In order to investigate hydrolysis behavior of bioresorbable plastic composites, β-tricalcium phosphate (β-TCP) /poly(l-lactide) (PLLA), long term immersion tests into phosphate buffered solution (PBS) with different pH were conducted. After the immersion tests, differential scanning calorimetry and tensile, bending and compressive tests were conducted on the specimen. The crystallinity of PLLA increased with increasing immersion period. The significant decrease in the mechanical properties of the specimens with 5.0wt％ β-TCP contents were not observed after 24 weeks immersion into PBS with pH7.4, whereas significant decrease were observed for the specimen with 9.5 and 14.0wt％ contents. For the immersion tests into PBS with pH6.4, the degradation was accelerated. The degradation in moduli was attributed to lower load capacity of β-TCP particles due to the bioresorption.
