Low hazard small-scale synthesis and chemical analysis of high purity nitroglycerine (NG)

A previously reported two-phase (99.5% fuming nitric acid/dichloromethane) batch method to prepare high purity 1,2,3-propanetriyl trinitrate (nitroglycerine, NG) was evaluated, simplified and adapted specifically for low hazard small-scale synthesis. The purity of the product, as determined by NMR spectroscopy, HPLC and IR spectroscopic analysis was found to be greater than 99%. The quick synthetic method is highly recommended when small amounts of highly pure NG are required for analytical and related purposes in the absence of a microreactor

Optimised accelerated solvent extraction of hexahydro‐1, 3, 5‐trinitro‐1, 3, 5 triazine (RDX) from polymer bonded explosives

An Accelerated Solvent Extraction (ASE) method was developed and optimised to extract hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine (RDX) from a polyurethane matrix. The ASE method development was benchmarked against Soxhlet extraction with a view to improving extraction efficiency in terms of time and solvent volume. Key parameters for the ASE method development involved selecting the most appropriate solvent, optimising static time, ensuring a safe oven temperature for explosives, determination of a sufficient number of rinse cycles and effective sample preparation. To achieve optimal extraction, cutting the PBX samples to maximise solvent exposure was essential. The use of acetone with a static time of 10 minutes at 100 °C with three rinse cycles achieved 97 %±10 % extraction of RDX from PBX in 40 minutes using 72 mL solvent. Extraction time was reduced from 48 hours and solvent use by half compared to the standard Soxhlet extraction. To validate the developed ASE method, two other PBX samples containing different quantities of explosive were also fully extracted using the same parameters. Overall, ASE efficiency was comparable to Soxhlet, which places the ASE as a good alternative and shows potential for implementation as a standard method for other polymer based explosives

Practical remediation of 3-nitro-1,2,4-triazol-5-one wastewater

Limiting environmental impact is a top priority for the chemical industry, and manufacturing practices need to be well controlled to avoid any potential contamination. In order to reduce waste streams during the processing of 3-nitro-1,2,4-triazol-5-one (NTO), potentially evironmental hazardous at concentrations of 1 g/l, we investigated the potential remediation and recycling of water using a wide range of commercial sorption media. We studied the effect of experimental conditions, including flow rate, initial contaminant concentration and temperature. This led to the selection of Amberlyst A26 OH in a batch process and Activated Carbon in continuous flow, as the most effective sorption methods. Using high performance liquid chromatography photodiode array detection (HPLC-PDA), NTO was quantified from solutions, before and after remediation, showing a complete removal from a 10 g/l NTO solution. Our purification method therefore appears to be suitable for the remediation of NTO-contaminated wastewater

Practical colorimetry of 3-Nitro-1,2,4-Triazol-5-One

A field ready colorimetric method of quantifying the concentration of aqueous 3‐nitro‐1,2,4‐triazol‐5‐one (NTO), several orders of magnitude below its environmental toxicity level, has been developed. The test allows for the immediate evaluation of the level of contamination in aqueous solution without the need for analytical equipment such as high pressure liquid chromatography (HPLC). The observed colours have been explained by the different NTO species present over the range of pH; these observations are supported by modelling and experimental results

Investigation into the environmental fate of the combined Insensitive High Explosive constituents 2, 4-dinitroanisole (DNAN), 1-nitroguanidine (NQ) and nitrotriazolone (NTO) in soil

Contamination of military ranges by the use of explosives can lead to irreversible environmental damage, specifically to soil and groundwater. The fate and effects of traditional explosive residues are well understood, while less is known about the impact of Insensitive High Explosives (IHEs) that are currently being brought into military service. Current research has focussed on the investigation of individual constituents of IHE formulations, which may not be representative of real-world scenarios when explosive residues will be deposited together. Therefore, this study investigated the fate and transport of the combined IHE constituents 2,4-dinitroanisole (DNAN), 1-nitroguanidine (NQ) and 3-nitro-1,2,4-triazol-5-one (NTO) in two UK soil types. Static experiments ran for 9 weeks to determine the fate of the combined explosive constituents in soil by monitoring the rate of degradation. Transport was examined by running soil column experiments for 5 weeks, with a watering regime equivalent to the average yearly UK rainfall. Both static and soil column experiments confirmed that DNAN and NTO started to degrade within twenty-four hours in soil with high organic content, and were both completely degraded within sixty days. NQ was more stable, with 80% of the original material recovered after sixty days. The major degradation product of DNAN in the test soils was 2-amino-4-nitroanisole (2-ANAN), with trace amounts of 4-amino-2-nitroanisole. NTO was rapidly degraded in soil with high organic content, although no degradation products were identified. Results supported work from literature on the individual constituents DNAN, NQ and NTO suggesting that the three explosives in combination did not interact with each other when in soil. This study should provide a useful insight into the behaviour of three combined Insensitive High Explosive constituents for the predication of soil and water contamination during military training

Influence of humidity on the decomposition process of double base rocket propellant

The decomposition mechanisms of the polymer cellulose nitrate (NC) which is used in double base (DB) rocket propellants, have been extensively studied, and the influence of storage temperature on the lifetime of these energetic formulations is well known. However, the impact of humidity and water on the polymer decomposition process is poorly understood. This paper studies the influence of humidity on the decomposition chemistry of NC and its impact on shelf life. Stabiliser consumption was first analysed by ageing the propellant in sealed vials at different humidity levels for 7 days at an isothermal temperature of 90 °C. Samples were also analysed using heat flow calorimetry (HFC) at isothermal temperatures of 80 °C, 90 °C, and 100 °C. The results indicates that stabiliser depletion increases with increasing water content. Life assessment calculations (AOP 48 ed2) show that increasing the absolute humidity from 6 to 22 g m-3 will decrease the propellant life from 11 to 6 years (25 °C equivalents). The HFC results follow the same trend as the stabiliser depletion where greater absolute humidity increases the heat flow by up to 400 %. Unlike the pass/fail criteria for stabiliser depletion, the HFC samples passed the 10-year (25 °C equivalent) life criteria (STANAG 4582). A multi-temperature (80, 90, 100 °C) kinetic analysis of the initial heat flow showed that the heat flow rate increased with increasing humidity, but the activation energy for all humidity levels remained at 131 (± 3) kJ mol−1

Characterization of water droplets size distribution in aviation turbine fuel: ultrasonic homogeniser vs high shear speed mixer

Pumps, pressure drops across fittings, and flight operations (such as turning manoeuvres, take-off, and landing) are some of the many sources of turbulence mixing and shearing in aircraft fuel systems, therefore, making it an inevitable condition. Literature established that shearing conditions would influence the droplets and droplets size distribution in an oil/water emulsion. So, low intensity shearing conditions could be beneficial as it promotes droplets coalescence, which could be a driving force for a weak emulsion. However, to date no experimental data has shown the influence homogenising intensity and total water content has on dispersed water droplets size distribution in aviation fuel. Therefore, to expand knowledge of quantification of measurements of dispersed water droplets in aviation fuel, this study characterizes dispersed water droplets in aviation turbine fuel, varying available laboratory homogenising devices and water content. Results presented show that droplets count increases with water concentration and shearing effect. To provide more statistical evidence, kurtosis and skew values were calculated from the extrapolated data and compared with data from a hexanol/water mixture given that hexanol is likely to form a stable emulsion. Experimental results show that the higher the homogenising intensity the more stable the emulsion is likely to be with a higher kurtosis and skew value close to that for the hexanol/water mixture. Therefore, observations show that mild shearing conditions (high shear mixing in this case) could help promote droplets coalescence, leading to a better separation ability.Engineering and Physical Sciences Research Council (EPSRC): EP/N509127/1. Airbus Operations, Filton, Bristol (Reference ID: 1100152106), United Kingdom

Temperature dependence of the electrochemical behavior of the 690 Ni-base alloy between 25 and 325 °C

International audienceThe electrochemical behavior and the chemical composition of passive films formed on the Alloy 690 at room temperature in borate buffer solution (pH = 9.0) was studied with different techniques for two surface finishings. XPS and quantum yield measurements showed the presence of Ni and Cr oxides and hydroxides for passive films formed on both the as received and the mechanically polished one, whereas the presence of mixed spinel type Ni (1-x) Fe x Cr 2 O 4 was only observed on the as received material. Additionally, Electrochemical Impedance Spectroscopy (EIS) highlighted a higher corrosion resistance for the as received alloy in comparison with the mechanically polished alloy, which was linked to the chemical composition of the oxide film. Electrochemical measurements were performed before, during, and after oxidation of the Alloy 690 of Steam Generator (SG) tube of Pressurized Water Reactor (PWR) at high temperature and high pressure in the simulated primary circuit of PWR. At high temperature, the interface becomes electrochemically active yielding the precipitation of the corrosion products which form a few tens of nm thick diffusion barrier for the released metal cations. This overlayer is built on the top of a few nm thick, Cr rich inner layer at the alloy/oxide interface which was found to behave similarly to that initially formed at ambient temperature. It is concluded that high temperature oxidation in the static condition of an autoclave at 325°C does not promote a better passivation state than the one already existing initially