Preparation And Performance Studyies Of Hydroxyapatite Particles Reinforced Polycaprolactone Composites

During the last twenty years, hydroxyapatite (HA) has been advanced toward one of the most important bone substitute materials for its excellent biocompatibility, bioactivity and osteoconduction. However, the brittleness and the relatively low mechanical strength of HA oppose to some applications of HA as a bone substitute. Therefore, HA has been combined with a series of both natural and synthetic polymers to take advantage of its osteoconducting properties and its strengthening effect on the polymers.In this study, In order to meet the clinical needs of bone implant materials, composites of polycaprolactone reinforced by hydroxyapatite granules and rods were prepared via melt-blending, solvent-blending and solvent-melt-blending. Their mechanical properties were tested by quasi-static mechanical testing. Other means, FTIR DSC and SEM, were also employed to detective the characteristics and micro-structure of composites. The results showed that there were no chemical bonding existing between HA and PCL matrix prepared via these three methods. The tensile strength and Young's modulus of PCL were increased evidently by the addition of HA. The mechanical strength of PCL reinforced by HA granules was better than that of PCL reinforced by HA rods. And the solvent-melt-blending is optimal among these three methods.On this basis, three silane coupling agents were applied to modify surface of HA particles in order to determine the effects of silane coupling agents on mechanical properties of HA/PCL composites. The tensile strength and elastic modulus of composites modified with silane were improved optimally as the silane content was at 2% to HA. The tensile strength of composite reinforced by HA treated with KH560, KH570 and KH792 were improved 16.4%, 23.4% and 34.5% respectively with the elastic modulus being increased over 2 times. The use of silane coupling agents improve effectively both the dispersion of HA particles in PCL matrix and the bonding between two components.This study also evaluated the bioactivities and biocompatibilities of HA/PCL before and after silanation through the SBF immersion and cell culture experiments, respectively. The biomineralization result showed that the surfaces of all composites were covered by a coating of HA after immersion in 2SBF for 21 days, which indicated the composites we prepared had good bioactivity. The cell culture experiment on surfaces of composites showed that the composites before and after treated with KH570 and KH792 had good biocompatibility, whereas the composite treated with KH560 made against the cell adhesion and increment.