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Urea-formaldehyde (UF), also known as urea-methanal, so named for its common synthesis pathway and overall structure, [1] is a nontransparent thermosetting resin or polymer. It is produced from urea and formaldehyde. These resins are used in adhesives, plywood, particle board, medium-density fibreboard (MDF), and molded objects.
The structure of the molecule of urea is O=C(−NH 2) 2.The urea molecule is planar when in a solid crystal because of sp 2 hybridization of the N orbitals. [8] [9] It is non-planar with C 2 symmetry when in the gas phase [10] or in aqueous solution, [9] with C–N–H and H–N–H bond angles that are intermediate between the trigonal planar angle of 120° and the tetrahedral angle of 109.5°.
Of all aldehydes, formaldehyde is produced on the largest scale, about 6 000 000 tons per year. It is mainly used in the production of resins when combined with urea, melamine, and phenol (e.g., Bakelite). It is a precursor to methylene diphenyl diisocyanate ("MDI"), a precursor to polyurethanes. [7]
In approximate order of decreasing consumption, products generated from formaldehyde include urea formaldehyde resin, melamine resin, phenol formaldehyde resin, polyoxymethylene plastics, 1,4-butanediol, and methylene diphenyl diisocyanate. [40] The textile industry uses formaldehyde-based resins as finishers to make fabrics crease-resistant. [50]
Wrinkle resistant treatments have been used since 1929, when cotton fabrics were treated with a solution of urea and formaldehyde. The chemical treatment stiffened the fabric, thus making it wrinkle-resistant. [3] Starting in the 1940s, a series of urea-formaldehyde derivatives were introduced.
The Biden administration has officially determined the chemical formaldehyde poses an “unreasonable” risk to human health and should be regulated. The Environmental Protection Agency (EPA ...
Adding urea to MF resins has been shown to lower the amount of free formaldehyde below the legal limit and is often used for this purpose. [1] Another complication with MF resins is the low solubility of melamine in water. [16] Because of this and the free formaldehyde content, MF resins are not used as commonly in the field of wood modification.
The result was Aerolite, a urea-formaldehyde adhesive which unlike conventional glues of the time, resisted water and micro-organisms. Further research showed that gap-bridging hardeners incorporating formic acid enabled Aerolite to be used as an assembly adhesive. Aerolite was the first adhesive of its type to be invented and manufactured in ...