A Noncovalent Compatibilization Approach to Improve the Filler Dispersion and Properties of Polyethylene/Graphene Composites

Graphene was prepared by low temperature vacuum-assisted thermal exfoliation of graphite oxide. The resulting thermally reduced graphene oxide (TRGO) had a specific surface area of 586 m(2)/g and consisted of a mixture of single-layered and multilayered graphene. The TRGO was added to maleated linear low-density polyethylene LLDPE and to its derivatives with pyridine aromatic groups by melt compounding. The LLDPE/TRGO composites exhibited very low electrical percolation thresholds, between 0.5 and 0.9 vol %, depending on the matrix viscosity and the type of functional groups. The dispersion of the TRGO in the compatibilized composites was improved significantly, due to enhanced noncovalent interactions between the aromatic moieties grafted onto the polymer matrix and the filler. Better dispersion resulted in a slight increase in the rheological and electrical percolation thresholds, and to significant improvements in mechanical properties and thermal conductivity, compared to the noncompatibilized composites. The presence of high surface area nanoplatelets within the polymer also resulted in a substantially improved thermal stability. Compared to their counterparts containing multiwalled carbon nanotubes, LLDPE/TRGO composites had lower percolation thresholds. Therefore, lower amounts of TRGO were sufficient to impart electrical conductivity and modulus improvements, without compromising the ductility of the composites.