Thermal conductivity and diffusivity of carboxyl-terminated copolymer of polybutadiene and acrylonitrite (CTBN) and hydroxyl-terminated polybutadiene (HTPB) liquid rubber-modified epoxy blends were investigated. A good agreement was observed between the calculated values of the specific heat estimated from thermal conductivity, diffusivity, and density measurements and the DSC results. Measurements of the thermal conductivity values of HTPB/Epoxy blends were in good agreement with three simple theoretical models, which have been used thereafter for the estimation of the unknown value of the thermal conductivity of CTBN (k(CTBN) = 0.24 Wm(-1)K(-1)). The morphology of the rubber-modified epoxy blends has been quantified and indicate a tendency towards co-continuous phase upon the inclusion of higher weight percentage of rubber (>= 30 wt %). Moreover, we notice a significant enhancement of the thermal conductivity during this morphological shift. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 116: 3232-3241, 2010