Lifetime prediction of boron potassium nitrate (BKNO3) pyrotechnic by accelerated aging method

Boron Potassium Nitrate (BPN) pyrotechnic, composed of boron, potassium nitrate and binder, is widely used in military applications as retractable actuators, rocket motor igniters and gas generators. After years of storage, boron and potassium nitrate in the composition can react, and composition can degrade resulting in performance loss. As a result, it is essential that the service life in which the performance of the composition will not decrease should be determined. In this thesis study, determination of the service life of BPN pyrotechnic is aimed. In this context, firstly different BPN compositions with and without binder, and different boron/potassium nitrate ratios were prepared. Effect of the composition formulation on the pyrotechnic performance (calorific output) and aging kinetic is studied. As the performance result of the compositions compared, it is seen that the existence of binder in the composition has no effect on BPN performance. Moreover fuel (boron) rich BPN compositions showed higher performance than the compositions with relatively lower boron ratio. Furthermore, by using DSC/DTA analysis and ASTM E698-11 Standard (Flynn/Wall/Ozawa Method), decomposition (aging) kinetics which assumed as first order of the all BPN pyrotechnics were determined with respect to temperature, and decomposition ratio of the compositions were calculated and compared for 25 ºC – 10 years storage condition. Results showed that the decomposition ratios of the all the BPN pyrotechnics were negligible regardless of the existence of binder and boron/potassium nitrate ratio of the formulation. In the next stage of the thesis, accelerated aging study was performed on the BPN 1 composition which is used in military systems and change in the calorific output was investigated as a performance indicator; and service life was determined. For this purpose, unaged BPN 1 composition's kinetic equation was determined with respect to temperature. With this equation, it is determined that to achieve the decomposition ratios at 25 ºC for 10, 20 and 30 years; accelerated aging at 50 ºC for 8, 16 and 24 days were required. After the aging studies at these conditions, it was seen that there is negligible change in the calorific outputs of the composition and it is concluded that within hermetic conditions (with no oxygen and moisture effect) BPN 1 has a service life of minimum 30 years at 25 ºC. Keywords: BPN Pyrotechnic, Boron Potassium Nitrate, Binder, Decomposition Kinetics, Accelerated Aging, Lifetime Prediction