Curing of epoxy resins with dicyandiamide: NMR and IR investigation of isolated main products

Pfitzmann, A.; Fliedner, E.; Fedtke, M.

doi:10.1007/bf00308542

Cited by 16 publications

(13 citation statements)

References 11 publications

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“…For example, at 130 °C, the two peaks at 120 (cyano group) and 164 ppm are from the residual DCDA while those at 170 and 158 ppm are related to carbon atoms in O containing intermediates. [31][32][33] No polymerization was expected at 130 °C, thus NMR spectra show the mixture of unreacted and formic acid treated DCDA. This is further confirmed by FTIR, which shows the features of both DCDA and cyanuric acid.…”

Section: The Design Of Polymerization Pathwaymentioning

confidence: 99%

Bandgap Engineering of Organic Semiconductors for Highly Efficient Photocatalytic Water Splitting

Wang

Silveri

Bayazit

et al. 2018

Advanced Energy Materials

156

101

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activity is highly dependent on the electronic structure of the photocatalyst, it is crucial to adjust the bandgap in order to utilize the highest possible proportion of visible photons and achieve the target of 10% solar to fuel conversion efficiency. [2] Moreover, bandgap tunable semiconductors are especially useful in the construction of a Z-scheme for water splitting, which is considered to be a more promising approach to solar H 2 production than the single photocatalyst-based water splitting system. [3][4][5][6][7][8] A Z-Scheme requires an appropriate match of redox potentials between two photocatalysts and two mediators. So far, the strate-

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Section: The Design Of Polymerization Pathwaymentioning

confidence: 99%

Bandgap Engineering of Organic Semiconductors for Highly Efficient Photocatalytic Water Splitting

Wang

Silveri

Bayazit

et al. 2018

Advanced Energy Materials

156

101

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“…27,28 Instead, we prefer the suggestion that it arises from urethane ester groups. These could be present either in an open form, as proposed by Zahir,4 or in a five-membered oxazolidinone ring, as proposed by Davidson, 6 Gilbert et al, 13 and Pfitzmann et al 14,15 The latter is more likely. The carbonyl band has been reported to absorb at 1730 cm Ϫ1 in oxazolidone, 28,29 at 1750 cm Ϫ1 in 3-methyl-2-oxazolidinone, 28 at 1760 cm Ϫ1 in oxazolidinones formed by isocyanate-epoxy reactions, 30 and almost always around 1750 cm Ϫ1 in a series of alkyl oxazolones (like oxazolidinones but with a CAC double bond in the ring).…”

Section: General Discussion and Conclusionmentioning

confidence: 94%

“…Finally, Grenier-Loustalot et al, 16 like Saunders, attributed this peak to ureas formed by reaction between nitrile and hydroxyl groups. However, both Grenier-Loustalot 16 and Pfitzmann 15 also provided evidence that at high temperatures nitrile groups disappear through rearrangement to form a melamine ring structure. The variety of mechanisms proposed confirms the complexity of the reaction and the need for further work in order to elucidate the details.…”

mentioning

confidence: 95%

“…The disappearance of CAN groups was also explained in terms of hydrolysis. The mechanism proposed by Pfitzmann and coworkers 14,15 combines aspects of the Zahir and Gilbert mechanisms. Like Zahir, they postulated the formation of tautomeric oxazoline and oxazolidine rings, but suggested that they are formed by direct reaction of epoxide rings with one of the CAN bonds in the carbodiimide tautomer of DICY.…”

mentioning

confidence: 98%

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Effect of copper on the curing and structure of a DICY-containing epoxy composite system

Gundjian

Cole

2000

J. Appl. Polym. Sci.

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ABSTRACT:The curing and structure of an epoxy system containing dicyandiamide (DICY) as hardener were studied as a function of temperature and the presence or absence of copper with the use of differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy in photoacoustic mode (FTIR-PAS). Spectroscopic analysis of specimens taken from the DSC helped to clarify the reaction mechanism in terms of the different schemes that have been proposed. The initial stages, corresponding to the first peak in the DSC exotherm, involve the usual epoxide-amine reactions closely followed by a reaction between DICY nitrile groups and hydroxyl groups to form structures containing iminoether and urea groups. These reactions are slightly retarded in the presence of copper. At higher temperatures, corresponding to the second peak in the exotherm, these structures are transformed into others believed to contain urethane ester groups. This reaction, which may be considered to constitute a form of degradation, is significantly accelerated in the presence of copper. The effect is particularly large around 180°C, a temperature commonly used to cure such systems, so the results have important practical implications, for example, in the lamination of circuit boards.

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“…7). The oxirane rings react with the amine groups [8,11,[26][27][28][29][30][31][32][33][34][35]. At some temperature, their consumption exceeds the supply of Dicy molecules from the dissolving particles.…”

Section: Curing Of Ep Accel and Ep N-filledmentioning

confidence: 99%

Functional nano fillers in epoxy-dicyandiamide adhesives for prolonged shelf life and efficient cure

et al. 2011

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Shelf life at room temperature and curing behaviour at elevated temperature are studied for hot-curing accelerated epoxies (EP, diglycidylether of bisphenol A plus dicyandiamide (Dicy)) by FTIR-spectroscopy and modulated DSC. The accelerator is added either directly or with nano-zeolite filler to the EP. Due to the immobilisation of the accelerator in the pores of the nano-zeolite, the shelf life of this EP is 5 times longer than for the EP containing free accelerator. While the free accelerator acts during the whole heating step to curing temperature, the nano-zeolite does not release the accelerator before ca. 100 °C. As monitored by light microscopy, the released accelerator not only supports the curing but also stimulates the dissolution of the solid Dicy. As the result, network formation at 170 °C finishes within less than 25 minutes for the nano-filled EP.

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Curing of epoxy resins with dicyandiamide: NMR and IR investigation of isolated main products

Cited by 16 publications

References 11 publications

Bandgap Engineering of Organic Semiconductors for Highly Efficient Photocatalytic Water Splitting

Bandgap Engineering of Organic Semiconductors for Highly Efficient Photocatalytic Water Splitting

Effect of copper on the curing and structure of a DICY-containing epoxy composite system

Functional nano fillers in epoxy-dicyandiamide adhesives for prolonged shelf life and efficient cure

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