Understanding the best method to disperse the graphene into the SMC is key to getting the desired results. “There are multiple ways of dispersing powders into resin systems that are very well known. The tricky part is figuring out the process parameters: What are the steps? Where do you put it in? How long do you process it for? It’s the details of the process that are unique,” says Jalloul.
Functionalizing the Additive
MITO Materials doesn’t produce graphene. Instead, the company functionalizes or enhances it. Functionalization involves adding other elements to the graphene to improve its solubility, enhance its strength or improve its bonding to a host matrix material.
MITO initially functionalized graphene oxide with an epoxide polyhedral oligomeric silsesquioxane (POSS®) to produce its E-GO product.
“We give the graphene a chemical bath and use the points on the graphene oxide to attach the POSS, then we filter it and dry it. The use of POSS helps ensure a good dispersion of graphene in the polymer system and helps impart the strength, energy dispersion, toughness and durability of the material,” says Hailey Keith, who co-founded the company with her husband Kevin.
At a concentration of just 0.1% of the polymer’s weight, the functionalized graphene can boost the performance of both thermoset and thermoplastic composite materials between 20% and 135% above baseline. With functionalized graphene, manufacturers may be able to get a cheaper resin to perform as well as or even better than a more expensive resin, according to the company.
One sporting goods manufacturer is already selling skis that incorporate MITO’s E-GO graphene.
“Folsom Custom Skis did field tests with us for six months, making three pairs of skis with 10 grams of E-GO per ski, which came out to about a 1% concentration,” says Kevin Keith. “They found that they not only increased flex strength by 35% but also increased the dampening properties of the skis by 100%.” Addling graphene also reduced the weight of the skis by 20%.
MITO is currently working with a large, national semi-trailer manufacturer that is transitioning from a combination of steel and composite trailers to fiber-reinforced composite trailers. “They’re able to shed about 35% of the trailers’ original weight just by moving to an all-composites floor and sidewalls,” Kevin Keith explains. “The problem with the esters is that they don’t have the same wear properties as the metals; even the custom formulations from their resin supplier wouldn’t meet specs.”
The manufacturer is currently testing FRP components made with the functionalized graphene. The results have been promising so far, and the manufacturer may eventually be able to transition to an all-composite trailer.
“Assuming just half the U.S. fleet adopts this significantly lighter trailer, which has the same load capacity, it would save $12 billion in fuel each year and save 57 million metric tons of CO2 from entering the atmosphere,” Keith says.
Optimized for Every Application
Calculating the right amount of graphene to include in a composite material is a balancing act. While a certain percentage of graphene might provide optimal mechanical properties to a composite material, a higher percentage may be required if the customer wants to take advantage of its electrical properties as well.
“We have to work with customers quite closely to find a solution, and we often have to make compromises. You have to optimize each system one by one,” Hodge says. Versarien has developed a large database of how graphene works with various polymers that can help customers determine how well the nanomaterial would work for their application.
MITO has developed similar reference materials. “What we found missing for graphene was a bridge into composites. Clients need to understand how graphene is going to interact and integrate into different host materials, what properties and challenges they can expect or what they can solve for within these different polymers,” says Keith.
Adoption Across Industries
Graphene is not a miracle additive; adding it to a composite won’t automatically solve every problem that a manufacturer has with a particular composite component. But as more graphene materials become available at different price points and with different capabilities, and as composites manufacturers and their customers become more knowledgeable about the material, graphene will likely become a more common element in the manufacturing mix. In the aircraft industry, for example, graphene’s high conductivity could enable manufacturers to use it for sensors.
“If you’ve got an electric field flowing through your structure, and that electric field is interrupted because of impact damage or some internal damage, graphene’s conductive pathway can be used as a structural health monitoring sensor,” says Hodge. Versarien is also working with Airbus and other European partners to use graphene as an electrothermal heater for aircraft anti-icing and de-icing applications.
On the sustainability front, graphene could be useful in enhancing the properties of bio-derived composite materials. A small amount of graphene added to those composites could improve the usually lower performance of biomaterials, ultimately leading to significant reductions in carbon emissions.
Graphene could be included in mixes to produce fire-resistant coatings for composite components or to enhance the properties of shoes, fishing rods and golf clubs. Graphene composite pipes can cool more efficiently than pipes made with other materials, making them ideal for the oil, gas and similar industries.
Graphene also has another important advantage. “Whether it’s a thermoplastic or an epoxy system, graphene can be added in the liquid phase [of composite manufacturing] relatively easily, without changing the processes or requiring additional capital equipment,” Barkan says.
“I firmly believe that just like nickel is a standard ingredient in stainless steel and just like carbon black is a standard ingredient in tires, graphene will become a standard ingredient in advanced composites applications,” Barkan adds. By the end of the year, he expects some resin companies will offer resin systems that come preloaded with graphene.
“It will be provided as a premium grade, better performing product, and the manufacturers and the fabricators won’t have to do anything different,” says Barkan. “They will just get better composites.”
Mary Lou Jay is a freelance writer based in Timonium, Md. Email comments to mljay@comcast.net.
