In Situ Exfoliation of Graphite into Graphene Nanosheets in Elastomer Composites Based on Diels–Alder Reaction during Melt Blending

We developed a new technique to in situ exfoliate graphite into graphene nanosheets and simultaneously prepare graphene nanosheets/elastomer composites based on the Diels–Alder (DA) reaction under strong shearing force transferred by the hydrogenated nitrile butadiene rubber (HNBR) during melt mixing. To realize the DA reaction, expanded graphite (EG) was used as a diene and maleic anhydride (MA) was chosen as the dienophile. The results show the efficient functionalization and exfoliation of EG into MA-functionalized graphene nanosheets (MAG), the good dispersion of MAG, and the formation of the MAG network structure in MAG/HNBR composites at low content of MAG (∼1 wt %). These result in the significant increase in stress at certain strain and the electrical conductivity of MAG/HNBR composites over that of neat HNBR and EG/HNBR composites with 1 wt % MAG. Unlike the method used in solution, this method could be applied in industry for large-scale preparation of graphene nanosheets and their elastomer composites.