Polyurethane (PU) elastomers are largely used in the field of high-energy composites such as composite solid propellants (CSPs) and high-energy polymer-bonded explosives (PBXs) due to their distinguished characteristics. Conventional PU binders are mostly non-energetic materials, and consequently reduce the energy performance significantly. Nitrocellulose (NC), is an energetic polymer widely used as an ingredient in propellants, explosives, fireworks, and gas generators, may be introduced in PUbased compositions to overcome their performance drawback. In this context, PU/NC polymer blends at different mass ratios were prepared in the present work using hydroxyl-terminated polyester prepolymer (Desmophen® 1200) and nitrocellulose (NC) by solution blending process. The physico-chemical structure of the prepared PU/NC polymer composites were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and density measurements. The thermal decomposition behavior was investigated by differential scanning calorimetry (DSC). Based on the obtained DSC results, the Arrhenius parameters were computed by different isoconversional kinetic approaches, namely, iterative Kissinger-Akahira-Sunose (It-KAS), iterative Flynn-Wall-Ozawa (It-FWO) and Vyazovkin's nonlinear integral method coupled with compensation effect (VYA/CE). Additionally, in order to highlight the influence of the introduction of the NC to the binder composition on the performance of a composite propellant, the theoretical performances, namely, theoretical specific impulse, the adiabatic flame temperature, as well as the ideal exhaust gaseous species were determined based on NASA Lewis Code, Chemical Equilibrium with Application (CEA).

Abstract:One of the objectives of gun propellant research is to develop green formulations of gunpowder that should be less temperature sensitive than the current gun propellant. The temperature sensitivity of these new green formulations of the propellant should be measured to identify the less temperature sensitive green formulations. However, there are deficiencies in the methodologies for the measurement of the temperature sensitivity of gun propellants. Therefore, the aim of this investigation was to fill the gap by establishing a method for the measurement of the temperature sensitivity of deterred gun propellants by closed vessel tests. The temperature sensitivity of the burning rate of ball propellants and the temperature coefficients of gun performance were determined using closed vessel tests and ballistic firing, respectively. Specific definitions of temperature sensitivity and temperature coefficients were evaluated. The relation between these parameters has never been explicitly investigated previously. Assessing the temperature sensitivity of propellants by closed vessel tests is of added value to the range of ballistic tests if the results of these tests can be well correlated to the results of ballistic firings. Therefore, a comparison between both parameters was made. A correspondence has been observed between the temperature sensitivity of the propellant burning rate, as obtained from closed vessel tests, and the temperature coefficients as obtained from ballistic firings.

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