Examination of Firearms Review: 2007 to 2010 - Interpol

of the 33 samples were able to be differentiated with the authors concluding that
SEM/EDS offered the best discrimination capability.
The two remaining papers discussed clearcoat refinish systems and were
published by members of the Akzo Nobel Car Refinish group in the Netherlands.
The first paper discussed the interaction of the basecoat and clearcoats within a
refinish system and made several observations based on testing done using
FTIR and SEM/EDS.[149] The authors describe evidence of strong interaction
between the clearcoat with the basecoat. They suggest that the data revealed
isocyanurate crosslinker in polyurethane clearcoats penetrated to a large extent
into the basecoat, even to the point of being detected at the basecoat/substrate
interface. The authors discussed the improved mechanical properties of the
basecoat observed in this system as attributable to an in-situ crosslinking of the
basecoat binder, where the Tg and crosslink density of the basecoat increased.
When the interaction of the basecoat to a UV-clearcoat was studied, the
interaction appeared to be much less between the two layers due to the high
cure rate. The authors state that the curing process used prevented diffusion of
the crosslinker into the basecoat. Lastly, they noted that stabilizers such as
hindered amine light stabilizers (HALs) and UVAs also diffused into the basecoat
thereby providing better weathering protection.
The second paper, authored by some of the members of this same research
group, reported on the development of a waterborne UVA curable clearcoat
refinish, concluding in part that the coating under development demonstrated
good gloss retention even after two years of exposure in environmental
conditions common to Florida.[150]
10. Spectroscopic Methods
Scientists at the Leibniz Institute of Surface Modification published work on the
use of near infrared spectroscopy to monitor polymer coat curing via UV light and
the resulting coating thickness in-line during production. The precision of the
measurement was determined to be less than 1 micrometer at best. [151]
Comparative studies of small samples of automotive coatings using visible
microspectrometry were also reported on by researchers in Poland. [152;153]
In another study, paint cross sections were characterized by Joseph, et al. using
mapping and linear imaging capabilities with attenuated total reflectance (ATR)
microscopy.[154] In this work, two different FTIR microscopy systems were
studied: one with a conventional DTGS detector; and, one with FTIR mapping
capabilities using a novel integrated system with raster scanning in ATR mode.
The latter system was found to provide a better signal-to-noise ratio with shorter
acquisition time when compared to the conventional system. The authors state
that this newly developed system has features of particular benefit to the
identification and spatial locality of thin organic layers within a paint cross section
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