Recent progress in the synthesis and modification of green oxidizers and their application in solid rocket propellant formulations during these last few decades are reviewed.
Abstract:In this paper, the thermal behavior and decomposition kinetics of trinitrohexahydrotriazine (RDX) and its polymer bonded explosive (PBX) containing a hydroxyl-terminated polybutadiene (HTPB) based polyurethane binder in the ratio 80% RDX/ 20% HTPB were investigated using various experimental techniques and analytical methods. The HTPB polyurethane matrix contains other additives and was cured using hexamethylene diisocyanate (HMDI). Thermogravimetric analysis (TGA), Differential Scanning Calorimetry (DSC), Vacuum Stability Test (VST) and Ignition Delay Techniques were applied both isothermally and non-isothermally. The kinetic parameters were determined using both the isoconversional (model free) and the model-fitting methods. For comparison, Advanced Kinetics and Technology Solution (AKTS) software was also used. It was found that the addition of an HTPB-based polyurethane matrix to pure RDX decreased its decomposition temperature. It was also found that RDX/ HTPB has a lower activation energy than pure RDX. The polyurethane matrix had a significant effect on the decomposition mechanism of RDX resulting in different reaction models. It was concluded that the activation energies obtained using the Ozawa, Flynn, and Wall (OFW) and Kissinger-Akahira-Sunose (KAS) methods were very close to the results obtained via the AKTS software lying in the range 218.3-220.2 kJ·mol −1. The VST technique yielded kinetic parameters close to those obtained using TG/DTG. On the other hand, the Ignition Delay Technique yielded different and inconsistent kinetic parameters.
A new propellant formulation (NC‐BTNEOx) based on bis(2,2,2‐trinitroethyl)oxalate (BTNEOx) as a high energy dense oxidizer (HEDO) mixed with nitrocellulose (NC) matrix was prepared and studied. BTNEOx was prepared and characterized by nuclear magnetic resonance (NMR) and X‐ray diffraction (XRD). Photos of the prepared formulation obtained by scanning electron microscope (SEM) clarified a good mixing of the nitrocellulose (NC) matrix with BTNEOx. A smokeless burning was observed and recorded for the prepared NC‐BTNEOx by a high speed camera. The thermal behavior and decomposition kinetics of the NC matrix, BTNEOx and their mixture have been investigated nonisothermally by using thermogravimetric analysis (TGA) and Differential scanning calorimetry (DSC). Isoconversional (model‐free) methods; Kissinger, Ozawa and Flynn−Wall (OFW) and Kissinger−Akahira−Sunose (KAS), were used to determine the kinetic parameters of the studied samples. The results proved that BTNEOx has melting temperature at 104.1 °C and maximum peak temperature at 200.6 °C, also it has effective activation energy in the range of 107–110 kJ/mol. The prepared NC‐BTNEOx has no endothermic peak and has exothermic peak at 201.7 °C which means that a composite might be formed due to the mixing of BTNEOx with NC. The prepared NC‐BTNEOx has effective activation energy in the range of 172–180 kJ/mol. BTNEOx required more study to proof the possibility of replacing the nitroglycerine in a smokeless double base propellant.
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