" structure with the PTFE matrix. PTFE provides rigidity, heat resistance, and skeletal support, while PFA provides toughness, adhesion, and fluidity. This structure can most effectively transfer and disperse stress, avoid localized failure, and significantly enhance the mechanical properties of the polytetrafluoroethylene material.

[0142] Compared to Example 3, the main difference in Comparative Example 2 is that the mixture of perfluoroalkoxy polymer resin emulsion and PTFE was pre-sintered. As shown in Table 1, the PTFE material prepared in Comparative Example 2 has a lower air permeability, exhibiting poor air permeability. The process in Comparative Example 2 allows PFA to fully melt and fill the gaps between PTFE resin particles during the pre-sintering stage, forming a denser microstructure, resulting in lower air permeability than the present invention. Furthermore, the high-temperature molten state of PFA during pre-sintering interferes with the crystallization behavior of PTFE. PTFE crystallizes in the PFA melt environment, and its crystallization kinetics, crystal structure, and crystallinity may all change. The process of mixing before pre-sintering determines that PFA has already melted and participated in the blending before the PTFE skeleton is formed. This blended morphology cannot be reversed to the "PTFE skeleton-PFA filling" characteristic structure constructed in the present invention in any subsequent heat treatment step. Therefore, even if Comparative Example 2 undergoes final sintering, it cannot achieve the target microstructure and air permeability sought by the present invention.

[0143] Compared with Example 1, the main difference in Comparative Example 3 is that the solid mass ratio of the pre-sintered material to the perfluoroalkoxy polymer resin emulsion is 1:0.5. As shown in Table 1, the polytetrafluoroethylene material prepared in Comparative Example 3 has a lower air permeability, exhibiting poor air permeability. In Comparative Example 3, the amount of PFA added is too high, causing it to transform from a filler phase to a continuous phase, completely encapsulating or even "submerging" the PTFE skeleton. This thoroughly fills the pores of the PTFE skeleton, effectively blocking gas transmission channels and drastically reducing air permeability. At this point, the material properties are closer to those of the PFA bulk, losing the synergistic advantages of the "PTFE skeleton-PFA filler" composite structure.

[0144] The main difference between Example 1 and Example 2 is that the sintering temperature is 340℃. Table 1 shows that the polytetrafluoroethylene (PTFE) material prepared in Example 1 has better air permeability; appropriately lowering the sintering temperature is beneficial to improving the air permeability of the PTFE material. Table 2 shows that the PTFE material prepared in Example 2 exhibits better mechanical properties; appropriately increasing the sintering temperature is beneficial to improving the mechanical properties of the PTFE material.

[0145] This is because, at higher temperatures, PTFE and PFA resins can fully melt, significantly enhancing the viscous flow effect of the materials. The more fluid PFA melt can rapidly penetrate and fully fill the gaps between PTFE particles, while the PTFE melt, through slow flow, further promotes the fusion and tight bonding between particles. Under their synergistic effect, the pores inside the material shrink significantly; previously interconnected channels are closed or their diameters are reduced, ultimately leading to a decrease in the overall porosity of the material and an increase in the tortuosity of the internal pores, making it difficult for gas to penetrate. Therefore, the material obtained in Example 2 has lower air permeability and poorer air permeability. At the same time, the structure with more fully fused particles and fewer internal gaps also improves the material's density, making it less prone to breakage under stress, thus optimizing its mechanical properties.

[0146] Similarly, the main difference between Example 3 and Example 4 is that the sintering temperature is 340℃. The polytetrafluoroethylene material prepared in Example 4 exhibits poor air permeability and good mechanical properties.

[0147] Compared with Example 3, the main difference in Example 1 is that the solid mass ratio of the pre-sintered material to the perfluoroalkoxy polymer resin emulsion is 1:0.11. Table 1 shows that the polytetrafluoroethylene (PTFE) material prepared in Example 1 exhibits better air permeability; appropriately reducing the amount of perfluoroalkoxy polymer resin emulsion added is beneficial to improving the air permeability of the PTFE material. Table 2 shows that the PTFE material prepared in Example 3 exhibits better mechanical properties; appropriately increasing the amount of perfluoroalkoxy polymer resin emulsion added is beneficial to improving the mechanical properties of the PTFE material.

[0148] In Example 3, the increased PFA content led to a higher PTFE skeleton pore filling rate, an increase in blocked gas transport channels, and a decrease in permeability. The increased PFA content, which provides toughness, adhesion, and flowability, more effectively transferred and dispersed stress, thus enhancing the mechanical properties of the polytetrafluoroethylene material.

[0149] Similarly, compared with Example 4, the main difference in Example 2 is that the solid mass ratio of the pre-sintered material to the perfluoroalkoxy polymer resin emulsion is 1:0.11. The polytetrafluoroethylene material prepared in Example 4 exhibits poor air permeability and good mechanical properties.

[0150] Compared with Example 5, the main difference in Example 1 is that the solid mass ratio of the pre-sintered material to the perfluoroalkoxy polymer resin emulsion is 1:0.11. As shown in Table 2, the polytetrafluoroethylene material prepared in Example 5 has lower tensile strength and elongation at break, exhibiting weaker mechanical properties. This is because the amount of PFA added is too low, which cannot fully fill the pores and interparticle bonding sites of the PTFE skeleton, resulting in a lack of effective bonding between PTFE resin particles, significantly insufficient mechanical strength of the material, and a tendency for structural collapse. At the same time, PFA is scattered in the skeleton, making it difficult to form a continuous filling phase.

[0151] In summary, the polytetrafluoroethylene material prepared by this invention exhibits high and stable air permeability and excellent mechanical properties, achieving a good balance between air permeability and mechanical strength. The optimal air permeability is 571.59 mL·min at a pressure of 20 kPa. -1 ·cm -2 It boasts an optimal tensile strength of 10.46 MPa and an elongation at break of 85.16%. It has extremely high application value in fields such as battery explosion protection, waterproof and breathable structures for electronic devices, corrosion-resistant and breathable components for chemicals, and high-temperature gas filtration materials.

[0152] While specific embodiments of the present invention have been described above, those skilled in the art should understand that these are merely illustrative examples, and the scope of protection of the present invention is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, but all such changes and modifications fall within the scope of protection of the present invention.

Claims

1. A polytetrafluoroethylene material, characterized in that, The polytetrafluoroethylene material has a porous structure, which includes polytetrafluoroethylene resin and perfluoroalkoxy polymer resin, and the two are fused together on their surfaces; the mass ratio of the polytetrafluoroethylene resin to the perfluoroalkoxy polymer resin is 1:(0.05-0.4).

2. The polytetrafluoroethylene material as described in claim 1, characterized in that, It satisfies one or more of the following conditions: a. The thickness of the polytetrafluoroethylene material is 0.1-0.8 mm, for example, 0.5 mm; b. The pore size of the polytetrafluoroethylene material is 1-5 μm; c. The mass ratio of the polytetrafluoroethylene resin to the perfluoroalkoxy polymer resin is 1:(0.1-0.4), preferably 1:0.11 or 1:0.

25.

3. A method for preparing polytetrafluoroethylene material, characterized in that, The preparation method includes the following steps: S1. Pre-sinter the polytetrafluoroethylene resin raw material to obtain a pre-sintered material; S2. The mixture comprising the pre-sintered material and the perfluoroalkoxy polymer resin raw material is sintered to obtain the polytetrafluoroethylene material; the mass ratio of the pre-sintered material to the perfluoroalkoxy polymer resin raw material is 1:(0.05-0.4).

4. The method for preparing polytetrafluoroethylene material as described in claim 3, characterized in that, The preparation method of the polytetrafluoroethylene material satisfies one or more of the following conditions: a. The polytetrafluoroethylene resin raw material is prepared by suspension polymerization; b. D of the polytetrafluoroethylene resin raw material v 50 represents 100-260 μm; c. The perfluoroalkoxy polymer resin raw material is prepared by suspension polymerization; d. The D of the perfluoroalkoxy polymer resin raw material v 50 is 0.12-0.16μm.

5. The method for preparing polytetrafluoroethylene material as described in claim 3, characterized in that, The preparation method of the polytetrafluoroethylene material satisfies one or more of the following conditions: a. In step S1, the pre-sintering temperature is 350-360℃, for example, 360℃; b. In step S1, the pre-sintering time is 120-240 min, for example 240 min; c. In step S1, the pre-sintering process further includes crushing and / or sieving the pre-sintered material; wherein, the crushing method is preferably dry grinding; and the sieving method is preferably sieving through a sieve. d. In step S2, before sintering, the mixture is further subjected to molding treatment; wherein, the molding pressure is preferably 10-30 MPa, more preferably 20-25 MPa, for example 20 MPa; the molding time is preferably 1-10 min, more preferably 2-5 min, for example 3 min; the mold shape used for molding is optionally a hollow cylinder; e. In step S2, the sintering temperature is 300-400℃, preferably 330-360℃, for example 340℃ or 350℃; f. In step S2, the sintering time is 1-5 hours, preferably 2-4 hours, for example, 2 hours.

6. The method for preparing polytetrafluoroethylene material as described in claim 3, characterized in that, The preparation method of the mixture includes the following steps: stirring the pre-sintered material with the perfluoroalkoxy polymer resin raw material; The stirring speed is preferably 2000-6000 rpm, for example, 4000 rpm; The stirring time is preferably 5-30 min, for example 10 min.

7. The method for preparing polytetrafluoroethylene material as described in claim 3, characterized in that, The preparation method of the polytetrafluoroethylene material satisfies one or more of the following conditions: a. The pre-sintered material is the portion that can pass through an 80-mesh sieve but not through a 150-mesh sieve; b. The particle size of the pre-sintered material is 100-180μm; c. The perfluoroalkoxy polymer resin raw material is added to the reaction system in the form of an emulsion; wherein, the solid content of the emulsion is preferably 30 wt%-60 wt%, for example, 50 wt%; d. The mass ratio of the pre-sintered material to the perfluoroalkoxy polymer resin raw material is 1:(0.1-0.4), preferably 1:0.11 or 1:0.

25.

8. A polytetrafluoroethylene material, characterized in that, It is prepared using the method for preparing polytetrafluoroethylene material as described in any one of claims 3-7.

9. The use of a polytetrafluoroethylene material as described in claims 1-2 or 8 in a breathable assembly.

10. The application of the polytetrafluoroethylene material as described in claim 9 in a breathable component, characterized in that, The breathable components are used in power battery explosion-proof valves, energy storage battery pressure balancing components, waterproof and breathable structures for electronic devices, chemical corrosion-resistant breathable components, or high-temperature gas filtration materials.

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