Plastic key to vehicle weight reduction

The use of different types of plastic is playing a vital role in increased fuel consumption.

The use of plastics in automotive applications is relentlessly going up. And the key driver is weight reduction being forced by environmental targets. Modern cars are rife with electronics, gadgets and safety systems which adds a significant amount of weight to the overall structure.

Yet OEMs are still expected produce significantly lower emissions than before, and as a consequence lightweight materials are the key initiator to get more miles to the gallon. Most of the environmental demands on cars should be solved by new materials. This move away from metal and glass has to be a way in which we solve a lot of these difficult issues.

And while plastics have long been producing plastic parts such as dashboards, interior trims and non-structural parts; "we are beginning to see plastic become structural components in cars," says Patrick Thomas, chief executive of Bayer Material Science. "It is no longer something you have to worry about in a crash that it will break and have no structural value left."

But the car industry is intensely conservative. So Bayer had to start by introducing the technology on the small quarter light in the back of the Smart. But, it is finding that as confidence grows it is finding more applications.

Plastic on external and structural parts has been and will continue to be incremental. But the massive weight reduction is the major benefit and often uses significantly less energy and CO2 to make than a glass equivalent.

The most prominent to date is perhaps the 'i-mode'. This uses a large curved roof made primarily from polycarbonate which would not have been possible with glass. It will also act as part of the vehicles primary structure.

Producing parts and primary structure in plastic gives design engineers much more freedom when it comes to integrating this area in the design as a whole. And, if the trend continues, this approach will have an effect on vehicle dynamics and engine requirements. "Every bit of weight removed reduces the size of the suspension system," says Thomas. "The trend you will see is far more cars, right the way through the range from Smart cars to large luxury cars will be using this type of technology."

This is particularly apt given electric and hybrid vehicle suffer from poor range. An obvious, and perhaps more straightforward, method of increasing this is to make the structure as light as possible. Polypropylene supplier JSP has seen the incorporation of its product, Arpro, in ever increasing applications within vehicles.

"Increasingly, as technology progresses and weight becomes evermore important, people keep looking at more areas on the car where they can do that," says Paul Compton, executive vice president and chief operating officer of JSP (Europe). "That driver means that design engineers are increasingly balancing the cost, the recyclability and the environment. And that is edging more use of plastics."

Polypropylene also has the advantage of being easy to recycle, provided it is pure. It does degrade slightly during this process which means it can not be used for primary structural components, but it does mean it can be reused in other applications.

Parts can be produced in polypropylene by a mould. This means it lends itself to being produced in larger single parts. "We have seen parts go from having 15 to 20 components to three," says Compton.

At the moment many of the parts made from polypropylene are hidden from view. But JSP are working to develop improved surface finish which is likely to boost application areas around a vehicle. "We can do different colours and textures already, but not to the extent where most consumers would want it in there car," says Compton. "But we are getting close to that. I think you will start to see that by 2011/12. And inevitably the penetration and opportunity to use these kind of materials in cars will go up."

Author
Justin Cunningham

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