Design,Preparation And Properties Of High Temperature Resistant,Waterproof And Salt Wet Resistant Coating For Combustible Cartridge Case

Combustible cartridge case is an important charge component which is very suitable for the weapon systems that need light load and small space.It is a kind of nitrocellulose-based porous materials which has a low ignition temperature and strong hygroscopicity.Thus,If the surface of the combustible cartridge case is not protected very well when it used in modern weapon with faster fire rate,it is easy to self-ignite in high-temperature gun barrel and absorb moisture in high-humidity and salt spray environment.These problems will worsen both the safety of gun operator and combustion performance of combustible cartridge case.However,they are not solved well by current research and industrial practice.Thus,if the high temperature-resistant performance,waterproof property and salt wet-resistant performance of combustible cartridge case are improved simultaneously,not only the power of the weapon system will be improved,but also the application field of combustible cartridges can be broadened.The purpose of this paper is to design and prepared a coating solution with excellent high-temperature thermal insulation performance and compact structure after curing to simultaneously improve the high temperature-resistant performance,waterproof property and salt wet-resistant performance of combustible cartridge case effectively.The followings are research contents and results of this paper.(1)The boron nitride modified epoxy resin-based coating solutions(BME-S0-S～BME-S4-S)were designed and prepared.The glass beads,sepiolite powder,silica aerogel and modified magnesium hydroxide were used as heat insulation fillers.The benzyl glycidol ether was used as the solvent.The curing agent 593,silane coupling agent KH550 and tween 80 were used as the additives.The results show that the thermal decomposition rate and thermal conductivity of each formula coating were lower than the control sample.At the test temperature of 240°C,the high temperature resistant time of the combustible cartridge case coated with the BME-S3-S coating solution was the longest.The average high temperature resistant time was 125.6 s which was increased by 74.44%compared with the control sample.The water contact angles on the surface of the combustible cartridge coated with the coating solutions were greater than that of the control sample.The water absorption of the combustible cartridge case coated with the BME-S3-S coating solution was the lowest.Its water absorption was 0.77% after 120 h which was decreased by97.87% compared with the control sample.The surface of the combustible cartridge case coated with the BME-S3-S coating solution suffered the least damage at a salt spray environment.(2)The phenolic epoxy resin modified silicone resin-based coating solutions(PEMS-S0-S～PEMS-S4-S)were designed and prepared.The glass beads,sepiolite powder,silica aerogel and modified magnesium hydroxide were used as heat insulation fillers.The benzyl glycidol ether was used as the solvent.The curing agent 593 and tween 80 were used as the additives.The results show that the thermal decomposition rate and thermal conductivity of each formula coating were lower than the control sample.At the test temperature of 240°C,the high temperature resistant time of the combustible cartridge case coated with the PEMS-S4-S coating solution was the longest.The average high temperature resistant time was 127.4 s,which was increased by 76.94% compared with the control sample.The water contact angles on the surface of the combustible cartridge coated with the coating solutions were greater than that of the control sample.The water absorption of the combustible cartridge case coated with the PEMS-S2-S coating solution was the lowest.Its water absorption was 1.55% after 120 h which was decreased by 95.71% compared with control sample.The surface of the combustible cartridge case coated with the PEMS-S4-S coating solution suffered the least damage at a salt spray environment.(3)The organic-inorganic composite silicone resin-based coating solutions(OI-S0-S～OI-S4-S)were designed and prepared.The glass beads,sepiolite powder,silica aerogel and modified magnesium hydroxide were used as heat insulation fillers.The benzyl glycidol ether was used as the solvent.The curing agent 593,silane coupling agent KH560 and tween 80 were used as the additives.The results show that the thermal decomposition rate of each formula coating was lower than the control sample.At the test temperature of 240°C,the high temperature resistant time of the combustible cartridge case coated with the OI-S1-S coating solution was the longest.Its average high temperature resistant time was 139.2 s which is increased by 93.33% compared with control sample.The water contact angles on the surface of the combustible cartridge coated with the coating solutions were greater than that of the control sample.The water absorption of the combustible cartridge coated with the OI-S1-S coating solution was the lowest.Its water absorption was 1.98% after 120 h which was decreased by 94.52% compared with control sample.The surface of the combustible cartridge case coated with the OI-S1-S coating solution suffered the least damage at a salt spray environment.Combined the above results,the coating solutions we designed can simultaneously improve the high temperature,waterproof,salt wet resistance of the combustible cartridge effectively.The formula of OI-S1-S is the best.The specific content of each part is: 40.32wt%organic-inorganic composite silicone resin,10.48wt% inorganic thermal insulation filler,16.13wt% curing agent and 33.07wt% auxiliary agent.The research results can provide a new way for study on protective coating of combustible cartridges case.