100% connected polymers

Plastics put hydrogen under pressure

When it comes to the car of the future, manufacturers and equipment suppliers are brimming with promising ideas. Weight reduction, improved aerodynamics and comfort. Polymers are very much in demand with regard to achieving those goals.

Development in fuel cells and hydrogen fuel cells continues, particularly among Japanese and Korean car manufacturers. Fuel cells function using a chemical reaction. They function much like a traditional electric battery, although a hydrogen fuel cell cannot store the electricity produced. It produces electricity continuously as long as it is supplied with hydrogen stored in a tank and oxygen from outside the vehicle.

A vehicle’s autonomy is therefore largely dependent on the amount of hydrogen stored in the tank. Guaranteeing a suitable range for vehicles equipped with this technology requires the gas to be compressed. Today, the most efficient tanks can withstand a gas pressurized to 500 bars (500 times atmospheric pressure). They are steel tanks with walls that are several centimetres thick and are therefore very heavy.

Composite materials using carbon fibres and a thermoplastic resin have a bright future for containing hydrogen pressurised to 700 bars, which is a crucial requirement for increasing the autonomy of fuel cell-powered vehicles.

By teaming up with Elbit System, a start-up specializing in fuel cells and super-capacitors, equipment maker Plastic Omnium successfully designed a tank that takes up no more space than a polyethylene gas tank, weighs only a few hundred grams and, above all, can withstand a pressure of 700 bars.

This is considerable and should enable fuel cell-powered vehicles to have a range of 600 kilometres. A record! The designers used polymers to achieve this feat. All we know is that this tank is made of a 5 mm-thick waterproof thermoplastic liner and a thick structure of carbon fibres. The difficulty resided in making it strong enough to maintain such a pressure. This was absolutely crucial, as it is easy to imagine the damage that a tank pressurized to 700 bars would cause in the event of an explosion.

Plastics are not cold-blooded

The revolution is not based solely and entirely on propulsion methods alone. There is a strong probability that electric vehicles in the near future will stand apart from their petrol-powered ancestors in terms of design. The other fundamental difference between an internal combustion vehicle and an electric vehicle lies in the size of the engine and transmission system.

Electric cars do not contain an invasive gearbox and although the cars have 2 to 4 motors, they are very small and can most often be placed discreetly at the four corners of the vehicle, right next to the wheels. As for the batteries, they are laid flat on the floor. Manufacturers are currently making their vehicles in fairly traditional shapes so as not to disrupt current design standards too much. That is why some of them are equipped with two trunks, one at the rear as is usual and the other at the front instead of the combustion engine.

The vehicles of the near future will probably look very different and most certainly offer a much more spacious passenger compartment.

Additionally, electric motors do not need a complex cooling system as they generate less heat. This adds volume (and reduces weight), except that this volume will have to be heated in winter to ensure passenger comfort. In a conventional motor vehicle, the heat released by the engine ends up in the air vents, and a simple fan suffices to diffuse it inside the passenger compartment. An electric motor, however, does not generate enough heat to warm up the passenger compartment. It is entirely possible to install heating elements inside electric vehicles, but they add mass and reduce autonomy because of the energy they require. The only viable solution to this problem involves perfecting new insulation technology.

As is the case in the building industry, polymers are the perfect materials for the job: they are flexible, easy to cut and, above all, ultra-light.

It is not yet known whether the car of the future will be fully autonomous. One thing is certain, however, and that is that the passenger compartment will become more spacious in electric cars.

Thus, all the body parts (roof, doors, bonnets, etc.) of these vehicles will be covered with a skin of expanded polymers such as polystyrene, polyphenyl ether and polyurethane. They will also contribute to the thermal insulation of the batteries, which remain very vulnerable to changes in temperature and which, as a general rule, do not do well in low temperatures. 

Polymers practice their scales

Manufacturers agree, and lovers of the accelerator pedal and the backfire heard when downshifting will certainly be disappointed by the car of the future. This is why the automotive industry is very careful not to make its next models too commonplace. From a marketing point of view, they would be difficult to sell if they were to be perceived as merely designed for travel. They have to retain a certain amount of sex appeal, and it is in the car’s interior that this particular game will be played out.

Having said that, interiors have evolved considerably since perceived quality became a key criterion, turning all cars into real cocoons. A comparison of two equivalent models, one from the 1980s and the other from 2010, reveals that the differences could not be more apparent! On-board electronics are a major factor, and polymers, which have already made a major contribution to visual and acoustic comfort, still have a lot to offer.

Let us recall once again that car manufacturers and equipment suppliers are making every effort to reduce the weight of their vehicles. They have gone over every part of the car with a fine-toothed comb in search of components whose weight could be reduced, including the most unexpected parts such as the audio system. The magnets inside the speakers can weigh up to 40 kilograms. Yet it seems hard to do without them, especially in luxury models which are veritable auditoriums thanks to the ten or so speakers judiciously placed around the passenger compartment.

It is now possible to have stereophonic sound without using loudspeakers and their heavy magnets by causing the polymers lining vehicle interiors to vibrate.

The German companies Continental and Sennheiser took up this challenge. The latter, already well known for its headphones, is interested in stepping into the world of cars and has taken the bold step of using plastics on the surfaces of the passenger compartment to reproduce a sound worthy of a philharmonic orchestra. In fact, the system sends electrical impulses through the polymers to make them vibrate and thus diffuse sound waves. The basic principle is that of a taut drumhead.

Of course, the dashboard and door panels will not shake when listening to a hard rock band. Thus, basic speakers will become a thing of the past. Electric actuators will make the trim around the doors, roof and rear parcel shelf shiver so that it emits sound in different frequency ranges. These companies have just reinvented the “two in one” concept since a headrest will no longer be solely a safety component, it will also be intended to provide comfort. We are promised a spatial sound... but the greater achievement lies in reducing the vehicle’s weight by several dozens of kilograms and thus increasing its autonomy by as many more kilometres.

Plastics reinvent the wheel

Another detail worth noting. You may have noticed that the wheels of electric vehicles, and more particularly those of BMWs, have a rather peculiar appearance. Manufacturers had accustomed us to mounting big and wide wheels intended to improve road handling, but also because their customers were quite fond of their sporty look.

It is quite the opposite in some electric vehicles, where the wheels have a large diameter and are particularly narrow. One could almost say that they resemble motorcycle wheels more than car wheels. For once, the purpose of this modification is not weight reduction, as these rims are not significantly lighter and are still made of metal. However, the thinness of the wheels improves their air penetration and aerodynamics. Road handling remains the same because the vehicles’ ground clearance is similar due to the large diameter of the wheels.

However, BMW have taken this a step further and improved the aerodynamics of the hubcaps. The result is surprising and goes contrary to all aesthetic conventions. Introducing ABS and aluminium inserts in the metal rim improves the wheel’s aerodynamics by 5%.

The same concept was developed at Tesla. The company decided to completely cover its rims with a particularly smooth ABS hubcap. According to tests, these wheels improve the vehicle’s efficiency by 3.4%, which translates into an additional 16 kilometres of range.

Nothing is left to chance at BMW where research was conducted into the design of its rims to improve their aerodynamics.

The subject is a broad one, and manufacturers assure us that they will be able to reduce their vehicles’ ecological footprint to almost nothing within the next 30 years or so. Breakthrough technologies, continuous evolution... It is impossible to tell what our vehicles will look like in the 2050s. Barring the extraordinary discovery of a new material buried deep in the earth, polymers will feature heavily in the design of the car of the future.