  Thermally expanded graphite (EG) polymer composite has high potential in
modern thermoelectronic industry due to cost effectiveness, excellent
electrical and thermal properties. In this study, we report that expanded
graphite polyetherimide(EG/PEID) composite has been fabricated by simple
solution mixing technique, reinforcing a low cost EG filler into host polymer
matrix, polyetherimide (PEID). This technique enables the inclusion of 3D
graphitic filler into polymer matrix retaining the worm structure of expanded
graphite, thus developing continuous network throughout the composite. In
result, ~19 orders of magnitude rise of the polymers electrical conductivity up
to 969 S/m has been achieved upon the inclusion of the 10wt% of EG filler.
Theoretical prediction using effective medium approach reveals the impact of an
imperfectly conducting interface and interfacial tunneling on electrical
conductivity of the composites. We also report that 10wt% EG filler composition
composite exhibits the thermal conductivity (k) value of 7.3W/mK, implying
significant enhancement of 3070% compared to pure PEID. Scanning Electron
Microscopy (SEM) represents the morphology of fillers and composites, revealing
the preserved structure of EG to develop the conductive pathway between polymer
and filler. Investigation on the structural properties before and after the
thermal expansion of EG fillers has been performed using Raman, X-ray
diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS) analysis. In
summary, a simple fabrication route of solution mixing has been demonstrated to
achieve an outstanding electrically and thermally conductive EG/PEID composite
without compromising the efficiency of EG filler structure. The expanded
graphite-based polymer composites can retain their outstanding properties in
wide range of thermal and electronic industry.
