High-strength PTFE-based composite material and preparation method thereof

Abstract

The invention discloses a high-strength PTFE (Polytetrafluoroethylene)-based composite material, which is prepared from the following components in percentage by weight: 60 to 75 percent of polytetrafluoroethylene, 10 to 25 percent of polyimide, 5 to 10 percent of modified potassium titanate whiskers, 5 to 10 percent of modified carbon nanotubes and 1 to 5 percent of nano zinc oxide particles. By adding the modified potassium titanate and the modified carbon nanotubes, the wear resistance is improved by 50% compared with that of unmodified potassium titanate and modified carbon nanotubes; the modified potassium titanate and the modified carbon nanotubes are added, so that the optimal mechanical properties are shown at high and low temperatures; the self-assembly modification improves the dispersibility of CNF in a matrix. The tensile strength and the bending strength at room temperature are respectively improved by 29.4% and 26.7%; and the temperature is increased by 2.8% and 20.4% respectively at high temperature.

Description

Technical Field

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

[0002] In the industrial field, the mainstream of the development of high-tech mechanical devices is towards high temperature, high pressure and large-scale development, which leads to increasingly complex and extreme use conditions (load and environment), and puts forward extremely high requirements on the reliability of mechanical structural components, especially oil-free lubricated dynamic sealing components. When facing high temperature (>180℃) and high pressure (20MPa) working conditions, traditional PTFE composite materials are very easy to creep and have a short service life, which seriously affects the continuity and safety of industrial processes. In order to achieve long-term safe and stable operation of these processes, the industry urgently needs self-lubricating materials with excellent mechanical properties under high temperature and high pressure. Summary of the invention

[0003] The object of the present invention is to provide a high-strength PTFE-based composite material and a preparation method thereof in view of the above-mentioned problems.

[0004] On the one hand, the present invention provides a high-strength PTFE-based composite material, comprising the following components in weight percentage: 60-75% polytetrafluoroethylene, 10-25% polyimide, 5-10% modified potassium titanate whiskers, 5-10% modified carbon nanotubes and 1-5% nano zinc oxide particles.

[0005] In some embodiments, the modified potassium titanate whiskers are prepared by the following steps:

[0006] Potassium titanate whiskers were added to n-heptane at room temperature and stirred magnetically;

[0007] Use a microsyringe to draw octadecyltrichlorosilane, and inject it into the suspension at once while stirring. Stir until the potassium titanate whiskers are evenly dispersed in the solution, and continue stirring.

[0008] After filtering, wash with acetone and alcohol for several times to remove free octadecyltrichlorosilane molecules;

[0009] The modified potassium titanate whiskers are vacuum dried at 60-80° C. for 1-5 h to finally obtain a sample.

[0010] In some embodiments, the mass volume ratio of the potassium titanate whisker to the octadecyltrichlorosilane is 5-10 g / mL, and the concentration of the potassium titanate whisker in n-heptane is 0.05-0.1 g / mL.

[0011] In some embodiments, the modified carbon nanotubes are prepared by the following steps:

[0012] At room temperature, the synthesized octadecyl phosphate was dissolved in ethanol, heated to 60-80°C and magnetically stirred for 30-60 min;

[0013] Add carbon nanotubes to the mixed solution under stirring, and continue stirring for 2-8 hours after the solution is evenly dispersed;

[0014] After filtering, the mixture was washed with alcohol several times to remove free octadecyl phosphate molecules;

[0015] The modified carbon nanotubes are vacuum dried at 60-80° C. for 1-5 h to finally obtain a sample.

[0016] In some embodiments, the mass ratio of the carbon nanotubes to the octadecyl phosphate is 5:1-10:1, and the concentration of the octadecyl phosphate in ethanol is 2.5-5 g / L.

[0017] On the other hand, the present invention provides a method for preparing a high-strength PTFE-based composite material, comprising the following steps:

[0018] Different contents of modified potassium titanate whiskers, modified carbon nanotubes, nano zinc oxide particles, polytetrafluoroethylene and polyimide are weighed as required, mixed evenly by mechanical stirring, hot-pressed, and then cooled to room temperature at 100-120°C / hr.

[0019] In some embodiments, the final molding temperature is 300-450° C., the final molding pressure is 8-10 MPa, and the holding time is 60-90 min.

[0020] In another aspect, the present invention provides a high-strength PTFE-based composite material for use in fields such as bearings, sliders, and seals that require long-term wear resistance.

[0021] On the other hand, the high-strength 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.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The invention improves the wear resistance of the modified potassium titanate and modified carbon nanotubes by 50% compared with the unmodified potassium titanate and modified carbon nanotubes; the modified potassium titanate and modified carbon nanotubes show the best mechanical properties at both high and low temperatures; the self-assembly modification improves the dispersibility of CNF in the matrix. The tensile strength and bending strength at room temperature are increased by 29.4% and 26.7% respectively; at high temperature, they are also increased by 2.8% and 20.4% respectively. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1This is a cross-sectional SEM image of the composite material obtained in Example 1;

[0025] Figure 2 The mechanical properties elongation at break of Example 1 and Comparative Example 1 at room temperature and high temperature (150°C);

[0026] Figure 3 The tensile strength of the mechanical properties of Example 1 and Comparative Example 1 at room temperature and high temperature (150°C);

[0027] Figure 4 The mechanical properties bending strength of Example 1 and Comparative Example 1 at room temperature and high temperature (150°C);

[0028] Figure 5 It is the impact strength of the mechanical properties of Example 1 and Comparative Example 1 at room temperature and high temperature (150°C). DETAILED DESCRIPTION

[0029] 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.

[0030] Embodiment 1:

[0031] Preparation of modified potassium titanate whiskers: 10 g of potassium titanate was added to 200 mL of n-heptane at room temperature and magnetically stirred; 1 mL of octadecyltrichlorosilane was drawn with a microsyringe and injected into the suspension at once under stirring, and the solution was stirred until the potassium titanate was evenly dispersed in the solution, and the stirring was continued for 20 minutes; after filtering, the solution was washed with acetone and alcohol for multiple times to remove free octadecyltrichlorosilane molecules; the modified potassium titanate was vacuum dried at 80°C for 5 hours to finally obtain a sample;

[0032] Preparation of modified carbon nanotubes: Dissolve 0.5g of synthesized octadecyl phosphate in 200ml of ethanol at room temperature, heat to 60°C and stir magnetically for 30min; add 5g of carbon nanotubes to the mixture under stirring, and continue stirring for 2h after the solution is evenly dispersed; filter and wash with alcohol several times to remove free octadecyl phosphate molecules. Dry the modified carbon nanotubes in vacuum at 80°C for 5h to obtain the sample.

[0033] Weigh 50g of modified potassium titanate whiskers, 50g of modified carbon nanotubes, 50g of nano zinc oxide particles, 650g of polytetrafluoroethylene and 200g of polyimide as needed, mix them evenly by mechanical stirring, hot press them, and then cool them to room temperature at 120°C / hr. The final molding temperature is 450°C, the final molding pressure is 10MPa, and the holding time is 60min.

[0034] The cross-sectional SEM image of the composite material prepared in Example 1 is as follows: Figure 1 As shown, there are many weak interface bonding areas between the modified potassium titanate whiskers and the matrix, and the modified potassium titanate whiskers are small in size and easy to agglomerate.

[0035] Comparative Example 1: 50 g of unmodified potassium titanate whiskers, 50 g of unmodified carbon nanotubes, 50 g of nano zinc oxide particles, 650 g of polytetrafluoroethylene and 200 g of polyimide were weighed as needed, mixed evenly by mechanical stirring, hot-pressed, and then cooled to room temperature at 120°C / hr. The final molding temperature was 450°C, the final molding pressure was 10 MPa, and the holding time was 60 min.

[0036] Mechanical properties test:

[0037] According to GB / T16421-1996 and GB / T16419-1996, the tensile strength and bending strength of the samples were measured using an electronic universal testing machine (SANS, Shenzhen, model CMT-4254). The experimental temperature was 23±2℃, the relative humidity was 50±5%, the tensile strain rate was 5mm / min, the bending strain rate was 1mm / min, the tensile sample size was 75×4×2mm, and the bending sample size was 40×3×2mm. The impact test used a simple beam impact testing machine (Chengde: XJJ-5) to measure the simple beam impact strength of the unnotched sample according to GB / T16420-1996, and the sample size was 40×3×2mm. Each data is obtained by the average value of 5 samples.

[0038] The mechanical properties of Example 1 and Comparative Example 1 are as follows Figures 2 to 5 As shown, wherein A is Comparative Example 1 and B is Example 1:

[0039] The mechanical properties of the material of Example 1 are improved compared with those of Comparative Example 1. At high temperatures, the mechanical strength of the material is lower than that at room temperature due to the enhanced movement of the polymer molecular chains, increased degrees of freedom, and weakened intermolecular forces. On the contrary, the elongation at break of the material is significantly improved. At room temperature, the elongation at break of the composite material of Example 1 is 150% higher than that of Comparative Example 1, and at 150°C, the elongation at break is increased by 250%. At high temperatures, the surface self-assembly modification does not significantly improve the strength of the material, and the tensile strength and bending strength are only increased by 2.8% and 20.4% respectively, while at room temperature, the tensile, bending and impact strength of the material are increased by 29.4%, 26.7% and 183% respectively, and the toughening effect is obvious. After the surface self-assembly modification of carbon nanotubes, the surface energy is reduced, the compatibility with the polymer matrix is ​​improved, the interface properties are improved, and the stress transfer between the filler and the matrix is ​​effectively improved, thereby improving the mechanical properties of the material.

[0040] Friction and wear performance test:

[0041] 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 2-5 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.

[0042] 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.

[0043] Table 1 Friction and wear properties of Example 1 and Comparative Example 1 under different test conditions

[0044]

[0045] The friction and wear properties of the composite materials of Example 1 and Comparative Example 1 are shown in Table 1. It can be seen from the data in the table that the friction and wear properties of the composite materials are not significantly improved as expected by filling the self-assembled surface modified potassium titanate and modified carbon nanotubes. Under the same friction conditions, the wear resistance of the modified potassium titanate and modified carbon nanotubes is improved, while the friction coefficient is higher than that of Comparative Example 1. Just as the surface self-assembly modification cannot significantly improve the mechanical properties of the material at high temperatures, the friction heat generated during the friction process will also reduce the performance of the composite material. The interfacial effect is weakened at high temperatures, and the surface modification plays a dispersing role, which slightly improves the wear resistance of the composite material.

[0046] In summary: the wear resistance of modified potassium titanate and modified carbon nanotubes is increased by 50% compared with unmodified potassium titanate and modified carbon nanotubes; the addition of modified potassium titanate and modified carbon nanotubes shows the best mechanical properties at both high and low temperatures; self-assembly modification improves the dispersion of CNF in the matrix. The tensile and flexural strengths at room temperature increased by 29.4% and 26.7% respectively; at high temperatures, they also increased by 2.8% and 20.4% respectively.

[0047] 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 high-strength PTFE-based composite material, characterized in that: The invention comprises the following components in weight percentage: 60-75% of polytetrafluoroethylene, 10-25% of polyimide, 5-10% of modified potassium titanate whisker, 5-10% of modified carbon nanotube and 1-5% of nano zinc oxide particles.

2. The composite material according to claim 1, characterized in that The modified potassium titanate whiskers are prepared by the following steps: Potassium titanate whiskers were added to n-heptane at room temperature and stirred magnetically; Use a microsyringe to draw octadecyltrichlorosilane, and inject it into the suspension at once while stirring. Stir until the potassium titanate whiskers are evenly dispersed in the solution, and continue stirring. After filtering, wash with acetone and alcohol for several times to remove free octadecyltrichlorosilane molecules; The modified potassium titanate whiskers are vacuum dried at 60-80° C. for 1-5 h to finally obtain a sample.

3. The composite material according to claim 2, characterized in that The mass volume ratio of the potassium titanate whisker to the octadecyltrichlorosilane is 5-10 g / mL, and the concentration of the potassium titanate whisker in n-heptane is 0.05-0.1 g / mL.

4. The composite material according to claim 1, characterized in that The modified carbon nanotubes are prepared by the following steps: At room temperature, the synthesized octadecyl phosphate was dissolved in ethanol, heated to 60-80°C and magnetically stirred for 30-60 min; Add carbon nanotubes to the mixed solution under stirring, and continue stirring for 2-8 hours after the solution is evenly dispersed; After filtering, the mixture was washed with alcohol several times to remove free octadecyl phosphate molecules; The modified carbon nanotubes are vacuum dried at 60-80° C. for 1-5 h to finally obtain a sample.

5. The composite material according to claim 4, characterized in that The mass ratio of the carbon nanotube to the octadecyl phosphate is 5:1-10:1, and the concentration of the octadecyl phosphate in ethanol is 2.5-5 g / L.

6. A method for preparing a high-strength PTFE-based composite material, characterized in that: The following steps are involved: Different contents of modified potassium titanate whiskers, modified carbon nanotubes, nano zinc oxide particles, polytetrafluoroethylene and polyimide are weighed as required, mixed evenly by mechanical stirring, hot-pressed, and then cooled to room temperature at 100-120°C / hr.

7. The preparation method according to claim 6, characterized in that: The final molding temperature is 300-450° C., the final molding pressure is 8-10 MPa, and the holding time is 60-90 min.

8. Use of the composite material according to any one of claims 1 to 5 in the fields of bearings, sliders, seals, etc. that require long-term wear resistance.

9. Use of the composite material obtained by the preparation method according to claim 6 or 7 in the fields of bearings, sliders, seals, etc. that require long-term wear resistance.

Images