Hexylamine (HA) functionalized reduced graphene oxide (RGO-HA) was prepared via the modification of graphene oxide (GO) with HA, followed by reduction with hydrazine hydrate. The structure of RGO-HA was confirmed using various characterization techniques. RGO-HA was easily dispersed in several organic solvents due to its hydrophobic nature. Accordingly, RGO-HA/polyurethane (PU) composites were synthesized using different amounts of RGO-HA for their potential application in the field of barrier materials. Fourier-transform infrared spectroscopy (FTIR), wide angle X-ray diffraction (WAXS) analysis, and field emission scanning electron microscopy (FESEM) showed that RGO-HA in PU was fully exfoliated and uniformly dispersed. The hydrogen gas barrier films were prepared by spray coating of RGO-HA/PU nanocomposite solutions on nylon films. Good attachment between the nylon surface and nanocomposite was confirmed by cross sectional field emission scanning electron microscopy. The nanocomposite coated nylon film having 43.3 wt% RGO-HA exhibited an 82% decrease in the hydrogen gas transmission rate (GTR) compared to a pure nylon film. The high reduction in GTR values of the coated films may motivate to use alkyl amine-modified reduced graphene oxide and PU nanocomposite for the future development of effective barrier materials. (C) 2015 Elsevier B.V. All rights reserved.