Urea-formaldehyde
1933320
219754146
2008-06-16T19:04:03Z
Rjwilmsi
203434
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[[Image:UreaFormaldehydeResin01.png|right]]
'''Urea-formaldehyde''', also known as '''urea-methanal''', named so for its common synthesis pathway and overall structure<ref>[http://www.chm.bris.ac.uk/webprojects2002/robson/uses_of_formaldehyde.htm Uses Of Formaldehyde<!-- Bot generated title -->]</ref>, is a [[transparency (optics)|transparent]] thermosetting [[resin]] or [[plastic]], made from [[urea]] and [[formaldehyde]] heated in the presence of a mild [[base (chemistry)|base]] such as [[ammonia]] or [[pyridine]]. These resins are used in [[adhesive]]s, finishes, [[Medium-density fibreboard|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]].{{Fact|date=April 2007}}. 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.<ref>http://www.nsc.org/EHC/indoor/formald.htm Environmental Health Center Formaldehyde FAQ</ref>
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.
==References==
{{Reflist}}
==External links==
* [http://www.plastiquarian.com/uf.htm Urea formaldehyde (Plastics Historical Society)]
* [http://www.cmhc-schl.gc.ca/en/co/maho/yohoyohe/inaiqu/inaiqu_008.cfm Urea-Formaldehyde Foam Insulation]([[Canada Mortgage and Housing Corporation]])
* [http://www.epa.gov/iaq/formalde.html#Levels%20in%20Homes Indoor Air Quality: Formaldehyde](US [[United States Environmental Protection Agency|Environmental Protection Agency]])
* [http://www.hse.gov.uk/lau/lacs/37-9.htm UFFI] (UK [[Health and Safety Executive]])
[[Category:Polyamides]]
[[Category:Synthetic resins]]
[[Category:Plastics]]
[[Category:Thermosetting plastics]]
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[[ja:尿素樹脂]]
[[zh:尿素甲醛樹脂]]