The aim was to prepare and characterise poly(ethylene terephthalate) (PET) composites with hydrogen-reduced graphene (HG) created using thermally expanded intercalated graphite oxide. Melt dispersion (MD) and ultrasonicated solvent-dispersion (SD) methods were contrasted. The structure, response to modulated force, temperature and permeability to gases were measured. A commercially sourced research grade graphene, sourced from Cheap Tubes, was used for comparison. PET-HG was melt dispersed using a Haake mixer with 1%·w/w HG added. PET solution dispersion was performed using o-chlorophenol with ultrasonication. Characterisation techniques used were Raman spectroscopy and wide-angle X-ray scattering (WAXS). Properties were measured using dynamic mechanical analysis (DMA), thermogravimetry (TGA), oxygen permeation (MOCON) scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Low defect graphene (1%·w/w), with a Raman D/G peak ratio of 0.53 (lowest D/G ratio) and TGA mass loss of 0.38% (84% less oxygen groups) under nitrogen purge, in PET MD was found to increase tensile storage modulus (43%) and loss modulus (96%) compared with neat PET MD (at 20°C). Oxygen permeation increased when reduced graphene was added to PET. Melt dispersion of graphene in PET was not as effective as ultrasonic solvent dispersion of graphenes in solvent cast films. Stress-- strain showed decreased strain of 86% and lower hysteresis when graphene (1%) was melt dispersed into PET. [ABSTRACT FROM AUTHOR]