Effect of particle size distribution on stress development and microstructure of particulate coatings / Yan Wu in JOURNAL OF COATINGS TECHNOLOGY AND RESEARCH, Vol. 14, N° 2 (03/2017)  

[article]  inJOURNAL OF COATINGS TECHNOLOGY AND RESEARCH > Vol. 14, N° 2 (03/2017) . - p. 455–465 Titre : Effect of particle size distribution on stress development and microstructure of particulate coatings Type de document : texte imprimé Auteurs : Yan Wu, Auteur ; Lorraine F. Francis, Auteur Année de publication : 2017 Article en page(s) : p. 455–465 Note générale : Bibliogr. Langues : Américain (ame) Catégories : Carbonate de calcium broyé Copolymère styrène acrylate Dispersions et suspensions Granulométrie Latex Liants Microstructures -- Analyse Particules (matières) Revêtement -- Séchage Index. décimale : 667.9 Revêtements et enduits Résumé : The role of pigment particle size distribution on stress and microstructure development was studied for coatings prepared from aqueous suspensions of ground calcium carbonate (GCC) and latex binder. Stress development was monitored using a modified beam deflection technique under controlled environment. Microstructure was characterized by scanning electron microscopy (SEM) and cryogenic SEM. For coatings containing only GCC particles and no latex, a wide particle size distribution resulted in a significant particle size gradient in the cross-sectional microstructure and irregular stress development. With latex addition, uniform microstructures were observed in coatings with either wide or narrow GCC particle size distribution. GCC/latex coatings prepared using GCC with a wide particle size distribution developed a higher stress than those prepared using GCC with a similar average particle size but a narrow particle size distribution. The higher stress is related to the particle packing that results in smaller pore sizes and larger capillary pressures that drive compaction. In coatings prepared with the same GCC particles but different latex binders, the stress and cracking behavior of the coating depends on the latex properties. Note de contenu : - MATERIALS AND METHODS : Suspension systems - Drying stress measurement - Microstructure characterization - RESULTS AND DISCUSSION : Coatings prepared from GCC suspensions - Coatings prepared with GGC and styrene acrylate latex - Coatings prepared with GCC-W and different types of latex DOI : 10.1007/s11998-016-9866-5 En ligne : https://link.springer.com/content/pdf/10.1007%2Fs11998-016-9866-5.pdf Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=28160 [article]

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The reinforcing effect of crosslinkable waterborne polyurethane/polysiloxane composite emulsion by aqueous sol–gel method / Yan Wu in JOURNAL OF COATINGS TECHNOLOGY AND RESEARCH, Vol. 17, N° 1 (01/2020)  

[article]  inJOURNAL OF COATINGS TECHNOLOGY AND RESEARCH > Vol. 17, N° 1 (01/2020) . - p. 243-253 Titre : The reinforcing effect of crosslinkable waterborne polyurethane/polysiloxane composite emulsion by aqueous sol–gel method Type de document : texte imprimé Auteurs : Yan Wu, Auteur ; Junbao Wu, Auteur ; Yunxia Feng, Auteur Année de publication : 2020 Article en page(s) : p. 243-253 Note générale : Bibliogr. Langues : Américain (ame) Catégories : Angle de contact Caractérisation Composites à fibres de carbone -- Propriétés mécaniques Diffractométrie de rayons X Matériaux -- Renforcement Micrographie Polymères en émulsion Polyuréthanes Silicones Les silicones, ou polysiloxanes, sont des composés inorganiques formés d'une chaine silicium-oxygène (...-Si-O-Si-O-Si-O-...) sur laquelle des groupes se fixent, sur les atomes de silicium. Certains groupes organiques peuvent être utilisés pour relier entre elles plusieurs de ces chaines (...-Si-O-...). Le type le plus courant est le poly(diméthylsiloxane) linéaire ou PDMS. Le second groupe en importance de matériaux en silicone est celui des résines de silicone, formées par des oligosiloxanes ramifiés ou en forme de cage (wiki). Sol-gel, Procédé Thermogravimétrie Index. décimale : 667.9 Revêtements et enduits Résumé : A highly branched polysiloxane (S2) was prepared by an aqueous sol–gel process and used as an underlying crosslinker to modify silanized waterborne polyurethane (WPUS), and a novel crosslinked waterborne polyurethane (WPU)/polysiloxane composite with low VOC features was obtained. The good dispersibility of polysiloxane (S2) was proved by both TEM and DLS analyses, implying that the polysiloxane had an excellent intermiscibility with the WPU. The larger silsesquioxane network in the composite was proved by XPS, which was generated from the condensation of the Si–OH groups of polysiloxane and WPUS. On the basis of tensile results, the content of polysiloxane had a significant impact on the mechanical properties. The reinforcing and toughening synergy effect was found in the composite with a low concentration of S2. According to micrographs of the fracture surface, the dominating toughening mechanism was dependent on microcracks, while the high concentration of polysiloxane turned into silica particles in the WPU matrix, resulting in force concentration and degradation of the mechanical properties. However, the Young’s modulus increased with the increasing content of S2. Additionally, the incorporation of the crosslinked silsesquioxane structure also improved the hydrophobic properties and thermal stability of the composite. Note de contenu : - EXPERIMENTAL : Materials - Preparation of highly branched polysiloxane (S2) in aqueous medium - Preparation of waterborne polyurethane/polysiloxane composite emulsion - Characterization - RESULTS AND DISCUSSION : Characterization of highly branched polysiloxane - Dispersibility of aqueous polysiloxane - Siliceous structure - Mechanical properties - Micrographs of fracture surfaces - Dynamic mechanical properties - Microstructure during the film formation - XRD - Surface contact angle of composite - Thermogravimetric analysis DOI : 10.1007/s11998-019-00264-9 En ligne : https://link.springer.com/content/pdf/10.1007/s11998-019-00264-9.pdf Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=33742 [article]

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