The widespread application of plastics in the automotive industry does not just enable manufacturing of lighter and more energy-saving vehicles, it also improving car safety. As manufacturers fine-tune designs and introduce new materials, prejudices like “the stiffer, the safer” are eliminated. In this sense, the role of thermoplastics like expanded polypropylene (EPP) and expanded polystyrene (EPS) is critical to manufacture passive security systems in cars.
“Before, cars were much more resistant; now they deform at the slightest impact”. The association of safety with the solidity of rigid sheets, with angular shapes and without plastic, is a groundless stereotype. Since a vehicle must guarantee the safety of passengers, we expect that the passenger cabin may not be deformed.
Until the 1950’s, car manufacturers did not make any effort to improve passenger safety. It was considered that, the more rigid the car, the better it would protect passengers. This pattern of thought prevailed until Mercedes-Benz conducted tests with mannequins and discovered that the dangerous consequences of collisions can be reduced by introducing shock absorption zones.
When a collision occurs and car body parts have high resistance to deformation, the kinetic energy penetrates into the cabin and is absorbed by the passengers. However, if the impact zone is crushed, thereby absorbing a high amount of energy, the impact energy carried over to the passengers is reduced.
VEHICLE SAFETY - HOW THE PLASTIC SAVES LIVES
It turned out that active car safety systems such as: popular ABS, ASR, ESP and BAS systems are not enough. Modern car safety systems should take into account not only active but also passive vehicle safety. Passive safety feature is a system which automatically deploys when the car gets into a crash and helps to minimize the risk of injury of passangers and damage of car. How does it works?
The introduction of plastic components in passive safety systems marked a revolution in passenger safety. In a study conducted in 2015 by the National Highway Traffic Safety Administration (NHTSA) USA, it was determined that innovative safety technologies, many of which involved the application of plastics and composites, saved the lives of over 600,000 residents of the USA during the years 1960-2012.
The application of plastic in exterior car components is of decisive significance to shock absorption. Moreover, it reduces the weight of vehicles, which is one of the variables taken into consideration in the context of safety enhancement, since the greater the weight, the greater the kinetic energy, and the more severe the consequences in the event of an accident.
Knauf Industries Automotive manufacturers car parts from EPP and EPS, such as front and rear bumpers, grilles, and shock absorbers for front and rear plastic bumpers, which are the first line of defense in the event of a collision. The properties of these thermoplastics, much lighter and more flexible than materials traditionally applied in the automotive industry, afford an energy absorption capacity that is five times greater.
When an impact occurs, plastic elements absorb the energy, creating a “crumple zone”, which collapses like an accordeon and acts like a protective cushion to protect the car's passengers. These same properties serve to protect pedestrians, as an impact with a metal bumper is not the same as an impact with a bumper with 98% air content, as is the case with EPP.
But EPP and EPS do not only find applications in passive exterior safety components. They are also present in the passenger cabin: steering column housing, knee guards, side fillings of doors, etc. Other elements of passive safety in vehicles are car seats and headrests, including active front seat head restraints. Why are they so important for car safety?
Headrest as a part of passive vehicle safety system
Headrests appeared in the mid-1950's as a luxury accessory. In 1969, they became mandatory in all vehicles registered in the USA, but were not homologated in Spain until the last decade of the past century. Manufactured with the use of EPP, headrests and headrests cores are an essential safety component that mitigates the effects of a collision on the cervical segment of the spine.
In a report by the American Institute for Highway Safety published in 2017, it was indicated that the number of driver deaths dropped from 87 per million to 30 per million during the years 2002-2015 thanks to improvements in vehicle safety.
EPP FOR CHILD SAFETY
Finally, progress with regard to child safety should be indicated. The first, very primitive child car seats appeared in 1930. At the time, the car seat's function was essentially to avoid distracting the driver. Only in the 1960's were the first children’s car seats equipped with safety elements manufactured, and they became widespread in the 1980's. In Spain, many years passed before children's car seats became a mandatory element of child safety in vehicles, which happened in 2005. Here, it should be emphasized that children's car seats are mainly manufactured from expanded polypropylene.
Children's car seats elements manufactured from EPP by Knauf Industries Automotive are light, solid, and resistant to high loads. The absorb kinetic energy very well, without deforming, even after several impacts.
Safety is one of the fields in the automotive industry that is experiencing continuous development. The progress over the last few decades has been spectacular, and research is still ongoing to take full advantage of not only active, electronic safety systems in cars, but also take car of safety in the car using the benefits of the latest materials in manufacturing the passive safety features.