Modified arabinoxylan-based films: Grafting of functional acrylates by oxygen plasma and electron beam irradiation

Abstract

Oxygen plasma and electron beam irradiation were used to graft hydrophobic substances and by this way, to reduce water vapor permeability (WVP) of arabinoxylan-based (AX-based) films. Stearyl acrylate (SA) and stearyl methacrylate (SM) were used as reactive monomers. The homogeneous AX-based films, which were pre-activated by oxygen plasma and impregnated with a solution of SA before being exposed to an electron beam (EB), had contact angles that increased from 71° (untreated films) to 122° (treated films). A decrease of about 24% in the WVP was obtained and new chemical groupings were observed on the FTIR spectra of these films. Acrylate monomers were also dispersed into the arabinoxylan network. The copolymerization started by direct EB exposure (B treatment) or pre-activation with electron beam, impregnation with additional monomer and second EB irradiation (C treatment). The barrier efficiency against water vapor transfer was about 50% for SA-emulsified film modified by C treatment. These results were explained by a denser film structure and a better grafting level generated by higher monomer concentration in the film. The SA monomer, which was a linear molecule and more reactive than the SM monomer, was grafted onto arabinoxylan polymeric chains.