Processing of hydroxyapatite reinforced ultrahigh molecular weight polyethylene for biomedical applications.

A new method for processing hydroxyapatite/ultrahigh molecular weight polyethylene (HA/UHMWPE) composite has been developed by combining wet ball milling and swelling. Sintered HA particles were ground in ethanol to approximately 50 nm in diameter. The nano-sized HA particles were mechanically mixed with UHMWPE in the ball mill and then compression molded into solid slabs. The slabs were then swollen in a pharmaceutical grade paraffin oil to enhance the UHMWPE chain mobility and HA/UHMWPE interface adhesion before final hot press. The resultant composite exhibits a two-zone network structure formed by a homogeneous HA-rich phase and a UHMWPE-rich phase. This process resulted in a 90% increase in Young's modulus and a 50% increase in the yield strength of HA/UHMWPE composite, comparing with those of unfilled UHMWPE.