Effect of gamma irradiation on the physicochemical properties of sodium alginate solution and internally crosslinked film made thereof

Abstract

Research on using natural origin polymers as substitutes for petroleum-based plastics has been around for years owning to their renewable and sustainable characteristics. The use of ionizing radiation such as gamma (γ) rays for structural modification of natural polymers could broaden its application while protecting the environment. This study investigated the effect of γ-irradiation on the physicochemical properties of sodium alginate solution (SAS) and sodium alginate film (SAF) made thereof. The SAS was irradiated at 0 (control), 5, 10, 20, and 40 kGy before SAF was synthesized. Thermogravimetric analysis (TGA) revealed that the thermal stability of SAS decreased following the first-order degradation kinetics with every two-fold increment in γ-irradiation dose. Fourier transform infrared spectroscopy (FTIR) showed a decrease in the carbonyl group peak intensity for both SAS and SAF as the γ-irradiation dose increased. The critical dose to cause a significant decrease in the molecular weight of SA was determined to be 5 kGy. The water vapor permeability of SAF made using SAS irradiated up to 10 kGy improved by approximately 17% as compared with the control. Overall, this study contributed fundamental knowledge on sodium alginate chain modification induced by γ-irradiation and proposed that irradiated sodium alginate is a promising starting material for the synthesis of biopolymer film.