Mechanism of ultrahigh elongation rate of poly(D,L-lactide)-matrix composite biomaterial containing nano-apatite fillers

Abstract

This study aims to discuss the mechanism of ultrahigh elongation rate of nano-apatite/poly(D,L-lactide) (PDLLA) composite biomaterials prepared by combining traditional solution co-blending and hot pressing techniques. An ultrahigh elongation rate of PDLLA-matrix composite film with nano-apatite fillers was found in our tensile testing experiments. These surprising results could be expressly explained by the structure characteristics of PDLLA-matrix nanocomposites. The linear chains of the PDLLA-matrix materials were cross-linked and fixed by the nano-sized crystallites with high specific surface energy when nano particles were incorporated into PDLLA polymer to form composite. Structure change of the cross-linked PDLLA matrix caused the composite to exhibit high fixation strength between PDLLA molecular chains and nano-apatite particles by a large amount of the cross-link junctions and further brought on larger elastic and plastic deformation than one of pure PDLLA polymer. On the other hand, high nano-apatite contents in composites could lead to the early rupture owing to nano-apatite agglomeration and decrease the elongation rate of the composites.