Oxyfluorination-Controlled Variations in the Wettability of Polymer Film Surfaces

Abstract

The modification of polymer surfaces with fluorine–oxygen mixtures has been studied with wide variations in the process duration and percentage ratio between these gases in the mixture. The modification increases the hydrophilicity of the polymer surface, and, the higher the fraction of oxygen in the gas mixture and the longer the oxyfluorination time, the greater the increase in the hydrophilicity. The physicochemical properties of polymers, such as wettability, surface energy, and adhesion, may be regulated within rather wide ranges by varying oxyfluorination conditions. For example, in the case of polyolefins, the water contact angle changes from 78°‒87° for initial polymers to 49°‒60° for modified ones. For heterochain polymers, this range may be even wider and is for, e.g., poly(ethylene terephthalate) from 67° to 4°; i.e. almost complete water spreading over the polymer surface is achieved. The contribution of the polymer surface roughness to the observed values of the water contact angle has been determined before and after the chemical treatment. It has been shown that an increase in the wettability of the polymer surface as a result of oxyfluorination may be used to obtain polymer films capable of altering their wettability under subsequent tensile deformation.