An evaluation of an automotive clear coat performance exposed to bird droppings under different testing approaches
ABSTRACT 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: A unified platoon-based mathematical formulation called PAMSCOD is presented to perform arterial (network) traffic signal control while considering multiple travel modes in a vehicle-to-infrastructure communications environment. First, a headway-based platoon recognition algorithm is developed to identify pseudo-platoons given probe vehicles’ online information. It is assumed that passenger vehicles constitute a significant majority of the vehicles in the network. This algorithm identifies existing queues and significant platoons approaching each intersection. Second, a mixed-integer linear program (MILP) is solved to determine future optimal signal plans based on the current traffic controller status, online platoon data and priority requests from special vehicles, such as transit buses. Deviating from the traditional common network cycle length, PAMSCOD aims to provide multi-modal dynamical progression (MDP) on the arterial based on the probe information. Microscopic simulation using VISSIM shows that PAMSCOD can easily handle two common traffic modes, transit buses and automobiles, and significantly reduce delays for both modes under both non-saturated and oversaturated traffic conditions as compared to traditional state-of-practice coordinated-actuated signal control with timings optimized by SYNCHRO.Procedia - Social and Behavioral Sciences 01/2011; 17:462-489.
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ABSTRACT: Nanostructured hybrid clearcoats were produced using sol–gel based organic/inorganic precursors. To this end, clearcoats containing mixtures of a network former (tetraethyl ortosilicate; TEOS) and a network modifier (methacryloxy propyltrimethoxysilane; MEMO) and their hydrolyzed forms were prepared. Scanning electron microscope and atomic force microscope were utilized in order to investigate the morphology of different sol–gel prepared films. The mechanical properties of the bulk and surface of the clearcoats were studied by dynamic mechanical thermal analysis and nanoindentation techniques. The scratch resistance of the hybrid clearcoats was also studied by a laboratory carwash simulator. Decrease in glass transition temperature (Tg), cross-linking density, hardness and elastic modulus were seen for the clearcoat composed of hydrolyzed network modifier combined with hydrolyzed and non-hydrolyzed network former. However, a reverse effect was seen when the hydrolyzed TEOS and non-hydrolyzed MEMO was used. No improvement was observed using hydrolyzed MEMO in the clearcoat composition. Generally, results revealed improved mechanical properties of the clearcoat when the hydrolyzed network former was used together with non-hydrolyzed MEMO. Greater phase separation and silica cluster formation were seen for the clearcoats loaded with hydrolyzed MEMO compared with hydrolyzed TEOS.Journal of Sol-Gel Science and Technology 10/2012; 64(1). · 1.55 Impact Factor
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ABSTRACT: This work reports preparation of acrylic/melamine based clearcoats containing various loads of a reactive polysiloxane additive. The additive was incorporated into the clearcoat formulations up to 8 wt% to enhance its resistance against bird droppings. Contact angle measurements, ATR spectroscopy, energy dispersive X-ray analysis, appearance measurements together with different microscopic techniques were utilized to reveal the effects of additive on the properties of the coating prior and after exposure to pancreatin, the synthetic equivalent of natural bird droppings. Appearance measurements, as well as optical microscope images obviously indicated that the additive improved the clearcoats resistance against pancreatin. Results revealed that surface free energy of the films was reduced in the presence of additive. It was also found that at high concentrations of additive, a significant part of it remained in the bulk, forming a second phase. This resulted in a lack of sufficient reactive groups and lead to an under-cure state at the clearcoat surface.Progress in Organic Coatings 11/2012; 75(3):170–177. · 2.30 Impact Factor