A wear-resistant modified polytetrafluoroethylene composite material and its preparation method

Abstract

This invention discloses a wear-resistant modified polytetrafluoroethylene (PTFE) composite material and its preparation method. The modified PTFE composite material of this invention is prepared by filling PTFE with Ga / Al-LDHs and PEEK modification materials. It is prepared by high-speed blending, compression molding, hot sintering treatment and sample preparation. The modified PTFE composite material filled with Ga / Al-LDHs and PEEK has a low coefficient of friction, a low wear rate, high wear resistance, and maintains the excellent mechanical properties of PTFE. Moreover, the production process is simple and can realize large-scale industrial production.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high polymer material science, in particular to a wear-resistant modified polytetrafluoroethylene composite material and a preparation method thereof. BACKGROUND

[0002] Polytetrafluoroethylene has corrosion resistance, and almost does not react with strong acid, strong base (concentrated sulfuric acid, caustic soda, aqua regia), strong oxidant (potassium permanganate, peroxide, potassium dichromate) and the like, and is often used as a protective layer of a metal surface; polytetrafluoroethylene is an excellent insulator, and the molecular chain thereof has non-polarity and stable dielectric performance; polytetrafluoroethylene also has the characteristics of high and low temperature resistance, and still maintains excellent mechanical properties in a wide temperature range of -190-260 DEG C. Although polytetrafluoroethylene has a very low friction coefficient, the wear rate is large, and thus the wear resistance of polytetrafluoroethylene is poor, which greatly limits the application of polytetrafluoroethylene.

[0003] Filling modification is to add functional fillers in a polytetrafluoroethylene matrix resin for composite modification, so as to improve and overcome the defects of polytetrafluoroethylene, fully play the synergistic complementary effect of two or more components on the basis of maintaining the original advantages. Therefore, the present application adopts the method of filling modification to enhance the friction performance of the polytetrafluoroethylene composite material, wherein the fillers are composed of calcium-aluminum hydrotalcite (Ca / Al-LDHs) and polyether ether ketone (PEEK), and the friction performance can be maximally improved by filling modification to prepare high wear-resistant polytetrafluoroethylene composite material. Moreover, the present application has the advantages of simple process, low cost and suitability for mass production, and is conducive to industrialization and popularization. SUMMARY

[0004] The present application aims to provide a wear-resistant modified polytetrafluoroethylene composite material and a preparation method thereof, which uses Ca / Al-LDHs and PEEK as fillers to prepare the polytetrafluoroethylene composite material by synergistic effect. Another object of the present application is to maintain the excellent mechanical properties of the polytetrafluoroethylene composite material.

[0005] The technical scheme of the present application is as follows:

[0006] A wear-resistant modified polytetrafluoroethylene composite material is prepared by filling Ca / Al-LDHs and PEEK modified material in polytetrafluoroethylene; the Ca / Al-LDHs accounts for 1-12 wt% of the total weight of the modified polytetrafluoroethylene composite material, the PEEK accounts for 5-50 wt% of the total weight of the modified polytetrafluoroethylene composite material, and the polytetrafluoroethylene accounts for 94-38 wt% of the total weight of the modified polytetrafluoroethylene composite material.

[0007] The abrasion-resistant modified polytetrafluoroethylene composite material as described above, wherein the Ca / Al-LDHs account for 1-8 wt% of the total weight of the polytetrafluoroethylene composite material, the PEEK accounts for 10-54 wt% of the total weight of the polytetrafluoroethylene composite material, and the polytetrafluoroethylene accounts for 89-38 wt% of the total weight of the polytetrafluoroethylene composite material.

[0008] Specifically, the abrasion-resistant modified polytetrafluoroethylene composite material as described above, wherein the Ca / Al-LDHs account for 2-4 wt% of the total weight of the polytetrafluoroethylene composite material, the PEEK accounts for 20-30 wt% of the total weight of the polytetrafluoroethylene composite material, and the polytetrafluoroethylene accounts for 78-66 wt% of the total weight of the polytetrafluoroethylene composite material.

[0009] The method for preparing the abrasion-resistant modified polytetrafluoroethylene composite material as described above is performed according to the following steps:

[0010] (1) Mixing: mixing the polytetrafluoroethylene, the Ca / Al-LDHs and the PEEK by a high-speed mixing machine at 1000-1400 r / min for 15-25 minutes to obtain A product;

[0011] (2) Compression molding: pouring the A product into a cold mold press mold, and cold pressing the powder at a pressure of 35-55 MPa at room temperature for 10-30 minutes to obtain B product;

[0012] (3) Hot sintering treatment: placing the B product in a sintering furnace, increasing the temperature from room temperature to 322-332 ℃ at a temperature increasing rate of 0.5-1.5 ℃ / min, and heat treating at 322-332 ℃ for 55-65 min, then increasing the temperature to 370-380 ℃ at a temperature increasing rate of 0.5-1.5 ℃ / min and heat treating for 80-100 min, then decreasing the temperature from 370-380 ℃ to 322-332 ℃ at a temperature decreasing rate of 1-2 ℃ / min and heat treating for 55-65 min, turning off the power after the heat treatment is completed, and naturally cooling to room temperature, then cutting and sampling to obtain the polytetrafluoroethylene composite material.

[0013] In the step (1) as described above, mixing: mixing the polytetrafluoroethylene, the Ca / Al-LDHs and the PEEK by a high-speed mixing machine at 1200 r / min for 20 minutes to obtain A product.

[0014] In the step (2) as described above, compression molding: pouring the A product into a cold mold press mold, and cold pressing the powder at a pressure of 40-50 MPa at room temperature for 15-25 minutes to obtain B product.

[0015] In the aforementioned step (3), the thermal sintering treatment: the B product is placed in a sintering furnace, the temperature is increased from room temperature to 327℃ at a rate of 1℃ / min, and the temperature is kept at 327℃ for 60min, then increased to 375℃ at a rate of 1℃ / min and kept for 90min, then decreased from 375℃ to 327℃ at a rate of 1.5℃ / min and kept for 60min, after the keeping, the power is turned off, and it is naturally cooled to room temperature, then the sample is cut and prepared, and the modified polytetrafluoroethylene composite material is obtained.

[0016] Compared with the prior art, the present application has the following beneficial effects:

[0017] 1、The present application uses Ca / Al-LDHs and PEEK as synergistic fillers to fill polytetrafluoroethylene composites. Ca / Al-LDHs enhances the surface, soft micro-filler PEEK enhances the subsurface, and the combination of PTFE through surface and subsurface enhancement can achieve ultra-low wear rate. The wear rate of the polytetrafluoroethylene composite filled with Ca / Al-LDHs and PEEK is only 1 / 150-1 / 300 of that of pure polytetrafluoroethylene, and the modified polytetrafluoroethylene composite filled with Ca / Al-LDHs and PEEK has a low friction coefficient.

[0018] 2、The modified polytetrafluoroethylene composite filled with Ca / Al-LDHs and PEEK can maintain the excellent mechanical properties of polytetrafluoroethylene.

[0019] 3、The present application uses a filling modification method to enhance the wear resistance of polytetrafluoroethylene, and the production process is simple and can realize industrialized mass production. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 : Friction coefficient and wear rate of polytetrafluoroethylene composite with 0wt%, 1wt%, 2wt%, 4wt%, 8wt% and 12wt% Ca / Al-LDHs and 20wt% PEEK added respectively;

[0021] Figure 2 : Friction coefficient and wear rate of polytetrafluoroethylene composite with 0wt%, 5wt%, 10wt%, 20wt%, 30wt% and 50wt% PEEK and 4wt% Ca / Al-LDHs added respectively;

[0022] Figure 3 : Pure polytetrafluoroethylene and polytetrafluoroethylene composite product picture (A: pure polytetrafluoroethylene prepared in Example 1; B: polytetrafluoroethylene composite material prepared in Example 5). DETAILED DESCRIPTION

[0023] The application will be described in detail below by examples. It is necessary to point out that the following examples are only used to further illustrate the application and cannot be understood as limiting the protection scope of the application.

[0024] Example 1

[0025] Preparation of pure polytetrafluoroethylene: polytetrafluoroethylene powder was poured into a cold die mold, and the mixed powder was cold-pressed at a pressure of 40-50 MPa for 15-25 min at room temperature. After the mixed powder was treated by pressing, it was taken out of the cold die mold, trimmed to remove burrs, and made smooth and flat to obtain a composite sheet. The composite sheet was placed in a sintering furnace for heat treatment. The temperature of the sintering furnace was first increased from room temperature to 327℃ at a rate of 1℃ / min, and the sample was heat treated at 327℃ for 60 min. Then the temperature was increased to 375℃ at a rate of 1℃ / min and heat treated for 90 min. Then the temperature was decreased from 375℃ to 327℃ at a rate of 1.5℃ / min for 60 min. Finally, after the heat treatment was completed, the power was turned off and it was naturally cooled to room temperature. After the temperature of the furnace was cooled to room temperature, the heat-treated sheet was taken out of the furnace, and a CNC machine tool was used to cut and sample to prepare a pure polytetrafluoroethylene test sample.

[0026] Example 2

[0027] Material ratio: 0wt% Ca / Al-LDHs, 20wt% PEEK and 80wt% polytetrafluoroethylene.

[0028] Preparation method of modified polytetrafluoroethylene composite material: PEEK was added to polytetrafluoroethylene for high-speed blending, and the mixed powder was mixed in a high-speed mixing machine at 1200 r / min for 20 min. Then the mixed powder was poured into a cold die mold and cold-pressed at a pressure of 40-50 MPa for 15-25 min at room temperature. After the mixed powder was treated by pressing, it was taken out of the cold die mold, trimmed to remove burrs, and made smooth and flat to obtain a composite sheet. Then it was placed in a sintering furnace for heat treatment. The temperature of the sintering furnace was first increased from room temperature to 327℃ at a rate of 1℃ / min, and the sample was heat treated at 327℃ for 60 min. Then the temperature was increased to 375℃ at a rate of 1℃ / min and heat treated for 90 min. Then the temperature was decreased from 375℃ to 327℃ at a rate of 1.5℃ / min for 60 min. Finally, after the heat treatment was completed, the power was turned off and it was naturally cooled to room temperature. After the temperature of the furnace was cooled to room temperature, the heat-treated sheet was taken out of the furnace, and a CNC machine tool was used to cut and sample to obtain a polytetrafluoroethylene composite material.

[0029] Example 3

[0030] Material composition: 1wt% Ca / Al-LDHs, 20wt% PEEK and 79wt% polytetrafluoroethylene;

[0031] Preparation method of modified polytetrafluoroethylene composite material: Ca / Al-LDHs and PEEK are added to polytetrafluoroethylene and blended at high speed using a high-speed mixer at 1200 r / min for 20 minutes. The mixed powder is then poured into a cold molding die and cold-pressed at 40–50 MPa for 15–25 minutes at room temperature. After pressing, the powder is removed from the cold molding die, trimmed to remove burrs, and made smooth and flat to obtain composite sheet. The sheet is then placed in a sintering furnace for heat treatment. First, the temperature of the sintering furnace is increased from room temperature to 327℃ at a heating rate of 1℃ / min, and the sample is held at 327℃ for 60 minutes. Then, the temperature is increased to 375℃ at a heating rate of 1℃ / min and held for 90 minutes. Next, the temperature is decreased from 375℃ to 327℃ at a cooling rate of 1.5℃ / min and held for 60 minutes. Finally, after the holding is completed, the power is turned off and the sample is allowed to cool naturally to room temperature. After the furnace temperature has cooled to room temperature, the heat-treated sheet is removed from the furnace and then cut into samples using a CNC machine tool to obtain the polytetrafluoroethylene composite material.

[0032] Example 4:

[0033] Material composition: 2wt% Ca / Al-LDHs, 20wt% PEEK and 78wt% polytetrafluoroethylene;

[0034] The preparation method of the modified polytetrafluoroethylene composite material is the same as in Example 3.

[0035] Example 5:

[0036] Raw material ratio: 4wt% Ca / Al-LDHs, 20wt% PEEK and 76wt% polytetrafluoroethylene;

[0037] The preparation method of polytetrafluoroethylene composite material is the same as in Example 3.

[0038] Example 6:

[0039] Raw material ratio: 8wt% Ca / Al-LDHs, 20wt% PEEK and 72wt% polytetrafluoroethylene;

[0040] The preparation method of the modified polytetrafluoroethylene composite material is the same as in Example 3.

[0041] After cooling to room temperature, the heat-treated sheet is removed from the furnace to obtain the polytetrafluoroethylene composite material.

[0042] Example 7:

[0043] Raw material ratio: 12wt% Ca / Al-LDHs, 20wt% PEEK and 68wt% polytetrafluoroethylene;

[0044] The preparation method of the modified polytetrafluoroethylene composite material is the same as in Example 3.

[0045] Experimental Example 1: Tribological Test

[0046] The tribological tests of the modified polytetrafluoroethylene composite materials of Examples 1 to 7 were conducted in accordance with GB 3960-2016. The tribological properties of the samples were tested under a load of 200 N, a rotation speed of 200 r / min, and a wear time of 2 h.

[0047] Under the same test conditions, the coefficient of friction and wear rate of the pure polytetrafluoroethylene test sample were 0.184 and 16.517 × 10⁻⁶, respectively. -13 m 3 / Nm, the friction coefficient and wear rate of the modified polytetrafluoroethylene composite material with 0wt%, 1wt%, 2wt%, 4wt%, 8wt%, and 12wt% Ca / Al-LDHs and 20wt% PEEK are as follows: Figure 1 As shown in Table 1, compared to pure polytetrafluoroethylene (PTFE), the addition of Ca / Al-LDHs and PEEK reduced the friction coefficient and wear rate of the modified PTFE composite material. The modified PTFE composite material with 4 wt% Ca / Al-LDHs and 20 wt% PEEK exhibited the lowest wear rate, only 0.067 × 10⁻⁶. -13 m 3 / Nm, therefore, subsequent experiments used 4wt% Ca / Al-LDHs as a fixed amount, and PEEK and pure polytetrafluoroethylene as variables to study the performance.

[0048] Table 1: Measurement values ​​of friction coefficient reduction and wear rate

[0049]

[0050] Example 8:

[0051] Raw material ratio: 4wt% Ca / Al-LDHs, 0wt% PEEK and 96wt% polytetrafluoroethylene;

[0052] Preparation method of modified polytetrafluoroethylene composite material: Ca / Al-LDHs are added to polytetrafluoroethylene for high-speed blending at 1200 r / min for 20 minutes using a high-speed mixer. The mixed powder is then poured into a cold-molding mold and cold-pressed at 40–50 MPa for 15–25 minutes at room temperature. After pressing, the powder is removed from the cold-molding mold, trimmed to remove burrs, and made smooth and flat to obtain composite sheet. The sheet is then placed in a sintering furnace for heat treatment. First, the temperature of the sintering furnace is increased from room temperature to 327℃ at a heating rate of 1℃ / min, and the sample is held at 327℃ for 60 minutes. Then, the temperature is increased to 375℃ at a heating rate of 1℃ / min and held for 90 minutes. Next, the temperature is decreased from 375℃ to 327℃ at a cooling rate of 1.5℃ / min and held for 60 minutes. Finally, after the holding is completed, the power is turned off and the sample is allowed to cool naturally to room temperature. After the furnace temperature has cooled to room temperature, the heat-treated sheet is removed from the furnace and then cut into samples using a CNC machine tool to obtain the polytetrafluoroethylene composite material.

[0053] Example 9:

[0054] Raw material ratio: 4wt% Ca / Al-LDHs, 5wt% PEEK and 91wt% polytetrafluoroethylene;

[0055] The preparation method of the modified polytetrafluoroethylene composite material is the same as in Example 3.

[0056] Example 10:

[0057] Raw material ratio: 4wt% Ca / Al-LDHs, 10wt% PEEK and 86wt% polytetrafluoroethylene;

[0058] The preparation method of the modified polytetrafluoroethylene composite material is the same as in Example 3.

[0059] Example 11:

[0060] Raw material ratio: 4wt% Ca / Al-LDHs, 30wt% PEEK and 66wt% polytetrafluoroethylene;

[0061] The preparation method of the modified polytetrafluoroethylene composite material is the same as in Example 3.

[0062] Example 12:

[0063] Raw material ratio: 4wt% Ca / Al-LDHs, 50wt% PEEK and 46wt% polytetrafluoroethylene;

[0064] The preparation method of the modified polytetrafluoroethylene composite material is the same as in Example 3.

[0065] Experimental Example 2: Tribological Test

[0066] The tribological tests of the modified polytetrafluoroethylene composite materials in Examples 8-12 were conducted according to GB 3960-2016. The tribological properties of the samples were tested under a load of 200 N, a rotation speed of 200 r / min, and a wear time of 2 h.

[0067] Tribological tests were conducted on polytetrafluoroethylene composites modified with 0 wt%, 5 wt%, 10 wt%, 20 wt%, 30 wt%, and 50 wt% PEEK and 4 wt% Ca / Al-LDHs, with comparisons made with the tribological test results from Example 5. The coefficient of friction and wear rate are as follows: Figure 2 As shown in Table 2, the modified polytetrafluoroethylene composite material with 4 wt% Ca / Al-LDHs and 20 wt% PEEK had the lowest wear rate.

[0068] Table 2: Friction coefficient reduction and wear rate measurements

Claims

1. A wear resistant modified polytetrafluoroethylene composite material, characterized by: The modified polytetrafluoroethylene composite material is prepared from polytetrafluoroethylene, Ca / Al-LDHs and PEEK; the Ca / Al-LDHs accounts for 1-12 wt% of the total weight of the modified polytetrafluoroethylene composite material, the PEEK accounts for 5-50 wt% of the total weight of the modified polytetrafluoroethylene composite material, and the polytetrafluoroethylene accounts for 94-38 wt% of the total weight of the modified polytetrafluoroethylene composite material.

2. The wear resistant modified polytetrafluoroethylene composite of claim 1, wherein: The Ca / Al-LDHs accounts for 1-8 wt% of the total weight of the polytetrafluoroethylene composite material, the PEEK accounts for 10-54 wt% of the total weight of the polytetrafluoroethylene composite material, and the polytetrafluoroethylene accounts for 89-38 wt% of the total weight of the polytetrafluoroethylene composite material.

3. The wear resistant modified polytetrafluoroethylene composite material according to claim 1 or 2, characterized in that: The Ca / Al-LDHs accounts for 2-4 wt% of the total weight of the polytetrafluoroethylene composite material, the PEEK accounts for 20-30 wt% of the total weight of the polytetrafluoroethylene composite material, and the polytetrafluoroethylene accounts for 78-66 wt% of the total weight of the polytetrafluoroethylene composite material.

4. Process for the production of wear resistant modified polytetrafluoroethylene composites according to any one of claims 1 to 3, characterized in that: The preparation method is performed according to the following steps: (1) mixing: polytetrafluoroethylene, Ca / Al-LDHs and PEEK are mixed by a high-speed mixing machine at 1000-1400 r / min for 15-25 minutes to obtain A product; (2) compression molding: the A product is poured into a cold mold pressing mold, and the powder is cold pressed at a pressure of 35-55 MPa for 10-30 min under room temperature conditions to obtain B product; (3) heat sintering treatment: the B product is placed in a sintering furnace, the temperature is raised from room temperature to 322-332 ℃ at a heating rate of 0.5-1.5 ℃ / min, and then heat treated at 322-332 ℃ for 55-65 min, then raised to 370-380 ℃ at a heating rate of 0.5-1.5 ℃ / min and heat treated for 80-100 min, then reduced from 370-380 ℃ to 322-332 ℃ at a cooling rate of 1-2 ℃ / min and heat treated for 55-65 min, after heat treatment, the power is turned off, and it is naturally cooled to room temperature, then sample cutting and sample preparation are performed to obtain the polytetrafluoroethylene composite material.

5. The method for preparing the wear-resistant modified polytetrafluoroethylene composite material according to claim 4, characterized in that: In step (1), mixing: polytetrafluoroethylene, Ca / Al-LDHs and PEEK are mixed by a high-speed mixing machine at 1200 r / min for 20 minutes to obtain A product.

6. The method for preparing the wear-resistant modified polytetrafluoroethylene composite material according to claim 4, characterized in that: In step (2), compression molding: the A product is poured into a cold mold pressing mold, and the powder is cold pressed at a pressure of 40-50 MPa for 15-25 min under room temperature conditions to obtain B product.

7. The method of making a wear resistant modified polytetrafluoroethylene composite of claim 4, wherein: In step (3), heat sintering treatment: the B product is placed in a sintering furnace, the temperature is raised from room temperature to 327 ℃ at a heating rate of 1 ℃ / min, and then heat treated at 327 ℃ for 60 min, then raised to 375 ℃ at a heating rate of 1 ℃ / min and heat treated for 90 min, then reduced from 375 ℃ to 327 ℃ at a cooling rate of 1.5 ℃ / min and heat treated for 60 min, after heat treatment, the power is turned off, and it is naturally cooled to room temperature, then sample cutting and sample preparation are performed to obtain the modified polytetrafluoroethylene composite material.

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