Isothermal crystallization kinetics of chain-extended PET

The crystallization behaviour of a commercial modified PET (intrinsic viscosity 1.25dl/g) with high molecular weight was evaluated and compared to that of bottle grade PET. The cold and melt isothermal crystallization was analyzed by using the Avrami model. The higher molecular weight PET showed a slower crystallization kinetic compared to a bottle grade PET (IV 0.8dl/g). The Hoffman-Lauritzen analysis showed that the energetic barriers to nucleation and molecular mobility were higher for the modified PET. This resulted in a lower nucleation rate in both cold and melt crystallization.