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

• Published in: Starch - Stärke 2018-11, Vol.70 (11-12), p.n/a
• Main Authors: Bunkerd, Ratthaphat, Molloy, Robert, Somsunan, Runglawan, Punyodom, Winita, Topham, Paul D., Tighe, Brian J.
• Format: Article
• Language: English
• Subjects: 2‐ethylhexyl acrylate; Ascorbic acid; Biodegradability; Biodegradation; Blending; Cassava; cassava starch; Chemical modification; chemically‐modified starch; Grafting; Hydrogen peroxide; Hydrophobicity; Organic chemistry; Packaging; poly(2‐ethylhexyl acrylate); poly(lactic acid); Polylactic acid; Powder; Purification; Starch; Weight
• ISSN: 0038-9056; 1521-379X
• DOI: 10.1002/star.201800093

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. Native cassava starch is chemically modified by grafting with 2‐ethylhexyl acrylate (EHA) for improved blending with poly(lactic acid) (PLA). This is achieved by the grafted poly(2‐ethylhexyl acrylate) (g‐PEHA) improving the interfacial adhesion between the starch particles and the PLA matrix, as shown in the Figure. Addition of 10% starch‐g‐PEHA to the PLA produces a marked increase in film extensibility and toughness.