Study On The Synthesis And Properties Of GG-g-PAANa Superabsorbents

In this thesis, four kinds of different superabsorbents based on partly neutralized acrylic acid (AANa) are prepared using several kinds of different crosslinking agents according to the applications and recent researches on hygienic products. Guar gum (GG) and carboxymethyl guar (CMG) were introduced to graft with AANa, guar gum-graft-poly(sodium acrylate) (GG-g-PAANa) and carboxymethyl guar-graft-poly(sodium acrylate) (CMG-g-PAANa) superabsorbent polymers were prepared. Both the properties of the resultant superabsorbent and the variables that have influences on the properties of the superabsorbent were mainly discussed in this thesis. The main results were obtained as follows:(1) A series of superabsorbents based on partially neutralized acrylic acid were synthesized by solution polymerization using N,N'-methylene bisacrylamide (NNMBA), pentaerythritol triacrylate (PETA), ethylene glycol dimethacrylate (EGDMA) and dimethyl diallyl ammonium chloride (DMDAAC) as crosslinking agent, respectively. Furthermore, the polymers were surface-crosslinked using trimethylolpropane triglycidyl ether for improving the properties of swollen hydrogel. The effects of crosslinking agent on swelling kinetics, water absorbency under load, hydrogel strength, salt sensitivity and water retention of the superabsorbent were examined in detail before which the synthesis conditions were optimized. It was found that the properties of the superabsorbent crosslinked by PETA were better than that of NNMBA.(2) A modified superabsorbent was synthesized by solution polymerization of guar gum and partially neutralized acrylic acid. PETA was used as a crosslinking agent, ammonium persulfate as an initiator, and trimethylolpropane triglycidyl ether as a surface-crosslinker. The influences of major factors on water absorbency under atmospheric pressure (WA) in 0.9 wt% NaCl aqueous solution were investigated, such as monomer concentration, neutralization degree of AA. molar ratio of PETA to AA and ammonium persulfate (APS) to AA, mass ratio of GG to AA and trimethylolpropane triglycidyl ether (TMPTGE) to SAP1. Meanwhile, the effects of crosslinking agent categories, guar gum and surface crosslinking on properties of SAPs were studied, such as water absorbency under pressure and hydrogel strength. The WA and WAp of the SAP prepared under optimal conditions in 0.9 wt% NaCl aqueous solution were 55 and 11 g·g-1, respectively. The results revealed that surface crosslinked GG-g-PAANa exhibited high swelling rate and WAP and excellent mechanical properties after swelling.(3) With guar gum and chloroactic acid as raw materials, carboxymethyl guar was synthesized through a dry-process. A novel CMG-g-PAANa superabsorbent was synthesized by the solution copolymerization using ammonium persulfate as an initiator and PETA as a crosslinking agent. The copolymer was surface-crosslinked using trimethylolpropane triglycidyl ether. The synthesis conditions were optimized, and the water absorbency of the sample prepared at the optimal conditions was 68 and 54 g·g-1in 0.9 wt% NaCl solution and synthetic urine, respectively. The excellent swelling rate, salt resistant and dispersion, surface-drying after swelling were also observed, as a result of the excellent dissolubility and hydrophilicity of CMG.