Graphene has great promise in composites because it could make some structures, such as turbine blades, longer and lighter, but only if scientists can get the darn stuff to stick to resins. Graphene is highly inert which makes it difficult to bond with or disperse within other materials. Conventional methods for treating or functionalizing graphene involve thermal and chemical shocking agents. Although they allow for scalable production, the treatments can cause significant damage to the material’s structure and defects in the final product.
Recently, the developer of a plasma functionalization process for nanomaterials, UK based Haydale (www.haydale.com), reports of research that the treatment or functionalization of its graphene nanoplatelets (GNP), called HDPlas O2, significantly improves the nano-reinforcement of resin. The research conducted by the Material Science Department at AeroSpace Corporation has been published in the Journal of Applied Polymer Science.
The research reports significant strength improvements in toughened epoxy composites, such as a greater than two-fold increase in tensile strength and modulus of an epoxy composite using a number of HDPlas O2-functionalised GNP, manufactured by Haydale. The addition of increasing amounts of GNP resulted in strength increases of over 125% and toughness improvements of 100% over that of similarly cured, unreinforced material.
Furthermore, electrical conductivity in polymers such as epoxy resin is a desirable feature to give anti-static or lightning strike protection. Graphene has high conductivity in-plane. One target is to exploit this conductivity when embedded in a polymer or resin. This is work in progress.
The research results show the possibility of increasing tensile strength and tensile modulus, which opens the possibility to design longer, stiffer or lighter wind turbine blades. An important additional property implied by the results is that the strain-to-failure was not compromised by these increased tensile properties. Hence, toughness was maintained, which could result in more damage-tolerant blades. Similar performance enhancement would be expected for other composite structures.
“Graphene nanomaterials are gaining enormous interest as a new class of reinforcement for nanocomposites, promising revolutionary electrical, thermal, and mechanical properties,” said Haydale CEO Ray Gibbs. “The results in the research represent a step forward for the graphene industry in terms of seeing graphene’s potential in the composites market, and further highlights that functionalization by plasma is the key to realizing graphene’s potential. Following this research, we intend to test our functionalized nanomaterials in further research projects with raw material producers and end-application manufacturers.”
The company has commercialized its HDPlas surface functionalization process. Samples of graphene nanoplatelets (in dry powder form or ink) are available on the Haydale website or from Graphene Supermarket.
Haydale offer a customized functionalization process because the ‘one size fits all’ philosophy rarely produces optimum benefits. The company generally work with clients to develop a solution and have three customization stages a) choice of source graphene b) selection of appropriate chemical side-group and c) level or density of functionalization. The functionalized graphene produced then has to be integrated into an intermediary or carrier, an important aspect to consider. A feasibility program is normally the best way to optimize and reach a bespoke functionalization. Clients can also purchase generic samples to do their own experiments. On successful completion of a feasibility program, Haydale says it can supply modest quantities of powder, or master batch / dispersion to that specification, and if large quantities are required, will license the process into the supply chain. WPE