Grafted barley husk/poly (vinyl alcohol)/starch composite films: effect of fatty acid chain length and grafted barley husk loading

Abstract

The effect of incorporation of barley husk (BH) grafted with different fatty acids (lauric acid: LBH; palmitic acid: PBH; arachidic acid: ABH) on the physicochemical properties of cross-linked PVA/starch based composite films was studied at different loadings (0.2–2)%. Surface morphology of the films showed that grafted BH dispersed well within the matrix as compared to BH enabling them to provide the greatest reinforcing effect. Composite films containing grafted BH showed higher tensile strength, water resistant properties, thermal stability as well as barrier properties compared to composite films containing BH. At optimum loading (1%), tensile strength of the composite film, containing ABH, was 22.9 MPa, and 23.5% and 31.6% higher than films containing LBH (17.4 MPa) and PBH (18.54 MPa), respectively. Composite films prepared with ABH exhibited the highest values of water contact angle, water vapor, and oxygen permeability among all composite films owing to the incorporation of longest hydrophobic aliphatic chain and provides more hindrance for transmission. The activation energy values of thermal degradation for composite film directly indicate their thermal stability were calculated as 203.37, 222.62 and 366.52 kJ at 1% loading of LBH, PBH, and ABH, respectively. Thus, composite film containing ABH at 1% showed maximum improvement in physicochemical properties followed by composite films containing 1% PBH and LBH. This study provides the alternatives for choosing the most effective composite film, which can be a nature-friendly substitute for non-degradable packaging films and it may help to maintain the circular economy.

Graphical abstract