An investigation of the dehydration of superabsorbing polyacrylic hydrogels

Samples of super-absorbing hydrogels based on cross-linked poly(acrylic acid), having different cross-linking degrees, were synthesized using a procedure of simultaneous polymerization and cross-linking. The equilibrium swelling degrees of the synthesized hydrogel samples in water were determined at 25degreesC. A correlation was established between the equilibrium swelling degree and the cross-link density of the investigated hydrogels. The dehydration kinetics of the swollen hydrogels was investigated by non-isothermal kinetics (TG and DSC methods). The basic kinetic parameters of dehydration of the swollen hydrogels: reaction order, pre-exponential factor, and activation energy were determined. It was concluded that an increase in the cross-linking degree led to the decrease in the activation energy and to the increase in the pre-exponential factor. A possible mechanism of dehydration of super-absorbing polyacrylic hydrogels was discussed.