Fast and Light: The potential of plastics for the automotive industry

The challenge for the automotive industry to reduce CO₂ emissions and fuel consumption whilst still producing attractive modern vehicles has intensified over the last few years, as manufacturers strive to reach the lower emissions targets by the end of 2020.

Here, Bernd Sparenberg, and Söhnke Müller of materials compounder and distributor, ALBIS, share with BP&R the materials developments from the company's own portfolio that it believes can help solve such challenges.

As European car manufacturers work towards the 2020 deadline to ensure the average CO₂ emissions of their vehicles is under 95g per kilometer, three areas that are targeted for adjustment are smaller and more efficient engines, alternative drive trains, and lightweight construction concepts that reduce overall weight and fuel consumption.

Whilst the considerable potential around engines has been all but exhausted, lightweight construction has become highly prioritised in the automotive industry. It pays off – a 100 kilogram reduction in weight reduces fuel consumption by, on average, half a litre per 100 kilometers and saves somewhere between 8 and 10 grams of CO₂ per kilometer.

This concept is not just useful for conventional combustion engines, but is also highly sought after in the construction of electric vehicles. The motivation here is obviously different. The reduction in vehicle weight does not lead to a reduction in CO₂ emissions, but rather to an increase in vehicle performance and operating range.

A material of promise

A promising keyword in the context of future production is ‘carbon’. Indeed, compounds based on recycled carbon fibre have great potential, not only with regards to the weight savings, but also the sustainability aspect also of increasing importance in the automotive industry.

With the help of the technology developed by WIPAG Deutschland GmbH and its WIC PP and WIC PA product ranges, heavy and highly concentrated glass fibre PA compounds, for example, could be replaced with relatively lighter PP CF compounds.

WIPAG is a company, acquired by ALBIS Plastic, that specialises in the processing and production of carbon fibre-based compounds that can be injection-moulded and are made from CFRP production residues from the automotive and aviation industries in a closed-loop system. The weight reduction is huge. Switching material can save up to 30 percent for comparable characteristics and costs.

Another interesting aspect of this compound is the financial side. Even though, at first glance, the price per kilo seems higher than the PA compounds, for example, the PP carbon fibre components are more cost effective due to their lower density.

A good example of this is the sample calculation that the ALBIS team did for an Audi gas cap hinge arm. For the review, a polyamide 6 with a 50 percent glass fibre content was replaced by a polypropylene strengthened with 30 percent recycled carbon fibre.

The resultant significant weight reduction, which was greater than 30 percent, came from the difference in density between the glass fibre compound, with 1.58g per cm^3, and the carbon fibre alternative, with 1.05g per cm³.

Looking at the volume price calculation of the compound, the team saw a reduction in the material costs for the component of some five to ten percent. The apparent additional cost of the carbon fibre compound in Euro/kg disappeared when we looked at the litre price in Euro/l. The end customer buys based on volume, and not on the weight of a component.

Pedal to the metal

For the direct replacement of metal, ALBIS designed Tedur, the brand name for PPS-based compounds. Tedur is characterised by very high fixity/rigidity and dimensional stability, as well as by high internal pressure. Furthermore, the combined materials have excellent resistance to hydrolysis, chemicals and fuels, and also show high creep resistance even at high temperatures.

It is suitable for permanent operating temperatures of up to 240 degrees Celsius and can, therefore, be used for attachments that come into direct contact with the engine block, for example. An additional benefit of using the PPS instead of aluminium is not only a weight reduction, but is it only requires one processing step.

Filling the Gap

Weight and cost reductions were also the aim in the development of ALTECH NXT PP. These technical compounds, with a polypropylene base, are available with fibre glass and fibre glass/mineral fillers. Unlike standard PP, Altech Nxt has very high levels of rigidity and heat resistance, as well as resistance to aging.

It fills the gap that has existed until now between standard PP and polyamide and can even be used as a replacement for PA6 GF30. It can be directly replaced in components and tools and results in a weight reduction of around 15 percent. The difference in density is significant. PA6 GF30 comes in at 1.36 g/cm³, Altech Nxt PP GF35 at 1.18 g/cm³. This means a reduction in the amount of material needed. PP is, therefore, significantly cheaper than PA.

About the Authors Bernd Sparenberg is Vice President of Technical Compounds at ALBIS Plastic and Söhnke Müller is Director of Specialties.