Fabrication And Property Evaluation Of Biomedical Nanocomposites

Great breakthrough achievements with nanotechonology in the 90's has been applied in the biomedical research field in recent years, and nanocomposites as promising candidates for biomedical material become of great interest. Fabrication and property evaluation of Hydroxyapatite/Bacterial Cellulose (HAp/BC) and Nylon 6/Clay nanocomposites were investigated in the present study. HAp/BC nanocomposites were fabricated using a citric acid (CA) inducing method via the biomimetic route, taking the advantage of hydrogen bonding of CA to BC and its chelating ability of calcium ions. The fabricated HAp/BC composites were characterized by SEM, XPS, XRD and TEM. Thermal characterizations of HAp/phosphorylated BC nanocomposites were performed using TGA, DSC and DMA in order to investigate the compositions, thermal stability, and some thermo-mechanical behaviors of the nanocomposites. Moisture absorption behavior of Nylon 6/Clay nanocomposites and its influences on mechanical properties were also investigated in this study.The experimental results show that HAp nucleis can be formed on BC matrix and continue to grow. HAp in the nanocomposites is calcium deficient, which is similar to the natural bone. Thermal characterizations of HAp/BC nanocomposites have been conducted using TGA, DSC and DMA. The TGA results suggest that thermal decomposition of BC matrix in the HAp/BC nanocomposites starts at higher onset temperatures. The thermal stability of the nanocomposites is enhanced to a certain extent by the hydroxyapatite. Thermal behaviors show discrepancy between BC and its nanocomposites from the obtained DSC curves, with complex exothermic and endothermic reactions during the decomposition of BC, resulting from the addition of hydroxyapatite in the matrix. The DMA results demonstrate that HAp has a strong reinforcing effect on the elastic properties of the BC matrix. Moreover, the glass transition temperature (Tg) of HAp/BC shifts slightly to a higher temperature compared to that of pure BC,which can be ascribed to the decreased mobility of the BC polymer chains, due to the reinforcement of hydroxyapatite covering on the cellulose micro-fibrils in the nanocomposite.The diffusivity of nylon 6/clay nanocomposites is decreased with increasing clay content, which could be explained by the tortuous path model. Clay content doesn't affect the tensile strength of nanocomposites much, but can contribute to the increase of Young's modulus of nanocomposites. Moisture absorption hugely decreases mechanical properties of nylon 6/clay nanocomposites.