The use of rigid polyurethane (PU) foams in automobiles for energy management applications is not a new concept. It is well documented that its low density, moldability, and energy absorbing characteristics have had advantages for use in knee bolsters, door panel bolsters, steering wheel columns, head-rests, instrument panels, and other interior as well as exterior automotive applications.
Developing an “ideal” energy absorber, one that produces a square wave when both dynamically impacted and statically crushed, thus maximizing the energy absorption, is the goal of energy management. This ideal energy absorber would minimize the amount of vehicle occupant compartment space loss by reducing the energy absorbing bolster size required to decrease the impact loads imparted on the occupants during a collision.
When considering polyurethane rigid foams for energy absorbing materials, elimination of CFCs or HCFCs (hydrochlorofluorocarbons) has become an environmental and economic necessity. BASF Corporation's Urethane Applications Development Group in Wyandotte, Michigan has developed new CFC-free, water blown, low density, rigid, Energy Absorbing (EA) polyurethane foams to accomplish these goals. They are unique in their ability to efficiently absorb energy during an impact, rather than storing it as potential energy and then transferring this potential energy to the occupant which could increase the probability of injury.
The high efficiency of these energy absorbing foams minimizes interior space loss compared to other EA materials by reducing part size. These low density foams can be molded efficiently into a variety of shapes using existing PU processing equipment. This paper describes the development, properties, and processing of these new PU foams.