Moisture-induced effects on the tensile mechanical properties and glass-transition temperature of poly(vinyl alcohol) films

In this study, the effect of sorbed water on the tensile mechanical properties of noncrosslinked, thermally treated poly(vinyl alcohol) (PVA) films was studied. The Young's modulus, elongation at break, and tensile strength of the PVA films equilibrated at different relative humidities (0-86%) are reported, together with the depression of the glass transition of the polymer at each equilibrating humidity, as determined by temperature-modulated differential scanning calorimetry. The results indicate that drastic changes in the tensile properties were correlated with the transition of the hydrated polymer from the glassy to the rubbery state.