Kinetics of nonisothermal crystallization of uniaxially oriented poly(ethylene terephthalate)

The crystallization process of uniaxially oriented poly( ethylene terephthalate) (PET) was investigated by using DSC with a constant heating rate. The cold crystallization thermograms of uniaxially oriented PET exhibit multiple-overlapping peaks. This phenomenon was also confirmed by the isothermal DSC studies. A new method was proposed to obtain the crystallization kinetic parameters of polymers from the complicated DSC curves. The result indicated that the theoretical curve calculated from the new method shows a better agreement with the experimental data than that from the other methods. The crystallization process of uniaxially oriented PET was analyzed by using a model that involved three different crystallization mechanisms depending on different temperature ranges. The whole crystallization process of uniaxially oriented PET consists of three sub-processes. Crystallization mechanism was explained based on the change of the Avrami exponent and mass fraction of every sub-process with draw ratio.