Effect of ion energy fluence on the topography and wettability of low-density polyethylene exposed to inductively coupled argon plasma

Abstract

The topography and wettability of low-density polyethylene (LDPE) were modified by an inductively coupled Ar plasma. The extent and mechanisms of surface modification were correlated with the ion energy fluence, determined from the ion density measured with a Langmuir probe. The ion energy fluence was varied in the range of (0.3–6.3) × 105 J m−2 by changing the sample distance from the plasma power source. Physical and chemical changes of the plasma-treated LDPE surfaces were evaluated with an atomic force microscope, goniometer and x-ray photoelectron spectrometer. Images of plasma-treated and chemically etched LDPE surfaces provided insight into the mechanisms responsible for the topography changes observed at different length scales in terms of the sample distance (ion energy fluence). A significant effect of the nanoscale roughness on the contact angle of LDPE was observed for high ion energy fluence. The results demonstrate a strong effect of the ion energy fluence on the modification of the surface morphology and wettability of plasma-treated polymer surfaces.