A foamer therapy

A high strength-to-weight ratio makes polyurethane foam ideal for moulding in many engineering applications, but the unpredictable nature of foaming makes them difficult to work with.

In a bid to ensure that moulded items are as perfect as possible, two researchers from German chemical company Bayer are employing computer simulation methods.

Peter Wulf and Bolko Raffel are working on the behaviour of polyurethane foam — used widely as an insulating material and for impact-absorbing parts in the automotive industry — as it is injected into a closed mould. The behaviour of the foam as it is simultaneously pushed into the mould and expands is very complex, and can lead to problems.

'A foaming polyurethane system not only expands its volume considerably during the reaction time, but also radically changes its properties,' said Wulf. 'At the beginning it behaves like a liquid, but it becomes more and more viscous and then solidifies.'