Effect of nucleating agents on crystallization kinetics of PET

Effects of three nucleating agents concluding talc, sodium benzoate (SB) and an ionomer (Ion., Na+) on crystallization of poly(ethylene terephthalate) (PET) were studied by differential scanning calorimetry (DSC) and polarized optical microscope (POM), the parameters of crystallization kinetics were obtained through Avrami and Ozawa equations. The fold surface free energy sigma(e) of pure PET and PET/nucleating agent blends was calculated by Hoffman-Lauritzen theory. The results indicate that the three kinds of nucleating agents increase the crystallization rate constant through promoting their nucleating effect for PET crystallization, among which SB is the best one with the same content. The crystallization mode of PET might shift from three-dimensional growth to two-dimensional growth by the addition of the nucleating agents. The values of sigma(e) of PET/nucleating agent blends are much less than that of pure PET, and PET/SB (99:1) blend has the least value of sigma(e) (18.2 mJ/m(2)). The conclusion based on Hoffman theory is similar to the analysis by Avrami and Ozawa equations.