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A series of cross‐linked and physical blends of nitrocellulose (NC) with oxirane‐tetrahydrofuran copolyether (PEOT) in different proportions were prepared using toluene‐2,4‐diisocyanate (TDI) as a crosslinking agent. The critical mechanical properties were evaluated by a universal material tensile testing machine and the dynamic mechanical thermal analyses (DMA). The reaction mechanism of the crosslinking process as well as the interaction between NC and PEOT were studied through Fourier transform infrared spectroscopy (FT‐IR). It was shown that as the mass fraction of PEOT increases, the Tg of the polymer blends gradually decreases, which can reach as low as −22.3 °C. It was further indicated that the low‐temperature mechanical properties of NC were significantly improved after blending. In comparison to the physical blending polymers, the miscibility between NC and PEOT was improved after cross‐linking reaction with TDI. When the mass fraction of NC was 50 %, the tensile strength of NC/PEOT physical blend and NC/PEOT/TDI cross‐linked blend reaches 20.82 MPa and 24.93 MPa, respectively. The corresponding elongation at break of these two systems was 96.58 % and 102.7 %, which means the toughening effect of PEOT on NC could be enhanced by crosslinking. [ABSTRACT FROM AUTHOR]

In this study, the energetic 2,4,6,8,10,12‐hexanitrohexaazaisowurtzitane/2,4‐dinitro‐2,4‐diazapentane (CL‐20/DNDAP) cocrystals were successfully fabricated via an efficient self‐assembly strategy. The formation processes of CL‐20/DNDAP cocrystal in solvents of H2O, H2O/methyl acetate, and 2‐propanol have been investigated by using the powder X‐ray diffraction (PXRD) qualitative/quantitative analysis and scanning electron microscopy (SEM). Both theoretical and experimental studies confirmed that the most satisfying results can be achieved by using 2‐propanol at 30 °C with crystallization time of 2 h, with a high yield up to 98.2 %. The addition of sodium dodecyl benzene sulfonate (SDBS) is effective in controlling its morphology with a narrow size distribution. Furthermore, the cocrystal exhibits better thermal stability and improved mechanical sensitivity compared with the one prepared by spray drying method. This work provides a simple and convenient approach for the preparation of energetic cocrystals, and the CL‐20/DNDAP cocrystal with high energy and low sensitivity is desirable for various applications. [ABSTRACT FROM AUTHOR]

In this work, the preparation and combustion catalysis effects of Cu2O−PbO/GO and CuO−Bi2O3/GO nanocomposites were systematically investigated. It was shown that the burning rate of the DB propellants can be significantly enhanced by both the nanocomposite catalysts, with reduced pressure exponent. In particular, the Cu2O−PbO/GO induced a burn rate enhancement for DB propellant in pressure range of 2–14 MPa, with the maximum catalytic efficiency of 3.87 at 2 MPa. More interestingly, it resulted in "mesa" burning of DB propellant in the pressure range of 12–20 MPa (n=‐0.05). The CuO−Bi2O3/GO have the same effect with a burning rate increasing from 2.15 to 8.57 mm s−1 at 2 MPa. Similarly, for the RDX‐CMDB propellant, the GO‐based composites of Cu2O−PbO/GO and CuO−Bi2O3/GO showed evident catalytic activities. Plateau combustion was achieved in their presence, which is of great importance for practical applications. The catalysis effects of the two composites are closely related to the high dispersion of metal oxide particles and GO with excellent thermal conductivity. [ABSTRACT FROM AUTHOR]

Abstract: The performances of NEPE (Nitrate Ester Plasticized Polyether) propellants containing 1,1 diamino‐2,2‐dinitroethylene (FOX‐7) were evaluated by means of theoretical calculation, combustion, mechanical and sensitivity experiments. It was found that, by the replacement of Cyclotetramethylene tetranitramine (HMX) with FOX‐7 in NEPE propellants, the density (ρ) was maintained to be the same 1.80 g cm−3, whereas the combustion temperature (Tc) decreased from 3700 K to 3592 K. The meaN molecular weight of combustion gas (Mc) was slightly increased (from 27.28 to 27.48 g mol−1) and the theoretical specific impulse (Ispo) was decreased from 2615 to 2560 N s kg−1. The content of FOX‐7 was in the range of 0 % to 34 % in the formulation of NEPE propellant. It was also shown that the burning rate was increased along with the elevated pressure exponents from 0.44 to 0.48. Moreover, the tensile strength of the propellants at +20 °C and +50 °C was improved from 0.84 and 0.68 MPa to 1.06 MPa and 0.75 MPa, respectively, while the maximum elongation decreased from 64.1∼86.1 % to 32.5∼45.3 %. In terms of safety, the friction sensitivity of the propellant was improved (initiation probability decreases from 100 % to 88 % under pressure of 2.45 MPa) and the impact sensitivity (H50) increased from 6.74 N m to 9.31 N m (2.5 kg hammer). [ABSTRACT FROM AUTHOR]

Over the past 20 years, a number of scientists have conducted numerous fundamental investigations based on quantum chemistry theory into various mechanistic processes that seems to contribute to the sensitivity of energetic materials. A large number of theoretical methods that have been used to predict their mechanical and spark sensitivity are summarized in this article, in which the advantages and disadvantages of these methods, together with their scope of use are clarified. In addition, the theoretical models for thermal stability of explosives are briefly introduced as a supplement. It has been concluded that the current ability to predict sensitivity is merely based on a series of empirical rules, such as simple oxygen balance, molecular properties, and the ratios of C and H to oxygen for different classes of explosive compounds. These are valid only for organic classes of explosives, though some special models have been proposed for inorganic explosives, such as azides. An exact standard for sensitivity should be established experimentally by some new techniques for both energetic compounds and their mixtures. © 2013 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]