Effect of nanofiller shape on effective thermal conductivity of fluoropolymer composites

Abstract

Filler particle shape and size influence interconnectivity within a polymer matrix and both play a significant role in controlling the effective thermal conductivity of a composite. This study examines the effect of nanofiller particle shape in a polytetrafluorethylene (PTFE) matrix on thermal energy transport. Experimental measurements using a laser flash analysis method are performed on PTFE with three different shaped carbon fillers: nano-diamond spheres, carbon nanotubes (CNT) and graphene flakes. Filler concentration ranged from 0 to 30 %. The experimental results are coupled with a particle connectivity model to understand the relationship between energy transport and filler connectivity. Results show filler particles with more micron scale dimensions form better interconnected networks at lower volume concentrations than fillers with fewer micron scale dimensions. Filler connectivity influences effective conductivity: specifically, nano-diamond spheres showed negligible interconnectivity and result in negligible change in thermal conductivity. The CNT, with one-micron scale dimension (i.e., length) and flakes, with two-micron scale dimensions (i.e., length and height), both exhibited linear increases in interconnectivity and effective thermal conductivity. Graphene interconnectivity in PTFE is six times that of CNT and thermal conductivity is 0.5 W/mK, two times that of CNT, respectively. These results provide new insights on how to optimize nanoparticle structure to enhance thermal energy transport.

Preparation of PTFE/graphene nanocomposites by compression moulding and free sintering: A guideline

“…It is known that unfilled PTFE does experience mass loss during processing due to slight degradation of PTFE at temperatures above its melting point . The higher mass loss shown with increasing graphene loading might be explained due to the increased thermal conductivity attributed by the graphene nanoplatelet shape and presence which also accelerate thermo‐oxidative decomposition of the PTFE. Analysing the void content was only taken from a section (Region of interest, ROI) from the centre of each sample due to the amount of voids that would need to be processed.…”

“…The incorporation of nanofillers into PTFE has received a lot of attention in the past few years and has shown to be effective in improving the tribological properties and the thermal conductivity of PTFE. Yan et al .…”

“…showed that expanded graphite combined with other nanofillers give a synergistic effect to improve the mechanical properties of PTFE composites. However, there exists limited information regarding PTFE composites filled with graphene nanoplatelets and how it influences the physical properties of the PTFE . Furthermore, the proper fabrication methods of these nanocomposites are also relatively unestablished and very few articles address the preparation of nanofilled‐PTFE composites.…”

Epoxy composites with ceramic core–shell fillers for thermal management in electrical devices

“…Besides the matrix thermal conductivity, the thermal properties of a composite are also related to the kind of filler used, the grain size, the content of this filler, and its alignment in the matrix . The quality of the filler–epoxy matrix interface seems to be crucial in ensuring the precise control of the thermal properties of a composite .…”

A review on the role of interface in mechanical, thermal, and electrical properties of polymer composites

“…Therefore, the interfacial zones predominantly affect the thermal conductivity of the composite [245,246]. As a result, anything that can affect the interfacial regions (e.g., geometry of particles [247][248][249][250][251][252][253], aggregation [254][255][256], interfacial pressure [257], roughness [258][259][260], and the strength of interactions at the interfaces [261][262][263][264][265]) in the composites would influence their thermal conductivity. In this section, we will review the parameters affecting the interfacial interactions and their subsequent impact on the thermal conductivity of the composites.…”