Measurement of the Coefficient of Thermal Expansion for PBX 9502

Detonation performance modeling of PBX 9502 at elevated initial temperatures requires knowledge of the change in charge size with increasing temperature. Previous measurements of the coefficient of thermal expansion (CTE) of PBX 9502 have shown large variations across different studies, as well as anisotropic growth in directions parallel and perpendicular to the pressing direction [Skidmore et al., The Elusive Coefficients of Thermal Expansion in PBX 9502, LA-14003, 2003]. In this study, we examine the thermally induced change in the radial and axial dimensions of isostatically-pressed cylindrical pellets of PBX 9502 during a single heating event from 20 °C to 75 °C, with intermediate measurements taken at 40 °C and 60 °C. Two virgin lots [BAE20F755-002 and HOL88H891–008] and one recycled lot [HOL88B891–007] are examined. For each lot, two pellets were measured. We did not observe anisotropic growth for any of the pellets between 20 °C and 75 °C, with comparable thermal expansion rates observed in both radial and axial directions. Our new growth rates for PBX 9502 are analyzed and compared with prior measurements. We show that the length scaling ratio versus temperature is slightly lower than that obtained by Skidmore et al. [2003].