Radiation-synthesized polysaccharides/polyacrylate super water absorbents and their biodegradabilities

Different super water absorbents (SWA) based on polysaccharides/poly(acrylic acid) (PAAc) were prepared by gamma irradiation to be used as soil water retainers. Polysaccharides, kappa-carrageenan (seaweed and semirefined forms) and cassava starch were used in the preparation of SWA to improve biodegradability. Gel fraction of the different SWAs ranged from 31% to 97% and degree of swelling reached up to about 5890 g H2O/g dry gel. The physico-chemical and mechanical properties of the SWA were influenced by the degree of neutralization, macromolecular properties of the polysaccharide and irradiation dose. FTIR and TGA analyses showed successful incorporation of polysaccharides in the network structure through formation of covalent bond. Biodegradability test by microbial oxidative degradation analyzer (MODA) showed that cassava starch/PAAc SWA biodegraded at a rate of 42% in 85 days compared to 11% of pure PAAc. The cassava starch/PAAc SWAs retained water up to more than 20 days in sandy soil and still absorbed water after 62 days with wet/dry cycles in pot experiment.