Plasma treatment of wood-polymer composites: A comparison of three different discharge types and their effect on surface properties

Abstract

Three different discharge types, based on the principle of a dielectric barrier discharge at atmospheric pressure, were investigated with regard to their influence on the adhesion properties of a series of wood-polymer composites. Wood flour (Picea abies L.) filled polypropylene and various proportions of polyethylene were manufactured either through extrusion or injection molding. The composites' surfaces were activated by coplanar surface barrier discharge, remote plasma, and direct dielectric barrier discharge. The changes in wettability due to the pretreatment were investigated by contact angle measurement using the sessile drop method and calculation of surface free energy (SFE). It could be shown that wettability was improved by all three types of discharge, the contact angle decreased and the SFE correspondingly increased. X-ray photoelectron spectroscopy revealed an increase in the O/C ratio at the material's surface. An improvement in coating adhesion was demonstrated by crosscut and pulloff tests. (c) 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43376.