Wear-resistant and high-temperature-resistant PTFE-based composite material and preparation method thereof

Abstract

The invention discloses a wear-resistant and high-temperature-resistant PTFE-based composite material and a preparation method thereof. The composite material comprises the following components in percentage by weight: 60-75% of polytetrafluoroethylene, 10-25% of a polyimide composite material, 5-10% of potassium titanate whiskers, 5-10% of carbon fibers and 1-5% of glass fibers. The rolling friction part prepared from the fiber composite materials with different sizes can keep low wear rate in a high-load and high-temperature environment, so that the service life of the part is prolonged. The material is suitable for the fields where long-term wear-resistant application is needed, such as bearings, sliding blocks, sealing pieces and the like.

Description

Technical Field

[0001] The invention relates to the technical field of inorganic material composites, and in particular to a wear-resistant and high-temperature resistant PTFE-based composite material and a preparation method thereof. Background Art

[0002] In the field of air compressors, piston rings are annular components that are embedded in the piston grooves and play a role in sealing air and maintaining pressure in air compressors. The materials used to make piston rings need to have good wear resistance and elasticity. In high-pressure and unbalanced air compressors, the requirements for the wear resistance and high-temperature pressure resistance of piston ring materials are even more stringent.

[0003] At present, high-pressure oil-free lubricated wear-resistant plastic parts such as piston rings are mainly made of self-lubricating PTFE. Although PTFE has self-lubricating properties, the high temperature and high pressure generated during dynamic friction will cause the PTFE parts to stick and fall off and be squeezed and deformed, resulting in a short service life of the parts. Summary of the invention

[0004] The object of the present invention is to provide a wear-resistant and high-temperature resistant PTFE-based composite material and a preparation method thereof in view of the above-mentioned problems.

[0005] On the one hand, the present invention provides a PTFE-based composite material, comprising the following components in weight percentage: 60-75% polytetrafluoroethylene, 10-25% polyimide composite material, 5-10% potassium titanate whisker, 5-10% carbon fiber and 1-5% glass fiber.

[0006] In some embodiments, the polyimide composite material includes 1-5% of graphite, 1-5% of molybdenum sulfide, and the balance of polyimide.

[0007] In some embodiments, the potassium titanate whiskers have a diameter of 0.5 to 2.5 μm and a length of 2 to 30 μm, the carbon fibers have a diameter of 5 to 25 μm and a length of 10 to 300 μm, and the glass fibers have an average diameter of 10 μm and an average length of 80 μm.

[0008] In some embodiments, the potassium titanate whiskers are prepared by the following steps:

[0009] 1) Mixing of raw materials: Using titanium dioxide whiskers as titanium source and potassium hydroxide as potassium source, potassium hydroxide is first prepared into an aqueous solution, wherein the molar ratio of TiO 2 :K 2 O=1.9-2.0, then adding titanium dioxide whiskers into the prepared potassium hydroxide aqueous solution, and mixing them evenly under magnetic stirring at room temperature to obtain a precursor solution for hydrothermal reaction;

[0010] 2) Microwave hydrothermal reaction: the mixed solution in step 1) is placed in a polytetrafluoroethylene tank, and heated in an oven to achieve a hydrothermal reaction at a temperature of 120-150° C. for 4-12 hours. After the reaction is completed, the mixture is naturally cooled to room temperature;

[0011] 3) Cleaning and drying: pour out the upper alkali solution in the polytetrafluoroethylene tank and reuse it, wash the product deposited at the bottom of the tank with water several times until it is neutral, filter and dry to obtain potassium titanate whiskers.

[0012] In some embodiments, the titanium dioxide whisker is prepared by the following steps: potassium hydroxide and orthotitanic acid are mixed, and orthotitanic acid and potassium hydroxide are respectively calculated as TiO2 and K2O, and the mass ratio of the orthotitanic acid and potassium hydroxide is TiO2: 2 :K 2 O=0.1-3, high temperature calcination at 100-550°C for 0.2-6 hours to obtain alkali metal titanate, then the alkali metal titanate is cleaned with an acid solution, and finally dehydrated to obtain titanium dioxide whiskers.

[0013] In some embodiments, the acid solution contains H + The concentration is 10 -3 ~10 -1 mol / L.

[0014] On the other hand, the present invention provides a method for preparing a wear-resistant and high-temperature resistant PTFE-based composite material, comprising the following steps:

[0015] Carbon fiber, glass fiber, potassium titanate fiber, polytetrafluoroethylene, graphite, molybdenum sulfide and polyimide in different contents are weighed as needed, mechanically stirred and mixed evenly, hot-pressed and then cooled to room temperature at 120° C. / hr.

[0016] In some embodiments, the final molding temperature is 370° C., the final molding pressure is 10 MPa, and the holding time is 60 min.

[0017] On the other hand, the present invention provides a wear-resistant and high-temperature resistant PTFE-based composite material for use in fields such as bearings, sliders, and seals that require long-term wear resistance.

[0018] On the other hand, the wear-resistant and high-temperature resistant PTFE-based composite material obtained by the preparation method provided by the present invention is used in fields such as bearings, sliders, and seals that require long-term wear resistance.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The rolling friction parts prepared by the fiber composite materials of different sizes in the present invention can maintain a low wear rate in a high load and high temperature environment, thereby extending the service life of the parts. This material is suitable for fields requiring long-term wear resistance, such as bearings, sliders, seals, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The cross-sectional SEM image (х400) of the composite material obtained in Example 1;

[0022] Figure 2 The friction performance results of Examples 2-9 and Comparative Examples 1-16;

[0023] Figure 3 The wear performance results of Examples 2-9 and Comparative Examples 1-16 are shown. DETAILED DESCRIPTION

[0024] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0025] Embodiment 1:

[0026] Preparation of titanium dioxide whiskers: Potassium hydroxide and orthotitanic acid were mixed, and orthotitanic acid and potassium hydroxide were respectively 2 and K 2 O, and its mass usage ratio is TiO 2 :K 2 O=1, calcining at 450°C for 2 hours to obtain alkali metal titanate, then washing the alkali metal titanate with an acid solution, and finally dehydrating to obtain titanium dioxide whiskers;

[0027] Mixing of raw materials: titanium dioxide whiskers are used as titanium source and potassium hydroxide is used as potassium source. Potassium hydroxide is first prepared into an aqueous solution, wherein the molar ratio of TiO 2 :K 2 O=2, then add titanium dioxide whiskers into the prepared potassium hydroxide aqueous solution, and mix them evenly under magnetic stirring at room temperature to obtain a precursor solution for hydrothermal reaction;

[0028] Microwave hydrothermal reaction: Place the mixed solution in a polytetrafluoroethylene tank and heat it in an oven to achieve hydrothermal reaction. The hydrothermal temperature is 120°C for 12 hours. After the reaction is completed, cool it naturally to room temperature.

[0029] Cleaning and drying: pour out the upper alkali solution in the polytetrafluoroethylene tank and reuse it, wash the product deposited at the bottom of the tank with water several times until it is neutral, filter and dry to obtain potassium titanate whiskers;

[0030] According to needs, weigh 50g of carbon fiber with a diameter of 5-25μm and a length of 10-300μm, 10g of glass fiber with an average diameter of 10μm and an average length of 80μm, 50g of potassium titanate fiber with a diameter of 0.5-2.5μm and a length of 2-30μm, 600g of polytetrafluoroethylene, 10g of graphite, 10g of molybdenum sulfide and 180g of polyimide, mix them evenly with mechanical stirring, hot press them, and then cool them to room temperature at 120℃ / hr.

[0031] The cross-sectional SEM image of the composite material prepared in Example 1 is as follows: Figure 1 As shown, fibers of different sizes are stacked in an alternating pattern.

[0032] Example 2: The difference from Example 1 is that the overall content of carbon fiber, glass fiber and potassium titanate fiber is adjusted to 0% by mass.

[0033] Example 3: The difference from Example 1 is that the overall content of carbon fiber, glass fiber and potassium titanate fiber is adjusted to 5% by mass.

[0034] Example 4: The difference from Example 1 is that the overall content of carbon fiber, glass fiber and potassium titanate fiber is adjusted to 10% by mass.

[0035] Example 5: The difference from Example 1 is that the overall content of carbon fiber, glass fiber and potassium titanate fiber is adjusted to 15% by mass.

[0036] Example 6: The difference from Example 1 is that the overall content of carbon fiber, glass fiber and potassium titanate fiber is adjusted to 20% by mass.

[0037] Example 7: The difference from Example 1 is that the overall content of carbon fiber, glass fiber and potassium titanate fiber is adjusted to 25% by mass.

[0038] Example 8: The difference from Example 1 is that the overall content of carbon fiber, glass fiber and potassium titanate fiber is adjusted to 30% by mass.

[0039] Example 9: The difference from Example 1 is that the overall content of carbon fiber, glass fiber and potassium titanate fiber is adjusted to 35% by mass.

[0040] Comparative Example 1: The difference from Example 1 is that the overall content of carbon fiber and glass fiber is adjusted to 0% by mass.

[0041] Comparative Example 2: The difference from Example 1 is that the overall content of carbon fiber and glass fiber is adjusted to 5% by mass.

[0042] Comparative Example 3: The difference from Example 1 is that the overall content of carbon fiber and glass fiber is adjusted to 10% by mass.

[0043] Comparative Example 4: The difference from Example 1 is that the overall content of carbon fiber and glass fiber is adjusted to 15% by mass.

[0044] Comparative Example 5: The difference from Example 1 is that the overall content of carbon fiber and glass fiber is adjusted to 20% by mass.

[0045] Comparative Example 6: The difference from Example 1 is that the overall content of carbon fiber and glass fiber is adjusted to 25% by mass.

[0046] Comparative Example 7: The difference from Example 1 is that the overall content of carbon fiber and glass fiber is adjusted to 30% by mass.

[0047] Comparative Example 8: The difference from Example 1 is that the overall content of carbon fiber and glass fiber is adjusted to 35% by mass.

[0048] Comparative Example 9: The difference from Example 1 is that the overall content of potassium titanate fiber is adjusted to 0% by mass.

[0049] Comparative Example 10: The difference from Example 1 is that the overall content of potassium titanate fiber is adjusted to 5% by mass.

[0050] Comparative Example 11: The difference from Example 1 is that the overall content of potassium titanate fiber is adjusted to 10% by mass.

[0051] Comparative Example 12: The difference from Example 1 is that the overall content of potassium titanate fiber is adjusted to 15% by mass.

[0052] Comparative Example 13: The difference from Example 1 is that the overall content of potassium titanate fiber is adjusted to 20% by mass.

[0053] Comparative Example 14: The difference from Example 1 is that the overall content of potassium titanate fiber is adjusted to 25% by mass.

[0054] Comparative Example 15: The difference from Example 1 is that the overall content of potassium titanate fiber is adjusted to 30% by mass.

[0055] Comparative Example 16: The difference from Example 1 is that the overall content of potassium titanate fiber is adjusted to 35% by mass.

[0056] Performance Test:

[0057] The ring-to-ring sliding friction and wear test was carried out using the MPX-2000 wear tester from Xuanhua Testing Machine Factory. The rotating steel ring and the polymer material sample ring formed a friction pair, such as Figure 2-3 As shown. The upper specimen (a) of the friction pair is a steel ring with an inner diameter of 18 mm, an outer diameter of 36 mm, and a thickness of 8 mm, and is made of 45# steel that has been quenched at low temperature; the lower specimen (b) is a polymer composite material, and the friction contact surface is a ring surface with an inner diameter of 22 mm and an outer diameter of 24 mm. Before each experiment, the steel ring and the sample were polished to a certain roughness with 800-grit metallographic sandpaper, and then the sample block and the steel ring were ultrasonically cleaned in alcohol, and then dried in a constant temperature box to constant weight.

[0058] The experiment was conducted at room temperature and humidity of 50±5%, with loads ranging from 100 to 400N, and sliding speeds of 0.467m / s, 0.692m / s and 1.4m / s. Before the formal friction experiment, a 10-minute run-in was performed to ensure that the sample could fully contact the mating part. The formal friction and wear experiment lasted for 60 minutes. The wear amount was the weight loss measured on the same model of electronic scale (accuracy 0.1mg) before and after the test; the friction torque was collected by a computer during the friction process. The experimental results were all taken as the average of three times.

[0059] The friction torque is determined by the friction force between the upper and lower specimens, which causes the lower spindle, which is precisely positioned between two sets of rolling bearings, to generate a rotational torque. The torque pressure rod fixed on the lower spindle acts directly on a force sensor. The output signal of the sensor is converted into a digital signal through an amplifier and A / D conversion, and is connected to a computer with R485 to realize automatic data collection.

[0060] According to Coulomb's law: F = μ·N, where F is the friction force (N), μ is the friction coefficient, and N is the normal pressure (N). Since the product of the friction force F (N) and the friction radius r (m) of the sample is the measured friction torque M (N×m), the friction coefficient is calculated as follows:

[0061]

[0062] In order to ensure the final friction coefficient μ 0 To ensure the accuracy of the friction coefficient, the average μ value of each sampling point after the wear state stabilizes is taken. In this paper, the μ value of the last 60 minutes is averaged to obtain the final friction coefficient.

[0063] The wear resistance of composite materials is expressed by volume wear rate, which is the wear volume per unit load multiplied by the unit sliding distance. The calculation expression is:

[0064]

[0065] Where: △m is the wear weight loss of the sample, g; ρ is the density of the sample, g / mm 3 ;

[0066] Test #1 is the friction of different overall contents of carbon fiber, glass fiber and potassium titanate fiber;

[0067] Test #2 is the friction of different overall contents of carbon fiber and glass fiber;

[0068] Test #3 is the friction of the overall content of potassium titanate fiber;

[0069] from Figure 2 and 3 It can be seen that with the increase of fiber content, the friction coefficient of the composite material has a completely different trend of change. The friction coefficient of different carbon fiber, glass fiber and potassium titanate fiber composite materials is the largest, and gradually increases with the increase of fiber content. The surface of carbon fiber is an inert graphite structure, and its wettability with polymers is generally poor. During the friction process, when the carbon fiber is subjected to shear force, it is easy to escape from the matrix and gather on the friction surface to destroy the formation of the transfer film, so that the material directly rubs against the dual surface steel body, which increases the friction coefficient. The scale of glass fiber is comparable to that of carbon fiber. When the content is too high, the matrix cannot completely infiltrate the fiber, which reduces the pressure bearing capacity of the material and increases the wear rate.

[0070] Potassium titanate has high mechanical strength and protrudes from the wear surface during friction, playing a certain mechanical bearing role. It continuously fills the micro-pits and damaged parts of the wear surface during the wear process, playing a role in repairing the wear surface. Its fine structure plays a different rolling role between the friction surfaces than the traditional "micro-roller", reducing the friction coefficient and improving the wear resistance of the material.

[0071] From the experimental results, it can be seen that the rolling friction component prepared by using the fiber composite material of different sizes according to Example 1 of the present invention can maintain a low wear rate in a high load and high temperature environment, thereby extending the service life of the component. This material is suitable for applications requiring long-term wear resistance, such as bearings, sliders, seals, etc.

[0072] Finally, it should be noted that: technicians in this industry should understand that the present invention is not limited to the above-mentioned implementation cases. The above-mentioned embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which shall fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A wear-resistant and high-temperature resistant PTFE-based composite material, characterized in that: The invention comprises the following components in weight percentage: 60-75% of polytetrafluoroethylene, 10-25% of polyimide composite material, 5-10% of potassium titanate whisker, 5-10% of carbon fiber and 1-5% of glass fiber.

2. The composite material according to claim 1, characterized in that The polyimide composite material comprises 1-5% of graphite, 1-5% of molybdenum sulfide and the balance of polyimide.

3. The composite material according to claim 1, characterized in that The potassium titanate whisker has a diameter of 0.5 to 2.5 μm and a length of 2 to 30 μm, the carbon fiber has a diameter of 5 to 25 μm and a length of 10 to 300 μm, and the glass fiber has an average diameter of 10 μm and an average length of 80 μm.

4. The composite material according to claim 1, characterized in that The potassium titanate whiskers are prepared by the following steps: 1) Mixing of raw materials: Using titanium dioxide whiskers as titanium source and potassium hydroxide as potassium source, first prepare potassium hydroxide into an aqueous solution, wherein the molar ratio of TiO2:K2O=1.9-2.0, then add titanium dioxide whiskers into the prepared potassium hydroxide aqueous solution, and mix them evenly under magnetic stirring at room temperature to obtain a precursor solution for hydrothermal reaction; 2) Microwave hydrothermal reaction: the mixed solution in step 1) is placed in a polytetrafluoroethylene tank, and heated in an oven to achieve a hydrothermal reaction at a temperature of 120-150° C. for 4-12 hours. After the reaction is completed, the mixture is naturally cooled to room temperature; 3) Cleaning and drying: pour out the upper alkali solution in the polytetrafluoroethylene tank and reuse it, wash the product deposited at the bottom of the tank with water several times until it is neutral, filter and dry to obtain potassium titanate whiskers.

5. The composite material according to claim 4, characterized in that The titanium dioxide whisker is prepared by the following steps: potassium hydroxide and orthotitanic acid are mixed, orthotitanic acid and potassium hydroxide are calculated as TiO2 and K2O respectively, and the mass dosage ratio is TiO2:K2O=0.1-3, and high-temperature roasting is performed at 100-550°C for 0.2-6 hours to obtain alkali metal titanate, and then the alkali metal titanate is cleaned with an acid solution, and finally dehydrated to obtain titanium dioxide whiskers.

6. The composite material according to claim 5, characterized in that The acid solution contains H + The concentration is 10 -3 ~10 - 1 mol / L.

7. A method for preparing a wear-resistant and high-temperature resistant PTFE-based composite material, characterized in that: The following steps are involved: Carbon fiber, glass fiber, potassium titanate fiber, polytetrafluoroethylene, graphite, molybdenum sulfide and polyimide in different contents are weighed as needed, mechanically stirred and mixed evenly, hot-pressed and then cooled to room temperature at 120° C. / hr.

8. The preparation method according to claim 7, characterized in that: The final molding temperature is 370° C., the final molding pressure is 10 MPa, and the holding time is 60 min.

9. Use of the composite material according to any one of claims 1 to 6 in the fields of bearings, sliders, seals, etc. that require long-term wear resistance.

10. Use of the composite material obtained by the preparation method according to claim 7 or 8 in the fields of bearings, sliders, seals, etc. that require long-term wear resistance.

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