Physical model for shock-wave initiation of detonation of plastic-bounded TATB-based explosive

A physical model for the macrokinetics of shock-wave initiation of detonation in plastic-bounded TATB-based explosive is proposed that is based on the assumption of electronic energy transfer from hot spots. Results of numerical modeling of experiments on shock-wave initiation of detonation of LX-17 are presented. __________ Translated from Fizika Goreniya i Vzryva, Vol. 42, No. 5, pp. 117–126, September–October, 2006.     

Modified detonation macrokinetics model of a tatb-based explosive

A one-stage detonation macrokinetics model of a low-sensitivity heterogeneous explosive is considered. Within the framework of the model, we have managed to describe uniformly a wide class of experiments on initiation of aTATB-based plasticized explosive, including the initiation from the impact by a metallic plate and compact metallic fragments. Institute of Technical Physics, Snezhinsk 456770. Translated from Fizika Goreniya i Vzryva, Vol. 33, No. 1, pp. 94–97, January–February, 1997.     

Macrokinetics of Mechanosynthesis in Solid-Gas Systems. II. Experimental Studies. Analysis of Results

Results from experimental studies of the nonisothermal mechanochemical reaction in the titanium-nitrogen system. Experimental data are compared with simulation results. The effective kinetic parameters of mechanical activation of the reactant and the chemical reaction are determined from analytical relations. It is shown that the developed mathematical model is suitable for the analysis of the macrokinetics of nonisothermal chemical reactions in solid reactant-reactive gas systems. __________ Translated from Fizika Goreniya i Vzryva, Vol. 41, No. 5, pp. 92–99, September–October, 2005.     

Shock-wave sensitivity of a TATB-based plasticized explosive

The results of numerical modelling of experiments on the investigation of shock-wave sensitivity of a TATB-based explosive are presented. A model for the macrokinetics of decomposition of the explosive has been constructed within the framework of a hypothesis of hot spots.Russian Research Institute of Technical Physics, 454070 Chelyabinsk. Translated from Fizika Goreniya i Vzryva, Vol. 31, No. 1, pp. 103–108, January–February, 1995.     

Ignition of a system of hot spots in the presence of heat transfer through the side surface

An asymptotic analysis is used to study the ignition of a reactive cylindrical body in which, initially, there is a periodic system of hot spots. The effects of the heat transfer through the side surface of the cylinder and the adjacency of hot spots on the ignition regimes are studied. The solution shows that the critical ignition conditions depend considerably on the heat-transfer regime. The adjacency of the hot spots leads to finite changes in the parameters only if they are sufficiently close to each other. The results obtained for a heat-insulated side surface are compared with known solutions. Translated fromFizika Goreniya i Vzryva, Vol. 36, No. 2, pp. 17–21, March–April, 2000.     

Electronic Thermal Conductivity during Combustion-Wave Propagation from Hot Spots in Detonating TATB

A model for the electronic thermal conductivity of shock-compressed TATB is developed using experimental data on the growth kinetics of its electrical conductivity. It is shown that electronic thermal conduction can be the main mechanism of energy transfer from hot spots in detonating explosives. __________ Translated from Fizika Goreniya i Vzryva, Vol. 41, No. 5, pp. 100–103, September–October, 2005.     

Use of pulsed radiography in studies of shock wave initiation of TATB

Pulsed radiography is used to study the excitation of detonation in plasticized TATB. Conditions are determined for setting up experiments in which the outcome of shock loading is nonunique. Experiments in which desensitization and sensitization of TATB occur with preliminary loading of the samples are described. Translated fromFizika Goreniya i Vzryva, Vol. 35, No. 2, pp. 96–101, March–April 1999.     

Thermal decomposition of polyester polyurethane and its elastomers exposed to γ-radiation

The thermal-decomposition parameters of unplasticized and nitrate ester plasticized polyester polyurethane elastomers with unsaturated carbon—carbon bonds in the initial state and after irradiation with doses of 120–380 kGy (γ-quanta ⁶⁰Co) were determined using dynamic thermogravimetry and differential scanning calorimetry. __________ Translated from Fizika Goreniya i Vzryva, Vol. 42, No. 2, pp. 133–138, March–April, 2006.     

Dynamics of thermal explosion in the postinduction period

The dynamics of thermal self-acceleration of the reaction and heating is studied for gasless condensed compositions in the induction and postinduction periods up to complete transformation of the substance. It is shown that the propagation of the reaction over the sample is of a distinct frontal character in a broad range of values of the Biot criterion Bi and within the framework of the macrokinetics of “weak” deceleration.” Two qualitatively different mechanisms of front propagation are revealed. This is the normal propagation of the combustion front initiated by the ignition zone for large values of Bi. For small values of Bi, propagation of the front is the apparent effect, which is due to subsequent adiabatic self-ignition of separate portions of the substance uniformly heated during the induction period. In the second case, by the propagation velocity, we mean the “phase” velocity. Translated fromFizika Goreniya i Vzryva, Vol. 35, No. 6, pp. 65–70, November–December 1999.     

Physical model of low-velocity detonation in plasticized HMX

A physical model of low-velocity detonation in plasticized HMX is considered. In this model, a low-velocity detonation wave is a combination of a weak leading shock wave and a subsequent compression wave. This combination is formed by the simultaneous effects of energy release and spreading of the reacting medium. The main features of low-velocity detonation observed in experiments are reproduced in two-dimensional calculations. __________ Translated from Fizika Goreniya i Vzryva, Vol. 44, No. 1, pp. 102–112, January–February, 2008.     

Macrokinetics of physicochemical condensation in two-phase systems of the gas-solid body type

The macrokinetics of the phase evolution at the microscopic level under isothermal and nonisothermal conditions is analyzed theoretically within the framework of a two-scale approach for describing physicochemical condensation processes in two-phase systems. Scenarios are established for the transformation of the condensed particles in a chemically active medium, taking into account the exothermal nature of the reaction, the finiteness of heat- and mass-transfer rates, and the phase transformations. The equilibrium constant of the heterogeneous reactions is shown to have a significant effect on the conditions of evaporation, or the increase in the incipient condensation phase. An analytical criterion is obtained for controlling the phase transformation in a reaction-capable medium, and it is supported by numerical calculations. Translated fromFizika Goreniya i Vzryva, Vol. 34, No. 3, pp. 37–45, May–June 1998.     

Poly(vinyl chloride) plasticized with succinate esters: synthesis and characterization

Phthalates pose adverse health effects due to their propensity to leach and the most common, di(2-ethylhexyl) phthalate (DEHP) and di-n-octyl phthalate (DOP), are petroleum-based. Conversely, di-esters, succinates are biobased (produced from fermentation of biomass), biodegradable, and therefore potential sustainable replacements for phthalates. A series of succinates, di-octyl succinate (DOS), di-hexyl succinate (DHS), di-butyl succinate (DBS), and di-ethyl succinate (DES), were mixed with poly(vinyl chloride) (PVC). The interaction of the plasticizer ester carbonyl with PVC shows an average −5 cm⁻¹ shift of the carbonyl absorbance peak energy. The glass transition temperatures (T _g), were monitored by differential scanning calorimetry and dynamic mechanical analyses. The T _gs of DOS and DHS plasticized PVC were significantly lower than DOP plasticized PVC at a lower percent mass. On the other hand, PVC plasticized with either DBS or DES exhibited a similar trend in lowering the T _g as that of DOP plasticized PVC.     

Local structural instability and formation of hot spots in materials under mechanical loading

We have studied the formation of hot spot in materials under high-speed loading using the method of molecular dynamics. It is shown that the appearance of hot spots is associated with release of the elastic energy accumulated in the deficient region. The evolution of a hot spot is followed by intense energy release and by structural rearrangements near its location. The results obtained are of importance for understanding of the effects of mechanical activation of the components in solid-phase chemical reactions. Institute of Strength Physics and Material Science, Siberian Division, Russian Academy of Sciences, Tomsk 634048. Translated from Fizika Goreniya i Vzryva, Vol. 33, No. 2, pp. 143–146, March–April, 1997.     

Critical diameter and transverse waves of powder combustion

A critical review is given of the problem of powder extinction with a decrease in the sample diameter due to heat release. The results of our experimental studies of the critical combustion diameter are presented. A comparison of the experimental data on the critical diameter as a function of burning rate is shown to be the most informative. These functions follow a power law with an exponent of −1.15 to −1.17. The relations between the sizes of the cells (hot spots) formed by the set of transverse waves on the burning surface and the burning rate follow the same law. The sizes of the cells are 2.1–2.3 times smaller than the critical combustion diameter. It is also found that the transverse wave decays if its curvature exceeds a critical value. __________ Translated from Fizika Goreniya i Vzryva, Vol. 43, No. 2, pp. 72–78, March–April, 2007.     

Effect of plasticizer on the crystallization behavior of poly(lactic acid)

In this article, the spherulitic morphology and growth rate of the neat and plasticized poly(lactic acid) (PLA) with triphenyl phosphate (TPP) were compared and analyzed by polarizing optical microscopy with hot stage at a temperature range of 100?142°C. The spherulitic morphology of the neat PLA underwent a series of changes such as the typical Maltese Cross at less than 132°C, the disappearance of the Maltese Cross at 133°C, the irregular and distorted spherulites at higher than 134 and 142°C, respectively. For plasticized PLA, the spherulitic morphology exhibited the same changes as neat PLA, but these changes were shifted to lower temperature when compared with neat PLA. In the case of the spherulitic growth, neat PLA had the maximum value of 0.28 μm/s at 132°C, and plasticized PLA had higher values than that of neat PLA. Further analysis based on the Lauritzen–Hoffman theory was presented and results showed that the values of nucleation parameter K_g increased with TPP content. The crystallization behavior of PLA was analyzed by differential scanning calorimetry and wide‐angle X‐ray diffraction. The results showed that the degree of crystallinity of plasticized PLA markedly increased when compared with neat PLA sharply with the incorporation of plasticizer. The crystallization kinetics for the neat and plasticized PLA under isothermal crystallization at 114°C was described by the Avrami equation and the Avrami exponent is close to 2, implying that the crystallization mechanism did not change. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Estimation of polyunsaturated fatty acid content in lipids of aquatic organisms using thin-layer chromatography on a plain silica gel plate

We have designed a rapid method for the separation of polyunsaturated fatty acids (PUFA, ≥trienes) from non-PUFA, and for estimation of total amounts of PUFA in lipids of aquatic organisms. Lipids from thirty-one species, including marine and fresh water fishes, shell fishes, marine algae, and other aquatic animals, and from terrestrial organisms, were transesterified with sodium methoxide in methanol. The resulting fatty acid methyl esters were separated by thin-layer chromatography on commercially available plain silica gel plates with a developing solvent ofn-hexane/ethyl ether/acetic acid (95∶5∶1, by vol). All of the methyl esters from aquatic organisms tested separated into two spots, whereas those from terrestrial sources, except for linseed oil, showed a single unresolved spot. The upper and lower spots were scraped separately from the plate, and their fatty acid compositions were determined by gas-liquid chromatography. The lower spot was composed of PUFA having more than two double bonds, whereas components of the upper spot were saturated, monoenoic, and the greater part of the dienoic fatty acids. When the spots on the silica gel plate were stained with Coomassie brilliant blue, the amounts of PUFA in aquatic organisms could be estimated satisfactorily using a scanning densitometer. Presented in Japanese at the general Meeting of JSSF held in Mie University, Tsu-city, Japan, October 1994.     

Physical characteristics of plasticized epoxy system in the post-yield stage

Thermo-rheological analysis was conducted on epoxy–Versamid specimens drawn from different portions of beams subjected to a yield test. M_c values, characterizing the crosslink density and determined by a special method, show insignificant variation for unstressed (virgin), pre-yield, and post-yield zones of the material. It was concluded that the yielding process in the plasticized epoxy system consists mainly in disruption of physical bonds.     

Thermal Degradation of Plasticized Poly(<Emphasis Type="Italic">para</Emphasis>-Methoxystyrene) in Solid Films

The thermal effect on the stability of poly(para-methoxystyrene) in solid films was studied within a temperature range of temperature range of 298–363 K. The fluorescence spectrum of poly(para-methoxystyrene) was found to be mainly excimeric emission at room temperature. However, this emission is quenched at higher temperatures. Added terephthalate and phthalate plasticizers to poly(para-methoxystyrene) caused a quenching of the excimer emission and enhanced exciplex emission. Thermal heating of the solid films of the plasticized and non-plasticized polymer was accompanied by quenching of fluorescence emission at low temperature and brought about a change in the structure of the fluorescence spectrum at high temperatures. This may indicate that thermodestruction of these polymers starts from a random chain scission. In addition to that the presence of the plasticizer in the polymer backbone was found to accelerate thermal degradation of the polymer. This was proved by the infrared spectra of the heated and unheated plasticized solid films of poly(para-methoxystyrene). The binding energy or excimer formation was calculated in solid film.     

Optical properties of plasticized polycarbonate

Optical properties of polycarbonate plasticized by pentaerythritol tris(1,1,2,3,3,3‐hexafluoropropyl) ether (HFP), diheptadecyl‐o‐phthalate and pentaerythrityl tetrabenzoate (TBP) have been determined at wavelengths from 300 to 700 nm. X‐ray diffraction analysis, which was used to examine the polymer structure, showed that all the plasticized systems were amorphous. HFP and, especially, TBP impeded crystallization of the polymer. Plasticized polycarbonate films remained transparent over long periods of time even if they were heated at a temperature higher than the polymer glass transition temperature. © 2003 Society of Chemical Industry