Structural and functional characterization of rice starch-based superabsorbent polymer materials

Abstract

The aim of this work was to develop new, rice starch-based superabsorbent materials (SPAMs), degradable and eco-friendly. Indica rice starch-based SPAM had the best water absorption capacity (439 g water/g) with a relatively high amylose content (23.6%) that may enhance the interaction and structural strength of polymer chains through the formation of hydrogen-bond. Meanwhile, the rigidity and structure of branched chain of amylopectin can improve the water holding capacity, thus the glutinous rice starch (75.1% amylopectin content)-based SPAM also had good water absorption characteristics (399 g water/g). Regeneration rate has a certain correlation with water absorption rate, therefore, the indica rice starch-based SPAMs only lost 30% of their reswelling capacity when reused three consecutive times. On the other hand, the effects of 4 cations on SPAM water absorption were according the following order: K+ < Na+ < Ca2+ < Al3+. The formation of graft copolymer of sodium acrylate and rice starch was confirmed by Fourier Transform Infra-Red spectroscopy and X-Ray diffraction. The microstructure of SPAM showed a porous arrangement as observed by scanning electron microscopy. Finally, when present within the storage environment, the indica rice starch-based SPAM was effective in preventing rice grain moisture accumulation.