How Are the Properties of Starch-Based Composites Influenced by the Chemical Treatment of BSG?

Abstract

Lignocellulosic fibers from Brewer's spent grain (BSG) represent an ecologically and economically favorable alternative that can act as reinforcing agents for starch-based polymer composites. Biodegradable composites are produced using cassava starch and BSG of the Pilsen (P) and Weiss (W) types, which are subjected to mercerization (BSM), bleaching (BSP) and a combination of those treatments (BSB). By including treated BSGs, homogeneous matrices with starch are produced, without the presence of pores and/or cracks, as evidenced by the scanning electron microscopy (SEM) images. The tensile strength of the composites is improved by up to 80% and Young's modulus by up to 50% with the addition of BSB(P) and BSB(W) fibers, indicating the role of the materials as reinforcement agents. Bleaching and mercerization treatments are efficient in the exposition of hydroxyl groups of cellulose, resulting in higher hydrophilicity and water vapor permeability (WVP) of the composites containing the BSP and BSM fibers. Biodegradable composites incorporating BSG from the brewing industry have promising properties and can be a viable alternative to non-biodegradable polymeric packaging.