Study On Preparation And Properties Of Modified Hydroxyapatite Reinforced Ultra High Molecular Weight Polyethylene Composite

Hydroxyapatite (HA) is the main inorganic component of human hard tissue, and HA has superior biocompatibility and osseoconduction. In general, composites are prepared with HA and polymer to resolve brightness and lower impact resistance of HA. Moreover, the excellent biological properties of HA is also used. The composite has been widely used as material for bone defect repairing. But surface properties of HA different from polymer, so the bonding property of the interface between HA and polymer is lower. The damage occur in interface easily to break down the composites when implant it into the body. In order to resolve this problem, the surface of HA usually is modified. Such as compatibility between HA and polymer can be improved by modifying the HA surface with silane coupling agent. Furthermore, the surface of HA is modified by surfactant can changes surface hydrophilicity of HA, so compatibility between HA and polymer can be improved.In this paper, Hydroxyapatite (HA) was modified with stearic acid (SA), and the mechanism of surface modification was studied. Then HA/UHMWPE composite were prepared with modified HA and ultra high molecular weight polyethylene (UHMWPE). Effects of SA and HA contents on properties of HA/UHMWPE composite were studied.Hydroxyapatite (HA) was modified with stearic acid (SA), and then it was characterized by XRD, TEM, FTIR, XPS and activation ratio. The results show that XRD patterns and mircrographs of HA without changes obviously. It imply that the crystal structure of HA was not broken. The new vibrating peak of-COO-was found by FTIR on modified HA surface. It indicate that Ca2+ from HA surface and CH3(CH2)16COO- from SA to form ionic bond. The elements binding energy of HA surface are changes, and Ca2p and P2p move to higher binding energy. It demonstrates that the chemical environments of these elements are changes. The above results show that SA graft on the HA surface by reaction of elements of HA surface with it to form chemical bond. The tests of activation ratio indicate that the activation ratio is improved with increase SA contents. Activation ratio of HA to exceed 99% as SA contents is 3%. It without changes significantly when continues to increase SA contents.HA/UHMWPE composite were prepared with modified HA and UHMWPE by ball milling and hot press, and then it were characterized by XRD, SEM and mechanical tests. The XRD results show that HA did not take chemical reaction with UHMWPE and the chemical structures of HA are not changes in process of the composite preparing. The SEM results demonstrate that modified HA has good bonding property with UHMWPE matrix. Mechanical tests indicate that the elasticity modulus of the composites show an ascending trend with the increase of SA and HA contents. But the tensile and impact strengths have decline in varying degrees.