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P. Slobodian 《Journal of Thermal Analysis and Calorimetry》2008,94(2):545-551
Volumetric thermal analysis of semicrystalline poly(ethylene terephthalate), PET, with different content of crystalline phase
was carried out using mercury-in-glass dilatometry. The effect of crystals on the thermal properties of amorphous phase (glass
transition temperature, T
g, thermal expansion coefficients, α) were determined. At cold-crystallization (106°C, up to 4 h), crystalline content of 2.4–25.3
vol.% was achieved. Increasing content of crystalline phase broadens the glass transition region and increases T
g. The change of thermal expansion coefficient during glass transition is lower than that predicted by the two-phase model,
which indicates the presence of a third fraction — rigid amorphous fraction (RAF), whose content steadily increases during
crystallization. However, its relative portion (specific RAF) is significantly reduced. Further significant decrease in specific
RAF appears after annealing at a higher temperature. 相似文献