| In order to improve the barrier property of PLLA films, uniaxially stretched PLLA film was prepared by twin-screw extruder in this study. The thermal behavior, mechanical and barrier property, and thermal shrinking of both PLLA films were measured, and its effects of the surface morphology and crystallization were observed. The wide-angle X-ray diffraction results revealed that the crystallinity increase with the increase of draw ratio, and the α-crystal was produced in the PLLA film by uniaxially stretching. Moreover, the α-crystal was easy to form when the film was annealed at90℃. Based on the scanning electron microscopy observation, the film surface cracks occurred at a certain draw ratio of PLLA film. The crystallinity and crystallization rate are increased significantly during stretching. The barrier behavior results showed that, both stretched and annealed PLLA films exhibited much better oxygen and water vapor barrier than undrawn PLLA at middle draw ratio. The stretched PLLA film had a higher gas permeability coefficient than that of the stretched PLLA film. The shrink film shows an excellent thermal shrinking behavior, while the stretched film lost its thermal shrinking. The aging test results showed that the aged PLLA film exhibited much better gas barrier ability than imaged PLLA film.The application in garden stuff packaging contrasted the modified atmosphere packaging of PLLA films and PA/PL films. The results shows that the PLLA films still have a positive role in fresh-keeping, although the fresh-keeping of PLLA films is slightly inferior to PA/PE films. |
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