The Preparation And Properties Of Hydroxyapatite/Polylactide Composite Biomaterials

Poly lactide is an important biodegradable polymer, and hydroxyapatite is the basic component of human bones. The HA/PLA composites are typical representatives of inorganic/organic composite biomaterials. They have good biocompatibility and important applications in the field of bone repairs.Nowadays, There are many methods to prepare PLA/HA composites, such as melting blend method, aqua dispersion method and in-suit polymerization method. Those methods have many advantages, but applications are limited because of the low molecular weight of PLA after melt process, the interfusion of organic impurity, nonuniformity disperse of HA in PLA matrix and difficulty of batch production. In order to get over these disadvantages, we used original method - solution adsorption technique to prepare HA/PLA composite biomaterials. The method has many advantages and the HA/PLA composites prepared by solution-adsorption technique have good mechanical strength. When the content of HA was 10%, the tensile strength reached 43MPa, the bending strength come up to 128.0MPa, and the bending modulus come to 2.6GPa. The HA particles dispersed uniformly in the PLA matrix.As to the composites, the interface adhesion between enhanced materials and polymer matrix is very important to the performance. In the study, hydroxyapatite particles were modified respectively by y-methacryloxypopyl trimethoxysilane, poly vinyl alcohol and poly acrylic acid. Through the tests of contact angle and FT-IR of HA particles, it indicated that the new Si-O-P band appeared which was formed by interaction of the siliconate molecule and hydroxyapatite -OH groups. The modified HA particles were unhydrophilic. PVA reacted on the HA by right of mass hydrogen bonding and the chelation was formed between PAA and calcium ion on the surface of HA. The SEM and mechanical strength tests proved that the tensile and bending strengths increased remarkably, and the HA particles were packed by the PLA matrix tightly.In vitro 12 weeks' degradation experiments of composites, the alteration of pH values and the weights of composites changed indistinctively compared with pure PLA material. The existent of HA particles could neutralize the acid produced in theprocess of PLA degradation and avoid axenic inflammation.