Preparation And Mechanical Properties Of Carbon Fiber Reinforced Hydroxyapatite/Polylactide (CF/HA/PLA) Composites

As an important biodegradable material, poly(lacticacid) (PLA) has many particular properties, such as good biocompatibility and safety in vivo, that make it extensively used in medical applications, including sutures, bone fixation materials, wound dressings, and drug-delivery microspheres. Hydroxyapatite (HA), usually called bio-ceramic, has already been widely used in clinic due to its similarity to bone mineral in structure and composition, and its a good biocompatibility to human tissue However, the pure HA bioceramic is only suitable for the non-load-bearing applications because of its fragility, low mechanical strength, easy rupture, and weak fatigue resistance in the humoral surrounding.This article is focus on carbon fiber reinforced HA/PLA degradable biomaterial. In this kind of composites, the carbon fiber provides the mechanical strength, while PLA the degradability. HA has the structure and composition similar to human bone tissues as well as good biocompatibility due to the hydroxyl on the surface of HA. It may work as a buffer and lessen the degradation acidity. The mechanical strength of the composite has met the requirement of bone fixation.A novel composite of carbon fiber reinforced HA/PLA was developed. Carbon fiber was oxidized by nitric acid and lactide was connected directly onto the HA surface through chemical linkage. The production was characterized by IR spectra. The amount of grafted polymer determined by thermal gravimetric analysis (TGA) was about 5% in weight. By TEM, we can observe the particles grafted by PLA own cell-shell sphere structure and they dispersed stably in organic solvent such as chloroform. According to SEM, the carbon fibers, which were pulled out of the matrix under force, were wrapped by PLA and HA. It indicates that fiber surface treatment improves the adhesion of interface between fiber and the matrix. It also contributes to the sharply increases of composite strength compared to the fiber without any treatment. With surface modification of the components, we obtained composite with high mechanical properties. The dependence of flexural strength and modulus on HAcontent shows a peak value, which appears separately when containing 15% and 20% HA modified by lactide. There is a critical value for HA content. When HA content is below the critical value, the composite strength increases with more interface bound linkage between HA and PLA. Then it decreases if more HA is added due to the fragility and low mechanical properties of HA particles.We also investigated the synthesis of PLA, which was obtained by ring-opening polymerization and the synthesis conditions. The structures of lactide and PLA were identified by IR spectra and H-NMR. The molecular weight of the outcome depends on the catalyst content, polymerization time definitely. We didn't obtain high molecular weight PLA in the experiment. It may because the reaction system contained impurity which hampered the polymerization.