Engineering with Graphene for Multi-functional Coatings and Fibre-Composites

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Graphene is a material comprising a single layer of carbon atoms, yet particles can have linear dimensions potentially in the millimetre range. It has a remarkable set of properties that offer potential benefits when added to polymer materials, including toughening, electrical conductivity, self-lubrication and fire retardance. The intrinsic two-dimensional geometry of graphene has pros and cons; specifically, it directs us towards applications in thin layers, such as for coatings where its geometry can best be utilised. These applications also intrinsically require relatively small quantities of filler for a significant impact, thus making efficient use of relatively small quantities of graphene that are likely to be available initially. The combination of graphene with existing state-of-the-art commercial systems is a particularly promising route to rapid commercialisation through the enhancement of current materials.The overall aim of the proposed research is to show how graphene can be used in a composite engineering context, to improve the properties of current polymer-based materials. The key challenges are the dispersion and functionalisation of well-defined graphene material, and the development of processing routes to combine it with the selected polymer systems. It is essential to avoid agglomerates that act as defects, and to maximise the chemical interaction with the matrix to avoid unwanted delamination. Measurement of stress transfer in native graphene flakes indicate that they must remain flat over many tens of microns for efficient reinforcement; but the judicious use of non-damaging functionalisation routes should relax this requirement by at least an order of magnitude. Optimised surface chemistry is the key both to interaction with the matrix in-service and to effective processing of truly exfoliated graphite. We will exploit our specific, scalable, in-house routes to functionalised, dispersed graphenes with minimised framework damage. Thus the first challenge is to produce graphene in a scalable manner with the correct functionality to ensure good compatibility with the matrices used and optimum property improvement. The team have identified two potential routes, and as we do not know a priori which will be the most effective we will investigate both. These modified graphenes will be combined with matrices at modest loadings of a few percent, to create optimised composite systems sufficient to offer benefits to functional coatings in the applications described below. A further, fundamental aspect is the opportunity to create high graphene content composites and to control the graphene distribution in the formation of structures designed to take advantage of its unique intrinsic properties. To meet this challenge, we will develop three alternative routes for the creation of large area graphene-based films; these systems offer a more radical approach to even greater potential improvements. The basic mechanical and physical properties of the modified graphene and polymer blends will be measured to identify the most promising materials. We will combine these graphene materials with relevant matrices, especially epoxy/polyester resins for the following applications: mould release and functional coatings for composite parts, lightning-strike protection and improved barrier properties for fibre-composite aircraft and wind-turbine blades; tough, low permeability, scratch resistant, and self-lubricating functional coatings for applications in pipe networks (including valves) and mechanical systems; and fire-resistant coatings by virtue of enhanced barrier properties and char formation.