Title of article :
Changes in tensile properties for the PET films by the treatment
in supercritical carbon dioxide fluid
Author/Authors :
Yutaka Kawahara، نويسنده , , Tomohiro Kurooka، نويسنده , ,
Dohiko Terada، نويسنده ,
Issue Information :
دوهفته نامه با شماره پیاپی سال 2008
Abstract :
Poly (ethylene terephthalate) films were treated
in supercritical CO2 (s-CO2) fluid, and the modifications in
tensile properties were investigated. The yield load peaks
became ambiguous and the breaking strains and loads
decreased for the treated films. However, the tensile
modulus and the yield strain were almost unchanged after
the treatments. The yield strain is related to the interplay
between the amorphous entanglement density and the stability
of crystal blocks. WAXD patterns for the films were
hardly modified through the treatment. Thus the orientation
for the crystal blocks seems to be unchanged. Moreover,
laser Raman microprobe spectroscopic analyses revealed
that the orientation of molecular chains is almost retained
after the treatments. Thus it is natural to assume that the
interplay between the amorphous entanglement density and
the stability of crystal blocks will also be kept constant
even though the swelling of amorphous regions with s-CO2
occurs during the treatments. From differential scanning
calorimetry measurements, it was found that the heat of
fusion for the crystallites was a little increased without
shifting the peak position after the treatment. Therefore, the
increase in crystallinity is not due to the thickening or
crystal perfecting for primary lamellae, but due to the
secondary crystallization. The increase in crystallinity
caused by the secondary lamellae crystallized and combined
onto the primary lamellae seems to have reduced the
amorphous chains to be deformed easily at tensile tests.
Then the breaking strains and loads decreased for the
treated films.
Journal title :
Journal of Materials Science
Journal title :
Journal of Materials Science