مجله تحقیق و توسعه مواد پرانرژی
سال ششم شماره 2 (پیاپی 12، پاییز و زمستان 1389)

The size and shape of solid particles have a profound influence on the properties of propellants and explosive formulations. Among these properties, one can refer to sensitivity, mechanical properties, content of total solid, density, homogenity of formulation, burning rate, etc. Reducing particle size can lead to the reduction of defects, voids and inclusions of crystal and thereby it can reduce the sensitivity of the formulation and enhance its safety. In this paper, following a review of the changes of AP and nitramine (HMX, RDX) oxidizer properties, the role of the reduction of solid particles size in propellants and explosive formulations is examined.

Liquid explosive foam (LEXFOAM) based on nitro methane is used for demining. In this research، the optimization of the density and the phase separation of LEXFOAM formulation consisting of nitro methane، nitrocellulose، stearyl alcohol and ethoxylated stearyl alcohol was investigated. The phase separation (the separation of nitromethane from foam bed) is a process that decreases the foam quality and occurs in this formulation under the various conditions. In this study using cab-o-sil in the formulation، the phase separation became almost zero and furthermore proportional amount of nitromethane increased significantly without any phase separation. The explosion properties depend on the density of the explosive and in this formulation with zero phase separation، increase of the foam density during the time was determined. Addition of Al powder and replacement of TNT instead of nitromethane had led to very stable foams with well sensibility to explosive cap no. 8 showing low explosive velocity of 2400 and 2900 m/s. Calculation of explosive pressure and velocity using CHEETAH software showed that the addition of cab-o-sil to the formulation، which leads to an increase in the nitromethane content (to about 7%)، causes the increase in the rate of the explosion while the addition of Al powder into the formulation leads to no drastic change on the explosive properties of the foam and TNT replacement instead of nitromethane decreased the explosive velocity and pressure.

Energetic polymers are of interest for use as binders in propellants and explosives. The term energetic polymer implies to polymers that have energetic moieties such as nitro، nitrate or azidein in their structures. this group of polymers can without additives be deflagrated or detonated with the proper initiation system. Emergence of novel propellants having unique combination of high energy، has led to development of energetic polymers. In this paper، The important energetic polymers have been introduce and study properties، identification methods، synthesis and determination values for the energetic polymers heats of formation.

The detonating cord is a linear explosive system including uniform distribution of explosive materials along longitudinal direction. It has different applications depending on the mechanical properties، type، and amount of the explosive material utilized. In this article، an attempt has been made to explicate the design and manufacturing process of high charge detonating cord at 60 gr/m. Production of any type of detonating cord requires specified bushes، parts and raw material. Following the design of charging and forming bushes، contraction bushes، calculation of the width of polyester film، design of male and female bushes of extruder (based on diameter of prepared raw lint in lint texture) and design of packaging، the system was fabricated and then some test samples of it were prepared. The results indicate that the prepared samples have suitable properties such as density، resistance to impact، tension and explosion speed. After the verification of the initial specifications carried out in the plant، the product was successfully tested in Shahkooh Granite mine in Southern Khorasan province.

Using embedded metal wires in propellant grains is one of the methods used to increase the burning rate without changing the composition of the propellant، which is mostly used in the end burning grains. Although using embedded metal wires to increase the burning rate in propellants has some advantages، it includes some defects such as increasing of pressure exponent and temperature coefficient which cause higher dependency of burning rate on the pressure of combustion chamber. Coating metal wires is one of the ways to solve this problem and improve the performance of grains with embedded metal wires. Besides reducing pressure exponent and temperature coefficient، coating metal wires makes a strong bond between the propellant and metal wire. In this article، considering the coating composition، we discuss the mechanism of its influence on burning rate and other parameters such as pressure exponent.

Re-ignition phenomenon is premature extinction of solid propellant rocket motor and reigniting of it. It is important to study the reasons of this phenomenon because decreases in motor performance. In this work، a modified double base solid propellant was studied. The mechanism of premature extinction and re-ignition was characterized by comparison of performance tests of original and production motors. The results have shown that extinction in motor occurred due to rapid depressurization in motor. Then re-ignition phenomenon occurred as the result of re-combustion of a small part of extinguished propellant. Also it was shown that the presence of large particle size of oxidizer and incompetent distribution brings about low burning rate and depressurization rate which bring about this phenomenon subsequently.

Because the traditional solid propellant used in weapon systems are reached in saturated point as energetically and accessing to higher muzzle velocity (2000 m/s) of them is not practical، thus، development and improvement in ballistic efficiency of weapons by these propellants and their current production technology higher than certain amount is not possible. However، the improvement and development on ballistic characteristics of them has to needed to advanced new technology and propellant design or mortar charges. In this study، the trend of developed technology in the world with regard to modern propellants in order to accessing to objectives such as higher synthetically energy، improvement in efficiency and productivity in ballistic، development of more safe and compatible with environment، reducing of production cost and so are described.