An Autonomously Self‐Healing Silicone Polyurea Waterproof Coating for Combustible Cartridge Cases

Abstract

Abstract Nitrocellulose‐based combustible cartridge case (NC‐3C) is highly hygroscopic, which greatly limits its broader application. The effective strategy for NC‐3Cs to prevent moisture is the endowment of waterproof coatings. However, the traditional waterproof coatings for NC‐3Cs cannot self‐heal the inevitable mechanical microcracks suffered during handling and storage, which often gives moisture much more opportunities to destroy the internals. Therefore, it is necessary to develop a self‐healing waterproof coating for the protection of NC‐3Cs. Herein, a smart self‐healing silicone polyurea (SPU) elastomer based on dynamic reversible hydrogen bonds is designed as a waterproof coating for NC‐3Cs. The SPU elastomer shows an outstanding self‐healing efficiency of 99.06 % after 12‐hour self‐healing at room temperature. And it also can self‐heal its damages even when the ambient temperatures rise to 50 °C or drop to −18 °C. Moreover, the SPU‐coated NC‐3C can also self‐heal its microcracks in time after being scratched and obtains extremely low water absorptions (<0.20 %) after 24‐hour soaking, exhibiting good waterproof performance. Endowing the waterproof coating with self‐healing ability is a promising design strategy to repair the coating microcracks and improve the environmental adaptability of NC‐3C during handling and storage. This work pioneers a new design of self‐healing waterproof coating for NC‐3Cs, and it has a positive guiding significance to expend broader application of NC‐3C.