Nonisothermal crystallization kinetics and melting behavior of poly(butylene terephthalate) (PBT) composites based on different types of functional fillers

The influence of 10 wt.% of different functional mineral fillers viz, calcium carbonate (CaCO3), talc and wollastonite on the nonisothermal crystallization kinetis of poly(butylene terephthalate) (PBT) has been investigated by differential scanning calorimetry. Among them, talc showed significant nucleation effect by increasing the crystallization temperature by 12 C. However, analysis of melt crystallization data by different kinetic models like Jeziorny modified Avrami, Ozawa, and Liu-Mo revealed high rates of crystallization in case of CaCO3 and wollastonite filled composites. These results are further supported by the effective activation energy calculations by isoconversional method of Friedman. High crystallization temperatures in PBT/talc composite favored formation of more perfect crystals as evidenced by XRD and polarized optical microscopy. This resulted in single melting peak in PBT/talc composites at slow cooling rates as opposed to double melting peaks of PBT, whereas at high cooling rates the low temperature melting peak appears in the form of a shoulder. From this study it can be concluded that, though talc has a strong heterogeneous nucleating effect, the interfacial bonding between talc and PBT as shown by FTIR analysis, deters the diffusion of polymer chains into growing crystal, thereby decelerating the crystallization rate of PBT. (C) 2014 Elsevier B.V. All rights reserved.