Biocomposites derived from esterified rice starch reinforced with microcellulose fiber

Bio-based composites have garnered significant attention as environmentally friendly alternatives to conventional materials. Therefore, novel bio-based composites were developed by reinforcing microcellulose fiber (MCF) from rice straw in esterified rice starch. Two native rice starches, i.e. Mao-Noh (MN) and Majanu (MJ), were modified using a dry method with maleic anhydride (MA) as an esterifying agent, resulting in MA-modified starches, namely MAMN and MAMJ. Subsequently, MAMN and MAMJ were blended with varying amounts of microcellulose fiber. It was found that the biocomposite films from both esterified rice starches exhibited translucency. The moisture content, water vapor transmission, and water solubility of the biocomposite films decreased with increasing amounts of MCF. Tensile tests on the biocomposite films revealed that the tensile strength and modulus values tended to increase with higher MCF content. The maximum tensile strength and Young’s modulus values for biocomposite films with 10% (by weight) of MCF was found. However, when the MCF content was increased to 15% (by weight), the strength and Young’s modulus decreased. This confirmed the effective dispersion of MCF in the esterified starch and a strong interface interaction between cellulose fibers and modified starch, as revealed by SEM analysis. Furthermore, upon adding MCF to the esterified starch, the intensity of positions corresponding to the crystalline structure of ES and MCF was observed, correlating with the MCF content.