Synthesis Of Polymaleic Anhydride Superabsorbents Cross-linked With Chitosan

Superabsorbents, as slight cross-linked hydrophilic polymers, have the ability toabsorb and retain thousand times of aqueous solution of their weights and theabsorbed solution is hardly removed even be heated or under certain load. Therefore,they have been widely used in many fields, such as agriculture, horticulture, hygienicproducts, drug-delivery systems and gel actuators.In this study, a kind of superabsorbents based on the monomers maleicanhydride （MA）, acrylic acid （AA） was prepared by solution polymerization usingammonium peroxodisulfate （AP） and sodium bisulfite （NaHSO₃） as initiator,biodegradable N-maleyl chitosan （N-MACH） as cross-1inker. The optimal reactioncondition was based on the orthogonal experiment design. Effects of processparameters such as the amount of cross-linker, mass ratio of MA to AA,neutralization degree of AA and monomer concentration on the water absorbency ofsuperabsorbents were discussed. The swelling kinetics behaviors, water retentionratios at natural state, the repeated water absorbency and the effect of the solution pHon the swelling ratio were studied. In enzymatic degradation tests, the weight loss ofsuperabsorbent was investigated. In addition, to enhance the water absorbency ofsuperabsorbents in0.9%NaCl solution, butyl acrylate （BA）, polyvinyl alcohol（PVA）,2-acrylamide-2-methyl propane sulfonic acid （AMPS） and acrylamide （AM）was introduced to the system. It was proved that BA, PVA, AMPS and AM couldeffectively improve the water absorbency of superabsorbents in0.9%NaCl solution. 1. The optimal conditions of superabsorbents on distilled water and0.9wt%NaCl solution absorbency were as follows: monomer concentration20wt%,cross-linker concentration0.03g, the neutralization degree of AA50%and massratio of MA to AA5%.2. The absorbency of superabsorbents in distilled water and0.9wt%NaClsolution increased and then decreased with the increasing of maleic anhydridecontent, the neutralization degree of AA, the amount of the cross-linker and themonomer concentration.3. In distilled water or0.9wt%NaCl solution, P（MA-co-AA） superabsorbentsexhibited fast swelling kinetics.4. In different swelling media, the type and concentration of salt solution hadgreat impact on the absorbency of superabsorbents. In the same swelling media, theabsorbency rapidly decreased with the increasing of ion concentration; When the ionconcentration was same, the order of absorbency in the different valences cationssolution was as follows: NaCl≈KCl> CaCl₂≈MgCl₂> FeCl₃.5. P（MA-co-AA） superabsorbents has good water-retaining ability at naturalstate. After four days, the water retention rate were still greater than30%. The morethe amount of cross-linker, the better the water retention rate of superabsorbents.6. P（MA-co-AA） superabsorbents possessed excellent repeated waterabsorbency, can be recycled and have good practical value.7. The swelling ratios of P（MA-co-AA） superabsorbents have the sharp changewith the solution pH, the optimal pH range of application was pH=7-10.8. In the enzymatic degradation studies, the weight loss of P（MA-co-AA）superabsorbents decreased with the increasing of cross-linking density.9. AM and BA were added to make the water absorbency in distilled waterdecreased to some extent, but the water absorbency in0.9%NaCl solutioneffectively improved. 10. AMPS and PVA could effectively improve the water absorbency ofsuperabsorbents both in distilled water and0.9%NaCl solution.