No abstract

Automotive industries are increasingly interested in learning how to prolong the clearcoat resin lifetime and avoid its thermal, photochemical, and chemical degradation. While chemical degradation by acid rain has been well known since the beginning of the decade and the subject of many studies, chemical degradation of the automotive clearcoat by living organisms (except by bird droppings) is a newly recognized problem. In this work, we report the chemical degradation of the automotive clearcoat caused by oviposition of dragonflies. These insects, very common in Brazil, are attracted by the reflecting surface of cars exposed in the sun and lay eggs on them. We observed that the eggs, at the high temperatures (50 -92°C) of the car surface, can cause damage similar to that of acid rain. In experiments on resin-coated plates, we excluded the involvement of H 2 O 2 -or hydroquinone-derived radicals, of enzyme-catalyzed hydrolysis, and of photosensitizer-induced damage. The damage was very similar, however, to that produced by the sulfur-containing amino acids, cysteine and cystine, at high temperature. Due to this similarity, and because the eggs are rich in sulfur amino acids, we propose a mechanism involving cysteine and cystine residues in the clearcoat damage.