INFLUENCE OF TECHNOLOGICAL PARAMETERS AND EXTERNAL CONDITIONS ON THE SPEED OF DEVELOPMENT OF THE COMBUSTION PROCESS OF PYROTECHNIC METALIZED MIXTURES BASED ON FLUOROPLASTS

Abstract

In order to prevent premature fire-hazardous destruction of products, it is necessary to have a controlled database on the development of combustion of mixtures, and, first of all, on their burning rates under conditions of elevated heating temperatures and external pressures, with the help of which to quickly predict the conditions for the occurrence of explosive modes of combustion of mixtures during their forced activation. At the moment, there are no studies for pyrotechnic mixtures of metal fuel powders and fluoroplastics with additives of organic and inorganic substances of the influence of technological parameters (ratio and dispersion of components, compaction coefficient, amount and nature of additive of organic substances, diameter of the charge of the mixture, etc.) on the dependence of speed combustion of mixtures from elevated heating temperatures (up to 800 K) and external pressures (up to 107 Pa); models of their combustion in these conditions to determine the critical parameters of external thermal actions, the excess of which leads to the explosive development of combustion of mixtures and fire-hazardous destruction of products, and methods of preventing the specified destruction of products by adjusting technological parameters at the stage of manufacturing charges of mixtures have not been developed, which allows to increase the operating times of products in extreme operating conditions. The purpose of the work is to obtain a database on the burning rates of mixtures under conditions of elevated heating temperatures and external pressures for various values of technological parameters, which allows to estimate its permissible ranges of change. The objectives of the research are the study of the influence of technological parameters on the speed of development of the combustion process of pyrotechnic metallized mixtures based on fluoroplastics; study of the influence of external conditions on the speed of combustion of pyrotechnic mixtures made of metal fuel powders, fluoroplastics and organic substance additives. Samples of pyrotechnic mixtures have been made using standard methods for pressing powders of fluoroplastics, metal fuels (Mg, Al, etc.) with additives of organic and inorganic substances. Studies of the processes of ignition and burning of mixture samples have been carried out on standard pyrotechnic equipment. The regularities of the influence of technological parameters (ratio and dispersion of components, mixture compaction coefficient, diameter of its sample, coefficient of thermal conductivity of its shell) and external conditions (increased heating temperature and external pressure) on the speed of development of the combustion process of compacted mixtures of metal fuels, fluoroplastics and additives organic and inorganic substances have been established. Concentration limits of combustion of mixtures are found, within which the process of their combustion is stable. A wide class of organic and inorganic substances, the introduction of which in the form of small additives (up to 10...13%) in the composition of mixtures leads to a decrease in the burning rate and an increase in the resistance of their combustion process to external influences for various ranges of changes in technological parameters of the mixtures, has been established. Inorganic substances, the addition of which, on the contrary, leads to a sharp increase in the rate of development of the mixture combustion process and a decrease in its stability, especially in conditions of elevated heating temperatures and external pressures, have also been detected. It is shown for the first time that by adjusting the technological parameters of the mixtures (the ratio and nature of the components, the dispersion of metal fuels, the compaction coefficient, the diameter of the mixture samples and the coefficient of thermal conductivity of the shells) at the stage of their manufacture, without changing tactical and technical indicators of pyrotechnic products based on metallized fluoroplastic mixtures, with the help of a controlled change in the burning rate of mixtures (or the time of action of products in the conditions of their combat use), it is possible to prevent unstable, explosive modes of its development in conditions of external thermal influences, which lead to premature fire-hazardous destruction of products.