Recently, 5-amino-1H-tetrazole (5-ATZ) has been developed for practical use as a substitute for sodium azide, which has been conventionally used as a main component of gas generating agent for automobile airbags. This paper describes the study concerning fundamental combustion features of the mixtures of 5-ATZ and sodium perchlorate (SP) which has high oxygen content per unit mass. The 5-ATZ/SP mixture was consolidated to form test strands. An optical strand burner was used to measure the burning rate of the strands.
The burning rate for 5-ATZ/SP at 2 MPa was about 18 mm s-1 for a stoichiometric mixture which was higher than that of 5-ATZ/strontium nitrate (SrN) mixture. The decomposition of 5-ATZ/SP underwent three-stage process and at the second stage, near 720 K, the reaction between fuel and oxidizer occured. According to the closed vessel test, 5-ATZ/SP displayed 3.4 times larger pressure gradient than that of 5-ATZ/SrN mixture, suggesting the former's its superior performance as a gas generating agent. it was also found from the interpretation of the burning rates according to Granular Diffusion Flame model suggested by Summerfield, that combustion mechanism of the samples used in this study was is diffusion controlled.
According to the temperature history of the mixtures, an increase in burning rate with an increase in pressure is an increase in the amount of heat transfer from the gas phase to the solid phase because of the approach of the flame to the burning surface.
エアバッグのガス発生剤として用いられているアジ化ナトリウムは毒性があり，重金属との化合物は爆発性があるため，これに代わるガス発生剤の研究が盛んに行われている。本研究ではテトラゾール系化合物のうち一部のエアバッグに使用されている5-アミノ-1H-テトラゾールについて質量当たりの酸素含有量の多い過塩素酸ナトリウムとの混合物を作製し，燃焼特性について調べた。燃焼速度および密閉容器内の圧力発生速度は実用化されている5-アミノ-1H-テトラゾール/硝酸ストロンチウム系以上であることがわかった。粒状拡散炎モデルが適用できることを示し，0.7-5 MPaでは拡散過程が律速であることがわかった。TG-DTA-MS装置を用いて分解生成物の解析を行い，5-アミノ-1H-テトラゾール/過塩素酸ナトリウムは３段階で分解し，720 K付近で燃料と酸化剤の反応が起きることがわかった。燃焼面近傍の温度変化の測定から，圧力上昇により燃焼速度が増すのは火炎が燃焼表面に近づくためであることがわかった。