Boosting Thermal Stability of Energetic Cellulose Ester with Low Sensitivity: Integration of Nitrate with Acetate Propionate Moieties via Mild Nitration

The exploration of a practical strategy for insensitive energetic polymers is still very desirable but highly challenging. Energetic cellulose esters have been demonstrated as effective candidates, which were widely used in various fields. Herein, cellulose acetate propionates (CAP) with different molecular weights were employed as raw materials to produce nitrated cellulose acetate propionates (NCAP) via mild and homogeneous nitration. The resulting NCAP were characterized using FTIR, NMR, XRD, SEM, DSC-TG-FTIR, and elemental analysis (EA) for the characterization of chemical structures and morphologies. They exhibited nitrogen contents of 2.0% and 1.3%, respectively, with corresponding molecular weights of 83,911 and 233,684. Compared to the common nitrocellulose (NC), the NCAPs exhibited an increase in thermal decomposition temperature of up to 8.2 °C, and their impact sensitivity value improved from 57.69 to 155.2 cm. Furthermore, the insensitive NCAP were composited with nitrocellulose (NC) in different mass ratios. The influence of different NCAP molecular weights on the rheological and mechanical properties of NCAP/NC composites was also investigated. The resulting composites were further evaluated in terms of the thermal behaviors, combustion performance, and sensitivity. This work ultimately demonstrates that NCAP, derived from the commercial CAP, can be functionally modified into high-performance insensitive energetic polymers.