Radiation induced changes in crystallinity of Propylene-Ethylene copolymer Raju A.1, Rao B. Sanjeeva2,*, Ramesh S.3, Madhukar K.3 1Department of Physics, Rayalaseema University, Kurnool, Andhra Pradesh, India 2Department of Physics, Govt. Degree College, Mulugu, Telangana, India 3Department of Physics, Osmania University, Hyderabad, India *Corresponding author
Online published on 24 May, 2018. Abstract Exposure of polymers and copolymers to radiation induce changes in physico-chemical properties. In the article the authors report radiation induced changes in crystallinity and amorphousity, using spectroscopic and thermal techniques. To study the nature of radiation species formed due to irradiation, ESR spectra are recorded in the temperature range of 30–140°C. The ESR signal is observed decay below the crystalline melting temperature of PE copolymer (140°C) suggesting that the free radicals are trapped in amorphous regions of copolymer. Activation energy corresponding to free radical decay has been calculated using Bloch analysis. Change in thermal properties induced by gamma irradiation is measured using Differential Scanning Calorimetry DSC and Thermally Stimulated Luminescence TSLtechnique. The chemical change occurred in gamma irradiation are identified by Fourier Transform Infrared (FTIR) technique. Among various absorption bands, the 997 cm−I band (associated with the crystalline content) and 1180 cm−1 absorption bands (associated with amorphousity of the copolymers.) are used to study the variations in crystallinity and amorphousity of copolymer. Corresponding to these two states the free radical decay is found to follow to different rates, as observed from the Electron Spin Resonance (ESR) studies. Effect of post irradiation time on formation of free radicals has been investigated by recording ESR spectra at different post irradiation times and decay curves are drawn. Top Keywords PE Copolymer, FTIR Absorption Band, Degree of Crystallinity, ESR. Top |