A miscible PS/PPO blend was prepared and its miscibility was confirmed
by d.s.c. It was found that the miscibility of polymer blends could b
e evaluated by the measurement of their thermal diffusivity. The condu
ctivity in the liquid state was smaller than that estimated from a lin
ear-relation with the PPO content, but in the solid state, the conduct
ivity was larger than the estimated value. This phenomenon was conside
red to occur because the strong interactions of polymer chains in the
solid state increased the density (negative excess volume), resulting
in the increase of the thermal conductivity of the blend. Further, all
of Filippov, NEL and power law equations were found to be sufficientl
y adaptable to the experimentally determined thermal conductivities of
PS/PPO blend in the liquid state, but none of them could be adapted t
o that in the glass state. (C) 1997 Elsevier Science Ltd.