Chemical structure of networks resulting from curing of <i>N</i>,<i>N</i>‐diglycidylaniline‐type resins with aromatic amines. II. Detection and characterization of intermolecular etherification on model compounds

Attias, André Jean; Ancelle, J.; Bloch, B.; Lauprêtre, F.

doi:10.1002/pola.1990.080280702

Cited by 17 publications

(5 citation statements)

References 5 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…22 Line assignments for similar spectra have been reported earlier. [23][24][25] The ratio of intensities of the second to first dipolar sidebands (n 2 /n 1 ) of the 120-ppm peak in a two-dimensional DRSE experiment (spectra not shown) is a sensitive measure of averaging of the phenylene-ring 1 H- 13 C dipolar coupling by molecular motion. This ratio changes from about 1.3 in the absence of motion to 0.45 in the presence of large-amplitude motions such as ring flips.…”

Section: Sub-t G Tan δmentioning

confidence: 99%

Location of the Antiplasticizer in Cross-Linked Epoxy Resins by ²H, ¹⁵N, and ¹³C REDOR NMR

et al. 1998

View full text Add to dashboard Cite

Carbon-13 rotational-echo double-resonance (REDOR) NMR with 15 N or 2 H dephasing, combined with 15 N REDOR NMR with 13 C dephasing, has been obtained for a fully cross-linked epoxy resin prepared from a nominally uniform mixture of two parts of diglycidyl ether of Bisphenol A, one part of hexamethylenediamine, and 19% (by weight) antiplasticizer made from a carbonyl-13 C-labeled aromatic acetamide. The antiplasiticizer contains the hydroxypropyl ether moiety of the epoxy repeat unit. A partially cross-linked resin was formed from five parts of epoxide, one part of hexamethylenediamine, three parts of hexylamine, and 19% (by weight) antiplasticizer. Labels were introduced into the resin by replacing both methyl groups of the isopropylidene moiety of Bisphenol A with CD3 groups and by using [ 15 N2]hexamethylenediamine and [ 15 N]hexylamine (and their unlabeled counterparts) in various combinations. The antiplasticizer 13 C-carbonyl carbon is 4.9 ( 0.5 Å from an amine 15 N (with no preference for free or cross-linked sites) and 6.7 ( 1 Å from a quaternary carbon of the isopropylidene moiety.

show abstract

Section: Sub-t G Tan δmentioning

confidence: 99%

Location of the Antiplasticizer in Cross-Linked Epoxy Resins by ²H, ¹⁵N, and ¹³C REDOR NMR

et al. 1998

View full text Add to dashboard Cite

show abstract

“…Line assignments for similar spectra have been reported earlier. 11,12 The partially crosslinked resin has a resolved methyl-carbon peak (20 ppm) from the monoamine end group (Figure 3, top and middle). Variation in positions of the 15 N labels in the partially cross-linked resins has no effect on the 13 C spectra.…”

Section: Resultsmentioning

confidence: 99%

Determination of the Extent of Reaction of Amine Cross-Linked Epoxy Resins by Solid-State ¹³C and ¹⁵N NMR

et al. 1997

View full text Add to dashboard Cite

The chemical substitution of amine nitrogens in cured, 15 N-labeled epoxy resins has been determined by a combination of rotational-echo double-resonance 13 C NMR and dipolar rotational spinecho 15 N NMR. Amine-nitrogen substitution is at least 90% (that is, no more than 10% of all nitrogens have a directly bonded hydrogen) for resins formed from stoichiometric amounts of epoxide and either hexamethylenediamine or a 1:3 molar mixture of hexamethylenediamine and hexylamine. This direct measure of curing and cross-linking is consistent with indirect Fourier-transform infrared estimates of curing based on the disappearance of the deformation band of the epoxide ring. IntroductionEpoxy resins are widely used as matrices for highperformance carbon-fiber composites, 1 even though the understanding of the connection between the chemical structure and mechanical properties of the matrix is limited. We are investigating a series of model epoxies to improve this understanding. 2-6 The materials consist of di-epoxides cured with stoichiometric concentrations of diamines or mixtures of monoamines and diamines (Figure 1). The chemical structures of both epoxides and amines are varied from rigid aromatics to flexible aliphatics to alter the local mobilities of backbones and cross-links. An estimate of the cross-link density of the cured resin is usually made by assuming that all reactions are complete: that is, all epoxide rings are opened and all amine nitrogens are fully substituted. Viscoelastic measurements performed on these materials between -100 and +100°C have shown that the low-temperature onset of the mechanical-loss transition always occurs at the same temperature, independent of the chemical structure and the cross-link density, but that the width and intensity of the transition increase with increasing cross-link density. [4][5][6] In this paper we report the results of 13 C and 15 N NMR measurements on one of the epoxides of the series crosslinked with 15 N-labeled hexamethylenediamine or a mixture of [ 15 N]hexamethylenediamine and [ 15 N]hexylamine (and their unlabeled couterparts) in various combinations. The goal of these experiments is to measure directly the extent of reaction at the amine nitrogen centers and hence improve the determination of the cross-link density.

show abstract

“…This is most critical in cases in which two glycidyl units are located at the same atom; for example, a variety of reactions have been identified for tetraglycidyl diaminodiphenylmethane (Fig. 1) that lead to several cyclic structures 5–15…”

Section: Introductionmentioning

confidence: 99%

“…This was in close agreement with results from spectroscopic studies of cured resins reported elsewhere 9. However, the same group also claimed an overall degree of cyclization, including etherification reactions, of around 50–65% 5, 10, 11. For the resolution of these uncertainties, a study was performed with a special degradation technique by which the network was cleaved after curing and the amount of cycles was determined from the fragments.…”

Section: Introductionmentioning

confidence: 99%

“…1) that lead to several cyclic structures. [5][6][7][8][9][10][11][12][13][14][15] In addition to etherification reactions that occur preferentially during late curing stages at high temperatures, 5 the eight-membered ring (1) in Figure 1 is especially interesting. It is generated during curing by direct cyclization between the resin and curing agent, thereby reducing the effective crosslink density of the cured resin.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Assessment of cyclization and network defects in glycidylamine‐based epoxy networks by selective degradation

Stütz¹,

Tesch²

2003

J of Applied Polymer Sci

View full text Add to dashboard Cite

A special model system based on trimethylene glycol di(p-aminobenzoate) and its glycidyl derivative was evaluated to study the extent of cyclization in glycidylamine epoxies. The cured resins were degraded by alkaline hydrolysis, which left the cycles unaffected. The cycle concentration obtained by high-performance liquid chromatography was 15%. The oligomer distribution of the degradation products strongly indicated that up to 40% of the epoxy groups were lost to side reactions, and this resulted in a large number of structural defects in the network.

show abstract

Chemical structure of networks resulting from curing of N,N‐diglycidylaniline‐type resins with aromatic amines. II. Detection and characterization of intermolecular etherification on model compounds

Cited by 17 publications

References 5 publications

Location of the Antiplasticizer in Cross-Linked Epoxy Resins by ²H, ¹⁵N, and ¹³C REDOR NMR

Location of the Antiplasticizer in Cross-Linked Epoxy Resins by ²H, ¹⁵N, and ¹³C REDOR NMR

Determination of the Extent of Reaction of Amine Cross-Linked Epoxy Resins by Solid-State ¹³C and ¹⁵N NMR

Assessment of cyclization and network defects in glycidylamine‐based epoxy networks by selective degradation

Contact Info

Product

Resources

About

Chemical structure of networks resulting from curing of N,N‐diglycidylaniline‐type resins with aromatic amines. II. Detection and characterization of intermolecular etherification on model compounds

Cited by 17 publications

References 5 publications

Location of the Antiplasticizer in Cross-Linked Epoxy Resins by 2H, 15N, and 13C REDOR NMR

Location of the Antiplasticizer in Cross-Linked Epoxy Resins by 2H, 15N, and 13C REDOR NMR

Determination of the Extent of Reaction of Amine Cross-Linked Epoxy Resins by Solid-State 13C and 15N NMR

Assessment of cyclization and network defects in glycidylamine‐based epoxy networks by selective degradation

Contact Info

Product

Resources

About

Location of the Antiplasticizer in Cross-Linked Epoxy Resins by ²H, ¹⁵N, and ¹³C REDOR NMR

Location of the Antiplasticizer in Cross-Linked Epoxy Resins by ²H, ¹⁵N, and ¹³C REDOR NMR

Determination of the Extent of Reaction of Amine Cross-Linked Epoxy Resins by Solid-State ¹³C and ¹⁵N NMR