Effects of Functionalization on Thermal Properties of Single-Wall and Multi-Wall Carbon Nanotube - Polymer Nanocomposites

TL;DR

This study investigates how carboxylic functionalization of carbon nanotubes affects the thermal and electrical properties of polymer nanocomposites, revealing that functionalization enhances electrical conductivity but can impede thermal conductivity depending on nanotube type.

Contribution

It provides experimental insights into the contrasting effects of functionalization on thermal conductivity in single-wall versus multi-wall carbon nanotube-polymer composites.

Findings

Functionalized multi-wall nanotubes improve both electrical and thermal properties.

Small nanotube loadings (~1 wt%) boost electrical conductivity.

Larger loadings (~3 wt%) are needed for thermal conductivity enhancement.

Abstract

Carboxylic functionalization (-COOH groups) of carbon nanotubes is known to improve their dispersion properties and increase the electrical conductivity of carbon-nanotube - polymer nanocomposites. We have studied experimentally the effects of this type of functionalization on the thermal conductivity of the nanocomposites. It was found that while even small quantities of carbon nanotubes (~1 wt%) can increase the electrical conductivity, a larger loading fraction (~3 wt%) is required to enhance the thermal conductivity of nanocomposites. Functionalized multi-wall carbon nanotubes performed the best as filler material leading to a simultaneous improvement of the electrical and thermal properties of the composites. Functionalization of the single-wall carbon nanotubes reduced the thermal conductivity enhancement. The observed trends were explained by the fact that while surface functionalization increases the coupling between carbon nanotube and polymer matrix it also leads to formation of defects, which impede the acoustic phonon transport in the single wall carbon nanotubes. The obtained results are important for applications of carbon nanotubes and graphene flakes as fillers for improving thermal, electrical and mechanical properties of composites.