An evaluation of an automotive clear coat performance exposed to bird droppings under different testing approaches
Department of Polymer Engineering of Amirkabir University of Technology, P.O. Box 15875-4413, Tehran, IranProgress in Organic Coatings (Impact Factor: 2.36). 10/2009; 66(2):149-160. DOI: 10.1016/j.porgcoat.2009.06.010
In this study, the effects of two types of biological materials, i.e. natural bird droppings and pancreatin, on properties of an automotive acrylic melamine clear coat were studied. In addition, two different testing approaches including pre-aging and post-aging were utilized to investigate the biological resistance. To this end, effects of these biological materials on clear coat surface properties and appearance were investigated by different techniques including digital camera, SEM, AFM, optical microscopy and a gloss meter. In addition the mechanical properties of clear coats were evaluated by micro Vickers measurement and DMTA analysis. For further investigation FTIR analysis was utilized to have a more understanding of the failure mechanism.Results showed that the biological materials have an extremely vital effect on the appearance of the coatings. Decreasing of tg and hardness of the films made by pancreatin and bird droppings were observed and were attributed to the chemical alterations as proved by FTIR analysis. It was also found that the biological degradation occurred on the samples experienced the post-aged testing method was more severe than the samples exposed to pre-aged testing. On the other hands, although bird droppings and pancreatin revealed a same failure mechanism, the effect of the former was more severe. In addition, it has been shown that the enzymatic structure of biological materials is responsible for the catalyzing the hydrolytic degradation of clear coat at neutral pH. Therefore, the biological degradation mechanism may be regarded as an enzymatically induced hydrolytic cleavage.
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ABSTRACT: Biological resistance of coatings can be regarded as one of the main properties in automotive industries. This study aims to investigate the effects of biological materials on the mechanical performance of an automotive clear coat. To this end, two acrylic melamine clear coats containing different melamine cross-linker contents were used. In addition, biological resistance of these clear coats were studied at two different ageing processes including pre-ageing and post-ageing which involve various hot-cold, humid shockings and UV radiation of sunlight. By the aid of optical microscopy, micro Vickers and DMTA analyses, different optical and mechanical properties such as micro hardness, T g, cross-linking density and storage modulus were studied. Results revealed an inverse impact of both biological materials to decrease the clear coats mechanical attributes. In addition, a complicated effect of ageing conditions was observed for both clear coats exposed to these materials. It was shown that the coating having a higher mechanical properties and T g even resulted in a lower biological resistance.Journal of Thermal Analysis and Calorimetry 10/2010; 102(1):13-21. DOI:10.1007/s10973-009-0442-4 · 2.04 Impact Factor
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ABSTRACT: This work aims to study the effect of various natural and artificial biological compounds on an automotive acrylic/melamine clearcoat applied over silver and black basecoats containing pigments. The visual performance of the coating system was evaluated at different aging conditions. To this end, analytical techniques including optical microscopy, scanning electron microscopy, gonio-spectrophotometery, gloss measurement, ATR-FTIR spectroscopy, and DMTA analysis were utilized to investigate the optical and mechanical response of the system upon exposure to the biological materials. Results indicated different effects produced by gums and bird droppings on both silver and black systems at all aging processes. In addition, a more severe effect of biological attacks was observed on the clearcoat samples applied on the black basecoat which had experienced postaging conditions. However, it was found that pancreatin and bird droppings influence the coating systems more severely compared to the natural and synthetic Arabic gums. KeywordsDegradation-Electron microscopy-FTIRJournal of Coatings Technology and Research 11/2010; 7(6):677-689. DOI:10.1007/s11998-010-9254-5 · 1.30 Impact Factor
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ABSTRACT: In this work the effects of natural gum and its simulated compound (Arabic gum) on an acrylic based clear coat applied on different basecoats were studied. The experiments were conducted at various aging processes to simulate the real outdoor conditions by the aid of different analytical techniques including optical microscopy, scanning electron microscopy, ATR-FTIR spectroscopy, DMTA and micro hardness measurements, by which the chemical and mechanical responses of the system were investigated. Results showed that, Arabic and natural gums, due to their sticky nature in the slurry state, can strongly attach to the clear coat surface and perform a significant stress during the drying process. It was shown that, this stress was responsible for the surface cracks produced by gums, indicating a physical degradation mechanism. However, it was revealed that, biological materials could also affect the clear coat chemically. In addition, different surface cracks produced by gums on the clear coat applied on silver and black basecoats were observed and attributed to their surface chemistry and mechanical properties differences. It was shown that different amounts of aluminum flakes existed in the basecoat layers of silver and black system can effectively influence the curing degree of the clear coats applied on the se systems. This leads to different cross-linking density, toughness and surface chemistries. Therefore, different interactions of clear coats and gums, as well as stress distribution and relaxation behaviors of these two systems were found effective in such degradations. Comparison of the mechanical properties and visual effects of gums on clear coats indicated a more severe degradation under the post aging, due to the greater effect of UV light. KeywordsArabic gum-Acrylic/melamine-Cross-linking density-Physical and chemical degradationsJournal of Polymers and the Environment 12/2010; 18(4):545-557. DOI:10.1007/s10924-010-0201-4 · 1.67 Impact Factor
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