Insights into synergy-induced multifunctional property enhancement mechanisms in hybrid graphene nanoplatelet reinforced polymer composites

Abstract

Carbon-based hybrid composites have the potential to simultaneously enhance multiple material functional properties, compared to traditional biphasic composites. In this work, we demonstrate how taking a combined hybrid and hierarchical approach (i.e., polypropylene (PP)-based composite with graphene nanoplatelets (GNPs) coated on glass fibers (GFs), as a secondary micro-sized filler) is effective in multifunctional enhancement, without compromising the composites’ physical properties and mechanical performance. It is demonstrated that the volume exclusion and curvature effects of the highly oriented GFs, produces interconnected GNP clusters with relatively lower interstitial space. Hence, up to 6 orders of magnitude increase in direct-current electrical conductivity of the hybrid composites with 10 vol% GF was observed, relative to its biphasic counterpart. Also, at the percolation region, the hybrid composites reinforced with 10 vol% GF, have demonstrated an approximate 723 % increase in real permittivity. These improvements result in a synergy-induced Ku-band electromagnetic interference shielding effectiveness (EMI SE) of 20.56 dB, which is 81 % higher than that of the biphasic counterpart. Thermal conductivity measurements also showed considerable synergistic effect between the two fillers, whereby the thermal conductivity of the biphasic nanocomposite with 10 vol% GNP increased from 0.67 to 1.09 W/m·K for the hybrid composite containing 10 vol% GF. Such enhancements are accompanied by an approximate 109 % improvement in tensile strength, proving the efficacy of the hybrid approach to simultaneously enhance multiple properties, thereby meeting the requirements for novel practical applications.