Optimisation of the gelation process and performance characterisation of nitrogen-containing Guanylurea double-based...

The gelation process of double-base propellants critically governs their processability and terminal ballistic performance, yet a systematic understanding of the rheological behaviour under the coupled influence of multiple processing parameters remains limited. To address this gap, this study systematically investigates the relationship between rheological properties and comprehensive performance by examining four key variables. A series of gelation samples were prepared using a kneading process. Steady-state shear data were acquired via capillary rheometry, and rheological modelling and analysis were performed using the different equations. Furthermore, the thermal decomposition, combustion, and mechanical performance were characterised for samples prepared under the selected rheologically optimised conditions. Experimental results demonstrate that the material exhibits significant pseudoplastic behaviour. The apparent viscosity decreased by up to 28.9% and 78.8% with increasing gelation time and solvent-to-nitrocellulose ratio, respectively. It showed a non-monotonic trend, first decreasing and then increasing with rising temperature, and increased significantly with a higher ethanol proportion. Based on coupled parameter analysis, an empirical model incorporating temperature and shear rate was established: η(T, γ) = 7336.744·exp(703.12/T)·γ^ (0.2996 - 0.00372T), which effectively predicts viscosity variations. The optimised gelation parameters were determined as follows: time, 80 min; temperature, 50 °C; solvent ratio, 2 : 3 (ethanol : acetone); and solvent-to-nitrocellulose ratio, 0.5. Samples prepared under the selected rheologically optimised conditions exhibited stable combustion performance, with the burning rate approximately 24% higher under high-temperature conditions than at room temperature. Thermal analysis revealed that the decomposition peak temperatures for NC/NG and nitroguanidine were 192.4 °C and 207.1 °C. Mechanical testing demonstrated favourable deformability and structural stability for these samples. The performance characteristics achieved under the selected rheologically optimised processing window are documented in this study, providing a reference for process design. A comparative assessment against non-optimised conditions is planned for future work to more definitively establish the causal relationship between rheological optimisation and enhanced material performance.