The effect of glycidyl azide polymer on the stability and explosive properties of different interesting nitramines.

Preparation of glycidyl azide polymer (GAP) and its influence on the stability and explosive properties of polymer bonded explosives (PBXs) based on several cyclic nitramines, namely ß-1,3,5,7-tetranitro-1,3,5,7-tetrazocane (ß-HMX), 1,3,5-trinitro-1,3,5-triazinane (RDX), ε-2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (ε-CL-20) and cis-1,3,4,6-tetranitrooctahydroimidazo-[4,5-d]imidazole (BCHMX) are discussed. Impact and friction sensitivity were determined. Combustion heat and detonation velocity of the studied samples were measured. The detonation parameters were obtained by the EXPLO 5 thermodynamic code. The compatibility between the energetic polymeric matrix and the studied nitramines was discussed following a vacuum stability test. The relationship between performance and sensitivity was studied in comparison with literature HTPB compositions. The results showed that the GAP matrix increased both the detonation velocities of its PBXs by more than 500 m s-1 and the heat of explosion by nearly 1.13-1.16 times in comparison to PBXs based on HTPB for each individual explosive. The compatibility of BCHMX to the GAP matrix seems to be better than that of CL-20/GAP.

The mechanisms for desensitization effect of synthetic polymers on BCHMX: Physical models and decomposition pathways.

The project involves determination of the activation energies and physical models for thermolysis of BCHMX and its PBXs. The initial decomposition pathways were also proposed on the basis of molecular dynamic simulation. The goal is to find the mutual relationships among the physical models, decomposition pathways, and the impact sensitivities for BCHMX and its PBXs. It has been shown that the physical model of the first step of BCHMX thermolysis is close to first order and the second step is governed by a first order autocatalytic model, which turns to "2D or 3D Nucleation and Growth" models under the effect of polymeric binders probably due to their hindrances on topochemical reaction of BCHMX. Simulation results show that the scission of N-NO2 is the initial step for BCHMX pyrolysis, followed by HONO and HNO eliminations, where the latter is due to nitro-nitrite rearrangement. Under the effect of hydrocarbon polymers, the HONO/HON elimination and collapse of ring structure of BCHMX occur earlier without changing the time for N-NO2 scission, which might be the reason why those polymers have little effect on the thermal stability of BCHMX, while they could make it decompose almost in a single complex step.

Multi-stage decomposition of 5-aminotetrazole derivatives: kinetics and reaction channels for the rate-limiting steps.

The thermal behavior, decomposition kinetics and mechanisms of 1-amino-1-(tetrazol-5-yldiazenyl) guanidine (tetrazene) and 2-(tetrazol-5-yldiazenyl) guanidine (MTX-1) have been investigated using DSC, TG techniques, and quantum chemical calculations. It has been found that MTX-1 is much more stable than tetrazene and MTX-1, and both of them decompose in three steps with different kinetic parameters. Tetrazene is melted-dehydrated at 128.4 °C with a heat absorption of 50 J g(-1) and then it starts to decompose at around 118.6 °C with a peak temperature of 126.3 °C covered by a heat release of 1037 J g(-1) at a heating rate of 1.0 °C min(-1), while MTX-1 starts at 167.7 °C with a main peak of 191.1 °C covered by a heat change of 1829 J g(-1) under the same conditions. The activation energy is almost the same for their first decomposition steps (225 kJ mol(-1)), which are controlled by a three dimensional nucleation and growth model (A3). The mechanisms of the rate-limiting steps are supported by quantum chemical calculations. They could undergo a similar rate-limiting chemical process producing 1H-tetrazole and N2 for both cases, while the former also produces aminocyanamide and the latter produces cyanamide.

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.

cis-1,3,4,6-Tetranitrooctahydroimidazo-[4,5-d]imidazole (BCHMX), its properties and initiation reactivity.

Using the (15)N NMR chemical shifts of nitrogen atoms in nitramino groups of cis-1,3,4,6-tetranitrooctahydroimidazo-[4,5-d]imidazole (bicyclo-HMX or BCHMX) and additional 10 nitramines, we have assessed its reactivity in detonation, under the influence of impact, and by action of electric spark. It is stated that the thermal stability of BCHMX is higher than that of 1,3,5-trinitro-1,3,5-triazinane (RDX). The longest NN bond in the BCHMX molecule (1.412(4)A) is the cause for its higher impact reactivity, which is at the level of that of penterythritol tetranitrate (PETN). In the experimentally determined detonation velocity, BCMX can be slightly better performing than RDX. From the standpoint of friction sensitivity, BCHMX is similar to 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX). Attention was also focused on the solubility-temperature dependence of BCHMX in acetone, acetonitrile, ethyl acetate, dimethyl sulfoxide, tetrahydrofurane, and nitromethane. X-ray crystallographic study of BCHMX (C(4)H(6)N(8)O(8), M(r)=294.17), has been carried out at the temperature of 150K with the following results: a=8.5430(8), b=6.9480(6), c=8.7780(8)A, alpha=90.0(7) degrees , beta=102.452(11) degrees , gamma=90.0(9) degrees , V=508.777(8)A(3), Z=2, D(x)=1.920 g cm(-3), lambda(Mo Ka)=0.71073A, micro=0.169 cm(-1), F(000)=856, final R=0.0414 for 1254 independent observed reflections. In the BCHMX crystal there were found more short contacts in the molecular crystal of BCHMX data of Gilardi creating extensive supramolecular architecture.

Some properties of explosive mixtures containing peroxides Part I. Relative performance and detonation of mixtures with triacetone triperoxide.

This study concerns mixtures of triacetone triperoxide (3,3,6,6,9,9-hexamethyl-1,2,4,5,7,8-hexoxonane, TATP) and ammonium nitrate (AN) with added water (W), as the case may be, and dry mixtures of TATP with urea nitrate (UN). Relative performances (RP) of the mixtures and their individual components, relative to TNT, were determined by means of ballistic mortar. The detonation energies, E0, and detonation velocities, D, were calculated for the mixtures studied by means of the thermodynamic code CHEETAH. Relationships have been found and are discussed between the RP and the E0 values related to unit volume of gaseous products of detonation of these mixtures. These relationships together with those between RP and oxygen balance values of the mixtures studied indicate different types of participation of AN and UN in the explosive decomposition of the respective mixtures. Dry TATP/UN mixtures exhibit lower RP than analogous mixtures TATP/AN containing up to 25% of water. Depending on the water content, the TATP/AN mixtures possess higher detonability values than the ANFO explosives. A semi-logarithmic relationship between the D values and oxygen coefficients has been derived for all the mixtures studied at the charge density of 1000 kg m(-3). Among the mixtures studied, this relationship distinguishes several samples of the type of "tertiary explosives" as well as samples that approach "high explosives" in their performances and detonation velocities.

Some properties of explosive mixtures containing peroxides Part II. Relationships between detonation parameters and thermal reactivity of the mixtures with triacetone triperoxide.

This study concerns mixtures of triacetone triperoxide (3,3,6,6,9,9-hexamethyl-1,2,4,5,7,8-hexoxonane, TATP) and ammonium nitrate (AN) with added water (W), as the case may be, and two dry mixtures of TATP with urea nitrate (UN). Relative performances (RP) of the mixtures and their individual components, relative to TNT, were determined by means of ballistic mortar. Thermal reactivity of these mixtures was examined by means of differential thermal analysis and the data were analyzed according to the modified Kissinger method (the peak temperature was replaced by the temperature of decomposition onset in this case). The reactivity, expressed as the EaR(-1) slopes of the Kissinger relationship, correlates with the squares of the calculated detonation velocities for the charge density of 1000 kg m(-3) of the studied energetic materials. Similarly, the relationships between the EaR(-1) values and RP have been found. While the first mentioned correlation (modified Evans-Polanyi-Semenov equation) is connected with the primary chemical micro-mechanism of the mixtures detonation, the relationships in the second case should be connected with the thermochemical aspects of this detonation.

Decomposition of some polynitro arenes initiated by heat and shock Part II: Several N-(2,4,6-trinitrophenyl)-substituted amino derivatives.

Samples of 2,4,6-trinitroaniline (PAM), 2,4,6-trinitro-N-(2,4,6-trinitrophenyl)aniline (DPA), N,N'-bis(2,4,6-trinitrophenyl)-3,5-dinitropyridine-2,6-diamine (PYX) and N,N',N''-tris(2,4,6-trinitrophenyl)-1,3,5-triazine-2,4,6-triamine (TPM) were exposed to heat or to shock and then analysed chromatographically (LC-UV and LC/MS). It was found that the main identified decomposition products of these two incomplete initiations are identical for each of the compounds studied. It has been stated that the chemical micro-mechanism of the primary fragmentations of their low-temperature decomposition should be the same as in the case of their initiation by shock, including fragmentation during their detonation transformation.

Decomposition of some polynitro arenes initiated by heat and shock Part I. 2,4,6-Trinitrotoluene.

Samples of 2,4,6-trinitrotoluene (TNT) exposed to heat or to shock and residues after their detonation have been analyzed chromatographically (LC-UV and LC/MS). It was found that the main identified decomposition intermediates are identical in all the three cases. 4,6-Dinitro-2,1-benzoisoxazole and 2,4,6-trinitrobenzaldehyde are the most reactive from them. It has been stated that the chemical micro-mechanism of the primary fragmentations of shock-exposed TNT molecules and/or its detonation transformation should be the same as in the case of its low-temperature thermal decomposition.

New aspects of initiation reactivities of energetic materials demonstrated on nitramines.

A brief survey is presented of the author's results obtained from studies of the chemical micro-mechanisms of nitramines initiation from the point of view of organic chemistry. The relationships have been presented and discussed between the characteristics of impact and electric spark sensitivities, detonation and thermal decomposition, on the one hand, and (15)N NMR chemical shifts of nitrogen atoms of nitramino groups, on the other. In the case of the impact sensitivity, the said relationships involve the (15)N shifts of the amino nitrogen atoms carrying the nitro group primarily split off from the molecule. In the case of the initiation by shock, heat and electric spark, the (15)N shifts of nitrogen atoms in the primarily split off nitro groups themselves are involved. Also, the relationships are presented between the characteristics of thermal reactivity and values of the electronic charges at the nitro groups that are primarily split off. It has been stated that the chemical micro-mechanisms of primary fission processes of molecules of nitramines in the initiation by mechanical stimuli (inclusive the detonation course) and electric spark should be the same as in the case of their low-temperature thermal decomposition. It has been found that the electron structure and close neighbourhood of nitrogen atom of the primarily leaving nitro group is a dominant factor in initiation by shock, electric spark and heat. In the case of initiation by impact a key role plays characteristics of amino nitrogen atoms which are carriers of these most reactive nitro groups. Also mentioned is relevance of the modified Evans-Polanyi-Semenov relationship. On the basis of the findings presented it also has been stated that the detonation transformation itself of the nitramines should be preceded by an induction period.

Thermal reactivity of some nitro- and nitroso-compounds derived from 1,3,5,7-tetraazabicyclo[3.3.1]nonane at contamination by ammonium nitrate.

Thermal reactivity of 3,7-dinitro-1,3,5,7-tetraazabicyclo[3.3.1]nonane (DPT), 3,7-dinitroso-1,3,5,7-tetraazabicyclo[3.3.1]nonane (DNPT), 1,3,5-trinitroso-1,3,5-triazinane (TMTA or R-salt), 1,3,5-trinitro-1,3,5-triazinane (hexogen or RDX), 1,5-diacetyl-3,7-dinitro-1,3,5,7-tetrazocane (DADN), alpha-modification of the 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (octogen or HMX) and of their mixtures with 2wt.% of ammonium nitrate (AN) has been examined by means of non-isothermal differential thermal analysis. The resulting data were analyzed according to the Kissinger method. The reactivity was expressed as the E(a)R(-1) slopes of the Kissinger relationship. A relatively high reactivity has been found with mixtures of DPT and DNPT with AN. Electronic charges q(N) at nitrogen atoms in molecules of the compounds studied were calculated by means of ab initio DFT B3LYP/6-31G** method. The relationships were confirmed between the slopes E(a)R(-1) and the q(N) values for the nitrogen atoms primarily undergoing reaction. On the basis of these relationships it is stated that the destabilizing effect of AN is due to acidolytic attack of nitric acid (resulting from dissociation of ammonium nitrate) at the nitrogen atoms with the most negative q(N) values in the molecules of the compounds studied.

Some characteristics of 3,7-dinitro-, 3,7-dinitroso- and dinitrate compounds derived from 1,3,5,7-tetraazabicyclo[3.3.1]nonane.

The paper presents a set of some literature data and the authors' own experimental results of stability, sensitivity and explosion parameters of energetic Mannich N-bases, 3,7-dinitro-1,3,5,7-tetraazabicyclo[3.3.1]nonane (DPT), 3,7-dinitroso-1,3,5,7-tetraazabicyclo[3.3.1]nonane (DNPT) and hexamethylenetetramine dinitrate (HEXADI). Both their chemical and thermal reactivities are discussed. The results of small-scale cook-off test, determination of initiation ability, detonation velocity, impact sensitivity and performance show that the lowest process safety risks are connected with HEXADI.