(EP3319935) A composition and a method are provided for graphene reinforced polyethylene terephthalate (PET). Graphene nanoplatelets comprising a suitable initial surface area are added to a solvent for producing PET. In some embodiments, the solvent comprises ethylene glycol. The solvent and graphene nanoplatelets are sonicated to disperse the nanoplatelets within the solvent. The solvent and graphene nanoplatelets are centrifuged to remove nanoplatelet agglomerates within the solvent. A supernatant solution of dispersed graphene nanoplatelets and solvent is decanted and then used for in-situ polymerization of the graphene reinforced PET comprising a continuous matrix of PET with a dispersed graphene reinforcement phase. The graphene reinforcements comprise a minimal number of layers of two-dimensional mono-atomic carbon sheets. In some embodiments, the number of layers ranges between 1 layer and 7 layers. The graphene reinforced PET preferably comprises a concentration of graphene nanoplatelets being less than substantially 2% weight fraction of the graphene reinforced PET.