Improved interfacial properties for largely enhanced thermal conductivity of poly(vinylidene fluoride)-based nanocomposites via functionalized multi-wall carbon nanotubes

Interfacial properties between fillers and polymer matrix are crucial for the enhanced thermal conductivity of composites. Considering that vinyl-containing groups can be compatible with poly(vinylidene fluoride) (PVDF) matrix, triethoxyvinylsilane (YDH-151) functionalized multi-wall carbon nanotubes (s-MWCNTs) were prepared and blended into PVDF to achieve high thermal conductive s-MWCNTs/PVDF nanocomposites. Functionalized s-MWCNTs not only showed better dispersion, but also significantly increased the interfacial compatibility with PVDF, contributing to the largely enhanced thermal conductivity. A thermal conductivity of 1.552 W/(m·K) was achieved in s-MWCNTs/PVDF composite with 10 wt% s-MWCNTs loading, about 9 times in comparison to that of pure PVDF matrix, which was much higher than that of the non-functionalized MWCNTs/PVDF composite (0.478 W/(m·K)) under the same loading weight. The enhanced thermal conductivity was verified by both theorical and experimental results. A classic Effective Medium Theory model proved that YDH-151 functionalization on MWCNTs significantly improved their dispersibility in PVDF matrix, and more importantly reduced the interfacial thermal resistance of composite, which was 68% lower than that of original MWCNTs/PVDF composite. Experimental rheological measurement confirmed the improved interfacial properties greatly promoted the formation of denser MWCNTs network structure in nanocomposites. This work highlights an effective strategy for realizing excellent thermal conductive polymeric composites and provides useful information to further reveal the mechanism of thermal conductivity.