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09. June 2021

Urea-resistant EPDM gaskets and hoses

EPDM is used for a very wide range of applications in the automotive industry, e.g., for hoses and seals in the vehicle that come into contact with the aqueous urea solution AdBlue and must therefore have sufficient resistance to urea. Carbon black N990 is often used as a filler in such applications. This study investigates the substitution of this carbon black with a Neuburg Siliceous Earth-based mineral filler.

REM image of the Neuburg Siliceous EarthREM image of the Neuburg Siliceous Earth

M. Aufmuth, H. Oggermüller, T. Brandmeier

Selective catalytic reduction (SCR) for exhaust gas after-treatment using aqueous urea solution (AdBlue; AUS 32) has long established itself as a method for making diesel engines more environmentally friendly. The strain placed on the elastomer components by the interaction of basicity and temperature of this reaction is not to be neglected, and a high performance of the formulation and the raw materials is crucial. In the study published in RFP Rubber Fibres Plastics 02 2021 the mineral filler Aktisil VM 56 is compared with a thermal carbon black N990. Aktisil VM 56 is based on Neuburg Siliceous Earth, a naturally occurring mixture of corpuscular, amorphous silica and lamellar kaolinite, surfacetreated with a vinyl silane.

One field of application for Aktisil VM 56 is, for example, hoses and mouldings of EPDM. Here Aktisil VM 56 not only improves the vulcanisation speed or the mechanical properties of the parts, but can also prevent the efflorescence of fission products. In addition, Aktisil VM 56 can be used as a substitute for carbon black, enabling the costs to be optimised.

The substitution of carbon black N990 with Aktisil VM 56 offers a number of advantages. A higher modulus at 100 % elongation is achieved, as well as a shorter vulcanisation time which results in a reduction in the cycle time. This can be achieved with an absolutely comparable resistance to Ad-Blue. During extrusion, Aktisil VM 56 exhibits a higher surface quality and a better stability. The Neuburg Siliceous Earth also prevents not only the blooming, eliminating the need for a subsequent cleaning process, but also ensures that the vulcanisates can be processed to produce parts that can be distinguished by colour. Furthermore, the blend costs are reduced significantly by the use of Aktisil VM 56. The use of Neuburg Siliceous Earth is in compliance with the specifications of VW TL 52686.

M. Aufmuth, H. Oggermüller, T. Brandmeier, RFP Rubber Fibres Plastics, 02 2021, 74-78.


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