title: The effect of environmental degradation on the characterisation of automotive clear coats by infrared spectroscopy.
abstract: This paper presents a study into the chemical changes occurring within automotive clear coats as a result of environmental weathering, and their potential effect upon the characterisation of samples using infrared spectroscopy combined with chemometric modelling. Testing of three samples, collected from separate vehicles, exposed to the outside environment revealed no changes in model predictions over a 175 day period; however, incorrect predictions were observed following 435 days of exposure. Inspection of the corresponding infrared spectra revealed that these changes were likely due to the hydrolysis and photodegradation of polymer chains present in the clear coat, which were not observed in samples stored away from the outside environment over a one-year period. Analysis of previously weathered samples using synchrotron infrared microscopy found these changes occurred in a top-down fashion rather than within the bulk of the clear coat. This indicates that although weathering may affect the surface characterisation of clear coats over time, the targeting of deeper portions of the clear coat layer may still provide useful information as to the identity of the vehicle.
authors.affiliation: Nanochemistry Research Institute, GPO Box U1987, Perth, Western Australia 6845, Australia; Department of Chemistry, Curtin University, GPO Box U1987, Perth, Western Australia 6845, Australia.
authors.forename: Karin J
authors.initials: KJ
authors.lastname: van der Pal
authors.affiliation: Nanochemistry Research Institute, GPO Box U1987, Perth, Western Australia 6845, Australia; Department of Chemistry, Curtin University, GPO Box U1987, Perth, Western Australia 6845, Australia.
authors.forename: Georgina
authors.initials: G
authors.lastname: Sauzier
authors.affiliation: Nanochemistry Research Institute, GPO Box U1987, Perth, Western Australia 6845, Australia; Department of Chemistry, Curtin University, GPO Box U1987, Perth, Western Australia 6845, Australia.
authors.forename: Mark
authors.initials: M
authors.lastname: Maric
authors.affiliation: Department of Chemistry, Curtin University, GPO Box U1987, Perth, Western Australia 6845, Australia.
authors.forename: Wilhelm
authors.initials: W
authors.lastname: van Bronswijk
authors.affiliation: ChemCentre, PO Box 1250, Bentley Delivery Centre, Western Australia 6983, Australia.
authors.forename: Kari
authors.initials: K
authors.lastname: Pitts
authors.affiliation: Nanochemistry Research Institute, GPO Box U1987, Perth, Western Australia 6845, Australia; Department of Chemistry, Curtin University, GPO Box U1987, Perth, Western Australia 6845, Australia. Electronic address: S.Lewis@curtin.edu.au.
authors.forename: Simon W
authors.initials: SW
authors.lastname: Lewis
keywords: Automotive clear coat; Environmental degradation; Forensic science; IR spectroscopy