Research On The Preparation And Mechanism Of SAP Based On Wheat Starch

Super absorbent polymer (SAP) is a special feature with three dimensional network structure of the polymer. It is a new type material with absorbing several times, even thousands times than its own weight. In this paper, a graft copolymer was synthesized by copolymerization of acrylic acid onto wheat starch, with N,N’-methylene diacrylamide as cosslinking agent and ammonium persulfate as the initiator, three great performance super absorbent polymer were synthesized:wheat starch-acrylic acid super absorbent polymer, high gel strength of super absorbent polymer and porous structure super absorbent polymer. Respectively, the suction mechanism of super absorbent polymer was studied. Details are as follows:(1) Super absorbent polymer was prepared with wheat starch and arylic acid by the methods of solution. The reference index of SAP was water absorbent rate. Many factors such as ammonium persulfete, N, N-dimethylform-amide, polymerization time, polymerization temperature and acrylic acid by NaOH were studied systemically. The surface sturcture and thermal property were analyzed by FT-IR and X-ray. The optimum conditions were found as follows:when the dosage of cross-linker, ammonium persulfete, polymerization time, polymerization temperature were 0.03%,0.11%, 1h, 50℃ respective and the degree of AA was 60%, the rate of absorb water reached maximum values, which was 1320g/g. FT-IR and X-ray analysis showed that the SAP was a product copolymer by wheat starch and arylic acid.(2) The high gel strength of SAP was based on the wheat starch, kaolin clay, maleic acid and acrylic acid. The effect of different process conditions such as cross-linking agent, starch/water, maleic acid and kaolin clay on the water absorption and gel properties of the SAP were systematically optimized. Moreover, the membership was introduced to examine the overall impact of scores. The result showed that:when kaolin clay was 5.62%, the mass fraction of cross linker was 0.07%, maleic acid was 12.87%, starch/water was 6%, the overall scores of SAP was 0.615. The study of water retention and repeated-water-absorption showed that the high gel SAP had good water retention capacity and repeated-water-absorption capacity.(3) The porous structure super absorbent polymer was prepared by the methods of solution. The surface sturcture and thermal property were analyzed by SEM. The effect of different process conditions concluding agent of Aspergillus niger, incubation time, incubation temperature, amount of NaOH on the absorption rate of the porous structure SAP were systematically optimized. The results showed that the dosage of Aspergillus niger was 15.05%, the reaction temperature was 48.45℃, incubation time was 3.06d, the amount of NaOH was 8g, porous structure SAP reached the maximum absorption rate, which was 59.91g/(g*h),86.1% higher than ordinary SAP of the same particle size. SEM analysis showed that SAP could be formed porous structure by Aspergillus niger.(4) The fluid and salt ions adsorption rate of the super absorbent polymer (SAP) was determinated in NaCl、KCl、 MgCl2、and CaCl2 solution, and the adsorption characteristics of SAP thermodynamics and kinetics of NaCl and CaCl2 were studied. The results showed that the salt ions adsorption rate of SAP was related to the cation valence of the solution, the bivalent cation adsorption ability was far less than monovalent cations. The equilibrium constant b and speed constant ks of adsorbing Na+ and K+were much greater than that of absorbing Mg2+and Ca2+, and the higher the temperature the greater the equilibrium constant b and speed constant ks. The adsorption thermodynamics of NaCl、KCl、MgCl2 and CaCl2 was complied with the laws of Langmuir equation. The adsorption kinetics result illustrated that the adsorption thermodynamics was fit to the Pseudo-second order equation.