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Raw multi-walled carbon nanotubes (r-MWCNTs) and Cu nanoparticles are dispersed in an epoxy matrix in varying quantities to create composite polymers with enhanced thermal conductivities. A study was then conducted to determine if the boundary thermal contact resistance could be reduced by increasing the thermal conductivity. The boundary thermal contact resistance was found to be approximately constant across all samples containing the copper nanoparticles. The boundary thermal contact resistance was found to be much higher for the composite samples containing only r-MWCNTs than the other composites because of the high elasticity modulus of the nanotubes.
Four different paraffin-based nanocomposite phase change materials (PCMs) were prepared by dispersion of 20 v. % of graphene, multi-walled carbon nanotubes (MWCNTs), aluminum, or TiO2 nanoparticles into a paraffin matrix. It was found that the two carbon-based nanoparticles reduced the time required for melting and solidification of the PCM by a greater amount than the two other nanoparticles. The graphene-paraffin PCM was found to reduce the melt and re-solidification time by the greatest amount (~30%), and the authors attributed this to the enhanced thermal conductivity in this nanocomposite PCM, which was nearly 2800% higher than that of the pure paraffin PCM. In addition to the reduced melt and re-solidification time, the graphene-paraffin PCM was also found to increase the amount of the thermal energy that can be recovered from the PCM by 11%.
The thermal conductivities of four composite paraffin phase change materials (PCMs) containing embedded multi-walled carbon nanotubes (MWCNTs) with varying dimensions were determined. The goals of this study were to investigate the interfacial thermal resistance between two MWCNTs, and to investigate the ballistic and diffusive components of the thermal resistance at the interface. It was found that the thermal conductivity of the composite PCMs increased with the diameter of the MWCNT used as filler. This result was unexpected, as smaller nanotubes usually have a higher thermal conductivity. It was determined that larger diameter nanotubes have less interfacial thermal resistance due to a decrease in ballistic phonon scattering that occurs as a result of the increased contact area between the nanotubes.
Polytetramethylene ether glycol (PTMEG) was used to functionalize multi-walled carbon nanotube (MWNT) by grafting to produce MWNT-g-PTMEG. These functionalized nanotubes were then dispersed in thermoplastic polyurethane (TPU) to form a TPU/MWNT nanocomposite. It was found that the functionalization resulted in improved dispersion of the nanotubes in the TPU material. The tensile strength and elongation at break of the nanocomposite were also enhanced by the addition of the nanotubes in comparison to pristine TPU. The thermal conductivity was enhanced by the addition of MWNTs in contents of 3 wt. % or higher, but appeared relatively unchanged at lower filler contents.
