Study on the double cold crystallization peaks of poly(ethylene terephthalate) 3. The influence of the addition of calcium carbonate (CaCO 3)

Abstract

The appearance of double cold crystallization peaks in differential scanning calorimetry (DSC) heat scan for poly(ethylene terephthalate) (PET) samples properly treated before analysis was considered to have relation to the co-existence of two kinds of amorphous regions: interlamellar amorphous regions and complete amorphous regions between spherulites. The change in peaks positions, height and shape with the pre-treatment history reflects the corresponding change in amorphous regions. In this work, the influence of an additive, calcium carbonate (CaCO 3) on the cold crystallization behavior of PET was further studied using DSC. DSC study showed that the addition of CaCO 3 affected the double cold crystallization peaks of PET greatly, indicating that CaCO 3 exerted an influence on two amorphous regions of PET during the pre-treatment stage because the cold crystallization peak originated from the crystallization of remainder amorphous regions after thermal treatment. Specially, results revealed that the interspherulitic amorphous region was strongly reduced during the early pre-treatment stage of PET samples, resulting from the efficient nucleation effect of CaCO 3. The observation further revealed that CaCO 3 affects the cold crystallization behavior of PET to different degree, depending on the method of pre-thermal treatment. The difference is related to the temperature dependence of nucleation and chain diffusion.