Mechanical Properties of .BETA.-Tricalcium Phosphate/Polylactic Acid Composites Prepared through Ball-Milling

Composites synthesized from β-tricalcium phosphate (β-TCP) and polylactic acid (PLA) are attracting attention as novel bone substitutes owing to their bioresorbability and high workability. The preparation of this type of composite through stirring of the starting materials and subsequent pressing has been previously reported. In this study, we attempted ball-milling after the stirring of the starting materials in the preparation of the β-TCP/PLA composites. Effect of ball-milling time on mechanical properties of the composites was examined. A slurry was prepared from β-TCP and PLA with a molecular weight of 120000 to 200000 in a mass ratio of 75 : 25. This was ball-milled at ambient temperature for periods up to 48 h, and then hot-pressed to form dense composites. The mechanical properties of the composites were evaluated using a three-point bending test. The bending strength of the composites increased with increasing ball-milling time and decreased with increasing molecular weight of the PLA. In particular, composites prepared from PLA with a molecular weight of 120000 that were ball-milled for 48 h showed a mechanical strength of 80 MPa, which is nearly equal to that of human cortical bone. The increase in bending strength is attributed to a decrease in the size of the β-TCP aggregates due to ball milling.