Effect of the crystallinity on the mechanical behavior of poly (L-Lactic acid) (PLLA) have been investigated by means of microhardness, tensile, dynamical mechanical analysis (DMA). The crystallization kinetic of time and temperature effect was studied by Fourier Transform Infrared Spectroscopy (FTIR). The formation of 103 helix structure, which is attributed to the α form crystal of PLLA, was measured to calculate the Avrami parameters. From differential scanning calorimetric (DSC) and X-Ray Difraction (XRD) results, it indicated that the crystallinity increased with increasing crystallized temperature (90 0C to 120 0C for 24hr). Moreover, microhardness increasement has been observed for different crystallization temperatures, which is correlated with the development of crystallinity. Tensile test revealed that the crystallinity constrained the amorphous chain in the cold crystallization system. The strain of PLLA decreases gradually with increasing crystallization temperature. DMA curves exhibit the different viscous and elastic properties, showed that the sample can absorb the energy. Samples with higher crystallinity showed low tan delta result, represented that the sample are stiff, brittle and less viscous ability. In this study, we connect the relationship between crystallinity and mechanical properties of PLLA films. And we have found the crystallization temperature will affect the crystallinity of sample.

Effect of the crystallinity on the mechanical behavior of poly (L-Lactic acid) (PLLA) have been investigated by means of microhardness, tensile, dynamical mechanical analysis (DMA). The crystallization kinetic of time and temperature effect was studied by Fourier Transform Infrared Spectroscopy (FTIR). The formation of 103 helix structure, which is attributed to the α form crystal of PLLA, was measured to calculate the Avrami parameters. From differential scanning calorimetric (DSC) and X-Ray Difraction (XRD) results, it indicated that the crystallinity increased with increasing crystallized temperature (90 0C to 120 0C for 24hr). Moreover, microhardness increasement has been observed for different crystallization temperatures, which is correlated with the development of crystallinity. Tensile test revealed that the crystallinity constrained the amorphous chain in the cold crystallization system. The strain of PLLA decreases gradually with increasing crystallization temperature. DMA curves exhibit the different viscous and elastic properties, showed that the sample can absorb the energy. Samples with higher crystallinity showed low tan delta result, represented that the sample are stiff, brittle and less viscous ability. In this study, we connect the relationship between crystallinity and mechanical properties of PLLA films. And we have found the crystallization temperature will affect the crystallinity of sample.

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