Home > Case > Content

Improvement of friction and wear properties of ultra high molecular weight polyethylene by filler

Jun 28, 2019

Ultra High Molecular Weight Polyethylene (UHMW-PE) is a new type of engineering plastic. It was invented by German scientists in 1958. By the end of the 1960s, industrial production was realized abroad. China officially put into production in the late 1970s. Starting from the age of toughness, it has excellent characteristics such as wear resistance, corrosion resistance, impact resistance, self-lubrication, small friction coefficient and low temperature resistance. It is called “magic plastic” in foreign countries. Although ultrahigh molecular weight polyethylene has many excellent properties, it also has many disadvantages such as low hardness, low strength, poor temperature resistance, and poor creep properties. In order to compensate for these deficiencies and further improve the wear resistance, it may be modified with a filler (ultrafine glass microbeads, molybdenum disulfide, talc, glass fiber, carbon fiber, polytetrafluoroethylene). In addition, different modifications should be made according to the conditions and requirements of the application conditions. There have been many reports on the performance, processing technology, modification and application of ultra-high molecular weight polyethylene. There are few reports on the performance test of friction and wear in China, while ultra-high molecular weight polyethylene is resistant to wear and tear. The good toughness has attracted people's attention and application. Therefore, the author used the M-200 friction and wear tester to carry out the friction and wear test of the ring (45# steel) block, and carried out the ultra high molecular weight polyethylene with the corrosion wear tester. Sand abrasion test. 2 Experimental equipment, equipment, raw materials and additives 2.1 Raw materials and additives Ultra high molecular weight polyethylene: white powder, M-II type (molecular weight 2.5 million); antioxidant; coupling agent; ultrafine glass beads, 450 mesh; carbon fiber ; PTFE: Model 7A-J (about 200 mesh); glass fiber; talcum powder: 200 mesh.   2.2 Experimental equipment Test machine: M-200 type wear test machine, model: MSH type, the speed is selected as 683rpm. 2.3 Test instrument Weighing instrument: Xiangyi Yidaojin electronic analytical balance AEL-200. 3 Test 3.1 Ring block test The test machine is the M-200 type wear test machine. The ring block size is: Φ40×12, 14×14. In order to load more accurately, the spring loading device is changed to lever loading, and the lever arm is used. The ratio is 3:1. The experiment is divided into oil lubrication and oilless lubrication. When the oil is not lubricated, the friction coefficient and the wear amount are tested. When the oil is lubricated (normal oil drip lubrication), the friction coefficient is only tested because the wear amount is too small. The test piece should be cleaned before testing and weighing, the cleaning agent is made of acetone, and the cleaning device is H66005 ultrasonic cleaner. The cleaning time depends on the size of the test piece and the degree of soiling. The cleaning time of this experiment was 15 min. The test of wear amount is carried out according to GB3960-88 "Test method for sliding friction and wear of plastics". Ring block test, the ring is 45# steel, the surface roughness is 0.8μm, the block is ultra-high molecular weight polyethylene plastic, the test piece load is 200N, the ring rotation speed is 200rpm, and the running time is l0min (through the pre-test due to the long time) The surface of the plastic heat is melted, so the running time is 10 minutes).   3.2 Mortar wear test The sand pad wear test is carried out on the corrosion wear test machine. The schematic diagram of the test device is shown in Figure 1. The speed is high speed (683 rpm) in low speed. Quartz sand: 40 to 70 mesh. The ratio of sand to water (volume ratio) is 1:4 (water is tap water). The geometrical dimensions and surface finish of each test piece are as uniform as possible, and four test pieces can be tested at one time. Figure 2 Relationship between additive ratio and wear amount in ring block wear test 4 Experimental results and analysis 4.1 Effect of additive ratio on wear amount in ring block wear test Figure 2 is the relationship between additive ratio and wear amount in ring block wear test . Can be seen from the figure. When the proportion of the additive is ≤5%, the wear amount is significantly reduced as the proportion of the additive increases, that is, the wear resistance is improved. When the proportion of the additive is more than 20%, the wear amount decreases slowly, and even the individual wear amount increases. This indicates that the wear resistance of the ultrahigh molecular weight polyethylene is no longer increased when the proportion of the additive reaches a certain value, that is, the saturation value is reached. This is because these inorganic additives have poor compatibility with ultra-high molecular weight polyethylene. Although these additives are coupled by a coupling agent, the addition ratio should not be too high and should not exceed their respective "saturation values". Otherwise, Wear resistance, impact strength, tensile strength, etc. are reduced.   4.2 Effect of additive ratio on wear during mortar abrasion test Figure 3 is a plot of the ratio of additive to wear during the sand abrasion test on a corrosion and wear tester. The relative wear rate is the ratio of the amount of wear to the weight of the test piece before wear. It can be seen from Fig. 3 that the amount of wear increases with the increase of the proportion of the additive, and a phenomenon different from that of the ring block occurs. This shows that friction and wear are closely related to working conditions, and are greatly affected by working conditions. The wear of the same material under different working conditions is completely different. It also shows that the mechanism of friction and wear is very complicated and difficult to determine.   4.3 Effect of different additives and ratios on the friction coefficient in the ring block test Figure 4 is the relationship between different additives and different proportions and friction coefficient in the ring block test. It can be seen from Fig. 4 that the addition of glass fiber and talc has a great influence on the friction coefficient, which increases the friction coefficient; the addition of glass beads and carbon fiber has little effect on the friction coefficient, and the addition of polytetrafluoroethylene can reduce the friction coefficient. Although ultrahigh molecular weight polyethylene has many excellent properties, it also has many shortcomings, and it is generally modified differently according to different needs in application. For example, when used as a bearing or a bushing, an additive is required to make the ultrahigh molecular weight polyethylene have a low friction coefficient and wear resistance; when used as a roller, an additive is required to enable the ultrahigh molecular weight polyethylene to meet wear resistance requirements. In addition, the cost of additives and the like should be considered.    5 Conclusions (1) When the ring block wears, the wear amount decreases with the increase of the additive ratio; (2) The wear amount increases with the increase of the additive ratio when the sand is worn; (3) The addition of glass fiber and talcum powder increases the friction coefficient. (4) Adding carbon fiber and glass microbeads have almost no effect on the friction coefficient; (5) Adding PTFE can reduce the friction coefficient; (6) Adding glass beads to the overall performance and price is ideal. It can improve the comprehensive performance and reduce the cost. Ultra-high molecular weight polyethylene modified with ultra-fine glass beads has been used in mining and other machinery, and more than ten kinds of ultra-high molecular weight polyethylene products have been developed, and the application effect is good.