GNP DISPERSION BY REACTIVE EXTRUSION FOR THERMALLY CONDUCTIVE POLYMER NANOCOMPOSITES

Thermally conductive polymer nanocomposites are of great interest in substituting metal components in all those applications where corrosion resistance, lightweight and processability are required. Nanoparticles with extremely high thermal conductivity (Carbon Nanotubes, Graphene and Graphene Nanoplatelets, hexagonal Boron Nitride) are expected to confer a huge improvement to polymer thermal properties. Recently, Graphene Nanoplatelets (GNP) have become an interesting option due to their geometry, which allows to obtain an higher contact between nanoparticles [1,2,3]. However, it is critical to obtain a good dispersion degree of GNP in polymer matrix, especially during melt mixing. In this work, a GNP with an expanded structure has been melt mixed with cyclic butylene terephthalate (CBT). These mixed oligomers are known to have a very low viscosity that can allow to a complete filling of the expanded structure, which is preliminar to the obtainment of a good exfoliation degree. This can lead to an higher contact between nanoparticles, with a consequent improvement in the thermal conductivity of the nanocomposite. Moreover, in a second step, during melt mixing a tin catalyst was added to the compound; this is known to open the cyclic structure, starting CBT polymerization into poly (butylene terephthalate) (pCBT). During polymerization the molecular weight, and the viscosity, of the molten system increase, and consequently raise the shear stresses that can have a key role in the optimization of the exfoliation degree. This, combined to the higher crystallinity of pCBT respect to CBT, can push to the obtainment of high thermally conductive polymer nanocomposites