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Auteur Xiaohong Gu |
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Ajouter le résultat dans votre panier Affiner la rechercheAccelerated UV weathering of polymeric systems : recent innovations and new perspectives / Joannie W. Chin in COATINGS TECH, Vol. 3, N° 2 (02/2006)
Titre : Accelerated UV weathering of polymeric systems : recent innovations and new perspectives Type de document : texte imprimé Auteurs : Joannie W. Chin, Auteur ; Tinh Nguyen, Auteur ; Xiaohong Gu, Auteur ; Eric Byrd, Auteur ; Jonathan Martin, Auteur Année de publication : 2006 Article en page(s) : p. 20-26 Note générale : Bibliogr. Langues : Américain (ame) Index. décimale : 667.9 Revêtements et enduits Résumé : Polymeric materials used in an outdoor environment are subjected to a wide variety of environmental factors, including solar ultraviolet (UV) radiation, temperature, and moisture, in a process known as weathering. Understanding the factors that govern the weathering performance of commercial polymeric materials has great practical importance, as does the ability to relate laboratory performance of a polymeric system to its performance in the field. At present, the full potential of these materials is inhibited by the absence of a methodology for accurately predicting their service life during exposure in their end-use environments. A reliability-based methodology utilizing total effective dosage as an exposure metric has been proposed as an alternative to the conventional methodology for carrying out laboratory and outdoor weathering studies. The use of this proposed methodology involves not only a shift in paradigm but also in the way that laboratory and outdoor weathering experiments are carried out. The concepts of reciprocity and additivity, which were first introduced by the photographic community and then studied by the medical and biological communities, are also proposed as models for synthetic polymeric systems. En ligne : https://drive.google.com/file/d/1sdM_jq9cpGhaWi6mm-LpkVhp6zk44N5p/view?usp=drive [...] Format de la ressource électronique : Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=5491
in COATINGS TECH > Vol. 3, N° 2 (02/2006) . - p. 20-26[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 005876 - Périodique Bibliothèque principale Documentaires Disponible
Titre : Advanced techniques for nanocharacterization of polymeric coating surfaces Type de document : texte imprimé Auteurs : Xiaohong Gu, Auteur ; N.-K. Chang, Auteur ; Diep Nguyen, Auteur ; Y. C. Jean, Auteur ; Jonathan W. Martin, Auteur ; Tinh Nguyen, Auteur ; Li-Piin Sung, Auteur ; Mark R. VanLandingham, Auteur ; Michael J. Fasolka, Auteur ; T.-Y. Wu, Auteur Année de publication : 2004 Article en page(s) : p. 191-200 Note générale : Bibliogr. Langues : Américain (ame) Catégories : Chimie des surfaces
Durée de vie (Ingénierie)
Epoxydes
Fluoropolymères
Microscopie à force atomique
Morphologie (matériaux)
Prévision, Théorie de la
Résistance à l'abrasion
Revêtements organiques
Surfaces -- AnalyseIndex. décimale : 667.9 Revêtements et enduits Résumé : Surface properties of a polymeric coating system have a strong influence on its performance and service life. However, the surface of a polymer coating may have different chemical, physical, and mechanical properties from the bulk. In order to monitor the coating property changes with environmental exposures from the early stages of degradation, nondestructive techniques with the ability to characterize surface properties with micro- to nanoscale spatial resolution are required. In this article, atomic force microscopy has been applied to study surface microstructure and morphological changes during degradation in polymer coatings. Additionally, the use of AFM with a controlled tip-sample environment to study nanochemical heterogeneity and the application of nanoindentation to characterize mechanical properties of coatings surfaces are demonstrated. The results obtained from these nanometer characterization techniques will provide a better understanding of the degradation mechanisms and a fundamental basis for predicting the service life of polymer coatings. DOI : 10.1007/s11998-004-0012-4 En ligne : https://link.springer.com/content/pdf/10.1007%2Fs11998-004-0012-4.pdf Format de la ressource électronique : Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=3899
in JOURNAL OF COATINGS TECHNOLOGY AND RESEARCH > Vol. 1, N° 3 (07/2004) . - p. 191-200[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 000587 - Périodique Bibliothèque principale Documentaires Disponible
Titre : Critical role of particle/polymer interface in photostability of nano-filled polymeric coatings Type de document : texte imprimé Auteurs : Xiaohong Gu, Auteur ; Guodong Chen, Auteur ; Minhua Zhao, Auteur ; Stephanie S. Watson, Auteur ; Tinh Nguyen, Auteur ; Joannie W. Chin, Auteur ; Jonathan W. Martin, Auteur Année de publication : 2012 Article en page(s) : p. 251-267 Note générale : Bibliogr. Langues : Américain (ame) Catégories : Essais accélérés (technologie)
Interfaces (Sciences physiques)
Nanoparticules
Oxyde de zinc
Photodétérioration
Polyuréthanes
Résistance au rayonnement ultraviolet
Revêtements en phase aqueuse:Peinture en phase aqueuseIndex. décimale : 667.9 Revêtements et enduits Résumé : Nanoparticle-filled polymeric coatings have attracted great interest in recent years because the incorporation of nanofillers can significantly enhance the mechanical, electrical, optical, thermal, and antimicrobial properties of coatings. Due to the small size of the fillers, the volume fraction of the nanoparticle/polymer interfacial area in nano-filled systems is drastically increased, and the interfacial region becomes important in the performance of the nano-filled system. However, techniques used for characterizing nanoparticle/polymer interfaces are limited, and thus, the mechanism by which interfacial properties affect the photostability and the long-term performance of nano-filled polymeric coatings is not well understood. In this study, the role of the nanoparticle/polymer interface on the ultraviolet (UV) stability of a nano-ZnO-filled polyurethane (PU) coating system was investigated. The effects of parameters influencing the particle/polymer interfacial properties, such as size, loading, surface modification of the nanoparticles, on photodegradation of ZnO/PU films were evaluated. The nature of the interfacial regions before and after UV exposures were characterized by atomic force microscopy (AFM)-based techniques. Results have shown that the interfacial properties strongly affect chemical, thermo-mechanical, and morphological properties of the UV-exposed ZnO/PU films. By combining tapping mode AFM and novel electric force microscopy (EFM), the particle/polymer interfacial regions have been successfully detected directly from the surface of the ZnO/PU films. Further, our results indicate that ZnO nanoparticles can function as a photocatalyst or a photostabilizer, depending on the UV exposure conditions. A hypothesis is proposed that the polymers in the vicinity of the ZnO/PU interface are preferentially degraded or protected, depending on whether ZnO nanoparticles act as a photocatalyst or a photostabilizer in the polymers. This study clearly demonstrates that the particle/polymer interface plays a critical role in the photostability of nano-filled polymeric coatings. Note de contenu : - EXPERIMENTAL : Materials and specimen preparation - High UV radiant laboratory exposure - Measurements
- RESULTS AND DISCUSSION : Thermo-mechanical properties of nano-filled coatings and their relationship with interfacial interactions - Detecting embedded nanoparticle/polymer interface using AFM-based techniques - Role of nanoparticle/polymer interface in photostability of nano-filled polymeric coatingsDOI : 10.1007/s11998-011-9326-1 En ligne : https://link.springer.com/content/pdf/10.1007%2Fs11998-011-9326-1.pdf Format de la ressource électronique : Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=15950
in JOURNAL OF COATINGS TECHNOLOGY AND RESEARCH > Vol. 9, N° 3 (05/2012) . - p. 251-267[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 14188 - Périodique Bibliothèque principale Documentaires Disponible
Titre : Degradation modes of crosslinked coatings exposed to photolytic environment Type de document : texte imprimé Auteurs : Tinh Nguyen, Auteur ; Xiaohong Gu, Auteur ; Mark R. VanLandingham, Auteur ; Eric Byrd, Auteur ; Rose Ann Ryntz, Auteur ; Jonathan W. Martin, Auteur Année de publication : 2013 Article en page(s) : p. 1-14 Note générale : Bibliogr. Langues : Américain (ame) Catégories : Fourier, Spectroscopie infrarouge à transformée de
Microscopie à force atomique
Photochimie
Photodétérioration
Polymères réticulés
Revêtements -- Détérioration
Revêtements -- Effets du rayonnement ultravioletIndex. décimale : 667.9 Revêtements et enduits Résumé : The objective of this study is to assess the degradation modes of crosslinked coatings exposed to photolytic environments. Three model crosslinked coatings were exposed in various ultraviolet environments. Atomic force microscopy and Fourier transform infrared spectroscopy were used in following nanoscale physical and chemical degradation during exposures. Results indicated that photodegradation of crosslinked coatings is a spatially localized (inhomogeneous) process in which nanometer-sized pits are initially formed; these pits deepen and enlarge with exposure. A conceptual model is proposed to explain the inhomogeneous degradation mode. The model proposes that nanosize “hydrophilic” domains are dispersed randomly with the highly crosslinked units. These hydrophilic domains, which are energetically preferred, comprise polar, unreacted and partially polymerized molecules, chromophores, and other additives. Photodegradation initiates at degradation-susceptible hydrophilic domains spreading to surrounding areas contiguous with the initiation site. Note de contenu : - EXPERIMENTAL PROCEDURES : Materials and sample preparation - exposures and apparatus - Degradation measurements
- RESULTS AND DISCUSSION : Amine-cured epoxy - Acrylic urethane - Acrylic melamine
- CONCEPTUAL MODEL FOR THE INHOMOGENEOUS DEGRADATIONDOI : 10.1007/s11998-012-9455-1 En ligne : https://link.springer.com/content/pdf/10.1007%2Fs11998-012-9455-1.pdf Format de la ressource électronique : Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=17467
in JOURNAL OF COATINGS TECHNOLOGY AND RESEARCH > Vol. 10, N° 1 (01/2013) . - p. 1-14[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 14636 - Périodique Bibliothèque principale Documentaires Disponible 15124 - Périodique Bibliothèque principale Documentaires Disponible
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 : Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=3802
in JOURNAL OF COATINGS TECHNOLOGY AND RESEARCH > Vol. 2, N° 7 (07/2005) . - p. 547-556[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 002327 - Périodique Bibliothèque principale Documentaires Disponible
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