  Different types of graphene-related materials (GRM) are industrially
available and have been exploited for thermal conductivity enhancement in
polymers. These include materials with very different features, in terms of
thickness, lateral size and composition, especially concerning the oxygen to
carbon ratio and the possible presence of surface functionalization. Due to the
variability of GRM properties, the differences in polymer nanocomposites
preparation methods and the microstructures obtained, a large scatter of
thermal conductivity performance is found in literature. However, detailed
correlations between GRM-based nanocomposites features, including nanoplatelets
thickness and size, defectiveness, composition and dispersion, with their
thermal conductivity remain mostly undefined. In the present paper, the thermal
conductivity of GRM-based polymer nanocomposites, prepared by melt
polymerization of cyclic polybutylene terephtalate oligomers, exploiting 13
different GRM grades, was investigated. The selected GRM, covering a wide range
of specific surface area, size and defectiveness, secure a sound basis for the
understanding of the effect of GRM properties on the thermal conductivity of
their relevant polymer nanocomposites. Indeed, the thermal conductivity
obtained appeared to depend on the interplay between the above GRM feature. In
particular, the combination of low GRM defectiveness and high filler
percolation density was found to maximize the nanocomposites thermal
conductivity.
