Curing of epoxy resins with dicyandiamide

Fedtke, M.; Domaratius, F.; Pfitzmann, A.

doi:10.1007/bf00294867

Cited by 29 publications

(11 citation statements)

References 8 publications

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“…The authors of [17,18] suggested that, together with the described processes, at elevated temperatures the carbodiimide tautomeric form of DCDA undergoes a cycloaddition reaction with the epoxy ring with the formation of oxazoline or tautomeric oxazolidine. In addition, carbodiimide can interact with alcohols with the formation of isoureas; with water, with the formation of ureas or urethanes; or with itself, yielding melamine derivatives.…”

Section: Resultsmentioning

confidence: 99%

“…The curing process of epoxy oligomers under the influence of DCDA was studied quite well in the last half century [15][16][17][18][19][20][21][22], and the large number of possible mechanisms of the occurrence of reactions of interac tions with DCDA, its products of destruction, and epoxy oligomers and activating additives has been described recently; however, the detailed mechanism of interaction of DCDA has not been worked out yet. Basic schemes of the reaction of interaction of DCDA and products of its destruction with epoxy groups are shown below.…”

Section: Resultsmentioning

confidence: 99%

“…To reduce the cur ing temperature, activators/accelerators of different composition are used. As accelerators, dimethylben zylamine (DMBA) [15], imidazoles [17,18], and sub stituted ureas [23,24] are used.…”

Section: Resultsmentioning

confidence: 99%

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A study of the mechanism of curing of the dicyandiamide-epoxydiane oligomer system in the presence of asymmetrical urea

Chursova¹,

Ткачук²,

Panina³

et al. 2015

Polym. Sci. Ser. D

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Catalyzed epoxy systems have been studied consisting of an ED 20 epoxy diane oligomer ED 20, a curing catalyst (dicyandiamide (DCDA)), and an accelerator (an asymmetric urea based on toluene diiso cyanate). The chemical composition and structure of the catalyzed epoxy systems have been established by IR and NMR spectroscopy in the initial and cured states. The influence of the composition of the complex catalyst system of curing on the mechanisms of chemical transformation of epoxy system has been consid ered. It is shown that the products of interaction of epoxydiane oligomers with DCDA in the presence of the accelerator-asymmetric urea of Dyhard UR500 brand-is a complex system consisting of chains of poly esters produced by a chain growth mechanism and amine sites, as well as interaction products of epoxy groups with imines, isocyanates, and hydroxyl groups with nitriles.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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A study of the mechanism of curing of the dicyandiamide-epoxydiane oligomer system in the presence of asymmetrical urea

Chursova¹,

Ткачук²,

Panina³

et al. 2015

Polym. Sci. Ser. D

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“…MDA, which has excellent mechanical and electrical properties, is the most widely used aromatic curing agent, but recently has been classified as a potential human carcinogen and its volume has been declining. Alkyl-substituted MDAs such as tetraethyl-MDA have been developed with lower toxicity and improved performance (108,109). However, none of the replacement products has the performance/cost combination of MDA.…”

Section: Coreactive Curing Agentsmentioning

confidence: 99%

“…One study proposed the initial reaction of all four active hydrogens with epoxy resin catalyzed by tertiary amine catalysts followed by epoxy homopolymerization. The last step involves reactions between the hydroxyl groups of the epoxy resin with the cyano group (108,109). One of the more recent and plausible mechanism of DICY cure with epoxies is that of Gilbert and co-workers (111).…”

Section: Coreactive Curing Agentsmentioning

confidence: 99%

Epoxy Resins

Pham¹,

Marks²

2004

Encyclopedia of Polymer Science and Technology

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Epoxy resins are an important class of polymeric materials, characterized by the presence of more than one three-membered ring known as the epoxy, epoxide, oxirane, or ethoxyline group.The word "epoxy" is derived from the Greek prefix "ep," which means over and between, and "oxy," the combining form of oxygen (1). By strict definition, epoxy resins refer only to uncross-linked monomers or oligomers containing epoxy groups. However, in practice, the term epoxy resins is loosely used to include cured epoxy systems. It should be noted that very high molecular weight epoxy resins and cured epoxy resins contain very little or no epoxide groups. The vast majority of industrially important epoxy resins are bi-or multifunctional epoxides. The monofunctional epoxides are primarily used as reactive diluents, viscosity modifiers, or adhesion promoters, but they are included here because of their relevance in the field of epoxy polymers.Epoxies are one of the most versatile classes of polymers with diverse applications such as metal can coatings, automotive primer, printed circuit boards, semiconductor encapsulants, adhesives, and aerospace composites. Most cured epoxy resins provide amorphous thermosets with excellent mechanical strength and toughness; outstanding chemical, moisture, and corrosion resistance; good thermal, adhesive, and electrical properties; no volatiles emission and low shrinkage upon cure; and dimensional stability-a unique combination of properties generally not found in any other plastic material. These superior performance characteristics, coupled with outstanding formulating versatility and reasonable costs, have gained epoxy resins wide acceptance as materials of choice for a multitude of bonding, structural, and protective coatings applications.Commercial epoxy resins contain aliphatic, cycloaliphatic, or aromatic backbones and are available in a wide range of molecular weights from several hundreds to tens of thousands. The most widely used epoxies are the glycidyl ether derivatives of bisphenol A (>75% of resin sales volume). The capability of the highly strained epoxy ring to react with a wide variety of curing agents under diverse conditions and temperatures imparts additional versatility to the epoxies. The major industrial utility of epoxy resins is in thermosetting applications. Treatment with curing agents gives insoluble and intractable thermoset polymers. In order to facilitate processing and to modify cured resin properties, other constituents may be included in the compositions: fillers, solvents, diluents, plasticizers, catalysts, accelerators, and tougheners.Epoxy resins were first offered commercially in the late 1940s and are now used in a number of industries, often in demanding applications where their performance attributes are needed and their modestly high prices are justified. However, aromatic epoxies find limited uses in exterior applications because of their

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Epoxy Resins

Pham¹,

Marks²

2004

Kirk-Othmer Encyclopedia of Chemical Technology

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Epoxy resins are reactive intermediates used to produce a versatile class of thermosetting polymers. They are characterized by the presence of a three‐membered cyclic ether group commonly referred to as an epoxy group, 1,2‐epoxide, or oxirane. The most widely used epoxy resins are diglycidyl ethers of bisphenol A derived from bisphenol A and epichlorohydrin. The outstanding performance characteristics of the thermosets derived from bisphenol A epoxies are largely conveyed by the bisphenol A moiety (toughness, rigidity, and elevated temperature performance), the ether linkages (chemical resistance), and the hydroxyl and epoxy groups (adhesive agents). In addition to bisphenol A, other starting materials such as aliphatic glycols and both phenol and o ‐cresol novolacs are used to produce specialty resins. Epoxy resins may also include epoxide‐bearing compounds based on aromatic amine, triazine, and cycloaliphatic backbones. A variety of reagents have been described for converting the liquid and solid epoxy resins to the cured state, which is necessary for the development of the ultimate end‐use properties. The curing agents or hardeners are categorized as either catalytic or coreactive. Catalytic curing agents initiate resin homopolymerization, either cationic or anionic, as a consequence of using a Lewis acid or base in the curing process. Coreactive curing agents are polyfunctional compounds typically possessing active hydrogens that are employed up to stoichiometric quantities with epoxy resins. The important classes of coreactive curing agents include multifunctional amines and their amide derivatives, polyphenols, polymeric thiols, polycarboxylic acids, anhydrides, phenol–formaldehyde novolacs and resoles, and amino–formaldehyde resins. The largest single use of epoxy resins is in the protective coatings market where high corrosion resistance and adhesion to substrates are important. Epoxies have gained wide acceptance in protective coatings and in electrical and structural applications because of their exceptional combination of properties such as toughness, adhesion, chemical and thermal resistance, and good electrical properties.

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Curing of epoxy resins with dicyandiamide

Cited by 29 publications

References 8 publications

A study of the mechanism of curing of the dicyandiamide-epoxydiane oligomer system in the presence of asymmetrical urea

A study of the mechanism of curing of the dicyandiamide-epoxydiane oligomer system in the presence of asymmetrical urea

Epoxy Resins

Epoxy Resins

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