Injection moulding of hydroxyapatite composites

Hydroxyapatite (HA) is an important bioceramic with tremendous potential for biomedical applications. Its unique bioactivity promotes rapid bone growth and strong interfacial fixation that has particular benefit to orthopaedic and dental applications. Although it possesses good biocompatibility. its mechanical properties in terms of toughness and modulus values are still not comparable to those of cortical bone, which has severely limited its usage to mainly low-stress applications. Composite blending with a low modulus polymeric material introduces new improvement possibilities, but often requires high HA loading to attain useful properties. This high loading creates poor flow characteristics which hinders processing, in this study the critical powder loading and the rheological behaviour of hydroxyapatite-high density polyethylene (HA-HDPE) composites are studied using a capillary rheometer to ascertain the injection mouldability of the composite system. The mechanical properties of the injection moulded composites are evaluated by tensile testing. The effects of coupling agents and lubricant on the flow and mechanical property of HA-HDPE composite are examined in addition to the post heat-treatment of the composites.