Processing Of Poly-L-Lactide/Î'-Tricalcium Phosphate Composites

Poly-L-lactide/β-tricalcium phosphate composites (PLLA/β-TCP) were prepared and processed into bioresorbable rods with high strength for bone fixation by the method of compression molding. Then PLLA/β-TCP composite nanofiber mats were prepared and characterized. The processing of the methods were studied detailedly.PLLA with Mηof over 200000 was synthesized by ring-opening polymerization of lactide and theβ-TCP was prepared by wet method. The PLLA/β-TCP composite was obtained by mixing PLLA andβ-TCP particles. Scanning electron microscopy (SEM) photographs of the composites showed a good dispersion ofβ-TCP in the matrix of PLLA.Compression molding was used to process PLLA and PLLA/β-TCP composite rods. The effects of molding temperature, pressure, Mηof PLLA, ratio of PLLA/β-TCP and the size ofβ-TCP on the mechanical properties were studied in detail. The morphological structure of cross-section and surface of the rod were observed by SEM. The results show that the extent of fibrillation reduced at an over-high molding temperature, and much separation between the fibrils of PLLA can be observed at lower temperature. Some disfigurement can be observed under inadequate molding pressure. The addition of theβ-TCP enhanced the strength to a certain extent. The PLLA/β-TCP composite rods with weight ratio of PLLA/β-TCP about 80/20 were molded at compression temperature of 105~110℃and pressure of 260~300MPa, then PLLA/β-TCP composite rods were obtained with high bending strength of over 230MPa and bending modulus of over 3.2GPa.Finally, the PLLA/β-TCP composite was processed by electrospinning. The effects of polymer concentration,β-TCP/PLLA ratio, feed rate, voltage, and distance between the tip and the receiver on the structure of nanofiber mats were investigated in detail. The nanofiber mats were characterized by SEM. The results show that the range of the diameters of the fibers is from 100nm to 3μm. The higher the concentration is, the bigger the diameter of nanofibers. The tensile strength and Young's modulus of the nanofiber mats decrease with increasing the content ofβ-TCP.