The Influence of DC discharge afterglow treatment on poly(ethylene terephthalate) surface properties

Abstract

In this work, we investigated the effects of gas flow rate, processing time and distance from plasma region on the modification of poly(ethylene terephthalate) (PET) films under conditions of afterglows of atmospheric pressure discharges in air and argon. Both original and plasma-modified surfaces were studied by FTIR, AFM, XPS and contact angle measurements. It was found that the remote treatment 1) results in increasing PET surface hydrophilicity, but in decreasing contact angles (by ∼ 3 times compared with the original sample); 2) leads to the destruction of ester groups as well as to the formation of new C-O groups; and 3) causes an increase in average surface roughness (from 1.4 nm for untreated PET to 2.2 and 4.4 nm for PET modified by air and argon afterglows, respectively). The set of experimental techniques together with plasma modeling provided the information on plasma emission properties, gas temperature, reduced electric field strength, discharge geometry and densities of plasma active species. Based on these data, the modification mechanism involving UV photons and O atoms was proposed.