There are more than 1 billion cars on the world's roads, and this figure is expected to grow to 2.5 billion by 2050. This will have severe consequences because cars will make an even greater contribution to CO₂ emissions than they do now. This is why policymakers, chief among them the European Union, are putting strong pressure on automakers to significantly reduce the CO₂ emissions of their vehicle fleets.

The automotive industry is pursuing several, often-intermeshing approaches to make mobility more climate-friendly. Plastics are playing an important role. With their low weight and widely adjustable property profile, they could become a crucial material for "green" mobility.

Lanxess, a leading development partner of the automotive industry, expects the amount of plastics used in automobile manufacturing to increase from some 16% today to around 25% in 2020. In 2011, the specialty chemicals company generated sales of approximately €1.5 billion with products and technologies for "green mobility," which accounted for 17% of overall sales.

25% Lighter

Plastics are ideal materials for lightweight construction. It is now possible to make lightweight front-end carriers entirely of plastic. The new Skoda Octavia, for instance, has a front-end carrier made of Durethan DP BKV 60 H2.0 EF, a polyamide 6 from Lanxess that, despite being highly reinforced with 60% glass fibers, still exhibits easy-flow characteristics (figure 1). It is about 1.2 kilograms or 25% lighter than a virtual carrier designed from a standard polyamide 6 with 30% glass fibers.

One special feature of this component is that the top support, located between the fenders, is also composed entirely of the high-performance polyamide - even though this area is exposed to high mechanical forces near the hood lock and has to be very thin because of the lack of space. The design's success is due to the extremely high stiffness and strength of the high-tech polyamide. The lightweight component was engineered by Faurecia Kunststoffe Automobilsysteme GmbH, Ingolstadt.

New Polyamides - Heat-Resistant up to 230°C

Polyamide innovations are also helping improve "green" mobility in the engine compartment. New, fuel-saving engine concepts such as forced-induction engines and/or increasingly small installation spaces have caused temperatures in this area to rise significantly in recent times. Polyamide 6 and 66, previously used in the production of air- and media-bearing blow-molded parts, such as air tubes, inlet pipes and coolant pipes, are therefore facing completely new challenges in terms of heat resistance. Lanxess has therefore introduced XTS1 and XTS2 - two new high-tech, heat-stabilizing systems for the polyamide Durethan. The continuous service temperatures of the XTS1 polyamides are 60°C higher than previous heat-stabilizing systems at 200°C (figure 3). The polyamides in the XTS2 series can even withstand continuous service temperatures of up to 230°C, which Lanxess believes is not possible with standard heat stabilizers currently on the market. This big leap in heat resistance was unthinkable just a few years ago.

The XTS2 series provides an alternative to costly heat-stabilized specialty thermoplastics, such as fully and semi-aromatic polyamides and polyphenylene sulfide, and is ideal for high-tech applications in the engine compartment that are subject to unusually high temperatures. The first representative of the XTS1 series is Durethan BKV 30 XTS1 (30% glass fibers). Its tensile strength at break falls by only around 5%, even after 2,000 hours of hot-air storage at 200°C. One particular strength of this polyamide 6 over many other high-temperature-stabilized thermoplastics is that it is easy to work with in a stable process.

Fuel-Efficient Tires

Around a quarter of CO₂ emissions and a fifth of vehicle fuel consumption is attributable to the rolling resistance of tires, which depends primarily on the tire rubber. The properties of the rubber determine how long a tire lasts, how well it grips the road surface and how high the rolling resistance is.

In the past, Lanxess developed solution styrene-butadiene rubbers (SSBR) for tread mixes and carcasses, and neodymium polybutadienes (Nd-PBR) for tire treads that cut the rolling resistance of tires by up to 30%. This was achieved without compromising on the tires' wet grip and durability.

Recent new products include the NdBR rubbers Buna CB PBR 4076 and PBR 4065 (figure 4). They exhibit high molar masses, which are associated with low rolling-resistance values coupled with good processability. This is surprising, because high molar masses normally go hand-in-hand with high Mooney viscosities, which adversely affects the processing properties. This is not the case with the two new NdBR rubbers. Buna CB PBR 4065, for example, matches the tire performance of the high-Mooney grade Buna CB 22 but can be processed in the same way as Buna CB 24, which has a far lower viscosity.

Thermoplastic High-Performance Composites

The front-end carrier of the Octavia is just one example of Lanxess' expertise in lightweight construction. A short time ago, the specialty chemicals company reinforced its unique position in lightweight construction by acquiring Bond-Laminates GmbH. As demonstrated by Tepex, the Brilon-based company is an outstanding manufacturer of lightweight, continuous-fiber-reinforced, high-performance composites based on thermoplastics. Tepex is one of the few high-tech materials of its kind to be used in the large-scale volume production of a wide range of lightweight components.

Lanxess is now a single-source supplier of performance composites and compounds proven in large-scale production, complete with the associated applications know-how for the volume production of lightweight components. In many cases, Tepex offers a high-performance and cost-effective alternative to carbon-fiber-reinforced thermoset lightweight materials. Used instead of sheet metal, it will also noticeably improve the lightweight construction potential of plastic/"metal" composite technology (figure 2).