Effects of Stress Level and Temperature on the Time Dependent Morphological and Physical Properties of PVA Fibers
Vol. 54, No. 2, pp. 73-79,
Apr. 2017
10.12772/TSE.2017.54.073
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Abstract
The effects of the stress level and heat treatment temperature on the morphological
and physical properties of poly(vinyl alcohol) (PVA) fibers were investigated with
regard to treatment time. The PVA fibers were heat treated at three different temperatures
(210, 220, and 230℃) and stress levels (0.05, 0.15, and 0.25 g/d). Increase in shrinkage was observed with an increase in the heat treatment time when treated at 220 and 230℃
beyond 15 min, while a little extension was observed at 210 ℃. The shrinkage in the PVA
fibers heat treated at 230℃ increased with a decrease in stress levels, exhibiting a different
dependence of the shrinkage on the heat treatment time. The WAXS patterns of the PVA
fibers heat treated at 230℃ at 0.15 g/d showed that the crystalline peaks became sharp
with time up to 15 min beyond which they became dull. The degree of crystallinity, determined from the density measurement, was maximum when heat treated for 5 min regardless of the temperature and the stress level. However, the degree of crystallinity when further treated at 220 and 230℃ decreased, while that showed little change when treated at 210℃. In addition, the variation of the degree of crystallinity with heat treatment time was in good agreement with that of the degree of amorphous orientation. In the DSC thermograms, a greater dependence of the melting temperature and the heat of fusion on the
heat treatment time was observed at higher heat treatment temperatures and lower stress
levels.
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