Unveiling the impact of nitrocellulose-enveloped nCuO on the thermal characteristics of ammonium nitrate-based solid composite propellants utilizing polyurethane/nitrocellulose blend binders

This study investigates the combined effects of coated nano copper oxide (NC@nCuO) and polyurethane (PU) modification on the thermal degradation kinetics and combustion properties of ammonium nitrate-based solid composite propellant. Nitrocellulose (NC) is used as a coating for nCuO, forming a core-shell structure, and as a binder in a PU/NC blend. Surface modification of ammonium nitrate was achieved through repeated spray coating. The formulations underwent thorough thermal characterization using thermogravimetry (TG) and differential scanning calorimetry (DSC) analyses. TG analysis showed a significant decrease in thermal degradation temperature due to AN modification with NC@nCuO and the use of PU/NC as a binder. Isoconversional kinetic methods (it-KAS, it-FWO, and VYA/CE) based on DSC tests were used to predict kinetic parameters, revealing a substantial impact of NC-coated nCuO and PU modification on the reactivity of the propellant, reducing the activation energy from 125 kJ/mol (reference) to 99 kJ/mol (nCuO) and 94 kJ/mol (NC@nCuO). Additionally, combustion tests were conducted. The results showed that the introduction of nCuO reduces the ignition delay by 5.25 ms and the combustion duration by 0.06 ms, while NC@nCuO further reduces these by 8.17 ms and 0.12 ms, respectively. Additionally, there is a 23% and 65% increase in flame intensity relative to the reference formulation after the incorporation of nCuO and NC@nCuO, repectively.