Synthesis and Characterization of Chemically-Modified Cassava Starch Grafted with Poly(2-Ethylhexyl Acrylate) for Blending with Poly(Lactic Acid)

Abstract

© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Native cassava starch (CS) is chemically modified by grafting with 2-ethylhexyl acrylate (EHA) monomer to make it more hydrophobic for improved blending with poly(lactic acid) (PLA). Grafting is carried out using CS:EHA weight ratios of 2:1, 1:1, 1:2, and 1:3 in a methanol-water solvent mixture at 45 °C for 48 h. L-Ascorbic acid and hydrogen peroxide are used as the redox initiating system. Following purification, the poly(2-ethylhexyl acrylate)-grafted starch, starch-g-PEHA, is obtained either as a finely divided powder or as a slightly tacky solid with % grafting values in the range of 13–26% by weight. The main objective of this chemical modification is to improve the interfacial adhesion between the starch particles and the PLA matrix through the hydrophobic PLA-PEHA interactions. PLA/starch-g-PEHA blends are prepared in the form of solution-cast films with weight ratios ranging from 100/0 to 60/40. Tensile testing of the films shows a marked increase in extensibility and toughness up to a loading of 10% starch-g-PEHA above which the properties deteriorated rapidly due to starch particle aggregation. Thus, for potential use as biodegradable film packaging, the best properties are obtained for the PLA/starch-g-PEHA 90/10 blend.