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 eVect 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 Ž ller to reinforce
the polymeric matrixes. The SCORIM processing enhanced the unidirectional
mechanical properties substantially. The incorporation of hydroxyapatite into
the polymer matrix had a stiVening eVect but also reduced the strength and
toughness. Generally, the mechanical properties deteriorated substantially
in vitro. Reinforcement by hydroxyapatite was found to be less eVective than
expected in a wet environment.