Structure–Property Relationships in Epoxy-Amine Networks of Well-Controlled Architecture

This research work is aimed to understand the effect of epoxy resin chemistry on the viscoelasticity of the cured epoxy thermosets. In this article, two model systems are selected based on epoxy‐amine reactants. In the model Systems I, the functionality of the epoxy is varied. In model System II, the pendant (side) chain length in the amine is varied. It is found that by varying the initial properties (e.g., functionality, pendant chain length, mixing ratio (r), aromaticity, etc.) the network properties (crosslink density and flexibility) of the cured (or hardened) epoxy changed. The changes (or shift) in the viscoelastic properties (or viscoelasticity) of the cured epoxy is mainly due the changes in the network properties. Further, to study the time and temperature effects the viscoelastic master curves for the two model systems are generated using Time‐Temperature‐Superposition (TTS) principle. The shift in the viscoelastic master curves is modeled with a simple Kohlrausch‐Williams‐Watts (KWW) fit function. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

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“…The crosslink density can be also calculated from Miller and Macosko theory. The calculated crosslink density i.e., ν

_{c}^{italicM & italicM}

values for all the samples in model systems (see Table III) can be compared with that of Halary 21…”

Section: Resultsmentioning

confidence: 99%

Tailoring the viscoelasticity of epoxy thermosets

Nakka

Jansen

Ernst

2012

J of Applied Polymer Sci

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“…To analyze the effect of ν

_{italicc}^{calc}

(determined by the Miller–Macosko theory) on T g , ν

_{italicc}^{calc}

has been plotted against T g and is shown in Figure 10. ν

_{italicc}^{calc}

and ν

_{italicc}^{meas}

can be compared with the theoretical crosslink density of Halary's work 10 . T g increased linearly with the increase in ν

_{italicc}^{calc}

.…”

Section: Resultsmentioning

confidence: 99%

Effect of the epoxy resin chemistry on the viscoelasticity of its cured product

Nakka¹,

Jansen²,

Ernst³

et al. 2008

J of Applied Polymer Sci

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A detailed study investigating the relation between the initial resin composition and mixing ratio on the viscoelastic behavior was performed. The resin system, containing a difunctional aromatic epoxy (DER 332), was mixed with three aliphatic amines containing functionalities of 2, 3, and 4 in different stoichiometric mixing ratios and was cured. For each of the cured mixtures, the viscoelastic master curve and corresponding shift factors were determined. Depending on the crosslink density, the viscoelastic curves shifted by about 12 decades with respect to the frequency scale. This shift in the viscoelastic curve was predicted by the combination of the Miller-Macosko theory for crosslink density with a parameterized Havriliak-Negami model for the master curve. A single set of 9 parameters turned out to be sufficient to describe all viscoelastic data.

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“…crosslinked molecular network structure, glass transition temperature, moisture uptake, etc.) [50,51]; -development of fibre waviness [52]; -generation of matrix and transverse plies cracking (with the very first thermosetting matrix used in composites) [56]; -modifications of mechanical properties (i.e. moduli, ultimate strengths, fracture behaviour, etc.…”

Section: Process-induced Stresses: a Brief Overview Of Backgroundmentioning

confidence: 99%

Designing curing conditions in order to analyse the influence of process-induced stresses upon some mechanical properties of carbon / epoxy laminates at constant Tg and degree of cure

Olivier

Sawi

2010

Int J Mater Form

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In the aim to study of the effects of processinduced stresses upon some mechanical properties of simple stacking sequence composite laminates, three different cure cycles were designed. This was achieved on the basis of a cure kinetics modelling. A minimum number of curing parameters were modified in order to restrain changes in material physical properties. Those latter were determined from the molecular network of the thermosetting matrix to the fibres volume fraction and thermal expansion of the laminated plates. The level of processinduced stresses generated by the three cure cycles was assessed by measuring the out-of-plane deflection on unsymmetrical laminated strips. Manufactured laminates were submitted to a set of tensile tests in order to determine the changes in their mechanical properties due to the different curing conditions. All the mechanical tests were followed by acoustic emission. This has enabled to distinguish the occurrence of the various damaging processes with respect to curing conditions and therefore process-induced stresses. Lastly, process-induced stresses on a micromechanical level were theoretically determined. This determination has enabled a first analysis of the effects of process-induced stresses upon mechanical properties to be settled.

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Structure–Property Relationships in Epoxy-Amine Networks of Well-Controlled Architecture

Cited by 37 publications

References 16 publications

Tailoring the viscoelasticity of epoxy thermosets

Tailoring the viscoelasticity of epoxy thermosets

Effect of the epoxy resin chemistry on the viscoelasticity of its cured product

Designing curing conditions in order to analyse the influence of process-induced stresses upon some mechanical properties of carbon / epoxy laminates at constant Tg and degree of cure

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