Hydrophobic Properties of Ethylene-Vinyl Alcohol Copolymer Treated with Plasma Source Ion Implantation

The industrial use of ethylene-vinyl alcohol copolymer (EVOH) film is limited because it is easily degraded by moisture. The plasma source ion implantation (PSII) technique with CF₄ or CH₄ gas was used for the EVOH film to improve the surface hydrophobic properties. Variables examined in implantation were ion energy (0-10 keV), treatment time (5 s-5 min), and ion species. The hydrophobic properties of EVOH films were greatly enhanced after a CF₄ PSII treatment, as evidenced by an increased contact angle from 66° to above 100° at -5 keV, and remained relatively unchanged during the period of 28 days. X-ray photoelectron spectroscopy, atomic force microscopy, and O₂ permeability were used to characterize the surface properties of EVOH films treated with PSII. The improved hydrophobic properties were closely related to the formation of fluorine-containing functional groups such as CF, CF₂, and CF₃ on the modified surface. The percentage distribution of carbon functional groups supports the role of CF₂ and CF₃ groups in surface modification.