Mixture Of Ammonium Perchlorate Research Articles

Model of Impact Initiation of Composite Explosive Solid Systems

A model of mechanical initiation of solid explosives, applicable for analysis of sensitivity of individual substances and composite explosives, is developed. The model includes a system of equations of work softening of a high explosive charge under an impact, resulting dissipative heating, and heat release due to chemical reactions between the components of the explosive mixture. The critical parameters and reaction kinetics were numerically calculated for initiation of charges consisting of a mixture of ammonium perchlorate and polymethylmethacrylate. The results are compared to experimental data on sensitivity of this mixture to the impact. Key words: high explosive, impact, explosion, impact sensitivity.

Approximate Method for Calculating the Impact Sensitivity Indices of Solid Explosive Mixtures

An approximate method is proposed to calculate the impact sensitivity indices (critical initiation pressure and critical charge thickness) for solid explosive mixtures (explosive compositions and mixtures of an oxidizer with a fuel). The calculation is based on some model concepts of the physicochemical and explosive properties of reactive mixtures. Test calculations of the sensitivity indices were performed for mixtures of HMX and TNT and mixtures of ammonium perchlorate with polymethylmethacrylate (PMMA) and TNT, and the results are compared with data of laboratory experiments on an impactor.

Combustion of ammonium perchlorate based mixture with and without black powder, studied by d.s.c. and TG/DTG

While pure ammonium perchlorate (AP) decomposes in two stages (at 330 and 460 °C), addition of charcoal causes the exothermic decomposition of AP and oxidation of carbon to take place near the first stage in the temperature range 310–330 °C. Although the presence of sulphur does not alter the decomposition of pure AP, its presence in a binary mixture of AP and charcoal increases the temperature of decomposition/oxidation and is vital for the ignitability of the mixture. The presence of an AP based ternary mixture in black powder results in the combustion of the whole system at around 350 °C.

Combustion studies on ammonium perchlorate/trimethylammonium perchlorate mixtures

A study of the burning rates of compressed mixtures of ammonium perchlorate (AP) and trimethylammonium perchlorate (TMAP) has been carried out at ambient pressure. The overall increase in the linear burning rate, showing a maximum at a composition having 80% TMAP, has been discussed in terms of factors such as stoichiometry, presence of faster burning component, and eutectic melt formation. The thermal decomposition studies of the mixtures, using isothermal thermogravimetry and differential thermal analysis techniques, indicate the possibility of eutectic melt formation.

Mechanism of catalytic additive effects on diethylnitramine dinitrate combustion rates

Burning of DINA (diethylnitramine dinitrate, (O 2NOCH 2CH 2) 2NNO 2) at atmospheric pressure has been investigated. The burning rate is shown to be determined by the rate of heat evolution in the reaction zone of the condensed phase (the C-phase) as well as by the heat flux from the gas phase. Two groups of additives are differentiated: (1) compounds such as ammonium persulfate, hydrazine sulfate, and hydroxylamine sulfate, which increase the burning rate through the intensification of heat evolution in the C-phase and (2) compounds of hexavalent chromium and composite additives, including soot and lead and copper compounds, which accelerate burning as a result of additional heat flux from incandescent condensed particles formed on the burning surface and heated to a temperature of 1000–1200°C by the heat from heterogeneous catalytic reactions. In the case of the chromium compounds, the active substance responsible for the effect is found to be Cr 2O 3 formed in a combustion wave as a result of oxidation-reduction processes and thermal decomposition of initial additives. The second mechanism of the action of additives is shown to be widely spread. In particular, incandescent particles on a burning surface occur when chromium containing additives is introduced into picric acid, RDX, nitrocellulose, and double-base propellant, as well as in a mixture of ammonium perchlorate or ammonium nitrate with combustible components. It has been proved experimentally that fast-burning picrates are formed in the reaction zone of the C-phase when picric acid burns with salts of chromium acids as additives. The increase in the burning rate with these additives is found to be caused by the joint action of picrates and chromic oxide formed in the combustion process; however, the contribution of the latter is far greater.

Investigation of the thermal structure of the burning zone in condensed mixtures by fine thermocouples

Temperature profiles through combustion waves in mixtures of ammonium perchlorate (AP) with polymethylmethacrylate (PMM), paraform (PF), and sulphur were obtained by fine W5%Re–W20%Re thermocouples embedded in the strands. The surface temperature, T s , increased with pressure, p (for AP + PF, α = 1 mixture-from 460 °C at p = 0.3 atm to 580 °C at p = 1 atm) and there was a corresponding rise in the burning rate. In contrast, the addition of a catalyst (Cu 2O) had no effect on T s despite a considerable (1.7–1.95 times) increase in the burning rate. The slopes of ln( T − T 0) = f( x) curves reveal a marked increase at T = T ∗ (where T ∗ ranges from 200 °C to 310 °C), probably due to the phase change AP (orthorhombic) → AP (cubic). The departure of T ∗ from the well-known value 240 °C may be ascribed to errors in the thermocouple measurements and to the gasification of PF at T < T ∗ at low pressures. The profiles T( x) and ϕ( x) (where ϕ = dT dx ) were obtained theoretically from a solution of the heat flow equation for a medium with a phase change. An estimate was obtained for the value of ( ϕ 240°+ dT − ϕ 240°− dT ) equal to 1.69 × 10 5 ṁ deg C/cm for the preheat zone in pure AP (where m is mass burning rate). Two maxima of ϕ were observed in the gas phase. The first appears when the thermocouple traverses the NH 3 + HClO 4 flame. The value ( ϕ max) 1 increased with pressure at p ⩽ 1 atm (for AP + PMM, α = 0.75 mixture—from 2.1 × 10 5 deg C/cm at p = 0.34 atm to 4.9 × 10 5 deg C/cm at p = 1 atm). At p = 1 atm ( ϕ max) 1 decreased with increasing p, probably due to thermal inertia of the thermocouple. A simple relationship was obtained for the maximum thermal gradient recorded by a thermocouple. The heat balance at the burning surface is considered. For the mixture under investigation the heat production in the condensed phase at p≤1 atm was insignificant. The addition of Cu 2O increased the thermal gradient in the gas phase near the surface and the burning velocity by about the same extent.

Condensed phase reactions in solid propellants

The paper investigates the cause for the difference between differential scanning calorimetric results and mass spectrometric studies on polystyrene (PS) ammonium perchlorate (AP) propellants as related to the method of preparation of the propellant and the difference in experimental conditions by the use of mass spectrometry. Sufficient time is given for the product sublimates to interact with each other and attain equilibrium. It is shown that the propellant decomposition is a nonadditive phenomenon and that even a physical mixture of AP and PS does not yield additive decomposition products of its components. Results on the identification of a yellow compound containing chlorine in the bulk of the propellant suggest a condensed phase reaction. The occurrence of the reaction in the porous condensed phase of the propellant may explain the larger exothermicity of the propellant compared to the additive heats of decomposition of its components.

Mechanism of initiation of an explosion by impact in mixtures of ammonium perchlorate with combustible additives

Mechanism of initiation of an explosion by impact in mixtures of ammonium perchlorate with combustible additives

Effect of aluminum on the burning of ammonium perchloratepolyformaldehyde mixtures

We have investigated the effect of aluminum content and aluminum particle size on the burning of a stoichiometric mixture of ammonium perchlorate and polyformaldehyde. It has been established that:

Effect of iron oxide on the combustion of condensed mixtures

We have invest igated the effect of-l% FezO 3 on the burning rate of model mixtures of ammonium perchlorate (AP) + polystyrene (PS) and ammonium perchlorate + po lymethyl methacry la te (PMM) when var i ous physical parameters are varied (pressure, component ra t io a, in i t im temperature T 0, presence of inert diluents--NH4C1 and AlzOa). The effect ive par t ic le sizes were approximate ly 9 p for AP ( technical), 5 g for PS (technical) , 3 g for PMM (technical) , 1 .8 g for Fe203 (ana ly t ica l grade), 12 # for NH4C1 (ana ly t ica l grade), and 8 p for AlzOs (ana ly t ica l grade). The components were mixed on t racing cIoth with a rubber stopper for one hour. From the finished mixture we pressed charges 8 mm in d iameter and 8 -10 mm ta l l with a re la t ive density 6 = P/Pmax = 0 .950.99. The exper iments were conducted in a constant-pressure bomb in nitrogen. The burning t i m e w was measured using a quartz pressure transducer. The average burning rate u = h / r was ca lcula ted . We charac ter ize the effect ol~ the Fe2Os by means of the quant i ty z = u/n0, where u and u0 are the burning rates of the mixture with and without the addit ion of FezOa.

Temperature coefficient of burning rate of condensed mixtures at different component ratios

1. The dependence of the burning rate u on the initial temperature T0 has been studied for model mixtures of ammonium perchlorate and polystyrene, polymethyl methacrylate, polyformaldehyde, and bitumen. In all cases, with increase in T0 the burning rate increases monotonically. The relation u(T0) may conveniently be characterized by the temperature coefficient β=(d ln u)/(d T0). 2. The temperature coefficient strongly depends on the fuel-oxidizer ratio α. The curve β(α) has a minimum, whose position coincides with that of the maximum burning rate. 3. For mixtures not too far from stoichiometric the temperature coefficient increases with increase in the oxidizer particle size. 4. The experimental results are in agreement with the notion that the value of β is determined by the temperature Tg in the zone that influences the burning rate; if Tg is large, β is small and, conversely, if Tg is small, β is large.

Burning of mixtures of ammonium perchlorate and various organic substances

1. The burning rate of mixtures of ammonium perchlorate and fuels of various chemical structure has been investigated. 2. It has been established that the burning rate of the mixtures depends on the calorific value of fuels of similar structure, or, if the calorific value is the same, on the strength of the chemical bonds and the structure of the molecules.

Upper concentration limit of combustion of condensed mixtures

1. We have determined the position of the upper concentration limit of combustion for mixtures of ammonium perchlorate and polystyrene and polymethyl methacrylate. For the AP+PS mixture the limiting excess of fuel (at which the mixture still burns) is 2\2-3 times greater than for the AP+PMM mixture. In all cases αu is the greater, the higher the pressure and the larger the oxidizer particle size. In these experiments the richest mixture still capable of burning (at p=100 atm and dox=140–320 μ) corresponded to α≃0.055 (about 67% fuel) for polystyrene and to α≃0.12 (∼60% fuel) for polymethyl methacrylate. 2. We have determined the burning rate at the upper limit uu. For the AP+PS mixture uu is almost constant at all p and dox and corresponds to about 1mm/sec. For AP+PMM the value of uu is generally higher than for AP+PS and decreases with increase in p and dox. 3. The results of the experiments can be explained on the basis of the influence (\ldactive combustion\rd) zone concept.