L-261 TNT Exudation, Crystal Growth and Ageing
August 2020Dr. Ernest L. Baker, Dr. Matthew R. Andrews, Dr. Kevin M. Jaansalu
For trinitrotoluene (TNT) and explosive formulations containing TNT (e.g. Composition B), TNT exudation in projectiles, bombs, and rockets has been a recurring problem since the early 1920s. TNT exudate typically has an oily appearance and dries to a somewhat black colour. The formation of exudate is associated with TNT impurities. Exudate by itself appears to be no more sensitive than TNT. However, if mixed with sand or grit, it can be very sensitive to impact or friction. Munitions that have TNT exudate in any part of the munition except were the design allows, should not be considered as safe and suitable for service. TNT exudate is formed due to the presence of DNT, and other impurities within TNT, combined with the high temperatures that can be experienced in the service environment of munitions filled with TNT containing explosive compositions. Older TNT manufacturing methods leave significant impurities within the TNT, whereas more modern methods have improved the quality of the processed TNT, removing most but not all impurities. Test standards have been developed to measure the percentage mass of exudate contained in explosive compositions. Another potential issue with aged TNT and explosive formulations containing TNT is crystal growth. There is some discussion within the munitions safety (MS) community that TNT crystals can grow within cavities of aged munitions. However, unless you are dealing with older munitions of 1920s or possibly 1930s, we believe that internal fill exudate and TNT crystal growth does not constitute a major concern for munition safety hazards if standard munition handling practices are observed.