Polyurethane gives tram-makers greater flexibility

Kassel, Germany – The new face of trams in Berlin, Adelaide and Seattle relies on flame retardant flexible polyurethane components.

Hubner, which has been using the material for 30 years, makes the components. The company prefers polyurethane because it is 'highly robust and highly flexible.' The grade used is not truly elastic, it takes a few seconds for the foamed material to return to its original shape. This is important because it influences the Head Impact Criterion (HIC) in pedestrian safety.

On the HIC scale 850 means slight injuries in collision and 1300 is likely to be fatal.

Traditional fibre-reinforced materials have a HIC value of at least 1200, polyurethane materials are in the 600-650 range, said Hubner. In addition, the company said that the polyurethane construction does not splinter and there is no damage from flying fragments. The front-ends comply with EN45545 a European standard for flammability on the railways.

Finally, polyurethane offers designers a great deal of flexibility. This enables complex construction and it is possible to integrate fittings.