Synthesis And Characteristics Of Starch Sulfate Based Amphoteric Superabsorbent Resins

The super absorbent resin is a newly developed functional macromolecular material in recent 30 years. It is applied widely in many domains such as: agriculture, horticulture, medical treatment, sanitation, architecture, commodity, grocery and environment. On the basis of reviewing the synthesis and application of super absorbent, especially on starch-based absorbents, a series of starch sulfate-based amphoteric hydrogels were synthesized, as well as their characteristics were studied.An amphoteric hydrogel was synthesized by graft copolymerization blending of acrylic acid (AA) and diallydimethylammonium chloride (DMDAAC) onto sodium starch sulfate (SSS) and showed a high water-absorbent and salt-tolerant capacity. The effect of polymerization conditions on water absorbent capacity was investigated. The maximum water absorbent capacity in deionized water and saline solution reached 2421 and 156 g/g respectively. High water absorbency was obtained in a wide pH range of 4~10, and swelling capacity was 156 g/g in 0.1 M saline solution and 348 g/g under a load of 218 kg/m2. Besides, the hydrogel showed good swelling reversibility and kept a swelling of 645 g/g in deionized water even after a repeated swell-dry process for 24 .timesIn order to enhance the strength and salt-resistance of the absorbent, sodium starch sulfate (SSS) was grafted with AA, blended with cationic polymer polydiallydimethylammonium chloride (PDMDAAC) to prepare a series of semi-interpenetrating polymer network hydrogel(semi-IPN). The maximum water absorbent capacity in deionized water and saline solution reached 2006 and 133 g/g respectively. The results showed the hydrogel kept a high swelling in a wide pH range and good salt tolerance. The swelling capacity was 416 g/g under a load of 218 kg/m2, Besides, the controlled release of NH4Cl was discussed.To contrast the swelling capacity of AA and AM, acrylamide (AM) and DMDAAC were grafted into sodium starch sulfate (SSS) to make a amphoteric hydrogel. The results testified that salt bond was a potential crosslinking factor in the amphoteric hydrogel. The maximum swelling capacity in distilled water and saline solution reached 1493 and 91 g/g respectively. The hydrogel showed a high swelling of 209 g/g even in 0.1 M saline solution and a certain adsorbency reversibility.Sodium starch sulfate (SSS)-g-AA-semi-IPN-,PDMDAAC hydrogel was prepared by a sequential method.. The maximum water absorbent capacity in deionized water and saline solution reached 1246 and 115 g/g respectively. The results showed that high water absorbency appeared from pH 4 to 10, and swelling capacity in 0.1 M saline solution was 114 g/g. Moreover, the absorbency kept 286 g/g under load 218 kg/m2, and showed certain swelling reversibility. Then the controlled release of KCl was investigated.