Researchers from Polytechnic University of Turin assessed electrical and thermal conductivity of composites, which contain carbon-based fillers in an epoxy matrix
Carbonaceous materials are used as filler for polymers owing to their ability to enhance some mechanical properties and decrease cost of the materials. Carbon nanotubes (CNTs) and graphene or graphene-like nanoplatelets (GNPs) are major components that are highly studied for their mechanical, electrical, and thermal properties. Now, a team of researchers from Polytechnic University of Turin developed composites with very small amount of fillers and good electrical and thermal conductivity. The team assessed combinations of CNTs with graphite and graphene and used an epoxy resin as a matrix to leverage advantages of calendaring process.
The calendaring technique enabled to produce composites with carbon-based filler that was homogeneously dispersed in an epoxy matrix. The team enhanced the processing parameters to optimize the conductivity of these composites. A conductive network was formed when the filler load reached the percolation threshold. This in turn helped to significantly enhance electrical conductivity. The formation of percolation paths did not have any impact on the mechanism for thermal conductivity.
The team also found that CNTs were superior to GNPs in terms of optimizing the electrical conductivity. However, the efficiency of GNPs in enhancing thermal conductivity was more than CNTs. Hybrid composites that included feeble concentrations of two fillers demonstrated varying aspect ratios. These composites depicted electrical conductivity that was six orders of magnitude higher than the net matrix. The phenomenon can be accredited to the preferred orientation of the fillers, which is a result of calendaring that led to a synergetic effect that decreased the percolation threshold. The team did not observe synergetic effects for the thermal conductivity. This can be attributed to no benefits offered by combining different fillers. The research was published in the journal MDPI Materials on May 9, 2019.