Synthesis, characterization, and swelling properties of a novel tapioca-g-Poly(Acrylic acid−2−acrylamido−2−methylpropane sulfonic acid)/ammonium polyphosphate superabsorbent polymer

Abstract

In this study, a novel superabsorbent polymer tapioca starch-g-poly(acrylic acid-2-acrylamido-2-methylpropane sulfonic acid)/ammonium polyphosphate (TS-g-AA-AMPS/APP) was synthesized based on the graft copolymerization of tapioca starch (TS) with acrylic acid (AA) and 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) via free radical polymerization in aqueous solution with ammonium polyphosphate (APP) additive added for study. The synthesized superabsorbent polymer material was characterized by Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FE-SEM), energy-dispersive x-ray spectroscopy (EDS), and thermogravimetric analysis (TGA). Research investigating the material synthesis conditions to absorbance in distilled water and 0.9 wt% NaCl solution has also been studied. Under optimal synthesis conditions, the absorbance in distilled water and 0.9 wt% NaCl solution were 416 g g−1 and 61 g g−1, respectively, for the sample with 3 wt% APP content. The introduction of APP units has improved the absorption properties of the material such as the water retention capacity reaching 55.25% in 10 h at 60 °C. TS-AA-AMPS/APP exhibits reversible swelling ability, with the swelling level not being reduced compared to the initial after 5 swelling-drying cycles at 60 °C, and water absorption reaches swelling equilibrium after about 270 min. Additionally, TGA thermogravimetric analysis results showed an improvement in the thermal stability of TS-AA-AMPS/APP compared to the pure polymer. These results show that the TS-AA-AMPS/APP polymer with excellent swelling properties, low production cost, and environmentally friendly has the potential for practical applications in agriculture, gardening, and water retention materials.