Good Chemical Resistance
Polyamide 6 and 66 are established materials for under-the-hood components such as intake manifolds, coolant pipes and oil modules. Recently, this class of materials has also had to face new challenges in the form of chemical resistance. For instance, a new technology that is used to remove climate-damaging nitrogen oxides from the exhaust of diesel engines with the aid of AdBlue urea solutions has been gaining in importance for cars and trucks.
Accordingly, Lanxess AG, Leverkusen, Germany, has employed the accelerated aging tests stipulated in the DBL 5419 delivery specifications to investigate how resistant various grades of Durethan containing their various heat stabilizers are to AdBlue urea solutions. With good results: for instance, Durethan AKV 35 H3.0 (PA66 GF35), which has been optimized for applications with AdBlue, shows next to no change in mechanical properties at a storage temperature of 60°C after 28 days. Even the composition of the AdBlue solution varies approximately within the tolerance limits when in contact with the polyamide. This can be attributed to low-ion stabilization and other components of the optimized formulation. Lanxess intends to use the experience gained from the tests to optimize the formulations of other grades of Durethan as necessary.
AdBlue is a high-purity, clear, 32.5-percent solution of urea in water. It is held in an additional tank in the vehicle and injected into the pre-cleaned stream of exhaust gas from the diesel engine by a special valve. The high temperature of the exhaust gases releases ammonia from the urea. The ammonia subsequently reduces about 90% of the nitrogen oxides to harmless nitrogen and water in the SCR catalytic converter (selective catalytic reduction). This allows the engines to satisfy the pending, more stringent international exhaust gas emission standards such as Euro 5 and Euro 6, which become binding in 2009 and 2014, respectively. The rights to the AdBlue brand are held by the Association of the Automotive Industry (Verband der Automobilindustrie – VDA).
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