Material benefits

It’s a truism of design that form is dictated by function, but it’s also heavily influenced by materials. In the automotive industry the shape of vehicles and the way they are made have long depended on the materials used to make them: predominately steel and glass. But now polymer scientists are developing new materials that are as strong as their traditional forebears, but considerably lighter. With this advent, the look of cars, and the way they are built, is changing rapidly.

From the point of view of materials developers, closer co-operation with customers involves a great deal of study. According to Hartmut Löwer, head of innovation and research for Bayer MaterialScience’s polycarbonates business, it’s a process where supplier and customer have to educate each other. ‘It’s a matter of survival, that we both understand the requirements of the other side,’ he said.

Bayer, one of Germany’s largest chemical companies, dominates its home town of Leverkusen, with its illuminated logo visible from several miles away. Its name is known from the Bayer brand of aspirin in the US, to the local football team Bayer Leverkusen. But it’s also a major player in the field of specialist polymers and, along with General Electric, is one of the world’s largest manufacturers of the hard, clear plastic polycarbonate that it sells under the trade name Makrolon.

A Leverkusen native, Löwer holds a PhD in organic chemistry, and has been working for Bayer since 1982. His career has been spent entirely within the plastics division, working in the marketing, production, research and product management parts of the company. In 2004 he took control of research and innovation for the business, whose products are used in applications as diverse as needleless syringes, the clear component of CDs and DVDs, and in the new generation of holographic display systems that are currently under development. But increasingly Bayer’s plastics are finding their way into the automotive arena as an alternative to glass.

Löwer describes Bayer MaterialScience’s research effort as a mixture of technology push and pull. ‘That’s a very operational view of innovation,’ he said. ‘You have to look at things from a future-oriented view, scouting for new areas, for new applications, for new possibilities for our products. So there are two ways of creating ideas and activities: one from the business itself, from contacts with customers and analysis of market trends; and the other from general ideas about utilisation of our products and product lines: what we can develop.’

Polycarbonate’s gradual penetration into the automotive sector is an example of ‘technology push’, Löwer said. ‘We saw certain potentials for replacing glass with polycarbonate, and how we could develop technology to do that. Then we approached the market and told them what wonderful things they could do if they used this technology.’

In this case, the ‘wonderful things’ included an almost unlimited scope in shape and a 30 per cent weight saving over glass. The first application where polycarbonate made an impact was in headlamp lenses and complete headlamp clusters. ‘That took place in the mid-1980s when the advanced properties of the polymer over glass finally came to be recognised and the car creators saw what sort of design possibilities there were with the plastic material. Polycarbonate was the material of choice because of transparency, physical strength and heat tolerance,’ Löwer said.

Despite this, it took five to seven years for polycarbonate to become accepted as a headlamp material, a time lag that Löwer said relates to the development cycle of new cars. He estimates that 80 per cent of headlamps are now made from polycarbonate. Moreover, its use has become one of the main influences on the shape of the front end of cars, as designers incorporate its ability to adopt almost any shape into their new models. And as Bayer’s researchers work further on the polymer properties, this is set to have an impact on the other transparent parts of the car.

‘I think it’s a general trend for manufacturers to create more transparency in the car environment, with bigger windows, transparent roofs — people like to drive in a cabriolet-type environment,’ Löwer commented. ‘But the need for a lot of glass would create a lot of weight and would limit the design capabilities because in glass you can’t achieve the curvature.’

Polycarbonate windows, which are made by a multi-component injection moulding process, were first used by Mercedes-Benz for the rear window in the C-Class sports coupé. It’s now also being employed in roof units, such as the panoramic roof of the Smart Forfour, and the louvre roofs of the Mercedes A and B-Class. Bayer and GM, who worked on the automotive glazing development in a joint venture called Exatec, had to overcome several problems for these applications, including creating coatings to impart scratch resistance without compromising the transparency of the polymer, and incorporating the ability to embed mechanisms to defrost the glazing in cold weather.

Despite this, Löwer said that the current glazing applications are ‘relatively undemanding’ as far as material properties are concerned. ‘We are not far along the learning curve with polycarbonate glazing,’ he said. The next phase is to develop grades for moveable side-windows, which will need greater scratch resistance to allow them to be wound up and down repeatedly. The toughest application of all, windscreens, is likely to take even longer. ‘Small scratches in the surface would immediately pose a security and safety threat for the driver,’ Lö wer explained. ‘We aren’t looking at windscreens at all at the moment — we want to get the experience with lesser-demanding windows and slowly grow into that.’

Löwer sees the gradual meshing of the development processes of plastics makers and car manufacturers. ‘We need to educate the car manufacturers on what you can do when you process polymer materials, so they can be incorporated into the earliest stages of the design of the car,’ he said. ‘On the other hand, we need to understand what drives development of the next generation of vehicles so we can adapt our products and develop ideas. It’s a question of talking and co-operating in a very concentrated fashion.’

To stimulate discussion in the industry, Bayer MaterialScience also works with concept car specialists to demonstrate how polymers might be used. Its latest model, developed with Swiss firm Rinspeed and unveiled earlier this month at the Geneva motor show, is the ZaZen, a heavily modified Porsche Carrera with a one-piece roof dome made of Makrolon.

The two teams also joined forces at last year’s show to present the Senso, which used electroluminescent polymers to change the appearance of the interior in line with the driver’s mood, using data from sensors that measure his/her heart rate and analyse driving behaviour. Although Löwer concedes this is a far-fetched application, it’s a useful demonstration ‘of what you can do when you think a bit outside the box, and consider applications where today there are no plastic materials’.

Electroluminescent films could be used to illuminate parts of the car where it would be difficult to install or maintain light bulbs or LEDs, he said, such as recesses in door panels and dials and switches in the dashboard and control panels. ‘And if you carry these ideas to their extreme, there are many, many more things you can do,’ he said.