Synthesis of Water Absorbing polymers by inverse suspension polymerization

Abstract

This research concerns the synthesis of high-water absorbing poly- mers (HWAPs) by inverse suspension polymerization. Beginning the synthesis with copolymerization of acrylamide (Am) and potassium acrylate(KA) find N,N’ –methylenebisacrylamide (N,N’ -MBA) as a crosslinker via the inverse suspension technique, the synthesized beads were collected by precipitation with excess methanol. The water absorbency of the synthesized copolymers was measured by swelling in distilled water. The effects of the influencial parameters on the syntesis of HWAPs were studied and the finding elucidated the following appropriate conditions for the optimum water absorbency of the beads: The amount of the initiator (ammonium persulfate ; (NH4) 2S2O8) was 1.4 g/1 of the suspension; the polymerization temperature was 60 ˚C for a thermal initiation of Am:KA at 71:29 molar ratio of the total monomer concentration of 7 molar in the absence of N,N’ -MBA",which produced the best HWAP having water absorbency of 347 g/g. Crosslink with N,N’ -MBA by thermal and redox initiation did not improve the water absorbency of the copolymer. The synthetic copolymers were investigated for the functional groups, structure, thermal properties, and surface morphology by IR, NMR, DSC and SEM, respectively. The effects of KCl and MgCl2 solutions on the water absorbency of the best copolymer were studied and found that the water absorbency decreases as the salt concentration increases due to the more rapidly decreasing of the osmotic pressure differential between the inside and outside of the gel, thus allowing less water to be absorbed.