Water Absorption Enhancement of Sodium Poly Acrylate and Poly(2-Acrylamido-2-Methylpropane Sulphonic Acid) Based Hydrogel Mixtures

Hydrogels are hydrophilic polymers which are cross-linked to form three-dimensional structures, which can absorb, swell and retain huge amounts of water or aqueous fluids. This paper reports the preparation and characterisation of Poly(2-Acrylamido-2-Methylpropane Sulphonic Acid) (PAMPS) hydrogel with different crosslinking intensities. 2-Acrylamido-2-methylpropane sulfonic acid (AMPS) monomer was purchased from Alfa Aesar Company as reagent grade. It was used as received (>98% purity) without any further purification. PAMPS hydrogel was prepared by free radical crosslinking solution polymerization of AMPS in water at room temperature under a nitrogen blanket in cylindrical glass tubes. The characteristics of the obtained PAMPS hydrogel were compared with those of commercial sodium polyacrylates hydrogel. It was found that decreasing the crosslinker weight improved the absorbance capacity but to a limit. The suggested reasons were discussed. The mixture showed higher absorbance rate than PAMPS, and bigger absorbance capacity than sodium polyacrylates. This paper investigates the effect of crosslinker ratio on the swelling capacity of PAMPS. It was found that as the crosslinking ratio decreases, the porosity of the hydrogel increases, thus improving the swelling capacity.