The highly water-absorbing polymers were prepared by the reaction of acrylic acid as a graft\rmonomer and natural starch (eg. rice starch, sticky rice starch or corn starch) as the backbone\rusing water hydrogen peroxide and vitamin C as solvent, initiator and catalyst, respectively. The\rreaction was carried out by mixing of starch in distilling water and stirring at 60-70 ℃ for 3\rhours and then cooled to 30℃ Acrylic acid was added and the pH was adjusted to 6-9 by the\raddition of limestone powder. To the stirred mixture were then added hydrogen peroxide (30%\rv/v) and vitamin C and continued stirring for 3 hours until the solution became viscous The\rviscous solution was neutralized with potassium hydroxide (30%v/v) to give the pH for 6.5-7\rand allowed to cool to room temperature overnight. The resulting solution was spread on\rwinnowing baskets and allowed to dry under the sun to yield a continuous absorbent polymer\rfilm. The absorbent polymer film was ground and yield of white powder, The above procedure\rwas repeated by using another types of starch. The ability of starch slurry to swell on heating, by\rabsorption of water, is it’s most important practical property. Rice starch has very low swelling\rcapacity in aqueous media compare with sticky rice starch and corn starch. The capacities of\rwater-absorbing polymer were tested by placing polymer powder in the beaker and adding of\rwater until it swell and cannot absorb more water. The polymers were found to be an excellent\rwater absorbent, which absorbed water about 248, 245 and 167 times in weight of polymer for\rcorn starch, sticky rice starch and rice starch, respectively. The water retention was calculated by\rmeasuring the amount of water releasing after every week for 10 weeks. They have also good\rwater retention capacity. The swollen polymers were mixed with soil in ratio 1:3 and the\rincreasing water holding capacity of soils which promotes more efficient plant growth in pot were\rtest. It was found that the soil could be absorbed water for 10 weeks. It is possible to use highly\rwater-absorbing polymers from natural starch in agriculture because they are low in cost and the\rpolysaccharide main portion of the product is biodegradable
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