The mechanical property and tribological behavior of UHMWPE: Effect of molding pressure

The ultra-high molecular weight polyethylene (UHMWPE) samples were prepared with three pressure of 10 MPa, 15 MPa and 20 MPa in this paper. Then these samples were applied to do bulk hardness measurement, scratch testing and punch testing. Meanwhile, the friction and wear behavior of UHMWPE samples were studied by using of Si3N4 ball sliding on UHMWPE disc under plasma lubrication. The eight-figure sliding track was generated on the UMT tribotester. The experiment results indicate that the molding pressure has significantly influence on the mechanical property and tribological behavior of UHMWPE samples. Among three UHMWPE samples prepared with pressure of 10 MPa, 15 MPa and 20 MPa, the UHMWPE sample molded in pressure of 15 MPa obtains the highest values of bulk hardness up to 28.5 MPa, the scratch coefficients up to 3.41 and the punch breaking loads up to 201.6 N. The coefficients of friction of this UHMWPE sample result in the lowest value around 0.025, the lowest wear mass loss of 0.93 mg is obtained for 10,000 cycles testing. There is no apparent difference in the frequency distribution of worn particles with respect to particle size for the UHMWPE samples from three levels of molding pressure. The wear particle size concentrates at about 8 μm. The microstructures of UHMWPE are influenced by compression pressure. Low compression pressure of 10 MPa results in grain defects to reduce the bonding strength between grain boundaries. The compression pressure of 20 MPa results in stress-induced orientation microstructure in UHMWPE.