Fluororubber material for helicopter lip-shaped oil seal and preparation method of fluororubber material

Abstract

The invention provides a fluororubber material for a lip-shaped oil seal of a helicopter and a preparation method of the fluororubber material. The fluororubber material comprises 95-105 parts by mass of peroxide fluororubber, 5-15 parts by mass of carbon fibers, 3-12 parts by mass of graphite powder and 1-4 parts by mass of a plasticizing aid. The carbon fiber, the graphite powder, the plasticizing aid and other materials are added into the fluororubber, so that the high-temperature-resistant, low-temperature-resistant and high-wear-resistant rubber sealing material is obtained, can be suitable for a wide-temperature-range working condition environment of-56 DEG C to 250 DEG C and a high-vibration and large-eccentricity working condition for a long time, and is suitable for a lip-shaped oil seal for a helicopter engine and a traditional system; the cable has the characteristics of high and low temperature resistance, aviation hydraulic oil resistance, long service life and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of fluororubber materials, and in particular to a fluororubber material for a helicopter lip oil seal and a preparation method thereof. Background Art

[0002] Fluororubber refers to a synthetic polymer elastomer containing fluorine atoms on the carbon atoms of the main chain or side chain. It not only has good mechanical properties, but also has high resistance to high temperature, oil and corrosion by various chemicals. Its comprehensive performance is particularly excellent, so it has a wide range of applications, especially in the production of special sealing products. It is an indispensable material in modern aviation, missiles, rockets, space navigation and other cutting-edge science and technology and other industries.

[0003] Despite its excellent performance, fluororubber still has many shortcomings when used in helicopter lip oil seals. Currently commonly used fluororubber materials tend to harden and become brittle at temperatures below -20°C, causing seal failure in helicopters in extremely cold environments. Furthermore, traditionally formulated fluororubber materials are susceptible to wear under high-speed eccentric vibration conditions, resulting in a service life typically less than 1,000 hours, which cannot meet the long-term 2,000-hour flight requirements of helicopters. Furthermore, conventional fluororubber has a tensile strength of approximately 10-15 MPa, making it difficult to withstand the high vibration loads of helicopters. Summary of the Invention

[0004] The present invention adds carbon fiber, graphite powder, plasticizer and other materials to peroxide fluororubber to obtain a low-temperature and high-temperature resistant, highly wear-resistant rubber sealing material. The fluororubber sealing material can be applied to a wide temperature range of -56°C to 250°C for a long time, high vibration, and large eccentricity working conditions. It is suitable for helicopter lip oil seals and has the characteristics of high-temperature and low-temperature resistance, resistance to aviation hydraulic oil, and long service life.

[0005] The invention provides a fluororubber material for a helicopter lip oil seal, comprising: 95 to 105 parts by mass of peroxide fluororubber, 5 to 15 parts by mass of carbon fiber, 3 to 12 parts by mass of graphite powder, and 1 to 4 parts by mass of a plasticizer.

[0006] In one embodiment of the present invention, the composition includes: 100 parts by mass of peroxide fluororubber, 5 parts by mass to 15 parts by mass of carbon fiber, 3 parts by mass to 12 parts by mass of graphite powder, and 1 part by mass to 4 parts by mass of a plasticizer.

[0007] In one embodiment of the present invention, the composition includes: 100 parts by mass of peroxide fluororubber, 5 parts by mass to 15 parts by mass of carbon fiber, 3 parts by mass to 10 parts by mass of graphite powder, and 2 parts by mass to 3 parts by mass of a plasticizer.

[0008] In one example of the present application, it comprises: 100 parts by mass of peroxide fluororubber, 6-13 parts by mass of carbon fiber, 5-11 parts by mass of graphite powder, 1.5-3 parts by mass of plasticizing aid.

[0009] In one example of the present application, it comprises: 100 parts by mass of peroxide fluororubber, 8-12 parts by mass of carbon fiber, 9.5-10.5 parts by mass of graphite powder, 1.5-2.5 parts by mass of plasticizing aid.

[0010] In one example of the present application, it comprises: 100 parts by mass of peroxide fluororubber, 10 parts by mass of carbon fiber, 10 parts by mass of graphite powder, 2 parts by mass of plasticizing aid.

[0011] In the present application, the peroxide fluororubber is synthesized using vinylidene fluoride, perfluoromethyl vinyl ether, fluorine-containing olefin and a small amount of vulcanization point monomer, has a fluorine content of 63%, a Mooney viscosity of 20MU-65MU, a density of 1.825g / cm 3 , and a glass transition temperature of -40℃. The peroxide fluororubber in the present application is commercially available, and can be FKM-G226LT or FKM-G22XLT of Zhonghao Chen Guang Chemical Research Institute Co., Ltd.

[0012] In one example of the present application, the carbon fiber has a carbon content ≥96% and a particle size of 200-1000 mesh.

[0013] In one example of the present application, the carbon fiber has a carbon content ≥97% and a particle size of 200-800 mesh.

[0014] In one example of the present application, the carbon fiber has a carbon content ≥98% and a particle size of 250-400 mesh.

[0015] In one example of the present application, the carbon fiber has a carbon content ≥98.5% and a particle size of 250-350 mesh.

[0016] The carbon fiber in the present application uses high-purity carbon fiber, and is commercially available, and can be T700 of Cangzhou Zhongli New Material.

[0017] In one example of the present application, at least 85% of the particles in the graphite powder have a particle size ≤3μm.

[0018] In one example of the present application, at least 88% of the particles in the graphite powder have a particle size ≤2.5μm.

[0019] In one example of the present application, at least 90% of the particles in the graphite powder have a particle size ≤1μm.

[0020] The graphite powder in the present application is commercially available, and S-0 from Qingdao Henglide Graphite Co., Ltd. is preferred.

[0021] In one example of the present application, the plasticizing aid is a fluorine wax with a melting point of 40-70 DEG C.

[0022] In one example of the present application, the plasticizing aid is a fluorine wax with a melting point of 50-58 DEG C.

[0023] In one example of the present application, the plasticizing aid is a fluorine wax with a molecular weight of 1800-2200.

[0024] In one example of the present application, further comprising: 3-12 parts by mass of a heat-resistant acid-adsorbing agent, 5-30 parts by mass of a reinforcing filler aid, 1-4 parts by mass of a vulcanizing agent, and 2-6 parts by mass of a co-crosslinking agent.

[0025] In one example of the present application, further comprising: 3.5-8 parts by mass of a heat-resistant acid-adsorbing agent, 15-29 parts by mass of a reinforcing filler aid, 1.5-3.5 parts by mass of a vulcanizing agent, and 2.5-5 parts by mass of a co-crosslinking agent.

[0026] In one example of the present application, comprising: 100 parts by mass of a peroxide fluororubber, 8-12 parts by mass of carbon fibers, 9.5-10.5 parts by mass of graphite powder, 1.5-2.5 parts by mass of a plasticizing aid, 4-6 parts by mass of a heat-resistant acid-adsorbing agent, 23-27 parts by mass of a reinforcing filler aid, 2-3 parts by mass of a vulcanizing agent, and 3-4 parts by mass of a co-crosslinking agent.

[0027] In one example of the present application, further comprising: 100 parts by mass of a peroxide fluororubber, 10 parts by mass of carbon fibers, 10 parts by mass of graphite powder, 2 parts by mass of a plasticizing aid, 5 parts by mass of a heat-resistant acid-adsorbing agent, 25 parts by mass of a reinforcing filler aid, 2.5 parts by mass of a vulcanizing agent, and 3.5 parts by mass of a co-crosslinking agent.

[0028] In one example of the present application, the heat-resistant acid-adsorbing agent comprises at least one of magnesium oxide and zinc oxide.

[0029] The reinforcing filler aid comprises at least one of thermal-cracking carbon black and calcium silicate.

[0030] The vulcanizing agent comprises at least one of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, hexamethylene diurea, and ethylenediamine urea.

[0031] The co-crosslinking agent comprises at least one of triallyl isocyanurate, triallyl isocyanurate, triallyl isocyanurate, and trimethylolpropane triacrylate.

[0032] In one example of the present application, the heat-resistant acid-adsorbing agent is magnesium oxide;

[0033] In one example of the present application, the heat-resistant acid-adsorbing agent is zinc oxide;

[0034] In one example of the present application, the heat-resistant acid-adsorbing agent is a mixture of magnesium oxide and zinc oxide;

[0035] In one example of the present application, the heat-resistant acid-adsorbing agent is a mixture of magnesium oxide and zinc oxide in a mass ratio of 1:1.

[0036] In the present application, the acid-adsorbing agent is mainly used to neutralize the acidic by-products generated in the vulcanization process of fluororubber, such as hydrogen fluoride, to prevent corrosion of the equipment and the rubber compound, and at the same time, to optimize the vulcanization reaction, improve the flowability of the rubber compound, and improve the process performance. Commonly used can be single magnesium oxide (active value of 30-150), zinc oxide, or a mixture of the two.

[0037] In one example of the present application, the reinforcing and filling aid is thermal cracking carbon black. Thermal cracking carbon black has a large particle size and low structure, which can improve heat resistance, oil resistance, and chemical corrosion resistance, reduce compression permanent deformation, maintain rubber elasticity, and reduce costs, etc. In fluororubber, the addition of thermal cracking carbon black has small hardness improvement, improved processability, and excellent comprehensive performance.

[0038] In one example of the present application, the reinforcing and filling aid is calcium silicate.

[0039] In one example of the present application, the reinforcing and filling aid is modified calcium silicate. The modified calcium silicate used in the present application is a commercially available product. Generally, the modified calcium silicate treated with a coupling agent improves the reinforcing and dispersing properties of ordinary calcium silicate and improves the process performance in vulcanization production.

[0040] In one example of the present application, the reinforcing and filling aid is a mixture of thermal cracking carbon black and modified calcium silicate.

[0041] The thermal cracking carbon black and the modified calcium silicate in the present application are commercially available. When used, N990 carbon black and modified calcium silicate BS-003F from Bosixin Material Co., Ltd. are preferred.

[0042] In one example of the present application, the reinforcing and filling aid is a mixture of thermal cracking carbon black and modified calcium silicate in a mass ratio of 1:(0.5-1.5).

[0043] In one example of the present application, the reinforcing and filling aid is a mixture of thermal cracking carbon black and modified calcium silicate in a mass ratio of 1:1.

[0044] In one example of the present application, the vulcanizing agent is 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, and the active ingredient content is 45%.

[0045] The 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane in the present application is commercially available, and a liquid product with a content of more than 95% can be selected, or a powdery product with a content of 45%-50% using white carbon black (active ingredient silicon dioxide) as a carrier can be selected.

[0046] In one example of the present application, the co-crosslinking agent is triallyl isocyanurate, and the active ingredient content is 70%.

[0047] A preparation method of a fluororubber material for a helicopter lip oil seal, for preparing the above fluororubber material, the specific preparation method is as follows:

[0048] S100: plasticize the raw peroxide fluororubber;

[0049] S200: then sequentially add a heat-resistant acid-absorbing agent, carbon fiber, graphite powder, a reinforcing and filling aid, and a plasticizing aid, and mix;

[0050] S300: further add a vulcanizing agent and a co-crosslinking agent to obtain a mixed material;

[0051] S400: vulcanize the mixed material to obtain a fluororubber material for a helicopter lip oil seal.

[0052] In one example of the present application, S100 includes the following steps: plasticize the raw peroxide fluororubber in a two-roll open mill to 60-80℃.

[0053] In one example of the present application, S200 includes the following steps: then sequentially add a heat-resistant acid-absorbing agent, carbon fiber, graphite powder, a reinforcing and filling aid, and a plasticizing aid, and mix for 20-30min until uniform.

[0054] In one example of the present application, S300 includes the following steps: further add a vulcanizing agent and a co-crosslinking agent, and pass through the mill 15 times to obtain a mixed material.

[0055] In one example of the present application, S400 specifically includes the following preparation steps:

[0056] S410: once-vulcanize the mixed material, control the vulcanization temperature to be 170-180℃, the vulcanization time to be 10-15min, and the vulcanization pressure to be 10-15MPa, to obtain a once-vulcanized material;

[0057] S420: secondary vulcanization is carried out on the primary vulcanized material, the vulcanization temperature is controlled to be 220-240 DEG C, and the vulcanization time is controlled to be 5-7 h, thereby obtaining the fluororubber material for the lip-shaped oil seal of the helicopter.

[0058] In one example of the present application, in S410, the mixing material is primary vulcanized, the vulcanization temperature is controlled to be 175 DEG C, the vulcanization time is controlled to be 10 min, and the vulcanization pressure is 12 MPa, thereby obtaining the primary vulcanized material.

[0059] In one example of the present application, in S420, the primary vulcanized material is secondary vulcanized, the vulcanization temperature is controlled to be 230 DEG C, and the vulcanization time is controlled to be 6 h, thereby obtaining the fluororubber material for the lip-shaped oil seal of the helicopter.

[0060] Compared with the prior art, the present application has the following advantages:

[0061] (1) The present application effectively improves the low-temperature toughness and strength of the fluororubber material by using the synergistic effect of carbon fibers, graphite powder and plasticizing aids, so that the fluororubber material can maintain elasticity at a temperature of -56 DEG C and excellent wear resistance at low temperature, and the fluororubber material of the present application can ensure that the lip-shaped oil seal has no leakage for 10 cycles of continuous start-up at low temperature and has no leakage in a 2400-hour dynamic sealing performance test.

[0062] (2) The high-purity carbon fibers and graphite powder added in the fluororubber material of the present application have both lubricating and dry wear resistance, which can effectively improve the lubricating and wear resistance, thereby ensuring that the wear rate of the lip-shaped sealing lip is less than 0.1 mm.

[0063] (3) The graphite powder added in the fluororubber of the present application can form a dense barrier layer with the fluororubber matrix, thereby effectively reducing the volume change rate of the fluororubber. BRIEF DESCRIPTION OF DRAWINGS

[0064] Figure 1 The figure is the result of the dry wear test of the oil seal of formula 1 in the second example of the present application.

[0065] Figure 2 The figure is the result of the dry wear test of the oil seal of formula 2 in the second example of the present application.

[0066] Figure 3 The figure is the result of the dry wear test of the oil seal of formula 3 in the second example of the present application.

[0067] Figure 4 The figure is the result of the dry wear test of the oil seal of formula 4 in the second example of the present application.

[0068] Figure 5 The figure is the result of the dry wear test of the oil seal of formula 5 in the second example of the present application.

[0069] Figure 6This is an electron microscope image of the wear surface of Formula 0 in Example 3 of the present invention;

[0070] Figure 7 This is an electron microscope image of the wear surface of Formula 1 in Example 3 of the present invention;

[0071] Figure 8 This is an electron microscope image of the wear surface of Formula 2 in Example 3 of the present invention;

[0072] Figure 9 This is an electron microscope image of the wear surface of Formula 3 in Example 3 of the present invention;

[0073] Figure 10 This is an electron microscope image of the wear surface of formula 4 in Example 3 of the present invention. DETAILED DESCRIPTION

[0074] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below.

[0075] Example 1:

[0076] This embodiment provides a method for preparing a fluororubber material for a helicopter lip oil seal, and the specific steps are as follows:

[0077] S100: Plasticize the peroxide fluororubber raw rubber in a two-roll mill to 60℃-80℃;

[0078] S200: Then add the heat-resistant acid absorbent, carbon fiber, graphite powder, reinforcing filling additive, and plasticizer in sequence, and mix for 20-30 minutes until uniform;

[0079] S300: Add vulcanizing agent and co-crosslinking agent, pass through 15 times to obtain the mixed material;

[0080] S400: The mixed material is subjected to primary vulcanization, with the vulcanization temperature controlled at 175°C, the vulcanization time controlled at 10 minutes, and the vulcanization pressure controlled at 12 MPa, to obtain a primary vulcanized material; the primary vulcanized material is subjected to secondary vulcanization, with the vulcanization temperature controlled at 230°C, and the vulcanization time controlled at 6 hours, to obtain a fluororubber material for helicopter lip oil seals.

[0081] Among them, the specific formula of the fluororubber material is as follows: 100 parts by mass of peroxide fluororubber, 10 parts by mass of carbon fiber powder (300 mesh), 10 parts by mass of graphite powder (particle size 2.3 μm), 2 parts by mass of fluorowax, 5 parts by mass of zinc oxide, 25 parts by mass of thermal cracked carbon black / modified calcium silicate composite, 2.5 parts by mass of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, and 3.5 parts by mass of triallyl isocyanurate.

[0082] (1) The fluororubber material prepared above and a common fluororubber material are respectively subjected to performance testing, and the test results are shown in Table 1. Among them, the experimental group is the fluororubber material of the application; the comparison group is a common fluororubber, and the formula is as follows: 100 parts by mass of 26 type fluororubber raw rubber, 6 parts by mass of acid absorber magnesium oxide-150, 5 parts by mass of calcium hydroxide, 5 parts by mass of reinforcing filler N990, 15 parts by mass of barium sulfate, 25 parts by mass of modified calcium silicate, 2 parts by mass of lubricant palm wax, 1.6 parts by mass of vulcanizing agent bisphenol AF, and 0.5 parts by mass of accelerator BPP.

[0083] Table 1

[0084]

[0085]

[0086] It can be seen from the above test results that the fluororubber material provided by the application has better mechanical properties, low-temperature toughness and wear resistance.

[0087] (2) The fluororubber material prepared above is subjected to low-temperature start-up test, and the test procedure refers to GB / T13871.4-2023 "Rotary shaft lip seal with elastomer material for sealing element Part 4: Performance test procedure", and the test is carried out according to the following method:

[0088] ① Measure the outer diameter size of the lip seal before installation and the inner diameter size of the main lip after spring installation, and record the measurement results, and check whether the lip seal lip size meets the drawing requirements;

[0089] ② Install the lip seal on the test bench, adjust the test parameters as required and record them respectively;

[0090] ③ Inject lubricating oil into the sealing cavity, and the lubricating oil is 1 / 4 higher than the lip seal. After keeping the lip seal and the lubricating oil at-56℃ for 16 hours, start the test bench, and one cycle is from the temperature of the lubricating oil rising to room temperature, and 10 cycles are continuously carried out;

[0091] ④ Measure the temperature before each cycle test and record it, and check the oil leakage after starting the test bench every cycle and record it;

[0092] ⑤ After the test, take down the lip seal, measure the lip size and wear width and record them.

[0093] Test results:

[0094] After 10 cycles of continuous operation, the sealing performance is excellent during and after the test, and no leakage occurs. It can be seen from the test results that the fluororubber material of the application can continuously start the lip seal at-56℃ for 10 cycles without any leakage.

[0095] (3) Dynamic sealing performance test was performed on the fluororubber material prepared above, and the test procedure referred to GB / T13871.4-2023 “Rotating Shaft Lip Seal for Elastomer Materials Part 4: Performance Test Procedure”, and the test was performed according to the following method:

[0096] ① The sealing performance test was performed for 20 hours as a cycle, 14 hours in each cycle was operated at rated speed, and 6 hours was operated at maximum speed, and after one cycle of operation, the test bench was stopped for 4 hours, and then the next cycle of bench test was performed (if the stop time exceeded 4 hours due to weekend or holiday, it was counted as 4 hours);

[0097] ② The outer diameter size of the lip oil seal before installation and the inner diameter size of the main lip after spring installation were measured, and the measurement results were recorded, and whether the lip size of the lip oil seal met the requirements of the drawing was checked;

[0098] ③ The lip oil seal was installed on the test bench, and the test parameters were adjusted according to the requirements and recorded;

[0099] ④ The oil was injected into the sealing cavity, and the oil covered 1 / 4 of the lip oil seal. After the medium temperature was raised to 120℃ under the environment temperature of -56℃, the test bench was started, and after 14 hours of operation at rated speed, the speed was adjusted to maximum speed, and after 6 hours of continuous operation, the test bench was stopped for 4 hours. The leakage of the lip oil seal was checked before and after the start of the test bench, and the results were recorded;

[0100] ⑤ After the test was completed, the lip oil seal was taken off, the main lip size was measured and recorded, the wear condition of the lip was observed, and the wear width was measured and recorded;

[0101] ⑥ If the running time during the test did not reach the required running hours, i.e. leakage occurred, the test was terminated.

[0102] Test results:

[0103] Under the specified working conditions, the test lasted for 2400 hours, and there was no oil leakage during and after the test, and the sealing performance was excellent.

[0104] (4) Dry friction test was performed on the fluororubber material prepared above, and the test method was as follows: the lip oil seal was pressed into the mounting seat hole, the sealing lip was wiped with 120# gasoline, the test shaft was degreased, and then it was installed on the dynamic sealing test machine, and according to the actual working condition, the test was operated for 30 minutes under the test condition of linear speed 15m / s.

[0105] After the test was completed, the oil seal was taken off, and the wear width and surface morphology of the sealing lip were checked.

[0106] The cross section of the sealing lip of the oil seal was cut, and the wear width was measured by using optical tools such as tool microscope or projector.

[0107] Test results:

[0108] 1) No melting and cracking phenomenon on the lip wear surface of the lip seal.

[0109] 2) After the dry friction test, the contact width of the sealing lip of the lip seal is less than 0.1 mm.

[0110] Example Two:

[0111] The fluororubber with different ratios of graphite powder and carbon fiber was tested, and the test formula is shown in Table 2. Among them, other additives include: 2 parts by mass of fluorine wax, 5 parts by mass of zinc oxide, 25 parts by mass of thermal cracking carbon black / modified calcium silicate compound, 3.5 parts by mass of triallyl isocyanurate.

[0112] Table 2

[0113] Formulation 1 2 3 4 5 Raw rubber 100 100 100 100 100 Carbon fiber 0 5 10 10 5 Graphite 0 5 10 5 10 Vulcanizing agent 2.5 2.5 2.5 2.5 2.5 Other additives 35.5 35.5 35.5 35.5 35.5

[0114] The fluororubber of the above formula was tested for performance, and the test results are shown in Table 3.

[0115] Table 3

[0116]

[0117]

[0118] As can be seen from the test results in Table 2, the fluororubber of formula 3 has better wear resistance.

[0119] Example Three:

[0120] The fluororubber with a ratio of graphite powder to carbon fiber of 1:1 was tested, and the test formula is shown in Table 4.

[0121] Table 4

[0122]

[0123] The fluororubber of the above formula was tested for performance, and the test results are shown in Table 5.

[0124] Table 5

[0125]

[0126]

[0127] As can be seen from the above table, with the increase of the amount of carbon fiber and graphite, the minimum torque (ML) and the maximum torque (MH) of the fluoroelastomer material both have a trend of increasing. The increase of ML of the fluoroelastomer material may be due to the fact that the carbon fiber does not exhibit a viscous flow state at high temperature, and its addition reduces the fluidity of the fluoroelastomer material. The increase of MH of the fluoroelastomer material is greater than that of ML, that is, the difference between MH and ML is on the rise, indicating that the carbon fiber and graphite play a role in increasing the crosslinking points during vulcanization, thereby increasing the crosslinking density. Compared with the fluoroelastomer material without filling carbon fiber and graphite, the fluoroelastomer material with the addition of carbon fiber and graphite has a shorter scorch time, which has an accelerating effect on the initial vulcanization, but has little effect on the normal vulcanization time of the fluoroelastomer material. It is analyzed that the carbon fiber and graphite distributed in the mixing rubber at the initial stage of vulcanization play a role as rubber crosslinking points, thereby reducing the time of initiator decomposition reaction and initiator-induced fluoroelastomer molecular crosslinking reaction, and improving the formation rate of effective crosslinking points, which is manifested as the reduction of scorch time, but the effect gradually decreases in the subsequent vulcanization process, so the normal vulcanization time changes little.

[0128] At the same time, with the increase of the amount of carbon fiber and graphite, the tensile strength and elongation at break of the fluoroelastomer material both show a downward trend. It is analyzed that the length of the carbon fiber and graphite is too short, and the number of end heads in a unit cross section is relatively large, which is very easy to be peeled off at the end head part during the stretching process, so that it cannot play a role in bearing the tensile stress, resulting in the decrease of the tensile strength; and the rubber deformation ability is also decreased, which is manifested as the decrease of the elongation at break.

[0129] Moreover, the fluoroelastomer material without the addition of carbon fiber and graphite has a high friction rate, as shown in Figure 6 , in the sliding process, the surface produces tongue-shaped objects due to repeated tearing, and is further rubbed into curled shape and falls off from the surface layer of the rubber to form curled debris. As shown in Figure 7 , when the total amount of carbon fiber and graphite is 5 parts, due to the interaction between the carbon fiber and the fluoroelastomer, it has a certain tear resistance, the tongue-shaped objects are not peeled off, and the wave-shaped stripes are formed on the friction surface, so the wear rate is reduced. It is inferred that the wear mechanisms of the above two samples are mainly adhesive wear. When the amount of carbon fiber and graphite increases to 10 parts, the wear surface of the sample is relatively smooth, as shown in Figure 8 , the carbon fiber and graphite are uniformly distributed, and the fiber is worn. During friction, the carbon fiber and graphite bear the main stress, the wear and fracture of the fiber itself reduce the direct contact of the steel ring surface microconvex body with the rubber material, which plays a role in reducing friction, so there is no tearing of the rubber. At this time, the wear of the composite material is mainly abrasive wear, and the wear rate reaches the minimum value. When the amount of carbon fiber and graphite increases to 15 and 20 parts, due to the high content of the fiber, the dispersion is poor, the interfacial bonding force is poor, and many fibers are extracted from the matrix to leave indentations, forming friction defects, as shown in Figure 9 ,Figure 10 As shown, the wear rate is increased again. In view of the influence of the carbon fiber and the graphite on the friction coefficient and the wear rate of the rubber material, 10 parts of the carbon fiber and the graphite are selected for filling.

[0130] Example Four

[0131] The vulcanization system of the rubber body material not only relates to the physical and mechanical properties of the material, but also affects the vulcanization characteristics of the material. The former has an important influence on the service life of the lip-shaped oil seal, such as the tensile strength, the compression permanent set rate, the heat aging decay rate, etc. The influence on the vulcanization characteristics affects the production efficiency and the waste rate in the product manufacturing process. Therefore, the determination of the mixing ratio of the vulcanization system is the most critical in the mixing ratio adjustment process of the rubber body material.

[0132] The vulcanization system of the peroxide vulcanized fluororubber is composed of a peroxide vulcanizing agent (2,5-dimethyl-2,5-di(tert-butyl peroxy) hexane) and a peroxide vulcanization co-crosslinking agent TAIC (triallyl isocyanurate), and is polymerized in the form of free radical crosslinking, including two processes: (1) the peroxide double 2,5 is decomposed by heating to generate free radicals, which then absorb H on the tertiary carbon atom in the fluororubber polymer chain or the active point on the crosslinking point monomer to form a polymer free radical. (2) The polymer free radicals are combined or crosslinked by a bridging agent to form a three-dimensional network crosslinked structure. The co-crosslinking agent TAIC can more effectively utilize the free radicals of the peroxide, rapidly react with the polymer free radicals generated by the hydrogen abstraction reaction, and this reaction is faster than the polymer chain scission reaction, and the generated polymer free radicals are more stable, thereby achieving the purpose of improving the crosslinking efficiency.

[0133] Different amounts of co-crosslinking agents and different amounts of vulcanizing agents have different influences on the vulcanization characteristics and mechanical properties of the fluororubber material.

[0134] The fluororubber with different contents of vulcanizing agents was tested for performance, and the test formula is shown in Table 6. Among them, other reagents include: 10 parts by mass of carbon fiber powder, 10 parts by mass of graphite powder, 2 parts by mass of fluorine wax, 5 parts by mass of zinc oxide, 25 parts by mass of thermal cracking carbon black / modified calcium silicate compound, the vulcanizing agent used is 2,5-dimethyl-2,5-di(tert-butyl peroxy) hexane, and the co-crosslinking agent is triallyl isocyanurate.

[0135] Table 6

[0136] Formulation 1 2 3 4 5 Raw rubber 100 100 100 100 100 Vulcanizing agent 2 2.5 3.5 4 4.5 Co-crosslinking agent 3.5 3.5 3.5 3.5 3.5 Other agent 52 52 52 52 52

[0137] The fluororubber with the above formula was tested for performance, and the vulcanization characteristic test results are shown in Table 7, and the physical property test results are shown in Table 8.

[0138] Table 7

[0139] Formulation 1 2 3 4 5 ML 1.32 1.29 1.28 1.15 1.17 MH 12.76 13.98 14.02 13.96 13.52 T10 0.66 0.48 0.39 0.32 0.3 T90 2.12 2.04 2.02 1.98 2.02

[0140] From the above test results, it can be seen that as the amount of vulcanizing agent increases, T10 continuously decreases, the scorch period of the fluoroelastomer material becomes shorter and shorter, and the operation safety becomes worse and worse. When the amount of vulcanizing agent is more than 2.5 parts, the change of MH is not obvious, which indicates that the excess vulcanizing agent does not play a role and the crosslinking point is saturated.

[0141] Table 8

[0142]

[0143]

[0144] From the above test results, it can be seen that when the amount of vulcanizing agent is greater than 2.5 parts, it has little effect on the tensile strength and compression set of the fluoroelastomer material. It can be seen that when the amount of vulcanizing agent is 2.5 parts, the vulcanization operation safety and the physical and mechanical properties of the rubber material are optimal.

[0145] The fluoroelastomer materials with different amounts of co-crosslinking agent were tested for performance, and the test formula is shown in Table 9. Among them, other reagents include 10 parts by mass of carbon fiber powder, 10 parts by mass of graphite powder, 2 parts by mass of fluorine wax, 5 parts by mass of zinc oxide, 25 parts by mass of thermal cracking carbon black / modified calcium silicate compound, and the vulcanizing agent used is 2,5-dimethyl-2,5-di(tert-butyl peroxy) hexane, and the co-crosslinking agent is triallyl isocyanurate.

[0146] Table 9

[0147] Formulation 6 7 8 9 10 Raw rubber 100 100 100 100 100 Vulcanizing agent 2.5 2.5 2.5 2.5 2.5 Co-crosslinking agent 3 3.5 4 4.5 5 Other agent 52 52 52 52 52

[0148] The fluoroelastomer of the above formula was tested for performance, and the vulcanization characteristic test results are shown in Table 10, and the physical property test results are shown in Table 11.

[0149] Table 10

[0150] Formulation 6 7 8 9 10 ML 1.18 1.29 1.3 1.34 1.3 MH 11.78 13.98 14.68 15.22 15.96 T10 0.63 0.48 0.35 0.3 0.29 T90 2.62 2.04 1.99 2.02 1.97

[0151] From the above test results, it can be seen that as the amount of co-crosslinking agent increases, the ML and MH of the fluoroelastomer material continuously increase, and the tensile strength continuously increases, because the co-crosslinking agent continuously participates in crosslinking, increasing or growing the crosslinking network; but T10 is shortened obviously, and the operation safety of the fluoroelastomer material gradually becomes worse.

[0152] Table 11

[0153] Formulation 6 7 8 9 10 Hardness (Shore A) 75 76 77 77 77 Tensile strength (MPa) 15 17.6 17.8 18.1 18.5 Tensile elongation (%) 277 235 209 199 182 Compression set (%) 28 23 22 23 22

[0154] The test results above show that the tensile strength of fluororubber increases with increasing co-crosslinking agent dosage. When the co-crosslinking agent dosage exceeds 3.5 phr, the increase in tensile strength and the decrease in compression set slow down, and the impact becomes smaller, while the hardness of the vulcanized rubber continues to increase. This is because the crosslinking density of the fluororubber material increases with increasing co-crosslinking agent dosage. However, too low or too high a crosslinking density can cause insufficient crosslinking or brittleness in the vulcanized rubber. Therefore, the optimal co-crosslinking agent dosage is 3.5 phr.

[0155] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the scope defined by the claims.

Claims

1. A fluororubber material for helicopter lip oil seal, characterized in that: include: 95-105 parts by mass of peroxide fluororubber, 5-15 parts by mass of carbon fiber, 3-12 parts by mass of graphite powder, and 1-4 parts by mass of a plasticizer.

2. The fluororubber material according to claim 1, characterized in that: The carbon fiber has a carbon content of ≥96% and a particle size of 200-1000 meshes.

3. The fluororubber material according to claim 1, characterized in that: At least 85% of the graphite powder particles have a particle size of ≤3 μm.

4. The fluororubber material according to claim 1, characterized in that: The plasticizing aid is fluorine wax with a melting point of 40°C-70°C.

5. The fluororubber material according to any one of claims 1 to 4, characterized in that: Also includes: 3 to 12 parts by mass of a heat-resistant acid absorbent, 5 to 30 parts by mass of a reinforcing and filling auxiliary, 1 to 4 parts by mass of a vulcanizing agent, and 2 to 6 parts by mass of a co-crosslinking agent.

6. The fluororubber material according to claim 5, characterized in that: The heat-resistant acid absorbent comprises at least one of magnesium oxide and zinc oxide; The reinforcing and filling auxiliary agent comprises at least one of thermal cracking carbon black and calcium silicate; The vulcanizing agent comprises at least one of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, hexamethylenediaminocarbamate, and ethylenediaminecarbamate; The auxiliary cross-linking agent comprises at least one of triallyl isocyanurate, triallyl isocyanurate, trimethylolpropane triacrylate, and trimethylolpropane trimethacrylate.

7. The fluororubber material according to claim 6, characterized in that: include: 100 parts by mass of peroxide fluororubber, 8-12 parts by mass of carbon fiber, 9.5-10.5 parts by mass of graphite powder, 1.5-2.5 parts by mass of plasticizer, 4-6 parts by mass of heat-resistant acid absorbent, 23-27 parts by mass of reinforcing and filling additive, 2-3 parts by mass of vulcanizing agent, and 3-4 parts by mass of co-crosslinking agent.

8. The fluororubber material according to claim 7, characterized in that: The carbon fiber has a carbon content of ≥98.5% and a particle size of 250-350 meshes, and at least 90% of the particles in the toner have a particle size of ≤1 μm.

9. A method for preparing fluororubber material for helicopter lip oil seal, characterized in that: For preparing the fluororubber material according to any one of claims 1 to 8, the specific preparation method is as follows: S100: Plasticizing the peroxide fluororubber raw rubber; S200: Then add the heat-resistant acid absorbent, carbon fiber, graphite powder, reinforcing and filling additives, and plasticizer in sequence and mix them; S300: adding a vulcanizing agent and a cross-linking agent to obtain a mixed material; S400: vulcanizing the mixed material to obtain a fluororubber material for a helicopter lip oil seal.

10. The preparation method according to claim 9, characterized in that The S400 specifically includes the following preparation steps: S410: performing primary vulcanization on the mixed material, controlling the vulcanization temperature at 170° C.-180° C., the vulcanization time at 10 min-15 min, and the vulcanization pressure at 10 MPa-15 MPa to obtain a primary vulcanized material; S420: performing secondary vulcanization on the primary vulcanized material, controlling the vulcanization temperature at 220° C.-240° C. and the vulcanization time at 5 h-7 h, to obtain the fluororubber material for the helicopter lip oil seal.

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