Multistage thermal decomposition in films of cadmium chloride-doped PVA–PVP polymeric blend

Abstract

Films of cadmium chloride (CdCl2) doped polyvinyl alcohol (PVA)–polyvinyl pyrrolidone (PVP) polymer blend have been studied using thermogravimetry (TG) and differential scanning calorimetry (DSC), for doping levels ranging from 0.0 mass% to 50.5 mass%. At high doping levels (beyond 10.2 mass%), TG scans of these films showed several stages of decomposition at temperatures beyond 100 °C, indicating that the incorporation of CdCl2 results in deterioration of PVA–PVP blend, on thermal activation. The presence of melting peaks, which is due to melting of crystalline regions in CdCl2-doped PVA–PVP blend samples and the occurrence of thermal decomposition, in different stages, is confirmed by DSC curves. There is a decrease in decomposition temperature of the doped PVA–PVP blend, with an increase in salt (CdCl2) concentration. Kinetic analysis has been performed using iso-conversional models, using Flynn–Wall–Ozawa (FWO) equation, Kissinger–Akahira–Sunose (KAS) equation and Kissinger relation at four different stages of thermal decomposition, for the 10.2 mass% CdCl2-doped PVA–PVP blend. The higher values of activation energy, Ea= 197.5, 196.0 and 175.3 kJ mol−1 obtained from FWO, KAS and Kissinger models reveal that CdCl2-doped PVA–PVP sample has more thermal stability when compared to the undoped PVA–PVP blend.