Functionalizing graphene to alter its surface chemistry and surface energy may assist in dispersion, but there are drawbacks. “The problem is that if you don’t think it through very carefully, in the process of altering [graphene] to get good dispersion you may actually degrade or destroy the very properties that you are putting it in for,” says Steven Rodgers, technology consultant and principal, EmergenTek, and a board member of the National Graphene Association. If you’re incorporating graphene for its electrical properties, for example, introducing certain chemicals could tie up a graphene sheet’s receptors, reducing the ability of electrons to transfer between sheets.
In addition, there are concerns about how the use of graphene powder could impact workers’ health. The National Institute for Occupational Safety and Health is currently conducting exposure studies; in the meantime, they advise companies to use the same precautions they would with any potentially hazardous dust.
Ensuring the quality and consistency of the graphene supply is another problem. Even a small discovery or commercial development has the potential of exploding the world’s need for graphene, says Rodgers.
“There are a wealth of suppliers out there but not all of the people who claim to be selling graphene have a quality product,” says Dickie. “We need to generate confidence in graphene material. The adoption of graphene by several big industries is helping to build on that, and companies are starting to test the materials extensively with a view to producing graphene-based products in the near future.”
This quality assurance process will be made a little easier because some of the necessary equipment and procedures developed for carbon nanotubes could be used for graphene as well, Rodgers notes.
Moving Mainstream
Ford Motor Company has been a leader in the adoption of graphene-enhanced composite materials. In October 2018, it announced that it would include foam made with graphene in more than 10 under-hood components, including pump covers and fuel line covers, on the Ford F-150 and Mustang.
Debbie Mielewski, Ford’s senior technical leader in materials sustainability, says the company had little success when it introduced graphene into hard plastics in 2011. A few years later, however, summer interns tried incorporating graphene into urethane foam. Although the graphene dispersed well, the 1% to 5% graphene loads they first tried produced good, but not outstanding results for temperature and sound absorption.
To save money, the team began reducing the amount of graphene in the foam. “That’s where things got really interesting. Every time we cut back on the amount of graphene, the properties went up,” says Mielewski. At these lower amounts, the graphene was less likely to interact with other graphene. “You want it singularly dispersed and doing its job separately,” she adds.
Working with XG Sciences and Eagle Industries, the team eventually settled on a foam that included 0.2% by weight graphene. “We got a 25% improvement in high-temperature properties and an almost 30% improvement in noise absorption properties,” Mielewski says. “All of a sudden we were able to take advantage of this really interesting molecule, since 0.2% by weight was certainly affordable. Since it also nucleated the foam more uniformly, we were able to use less urethane. So we balanced the cost, and we got all these improvements.” She says the graphene helps absorb the sound much better, gives a quieter ride in the cabin and can withstand the heat – all important qualities under the hood.
There’s also room for improvements. Last summer, Ford interns reduced the graphene load down to 0.05% and the parts performed even better.
Ford might someday use graphene urethane foams for engine covers and for headliners and door panels in vehicle cabins. “We’re also thinking about going back to hard plastics, but you have to be a little more creative because I think [graphene] is not going to be easy to distribute there,” Mielewski says.
Meanwhile, in Europe, Briggs Automotive Company has reduced the weight of its single-seat racer by more than 15% using graphene-enhanced prepreg for the body panels. The tooling for the parts, also made from graphene-enhanced prepreg, enabled the automaker to reduce the process time. “They could heat the tooling up quicker and cool it down quicker,” says Dickie.
Barkan suggests that Ford’s use of graphene may be a catalyst for its inclusion in more composite parts. “Many companies are somewhat conservative. They don’t want to be the first. They want to see that somebody else has proven the market,” he says. “So I think when we see a large-scale manufacturer using graphene in a way that takes them a step change up in competitiveness – when they get a 25% to 30% improvement for a class of materials – the rest of the competitive field has to decide how they’re going to act.”
Expanding Possibilities
Composite materials containing graphene are now being used in the manufacture of everything from golf balls, sports racquets and training shoes to fire retardance coatings and construction materials.
“One company, Haydale, has just come out with a prepreg material specifically designed to be used for lighting strike protection,” says Barkan. “That would eliminate having to use a copper mesh or a silver nanowire mesh to protect aircraft.” That same technology could be used for unmanned aerial vehicles and offshore wind turbine blades.
GEIC is working with industry customers on construction materials, incorporating graphene into concrete and asphalt mixes. Adding very small amounts of graphene powder to concrete mixes dramatically increases concrete’s compressive strength and reduces the amount that builders need by 30%. Since concrete production releases a lot of CO2 into the atmosphere, the use of graphene provides an environmental benefit.
Putting graphene into polymers, foams and textiles can improve their fire retardancy. “Several industries looking at fire prevention in aerospace have had some very positive results in thermoplastics and textile materials,” says Scullion. This flame retardancy is usually just one of the many beneficial properties that graphene delivers for these applications.
Graphene imparts anti-biofouling and anti-corrosion properties to coatings, and that could have a global economic impact. “Biofouling on the hulls of commercial ships costs the shipping industry $36 billion a year in extra diesel fuel because it creates a drag in the water,” says Rodgers. “Corrosion on bridges, rebar, automobiles globally costs us about $2.4 trillion dollars.”
Because graphene is a very flexible material, it can be used as a sensor in composite products. Crash helmets and sports helmets could be designed so that they measure the impact of a ball or other object; if someone gets hit in the head it would be easier to tell if they had a concussion and needed further medical attention. Incorporated into vehicle parts, graphene could provide a variety of more sensitive and less power-consuming sensors.
“With graphene, composites manufacturers can take advanced composites, which are already amazing, and make them even better,” says Barkan. Composites with graphene may now be able to compete directly with metals because of the strength improvements the nanomaterial imparts. Adding graphene to thermoplastics raises the thermal deformation temperature, so they can now be used in applications in temperature ranges where they couldn’t be used before.
While graphene may not be a wonder material, its multiple properties should open up a wide range of new opportunities for the composites industry.
“As prices for graphene and graphene-related materials come down and the methods for making graphene at scale are refined, we should start to see more and more graphene composites in the market,” says Scullion. “The incredible properties that graphene materials can bring mean that there is a huge drive to make this happen.”
