Extending Transient Plane Source-Based Measurements for the Accurate Determination of Thermal Transport Properties in Polymers

Licentiate thesis, 2024

The Transient Plane Source (TPS) method is widely used for measuring the thermal conductivity and thermal diffusivity of materials, including the apparent cross-plane thermal conductivity of films, which incorporates the influence of thermal contact resistance. However, to precisely determine the intrinsic cross-plane thermal conductivity of films, the measurement procedure should be refined to decouple thermal contact resistance. Additionally, the TPS method has been adapted into the Transient Plane Source Scanning (TPPS) method to directly measure the heat capacity. While effective for materials with a thermal conductivity exceeding 1 W/(mK), the TPPS method may underestimate the heat capacity of materials with a low conductivity, such as polymers.
This thesis addresses these issues in two parts:
First, it explores the application of TPS in determining the intrinsic thermal conductivity of film samples. Thermal contact resistance in the measurements was carefully analysed considering experimental conditions such as sample thickness, mounting force, and the use of thermal interface materials. Finally, an optimized TPS-based method was proposed, which considerably mitigates the thermal contact resistance and provides the precise determination of intrinsic cross-plane thermal conductivity in polymer films.
Second, this thesis utilizes a finite-element numerical model to investigate the TPPS method for heat capacity measurement. Unlike conventional numerical models that require preset material properties, several key material properties in our model were tuned using experimental data. This enables the model to accurately simulate the experimental process. Consequently, the model provides correct heat capacity determinations for samples across a spectrum of thermal conductivities.