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Abstract
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As a commercially available biodegradable and bio-based polymer, Poly
(lactic acid) is accepted to be a promising potential to replace the conventional
polymers in packaging applications. Oriented PLA films are
obtained through stretching at temperatures above the glass transition
temperature. The present study evaluated the effects of both temperature
and drawing speed during stretching on the tensile behavior and surface
morphology of PLA films. The results showed that increasing the drawing
speed enhanced the strain hardening behavior. Conversely, there was a noticeable
reduction in strain hardening as stretching temperature increased
from 70 to 80 °C. Besides, stretching at 90 °C eliminated, thoroughly, the
strain hardening behavior at lower drawing speeds. However, stretching
the PLA film at 90 °C and at a high drawing speed (30 mm/sec) stimulated
the strain hardening behavior demonstrating chain extension exceeded the
chain relaxation at such a high drawing speed. The surface morphology of
PLA films observed by scanning electron microscopy (SEM) revealed no
crystalline structures on the film surface of PLA films stretched at 70 and
80 °C. The SEM image of PLA film stretched at 90 °C showed the formation
of crystalline lamellae which is attributed to the cold crystallization
during the stretching.
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