Friction Sensitivity of Pyrolants

Sodium azide is not as sensitive as lead azide or silver azide to friction or mechanical shock. Since sodium azide reacts with metal oxides to generate nitrogen gas, mixtures of sodium azide and metal oxides are used as pyrolants in gas generators. However, sodium azide reacts with copper and silver to form the corresponding azides, both of which are detonable pyrolants. 

Fig. 11.21 shows the results of TG and DTA measurements on mixtures of AP particles and catalysts. The endothermic peak observed at 513 K is caused by the crystal structure transformation of AP from orthorhombic to cubic. A two-stage exothermic decomposition occurs in the range 573-720 K. The decomposition of the AP is seen to be drastically accelerated by the addition of catocene. The exothermic peak accompanied by mass loss occurs before the AP crystal transformation. Although the AP is sensitized by the addition of carborane, no effect is seen on the AP decomposition. The results indicate that carborane acts as a fuel component in the gas phase but does not catalyze the decomposition of AP. Thus, the critical friction energy is lowered due to the increased reaction rate in the gas phase. The results imply that the initiation of ignition by friction is caused by the ignition of the gaseous products of the AP pyrolants.PI... 

---