Study on the double cold crystallization peaks of poly(ethylene terephthalate) - 3. The influence of the addition of calcium carbonate (CaCO3)

The appearance of double cold crystallization peaks in differential scannin g calorimetry (DSC) heat scan for poly(ethylene terephthalate) (PET) sample s properly treated before analysis was considered to have relation to the c oexistence of two kinds of amorphous regions: interlamellar amorphous regio ns and complete amorphous regions between spherulites. The change in peaks positions, height and shape with the pre-treatment history reflects the cor responding change in amorphous regions. In this work, the influence of an a dditive, calcium carbonate (CaCO3) on the cold crystallization behavior of PET was further studied using DSC. DSC study showed that the addition of Ca CO3 affected the double cold crystallization peaks of PET greatly, indicati ng that CaCO3 exerted an influence on two amorphous regions of PET during t he pre-treatment stage because the cold crystallization peak originated fro m the crystallization of remainder amorphous regions after thermal treatmen t. Specially, results revealed that the interspherulitic amorphous region w as strongly reduced during the early pre-treatment stage of PET samples, re sulting from the efficient nucleation effect of CaCO3. The observation furt her revealed that CaCO3 affects the cold crystallization behavior of PET to different degree, depending on the method of pre-thermal treatment. The di fference is related to the temperature dependence of nucleation and chain d iffusion. (C) 2000 Elsevier Science Ltd. All rights reserved.