Polypropylene provides an economic aid to automotive industry recovery and advance
In its fight to overcome the many challenges posed by current market conditions, restructuring and cost reduction have become the focus of the automotive industry, but, while economic recovery is paramount it is not the only hurdle to survival. At the same time as balancing their books auto manufacturers in Europe will have also to meet impending tough EU directives requiring the improved environmental performance of vehicles coming off their production lines in the future.
Key is the European Commission’s ongoing drive to improve vehicle fuel economy and limit CO2 emissions as part of its climate protection programme. Currently passenger vehicles account for around 12% of the EU’s carbon emissions: generating an average of 160 grams of CO2 per car, per kilometre. Proposed legislation to limit the permissible emission level for new cars is aimed at reducing that number to 130 grams for 65% of each auto manufacturers’ new car registrations in 2012. That figure will be progressively scaled-up to include 100% of all new registrations by 2015. This will require increasingly greater vehicle fuel efficiency than at present.
At first glance the need to achieve vehicle improvements in tandem with economic restructuring appears to make the challenge for automakers impossibly onerous. However the two things need not be mutually exclusive as each can hold part of the overall solution – a better performing more sustainable product is a vital component of recovery, and represents a valuable long-term asset.
The material solution
Over recent years polypropylene (PP) has had a steadily growing role in enabling automotive designers and engineers to improve vehicle technology. Light weight, optimal balance of mechanical properties and excellent surface finish allow it to replace metal at lower cost in an expanding range of exterior, interior and under-the-bonnet, applications. Moreover, combined with ease of processing, enhanced part integration possibilities and outstanding end-use performance, PP positively encourages innovation.
The advantages of PP ideally position it as an important economic resource for the industry in satisfying the tougher environmental challenges it now faces. At 15-20% lighter than other plastics, PP offers the potential to bring higher weight savings to auto manufacturing. This represents a significant contribution to meeting lower fuel consumption and lower CO2 emission targets. Thus benefitting both the end-user and the environment.
Put in perspective, a weight reduction of 100 kg can achieve a fuel saving of between 0,3-0,5 L per 100 km. That equates with a reduction in CO2 emissions of approximately 6 -7 gm per km. Added to this, manufacturing in PP leaves a substantially smaller carbon footprint than steel and, taken over a life cycle, the water footprint of PP is around 50 times smaller than steel. Also, less energy is required for the production of a part in PP, thereby further lowering the environmental burden while enhancing manufacturing cost efficiency.
Realising the benefits
For more than 40 years Borealis has been at the forefront of PP technology and pioneered many of its advances. Today, through its automotive-dedicated Mobility business unit, the company is engaged in translating that knowledge and experience into PP product and application innovations that provide cutting-edge solutions to serve the industry’s current and future needs.
“Weight reduction is always central to our programme,” says Harald Hammer, Mobility unit’s vice president. “But recent and anticipated legislation on lowering vehicle CO2 emissions is giving it added impetuous. Not so long ago weight savings and any consequent lowering of fuel consumption, although aimed for, were seen as an added benefit, now achieving them has become a necessity.”
For manufacturers not meeting emission targets the penalties can potentially be very high. Fines up to euro 95 per gram of emissions in excess of specified levels and could have an unwelcome impact on the costs of new car registrations.
According to Hammer as important as weight saving is, it should not be at the expense of other key objectives such as parts integration and ease of processing. “Those sorts of compromise inevitably have a negative influence that outweighs the gains made elsewhere,” he says. “Key is to ensure through thorough evaluation that the material is selected or developed according to the specific operating demands of the part or component, in line with the other parameters set by the OEM or Tier One.”
Recent examples of successfully innovated solutions include a multi-model air intake manifold (AIM) for VW and the BMW X5 fender
VW Air intake manifold
For over 20 years, glass fibre reinforced PA66 and PA6 have been replacing metal as the materials of choice for AIMs at VW. This has largely been due to the better technical functionality of the plastic AIM, which includes optimised airflow across smoother surfaces, together with wider design freedom and lower final unit cost.
However, over time with major improvements in engine performance and harsher under-bonnet environments, standard PA materials are seen to be reaching their performance limits. Because of this VW and Tier One supplier MAHLE were seeking the next-step material solution.
As well as to meet the new technical challenges, VW also sought to satisfy its commercial needs through lower system cost than that of the existing PA solution. This had to be done without significant changes in part and tool design and with no modification of existing specifications. The system also had to be environmentally friendly, deliver better acoustical behaviour and meet essential functional criteria including: long-term high heat and chemical resistance, vibration resistance combined with high fatigue performance and operating temperature between -40°C and 120°C with a peak of 140°C.
The challenge was met by Borealis’ Xmod™ GB306SAF – 9502, a high performance 36% glass fibre reinforced PP compound. This injection moulding material offers an excellent balance of high impact strength and stiffness, is easy to process and is specifically tailored for AIM applications exposed to high heat and loads.
In addition to satisfying the criteria set by VW and MAHLE, Xmod™ delivered a technically comparable alternative to PA at lower system cost and with a valuable 15% reduction in weight.
BMW X5 fender
From the outset of its development BMW was totally committed to improving every design parameter of its X5 SUV model, from aesthetic appearance to mechanical performance. Alongside technical excellence, BMW’s aim was to reduce vehicle weight and lower production costs. Towards this goal one element of the programme was a fully integrated fender module - the first of its kind in the world. This involved the consolidation of all key fender parts and functions including headlamp reinforcements, wheel housing, cleaning systems, airbag sensors and cooling devices.
To achieve this highly integrated Class A body component required a material that combined exceptional surface quality with low thermal expansion – to ensure mechanical compatibility with adjacent steel body parts - high dimensional stability and ease of processing. It had also to provide good deformation characteristics to meet BMW’s criteria for a higher level of pedestrian safety in the event of low-speed collisions.
These demands were met in full by Daplen™ EF341AE, a PP-based ThermoPlastic Olefin (TPO) compound specifically tailored to meet the requirements of this first all-plastic, single module fender. Development of the material resulted from long-term co-operation between Borealis, component manufacturer Plastic Omnium Auto Exterior and the BMW Group.
In addition to satisfying all of the performance criteria set by BMW, Daplen also met Plastic Omnium’s specific requirements in respect of off-line painting and, as a ready-to-use material, ease of processing. To help facilitate production Borealis provided the component manufacturer with mould design and process management support.
Recognised as a technological breakthrough and a step change and standard setter in vehicle innovation, the BMW X5 fender delivered a 50% lighter weight alternative to traditional steel components.