Starch/Cellulose Biocomposites Prepared by High-Shear Homogenization/Compression Molding

Abstract

Rice straw (Oryza sativa Linn.) was subjected to steam treatment in an alkali solution to solubilize hemicelluloses and lignin seal surrounding the cellulose bundles. After consecutive steps of physico-chemical treatment, microfibers were fibrillated using high-shear homogenizer yielding cellulose nanofibers with an average diameter of 40 nm. Isolated cellulose fibers contained 87 %w/w and 61 %w/w holo-cellulose and alpha-cellulose, respectively. For biocomposites formation, a set of experiments was performed to investigate the influence of cellulose nanofibers on mechanical and physical properties of biocomposites formed by compression molding technique. It was found that starch biocomposites made from 50 %w/w cassava starch and 6 %w/w glycerol provided a good result on shape stability with relatively high modulus and tensile strength. Adding 30 %w/w cellulose nanofibers increased tensile strength and modulus of biocomposites up to 36%. Since more energy is required to degrade polymeric glucose chains of cellulose compared with starch and glycerol, thermogravimetric analysis (TGA) showed that adding 30 %w/w fibers enhanced the decomposition temperature of biocomposites for approximately 10 ℃. Scanning electron microscope (SEM) images illustrated alignment of cellulose fibers on the surface of biocomposites.