Epoxy resin curing agents Ureas

Uses Mfg. of phenolic and thermosetting resins, furan polymers, urea-formaldehyde resins wetting agent foundry sand binders corrosion-resist, resins intermediate for esterification and etherification paints solvent, plasticizer for phenolic resins solvent for dyes and resins nonreactive epoxy resin diluent vise, reducer, cure promoter, and carrier in amine-cured epoxy resins gel retarder in casein/protein glues polymer sealants/cements synthetic flavoring agent in foods and pharmaceuticals cosmetics ingred. in food-pkg. adhesives... 

Hexamethylenetetramine (Hexamine) - te-tr9- inen [ISV hexa- + methylene + tetra-+ amine] (1888) (HMT, methenamine, and urotropine) n. (CH2)6-N4. A bicyclic compound, the reaction product of ammonia and formaldehyde. It is used as a basic catalyst and accelerator for phenolic and urea resins, and a solid, catalytic-type curing agent (hardener) for epoxies See image). 

Epoxy resins may be converted to the thermoset state through the epoxy groups by reaction with well over 50 different classes of chemical compounds. Amines, polyamides, anhydrides, Lewis acids, ureas, melamine, imidazoles, BFj amine complexes, imides, and so forth, have been commonly used as cure agents for epoxy resins [53]. 

The use of substituted ureas as curing agents for epoxy resins has been the subject of few studies. Ywakura and Izawa [70] analyzed the reactions between phenylglycidyl ether and substituted ureas. In every case, the reaction, carried out under mild conditions (T = 90°C, t = 1 h, mol ratio of epoxy/urea = 1-3, with or without the use of NfCiHs), as catalyst), led to the formation of a 2-oxazolidone and a secondary amine ... 

Figure 6 Chemical formulae of the catalysts and co-reactants used as curing agents of epoxy resins electrophilic 33 and nucleophilic 34-36 catalysts, dicyandiamide 37, ureas 38, 39, imidazoles 40-47, aliphatic amines 48, 49, polyamide 50, and cycloaliphatic...

Copper surfaces may be stuck with urea formaldehyde resins or, if these are too brittle to suit the application, they may be used as a priming coat above which some other adhesive is applied. Epoxy resins vary in their behaviour towards copper owing to differences in the curing agent employed. Anhydride curing agents are known to be... 

It is important to point out that in spite of the ease of use, these resinous mortars, like many other chemical compositions, are toxic and adequate precautions must be taken to protect the health of the applicators. For example, the skin should be protected from the setting agents used in phenolic, urea, furan, and epoxy cements and adequate ventilation should be provided during the application of polyurethane and polyester cements to prevent the inhalation of volatile isocyanates and styrene respectively. However, once they are cured, these resinous cements are not hazardous. Actually, they are important energy conserving materials of construction. 

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