Over the last five years, Defence R&D Canada has explored efficient and clean methods to dispose of Insensitive Munitions. Those munitions, that were designed to withstand various aggressions, are bound to be more difficult to destroy. The results of the work performed to date lead us to believe that the amount of explosives spread during an EOD operation is directly proportional to the insensitiveness of the explosive. Some explosives, such as 3-Nitro-1,2,4triazol-5-one (NTO) or Ammonium Perchlorate, appear to be difficult to detonate completely during blow-in-place operations. Another observation is related to the difficulties encountered using the current EOD methods when Insensitive Munitions must be destroyed in the field. Results of deposition tests ran on snow will be presented and discussed for their significance. During the tests, snow samples are collected and analyzed to determine the residual amounts of IM ingredients after either a high-order scenario, usually obtained when the munition is fired, or a blow-in-place reaction, occurring when a round is destroyed by a donor charge to eliminate the safety risk. During those tests, many different disposal methods were explored, i.e. one or many blocks of Composition C-4, placed at various locations, and shaped charges aimed at various points on the munitions. For some items tested, only a large shaped charge was efficient enough to eliminate any significant spread of explosives, and results obtained with other configurations always showed larger amounts of explosives residues at the detonation point for blow-in-place scenarios. Our conclusion is that new methods have to be designed to efficiently destroy Insensitive Munitions (IM). Those methods will include shaped charges, cutting charges, thermite mixes, high-power lasers and any other technology that will promote clean high order detonations or clean burning reactions. Our efforts identify those new methods will be presented, including one where the formulations are slightly modified to promote clean disposal. It appears that the EOD operators will have to be better equipped, but also possess higher skill levels than in the past to implement those clean methods.

The sensitivity of nanothermites to electrostatic discharge (ESD) has been noted by many authors. In the present work, nanothermites have been prepared using aluminium fuels with oxide (O-Al), palmitic acid (L-Al) and Viton (V-Al) passivation and CuO, Fe2O3 and MoO3 oxidants, as well as binary oxidant mixtures. Fuel- and oxidant-based ESD sensitivity trends of O-Al approximate to L-Al >> V-Al and MoO3 >> CuO approximate to Fe2O3 were observed with binary oxidants affording intermediate sensitivities. In the majority of cases, with the exception of high proportions of MoO3 oxidant, nanothermites containing V-Al fuel were the least sensitive to ESD at > 0.156 J. Resistivity measurements have been made for the fuels and oxidants and follow the trends V-Al >> O-Al approximate to L-Al and MoO3 >> Fe2O3 > CuO. V-Al resistivity of ca. 10(11) vertical bar Omega.cm exceeds that of the oxidants studied. An ESD sensitivity trend, based on a reduced proportion of spark current carried by the aluminium fuel, is proposed and was consistent with the observed ESD and resistivity data.

Nanothermites can provide high energy densities and reaction rates but can also display extreme friction sensitivities. Additives that provide friction modification offer the potential to reduce the friction sensitivity of nanothermites. In the present work, MoS2, graphene, and hexadecane additives were dispersed in MoO3 prior to nanothermite formation with the aim of reducing friction sensitivity. Nanothermites were subsequently prepared using a palmitic acid–passivated nano-aluminum (L-Al) and additive-containing nano-MoO3 by the resonant acoustic mixing of dry powders. In general, the incorporation of additives results in a reduction in friction sensitivity with the baseline minimum ignition friction rising from 10 to 120 N using 0.5% wt/wt micrometer-sized MoS2 or 5% wt/wt hexadecane. However, the relationships between loading and performance are complex and vary by additive; for example, the friction sensitivity dependence using micrometer-diameter MoS2 displays a maximum at 0.5% wt/wt and declines to 7 N using 5% MoS2.

Many nation's armed forces are undertaking efforts to minimize the environmental impacts of live-fire military training. Based on this, the Canadian Department of National Defence has undertaken a project to examine potential alternatives to the use of Composition C4, an RDX-based plastic explosive. Plastic explosives are widely used by all armed forces for both military engineering tasks and explosive ordnance disposal and their use may lead to the deposition of explosives in the environment, namely RDX, in the case of C4. RDX is very stable in the environment, water soluble, and moves relatively rapidly towards surface and groundwater bodies. One option identified as a potential RDX-free formulation is a pentaerythritol tetranitrate (PETN) based plastic explosive, commercially available in Germany and referred to as Seismoplast. In order to measure the environmental impacts of this formulation, a deposition rate study was conducted. These tests consist of evaluating the detonation efficiencies of munitions during detonation scenarios representative of military training. Data generated from these tests are the deposition masses of the energetic components in the explosive filler, which in this case is PETN. To achieve this objective, seven blocks of Seismoplast were open detonated over a surface of pristine snow, and post-detonation surface samples were collected to measure residual PETN. The trial demonstrated that less than 1 x 10(-7)% of PETN is deposited upon detonation of Seismoplast. The energetic material deposition rates obtained in this trial are much lower than rates obtained for the RDX-based C4 currently in-service within Canada. Switching from a RDX-based plastic explosive to one based on PETN may be an interesting option through which the Department of National Defence can reduce the environmental impact of its activities.

For the last two decades, DRDC Valcartier has been involved in the synthesis of energetic thermoplastic elastomers (ETPEs) based on Glycidyl Azide Polymers (GAPs). These ETPEs are copolyurethane thermoplastic elastomers, physically crosslinked rubbery materials that can be dissolved in organic solvent and recycled or can be used as the binder for insensitive melt cast explosives. The mechanical properties of these ETPEs were adjusted to serve as binders in melt cast explosive formulations and give the insensitive character to the formulations. An insensitive explosive named "XRT" for "eXperimental Rubbery TNT" was developed and led directly to the development of a new insensitive recyclable green explosive (GIM). A major project named "RIGHTTRAC" for "Revolutionary Insensitive Green and Healthier Training Technology with Reduced Adverse Contamination" was initiated two years ago and aims at producing a greener weapon. Work was conducted on XRT and GIM explosives to test their performance and sensitivity, their fate and behaviour into the environment, their recycling and value as ingredients to produce a greener munitions based on these concepts. Since ETPEs are recyclable, the ease of recycling and reuse of the ingredients of the new formulations at the end of their life cycle was studied. This paper will describe the syntheses of the ETPEs, the preparation of the XRT and GIM explosives and the results obtained so far describing their properties, insensitive character, recycling, fate and behaviour of formulations and ageing testing.

The revolutionary insensitive, green, and healthier training technology with reduced adverse contamination (RIGHTTRAC) program is a 5-year technology demonstration program (TDP) aimed at showing that green and insensitive munitions have better properties than current munitions, and that it is feasible to implement safer weapon solutions that would ease the environmental pressure on ranges and training areas and decrease the health hazards for the users. The goals of this TDP are to reach a near-zero dud rate and to eliminate the potential for research development explosive (RDX) contamination as well as the use of toxic and carcinogenic compounds. This will be done by performing significant improvements to the fuzing system, the main explosive charge and the gun propellant. The vehicle used for this demonstration is a 105-mm army artillery munition (high-explosive M1), currently filled with Composition B (a 60:40 RDX:TNT mix) and using a single-base gun propellant (M1 formulation). The aim of this communication is to provide an overview of the project and to describe the steps taken to evaluate the environmental properties of the chosen propellant and explosive formulations. At its completion, it is believed that this project will have provided the required data to assess the long-term effects of the munitions on the environment right at an early stage of the weapon development cycle, and that this can be cost effective in the long run. This will help sustain military training while preserving our resources, as well as shaping the future of weapon system development.

This paper uses the thermochemical behaviour of reacting species to differentiate between the combustion of gas phase and condensed phase detonation products in the fireball of an explosion. Experiments were carried out involving the detonation 15g charges of C-4 and Detasheet-C explosives in a closed vessel. The initial partial pressure of oxygen in the vessel was varied in order to control the extent of the secondary afterburn reactions, and the total heat release was measured using the calorimeter that contained the closed vessel. A simple model that independently describes the evolution of heat from the gas phase and condensed phase detonation products as a function of oxygen consumption was developed, and was used to show that condensed phase products react much more effectively in the fireball than gas phase reactions, because the transport properties of particulates entrained in a turbulent flow gives them an advantage when it comes to the manner in which they mix with the surrounding air. An additional set of trials employing the entrainment of an external combustible material further confirms the importance of particle combustion in explosive fireballs.

A short experimental study demonstrated that the plate dent test is very sensitive to the last few centimeters of explosives at the bottom of the cylinders. The tests were performed by simply detonating an explosive cylinder with a small thickness (12.7-25.4 mm) of a different explosive (faster, slower, inert) at the bottom. The study will present how those small thicknesses influence the dent depth and hence the reported performance. Cylinders of explosives were cast and then cut to determine the extent of sedimentation of the HMX particles. Densities were taken at various places and concentrations of HMX were extrapolated from those. It was found that there was a difference of 22% in the percentage of HMX from the bottom and the top of the cylinder (66% vs. 44%; theoretical average was 52.8%). The explosive at the bottom was then significantly different and more powerful than the one at the top. The study will also demonstrate how the situation can be worse in real artillery shells. Given the results of the plate dent experiments reported before, it will be demonstrated how in theory one could be misled on the plate dent test by letting particles settle. Simple precautions can be taken to eliminate this variable and to ensure that the results of the plate dent test are meaningful. It also serves as a reminder that the composite explosives that we test, especially the melt-cast explosives, have large variations in their composition from sample to sample.

This paper discusses the development of a fiber optic probe that can obtain temperature measurements from the interior of explosive fireballs, which are generated when unreacted detonation products react with oxygen in the surrounding air. Signatures of the thermochemical environment and chemical species involved can often be deduced from their light emissions, but the limited optical depth of fireballs means that remote sensing techniques can only sample emissions from the outer shell. By developing a protected fiber optic probe that can be placed adjacent to an exploding charge, giving it the ability to become enveloped by the fireball, the thermal radiation from the interior of the fireball can be sampled. Measurement from five shots using Detasheet-C explosives were carried out and could be obtained over the course of about 20 ms. Blackbody-type radiation with temperatures in the 1600 K to 1900 K range were observed, peaking at about 1850 K after 12 ms. The magnitude and time behavior of the temperature was not significantly different when taken at different locations within the fireball, indicating that temperature is fairly uniform throughout. The lack of specific spectral emission lines implies that in the interior of the fireball any combustion that occurred was probably primarily with carbonaceous soot, though differences in optical depth at different locations in the fireball indicate that it was much more fuel-rich closer to the center.

For years, DRDC Valcartier has invested efforts at developing energetic thermoplastic elastomers (ETPEs) based on linear glycidyl azide polymers to serve as energetic binders and replacing the thermoset matrix in insensitive explosives. It was first observed that introducing ETPEs in their melted form was not an easy task because high and nonpractical viscosities were encountered in the process. It was discovered that 2,4,6-trinitrotoluene (TNT) could be used in its melted form as an organic solvent to dissolve the ETPE and allow its incorporation into the insensitive formulations. Using these ETPEs led to the development of a greener insensitive melt-cast explosive named green insensitive munitions (GIM). This new explosive was intensely studied. The mechanical properties and proportions of ETPE in the formulations were optimized to obtain a melt cast with low viscosity while leading to an insensitive explosive formulation. Work was conducted on GIM explosives to test their performance and sensitivity, fate and behavior with regard to the environment, their recycling capability, and toxicity. This paper describes the results of all experiments conducted so far to test these aspects of GIM explosives. The preparation of the ETPEs and the GIM explosives will also be briefly described.

Traditionally, the evolution and rise of the dust and soot cloud resulting from high explosive detonations has been divided into two stages, with specific models used for each stage. In this study, based on the assumption that cloud formation progresses smoothly from stage to stage, a simple cloud rise model has been developed based on three sets of field tests of high explosive detonations (25×10−3 to 4.5 kg of detasheet and C-4). This model provides a good fit to observations and measurements of clouds from detonations both at ground level and 1 m above the ground. It was also found that the detonation height has a noticeable influence on cloud rise before reaching its effective height, but the influence is minor on the subsequent cloud rise.

The decomposition of urea nitrate (UN) was studied using adiabatic and non-isothermal calorimetry techniques. Gas species released were identified and quantified in situ using TG-infrared spectroscopy/mass spectrometry and molar proportions of these gases were evaluated. A decomposition mechanism at high temperature was proposed based on the nature and sequences of gaseous species observed combined with literature data on decomposition of intermediate products formed. Non-isothermal decomposition kinetics of urea nitrate were measured using variable heating rates to give activation energies E/kJ mol(-1) = 206 and 113 with preexponential factors Ln Z/min(-1) = 47 and 21, in a closed and open system, respectively. In these systems the major UN decomposition step is strongly coupled to an endothermic dissociation reaction. Species remaining after this exothermic decomposition showed only minor exothermicity at higher temperatures. This is contrasted with the onset to adiabatic decomposition which occurred similar to 30 degrees C below the apparent melting point (155-156 degrees C), and where solid (condensed) species are available. (C) 2011 Elsevier B.V. All rights reserved.

Aging and degradation of urea nitrate below the melting point, at 100 degrees C, was studied by using thermal analysis and spectroscopic methods including IR, Raman, H-1 and C-13 NMR techniques. It was found that urea nitrate was completely degraded after 72h at 100 degrees C into a mixture of solids (69%) and released gaseous species (31%). The degradation mechanism below the melting point was clearly identified. The remaining solid mixture was composed of ammonium nitrate, urea and biuret while unreacted residual nitric and isocyanic acids as well as traces of ammonia were released as gaseous species at 100 degrees C. The thermal stability of urea nitrate, under extreme storage conditions (50 degrees C), was also examined by isothermal nano-calorimetry. (C) 2011 Elsevier B.V. All rights reserved.

This paper explores how particles interact with one another in the fireball of an explosion. The dispersal of a tracer, powdered lanthanum oxide (as La2O3), is investigated, as are the effects of the entrainment of soil in the explosive fireball. Experiments have involved detonating 15 g charges of C-4 in a sealed 5 L detonation vessel under atmospheres of nitrogen or air, and in contact with quartz sand, black earth, or clay. It has been found that particle interactions serve to increase the overall size of particles because the particles fuse together, deposit onto one another, and form agglomerates. As bigger particles are heavier and less able to stay suspended in the air, particle interactions with soil serve to decrease the quantity of the powdered tracer that remains aerosol sized. Essentially, particle interactions in the fireball reduce the number of particles that are small enough to stay suspended in the air.

The objective of this paper is to show that explosives may potentially be detected by passive standoff FTIR radiometry. It is demonstrated that many explosives exhibit a signature (fingerprint) in the longwave infrared (LWIR) region (i.e., 8 – 14 μm). Simulations using the radiative transfer model, MODTRAN4, clearly suggest that such materials can be identified when a thermal contrast exists between the material and its environment. The explosives considered in this study include octogen (HMX), trinitrotoluene (TNT), cyclonite (RDX), and the plastic explosives, C-4 and Detasheet-C. In addition, passive FTIR measurements of HMX have been performed in the field at standoff distances up to 60 m. The development of a passive standoff detection capability based on FTIR radiometry may be a potentially useful addition to the arsenal of measurement techniques that currently exist for the detection and identification of explosive threats.

An attempt was made to introduce CL-20 in a TNT/energetic thermoplastic elastomer (ETPE)-based melt cast formulation, to obtain an insensitive composition with reduced adverse environmental properties. A loading limit of 42% w/w of CL-20 in melted TNT was observed, while it should have been around 70%. This paper describes the investigation that was undertaken to understand the observed phenomena. It was demonstrated that CL-20 undergoes structural alterations in melted TNT. The relative solubility of CL-20, RDX and HMX in melted TNT was determined and the alpha-, beta-, gamma- and epsilon-CL-20 were prepared and characterized using Raman spectroscopy and DTA. CL-20 was mixed in melted TNT, as much as 4.2 g of CL-20 dissolved in 100 g of TNT. This allowed a transformation from epsilon to beta-CL-20 and a modification of CL-20 particle size and distribution. The later modification induced a raise in CL-20 specific surface and was responsible for the loading limit, while the transformation to beta- CL-20 caused an increase in sensitivity and a decrease in density. This indicates that the use of CL-20 in TNT melt cast is not promising. Our study also showed that CL-20 is sensitive to morphological transformations, which should be taken into consideration in future processing using this compound.

Ultrafine metal powders have been identified as very promising fuels for future energetic material formulations. However, the large specific surface area that gives these powders a high reactivity also makes them particularly difficult to remain in a nonoxidized state. They also agglomerate easily during compounding processes due to strong particle-to-particle interactions. The coating of the particles with a polymer may offer a solution to these problems. We investigated two in situ polymerization processes using thermoplastic and thermoset coatings. Polyolefins such as polyethylene and polypropylene were obtained using a modified Ziegler-Natta reaction scheme. This process was found to be flexible enough to control the amount of polyethylene grafted onto the powders. The second type of coating was based on polyurethane chemistry. Nanometric-sized aluminum and boron powders were treated and characterized by means of thermogravimetric analysis, electronic microscopy, and x-ray photoelectron microscopy. The barrier properties of the polymer layer grafted onto the particles were evaluated using a chemical digestion method and thermoanalytical techniques. Polyethylene-coated particles showed a better resistance to early aging under stringent conditions of humidity and temperature and therefore would be expected to demonstrate a longer shelf life in a propellant formulation.

Ultra-fine metallic particles have demonstrated recently their potential in tailoring the performance of energetic materials. DRDC Valcartier has explored methods to create controllable nanometric coatings on metallic particles and has opted to use polymers to treat the particles. Those coatings can have multiple positive effects. For example, in the case of aluminium, small particles are very reactive and tend to cause interations with the surrounding media. One example is the ageing of aluminium nanoparticles in the presence of air and humidity. Ultra-fine particles age much faster than micron-size particles. The long-term stability of energetic material mixes containing ultra-fine particles will be affected by this reactivity, and coatings would help to solve this problem. Another example is the interaction of aluminium nanoparticles with nitramines that causes gassing. Three coating methods will be presented: by thermoplastics using a Ziegler-Natta reaction, by thermosets through a polycondensation reaction initiated at the surface of the particles, and in-situ coating of particles by on-line polymerization during the plasma production of powders. The results of coating experiments using those methods will be presented. It will be shown that, for aluminium particles, adequate dispersion is a challenge and affects the results of the coating experiments. To assess the performance of the coating methods, ageing tests were carried out on coated and uncoated nanoparticles. The results of ageing tests with those methods will be presented and compared. It will be shown that the polymer coatings reduce significantly the loss of active metal content during accelerated ageing tests. Since the purpose of the powders is to be used in energetic materials, a study on the rheological effects of the coated particles in polymeric solutions will be presented as well. Coated particles increase the relative viscosity of HTPB-Al solutions by a factor of 100 at low shear rates, but much less with PPG.

Ultrafine aluminum powder was identified as very promising fuels for novel energetic materials formulations. However, the large specific surface area of this powder facilitates its oxidation and greatly reduces its shelf life. Therefore, different coating processes were proposed to solve this problem. The rheology of viscous suspensions of nanoparticles still remains poorly understood and the effect of the coating of such particles on the flow behavior is even more difficult to assess. We have studied the rheology of ultrafine aluminum suspensions in three low molecular weight polymers of different viscosities: a hydroxy-terminated polybutadiene, a polypropylene glycol, and a polysiloxane. The nanosize aluminum powder was previously coated by a thin layer of high-density polyethylene using an in situ polymerization process. The rheological characterization of the suspensions was conducted by the means of steady and oscillatory shear flow measurements for noncoated and coated particles. The effect of the coating process on the rheology of the suspensions is discussed in terms of the interactions between the particles and the suspending fluids.