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INFRARED AND RAMAN SPECTROSCOPY OF AUTOMOTIVE PAINTS FOR FORENSIC IDENTIFICATION OF NATURAL WEATHERING

Abstract

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 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 outdoor environment up to seven years. Paint samples were extracted from two vehicle panels of different degradation level for chemical comparison. For rapid and full determination of changes in composition of paint layers, we collected in situ IR and Raman spectra from the surface of the paint chips. As well we recorded Raman images of cross-sections to show an effect of alternation in stratigraphy and 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 exposure time to natural weathering, the color of the vehicle and 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 a proper sample collection and an analysis of different vehicle panels that forensic scientist shall take into consideration at the crime scene.

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Publication details

The article was received on 20 Nov 2017, accepted on 27 Jan 2018 and first published on 29 Jan 2018


Article type: Paper
DOI: 10.1039/C7AY02684F
Citation: Anal. Methods, 2018, Accepted Manuscript
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    INFRARED AND RAMAN SPECTROSCOPY OF AUTOMOTIVE PAINTS FOR FORENSIC IDENTIFICATION OF NATURAL WEATHERING

    A. G. Gomes de Oliveira, E. Wiercigroch, J. A. Gomes and K. Malek, Anal. Methods, 2018, Accepted Manuscript , DOI: 10.1039/C7AY02684F

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