Epoxy compounds curing

Thermodynamics of the epoxy compound curing with amines is interesting from two points of view. It concerns all the numerous elementary reactions resulting in the formation of H-complexes in the reaction system and the process as a whole, as well. 

The second important feature of the reaction mechanism of the epoxy compound curing under the action of amines (primary, secondary and tertiary) and their mixtures consists in formation of various hetero-, auto-, inter- and intramolecular donor-acceptor complexes between the components of the reaction system — the starting substances and reaction products. Consideration of this complex formation can adequately explain the reaction kinetics. 

Epoxy Resins. Urethane and ester-extended hydantoia epoxy resins cured with several compounds seem to have better properties than the previous ones (98). These resins are prepared from hydantoias such as (21) (99,100). 

Cyanamide and its aromatic derivative, such as 4,4 -methylene bis(phenyl cyanamide), were reported to cure an epoxy resin at elevated temperatures.(4) It is also well known that the dimer of cyanamide (dicyandiamide) is the most important epoxy curing agent in one-package epoxy compounding.(5) Unfortunately, this dimer precipitates from the dispersion causing uneven mixing upon standing. 

Curing of One-Package, Thermosetting Epoxy Compounds. The thermo-setting epoxy resin mixture was cured at 160°C for 2 hours. 

CURING-POLYMERIZATION REACTIONS OF EPOXY COMPOUNDS AND RESINS... 

A great number of investigations has been devoted to the chemistry of epoxy, compounds and clarification of the mechanism of curing of epoxy oligomers with various hardeners, summarized in monographs 1,12,19-23) and reviews24-251, which have become, however, somewhat obsolete. 

Since the mechanism of curing of epoxy compounds with primary and secondary amines differs essentially from that using tertiary amines, we shall consider this case separately. 

Tertiary amines (TA) may be utilized both as independent curing agents for epoxy resins and as catalysts in the reaction of epoxy compounds with alcohols, phenols, carboxylic adds and their anhydrides i - 5. Besides, the three-... 

TA can be effetive additives for controlling the reaction rate in the curing of epoxy compounds with primary amines. 

This transformation or conversion is accomplished by the addition of a chemically active compound known as a curing agent or catalyst. Depending on the particular details of the epoxy formulation, curing may be accomplished at room temperature, with the application of external heat, or with the application of an external source of energy other than heat such as ultraviolet (uv) or electron beam (EB) energy. 

Visible light cured epoxy adhesives and coatings have been developed for architectural, industrial, and maintenance applications and for products difficult to heat or uv/EB cure because of their size. These are clear, one-part epoxy resins that cure by exposure to visible light for a few hours. They are formulated with cycloaliphatic epoxy compounds and a cationic photoinitiator that generates a strong acid when exposed to sunlight. 

The last example shows that the value of the substitution effect characterized by the ratio Q in not a universal constant and may depend on the structure of the reference epoxy compound. Phenylglycidyl or p-tolylglycidyl ethers are apparently good reference compounds for curing of DGEBA, but they may be not that good as models for DGA, TGDDM and some other polyepoxides. 

On the other hand, the mbbery nature of the polymerized oil may be used as toughening, rigid epoxy materials because it is phase separated into spherical domains when mixed and cured with bisphenol-A epoxy compounds (72-75). A... 

Epoxy compound IV exliibits a minimum of side reactions in the presence of ammonium perchlorate. Epoxy curing agent II shows a high reaction rate but side reactions dominate n the presence of ammonium perchlorate. The compound HITA (Vican be subjected lo various transfomiations shown in scheme 16). They also possess similar properties as V but are less active. Zirconium... 

Polyethylene and Polypropylene Acceptable bonds have been obtained between treated polyolefin surfaces with polar adhesives, such as epoxies, or solvent cements containing synthetic rubber or phenolic resin. The solvent adhesives are applied to both surfaces and the solvents allowed to evaporate before the parts are joined. Recommended epoxies are the anhydride-cured and amine-cured types. Also suitable is a two-component, polyamide-modified epoxy compound. Other adhesives that provide adequate bond strength to treated polyolefins include styrene-unsatmated polyester and solvent-type nitrile-phenolic (15). 

E. W. Flick, Epoxy Resins, Curing Agents, Compounds and Modifiers, 2nd edn., William Andrew Publishing/Noyes, Norwich/New York, 1993. 

Chemical analysis of an insulator from one supplier indicated polymer fragments and curing byproducts, as shown in Figure 10-13. In contrast, an analysis of an insulator from another supplier indicated significant differences. In the second case, traces of polymer fragments were found in addition to thorough crosslinking of the epoxy compound. 

We have investigated the recovered glassfiber-resin powder for its properties as a filler for epoxy resin compounds which are used as paints or adhesives, and compared it to conventional fillers, such as talc and calcium carbonate. The epoxy resin compound, composed of bisphenol A type epoxy resin (50.0wt%), aliphatic polyamine type hardener (18.0wt%) and filler (32.0%), was prepared. Strength and thermal expansion properties were measured for the molded epoxy resin compound cured 23°C for 7 days. Viscosity was measured for the epoxy resin compound before adding the hardener. Adhesive strength was measured by tearing two ferric boards bonded with the epoxy resin compound which was composed of bisphenol A type epoxy resin (49.2wt%), polyaminoamide type hardener (18.0wt %), and filler (32.8wt%), and was cured at 23°C for 7 days. 

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