ABSTRACT
In order to improve the mechanical properties and thermodynamic stability of the long needle-like raw material Nitroguanidine (NQ), it was pulverized by a mechanical pulverization method and dried by a spray drying method, and three ultrafine NQ samples with different aspect ratios (2.26, 1.87, and 1.25) were prepared. The samples were tested and characterized by scanning electron microscopy, digital imaging particle size analysis, X-ray diffraction, and differential scanning calorimetry (DSC), and the impact sensitivity and bulk density of the raw NQ and ultrafine NQ samples were also tested. The results show that ultrafine NQ has the smallest particle size D50 of 9.18 µm, with uniform particle size distribution, unchanged crystal structure, and no introduction of impurities, and the impact sensitivity was the same as that of the feedstock NQ, which was 0. In addition, with the decreasing aspect ratio of the NQ particles, their apparent activation energy increased, and the energy required to be absorbed in the thermal decomposition increased; their thermal stability was also better.
ABSTRACT
This paper studies the influence of moisture content on the thermal stabilities of double-base propellant and multi-nitro ester propellant. The thermal behaviors and chemical kinetic parameters of the above two propellants and their mixtures with water were analyzed by using a CALVET heat flux calorimeter, C80. The thermal decomposition mechanisms of these two propellants with water were conjectured based on the tests. And then, the self-accelerating decomposition temperatures (SADT) of these two propellants and their mixtures with water were calculated and compared according to the kinetic parameters and Semenov model. The results show that the thermal decomposition mechanism of double-base propellant with water may be changing with the varying moisture content by transferring hydrogen proton (H(+)). However, the thermal decomposition mechanism of multi-nitro ester propellant with water may be unchanging due to the excess of formaldehyde (HCHO). Water plays the external physical factor on the thermal decomposition of multi-nitro ester propellant, and it plays both the physical and the chemical factors on the thermal decomposition of double-base propellant. The SADTs of their mixtures with water are much lower than that of pure propellants, and keep decreasing with the increasing of moisture content.
