Studying the effects of the chemical structure of an automotive clearcoat on its biological degradation caused by tree gums / Bahram Ramezanzadeh in JOURNAL OF COATINGS TECHNOLOGY AND RESEARCH, Vol. 8, N° 3 (05/2011)  

[article]  inJOURNAL OF COATINGS TECHNOLOGY AND RESEARCH > Vol. 8, N° 3 (05/2011) . - p. 375-387 Titre : Studying the effects of the chemical structure of an automotive clearcoat on its biological degradation caused by tree gums Type de document : texte imprimé Auteurs : Bahram Ramezanzadeh, Auteur ; Mohsen Mohseni, Auteur ; H. Yari, Auteur Année de publication : 2011 Article en page(s) : p. 375-387 Note générale : Bibliogr. Langues : Américain (ame) Catégories : Automobiles -- Vernis Biodégradation Gomme arabique Vernis -- Détérioration Index. décimale : 667.9 Revêtements et enduits Résumé : The effects of artificial and natural tree gums on the mechanical, chemical, and aesthetic performances of two automotive acrylic/melamine clearcoats were studied. To this end, two clearcoats with different acrylic/melamine ratios were investigated. Biological experiments were performed under post-aging conditions using an accelerated weathering test. Analytical techniques including optical microscopy, scanning electron microscopy (SEM), gloss measurement, FTIR, and DMTA analyses were utilized to reveal the responses of the coating system upon exposure to the aforementioned biological materials. Contact angle measurements were also conducted to estimate the surface energy of the coatings. Greater crosslinking density, together with a higher T g and damping behavior of the clearcoat, indicative of a greater degree of cure, were obtained as the ratio of melamine crosslinker increased. It was shown that both Arabic and natural tree gums could strongly attach to the clearcoats’ surface, imposing a significant stress during the drying process, thereby leading to a physical failure. In addition, the acidic nature of these biological materials leads to a chemical alteration in the clearcoats’ structure. The greater crosslinking density and lower hydrophilicity of the clearcoats containing higher melamine crosslinker were responsible for the weaker interaction of gums with the surface. This showed a greater capability for stress damping. Small surface cracks with fracture morphology on the coatings exposed to biological materials at higher exposure times (in the xenon test) were also observed. This is discussed based on the adhesion of the coatings to gums at longer exposure times, because of significant stress. Note de contenu : - EXPERIMENTAL : Sample preparation - Biological test - Instrumentation. - RESULTS AND DISCUSSION : Clearcoat properties - Microscopic analysis - Effect of arabic gum on clearcoat chemical structure - Effect of arabic gum on clearcoat mechanical properties - Appearance analysis. DOI : 10.1007/s11998-010-9312-z En ligne : https://link.springer.com/content/pdf/10.1007%2Fs11998-010-9312-z.pdf Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=11677 [article]

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The role of basecoat pigmentation on the biological resistance of an automotive clearcoat / Bahram Ramezanzadeh in JOURNAL OF COATINGS TECHNOLOGY AND RESEARCH, Vol. 7, N° 6 (11/2010)  

[article]  inJOURNAL OF COATINGS TECHNOLOGY AND RESEARCH > Vol. 7, N° 6 (11/2010) . - p. 677-689 Titre : The role of basecoat pigmentation on the biological resistance of an automotive clearcoat Type de document : texte imprimé Auteurs : Bahram Ramezanzadeh, Auteur ; Mohsen Mohseni, Auteur ; H. Yari, Auteur Année de publication : 2010 Article en page(s) : p. 677-689 Note générale : Bibliogr. Langues : Américain (ame) Catégories : Automobiles -- Vernis Biodégradation Fourier, Spectroscopie infrarouge à transformée de Microscopie électronique Salissures biologiques Vernis -- Détérioration Index. décimale : 667.9 Revêtements et enduits Résumé : This work aims to study the effect of various natural and artificial biological compounds on an automotive acrylic/melamine clearcoat applied over silver and black basecoats containing pigments. The visual performance of the coating system was evaluated at different aging conditions. To this end, analytical techniques including optical microscopy, scanning electron microscopy, gonio-spectrophotometery, gloss measurement, ATR-FTIR spectroscopy, and DMTA analysis were utilized to investigate the optical and mechanical response of the system upon exposure to the biological materials. Results indicated different effects produced by gums and bird droppings on both silver and black systems at all aging processes. In addition, a more severe effect of biological attacks was observed on the clearcoat samples applied on the black basecoat which had experienced postaging conditions. However, it was found that pancreatin and bird droppings influence the coating systems more severely compared to the natural and synthetic Arabic gums. DOI : 10.1007/s11998-010-9254-5 En ligne : https://link.springer.com/content/pdf/10.1007%2Fs11998-010-9254-5.pdf Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=10394 [article]

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The weathering performance of acrylic melamine automotive clearcoats containing hydrophobic nanosilica / H. Yari in JOURNAL OF COATINGS TECHNOLOGY AND RESEARCH, Vol. 11, N° 3 (05/2014)  

[article]  inJOURNAL OF COATINGS TECHNOLOGY AND RESEARCH > Vol. 11, N° 3 (05/2014) . - p. 351-360 Titre : The weathering performance of acrylic melamine automotive clearcoats containing hydrophobic nanosilica Type de document : texte imprimé Auteurs : H. Yari, Auteur ; Siamak Moradian, Auteur ; N. Tahmasebi, Auteur Année de publication : 2014 Article en page(s) : p. 351-360 Note générale : Bibliogr. Langues : Américain (ame) Catégories : Analyse thermomécanique dynamique Automobiles -- Vernis Mélamine La mélamine, de nom chimique 1,3,5-triazine-2,4,6-triamine, est parfois dénommée cyanuramide ou cyanurotriamine. Sa formule brute est C3H6N6. Les "résines mélamine-formaldéhyde" ou "mélamine-formol" (sigle MF) sont appelées "mélamine" dans le langage courant. Elles font partie de la famille des aminoplastes qui regroupe des résines thermodurcissables aminées, issues d'un comonomère tel l'urée ou la mélamine, parfois le thiocarbamide, le cyanamide hydrogène ou le dicyandiamide ; le second comonomère étant le formaldéhyde. Nanoparticules Polyacryliques Silice La silice est la forme naturelle du dioxyde de silicium (SiO2) qui entre dans la composition de nombreux minéraux. La silice existe à l'état libre sous différentes formes cristallines ou amorphes et à l'état combiné dans les silicates, les groupes SiO2 étant alors liés à d'autres atomes (Al : Aluminium, Fe : Fer, Mg : Magnésium, Ca : Calcium, Na : Sodium, K : Potassium...). Les silicates sont les constituants principaux du manteau et de l'écorce terrestre. La silice libre est également très abondante dans la nature, sous forme de quartz, de calcédoine et de terre de diatomée. La silice représente 60,6 % de la masse de la croûte terrestre continentale. Vernis -- Détérioration Vernis -- Effets du climat Vernis -- Propriétés thermomécaniques Viscoélasticité Index. décimale : 667.9 Revêtements et enduits Résumé : This work is an attempt to study the effect of weathering on various properties of a typical acrylic melamine clearcoat containing various loads of nanosilica. It was found that nanosilica caused an incomplete curing process of the acrylic melamine clearcoat, leading to a lower crosslink density and also less Young’s modulus of clearcoat compared to the pure clearcoat. Thermo-mechanical analyses showed that incomplete curing of nanocomposites induced post-curing reactions during weathering, leading to an increase of crosslinking density and Young’s modulus of nanocomposites. Viscoelastic studies showed that incorporation of nanosilica into acrylic melamine resulted in more plastic behavior and higher elongation at break of clearcoats during weathering. In addition, gloss retention, surface topology, and chemical structure investigations revealed that nanosilica particles enhanced weathering performance of clearcoats. This was explained by UV–Visible spectroscopy which confirmed the ability of silica to absorb the harmful incident rays, protecting the clearcoat against weathering degradation. Note de contenu : - EXPERIMENTAL : Investigated paint systems - Weathering conditions - Characterization - RESULTS AND DISCUSSION : Appearance - FTIR spectroscopy - UV-Visible spectroscopy - Dynamic mechanical thermal analysis - Viscoelastic properties DOI : 10.1007/s11998-013-9541-z En ligne : https://link.springer.com/content/pdf/10.1007%2Fs11998-013-9541-z.pdf Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=21454 [article]

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