MECHANICAL AND TRIBOLOGICAL PROPERTIES OF SHORT DISCONTINUOUS UHMWPE FIBER-REINFORCED UHMWPE

The tribological properties of Ultra-High Molecular Weight Polyethylen e have generated new concern regarding the long-term clinical performa nce of total joint replacements. To extend the lifetime of artificial joints, it is necessary to decrease the wear rate of UHMWPE. One possi ble 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 UH MWPE fiber. The electrostatic attraction could be responsible for the coherence of the two components, leading a composite with fairly unifo rmly distributed and randomly oriented fibers was obtained. With this method a fiber volume fraction up to 60 volume percent could be achiev ed. In this composite the matrix and fibers are of the same chemical n ature. The inherent chemical compatibility of the composite components is likely to promote good bonding at the interface, through which a c omposite with excellent mechanical properties is made. The ultimate st ress and modulus of the 60 volume percent composite show an improvemen t of 160 and 600 percent, respectively, in comparison with the neat UH MWPE. 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 UHMWP E fibers.