Reflection Infrared Spectral Signatures of Vehicle Paints

Author: Caroline O'Driscoll

O'Driscoll, Caroline, 2019 Reflection Infrared Spectral Signatures of Vehicle Paints, Flinders University, College of Science and Engineering

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Infrared spectroscopy has long been used as a technique for the identification and classification of vehicle paints. Vibrational spectroscopy allows for identification of the chemical components of paint formulations, particularly the organic binders. For forensic analyses, this is of particular importance as it allows for the comparison and exclusion of paint evidence. For the defence sector and law enforcement, measuring the spectral signature of a vehicle paint is a useful capability for comparison and identification of unknown vehicles. For such applications reflection is the only viable method of spectral acquisition as there is a requirement for passive sampling.

Reflection infrared micro-spectroscopy could allow for non-destructive analysis of paint samples with the potential for further development to stand-off techniques for in-situ measurements – an advantage over the destructive transmission techniques which require dissection of the paint layers prior to analysis. However, the nature of layered samples and reflection techniques means a number of photo-physical phenomena can complicate and ‘contaminate’ the original signature of the paint, distorting the appearance of reflection spectra.

This dissertation describes the reflection system for multi-layered, absorbing and reflecting paint samples and then outlines a number of the photo-physical phenomena present in reflection infrared micro-spectroscopy measurements. The dissertation then outlines a correction sequence that models and corrects for the contaminations that most strongly affect the spectra of vehicle paints. While the correction sequence is successful for a number of paints analysed, there are some residual anomalies which show that describing the effects present in reflection measurements is a crucial step to the further understanding and development of reflection infrared spectroscopy techniques.

Keywords: Infrared spectroscopy, spectroscopy, forensic chemistry, vehicle paint, photo-physical phenomena, physical chemistry, spectroscopy, reflection effects, reflection spectra, infrared micro-spectroscopy, infrared microscopy, paint, reflection, infrared

Subject: Forensic & Analytical Chemistry thesis

Thesis type: Doctor of Philosophy
Completed: 2019
School: College of Science and Engineering
Supervisor: Paul Kirkbride