Effects of Atmospheric Plasma Treatment on the Surface Properties of Wood-Plastic Composites

Abstract

Wood-plastic composites are a group of materials with potential to penetrate markets currently dominated by plastic or wood products. The surface properties of wood-plastic composite materials have been found to be similar to those of polyolefin materials, thereby presenting a challenge to the use of adhesive joining methods. Plasma chemistry can be performed to improve the adhesive properties of polyolefin materials. In this research, the effect of atmospheric plasma treatment on polypropylene and spruce (Picea abies) wood-plastic composite surfaces is investigated by contact angle measurement with sessile drop method and tensile strength tests of glued samples. The plasma treatment is performed on extruded WPC profiles. Confocal Raman microscopy and scanning electron microscopy are used for analysis of the material surface. The results show an increase in the contact angle of plasma treated WPC materials and an improvement in the tensile strength of glued samples following plasma treatment. Observation of the Raman spectrum indicates an increase in polar groups after plasma treatment. Scanning electron microscopy shows changes in the surface of the treated samples, which can be seen as increased porosity, possibly due to etching as a result of the plasma treatment. It is concluded that atmospheric plasma treatment for adhesion improvement of WPC materials can therefore be applied successfully, although it has a mechanical effect on the surface of the material.