Molecular Modification of Hydroxyapatite to Introduce Interfacial Bonding with Poly (Lactic Acid) in Biodegradable Composites

Abstract

Six silane-modified hydroxyapatite (HA) / poly(lactic acid) (PLA) composites at 20% volume HA are prepared through absorption in liquid phase, volatilization, milling, and hot-press molding. Bending testing results indicate that their bending strengths are higher than that of control HA composite (unmodified HA composite) and the maximum strength enhances 27.8%. Calcium precipitation and calcium release experiments are designed to examine the bioactivity of the modified HA. The results show that the presence of the modification coating does not really impair the bioactivity and mineralization tendency of HA particles. Relationship of swelling property of the composites as function of time is investigated. Swelling equilibriums of silane-modified HA / PLA composites are reached after 48 h or 72 h, but the equilibrium of the unmodified HA / PLA composite is reached within 24 h. The swelling experiment also suggests that the desired swelling property of the composites could be achieved by changing modification molecules of HA according to necessity. Finally, SEM micrographs show that there is an improved interfacial binding between the modified HA and PLA matrix.