Study on starch-graft-acrylamide/mineral powder superabsorbent composite

A novel starch-graft-acrylamide/mineral powder superabsorbent composite with water absorbency about 4000 times is synthesized by graft-copolymerization reaction among acrylamide, potato starch and mineral ultrafinepowder, followed by hydrolysis with sodium hydroxide. It is found that the composite doped with kaolinite powder possess higher water absorbency than those doped with bentonite or sercite powder, since the kaolinite powder can moderately disperse in the water and cross-link with acrylamide and starch. By controlling the amount of NaOH and reaction time during saponification process, the hydrophilic groups on the composite can be adjusted, it is found that the collaborative absorbent effect of −CONH2, −COONa and −COOH groups is superior to that of single −CONH2, −COONa or −COOH group. By the IR characterization, the polymerization reaction mechanism and structure of the composite is supposed, the mineral ultrafinepowder as a cross-linking point play an important role in the formation of network structure of the superabsorbent composite.