Contact angle analysis of corona treated polypropylene films

Abstract

In this work, the effect of the surface modification of polypropylene films via corona treatment was investigated. Polypropylene films were treated with negative and positive corona discharge, at atmospheric pressure, for 5 minutes, at two different temperatures – 25 °C and 90 °C. The changes in the surface free energy were investigated by means of contact angle measurements. The Bickerman's method was applied to determine the polar and dispersion components of the polymer surface free energy, on the basis of the theory of Owens, Wendt, Kaelble and Uy. Atomic force microscopy was used to analyze the polymer surface morphology changes of the films with temperature. According to the findings, in all cases the corona treatment increases the surface free energy of polypropylene films and its polar part, in comparison with the untreated samples. The effects of negative and positive corona polarities display some specific features which could be associated with different charged group introduced onto the film surface during the corona treatment. The total final effect depends on the simultaneous action of the two competing factors – temperature and corona polarity. The most pronounced effect was observed for high temperature negative corona treatment.