Ultrasonic synthesis and properties of a sodium lignosulfonate–grafted poly(acrylic acid-co-acryl amide) composite super absorbent polymer

Abstract

A new method (ultrasound synthesis) has been applied to prepare a sodium lignosulfonate–grafted poly(acrylic acid-co-acryl amide) superabsorbent polymer (SL–P(AA-co-AM)) and the success was confirmed by FTIR (Fourier transform infrared spectroscopy), SEM (scanning electron microscopy) and TG/DSC (thermogravimetry/differential scanning calorimetry). The synthetic conditions of SL–P(AA-co-AM) were optimized by L₁₆(4)⁵ orthogonal experiment. The maximum water absorbency (1350 g g⁻¹) and physiological saline absorbency (96 g g⁻¹) were achieved under the optimized synthetic conditions. Adjusting the pH and existence of metal ions have negative effects on the water absorbency of SL–P(AA-co-AM), while the rising temperature has a positive influence on it. The swelling behaviors of SL–P(AA-co-AM) were also investigated, and the results revealed that the water diffusion in this superabsorbent was non-Fickian transport, and the swelling process fitted the Schott model. In additional, both water absorbency and physiological saline absorbency of SL–P(AA-co-AM) were improved versus the P(AA-co-AM) superabsorbent.