The temperature‐dependence of some mechanical properties of a cured epoxy resin system

Gupta, V. B.; Drzal, L. T.; Lee, C. Y.-C.; Rich, Michael J.

doi:10.1002/pen.760251305

Cited by 220 publications

(144 citation statements)

References 21 publications

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“…In contrast, the origin of  transition is still a subject of discussion in the literature [15][16][17][18]. It is often associated with the presence of water [15] or unreacted epoxy groups [16][17]. It is also sometimes assigned to rotations of p-phenylene rings [18].…”

Section: Effect Of Oxidation On the Viscoelastic Properties Of Epoxy mentioning

confidence: 99%

“…In epoxy networks, they are rotations (of crankshaft type) of CC bonds localized in the hydroxypropylether unit [13][14]. In contrast, the origin of  transition is still a subject of discussion in the literature [15][16][17][18]. It is often associated with the presence of water [15] or unreacted epoxy groups [16][17].…”

Section: Effect Of Oxidation On the Viscoelastic Properties Of Epoxy mentioning

confidence: 99%

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Oxidation induced changes in viscoelastic properties of a thermostable epoxy matrix

2013

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is an open access repository that collects the work of Arts et Métiers ParisTech researchers and makes it freely available over the web where possible. AbstractThe thermal ageing of a neat epoxy matrix has been studied at 200°C in air by three complementary analytical techniques: optical microscopy, mechanical spectrometry and nanoindentation. Thermal oxidation is restricted in a superficial layer of about 195 µm of maximal thickness. It consists in a predominant chain scission process involving, in particular, chemical groups whose β motions have the highest degree of cooperativity and thus, are responsible for the high temperature side of β dissipation band. As a result, chain scissions decrease catastrophically the glass transition temperature, but also increase significantly the storage modulus at glassy plateau between T β and T α . This phenomenon is called "internal antiplasticization". Starting from these observations, the Di Marzio and Gilbert's theories have been used in order to establish relationships between the glass transition temperature and number of chain scissions, and between the storage modulus and β transition activity respectively. The challenge is now to establish a relationship between the transition activity and the concentration of the corresponding chemical groups.

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Section: Effect Of Oxidation On the Viscoelastic Properties Of Epoxy mentioning

confidence: 99%

Section: Effect Of Oxidation On the Viscoelastic Properties Of Epoxy mentioning

confidence: 99%

Oxidation induced changes in viscoelastic properties of a thermostable epoxy matrix

2013

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“…Il a souvent ŽtŽ observŽ quÕˆ tempŽrature ambiante, la masse volumique dÕun syst•me Žpoxy diminue quand la densitŽ de rŽticulation augmente, lorsque celle-ci est contr™lŽe par la cuisson ou par les proportions du mŽlange [42,43,[64][65][66][67][68][69]. Des auteurs [42,43,67,[69][70][71] En revanche, la diminution de la densitŽ de rŽticu-lation par augmentation de la taille des prŽpolym•res [50] ou par lÕajout dÕextendeurs de maille [21] entra"ne une diminution de la masse volumique.…”

Section: Influence De La Masse Volumique Sur Les Propriétés Des Résinunclassified

“…Des auteurs [42,43,67,[69][70][71] En revanche, la diminution de la densitŽ de rŽticu-lation par augmentation de la taille des prŽpolym•res [50] ou par lÕajout dÕextendeurs de maille [21] entra"ne une diminution de la masse volumique. Il nÕy a pas, dans ce cas, dÕextrŽmitŽ de cha"nes pouvant jouer le r™le dÕantiplastifiant.…”

Section: Influence De La Masse Volumique Sur Les Propriétés Des Résinunclassified

Résines époxy réticulées par des polyamines : structure et propriétés

Barrère

Maso

1997

Rev. Inst. Fr. Pét.

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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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“…T h e relationships between packing coefficient and crosslink density were derived with the V, values as per schemes A and B and the following results were obtained: Scheme A: p*/p,* = 1.0025 -0.0025n/nS (2) Scheme B: p*/p,* = 1.0034 -0.0034n/nS ( 3 )…”

Section: The Packing Coefficientmentioning

confidence: 99%

Molecular packing in nonstoichiometric epoxide–amine networks

Gupta¹,

Brahatheeswaran²

1989

J of Applied Polymer Sci

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Some studies on a difunctional, diglycidyl ether of Bisphenol-A (DGEBA) type epoxy resin, viz., Epon 828 of shell cured with different amounts of a tetrafunctional curing agent, viz., metaphenylene diamine (mPDA) [Fig. l(b)] had that the sample cured with stoichiometric amount of curing agent, i.e., 14.5 parts of mPDA by weight per hundred parts of resin (phr), had the highest crosslink density and the highest glass transition temperature (Tg). However, this sample had the smallest bulk density at room temperature compared to the densities of the nonstoichiometric samples studied. It was suggested that, among other reasons, this could arise because the crosslink site did nokprovide a suitable environment for close packing of molecules and, therefore, when a sample was cooled from the final curing temperature to room temperature, the molecular packing in the sample with the highest crosslink density was relatively poor. Support for this observation has also come from wide angle X-ray scattering studies on these sample^,^ which showed that the average intermolecular distance was the largest in the most highly crosslinked samples. Poor molecular packing in highly crosslinked samples cured with stoichiometric amounts of curing agent in relation to those cured with nonstoichiometric amounts has been inferred from their low bulk density in other epoxide systems Recently, Bellenger et a1.6 have published the results of their calculations of the Van der Waals Volumes (V,) and packing coefficients for one of the nonstoichiometric samples reported in the earlier studies,'.' viz., the sample cured with 10 phr of mPDA and also for the stoichiometric sample (14.5 phr). They found on analysis of the data for these two samples that the packing density increases with crosslink density and concluded that the bulk density variations cannot therefore be directly assimilated by variations in the degree of molecular packing as they could arise from the changes in V, as a result of the epoxide-amine addition reaction. The purpose of the present communication is to show that the above analysis is very sensitive to the values of V , used by the authors.V , values for the network were calculated by Bellenger et al.6 from the group contribution values given by Bondi in his book: which suggests a value of 3.7 cm3/mol for oxygen. In an earlier publication,8 Bondi discussed the approximations involved in calculating V, which result from the assumptions that have to be made in obtaining bond distances, bond angles, and contact distances. As regards the group contribution of oxygen, Bondi has emphasized the lack of good contact distance data. He has further stated that as a result of being too deeply buried within the molecule for frequent (or any) collision with neighboring molecules, the "effective volume" occupied by ether oxygen differs from molecule to molecule. In ethylene oxide, on the other hand, the ether oxygen is sufficiently exposed to yield a value of V, = 5.5 m3/mol. In alkyl ethers, especially polyethers, V, = 3.7 cm3/mol and i...

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The temperature‐dependence of some mechanical properties of a cured epoxy resin system

Cited by 220 publications

References 21 publications

Oxidation induced changes in viscoelastic properties of a thermostable epoxy matrix

Oxidation induced changes in viscoelastic properties of a thermostable epoxy matrix

Résines époxy réticulées par des polyamines : structure et propriétés

Molecular packing in nonstoichiometric epoxide–amine networks

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