The examination of UV-absorbers in 2-coat metallic and non-metallic automotive paints

Stoecklein, W.; Fujiwara, Haruo

doi:10.1016/s1355-0306(99)72046-0

Cited by 21 publications

(13 citation statements)

References 4 publications

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“…This could be due to the light absorbers found in clear coats, which typically absorb between 290 and 350 nm. 2 An additional area of positive correlation for PC2 is highlighted on the central objects plot by a dotted box (from 275-285 nm).…”

Section: Resultsmentioning

confidence: 99%

“…By the 1980s, the clear coat system became popular, and in the 1990s, new types of paint binders were introduced as well as paint that contained lower amounts of volatile organic compounds (VOCs) to meet new environmental standards. 2 Automotive clear coats currently used are applied either by a liquid application (i.e., acrylic melamine and acrylic carboxy epoxy) or a powder coating (i.e., acrylic carboxy epoxy and acrylic urethane). 3 Almost all clear coats contain light stabilizers such as hindered amine light stabilizers (HALS).…”

Section: Introductionmentioning

confidence: 99%

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Characterization of Automotive Paint Clear Coats by Ultraviolet Absorption Microspectrophotometry with Subsequent Chemometric Analysis

et al. 2010

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Clear coats have been a staple in automobile paints for almost thirty years and are of forensic interest when comparing transferred and native paints. However, the ultraviolet (UV) absorbers in these paint layers are not typically characterized using UV microspectrophotometry, nor are the results studied using multivariate statistical methods. In this study, measurements were carried out by UV microspectrophotometry on 71 samples from American and Australian automobiles, with subsequent chemometric analysis of the absorbance spectra. Sample preparation proved to be vital in obtaining accurate absorbance spectra and a method involving peeling the clear coat layer and not using a mounting medium was preferred. Agglomerative hierarchical clustering indicated three main groups of spectra, corresponding to spectra with one, two, and three maxima. Principal components analysis confirmed this clustering and the factor loadings indicated that a substantial proportion of the variance in the data set originated from specific spectral regions (230-265 nm, 275-285 nm, and 300-370 nm). The three classes were well differentiated using discriminant analysis, where the cross-validation accuracy was 91.6% and the external validation accuracy was 81.1%. However, results showed no correlation between the make, model, and year of the automobiles.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Characterization of Automotive Paint Clear Coats by Ultraviolet Absorption Microspectrophotometry with Subsequent Chemometric Analysis

et al. 2010

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“…UV microscopy [22][23][24][25] has both advantages and disadvantages in comparison with extraction techniques. A major advantage is that, since the method requires no extraction of the UVA, reactable UV absorbers can be detected and quantified as easily as nonreactable UVAs.…”

Section: Microtomementioning

confidence: 99%

Use of reactable light stabilizers to prevent migration and to improve durability of coatings on plastic substrates

Cliff¹,

Kanouni²,

Peters³

et al. 2005

J Coat. Technol. Res.

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One of the challenges of coating plastic substrates for exterior automotive applications involves the tendency for light stabilizers, which inhibit UV degradation of the coating, to migrate out of the topcoat and into the underlying plastic substrate. The consequent depletion of the stabilizer from the topcoat could account for significantly poorer durability for coatings applied on plastic than on a nonpermeable substrate such as steel.These studies investigate the migration of both nonreactable and reactable UV absorbers (UVAs) and hindered amine light stabilizers (HALS) in fully formulated 2K urethane coatings applied on thermoplastic olefin (TPO) and steel substrates. Extensive migration of the nonreactable stabilizers occurs during accelerated exposure of the cured coating, and this migration correlates with poorer performance on TPO. Functionalization of the stabilizer with a group which covalently reacts into the coating will prevent much of this migration, and the improved degree of retention of the reactable light stabilizers in the topcoat correlates with improved performance on TPO substrates. In addition, stabilizer variables, such as the type and extent of functionalization as well as their chemical structure, have an effect on both the migration and performance of the stabilizers. T he use of plastics for automotive structural components has increased dramatically in recent years. Most of these plastic parts require coatings that are not only matched with the steel body in color and appearance, but that also meet the same durability criteria. Historically, coatings on plastic parts have not been able to match steel coatings in weatherability. Problems in durability may result from the somewhat different composition of the flexible plastic coating versus rigid coatings. They may also be caused by the migration of low molecular weight components from the plastic into the coating 1 as well as the migration of light stabilizers from the coating into the plastic. [2][3][4] In this article, we demonstrate that the latter mechanism-migration of conventional stabilizers out of the topcoat and into the plastic substrates-can account for a significant portion of the poorer performance observed in coatings applied on plastic versus on steel. Figure 1 illustrates a typical coating system construction for coatings on steel and on TPO. Although some limited migration of light stabilizers from the topcoat (basecoat + clearcoat) into the primer layers on the steel can occur, this is largely prevented by prebaking the primers before applying the basecoat and clearcoat layers, as well as by their highly crosslinked nature. In any case, any migration would be limited to the coating layers, since no migration into the steel substrate could take place. In contrast, all the paint layers on the TPO were applied wet-on-wet-on-wet. In addition, the TPO, which is much thicker than the two primer layers on steel, and is also noncrosslinked, can act as a virtually unlimited "sink" for the migration of stabilizers, resulting in...

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“…VIS microspectrometry is widely applied in forensic laboratories to comparative studies of car paint traces (Cousins et al 1984;Fuller 1985;Nowicki and Patten 1986;Wilkinson, Locke, and Laing 1988;Laing 1982;Cousins 1989;Taylor 1989;Stoeklein and Fujiwara 1999;Massonnet and Stoecklein 1999;Takagi, Watanabe, and Baba 2005;Takagi, Sato, and Baba 2007;Kopchick and Bommarito 2006). In several papers (Wilkinson et al 1988;Laing 1982;Cousins 1989;Stoeklein and Fujiwara 1999;Kopchick and Bommarito 2006) authors showed the superiority of this method over traditional visual methods and established procedures for carrying out these measurements in casework.…”

Section: Introductionmentioning

confidence: 99%

“…In several papers (Wilkinson et al 1988;Laing 1982;Cousins 1989;Stoeklein and Fujiwara 1999;Kopchick and Bommarito 2006) authors showed the superiority of this method over traditional visual methods and established procedures for carrying out these measurements in casework. Reflectance spectra measured for small paint samples were used to identify the pigments by comparing the spectrum of the unknown paint with a collection of reflectance spectra of paints containing known single pigments (Stoeklein and Fujiwara 1999). In some cases thin layer chromatography followed by microspectrometry of the separated spots was used (Fuller 1985;Massonnet and Stoecklein 1999).…”

Section: Introductionmentioning

confidence: 99%

Comparative Analysis of Car Paint Traces in Terms of Color by VIS Microspectrometry for Forensic Needs

2010

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The usefulness of VIS microspectrometry for comparison of very small car paint traces was studied. Eighteen samples of solid and metallic paints taken from new and repainted cars were examined. Each sample was measured in both transmittance and reflectance mode (on top surface and on cross-section). Using the CIELAB units the repeatability of the color measurement was assessed. A criterion allowing two parts of the same sample and two samples of the same color to be distinguished was established. The method was proved to be an useful instrumental tool-complementary to other analytical methods (e.g., IR spectrometry)-in examination of car paint traces for forensic purposes.

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The examination of UV-absorbers in 2-coat metallic and non-metallic automotive paints

Cited by 21 publications

References 4 publications

Characterization of Automotive Paint Clear Coats by Ultraviolet Absorption Microspectrophotometry with Subsequent Chemometric Analysis

Characterization of Automotive Paint Clear Coats by Ultraviolet Absorption Microspectrophotometry with Subsequent Chemometric Analysis

Use of reactable light stabilizers to prevent migration and to improve durability of coatings on plastic substrates

Comparative Analysis of Car Paint Traces in Terms of Color by VIS Microspectrometry for Forensic Needs

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