Climate-friendly and efficient solutions based on PU systems

In the automotive industry, the current climate debate has given new weight to the subject of lightweight construction. According to estimates by Daimler AG, reducing vehicle weight by 100 kg decreases fuel consumption by 0.3 l/100 km and leads to a reduction in carbon dioxide emissions of 750 g. The potential for reducing weight is particularly high in the body, because it makes up over 40 % of a vehicle’s total weight.

Bayer MaterialScience (BMS) has developed a variety of technologies for using polyurethane composites to reduce the weight of body parts while simultaneously enabling efficient manufacturing. One example is the design of roof modules and antenna covers based on a pre-coated thermoplastic film, which is backmoulded with a polyurethane foam system reinforced with long glass fibres. The coating system is not fully cured until after thermoforming, and lends the component a Class A surface.

Another technology, PU sandwich construction, even enables weight reductions of up to 80 % in trunk floors and cargo beds. In the manufacturing process, a paper honeycomb core between glass fibre mats is impregnated with a two-component PU spray system and then press moulded.

The two technologies can be combined, for example, to produce roof modules. BMS estimates that these methods can reduce weight by about 25 %.

Another important technology in vehicle body engineering is the reaction injection moulding (RIM) process, in which a polyurethane mixture is injected into a mould and cured. In this case, one advantage over injection moulding with thermoplastic materials is the low locking force, which enables the use of less expensive moulds, such as those made of aluminium.

The company has also developed various PU composite technologies for applications outside the automotive industry. Reinforcing thermoformed thermoplastic films with the Multitec polyurethane spray system is an economical and environmentally compatible solution for fabricating bathtubs and shower trays, says BMS. Compared to the conventional material, the system cures faster, bonds very well to the film and eliminates the use of solvents.

The pultrusion process is another highly promising option, in which reinforcing fibres are impregnated with a PU system and the composite is then shaped and cured at an elevated temperature. Polyurethane offers an advantage for this technology over conventional materials by allowing the use of continuous glass fibres and enabling continuous and thus efficient production of such things as window frames and railroad ties.