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In-situ cure and cure kinetic analysis of a liquid rubber modified epoxy resin / Raju Thomas in Industrial & engineering chemistry research, Vol. 51 N° 38 (Septembre 2012) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 51 N° 38 (Septembre 2012) . - pp. 12178–12191 Titre : In-situ cure and cure kinetic analysis of a liquid rubber modified epoxy resin Type de document : texte imprimé Auteurs : Raju Thomas, Auteur ; Christophe Sinturel, Auteur ; Jurgen Pionteck, Auteur Année de publication : 2012 Article en page(s) : pp. 12178–12191 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Kinetics  In  situ Résumé : The in-situ cure and cure kinetics of an epoxy resin based on diglycidyl ether of bisphenol A (DGEBA) polymerized with an anhydride hardener and its mixtures with a liquid polybutadiene rubber having hydroxyl functionality (HTPB) were studied using Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) in an isothermal mode. The cure reaction was monitored in-situ by FTIR spectroscopy by observing variation in intensity of epoxy, anhydride, and ester bands. The cure reaction mechanisms by which the network structure of epoxy was developed were discussed. Isothermal mode DSC measurements were performed at selected temperatures. The reaction followed an autocatalytic mechanism, and kinetic analysis was done by a phenomenological model developed by Kamal. Good fits were obtained between the autocatalytic model and the experimental data up to the vitrification state. Afterward, the reaction became diffusion controlled. The reaction during the later stages of cure was explained by introducing a diffusion factor, which agreed well with the kinetic data. The nature of the developing morphology of modified epoxies was analyzed by optical microscopy (OM) and small angle laser light scattering (SALLS) technique. The ultimate morphology of the cured blends was analyzed using scanning electron microscopy (SEM). The cure kinetics has been correlated with the developed morphology to get insight into the mechanism of reaction-induced microphase separation. ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=26399667 [article] In-situ cure and cure kinetic analysis of a liquid rubber modified epoxy resin [texte imprimé] / Raju Thomas, Auteur ; Christophe Sinturel, Auteur ; Jurgen Pionteck, Auteur . - 2012 . - pp. 12178–12191. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 51 N° 38 (Septembre 2012) . - pp. 12178–12191 Mots-clés : Kinetics  In  situ Résumé : The in-situ cure and cure kinetics of an epoxy resin based on diglycidyl ether of bisphenol A (DGEBA) polymerized with an anhydride hardener and its mixtures with a liquid polybutadiene rubber having hydroxyl functionality (HTPB) were studied using Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) in an isothermal mode. The cure reaction was monitored in-situ by FTIR spectroscopy by observing variation in intensity of epoxy, anhydride, and ester bands. The cure reaction mechanisms by which the network structure of epoxy was developed were discussed. Isothermal mode DSC measurements were performed at selected temperatures. The reaction followed an autocatalytic mechanism, and kinetic analysis was done by a phenomenological model developed by Kamal. Good fits were obtained between the autocatalytic model and the experimental data up to the vitrification state. Afterward, the reaction became diffusion controlled. The reaction during the later stages of cure was explained by introducing a diffusion factor, which agreed well with the kinetic data. The nature of the developing morphology of modified epoxies was analyzed by optical microscopy (OM) and small angle laser light scattering (SALLS) technique. The ultimate morphology of the cured blends was analyzed using scanning electron microscopy (SEM). The cure kinetics has been correlated with the developed morphology to get insight into the mechanism of reaction-induced microphase separation. ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=26399667

Studies on stress relaxation and thermomechanical properties of poly(acrylonitrile-butadiene-styrene) modified epoxy−amine systems / Jyotishkumar P in Industrial & engineering chemistry research, Vol. 50 N° 8 (Avril 2011) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 50 N° 8 (Avril 2011) . - pp. 4432–4440 Titre : Studies on stress relaxation and thermomechanical properties of poly(acrylonitrile-butadiene-styrene) modified epoxy−amine systems Type de document : texte imprimé Auteurs : Jyotishkumar P, Auteur ; Jurgen Pionteck, Auteur ; Rudiger Hassler, Auteur Année de publication : 2011 Article en page(s) : pp. 4432–4440 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Thermomechanical  properties Résumé : Epoxy networks based on diglycidyl ether of bisphenol A cured with diamino diphenyl sulfone and modified with poly(acrylonitrile-butadiene-styrene) (ABS) were prepared according to two different cure schedules, one with a single step curing and the other with two step curing. The samples were carefully analyzed by thermomechanical analysis (TMA) to understand the physical aging phenomenon. The TMA runs on samples with single curing step are strained and show “bumps” in the expansion traces indicating that internal stress relaxation takes place during heating. On the other hand, the samples prepared by two-step curing were not strained and hence no bumps occurred. The ABS modified epoxy blends were further characterized by Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), mechanical tests using a universal testing machine, and field emission scanning electron microscopy (FESEM). The FTIR spectroscopy study confirms that the epoxy/amine reaction was complete, irrespective of the cure schedule used. TEM micrographs reveals heterogeneous morphology for all the blends studied. DSC and TGA were employed to evaluate the thermal stability of epoxy/ABS blends. The mechanical properties of both strained and unstrained samples were investigated in detail and are correlated to the blend morphologies. The result shows that the mechanical and morphological properties are affected by blending with the thermoplastic but not with the cure schedule used. The addition of low ABS amounts (≤6.9 wt %) in the epoxy resin resulted in epoxy matrix/ABS particle morphologies leading to more than 100% increase in tensile toughness compared to neat cross-linked epoxy. FESEM micrographs of fractured surfaces proved fracture mechanisms such as nanocavitation, crack path deflection, crack pinning, ductile tearing of the thermoplastic, and local plastic deformation of the matrix. In contrast, when cocontinuous morphologies are formed at higher ABS loadings the mechanical properties are much lower than those formed for the neat epoxy system. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie1016915 [article] Studies on stress relaxation and thermomechanical properties of poly(acrylonitrile-butadiene-styrene) modified epoxy−amine systems [texte imprimé] / Jyotishkumar P, Auteur ; Jurgen Pionteck, Auteur ; Rudiger Hassler, Auteur . - 2011 . - pp. 4432–4440. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 50 N° 8 (Avril 2011) . - pp. 4432–4440 Mots-clés : Thermomechanical  properties Résumé : Epoxy networks based on diglycidyl ether of bisphenol A cured with diamino diphenyl sulfone and modified with poly(acrylonitrile-butadiene-styrene) (ABS) were prepared according to two different cure schedules, one with a single step curing and the other with two step curing. The samples were carefully analyzed by thermomechanical analysis (TMA) to understand the physical aging phenomenon. The TMA runs on samples with single curing step are strained and show “bumps” in the expansion traces indicating that internal stress relaxation takes place during heating. On the other hand, the samples prepared by two-step curing were not strained and hence no bumps occurred. The ABS modified epoxy blends were further characterized by Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), mechanical tests using a universal testing machine, and field emission scanning electron microscopy (FESEM). The FTIR spectroscopy study confirms that the epoxy/amine reaction was complete, irrespective of the cure schedule used. TEM micrographs reveals heterogeneous morphology for all the blends studied. DSC and TGA were employed to evaluate the thermal stability of epoxy/ABS blends. The mechanical properties of both strained and unstrained samples were investigated in detail and are correlated to the blend morphologies. The result shows that the mechanical and morphological properties are affected by blending with the thermoplastic but not with the cure schedule used. The addition of low ABS amounts (≤6.9 wt %) in the epoxy resin resulted in epoxy matrix/ABS particle morphologies leading to more than 100% increase in tensile toughness compared to neat cross-linked epoxy. FESEM micrographs of fractured surfaces proved fracture mechanisms such as nanocavitation, crack path deflection, crack pinning, ductile tearing of the thermoplastic, and local plastic deformation of the matrix. In contrast, when cocontinuous morphologies are formed at higher ABS loadings the mechanical properties are much lower than those formed for the neat epoxy system. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie1016915