Kapton® film Offers Reliability in Seat Sensor Applications

Kapton® film Offers Reliability in Seat Sensor Applications

New cars today are equipped with airbag systems that protect not only the driver and front seat passenger in the case of an accident, but also include side air bags for vehicle side collision protection.

Challenge: Safer, reliable passenger air bag deployment

Systems are needed which not only detect whether the front passenger seat is occupied, but also how the airbag is to be activated in the event of a collision.

Solution: DuPont™ Kapton® encases electrical seat sensors

The solution to defining occupant classification was developed by DuPont and a customer in the form of a sensor mat placed under the upholstery of the front passenger seat. This application has been in commerical use since 2002.

The mat is constructed of two sandwiched substrates consisting of thermally stabilized Kapton® polyimide film, on which pressure-sensitive layers and electrodes are printed. The sensor cells emit signals at varying strengths depending on the pressure applied.A special surface treatment ensures optimum adhesion of the layers and electrodes to the film.

If an adult sits on the passenger seat, or a child car seat is placed on it, electrical signals are emitted: weak signals where there is little or no pressure, strong where the pressure is high. A specially developed electronic system computes the load distribution on the seat from the pattern of signals. This information enables the system to decide, in the event of an accident, whether the passenger seat airbag should be activated or not. One of the keys to the very sensitive response is the softness and elasticity of Kapton® which enables the mat to follow the determination of the seat almost exactly.

Because Kapton® film is relatively soft and flexible, it follows the formation of the seat exactly, permitting extremely sensitive measurement. Most importantly, the properties of Kapton® remain constant under extreme temperature ranges, even after years of constant use.

Such potential life savers that are able to recognize who or what is occupying the front seat passenger are compulsory for all new vehicles, according to the revised U.S. regulation Federal Motor Vehicle Safety Standard (FMVSS) 208, with a transition period that extended to September 2005. The regulation requires that an airbag be deactivated if the passenger seat is occupied by a child up to 21 pounds (9.8 kilograms) in a child safety car seat. On the other hand, the system must ensure that the airbag will inflate if the passenger seat is occupied by a small person up to 105 pounds (47.8 kilograms).

The demand for life saving occupant classification systems is enormous. As many at 16 million cars per year were required to be equipped with these systems beginning in 2006 in the U.S.A. considerable number of them will be fitted with systems featuring Kapton® film, by many car manufacturers, such as BMW, General Motors, Hyundai and Kia.Along with the use of occupant classification sensors, the increased awareness of parents and drivers regarding auto safety has contributed to providing the best protection for both children and adult passengers, leading to the substantial reduction of fatalities in the U.S.

This information corresponds to our current knowledge on the subject. It is offered solely to provide possible suggestions for your own experimentations. It is not intended, however, to substitute for any testing you may need to conduct to determine for yourself the suitability of our products for your particular purposes. This  information may be subject to revision as new knowledge and experience becomes available. Since we cannot anticipate all variations in actual end-use conditions, DuPont makes no warranties and assumes no liability in connection with any use of this information. Nothing in this publication is to be considered as a license to operate under or a recommendation to infringe any patent right.

 

Caution: Do not use in medical applications involving permanent implantation in the human body. For other medical applications, see “DuPont Medical Caution Statement:, H-51459 or H-50102-2.