Contrasting role of carbon nanofillers in electrical conduction and mechanical strength of epoxy composites: an investigation

Abstract

Role of hybrid carbon fillers at electrical percolation of polymers is well established but its influence of mechanical strength is not well understood. At percolation, electrical conductivity of 0.22 S/m is achieved with 2 wt.% of multiwalled carbon nanotube and 3 wt.% of graphene nanoplatelets, but the tensile strength is observed to decrease at percolation. The tensile strength of the composites at 25 °C varies from 544.52 to 751.46 MPa with strain ranging from 5 to 6%. The composite with 2 wt.% of graphene and multiwalled carbon nanotube reveals 38% increase over the unfilled epoxy composite at 25 °C but at electrical percolation the increase is by 19%. Tensile modulus improves with individual carbon fillers but decreases with hybrid fillers. The flexural strength of the composite with 2 wt.% of the carbon fillers at 25 °C is highest at 1541.58 MPa and the flexural modulus is 65.36 GPa, but reduces to 1411.2 MPa and 59.84 GPa at electrical percolation. The Barcol Hardness of composites shows minimal reduction, and the density of the composites is observed to change minimally with incorporation of the carbon nanofillers. Study emphasizes the precise estimation of electrical percolation with good balance of electrical and mechanical properties.