We report thermal expansion measurements and coefficient of thermal expansion (CTE) for LX-17-1 (92.5 wt.% 1,3,5-triamino-2,4,6-trinitrobenzene (TATB), 7.5 wt.% Kel-F 800) from 300 to 558 K. Samples uniaxially-compressed at 300 K show an axial CTE of (2.7 + 0.42T) x 10(-6) K-1 and a radial CTE of (48 + 0.16T) x 10-6 K-1; the different axial and radial CTE indicate a small degree of alignment of the TATB molecules under uniaxial compression. LX-17-1 that was pressed in a die heated to 375 K showed additional growth in the 350-400 K temperature range during heating; apparently residual strain is produced in the heated Kel-F during pressing and is released when the material is reheated and the Kel-F softens. We observed irreversible "ratchet" growth from temperature cycling. and also found that LX-17-1 continues to expand when held at 524558 K for periods of 4-5 h. Self-heating during thermal soak at 546-566 K indicated exothermic thermal decomposition.