Early graphene adopters lead way for greater commercialisation

After years of development, graphene is set for commercialisation. Here, we find out the applications that are likely to benefit and the techniques that have been developed to make series production possible. James Bakewell reports.

Discovered just over a decade ago by researchers at the University of Manchester, graphene has been trumpeted as displaying almost mythical mechanical, electrical and thermal properties. However, commercial applications of graphene have so far been limited, due primarily to the expense and complexity of the processes used to produce the material.

This state of affairs will change in the near future, and composites are likely to be in the vanguard. Graphene nanoplatelets (GNPs), for example, typically consist of 50 – 100 layers of graphene. They are relatively cheap to produce because they are mined from sustainable sources and they can be used to enhance and tailor the mechanical, thermal and electrical properties of composites.

By incorporating GNPs supplied by graphene specialist Haydale into carbon fibre reinforced plastics (CFRPs), researchers at Cardiff University have observed a 13% increase in compression strength and a 50% increase in compression-after-impact performance in comparison with conventional CFRPs.

Meanwhile, researchers at Michigan State University (MSU) have shown that when just a 3% loading of GNPs – supplied by MSU spin-out XG Sciences – is added to a standard sheet moulding compound (SMC) formulation, the resulting composite is stronger by 40%, stiffer by 20% and demonstrates a massive 80% increase in impact strength.

In addition, increasing the electrical conductivity of composites through the addition of GNPs could render the copper meshes that currently protect aerospace structures from lighting strikes unnecessary, reducing the weight and the cost of manufacturing these parts.

In the case of the MSU research, it was found that the GNP-enhanced SMC was electrically conductive enough to be electrostatically painted, without the need for an additional coating process used to enable the painting of most SMC parts.

GNPs can also be used to increase the thermal conductivity of composites. This could be particularly useful for the production of tooling, enabling an increase in the rates at which a mould could be heated and cooled.


All set for application
The potential of GNPs for enhancing the properties of composites is significant. Indeed Haydale has signed a collaboration agreement with Alex Thompson Racing (ATR) to explore the use of these materials on future concepts of ATR’s HUGO BOSS IMOCA 60 racing yacht. But, as with any ‘new’ material, converting potential into commercial reality is a big challenge.

Managing director of Haydale subsidiary Haydale Composite Solutions (HCS), Gerry Boyce, is confident that his company can meet this challenge. Formerly known as EPL Composite Solutions, HCS was acquired by Haydale in late 2014 to bring its functionalised GNPs to the composites market.

Boyce says: “We have spent the last 23 years introducing composite materials to the market, and in that time span were ‘new materials’ in what we call first-adopter scenarios.”

Haydale is targeting 1–2% of the resins market, which in 2007 stood at five million tonnes. The company’s core technology enables it to functionalise the surfaces of GNPs in a cost-effective manner. The surfaces of GNPs do not react chemically, which means that untreated they tend to agglomerate and do not bond well with resin materials. This has been a key obstacle to their use in resins for composites.

Functionalisation activates the surfaces of GNPs through the addition of various chemical end groups. Conventional methods for functionalising the surfaces of GNPs involve thermal and chemical shocking agents that, while allowing for scalable production, can cause significant damage to the material’s structure, leading to defects in the final product.

In contrast, Haydale’s plasma process does not employ wet chemistry, and the company claims that it reduces damage to the GNPs being processed by removing impurities inherent in the raw material. The functionalisation process can be tailored to an individual resin, and the desired material properties enhanced. The technology also does not consume much energy and is environmentally friendly; definite advantages in today’s market place.

Building on this technology, Haydale is involving itself at every stage of the supply chain for GNP-enhanced composites. The company has recently set-up partnerships with UK-based graphene producer 2-D Tech and Australian mining concern Talga Resources, which will provide it with a secure supply of GNPs for it to functionalise.

Haydale has also formed (as yet unannounced) partnerships with a polyester resin supplier and an epoxy resin supplier. It will supply these companies with resin masterbatches containing 25–30% loadings of GNPs. These resin suppliers will then dilute the masterbatches to the required concentrations for a given application.
“The beauty of this approach,” says Boyce, “is that the resin companies aren’t handling the GNP powders themselves; they are already in a very safe form to handle.”

Haydale currently has the capacity to produce 100tonnes of this GNP-enhanced resin at an average of 2% loading by weight, and the company could scale this up rapidly if demand requires.

Boyce continues: “We can add another 100tonnes in a matter of weeks by putting in additional reactors for our plasma treatment process. Every 12–16 weeks, we could add quite a considerable amount of capacity. If it starts to really take off, then maybe we would consider taking a licensing approach to a resin supplier, for example.”

The primary responsibility of HCS will be to work with its customers to develop specific applications for graphene-enhanced composites.

Boyce says: “All of [HCS’] customers are OEMs in the energy, infrastructure and transport markets, so we design and develop structures for the ultimate end-user of the product.

“By adding the [GNPs] into the resin and seeing what uplifts we can get, we can immediately target those applications that will offer a major benefit – a cost saving or a performance enhancement – to one of our customers.”

Shortly after being acquired by Haydale, HCS set up an aerospace business unit. Boyce explains: “We see aerospace as a very important market for doing front end, leading edge research and development with these advanced materials, the spin-offs of which could be in other markets that are less regulated. And it will be those less regulated markets that will be the early adopters.”

Author
James Bakewell

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