| Summary: | 碩士 === 長庚大學 === 化工與材料工程研究所 === 92 === In this study, poly(L - lactide) (PLLA)/ poly(ethylene glycol) (PEG) blends were prepared by solution mixing technique. The effects of “ PEGs’ molecular weight (MW: 1.5k, 6k, and 2M) ” and “ thermal history ” on thermal properties and phase morphology of the blends were investigated through differential scanning calorimeter (DSC), wide angle x-ray diffractometer (WAXD), thermogravimetric analyzer (TGA), and polarized optical microscope (POM). The DSC results showed that the crystallization ability of PLLA was promoted by blending with PEG. The Tm of PLLA in the blends decreased with increasing both of the PEG content and the heat treatment time; the decrement was more serious for lower MW PEG blends. This phenomenon indicated the blends with lower MW PEG were more miscible. In addition, for the PLLA/PEG(1.5k):50/50 blend, the Tm of PLLA depressed seriously with increasing heat treatment time due to possible occurrence of chemical interaction between PLLA and PEG. The WAXD results showed that if the chemical interaction occurred in the blends during longer heat treatment time, the crystal structure of PLLA and PEG were not affected. The TGA results showed that the thermal stability of PEG was higher than that of PLLA. For the blends, the thermal stability of PLLA depressed with increasing PEG content, and this phenomenon was more evident for the PLLA/PEG(1.5k):50/50 system. The POM results indicated that PLLA and PEG(1.5k, and 6k) were miscible in the melt over the composition range investigated, but PLLA and PEG(2M) were phase-separated. In addition, when PEG content was larger than 30 %, the PEG phase located between the PLLA spherulites appeared, also, the spherulite of PLLA in the blends was larger as the PEG content increased. For the PLLA/PEG(1.5k, and 6k) blend systems, the spherulites of PLLA showed more imperfectly ringe patterns with increasing PEG content.
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