Electrostatic Desensitization and Combustion Enhancement of GATo Propellants Using CuCr₂O₄/Polypyrrole Composite Catalysts

In an effort to address the inherent trade-off between electrostatic safety and combustion performance in solid propellants, a series of CuCr₂O₄/polypyrrole (PPy) composite catalysts with tunable microstructures was designed in this study. CuCr₂O₄/PPy composite catalysts with CuCr₂O₄ loadings of 10, 30, and 50 wt% were synthesized via the hydrothermal method and in-situ polymerization. The microstructural evolution was characterized by electron microscopy, X-ray diffraction, and N₂ physisorption. These composites were incorporated at 2 wt% into GATo propellants, a Composite Modified Double-Base (CMDB) propellant, and their effects on electrical resistivity, thermal decomposition, burning rate, and sensitivities were systematically evaluated. The specific surface area of the composites decreased progressively from 52.7 m²/g (10 wt% CuCr₂O₄, 1#) to 38.1 m²/g (50 wt% CuCr₂O₄, 3#), confirming a microstructural transition from a continuous PPy network to agglomerated CuCr₂O₄ particles. The composite with low CuCr₂O₄ loading (10 wt%) imparted the lowest electrical resistivity and the most significant safety enhancement, while slightly improving the combustion performance of the GATo propellant: the negative electrostatic sensitivity threshold increased by 38% (from 1.78 J to 2.45 J), and the impact sensitivity threshold improved by 150% (from 4.0 J to 10.0 J). In contrast, the composite with high CuCr₂O₄ loading (50 wt%) achieved the highest combustion performance while reducing the sensitivity of the GATo propellant: the burning rate increased by 44% (from 3.79 to 5.47 mm/s), and the exothermic peak temperature decreased by 5.3°C.