This part of ISO 22007 specifies a temperature wave analysis method for the determination of the thermal diffusivity of thin films and plates of plastics in the through-thickness direction. The method can be used on plastics in either the solid or molten state, and having either an isotropic or an orthotropic structure. The method covers values of the thermal diffusivity, α, in the range 1,0 × 10−8 m2·s−1 < α < 1,0 × 10−4 m2·s−1. Measurements can be performed either in air or in another atmosphere, e.g. an inert gas, at atmospheric pressure or at other, reduced or elevated, pressures, or under a vacuum, at a variety of temperatures.