PHASE-BEHAVIOR AND TRANSESTERIFICATION IN POLY(ETHYLENE 2,6-NAPHTHALATE) AND POLY(ETHYLENE-TEREPHTHALATE) BLENDS

The effect of transesterification on the phase behaviour in poly(ethyl ene 2,6-naphthalate) and poly(ethylene terephthalate) blends was inves tigated by using differential scanning calorimetry. The transesterific ation between the two polymers was confirmed by LH nuclear magnetic re sonance. The blend samples heat treated for up to 11 min at 280 degree s C show two glass transitions, which approach closer with the increas e of reaction time. After 13 min, a single glass transition is observe d, and the glass transition range becomes narrow with the lapse of rea ction time. From the glass transition behaviour, the phase composition s and the phase fractions were determined as functions of reaction tim e at 280 degrees C. The composition difference between ethylene 2,6-na phthalate (EN)-rich and ethylene terephthalate (ET)-rich phases decrea ses as the transesterification proceeds. On the other hand, though the weight fractions of the EN-rich phase, the ET-rich one and the interf acial zone tend to change with the lapse of time, the changes are smal l in magnitude. (C) 1997 Elsevier Science Ltd.