Тұс талмайтын мочевина-формальдегид шайыры

Non transparent thermosetting resin
Urea formaldehyde (UF), also known as urea methanal, so named for its common synthesis pathway and overall structure, 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. In agriculture, urea formaldehyde compounds are one of the most commonly used types of slow release fertilizer. UF and related amino resins are a class of thermosetting resins of which urea formaldehyde resins make up 80% produced worldwide. Examples of amino resins use include in automobile tires to improve the bonding of rubber, in paper for improving tear strength, and in molding electrical devices, jar caps, etc.

UF was first synthesized in 1884 by Dr Hölzer, who was working with Bernhard Tollens, neither of whom realized that the urea and formaldehyde were polymerizing. In the following years a large number of authors worked on the structure of these resins. In 1896, Carl Goldschmidt investigated the reaction further. He also obtained an amorphous, almost insoluble precipitate, but he did not realize that polymerization was occurring; he thought that two molecules of urea were combining with three molecules of formaldehyde. In 1897 Carl Goldschmidt patented the use of UF resins as a disinfectant. General commercialisation followed this and in the following decades, more and more applications were described in the literature. In 1919, Hanns John (1891–1942) of Prague, Czechoslovakia, obtained the first patent for UF resin in Austria. Urea formaldehyde was object matter of judgment via the European Court of Justice (now CJEU) of 5 February 1963, Case 26–62 Van Gend & Loos v Netherlands Inland Revenue Administration.

Urea formaldehyde resin's attributes include high tensile strength, flexural modulus, high heat distortion temperature, low water absorption, mould shrinkage, high surface hardness, elongation at break, and volume resistance. It has a refractive index of 1.55.

The chemical structure of UF polymer consists of [(O)CNHCH2NH]n repeat units. In contrast, melamine formaldehyde resins feature NCH2OCH2N repeat units. Depending on the polymerization conditions, some branching can occur. Early stages in the reaction of formaldehyde and urea produce bis(hydroxymethyl)urea.

About 20 million metric tons of UF are produced annually. Over 70% of this production is then put into use by the forest products industry for bonding particleboard, MDF, hardwood plywood, and laminating adhesive.