Characterization of Gamma Irradiated Polymer Blends

Abstract

Films of miscible polymer plends based on poly vinyl alcohol (PVA) /polyacrylamide (PAM) and poly(vinyl acetate) (PVAc)/poly(methyl methacrylate) (PMMA) were prepared by the solution casting technique using water and benzene as common solvents, respectively. The thermal, mechanical and morphological properties of these blends before and after exposure to various doses of gamma radiation have been investigated. The visual observation and colour reflectance measurements showed that PVAlPAM blends are compatible over a wide range of composition. Moreover, the DSC thermograms showed the appearance of a single glass transition temperature (Tg) not that of PVA or PAM homopolymers giving further supports to the complete compatibility of such blends and the occurrence of crosslinking. These findings were demonstrated by the SEM micrographs of the fracture surfaces and the tensile mechanical properties. The TGA thermograms showed that the unirradiated PVA possesses higher thermal stability than PAM homopolymer or their blends and this stability was slightly improved after exposure to gamma radiation. Thermogravimetric analysis (TGA) of PVAc/PMMA blends showed that the rate of reaction (Tmax) occurs and the kinetic parameters of the thermal decomposition. The rate of reaction curves of the individual homopolymers or their blends, before or after y-irradiation, displayed similar trends, in which the Tmax corresponding to all the polymers was found to exist in the same position but with different values. These findings and the visual observations of the blend solutions and the transparency of the films give supports to the complete miscibility of these blends. In conclusion, y-irradiation improved the thermal stability of PVAc/PMMA blends even though PMMA polymer is a y-irradiation degradable. Also the IR spectra confermed miscibility of PVAc/PMMA blends and that the absorption bands of the different functional groups were affected. Also, the DSC scans of the pure PVAc and pure PMMA and their blends at different compositions. showed the appearance of single glass transition temperature, which is not for either pure PVAc or pure PMMA polymers.