Characterization of exfoliated graphite nanoplatelets/polycarbonate composites: electrical and thermal conductivity, and tensile, flexural, and rheological properties

Exfoliated graphite nanoplatelets (GNP) can be added polymers to produce electrically conductive composites. In this study, varying amounts (2-15 wt%) GNP were added to polycarbonate (PC) and the resulting composites were tested for electrical conductivity (1/electrical resistivity), thermal conductivity, and tensile, flexural, and rheological properties. The percolation threshold was approximately 4.0 vol% (6.5 wt%) GNP. The addition of GNP to polycarbonate increased the composite electrical and thermal conductivity and tensile and flexural modulus. The 8 wt% (5.0 vol%) GNP in polycarbonate composite had a good combination of properties for electrostatic dissipative applications. The electrical resistivity and thermal conductivity were 4.0 x 10(7) ohm-cm and 0.37 W/m.K, respectively. The tensile modulus, ultimate tensile strength, and strain at ultimate tensile strength were 3.5 GPa, 58 MPa, and 3.5%, respectively. The flexural modulus, ultimate flexural strength, and strain at ultimate flexural strength were 3.6 GPa, 108 MPa, and 5.5%, respectively. Ductile tensile behavior is noted in pure polycarbonate and in samples containing up to 8 wt% GNP. PC and GNP/PC composites show shear-thinning behavior. Viscosity of the composite increased as the amount of GNP increased dueto a volume-filling filler effect. The viscosity of the GNP/PC composites are well described by a Kitano-modified Maron-Pierce model.