Crosslinking of epoxy-modified phenol novolac (EPN) powder coatings : particle size and adhesion / B. D. Pennington in JOURNAL OF COATINGS TECHNOLOGY (JCT), Vol. 71, N° 897 (10/1999)

[article]  inJOURNAL OF COATINGS TECHNOLOGY (JCT) > Vol. 71, N° 897 (10/1999) . - p. 135-142 Titre : Crosslinking of epoxy-modified phenol novolac (EPN) powder coatings : particle size and adhesion Type de document : texte imprimé Auteurs : B. D. Pennington, Auteur ; J. C. Grunlan, Auteur ; M. W. Urban, Auteur Année de publication : 1999 Article en page(s) : p. 135-142 Note générale : Bibliogr. Langues : Américain (ame) Index. décimale : 667.9 Revêtements et enduits Résumé : These studies were undertaken to examine how particle size of epoxy phenol novolac (EPN) powder coatings may affect adhesion to metal substrates. Particle sizes of 21 and 83 ?m diameter were utilized. DSC analysis shows that the activation energies of crosslinking for the 21 ?m particle size is 41 kJ/mol and 58 kJ/mol for 83 ?m particle size which is attributed to the effect of particle size, and time-temperature-particle size (TTPS) parameters are used to describe powder-liquid-solid film transformation process. Although, the TTSP term represents a combination of intrinsic and extrinsic properties. We believe that this is the TTPS term that adequately describes the processes in which, in order for crosslinking reactions to occur, particles must initiate the flow. Quantitative attenuated total reflectance (ATR) Fourier transform infrared (FTIR) spectroscopic analysis was used to follow crosslinking processes by monitoring the decrease of oxirane concentration, and showed that for thermal cure at 185°C for 20 min, the oxirane concentration decreases at a similar rate for 21 ?m and 83 ?m particle sizes. The results of pull-off adhesion measurements from an Al substrate show that when the 21 ?m particle size is crosslinked for 10 min at 110, 140, and 170°C, adhesion is consistently higher than for the same coating system at 83 ?m particle size. This difference is attributed to the finite time required for powder particles to reach a proper melt viscosity, followed by reactions of functional groups leading to crosslinking. Extended cure times to 120 min for the 83 ?m particle resulted in adhesion similar to the 21 ?m particle size. Note de contenu : - Sample preparation - DSC measurements - Spectroscopic measurements - Adhesion measurements Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=17945 [article]

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Interfacial studies of crosslinked urethanes : Part III. Structure-property relationships in polyester waterborne polyurethanes / M. W. Urban in JOURNAL OF COATINGS TECHNOLOGY (JCT), Vol. 71, N° 888 (01/1999)

[article]  inJOURNAL OF COATINGS TECHNOLOGY (JCT) > Vol. 71, N° 888 (01/1999) . - p. 75-85 Titre : Interfacial studies of crosslinked urethanes : Part III. Structure-property relationships in polyester waterborne polyurethanes Type de document : texte imprimé Auteurs : M. W. Urban, Auteur ; C. L. Allison, Auteur ; C. C. Finch, Auteur ; B. A Tatro, Auteur Année de publication : 1999 Article en page(s) : p. 75-85 Note générale : Bibliogr. Langues : Américain (ame) Catégories : Chimie des surfaces Cinétique chimique Couches minces Fourier, Spectroscopie infrarouge à transformée de Interfaces (Sciences physiques) Polyaddition Polyesters Polyurée Polyuréthanes Réactions chimiques Réticulation à l'humidité Revêtements en phase aqueuse:Peinture en phase aqueuse Spectroscopie de réflectance Index. décimale : 667.9 Revêtements et enduits Résumé : These studies examine crosslinking reactions of polyurethanes (PURs) using attenuated total reflectance Fourier-transform (ATR FTIR) spectroscopy and show that higher relative humidity (RH) accelerates the crosslinking reactions leading to the formation of polyurethane and polyurea. Concentration levels of unreacted isocyanate (NCO) are greater at the film-air (F-A) interface than the film-substrate (F-S) interface. In contrast to the previous studies on polyacrylate emulsion urethanes, no stratification was detected between 0.65 to 1.14 um near the F-A and F-S interfaces. This behavior is attributed to equivalent weight differences, 3100 g/eg for polyacrylate and 1140 g/eq for polyester. Solvent evaporation experiments show that approximately 10% of the initial water concentration remains in the film for extended periods of time, resulting in reactions leading to the fomation of urea near the F-S interface.Pur film formation occurs in two stages, a solvent vapor pressure controlled stage, followed by a diffusion controlled stage. The duration of each stage depends on several factors, including the amount of shear induced on the shear thinning waterborne urethanes, which subsequently affects the exposure of isocyanate aggregates to water. Increased RH significantly affects structure-property relationships of waterborne PURs due to urea formation, which alters the glass transition temperature, storage modulus, crosslink density, and film hardness. Note de contenu : - EXPERIMENTAL : Sample preparation - Analytical methods Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=17816 [article]

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The effect of polyurethane curing conditions on the delamination of pressure sensitive films / B. W. Ludwig in JOURNAL OF COATINGS TECHNOLOGY (JCT), Vol. 66, N° 839 (12/1994)

[article]  inJOURNAL OF COATINGS TECHNOLOGY (JCT) > Vol. 66, N° 839 (12/1994) . - p. 59-67 Titre : The effect of polyurethane curing conditions on the delamination of pressure sensitive films Type de document : texte imprimé Auteurs : B. W. Ludwig, Auteur ; M. W. Urban, Auteur Année de publication : 1994 Article en page(s) : p. 59-67 Note générale : Bibliogr. Langues : Américain (ame) Catégories : Adhésifs sensibles à la pression Analyse spectrale Automobiles -- Revêtements:Automobiles -- Peinture Délaminage Dioxyde de carbone Films plastiques polymères vinyliques Polyuréthanes Réticulation (polymérisation) Revêtements bi-composant:Peinture bi-composant Index. décimale : 667.9 Revêtements et enduits Résumé : The application of vinyl films as graphics materials to the surface of urethane coatings used in OEM and vehicle refinishes is a common practice. However, if urethane coatings are not properly cured, the vinyl films may delaminate due to the evolution of gases within the coatings. In this study, the influence of curing temperature and time on the extent of delamination observed for several vinyl films having various degrees of permeability was examined. Using a newly developed «photoacoustic umbrella» Fourier transform infrared spectroscopy (PA FTIR) technique, CO2 has been identified as the gas responsible for the delamination of the graphics films. The mechanism of CO2 production and its relationship to the curing conditions are also discussed. Note de contenu : - Coating preparation - Testing of pressure sensitive vinyl films - Spectoscopic measurements Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=18728 [article]

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