| Summary: | 碩士 === 台北醫學院 === 口腔復健醫學研究所 === 89 === Poly-L-Lactide (PLLA) was used to prepare objects as useful dental/orthopedic biomaterial in this investigation. Samples were prepared by compression molding in the study. PLLA was heated at 220 C in air atmosphere and nitrogen atmosphere, respectively, to achieve a molten phase for molding. The PLLA was then molded immediately by with hot press, followed by cooling in nitrogen atmosphere or in air atmosphere. PLLA film used for the annealing experiment was obtained through the solvent-casting method. Annealing of PLLA films was performed under different annealing time. The basic characterization of the prepared PLLA samples were performed by differential scanning calorimeter and X-ray diffraction pattern for thermal properties and crystallinity, and by material testing system for mechanical strength. The bending strength of samples prepared under nitrogen atmosphere (115.9 + 1.3 MPa) (or under vacuum) was better than that of samples prepared under air atmosphere (76.9 + 1.8 MPa). The thermal property of the sample prepared under nitrogen atmosphere (or under vacuum) was more stable than that of samples prepared under air atmosphere. The crystallinity and melting temperatures of PLLA film increased with annealing time. The enthalpy of crystallization, melting peak and X-ray diffraction angle were change depended on the annealing time, the effect factors included recrystallization and thermal degradation effect. The bending strength of PLLA/PDLLA specimen that prepared by injection molding and via thermal treatment was reached 146 MPa . These results suggest that better PLLA objects can be obtained under optimal conditions, as described above.
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