Abstract:Multi-component gel propellant systems were obtained using carboxymethyl cellulose nitrate glycerol ether (CMNGEC) as gelling agent. The combustion flame characteristics, combustion residues and system stability of the gel propellant systems were analyzed by flat flame test, thermogravimetry-derivative thermogravimetry, differential scanning calorimetry techniques and high speed centrifugal stability test. Results show that the combustion behavior of CMNGEC system contains processes of periodic swelling, cracking, jet and burning of gelling agent, and the combustion residues are less than that of SiO₂ gel propellant system. The thermal decomposition of CMNGEC gel propellant system can be divided into three stages: the volatilization of liquid component, thermal decomposition of CMNGEC gelling agent and thermal decomposition of ammonium perchlorate. When the content of gelling agent is up to 3%, the gel propellant system is stable at 670 g, 2000 g and 7000 g centrifugation conditions for 30 min and the liquid precipitation rate is less than 1%.

Abstract:The curing reaction kinetics of dimeryl diisocyanate (DDI) / hydroxyl-terminated polybutadiene (HTPB) system was studied using Fourier transform infrared (FT-IR)spectra and compared with that of isophorone diisocyanate (IPDI)/HTPB system. The application of DDI in HTPB propellant was preliminary explored. Results show that the curing reaction of DDI/HTPB system appears as the second-order reaction and the apparent activation energy is 37.02 kJ·mol^-1, which decreases by 3.5 kJ·mol^-1 compared with that of IPDI/HTPB system, revealing that the reactivity of DDI is slightly higher than that of IPDI. And DDI has a moderate reactivity, which can be used as low-toxic curing agent in HTPB propellant. The DDI/HTPB system possesses better mechanical properties at room temperature with the tensile strength of 0.85 MPa, and the strain at maximum load of 44.1%. The room temperature mechanical property of DDI/HTPB system can meet the requirements of mechanical properties at room temperature basically for propellant.

Abstract:The PBAMO/GAP random block energetic thermoplastic elastomer (ETPE) was synthesized via a solution polymerization using poly(3, 3-bis(azidomethyl)oxetane) (PBAMO) as hard segment prepolymer, glycidyl azide polymer (GAP) as soft segment prepolymer, toluene diisocyanate (TDI) as curing agent, 1, 4-butanediol (BDO) as chain extender. The structure of the ETPE was characterized by IR, gel permeation chromatography (GPC) and X-ray diffractomer (XRD). Results show that, the number average molecular weight of the copolymer can be up to above 34000. The imino groups of carbamate in the elastomer form the hydrogen bond with azido group, and the crystallinity of PBAMO in copolymer is 16.6%. The optimal experimental conditions obtained by optimizing the synthesis process are determined as :in the chain extension stage, T=130 ℃, t=40 h, M_n (PBAMO)=4100, m(PBAMO):m(GAP)=1:1, R=1.0, w (TDI+BDO)=30%.

Abstract:A nitrato-typed thermoplastic elastomer(NTPE)was synthesized by using two-step solution polymerization method with dichloroethane as solvent, poly(3-nitratomethyl-3-methyloxetane) as soft segments, toluene 2, 4-diisocyanate and 1, 4-butanediol as hard segments.Its structure was characterized by infrared radiation and nuclear magnetic resonance and the thermal properties were studied by differential scanning calorimetry and thermogravimetry differential thermogravimetry. Results show that when mass fraction of hard segment is 40%-45% and isocyanate index is 1.02, the mechanic property of NTPE is better than that of others, and NTPE has the typical features of nitratotyped polyetherbased polyurethane. The glass transition temperature and peak decomposition temperature of NTPE is -11.71 ℃ and 220.4 ℃, respectively. The mass loss of overall reation(175-523.63 ℃) is 84.44%, which indicates that NTPE has good thermal stability.

Abstract:To achieve the isocyanate-free curing of glycidyl azide polymer (GAP), the curing reactivity and properties of the films under multiple acetylene-terminated compound (TPTM) curing system and triisocyanate (N100) curing system were studied via FT-IR technology, test machine and optical microscope. The curing reaction kinetics of TPTM curing system was explored by differential scanning calorimetry. Results indicate that GAP and TPTM can happen 1, 3-dipolar cycloaddition reaction to form triazole cross linking system at 60 ℃, and the curing reactivity is much better than that of N100 curing system. The effect of TPTM content on activation energy is slight, but on the reaction mechanism is little.The kinetic equation obtained can well predict the curing process in actual application. With the mass fraction of TPTM increasing from 3% to 9.7%, the tensile strength of TPTM curing films increases from 0.16 MPa to 0.82 MPa, and the elongation at break decreases from 149% to 17%. When the mass fraction of TPTM is 4%, the TPTM curing films meet N100 curing system in actual application on the mechanical properties (the mass fraction of N100 is about 10%) and there is no air hole in the films.

Abstract:The physical blends of nitrocellulose(NC)/hydroxy terminated polyether(HTPE) with different proportions and NC/HTPE/toluene-2, 4-diisocyanate (TDI) cross-linked polymers were prepared by a solution mixing method. The compatibility of NC and HTPE were studied by the enthalpy of mixing method. The dynamic mechanical properties of the blends were analyzed by dynamic thermal mechanical analysis. The crosslink reaction state between NC and HTPE as well as the interaction between the molecules were studied by means of Fourier transform infrared (FT-IR) spectroscopy. Results show that two polymers are a partial miscible system and the degree of miscibility is relevant with the constitution of the blends. With the proportion of HTPE increase, the glass transition temperature of the blend system decreases gradually. When the mass fraction of NC is 30%, the T_g of NC/HTPE physical blend system is -9.8 ℃, while the T_g of the chemical crosslink system is -1.4 ℃, both the T_g of the two systems reduced greatly in contrast with the T_g of NC. Compared with the NC/HTPE physical blend system, the chemical cross-linking can make the compatibility of NC and HTPE increase. The characteristic absorption peak of isocyanate group at 2270 cm^-1 disappears after crosslink, demonstrating that the crosslink reaction is relatively complete. The stretching vibration absorption peak of hydroxy and nitro group of NC after blending shifts to low wave numbers, indicating the existence of hydrogen bond interaction between NC and HTPE. After crosslinking, the shift of hydroxy and nitro group decreases, showing that the hydrogen bond interaction between NC and HTPE is partly substituted by chemical bond interaction.

Abstract:In order to study the effects of RDX on the safety performance of nitramine modified double base propellants(MDBP), detonator sensitivity test, shock sensitivity test, detonation safety test and detonation velocity test were carried out respectively according to GB14372-1993 and GJB772A-1997 for nitramine modified MDBP samples with different content of RDX(18.0%~55.1%) and a common MDBP sample. Results show that with increasing of RDX content, the propellant has higher sensitivity to shock wave and detonator, lower detonation safety, and its detonation velocity of propellant increases. Detonator could explode the propellant at -5 ℃directly when the content of RDX in propellant is 34%. The critical gap thickness is up to 33.5 mm, the propagation critical diameter of detonation 8 mm and the detonation velocity more than 8000 m·s^-1 when the content of RDX is 55.1%.

Abstract:In low temperature accelerated aging test method, using maximum tensile strength(σ_m) and maximum elongation(ε_m) under uniaxial stretching conditions as aging propellant characteristic parameters, the characteristic changing trend of propellant with different strain level in structural tester at -28 ℃ was studied. Results indicate that the main reason of the aging of propellant with strain is due to the stress damage under low temperature. The dynamic mechanical analysis (DMA)test validates that the damage of the propellant happenes. The σ_m of the propellant increases and the ε_m is waved with time gradually under normal temperature tension tests with the stretching speed of 100 mm·min^-1, and the test temperature(23±2) ℃. And a fter 19 weeks low temperature aging, the σ_m of 15% strain structural tester was increased by nearly 30%. The σ_m of the propellant increases and ε_m was decreased greatly with time change under low temperature tension test with stretching rate of 500 mm·min^-1and (-55±2) ℃. And after 19 weeks low temperature aging, the σ_m of 15% strain structural tester increases by nearly 11% and the ε_m decreases by nearly 29%. The ageing mechanism of propellant with strain under low temperature may be physical damage due to the effect of stress or strain, including net cohesion damage and the interface dewetting between solid grains and binder.

Abstract:Hydroxylammonium 2-dinitromethyl-5-nitrotetrazolate (HADNMNT) was synthesized via neutralization reaction with hydroxylamine, using 2-dinitromethyl-5-nitrotetrazole (HDNMNT) as raw material. Its structure was characterized by FTIR, ¹H NMR, ¹³C NMR, ¹⁵N NMR and elemental analysis. The thermal stability of HADNMNT was studied by DSC. The detonation velocity and detonation pressure of HADNMNT were calculated by a density function theory and K-J equation. The theoretical specific impulse of monopropellant HADNMNT was calculated by the principle of minimum free energy under the standard state(pressure is 68.9 MPa, expansion ratio is 70:1). Results show that the yield of HADNMNT is 98.4%, and the peak temperature of DSC curve at a heating rate of 10 ℃·min^-1 is 145.3 ℃. Its detonation velocity, detonation pressure and specific impulse are 9.240 km·s^-1, 39.54 GPa and 2639.8 N·s·kg^-1, respectively.

Abstract:The density functional theory (DFT) calculation method was used to investigate electronic structures, energy gaps and sensitivities of N-aminopolynitrodiazoles at B3LYP/aug-cc-pVDZ level. The heat of formation (HOF) in the solid phase and the density were predicted by the Politzer model. Thermal stabilities were predicted by bond dissociation energies (BDEs), and all the compounds were with high BDEs in the range of 238.94 kJ·mol^-1 to 283.95 kJ·mol^-1. Kamlet-Jacob equations were employed to predict the detonation performance of the title compounds. Results show that 1-amino-3, 4, 5-trinitropyrazole (8.99 km·s^-1, 36.12 GPa) and 1-amino-2, 4, 5-trinitroimidazole (8.92 km·s^-1, 35.56 GPa) exhibit comparable detonation performance to those of cyclotrimethylenetrinitramine (RDX, 8.75 km·s^-1, 34.7 GPa) and cyclotetramethylenetet-ranitramine (HMX, 9.1 km·s^-1, 39.00 GPa). Considering thermal stability and detonation performance, 1-amino-3, 4, 5-trinitropyrazole and 1-amino-2, 4, 5-trinitroimidazole can be used as potential high energy density materials.

Abstract:To study the influence of the vapor-liquid two-phase concentrations of n-decane sprays under the same particle size condition on explosion parameters, the n-decane sprays with different concentration of vapor-liquid two-phase based on Sauter mean diameter D₃₂ were studied by an optical measurement system of particle size and concentration of liquid spray and a 20 L double pulse pneumatic spray multiphase explosion test system. The explosion parameters were measured. Results show that under the conditions of D₃₂ as 38.11 μm and ignition energy as 40.32 J, the low flammability limit(LFL) total concentration of vapor-liquid two-phase n-decane sprays is 199.29 g·m^-3, corresponding liquid-phase mass concentration is 151.34 g·m^-3 and vapor-phase volume concentration is 0.77%(V/V). The maximum detonation temperature peak and maximum detonation pressure peak in the flammable range of concentration is 812 ℃ and 0.97 MPa respectively. Under the condition of D₃₂ as 38.11 μm, the influence of liquid-phase concentration of n-decane sprays on the LFL is smaller, whereas the dominant factor affecting the LFL of n-decane sprays is vapor-phase concentration.

Abstract:The washing process and deacidification kinetics for RDX were investigated using the ultrasonic technique. The effects of ultrasonic time, temperature, ultrasonic frequency and ultrasonic power on the washing and deacidification for acidiferous RDX with acidity as the evaluation indicator by the single factor test were discussed. The conditions of ultrasound-assisted washing process were optimized by orthogonal experiment. The related dynamic model was deduced and the activation energy was obtained. Results reveal that, the influence order of four factors is ultrasonic time>ultrasonic frequency>temperature>ultrasonic power, the optimum parameters are ultrasonic time of 70 min, temperature of 35 ℃, ultrasonic frequency of 40 kHz, ultrasonic power of 85%.The deacidification process is in conformity with pseudo-first order kinetics, the activation energy is calculated as 7.105 kJ·mol^-1, and the results of model analysis are verified by the results of experiments. Ultrasonic treatment brought about no changes of the molecular structure and representative functional groups of RDX.

Abstract:In order to characterize macroscopic mechanical properties of heterogeneous propellant by microphysical parameters, the compressive property and shock resistance of single-base gun-propellant containing different amount of RDX(0% (binder), 10%, 20%, 30%, 35%) were tested at -40, 20, 50 ℃, and the surface contact angle of binder was measured at 20, 30, 40 ℃ and 50 ℃. Then, the surface energy of binder and the interface energy between binder and RDX were calculated and the microscopic parameter-adhesive energy per mass of RDX and binder(E^d) was defined. The relationships between E^d and mechanical property parameters(yield stress σ, volume deformation impact energy D) were obtained. Results show that σ and D decline in an exponential function with E^d, which is consistent with the macroscopic test: with the increasing of RDX, the E^d decreases, σ and D both increase. It turns out that macroscopic mechanical properties of single-base gun-propellant can be characterized by microphysical parameter.

Abstract:The response regulations of electrostatic discharge (ESD) conditions for firing device materials of an electric explosive device (EED) and its damages under an electrostatic environment were studied. The ESD process for discharge models under different high static voltage conditions was simulated and analyzed by the ESD models from Institute of Electrical and Electronic Engineers (IEEE) standard and Sandia laboratory standard. Energy values produced by discharge were determined and compared and analyzed with those of physical form transformation property of firing materials in a typical EED. The damage situation of ESD to a typical EED was predicted. Results show that peak discharge current increases with increasing the initial electrostatic voltage, while the other parameters of current waveform unchanges. For a typical firing device consisting of Ni-Cr bridge wire with a diameter of 40 μm and lead styphnat, the temperature in bridge wire can reach the melting point of tin solder, decomposition and ignition points of explosive at the initial voltage of 20 kV, making bridge wire fuse at 40 kV in IEEE standard. ESD model; while in Sandia laboratory standard ESD model, the temperature in bridge wire can reach the melting point of tin solder at 20 kV, decomposition and ignition points of explosive at 25 kV and melting point of bridge wire at 50 kV.

Abstract:In order to analyse the electrostatic hazard of micro-nano energetic materials, the electrostatic accumulation experiments were carried out with industry and nano RDX, HMX explosive using different standard sieve instead of the chute. The electrostatic accumulation of RDX and HMX were obtained by Faraday cylinder, and their electrostatic hazards were analyzed. The influences of explosive powder quantity and particle size on the electrostatic accumulation under condition of the 50 aperture standard sieve were studied. The electrostatic hazards of nano RDX sieved with different aperture standard sieves were compared. Results show that the more the amount of explosive is, the greater the electrostatic accumulationis. There is certain linear relationship between the standard sieve aperture and the electrostatic accumulation. The average mass charge density of nano RDX and HMX with the particle size of 80 nm are -21.1 and -8.1 μC·kg^-1 respectively, and are about 3.6 times of those of industrial RDX and HMX respectively, indicating a high electrostatic hazard. The electrostatic accumulation of RDX is about 2.6 times of those of HMX in the same particle condition.

Abstract:The critical temperature of thermal explosion (T_cr) of PBX-A explosive chargers containing (AP) with diameter of 10, 15, 20, 30 mm and 40 mm and ratio of length to diameter of 1:1 was measured by self-developed test device of determining the critical temperature of thermal explosion of explosives and propellants. The critical temperature of thermal explosion and 5 s explosion temperature of PBX-A before and after aging 70 days under 85 ℃ was measured by the T_c measurement and an explosion temperature test apparatus. The degree of responses to the constant temperature heat stimulus, critical temperature of thermal explosion of charge with different diameter, relationship between time to ignition (t) and temperature (T) and change of thermal performance of PBX-A explosive before and after aging was obtained. Results show that the combustion of unconstrained PBX-A explosive charger with diameter of less than 40 mm only occurs at a constant temperature. The value of T_cr extrapolated by the fitting equation is over 120 ℃ for PBX-A explosive charger with diameter of 1 m and ratio of length to diameter ratio of 1:1. The linear relationship between lnt and 1/T can be true only in a very narrow temperature range. The T_cr of PBX-A explosive charger after aging 70 days under 85 ℃ does not change, however, its 5s explosion temperature decreases by 4.6 ℃.

Abstract:As a kind of new rocket propellant, gelled propellant is thought to integrate the advantages of traditional liquid propellant and solid propellant. Gelled propellant′s special non-Newtonian rheological characteristics make it difficult to be atomized and atomization is one of the key problems of gel propulsion technology. Jet impingement atomization was the mainly used atomization method. The statuses of research on experiment, theory and simulation of gelled propellant jet impingement atomization were reviewed. From the discussion, the following conclusions could be drawn: firstly, in aspect of atomization experiment, with the analysis of experiment obtained atomization data, the influences of rheology and impinging parameters on atomization could be got, but hardly any quantitative result could be concluded. Secondly, in aspect of atomization theory, the liquid sheet characteristics, such as liquid sheet shape, liquid sheet breakup length, etc., could be predicted by the stationary antisymmetric wave theory and the linear stable theory, but the accuracy of the prediction was not so high and the atomization theory should be further improved. Thirdly, in aspect of atomization simulation, the main developing processes of jet impinging atomization could be simulated with both traditional mesh based methods and newly developed mesh free methods, but the simulation results was fairly rough and the atomization simulation was still on in a fledging period. In a word, the mechanism of the gelled propellant atomization was still beyond being fully understood, future work could be carried in the following aspects: to develop a quantitative gelled propellant atomization characterizing method, to develop a new non-Newtonian rheological based and impingement included atomization theory, to improve the numerical simulation methods according to the characteristics of jet impingement atomization of gelled propellant, etc.

Abstract:The cyclotetramethylene tetranitramine (HMX)/ammonium perchlorate (AP)/energetic polymer (EP) nanocomposite was prepared by a co-precipitation method using a novel EP as matrix. Its structure and properties were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), specific surface area (Brunauer-Emmett-Teller (BET)) measurement, Infrared (IR) spectrometry, and differential scanning calorimetry (DSC). Results show that the HMX/AP/EP nanocomposite possesses the three-dimensional nano-network structure. The HMX and AP particles are uniformly deposited on EP, whose size is in the range of 50-200 nm. HMX, AP and EP are closely bonded each other with good compatibility. The thermal decomposition temperature of the HMX/AP/EP nanocomposite is far lower than that of HMX. When the oxygen balance of HMX/AP/EP nanocomposite is zero, its decomposition heat is up to 2570 J·g^-1.Compared with the characteristic drop height of impact sensitivity (H₅₀) of 27 cm of HMX, the value of H₅₀ of the HMX/AP/EP nanocomposite is 50.49 cm, revealing that the latter has lower mechanical sensitivity.

Abstract:1, 3-Di(azido-acetoxy)-2-methyl-2-nitropropane(DAMNP) was designed and synthesized via two-step reactions of esterification and azidonation using 2-methyl-2-nitro-1, 3-pro-panediol as raw material with a total yield of 84.7% and a purity up to 98.3%. Its structure was characterized by infrared spectroscopy (IR), nuclear magnetic resonance (NMR) and elemental analysis. The thermal behavior of DAMNP was studied by differential scanning calorimetry(DSC) and thermogravimetry-derivative thermogravi-metry(TG-DTG). Results show that it has a glass transition temperature at -50.73 ℃ and an exothermic decomposition peak at 227.6 ℃, indicating a better stability. The main properties of DAMNP was tested as following density 1.38 g·cm^-3, impact sensitivity H₅₀ 69.2 cm (falling weight 2 kg), friction sensitivity 4%(pendulum angle 66°).

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