| 초록 |
Biodegradable polymeric internal fixation devices are superior to metallic or ceramic fixation devices in many aspects, e. g., no need for the second removal operation, no corrosion problems, and safe reduction of the fracture. However, such polymers show lower strengths than metallic or ceramic fixation devices and thus are not suitable for the high strength end-uses such as femur. Polylactic acid (PLLA) is one of the most widely used biodegradable polymers and has various applications for internal fixation devices of lower strength materials. Processing method is reason for lower strengths, that is, melt processing accompanies molecular degradation leading to the decrease in mechanical properties. In this study vacuum compression molding and solid-state extrusion technique were employed for the minimization of molecular degradation and the improvement of mechanical properties of PLLA . Billets machined out from the vacuum compression-molded PLLA were solid-state extruded through circular and rectangular dies to produce rods and plates. Extrusion was performed at 130℃ which is above Tg and below Tm, and draw ratio and drawing rate were varied. On the basis of the measurements of the orientation and crystallinity of extruded PLLA, effects of initial billet morphology, draw ratio, drawing rate on the mechanical properties of PLLA were discussed. |
