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Co-crystallization of cyclic nitramines with sterically crowded molecules, i.e., ε-2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (ε-CL-20) with cis-1,3,4,6-tetranitrooctahydroimidazo-[4,5-d]imidazole (BCHMX), is very difficult, but the co-agglomeration (slurry method) of their mixed micro-co-particles gives very good results. CL-20 is present in these co-agglomerates (CACs) in its β-form. Besides the medium of co-agglomeration, also the molar ratio is very important; it is possible to obtain β-CL-20/BCHMX (molar 1.8/1.0) with the impact sensitivity of 14.9 J. The density of these CACs approaches 99.6% of the density of the β-CL-20 crystals. Based on the application of the Raman, FTIR and PXRD techniques, it has been proved that the agglomeration of CL-20/BCHMX micro-co-particles leads to the formation of CACs mostly with the properties of co-crystals (CCs). This also seems to be confirmed by the relationships between the heat of formation and ring-deformation vibrations (in plane) and between the impact sensitivity and the difference in the asymmetric NO2 stretching vibrations in pure CL-20 and its CACs. The CACs studied have lower detonation energies than would be consistent with the percentage of individual coformers in these crystals. An examination of the most sensitive CACs (1.2 J) as a detonator primer has shown the absence of its required acceleration capabilities in the given detonator design. A comparison with literature data and our unpublished preliminary results indicates that the CACs and CCs of this type could have potential beneficial applications in propellants. [ABSTRACT FROM AUTHOR]

Mixtures of 1,3,5-trinitroso-1,3,5-triazinane (TMTA) with 1,3,5-trinitro-1,3,5-triazinane (RDX), cis-1,3,4,6-tetranitro-octahydroimidazo-[4,5-d]imidazole (BCHMX) and ɛ-2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20), respectively, have been investigated by DSC and TGA techniques. It has been found that there are two endothermic peaks at about 96 °C and 107 °C, due to polymorphic transition and melting of TMTA, whereas only small endothermic peaks were observed in the temperature region of 92.8–95.0 °C for mixtures of RDX-TMTA, BCHMX-TMTA and CL-20-TMTA. These differences in exothermic temperatures of the pristine TMTA versus its mixtures could be a result of co-crystals formation. Moreover, only one complex step for decomposition of TMTA and RDX-TMTA was observed, while at least two steps were found for BCHMX-TMTA and CL-20-TMTA mixtures. TGA measurements showed that a mass loss of TMTA begins at 89.3 °C and has a peak temperature of 185.9 °C. In contrast, the mass loss of RDX-TMTA mixture begins at 142.9 °C and has a peak temperature of 227.6 °C, evidently showing a behavior of a single compound. On the other hand, the activation parameters for the first step decomposition of the BCHMX-TMTA (2.355 J g −1 ) and CL-20-TMTA mixtures were found to be very close to that of TMTA (1.320 J g −1 ), strongly indicating that most probably TMTA undergoes decomposes during the first decomposition steps of these mixtures. [ABSTRACT FROM AUTHOR]

Highlights: [•] The thermal behavior of Fluorel bonded explosives (PBXs) containing cyclic nitramines have been investigated. [•] Their decomposition kinetics parameters have been calculated by modified Kissinger–Akahira–Sunose (KAS) method. [•] It has been found that Fluorel matrix has a significant effect on the activation energy distribution of cyclic nitramines. [•] The Fluoropolymer is chemical incompatible cyclic nitramines with crowded molecule such as BCHMX. [Copyright &y& Elsevier]

Highlights: [•] The effects of Viton A binder on the thermal behavior of cyclic nitramines have been investigated by using non-isothermal techniques. [•] The decomposition kinetics parameters have been calculated by modified Kissinger-Akahira-Sunose method. [•] As a thermostable polymer, Viton A could inhibit the initial autocatalysis effect of cyclic nitramines. [•] It would improve the thermal stability of corresponding PBXs containing RDX, β-HMX and ε-CL-20. [Copyright &y& Elsevier]

The zero-order reaction rates (specific rate constants) for isothermal decomposition at 120 °C of plastic bonded explosives (PBXs) were measured by means of the Czech vacuum stability test, STABIL. The PBXs are based on 1,3,5-trinitro-1,3,5-triazinane (RDX), β-1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX), cis-1,3,4,6-tetranitro-octahydroimidazo-[4,5- d] imidazole (BCHMX), and ε-2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (ε-HNIW, ε-CL-20) with 9 wt.% of the C4 type matrix, i.e., a matrix containing 25 wt.% of polyisobutylene, 59 wt.% of dioctyl sebacate and 16 wt.% of the oil HM46. Dependencies were found between the specific rate constants mentioned and the detonation velocities of the PBXs, and consequently between these constants and the impact of pure explosive fillers, i.e., RDX, β-HMX, ε-HNIW, RS-ε-HNIW, and BCHMX and, at the same time, the corresponding PBXs. The results obtained are compared with those from a recent analogous study of PBXs using an SBR (Formex P1) binder which could increase the PBXs' reactivity in comparison with C4 matrix. These results also help to dispel a widely held view about HNIW being a relatively sensitive explosive. [ABSTRACT FROM AUTHOR]

Abstract: The thermal behavior and decomposition kinetics of C4-bonded PBXs based on some attractive cyclic nitramines were investigated by means of nonisothermal TG and DSC techniques. It has been shown that only a single decomposition process has been observed for RDX-C4 while an obvious two-step process for mixture of BCHMX-C4 CL-20-C4, and HMX-C4. The onset temperature of the exotherms were observed at 216.3, 238.7, 279.2 and 236.7°C with the peak temperatures of 235.1, 279.0, 231.2 and 233.7°C for RDX-C4, BCHMX-C4, HMX-C4 and CL-20-C4, respectively. Their corresponding exothermic decompostion processes were covered by energy changes of 1749, 1938, 1213 and 2639Jg−1, which are lower than that of their pure cyclic nitramines. It was also proved that C4 matrix has significant effect on the activation energy distribution of RDX, BCHMX and CL-20, whose initial autocatalysis effect was inhibited or weakened. With regard to HMX-C4, the activation energy of its initial step is much lower than that of the second step. [Copyright &y& Elsevier]

Thermal behavior and decomposition kinetics of Formex-bonded PBXs based on some attractive cyclic nitramines, such as 1,3,5-trinitro-1,3,5-triazinane (RDX) and 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX). Actually, cis-1,3,4,6-tetranitrooctahy droimidazo-[4,5-d]imidazole (BCHMX) and 2,4,6,8,10,12-hexanitro-2,4,6,8,10, 12-hexaazaisowurtzitane (CL-20), was investigated by means of nonisothermal thermogravimetry (TG) and differential scanning calorimetry (DSC). It was found that the mass loss rate of PBXs involved in this research depends greatly on heating rate and the residue of the decomposition of these PBXs decreases with the heating rate. The onset of the exotherms was noticed at 215.4, 278.7, 231.2 and 233.7 °C with the peak maximum at 235.1, 279.0, 231.2 and 233.7 °C for RDX-Formex, HMX-Formex, CL-20-Formex, and BCHMX-Formex, respectively. Their corresponding exothermic changes were 1788, 1237, 691, and 1583 J g. It was also observed that the dependence on the heating rate for onset temperatures of HMX- and BCHMX-based PBXs was almost the same due to their similar molecular structure. In addition, based on nonisothermal TG data, the kinetic parameters for thermal decomposition of these PBXs were calculated by isoconversional methods. It was shown that the Formex base has great effects on the activation energy distribution of nitramines. It was further found that the kinetic compensation effects occurred during the thermal decomposition of nitramine-based PBXs, and they almost have the same compensation effects due to similar decomposition mechanism. [ABSTRACT FROM AUTHOR]

The zero-order reaction rates (specific rate constants) of isothermal decomposition at 120 °C of plastic bonded explosives (PBXs) were measured by means of the Czech vacuum stability test, STABIL. The PBXs are based on 1,3,5-trinitro-1,3,5-triazinane (RDX), 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX), cis-1,3,4,6-tetranitro-octahydroimidazo-[4,5- d]imidazole (BCHMX), and ε 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (ε-HNIW, ε-CL-20) with 13 wt% of the Formex P1 type matrix, i.e., a matrix of the explosive with pentaerythritol tetranitrate (PETN) bound by 13 wt% of a mixture of 25 wt% of styrene-butadiene rubber and 75 wt% of an oily material. Dependencies were found between the specific rate constants mentioned and the detonation velocities of PBXs, and consequently between these constants and the impact and electric spark sensitivities of pure explosive fillers, i.e., RDX, HMX, HNIW, BCHMX, and PETN. It is stated that the higher impact or electric spark sensitivity of their pure explosive fillers corresponds to the higher thermal reactivity of the given PBXs. [ABSTRACT FROM AUTHOR]

Abstract: In order to evaluate the actual pros and cons in the use of new nitroamines for solid rocket applications, the combustion properties of double-base propellants containing nitrogen heterocyclic nitroamines such as RDX, TNAD, HMX and DNP are experimentally investigated by means of high-speed photography technique, thermogravimetry (TG) and differential scanning calorimetry (DSC). It was indicated that DNP and TNAD can yield a lower pressure exponent than that of RDX and HMX, especially, TNAD-CMDB can give plateau burning at higher pressure with higher burning rates (, ) than that of RDX and HMX. It was also concluded that the rate of change in space of the temperature gradient is negligible for these propellants and the rate of mass diffusion is assumed to be small compared with the rate of mass convection. Furthermore, the reaction of CH2O + NO2 → CO + NO + H2O is probably the most important one in the foam layer of the propellants containing nitrogen heterocyclic nitroamines and the thermodynamic phase transition consisting of both evaporation and condensation of NC, HMX, TNAD, RDX and DNP, are considered to provide a complete description of the mass transfer process. [Copyright &y& Elsevier]

Abstract: In order to evaluate the actual pros and cons in the use of new nitroamines for solid rocket applications, the combustion properties of double-base propellants containing nitrogen heterocyclic nitroamines such as RDX, TNAD, HMX and DNP are investigated by means of high-speed photography technique, Non-contact wavelet-based measurement of flame temperature distribution. The chemical reactions in different combustion zone which control the burning characteristics of the double-base propellant containing nitrogen heterocyclic nitroamines were systematically investigated and descriptions of the detailed thermal decomposition mechanisms from solid phase to liquid phase or to gas phase are also included. It was indicated that the thermodynamic phase transition consisting of both evaporation and condensation of NC+NG, HMX, TNAD, RDX and DNP, are considered to provide a complete description of the mass transfer process in the combustion of these double-base propellants, and the combustion mechanisms of them are mainly involved with the oxidation mechanism of the NO2, formaldehyde (CH2O) and hydrogen cyanide (HCN). The entire oxidation reaction rate might be dependent on the pressure of the combustion chamber and temperature of the gas phase. [Copyright &y& Elsevier]

Abstract: DNP, a nitramine, has been studied with regard to the kinetics and mechanism of thermal decomposition, using thermogravimetry (TG), differential thermal analysis (DTA), infrared (IR) spectroscopy, and differential scanning calorimetry (DSC). The IR spectra of DNP have also been recorded and the kinetics of thermolysis has been followed by non-isothermal TG. The activation energy of the solid-state process was determined using Flynn–Wall–Ozawa method. The actual reaction mechanism obeyed nucleation and growth model, Avramie Erofeev function (n =1) with integral form G(α)=−ln(1− α) (α =0.10–0.65). E a and A were determined to be 116.51kJ/mol and 1010.52 s−1. The T/Jump FT-IR analysis showed that CH2O, NO2, and NO are produced in larger amounts than CO2 and HCN. The cleavage of the N–N and C–N bond appears to be the primary step in the thermolysis of DNP. [Copyright &y& Elsevier]

The zero-order reaction rates (specific rate constants) of isothermal decomposition at 120 °C of plastic bonded explosives (PBXs) in the first six hours of decomposition were measured by means of the Czech vacuum stability test, STABIL. The PBXs were filled by RDX (1,3,5-trinitro-1,3,5-triazinane), β−HMX (β−1,3,5,7-tetranitro-1,3,5,7-tetrazocane), BCHMX and ϵ-CL20 (ϵ-2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane, ϵ-HNIW) and, in one case, on a mixture of BCHMX and 3-nitro-1,2,4-triazol-5-one (NTO), in a 1:1 wt. ratio. These nitramines were bonded by 9% by wt. of softened polyisobutylene matrix, 13% by wt. of softened polystyrene-butadiene matrix, 18% by wt. of crosslinked hydroxyl-terminated polybutadiene, 12% by wt. of polydimethylsiloxane and by 40% of TNT. The relationships of specific rate constants with experimental detonation velocities, impact and friction sensitivities of these PBXs are shown and discussed. It is postulated that this approach provides results which are applicable to studies of initiation reactivity of energetic materials and which are fully comparable with those of other methods of investigation in this area. [ABSTRACT FROM AUTHOR]