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05 Mar 2008  -  Germany

PU sandwich composites with a thermoplastic core

High stiffness, good impact strength and low weight are just some of the advantages of sandwich composites made with honeycomb or corrugated paper cores and glass fiber mats bonded together with the Baypreg® F polyurethane spray system from Bayer MaterialScience. Typical automotive applications include trunk floors, floor and spare-wheel covers and sunroof panels. Until now, paper honeycomb structures have predominantly been used as lightweight core elements, but in order to extend the property spectrum of this type of polyurethane composites, Bayer MaterialScience has been searching for alternatives. A recent development project has revealed that thermoplastics, and specifically polycarbonate, are admirably suited to the task. “Polyurethane composites with a thermoplastic core have considerable advantages over their paper honeycomb equivalents. Above all, they are insensitive to moisture and humidity, making them a logical choice for exposed applications inside and outside the vehicle, such as seatbacks, seat shells and wind deflectors for trucks,” says Dr. Stephan Schleiermacher, an expert in polyurethane car components at Bayer MaterialScience.

To manufacture a lightweight sandwich part of this kind, the thermoplastic core is embedded between two glass fiber facing layers, and impregnated on both sides with a heat-activated, two-component Baypreg® F polyurethane spray system. After this, the package is compression molded at 130 to 140 °C to give it the desired shape. All the parts of the composite are bonded permanently to one another with the low-foaming Baypreg® F. Depending on the geometry, the sandwich part can be demolded in less than a minute. Subsequent energy-intensive annealing is unnecessary. The result is a stable sandwich composite with excellent strength and stiffness properties. “This means that economical production with short cycle times is possible even for large moldings,” says Schleiermacher.
The new polyurethane composite is another example of how BaySystems® – the umbrella brand of the company’s global polyurethane systems business – has helped Bayer MaterialScience to develop innovative solutions based on proven polyurethane materials. “We have now optimized the materials and the processing expertise for these new polyurethane composites with a thermoplastic core to such an extent that we can enter into specific application-related development cooperation projects with automotive systems suppliers and OEMs at any time,” notes Schleiermacher.

About Bayer MaterialScience:
With 2007 sales of EUR 10.4 billion, Bayer MaterialScience 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 sports and leisure industries. Bayer MaterialScience has 30 production sites around the globe and employed approximately 15,400 people at the end of 2007. Bayer MaterialScience is a Bayer Group company.

Source : Bayer Material Science