Modeling solid thermal explosion containment on reactor HNIW and HMX

Effects of α-Fe 2 O 3 nanoparticles on the thermal behavior and non-isothermal decomposition kinetics of nitrocellulose

Nano metal oxides are common combustion catalysts for enhancing the burning rate of solid propellants. Cr2O3 nanoparticles (NPs) are efficient combustion catalysts for the pyrolysis of energetic components. In this study, Cr2O3 NPs were synthesized via a modified sol–gel method and further used for studying the thermal decomposition of nitrocellulose (NC). Differential scanning calorimetry (DSC) and thermogravimetry-Fourier-transform infrared spectroscopy (TG-FTIR) analyses indicate that the Cr2O3 NPs can be safely used with NC and the mechanism of the reaction between Cr2O3/NC and pure NC follows the Avrami–Erofeev equation: f(α) = 3(1 − α)[−ln(1 − α)]1/3/2. The peak temperature and activation energy (Ea) for the thermal decomposition of Cr2O3/NC are lower than those of pure NC. NO2 was detected at a lower temperature after NC was mixed with Cr2O3 NPs; this indicated the catalytically accelerated bond cleavage of NC by Cr2O3 NPs.

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Compatibility and thermal decomposition mechanism of nitrocellulose/Cr2O3 nanoparticles studied using DSC and TG-FTIR

Recently, both aniline-based compounds and their eutectic composition were found to be efficient stabilizers for nitrocellulose-based propellants. In this study, compatibility of nitrocellulose with two aniline-based compounds, viz, N-(2-methoxyethyl)-p-nitroaniline (MENA) and N-(2-acetoxyethyl)-p-nitroaniline (ANA), and their respective eutectic (MENA + ANA) has been investigated by nonthermal techniques (FTIR and XRD) and thermal techniques (DSC and VST according to STANAG 4147 requirements). The compatibility and the thermal stability of NC mixtures were further probed using stability tests (B&J and VST), kinetic modeling via fitting and free models on VST data, the determination of the isokinetic temperature, as well as the prediction of the storage lifetime. MENA was found to be compatible with NC. However, compatibility issues appeared once ANA is present in the NC mixtures. Finally, it was found that the lack of compatibility between nitrocellulose and stabilizer affects adversely the thermal stability and reduces significantly the storage lifetime of these mixtures.

Compatibility of nitrocellulose with aniline-based compounds and their eutectic mixtures

The purpose of this research was to improve the stability of carbamazepine (CBZ) bulk powder under high humidity by surface modification. The surface-modified anhydrates of CBZ were obtained in a specially designed surface modification apparatus at 60°C via the adsorption of n-butanol, and powder x-ray diffraction, Fourier-Transformed Infrared spectra, and differential scanning calorimetry were used to determine the crystalline characteristics of the samples. The hydration process of intact and surface-modified CBZ anhydrate at 97% relative humidity (RH) and 40±1°C was automatically monitored by using isothermal microcalorimetry (IMC). The dissolution test for surface-modified samples (20 mg) was performed in 900 mL of distilled water at 37±0.5°C with stirring by a paddle at 100 rpm as in the Japanese Pharmacopoeia XIII. The heat flow profiles of hydration of intact and surface-modified CBZ anhydrates at 97% RH by using IMC profiles showed a maximum peak at around 10 hours and 45 hours after 0 and 10 hours of induction, respectively. The result indicated that hydration of CBZ anhydrate was completely inhibited at the initial stage by surface modification of n-butanol and thereafter transformed into dihydrate. The hydration of surface-modified samples followed a 2-dimensional phase boundary process with an induction period (IP). The IP of intact and surface-modified samples decreased with increase of the reaction temperature, and the hydration rate constant (k) increased with increase of the temperature. The crystal growth rate constants of nuclei of the intact sample were significantly larger than the surface-modified samples at each temperature. The activation energy (E) of nuclei formation and crystal growth process for hydration of surface-modified CBZ anhydrate were evaluated to be 20.1 and 32.5 kJ/mol, respectively, from Arrhenius plots, but the Es of intact anhydrate were 56.3 and 26.8 kJ/mol, respectively. The dissolution profiles showed that the surface-modified sample dissolved faster than the intact sample at the initial stage. The dissolution kinetics were analyzed based on the Hixon-Crowell equation, and the dissolution rate constants for intact and surface-modified anhydrates were found to be 0.0102±0.008 mg1/3 min−1 and 0.1442±0.0482 mg1/3·min−1. The surface-modified anhydrate powders were more stable than the nonmodified samples under high humidity and showed resistance against moisture. However, surface modification induced rapid dissolution in water compared to the control.

William F. Bryant

Papers

Microcalorimetry and DSC study of the compatibility of energetic materials