Improvement in High Temperature‐Resistant Performance and Waterproof Property of Combustible Cartridge Case with BEMS Resin Based Composite Coating

Abstract

AbstractCombustible cartridge case (CCC) is an important charge component which is very suitable for the weapon systems that need light load. It is a kind of nitrocellulose‐based porous material which has a low ignition temperature and strong hygroscopicity. Thus, if the surface of the CCC is not protected very well when it is used in modern weapon with faster fire rate, it will be easy to self‐ignite in the high‐temperature gun barrel and absorb moisture in a high‐humidity environment. These problems will worsen both the safety of gun operators and the combustion performance of CCC. However, they are not solved well by current research and industrial practice. Herein, we designed a new composite coating which can improve both the high temperature‐resistant performance at a higher temperature and waterproof property of CCC. The boron nitride (BN) and epoxy resin were used to modify silicone resin. The BN and epoxy modified silicone (BEMS) resin, inorganic adiabatic fillers and other additives were mixed together to prepare a BEMS resin based composite coating solution, and then the solution was sprayed on the surface of the combustible cartridge case to form a protective coating. The chemical structure of BEMS resin was investigated by FTIR. The thermal stability of coating films was analyzed by TGA. The high temperature‐resistant performance, water contact angle on the surface and waterproof property of the coated CCC were analyzed by muffle furnace experiment, water contact angle tester and immersion test, respectively. Results show that boron nitride and epoxy resin were successfully grafted on silicone resin chains. Compared with control samples, the thermal decomposition rate of the prepared coating films is significantly reduced. The coated CCC will keep 108.8 seconds while not burning at 230 °C. The heat resistant time increased by 16.74 % at 230 °C. The water contact angle on the surface of the coated CCC can reach 105.71° which was improved by 67.01°. After being soaked for one hour, the water absorption of the coated CCC is reduced by 96 % in distilled water and by 99 % in 3.5 wt % of sodium chloride solution. Compared with most present coatings, the new BEMS resin based composite coating which we designed can improve both the high temperature‐resistant performance and waterproof property of the CCC significantly and effectively. It provided a new way for study on the protective coating of CCC.