Film formation from surfactant-free, slightly crosslinked, fluorescein-labeled polystyrene particles / Saziye Ugur in JOURNAL OF COATINGS TECHNOLOGY AND RESEARCH, Vol. 1, N° 4 (10/2004)  

[article]  inJOURNAL OF COATINGS TECHNOLOGY AND RESEARCH > Vol. 1, N° 4 (10/2004) . - p. 305-313 Titre : Film formation from surfactant-free, slightly crosslinked, fluorescein-labeled polystyrene particles Type de document : texte imprimé Auteurs : Saziye Ugur, Auteur ; Abdelhamid Elaissari, Auteur ; Önder Pekcan, Auteur Année de publication : 2004 Article en page(s) : p. 305-313 Note générale : Bibliogr. Langues : Américain (ame) Tags : 'Etude  expérimentale'  Fluorescéine  'Marquage  'Méthode  d'étude'  'Diffusion  mutuelle'  'Mécanisme  de  formation'  'Propriété  filmogène'  'Traitement  thermique'  Latex  'Polymère  réticulé'  Polystyrène Index. décimale : 667.9 Revêtements et enduits Résumé : A steady state-fluorescence (SSF) technique for studying film formation from surfactant-free, slightly crosslinked polystyrene (PS) latex particles is reported. The powder films were prepared from fluorescein (F)-labeled PS particles at room temperature. The mechanically strong films were obtained by annealing these films at elevated temperatures in 5, 10, 20, and 30 min time intervals above the glass transition (Tg) temperature of polystyrene. Scattered light (Is) and fluorescence (IF) intensities from F were monitored after each annealing step to investigate the three different film formation stages called void closure, healing, and interdiffusion. The evolution of transparency of the latex films was monitored by using a photon transmission technique. Scanning electron microscopy (SEM) was employed to detect the variation in physical structure of the annealed latex films. Onset temperature for void closure, Tm, and healing temperatures, Th, were determined and corresponding activation energies were measured. Void closure and interdiffusion stages were also modeled and the related activation energies were also determined. It was observed that lower energy is needed for the void closure process than interdiffusion of chains across the particle-particle boundaries. DOI : 10.1007/s11998-004-0032-0 En ligne : https://link.springer.com/content/pdf/10.1007%2Fs11998-004-0032-0.pdf Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=3861 [article]

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Films formed from polystyrene latex/clay composites : A fluorescence study / Saziye Ugur in JOURNAL OF COATINGS TECHNOLOGY AND RESEARCH, Vol. 2, N° 7 (07/2005)  

[article]  inJOURNAL OF COATINGS TECHNOLOGY AND RESEARCH > Vol. 2, N° 7 (07/2005) . - p. 565-575 Titre : Films formed from polystyrene latex/clay composites : A fluorescence study Type de document : texte imprimé Auteurs : Saziye Ugur, Auteur ; Önder Pekcan, Auteur ; Ayse Alemdar, Auteur Année de publication : 2005 Article en page(s) : p. 565-575 Note générale : Bibliogr. Langues : Américain (ame) Tags : 'Propriété  optique'  'Spectrométrie  de  fluorescence'  'Etude  Morphologique'  Transparence  Recuit  'Relation  mise  en  oeuvre  structure'  'Effet  concentration'  la  température'  propriété'  Montmorillonite  'Formation  film'  'Matériau  renforcé'  Dispersion  composite'  Argile  Latex  Polystyrène Index. décimale : 667.9 Revêtements et enduits Résumé : This study reports a steady-state fluorescence (SSF) technique for studying film formation from surfactant-free polystyrene (PS) latex and Na-montmorillonite (SNaM) composites. The composite films were prepared from pyrene (P)-labeled PS particles and SNaM clay at room temperature and annealed at elevated temperatures in 10-min intervals above glass transition temperature (Tq) of polystyrene. During the annealing processes, the transparency of the film improved considerably. Scattered light (IS) and fluorescence intensity (IP) from P were measured after each annealing step to monitor the stages of film formation. Evolution of transparency of composite films was monitored by using photon transmission intensity, Itr. Scanning electron microscopy (SEM) was used to detect the variation in physical structure of annealed composite films. Minimum film formation temperature, T0' and healing temperatures, Th' were determined. Void closure and interdiffusion stages were modeled and related activation energies were determined. It was observed that both activation energies increased as the percent of SNaM was increased in composite films. DOI : 10.1007/s11998-005-0016-8 En ligne : https://link.springer.com/content/pdf/10.1007%2Fs11998-005-0016-8.pdf Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=3804 [article]

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A fluorescence study on dissolution of polymeric glasses prepared in various molecular weights / Önder Pekcan in JOURNAL OF COATINGS TECHNOLOGY (JCT), Vol. 75, N° 944 (09/2003)

[article]  inJOURNAL OF COATINGS TECHNOLOGY (JCT) > Vol. 75, N° 944 (09/2003) . - p. 55-63 Titre : A fluorescence study on dissolution of polymeric glasses prepared in various molecular weights Type de document : texte imprimé Auteurs : Önder Pekcan, Auteur ; Saziye Ugur, Auteur Année de publication : 2003 Article en page(s) : p. 55-63 Note générale : Bibiogr. Langues : Américain (ame) Tags : Cinétique  Polymère  vitreux  Gel  colloïdal  Polymérisation  masse  Désorption  Relation  moléculaire  propriété  Méthode  mesure  Dissolution  Gonflement  Fluorescence  Extinction  luminescence  radicalaire  Polyméthacrylate  méthyle Index. décimale : 667.9 Revêtements et enduits Résumé : Polymethyl methacrylate (PMMA) discs in various molecular weights, Mw, were prepared by free-radical polymerization of methyl methacrylate (MMA). Pyrene (P) was introduced during polymerization as a fluorescence probe to monitor the gelation and dissolution processes in chloroform vapor and solvent, respectively. In-situ steady state fluorescence (SSF) experiments were performed to monitor vapor uptake and chain desorption processes. Direct illumination of PMMA discs were performed to excite the P molecules embedded inside the PMMA glass. Variation in P intensity, I, was monitored during the swelling of the PMMA material exposed to chloroform vapor. It was observed that PMMA film swells like a crosslinked polymeric gel at early times by obeying the Li-Tanaka equation. Swelling time constants, tc, of PMMA discs were measured and found to have a strong correlation with the molecular weight, of PMMA. In a separate experiment, when the PMMA discs were in chloroform, desorption of PMMA chains from glass discs was monitored by observing the change of pyrene fluorescence intensity. A diffusion model with a moving boundary was employed to quantify the fluorescence data observed from dissolving PMMA discs made at various molecular weights. It was observed that desorption coefficient, D, decreased by increasing Mw by obeying the D»Mw–1 law. Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=5573 [article]

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UV-visible technique for studying powder coatings and their dissolution / Önder Pekcan in JOURNAL OF COATINGS TECHNOLOGY (JCT), Vol. 73, N° 923 (12/2001)

[article]  inJOURNAL OF COATINGS TECHNOLOGY (JCT) > Vol. 73, N° 923 (12/2001) . - p. 51-60 Titre : UV-visible technique for studying powder coatings and their dissolution Type de document : texte imprimé Auteurs : Önder Pekcan, Auteur ; Ertan Arda, Auteur Année de publication : 2001 Article en page(s) : p. 51-60 Note générale : Bibliogr. Langues : Américain (ame) Tags : Etude  expérimentale  Spectrométrie  UV  visible  Recuit  Traitement  thermique  Heptane  Chloroforme  Solvant  organique  Dissolution  Méthacrylate  de  méthyle  polymère  Latex  Formation  film  Peinture  poudre  Matériau  revêtement Index. décimale : 667.9 Revêtements et enduits Résumé : UV-Visible (UVV) technique was used to monitor powder coating and its dissolution processes from hard latex particles. Three sets of latex coatings were prepared from poly(methyl methacrylate) (PMMA) particles. The first set of coatings was annealed at elevated temperatures in various time intervals during which reflected photon intensity, Irf, was measured. The second set of coatings was annealed at various temperatures in 10 min time intervals during which transmitted intensity, Itr, was measured. Irf first decreased and then increased as the annealing temperature was increased. Decrease in Irf was explained with the void closure mechanism due to viscous flow. Increase in Itr and Irf against time and temperature were attributed to an increase in crossing density at the junction surface. The activation energy of viscous flow, delta H, was measured and found to be around 8 kcal/mol and the back and forth activation energies (delta Erf and delta Etr) were measured and found to be around 49 and 53 kcal/mol for a reptating polymer chain across the junction surface. Diffusion of solvent molecules (chloroform) into the annealed latex coatings was followed by desorption of PMMA chains for the third set of films. Desorption of pyrene, P, labeled PMMA chains was monitored in real-time by the absorbance change of pyrene in the polymer-solvent mixture. A diffusion model with a moving boundary was employed to quantify real-time UVV data. Diffusion coefficients of desorbed PMMA chains were measured and found to be between 2 and 0.6 x 10-11 cm2 s-1 in the 100 and 275°C temperature range. Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=5771 [article]

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