1. Field of the Invention
This invention relates to an ignition enhancer coating composition for alkali metal azide-containing pyrotechnic propellant compositions, especially those propellants suitable for use in inflating an inflatable device, such as a vehicle safety restraint.
2. Description of the Prior Art
Various pyrotechnic propellants have been prepared for generating a gas upon combustion in order to inflate an air bag or similar safety restraint in a vehicle so as to restrain movement of an occupant in the event of a sudden deceleration of the vehicle, such as caused by a collision. In order to be employed as restraints, several criteria must be met. The pyrotechnic must be capable of producing non-toxic, non-flammable and essentially smokeless gases over a wide variety of temperatures and other environmental conditions. The gases that are generated must be ignited at a sufficiently low temperature so as not to destroy the restraint or injure the occupant. The pyrotechnic device must also be safe to handle and must be capable of generating a substantial amount of gas within a very short period of time, e.g., less than about 100 milliseconds.
The present leading candidates for commercialization in an all-pyrotechnic inflation system are alkali metal azide-based compositions. Such compositions exhibit excellent gas generating properties and produce a gas which consists almost totally of non-toxic nitrogen gas.