Investigation of thermal behavior and decomposition kinetic of PET/PEN blends and their clay containing nanocomposites

Blends of Poly(ethylene terephthalate), (PET), and poly(ethylene naphthalene 2,6-dicarboxylate), (PEN), were prepared in a twin-screw extruder. Samples were investigated by differential scanning calorimetry (DSC) and proton nuclear magnetic resonance (¹H NMR) measurements to evaluate the extent of transesterification reaction. X-ray diffraction (XRD) test was performed to examine the effect of transesterification reactions on crystalline structure of the blends. Thermogravimetry analysis (TGA) was used to study thermal decomposition of the blends which could be explained by the level of transesterification reaction for various blend compositions. The kinetic of the decomposition reaction was analyzed by Freeman-Carroll and Chang models. It was found that these two methods were acceptable models for describing the thermal decomposition of the blends however, the Chang model showed better correlation with the experimental data as compared to the other model. Results revealed that progress of transesterification reaction in blends depends on temperature and mixing time, which have dominant role in thermal behavior and decomposition kinetic of the blends. Effect of nanoclay on transesterification reactions and degradation behavior was also investigated. It was found that the nanoclay inhibited the transesterification reactions and reduced the thermal stability of the blends. PET degraded much faster than PEN in O₂ environment while, an opposite trend was observed in N₂ atmosphere.