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By Douglas Bohn of Orr & Boss Consulting Incorporated
Smart coatings mean many different things to different people and take on many forms with multiple categories of smart coatings. But one thing is agreed on: they do add value to the end use products. This value creation means that developing and selling smart coatings can help coatings companies increase their product differentiation through helping their customers develop unique and innovative products. Smart coatings represent an excellent opportunity for the coatings industry.
Definition of a smart coating
There is no agreed definition of a smart coating. Thus, the term smart coating gets used quite a bit and has different definitions depending upon the situation. We are defining smart coatings as one with properties that allow it to respond to changes in outside conditions/stimuli like heat, light, changes in pH or any other change in outside/external conditions to provide a desired performance benefit. To be considered smart, the coating needs to provide a function beyond the decorative and protective features that all types of coatings provide. Thus, sometimes the terms smart coatings or functional coatings are used interchangeably. Although in reality, smart coatings are a sub-set of functional coatings.
Types of smart coatings
There are many examples of coatings that would fit this definition. Some have been around for a while. Examples include self-healing, photochromatic coatings that change colour based on light, thermochromic coatings that change colour based on heat, self-cleaning coatings and coatings that transform pollution into harmless products.
Industry trends, such as continued Health, Safety, and Environment (HSE) responsibility, energy efficiency and ability to fill currently identified performance gaps of existing products in various end-use segments, will continue to drive innovation. Encapsulation technologies, with applications across several end-use industries such as marine, medical and even corrosion, have been developed that enable the timely release of active substances, For example, use of ingredients that first provide detection of corrosion and then provide on-demand delivery of corrosion inhibitors reduce maintenance costs and extend service-life of costly assets.
Industry will continue to push for longer-lasting performance, enhanced sustainability, more use of lightweight materials, including materials that do not corrode, such as composites. Likewise, use of materials that support increased digitisation to provide end-user/consumer benefits will increase in demand and drive continued innovation.
Self-healing coatings are those coatings that heal by themselves. Often, they require the use of a heat gun for the self-healing process to be initiated. These types of coatings have found applications in automotive, where small cracks in the coatings surface can be repaired without repainting the car. Also, there is some use in protective coatings where the main function is corrosion control. Any small crack in the coatings can initiate corrosion, thus a quick and simple way to repair small scratches can reduce corrosion.
Thermochromic coatings are those coatings that reversibly change colour when heat or cold is applied. Some of these are used in safety applications. One example is in kitchenware, where pot handles change colour when heated, thus improving safety in the kitchen. Another example is the development of coatings that turn white at higher temperatures but are solid colours at lower temperatures. These products are being developed to lower energy use in buildings by reflecting heat in the summer months and absorbing heat in the winter months. In this way they act as a cool roof coating in the summer.
Photochromatic coatings are those that change colour based on light. One everyday example of this is transition coatings for eyewear that turn into prescription sunglasses outside but function as normal glasses indoor. In this example, the coatings on the lens react with the light to change its structure and darken.
Self-cleaning and pollution reducing coatings
There are two types of self-cleaning coatings: hydrophobic and hydrophilic. Hydrophobic coatings work on the lotus-leaf effect, where the surface tension of the coatings causes water to form tightly bound spherical droplets that roll away from the surface and carry the dirt with them. The other type of self-cleaning coating is hydrophilic. In these coatings, organic dirt on the surface is broken down through a photocatalytic reaction when it is exposed to sunlight. There are coatings on window surfaces that are commercially available that are self-cleaning.
Photocatalytic paints can also be used to reduce nitrous oxide (NOx), sulfuric oxides (SOx), and Volatile Organic Compounds (VOCs). The mechanism by which this is achieved is similar to the hydrophilic self-cleaning coating. TiO2 is used as the catalytic surface where the reaction takes place. In this way, the coating can be used to improve air quality in cities with lots of automobile traffic.
Examples of smart coatings
There are many examples of smart coatings. Some of these were discussed in the previous section but they include self-cleaning coatings on windows, photocatalytic coatings used to clean pollution in cities, thermochromic coatings used on handles of cookware and self-healing coatings used in protective or automotive applications.
Another application that is ripe for the use of smart coatings is in the automotive industry. Self-driving cars and increased safety equipment on the cars is reliant on LiDAR technology. This means that the cars need to be kept clean and thus self-cleaning coatings can fill that need. Also, snow and ice cannot build up on the exterior of the cars for the LiDAR systems to work, so anti-icing coatings are needed. The further development of increased safety systems on cars will require the continued development of smart coatings.
Another example of a smart coating in an automotive application is BMW’s recent colour changing car. Pigments in the surface coating actually stratify themselves on the coating surface in response to an electrical field being applied.
A final example is display screens on electronic devices. The screens often use easy to clean, anti-fingerprint and antiglare coatings. These screens are oleophobic and thus reject oil; fingerprints wipe easily off of the screen.
Market size of the global smart coatings market
Given that there is no universal definition of smart coating, sizing the market can be difficult. If we use the definition given above, smart coatings are those with properties that respond to outside conditions, then we believe the global market size is in the US$2-$4bn range.
As the research into these markets continues, and coatings companies continue to innovate, we expect smart coatings will continue to grow in use. The main thing holding back the use of smart coatings is that the coating still needs to have the original decorative and protective features while also adding the functional feature of the smart coating. Furthermore, the coating needs to be reasonably priced. Normally, smart coatings are higher priced than standard coatings and this sometimes limits their use to niche applications. So, the coatings formulator has a difficult balancing act: maintaining the decorative and protective features of the current coating system, adding a smart or functional feature and keeping cost reasonable. This challenging balancing act is really what limits the further use of smart coatings technology.
There are many examples of smart coatings in use. Since smart coating adds functionality beyond the decorative and protective features of most coatings, they add value to the end use product. By adding value and functionality, they are helping the coatings customer create value. The ability of these types of coatings to increase value throughout the customer chain means that the innovation and differentiation will allow coatings companies to capture more of the value.
Finally, industries’ increased use of artificial intelligence, machine learning and greater connectivity to facilitate monitoring of asset condition status will drive further innovation in resins, additives and materials used. The recent pandemic has also highlighted the need for enhanced antimicrobial and antiviral coatings, that reliably deliver sanitising performance for touch services after multiple cleanings.