How to reveal latent degradation of coatings provoked by UV-light |
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Authors: | J-F Larché P-O Bussière J-L Gardette |
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Institution: | a Clermont Université, Université Blaise Pascal, Laboratoire de Photochimie Moléculaire et Macromoléculaire, BP 10448, F-63000 Clermont-Ferrand, France b CNRS, UMR 6505, LPMM, F-63173 Aubière, France c Clermont Université, Ecole Nationale Supérieure de Chimie, Laboratoire de Photochimie Moléculaire et Macromoléculaire, BP 10448, F-63000 Clermont-Ferrand, France d PSA-Peugeot-Citroën, Direction Technique et Industrielle, Route de Gisy, 78140 Velizy Villacoublay, France |
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Abstract: | This paper deals with predictions of the service life of the two main technologies used for automotive clearcoats: acrylic-melamine and acrylic-urethane. This work demonstrates that the UV-light irradiation leads to chain scissions and crosslinking for the unstabilised and stabilised formulations. Mechanisms are proposed to explain the dramatic increase in the values of the mechanical properties for the two technologies as a function of the ageing time. For a determined critical value of the mechanical properties, water acts to reveal the latent damage by leading to the formation of cracks. Moreover, when the polymer reaches a certain level of network densification due to UV-light irradiation, the system cannot accept the stress induced by the water inflation/deflation and cracks will occur. Other solvents were also tested to understand the effects of polarity on the formation of the cracks. |
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Keywords: | Photo-ageing Water Clearcoat Cracking Acrylic Urethane Melamine |
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