Novel Ammonium Nitrate-Based Formulations for Airbag Gas Generation

Abstract

In recent years, there have been researches and developments (R&D) using ammonium nitrate (AN) as an oxidizer of novel azide-free gas-generating agents in automobile airbag systems. AN theoretically generates only clean gases during decomposition, and it also has advantages of higher gas yield, less residue, and lower cost as compared to conventional oxidizers such as potassium perchlorate (KP), strontium nitrate (SrN), and basic copper nitrate (BCN). However, AN has a number of disadvantages, such as low ignitability, low burning rate, multiple crystal transitions at various temperatures, and hygroscopic property. For the AN-based mixtures to be effective as gas-generating agents in automobile airbag systems, their burning performances need to be improved. In this review, a brief overview of the automobile airbag system, including its activation process and its history, is given, followed by reviews of the past and present ingredients used for pyro-type gas-generating agents, and some studies on the burning characteristics of AN-based gas-generating agents, including the recent studies where fuel compound in fuel compound/AN/additive mixture is one of tetrazole compound, e.g., aminoguanidinium 5,5′-azobis-1H-tetrazolate (AGAT); guanidine-derivative compound, e.g., guanidine nitrate (GN); or azo compound, e.g., azodicarbonamide (ADCA).