PNNL

Abstract

The surface modification of a PET (polyethylene terephthalate) and UV-cured acrylic (tripropyleneglycol diacrylate) film induced by remote N2 and Ar microwave plasmas (2.45 GHz) was compared by in-situ XPS measurements. Both N2 and Ar plasma treatments led to destruction of the initial oxygen groups. The destruction of ester groups was much faster for the acrylic that for the PET, and the destruction of ether groups was much faster than that of ester groups within the acrylic film. Amoung the plasma gases, N2 was much more effective than Ar in the case of PET, but their difference was negligible in the case of acrylic film. The higher stability of PET surface was attributed to the presence of rigid aromatic backbone, which protected the ester groups from plasma UV irradiation and stabilized the free radicals. The lower stability of acrylic film was associated with the presence of weak ether groups. Parallel to these destructive reactions, the surface chemically restructured, becoming more resistant to subsequent plasma attacks. New functional groups were created, attributed to carbonyl in the case of Ar, and carbonly/amide and amine in the case of N2 plasma treatments. The formation of these new functional groups was very small compared to the loss of ether and ester groups, suggesting that the destruction of ether and ester proceeded mainly through elimination of the entire groups.