Composites in Manufacturing hears how Huntsman Advanced Materials is researching opportunities for developing graphene-enhanced composite solutions, with a view to incorporating graphene into its Araldite epoxy resins.
Ultra-light yet immensely tough, graphene is stronger than steel, but incredibly flexible. It also conducts electricity better than copper and can act as a barrier that not even helium can pass through. A myriad of unprecedented attributes has seen this material rapidly gain acceptance as a key enabler in a growing number of applications. And for the early adopters, it’s already demonstrating its promise.
Sectors including medical, renewable energy and automotive in particular have been quick to investigate uses of the material – with improved photovoltaic cells benefitting from its excellent conductivity and transparency, stronger car tyres that last longer thanks to its improved heat dissipation and pioneering research activities suggesting how the placement of graphene on the internal surfaces of intravenous catheters will improve the efficacy of chemotherapy treatments.
Championed as ‘the miracle material of the 21st Century’ even before its pioneers were awarded the Nobel Prize in Physics in 2010, commercial applications of graphene have been limited in some degree due to cost but also because of the complexity of processes involved in producing the material. However, with hundreds of companies and start-ups now involved in graphene research activities, this situation is likely to change and the market for polymer composites is expected to be a major beneficiary.
Developing the technology
Established processing technologies that are energy and materials-efficient make polymer composites an ideal area for innovation, as one of the simplest and effective ways of realising graphene’s potential is in combination with existing products.
Composed of two or more products, composite materials combine the physical properties of the individual materials they are made from to form a superior material offering better properties than any individual component.
Epoxy resins are thermosetting polymers which are well known for their high-quality performance in different industrial applications for corrosion protection, thermal stability, mechanical strength, moisture, corrosion and impact resistivity, and so on. With a worldwide market of approximately $13.5 billion, the epoxy resins market is well correlated to its end-user application industry’s growth and widening reach in industrial applications.
However, many of these applications would benefit from further development of the epoxy to increase properties such as strength, toughness, heat and electrical conductivity. With its exceptional properties, high aspect ratio and low density, graphene is ideally placed to further the development of a new generation of Araldite epoxy resins.
Huntsman’s research involves using a low temperature plasma (under 100˚C) patented by one of its partners, Haydale Composite Solutions, which activates and allows modification of the nanomaterial’s surface energy and enables dispersion into a host medium, such as resin. Without using chemical acid treatments which can cause damage and degrade functional performance, this process maintains the structural integrity and mechanical strength of the final product.
Taking test plates cast from the activated graphene mixed into master batches of various concentrations of Araldite epoxy resins, Huntsman has been conducting a series of physical, electrical and thermal tests in the continued evaluation of the composite performance.
So far, an Araldite Euremelt hot melt resin and a general purpose epoxy resin have been specified to look at developing new prepreg applications using the former and also advance other types of composite processes, such as filament winding and resin transfer moulding (RTM), with the latter.
Achieving property increases
Initial results have shown that these Araldite graphene reinforced resins offer greater dimensional and thermal stability in addition to improved impact resistance, properties that through further investigation could offer major performance benefits.
David Hatrick, European technology director (pictured right)
One particular area identified for future development is the market for electronic devices, where the electrical conductive properties of graphene-enhanced systems could help with electrostatic discharge and dispersion of excess heat, issues frequently linked to mobile phones and other portable devices.
Research into utilising graphene’s electrical conductive properties in prepregs to improve the protection of composites against lightning strikes is also in place. In the future, it’s expected that there will be many application areas for structures prone to lightning strikes, such as aircraft, wind turbines and tall buildings.
“We continue to make good progress in collaborative developments and have been particularly impressed with the improvements already made in the areas of thermal, electrical and mechanical performance,” comments David Hatrick, European technology director of Huntsman Advanced Materials.
The excellent thermal conductive properties identified mean that these graphene-enhanced nanocomposite systems should theoretically be able to manage the dissipation of heat generated by the exothermic curing of the resin more effectively in the casting process and tests continue in this area. Harnessing graphene to solve this issue could potentially reduce cracking or voids occurring due to expansion and this would allow large volumes of composite material to be cast.
Introducing graphene components into the composite mix could also deliver parts with high surface energy, improving the performance of coatings and paint finishes and reducing the need for primers.
As tests have also shown that the graphene-enhanced resin is stronger and lighter than traditional materials, there’s also scope to manufacture parts using less material, factors that could potentially move this technology from the high-end into the mass market for a wide range of applications – from sports equipment through to the mainstream automotive market.
“This work is set to deliver the platform for a new range of graphene-enhanced Araldite resins which will benefit the industrial composites, automotive, aerospace and other markets besides,” concludes Hatrick. “We are now focused on the further demonstration of these resins in composites manufactured with a range of typical processes used by our end customers.”
Stronger than a diamond yet a million times thinner than a human hair, the properties of graphene are astounding. The market for this material may still be in its infancy, but graphene is already being hailed as one of the most disruptive technologies of our time. For the composite market, there is no doubt that using graphene could open up a host of new possibilities. Here, John Cove, marketing manager of test and measurement specialist, Starrett, discusses the impact this new technology will have on product design and manufacturing.
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