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EN
The effect of the initial temperature on the mechanical properties of spherical single base gun propellant was investigated by means of a compression test, which consisted of compression of a propellant bed conditioned at various initial temperatures. Following this mechanical treatment, the pressed grains (after thermal conditioning at ambient temperature) were tested in a closed vessel. The results from the combination of compression and closed vessel tests supported the assumption that there are two phenomena occurring inside the cartridge at low temperatures which compensate each other; the first is a decrease in the burning rate as the initial temperature is decreased, and the second is grain fracturing occurring on ignition. Additionally, a specific parameter, the specific surface area, turns out to be an appropriate parameter for quantifying the mechanical damage to the propellant grain resulting from the compression test. Tests on the aged propellant have also been conducted.
EN
In our previous investigation, we measured the global temperature sensitivity coefficient of a deterred spherical single base gun propellant following an experimental procedure that did not allows us to determine the local temperature sensitivity coefficients of the deterred and undeterred parts of the investigated propellant. In this paper, we propose an experimental methodology to measure the local temperature sensitivity coefficients of both parts of the spherical deterred gun propellant. This methodology can be summarized as follows: Firstly, we separated the ranges of pressure where the combustion of the deterred and the undeterred parts of the spherical propellant occurs by means of infrared (IR) microscopy measurements. Then the burning rate of the propellant as a function of pressure was calculated according to STANAG 4115 at different initial temperatures. Finally, we determined the local temperature sensitivity coefficients of each part of the spherical propellant.
EN
One of the objectives of gun propellant research is to develop green formulations of gunpowder that should be less temperature sensitive than the current gun propellant. The temperature sensitivity of these new green formulations of the propellant should be measured to identify the less temperature sensitive green formulations. However, there are deficiencies in the methodologies for the measurement of the temperature sensitivity of gun propellants. Therefore, the aim of this investigation was to fill the gap by establishing a method for the measurement of the temperature sensitivity of deterred gun propellants by closed vessel tests. The temperature sensitivity of the burning rate of ball propellants and the temperature coefficients of gun performance were determined using closed vessel tests and ballistic firing, respectively. Specific definitions of temperature sensitivity and temperature coefficients were evaluated. The relation between these parameters has never been explicitly investigated previously. Assessing the temperature sensitivity of propellants by closed vessel tests is of added value to the range of ballistic tests if the results of these tests can be well correlated to the results of ballistic firings. Therefore, a comparison between both parameters was made. A correspondence has been observed between the temperature sensitivity of the propellant burning rate, as obtained from closed vessel tests, and the temperature coefficients as obtained from ballistic firings.
EN
Propylene Glycol Dinitrate (PGDN) is a liquid nitrate ester explosive which has been used as a gelatinating agent in some energetic formulations. The aim of the present work was to assess whether PGDN could be used as a detection taggant. The PGDN was synthesized in the laboratory using laboratory grade propylene glycol (PG). The purity of the synthesized PGDN was assessed using gas chromatography-mass spectrometry (GC/MS) and Fourier transform infrared spectroscopy (FTIR). A study of the thermal decomposition of PGDN was carried out using both DSC and thermogravimetry-mass spectrometry analysis (TG/MS) methods. The gases produced during thermal decomposition were identified by mass spectrometry and the influence of the heating rate was investigated. The duality of DSC-TGA was highlighted by studying the complementarity between these two methods. Vapour pressure and enthalpy of vaporisation of PGDN were considered as the foremost taggant characteristics, and were estimated using TGA and taking benzoic acid as the reference. The vapour pressure of PGDN at ambient temperature is 2.54 Pa, therefore the PGDN could be a good candidate as a detection taggant compared to other explosive taggants (Nitroglycerin, EGDN, DMNB and PDCB).
5
EN
Currently, E-smoking cigarettes are widely used and occur within all classes of society. This work investigated the use of E-smoking liquids for the synthesis of Nitroglycerin (NG) and 1,2-Propylene Glycol Dinitrate (PGDN), both considered as nitroester liquid high explosives. Two kinds of E-smoking liquids (10 mL) were investigated: nicotine free and with nicotine (10 mg/mL). Quantitative analysis of the glycerin and propylene glycol (PG) present in the E-smoking liquids was carried out by gas chromatography-mass spectrometry (GCMS), with calculation of the accuracy and precision parameters. The percentage of glycerin was (10-13 wt.%) and percentage of propylene glycol was (40-70 wt.%) The synthesis of pure NG and pure PGDN were performed with laboratory grade glycerin and propylene glycol and compared to the samples obtained from the E-smoking liquid. Differential Scanning Calorimetry (DSC) was used for the determination of the activation energy and the heat of decomposition for each synthesized explosive, using the Ozawa and Kissinger models. The brisance index was assessed by the witness plate test and compared with some conventional explosives (TNT and C4). Finally, the influence of nicotine (less than 2 wt.%) on the synthetic process and the detonic properties of the explosive mixture was studied.
EN
Emulsion explosives are used in a wide range of applications, amongst which some in closed vessels, where the properties at short range need to be known. A series of tests with spherical charges has been carried out to determine the TNT-equivalent at short range of an explosive emulsion based on both peak overpressure and impulse. Generally, the value is found to be constant over the considered range, with a value of 1 for overpressure and of 0.7 for impulse. In most common applications, explosive charges are not spherical. Experiments with cylindrical charges have been performed to study the infuence of (1) the shape of the charge (length-to-diameter ratio) and (2) the location of initiation (central or at one end). At the considered range, increasing L/D increases the peak overpressure and the impulse perpendicular to the axis, but decreases these effects on the axis. The central initiation causes the largest effects on the centreline. The initiation at one end causes a shift in the location of the peak overpressure, but the highest impulse remains on the centreline.
EN
A calibration procedure for quantitative determination of dibutylphthalate concentration in a double base propellant is established. The best results are obtained by dividing an absorption band, characteristic of the dibutylphthalate, by an absorption band characteristic of the double base mixture. The influence of the nitroglycerin concentration on the linear calibration curve is investigated and it is shown that a linear relationship can be obtained for different concentrations of nitroglycerin by multiplying the absorbance ratio by the nitrocellulose concentration. The developed analysis protocol is applied to characterize quantitatively the deterrent concentration profile of a flattened ball propellant. Since the measured profile in a given propellant grain is dependent of the orientation of the analysed cross-section, geometrical and concentration factors are used to eventually describe the profile perpendicularly to the grain surface. The validated experimental procedure is then applied to study the characteristic of the diffusion process of the deterrent throughout the grain by artificial ageing at different temperatures. From these results, diffusion coefficients and diffusion activation energy of 154 ± 15 kJ/mol have been obtained. Furthermore, a simulation program has been used to validate the used procedure for the calculation of the diffusion coefficient.
EN
The physical ageing of a spherical deterred propellant has been monitored by infrared microscopy, closed vessel tests and ballistic firing. This result has been compared with the ageing of a flattened spherical propellant; it has been observed that the ageing of the spherical propellant is far less important. The difference between the two propellant types could be due to a difference in their nitrocellulose structure.
EN
Different gaseous ignition systems have been used for the characterization of spherical deterred propellants in closed vessel tests. It has been observed that, with an appropriate ignition system, a good correlation is obtained between closed vessel tests, deterrent concentration profiles and ballistic firing.
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