Determination of the thermal conductivity

Plastics by nature have a low thermal conductivity of mostly < 0.1 W/mK. By adding suitable fillers, the thermal conductivity of the sample can be increased by a factor > 100.

The thermal conductivity of a material, given in W/mK, is the amount of heat that passes through a body of a given cross-section in a given unit of time under steady-state conditions. Thermal conductivity can be measured by various methods. One of the most common methods is the laser flash method, which is also used in the BARLOG Plastics test laboratory. In the laser flash method, a heat pulse is generated on the underside of the test specimen, and an IR detector measures the temperature rise on the upper side of the test specimen.

Due to the flow behavior of plastics and the orientation of fillers depending on the processing parameters and component geometry, very different thermal conductivities can be obtained with the same material on different components. The laser flash method allows the thermal conductivity to be measured in different sample directions. Thus, on the one hand, the thermal conductivity can be measured through the component wall thickness, but also in the longitudinal direction.

This method can provide valuable information for material qualification already during product development. Thus, it can be determined in advance whether a material has a high anisotropy of thermal conductivity and thus whether large differences must be expected in the various measurement directions on the component.