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Effects of storage aging on the properties of epoxy prepregs / Yingfeng Yu in Industrial & engineering chemistry research, Vol. 48 N° 9 (Mai 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N° 9 (Mai 2009) . - pp. 4340–4345 Titre : Effects of storage aging on the properties of epoxy prepregs Type de document : texte imprimé Auteurs : Yingfeng Yu, Auteur ; Huihuang Su, Auteur ; Wenjun Gan, Auteur Année de publication : 2009 Article en page(s) : pp. 4340–4345 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Epoxy  prepregs  Storage  Fourier  transform  spectroscopies  Dynamic  mechanical  analysis  Rheological  analysis  Time-resolved  light  scattering  Optical  microscopy Résumé : Changes in the properties of epoxy prepregs during storage are of both industrial and theoretical interest. It would be very helpful to have a test, suitable for production use, to determine when a prepreg has aged beyond acceptable limits. In this article, different epoxy prepregs aged under various conditions were studied by near-infrared (NIR) and mid-infrared (MIR) Fourier transform spectroscopies, dynamic mechanical analysis (DMA), rheological analysis, time-resolved light scattering (TRLS), and optical microscopy (OM). A very good relationship between storage aging time and curing conversion was obtained by NIR measurements. Furthermore, the rheological study showed that both the viscosity and the gelation time changed with storage aging. Changes in the glass transition temperatures of epoxy prepregs can result from either curing or phase separation during storage aging. The TRLS and OM results showed that structural evolution might occur during storage for some prepregs. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie8018005 [article] Effects of storage aging on the properties of epoxy prepregs [texte imprimé] / Yingfeng Yu, Auteur ; Huihuang Su, Auteur ; Wenjun Gan, Auteur . - 2009 . - pp. 4340–4345. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N° 9 (Mai 2009) . - pp. 4340–4345 Mots-clés : Epoxy  prepregs  Storage  Fourier  transform  spectroscopies  Dynamic  mechanical  analysis  Rheological  analysis  Time-resolved  light  scattering  Optical  microscopy Résumé : Changes in the properties of epoxy prepregs during storage are of both industrial and theoretical interest. It would be very helpful to have a test, suitable for production use, to determine when a prepreg has aged beyond acceptable limits. In this article, different epoxy prepregs aged under various conditions were studied by near-infrared (NIR) and mid-infrared (MIR) Fourier transform spectroscopies, dynamic mechanical analysis (DMA), rheological analysis, time-resolved light scattering (TRLS), and optical microscopy (OM). A very good relationship between storage aging time and curing conversion was obtained by NIR measurements. Furthermore, the rheological study showed that both the viscosity and the gelation time changed with storage aging. Changes in the glass transition temperatures of epoxy prepregs can result from either curing or phase separation during storage aging. The TRLS and OM results showed that structural evolution might occur during storage for some prepregs. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie8018005

Rheological study of epoxy systems blended with poly(ether sulfone) of different molecular weights / Yingfeng Yu in Industrial & engineering chemistry research, Vol. 47 N° 23 (Décembre 2008) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 47 N° 23 (Décembre 2008) . - p. 9361–9369 Titre : Rheological study of epoxy systems blended with poly(ether sulfone) of different molecular weights Type de document : texte imprimé Auteurs : Yingfeng Yu, Auteur ; Minghai Wang, Auteur ; David Foix, Auteur Année de publication : 2009 Article en page(s) : p. 9361–9369 Note générale : Chemistry engineering Langues : Anglais (eng) Mots-clés : Rheological  study  Epoxy  systems  ether  sulfone Résumé : In this work, the rheological behavior and structural transitions in poly(ether sulfone) (PES)-modified epoxy systems during phase separation were studied by rheometry instrument, scanning electronic microscopy, time-resolved light scattering, and differential scanning calorimetry. The molecular weight and concentration of PES have profound effects on rheological behavior of modified epoxy systems. It was found that the evolution of complex viscosity is closely connected to the molecular weight of PES. Blends with higher molecular weight PES tend to have a lower conversion at the onset of phase separation and show quicker increase of viscosity with curing process. The complex viscosity exhibits an exponential growing process during phase separation at various temperatures. The relaxation time of rheological growth depends on both molecular weight of PES and test frequency. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie800845p#afn1 [article] Rheological study of epoxy systems blended with poly(ether sulfone) of different molecular weights [texte imprimé] / Yingfeng Yu, Auteur ; Minghai Wang, Auteur ; David Foix, Auteur . - 2009 . - p. 9361–9369. Chemistry engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 47 N° 23 (Décembre 2008) . - p. 9361–9369 Mots-clés : Rheological  study  Epoxy  systems  ether  sulfone Résumé : In this work, the rheological behavior and structural transitions in poly(ether sulfone) (PES)-modified epoxy systems during phase separation were studied by rheometry instrument, scanning electronic microscopy, time-resolved light scattering, and differential scanning calorimetry. The molecular weight and concentration of PES have profound effects on rheological behavior of modified epoxy systems. It was found that the evolution of complex viscosity is closely connected to the molecular weight of PES. Blends with higher molecular weight PES tend to have a lower conversion at the onset of phase separation and show quicker increase of viscosity with curing process. The complex viscosity exhibits an exponential growing process during phase separation at various temperatures. The relaxation time of rheological growth depends on both molecular weight of PES and test frequency. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie800845p#afn1