Structural and chemical comparison between moderately oxygenated and edge oxygenated graphene: mechanical, electrical and thermal performance of the epoxy nanocomposites

Abstract

Two different graphitic powders, namely: moderately-oxidized graphene oxide (mGO) synthesized via a chromium-based technique and a commercial edge-oxidized graphene oxide (eGO), were characterized and incorporated into an epoxy resin, suitable for wind turbine blade structural components. Raman spectroscopy, X-ray photoelectron spectroscopy and thermogravimetric analysis revealed low oxygen content, but divergent structural characteristics for both powders confirming the increased basal-plane functionality of mGO compared to the peripherally decorated eGO. It is also shown that the eGO, displays carbon-based impurities. The inclusion of mGO, into the epoxy resulted in an initial glass transition temperature (Tg) increase (~ 5 °C at 4.4 vol.% mGO) but thereafter Tg decreased sharply. On the contrary, the inclusion of eGO resulted only in a progressive Tg increase. Introduction of just 1 vol.% of eGO deteriorated the tensile strength (~ 15% reduction) of the epoxy, while the strength of the mGO-filled samples was retained. Inclusion of mGO results in a percolation threshold (increase from 4.6 × 10−16 to 6 × 10−9 S/cm) at 0.53 vol.%; in contrast, at the same filler content, the eGO-filled systems are characterized by drastically lower conductivity values (3.4 × 10−16 S/cm). Nevertheless, further analysis indicates similar intrinsic conductivity (~ 10−6 S/cm) for the two fillers. Finally, the maximum achieved thermal conductivity increase with mGO was 200% (at 9.13 vol.%) compared with the unfilled epoxy, while the respective increase with eGO was 150% (at 18 vol.%).