Modified rice husk as component in recyclable and biodegradable epoxy thermosets

Abstract

Rice husk (RH), an abundant agricultural residue, was successfully chemically modified and used as a component in reprocessable and biodegradable epoxy thermosets. First, RH was subjected to alkaline treatment to increase the cellulose content followed by succinylation and curing with trimethylolpropane triglycidyl ether to form the thermoset films. The chemical structure of the different intermediates and thermosets was confirmed by Fourier transform infrared spectroscopy. The developed thermoset films had good solvent resistance against common organic solvents and good thermal stability as measured by thermogravimetry with peak temperatures of 347–387 ℃, char residues of 16–20% and limiting oxygen index values of 24–26%, respectively. The films could be thermally reprocessed by hot-pressing with excellent recovery of the mechanical properties (92–96% recovery of tensile stress). Furthermore, 80–84% biodegradation during 150 days under mesophilic home composting conditions was demonstrated by cumulative CO2 evolution. These results indicate promising potential for the developed RHs thermosets as replacements for petroleum-based plastics in e.g. packaging and agricultural applications.