Mechanical and tribological properties of short discontinuous UHMWPE fiber reinforced UHMWPE

Abstract

The tribological properties of Ultra-High Molecular Weight Polyethylene have generated new concern regarding the long-term clinical performance of total joint replacements. To extend the lifetime of artificial joints, it is necessary to decrease the wear rate of UHMWPE. One possible solution is the incorporation of UHMWPE fibers. Mixing of the two components was accomplished by swirling the UHMWPE powder and chopped UHMWPE fibers with compressed nitrogen. During this mixture procedure opposite surface charges will be generated on the UHMWPE powder and UHMWPE fiber. The electrostatic attraction could be responsible for the coherence of the two components, leading a composite with fairly uniformly distributed and randomly oriented fibers was obtained. With this method a fiber volume fraction up to 60 volume percent could be achieved. In this composite the matrix and fibers are of the same chemical nature. The inherent chemical compatibility of the composite components is likely to promote good bonding at the interface, through which a composite with excellent mechanical properties is made. The ultimate stress and modulus of the 60 volume percent composite show an improvement of 160 and 600 percent, respectively, in comparison with the neat UHMWPE. The wear rates were determined with a pin-on-roll apparatus with a nominal contact stress of 3 MPa at a sliding velocity of 0.24 m/s. The volumetric wear rate decreases with the incorporation of the UHMWPE fibers.