FYI : REHAU Chooses Engage® for BMW 5 AND 6 Series Bumpers

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BMW, noted for an evolutionary rather than revolutionary approach to exterior styling, surprised the motoring world early in the millennium with a radical new design language. Inspired by Chris Bangle, director of BMW Group Design, the exciting "new look" first seen in the 7 Series, was translated into the new 5 Series in 2003, and most recently in the striking new 6 Series Coupé and Convertible.



REHAU chose DuPont Dow Engage® polyolefin elastomer as an impact modifier for the front and rear bumper moldings of the new BMW 5 and 6 Series cars because it endows high impact resistance at lower temperatures, higher stiffness of the part, and good value-in-use economics.

Such a departure from BMW's traditional styling also demanded a new look at materials to interpret the bold new lines from design studio to reality. The integral front and rear bumper units are a good example. These parts had to follow design and function, not only in complicated molding geometries, but in saving weight and resisting low speed impact at the same time - a tough order for metals.

The solution was to choose a high performance blend of plastic polymers, compounded and molded by REHAU AG + Co, of Rehau, Germany, with impact resistance endowed by DuPont Dow Engage® polyolefin elastomer. The result is a series of large front and back end moldings for the BMW Series 5 and Series 6 that enhance the look and practicality of these superb top-of-the-range cars.

"Why we chose Engage®"

REHAU is a leading global polymer system supplier to customers in automotive, general industry and construction. Dr. Rainer Goller, head of the company's automotive materials development department, comments on the selection of the DuPont Dow polyolefin elastomer to help meet BMW's demanding specifications.

"We chose Engage® as an impact modifier for these new BMW moldings because it gives us high impact resistance at lower temperatures and at the same time a higher stiffness of the part," he says. "But another key reason for the decision to use Engage® was good value-in-use economics."

Features valued highly by automotive OEMs

Dr. Dieter Gerlach, DuPont Dow scientist involved in technical service and development, explains many additional reasons why Engage® is now so widely specified by the automotive industry as a leading impact modifier of hard TPO compounds.

"The rapid adoption of Engage® is driven first by its easy-processing characteristics, and its compatibility with other polymers in TPO blends. Engage® in pellet form is a cost-effective replacement of EPDM, particularly because it can go directly into the extruder, unlike EPDM in bale form which requires pre-mixing in a masterbatch," says Gerlach.

"But it is in the economics of molding and end-use performance that the advantages of Engage® really become evident. It endows hard TPO compounds with an excellent balance of stiffness, flexibility and resilience. The polymer's high strength at low density permits thin walled structures that save weight while retaining rigidity."

"The viscosity of Engage® enables the formation of complicated geometries in molding and assists with undercuts in the structure. In addition, its low thermal expansion permits good bonding to metal, it accepts paint finishes well, and is easily recycled. These are prime features valued highly by automotive OEMs," Dr. Gerlach concludes.

About DuPont Dow Elastomers

DuPont Dow Elastomers, a global supplier of specialty elastomers with headquarters in Wilmington, Del., is a joint venture between the DuPont Company and The Dow Chemical Company, with more than $1 billion in sales. The company is a leading producer of chloroelastomers, ethylene elastomers and fluorinated elastomers, serving the automotive, chemical, construction, general rubber, plastics and wire and cable industries.

REHAU chose DuPont Dow Engage® polyolefin elastomer as an impact modifier for the front and rear bumper moldings of the new BMW 5 and 6 Series cars because it endows high impact resistance at lower temperatures, higher stiffness of the part, and good value-in-use economics