A type of amino resin made from melamine and formaldehyde. The first step in resin formation is the production of trimethylol melamine, C3N3(NHCH2OH)3, the molecules of which contain a ring with three carbon and three nitrogen atoms, the —NHCH2OH groups being attached to the carbon atoms. This molecule can combine further with others of the same kind by a condensation reaction. Excess formaldehyde or melamine can also react with trimethylol melamine or its polymers, providing many possibilities of chain growth and cross-linking. The nature and degree of polymerization depend upon pH, but heat is always needed for curing. Melamine resins are more water- and heat-resistant than urea resins. They may be water-soluble syrups (low molecular weight) or insoluble powders (high molecular weight) dispersible in water. Widely used as molding compounds with α-cellulose, wood flour, or mineral powders as fillers and with coloring materials; also for laminating, boil-proof adhesives, increasing wet strength of paper, textile treatment, leather processing, and for dinnerware and decorative plastic items.Butylated melamine resins are formed by incorporating butyl or other alcohols during resin formation, whereupon the —NHCH2OH groups convert to —NHCH2OC4H9. These resins are soluble in paint and enamel solvents and in surface coatings, often in combination with alkyds. They give exceptional curing speed, hardness, wear resistance, and resistance to solvents, soaps, and foods.Melamine-acrylic resins are water soluble and used for formation of water-base industrial and automotive finishes. See Urea-formaldehyde Resin.
