SINTHESYS OF HYDROGEL COPOLYMER OF KONJAC STARCHWITHACRYLICACID, ACRYLAMIDE AND METHYLENEBISACRYLAMIDE FOR SOILAMENDMENT. Graft copolymer hydrogel of konjac starch, acrylic acid, acrylamide and N,N-methylenebisacrylamide was synthesized by techniques of polimerisation in solution with water as solvent and initiator of potassium persulfate. Konjac starches were obtained by homogenizing Konjac tuber with water and washed it with methanol several times. Konjac starch obtained with this method can produce a clear solution with up to 5 %w/w solubility. Polymerization in solution was done without nitrogen gas bubbling. The resulting hydrogel determined its water absorption and it chemical structure based on the FT-IR spectra. Based on the weight of the resulting hydrogel, the synthesis proceeds in 100 % polymerization at a temperature of 55 oC. The resulting hydrogel at certain polymerization conditions has water absorption of up to 51 times of its weight. The polymerization condition was achieved at Konjac starch concentration ratio to acrylic acid, acrylamide and N,N-methyl enebisacrylamide = 1: 3: 3: 0.01. Graft copolymer hydrogel was then used as an amendment for sandy soil to control the soil ability to store and evaporate thewater. Sandy soil mixed with 0.5 %w/whydrogel can absorb water up to two and a half times than in the absence of hydrogel and hold more than half of the water that is absorbed during the equilibrium evaporation and absorption ofwater. Equilibrium evaporation and water absorption was reached after 5 days at temperatures of 23-29 oC and humidity of 40-83 %.
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