Thermal Management in Polymer Composites: A Review of Physical and Structural Parameters

Contrary to expectation, the thermal conductivity of carbon-polymer nanocomposites has been reported to be low near the lower boundary of the rule of mixtures. Various dispersing processes have been developed to achieve uniform dispersion of the nanocarbon fillers, including an in situ polymerization process based on ring-opening polymerizable oligoesters. However, even if the nanofiller is well dispersed, phonon scattering due to the interfacial thermal resistance at the nanofiller-matrix interface and the contact thermal resistance at the nanofiller-nanofiller interface is inevitable, and this is the main cause of the low thermal conductivity of the nanocomposite. When the nanofiller is incorporated in a high content, the interfacial thermal resistance can be overcome by forming a contacted three-dimensional (3D) filler network between the fillers. Recently, thermal percolation behavior has been reported to occur in composite materials with sufficiently high carbon filler content. Also, the thermal conductivity can be synergistically improved by the simultaneous incorporation of fillers of different sizes and shapes, forming a contacted 3D filler network. It can be concluded that large fillers with high thermal conductivity are suitable for thermally conductive composites, while nanofiller is advantageous for heat-insulating composites.