What is a coating?
A coating is a covering that is applied to the surface of an object. The purpose of applying the coating may be decorative, functional, or both. Coatings are ubiquitous and can be found on walls, furniture, on all sorts of wires and printed circuits, the outside of houses and cars, and much more. In addition, the decorative duties of coatings span quite a broad spectrum.
Decorative coatings are mainly used for their color, texture or other visual property. Functional coatings are applied to change the surface properties of the substrate, such as adhesion, wettability, corrosion resistance, wear resistance and more. In some cases, the coating adds an entirely new property such as a magnetic response or electrical conductivity and forms an essential part of the finished product.
Coatings may be used in various processes, that are roughly divided into: vapor deposition, spraying, chemical and electrochemical techniques, roll-to-roll coating processes and other, less prominent techniques.
What is graphene?
Graphene is a two dimensional layer of carbon atoms, arranged in the form of a honeycomb lattice. It is touted as a “miracle material” because it is endowed with an abundance of astonishing traits - this thin, one atom thick substance is the lightest, strongest, thinnest material known to man, as well as the best heat and electricity conductor ever discovered - and the list does not end there. Graphene is the subject of relentless research and is thought to be able to revolutionize whole industries, as researchers work on many different kinds of graphene-based materials - each one with unique qualities and purpose.
Graphene for coatings
The vast selection of extraordinary properties that graphene possesses can open the door to many interesting types of coatings, paints, inks and more. Graphene's high resistivity can make for durable coatings that do not crack and are resistant to water and oil; its excellent electrical and thermal conductivity can be used to make various conductive paints, and a strong barrier effect can contribute to extraordinary anti-oxidant, scratch-resistant and anti-UVA coatings.
Graphene enables a wide array of functional coatings and paints, for many possible applications. Among these can be high performance adhesives enabled by graphene's high adhesion property, anti-bacterial coatings, solar paints (capable of absorbing solar energy and transmitting it), paints that provide isolation for houses, anti-rust coatings, anti-fog paints and UV ray blockers, non-stick coatings for various domestic applications (like frying pans and countertops) and even a much-hyped possibility (currently under scientific examination) of a coating that turns a regular wall into a screen.
Graphene-enhanced products are yet to reach widespread commercialization. Nonetheless, given graphene’s impressive array of properties and the vigorous R&D that is taking place, graphene-enhanced coatings should not be too far away.
The Sixth Element Materials, a Chinese company that focuses on R&D, mass production and sales of graphene and related materials, showcased its graphene-zinc anti-corrosion primer used for offshore wind power tower, that can come at a competitive price compared with zinc rich epoxy primer.
Garmor, the University of Central Florida spin-off formed to develop a new graphene oxide flakes production process, has developed graphene oxide-based coatings useful for limiting UV radiation damage to sensors and polymers. Garmor's transparent GO-films are reportedly derived from a commercially-viable and scalable process that can be readily implemented with minimal constraints.
The Spain-based Graphenano announced the launch of a graphene-based series of paints and coatings called Graphenstone in 2014. These are said to be very strong and also acts as a protective layer against environmental damage. Graphenstone is made from a graphene powder and limestone powder.
The British Electro Conductive Products released a sprayable transparent conductive coating based on a CNT and graphene platelets (GNP) hybrid material. TBA are targeting the food, electronics, pharmaceuticals and petrochemicals markets.The new ATEX-compliant product is available as a clear, anti-static aerosol, and it should also be available as bulk paint. Its application will safeguard electronic equipment used in explosive environments and bring it up to European standards.
The latest graphene coating news:
Graphene oxide and alginate combine to create new ‘smart’ material with potential biomedical, environmental uses
Researchers at Brown University, the University of Wisconsin and the National University of Singapore have developed a way of reinforcing hydrogel materials made from alginate, a natural material derived from seaweeds that’s currently used in a variety of biomedical applications, by incorporating graphene oxide into its structure.
This produces a material that can be 3D printed into structures that are stiffer and more fracture resistant than alginate alone - an important achievement as alginate tends to be fragile and thus hard to work with. Furthermore, the material is also capable of becoming stiffer or softer in response to different chemical treatments, meaning it could be used to make “smart” materials that are able to react to their surroundings in real time. In addition, alginate-GO retains alginate’s ability to repel oils, giving the new material potential as an anti-fouling coating.
Rice University scientists have developed a graphene-based epoxy for electronic applications. Epoxy combined with graphene foam invented in the Rice lab of Prof. James Tour) is reportedly substantially tougher than pure epoxy and far more conductive than other epoxy composites, while retaining the material's low density. It could improve upon epoxies in current use that weaken the material's structure with the addition of conductive fillers.
By itself, epoxy is an insulator, and is commonly used in coatings, adhesives, electronics, industrial tooling and structural composites. Metal or carbon fillers are often added for applications where conductivity is desired, like electromagnetic shielding. The trade-off, however, is that more filler brings better conductivity at the cost of weight and compressive strength, and the composite becomes harder to process. The Rice solution replaces metal or carbon powders with a 3D foam made of nanoscale sheets of graphene.
Sweden-based Applied Nano Surfaces (ANS) launched a new product, Tricolit GO, one of the first graphene-enhanced low-friction coatings on the market today. Tricolit is available now from ANS, in easy-to-apply spray cans or in bulk. The product can be used to reduce friction and wear. ANS claims that the use of graphene allows a tenfold increase in the coating’s mechanical strength and abrasion-resistance.
We have talked to ANS CTO, Boris Zhmud, and he revealed that ANS uses graphene dispersions from UK-based Applied Graphene Materials. Tricolit GO is still considered an "experimental" product. The development was financed by Sweden's SIO-Grafen.
Versarien recently announced it will be collaborating with fire retardant coatings supplier Advanced Insulation to work on a graphene project.
The collaboration will focus on incorporating Versarien's Nanene few layer graphene nano-platelets into sub-sea insulation materials to improve tear resistance and reducing water absorption of these materials.
Greece-based industrial paint producer Hydroton has launched a new graphene-enhanced zinc epoxy paint - the 23303 ZINCTON GNC. This is a two-component epoxy based coating that offers improved cathodic protection due to the addition of the graphene, compared to epoxy zinc rich primers.
The new primer also offers improved adhesion to metal and as the zinc content is low, it is still cost effective. It is recommended for applications in highly corrosive environments.