PTFE-ceramic powder composite material, co-condensation preparation method and application thereof

Abstract

The application discloses a PTFE-ceramic powder composite material, a co-condensation preparation method and application, and relates to the technical field of polytetrafluoroethylene. The application is characterized in that a bifunctional grafting agent is prepared by means of ultraviolet click reaction of mercaptopropyl trimethoxysilane and allyl phosphonic acid diethyl ester, the bifunctional grafting agent is loaded on an alumina porous sheet, and the grafted alumina porous sheet is added into a polytetrafluoroethylene emulsion; the polytetrafluoroethylene emulsion is added into a ceramic powder slurry, and co-condensation, demulsification and hot-pressing preforming are carried out; during pre-hot-pressing forming, the polytetrafluoroethylene in the pores is softened by heat, and is fully filled in the pore space under the action of pressure, a large number of dense connection points are formed after cooling, the polytetrafluoroethylene matrix is firmly combined with the alumina skeleton, and the thermal degradation of the polytetrafluoroethylene caused by single high-temperature sintering is avoided; finally, a finished product composite material is prepared by means of forming and sintering.

Description

Technical Field

[0001] This invention relates to the field of polytetrafluoroethylene (PTFE) technology, specifically to a PTFE-ceramic powder composite material, a co-condensation preparation method, and its application. Background Technology

[0002] Polytetrafluoroethylene (PTFE) is widely used in sealing, bearings, electronic substrates, and other fields due to its excellent chemical stability, low coefficient of friction, and good dielectric properties. To improve its creep resistance, hardness, and thermal conductivity, ceramic powders (such as alumina, silicon dioxide, boron nitride, etc.) are often introduced to prepare PTFE-based composite materials.

[0003] Currently, the mainstream methods for preparing PTFE-ceramic composites mainly include: 1. Dry mixing: PTFE fine powder and ceramic powder are directly mechanically mixed. Although this method is simple, the mixing uniformity is poor, and filler agglomeration is prone to occur, resulting in uneven performance of the composite material. Furthermore, the interfacial bonding between the ceramic filler and the PTFE matrix is ​​weak during subsequent sintering.

[0004] 2. Wet mixing-demulsification: This method typically involves first dispersing ceramic powder in water, then adding PTFE emulsion. Demulsification is achieved by adding electrolytes such as acids or salts (e.g., hydrochloric acid, nitric acid, potassium chloride) or through mechanical stirring. While this method improves uniformity, it introduces additional chemicals that require repeated washing to remove. The process is lengthy, wastewater treatment is costly, and residual ions may affect the dielectric properties of the composite material, especially electronic materials.

[0005] In addition, preventing premature demulsification during the transportation and processing of PTFE emulsions is also a technical challenge.

[0006] Therefore, there is an urgent need in this field for a preparation method that can achieve efficient and uniform composite of PTFE and ceramic fillers, while avoiding the introduction of difficult-to-remove impurity ions, and which is simple and environmentally friendly. Summary of the Invention

[0007] The purpose of this invention is to provide a PTFE-ceramic powder composite material, a co-condensation preparation method, and its application, in order to solve the problems existing in the prior art.

[0008] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a method for co-condensing PTFE-ceramic powder composite material, comprising the following preparation steps: (1) Allylphosphonate diethyl ester, mercaptopropyltrimethoxysilane, photoinitiator benzoin dimethyl ether and anhydrous ethanol are mixed and placed under 365nm ultraviolet light for 0.5~1.5h. The solvent is removed by rotary evaporation to obtain a bifunctional grafting agent. (2) Immerse the porous alumina sheet in a bifunctional grafting agent aqueous solution for 15 min, filter and dry it, then immerse it in polytetrafluoroethylene emulsion, and obtain the loaded porous alumina sheet by pressure-assisted impregnation and drying. (3) Add ceramic powder to alcohol and stir to disperse evenly to obtain ceramic slurry. Under stirring conditions, add loaded alumina porous sheets, followed by polytetrafluoroethylene emulsion. Alcohol is used to simultaneously achieve dispersion, demulsification and co-coagulation to form co-coagulated material. (4) Pour the coagulated slurry into a steel mold and pre-form it under constant temperature and pressure. After cooling, a pre-formed blank is obtained. (5) Perform stepwise high-temperature sintering and molding. Place the preformed blank in an atmosphere sintering furnace, introduce a protective atmosphere, raise the temperature and hold it for sintering, and then cool it with the furnace to obtain polytetrafluoroethylene composite ceramic material.

[0009] Furthermore, in step (1), the mass ratio of allyl phosphonate diethyl ester, mercaptopropyltrimethoxysilane, photoinitiator benzoin dimethyl ether, and anhydrous ethanol is 1.6~1.9:2.2~2.5:0.060~0.065:78.

[0010] Furthermore, in step (2), the porous alumina sheet has a porosity of 40% and an average pore size of 50 μm.

[0011] Furthermore, in step (2), the solid-liquid ratio of the porous alumina sheet and the aqueous solution of the bifunctional grafting agent is 1:10 to 1:15, and the solid content of the polytetrafluoroethylene emulsion is 60%.

[0012] Furthermore, in step (2), the pressure of pressure-assisted impregnation is 0.5~1.2MPa, the impregnation time is 30~70min, and the drying temperature is 70~90℃.

[0013] Furthermore, in step (3), the ceramic powder is one or more of alumina and silicon dioxide, with an average particle size of 0.1 μm to 20 μm.

[0014] Furthermore, in step (3), the mass ratio of the loaded alumina porous sheet to the ceramic powder is 1~10:100, the mass ratio of polytetrafluoroethylene pure resin to the ceramic powder is 0.5~1.5:1, and the solid content of the polytetrafluoroethylene emulsion is 60%.

[0015] Furthermore, in step (4), the temperature of hot pressing preforming is 80~120℃, the pressure is 10~20MPa, and the hot pressing time is 2h.

[0016] Furthermore, in step (5), the protective atmosphere is nitrogen; the heating rate is 5℃ / min; the sintering temperature is 360~400℃; and the holding sintering time is 2h.

[0017] Furthermore, the composite material is used in the preparation of sealing materials, bearing materials, and electronic substrate materials.

[0018] Compared with the prior art, the beneficial effects achieved by the present invention are: First, a bifunctional grafting agent was prepared by UV-Vis click reaction using mercaptopropyltrimethoxysilane and diethyl allylphosphonate. This bifunctional grafting agent formed a uniform coupling layer on the surface of porous alumina sheets. On one side, this layer adhered stably to the alumina framework through siloxane hydrolysis products, while on the other side, it bonded to the ceramic powder surface through phosphonate groups, connecting the ceramic powder and the porous sheets. This further enhanced the interfacial bonding and suppressed crack initiation caused by localized stress concentration. Next, the grafted porous alumina sheets were added to a polytetrafluoroethylene (PTFE) emulsion. Pressure-assisted impregnation impregnated the PTFE emulsion into the pores of the porous alumina sheets, achieving initial fixation within the pores to obtain a doped PTFE emulsion. Secondly, the polytetrafluoroethylene (PTFE) emulsion is added to the ceramic powder slurry for co-coagulation, demulsification, and hot-pressing preforming. This application uses alcohol as both the dispersion medium for the ceramic filler and the demulsifier for the PTFE emulsion, combining multiple steps of dispersion, mixing, demulsification, and co-coagulation into a single operation unit. This significantly simplifies the process, improves production efficiency, and during preheating and pressing, improves the uniformity and interfacial continuity of the green body. Simultaneously, the PTFE within the pores softens upon heating and fully fills the pore space under pressure, forming numerous dense connection points upon cooling. This firmly bonds the PTFE emulsion to the alumina skeleton, significantly limiting the sliding tendency of the PTFE molecular chains under external force, improving dimensional stability, and enhancing the bonding strength between the two phases. Finally, the composite material is sintered to obtain the final product. The synergy between preheating and subsequent high-temperature sintering avoids the thermal degradation of PTFE that might occur with a single high-temperature sintering, achieving uniformity of the material's internal structure through stepwise densification. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] To more clearly illustrate the method provided by the present invention, the following embodiments are provided in detail. The test methods for various indicators of the PTFE-ceramic powder composite material prepared in the following embodiments are as follows: Mechanical properties: The PTFE-ceramic powder composite materials prepared by Examples 1-5 and Comparative Examples 1-4 of the same mass were tested according to GB / T 9341-2008 standard for flexural strength and according to GB / T 1040.2-2006 standard for tensile strength to evaluate the mechanical load-bearing capacity of the materials.

[0021] Dimensional stability: The PTFE-ceramic powder composite materials prepared by Examples 1-5 and Comparative Examples 1-4 of the same mass were tested for the coefficient of linear expansion in the range of -30℃ to 120℃ according to GB / T 1036-2008; at the same time, the thermal shrinkage rate of the samples after being placed at a constant temperature of 150℃ for 24 hours was tested to evaluate the dimensional stability of the materials during long-term service.

[0022] Interfacial bonding performance: The PTFE-ceramic powder composite materials prepared by Examples 1-5 and Comparative Examples 1-4 of the same mass were tested by the interfacial shear strength test method to evaluate the interfacial bonding strength between the ceramic phase and the polytetrafluoroethylene body and the crack initiation resistance.

[0023] Wear resistance: The PTFE-ceramic powder composite materials prepared by Examples 1-5 and Comparative Examples 1-4 of the same mass were tested according to GB / T 3960-2016 standard to evaluate the service wear resistance of the materials by measuring the coefficient of friction and wear amount.

[0024] Example 1 (1) Allyl phosphonate diethyl ester, mercaptopropyltrimethoxysilane, photoinitiator benzoin dimethyl ether and anhydrous ethanol are mixed and placed under 365 nm ultraviolet light for 0.5 h. The solvent is removed by rotary evaporation to obtain a bifunctional grafting agent. The mass ratio of allyl phosphonate diethyl ester, mercaptopropyltrimethoxysilane, photoinitiator and anhydrous ethanol is 1.6:2.2:0.060:78. (2) The porous alumina sheet was immersed in a bifunctional grafting agent aqueous solution for 15 min, filtered, dried, and then immersed in polytetrafluoroethylene emulsion. After pressure-assisted impregnation and drying, the loaded porous alumina sheet was obtained. The porosity of the porous alumina sheet was 40% and the average pore size was 50 μm. The solid-liquid ratio of the porous alumina sheet and the bifunctional grafting agent aqueous solution was 1:10, and the solid content of the polytetrafluoroethylene emulsion was 60%. The pressure for pressure-assisted impregnation was 0.5 MPa, the impregnation time was 30 min, and the drying temperature was 70 °C. (3) Add ceramic powder to alcohol and stir to disperse evenly to obtain ceramic slurry. Under stirring conditions, add alumina porous sheets, followed by polytetrafluoroethylene emulsion. Alcohol is used to simultaneously disperse, demulsify and co-coagulate to form a co-coagulated material. The ceramic powder is alumina with an average particle size of 0.1 μm. The mass ratio of alumina porous sheets to ceramic powder is 1:100. The mass ratio of polytetrafluoroethylene pure resin, alcohol and ceramic powder is 0.5:2:1. The solid content of polytetrafluoroethylene emulsion is 60%. (4) The coagulated slurry is poured into a steel mold and pre-formed under constant temperature and pressure. After cooling, a pre-formed blank is obtained. The temperature of the hot pressing pre-forming is 80℃, the pressure is 10MPa, and the hot pressing time is 2h. (5) Perform stepwise high-temperature sintering and molding. Place the preformed blank in an atmosphere sintering furnace, introduce a protective atmosphere, heat up and hold for sintering, and cool with the furnace to obtain polytetrafluoroethylene composite ceramic material. The protective atmosphere is nitrogen. The heating rate is 5℃ / min, the sintering temperature is 360℃, and the holding sintering time is 2h.

[0025] Example 2 (1) Allyl phosphonate diethyl ester, mercaptopropyltrimethoxysilane, photoinitiator benzoin dimethyl ether and anhydrous ethanol are mixed and placed under 365 nm ultraviolet light for 0.8 h. The solvent is removed by rotary evaporation to obtain a bifunctional grafting agent. The mass ratio of allyl phosphonate diethyl ester, mercaptopropyltrimethoxysilane, photoinitiator and anhydrous ethanol is 1.7:2.3:0.062:78. (2) The porous alumina sheet was immersed in a bifunctional grafting agent aqueous solution for 15 min, filtered, dried, and then immersed in polytetrafluoroethylene emulsion. After pressure-assisted impregnation and drying, the loaded porous alumina sheet was obtained. The porosity of the porous alumina sheet was 40% and the average pore size was 50 μm. The solid-liquid ratio of the porous alumina sheet and the bifunctional grafting agent aqueous solution was 1:12, and the solid content of the polytetrafluoroethylene emulsion was 60%. The pressure for pressure-assisted impregnation was 0.8 MPa, the impregnation time was 45 min, and the drying temperature was 75 °C. (3) Add ceramic powder to alcohol and stir to disperse evenly to obtain ceramic slurry. Under stirring conditions, add alumina porous sheets, followed by polytetrafluoroethylene emulsion. Alcohol is used to simultaneously disperse, demulsify and co-coagulate to form a co-coagulated material. The ceramic powder is silicon dioxide with an average particle size of 10 μm. The mass ratio of alumina porous sheets to ceramic powder is 5:100, the mass ratio of polytetrafluoroethylene pure resin, alcohol and ceramic powder is 1.0:2:1, and the solid content of polytetrafluoroethylene emulsion is 60%. (4) The coagulated slurry is poured into a steel mold and pre-formed under constant temperature and pressure. After cooling, a pre-formed blank is obtained. The temperature of the hot pressing pre-forming is 100℃, the pressure is 15MPa, and the hot pressing time is 2h. (5) Perform stepwise high-temperature sintering and molding. Place the preformed blank in an atmosphere sintering furnace, introduce a protective atmosphere, heat up and hold for sintering, and cool with the furnace to obtain polytetrafluoroethylene composite ceramic material. The protective atmosphere is nitrogen. The heating rate is 5℃ / min, the sintering temperature is 380℃, and the holding sintering time is 2h.

[0026] Example 3 (1) Allyl phosphonate diethyl ester, mercaptopropyltrimethoxysilane, photoinitiator benzoin dimethyl ether and anhydrous ethanol are mixed and placed under 365 nm ultraviolet light for 1.0 h. The solvent is removed by rotary evaporation to obtain a bifunctional grafting agent. The mass ratio of allyl phosphonate diethyl ester, mercaptopropyltrimethoxysilane, photoinitiator and anhydrous ethanol is 1.75:2.35:0.063:78. (2) The porous alumina sheet was immersed in a bifunctional grafting agent aqueous solution for 15 min, filtered, dried, and then immersed in polytetrafluoroethylene emulsion. After pressure-assisted impregnation and drying, the loaded porous alumina sheet was obtained. The porosity of the porous alumina sheet was 40% and the average pore size was 50 μm. The solid-liquid ratio of the porous alumina sheet and the bifunctional grafting agent aqueous solution was 1:13, and the solid content of the polytetrafluoroethylene emulsion was 60%. The pressure for pressure-assisted impregnation was 1.0 MPa, the impregnation time was 50 min, and the drying temperature was 80 °C. (3) Add ceramic powder to alcohol and stir to disperse evenly to obtain ceramic slurry. Under stirring conditions, add alumina porous sheets, followed by polytetrafluoroethylene emulsion. Alcohol is used to simultaneously disperse, demulsify and co-coagulate to form a co-coagulated material. The ceramic powder is a mixture of alumina and silica (mass ratio 1:1) with an average particle size of 15 μm. The mass ratio of alumina porous sheets to ceramic powder is 7:100, the mass ratio of polytetrafluoroethylene pure resin, alcohol and ceramic powder is 1.2:2:1, and the solid content of polytetrafluoroethylene emulsion is 60%. (4) The coagulated slurry is poured into a steel mold and pre-formed under constant temperature and pressure. After cooling, a pre-formed blank is obtained. The temperature of the hot pressing pre-forming is 110℃, the pressure is 18MPa, and the hot pressing time is 2h. (5) Stepwise high-temperature sintering is carried out. The preformed blank is placed in an atmosphere sintering furnace, and after the protective atmosphere is introduced, the temperature is raised and held for sintering. After cooling in the furnace, polytetrafluoroethylene composite ceramic material is obtained. The protective atmosphere is nitrogen. The heating rate is 5℃ / min, the sintering temperature is 390℃, and the holding sintering time is 2h.

[0027] Example 4 (1) Allyl phosphonate diethyl ester, mercaptopropyltrimethoxysilane, photoinitiator benzoin dimethyl ether and anhydrous ethanol are mixed and placed under 365 nm ultraviolet light for 1.2 h. The solvent is removed by rotary evaporation to obtain a bifunctional grafting agent. The mass ratio of allyl phosphonate diethyl ester, mercaptopropyltrimethoxysilane, photoinitiator and anhydrous ethanol is 1.8:2.4:0.064:78. (2) The porous alumina sheet was immersed in a bifunctional grafting agent aqueous solution for 15 min, filtered, dried, and then immersed in polytetrafluoroethylene emulsion. After pressure-assisted impregnation and drying, a loaded porous alumina sheet was obtained. The porosity of the porous alumina sheet was 40% and the average pore size was 50 μm. The solid-liquid ratio of the porous alumina sheet and the bifunctional grafting agent aqueous solution was 1:14, and the solid content of the polytetrafluoroethylene emulsion was 60%. The pressure for pressure-assisted impregnation was 1.1 MPa, the impregnation time was 60 min, and the drying temperature was 85 °C. (3) Add ceramic powder to alcohol and stir to disperse evenly to obtain ceramic slurry. Under stirring conditions, add alumina porous sheets, followed by polytetrafluoroethylene emulsion. Alcohol is used to simultaneously disperse, demulsify and co-coagulate to form a co-coagulated material. The ceramic powder is silicon dioxide with an average particle size of 18 μm. The mass ratio of alumina porous sheets to ceramic powder is 9:100, the mass ratio of polytetrafluoroethylene pure resin, alcohol and ceramic powder is 1.4:2:1, and the solid content of polytetrafluoroethylene emulsion is 60%. (4) The coagulated slurry is poured into a steel mold and pre-formed under constant temperature and pressure. After cooling, a pre-formed blank is obtained. The temperature of the hot pressing pre-forming is 115℃, the pressure is 19MPa, and the hot pressing time is 2h. (5) Stepwise high-temperature sintering is carried out. The preformed blank is placed in an atmosphere sintering furnace, and after the protective atmosphere is introduced, the temperature is raised and held for sintering. After cooling in the furnace, polytetrafluoroethylene composite ceramic material is obtained. The protective atmosphere is nitrogen. The heating rate is 5℃ / min, the sintering temperature is 395℃, and the holding sintering time is 2h.

[0028] Example 5 (1) Allyl phosphonate diethyl ester, mercaptopropyltrimethoxysilane, photoinitiator benzoin dimethyl ether and anhydrous ethanol are mixed and placed under 365 nm ultraviolet light for 1.5 h. The solvent is removed by rotary evaporation to obtain a bifunctional grafting agent. The mass ratio of allyl phosphonate diethyl ester, mercaptopropyltrimethoxysilane, photoinitiator and anhydrous ethanol is 1.9:2.5:0.065:78. (2) The porous alumina sheet was immersed in a bifunctional grafting agent aqueous solution for 15 min, filtered, dried, and then immersed in polytetrafluoroethylene emulsion. After pressure-assisted impregnation and drying, the loaded porous alumina sheet was obtained. The porosity of the porous alumina sheet was 40% and the average pore size was 50 μm. The solid-liquid ratio of the porous alumina sheet and the bifunctional grafting agent aqueous solution was 1:15, and the solid content of the polytetrafluoroethylene emulsion was 60%. The pressure for pressure-assisted impregnation was 1.2 MPa, the impregnation time was 70 min, and the drying temperature was 90 °C. (3) Add ceramic powder to alcohol and stir to disperse evenly to obtain ceramic slurry. Under stirring conditions, add alumina porous sheets, followed by polytetrafluoroethylene emulsion. Alcohol is used to simultaneously disperse, demulsify and co-coagulate to form a co-coagulated material. The ceramic powder is alumina with an average particle size of 20 μm. The mass ratio of alumina porous sheets to ceramic powder is 10:100, the mass ratio of polytetrafluoroethylene pure resin, alcohol and ceramic powder is 1.5:2:1, and the solid content of polytetrafluoroethylene emulsion is 60%. (4) The coagulated slurry is poured into a steel mold and pre-formed under constant temperature and pressure. After cooling, a pre-formed blank is obtained. The temperature of the hot pressing pre-forming is 120℃, the pressure is 20MPa, and the hot pressing time is 2h. (5) Perform stepwise high-temperature sintering and molding. Place the preformed blank in an atmosphere sintering furnace, introduce a protective atmosphere, heat up and hold for sintering, and cool with the furnace to obtain polytetrafluoroethylene composite ceramic material. The protective atmosphere is nitrogen. The heating rate is 5℃ / min, the sintering temperature is 400℃, and the holding sintering time is 2h.

[0029] Comparative Example 1 The difference between Comparative Example 1 and Example 2 is that step (1) is omitted, and the bifunctional grafting agent solution in step (2) is replaced with KH550 solution; the remaining steps are the same as in Example 2.

[0030] Comparative Example 2 The difference between Comparative Example 2 and Example 3 lies in step (2), where pressure-assisted impregnation is not used; the remaining steps are the same as in Example 3.

[0031] Comparative Example 3 The difference between Comparative Example 3 and Example 3 lies in step (3). Step (3) does not use the one-step co-coagulation demulsification process of anhydrous ethanol. Instead, deionized water is used as the dispersion medium to prepare the ceramic slurry. After mixing, calcium chloride demulsifier is added to perform demulsification. The remaining steps are the same as in Example 3.

[0032] Comparative Example 4 The difference between Comparative Example 4 and Example 3 lies in step (4). In step (4), hot pressing pre-forming is not performed. After the mixed slurry is dried, it is directly put into the sintering furnace and heated to 390°C in one step for sintering. The remaining steps are the same as in Example 3.

[0033] Comparative Example 5 The difference between Comparative Example 5 and Example 3 is that steps (1) and (3) are omitted. In step (3), the loaded alumina porous sheet is not added, and the conventional composite material is prepared by directly blending and sintering ceramic powder with polytetrafluoroethylene emulsion. The remaining steps are the same as in Example 3.

[0034] Example of effect Table 1 below shows the performance analysis results of the PTFE-ceramic powder composite materials of Examples 1 to 3 and Comparative Examples 1 to 5 of the present invention.

[0035]

[0036] A comparison of experimental data from the examples and comparative examples reveals that the present invention uses mercaptopropyltrimethoxysilane and diethyl allylphosphonate to prepare a bifunctional grafting agent via a UV-click reaction. This bifunctional grafting agent forms a uniform coupling layer on the surface of the porous alumina sheet. On one side, this layer adheres stably to the alumina framework through siloxane hydrolysis products, while on the other side, it bonds to the ceramic powder surface through phosphonate groups, connecting the ceramic powder and the porous sheet, further enhancing interfacial bonding and inhibiting crack initiation caused by localized stress concentration. The grafted porous alumina sheet is then added to a polytetrafluoroethylene (PTFE) emulsion, and pressure-assisted impregnation is used to impregnate the PTFE emulsion into the pores of the porous alumina sheet, allowing for initial fixation within the pores, resulting in a doped PTFE emulsion. Secondly, the polytetrafluoroethylene (PTFE) emulsion is added to the ceramic powder slurry for co-coagulation, demulsification, and hot-pressing preforming. This application uses alcohol as both the dispersion medium for the ceramic filler and the demulsifier for the PTFE emulsion, combining multiple steps of dispersion, mixing, demulsification, and co-coagulation into a single operation unit. This significantly simplifies the process, improves production efficiency, and during preheating and pressing, improves the uniformity and interfacial continuity of the green body. Simultaneously, the PTFE within the pores softens upon heating and fully fills the pore space under pressure, forming numerous dense connection points upon cooling. This firmly bonds the PTFE emulsion to the alumina skeleton, significantly limiting the sliding tendency of the PTFE molecular chains under external force, improving dimensional stability, and enhancing the bonding strength between the two phases. Finally, the composite material is sintered to obtain the final product. The synergy between preheating and subsequent high-temperature sintering avoids the thermal degradation of PTFE that might occur with a single high-temperature sintering, achieving uniformity of the material's internal structure through stepwise densification.

[0037] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No markings in the claims should be construed as limiting the scope of the claims.

Claims

1. A method for co-condensing PTFE-ceramic powder composite materials, characterized in that, The preparation steps include the following: (1) Allylphosphonate diethyl ester, mercaptopropyltrimethoxysilane, photoinitiator benzoin dimethyl ether and anhydrous ethanol are mixed and placed under 365nm ultraviolet light for 0.5~1.5h. The solvent is removed by rotary evaporation to obtain a bifunctional grafting agent. (2) Immerse the porous alumina sheet in a bifunctional grafting agent aqueous solution for 15 min, filter and dry it, then immerse it in polytetrafluoroethylene emulsion, and obtain the loaded porous alumina sheet by pressure-assisted impregnation and drying. (3) Add ceramic powder to alcohol and stir to disperse evenly to obtain ceramic slurry. Under stirring conditions, add loaded alumina porous sheets, followed by polytetrafluoroethylene emulsion. Alcohol is used to simultaneously achieve dispersion, demulsification and co-coagulation to form co-coagulated material. (4) Pour the coagulated slurry into a steel mold and pre-form it under constant temperature and pressure. After cooling, a pre-formed blank is obtained. (5) Perform stepwise high-temperature sintering and molding. Place the preformed blank in an atmosphere sintering furnace, introduce a protective atmosphere, raise the temperature and hold it for sintering, and then cool it with the furnace to obtain polytetrafluoroethylene composite ceramic material.

2. The method for co-condensing PTFE-ceramic powder composite material according to claim 1, characterized in that, In step (1), the mass ratio of allyl phosphonate diethyl ester, mercaptopropyltrimethoxysilane, photoinitiator benzoin dimethyl ether, and anhydrous ethanol is 1.6~1.9:2.2~2.5:0.060~0.065:

78.

3. The method for preparing a PTFE-ceramic powder composite material by co-aggregation according to claim 1, characterized in that, In step (2), the porous alumina sheet has a porosity of 40% and an average pore size of 50 μm.

4. The method for co-condensing PTFE-ceramic powder composite material according to claim 1, characterized in that, In step (2), the solid-liquid ratio of the porous alumina sheet and the aqueous solution of the bifunctional grafting agent is 1:10 to 1:15, and the solid content of the polytetrafluoroethylene emulsion is 60%.

5. The method for co-condensing PTFE-ceramic powder composite material according to claim 1, characterized in that, In step (2), the pressure for pressure-assisted impregnation is 0.5~1.2MPa, the impregnation time is 30~70min, and the drying temperature is 70~90℃.

6. The method for preparing a PTFE-ceramic powder composite material by co-aggregation according to claim 1, characterized in that, In step (3), the ceramic powder is one or more of alumina and silicon dioxide, with an average particle size of 0.1 μm to 20 μm.

7. The method for co-condensing PTFE-ceramic powder composite material according to claim 1, characterized in that, In step (3), the mass ratio of the loaded alumina porous sheet to the ceramic powder is 1~10:100, the mass ratio of polytetrafluoroethylene pure resin to the ceramic powder is 0.5~1.5:1, and the solid content of the polytetrafluoroethylene emulsion is 60%.

8. The method for preparing a PTFE-ceramic powder composite material by co-aggregation according to claim 1, characterized in that, In step (4), the temperature of hot pressing preforming is 80~120℃, the pressure is 10~20MPa, and the hot pressing time is 2h.

9. The method for preparing a PTFE-ceramic powder composite material by co-aggregation according to claim 1, characterized in that, In step (5), the protective atmosphere is nitrogen; the heating rate is 5℃ / min; the sintering temperature is 360~400℃; and the holding sintering time is 2h.

10. The application of a PTFE-ceramic powder composite material according to any one of claims 1-9 in the preparation of sealing materials, bearing materials, and electronic substrate materials.

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