STUDY OF Mg-Sr(NO_3)_2 COMPOSITION WITH DIFFERENT ADDITIVES FOR IR FLARES AND TRACER APPLICATIONS

摘要

In addition to the fuel and oxidiser the pyrotechnic compositions contain other ingredients which act as binder, burning rate modifier or colour intensifier. A number of researcher workers have studied Mg-Sr(NO_3)_2 compositions, with binders, for different applications. The data generated includes ignition temperature, calorific value, heat of reaction and luminous output. The binders studied are halogenated compounds, boiled linseed oil, carbon black and graphite. A few scientists have done theoretical predictions on the performance of pyrotechnic compositions. They have correlated the products of combustion to the IR output of the compositions. Nadler studied Mg ― NH_4ClO_4 ― Binders compositions for their IR output in 2 ― 3 μm and 3 ― 5 μm region. According to him Mg, MgO, SrO, CO; CO_2, and H_2O contribute to the IR output. Yong and Smith have carried out theoretical study on MTV ( Mg ― Teflon ― Viton ) composition and inferred that IR output is from hot carbon particle. With the above background , a systematic study on Mg-Sr(NO_3)_2 with different additives like Anthracene, Viton, Polyester resin and Polyvinyl chloride was taken up. The proportion of the ingredients was Mg-45% , Sr(NO_3)_2-45% and additive-10%. The effect of additives on sensitivity, ignition temperature, heat output and burning rate was determined. The effect of products of combustion on IR output was analysed. It was observed that compositions with Polyester resin and Viton give higher heat output while the composition with Anthracene gives lowest heat output. Viton based composition was found to be fast burning as compared to the other compositions. Sensitivity figures show that all compositions are fairly safe for handling, storage and transportation. To know the species formed in the flame, thermochemical calculations were made using REAL program. MgO SrO, C , CO , CO_2, H_2O are the major products predicted in the flame. In addition composition with Viton produced inorganic fluorides, while with Polyvinyl chloride, inorganic chlorides were formed. Attempt has been made to correlate the products predicted in the flame with the IR output experimentally obtained. It was observed that Antharacene based composition gives highest IR output due to unburnt carbon particles in the flame. Though heat output and burning rate of composition containing Viton is high IR output is low.