Mercedes achieves a precision landing with the Broad Bake structural adhesive

Design changes in the sill area of electric vehicles to protect the battery require either a complex dryer conversion or the development of a new 1K Broad Bake structural adhesive. Together with DuPont, a precision landing was achieved and such a structural adhesive has been in series production at Mercedes since the beginning of 2023.

Mercedes has been using 1-component structural adhesives based on epoxy resin in the bodywork area for over 25 years to ensure the high crash and operational strength of the vehicle body. In the cathodic dip coating dryer, the cross-linking of the 1K structural adhesive takes place over time and temperature. The structural adhesive only develops its final performance in terms of mechanical strength, adhesive strength and corrosion protection if the process window is precisely adhered to. However, new sill designs, as have become necessary in the construction of electric vehicles to protect the batteries, result in slower heat transfer. This means that the required object holding times and object temperatures in the dryer can no longer be achieved under the previous production conditions.

>The first step in the development of new 1K Broad Bake structural adhesives was to clarify whether it was even possible to achieve the required properties in terms of adhesion, a cohesive fracture pattern - i.e. a fracture within the adhesive - mechanical strength and, above all, corrosion protection at the reduced curing temperatures. As part of the Mercedes-Benz specification, long-term partner DuPont developed a 1K Broad Bake structural adhesive. This was successfully tested on electric vehicles with regard to corrosion protection as well as crash and operational stability. A functioning 1K broad beacon structural adhesive with the required property profile was available in time for final validation. Approval for the 1K Broad Bake structural adhesive was then granted as early as 2022.