Crystallization behavior of partially melted poly(ether ether ketone) Influence of pre-crystallization conditions

The crystallization behavior of partially melted poly(ether ether ketone) (PEEK) was investigated by differential scanning calorimetry. The influence of pre-crystallization conditions was studied in details. After partial melting, the maximum peak shifts to higher temperature by 8.4-11.8 A degrees C during subsequent cooling, indicating that self-nucleation remarkably enhanced the overall crystallization rate of PEEK. An interesting finding is that the self-nucleation temperature domain of PEEK is way outside the melting curve, and its magnitude is greatly large (28-35 A degrees C). Moreover, samples that were pre-crystallized nonisothermally or from the glassy state exhibit a larger self-nucleation effect, and a larger self-nucleation temperature domain. The isothermal crystallization data were analyzed by the Avrami model. The Avrami exponent is found to be remarkably different for melts with and without self-nucleation effects, indicating that self-nucleation changes the crystallization mechanism of PEEK.