Composite materials of thermoplastic starch and fibers from the ethanol–water fractionation of bagasse

The aim of this study was to evaluate the potential of the fibrous material obtained from ethanol–water fractionation of bagasse as reinforcement of thermoplastic starches in order to improve their mechanical properties. The composites were elaborated using matrices of corn and cassava starches plasticized with 30 wt% glycerin. The mixtures (0, 5, 10 and 15 wt% bagasse fiber) were elaborated in a rheometer at 150 °C. The mixtures obtained were pressed on a hot plate press at 155 °C. The test specimens were obtained according to ASTM D638. Tensile tests, moisture absorption tests for 24 days (20–23 °C and 53% RH, ASTM E104), and dynamic-mechanical analyses (DMA) in tensile mode were carried out. Images by scanning electron microscopy (SEM) and X-ray diffraction were obtained. Fibers (10 wt% bagasse fiber) increased tensile strength by 44% and 47% compared to corn and cassava starches, respectively. The reinforcement (15 wt% bagasse fiber) increased more than fourfold the elastic modulus on starch matrices. The storage modulus at 30 °C (E30 °C′) increased as the bagasse fiber content increased, following the trend of tensile elastic modulus. The results indicate that these fibers have potential applications in the development of biodegradable composite materials.

Research highlights
► Fibers from the ethanol–water fractionation of bagasse have applications in biodegradable composite.
► The reinforcement of thermoplastic starches increased their strength and stiffness.
► The reinforcement with 15 wt% bagasse fiber quadrupled the elastic modulus of thermoplastic starches.
► The content of bagasse fibers affected the rate of moisture absorption.
► Smaller contents of bagasse fibers would be more appropriate for the dispersion of fibers in the matrix.