Résines époxy réticulées par des polyamines : structure et propriétés

Abstract

Cet article fait le point sur l'état actuel des connaissances concernant les résines époxy réticulées par des polyamines, et plus particulièrement sur :-la réticulation ; -la structure et la morphologie des systèmes réticulés et les paramètres qui les influencent ; -les relations entre la structure et les propriétés sur une très large gamme de températures.Malgré les nombreuses études réalisées, beaucoup de points apparaissent encore controversés, notamment en ce qui concerne les relations structure/propriétés dans le domaine des tempéra-tures d'utilisation, c'est-à-dire entre la transition secondaire b et la transition a (transition vitreuse). S'il est maintenant admis que le module à l'état vitreux est gouverné par l'importance des mouvements des séquences hydroxypropyléther formées lors de la réti-culation, les résultats concernant les propriétés mécaniques aux grandes déformations (allongement et contrainte à rupture, énergie de propagation de fissures) sont beaucoup plus discutés. Les tendances obtenues semblent dépendre de la manière utilisée pour faire varier la densité de réticulation (cuisson, proportions du mélange, extenseurs de mailles, prépolymères de différentes longueurs, etc.), du système ou encore de l'auteur. Les désaccords entre chercheurs pourraient provenir des conditions de préparation des échantillons, notamment de la vitesse de refroidissement en fin de cuisson et des conditions dans lesquelles sont réalisés les essais mécaniques, comme la vitesse de déformation. EPOXY RESINS CROSSLINKED WITH POLYAMINES: STRUCTURE AND PROPERTIESThis paper sums up the current state-of-the-art on epoxy resins crosslinked with polyamines, and more particularly on:-the crosslinking reactions; -the structure and morphology of crosslinked systems and the parameters that influence them; -the relationships between structure and properties over a wide range of temperatures.In spite of numerous studies devoted to these polymers, many points remain controversial, notably concerning the relationships between structure and properties in the temperature range of interest to most users, which is between the b transition temperature and the a transition temperature (glass transition). If it is now widely accepted that the modulus in the glassy state is mainly controlled by the amplitude of the motions of hydroxypropylether groups created during the crosslinking reactions, the results regarding the ultimate mechanical properties (stress and deformation at break, crack propagation energy) are much more Copyright © 1997, Institut français du pétrole debated. The trends obtained appear to depend upon either the way the crosslink density has been modified (cure cycle, mixture composition, chain extenders, prepolymers of different lengths and flexibilities), or the polymers studied or even the authors. The discrepancies between authors could be due to the sample preparation, particularly the cooling rate at the end of the cure cycle, or the testing conditions, e.g. the strain rate. RESINAS EPOXÍDICAS RETICULADAS POR POLIAMINAS...

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Butyl Rubber-Based Composite: Thermal Degradation and Prediction of Service Life Time 

“…The disappearance of the peak corresponding to the secondary transition temperature associated with the local molecular movement is observed in the aged sample. It can be attributed by the presence of MWF in elastomer matrix and leads to a better "molecular lubrication" due to the plasticization affect [63]. Regard to the reduction of Tg, since the glass transition temperature varies linearly with the molar mass and the molecular loss lead to a shift of the Tg to lower temperature areas [64].…”