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This document specifies a method for the determination of the thermal conductivity and thermal diffusivity, and hence the specific heat capacity per unit volume of plastics. The experimental arrangement can be designed to match different specimen sizes. Measurements can be made in gaseous and vacuum environments at a range of temperatures and pressures.

This method gives guidelines for testing homogeneous and isotropic materials, as well as anisotropic materials with a uniaxial structure. The homogeneity of the material extends throughout the specimen and no thermal barriers (except those next to the probe) are present within a range defined by the probing depth(s) (see 3.1).

The method is suitable for materials having values of thermal conductivity, , in the approximate range 0,010 W m ¹ K ¹ <   < 500 W m ¹ K ¹, values of thermal diffusivity, , in the range 5 × 10 ⁸ m² s ¹ <   < 10 ⁴ m² s ¹, and for temperatures, T, in the approximate range 50 K < T < 1 000 K.

NOTE 1   The specific heat capacity per unit volume, C, C =     c_p, where is the density and c_p is the specific heat per unit mass and at constant pressure, can be obtained by dividing the thermal conductivity, , by the thermal diffusivity, , i.e. C =  / , and is in the approximate range 0,005 MJ m ³ K ¹ < C < 5 MJ m ³ K ¹. It is also referred to as the volumetric heat capacity.

NOTE 2   If the intention is to determine the thermal resistance or the apparent thermal conductivity in the through-thickness direction of an inhomogeneous product (for instance a fabricated panel) or an inhomogeneous slab of a material, reference is made to ISO 8301, ISO 8302 and ISO 472.

The thermal-transport properties of liquids can also be determined, provided care is taken to minimize thermal convection.