Effects of the wollastonite fiber modification on the sliding wear behavior of the UHMWPE composites

The effects of wollastonite fiber additions and, particularly, the surface modification of the wollastonite fibers, on the sliding wear behavior of the ultra-high molecular weight polyethylene (UHMWPE) composites were investigated. Needle-shaped wollastonite fibers had an average aspect ratio of 15:1. The UHMWPE had a molecular weight of about 2.5 millions. The composites were prepared by first cold-pressing, then sintering and hot-pressing. A grey cast iron was used as the counterface on a block-on-ring tester. The sliding velocity during sliding tests was 0.53 m/s. The results showed that the sliding friction coefficient of the UHMWPE composites increased with the fiber content increased. The wear resistance of the UHMWPE composite was the highest when the wollastonite fiber content was about 10 wt.% and was decreased as the applied normal load was increased. It was found that the silane modification, titanate modification, and silane–titanate combined modification of the wollastonite fibers improved the wear resistance, tensile strength, and impact resistance of the UHMWPE composites as well. The examination of the worn surfaces of the composites by scanning electron microscopy showed that the plastic deformation, plowing and cutting were the main wear mechanisms of the composite and there existed the strain fatigue wear and the abrasive wear features for the composites containing the wollastonite fibers without surface modification and at the higher normal load.