Graphene is potentially the perfect barrier material, being impermeable even to the smallest gas molecules, but in practice it is difficult to achieve defect‐free graphene layers at large scale. Here, exceptional barrier performance for laminates comprising graphene nanoplatelet (GNP) paper sandwiched between two discs of polyamide 11 (PA11) is demonstrated. Results are compared with sandwich structures incorporating melt‐processed GNP/PA11 composites, and with chemical vapor deposition (CVD) monolayer graphene transferred onto PA11. PA11 is of interest as a polymer commonly utilized within the oil and gas industry for antiwear and barrier layers in flexible risers. Permeation studies were undertaken for a feed mixture of carbon dioxide (CO2) with 1.48% hydrogen sulfide (H2S) at a temperature of 60 °C and pressures up to 400 bar, providing the first data for the performance of graphene as a barrier to a supercritical fluid. Whereas a GNP/PA11 composite and a CVD graphene monolayer have little effect on permeability, compared to a pure PA11 control sample, a GNP/PA11 laminate reduces CO2 permeability by more than an order of magnitude, and reduces H2S permeability to an undetectable level.

Flexible pipes used to transport crude oil and gas from the seafloor to the surface are made of layers of a polyamide and strengthening steel. In article number https://doi.org/10.1002/admi.201800304 by Thomas P. Raine, Bernadette Craster, Peter M. Budd and co‐workers, it is shown how the polyamide can be made a much more effective barrier to carbon dioxide and hydrogen sulfide at high pressure by addition of a graphene layer.