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Influence of polymer additives in polypropylene on coating adhesion

: Weber, Katharina; Keuerleber, Markus; Wegmann, Volker

Hilt, M. ; Federation of Associations of Technicians in the Paint, Varnish, Enamel, and Printing-Ink Industries of Continental Europe -FATIPEC-; The Oil & Colour Chemists' Association -OCCA-:
ETCC 2018, European Technical Coatings Congress. Book of Abstracts : 26-29 June 2018, Amsterdam, The Netherlands
Amsterdam, 2018
25 Folien
European Technical Coatings Congress (ETCC) <4, 2018, Amsterdam>
Conference Paper
Fraunhofer IPA ()
Polypropylen (PP); Polymer; Lackiertechnik; Substrat; Beschichten

Polypropylene-based polymers gain in importance for exterior applications. When it comes to high quality applications, e.g. for the automotive sector, the plastic parts have to be coated. As a result of the required steam jet test (DIN EN ISO 16925:2014-06) in connection with a climatic change test, an increase of adhesion failure is observed in quality tests. It is anticipated that polymer additives have a significant influence on the coating adhesion because of their migration to the substrate surface. However, systematic investigations of this effect are not yet publically available.
We therefore report a detailed study on early indicators for a weakening of the coating adhesion due to the type and critical amount of additives used in the PP-substrate. An analytical approach for the detection and the determination of the surface load of polymer additives such as stabilizers, flow additives and release agents is presented. The aim is to derive knowledge of the critical amount of additive migration to the surface for different additive types. Furthermore, we address the question of how different cleaning and activation processes can reduce the additive coverage on the PP-substrate and thus improve the adhesion. Surface cleaning and pretreatment processes such as dry ice snow cleaning, powerwash, flaming and plasma activation will be compared systematically.
The results to date indicate that the increase of the release agent is most critical for both the coating adhesion and the overall appearance of the coating due to wetting problems of the base coat. Analytical evidence of the release agent migration up to the primer surface was found via infrared spectroscopy. An analytical GC-MS method for the detection of different additive components with the perspective for quantitative analysis in combination with solvent rinsing of the PP-surface is presented. All analytical results are linked to the corresponding adhesion tests.