Preparation of ADN-based energetic composite microspheres with excellent anti-moisture absorption and safety

Ammonium dinitramide (ADN) is an ideal solid composite propellant oxidizer. But it also exhibits high hygroscopicity and low safety. Solving these issues will be crucial of ADN in practical applications. In this study, three ADN-based energetic composite microspheres were prepared by suspension assembly process coating ADN with different polymeric materials (glycidyl azide polymer (GAP), fluorine rubber(F2602), and hydroxyl-terminated block copolyether(HTPE)). The experimental results showed that the three prepared samples were spherical particles with regular morphology and uniform particle size. The crystal structure was not changed. The contact angle, moisture absorption and mechanical sensitivity test showed that the ADN-based energetic composite microspheres have low moisture absorption and mechanical sensitivity. In particular, the ADN/F2602 sample, which possesses a lotus-like hydrophobic effect, exhibits a 57.24 % reduction in water absorption compared to the raw ADN, and the contact angle of ADN/F2602 (93.91°) is 4.24 times higher than that of the raw ADN (22.15°). The critical friction susceptibility of ADN/F2602 (168 N) is 2.1 times higher than that of raw ADN (80 N), and the critical impact susceptibility of ADN/F2602 (17 J) is 2.43 times higher than that of raw ADN (7 J). The combustion test showed that the combustion duration of ADN/F2602 increased from 1.353 s to 1.578 s for the raw ADN, and the flame intensity was enhanced. The successful ignition and flame stabilization of ADN/F2602 samples after 24 h storage under a relative humidity of 60 % indicates its good energy release performance in a propellant. Through this study, F2602 as a capping material has good anti-hygroscopic effect, mechanical insensitivity and combustion stability for ADN, which can support the application of ADN as an oxidizer in composite solid propellants.