Radiation modification of water absorption of cassava starch by acrylic acid/acrylamide

Graft copolymerizations of acrylamide and/or acrylic acid onto cassava star ch by a simultaneous irradiation technique using gamma-rays as the initiato r were studied with regard to various parameters of importance: the monomer -to-cassava starch ratio, total dose(kGy), dose rate (kGy h(-1)), acrylamid e-to-acrylic acid ratio, and the addition of nitric acid and maleic acid as the additives. Grafting parameters were determined in relation to the wate r absorption of the saponified graft copolymer. The water absorption of the saponified graft copolymer in salt and buffer solutions of different ionic strengths was also measured, from which the superabsorbent properties are found to be pH sensitive. The starch graft copolymers of acrylamide and acr ylic acid give higher water absorption than the starch graft copolymers of either acrylamide or acrylic acid alone. The porosity of the saponified sta rch graft copolymers prepared by the acrylamide/acrylic acid ratios of 70:3 0 and 50:50 was much higher than the porosity of copolymers in terms of fin e networks. Ionic strength and multi-oxidation states of the saline and buf fer solutions markedly decreased the water absorption of the saponified cas sava starch grafted superabsorbent polymers. (C) 2000 Published by Elsevier Science Ltd.