| Summary: | 碩士 === 元智大學 === 化學工程與材料科學學系 === 99 === 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.
|
|---|
