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Linear amorphous high polymers may be made anisotropic by drawing them at temperatures above the glass‐transition temperature and thereafter cooling down in the stretched state. With measurements on polystyrene, poly methylmethacrylate, polyvinylchloride, and polycarbonate it can be shown that thermal conductivity in the direction of Stretch is greater and perpendicular to this direction lower than in the un‐stretched isotropic state. The degree of anisotropy depends on the degree of stretch and on the molecular structure of the polymeric chain. By measuring the anisotropy of thermal expansion it can be demonstrated that thermal expansivity in the direction of stretch will become lower and perpendicular to this direction greater than in the isotropic polymer. There exists a close relation between the anisotropy of thermal conductivity and thermal expansivity. From measurements on polyvinyichloride it follows that anisotropy of thermal conductivity remains rather unchanged when heating the polymer to temperatures above the glass‐transition range in the stretched state. Therefore it may be expected that also strained elastomers will have anisotropy in thermal conductivity. Measurements on several strained elastomers in this direction perpendicular Lo strain had been done which show that strained elastomers with strong polar side‐groups have a considerable amount of anisotropy, while aliphatic polymers like natural rubber and polyisobutylene have no remarkable effects.

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