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 relate 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, such as jar caps.

Urea-formaldehyde is pervasive. Examples include decorative laminates, textiles, paper, foundry sand molds, wrinkle-resistant fabrics, cotton blends, rayon, corduroy, etc. It is also used as wood glue. UF was commonly used when producing electrical appliances casing e.g. desk lamps. Foams have been used as artificial snow in movies.

 

Agricultural use

Urea-formaldehyde compounds are a widely used as slow-release sources of nitrogen in agriculture. The rate of decomposition into CO2 and NH3 depends on the length of the urea-formaldehyde chains and it relies on the action of microbes found naturally in most soils. The activity of these microbes, and the rate of ammonia release, is temperature-dependent. The optimum temperature for microbe activity is around 70–90 °F (21–32 °C).

 

Foam insulation

 

Urea-formaldehyde insulation

Urea-formaldehyde foam insulation UFFI commercialisation dates to the 1930s as a synthetic insulation with thermal conductivity of 0.0343 to 0.0373 W/mK.

 

UFFI is a foam with similar consistency to shaving cream, that is easily injected or pumped into voids. It is normally made on site using a pump set and hose with a mixing gun to mix the foaming agent, resin, and compressed air. The fully expanded foam is pumped into areas in need of insulation. It becomes firm within minutes, but cures within a week. UFFI is generally found in homes built or retrofitted from the 1930s to the 1970s, often in basements, wall cavities, crawl spaces and attics. Visually, it looks like oozing liquid that has been hardened. Over time, it tends to vary in shades of butterscotch, but new UFFI is a light yellow colour. Early forms of UFFI tended to shrink significantly. Modern UF insulation with updated catalysts and foaming technology have reduced shrinkage to minimal levels (between 2 and 4%). The foam dries with a dull matte colour with no shine. When cured, it often has a dry and crumbly texture.