| 초록 |
Biodegradable polymeric implants have a lot of advantages over metallic or ceramic fixation devices, such as good bio-compatibility, safe reduction of the fracture due to their progressive transfer of stresses to the healing bone, no corrosion problems, and no need for the second removal operation. However, they show lower strength than metallic or ceramic counterparts and thus are not suitable for femur implants which require high strength. Poly(L-lactic acid) is one of the most widely used biodegradable polymers and has various applications for internal fixation devices with lower strength. The lower strength of PLLA in related to the melt processing, which leads to decreased molecular weight. 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. The mechanical properties of the crystalline PLLA, in general, strongly depend on the chain orientation and crystallinity. We report the effects of extrusion variables, including the extrusion draw ratio(DR), draw rate, molecular weight and so on.
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