R Rafeie - Department of Polymer Engineering and Color Technology, Amirkabir University of Technology, Tehran, Iran
M Mohseni - Department of Polymer Engineering and Color Technology, Amirkabir University of Technology, Tehran, Iran
M Mahdavi - Department of Polymer Engineering and Color Technology, Amirkabir University of Technology, Tehran, Iran
H Yari - Department of surface coating and corrosion, Institute for color science and technology, Tehran, Iran

Environmental factors can deteriorate the automotive coatings significantly. Such as UV radiations, humidity, hot-cold shock and destructive chemical compounds. Furthermore, some natural materials such as bird droppings and tree gums have potential to degrade the coatings as well. The present work aims to study the mechanism of degradation for twoautomotive refinish coating (PU based) systems exposed to two types of biological materials, i.e. Arabic gum and the simulated bird dropping, pancreatin. To reach this goal, effects of these biological materials on surface properties and appearance were studied using different techniques including digital camera, FT-IR spectroscopy, optical microscope and gloss measurements. In addition, thermo-mechanical behavior of coatings was examined by DMTA. It was found that cross-linking had a crucial role on the biological resistance of clearcoat. The higher cross-linking enhanced biological resistance.

Refinish clearcoat, Pancreatin, Arabic gum, cross-linking, Biological degradation