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[edit] In A Nutshell
Urea-formaldehyde, also known as urea-methanal, named so for its common synthesis pathway and overall structure, is a transparent thermosetting resin or plastic, made from urea and formaldehyde heated in the presence of a mild base such as ammonia or pyridine. These resins are used in adhesives, finishes, MDF, and molded objects. Urea-formaldehyde resin's attributes include high tensile strength, flexural modulus and heat distortion temperature, low water absorption, mould, high surface hardness, elongation at break, and volume resistance.
Urea formaldehyde was commonly used when producing electrical appliances casing i.e. desk lamps. It is now mostly replaced by melamine resin. Urea-formaldehyde foam insulation started being used in the 1950s. In the 1980s, concerns began to develop about the toxic formaldehyde vapor emitted in the curing process, as well as from the breakdown of old foam. Consequently, its use was discontinued.
Urea formaldehyde is also used in agriculture as a controlled release source of nitrogen fertilizer.Urea formaldehyde’s rate of decomposition into CO2 and NH3 is determined by the action of microbes found naturally in most soils. The activity of these microbes, and therefore the rate of nitrogen release, is temperature dependent. The optimum temperature for microbe activity is approximately around 70°-90°F.
[edit] Definitions
Urea
- Urea is an organic compound with the chemical formula (NH2)2CO and is also known by the International Nonproprietary Name (rINN) carbamide, as established by the World Health Organization. For example, the medicinal compound hydroxyurea (old British Approved Name) is now hydroxycarbamide. Other names include carbamide resin, isourea, carbonyl diamide, and carbonyldiamine.
- The term urea or carbamide is also used for the class of chemical compounds sharing the same functional group RR'N-CO-NRR' based on a carbonyl group flanked by two organic amine residues. They can be accessed in the laboratory by reaction of phosgene with primary or secondary amines. Example of ureas are the compounds carbamide peroxide, allantoin, and Hydantoin. Ureas are closely related to biurets and related in structure to amides, carbamates, diimides, carbodiimides, and thiocarbamides.
- Hazards;
- Urea can be irritating to skin and eyes. Too high concentrations in the blood can cause damage to organs of the body. Low concentrations of urea such as in urine are not dangerous. It has been found that urea can cause algal blooms to produce toxins, and urea in runoff from fertilizers may play a role in the increase of toxic blooms.
- Repeated or prolonged contact with urea in fertilizer form on the skin may cause dermatitis. The substance also irritates the eyes, the skin, and the respiratory tract. The substance decomposes on heating above melting point, producing toxic gases, and reacts violently with strong oxidants, nitrites, inorganic chlorides, chlorites and perchlorates, causing fire and explosion hazard. Want to know more
Formaldehyde
- Formaldehyde is a chemical compound with the formula H2CO. It is the simplest aldehyde—an organic compound containing a terminal carbonyl group: it consists of exactly one carbonyl. It was first synthesized by the Russian chemist Aleksandr Butlerov (1828-1886), but was conclusively identified by August Wilhelm von Hofmann. Formaldehyde exists in several forms aside from H2CO: the cyclic trimer trioxane and the polymer paraformaldehyde. It exists in water as the hydrate H2C(OH)2. Aqueous solutions of formaldehyde are referred to as formalin. "100%" formalin consists of a saturated solution of formaldehyde (roughly 40% by mass) in water, with a small amount of stabilizer, usually methanol to limit oxidation and polymerization.
- Formaldehyde is an intermediate in the oxidation (or combustion) of methane as well as other carbon compounds, e.g. forest fires, in automobile exhaust, and in tobacco smoke. It is produced in the atmosphere by the action of sunlight and oxygen on atmospheric methane and other hydrocarbons; thus, it becomes part of smog. Small amounts of formaldehyde are produced as a metabolic by product in most organisms, including humans.
- Hazards;
- Formaldehyde can be toxic, allergenic, and carcinogenic. Because formaldehyde resins are used in many construction materials it is one of the more common indoor air pollutants. At concentrations above 0.1 ppm in air formaldehyde can irritate the eyes and mucous membranes, resulting in watery eyes. Formaldehyde inhaled at this concentration may cause headaches, a burning sensation in the throat, and difficulty breathing, as well as triggering or aggravating asthma symptoms.
- Formaldehyde is classified as a probable human carcinogen by the U.S. Environmental Protection Agency. The International Agency for Research on Cancer (IARC) has determined that there is "sufficient evidence" that occupational exposure to formaldehyde causes nasopharyngeal cancer in humans. Want to know more
