Dynamic mechanical and 13C n.m.r. investigations of molecular motions involved in the β relaxation of epoxy networks based on DGEBA and aliphatic amines

Heux, Laurent; Halary, Jean Louis; Lauprêtre, F.; Monnerie, L.

doi:10.1016/s0032-3861(96)00694-5

Cited by 109 publications

(86 citation statements)

References 27 publications

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“…For the sample corresponding to the theoretically ideal stoichiometric formulation, HP = 100 %, a broad β relaxation process can be observed starting at frequencies higher than 1 MHz and extending down to frequencies around 10 Hz. The breadth of this relaxation suggests that it is related to a distribution of segmental motions with different activation energies, where the motions with low activation energy are responsible for the high-frequency part of the relaxation and the motions with high activation energy are responsible for the lowfrequency part [29]. The peak of this relaxation is at approximately 4×10 4 Hz and its strength is ~0.6 (evaluated by calculating the increase in between 1 MHz and 10 Hz).…”

Section: Dielectric Spectramentioning

confidence: 99%

“…However, the reduction in the β relaxation strength is sharper than that predicted by the concentration of the crosslinking nodes. This might be caused by the reduction of the activation energy of some of the segmental motions that contribute to this relaxation with reducing the crosslinking density [29], which suggests that part of the relaxation moves to higher frequencies. Two consequences of this explanation would be expected.…”

Section: Dielectric Spectramentioning

confidence: 99%

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Effect of resin/hardener stoichiometry on electrical behavior of epoxy networks

Alhabill

Ayoob

Andritsch

et al. 2017

IEEE Trans. Dielect. Electr. Insul.

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By changing the ratio of resin to hardener, a series of epoxy resin samples has been produced with differing network structures and different retained chemical functionalities. The resulting materials were characterized by thermal analysis, dielectric spectroscopy, DC conductivity, and DC and AC breakdown strength measurements, to explore the effect of network structure and chemical composition on molecular dynamics and electrical properties. Differential scanning calorimetry showed that the glass transition temperature is primarily determined by the crosslinking density and indicates that, under the range of conditions employed here, side reactions, such as etherification or homopolarization, are negligible. Conversely, changes in DC conductivity with resin stoichiometry appear to occur as a result of changes in the chemical content of the system, rather than variations in network structure or dynamics. Specifically, we suggest that the DC conductivity is markedly affected by the residual amine group concentration in the system. While DC conductivity and DC breakdown appear broadly to be correlated, AC breakdown results indicated that this parameter does not vary with changing stoichiometry, which suggests that the AC and DC breakdown strengths are controlled by different mechanisms.

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Section: Dielectric Spectramentioning

confidence: 99%

Section: Dielectric Spectramentioning

confidence: 99%

Effect of resin/hardener stoichiometry on electrical behavior of epoxy networks

Alhabill

Ayoob

Andritsch

et al. 2017

IEEE Trans. Dielect. Electr. Insul.

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“…Plastic deformation is associated to secondary transition below T g , which is often called b transition. The b transition in networks based on DEGBA is attributed to local motions linked to hydroxyether segments [11]. As a result, plastic deformation (cooperative motions) is activated by this local mobility for a given state stress.…”

Section: Introductionmentioning

confidence: 99%

Origin of epoxies embrittlement during oxidative ageing

2017

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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. b s t r a c tThermal oxidation of three epoxy resins prepared from flexible or rigid prepolymers and hardeners was studied by monitoring epoxy mechanical and physical changes. The physical changes were followed by mass measurements, glass transition temperature using DSC and sub-glass b transition using DMA. It was put in evidence that embrittlement is not directly associated to T g or mass loss changes since epoxy network based on isophorone diamine (IPDA) hardeners were shown to undergo mainly a chain scission at the beginning of exposure process whereas epoxy network based on trioxatridecane diamine (TTDA) hardeners exhibits a crosslinking process with a significant mass loss. The only common feature for both epoxy systems to understand embrittlement is the drop of amplitude of b transition with oxidation.

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“…PAMS/DGEBA network presents a broad relaxation (b 2 ) centered at about À50 C (Fig. 5c) which is attributed to a complex set of motions that involve both the hydroxypropylether group OeCH 2 eCHOHeCH 2 and the DGEBA ring flips, as it is commonly found in epoxy resins [25]. The Fig.…”

Section: Low Temperature Relaxationsmentioning

confidence: 87%

Critical examination of chemically modified hybrid thermosets: Synthesis, characterization and mechanical behavior in the plateau regime of polyaminosiloxane-nitrile-DGEBA

Loayza

Cabanelas

González

et al. 2015

Polymer

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Poly(3-aminopropylmethylsiloxane) has been modified with acrylonitrile via aza Michael addition and a broad range of modified oligomers have been prepared with CN:NH 2 ratio ranging between 0.1 and 1. NMR and FTnIR analysis reveals that acrylonitrile modification proceeds without formation of tertiary amines. Modified oligomers have been characterized by DSC and analysis of Tg reveals that the adducts are self-associated probably due to weak hydrogen bonding and dipole interactions. The modified oligomers with a modification degree higher than 0.4 were miscible with DGEBA. The low and high temperature relaxations of the cured thermosets have been measured by DMTA. In addition to the commonly observed b 2 relaxation, a new b 1 process linked by an isosbestic point to b 2 has been found. b 1 is attributed to an extended segment comprising the pendant propionitrile group as well as the ami-nopropyl segment that connects tertiary amines to the polysiloxane backbone. Elastic modulus as well as the a relaxation can be tuned from high Tg and high rubbery modulus to low Tg and high damping thermosets changing the nitrile content. The experimental network structure obtained from elastic measurements and the Tg were related through well established structure-property relations.

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Dynamic mechanical and 13C n.m.r. investigations of molecular motions involved in the β relaxation of epoxy networks based on DGEBA and aliphatic amines

Cited by 109 publications

References 27 publications

Effect of resin/hardener stoichiometry on electrical behavior of epoxy networks

Effect of resin/hardener stoichiometry on electrical behavior of epoxy networks

Origin of epoxies embrittlement during oxidative ageing

Critical examination of chemically modified hybrid thermosets: Synthesis, characterization and mechanical behavior in the plateau regime of polyaminosiloxane-nitrile-DGEBA

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