PET/PPO共混物的结晶及熔融行为

本文用扫描量热法(DSC)研究了聚对苯二甲酸乙二脂(PET)与聚2,6—二甲基—1,4—对苯醚(PPO)共混物从熔体及玻璃态的等温结晶动力学以及结晶后试样相应的熔融行为。结果表明,PET及其共混物的等温结晶过程均符合Avrami方程,但Avrami指数n及结晶速率常数K值均与共混物组成及起始结晶状态有密切关系;从熔体结晶的表现活化能△E值要比玻璃态结晶的△E值高,并且受组成影响较明显。非晶的PPO组分在含量较低时能加速PET的结晶,使之达到比纯PET高的结晶度,但含量高达50％时,结晶速率及结晶度均略有下降,这与共混物织态结构改变有关。相同组成的共混物从玻璃态结晶比从熔体结晶所达到的结晶度高,但起始熔融温度低,熔程宽,表明生成较多的不规整的微晶体。

CRYSTALLIZATION AND MELTING BEHAVIORS OF PET / PPO BLENDS

The isolatermal crystallization kinetics from melt and glassy state were studied by differential scanning calorimetry for the blends of poly(ethylene terephthalate) and poly(2,6-dimethyl-1,4-phenylene oxide) (PPO). It was found that the crystallization behavior of PET and its blends with PPO could be well described by Avrami equation, however, the Avrami exponent n as well as overall crystallization rate constant K are highly dependent on the composition of the blends and the initial crystallization conditions. The apparaent activity energy crystallized from melt is higher than that from glassy state, moreover, more dependent on the composition. PPO is an uncrystallized component in the blends but which could partly play a role of nucleating agent in the crystallization of PET, consequently, promote its crystallization rate; as the amount of PPO reached up to 50%, the rate slightly decreased, which maybe associate with their difference in the textures. It is also noted that with the same composition, the crystallinity of PET in the blends formed from the glassy state is higher than that formed from melt but the former has lower onset temperature and more broad range of melting.