Trends and drivers for functional coatings

Functional coatings have been an exciting field in coatings development for several years. There is a great demand for functional or smart coatings that can support the transition to a sustainable economic model.

How is the situation at the market for functional coatings? Image source: Kenstocker

A ChemQuest Group forecast identifies the following applications as value growth leaders: high-value coatings for office furniture, coatings used in the IT industry, some areas of coatings for lighting fixtures, and highly reflective materials.

R&D activities are increasingly focused on functional coatings and more colour options in IT equipment, especially phones. The requirements for functional properties are constantly increasing. Improved colour durability is just as important as high scratch resistance. Other functionalities such as anti-fingerprint, anti-glare, anti-reflective, soft-touch and easy-to-clean optimise the haptic and optical performance of devices. The antimicrobial functionality of surfaces is also becoming increasingly important. Users in the IT market are likely to be willing to pay even more for these properties, resulting in higher revenues.

Functional properties are not only important for IT use, but also in many other application areas. The need for antimicrobial surfaces will increase sharply in medical applications, but also in construction and in the food and packaging industries. The transportation market is demanding more innovation for anti-icing coatings, anti-fouling, self-cleaning and self-healing coatings, and a constant need for new corrosion protection solutions.

In the future, it will become increasingly difficult, but also more important, to combine as many functional properties as possible in one coating system. Dr Victoria Scarborough, of ChemQuest says, “smart coatings respond to external stimuli to enable certain functions such as self-cleaning, self-healing or ice removal. While many companies have developed so-called smart technologies to incorporate into their existing products, three global megatrends point to future technology drivers.” According to Scarborough, these are healthcare, electric vehicle development and climate change. The global pandemic has increased the need for smart antimicrobial (AM) technology. AM agents require high specificity and mechanisms of action against pathogens to effectively combat infectious diseases.

Thierry Destruhaut of PPG Industries also sees these global trends. “In the mobility and construction industries, for example, there is a need for breakthrough functional coatings that help reduce environmental impact and greenhouse gas emissions,” Destruhaut notes. In the area of mobility, he cites some examples that can make electric vehicles and autonomous vehicles more efficient and safer: Low-noise coatings to reduce interior noise in electric vehicles. Since electric vehicles are four times quieter than vehicles with conventional engines, smart coatings are needed to ensure that drivers of electric vehicles are not aware of ambient noise, which is normally masked by the sound of conventional engines. Another example are electrochromic coatings that instantly change colour or go from transparent to opaque at the touch of a button.

  • Fire-retardant coatings that protect electric vehicle batteries.
  • A new generation of heating inks for more energy-efficient seat heating systems.
  • Coatings that maximise near-infrared reflectivity to improve a vehicle’s detectability by the radar/lidar sensors of autonomous vehicles.
  • Easy-to-clean coating technology that allows dirt and water to be quickly and easily washed off sensor lenses and improve driving safety.

For the construction industry, smart coatings should be developed to help improve the energy efficiency of buildings. The goal, Destruhaut said, is to achieve carbon-neutral homes and improve indoor air quality. Coatings for energy management are key, as heating and cooling buildings account for the largest share of CO2 emissions. Therefore, coatings must contribute to thermal insulation or heat reflection. New insulating materials are being developed, as well as energy-reflective coatings that reflect infrared or UV light. Other examples according to Destruhaut include:

  • Coatings for indoor air purification are needed to reduce pollutants present in indoor air. The coatings should not only emit chemicals, but they should also make a positive contribution to indoor air quality.
  • Easy-to-clean and even antimicrobial coatings are also a focus area to improve hygiene and reduce the risk of disease transmission. Smog/exterior pollution can also be reduced through the use of photocatalytic exterior coatings.

Potential exists in several application areas

For Dr Gesa Patzelt of Fraunhofer IFAM, the widely known functional coatings have further potential, for example, anti-fouling, anti-icing, anti-contamination, or easy-to-clean properties. “Another topic is friction resistance-reducing coatings, which include sharkskin. Here, however, there are further developments that are of particular interest to the marine industry and include the areas of air lubrication and damping of turbulent flows to reduce the frictional resistance of surfaces.” In addition, anti-microbial and anti-viral coatings are gaining importance due to the current situation, Patzelt points out. “Another extremely interesting topic is barrier coatings, which offer great potential for various industries. Examples include the packaging industry, the electronics industry, but also the new hydrogen technologies”. Nature serves as a source of ideas in many R&D efforts. “Bionic models for functional coatings include the pitcher plant for hydrophobic-oleophobic coatings, while the water spider, water fern and penguin plumage serve as examples for air lubrication. The scale-like structures of pine cone animals and the structure of mother-of-pearl inside abalone ears served as inspiration for the barrier coatings, whose properties are due to specially arranged, platelet-shaped particles,” explains Patzelt.

Destruhaut also points to nature in developments by the coatings manufacturer as the basis for heat-reflective coatings for the aerospace and construction segments. “Right now, our main focus is on learning how to make our chemical resin building blocks from natural, renewable resources as opposed to fossil fuels. Also, if we manage to copy and reproduce processes of how plant photosynthesis absorbs carbon from the air, it could be a big help in limiting global warming,” he says. The focus of PPG’s research and development teams is on developing more sustainable coatings.

Patzelt believes that functional coatings with intrinsic functions, whose properties are incorporated into the binder or anchored to the coating surface, will experience greater demand on the market. No additional conditions would have to be met here. “Extrinsic functions, whose properties are activated by a trigger such as UV radiation, humidity or pH changes, are nevertheless of great interest for special applications,” Patzelt emphasises.

Several challenges

The biggest challenge for functional coatings is long-term durability. “The properties of functional coatings are based on a defined surface chemistry, which in some cases is combined with special surface structures. The stability of the surface structure can be achieved by specific formulation of the coating systems, whereas the durability makes the surface chemistry much more difficult to realise,” Patzelt says. However, new binders exist that show significantly improved resistance to environmental influences, especially UV irradiation. Emerging technologies generally involve higher costs. Therefore, it is important that the functional benefits of the coatings are fully reflected in customers’ decisions, explains Destruhaut. “In this regard, credible performance standards are needed to quantify the benefits of smart coatings. For example, whole-life life cycle analysis can be a very useful tool to evaluate the benefits of an environmentally friendly smart coating.” Finally, there are still some gaps in the science that need to be filled. For example, you read a lot in the press about coatings that can generate electricity or capture carbon from the air, but we think it’s going to take quite a while for the science to progress in these cases to make them viable.” For Scarborough, managing the risks associated with commercialisation is among the biggest challenges with smart technologies

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