THERMAL CONDUCTIVITY ENHANCEMENT OF POLYMERS VIA STRUCTURE TAILORING

Polymers are usually known for their low thermal conductivity. However, the demand in industries for polymers with high thermal conductivity has increasingly grown due to their low density, low cost, flexibility, and good environmental resistance compared with conventional substances of high thermal conductivity. Composites filled with high thermal conductivity nanofillers will increase thermal conductivity (k); however, it has been clearly observed that the mechanical properties will deteriorate along with this process. Instead, increasing the intrinsic thermal conductivity of polymers themselves is more important. This review focuses on the mechanism of increasing k from the perspectives of polymer intrinsic structure tailoring: crystallinity, orientation of the crystallites, crystalline grain size, and alignment of the molecular chain in the amorphous region. Structure tailoring methods of increasing/improving these four factors are critically reviewed and discussed. Accurate thermal characterization methods are critically reviewed for these structure-tailored polymers in low dimensions. The transient electro-thermal and pulsed laser-assisted thermal relaxation 2 techniques provide some of the best and most accurate thermal conductivity measurements with high physics control.