Impact Sensitivity of Pyrotechnics: A Model Based on Activation Energy
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Impact Sensitivity of Pyrotechnics: A Model Based on Activation Energy S. P. Sivapirakasama , K. Harisivasri Phanindraa , J. Rohina , and S. L. Aravinda
UDC 662.215.4
Published in Fizika Goreniya i Vzryva, Vol. 56, No. 5, pp. 106–115, September–October, 2020. Original article submitted August 16, 2019; revision submitted October 3, 2019; accepted for publication December 24, 2019.
Abstract: This paper introduces a simple and new correlation between the impact sensitivity and activation energy for pyrotechnic compositions where both the fuel and oxidizer are inorganic in nature. The database consists of various drop height (impact sensitivity) and activation energy values obtained from in-house experimentation and various literature studies. This paper also proposes a method to calculate the activation energy from the thermal properties obtained using only single-heating-rate differential scanning calorimetry experimental data. The correlation coefficient between the impact sensitivity and activation energy is found to be 0.84. Keywords: pyrotechnics, impact sensitivity, thermal sensitivity, activation energy, prediction model, differential scanning calorimetry. DOI: 10.1134/S0010508220050111
INTRODUCTION
The chemicals used for manufacturing fireworks are sensitive to friction, impact, heat, and static electricity [1, 2]. Most of the accidents occur due to friction and impact during activities like loading and unloading of boxes, filling, rolling of chemicals, etc. [2]. Therefore, it is important to determine the sensitivity and to take appropriate safety measures. According to the United Nations (UN) guidelines [3], the impact sensitivity value is measured as the minimum drop height at which a drop mass (minimum of 2, 5, or 10 kg) can trigger a reaction in a BAM fall hammer experimental setup. However, the impact test results can also be affected by test conditions, such as humidity, temperature, surface roughness, etc. In this work, a predictive approach for determining the impact sensitivity using a
National Institute of Technology, Tiruchirappalli-620015, India; [email protected].
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mathematical modeling is proposed, which can help in creating a standard sensitivity database, despite varying test conditions. Kamlet and Adolph [4] derived linear correlations between the oxygen balance (OB100 ) and impact sensitivity logH for a large range of solid explosives and found that compounds with the oxygen balance close to zero were highly sensitive. Wang et.al [5] studied the relationship between the impact sensitivity and the Mulliken net charges of the nitro-group (QNO2 ); compounds with more negative values of QNO2 were found to be insensitive. This method is applicable to only those nitro-compounds, in which the C NO2 , N NO2 , or O NO2 bond is the weakest bond. Keshavarz [6] developed an empirical relation to predict the impact sensitivity of energetic compounds having the general structure Ca Hb Nc Od . In addition to the above-mentioned models for sensitivity prediction, there are also other prediction models, w
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