Synthesis And Performance Studies Of The PAA-AM And St.-AA-AM Super Absorbent Polymer

SAP (Super Absorbent Polymer) is a kind of weak cross linked polymer whichhas three-dimensional network structure. It manifests an indispensible role in people’sdaily life due to its excellent water absorbency ability and water retention ability.Meanwhile it is also a hot topic in recent investigations. In this paper, the influence ofreaction conditions on the SAP were discussed, and the optimal synthesis conditionsof PAA-AM SAP and St.-AA-AM SAP were obtained. The products are tested andcharacterized to inspect the performance.In the first part, the PAA-AM SAP was prepared by means of aqueous solutionpolymerization. The factors that influence the water absorbency and salt waterabsorbency were investigated, including the neutral degree, the neutralization degreeof AA, initiators and their concentrations, cross linking concentration. The optimalreaction condition was obtained. Results show the optimal reaction conditions ofpreparing PAA-AM SAP are as follow: reaction temperature of30℃, reaction time of3h, monomer concentration of25%, n(AA): n(AM) is4:1, neutral degree of75%; TheN,N-methylene double acrylamide (NMBA) is utilized as the cross-linking agentand the concentration is0.04wt%; the redox initiator is potassium persulfate (KPS)and sodium bisulfite and its concentration is0.3wt%. Under the optimal conditions,the absorbency of the synthetic resin to water and wt0.9%NaCl solution is980g/gand95g/g respectively. By mixing SAP with soil, water absorbency ability and waterretention ability are enhanced by introducing superabsorbent soil materials.In the second part, the St.-AA-AM SAP was prepared by starch graft. The effectof starch dosage, neutralization, monomer ratio, dosage of initiator, dosage ofcross-linking on that influence the water absorbency and salt water absorbency isstudied. The results show that the optimal conditions of preparing St.-AA-AM SAPwere as fallows: m(AA): m(AM）=4:1, dosage of starch of17.5%, monomerconcentration of20%, neutral degree of75%, the redox initiator is potassiumpersulfate (KPS) and sodium bisulfite and its concentration is0.4wt%; the0.15wt%N,N-methylene double acrylamide (NMBA) is utilized as the cross-linking agent with pasting time of40min, pasting temperature of75℃, reaction time of2h, reactiontemperature of30℃; The settling time is24h. Under these optimal conditions, theabsorbency of the synthetic resin to water and wt0.9%NaCl solution was647g/g and123g/g respectively. It’s observed that the St.-AA-AM SAP prepared in the lab ismuch better than commercially available SAP by comparing various performancecapabilities.