Plastics and cars: a shared history
All those years ago…
It was in the 1970s that polymers were first used to decorate vehicle interiors: skins, coverings, woodwork, and more. Thanks to their ability to withstand impacts and ageing, polymers, and, in particular, thermosetting and subsequently, thermoplastic resins, would be used widely for external applications in the 1980s/90s: headlights, bumpers, fenders and then tailgates. Polymers would first appear in semi-structural parts in the decade between 2000 and 2010. This was when manufacturers began their efforts to reduce their vehicles’ weights and replace traditional materials such as steel and aluminium. An example of this is the body of the electric BMW i3 which comprises plastics reinforced with carbon fibers (CFRP). Thanks to entirely automated gluing methods, around 150 parts are assembled, which is around a third of thenumber found in a conventional design made from steel sheets.
Most families of plastics have now found their way into cars.While the body absorbs half of the volume of plastics produced for the automotive industry, the rest is found in the parts located in the passenger compartment (40%) and in the engine space (10%). The external parts of the body, such as the bumpers, fenders, the bonnet and the tailgate are mostly made up of polypropylene (PP): thanks to its mechanical properties and its fairly affordable prices, it alone accounts for around 40% of the plastics used in the automotive industry. For over thirty years, the lightweight and highly durable polycarbonate has been used to manufacture the optics in the headlights. ABS, polyurethanes and polyethylenes reign supreme in the passenger compartment. Under the bonnet, polyamide is used for parts that have to withstand high temperatures.
Generally considered one of the world’s most high-performance materials, the PEEK thermoplastic, which combines thermal properties with excellent mechanical properties, is able to withstand a constant operating temperature of 250°C.
Plastics have made themselves indispensable for safety. State-of-the-art bumpers and energy-absorbing parts optimise the safety of the occupants and pedestrians alike. A plastic bumper is on average lighter than a bumper made from other materials and absorbs four to five times more energy. Seatbelts are made from polyamide or polyester fibres, and airbags are made from high-strength nylon. Under the bonnet, plastics also contribute to keeping passengers safe. In the event of an accident, a plastic drive shaft will not perforate the tank or penetrate the passenger compartment, unlike a traditional drive shaft./p>
Time for a diet!
During the decade between 2010 and 2020, the increasing use of plastics in cars provided manufacturers with solutions to comply with environmental requirements and the regulation aimed at reducing emissions. Within the European Union, per-car CO2 emission thresholds will need to be reduced from 130 to 95 g/km by 2020. In order to meet this target, manufacturers are investing in creating lighter vehicles, by replacing metal with composite materials. Lightweight and resistant, plastics also offer designers great freedom in their creations. Overall, composite materials can potentially lighten vehicles by 200 to 300 kg. This type of result will greatly depend on innovations in the industry of the chemistry of materials, in particular for structural parts and windows.
EUsing composite materials instead of steel in structural parts is a technological breakthrough which could potentially lighten vehicles by up to 30% of their weight. Using fiberglass-reinforced composite materials makes it possible to mass-produce parts such as tailgates, spare wheel compartments and the trunk floor. Some equipment manufacturers are using carbon fibre-reinforced composite materials for parts manufactured in smaller series. To date, the automotive industry remains the largest consumer of composite materials by volume
Thermoplastic composites: green lights all the way
Thermoplastics are a solution for the future due to the fact that they are lightweight, resistant and recyclable. Thermoplastics* offer the same advantages over metals as thermosetting materials in terms of weight reduction, in addition to being recyclable. Although thermoplastic composites currently only make up 5% of the composites market, that share could one day reach up to 50 %. The French Agency for the Environment and Energy Management (ADEME) did not make a mistake by supporting the Compofast project, coordinated by Arkema, as early as 2012. Its aim: to develop thermoplastic composites intended to lighten vehicles and which match the constraints of cost and rate of mass production in the automotive industry.
Thermosetting and thermoplastics
*Thermosetting materials can only be shaped once, unlike thermoplastics; the finished products cannot be re-shaped (without causing degradations) through heating. Thermosetting materials are therefore non-recyclable.