Schwalbach, Germany --Dow Automotive's newly developed system for the structural bonding of aluminium roofs with steel car bodies has been used on the new BMW 7 Series.
This use of the Betamate two-component (2K) polyurethane adhesive "demonstrates the effectiveness of bonding as an assembly technology for both lightweight constructions and mounting processes," said a 10 March Dow statement. Dow adds that these are "crucial factors for the hybrid construction of materials, where significant weight reduction advantages only come into play through use of a combination of materials."
As well as specific assembly demands such as a steel/aluminium combination that does not allow for welding, the different thermal expansion coefficient of both materials is a crucial factor to take into account.
"Here, Dow Automotive's new bonding system provides a sustainable solution in two respects," said Orhan Imam, Dow Automotive market development manager for 2K PU adhesives. "Compared to currently available adhesive systems, it is flexible enough to offset the different expansion coefficients while simultaneously guaranteeing the necessary structural system stability at even higher temperatures."
Dow Automotive achieves this due to the improved glass transition temperature (Tg) of it its new 2K PU adhe-sives. BMW and Dow Automotive developed an improved 2K technology based on the Betamate 2K polyurethane adhesive range. for the German car maker's new 7 Series.
Dow says this is the first time a 2K bonding system has been directly used on the assembly line to assemble an aluminium roof module. In addition to its technological advantages in flexibility and simultaneous stability, the solution developed for BMW also has assembly advantages, providing an economically attractive solution for OEMs, the company added.