Plasma and ion beam surface treatment of polyethylene

Plasma treatment is a widely used technique for altering the surface properties of polymers. The present paper deals with the surface modification of polyethylene foils in a capacitively coupled industrial r.f. (13.56 MHz) plasma system. The treated surfaces were investigated by scanning electron microscopy and contact angle measurement. Also etch rates of PE for different plasma parameters were measured. Different sample positions, directly upon the cathode and inside the plasma, distinguished by different ion bombardment due to a d.c. self bias of the cathode, were used for processing. This caused different etch rates, surface structures and roughness. Owing to the creation of polar groups on the surface, the surface tension generally increases with the duration of the plasma treatment. Depending on the sample position, different contributions of polar and dispersion components of the surface tension were found. Even short plasma treatments showed good spatial homogeneity of surface tension. This was independent of the spatial distribution of the plasma density. Ion beam treatment generally showed results similar to those with the plasma treatment, although the effect of the ion energy was more significant for ion beam treatment.