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Resistant to Urea Solutions
Automotive producers have recently developed systems for the selective catalytic reduction (SCR) of nitrogen oxides in diesel engines, with a 32.5 % aqueous urea solution acting as reduction agent. The German association of automotive manufacturers (VDA) has listed this solution under the name AdBlue. When heated above 60°C, AdBlue decomposes into carbon dioxide and ammonia, if in contact with water. The ammonia then reacts with the nitrogen oxides, and generates water and nitrogen, thus reducing emission of nitrogen by approx. 90 %.

AdBlue poses high requirements to the ducts in the SCR systems: they need to resist urea and ammonia, and the gas mixture that might flow back from the catalytic converter. The urea solution is heated up to 60°C, but will freeze at -11°C and expand. It is thus indispensable to provide for good resistance to hydrolysis and bursting pressure, at high temperatures, as well as high impact resistance and elasticity, at low temperatures.
Several Vestamid polyamide 12 molding compounds fulfill all of these requirements. Evonik Degussa GmbH in Marl, Germany, offers various products to support automotive producers in developing their own individual systems.

All Vestamid compounds were submitted to recirculation testing with AdBlue, at temperatures of 60 and 80°C (environmental temperature 40 and 50°C, respectively) over a period of 5,000 h, in order to detect changes in their mechanical properties. The types examined showed excellent results concerning the values of elongation at break and fracture resistance, bursting pressure, and, most of all, cold impact strength at -40°C. Of all variants tested, Vestamid LX9008 is best suited to meet all requirements, while Vestamid L2140 and X7293 are currently applied in SCR systems.
Evonik Industries AG
Rellinghauser Straße 1
DE - 45128 Essen
Telephone: +49 201 177-01
Fax: +49 201 177-3475

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