Stability of poly(p-phenylenediamine) on nitrocellulose prepared by spiral gas-solid two-phase flow-assisted mechanochemistry

In this work, the application of poly( p -phenylenediamine) (PpPD) as a potential propellant stabilizer is reported for the first time, and establish a solvent-free, continuous, and efficient mechanochemical synthesis method based on spiral gas-solid two-phase flow (S-GSF). Structural and morphological characterization results show that PpPD prepared by this method boasts advantages including high purity, high yield, mild reaction conditions, and easy scalability, with a space-time yield reaching 46.25 kg⋅m -3 ⋅h -1 . In addition, the product is characterized by smaller particle size and more uniform distribution, which enhances the compatibility of the composites. After adding 3% (mass fraction) of PpPD to nitrocellulose, the nitrogen oxides produced by the decomposition, could be effectively reduced by 37.4%, and its stabilizing effect was better than that of DPA and C2. The thermal stability TGA loss was reduced by 52.5%. Electrostatic potential analysis and aromatic nitration theory indicated that the secondary amine sites of PpPD had high electron density and exhibited an obvious scavenging effect on NO x . We demonstrate that poly( p -phenylenediamine) (PpPD) is an efficient, non-toxic propellant stabilizer. To overcome the limitations of conventional batch synthesis, we developed a solvent-free, continuous mechanochemical process based on spiral gas-solid two-phase flow, which produces high-purity PpPD with a space-time yield of 46.25 kg m -3 h -1 under mild conditions. The nanosized PpPD particles improve composite compatibility. Thermal analysis verifies that PpPD significantly stabilizes nitrocellulose and avoids forming carcinogenic nitrosamines during NO x capture, with the stabilization mechanism elucidated via theoretical and computational studies. (1) A novel stabilizer PpPD was synthesized via S-GSF method, which features shortened reaction time, minimized solvent consumption and improved product yield. (2) An aromatic nitrification mechanism for PpPD is proposed, where its secondary amine sites capture NO x and inhibit toxic byproduct formation. (3) Sustainable synthesis of a low-toxicity, high-efficiency stabilizer is achieved, offering a new strategy for green stabilizer development.