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Abstract
Titanium hydride/potassium perchlorate (THPP) is a pressure producing pyrotechnic composition consisting of a mixture of titanium dihydride and potassium perchlorate with a small percentage of a Viton binder. The initial phase of the study focused upon chemical analysis of THPP downloaded from parts ranging up to 25 years in age. The DSC curves were too erratic for kinetic analysis; however, high resolution TG curves for the THPP samples revealed a significant difference in the temperature at which the aged materials began displaying mass loss. Isothermal DTA and variable heating rate TG kinetic analysis were employed to determine the activation energy of the THPP.
Introduction Pyrotechnic compositions are typically composed of finely divided mixtures of metallic or non-metallic elements as reducing agent with inorganic oxidizing agents to chemically generate heat, light, or color and
269/270 639 – 639 . 10.1016/0040-6031(95)02671-1 . 6 Charsley , E. L. , Warrington , S. B. , Griffiths , T. T. and Queay , J. , Proc. 14th International Pyrotechnic
Abstract
Some applications of thermal analysis (TA) and temperature profile analysis (TPA) to the study of a variety of binary pyrotechnic systems are described. Factors that effect the combustion of such fuel/oxidant mixtures are discussed. Trends in burning behaviour and the experimental limitations of the techniques available are identified.
Simultaneous TG-DTA-MS and TG-DSC have been used to investigate the complex reaction which takes place in the region of 300°C when the chlorinated rubber Alloprene is added to pyrotechnic compositions containing equal parts by weight of titanium and sodium nitrate. The results have been compared with those obtained for the titanium-strontium nitrate-Alloprene system.
Abstract
The thermal behavior of metal, oxide, and oxidizer mixtures, some with fluorine compound additions, has been studied in order to examine the influence of thermal properties on the initiation conditions for chemical reaction of pyrotechnic powders under dynamic loading conditions. The autoignition energies of the mixtures obtained from thermal analyses were compared with shock initiation energies, determined from planar shock measurements. Although some mixtures showed an approximate equivalency between the energies obtained from the two different experiments, the experimental results indicated that any comparison should be made with great care.
Thermogravimetry (TG) and differential scanning calorimetry (DSC) have been used to examine the thermal behaviour, in N2 and in air, of the Si/Sb2O3, Si/KNO3, Si/Fe2O3 and Si/SnO2 pyrotechnic systems, in relation to the behaviour of the individual constituents.
Abstract
Results of high thermal resolution microcalorimetric and dilatometric measurements performed on reducer — polytetrafluoroethylene (M-PTFE) pyrotechnic compositions have been discussed. The materials were selected for the study because of their behaviour in combustion tests. Two complementary thermal properties, i.e. the specific heat and coefficient of linear thermal expansion (CLTE), have been analysed in detail. The specific heat was obtained from DSC measurements performed from −20 to 375C. Measurements of CLTE and linear expansion were carried out from −40 to 270C. In both cases the measurements were performed on thermocycling with the high thermal resolution preserved. A special attention has been paid to a two-stage phase transition occurring just below the room temperature.
Abstract
The ageing characteristics of pyrotechnic compositions are influenced not only by temperature, but also by surrounding effects as humidity and vibrations. In this paper the thermal stability of the pyrotechnic system magnesium–sodium nitrate will be investigated. In an inert helium atmosphere two steps of mass loss, which were not completely separated from each other, were observed in the temperature range from 65 to 265C: a mass loss of about 15% between 65 and 160C and about 34% between 160 and 265C. It is assumed that these two steps are caused by different processes. The separation between the two steps was not or hardly detectable for measurements that were performed in a nitrogen atmosphere. Using MS and FTIR (mass spectrometry/Fourier transform infrared spectroscopy) the evolved gases were analysed. Only above about 170C evolving gases were detected (which means that during the first step no gases were detectable). The detected gas mainly consists of CO2, CO and N2O, with smaller amounts of NO2, NO and possibly HCN. A third step of mass loss (8–9%) was observed above 314C. The process which caused this step of mass loss is considered not to contribute significantly to the ageing of the material at much lower temperatures of maximum 80C, which is of interest in view of the use of the materials. Kinetic parameters for the processes which caused the first and the second step of mass loss were evaluated from kinetic analysis of the measured TG curves. By using these results the conversion can be predicted as a function of time and temperature. However, it must be considered that the inaccuracy of the predictions increases if the temperature for which the prediction is calculated is further away from the temperature at which the experiments were performed. This is caused by the exponential form of the kinetic equations. The calculations show that in particular the reaction which causes the first step of mass loss can run relatively quickly in the temperature range 25–80C, which could result in ageing of the material during storage at these conditions. The reaction which causes the second step of mass loss clearly runs at a much lower rate.
Adiabatic thermokinetics and process safety of pyrotechnic mixtures
Atom bomb, Chinese, and palm leaf crackers
numerous thermal measurement techniques to characterize the hazardous nature of pyrotechnic mixtures, accelerating rate calorimetry (ARC) is the only adiabatic and versatile calorimetry that produces reliable data. Because ARC measurements are conducted
