Measurement of the extent of reaction of an epoxy–cycloaliphatic amine system and influence of the extent of reaction on its dynamic and static mechanical properties

Jordan, Catherine; Galy, Jean; Pascault, Jean‐Pierre

doi:10.1002/app.1992.070460513

Cited by 68 publications

(51 citation statements)

References 31 publications

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“…Additionally, the peak of this relaxation moves slightly to higher frequencies. Comparable trends for the relaxation strength and breadth have been reported for similar epoxy/amine systems when reducing the crosslinking density [6,30]. Many studies have claimed that the β relaxation in such systems is associated with the crankshaft rotation of the hydroxyether group (-CH(OH)-CH2-O-) that is generated at each crosslink point due to the reaction between the epoxy and amine groups [6,30,31].…”

Section: Dielectric Spectramentioning

confidence: 90%

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: 90%

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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show abstract

“…6,22 However, at intermediate stages of cure the networks are less well defined as there is a distribution of EDA molecules that have reacted with zero, one, two, three, or four epoxide groups. 13,19,20,23 For our case, Flory's equation [eq. (2)] predicts the gel point to be at a critical conversion (x c ) of about 0.58.…”

Section: T G -Conversionmentioning

confidence: 99%

Aspects of network formation in glassy thermosets

Detwiler

Lesser

2010

J of Applied Polymer Sci

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Aspects of network formation and the physical properties of stoichiometric amine-cured epoxy resins are investigated. The state of network formation is systematically controlled by using isothermal cure conditions and a linear temperature ramp condition. Affine deformation in compression at a constant true strain rate is used to measure the true stress-strain response from small strains to large strains. Beginning with the low-strain responses and continuing through yielding, partially cured samples demonstrate characteristics of physical ageing that diminish as the networks approach full conversion. The postyield properties are characterized by a strong dependence on network connectivity with little influence of the curing method. The mechanical responses are also applied to necking and shear banding analyses. The resins are unable to achieve stable necking in tension. However, shear bands are able to be stabilized, as predicted by a model developed in this work. These results suggest that physical ageing is inherent in epoxy network formation, and the resulting strain localization significantly degrades the mechanical integrity of epoxy resins in the partially cured state, regardless of the cure conditions.

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“…It is essential to design the optimal curing conditions for each resin system to obtain the optimal properties. It has been established that the stiffness and impact behavior have an optimum at an 80% epoxy conversion and decrease with higher extents of reaction, 30 and a higher crosslink density lowers the modulus of epoxy. 7 To better understand each property of this system, we compared the mechanical properties of the resins cured under the same heat source.…”

Section: System Containing 1% Acceleratormentioning

confidence: 99%

“…There have been many researchers using DSC to determine the degree of conversion of an epoxy resin from microwave curing 7,18,20,21,30,33 and thermal curing. 40 -48 When the samples were not completely cured, the exothermic peak was obtained from the first heating scan.…”

Section: Extent Of the Conversionmentioning

confidence: 99%

Comparison of microwave and thermal cure of epoxy–anhydride resins: Mechanical properties and dynamic characteristics

Tanrattanakul

Saetiaw

2005

J of Applied Polymer Sci

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ABSTRACT:The objective of this work was to compare the mechanical properties of epoxy resins cured by thermal heating and microwave heating. Epoxy-anhydride (100:80) resins were cured in a domestic microwave oven and in a thermal oven. The hardening agents included methyl tetrahydrophthalic anhydride and methyl hexahydrophthalic anhydride. Three types of accelerators were employed. Thermal curing was performed at 150°C for 20 and 14 min for resins containing 1 and 4% accelerator, respectively. Microwave curing was carried out at a low power (207 or 276 W) for 10, 14, and 20 min. All cured resins were investigated with respect to their tensile properties, notched Izod impact resistance, and flexural properties (three-point bending) according to ASTM standards. The tan ␦ and activation energy values were investigated with dynamic mechanical thermal analysis, and the extent of conversion was determined with differential scanning calorimetry. The differences in the mechanical properties of the thermally cured and microwavecured samples depended on the resin formulation and properties. Equivalent or better mechanical properties were obtained by microwave curing, in comparison with those obtained by thermal curing. Microwave curing also provided a shorter cure time and an equivalent degree of conversion. The glass-transition temperatures (tan ␦) of the thermally and microwave-cured resins were comparable, and their activation energies were in the range of 327-521 kJ/mol.

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Measurement of the extent of reaction of an epoxy–cycloaliphatic amine system and influence of the extent of reaction on its dynamic and static mechanical properties

Cited by 68 publications

References 31 publications

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

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

Aspects of network formation in glassy thermosets

Comparison of microwave and thermal cure of epoxy–anhydride resins: Mechanical properties and dynamic characteristics

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