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28 Mar 2007  -  Germany

Lightweight components for the automotive industry

Thanks to advances in materials and processes, polyurethane fiber composite materials based on Baypreg® F now perform even better. It is even possible to achieve a pronounced deformation of surfaces as in the case of domes. Sharp-edged areas can also be produced with great precision. 

Their combination of low weight and high flexural strength has played a key role in the breakthrough of polyurethane fiber composite materials in automotive construction. Current examples include the trunk floor of the new Mercedes-Benz A, B and S Class produced by Intier Automotive Näher GmbH in Rastatt, Germany. Other large-series production runs include the support for the load floor of the Opel Meriva and Opel Corsa, which are produced by Grupo Desarrollo Empresarial S.L.U. in Spain. In all three moldings, the sandwich construction is bonded with the Baypreg® F polyurethane system from Bayer MaterialScience AG. “Thanks to advances in polyurethane materials and production methods, it has been possible to further improve the performance of these polyurethane fiber composite materials,” says Dr. Dirk Wegener, an expert in polyurethane composites at Bayer MaterialScience.

The basic work of designing the Opel Vectra and Golf Plus loading floors was performed by the polyurethane processing development team from Bayer MaterialScience in conjunction with HONSA. The ready-to-use process for series production was developed at Hennecke GmbH, a subsidiary of Bayer MaterialScience. Hennecke GmbH, a manufacturer of polyurethane processing machinery based in Sankt Augustin near Bonn, Germany, markets this continuously optimized version of its CSM (Composite Spray Molding) spray technology under the name CompurTec.

The manufacture of a lightweight sandwich component made of polyurethane fiber composite materials involves spraying a package consisting of a light honeycomb core (e.g. cardboard) and two fiber outer layers on both sides with the heat-activated 2-component polyurethane system Baypreg® F and compressing it in a compression mold at approximately 130 °C. This enables components to be manufactured with weights of significantly less than three kilograms per square meter, i.e. up to 60 percent lighter than corresponding components made of conventional materials such as wood or sheet metal. The high flexural strength of the sandwich components is a result of the 0.4 to 0.6 millimeter thick, fiber-reinforced outer layers. The modulus of elasticity of the outer layers is around 13,000 MPa, as a result of which only moderate deformation takes place even under heavy load.

"The aim of our work was to improve the overall plasticity and component quality in critical areas such as edges and supporting points so that moldings could be produced in attractive designs without the need for finishing," explains Hans-Guido Wirtz, an expert in polyurethane processing technology at Bayer MaterialScience. To achieve this, the polyol formulation for Baypreg® F was further improved and the means provided to insert additional cut glass fibers locally during the polyurethane spraying process. "These measures enable large wall thickness variations of up to 50 millimeters, for example. It is also easier to produce large components with complex three-dimensional geometry. It is even possible to achieve a pronounced deformation of surfaces as in the case of domes. Sharp-edged areas can also be produced with great precision," concludes Wegener. He sees the potential for further applications for polyurethane fiber composite materials in automobile interiors: "Applications under consideration include multi-dimensional, contoured vehicle floors, trough-shaped trunk floors, seat wells and rear sear backs as well as cabin floors in truck construction."

About BaySystems®:
With effect from March 1, 2007, Bayer MaterialScience AG has combined its entire global polyurethane systems business under the umbrella brand of BaySystems®. This change affects not only existing product brands in this segment – including Baypreg® – but also the global network of polyurethane systems houses. 

About Bayer MaterialScience:
With 2006 sales of 10.161 billion euros (continuing operations), Bayer MaterialScience AG is among the world’s largest polymer companies. Business activities are focused on the manufacture of high-tech polymer materials and the development of innovative solutions for products used in many areas of daily life. The main segments served are the automotive, electrical and electronics, construction and the sports and leisure industries. At the end of 2006, Bayer MaterialScience had 30 production sites and employed approximately 14,900 people around the globe. Bayer MaterialScience is a Bayer Group company.

Source : Bayer