Abstract
Measurements of specific heat at temperatures within the range –70°C to 120°C were obtained for the PET-water system at four different water concentrations. Water-fusion peaks for sorbed water were found in the range –15°C to 0°C. The amount of sorbed water at saturation at 0°C was 1.26 g/100 g PET, and the amount of sorbed water freezable on cooling to –70°C was 0.64 g/100 g. Integral and incremental heats of fusion of sorbed water were determined. The incremental heat, i.e., the heat necessary to melt 1 g of sorbed, freezable water, did not vary with water concentration and had the value 79 cal/g, not significantly different from bulk water. The state of the sorbed water is discussed. The specific heat data for PET is compared with previous results.

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