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Reduction of air bubbles in spray-applied coatings / Matthew S. Gebhard in JOURNAL OF COATINGS TECHNOLOGY (JCT), Vol. 66, N° 830 (03/1994)

[article]  inJOURNAL OF COATINGS TECHNOLOGY (JCT) > Vol. 66, N° 830 (03/1994) . - p. 27-39 Titre : Reduction of air bubbles in spray-applied coatings Type de document : texte imprimé Auteurs : Matthew S. Gebhard, Auteur ; L. E. Scriven, Auteur Année de publication : 1994 Article en page(s) : p. 27-39 Note générale : Bibliogr. Langues : Américain (ame) Tags : Peinturage  Pulvérisation  'Bulle  air'  'Peinture  eau'  Défaut  'Etude  expérimentale'  'Photographie  rapide'  'Technique  vidéo' Index. décimale : 667.9 Revêtements et enduits Résumé : Microfoam (i.e., tiny (10 μm) air bubbles) in spray-applied coatings is a frequently encountered problem which may be aggravated in water-based coatings. This paper describes recent work to understand the dynamics of the microfoam formation and dissipation process. The data indicate that the majority of microfoam does not form by the splashing of atomized drops on the building liquid film. In fact, the atomized drops arrive at the substrate with numerous air bubbles, and poor atomization is observed to be a key to the problem. It is found that air bubbles dissipate through a dissolution mechanism and not the generally accepted rise and rupture mechanism. The dissolution is driven by surface tension and is mediated by diffusion through the liquid. The experimental data are found to agree with the Epstein and Plesset model, with lower diffusion coefficients, lower air solubility, and lower surface tension reducing the dissolution rate. This study has led to a novel solution to the problem and involves using carbon dioxide (CO2) as the driving gas instead of air. It is found that this leads to a significant reduction in entrapped air in conventional, high volume low pressure (HVLP), and air-assisted airless spray techniques. This approach is found to work because of the much higher solubility of CO2 in water versus air in water. Note de contenu : - EXPERIMENTAL : High-speed video microscopy - High-speed photography - Dissolution measurements - Determination of diffusion coefficients - Spray applications using CO2 and air - RESULTS AND ANALYSIS : High-speed video microscopy - High-speed photography - Microfoam dissipation in spray-applied coatings - Dissolution measurements - Determination of diffusion coefficients - Spray applications using CO2 and air Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=18606 [article]

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Novel epoxy resins for container waterborne coatings with improved flexibility / Duane S. Treybig in JOURNAL OF COATINGS TECHNOLOGY (JCT), Vol. 66, N° 830 (03/1994)

[article]  inJOURNAL OF COATINGS TECHNOLOGY (JCT) > Vol. 66, N° 830 (03/1994) . - p. 41-45 Titre : Novel epoxy resins for container waterborne coatings with improved flexibility Type de document : texte imprimé Auteurs : Duane S. Treybig, Auteur ; David P. Sheih, Auteur Année de publication : 1994 Article en page(s) : p. 41-45 Note générale : Bibliogr. Langues : Américain (ame) Tags : 'Peinture  eau'  Liant  'Epoxyde  résine'  Feuil  'Propriété  mécanique'  Flexibilité  Utilisation  Bidon Index. décimale : 667.9 Revêtements et enduits Résumé : New two-piece can technologies are increasing market demand for more flexible can coatings. In response to the demand, several different waterborne epoxy resin systems have been prepared by synthesizing epoxy resin with new flexible backbones and converting them to onium forms. More specifically, the coating epoxy resins were made by modifying the resin backbone with extended aliphatic spacers of either bisphenol or diepoxide structures. These flexible epoxy resins were then converted to onium forms by reacting the epoxide group with an aqueous mixture of lactic acid and nicotinamide. When the resulting aqueous dispersions are formulated and cured with melamine-formaldehyde resin, the resultant coatings exhibit improved flexibility and pasteurization resistance as compared to coatings from high molecular weight diglycidyl ether of bisphenol A epoxy resin controls. The new epoxy resin backbone chemistry, waterborne conversion chemistry, and coating properties are described in this paper. Note de contenu : - EXPERIMENTAL : Materials - Resin advancement - Onium conversion - Coating formulation - Coating tests Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=18607 [article]

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Aqueous polyurethanes - polymer colloids with unusual colloidal, morphological, and application characteristics / R. Satguru in JOURNAL OF COATINGS TECHNOLOGY (JCT), Vol. 66, N° 830 (03/1994)

[article]  inJOURNAL OF COATINGS TECHNOLOGY (JCT) > Vol. 66, N° 830 (03/1994) . - p. 47-55 Titre : Aqueous polyurethanes - polymer colloids with unusual colloidal, morphological, and application characteristics Type de document : texte imprimé Auteurs : R. Satguru, Auteur ; J. McMahon, Auteur ; J. C. Padget, Auteur ; R. G. Coogan, Auteur Année de publication : 1994 Article en page(s) : p. 47-55 Note générale : Bibliogr. Langues : Américain (ame) Tags : 'Peinture  eau'  Liant  'Uréthanne  polymère'  'Dispersion  colloïdale'  Granularité  Morphologie  'Formation  film'  Feuil  'Propriété  mécanique'  Dureté Index. décimale : 667.9 Revêtements et enduits Résumé : Aqueous polyurethane dispersions are becoming an increasingly important class of materials in the surface coatings industry. Because of the synthetic procedure employed in the preparation of aqueous polyurethanes, they differ significantly from typical emulsion polymers in terms of colloid stability characteristics and particle morphology. Fluorescence spectroscopy and small angle neutron scattering techniques demonstrated that the particles in a polyurethane dispersion are swollen with water. The consequences of this morphology in terms of the ability to combine low film forming temperature with good film hardness is discussed. The particle size distribution of aqueous polyurethanes was found to be broader than that of typical emulsion polymers. Results are presented which demonstrate how control over average particle size and colloid stability can be achieved in aqueous polyurethanes. Note de contenu : - INTRODUCTION : Polyurethane dispersions - RESULTS AND DISCUSSION : Cooloidal porperties-particle size distribution - Colloid stability - Particle size control - Particle morphology - Film formation and film hardness Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=18608 [article]

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Foam stability and foam fractionation of water-reducible acrylic polymer systems / Rebecca Twite in JOURNAL OF COATINGS TECHNOLOGY (JCT), Vol. 66, N° 830 (03/1994)

[article]  inJOURNAL OF COATINGS TECHNOLOGY (JCT) > Vol. 66, N° 830 (03/1994) . - p. 57-63 Titre : Foam stability and foam fractionation of water-reducible acrylic polymer systems Type de document : texte imprimé Auteurs : Rebecca Twite, Auteur ; Jiandong Zhu, Auteur ; Gordon P. Bierwagen, Auteur Année de publication : 1994 Article en page(s) : p. 57-63 Note générale : Bibliogr. Langues : Américain (ame) Tags : 'Peinture  eau'  Défaut  Moussage  Liant  'Acrylique  dérivé  polymère' Index. décimale : 667.9 Revêtements et enduits Résumé : Foaminess of water-reducible polymer systems continues to pose problems inhibiting maximum effectiveness of these materials in industry. With this in mind, studies were initiated using water-reducible acrylic polymers, testing of the dynamic foam stability of this polymer at concentrations typical to industrial use (circa 20% by weight), and performing separations of the polymers by means of foam fractionation. The dynamic foam test consists of measuring the steady-state foam volume in relation to varied gas flow rates in a column provided with a gas frit and space for a fixed liquid volume of foaming liquid. Foam volume vs gas flow rate provides an efficient method in comparing foam stabilities of different water-reducible systems. Foam fractionation is an effective way of separating the surface active/foam stabilizing species in a system. Different aspects under consideration when characterizing the fractions are molecular weight distribution, surface tension, solids composition, and qualitative end-group analysisby by means of FTIR. Results reported include the ranking of polymer solutions by relative foaminess, and the characterization of the various fractions obtained by the foam fractionation of one typical W/R acrylic polymer. A comparison between microemulsions and W/R polymers is embarked. Note de contenu : -INTRODUCTION -PROCEDURES : Polymer synthesis - Preparation of solutions - Foaminess - Foam fractionation - Testing of solution properties -RESULTS : Foaminess - Foam fractionation -SUMMARY AND CONCLUSIONS -FUTURE WORK Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=18612 [article]

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A critique of the taguchi approach-part I : a presentation of some deficiencies and how these limit its efficiency and validity / John McGovern in JOURNAL OF COATINGS TECHNOLOGY (JCT), Vol. 66, N° 830 (03/1994)

[article]  inJOURNAL OF COATINGS TECHNOLOGY (JCT) > Vol. 66, N° 830 (03/1994) . - p. 65-70 Titre : A critique of the taguchi approach-part I : a presentation of some deficiencies and how these limit its efficiency and validity Type de document : texte imprimé Auteurs : John McGovern, Auteur Année de publication : 1994 Article en page(s) : p. 65-70 Note générale : Bibliogr. Langues : Américain (ame) Index. décimale : 667.9 Revêtements et enduits Résumé : The emphasis in the Taguchi method of quality control, on using experimental design to improve the quality and performance of products and processes by designing them to be insensitive to noise factors, is viewed by many statisticians as his major contribution. The statistical tools he proposes to achieve his goal have been shown to be less efficient and more complicated than other existing methods. These alternative methods of analysis are recommended by some eminent statisticians as the preferred tools to analyze data from designed experiments. Note de contenu : - Introduction - Design of experiments - a brief history - Taguchi methods - Strengths and weaknesses of the taguchi method - Conclusions Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=18613 [article]

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