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Infrared and Raman spectroscopy of automotive paints for forensic identification of natural weathering†
Analytical Methods ( IF 3.1 ) Pub Date : 2018-01-29 00:00:00 , DOI: 10.1039/c7ay02684f
Andrey Giovanni Gomes de Oliveira 1, 2, 3 , Ewelina Wiercigroch 4, 5, 6, 7 , Juliano de Andrade Gomes 3, 8, 9, 10 , Kamilla Malek 4, 5, 6, 7
Affiliation  

Natural weathering of automotive paint modifies the original chemical composition of this multi-layered material. As a result, the reliability of spectral forensic analysis decreases depending on the degradation level of the sample. In this work, impounded vehicles with different colors (white, red and silver) containing a similar clearcoat composition (acrylic urethane styrene) were analyzed by Infrared and Raman spectroscopy. After being seized by the Brazilian Police, these vehicles were left exposed to the outdoor environment for up to seven years. Paint samples were extracted from two vehicle panels of different degradation levels for chemical comparison. For rapid and full determination of changes in the composition of paint layers, we collected in situ IR and Raman spectra from the surface of the paint chips. We also recorded Raman images of cross-sections to show an effect of alternation in stratigraphy and the composition of paint layers on the routinely used in situ analysis. Both modes of IR and Raman measurements are suitable to reveal degradation processes of vehicle paints and their analysis revealed that the deterioration process is strongly dependent on several factors such as the exposure time to natural weathering, the color of the vehicle and the degradation degree of the protective layer – clearcoat. This case report not only describes valuable data of natural weathering of original manufacturer paints but also shows the importance of proper sample collection and analysis of different vehicle panels that forensic scientists shall take into consideration at the crime scene.

中文翻译:

汽车涂料的红外和拉曼光谱法,用于法医鉴定自然风化

汽车漆的自然风化改变了这种多层材料的原始化学成分。结果,光谱法医学分析的可靠性根据样品的降解水平而降低。在这项工作中,通过红外和拉曼光谱法分析了包含相似清漆成分(丙烯酸氨基甲酸酯苯乙烯)的具有不同颜色(白色,红色和银色)的被扣留车辆。这些车辆在被巴西警察扣押后,被暴露在室外环境中长达七年之久。从两个具有不同降解水平的汽车面板上提取油漆样品,以进行化学比较。为了快速全面地确定涂料层组成的变化,我们就地收集油漆碎片表面的红外和拉曼光谱。我们还记录了横截面的拉曼图像,以显示地层交替和漆层组成对常规现场使用的影响分析。红外和拉曼测量的两种模式都适合揭示汽车涂料的降解过程,而其分析表明,降解过程很大程度上取决于几个因素,例如自然风化的暴露时间,车辆的颜色以及涂料的降解程度。保护层–清漆。该案例报告不仅描述了原始制造商油漆的自然风化的宝贵数据,而且还表明了法医在犯罪现场应适当考虑的样本采集和分析不同车板的重要性。
更新日期:2018-01-29
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