| Summary: | 博士 === 國立臺灣科技大學 === 材料科學與工程系 === 100 === this study, Poly (lactic acid) (PLA) is modified with Poly (butylene adipate-co- terethphlate) (PBAT), Ethylene and Glycidyl Methacrylate Copolymer (EGMC) and FePol to improve the mechanical properties, respectively. The corresponding PLA blends were prepared by melt-blending PBAT, FP and EGMC with PLA. Several investigations, including Fourier transform infrared spectroscopy, Differential scanning calorimetry (DSC) , wide angle X-ray diffraction (WAXD), and thermal, dynamic, mechanical, and weight loss percentage analysis of the PLA/PBAT, PLA/FP and PLA/EGMC blends were performed to understand the significantly improved mechanical properties of the specimens. The presented work was divided into three parts:
In the first part, the percentage crystallinity (Xc), peak melting temperature (Tm) and onset re-crystallization temperature (Tonset) values of PLA/PBAT specimens reduce gradually as their PBAT contents increase. However, it is worth noting that the Tg values of PLA molecules found by DSC and DMA analysis reduce to the minimum value as the PBAT contents of PLAxPBATy specimens reach 2.5 wt%. Further morphological and DMA analysis of PLA/PBAT specimens reveal that PBAT molecules are compatible with PLA molecules at PBAT contents equal to or less than 2.5 wt%, since no distinguished phase-separated PBAT droplets and tan δ transitions were found on the fracture surfaces and tan δ curves of PLA/PBAT specimens, respectively. In contrast to PLA, the PBAT specimen exhibits highly deformable properties. After blending proper amounts of PBAT in PLA, the inherent brittle deformation behavior of the PLA specimen was successfully improved.
In the second part, the percentage crystallinity, peak melting temperature and onset re-crystallization temperature values of PLA/FP specimens reduce gradually as their FP contents increase. However, the glass transition temperatures of PLA molecules found by DSC and DMA reduce to the minimum value as the FP contents of PLAxFPy specimens reach 6 wt%. Further DMA and morphological analysis of PLA/FP specimens reveal that FP molecules are compatible with PLA molecules at FP contents equal to or less than 6 wt%, since no distinguished phase-separated FP droplets and tan δ transitions were found on fracture surfaces and tan δ curves of PLA/FP specimens, respectively. In contrast to PLA, the FP specimen exhibits highly deformable and tearing properties. After blending proper amounts of FP in PLA, the inherent brittle deformation and poor tearing behavior of PLA was successfully improved.
In the third part, the tensile and tear strength values of PLAxEGMCy blown-film specimens in machine and transverse directions improve significantly, and reach their maximal values as their EGMC contents approach an optimum value of 6 wt. %. The melt shear viscosity values of PLAxEGMCy resins, measured at varying shear rates, are significantly higher than those of the PLA resin, and increase consistently with their EGMC contents. Differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) of PLA and PLAxEGMCy specimens reveal that the percentage crystallinity, peak melting temperature, and onset re-crystallization temperature values of PLAxEGMCy specimens reduce gradually as their EGMC contents increase. In contrast, the glass transition temperatures of PLAxEGMCy specimens increase gradually in conjunction with their EGMC contents. Further DMA and morphological analysis of PLAxEGMCy specimens reveal that the EGMC molecules are compatible with PLA molecules at EGMC contents equal to or less than 2 wt. % because no phase-separated EGMC droplets and tan δ transitions were found on fracture surfaces and tan δ curves of PLAxEGMCy specimens, respectively.
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