Solid-state photo-cross-linking of cassava starch: improvement properties of thermoplastic starch

Photo-cross-linked thermoplastic cassava starch was prepared using 3% of sodium benzoate. Sodium benzoate was used as photo-initiator which induced cross-linking formation. The thermoplastic cassava starch was irradiated at different irradiation times ranging from 30 to 480 min. Photo-cross-linking kinetics were investigated and found that the cross-linking reaction increased proportionally with an irradiation time up to 120 min. The result of the swelling test and moisture absorption measurement showed improved moisture resistivity and the gel mass fraction. Nevertheless, the tensile strength increased, while the elongation at break and swelling degree reduced by the irradiation time. The carboxylate formation was observed in the FT-IR spectrum from the decomposition of sodium benzoate upon the photo-irradiation. Based on the carboxylate index, it was found that an increase in irradiation time thereby increases the carboxylate formation which correlated to an increase in the gel mass fraction.