Synthesis and properties of sodium alginate/Na⁺rectorite grafted acrylic acid composite superabsorbent via ⁶⁰Coγ irradiation

Sodium alginate/Na⁺rectorite-graft-poly acrylic acid (SA/Na ⁺REC-g-PAA) composite superabsorbent was prepared via ⁶⁰Coγ irradiation in methanol solution and nitrogen protection. The effect of the preparation conditions on graft ratio, graft efficiency and absorption of water were investigated. The structure and morphology were analyzed by IR, XRD, TEM and SEM. The results showed that the optimal condition was that the amount of Na⁺REC was 2 wt%, the ratio of SA/Na ⁺REC to AA was 10 wt%, total dose was 9.0 kGy and volume ratio of methanol to water was 8:2. SEM showed that it is much easier to obtain porous products through ⁶⁰Coγ irradiation than chemical initiator. The mechanism of graft copolymerization via ⁶⁰Coγ irradiation was discussed. The water absorption of the graft copolymer in salt solutions of different ionic strengths was also measured, from which the superabsorbent properties are found to be saline sensitive. Ionic strength markedly decreased the water absorption of the sodium alginate grafted superabsorbent composites.