Abstract
Polyvinyl alcohol (PVA) is a hydrophilic, biodegradable, semicrystalline polymer with a wide array of commercial uses ranging from textiles and packaging to medicine. Film samples of PVA were investigated to assess crystallization and melting behavior during self-nucleation experiments and thermal degradation, using differential scanning calorimetry (DSC) and thermogravimetric (TG) analysis, respectively. TG results show that degradation occurred at temperatures in excess of 200 °C which is close to the observed peak melting temperature of 223 °C. PVA was heated to various self-nucleation temperatures, T s, within its melting range, and then cooled and reheated. Three distinct crystallization regimes were observed upon cooling, depending upon the self-nucleation temperature (T s) selected. At low values of T s, T s < 227 °C, PVA only partially melts, and upon cooling the residual crystals anneal and become more stable. At intermediate values of T s, 228 °C < T s < 234 °C, PVA was found to crystallize exclusively from self-nucleation. For T s > 235 °C, the PVA melts completely and absence of self-nucleation sites causes crystallization to occur at lower temperatures.
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