Chemical reactivity between teflon surfaces subjected to argon plasma treatment and atmospheric oxygen

Abstract

Surface modification of two Teflon polymers, perfluoroalkoxyl resin (PFA) and polytetrafluoroethylene (PTFE), induced by argon plasma treatment using a 13.56 MHz radio frequency generator and subsequent air exposure has been investigated by x-ray photoelectron spectroscopy (XPS) and electron spin resonance (ESR). Chemical species assigned to peroxy radicals (two types) were generated along with the development of a heavily cross-linked or branched structure at the surface region. The dependence of the XPS and ESR spectra on the time and power of the plasma treatment indicated that the formation of the peroxy radicals was parallel to the incorporation of oxygen at the surfaces. The analysis of the XPS and ESR spectra suggested that the peroxy radicals consist of two types of oxygens bonded to a carbon in the multiply cross-linked structures, and to a carbon arising from the scission of the main chain in the polymer, respectively. The former is considered to be located on or near the surfaces, and the latter in the more deep region. The relative contribution of the two peroxy radicals for PFA differed from that for PTFE, while the surface chemical structures for both polymer were almost the same. The oxygen of the peroxy radicals was eliminated by UV (253.7 nm) irradiation in vacuum. For PFA UV-irradiated in air for a certain time the chain scission peroxy radical was found to be produced without a change in the surface chemical structure. The effect of the argon plasma treatment on Teflon surfaces is considerably different from that of oxygen plasma treatment [1].