An improved accelerated weathering protocol to anticipate Florida exposure behavior of coatings / Mark Nichols in JOURNAL OF COATINGS TECHNOLOGY AND RESEARCH, Vol. 10, N° 2 (03/2013)  

[article]  inJOURNAL OF COATINGS TECHNOLOGY AND RESEARCH > Vol. 10, N° 2 (03/2013) . - p. 153-173 Titre : An improved accelerated weathering protocol to anticipate Florida exposure behavior of coatings Type de document : texte imprimé Auteurs : Mark Nichols, Auteur ; John Boisseau, Auteur ; Lynn Pattison, Auteur ; Don Campbell, Auteur ; Jeff Quill, Auteur ; Jacob Zhang, Auteur ; Don Smith, Auteur ; Karen Henderson, Auteur ; Jill Seebergh, Auteur ; Douglas Berry, Auteur ; Tony Misovski, Auteur ; Cindy Peters, Auteur Année de publication : 2013 Article en page(s) : p. 153-173 Note générale : Bibliogr. Langues : Américain (ame) Catégories : Automobiles -- Revêtements:Automobiles -- Peinture Avions -- Revêtements:Avions -- Peinture Durée de vie (Ingénierie) Essais accélérés (technologie) Revêtements -- Détérioration Vieillissement Index. décimale : 667.9 Revêtements et enduits Résumé : A new accelerated weathering protocol has been developed which closely replicates the performance of automotive and aerospace coating systems exposed in South Florida. IR spectroscopy was used to verify that the chemical composition changes that occurred during accelerated weathering in devices with a glass filter that produced a high fidelity reproduction of sunlight’s UV spectrum matched those that occurred during natural weathering. Gravimetric water absorption measurements were used to tune the volume of water absorption during accelerated weathering to match that which occurred during natural weathering in South Florida. The frequency of water exposure was then scaled to the appropriate UV dose. A variety of coating systems were used to verify the correlation between the physical failures observed in the accelerated weathering protocol and natural weathering in South Florida. The new accelerated weathering protocol correctly reproduced gloss loss, delamination, cracking, blistering, and good performance in a variety of diverse coating systems. For automotive basecoat/clearcoat paint systems, the new weathering protocol shows significant acceleration over both Florida and previous accelerated weathering tests. For monocoat aerospace systems, the new weathering protocol showed less acceleration than for automotive coatings, but was still an improvement over previous accelerated tests and was faster than Florida exposure. Note de contenu : - EXPERIMENTAL : Materials - Natural weathering - Accelerated weathering - PAS-FTIR spectroscopy - Ultraviolet - Gloss and color change - Visual evaluation - Water sorption - RESULTS : Water absorption - Photochemistry - Physical failures of paint systems - Aerospace coatings - DISCUSSION : Water absorption - Spectral match to sunlight - Cyclic conditions - Acceleration of new tet protocol - Positive controls - UVA longevity - Aerospace coatings DOI : 10.1007/s11998-012-9467-x En ligne : https://link.springer.com/content/pdf/10.1007%2Fs11998-012-9467-x.pdf Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=18235 [article]

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Principles of accelerated weathering : evaluations of coatings / Mark Nichols in COATINGS TECH, Vol. 17, N° 1 (01/2020)  

[article]  inCOATINGS TECH > Vol. 17, N° 1 (01/2020) . - p. 18-25 Titre : Principles of accelerated weathering : evaluations of coatings Type de document : texte imprimé Auteurs : Mark Nichols, Auteur Année de publication : 2020 Article en page(s) : p. 18-25 Note générale : Bibliogr. Langues : Américain (ame) Catégories : Essais accélérés (technologie) Photo-oxydation Résistance aux conditions climatiques Revêtements -- Détérioration:Peinture -- Détérioration Index. décimale : 667.9 Revêtements et enduits Résumé : One of paint’s most important attributes is its ability to maintain performance for an extended period of time in its intended service environment. That environment may be an interior wall in a single family home, the outside of an underground pipeline, or the exterior of a vehicle. The service environment is different in all three cases, but the ability to maintain the paint’s functions—aesthetics, adhesion, corrosion protection, and mechanical performance—is still required. Objects that predominantly reside outdoors are subjected to one of the most challenging service environments for coatings. Exposure to solar radiation, temperature fluctuations, rain, snow, and environmental fallout (acid rain), challenge the performance of most coatings. Examples of painted objects that are exposed to such environments include automobiles, aircraft, infrastructure (bridges and roads), houses, and buildings. To achieve long-term performance, exterior coatings require resistance to degradation by UV radiation, resistance to hydrolysis, and resistance to erosion by rain and snow. The durability of a coating is typically assessed by exposing it at selected outdoor locations to quantify the coating’s real-world performance. While natural exposure outdoors is a reliable method of assessment, natural exposure provides little acceleration. A coating that performs acceptably after five years of Florida exposure means that the coating will survive five years of exposure in Florida, but this says nothing about its performance after 5.5 years or 10 years. It does mean that the coating may survive longer than five years in a less harsh environment, but the failure mode may change, as environmental loads can vary dramatically from region to region.1 Thus, it is impractical to develop coatings using natural outdoor exposure as a method to assess their long-term durability, as product development time cycles are not compatible with test methods that take five-plus years to perform. Coating formulators, therefore, rely heavily on accelerated weathering tests to develop and optimize coating formulations. Accelerated weathering tests attempt to degrade a coating at a faster rate than that which occurs during natural exposure. However, to be reliable and useful, the increased rate of degradation must not sacrifice the accuracy of the results, meaning the correlation between accelerated weathering results and natural weathering results must be quite high. Unreliable results produced quickly are not useful, and can potentially be quite damaging to a company’s reputation and bottom line. The bulk of this article will discuss the science behind paint degradation and the various methods used to assess paint weatherability. Note de contenu : - Paint degradation chemistry - Coating stabilization - Natural weathering testing - Accelerated weathering tests - Post-exposure testing - Correlation to outdoor exposure - Fig. 1 : Reaction schematic for photooxidation in polymers - Fig. 2 : Painted panels in exposure racks in south Florida. (Upper) automative coatings exposed at 5° south and (lower) architectural coatings exposed at 90° south - Fig. 3 : QUV accelerated weathering chamber - Fig. 4 : The spectral power distribution of UV-A and UV-B bulbs used in a QUV accelerated weathering instrument. The spectrum of sunlight is also shown as a reference - Fig. 5 : Weather-Ometer accelerated weathering instrument - Fig. 6 : Spectral power distribution of xenon-arc lamps filtered with boro/boro and quartz/boro filter combinations. Sunlight spectrum also shown for reference ; SPD of sunlight, Righlight, and boro/boro filtered light on log scale to demonstrate the fidelity of the match between sunlight and Righlight filter combination - Fig. 7 : Fresnel-type accelerated outdoor exposure device - Table 1 : Accelerated weathering test conditions En ligne : https://drive.google.com/file/d/1WnhA_OsUarcCoYy3KIMGK5ZYelbOuCni/view?usp=share [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=33600 [article]

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Using fracture mechanics to characterize organic coatings / Mark Nichols in COATINGS TECH, Vol. 2, N° 21 (10/2005)  

[article]  inCOATINGS TECH > Vol. 2, N° 21 (10/2005) . - p. 62-67 Titre : Using fracture mechanics to characterize organic coatings Type de document : texte imprimé Auteurs : Mark Nichols, Auteur Année de publication : 2005 Article en page(s) : p. 62-67 Note générale : Bibliogr. Langues : Américain (ame) Index. décimale : 667.9 Revêtements et enduits Résumé : The multitude of ways in which a coating can fail are well known to both users and producers of organic coatings. Many failures are gradual and are aesthetic in nature only, such as gloss loss and color fade. Others are more mechanical in nature such as cracking or peeling. These mechanical failures can lead to a loss of substrate protection or corrosion, which may compromise the structural integrity of the painted component as well as produce an unacceptable appearance. By understanding the manner in which these failures occur one can design coating systems in a more robust fashion to prevent them. Most of the mechanical failures that occur in coatings are due to cracks propagating within the coating, at an interface between the coating and a substrate, or between two coating layers (Figure 1). To truly understand how these cracks propagate, the principals of fracture mechanics must be applied to the coating system. Fracture mechanics is the discipline that quantitatively describes how cracks propagate in materials and at interfaces. This approach has been used extensively to understand and predict the performance of aluminum aircraft alloys as well as high strength composite materials. Its application to coatings technology was only initiated in the last decade.1,2 However, recent advances have made it a powerful tool to understand the performance of many organic coatings. This article aims to introduce the reader to the principals of fracture mechanics and how the application of these principals to organic coating characterization can improve the durability and performance of coating systems. En ligne : https://drive.google.com/file/d/1tdiz5rKWSQdyCWVfxZBKUtZnGtYAv-y4/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=5495 [article]

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