Polyisocyanate bridged environmental graphene/epoxy nanocomposite coatings with excellent anticorrosion performance

[Display omitted] •Reduced graphene (RGO) was functionalized by polyisocyanate with isocyanurate-ring.•Polyisocyanate (Tri-HDI) can more effectively exfoliate RGO and improve its dispersibility.•Modified RGO adsorbed on colloidal particles can stabilize nanocomposite emulsion.•Excellent tensile strength and water resistance were simultaneously achieved.•The nanocomposite coating possessed prominent long-term anticorrosion properties. Diisocyanates functionalized graphene nanosheets with high level exfoliation have been demonstrated as effective anticorrosion fillers in waterborne polymer coatings. However, diisocyanates can cause potential environmental and health hazard. Here, we propose to use polyiscocyanate (Tri-HDI) with an isocyanurate-ring structure yet low volatility and toxicity, to functionalize reduced graphene (RGO). Compared with hexamethylene diisocyanate (HDI), the incorporation of Tri-HDI simultaneously increased the exfoliation degree and the dispersibility of RGO. The reactivity between Tri-HDI and GO was also enhanced, resulting in the increase of graft ratio. The addition of Tri-HDI-RGO (Tri-HDIG) was able to improve the colloidal stability of waterborne epoxy resin (ER), as well as the interaction and compatibility between Tri-HDIG and ER. The tensile strength of ER/Tri-HDIG thereby increased from 50.1 MPa to 81.8 MPa, and the water absorption decreased from 18.0 % to 5.90 %. The long-term corrosion resistance of ER/Tri-HDIG also got significant improvement, its impedance modulus increased by 5 orders of magnitude compared to pure ER coating. The broad applicability of Tri-HDIG as functional nanofiller in polymer matrixes has been confirmed.