Kinetics of poly(vinyl chloride) thermal degradation by ionizing radiation

Abstract

In this study, the relationship between ionizing radiation treatment and thermal degradation kinetics of Poly (vinyl chloride) (PVC) polymer film was investigated. The unirradiated and 25 kGy irradiated samples treated with gamma rays or electron beam radiation were submitted to thermogravimetric analysis (TGA) at different heating rates (10 – 30 K.min-1). The TGA data was used to obtain the apparent activation energy values (Ea) according to Flynn-Wall-Ozawa method. TGA analysis suggested that electron beam radiation promotes a slight increase on maximum temperature for dehydrochlorination reaction on PVC. Gamma-rays irradiation caused a small reduction of maximum temperature of HCl evolution of PVC. Thermal degradation kinetics results showed that 25 kGy irradiated samples presents an apparent activation energy values from 104 - 109 KJ.mol-1. The apparent Ea values suggested that 25 kGy gamma radiation or 25 kGy electron beam radiation convert PVC polymer films more prone to HCl evolution due to radiolysis of polymer. Evaluation of the Ea values by Flynn-Wall-Ozawa method allows a good analytical instrument to comprehend dehydrochlorination reaction on irradiated PVC polymer films.