Microstructure and morphology of amine-cured epoxy coatings before and after outdoor exposures - an AFM study / Xiaohong Gu in JOURNAL OF COATINGS TECHNOLOGY AND RESEARCH, Vol. 2, N° 7 (07/2005)  

[article]  inJOURNAL OF COATINGS TECHNOLOGY AND RESEARCH > Vol. 2, N° 7 (07/2005) . - p. 547-556 Titre : Microstructure and morphology of amine-cured epoxy coatings before and after outdoor exposures - an AFM study Type de document : texte imprimé Auteurs : Xiaohong Gu, Auteur ; Y. C. Jean, Auteur ; Derek L. Ho, Auteur ; Jonathan W. Martin, Auteur ; Eric Byrd, Auteur ; Li-Piin Sung, Auteur ; Aziz Rezig, Auteur ; Joan Jasmin, Auteur ; Bouchra Kidah, Auteur ; David Martin, Auteur ; Mounina Oudina, Auteur ; Tinh Nguyen, Auteur Année de publication : 2005 Article en page(s) : p. 547-556 Note générale : Bibliogr. Langues : Américain (ame) Tags : Dégradation  photooxydante  photochimique  Propriété  chimique  Etude  expérimentale  Diffusion  neutron  centrale  Microscopie  force  atomique  Résistance  intempérie  Méthode  analyse  Durabilité  Epoxyde  résine  Structure  surface  Temps  exposition  Relation  mise  en  oeuvre  propriété  Amine  Durcissement(matière  plastique)  Vieillissement  produit  Matériau  revêtement  Morphologie  Microstructure Index. décimale : 667.9 Revêtements et enduits Résumé : Atomic force microscopy (AFM) has been used to study the morphology and microstructure of an amine-cured epoxy before and after outdoor exposure. Measurements were made from samples prepared in an essentially CO2-free, H2O-free glove box and from samples prepared in ambient conditions. For those prepared in a CO2-free glove box, AFM imaging was conducted on (1) an unexposed air/coating surface, (2) an unexposed coating bulk, (3) an unexposed coating/substrate interface, and (4) a field exposed air/coating surface. For samples prepared in ambient conditions, only the unexposed air/coating surface was investigated. The same regions of the exposed samples were scanned periodically by the AFM to monitor changes in the surface morphology of the coating as UV exposure progressed. Small angle neutron scattering and Fourier transfonn infrared spectroscopy (FTIR) studies were performed to verify the microstructure and to follow chemical changes during outdoor exposure, respectively. The results have shown that amine blushing, which occurs only under ambient conditions, had a significant effect on the surface morphology and microstructure of the epoxy. The surface morphology of the samples prepared under CO2-free, dry conditions was generally smooth and homogeneous. However, the interface and the bulk samples clearly revealed a two-phase structure consisting of bright nodular domains and dark interstitial regions, indicating an inhomogeneous microstructure. Such heterogeneous structure of the bulk was in good agreement with results obtained by small angle neutron scattering of unexposed samples and by AFM phase imaging of the degraded sample surface. The relationship between submicrometer physical changes and molecular chemical degradation is discussed. DOI : 10.1007/s11998-005-0014-x En ligne : https://link.springer.com/content/pdf/10.1007%2Fs11998-005-0014-x.pdf Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=3802 [article]

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Multiscale physical characterization of an outdoor-exposed polymeric coating system / Xiaohong Gu in JOURNAL OF COATINGS TECHNOLOGY AND RESEARCH, Vol. 6, N° 1 (03/2009)  

[article]  inJOURNAL OF COATINGS TECHNOLOGY AND RESEARCH > Vol. 6, N° 1 (03/2009) . - p. 67-79 Titre : Multiscale physical characterization of an outdoor-exposed polymeric coating system Type de document : texte imprimé Auteurs : Xiaohong Gu, Auteur ; Li-Piin Sung, Auteur ; Bouchra Kidah, Auteur ; Mounina Oudina, Auteur ; Cyril Clerici, Auteur ; Hu Haiqing, Auteur ; Debbie Stanley, Auteur ; Walter E. Byrd, Auteur ; Jerry Y. C. Jean, Auteur ; Tinh Nguyen, Auteur ; Jonathan W. Martin, Auteur Année de publication : 2009 Article en page(s) : p. 67-79 Note générale : Bibliogr. Langues : Américain (ame) Catégories : Analyse multiéchelle Brillance (optique) Caractérisation Dispersion rotatoire (optique) Microscopie à force atomique Microscopie confocale Morphologie (matériaux) Optique Revêtements protecteurs Rugosité Index. décimale : 667.9 Revêtements et enduits Résumé : Surface topography and gloss are two related properties affecting the appearance of a polymeric coating system. Upon exposure to ultraviolet (UV) radiation, the surface topography of a coating becomes more pronounced and, correspondingly, its gloss generally decreases. However, the surface factors affecting gloss and appearance are difficult to ascertain. In this article, atomic force microscopy (AFM) and laser scanning confocal microscopy (LSCM) measurements have been performed on an amine-cured epoxy coating system exposed to outdoor environments in Gaithersburg, Maryland. The formation of the protuberances is observed at the early degradation stages, followed by the appearance of circular pits as exposure continues. At long exposure times, the circular features enlarge and deepen, resulting in a rough surface topography and crack formation. Fourier Transform Infrared Spectroscopy (FTIR) study indicates that the oxidation and chain scission reactions are likely the origins of the surface morphological changes. The relationship between changes in surface roughness and gloss has been analyzed. The root mean square (RMS) roughness of the coating is related to nanoscale and microscale morphological changes in the surface of the coating as well as to the gloss retention. A near-linear dependence of RMS roughness with the measurement length scale (L) is found on a double logarithmic scale, i.e., RMS ~ L f. The scaling factor, f, decreases with exposure time. The relationship between surface topography, on nano- to microscales, and the macroscale optical properties such as gloss retention is discussed. Moreover, a recent development in using an angle-resolved light scattering technique for the measurement of the specular and off-specular reflectance of the UV-exposed specimens is also demonstrated, and the optical scattering data are compared to the gloss and the roughness results. DOI : 10.1007/s11998-008-9108-6 En ligne : https://link.springer.com/content/pdf/10.1007%2Fs11998-008-9108-6.pdf Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=4860 [article]

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