Sensitivity of the TATB-based explosive PBX-9502 after thermal expansion

The sensitivity of TATB-based explosive PBX-9502 is affected by non-reversible thermal expansion, or "ratchet growth." PBX-9502 is a plastic-bonded explosive consisting of 95 wt % TATB (2,4,6-trinitro-1,3,5-benzenetriamine) and 5 wt % Kel-F 800 binder (chlorotrifluoroethylene/vinylidine 3:1 copolymer). The magnitude of the increase in size and the corresponding increase in sensitivity is reported here for a particular pressing of PBX-9502, after repeated thermal cycling. The physical morphology of the expanded material is examined using scanning electron microscopy, in an effort to determine the increase in intergranular holes, intragranular cracks and fissures in the TATB crystals, and the change in the distribution of the Kel-F, all of which are suspected to affect the sensitivity of the material. These images support the proposed mechanism for ratchet growth. Sensitivity, growth of the reactive wave behind the shock front, and Hugoniot data are obtained from in-material particle velocity gauge records of the shock initiation process. Increases in sensitivity with growth and with elevated temperature are summarized in Pop plots. Sensitivity increases commensurate with the increase in voids.