4月 7, 2021
Kris Eisemon – Global Industry Manager, Thermoset Plastics
Paul Rettinger – Director Technology Thermoset – Americas
Santosh Yadav – Product Development Scientist, Thermoset
Despite only being discovered in 2004, graphene and graphene-enhanced materials have come a long way in the last seventeen years. At one atom thick, the material is among the thinnest materials used commercially and around 200 times stronger than steel. So, it’s no wonder why it’s found its way into a variety of applications, particularly in the composites industry.
Graphene brings a number of benefits in composite materials and has been used to enhance various properties, including:
The automotive, aerospace and sporting goods markets have capitalized on some of these benefits and introduced graphene-enhanced products to the market.
The automotive industry has used graphene to enhance composites and foams to improve mechanical properties, reduce noise, reduce weight, and improve thermal tolerance in vehicles already on the market.
In sporting goods, graphene has been used to improve toughness, reduce weight, and provide vibration dampening for equipment such as skis, bikes, tennis rackets, kayaks, fishing rods and a host of other products.
The market potential for graphene is substantial. The Graphene Council estimates that the total graphene market size will more than double in the next six years, reaching a value of $300 million by 2027.
The composites industry was among the earliest to commercialize graphene-enhanced products and represents the largest market for the material today. With all the benefits graphene technology can bring to composites, it is probably the most significant growth opportunity near term.
Despite the benefits of graphene for composite applications, there have been some implementation challenges.
Worldwide, there are more than two thousand small companies producing material that is claimed to constitute graphene. Consequently, there can be quite a bit of difference between grades of graphene that are produced and sold in commercial industry.
One dilemma is that each company has its own process for manufacturing, and each process results in a somewhat different grade of material.
For example, a “top-down” approach starts with graphite and uses chemical and/or mechanical processes to exfoliate layers of graphite until particles containing typically between five and twenty atomic layers of carbon are achieved.
At the other extreme, a “bottom-up” approach involves carbon vapor deposition of pyrolyzed carbon onto a sheet (e.g., copper) from which particles containing one to ten atomic layers of carbon can be removed.
The significance of these different processes is that not all grades of graphene are equal. Some may be better for one application, while a different grade of graphene may provide a completely different set of properties.
Another common issue is lot-to-lot variation of a given grade. Many of the companies producing graphene are relatively new (in fact, many of them are start-ups), and consequently, processes and quality control methods are not all fully developed. This can be frustrating for composites manufacturers who experience different properties between batches of graphene.
A third problem in achieving benefits lies in the method of incorporation.
Many companies are not comfortable handling nano-sized airborne particulates in their processes. There are handling and EHS concerns that need to be addressed. In addition, the simple mixing of dry powder into a polymer matrix is not the best route to homogeneous distribution of the graphene throughout the matrix, which is key to achieving desired properties.
Graphene can be extraordinarily difficult to properly disperse into a given polymer matrix. For this reason, composite manufacturers often rely upon dispersion experts to identify the best route for functionalizing and incorporating graphene into their polymer matrices.
Process and order of addition are extremely important. From the start of the process to the point at which the final part is molded, a single misstep can result in a failure to optimize the use of graphene.
But done properly, the benefits can be meaningful.
Using dynamic mechanical analysis (DMA), we found in our own work that incorporating as little as 0.01% (w/w) graphene into the polymer matrix resulted in a 10% increase in storage modulus of a given material.
As compared to the use of conductive carbon black, a properly developed graphene dispersion can provide electrostatic dissipative conductivity in a composite application at the fraction of the loading and with little impact to viscosity.
So far, we’ve reviewed the benefits of graphene and the implementation challenges that can make it difficult to achieve those benefits. And across the board, the primary source of these challenges is the delivery the graphene.
To fully realize the benefits of the technology, manufacturers need a reliable way to deliver graphene into the polymer matrix while achieving a homogeneous distribution and the desired properties.
Graphene dispersion technology has emerged as the primary solution to this challenge.
Graphene dispersion is the process of delivering graphene particles into a liquid material in way that creates a stable and consistent compound. Graphene can be dispersed through a number of methods, mainly through appropriate functionalization combined with mechanical milling.
Composite manufacturers that use pre-dispersed graphene can access a number of different advantages:
Sometimes, an off-the-shelf solution won’t meet all of the requirements of a manufacturing process. In those cases, a dispersion expert can help you diagnose failure modes and develop a custom solution that will fit with your objectives.
Despite the immediate success the material has had, the processes for working with graphene are still being developed. The key to successful implementation lies in the way you deliver the graphene into the polymer mix. With the right dispersion technology, you can leverage the benefits of graphene while managing the challenges that come with it.