Shear controlled orientation in injection moulding of starch based blends intended for medical applications

Biodegradable polymeric implants are considered to be good alternatives to metallic implants in several temporary applications. Aliphatic polyesters have been extensively investigated and have been employed in several biomedical applications. More recently, biodegradable starch based polymeric blends have also been considered as alternative materials. In this study, the effect of shear controlled orientation injection moulding (SCORIM) on the mechanical properties and degradation behaviour of starch-polylactide and starch-poly(ethylene-co-vinyl alcohol) blends has been investigated and compared with those produced by conventional injection moulding. The changes in these properties has also been studied when using an hydroxyapatite filler to reinforce the polymeric matrixes. The SCORIM processing enhanced the unidirectional mechanical properties substantially. The incorporation of hydroxyapatite into the polymer matrix had a stiffening effect but also reduced the strength and toughness. Generally, the mechanical properties deteriorated substantially in vitro. Reinforcement by hydroxyapatite was found to be less effective than expected in a wet environment.