Concentration profiles in phase-separating photocuring coatings / Hirokazu Yoshihara in JOURNAL OF COATINGS TECHNOLOGY AND RESEARCH, Vol. 16, N° 6 (11/2019)  

[article]  inJOURNAL OF COATINGS TECHNOLOGY AND RESEARCH > Vol. 16, N° 6 (11/2019) . - p. 1629-1636 Titre : Concentration profiles in phase-separating photocuring coatings Type de document : texte imprimé Auteurs : Hirokazu Yoshihara, Auteur ; Masato Yamamura, Auteur Année de publication : 2019 Article en page(s) : p. 1629-1636 Note générale : Bibliogr. Langues : Américain (ame) Catégories : Photoréticulation Polyfluorure de vinylidène Revêtements -- Séchage sous rayonnement ultraviolet Revêtements organiques Séparation (technologie) Spectroscopie Raman Terpolymère styrène anhydride maléïque Index. décimale : 667.9 Revêtements et enduits Résumé : We directly measured the local composition profiles in phase-separating photocurable thin films using confocal Raman spectroscopy. To avoid light scattering at phase interfaces, we developed a novel technique to replace the solvent with a monomer to match the reflective indices in the cured films. The results indicated that the concentration distribution of the polymer was uniform in solvent-free monomer/initiator binary solutions, while it was spatially nonuniform when the solvent-based films were thermodynamically unstable and promoted reaction-induced phase separation upon UV irradiation on the top surface. In the latter case, the film exhibited a dual-layer structure, in which the polymer concentration was almost uniform near the top surface, while concentration gradients developed near the bottom surface. The thickness of the top layer with a uniform concentration profile increased with the increase in the UV light intensity. These results implied that the propagation of the reaction front and the resulting light-driven transport of the solvent toward the bottom coating layer played key roles in the formation of nonuniform concentration profiles in photocuring solution coatings. DOI : 10.1007/s11998-019-00216-3 En ligne : https://link.springer.com/content/pdf/10.1007%2Fs11998-019-00216-3.pdf Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=33415 [article]

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Direct thickness measurement of doctor-bladed liquid film on gravure roll surface / Hidenobu Miura in JOURNAL OF COATINGS TECHNOLOGY AND RESEARCH, Vol. 12, N° 5 (09/2015)  

[article]  inJOURNAL OF COATINGS TECHNOLOGY AND RESEARCH > Vol. 12, N° 5 (09/2015) . - p. 827-833 Titre : Direct thickness measurement of doctor-bladed liquid film on gravure roll surface Type de document : texte imprimé Auteurs : Hidenobu Miura, Auteur ; Masato Yamamura, Auteur Année de publication : 2015 Article en page(s) : p. 827-833 Note générale : Bibliogr. Langues : Américain (ame) Catégories : Enduction Epaisseur -- Mesure Films plastiques Héliogravure Polyéthylène glycol Polyéthylène téréphtalate Index. décimale : 667.9 Revêtements et enduits Résumé : We provide experimental evidence that the liquid film remaining on a doctor-bladed gravure roll surface significantly influences the liquid transfer from the engraved roll surface to a moving substrate. The local free surface profiles of doctor-bladed liquid films were directly measured on both tri-helical grooves and lands (the nongrooved areas between grooves) at different roll speeds and blade thicknesses. The liquid film covered the roll surface with a finite thickness on the lands below the critical capillary number. An increase in the capillary number led to a transition from a fully filled to a starved configuration, in which the liquid barely remained on the lands and partly filled the grooves with a concave surface profile. The liquid transfer ratio monotonically decreased with a decrease in the liquid thickness on the gravure roll surface, obeying a single curve for different blade thicknesses. Furthermore, the decrease in liquid thickness promoted a flow instability transition from unstable dripping though a stable state with a uniform surface to a cascade. DOI : 10.1007/s11998-015-9714-z En ligne : https://link.springer.com/content/pdf/10.1007%2Fs11998-015-9714-z.pdf Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=24681 [article]

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Drying paths of phase-separating solution coatings exposed to humidity / Masato Yamamura in JOURNAL OF COATINGS TECHNOLOGY AND RESEARCH, Vol. 19, N° 1 (01/2022)  

[article]  inJOURNAL OF COATINGS TECHNOLOGY AND RESEARCH > Vol. 19, N° 1 (01/2022) . - p. 15-23 Titre : Drying paths of phase-separating solution coatings exposed to humidity Type de document : texte imprimé Auteurs : Masato Yamamura, Auteur Année de publication : 2022 Article en page(s) : p. 15-23 Note générale : Bibliogr. Langues : Américain (ame) Catégories : Azéotropes Diagrammes de phases Humidité -- Absorption:Eau -- Absorption Revêtement -- Séchage Séparation (technologie) Simulation par ordinateur Vapeur d'eau Index. décimale : 667.9 Revêtements et enduits Résumé : Drying process paths, i.e., time-dependent trajectories of solution compositions on a phase diagram, were examined for coatings of a water-immiscible acrylic monomer dissolved in ethanol and exposed to humidity. The absorption of water vapor quenched the solution into a thermodynamic nonequilibrium state and promoted a spontaneous phase separation when the water content in the solution exceeded a critical value. A simultaneous mass-loss and heat-flux measurement technique was proposed and adapted for phase-separating coatings to determine the evaporation rates of two volatile components with different latent heats of vaporization. The measured drying paths agreed with those predicted from a drying model that takes into account the gas-diffusion-limited evaporation and composition-dependent activities. The numerical predictions also revealed that the pseudo-azeotrope determined the critical drying conditions, under which any drying paths on the phase diagram did not cross the two-phase region, and thus the drying solutions remained stable. DOI : https://doi.org/10.1007/s11998-021-00483-z En ligne : https://link.springer.com/content/pdf/10.1007/s11998-021-00483-z.pdf Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=37141 [article]

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Ribbing instability of Newtonian fluid coated on a topographic surface / Masato Yamamura in JOURNAL OF COATINGS TECHNOLOGY AND RESEARCH, Vol. 17, N° 6 (11/2020)  

[article]  inJOURNAL OF COATINGS TECHNOLOGY AND RESEARCH > Vol. 17, N° 6 (11/2020) . - p. 1447-1453 Titre : Ribbing instability of Newtonian fluid coated on a topographic surface Type de document : texte imprimé Auteurs : Masato Yamamura, Auteur Année de publication : 2020 Article en page(s) : p. 1447-1453 Note générale : Bibliogr. Langues : Américain (ame) Catégories : Ecoulement visqueux Fluides newtoniens Fluides, Mécanique des Instabilités (physique) Rhéologie Surfaces (Physique) Topographie Index. décimale : 667.9 Revêtements et enduits Résumé : Periodic wavy patterns emerge and align in a transverse direction once a viscous fluid is coated onto a surface moving above a critical speed. In this study, we examine how this flow instability, which is usually referred to as ribbing, is triggered or damped on a moving topographic surface. To examine the transient flow behavior, the liquid first came into contact with a smooth surface, followed by a downstream surface with small-scale V-shaped grooves. Flow visualizations revealed a topography-induced flow stabilization and a matching of rib frequencies with the underlying groove patterns, depending on the groove geometry and capillary number. DOI : https://doi.org/10.1007/s11998-020-00375-8 En ligne : https://link.springer.com/content/pdf/10.1007/s11998-020-00375-8.pdf Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=34951 [article]

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Two-step migration of particles in evaporating bimodal suspension films at high Peclet numbers / Tomonori Tashima in JOURNAL OF COATINGS TECHNOLOGY AND RESEARCH, Vol. 14, N° 5 (09/2017)  

[article]  inJOURNAL OF COATINGS TECHNOLOGY AND RESEARCH > Vol. 14, N° 5 (09/2017) . - p. 965-970 Titre : Two-step migration of particles in evaporating bimodal suspension films at high Peclet numbers Type de document : texte imprimé Auteurs : Tomonori Tashima, Auteur ; Masato Yamamura, Auteur Année de publication : 2017 Article en page(s) : p. 965-970 Note générale : Bibliogr. Langues : Américain (ame) Catégories : Latex Particules (matières) Photoluminescence Produits chimiques -- Migration Revêtements -- Séchage -- Défauts:Peinture -- Séchage -- Défauts Index. décimale : 667.9 Revêtements et enduits Résumé : During the drying of bimodal colloidal suspensions containing particles of various sizes, smaller particles preferentially migrate to the top surface under particular drying conditions, leading to undesirable drying defects in batteries and in other coating applications. Despite extensive previous studies, the migration mechanism is far from being understood because few in situ observations are available to support the hypotheses. To remedy this, we use real-time photoluminescence (PL) microscopy to investigate the migration of small fluorescent latex particles co-dispersing with large nonemissive latex particles. Comparing the measured PL intensity with that predicted by a model allows us to determine the quantity of small particles near the evaporating surface. The results reveal that the fluorescent particles segregate in two steps: The primary segregation occurs early in the evaporation stage, whereas the secondary stepwise migration occurs when the air–liquid interface invades the particle consolidation layer. The latter migration is attributed to the flow-induced motion of small particles that move through interstitial spaces between large particles. DOI : 10.1007/s11998-017-9946-1 En ligne : https://link.springer.com/content/pdf/10.1007%2Fs11998-017-9946-1.pdf Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=29125 [article]

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