Evaluation of thermal transitions in Poly (butylene terephthalate)/15A MMT nanocomposites: Nonisothermal experiments and modelling using isoconversional methods

Highlights: • Study of PBT & PBT/15A MMT nanocomposites. • Activation energy using Friedman differential isoconversional method. • Use of isoconversional method for Estimation of Hoffman-Lauritzen parameters. - Abstract: Friedman's differential isoconversional approach is applied to obtain effective activation energy (E_α) for Poly (butylene terephthalate) and PBT/15AMMT nanocomposites. The presence of 15AMMT content has largely affected E_α values. Further Vyazovkin and Sbirrazzuoli's approach is used to determine Hoffman-Lauritzen parameters (K_g & U*). The crystallization regime transition (II–III) occurs for neat PBT at 189 °C and its nanocomposites is at 189–192 °C. K_g(III)/K_g(II) ratios are closer to theoretical value of 2. However the corresponding value of U* is inappropriately too low with negative sign (Correlation coefficient R² = 0.9–0.99) and which is however highly anomalous when compared to other polymers. Setting U* to 6300 J/mol, 4300 J/mol and 0 J/mol, resulted in poor K_g(III)/K_g(II) ratios and R². This imply that there is a considerable chain mobility during regime II crystallization which is explained in terms of rapid extraction of PBT chain segments by the force of crystallization, following the tube-reptation postulate.