Semtex 1A Research Articles

Applicability limits of the DAX test in plastic bonded explosives

The Disc Acceleration eXperiment (DAX) is one of the most recent experimental methods of performance characterization of new energetic materials. A cylindrical explosive charge accelerates a thin metallic disc and its velocity is measured continuously using photonic Doppler velocimetry. The detonation velocity is measured simultaneously. The DAX test can be used to obtain the Chapman-Jouguet (CJ) detonation pressure and to describe detonation products expansion using reduced amount of explosive. A series of DAX tests was performed at various charge diameters and disc thicknesses with Semtex 1 A plastic bonded explosive and sensitized nitromethane. The DAX-like evaluation was also applied to previously measured data of Semtex 1A and A-IX-1 explosives. The optimum disc thickness is determined by the disc to explosive mass ratio of 0.01–0.08. The repeatability of the Semtex 1 A detonation pressure results is about four times lower compared to the pressed and liquid explosives.

High Performance Sheet of PBX based on NTO

3-nitro-1,2,4-triazol-5-one (NTO) is a low sensitive high explosive which has been used in the formation of low sensitive ammunitions. In this study, the preparation method of NTO explosive was discussed. A sheet of PBX on the basis of NTO bonded by HTPB binder matrix was prepared (NTO-PBX). The formulation is investigated for explosive properties to understand the influence of NTO on the performance of the PBX sheet. Impact and friction sensitivities of NTO-PBX, heat of Combustion and Detonation velocity were specified. EXPLO5 code, version 5.04, was utilized to calculate the theoretical detonation characteristics of NTO-PBX. For comparison, Data-sheetC, EPX-1, Semtex 1A and Formex P1, were also studied. By comparing the obtained results, confirmation of some relationships was investigated. The detonation velocity of the NTO sheet explosive was the highest of all the studied samples. The experimental and calculated results of NTO-PBX and the other compositions are in a good agreement.

Spectroelectrochemistry of Non-Aromatic Explosives in Acetonitrile and the Influence of Superoxide

The spectroelectrochemistry of non-aromatic explosive compounds, namely two nitramines (RDX and HMX), a nitrate ester (PETN), and a plastic explosive composite (Semtex 1A) in acetonitrile (AN) is reported. The redox behavior of these compounds is studied using cyclic voltammetry while monitoring changes in UV absorbance to identify transient intermediates and product species. In search of a low-cost solution-phase detection technique for explosives, we compare the spectroelectrochemistry of these compounds in the presence and absence of naturally dissolved oxygen (2 mM in AN), where the superoxide radical is co-electrogenerated during analyte reduction. Free superoxide yields a prominent UV signal in this medium (λmax = 250 nm) that the explosives’ nitro or methylene groups attenuate stoichiometrically. Overlapping UV spectra of multiple species are deconvoluted using a new strategy, spectral regional baselining, for time- and potential-resolved spectroelectrochemical (SEC) analysis. SEC data for nitrite (NO2 -), nitrate (NO3 -), and nitromethane (CH3NO2) were also collected to support proposed reaction mechanisms for the transformation of explosives that include superoxide adducts and dimerized azoxy reduced intermediates. The findings expand the understanding of high-explosive solution-phase chemistry and offer a route to novel signal transduction for (electro-)chemical sensors for energetic materials.Figure 1. Spectroelectrochemistry of PETN in aerated acetonitrile with regions denoted for differential baseline analysis. (a) 3-D projected cyclic voltammogram (black) with UV absorbance from relevant wavelength (red, unscaled) as a function of time and potential; (b) full spectra (time domain) during cyclic voltammogram. Figure 1

Electroanalysis and Spectroelectrochemistry of Nonaromatic Explosives in Acetonitrile Containing Dissolved Oxygen.

In search of a rapid, low-cost, and solution-phase detection technique for explosives, the (spectro-)electrochemistry of compounds from two major nonaromatic classes, namely nitramines (RDX and HMX) and nitrate esters (pentaerythritol tetranitrate (PETN) and the plastic explosive composite Semtex 1A) in acetonitrile (AN) is reported. In electrochemical screening, 5 μg of explosive material was detectable in 10 s by multicomponent cyclic voltammetric (CV) analysis on unmodified glassy carbon under ubiquitous environmental influences (i.e., trace water and dissolved oxygen). The explosives were identified with high recoveries under a battery of proof-of-concept testing scenarios in various matrices. In AN containing naturally dissolved oxygen (approx. 2 mM), the superoxide radical is co-electrogenerated during analyte reduction. Free superoxide yields prominent signals that the explosives attenuate quantitatively. To gain further insight into the electrochemical transformation mechanism, spectroelectrochemistry was employed to monitor changes in ultraviolet (UV) absorbance during CV and identify transient intermediates and product species, which could be targeted by future chemical sensors. Overlapping UV spectra of multiple species are deconvoluted using a new strategy, spectral regional baselining, for time- and potential-resolved spectroelectrochemical (SEC) analysis. This study shows that dissolved oxygen, hitherto an interferent purposefully removed from the solution, can be exploited advantageously in electrochemical sensing. The work expands our understanding of high-explosive solution-phase chemistry and offers a novel route to signal transduction for the sensing of energetic materials.

Spectroelectrochemistry of Explosive Aliphatic Nitro Compounds

The spectroelectrochemical behavior of non-aromatic explosive compounds, namely two nitramines (RDX and HMX), a nitrate ester (PETN), and a plastic explosive composite (Semtex 1A) in acetonitrile is reported. The electrochemical behavior of these compounds using cyclic voltammetry is performed while monitoring the UV absorbance spectra of transient and product species in situ. In search of a low-cost solution-phase detection technique, we compare the spectroelectrochemistry of these compounds in the absence and presence of naturally dissolved oxygen (~2 mM in AcN), where the superoxide radical is co-electrogenerated during explosive analyte reduction. Free superoxide yields an intense UV signal in this medium (λmax = 250 nm) that the explosives attenuate to varying degrees. We deconvolute UV spectral data through time- and potential-resolved analyses coupled with electrochemical data. It is found that superoxide interacts with the explosives through unique, previously unreported ways, likely due to strongly polarized electrostatic potentials across the poly-nitro aliphatic molecules. Reaction mechanisms will be proposed and the findings expand the understanding of high-explosive solution chemistry and offer a route to novel signal transduction for (electro-)chemical sensors for energetic materials.Figure 1. Spectroelectrochemistry of the control solution, aerated 0.1 M TBAPF6 in acetonitrile. (a) CV (ν = 50 mV s-1) in time and potential domains with the superoxide absorbance at 250 nm plotted for qualitative visualization; (b) time-resolved, full-spectrum UV data recorded during the CV. Figure 1

The Influence of the Explosive Ordnance Disposal Suit on the Bomb Squad Safety

The article presents a study on the influence of shock wave on a Hybrid III anthropomorphic test device (ATD HIII) equipped with an explosive ordnance disposal (EOD) suit. The shock wave was generated by the detonation of SEMTEX 1A plastic explosive, formed in the shape of a 250 g, 500 g, and 840 g sphere, at a distance of 0.5 m, 1 m, and 2 m. The use of ATD allowed for determining parameters of damage to the human body as a result of the impact of overpressure wave. The experiments also included a measurement of such parameters as forces and moments on lower extremi-ties, acceleration of head and pelvis, and forces and moments on a neck simulator. Chest Wall Velocity Predictor (CWVP), calculated from the pressure measured on ADT’s chest, was adopted as the most critical parameter. It was revealed that the allowed distance of explosion of a 500 g pure explosive, which does not cause exceeding the allowed parameters, is 1 m.

Characteristics of a New Plastic Explosive Named EPX-1

EPX-1 is a new plastic explosive (in the research stage) which has been prepared for military and civilian applications. EPX-1 explosive contains pentaerythritol tetranitrate (PETN) with different particle size as explosive filler bonded by nonenergetic thermoplastic binder plasticized by dibutyl phthalate (DBP). In this paper, the production method of EPX-1 was described. The crystal morphology was studied by scanning electron microscope (SEM). Heat of combustion was determined experimentally. The compatibility of PETN with the polymeric matrix was studied by vacuum stability test. Sensitivities to impact and friction were measured. The detonation velocity was measured experimentally and the detonation characteristics were calculated by EXPLO5 thermodynamic code. For comparison, Semtex 1A, Semtex 10, Formex P1, and Sprängdeg m/46 were studied. It was concluded that PEX-1 has compatible ingredients, it has the highest detonation velocity of all the studied plastic explosives, and its sensitivity is in the same level of the studied plastic explosives except Semtex 1A.

The effect of polymer matrices on the thermal hazard properties of RDX-based PBXs by using model-free and combined kinetic analysis

In this paper, the decomposition reaction models and thermal hazard properties of 1,3,5-trinitro-1,3,5-triazinane (RDX) and its PBXs bonded by Formex P1, Semtex 1A, C4, Viton A and Fluorel polymer matrices have been investigated based on isoconversional and combined kinetic analysis methods. The established kinetic triplets are used to predict the constant decomposition rate temperature profiles, the critical radius for thermal explosion and isothermal behavior at a temperature of 82°C. It has been found that the effect of the polymer matrices on the decomposition mechanism of RDX is significant resulting in very different reaction models. The Formex P1, Semtex and C4 could make decomposition process of RDX follow a phase boundary controlled reaction mechanism, whereas the Viton A and Fluorel make its reaction model shifts to a two dimensional Avrami–Erofeev nucleation and growth model. According to isothermal simulations, the threshold cook-off time until loss of functionality at 82°C for RDX-C4 and RDX-FM is less than 500 days, while it is more than 700 days for the others. Unlike simulated isothermal curves, when considering the charge properties and heat of decomposition, RDX-FM and RDX-C4 are better than RDX-SE in storage safety at arbitrary surrounding temperature.

The Behavior of the Advanced Materials for Blast Energy Absorption under Low and High Velocity Load

This paper describes experimental investigation on the response of new advanced materials to low and high velocity load. Foams were designed using two types of porous lightweight spherical raw materials with dimensions of 30-100 μm, combined with polymer matrix. Prism shaped specimens were prepared and loaded to obtain physical-mechanical parameters bulk density, compressive and flexural strength under quasistatic load and impact strength. The load-displacement data were captured. The slab specimens were prepared of selected materials, covered with a layer of ballistic laminates on both surfaces to form the sandwich element and were subjected to the blast load of 100 g Semtex 1A from a distance of 10 cm. Blast energy absorption was measured on test rig STAND T0-B according to methodology M-T0-B VTÚO 10_09.

Effect of Different Polymeric Matrices on Some Properties of Plastic Bonded Explosives

AbstractMatrices based on polyisobutylene (PIB), polymethyl‐methacrylate (PA), Viton A 200, Dyneon FT 2481 (Fluorel), and polydimethyl‐siloxane binders were studied as desensitizers. A series of plastic explosives (PBXs) were prepared, based on four different nitramines, namely RDX (1,3,5‐trinitro‐1,3,5‐triazinane), β‐HMX (β‐1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocane), BCHMX (cis‐1,3,4,6‐tetranitro‐octahydroimidazo‐[4,5‐d]imidazole) and ε‐HNIW (ε‐2,4,6,8,10,12‐hexanitro‐2,4,6,8,10,12‐hexaazaisowurtzitane, ε‐CL‐20), bonded by the matrices mentioned. For comparison, pentaerythritol tetranitrate and certain commercial explosives based on it, Semtex 1A, Semtex 10 and Sprängdeg m/46, were used. Detonation velocities, sensitivities to impact and friction, and peak temperatures of thermal decomposition by differential thermal analysis technique (DTA) for all the explosives studied were determined. Heat of detonation was calculated by means of a thermodynamic calculation program (EXPLO 5 code). Fluoroelastomers have a neutral to positive effect on the thermal stability of nitramines and they have a significant effect on decreasing the friction sensitivity. However, their anti‐impact efficiency is the lowest in this study although they have a positive effect on performance of the corresponding PBXs. PA and PIB matrices markedly decrease thermal stability of nitramines, the anti‐impact influences of PIB‐binders are better than those of PA‐binders, while PA‐binders have a higher anti‐friction effect and slightly less negative influence on the performance of the PBXs in comparison with PIB mixtures. The polydimethyl‐siloxane matrix has a neutral effect on thermal stability of the nitramines studied, it has an influence on the volume thermochemistry of detonation comparable with that of fluoroelastomers although it does not provide comparable performance, and its corresponding PBXs have optimum sensitivity parameters.

Semtex 1A and H negative ion resonances for explosives’ detection

We present the results obtained in dissociative electron attachment to Semtex in the gas phase by making use of a crossed electron-molecular beam experiment. Energy dependence of partial cross sections has been measured in an electron energy range from 0 to 12 eV with an energy resolution of ∼80 meV. Semtex 1A and H are mixtures of two other explosives, i.e., royal demolition explosive – RDX (hexogen) and pentaerythritol tetranitrate – PETN (pentrite), appearing in different fractions. In fresh samples product anions from both explosives can be detected together with anions originating from volatile markers. After some time we only observe product ions formed upon dissociative electron attachment to PETN, which are not observed for a mixture of pure RDX and PETN. For both Semtex samples, an additional anionic feature at 210 m/ z can be assigned to the binder butyl rubber.

Study of Plastic Explosives based on Attractive Cyclic Nitramines Part I. Detonation Characteristics of Explosives with PIB Binder

AbstractFour plastic explosives based on energetic nitramines and a non‐energetic binder were prepared and studied. The nitramines were RDX (1,3,5‐trinitro‐1,3,5‐triazine), HMX (1,3,5,7‐tetranitro‐1,3,5,7‐tetrazine), BCHMX (cis‐1,3,4,6‐tetranitro‐octahydroimidazo‐[4,5‐d]imidazole) and HNIW (ε‐2,4,6,8,10,12‐hexanitro‐2,4,6,8,10,12‐hexaazaisowurtzitane, ε‐CL‐20). The binder was in all cases polyisobutylene (PIB) as in the standard composition C‐4. These powerful plastic explosives were compared to standard PETN‐based commercially available explosives Semtex 1A and Sprängdeg m/46. The detonation velocities were experimentally measured and compared to the ones calculated by the Kamlet–Jacobs method, CHEETAH and EXPLO5 Codes. The experimental detonation velocities as well as the calculated detonation parameters decrease in the following order: HNIW‐PIB>HMX‐PIB≥BCHMX‐PIB>RDX‐PIB>Sprändeg m/46≥Semtex 1A. Urizar coefficients for the various binders were calculated from experimental data.

Characterization of Three Types of Semtex (H, 1A, and 10)

AbstractSolid phase microextraction and solvent extraction were used with GC/MS to determine the vapor and compositional profile of three samples of Semtex (1A, H, and 10). Semtex is reported to contain PETN and/or RDX, along with plasticizers, binding materials, and fuel oil components. In an effort to differentiate and compare these three variations of Semtex, this report summarizes the headspace and solvent extraction results for each material. Components that can be used to differentiate varieties of Semtex were identified and all three Semtex profiles were distinguished.

The using of LS-DYNA for the simulation of heat transfer in explosives

The using of FEM and especially LS-DYNA3D code for the simulation of a heat transfer during the heating of the explosive charge is discussed in this paper. The characterization of explosive material properties (density, thermal conductivity, specific heat, heat of decomposition, the decomposition kinetics) is described. LS-DYNA3D code is used for the fitting of the appropriate kinetic model and for the simulation of the heat transfer during the slow cookoff test. The results of simulations are compared to the experimental values for the SEMTEX 1A plastic bonded explosive.

Identification of High Explosives Using Single-Particle Aerosol Mass Spectrometry

The application of single-particle aerosol mass spectrometry (SPAMS) to the real-time detection of micrometer-sized single particles of high explosives is described. Dual-polarity time-of-flight mass spectra from 1000 single particles each of 2,4,6-trinitrotoluene (TNT), 1,3,5-trinitro-1,3,5-triazinane (RDX), and pentaerythritol tetranitrate (PETN), as well as those of complex explosives, Composition B, Semtex 1A, and Semtex 1H, were obtained over a range of desorption/ionization laser fluences between 0.50 and 8.01 nJ/microm2. Mass spectral variability with laser fluence for each explosive is discussed. The ability of the SPAMS system to identify explosive components in a single complex explosive particle ( approximately 1 pg) without the need for consumables is demonstrated.

Thermal Decomposition of Pentaerythritol Tetranitrate

AbstractA chemical kinetic model for the thermal decomposition of the solid high explosive pentaerythritol tetranitrate (PETN) is developed for prediction of times to thermal explosion using the Chemical TOPAZ heat transfer computer code. The model is based on times to thermal explosion measured in a new One Dimensional Time to Explosion (ODTX) apparatus. ODTX experiments are reported for pure PETN and for Semtex 1A. The pure PETN results are accurately modeled using a four reaction decomposition process in which an autocatalytic process produces intermediate reaction product gases, which subsequently react in a second order gas phase process to produce the final reaction products. Semtex 1A exhibits longer times to explosion than PETN at low temperatures, indicating that its endothermic binder decomposition absorbs heat produced by PETN decomposition. This binder reaction is modeled as a first order endothermic process. Three experiments on 5.08 cm diameter unconfined cylinders of PETN ramp heated to explosion at different rates are reported. The PETN model accurately predicts the thermocouple records and explosion times for these unconfined experiments in which only intermediate gaseous products can form.