Abstract
An analysis is given of the problems associated with measuring thermal conductivity in poor conductors at low temperatures, and a new sample design is described. This design, which employs inward radial flow in a disc, has been used for obtaining measurements in a number of two-phase polymers between 13 and 100 K. The samples consisted of varying percentages of polymethylmethacrylate dispersed in a continuous phase of polyoxypropylated glycerol. In spite of the very small size of the dispersed phase (similar 50 Å and upwards), it was found that anomalous behaviour only occurred below similar 10 K. It is suggested that at these temperatures the important phonon wave-lengths have become greater than the scale of the disorder introduced by the dispersed phase and that the phonons are therefore subject to additional scattering.

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