Plasma treatment of PET and acrylic coating surfaces - I. In situ XPS measurements

The surface modification of poly(ethylene terephthalate) (PET) and UV-cured tripropyleneelycol diacrylate (acrylic) films induced by remote N-2 and Ar microwave plasmas (2.45 GHz) was compared by in-situ! XPS measurements. Bo th N-2 and Ar plasma treatments led to destruction of the initial oxygen-co ntaining groups. The destruction of ester groups was much faster fur the ac rylic than for the PET film, and the destruction of ether groups was much f aster than that of ester groups within the acrylic Blm. Among the plasma Ea ses, N-2 was more effective than Ar in the cast: of PET, but their differen ce was negligible in the case of the acrylic film. The higher stability of thc PET surface was attributed to the presence of a rigid aromatic backbone , which protected the ester groups from plasma UV irradiation and stabilize d the free radicals. The lower stability of the acrylic film was associated with the presence of weak ether groups. New functional groups were created , attributed to carbonyl in the case of Ar, and carbonyl/amide and amine in the case of N-2 plasma treatments. The Formation of these new Functional g roups was very small compared with the loss of ether and eater groups, sugg esting that the destruction of these oxygen-containing groups proceeded mai nly through elimination of the entire groups.