Aller sur edunet
Accueil
Résultat de la recherche
3 résultat(s) recherche sur le tag 'kinetic'
Ajouter le résultat dans votre panier Affiner la recherche Générer le flux rss de la recherche
Partager le résultat de cette rechercheAlkyl triphenylphosphonium bromide surfactant mediated reactions of p-nitrophenyl acetate / S. Moore in TENSIDE, SURFACTANTS, DETERGENTS, Vol. 44, N° 3/2007 (06-07/2007)
Titre : Alkyl triphenylphosphonium bromide surfactant mediated reactions of p-nitrophenyl acetate Type de document : texte imprimé Auteurs : S. Moore, Auteur ; P. R. Dafonte, Auteur ; K. K. Ghosh, Auteur ; S. Bal, Auteur ; R. M. Palepu, Auteur Année de publication : 2007 Article en page(s) : p. 176-181 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Catalyse
Micelles
SurfactantsTags : SN2 reaction kinetic parameters Micellar catalysis Pseudophase model Alkyl phosphonium bromide surfactants a-nucleophile a-effect hydroxamic acid Index. décimale : 668.1 Agents tensioactifs : savons, détergents Résumé : Archive Tenside Surfactants Detergents - Issue 2007/03 Back to overview
Alkyl Triphenylphosphonium Bromide Surfactant Mediated Reactions of p-Nitrophenyl Acetate
Kinetic measurements were performed for the hydrolysis of p-nitrophenyl acetate as a model compound in micellar media. This reaction was studied both in the presence and absence of various alpha-effect nucleophiles, and in depth analyses were performed using acetohydroxamic acid (AHA). Rate surfactant profiles were obtained in the absence and presence of the AHA nucleophile for the alkyl triphenylphosphonium bromides (CnPPh3Br) surfactant series. All rate surfactant profiles were analyzed using the pseudophase model and modified pseudophase model (In the presence of nucleophile) in order to obtain the regression parameters, including binding constants and rate constants in the micellar pseudophase. Studies in the presence of acetohydroxamic acid and the alkyl triphenylphosphonium surfactants were also conducted as a function of pH to obtain the p-Ka/sub> value of the acetohydroxamic acid in the micellar media.Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=3218
in TENSIDE, SURFACTANTS, DETERGENTS > Vol. 44, N° 3/2007 (06-07/2007) . - p. 176-181[article]Réservation
Réserver ce document
Exemplaires (1)
Code-barres Cote Support Localisation Section Disponibilité 007660 - Périodique Bibliothèque principale Documentaires Disponible 
Titre : Dimethyl secondary amine chain extenders : a conceptual approach to in situ generation of advanced epoxy resins for rapid-cure, low-VOC coatings Type de document : texte imprimé Auteurs : Frederick H. Walker, Auteur ; Rob Rasing, Auteur ; Gamini A. Vedage, Auteur ; Michael Cook, Auteur Année de publication : 2009 Article en page(s) : p. 283-313 Note générale : Bibliogr. Langues : Américain (ame) Tags : Poly(N-methylazetidine) Dimethyl-meta-xylylenediamine Pseudo-first-order kinetic Amine reactivity epoxy curing agent Epoxy resin coating Flexibility Crosslink density Miller-Macosko calculation Chain extender VOC Low temperature cure Environmental movement Electrochemical impedance Aine reaction mechanism Mannich base Index. décimale : 667.9 Revêtements et enduits Résumé : Advanced epoxy resin oligomers have traditionally been utilized for coatings that combine fast dry-to-touch speed and good flexibility--properties demanded in many markets such as marine and industrial maintenance coatings. Unfortunately, advanced epoxy resins require formulation with large quantities of solvent that make attainment of modern VOC regulations difficult or impossible. Coatings formulated from low molecular weight liquid epoxy resin, on the other hand, can easier meet VOC challenges, but dry slowly and tend to be brittle. This presentation explores the concept of using fast reacting, di-functional amine chain extenders to generate epoxy oligomers in situ as a means to meet these opposing property demands. Methylamine-terminated poly-(N-methylazetidine) (pNMAz, 1) is prepared in a two-step process involving the Michael addition of methylamine to acrylonitrile, followed by hydrogenation in a methylamine-containing atmosphere to yield an oligomer stream with an [M.sub.n] of about 250. Competitive pseudo-first-order kinetic measurements conducted in isopropyl alcohol indicate methyl-substituted disecondary diamines reacted approximately 3 to 3.6 times faster with phenyl glycidyl ether (PGE) than the primary amine meta-xylylenediamine (MXDA). These chain extenders can be formulated with traditional multi-functional amine crosslinkers to yield coatings with lower VOC, faster dry speed, and better flexibility compared to corresponding coatings formulated without the chain extender. DOI : 10.1007/s11998-009-9178-0 En ligne : https://link.springer.com/content/pdf/10.1007%2Fs11998-009-9178-0.pdf Format de la ressource électronique : Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=6111
in JOURNAL OF COATINGS TECHNOLOGY AND RESEARCH > Vol. 6, N° 3 (09/2009) . - p. 283-313[article]Réservation
Réserver ce document
Exemplaires (1)
Code-barres Cote Support Localisation Section Disponibilité 011503 - Périodique Bibliothèque principale Documentaires Disponible
Titre : Synthesis, characterization and thermodynamic parameters of anionic gemini surfactants with different spacer groups Type de document : texte imprimé Auteurs : H. El-sharkawy Ali, Auteur Année de publication : 2007 Article en page(s) : p. 281-286 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Adsorption
Caractérisation
Micelles
Surfactants -- Synthèse
Tension superficielle
ThermodynamiqueTags : 'Gemini surfactants' 'Critical micelle concentration' 'Surface tension kinetic micellization' 'Thermodynamics of Adsorption Index. décimale : 668.1 Agents tensioactifs : savons, détergents Résumé : The aim of this work is to investigate the micellization and adsorption thermodynamics (DmicH°, DmicG°, DmicS°, DadsH°, DadsG°, DadsS°) for three novel anionic Gemini surfactants with the same structure except the spacer length of the polymethylene chain have been synthesized based on nonylphenol (NP). The surface tension at cmc (Ycmc) and critical micelle concentration (cmc) of the surfactants in aqueous solutions have been investigated. C20 values (surfactant concentration in the solution phase that will reduce the surface tension of the solvent by 20 mNm–1) were also obtained. The critical micellar concentration (cmc) and the minimum average area per surfactant molecule (Amin) at the air-water interface of Gemini surfactant decrease with increasing number of methylene moieties in the spacer and, consequently, with the enhanced hydrophilic character of the molecule. The results were discussed with particular emphasis on the effect of the length spacer on the hydrophilic character of the spacer group. The surface studies of the molecules confirm that the exothermic values of the differential enthalpy of micellization (DmicH°) decrease as the methylene moieties are lengthened. Moreover, the values of the free energy (DmicG°) and entropy (DmicS°) of micellization indicate an entropy driven phenomenon for all surfactants. The effect of length spacer on surfactant adsorption for Gemini surfactants was utilized to calculate such thermodynamic parameters as the free energy of adsorption (DadsG°) and the heat of adsorption (DadsH°). The low value of DadsH° is an evidence for the physical adsorption of anionic surfactants. The relatively large value of entropic contribution (TDadsS°) indicates that the adsorption of anionic surfactants is entropically governed. Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=3204
in TENSIDE, SURFACTANTS, DETERGENTS > Vol. 44, N° 5/2007 (10-11/2007) . - p. 281-286[article]Réservation
Réserver ce document
Exemplaires (1)
Code-barres Cote Support Localisation Section Disponibilité 008403 - Périodique Bibliothèque principale Documentaires Disponible
