Preparation And Study On Properties Of G-HA/PLA Biocomposite

Biodegradable synthetic polymers have some advantages such as controllable capability, no immunogenicity and excellent biocompatibility and have been used widely in the field of biomedical field. Poly(lactic acid) (PLA), is one of the most investigated and utilized biodegradable polymers. Hydroxyapatite (HA) is the main natural inorganic component of bone. And with bioactivity, HA can be combined with bone compactly. The composite of these two materials can enhance the toughness to meet the demands of the mechanical property for the bone substitutes; on the other hand, the acid degradation production of PLA can be amortized by HA, which provides better environment for cell proliferation, regeneration and vessel development to fit the biological requirements for bone tissue engineering materials.However, due to the poor interface adhesion between inorganic nano-particles and polymer after blended physically, the mechanical properties could not meet the demands for bone repair. After implanted into human body, the interface between the nano-particle filler and the polymer matrix was destroyed firstly, which results in a sharp decrease of mechanical properties in little time. So, the improvement of the interfacial adhesion between the inorganic nano-particles and the polymer matrix has become the key technique in preparing HA/PLA composites.In order to improve the interface adhesion between inorganic nano-particles HA and PLA, the composite of modified HA and PLA was prepared. Firstly, HA surface was grafted by lactic acid oligomer to prepare modified HA (g-HA), then blended with PLA to get the g-HA/PLA composite. The microstructure, mechanical property, degradable property and thermal degradation property of the composites were investigated systematically by FTIR,'H-NMR, DSC, TG, water contact angle measurement and tensile test, etc. And the biosafety of the composites were tested The experimental results show that the grafting ratios of the lactic acid oligomer grafting on the surface of HA which increased with the monomer concentration. There are no obvious changes between the surface morphology of HA and g-HA particles. The hydrophilicity of the material was improved obviously after the grafting modification.The g-HA particles owned uniform dispersion in PLA matrix, enhanced the interface adhesion between the particle and matrix and increased the mechanical strength of the composites. And the g-HA particle slowed down the thermal degradation of PLA polymer matrix.In comparison with pure PLA, accelerated degradation in which was largely dependent on the content of g-HA was apparent for all composite materials in earlier period. The degradation rate of the composites slowed down in later period. The existent of g-HA particles could neutralize the acid produced in the process of PLA degradation and avoid axenic inflammation. It indicated that g-HA are efficient in enhancing the mechanical properties of composite materials during the period of experiment.The results of the biological evaluation show that the g-HA/PLA composites are safe and biocompatible materials with potential applications.