Use of Bismuth Chromate with Antimony Trisulphide in Delay Compositions

Antimony trisulphide is used with potassium perchlorate, barium chromate, and binder in delay compositions. The effect of substitution of barium chromate by bismuth chromate in the system barium chromate-antimony trisulphide-potassium perchlorate has been studied and reported here. These compositions contain 20% antimony trisulphide, 10% potassium perchlorate, and the remainder barium chromate/bismuth chromate. It is observed that the burning rate decreases from 0.43 to 0.23 cm/s with an increase in bismuth chromate content. The ignition temperature of these compositions determined by Differential Thermal Analysis (DTA) is found to be in the range 400 - 10°C, the same for all compositions.Theoretical calculations by a chemical equilibrium program (REAL) are used to discuss the possible reaction mechanism. Thermo gravimetry (TG)/Differential Scanning Calorimetry (DSC) data are reported. It is observed that the main exothermic peak of the compositions containing bismuth chromate shows at about 462°C as compared to the basic system, where it is at 498°C. These compositions are safe to handle, as suggested by sensitivity data.