Research On Friction Properties Of Ceramic Powder/High Density Polyethylene Composites

High density polyethylene(HDPE)is popular in the field of pipeline with its excellent performance.It is widely used in the fields of gas transportation,water supply,sewage,agricultural irrigation,fine particle solid transportation in mine and so on,and most of these applications require HDPE to have good friction performance.In order to improve the wear resistance of HDPE,this subject adopted the wear-resisting principle of "soft matrix plus hard point" and used ceramic powder which mainly composed of SiO2 as enhanced phase to prepare HDPE based composites.First of all,two methods were used to compound the raw materials(Grafting polyacrylamide with ceramic powder and adding coupling agent of KH550).and then Ceramic powder/high density polyethylene composites were prepared by melt blending and injection molding with twin screw extruder and injection molding machine.The dispersion of ceramic powder in HDPE matrix was observed by etching section and the compound method of ceramic powder and matrix was optimized by combining mechanical properties(tensile,impact)with microscopic interface observation.The friction properties of the composites under dry friction condition,water lubrication condition and after the boiling water bath treatment were tested by using the MMS-2A tester.The effects of loads and the amount of ceramic powder on the friction and wear properties of composites under various working conditions were studied.The hardness,grain morphology,grain size and crystal form of the composites were combined to analysis the friction properties of the composites.The wear mechanism of composites under different working conditions were discussed based on thermal stability of materials,the SEM morphology,surface energy spectrum,micro 3D topography and roughness parameters of friction surface.The test results showed that:ceramic powder dispersed uniformly in the HDPE matrix and was no large aggregates in the ceramic powder adding range of this test(520wt%).The Compound method of ceramic powder and HDPE matrix was better by KH550 modification method,the elastic modulus and impact strength of 5wt%ceramic powder/KH550/high density polyethylene(5wt%CPs/KH550/HDPE)composite increased by 13.8%and 8%respectively compared with that of pure HDPE and tensile strength reached 24.76MPa.The friction coefficient and wear rate of CPs/KH550/HDPE composites at 50N were fluctuated between 0.4815～0.5291 and 1.30～1.49×10-6 nm3·N-1·m-1 respectively under the dry friction condition,and when the load is 110N,the friction coefficient and wear rates of 20wt%CPs/KH550/HDPE composite increased by 11.5%and decreased by 38.8%respectively compared with pure HDPE.Besides,the wear mechanism of composites was changed from adhesive wear or/and fatigue wear to abrasive wear by adding ceramic powder.The friction coefficient and wear rate of CPs/KH550/HDPE composites under 50N and 150N load were all significantly less than those of pure HDPE and 20wt%CPs/KH550/HDPE composites decreased by 38.9%and 62.1%respectively compared with pure HDPE at 150N load under the condition of water lubrication,and the wear mechanism of pure HDPE was furrow cutting,while the CPs/KH550/HDPE composites was slight abrasive wear mechanism.CPs/KH550/HDPE composites still had good tribological properties after heating 5h and 10h at 100℃ water bath,and the wear rate of 10wt%CPs/KH550/HDPE after 5h water bath heating was 38%lower than that of pure HDPE,and the wear mechanism was changed from plastic deforming-ploughing of pure HDPE to abrasive wear.The addition of ceramic powder did not change the crystalline form of HDPE,but increased the bearing capacity of the composites because the hardness of the composites increased,and the ceramic powder had the effect of fine grain strengthening as well as improved the heat resistance of the composites,all these should be the main reasons for the good wear resistance of the CPs/KH550/HDPE composites.