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

Abstract

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 × 107 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.

Effect of Graphite Nanoplate Morphology on the Dispersion and Physical Properties of Polycarbonate Based Composites

“…As the sample break of the filled samples occurs at very low strains, in contrast to pure PC no strain hardening behavior is visible. Similar result of strong decrease in elongation at break starting at 10 wt % filler was reported by King et al for xGNP M5 material (compact structure type) in PC [53]. In our work, tensile strength decreases for all three GNP structures from 60 MPa of the unfilled polycarbonate to about 40 MPa.…”

Sub-critical gas-assisted processing using CO 2 foaming to enhance the exfoliation of graphene in polypropylene + graphene nanocomposites

“…Since at 0.5% graphene by weight the graphene-loaded samples are below the percolation threshold of 1% or greater, an appreciable increase in thermal conductivity was not expected [5] [6], [8], [56]. Interestingly, though, a decrease was observed and was largest in the SGAP samples (Fig.…”

Heat Transfer Capability of (Ethylene Glycol + Water)-Based Nanofluids Containing Graphene Nanoplatelets: Design and Thermophysical Profile

“…Nevertheless, unlike Krieger-Dougherty model, MP equation does not require the knowledge of intrinsic viscosity, which is not always an easy task when particles are not spherical [69, 70]. The Maron and Piece model [67] has already been successfully utilized to model viscosity enhancements of particles with different aspect rations such as fibers [71, 72] or platelets/flakes [73, 74] and can be written as follows: …”