Synthsis Of Biodegradable Superabsorbents

Superabsorbents are slight cross-linked hydrophilic polymers that can swell, absorb, and retain hundred or thousand times of water of their weights. Because of their excellent characteristics, superabsorbents are widely used in many fields. However, the synthetic polymers superabsorbents were not biodegradable and biocompatible, their toxicity might limit their use in agriculture and horticulture. Recently, many efforts have been focused on blending of monomer materials with biodegradable and cheap natural biopolymers, to produce superabsorbents. In this paper, a high-swelling superabsorbent was synthesized with biodegradable N-maleyl chitosan as cross-linker, acrylic acid (AA) and acrylamide (AM) as the monomers, ammonium peroxodisulfate (AP)–sodium bisulfite (NaHSO3) as redox initiation system, by means of aqueous solution polymerization. The optimal reaction conditions were obtained by the orthogonal experiments. Factors influencing the water absorbency of superabsorbent included monomer concentration, mole ratio of AA to (AA+AM), degree of neutralization of AA and cross-linker concentration. The swelling kinetics behaviors, water absorbency performance and water-retaining ability of superabsorbent were studied. The effect of the kinds and contents of swelling medium on the swelling ability was also discussed. In enzymatic degradation tests, the weight loss of superabsorbent was investigated.1. The optimal conditions of superabsorbents absorbency on distilled water were monomer concentration 20 wt%, mole ratio of AA to (AA + AM) 60%, the neutralization degree of AA 40%, cross-linker concentration 2%.2. The optimal conditions of superabsorbents absorbency on 0.9 wt% NaCl solution were monomer concentration 25 wt%, mole ratio of AA to (AA + AM) 60%, the neutralization degree of AA 50% and cross-linker concentration 1%.3. The absorbency of superabsorbents in distilled water and 0.9 wt% NaCl solution increased and then decreased with the increasing of monomer concentration, mole ratio of AA to (AA+AM) and degree of neutralization of AA.4. With the increasing of cross-linker concentration, absorbency in distilled water increased and then decreased, but it decreased all the time in 0.9 wt% NaCl solution.5. In distilled water and 0.9 wt% NaCl solution, P(AA-AM) superabsorbents exhibited fast swelling kinetics, decreased with increase of cross-linker concentration and monomer concentration.6. P(AA-AM) superabsorbents had remarkable water-retaining ability,up to 55 %, keeping in thermostated container (40°C) for 5 h.7. P(AA-AM) superabsorbents had the salt-tolerant ability: the swelling ratios decrease with increasing of salt concentration, high cation had great effect on the superabsorbent absorbency.8. The swelling ratios of P(AA-AM) superabsorbents had the sharp change with the solution pH, the appropriate condition of pH was 7-10.9. In the enzymatic degradation studies, superabsorbents exhibited fine biodegradable ability on the pepsin solution (37°C), the weight loss of P(AA-AM) superabsorbents decreased with the increasing of cross-linking density.