At the turn of the century, sales of vehicles in Western Europe reached an all-time high of 15 million units. The use of plastics in automobiles during the last century was significant - in fact, one might say that plastics form part of automobiles for as long as plastics exist at all.
The first automobiles entered markets in 1900. For many years, the side curtains in horse and buggy rigs were made up of cellulose nitrate sheet for. Later, cellulosics were used for molding the steering wheel, and phenolics and ureas were employed for electrical components and control knobs.
The real plastics revolution in automotive industry began in 1950, when thermoplastics made their debut. ABS (Acrylonitrile Butadiene Styrene), polyamide, polyacetal and polycarbonate - these new forms of plastics all widened the spectrum of products that could be made of plastic. Alloys (where metal is mixed with another element) and the blending of polymers made it possible to tailor properties for a wide range of product requirements. With single resins, this had previously not been possible.
During the 1960s thermoset composites began to be widely used in the automotive industry for instance in the form of complete monocoque ("single shell") bodies or in glass fibre reinforced polyester resin. Later, thermoset composites found their way into factory-made polyester/glass combinations that could be molded by compression and injection: Sheet Moulding Compounds (SMC) and Bulk Moulding Compounds (BMC).
Since those beginnings, the use of plastics components in automotive has undergone enormous growth - particularly in the last 20 years. In 2000, the average car vehicle consisted of over 105 kg of plastics. What makes plastics unique is that they can be molded into components of complex geometries, often replacing several parts at once. This reduces assembling complexity, the need for other materials and allows for integral fitments of cars. A reduction of costs on the assembly line is the outcome.
The light weight of plastics has been a real benefit to the car industry, not only by reducing overall car weight and thereby allowing for the reduction of fuel consumption to national legal provisions, but also by allowing more sophisticated components - including safety systems - to be incorporated into the modern car without creating considerable additional weight.
This also means that more sophisticated heating ventilation and climate control systems could be installed in today's cars. Entertainment and intelligent systems, not to mention airbags providing additional safety - they could all be integrated without excessively adding to overall weight.
Without plastics, it is estimated that today's cars would be around 200-300 kg heavier.
That saves us 0.5 litre per 100 km which represents 750 litres for a car with a lifetime of 150,000 km. Many types of polymers are used in more than 1,000 different parts of all shapes and sizes. Although up to 13 different polymers may be used in a single car model, just three "families" make up some 66 % of the total plastics used in a car: polypropylene (32 %), polyurethane (17 %) and PVC (16 %).
A quick look inside any model of car shows that plastics are now used in exterior and interior components such as bumpers, doors, safety and windows. Headlight and sideview mirror housing, trunk lids, hoods, grilles and wheel covers also count among the many usages of the familiar material. In other words, the passenger compartment is dominated by plastics.
Recent years have seen a veritable invasion of the under-bonnet region by plastics, leading to widespread adoption of large (1.5 to 2.5 kg) moldings for air intake manifolds. These are not only half the weight of their metal counterparts: they optimise the airflow to the engine, helping to make it more efficient, and also playing a valuable role in reducing noise levels. Molded in glass fibre reinforced nylon, these are highly sophisticated parts, marking the true arrival of plastics as engineering materials in their own right.
HOW PLASTICS SAVE WEIGHT IN CARS
The "invasion" of plastics in the engine compartment is by no means over. Automobile engineers are now working together closely to optimise other systems, integrating injection and blow moulded parts, and harnessing plastics and elastomers that give a range of properties from "soft" to "hard", but can be moulded simultaneously or in sequence, offering a better product without expensive assembly work.
Plastics are also finding their way into the structural design of cars. Intensive development of thermoplastics has opened the way to production of individual bodywork panels by injection moulding, to meet the high temperature of the paint stoving ovens used by the automotive industry, and electrically-conductive grades, for electrostatic painting.
The most complicated design problem the tank fuel system has been solved thanks to plastics. Another important area of development is in fuel systems. Again, this is an area which (for the safety of all) is a focal point for legislation, to conserve fuel and minimise emissions.
For more than a decade, all-plastics fuel tanks have been produced, by blow-moulding in ultra-high molecular weight high density polyethylene. These lightweight tanks by their good mouldability, give more design freedom to fit tanks in difficult spaces.
It is estimated that some 90 % of all new cars in Europe have plastics tanks, and the technology has been exported to North America, where about 70 % of cars now use this system.
Driver and passenger "cockpit" modules, complete doors, air control systems and fuel systems are even now being developed
In parallel, large plastics engineering groups are also emerging, both integrated with the new groups and independent of them. They not only have the molding equipment and the latest CAD/CAE systems, but decades of human skill in working with plastics to get the best value from these materials.
In short, plastics meet the challenges of an industry whose demands are greater than ever. While motorists want improved performance cars with greater comfort, reliability, fuel savings, style and lower prices, society demands lower pollution levels and increased recovery at end of life.
Continuous innovation is a key feature in the use of plastics in cars. As the needs increase, new plastic materials are being created to meet them.