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New additive to eliminate pinholes for water-based coating formulations / Jim Reader in COATINGS TECH, Vol. 18, N° 3 (03/2021)  

[article]  inCOATINGS TECH > Vol. 18, N° 3 (03/2021) . - p. 30-37 Titre : New additive to eliminate pinholes for water-based coating formulations Type de document : texte imprimé Auteurs : Jim Reader, Auteur ; Jos van Oosterwijk, Auteur ; Caixuan Xu, Auteur ; Ye Dai, Auteur ; Ruediger Mertsch, Auteur ; Shauna McAuliffe, Auteur ; Jianchang Tang, Auteur Année de publication : 2021 Article en page(s) : p. 30-37 Note générale : Bibliogr. Langues : Américain (ame) Catégories : Antimousse Automobiles -- Revêtements Couche de base Dépôt par pulvérisation Encre Formulation (Génie chimique) Piqures (défaut) Revêtements -- Défauts Revêtements en phase aqueuse -- Additifs Revêtements organiques Surfactants Tension superficielle Vernis bi-composant Viscosité Index. décimale : 667.9 Revêtements et enduits Résumé : Pinholes are a problem for formulators developing fast-drying, water-based coatings, especially in coatings cured at high temperature and applied at high wet film thickness. Pinholes are often caused by air or solvent vapor release from the film when the coating is too viscous to flow back and repair the holes. Pinholes also occur in baked coatings, as the trapped vapor regains mobility when the coating softens under heating, before crosslinking hardens the film, preventing flow back into the voids. Hydrocarbon-based defoamers help eliminate the foam and pinholes in these formulations, but their limited compatibility results in lower gloss, poor leveling and surface appearance. This paper describes a new additive that combines both deaeration of microfoam and modified surface drying for pinhole elimination. This new additive shows comparable pinhole elimination compared with hydrocarbon-based defoamers, but without compromising formulation compatibility or final coating appearance. Note de contenu : - New additive development - Fig. 1 : Pinholes in a spray applied automotive OEM basecoat - Fig. 2 : bubble release and pinhole formation in an applied film - Fig. 3 : Molecular defoamer mechanism to eliminate microfoam - Fig. 4 : Change in film fluidity of a water-based coating during drying - Fig. 5 : Influence of surfactants on open time of water-based, 2K clearcoat new anti-pinhole additive - Fig. 6 : a) Surface tension reduction with LA-W 1814 and b) Foam control in water-based primer - Fig. 7 : The "wedge" application test - Fig. 8 : Minimum film thickness for pinhole formation - Fig. 9 : Foam control and surface appearance of white basecoat sprayed with different anti-pinhole additives - Fig. 10 Panels of white basecoat containing different anti-pinhole additives - Fig. 11 : Foam and surface appearance of silver basecoat panels after clearcoat Application - Fig. 12 : a) Flop index and b) wave scan of silver basecoat panels after clearcoat application - Fig. 13 : Images of water-based plastic coating applied onto glass after high-speed stirring. (Panels are viewed from back of panel with backlighting) - Fig. 14 : Foam control in water-based packaging ink - Fig. 14 : - Table 1 : White basecoat formulation - Table 2 : Blue packaging ink formulation En ligne : https://drive.google.com/file/d/11XvghQD3eob_XhUd0fbNTfayVNfj_h-N/view?usp=share [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=35527 [article]

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Carbon nanotube-based optical black coatings for optical and infrared application / D. Carnahan in COATINGS TECH, Vol. 18, N° 3 (03/2021)  

[article]  inCOATINGS TECH > Vol. 18, N° 3 (03/2021) . - p. 38-44 Titre : Carbon nanotube-based optical black coatings for optical and infrared application Type de document : texte imprimé Auteurs : D. Carnahan, Auteur ; T. Morgan, Auteur Année de publication : 2021 Article en page(s) : p. 38-44 Note générale : Bibliogr. Langues : Américain (ame) Catégories : Nanotubes Noir (couleur) Permittivité La permittivité, plus précisément permittivité diélectrique, est une propriété physique qui décrit la réponse d'un milieu donné à un champ électrique appliqué. C'est une propriété macroscopique, essentielle de l'électrostatique, ainsi que de l‘électrodynamique des milieux continus. Elle intervient dans de nombreux domaines, notamment dans l’étude de la propagation des ondes électromagnétiques, et en particulier la lumière visible et les ondes utilisées en radiodiffusion. On la retrouve donc en optique, via l'indice de réfraction. Les lois gérant la réfraction et la réflexion de la lumière y font appel. Réfraction, Indice de Revêtements -- Propriétés optiques:Peinture -- Propriétés optiques Index. décimale : 667.9 Revêtements et enduits Résumé : From the very first paints to today, the discovery and development of the purest of materials and pigments has been a goal for artists and designers alike. The search for the blackest of black pigments is likely now at its end, or nearly so, with the development of carbon nanotube-based paints that swallow more than 99% of light across the visible spectrum. The focus of our paint development over the last five years has been on creating the blackest matte-black paints using carbon nanotubes and tailoring them for use across the ultraviolet, visible, and infrared. Vertically aligned carbon nanotube arrays (VANTA) hold the record as the world’s blackest, most highly absorbing materials, and this is due both to their chemical composition and their structure. The optical properties of carbon nanotubes are crystallographically dependent, as their structure is highly anisotropic. Nanotubes are similar to graphite, which has different in-plane and thru-thickness optical constants, except that in carbon nanotubes, the planes are wrapped into a tubular shape. As a result, VANTA coatings are not very black at grazing-angle incidence, due to that structural anisotropy. The VANTA coatings are synthesized at >500 °C, limiting the materials that can host such a material. To address this and other issues, we have researched and developed optically absorbing carbon nanotube-loaded paints (now marketed as Singularity Black). These use a more randomized structure that has been tailored for high-optical and infrared absorption at normal and grazing-angle incidence. This paper describes the structures necessary for highly absorbing black coatings and reviews the approach and data collected for two products, Singularity Black paint, and our version of vertically aligned nanotube arrays, adVANTA. Note de contenu : - Fig. 1 : SEM image of a cleaved adVANTA array showing the overall alignment and density of CNT - Fig. 2 : Fisher's group used FTDT simulations to model the dielectric function of CNTs. Using that data and we calculated the complex refractive index at 550 nm and estimage the index for a 45° condition analogous to a randomly aligned structure - Fig. 3 : When heated, the crosslinker and polymer bond strongly, locking the CNT in a porous network - Fig. 4 : Sequence of magnifications, showing the CNT network porosity at multiple size scales - Fig. 5 : THR of severan adVANTA coatings grown on several substrates - Fig. 6 : THR for singularity black coatings on stainless steel and aluminum - Fig. 7 : DRIFTS data for adVANTA arrays - Fig. 8 : DRIFTS data for singularity black coatings on Al with and without primer - Fig. 9 : Glare at low angles of incidence can be seen in standard processed VANTA (L) but not with the sprayed coating (R), owing to its random structure En ligne : https://drive.google.com/file/d/1wCdhfF8t7WHKnFm2qyWlkpkhtIeHU44F/view?usp=share [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=35528 [article]

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Coatings tech Vol. 18, N° 3 URL