Thermally expanded graphite polyetherimide composite with superior electrical and thermal conductivity

Abstract

Thermally expanded graphite (EG) polymer composite has high potential for application in the modern thermo-electronic industry due to cost-effectiveness and excellent electrical and thermal properties. In this study, we report electrical and thermal conductivity enhancement of expanded graphite/polyetherimide (EG/PEI) composite fabricated by a simple solution mixing technique. Expanded graphite has the potential to enable larger enhancement in properties relative to graphene nanoplatelets, through the creation of continuous graphitic networks in the composite. Solution casting technique enables preservation of worm structure of expanded graphite in the composite thus enabling the development of continuous graphitic networks throughout the composite, leading to superior property enhancement. Measurements reveal ∼19 orders of magnitude increase in electrical conductivity of composite (yielding values up to 969 Sm-1) through the inclusion of 10 wt% of EG filler, relative to pure polyetherimide (electrical conductivity ∼ 1.2 × 10−17 Sm−1). Theoretical prediction using an effective medium approach reveals the impact of continuous graphitic network on the electrical conductivity of the composites. We also find that composite with 10 wt% EG filler composition exhibits a thermal conductivity (k) value of 7.3 Wm−1K−1, representing a significant enhancement of ∼3070% compared to pure PEI (k ∼ 0.23 Wm−1K−1). Field Emmission Environment Scanning Electron Microscopy (FE-ESEM) reveals the preserved interconnected structure of EG within the composite allowing the development of a conductive interpenetrating network of polymer and filler. Raman spectroscopy, X-ray diffraction (XRD), and X-ray Photoelectron Spectroscopy (XPS) analysis are further used to characterize the fillers and EG/PEI nanocomposites. Our work identifies the solution casting method as a promising approach for developing high-performance EG/PEI composites in this work.