雙向延伸聚(L-乳酸)薄膜於不同熱處理過程後的 氣體滲透性能。

Abstract

The relationships among chain orientation, crystalline structure, crystallinity, free volume properties, and gas permeation properties of biaxial oriented poly(L-lactic acid) (BOPLLA) films were discussed in this study. The BOPLLA films were obtained from various treatments such as simultaneous and sequential biaxial stretching and then annealing with different lengths of time at 100, 130, or 160 oC, respectively. The crystal structure, lamellar behavior, and free volume properties of BOPLLA films were determined by wide angle X-ray diffraction (WAXD), small-angle X-ray scattering (SAXS), and Positron Annihilation Lifetime Spectroscopy (PALS), respectively. The oxygen gas permeability, diffusivity, and solubility were determined with a constant-volume variable-pressure permeation apparatus and the time-lag method. The results of WAXD indicated that increasing the annealing temperature and time will result in the increasing of crystallinity of BOPLLA. However, the in situ SAXS results from NSRRC revealed that the lamellar thickness of PLLA was maintained about the same as the annealing temperature increased from 100 to 130oC, and a rapid increased from 130 to 160oC possibly due to the α’- to α-form transition in the crystalline lattices. The α’- to α-form transition behavior can be also observed in the WAXD results of various films. IV In addition, the gas barrier property of the sequentially BOPLLA films is better than that of the simultaneously ones due to the orientated crystalline structure and higher crystallinity. The free volume properties obtained by PALS can generally explain the trend of oxygen diffusion coefficient of BOPLLA films prepared with various processing conditions.