Vacuum Stability Test Research Articles

III. Chemical compatibility study of gap based propellant by the DVST

Abstract To produce a clean propellant, we must use new energetic materials, whose effect on the chemical stability during long-term storage is unknown. A formulation including ammonium nitrate (AN), GAP, and BDNPAF was studied. This study was based on accelerated aging and gas evolution, using the vacuum stability test in conjunction with gas chromatography. Incompatibility between AN and the other ingredients was found to be responsible for the chemical degradation. The effect of various stabilizers was evaluated and N-methyl-4-nitroaniline proved to be the most efficient stabilizer for the formulation investigated.

The discontinuous vacuum stability test (DVST)

Abstract A method consisting of a modified mercury-free vacuum stability test used in conjunction with gas chromatography and FT-IR spectroscopy has been developed in order to perform a complete gas evolution analysis. This method whose reliability is easily controlled, has the potential of simplicity, low cost of equipment and good accuracy.

II. Sensitivity and reliability of the discontinuous vacuum stability test

Abstract Gas evolution, due to phase expansion, remains an attractive and sensitive method for stability evaluation. Unfortunately, this technique is also sensitive to errors. Numerous factors such as pressure, volume, temperature, volatiles, and solubility, may significantly affect the results. The effect of such factors is evaluated. A better control of the test conditions prevents errors and makes the discontinuous VST a fast and accurate technique for stability/compatibility evaluation.

Thermal decomposition of cured GAP-AP propellants containing catocene

Differential thermal analysis (DTA), thermogravimetric analysis (TGA) and a modified manometric vacuum stability test (MVST) were employed to investigate the thermal characteristics of cured glycidyl azide polymer (GAP)-ammonium perchlorate (AP) propellants in the presence of catocene. Various particle sizes of AP in propellants were examined. The results revealed that catocene plays an important role in catalyzing the decomposition of both AP and GAP. The DTA curves of propellants with larger particles of AP showed two exothermic reactions. However, only one exothermic reaction was found for propellants containing smaller particles of AP. The peak temperature ( T m) of the DTA curves and the onset temperature of the TGA patterns obviously shifted to a lower temperature as the catocene content increased in the propellants. Similar thermal behavior was also observed in the MVST measurements. The activiation energy of decomposition of the propellants was determined, based on the MVST results.

Study on Thermal Decomposition of Pentolites by modified vacuum stability apparatus and differential scanning calorimetry

AbstractA modified manometric vacuum stability test (VST) apparatus as well as a differential scanning calorimeter (DSC) were used to study the decomposition of pentolites (mixtures of PETN and TNT). The former operated isothermally at three heating temperatures (100°.C 110°C and 120°C), the latter with a constant heating rate. Various compositions of pontolites were examined. For the VST tests, heating periods were 40 hours except for experiments in which resulting pressures were higher than 760 mmHg. Using the ideal gas law, the volume of gaseous products was calculated from the pressure readings. The evolved gas volume from pentolites tested at 100°C is about as large as that from either pure PETN or pure TNT. However, the gas volumes released from pentolites heated at 110°C and 120°C are apparently larger than those from either PETN or TNT alone. In particular, a mixture of PETN and TNT with a 1:1 weight ratio releases a maximum volume of gas products. It is found by DSC analyses that decompositions temperature of TNT decreases as mixed with PETN.

Thermal decomposition of mixtures containing nitrocellulose and pentaerythritol tetranitrate

A modified manometric vacuum stability test (MVST) apparatus as well as a differential thermal analyzer (DTA) and a thermogravimetric analyzer (TGA) were used to study the decomposition of nitrocellulose (NC) and pentaerythritol tetranitrate (PETN) and their mixtures. Two NC samples with different nitrogen contents (12.6% and 13.4%) were investigated. The MVST apparatus was operated isothermally at three temperatures (100, 110 and 120°C) for 40 h, and the DTA and TGA experiments were performed with a constant heating rate (10°Cmin −1). The activation energies of the thermal decomposition reactions were determined from both the MVST and DTA test results. It was found that the activation energies for the decomposition of the mixtures fell between those of PETN and NC. The compatibility between NC and PETN was confirmed by the experiments.

Investigation of the decomposition processes in double‐base propellants and nitrocellulose under vacuum and oxygen

AbstractThere is described the application of an automated vacuum stability test in following the decomposition and stability of double‐base propellants and nitrocellulose. There is also described a manometric stability test of propellants based on the decomposition in oxygen. This method makes possible to determine small differences of chemical stability and to substitute the time consuming methods based on HPLC.

Investigation of the Decomposition Processes in Single‐Base Propellants under vacuum using a minicomputer‐controlled automated apparatus

AbstractThere is described the application of an automated vacuum stability test in following the decomposition and the stability of single base propellants. The relations of the propellant decomposition rate, evaluated from the loss of stabilizer, to the decomposition rate measured at the stability test were verified. The data obtained indicate the applicability of the vacuum test to check the chemical stability of propellants.

Thermal decomposition studies on double-base propellant compositions

Thermal reactivity studies were carried out in the temperature range 100–160‡ on two double-base propellant compositions which differ significantly in chemical composition, calorimetric value and ballistic characteristics. The course of decomposition was followed by two methods: (i) determining the rate of NO evolved with the Bergman and Junk method; (ii) estimating the volume of gases evolved in a vacuum stability test method. The activation energy values computed using the Arrhenius equation and the Jacobs-Kureishy method were comparable and in the range 134–170 kJ mol−1. In the temperature range 100–140‡, nitroglycerine volatilization was significant during the early stages of heating. Above 180‡, the rate of decomposition was very fast, leading to ignition of the propellant, followed by slow oxidation of the carbonaceous residues. The thermoanalytical data indicated a twostep decomposition process for propellant I, and a single-step process for propellant II.

Stability and compatibility testing using a microcalorimetric method

A microcalorimetric method is used for compatibility and stability studies. The high sensitivity of the instrument permits measurements at 60°C or even lower, i.e. under more realistic conditions than offered by conventional techniques like DTA and vacuum stability tests. The instrument consists of four independent calorimeters with a short thermal relaxation time, high sensitivity and excellent baseline stability. The calorimeters are placed in a common, precisely thermostated water bath. In compatibility studies, heat flow curves are recorded for the pure components and a mixture of these. A theoretical curve is constructed, which simulates a non-interacting system. The difference between the theoretical and the experimental curve for the mixture reflects the degree of interaction between the materials. A number of compatibility problems are discussed, including interactions in mixtures of TNT with amine/amide type polymers, polycarbonate — double base propellant interactions under various conditions and the influence of an anaerobic sealant on a high explosive and a propellant. Some results from stability measurements on an igniting compound are also presented.

Developments in vacuum stability testing - the inclusion of a data logger

A description is given of the design and performance of the AWRE vacuum stability apparatus incorporating a transducer, data logger and teleprinter for producing a direct print-out of the volume of gas produced on heating an explosive or a compatibility test mix. Reference is made to the applicability of this apparatus to the proposed NATO compatibility test.

Evaluation and Vacuum Stability Tests of Silicon Radiation Detectors

Tests have been carried out on a group of commercially available silicon radiation detectors of both diffused junction and surface barrier types. Measurements were made of reverse current and RMS noise level as a function of applied bias voltage in air and vacuum, alpha particle pulse height and energy resolution, and thickness of the sensitive surface dead layer. Long term stability was evaluated for samples in air and in vacuum by periodic measurements of reverse current, RMS noise voltage, and the pulse height and energy resolution for 5.8 Mev alpha particles. The samples in the vacuum tests were maintained at rated bias voltage and a pressure of approximately 10-6 Torr continuously for a period of six months. Only minor changes were observed in the performance characteristics of the devices. This work was sponsored by the Aeronautical Research Laboratory of Wright-Patterson Air Force Base, Office of Aerospace Research, United States Air Force.

Appendix I. Vacuum stability tests on Oppau salt and ammonium nitrate

Appendix I. Vacuum stability tests on Oppau salt and ammonium nitrate