Microstructure regulation and thermal behavior of nitroguanidine-based composite functional materials

Abstract Nitroguanidine (NQ) is a promising low-sensitivity energetic material with high energy density but suffers from poor interfacial compatibility and structural brittleness. In this work, an azide-functionalized polyurethane (A-PU) binder was designed to enhance the thermal and structural stability of NQ-based composites. A temperature shock treatment (liquid nitrogen immersion–thermal relaxation cycles) was applied to introduce prefabricated microcracks, enabling stress release and heat diffusion. Scanning electron microscopy (SEM) confirmed that A-PU formed a uniform coating around NQ crystals, while the cryogenic thermal cycling generated controlled microcracks along grain boundaries. The crack density increased from 0.25 to 1.15 μm −1 , and the mean pore size expanded from 0.12 μm to 0.38 μm. Differential scanning calorimetry (DSC) showed a reduction in decomposition peak temperature from 197 °C (pure NQ) to 185 °C (NQ–A-PU), accompanied by a higher exothermic intensity. Kinetic analysis using the Kissinger method revealed that the activation energy decreased from 251.2 to 193.1 kJ · mol −1 , indicating accelerated decomposition and improved interfacial energy transfer.