Thermal conductivity of Kapton-derived carbon

Heat treatment of translucent Kapton®HN polyimide films conducted in inert atmosphere yields black residues. Micro-Raman spectroscopy revealed that the residues obtained between 600°C and 1200 °C are mainly constituted of disordered carbon. Aside its standard application in the structural identification of carbon, the Raman technique has also been used as a means of evaluating the thermal conductivity of Kapton-derived carbon. The aim of this study is to know whether such a tool can also be appropriate for disordered carbon with coherent diameters lower than 2 nm and with variable quantities of heteroatoms (H, O, N). To achieve this aim, a comparative study was undertaken using two other conventional techniques, namely laser flash analysis and photothermal radiometry. It has been found that thermal conductivity increases linearly with the heat-treatment temperature of Kapton and reaches 1.905 Wm−1K−1 for the film heat-treated at 1200 °C. The comparison of the experimental results shows that the Raman thermometry is particularly sensitive for sp2 carbon and predicts quite well the general trend of thermal conductivity of materials. However, the precision is rarely better than 20%.