Sandwich-structured graphene oxide@poly (aminophenol-formaldehyde) sheets for improved mechanical and thermal properties of epoxy resin

Abstract We propose a wet chemical method to synthesize sandwich-structured graphene oxide@poly (aminophenol-formaldehyde) (GO@PAPF) sheets. It uses GO as the shape-directing agent, 3-aminophenol as the precursors of polymer layer, formaldehyde as crosslinking agent, and ammonia as catalyst. Morphology characterization shows that the prepared GO@PAPF sheet has a sandwich-like structure with a thickness of 40 nm. It has good dispersion stability in acetone and epoxy resin diluted with acetone. After standing for 48 h, no obvious precipitation was observed. The effects of GO@PAPF loading on the physicochemical properties of epoxy composites have been systematically investigated. The resulting GO@PAPF/epoxy composites demonstrated an improved tensile strength and impact strength. When the loading of GO@PAPF sheets was 1.5 wt%, the tensile strength reached the maximum of 121.6 MPa, which is 62.1% higher than that of pure epoxy resin. The corresponding elongation at break was 5.77%. In addition, the introduction of GO@PAPF sheets also improves the thermal stability of epoxy composites. The glass transition temperature of the epoxy composite containing 1.5 wt% GO@PAPF sheets has been increased from 169.5 °C for pure resin to 184.1 °C. Big interfacial area, strong interfacial force between GO@PAPF sheets and epoxy matrix, good dispersion of GO@PAPF sheets in epoxy matrix were responsible for the enhanced mechanical and thermal properties.