13C solid-state NMR analysis of the DGEBA/TETA epoxy system

Tavares, Maria Inês B.; d’Almeida, J.R.M.; Monteiro, Sérgio Neves

doi:10.1002/1097-4628(20001220)78:13<2358::aid-app120>3.0.co;2-t

Cited by 24 publications

(12 citation statements)

References 22 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…These characteristics are a direct consequence of the complete exhaustion of all the reactive sites on the hardener molecule, giving way to a rigid and brittle structure 30 . The existence of a more closely packed structure for these epoxy rich formulations was recently confirmed by solid state nuclear magnetic resonance measurements 31 . The brittleness of these formulations could be inferred directly from the shape of their engineering stress vs. strain curve, Fig.…”

Section: Resultsmentioning

confidence: 66%

“…However, as shown by solid state nuclear magnetic resonance experiments, more open macromolecular structures were developed on these two formulations during the first, and amine addition dominated, steps of the cure reaction 31 . This picture is particularly true for the stoichiomet- ric 13 phr formulation, which structure is significantly less tight than the ones from the epoxy rich formulations 31 . The net result observed is that, although recrystallization could still be occurring in some significant amount, better mechanical properties were obtained.…”

Section: Resultsmentioning

confidence: 96%

See 1 more Smart Citation

Ageing of the DGEBA/TETA epoxy system with off-stoichiometric compositions

2003

View full text Add to dashboard Cite

An investigation was carried out on the room temperature ageing of off-stoichiometric DGEBA/TETA epoxy formulations. The results obtained show that the epoxy rich mixtures have their inherent brittleness increased by the ageing treatment due to recrystalization of the unreacted epoxy monomers, although homopolymerization could also play a minor role. The initial reaction steps dominated by the amine addition reactions control the macromolecular structure and the mechanical performance of the stoichiometric and near stoichiometric formulation with excess of epoxy monomer. Plasticization due to absorbed -OH results on a significant increase of the deformability of these formulations. The amine rich mixtures have the more stable structures, although plasticization due to moisture absorption from the surrounding environment also produces an increase on the deformability of all, but one, of the formulations investigated. keywords: epoxy resins, ageing, mechanical propertiesoff-stoichiometric mixtures. For the particular system made of the triethylene tetramine, TETA, hardener and the DGEBA monomer the variation of the hardener to monomer ratio promotes strong changes on the mechanical behavior [18][19][20][21] . Of particular interest with respect to these changes is the very sharp increase in the impact strength, when amine rich mixtures were used 21 . The problem of working with off-stoichiometric mixtures is that latent reaction sites could remain on the macromolecular structure developed and under the proper conditions the structure can evolve, resulting in changes on the mechanical performance of the material. Temperature is clearly one external parameter that could cause changes to the system, but, even at room temperature, ageing due to exposure of the epoxy resin to humid environments could also be important [22][23][24] . The changes observed on the mechanical properties when the epoxy monomer to hardener ratio is varied, and the possible changes due to aging, are a direct consequence of the different macromolecular structures that are developed and/or the possible reactions that could occur given a

show abstract

Section: Resultsmentioning

confidence: 66%

Section: Resultsmentioning

confidence: 96%

Ageing of the DGEBA/TETA epoxy system with off-stoichiometric compositions

2003

View full text Add to dashboard Cite

show abstract

“…With this knowledge, it is possible to use nuclear magnetic resonance (NMR) to investigate and identify the components, because this method directly provides the composition, without having previous treatment 1. For this purpose, we have chosen different NMR techniques,2–10 including 13 C solution, magic angle spinning (MAS), cross‐polarization with magic angle spinning (CPMAS), variable contact time (VCT), and delayed contact time (DCT).…”

Section: Introductionmentioning

confidence: 99%

Efficient Synthesis of β‐Hydroxy Ketones from Allylic Alcohols by Catalytic Formation of Ruthenium Enolates

Bartoszewicz

Livendahl

Martín‐Matute

2008

Chemistry A European J

View full text Add to dashboard Cite

“…8,9 Many of the previous studies of resin curing by NMR were geared to elucidating structural information about intermediate and final reaction products. It is believed that this is the first application of this technique to measure thermodynamic parameters for the resin system curing process for oilfield applications.…”

Section: Measurement Of Thermodynamic Parametersmentioning

confidence: 99%

Kinetic Parameters for Dilute Epoxy Resins Measured by Nuclear Magnetic Resonance Spectroscopy

Rickman

Wilson

Weaver

2007

International Symposium on Oilfield Chemistry

View full text Add to dashboard Cite

fax 01-972-952-9435. AbstractThermosetting resins are employed in a wide variety of oilfield applications. The development of dilute resin formulations offers several advantages over conventional resin systems and new resin applications are making increasing use of dilute formulations. Knowledge of the thermodynamic properties of the resin system is essential to ensure that they perform as expected. We report here on the use of nuclear magnetic resonance, NMR, to measure activation energies, enthalpies, entropies, and frequency factors for the curing of a diglycidylether bisphenol A epoxy resin with a modified cycloaliphatic amine hardener. Results calculated with this technique are presented here and are in good agreement with values calculated using more conventional techniques.

show abstract

13C solid-state NMR analysis of the DGEBA/TETA epoxy system

Cited by 24 publications

References 22 publications

Ageing of the DGEBA/TETA epoxy system with off-stoichiometric compositions

Ageing of the DGEBA/TETA epoxy system with off-stoichiometric compositions

Efficient Synthesis of β‐Hydroxy Ketones from Allylic Alcohols by Catalytic Formation of Ruthenium Enolates

Kinetic Parameters for Dilute Epoxy Resins Measured by Nuclear Magnetic Resonance Spectroscopy

Contact Info

Product

Resources

About