Impact of electrical percolation on mechanical, thermal and flame properties of carbon filler‐epoxy composites

Abstract

AbstractHybrid combination of carbon fillers is utilized in an epoxy matrix to enhance DC/AC conductivity and dielectric constant. Influence at electrical percolation on mechanical strength, thermal stability, co‐efficient of thermal expansion (CTE), and flame properties have been investigated since proper balance of the properties is critical. Multiwalled carbon nanotube and graphene nanoplatelets of different weight proportions are incorporated in epoxy matrix to understand their impact of electrical, mechanical and thermal properties. It is observed that weight fraction of the carbon fillers at electrical percolation tends to deteriorate the mechanical and flame properties, minimally influences thermal stability while decreasing the CTE. The weight fractions below the electrical percolation are observed to enhance mechanical and flame properties as compared to percolation level. Though the formation of network of carbon fillers is responsible for enhancement of electrical conduction and CTE, the synergy of carbon fillers is not evident in mechanical and flame properties due to dominating influence of aspect ratio, orientation, and alignment. DC conductivity of 3 × 10−6 S/m, AC conductivity of 4 × 10−2 S/m at 8 MHz is observed at electrical percolation. However, composite reveals 5% to 10% reduction in mechanical strength, while the thermal stability and glass transition (126°C) are minimally affected at percolation. Co‐efficient of thermal expansion improves to 2 × 10−6/°C and heat deflection temperature increases to 140°C. Flame properties reveal divergent trends. The need for proper balance of electrical, thermal and mechanical properties at electrical percolation is emphasized.