Techniques for Controlling Exothermic Decomposition of Ammonium Perchlorate

摘要

In order to prevent or reduce premature reignition of extinguishable solid prepellant motors, a laboratory investigation has been made to search for methods that could eliminate or reduce the exothermicity of propellant grade ammonium perchlorate exposed to temperatures of 350-390C. It was found that ammonium perchlorate (AP) in which this first exothermic peak was eliminated could be prepared by heating the propellant grade AP to 365-390C for several minutes and allowing it to cool. Furthermore, this exothermic peak was eliminated by the pre-heating technique even when fluorocarbon polymer binder was in contact with the AP. This technique for preventing the first exotherm was successful in all samples of AP tested; the samples were from several sources and in several particle sizes. It was found that the temperature at which the first exotherm occurred could be raised as much as 45C by adding several percent of an ammonium salt (e.g., ammonium fluoborate) to the AP. The delayed exotherm was stronger than that found in AP to which no ammonium salt was added. This technique also was effective when fluorocarbon binder was in contact with the AP. Neither technique appeared to reduce the heat liberated by the deflagration of AP at 470-500C. Co-crystallized ammonium salts were also tested as AP additives. (Author)