STUDIES OF AGING AND COLD CRYSTALLIZATION EFFECTS ON MECHANICAL PROPERTIES OF POLY (L-LACTIC ACID) FILMS

• Main Authors: DWIE ASTUTI, 謝春鸞
• Other Authors: Po-Da Hong
• Format: Others
• Language: en_US
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/68902726280340920986

碩士 === 國立臺灣科技大學 === 材料科技研究所 === 97 === Temperature and time have important distribution to mechanical properties of Poly(L-Lactic Acid), PLLA films. The aging effect on the properties of PLLA films were investigated by using differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and Tensile Test. It was found that during isothermal heating at the temperatures below Tg, aging effects significantly affected the mechanical properties of PLLA films. The PLLA system tends to reach equilibrium state by chains arrangement. This process induces the rigidity of the sample. The effect of physical aging on PLLA films were shown in DMA and tensile result. The yield strength and tensile modulus increased with time and temperature of aging, while, the tensile strain decreased. The effects of cold crystallization condition were also studied at temperature above Tg. The crystallinity increased with crystallization time and temperature. DSC curves of cold crystallized PLLA films depicted a clear double melting behavior at Tc between 70° and 95° C. The results of DMA and tensile test revealed that the crystallinity affect the mechanical and dynamical properties of PLLA films. The crystallinity constrained the amorphous chains in the semicrystalline system. The strain of PLLA films decreased gradually with crystallization time and temperature. The tensile result has shown ductile failure behavior changed to brittle failure behavior.