Acrylic Superabsorbents:a Meticulous Investigation On Copolymer Composition And Modification

Super absorbent resin (SAR) is a new functional polymer material, which with the ability of highly liquid absorption performance and well water retention, and it has been widely used in various fields since the60th, these research work has been developing rapidly and has become a hot topic research at present stage. Relatively the polyacrylic acid (PAA) resin with many preparation methods, the cost of production was lower, high production efficiency, higher water absorbency that it had been got great attention.In order to improve the water absorbency, water retention and salt tolerance of PAA SAR. The free radical solution polymerization was mainly used in this paper:with acrylic acid (AA) and acrylamide (AM) as monomers in dipolymerization, the absorbency of the optimal product in deionized water was1147g/g, in0.9wt%NaCL solution was145g/g. The best production process was studied by six factors and five levels orthogonal table, which obtained from comparing the liquid absorption. One of the most important factor was the weight ratio of AA to AM which obtained by range analysis.In order to obtain the optimal performance SAR and controlling the copolymer composition during the copolymer process, the concentration of residual monomers were measured by ultraviolet spectrophotometer (UV) and gas chromatography (GC). And the monomer reactivity ratio of AA and AM was0.365and0.751which btained by integral method. Combined with the monomer conversion, the average copolymer composition of SAR was F1=0.625. The optimal preparation process to obtain PAA/AM SAR were mAA:mH2O=25%, mAA:mAM=1.8, mI:wAA=0.3%, mNMBA:mAA=0.03%, ND of75%and the reactivity temperature was60℃. Further study obtained that when the weight of AA was smaller than AM, the products obtained was soluble and the optimal preparation process to obtain the super molecular PAM/AA hydrogen were mAA:mH2O=30%, mAM:mAA=3, mI:mAM=0.3%, mCO(NH2)2:mAM=0.3%, T=20℃and molecular weight (Mr) of the optimal product was up to5.12×107, determined by ubbelohde viscosity. The monomer ratio of AA and AM were0.278and0.684which obtained by integral method too.In order to improve the solution absorbency and water retention, PAA/AM SAR was modified by polyvinyl alcohol (PVA), cellulose (CELL) and kaolin clay (KC). The chemical structures and the pore morphologies of copolymers were characterized by13C NMR, FTIR and SEM, respectively. The combination of solution absorbency, water retention, absorption ratio and the characteristics showed the sample modified by the feed AA and AM PVA significantly increased the deionized water absorbency to1617g/g, the swelling rate was8940g/min and KC enhanced the absorbency of0.9wt%NaCl up to189g/g, which was higher than the commercial products. And the CELL modified SAR was not only has good biodegradable properties, also with strongge water retention, which is widely used in agricultrural production.