Synthesis, Characterization And Properties Of Amphoteric Semi-IPN Superabsorbent Based On Starch Phosphate

Superabsorbents are new functional polymer materials, and it had very strong abilities of absorbing and retaining water. Superabsorbents are widely applied in industry, agriculture, architecture, medical treatment and hygiene and other fields. In this work, we studied systematically synthesis and property of semi-interpenetrating network amphoteric superabsorbent based on the review of literature. The main experiments are as follows:A novel amphoteric superabsorbent composed of starch phosphate grafted acrylic (AA) acid and polydimethyldiallylammonium chloride (PDMDAAC) was prepared by sequential semi-interpenetrating polymer networks (semi-IPNs) method. Starch phosphate was synthesized by a dry process. Acrylic acid was used as anion monomer, PDMDAAC as polycation, N, N'-methylene bisacrylamide (MBA) as crosslinker and ammonium persulfate (APS) as initiator respectively. The influences including the dose of crosslinker and initiator, AA and PDMDAAC, the neutralization of AA, the degree of substitution of starch phosphate on the swelling capacity of amphoteric superabsorbent were investigated in detail. Under the optimum condition, the swelling capacity of superabsorbent was 1612 g/g and 113 g/g in deionized water and 0.9 wt% NaCl solution, respectively. The swelling capacity in different concentration of salt solutions and different pH solutions, water retention capacity and swelling reversibility were investigated. Besides, the structure of superabsorbent was characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM).Starch phosphate with high degree of substitution and low molecular weight was synthesized by a acidifying process, followed by the graft polymerization of AA in the solution of poly [2-[(methacryloyloxy) ethyl]trimethylammonium] chloride (PDMC) to form semi-IPN amphoteric superabsorbent. The effects of polymerization conditions on water absorbent capacity were investigated. The maximum water absorbent capacity in deionized water and saline solution reached 2016 and 121 g/g, respectively in the optimum condition. The product showed excellent swelling capacity in the pH value of 4-12 and different salt solutions. The mechnical strength and swelling reversity of superabsorbents were also improved.The complex interaction between starch phosphate and polycations was studied by the measurement of particle size and conductivity etc. The absorption and release behaviors of calcium chloride by amphoteric superabsorbents were investigated. The adsorption thermodynamics was further studied in order to provide a guide for the practical application in agriculture.