POLYMER/GRAPHENE NANOCOMPOSITES FOR IMPROVED BARRIER PERFORMANCE

Abstract

The current reliance of modern society on fossil fuels, and in particular oil and gas, means that industry is forever searching for improved technologies to access and recover crude, from harder to reach and depleting reservoirs. A key innovation in the oil and gas industry is the unbonded flexible riser, a flexible pipeline designed to transfer high pressure crude mixtures from deep sea wells to floating platforms and ships. These risers consist of many concentric layers of barrier polymers, such as polyamide 11, and strengthening steel. Often, high partial pressures of ‘sour’ fluids, including CO2 and H2S, are found within the crude. Upon permeating through the polyamide 11 barrier layer, along with water, these sour fluids can corrode the steel armouring. Corrosion and subsequent weakening of the steel may lead the riser to fail and, in so doing, risks catastrophic ecological impact, economic challenges and threat to operator life. There is therefore a drive to improve the resistance of polyamide 11 to CO2 and H2S permeation. The impenetrable nature of graphene was used as a starting point for increasing the barrier properties of polyamide 11. This thesis reports the first instance of testing the barrier properties of graphene and its nanocomposites to supercritical fluids of any kind. CO2 and H2S permeability testing was carried out in the gas, liquid and supercritical states at gauge pressures from 2 to 400 bar. In situ polymerisations of the polyamide 11 monomer with graphene nanoplatelets and graphene oxide led to promising materials for improving the barrier properties of the polyamide. Industrially relevant twin-screw extrusion was used to incorporate graphene related materials directly into the polyamide matrix. Extensive voiding limited the efficacy of such materials in CO2 and H2S barrier applications. Chemical vapour deposition was used to synthesise large area graphene that was applied to the polyamide surface. Unavoidable tearing of the graphene led to a porous layer, which allowed unaffected transport of CO2 and H2S through the polyamide. Finally, by laminating a multi-layered graphene paper between two layers of polyamide 11, extraordinary barrier performance was achieved. Compared to pure polyamide, the graphene paper laminates provided up to an order of magnitude reduction in CO2 permeation, and reduced H2S permeation to undetectable levels, even at gauge pressures of up to 400 bar.

Date of Award	1 Aug 2018
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Peter Budd (Supervisor) & Ian Kinloch (Supervisor)