COLD CRYSTALLIZATION STUDIES ON PET PEN BLENDS AS REVEALED BY MICROHARDNESS/

The cold crystallization of amorphous films of poly(ethylene terephtha late) (PET) and poly(ethylene naphthalene-2,6-dicarboxylate) (PEN) ble nds, with different composition, prepared by co-precipitation from sol ution followed by melt-pressing for 2 min at 280 degrees C and quenchi ng in ice-water, was followed by measuring the microhardness, H, in re al time as a function of crystallization temperature and time. An anal ytical model was derived, relating properties of the individual compon ents to the blend microhardness based on an Avrami-type equation to ac count for the crystallization of the components upon heating. Fitting of the model to the experimental results revealed a two-step hardening process of the blends. The degree of transesterification of the blend s, can be estimated with this model. Finally, a removal of the physica l ageing, inducing a decrease in H of PET in the blend, was observed u pon heating above its glass transition temperature.