Influence of Firing Temperature on Properties of Gun Propellants

Abstract: Initial firing temperatures play an important role on the combustion rate of propellant. In gun propellants, initial temperature is a key factor for both accuracy and safety. Ideally, the initial temperature of the propellant should not influence the ballistic properties of the round. Nevertheless, constant initial temperature coefficients can not be achieved easily. This work focuses on the influence of the firing temperature on the ballistic properties, the mechanical integrity and the sensitivity to impact of nitrocellulose based propellants. Combustion rates have been determined by closed vessel tests. Ballistic properties have been investigated by firing 5.56 cartridges. The propellants have been conditioned at temperatures ranging from -54 °C to +71 °C before firing. The largest temperature coefficient is observed at high temperatures. The temperature sensitivity of the peak pressure in the combustion chamber can not be fully explained by the results from the closed vessel test. The authors speculated that the mechanical behaviour of the propellant grains at low temperatures influences also the overall ballistic properties of the round. Impact tests with propellants conditioned at low and high temperatures permit to investigate their mechanical strength under extreme temperatures and to better understand the propellant performance during firing. Tests on aged propellants have been conducted as well

Continuous monitoring of shelf lives of materials by application of data loggers with implemented kinetic parameters

The evaluation of the shelf life of, for example, food, pharmaceutical materials, polymers, and energetic materials at room or daily climate fluctuation temperatures requires kinetic analysis in temperature ranges which are as similar as possible to those at which the products will be stored or transported in. A comparison of the results of the evaluation of the shelf life of a propellant and a vaccine calculated by advanced kinetics and simplified 0th and 1st order kinetic models is presented. The obtained simulations show that the application of simplified kinetics or the commonly used mean kinetic temperature approach may result in an imprecise estimation of the shelf life. The implementation of the kinetic parameters obtained fromadvanced kinetic analyses into programmable data loggers allows the continuous online evaluation and display on a smartphone of the current extent of the deterioration of materials. The proposed approach is universal and can be used for any goods, any methods of shelf life determination, and any type of data loggers. Presented in this study, the continuous evaluation of the shelf life of perishable goods based on the Internet of Things (IoT) paradigm helps in the optimal storage/shipment and results in a significant decrease of waste

Preparation of aromatic diazo-ethers and study of their reactivity towards transition metals

The functionalization of aromatic halides or aromatic compounds bearing substituents like fluorosulfonate, by coupling with various nucleophiles in the presence of transition metals (Pd, Cu, Ni..) has become over the years the favoured method to build up new carbon-carbon or carbon-heteroatom bonds. However, this strategy requires the availability of brominated or iodinated derivatives (which are often expensive) or chlorinated compounds (which present a reduced reactivity). The triflates are a good alternative, though their price limits their use to specific, valuable products. We would like to present here our results in the preparation of aromatic diazo-ethers from anilines derivatives as well as a study of their reactivity in metal-catalysed coupling reactions. During our investigations, we have also prepared a diazoaminobenzene containing substrate. Although this compound was somewhat prepared by accident, we became rapidly interested in its unusual structure and eventually found it to be reactive under adjusted coupling conditions...(CHIM 3) -- UCL, 201

Identification of the Degradation Products from α‐Tocopherol Used as Stabiliser in “Green” Propellants through its Lifetime

peer reviewedStabilisers are added to gun and rocket propellants to react with species responsible for nitrate ester degradation during storage. The degradation products can be toxic and therefore harmful. There is a need to replace such stabilisers by “green” molecules and to study their degradation patterns through ageing. Propellant powders must remain chemically stable for a minimum of ten years when stored at temperatures equivalent to 25 °C [1]. α-Tocopherol is a natural product that has been known for decades in other fields (Vitamin E) such as the pharmaceutical, food and cosmetics industries. It can act as a ‘green’ stabiliser” for smokeless powders because its heat flow is stable over time. In this paper, we characterise its stabilisation mechanism by identifying its main degradation products that could form within the propellant in an oxidising environment and in the presence of nitric acid. Liquid chromatography (LC) and gas chromatography (GC) separations are performed in order to dissociate the compounds formed during ageing. Compounds are then analysed by APCI-timsTOF to obtain the molecular ion masses and then perform fragmentation spectra (MS/MS) to characterise their structure. In addition, using preparative HPLC-UV, the degradation products are collected and analysed by NMR, with the aim of identifying the molecules. These identification methods help to unravel the stabilisation mechanism under accelerated ageing conditions. A time-related fluctuation of the degradation products amounts is also observed, which indicates that the decomposition products also have a stabilisation effect. The three major α-tocopherol degradation products are identified as: 2,3-epoxy-α-tocopherylquinone, 5,6-epoxy-α-tocopherylquinone and α-tocored.Next Generation Powde

Identification of the Degradation Products from α‐Ionone Used as Stabiliser in “Green” Propellants through its Lifetime

peer reviewedA stabiliser is added to gun and rocket propellants to react with species responsible for degradation during decomposition. Propellant powder manufacturers and army personnel are confronted with toxicity during powder degradation and must replace current stabilisers with non-toxic molecules. According to the STANAG 4582 (North Atlantic Treaty Organization (NATO) Standardisation Agreement [1]), propellant powders must remain chemically stable for a minimum of ten years when stored at temperatures equivalent to an isothermal storage (25 °C). Single and double base smokeless powders with α-ionone as a “green” stabiliser are tested and the results show that the heat flow is stable over time and that the autocatalysis occurs 2 to 3 times later than in powders with conventional stabilisers. This stabiliser is efficient for all nitrate ester-based propellants. In the present paper, we identify and monitor the evolution of the main degradation products over time by nuclear magnetic resonance (NMR), mass spectrometry (MS) to unravel the stabilisation mechanism under accelerated aging conditions. A time-related fluctuation of their respective amounts (increasing then decreasing, then re-increasing, …) is observed, which indicates that the daughter products have also a stabilisation effect. The three major α-ionone daughter products are identified as: 3-oxo-α-ionone, 4-oxo-β-ionone and 4,5-epoxy-α-ionone