Abstract
Bioactive ceramics/poly-L-lactic acid (PLLA) composites have been expected as a material for the bone fracture fixations which have more biocompatibility than monolithic PLLA. In this study, monolithic PLLA and β-tricalcium phosphate (β-TCP)/PLLA composites containing three different β-TCP contents (5, 10, 15 wt%) were prepared by injection molding and hydrolysis behavior in simulated body environment were characterized. These specimens were immersed in phosphate buffered solution, and water absorption and molecular weight weremeasured. Water absorption of monolithic PLLA increased with increasing immersion time up to 14days, and then saturated, whereas water absorption of composites increased with increasing immersion timeup to 168 days. The composites with higher β-TCP contents showed larger water absorption. Number averaged molecular weight degradation of composites became faster for higher β-TCP content at the same immersion time. Number averaged molecular weight of 15 wt% composites decreased from 60,000 to 39,000 after 24 weeks immersion. Two layers model and three layers model were proposed to predict water absorption and number average molecular weight variation, respectively. To predict hydrolysis behavior of bioactive ceramics/PLLA composites more precisely, effect of water diffusion is considered in proposed models. Predictions based on the present models are in good agreement with experimental results and the effectiveness of the models was confirmed.
