CMC/Celite Superabsorbent Composites: Effect of Reaction Variables on Saline-absorbency under Load

Aseries of superabsorbent composites were synthesized through graft copolymerizationof acrylic acid (AA) onto carboxymethyl cellulose (CMC) in the presence of celite powder using N,N''-methylenebisacrylamide (MBA) as a cross-linking agent and ammonium persulphate (APS) as an initiator. The chemical structure and thermal properties of the composite hydrogels were characterized by FTIR spectroscopy and TGA methods, respectively. Morphology of the samples was examined by scanning electron microscopy (SEM). In free-state, the swelling conditions and hence the related data are not real, because in all their applications the swelling particles of superabsorbent must absorb aqueous solutions while they are under pressure. Therefore, the effect of the reaction variables (such as monomer and cross-linker concentrations and CMC/celite weight ratio) on the saline-absorbency under load (AUL) application was investigated. The AUL values were estimated using a simple AUL tester at two different pressures (0.3 and 0.9 psi). Surprisingly, the new synthesized composite samples exhibited about 86 g/g absorbency in 0.9% NaCl solution under 0.3 psi pressure. The AUL values considerably decreased withincreasing the MBA concentration, 53.4 g/g (CMC/celite = 0.5/1.5 and P = 0.3 psi) vs.42.4 g/g (CMC/celite = 0.5/1.5 and P = 0.3 psi). The ionic monomers increased saline-absorbency under load significantly and the effects of parameters such as monomer and cross-linker concentrations, and CMC/celite weight ratio were not considerably different from the free swelling. Therefore, this new synthesized composite may be considered as an excellent candidate for various industrial applications.