Graphite oxide/polyurea and graphene/polyurea nanocomposites: A comparative investigation on properties reinforcements and mechanism

Graphite oxide (GO) and graphene were incorporated into polyurea (PUA) via in situ polymerization and the properties reinforcements of the nanocomposites and the mechanism were compared and investigated through evaluating molecular weights, dispersion and interface interactions. As for the mechanical behaviors, 0.2 wt.% of graphene in the nanocomposites achieved the maximum increase in the tensile strength (80%). However, the tensile properties of PUA/GO nanocomposites decreased with the increase of GO contents. The GPC, TEM, FTIR and the immersion experiments indicate that the molecular weights of polyurea, dispersion of GO and the hydrogen bonds between the GO and PUA matrix are the three decisive factors for the deduced mechanical strength of PUA/GO nanocomposites. In contrast, due to the homogeneous dispersion and large mechanical strength of the graphene sheets, polyurea/graphene nanocomposites exhibited improved tensile strength, hardness and glass transition temperature. Moreover, it was found that the carbonyl, epoxy and hydroxyl groups in the graphite oxide influence the molecular weights and weakened the hydrogen bonds among polyurea molecules and those resulted in the deduced mechanical properties of polyurea.