Method of improving the wear resistance of polytetrafluoroethylene and crosslinked polytetrafluoroethylene

Abstract

This invention belongs to the field of polymer modification and provides a method for improving the wear resistance of polytetrafluoroethylene (PTFE) and cross-linked PTFE. The method includes the following steps: (1) providing a sintered PTFE block; (2) subjecting the sintered PTFE block to a first irradiation treatment using a first proton beam; (3) subjecting the material obtained in step (2) to a second irradiation treatment using a second proton beam; and (4) cooling the material obtained in step (3) to obtain cross-linked PTFE. By subjecting the sintered PTFE block to the first and second irradiation treatments, the obtained cross-linked PTFE exhibits a high degree of cross-linking and uniform distribution, and thus superior wear resistance.

Description

Technical Field

[0001] This invention belongs to the field of polymer modification, specifically, it relates to a method for improving the wear resistance of polytetrafluoroethylene and cross-linked polytetrafluoroethylene. Background Technology

[0002] Polytetrafluoroethylene (PTFE) is an excellent engineering plastic with superior chemical stability, an extremely low coefficient of friction, and good thermal stability, earning it the title of "King of Plastics" and leading to its widespread application in numerous fields. However, PTFE's poor radiation resistance and abrasion resistance limit its use in high-radiation fields such as outer space and nuclear reactors. This necessitates modification of PTFE, such as crosslinking modification, to better adapt it to the high-intensity impact and friction environments of mechanical operation. PTFE crosslinking modification typically involves inducing a crosslinking reaction to reduce its crystallinity; however, traditional methods often result in a low degree of crosslinking, limiting the improvement in PTFE's abrasion resistance.

[0003] Therefore, methods for improving the abrasion resistance of polytetrafluoroethylene still need to be improved. Summary of the Invention

[0004] The present invention aims to at least partially solve one of the technical problems in the related art.

[0005] In a first aspect, the present invention provides a method for improving the abrasion resistance of polytetrafluoroethylene, comprising the following steps:

[0006] (1) Provide polytetrafluoroethylene sintered blocks;

[0007] (2) The polytetrafluoroethylene sintered block is subjected to a first irradiation treatment using a first proton beam;

[0008] (3) The material obtained in step (2) is subjected to a second irradiation treatment using a second proton beam;

[0009] (4) Cool the material obtained in step (3) to obtain cross-linked polytetrafluoroethylene.

[0010] The method provided by the present invention involves subjecting the sintered polytetrafluoroethylene (PTFE) block to two irradiation treatments, resulting in a high degree of crosslinking and uniform distribution of the obtained crosslinked PTFE, thereby enabling the crosslinked PTFE to exhibit superior wear resistance.

[0011] According to an embodiment of the present invention, the energy E1 of the first proton beam is 0.3-1.5 MeV, and the dose F1 of the first proton beam is 0.1 × 10⁻⁶. 14 -9.5×10 14 ion / cm 2The energy E2 of the second proton beam is 0.3-1.5 MeV, and the dose F2 of the second proton beam is 0.1 × 10⁻⁶. 14 -9.5×10 14 ion / cm 2 Where E1≠E2. Therefore, by controlling the energies of the first and second proton beams to the aforementioned range, the sintered polytetrafluoroethylene (PTFE) block can be effectively cross-linked, while reducing the possibility of carbonization on the PTFE surface.

[0012] According to an embodiment of the present invention, the energy E1 of the first proton beam is 0.85-1.5 MeV, and the dose F1 of the first proton beam is 1 × 10⁻⁶. 14 -9×10 14 ion / cm 2 .

[0013] According to an embodiment of the present invention, the energy E2 of the second proton beam is 0.3-0.8 MeV, and the dose F2 of the second proton beam is 1×10⁻⁶. 14 -9×10 14 ion / cm 2 .

[0014] According to an embodiment of the present invention, the first irradiation treatment is performed under a vacuum degree not exceeding 1×10⁻⁶. -4 The experiment was conducted under the condition of Pa.

[0015] According to an embodiment of the present invention, the temperature of the first irradiation treatment is 325-360°C.

[0016] According to an embodiment of the present invention, the second irradiation treatment is performed under a vacuum degree not exceeding 1×10⁻⁶. -4 The experiment was conducted under the condition of Pa.

[0017] According to an embodiment of the present invention, the temperature of the second irradiation treatment is 325-360°C.

[0018] According to an embodiment of the present invention, step (1) includes: (1-1) cold pressing polytetrafluoroethylene powder to obtain a cold-pressed product; (1-2) sintering the cold-pressed product to obtain a polytetrafluoroethylene sintered block.

[0019] According to an embodiment of the present invention, the cold pressing conditions include: a pressure of 25-35 MPa; and / or a holding time of 0.5-2 min.

[0020] According to an embodiment of the present invention, the sintering includes: heating the cold-pressed product to 150-250°C at a heating rate of 2-6°C / min and holding it at that temperature for 1-3 hours, and then heating it to 360-380°C at a heating rate of 2-6°C / min and holding it at that temperature for 1-3 hours. This two-stage sintering process can reduce the risk of surface cracking in the PTFE sintered block, thereby improving the yield of the PTFE sintered block.

[0021] In a second aspect, the present invention provides cross-linked polytetrafluoroethylene prepared by the above method. The cross-linked polytetrafluoroethylene obtained by the method of the present invention exhibits a high degree of cross-linking and uniform distribution, thus demonstrating superior wear resistance. Attached Figure Description

[0022] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0023] Figure 1 This is a Srim program simulation diagram showing the relationship between injection depth and energy after proton beam irradiation of polytetrafluoroethylene sintered blocks in Comparative Examples 1 and 2.

[0024] Figure 2 These are the infrared spectra of cross-linked polytetrafluoroethylene from Example 1, Comparative Example 1, and Comparative Example 3.

[0025] Figure 3 These are X-ray diffraction patterns of cross-linked polytetrafluoroethylene from Examples 1, 1, and 3. Detailed Implementation

[0026] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0027] Irradiation modification is a method for modifying polytetrafluoroethylene (PTFE) materials. During irradiation, PTFE undergoes a cross-linking reaction, transforming its molecular structure from a highly linear to a network structure. However, irradiation using a proton beam with a single energy and dose results in incomplete and insufficient chemical reactions, leading to a low degree of cross-linking on the surface of the PTFE sample and limited improvement in its wear resistance.

[0028] Therefore, a first aspect of the present invention provides a method for improving the abrasion resistance of polytetrafluoroethylene, comprising the following steps:

[0029] (1) Provide polytetrafluoroethylene sintered blocks;

[0030] (2) The polytetrafluoroethylene sintered block is subjected to a first irradiation treatment using a first proton beam;

[0031] (3) The material obtained in step (2) is subjected to a second irradiation treatment using a second proton beam;

[0032] (4) Cool the material obtained in step (3) to obtain cross-linked polytetrafluoroethylene.

[0033] The method provided by this invention involves subjecting a sintered polytetrafluoroethylene (PTFE) block to a first irradiation treatment and a second irradiation treatment. These treatments cause the molecular chains of the PTFE block to break and crosslink, resulting in a more complete crosslinking reaction. The obtained crosslinked PTFE exhibits a higher degree of crosslinking and a more uniform distribution, thus demonstrating superior wear resistance. Specifically, when the PTFE block is irradiated with a high-energy proton beam, the CF bonds break, generating free radicals and free fluorine atoms. The main chain carbon, now unprotected by fluorine atoms, is exposed to irradiation, and the C-C bonds break, generating chain-end free radicals. These free radicals collide and combine, causing the PTFE molecular structure to change from a highly linear state to an H-type or T-type structure. Furthermore, the crosslinking reaction between free radicals is random and disordered, resulting in a random network structure of the obtained crosslinked PTFE. This invention utilizes a proton beam to perform two irradiation treatments on the PTFE block; the first irradiation treatment initially achieves intermolecular crosslinking, while the second irradiation treatment perfects the intermolecular crosslinking. Thus, the crosslinking induced by the two irradiations superimposed each other, making the resulting crosslinked system more uniform and complete, yielding crosslinked polytetrafluoroethylene with a high degree of uniform intermolecular crosslinking. Due to the strong intermolecular attraction of this crosslinked polytetrafluoroethylene, it is difficult to remove the molecules of crosslinked polytetrafluoroethylene under friction under an applied load, thereby giving the crosslinked polytetrafluoroethylene high wear resistance.

[0034] In some embodiments, the process of irradiating the polytetrafluoroethylene sintered block with a first proton beam and a second proton beam can be carried out in an electrostatic accelerator.

[0035] According to the present invention, the energy E1 of the first proton beam can be 0.3-1.5 MeV, for example, 0.3 MeV, 0.5 MeV, 0.8 MeV, 0.85 MeV, 1 MeV, 1.2 MeV, 1.3 MeV, 1.5 MeV, etc., and the dose F1 of the first proton beam can be 0.1 × 10⁻⁶. 14 -9.5×10 14 ion / cm 2 For example, a dose of 0.1 × 10 14 ion / cm 2 1×10 14 ion / cm 2 5×10 14 ion / cm 2 7×10 14 ion / cm2 8×10 14 ion / cm 2 9.5×10 14 ion / cm 2 The energy E2 of the second proton beam can be 0.3-1.5 MeV, for example, energies of 0.3 MeV, 0.5 MeV, 0.8 MeV, 0.85 MeV, 1 MeV, 1.2 MeV, 1.3 MeV, 1.5 MeV, etc., and the dose F2 of the second proton beam can be 0.1 × 10⁻⁶. 14 -9.5×10 14 ion / cm 2 For example, a dose of 0.1 × 10 14 ion / cm 2 1×10 14 ion / cm 2 5×10 14 ion / cm 2 7×10 14 ion / cm 2 8×10 14 ion / cm 2 9.5×10 14 ion / cm 2 Where E1≠E2. By controlling the energy and dose of the first and second proton beams to meet the aforementioned ranges, and ensuring that the energies of the first and second proton beams are different, effective cross-linking of the molecules in the polytetrafluoroethylene sintered block can occur during the irradiation process, while minimizing excessive energy and dose that could cause carbonization of the tetrafluoroethylene surface.

[0036] According to the present invention, the injection depths of the first and second proton beams can be independently set to 4-23 μm. This further reduces the risk of PTFE sintered blocks being broken down.

[0037] In some specific embodiments, the energy of the first proton beam is 0.85-1.5 MeV, and the dose is 1×10⁻⁶. 14 -9×10 14 ion / cm 2 .

[0038] In some specific embodiments, the injection depth of the first proton beam is 13-23 μm.

[0039] In some specific embodiments, the energy of the second proton beam is 0.3-0.8 MeV, and the dose is 1×10⁻⁶. 14 -9×10 14 ion / cm 2 .

[0040] In some specific embodiments, the injection depth of the second proton beam is 4-10 μm.

[0041] In some embodiments, the temperatures of the first irradiation treatment and the second irradiation treatment are independently 325-360°C, for example, 325°C, 338°C, 350°C, 360°C, etc. Irradiating the polytetrafluoroethylene sintered block within this temperature range allows the generated free radicals to collide and combine more fully under the action of thermal motion, and to undergo cross-linking, thereby obtaining cross-linked polytetrafluoroethylene with a high degree of cross-linking and uniform distribution.

[0042] In some embodiments, both the first and second irradiation treatments are performed under vacuum conditions to minimize energy loss or path deviation of the proton beam due to atmospheric molecular interference. Optionally, the vacuum level is no higher than 1 × 10⁻⁶. -4 Pa.

[0043] It is understandable that the first and second irradiation treatments can be performed consecutively during the irradiation process; that is, the second irradiation treatment is performed immediately after the first irradiation is completed.

[0044] According to the present invention, the polytetrafluoroethylene sintered block provided in step (1) can be obtained commercially or prepared by means of preparation, for example, by cold pressing and sintering polytetrafluoroethylene powder.

[0045] In some embodiments, step (1) may include:

[0046] (1-1) Polytetrafluoroethylene powder is cold-pressed to obtain a cold-pressed product;

[0047] (1-2) The cold-pressed product is sintered to obtain polytetrafluoroethylene sintered block.

[0048] In some embodiments, the Dv50 of the polytetrafluoroethylene powder is 12-18 μm.

[0049] In some embodiments, the pressure of the cold pressing is 25-35 MPa, for example, 25 MPa, 30 MPa, 35 MPa, etc.; the holding time of the cold pressing is 0.5-2 min, for example, 0.5 min, 1 min, 2 min. Under these conditions, polytetrafluoroethylene powder can be pressed into shape to obtain cold-pressed products, which can meet the requirements of the sample shape in the subsequent sintering process.

[0050] In some embodiments, the sintering process includes: heating the cold-pressed product to 150-250°C at a heating rate of 2-6°C / min and holding it at that temperature for 1-3 hours. For example, the heating rate can be 2°C / min, 3°C / min, 4°C / min, 5°C / min, 6°C / min, etc., the temperature can be 150°C, 200°C, 250°C, etc., and the holding time can be 1 hour, 2 hours, 3 hours, etc.; then heating it to 360-380°C at a heating rate of 2-6°C / min and holding it at that temperature for 1-3 hours. For example, the heating rate can be 2°C / min, 3°C / min, 4°C / min, 5°C / min, 6°C / min, etc., the temperature can be 360°C, 370°C, 380°C, etc., and the holding time can be 1 hour, 2 hours, 3 hours, etc. After the holding time is completed, the product can be allowed to cool naturally to room temperature. By employing a two-stage sintering process and controlling the heating rate during sintering within the aforementioned range, patterns or cracks on the surface of PTFE sintered blocks can be reduced or even eliminated, thereby improving the yield of PTFE sintered blocks.

[0051] In a second aspect, the present invention provides cross-linked polytetrafluoroethylene (PTFE) prepared by the above method. The cross-linked PTFE prepared using the method provided by the present invention exhibits a high degree of intermolecular cross-linking and uniform distribution, resulting in high wear resistance.

[0052] In this invention, during the proton beam irradiation of the polytetrafluoroethylene (PTFE) sintered block, the CF bonds in the PTFE sintered block break, and the reactive fluorine atoms react to generate small fluorine-containing gas molecules that escape, while the carbon atoms on the main chain remain in the cross-linked PTFE. This results in a decrease in the relative proportion of fluorine (F) and an increase in the relative proportion of carbon (C) in the cross-linked PTFE. Optionally, the ratio of fluorine atoms to carbon atoms in the cross-linked PTFE is 0.59-1.14, a value that can be measured using X-ray photoelectron spectroscopy.

[0053] The present invention will be described below through specific embodiments. It should be noted that the following embodiments are only for illustrating the present invention and should not be regarded as limiting the scope of the present invention.

[0054] In the following examples and comparative examples, the polytetrafluoroethylene powder was purchased from Shenzhen Xinyida Technology Co., Ltd., and its grade was MP1000.

[0055] Cross-linked polytetrafluoroethylene was prepared using a 1.7MV tandem electrostatic accelerator at the Nuclear Technology Application Laboratory of Peking University, which is equipped with a vacuum system and a heating system.

[0056] Example 1

[0057] (1) Preparation of polytetrafluoroethylene sintered blocks

[0058] Weigh 1.0g of polytetrafluoroethylene powder and place it in a circular mold with a diameter of 1cm. Use a hydraulic press to press the polytetrafluoroethylene powder in the circular mold to 30MPa and hold it at this pressure for 1min. Then release the pressure to obtain a cold-pressed product.

[0059] The cold-pressed product was placed in an alumina boat and sintered in a muffle furnace. The temperature was first raised to 200°C at a rate of 3°C / min and held for 2 hours. Then the temperature was raised to 380°C at a rate of 3°C / min and held for 2 hours. The product was then cooled to room temperature in the furnace to obtain a sintered polytetrafluoroethylene block.

[0060] (2) Preparation of cross-linked polytetrafluoroethylene

[0061] Turn on the vacuum and heating systems of the 1.7MV tandem electrostatic accelerator and control the vacuum level to 1×10⁻⁶. -4 At a temperature of 338℃, a proton beam irradiation was performed on a polytetrafluoroethylene (PTFE) sintered block using a proton accelerator. The PTFE sintered block was first subjected to a proton beam energy of 1.0 MeV and a dose of 5 × 10⁻⁶. 14 ion / cm 2 The first irradiation treatment was followed by a proton beam with an energy of 0.5 MeV and a dose of 5 × 10⁻⁶. 14 ion / cm 2 The material was subjected to a second irradiation treatment, and then the heating system was turned off. The material obtained after the two irradiations was cooled to room temperature, and finally the vacuum system was turned off to obtain blocky cross-linked polytetrafluoroethylene, which was designated as C1.

[0062] Example 2

[0063] The preparation of the polytetrafluoroethylene (PTFE) sintered block was the same as in Example 1, except that during the preparation of the crosslinked PTFE, the PTFE sintered block was first subjected to a proton beam with an energy of 1.2 MeV and a dose of 5 × 10⁻⁶. 14 ion / cm 2 The first irradiation treatment was followed by a proton beam with an energy of 0.5 MeV and a dose of 7 × 10⁻⁶. 14 ion / cm 2 The second irradiation treatment resulted in a cross-linked polytetrafluoroethylene sample, denoted as C2.

[0064] Example 3

[0065] The preparation of the polytetrafluoroethylene (PTFE) sintered block was the same as in Example 1, except that during the preparation of the crosslinked PTFE, the PTFE sintered block was first subjected to a proton beam with an energy of 1.5 MeV and a dose of 5 × 10⁻⁶. 14 ion / cm 2 The first irradiation treatment was followed by a proton beam with an energy of 0.3 MeV and a dose of 5 × 10⁻⁶.14 ion / cm 2 The second irradiation treatment resulted in a cross-linked polytetrafluoroethylene sample, denoted as C3.

[0066] Comparative Example 1

[0067] The preparation of the polytetrafluoroethylene (PTFE) sintered block was the same as in Example 1, except that during the preparation of the crosslinked PTFE, the PTFE sintered block only accepted a proton beam with an energy of 0.5 MeV and a dose of 5 × 10⁻⁶. 14 ion / cm 2 The cross-linked polytetrafluoroethylene sample prepared by irradiation treatment is designated as D1.

[0068] Comparative Example 2

[0069] The preparation of the polytetrafluoroethylene (PTFE) sintered block was the same as in Example 1, except that during the preparation of the crosslinked PTFE, the PTFE sintered block only accepted a proton beam with an energy of 1 MeV and a dose of 5 × 10⁻⁶. 14 ion / cm 2 The cross-linked polytetrafluoroethylene sample prepared by irradiation treatment is designated as D2.

[0070] Comparative Example 3

[0071] The polytetrafluoroethylene sintered block prepared in Example 1 was used as a comparative sample, and this sample was designated as D3.

[0072] Test case

[0073] 1. Density test

[0074] Density tests were performed on samples C1-C3 and D1-D3.

[0075] Test method: First, measure the buoyancy of the sample when it is immersed in water to obtain the volume of water displaced (i.e., the sample volume). Then measure the mass of the sample and divide the mass of the sample by the sample volume to obtain the sample density.

[0076] 2. Wear resistance test

[0077] Wear resistance tests were performed on samples C1-C3 and D1-D3.

[0078] Test Method: The sample to be tested is fixed on the stage of the wear resistance testing machine and rotated at a certain speed. A certain load is applied to the mechanical grinding head, causing friction between the grinding head and the rotating sample. After the wear resistance test time t, the friction area of ​​the sample will experience mass loss. Let Δm represent the mass difference of the sample before and after the wear resistance test (i.e., the mass lost due to friction), r represent the average radius of rotation, n represent the number of rotations per unit time, t represent the wear resistance test time, F represent the load applied to the grinding head, R is the grinding head radius, and l is the average width of the wear mark. The formula for calculating the wear depth h of the sample is as follows:

[0079]

[0080] During the test, the wear resistance test was conducted using a ball-and-disc friction loss tester under atmospheric conditions and at room temperature. The applied load F was 1 N, the grinding head radius R was 3.0 mm, the rotational radius r was 3.0 mm, the rotational speed n was 300 rpm, the wear resistance test time t was 15 min, and the density ρ was taken from the density of the sample in Table 1.

[0081] Table 1

[0082] Serial Number Friction loss mass (g) Wear depth (μm) <![CDATA[Sample density (g / cm 3 )]]> Example 1 <![CDATA[1.00×10 -4 ]]> 8.20 2.201 Example 2 <![CDATA[0.84×10 -4 ]]> 7.90 2.204 Example 3 <![CDATA[0.71×10 -4 ]]> 7.48 2.198 Comparative Example 1 <![CDATA[4.00×10 -4 ]]> 20.60 2.199 Comparative Example 2 <![CDATA[2.50×10 -4 ]]> 18.30 2.201 Comparative Example 3 <![CDATA[7.00×10 -4 ]]> 29.90 2.201

[0083] As can be seen from the table above, the wear resistance of the cross-linked polytetrafluoroethylene (PTFE) obtained by two irradiations in Examples 1-3 is significantly improved compared to the PTFE sintered block in Comparative Example 3 and the cross-linked PTFE obtained by one irradiation in Comparative Examples 1-2, as evidenced by a decrease in mass friction loss and wear depth. Therefore, the method provided by this invention can effectively improve the wear resistance of PTFE.

[0084] Figure 1 This is a simulation graph showing the relationship between injection depth and energy for proton beam irradiation of sintered polytetrafluoroethylene (PTFE) blocks. The simulation was performed using the Srim program. As shown in Figure a, the injection depth of a proton beam with an energy of 0.5 MeV is 6 μm, and the injection depth of a proton beam with an energy of 1.0 MeV is 16 μm. Through comparison... Figure 1 As shown in 'a' and 'b', when a proton beam irradiates a sintered polytetrafluoroethylene (PTFE) block, the energy loss is mainly electronic, while the nuclear energy loss is relatively small. Electronic energy loss refers to the energy lost through inelastic collisions between the incident particle and the outer electrons of the target atoms, which excites and ionizes the chemical bonds in the PTFE sintered block, leading to cross-linking. The magnitude of electronic energy loss is positively correlated with the degree of cross-linking in the PTFE; that is, the peak position of the electronic energy loss in the cross-linked PTFE reflects the location where the proton beam induces the highest degree of cross-linking.

[0085] Figure 2The results are obtained by using infrared spectroscopy to test the chemical structure of Example 1 (irradiated sample 2), the cross-linked polytetrafluoroethylene of Comparative Example 1 (irradiated sample 1), and the sintered polytetrafluoroethylene block of Comparative Example 3 (original sample). As can be seen from the figure, 1233 cm⁻¹ -1 The absorption peak at 1211 cm⁻¹ is caused by the stretching vibration of the C-C bonds in the PTFE backbone; -1 and 1154cm -1 The absorption peaks at 639 cm⁻¹ are caused by the asymmetric and symmetric stretching vibrations of the -CF₂- unit, respectively. -1 555cm -1 516cm -1 The absorption peaks at the specified locations are caused by out-of-plane rocking vibration, in-plane bending vibration, and in-plane rocking vibration of -CF2-, respectively. Furthermore, the figure shows that the peak intensities at the aforementioned locations of the cross-linked polytetrafluoroethylene obtained in Example 1 and Comparative Example 1 are lower than those at the aforementioned locations of the sintered polytetrafluoroethylene, with the decrease in peak intensity at the aforementioned locations of the cross-linked polytetrafluoroethylene in Example 1 being more pronounced. In addition, the figure also shows that the cross-linked polytetrafluoroethylene obtained in Example 1 and Comparative Example 1 exhibit absorption peaks at 1730 cm⁻¹. -1 983cm -1 778cm -1 730cm -1 and 720cm -1 A new absorption peak appears at 1300-1400 cm⁻¹, and another peak appears at 1300-1400 cm⁻¹. -1 The absorption band indicates that the sintered polytetrafluoroethylene (PTFE) block developed a new chemical structure after irradiation. Specifically, the cross-linked PTFE exhibits a high absorption band at 1730 cm⁻¹. -1 The absorption peak at 983 cm⁻¹ originates from the vibration of -CF = CF⁻; -1 The absorption peak at 778 cm⁻¹ originates from the -CF₃ of the side chain. -1 The absorption peak at 730 cm⁻¹ originates from the vibration of molecular chains in the amorphous PTFE component; -1 and 720cm -1 The double peak at 1300-1400 cm⁻¹ is a characteristic peak of the in-plane rocking vibration of -CH₂-, formed by the splitting of the peak in a long-chain saturated crystalline compound; -1 The nearby absorption bands are formed by the deformation vibrations of CH-containing groups.

[0086] Figure 3The results of crystallinity tests on cross-linked polytetrafluoroethylene (PTFE) of Example 1 (irradiated sample 2) and Comparative Example 1 (irradiated sample 1), and PTFE sintered block of Comparative Example 3 (original sample) were obtained using an X-ray diffractometer. It can be seen that the wave packet intensity of the diffraction peak of cross-linked PTFE of Example 1 near 2θ = 16° is greater than that of the cross-linked PTFE of Comparative Example 1 near 2θ = 16°. However, no wave packet was observed at 2θ = 16° in the diffraction peak of the PTFE sintered block. This indicates that there are non-crystalline components in the cross-linked PTFE. Meanwhile, both the sintered polytetrafluoroethylene (PTFE) block and the cross-linked PTFE exhibit diffraction peaks at 2θ = 18° and 32°. However, the diffraction peak intensity of the PTFE block is the strongest, followed by the cross-linked PTFE of Comparative Example 1, and the diffraction peak intensity of the cross-linked PTFE of Example 1 is the weakest. According to Bragg's equation, the X-ray diffraction angle remains unchanged and the peak position does not shift, indicating that the PTFE block undergoes a cross-linking reaction under proton beam irradiation. The resulting cross-linked PTFE has a decreased crystallinity and an increased amorphous component.

[0087] In the description of this specification, references to terms such as "some embodiments" indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment is included in at least one embodiment of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples, without contradiction. Additionally, it should be noted that in this specification, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features.

[0088] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for improving the wear resistance of polytetrafluoroethylene, characterized by, Includes the following steps: (1) Provide polytetrafluoroethylene sintered blocks; (2) The polytetrafluoroethylene sintered block is subjected to a first irradiation treatment using a first proton beam; (3) The material obtained in step (2) is subjected to a second irradiation treatment using a second proton beam; (4) Cool the material obtained in step (3) to obtain cross-linked polytetrafluoroethylene. The energy E1 of the first proton beam is 0.85-1.5 MeV, and the dose F1 of the first proton beam is 1 × 10⁻⁶. 14 -9×10 14 ion / cm 2 ; The energy E2 of the second proton beam is 0.3-0.8 MeV, and the dose F2 of the second proton beam is 1 × 10⁻⁶. 14 -9×10 14 ion / cm 2 .

2. The method according to claim 1, characterized in that, The first irradiation treatment satisfies at least one of the following conditions: at a vacuum of not higher than 1 x 10 -4 Pa; The temperature is 325-360℃.

3. The method of claim 1, wherein, The second irradiation treatment satisfies at least one of the following conditions: at a vacuum of not higher than 1 x 10 -4 Pa; The temperature is 325-360℃.

4. The method of claim 1, wherein, Step (1) includes: (1-1) Polytetrafluoroethylene powder is cold-pressed to obtain cold-pressed products; (1-2) The cold-pressed product is sintered to obtain polytetrafluoroethylene sintered block.

5. The method of claim 4, wherein, The conditions for cold pressing include: The pressure is 25-35 MPa; and / or the holding time is 0.5-2 min.

6. The method of claim 4, wherein, The sintering includes: The cold-pressed product is heated to 150-250°C at a heating rate of 2-6°C / min and held at that temperature for 1-3 hours. Then, it is heated to 360-380°C at a heating rate of 2-6°C / min and held at that temperature for 1-3 hours.

7. Crosslinked polytetrafluoroethylene prepared by the method according to any one of claims 1-6.

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