Concurrent physical aging and degradation of crosslinked coating systems in accelerated weathering / Shi Xiaodong in JOURNAL OF COATINGS TECHNOLOGY AND RESEARCH, Vol. 5, N° 3 (09/2008)  

[article]  inJOURNAL OF COATINGS TECHNOLOGY AND RESEARCH > Vol. 5, N° 3 (09/2008) . - p. 299-309 Titre : Concurrent physical aging and degradation of crosslinked coating systems in accelerated weathering Type de document : texte imprimé Auteurs : Shi Xiaodong, Auteur ; B. M. Dilhan Fernando, Auteur ; Stuart G. Croll, Auteur Année de publication : 2008 Article en page(s) : p. 299-309 Note générale : Bibliogr. Langues : Américain (ame) Catégories : Essais accélérés (technologie) Revêtements -- Détérioration:Peinture -- Détérioration Index. décimale : 667.9 Revêtements et enduits Résumé : Coating degradation is a combination of both chemical and physical processes; however, physical processes have not received much attention. Physical aging has a non-negligible effect on coatings’ mechanical properties and permeability etc. through the densification that continues as a polymer approaches its thermodynamic equilibrium below the glass transition temperature, T g. Observations in recent work showed that physical aging affects coatings’ mechanical property response during accelerated weathering and is, itself, affected by the associated chemical degradation. Two crosslinked coating systems were studied in order to compare different chemical compositions, their T g, and their thermal response in accelerated weathering. During thermal cycling, physical aging measured by enthalpy recovery exhibited different trends in the two coatings. A “rejuvenation” mechanism was observed in the coating with a T g between the top and bottom limits of the exposure cycle; continued aging was observed for the coating with a high T g. Stress relaxation tests detected aging and “memory” behavior over periods comparable with accelerated weathering cycles. Both thermal and mechanical responses changed in complicated and different ways as the coatings degraded. Different degrees of coating thickness reduction were observed in both isothermal relaxation and degradation. When various coatings are evaluated, simply judging their performance under the same weathering environment is not reliable since polymer relaxation behavior depends on the relationship between the exposure temperatures and the T g of each polymer. DOI : 10.1007/s11998-008-9081-0 En ligne : https://link.springer.com/content/pdf/10.1007%2Fs11998-008-9081-0.pdf Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=2974 [article]

Réservation

Réserver ce document

Exemplaires (1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
010633	-	Périodique	Bibliothèque principale	Documentaires	Disponible

Environmental and time dependence of moisture transportation in an epoxy coating and its significance for accelerated weathering / Shi Xiaodong in JOURNAL OF COATINGS TECHNOLOGY AND RESEARCH, Vol. 7, N° 4 (07/2010)  

[article]  inJOURNAL OF COATINGS TECHNOLOGY AND RESEARCH > Vol. 7, N° 4 (07/2010) . - p. 419-430 Titre : Environmental and time dependence of moisture transportation in an epoxy coating and its significance for accelerated weathering Type de document : texte imprimé Auteurs : Shi Xiaodong, Auteur ; Brian R. Hinderliter, Auteur ; Stuart G. Croll, Auteur Année de publication : 2010 Article en page(s) : p. 419-430 Note générale : Bibliogr. Langues : Américain (ame) Catégories : Epoxydes Revêtements -- Détérioration Revêtements -- Effets de l'humidité Revêtements:Peinture Tags : 'Revêtement  Epoxyde'  Détérioration  'Coefficient  de  diffusion'  'Cycle  température'  'Détérioration  accélérée'  'Transport  eau/humidité'  'Réparation  défauts' Index. décimale : 667.9 Revêtements et enduits Résumé : It is increasingly appreciated that water is one of the most important factors in the durability behavior of coatings. The rate of water transportation and the degree of saturation of polymeric coatings depends on exposure history, exposure environment, and the nature of a coating. The focus here is on the time taken for transport of water and the variation it causes in thermal and mechanical properties, which have also been shown previously to have time-dependence that leads to discrepancies between different weathering regimes. This paper studied the effect of moisture on coatings’ mechanical properties and the effect of moisture and temperature on recovery of surface indentation. The reduction of mechanical properties and the increasing rate of surface defect relaxation can be explained in terms of plasticization by water. Recovery of surface defects is related to the appearance and diffusion activity of coatings during exposure. Thermogravimetric analysis showed that the content of moisture in the sample is determined by the ambient humidity, temperature, and the rate of change in these environmental parameters. Diffusion coefficients were determined from the weight change data and an activation energy was obtained via Arrhenius equation. Changes in yellowness, as an example, and signature of chemical degradation, indicated that the cycling period in accelerated weathering may affect the degradation via the amount and distribution of moisture in coatings. Diffusion of moisture is typically slow and limits the possibility of complete drying or saturation in an exposure cycle. Results from the cumulative effect of many cycles will be different depending on the conditions DOI : 10.1007/s11998-009-9209-x En ligne : https://link.springer.com/content/pdf/10.1007%2Fs11998-009-9209-x.pdf Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=9764 [article]

Réservation

Réserver ce document

Exemplaires (1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
012362	-	Périodique	Bibliothèque principale	Documentaires	Disponible

Molecular relaxation phenomena during accelerated weathering of a polyurethane coating / B. M. Dilhan Fernando in JOURNAL OF COATINGS TECHNOLOGY AND RESEARCH, Vol. 5, N° 1 (03/2008)  

[article]  inJOURNAL OF COATINGS TECHNOLOGY AND RESEARCH > Vol. 5, N° 1 (03/2008) . - p. 1-9 Titre : Molecular relaxation phenomena during accelerated weathering of a polyurethane coating Type de document : texte imprimé Auteurs : B. M. Dilhan Fernando, Auteur ; Shi Xiaodong, Auteur ; Stuart G. Croll, Auteur Année de publication : 2008 Article en page(s) : p. 1-9 Note générale : Bibliogr. Langues : Américain (ame) Catégories : Essais accélérés (technologie) Polyuréthanes Pyrolyse La pyrolyse est la décomposition ou thermolyse d'un composé organique par la chaleur pour obtenir d'autres produits (gaz et matière) qu'il ne contenait pas. L'opération est réalisée en l'absence d'oxygène ou en atmosphère pauvre en oxygène pour éviter l'oxydation et la combustion (L’opération ne produit donc pas de flamme). Il s'agit du premier stade de transformation thermique après la déshydratation. Elle permet généralement d'obtenir un solide carboné, une huile et un gaz. Elle débute à un niveau de température relativement bas (à partir de 200 °C) et se poursuit jusqu'à 1 000 °C environ. Selon la température, la proportion des trois composés résultants est différente. Relaxation moléculaire Revêtements -- Détérioration Index. décimale : 667.9 Revêtements et enduits Résumé : Results from a polyester-urethane (PU) coating system under accelerated weathering showed that crosslink density, obtained from high-temperature modulus data, diminished due to chain scission. However, Tg and room-temperature tensile modulus both increased with weathering. Molecular relaxation phenomena in polymers have long been investigated to explore changes occurring in a polymer at temperatures below its glass transition and were explored for an explanation to supplement chemical degradation for these observations. Relaxation was quantified using "enthalpy recovery" which first increased with exposure, then diminished. The concurrent physical and chemical aging effects were characterized by tracking nonexponentiality in the spectrum of relaxation times, and the size of "co-operatively relaxing regions" deduced from relaxation around the glass transition. Mechanical relaxation in this coating extended longer than cycle periods typical of accelerated weathering, suggesting that frequency effects might be important when comparing accelerated to natural weathering. DOI : 10.1007/s11998-007-9077-1 En ligne : https://link.springer.com/content/pdf/10.1007%2Fs11998-007-9077-1.pdf Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=3608 [article]

Réservation

Réserver ce document

Exemplaires (1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
009979	-	Périodique	Bibliothèque principale	Documentaires	Disponible

Reduced indentation recovery temperature at the surface of a crosslinked epoxy coating in humid conditions / Shi Xiaodong in JOURNAL OF COATINGS TECHNOLOGY AND RESEARCH, Vol. 8, N° 4 (07/2011)  

[article]  inJOURNAL OF COATINGS TECHNOLOGY AND RESEARCH > Vol. 8, N° 4 (07/2011) . - p. 535-539 Titre : Reduced indentation recovery temperature at the surface of a crosslinked epoxy coating in humid conditions Type de document : texte imprimé Auteurs : Shi Xiaodong, Auteur ; Stuart G. Croll, Auteur Année de publication : 2011 Article en page(s) : p. 535-539 Note générale : Bibliogr. Langues : Américain (ame) Catégories : Epoxydes Microscopie à force atomique Nanoindentation Réticulation à l'humidité Revêtements:Peinture Transition vitreuse Index. décimale : 667.9 Revêtements et enduits Résumé : Relaxation of surface defects shows that the surface of a crosslinked epoxy system, under normal laboratory conditions, apparently has a softening transition temperature that is approximately 20°C lower than calorimetric measures of T g in the bulk. Physical aging data here confirms that this transition does resemble a glass transition. This observation is significant for properties that are determined by the surface of a coating. When ambient humidity is such that an epoxy may absorb significant quantities of moisture, it is plasticized, reducing its T g. When the relaxation of nanoindentations was measured in a humid environment, the value of this softening surface transition temperature was further reduced by 10°C. Thus, the surface properties of a polymer coating, such as wear, durability, friction, will depend not only on the ambient temperature, but also on whether the environment is humid. This is very important when such a coating responds to an environment that changes, e.g., natural weather. Note de contenu : - Surface transition temperature via indentation recovery - Humidity-induced recovery DOI : 10.1007/s11998-011-9335-0 En ligne : https://link.springer.com/content/pdf/10.1007%2Fs11998-011-9335-0.pdf Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=12147 [article]

Réservation

Réserver ce document

Exemplaires (1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
013158	-	Périodique	Bibliothèque principale	Documentaires	Disponible

Thermal-induced recovery of small deformations and degradation defects on epoxy coating surface / Shi Xiaodong in JOURNAL OF COATINGS TECHNOLOGY AND RESEARCH, Vol. 7, N° 1 (01/2010)  

[article]  inJOURNAL OF COATINGS TECHNOLOGY AND RESEARCH > Vol. 7, N° 1 (01/2010) . - p. 73-84 Titre : Thermal-induced recovery of small deformations and degradation defects on epoxy coating surface Type de document : texte imprimé Auteurs : Shi Xiaodong, Auteur ; Stuart G. Croll, Auteur Année de publication : 2010 Article en page(s) : p. 73-84 Note générale : Bibliogr. Langues : Américain (ame) Tags : Recovery/relaxation  Scratch  Defects  Roughness  Weathering  Glass  transition  Coatings Index. décimale : 667.9 Revêtements et enduits Résumé : Surface defects, which are dependent on the surface properties, determine the appearance, toughness, and other properties of coatings; thus, changes to the morphology of a damaged epoxy coating surface were investigated on annealing. Changes in mechanically produced indentations and scratches with annealing indicate a surface transition temperature about 10 degree lower than the measured bulk glass transition temperature (T g). Polymer molecules at a free surface, even in a crosslinked coating, may have higher mobility, and thus allow different relaxation activity from the bulk material. The eventual extent of deformation is a function of the annealing temperature and time. Results showed that the deformation profile diminished, driven by viscoelastic deformation and surface energy; the effect of structural relaxation will be further studied. When the surface features were generated by photodegradation, the roughness increased initially when temperature was increased, possibly due to phase coarsening, and then the roughness diminished during extended annealing. DOI : 10.1007/s11998-009-9176-2 En ligne : https://link.springer.com/content/pdf/10.1007%2Fs11998-009-9176-2.pdf Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=8349 [article]

Réservation

Réserver ce document

Exemplaires (1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
011962	-	Périodique	Bibliothèque principale	Documentaires	Disponible

---

1 (1 - 5 / 5)