Adhesion behaviour of polypropylenes after flame treatment determined by XPS(ESCA) spectral analysis

Abstract

In a number of automotive applications of polypropylene (PP) good paint adhesion is essential. For industrial applications, the initially poor adhesion properties of PP compounds are often improved by flame treatment, resulting in good paint adhesion on the PP parts. For control purposes, intensive and time consuming paint tests are required. To relate adhesion behaviour with the parameters used in the flame treatment modification, several methods are applied such as simple surface tension tests with inks (wetting tests), contact angle measurements and standard XPS(ESCA) measurements. Unfortunately a good correlation is rarely obtained between these tests and the desired adhesion behaviour under rigid test conditions. Good wetting, for example, is necessary, but is no guarantee for good adhesion. In this paper results are presented on the characterisation of flame treated PP compounds by XPS, as well as the predictive information obtained from the XPS study concerning the paint adhesion behaviour of the modified PP surfaces.