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.
Organic anticorrosion coatings (OACs) are the most effective, economical, and environmentally friendly protection strategy for metals. However, the traditional OACs usually inevitably suffer mechanical cracks during their service life. If not repaired in time, the resultant cracks in OACs will result in irreparable corrosion of the metal substrate. More detrimentally, these microcracks are not easily detectable at the initial stage. If OACs can autonomously heal their damage at the initial stage, the microcracks will be repaired in time and the metal substrate will be protected well. Thus, giving OACs the self-healing capability is a promising strategy for metal protection. Herein, an autonomously self-healing TiO 2 -reinforced silicone polyurea (SPU- g -TiO 2 ) elastomer was successfully designed as anticorrosion coating for Q235 carbon steel (QCS) protection. The SPU- g -TiO 2 elastomer matrix exhibited excellent stretchability with a maximum strain of 3826.72% and fast self-healing ability with an outstanding self-healing efficiency of 98.69% for 6 h without any external stimulus at room temperature. The QCS coated with SPU- g -TiO 2 showed excellent damage resistance and good anticorrosive ability, and it can self-heal the microcracks generated in its coating in time to prevent corrosive media corroding the internal mental substrate. This work has a positive guiding significance for the development of functional OACs to improve their protection for metallic materials. Highlights A bionic smart self-healing SPU- g -TiO 2 coating was successfully synthesized. The mechanical and self-healing properties are balanced using nanoparticles. The coating features excellent self-healing capability and stretchability. Q235 steel coated with SPU- g -TiO 2 shows good anticorrosive ability.
Silica/polyurea composite was prepared after surface modification of silica nanoparticles. Silica/polyurea composite was characterized by Fourier-transform infrared spectroscopy, ultraviolet spectroscopy, X-ray diffraction and transmission electron microscopy. The results indicate that
the helical polyurea has been successfully grafted onto the surfaces of the modified silica. Silica/polyurea composite exhibits clearly core–shell structure. The ultraviolet absorption and crystallizability of silica/polyurea are changed due to the shell of helical polyurea, which possesses
regular singlehanded conformation and interchain hydrogen bonds. The dielectric constant of silica/polyurea was also investigated. The result indicates that the interfacial interactions between organic shell and inorganic core increase the dielectric constant value being increased to 6.42
for silica/polyurea. The interchain hydrogen bonds of helical polyurea could also be the reason for the increasing of dielectric constant.
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