The construction industry is experiencing a paradigm shift from focusing solely on sustainability to embracing comprehensive resilient design, driven by increasingly severe weather events and rising financial risk. While sustainable design emphasizes minimizing environmental impact and resource conservation, resilience—the capacity to adapt and maintain functionality after a disturbance—demands a systems-based approach that addresses future-looking hazards like high winds, hail, fire, and flooding. This article argues that true durability requires building materials, including advanced coatings, to work collaboratively as integrated systems to resist extreme loads that exceed minimum building code requirements. It explores current design resources like LEED v5 and FM Global standards, and provides specific examples of how materials are engineered to resist hazards. These examples include multilayer roofing systems designed for very severe hail, and innovative coatings and membranes used in water-retention assemblies to manage urban storm runoff. Ultimately, resiliency is redefining what it means to create durable, lasting buildings, positioning systems-level thinking—rather than isolated product properties—as the foundation for a future-proof built environment.

Introduction

Resilient design has become a catchphrase within the construction and architecture communities. Over the last two decades, forward-thinking designers and building owners have focused not just on the now, but on the future, when determining their designs. This challenge started with a focus on sustainability. The U.S. Green Building Council (USGBC) defines sustainable design as “creating places that are environmentally responsible, healthful, just, equitable, and profitable.”¹ĚýSustainable solutions often refer to minimizing the burden on the natural environment, recycling, and conserving energy and other natural resources. These goals have created a multitude of industry buzzwords, including durability, recycled content, energy efficiency, and carbon neutral. However, sustainability is not the same as resiliency.

Resilience is defined by the Resilient Design Institute as “the capacity to adapt to changing conditions and to maintain or regain functionality in the face of stress or disturbance. Resilient design solutions often consider durability as well as the ability to keep a building functional after a weather event.”²ĚýSolutions such as having a generator to maintain power are very resilient, though not necessarily sustainable (Figure 1). To be truly resilient, designers and building product manufacturers must look at more than product properties such as Volatile Organic Compounds (VOC) and embodied carbon, often the go-to for sustainable design, and more at materials working together as systems. There is no one property that ensures resilience. Designers and manufacturers need to collaborate to create complete systems of materials that work together to achieve a successful outcome. The ultimate goal is for designed solutions to meet both sustainability and resiliency targets, such as slowing the release of storm water to prevent overloaded sewers while also using some of the captured rainwater for irrigation.

One example of resilient design is the Sand Palace, which was one of the only structures left standing in its area after Hurricane Michael in 2018. Built specifically to withstand severe storms, the house utilized advanced materials like insulated concrete forms (ICFs) and was designed to resist winds of up to 250 mph, significantly exceeding state building codes at the time. The homeowner explained that they deliberately went “above and beyond code” when making material and design decisions by consistently asking, “What would survive the big one?” It is estimated that the house cost 15-20% more as a result of these decisions. Although they did have to replace utilities and experienced the loss of the first floor along with one of the air handlers, the overall damage was minimal compared to the surrounding properties.

Resiliency has become an important design strategy for many reasons, but the primary driver is money. It is expensive to rebuild after severe weather events, and insurance companies are noticing. In some parts of the United States, it is becoming more expensive and more difficult to get insurance, particularly in coastal regions and areas prone to wildfire. For example, a 2024 report from the Senate Budget Committee shows that the nonrenewal rate in Florida increased 280% between 2018 and 2023.³ĚýAdditionally, FM Global, one of the largest insurers of commercial properties, continues to expand the areas where their buildings must meet very severe hail requirements.

On the residential side, prospective homebuyers are paying attention to the potential weather impacts on properties. In 2024, Zillow started posting hazard ratings for climate-related impacts such as flood, wildfire, wind, heat, and air quality on property listings.⁴ĚýAs with other trends within the construction industry, significant attention is paid when there are clear drivers to profits and losses. This article introduces published resources and references being used by designers to design for resilience. It then looks closely at specific examples in which coatings and other building materials work together as systems to withstand increased building loads.

Polyurethane (PU) networks exhibit the outstanding mechanical strength, thermal stability, and solvent resistance that is required for use in high-performance coatings, adhesives, and composites. However, the most common way to form these polymer networks is to use hazardous isocyanate-functional molecules. Moisture-cure urethane silane polymers have recently been used to form hybrid PU networks, thereby mitigating end-user exposure to hazardous isocyanate during application. However, while the applicator is not exposed to isocyanates, they are nonetheless used to synthesize these polymers. High-oleic soybean oil (HOSBO) was chosen for use in hybrid binders to explore potential beneficial properties, mainly enhanced hydrophobicity and reduced viscosity, and as a U.S.-produced renewable chemical, the fatty acid groups offer beneficial properties. For this project, isocyanate-free polyurethane-silane binders were formed by first reacting diethanolamine with HOSBO to form fatty acid diols, followed by transcarbamation reactions to form urethane linkages. The polymers were then end-capped with various secondary aminoalkoxysilanes via subsequent transcarbamation reactions. Reaction of these polymers with atmospheric moisture resulted in crosslinked hybrid networks with siloxane linkages. Surface-free energy (SFE) as well as thermal and mechanical energy were explored.

Introduction

Crosslinked polymer networks are in numerous consumer and industrial products, ranging from coatings for medical devices to foams for seat cushions.^1-4ĚýThe chemistry for these networks typically involves urethane, urea, ether, and thioether chemistries.^5-7ĚýAmong these, polyurethane and polyurea networks remain the most widely studied due to their rapid and efficient formation at room temperature, the ability to modify the backbone structure, as well as their excellent thermal and mechanical properties.^8,9ĚýThe most common way to form polyurethane networks requires the use of hazardous isocyanates.⁸ĚýHowever, isocyanate exposure can lead to a myriad of health issues, including skin and eye irritation, symptoms of asthma, and sensitization upon exposure.^10,11

A way to synthesize crosslinked networks while avoiding isocyanates is to make networks with siloxanes where an alkoxysilane is used as a crosslinker. These urethane-siloxane polymers also have the advantage of producing crosslinked networks with enhanced properties from the sol-gel region.^12-16ĚýFor example, silane-terminated polyurethane and poly(urethaneimide) networks demonstrate improved thermal stability, good adhesion to metals, elastomeric properties, and excellent moisture resistance.^17-20

In addition to avoiding isocyanates, there is interest in the polyurethane field to shift from petrochemical to renewable biobased raw materials, particularly soybean oil.^21,22ĚýPolyurethane networks are not necessarily hydrophobic and often rely upon incorporation of other materials and segments to make hydrophobic material.²³ĚýThe addition of the fatty acid chains is predicted to enhance hydrophobicity. Other benefits from the fatty acid chain include reduced viscosity and, by using the high oleic oil, reduced yellowing with a high content of chains with a single unsaturated group. Hybrid urethane-siloxane vegetable oilbased polymers have even been formed through isocyanates^24-27Ěýand cyclic carbonate chemistry.^28-30ĚýThe isocyanate-based networks have the same toxicity issue of the nonhybrid polyurethane while the cyclic carbonate-based networks form pendant hydroxyl groups, which may limit any enhancement to hydrophobicity. Rather than use these methods, the ester linkages of the oil can be utilized to incorporate other organic functionalities, such as alcohols and diols, which can be further reacted.³¹

Herein, a method is provided to form polyurethane-silane networks that circumvents the use of isocyanates and incorporates renewable biobased materials. In this work, a safer acylation reagent, 1,1′-carbonyldiimidazole (CDI), was used to form the urethane functional groups. These acylating groups were used to attach the fatty acid-based diol, which is based on high-oleic soybean oil (HOSBO), to the alkoxysilane crosslinker and to add chain extenders. These compounds were then used as binders to form clear polyurethane-siloxane networks. To our knowledge, there are no reports of polyurethane-siloxane networks based on HOSBO. This method allows for greater control of structure of the binders. Chain extenders have been explored in the binders. Thermal, mechanical, and surface properties of the resulting crosslinked networks were determined using several analytical techniques and compared with those of a control network.

Q: What role will formulation innovation play in advancing sustainability?

The formulation stage is key to achieving our sustainability goals. An old mentor of mine compared formulating to cooking. He would say that it’s not just about using the finest ingredients, but how you blend them together. Understanding how one ingredient influences and brings out the best in the next—and how they combine to define the consistency and taste of the final dish. I absolutely share that view.

Formulators know that if you change one component, it can affect the whole formulation: its stability, possible component aggregation, solids settling rate, pH range, viscosity, shear resistance, and film drying time. Getting the formulation right determines in-can behavior and therefore shelf life, as well as influencing coating application (e.g., spraying). New raw materials (like biomaterials) must be properly integrated to enable efficient manufacturing and effective industrial-scale application.

Significant R&D work is focused precisely on this topic. For example, clients who come to us looking for support with their formulation development are exploring the use of new or alternate raw materials, transitioning to water-based systems or reducing VOC (volatile organic compound) levels, and evaluating new formulations on numerous application processes to become more efficient and less energy intensive.

Q: Historically, sustainability and performance have often been seen as trade-offs. Do you believe that tension is narrowing, and why?

Yes, absolutely. Firstly, we’ve seen a change of mindset within the industry. This is not just a growing awareness but an actual acceptance that change is inevitable, and that thinking and acting sustainably is the only way forward. And secondly, innovation is advancing. Given the right motivation and encouragement, I believe we as an industry are capable of achieving great things.

The introduction of any new material (e.g., from sources independent of fossil fuels) is always accompanied by initial teething problems. It’s the nature of the game. But those problems can be overcome through innovation cycles. We gain a greater understanding of the new raw materials, their properties and behavior, and how best to integrate them into formulations that meet, or even exceed, the performance of current state-of-the-art coatings.

Recent innovations have already demonstrated a closing of the gap. The use of reactive polymer-bound surfactants has led to the development of durable, water-based latex coatings for exterior use. In Europe, Worlée is pioneering the use of sustainably made camelina oil in the manufacture of high-performance binders and additives. And Evonik has recently introduced a range of 100% plant-based biosurfactants (made via the fermentation of sugar) that exhibit enhanced wetting and color retention properties in waterborne coatings.

Q: How important is lifecycle thinking, including durability, maintenance cycles, and end-of-life considerations, when determining whether a coating is truly sustainable?

In the past, there was a tendency within our industry (when supplying to OEMs) to consider the sale of a coated end product as a convenient boundary for where our responsibility ended. Ease of application, appearance, performance, and a certain lifetime would encourage the OEM to buy more coating. But there was little consideration for what came after that.

Now, however, we are entering a period of increased accountability. And if we as chemists create a complex material (and a coating is certainly a multi-component complex system), then we are responsible for its makeup, its behavior, and the environmental impact throughout its lifetime. This begins with the sourcing of raw materials, continues through the energy usage and pollution evaluations of manufacturing and application, and now extends to beyond the lifetime of the coated end product. As more and more end products are evaluated for their potential to be reused, recycled, or even composted, we as an industry need to extend our considerations to that end-of-product-life moment.

This will pose one of our greatest challenges. For example, how do we get a protective coating that has been designed to weather the harshest environmental conditions to stop protecting, on demand, and break down into recyclable or biodegradable components?

Q: What are the biggest challenges in scaling sustainable coating technologies from the lab to full commercial production?

The old adage says that a chain is only as strong as its weakest link, and the supply chain required to support commercialization of a sustainable coating is not exempt from this. Furthermore, for the product to be truly sustainable, each step of the process needs to be in itself sustainable.

It begins with raw materials sourcing and the aim to reduce dependency upon materials derived from fossil fuels. Can renewable biomaterials be used? Are they realistically available in sufficient industrial quantity? Can they be used in existing formulations, or does the incorporation require use of surfactants or additives or stabilizers—and are these from sustainable manufacture in themselves?

Now consider the energy requirements of formulation and large-scale production. Might any viscosity, dispersion, or stability issues drive energy consumption up? Or is there a need to manage heat transfer, either to maintain temperature to keep things flowing or remove it from an exothermic step in the process?

Are any byproducts or pollutants created in the process, surpassing explosion safety limits or allowed waste gas levels. Alas, the same rules apply for sustainable coatings as to scaling any production.

Q: How can collaboration across the value chain—raw material suppliers, formulators, applicators, and end users—accelerate progress toward shared sustainability goals?

Let’s look at three coatings: an interior, decorative house paint sold in Scandinavia; a metallic-effect, high-gloss automotive coating; and a high-performance durable protective coating on an oil rig in the North Atlantic Ocean. Our industry serves all three scenarios, but each one has a specific set of performance, application, pricing, and environmental requirements and targets. The willingness to become more sustainable might be there, but in each case the path to reaching those sustainability goals is going to be different. Those individual pain points, restrictions, and limitations need to be shared throughout the supply chain for us to truly make progress. It needs communication. And then it needs collaboration.

We are looking at a paradigm change in our industry, with innovation taking place all along the supply chain. We are seeing the introduction of new raw materials, the creation of new formulations, the introduction of more efficient production processes and easier application processes with less energy requirements and lower emissions, and the goal of non-harmful coatings that can either degrade or be recycled when a product reaches end-of-life.

It’s a big task and only possible with close collaboration. One part of the chain directly influences the next. If we acknowledge and respect that, we will become increasingly effective.

Wayne Daniell, Ph.D., joined The ChemQuest Group in 2023. Over his extensive career, Daniell has founded and managed companies that developed nanomaterials and various coatings additives for use in markets such as consumer electronics, renewable energy, and white biotechnology. Daniell holds a bachelor’s degree in chemistry from the University of Reading, as well as a doctorate in chemistry from the University of Nottingham. A UK native currently based in Germany, Daniell speaks English and German.

In the simplest terms, sustainability could be defined as less waste and more efficiency. This could mean fewer processing steps, the use of fewer chemicals or other building blocks, or the ability to develop products that last hundreds of years without the need for constant maintenance.

In the coatings (paint) world, sustainability is usually looked at through the lens of fewer chemicals, biomaterial substitutions, shortened or fewer manufacturing steps, or outright chemical bans. Significant efforts are currently underway to reduce petroleum-based materials in the first place along with trying to make the new products last at least as long as their predecessors.

There is another way to look at materials sustainability. What if the pretreatment chemicals and coatings could be eliminated altogether? What if the oxide was also the color coat? What if the longevity of stainless steel could be exploited together with its oxidation potential? What if color could be imparted onto stainless steel strip using only one production operation for both steelmaking and coloring? What if these innovative ideas were actually more cost effective?

First Steps

In 1971, Allegheny Ludlum Steel Corporation took a step in that direction. While certainly not under the guise of sustainability, the company developed a process that produced black stainless steel for use in formed architectural products.¹ In this case, a stainless steel strip was produced by oxidizing the stainless surface to form a porous oxide coating and impregnating it with an alkali metal silicate, and then drying and fusing the silicate by heating between 1400 and 1600 °F. Temper rolling the finished product—a typical steel finishing process—allowed for flattening the strip to facilitate fabrication.

This process was an efficiency improvement over the original pre-1968 process where many more production steps were used. First, the strip was treated to obtain a black oxide and then coated with a water-soluble alkali metal silicate or a water-based thickened or gelled solution of sodium or potassium dichromate. The next step involved removing the water and subsequently heating the coated surfaces to a temperature high enough to form a uniform, black, porous oxide 1,000–500,000 Å thick. Excess coating and loose oxide were then scrubbed off with water.

In addition to reducing the number of processing steps, the 1971 process eliminated many quality problems. There was better thickness uniformity, less visibility of any spray or rolling pattern, good aesthetics, and better condensing humidity resistance, as depicted by the absence of white residue all over the strip. Steam testing, abrasion resistance, chemical resistance, mandrel bend, and impact testing were also improved to the point that this black stainless could be formed into tubes or building panels with decent aesthetics. With better oxide thickness control, color was also more uniform.

Fast Forward to 2013

Over the 40 years since the first steps in manufacturing blackened stainless, many material inventions and improvements have occurred. Stainless steel itself has become a more uniform product, with improved surface finishes that can now be used in a variety of aesthetic-critical applications. Base metal chemistry modifications and more controlled annealing atmospheres and temperatures have led to increased formability as well.

Alongside steel production maturation, the advent of affordable, usable nanotechnology opened a huge window for surface modification. Nanoparticle surface treatments were developed to reduce damaging oxidation and corrosion of stainless steel and other alloy components in oxidating and corrosive conditions.²

Improving the longevity of stainless steel at elevated temperatures was the genesis of this development. Power generation plants often have problems with damaging oxidation from accelerated high-temperature fire-side corrosion due to molten alkali salts. Other problems include accelerated medium-temperature fire-side corrosion due to low oxygen activity environments and the presence of sulfur and steam side oxidation of tubing, piping, and valves in fossil fuel-fired boilers.

Pressure has been placed on power plants to increase efficiency, meet stringent environmental regulations, and ensure plant reliability, availability, and maintainability—ideally while minimizing costs.³

Some of the nanoparticles used as surface treatments for corrosion and oxidation resistance include aluminum, silicon, scandium, titanium, yttrium, zirconium, niobium, lanthanum, hafnium, tantalum cerium oxide (nanoceria), and thorium. These nanoparticles do not really form coatings but rather are doping agents that become embedded within the oxide structure.

Over time, yttrium has become a preferred nanoparticle for these types of applications. Yttrium, particularly in the form of yttrium oxide nanoparticles (Y2O3 NPs), is considered superior because of its exceptional properties around high thermal stability, strong chemical stability, mechanical strength, and strong corrosion resistance. Perhaps the greatest attribute under the veil of sustainability is that yttrium has low toxicity. Because of its low toxicity, this nanoparticle is often used in biomedical applications.

Minimox® is one of the yttrium-based, self-protective alloy treatments that minimizes oxidation of alloys at elevated temperature. It changes the structure and/or chemistry of the thermal oxide, which becomes denser and more adherent than thermal oxide without Minimox® doping. Flaking, protrusions, and microvoids are eliminated, resulting in a smooth, dense, adherent surface.⁴

Depending upon the time and temperature of the annealing process, thin film oxides can be grown to thicknesses between 500 and 9,000 Ă… (1 Ă… = 0.1 nanometer). Oxidized surfaces doped with yttrium are characterized by excellent cyclic and isothermal oxidation, corrosion resistance in severe environments, and high resistance to severe heat and chemical environments. As a bonus, the thickness of the oxide can be controlled within a high-temperature annealing atmosphere to purposefully impart color onto a metal surface.

Modern Colored Steel

The black stainless steel for architectural applications referenced earlier in this article did not result in large volumes of product released into the field. Despite the excellent properties derived from the surface modification, stainless steel was too expensive for run-of-the-mill building applications. However, the idea of a black surface that did not require painting simmered in the background for many years. The thought of being able to colorize a surface using existing in-line annealing practices was a tantalizing thought. Black stainless manufactured using the existing in-line annealing process, without the addition of either paint or doping agents, was successfully accomplished in 2018.⁵ However, stainless remained an extremely expensive substrate for many applications.

It was determined that other substrates that were more in line with cost constraints of industries, such as appliance and automotive, would also benefit from this oxide modification methodology. Electrogalvanized steel (EG) was textured to the required product finish and the zinc coating was subsequently annealed. The resulting black substrate met all the requirements of appliance finish specifications for refrigerator door applications (the most stringent requirements in the appliance world). This “faux stainless” EG product was compared to black polished stainless and the GE Black PVD standard, and it was found to meet all requirements, including color (Figure 1), gloss, stain/aging, anti-fingerprinting, corrosion resistance, and mechanical properties—all at a much lower cost.

FIGURE 1 Black color comparison between standard product, black stainless steel and “faux stainless steel” textured electrogalvanized.

Finally, in 2023, a method of colorizing stainless steel using yttrium doping and annealing was developed. To prove the concept, stainless steel coils were coated with an aqueous yttrium pretreatment solution and batch annealed for several hours to oxidize the surface. Batch annealing is not particularly uniform, and is not the streamlined process of choice, but enough of the coil exhibited the required properties to move forward and optimize the process.

The basic idea was to dope the surface with an aqueous yttrium nano-solution using an in-line roll coater, followed by continuously annealing the strip while varying time and/or temperature in the annealing furnace to grow the oxide and obtain the desired color.⁶ Even keeping the annealing furnace atmosphere constant, varying line speeds (time in anneal) can allow for the efficient production of different colors. (See Table 1.) These colored stainless coils were fabricated and placed on structures in the Nashville, TN, area (Figure 2) and are still in place today.

FIGURE 2 Colored stainless panels on structures in the Nashville, TN, area.

All the aforementioned work has culminated in less waste and more efficiency. Technological improvements in substrate quality, steel processing, and nanotechnology have bolstered the development of a variety of products previously deemed impossible, too expensive, or of insufficient quality for commercial production. By looking at outside-the-box alternatives, it is possible to obtain color by manipulating the oxide and removing the organic coating completely.

References

1. Helgert, Harold. L; et.al. Method of Making Black Stainless Steel Sheet. U.S. Patent 3,556,871, January 19, 1971.
2. Kerber, Susan J. Nanoparticle Surface Treatment. U.S. Patent 8,568,538 B2.
3. Stott, F. H. Influence of Alloy Additions on Oxidation. Materials Science Tech. 1989, 5 (8), 734.
4. Material Interface Inc. Protecting Furnace Components with Minimox® Alloy Treatment. Minimox® Product Data Bulletin. 2016.
5. Myers, F.A. Black Steel. AK Steel Presentation, 2018.
6. Myers, F. A.; Price, L. R. Method of Colorizing Stainless Steel Using Strip Anneal Processing. U.S. Patent 11,584,997 B2, February 21, 2023.

Cynthia A. Gosselin, Ph.D.,Ěýis director at The ChemQuest Group,Ěýwww.chemquest.com. Email:Ěýcgosselin@chemquest.com.

Unbeknownst to many, microplastics do not originate solely in the ocean. In fact, most microplastic accumulation primarily occurs on land and then moves to the waterways. Oceans have been polluted between 83,000 to 236,000 tons of microplastics yearly. Agricultural soils of all kinds, including agricultural soils, have 107,000 to 730,000 tons of microplastics dumped into the soil each year through processed sewage, mulches, slow-release fertilizers, and even seed coatings.¹

During the last few years, there have been ongoing discussions about what defines a microplastic. Microplastics are plastic particles ranging in size from 5 mm to 1 nm. Primary microplastics are intentionally manufactured in smaller sizes for use in consumer cosmetics and biomedical products. Secondary microplastics are plastic waste particles that break down from larger plastic materials. Secondary microplastics brought about by degradation of larger discarded plastics are the subject of this article.

Only 1% of total microplastics are due to seed coatings.² However, with a rather forceful kick from the European Chemicals Agency (ECHA), seed manufacturers are being required to eliminate microplastics that are generated due to seed coatings by October 2028. The rest of the world is not far behind. In fact, France has pulled implementation ahead to January 1, 2027. California has already proposed legislation that would eliminate 75% of plastic waste by 2030. While this does not yet affect seed coatings, history suggests that a broader set of regulations will germinate from this legislation.

Certain seed coatings are exempt from the October 2028 regulation:³
• Liquids: Must not form films upon drying.
• Natural origin coatings: No chemical modifications allowed. Even the simplest chemical modification might cause eventual microplastic formation. Commercially used natural polymers can contain additives, processing aids, or impurities that could hinder biodegradation or contribute to microplastic pollution.
• Water soluble coatings: Must have a solubility of ≤ 2 g/l.
• Biodegradable: Not to be confused with compostable materials.
• Coatings with no carbon atoms in the molecular chain structure

Manufacturers have embraced the challenge of eliminating microplastics from seed coatings. Even though seed coatings are 1% of the problem, producers across the globe are determined to become ZERO percent contributors to microplastic pollution.

The first step has been to make the microplastic coating fragments that detach from seeds as biodegradable as possible. Degradation rates vary, and no standard has yet been set. The lowest degradation rate so far is ≤ 48 days obtained from some commercially available polymeric coating mixtures. Biodegradable plastic formulations degraded completely in 32 days. Coatings selectively doped with certain plant growth promoting bacterium (Bacillus subtilis) degraded in ≤24 days.⁴ A good start, but still not enough.

A Seed Coating Primer

The first question in eliminating a problem material is to determine whether the material is really needed. Seed coatings are critically important for:
• Promoting germination and robust growth
• Providing resistance to pests and fungal infections
• Improving drought tolerance through osmopriming⁵ (for germination in low-moisture soils)
• Facilitating mechanical planting
• Increasing overall yield

While there are significant advantages for coated seeds (higher germination percentage, healthier roots and shoots as well as stronger established plants), there are also disadvantages (limited shelf life of treated seed, pesticide breakdown, incomplete crop protection, and surplus cannot be repurposed for grain). However, when weighing the risks, the ability to feed the world trumps any disadvantage. Eliminating seed coatings is not practical, so improvements to guard against microplastic formation and pollution must be the conclusion.

There are three basic methods of seed protection: film coating, encrustation, and seed pelleting.⁶

Film coating involves applying thin layers of coating solution (a total of less than 10% seed weight) onto the seed surface (Figure 1). For precise control over thickness and composition, a rotating drum or fluidized bed apparatus is used. Film coating allows the seed to maintain the original size and shape. In addition to resistance to environmental stressors, these seeds are well suited for mechanical planting and precision field applications.

FIGURE 1. Schematic of various protective film coating layers applied to seeds.⁷

Seed encrusting forms a protective matrix around seeds that is 100–500% seed weight. This allows for targeted delivery and sustained release of active ingredients throughout germination and early growth for pest and disease resistance, even in adverse soil conditions. A film is not formed. Many organic farmers take advantage of seeds treated with this technique.

Pelleting agglomerates seeds into uniform spherical pellets by coating them with a mixture of binding agents and additives that is >500% seed weight. This technique is especially good for small seed crops and precision planting. The enhanced seed-to-soil contact leads to good moisture retention, better germination rates, and uniform stand establishment.

Commercial Seed Film Coating Materials

Traditional seed film coatings are manufactured from polyethylene glycol (PEG), polyvinyl alcohol (PVOH) or chitosan (a glucosamine polymer).

Polyethylene Glycol is effective for improving seed germination and seedling establishment of sorghum under adverse moisture conditions. Osmopriming strengthens the antioxidant system further by increasing the osmotic adjustment of the seed resulting in increased stress tolerance.⁸

Lignan-modified PEG has a high molecular weight, takes a little longer to dissolve, and is less easily converted into water. The high-viscosity solutions do not transport oxygen, leading to no absorption by the seed, eliminating genetic or physical damage. Coating with 5-lignin PEG improved the germination percentage of maize seeds from 86.6% to 93.3%.⁹

Polyvinyl alcohol seed film coatings are extremely useful because water solubility and mechanical strength can be controlled. These coatings are used as a binder for adhering layers to the seed surface. Seed physical properties are improved and the delivery of active ingredients can be controlled. PVOH coatings decrease dusting and improve germination.¹⁰

Chitosan is one of the truly natural seed treatments and growth enhancers. This glucosamine polymer is developed from a sugar that comes from the outer skeleton of shellfish like crab, lobster, and shrimp. The material bonds to seeds via hydrophobic or cation-Ď€ interaction. Chitosan is a cationic source in an aqueous solution. Free amine groups form crosslinked polymer networks with dicarboxylic acids to improve mechanical properties.¹¹

Unlike other polymeric materials used for film seed coatings, Chitosan influences the biochemistry and molecular biology of the plant cell. The targeted plasma membrane and nuclear chromatin causes changes in cell membranes, chromatin, DNA, calcium, MAP kinase, oxidative burst, reactive oxygen species, cellulose pathogenesis-related genes, and phytoalexins. It is an ecofriendly biopesticide that boosts the innate ability of plants to fight fungal infections.¹² In addition, it allows for an innate immunity response in developing roots that destroys parasitic cyst nematodes without harming beneficial nematodes and organisms.

The Future

Sometimes the additives used in current seed coating formulations can lead to microplastic free products. Acting as rheology modifiers, film formers, and stabilizers, these biodegradable materials help to create porous films and coatings, enabling early seed germination.

One example is a microfibrillated cellulose viscous material that under high shear can be sprayed onto seeds. Under high shear, the fibrils break apart, lowering viscosity and allowing for consistent coating. After application, when high-shear conditions are removed, the fibrils reconnect forming solid films while still allowing for complete drying of the coating. These additives assist with germination, reducing or eliminating seed dusting and enabling longer shelf-life stability of liquid formulations.¹³

Seed coatings themselves are undergoing a metamorphosis as well. Petroleum-based polymers cannot always be made biodegradable and, at the same time, fully functional. The ideal would be to develop completely natural coatings that leave no residue, disappear without a trace, and retain critical seed protection and nutrient properties. Supramolecular engineered proteins have been developed over the past 15 years. They perform as well as synthetic polymer-based coatings but decompose naturally. This serves two purposes: mitigating soil degradation and eliminating microplastic pollution in farm fields.¹⁴

Thinking even further outside the box, these supramolecular engineered proteins might be the foundation for producing plant-based protein products to replace traditional single-use and even multiple-use carbon-chain plastics without the threat of microplastic pollution.

References

1. Petersen, K. S. There is an Alarming Amount of Microplastics in Farm Soil–and Our Food Supply. Environmental Health News. January 27, 2021.
2. Nielson, A.. The Seed Sector’s Battle Against Microplastics. Seed World. April 29, 2024
3. Verney, C.; DeGassert, G. Microplastic Seet Coatings the Perform Better than Conventional Ones: Myth or Reality? Agropages AgNews. June 14, 2024.
4. Accinelli, C. et al. Degradation of Microplastic Seed Film-Coating Fragments in Soil. Chemosphere. V 226. July 29, 2019. Pages 645-650.
5. Harish, D., et al. Effect of hydropriming and Osmopriming on the Germination of Seedling Vigor in East Indian Sandalwood (Santalum album L.). Forests. V 14, P. 1076. 2023.
6. Sharma, S. Enhanced Crop Potential: Exploring Seed Coating Techniques and Applications. LinkedIn. May 14, 2024.
7. King Quenson Group. A Farmer Friendly Technique for Producing Crops. King Quenson News. September 3, 2023.
8. Zang, Fei, et al. Seed Priming with PEG Induces Physiological Changes in Sorghum Seedling Under Suboptimal Soil Moisture Environments. National Institute of Health. October 15, 2015.
9. Yahong, G., et al. Preparation of Lignin Polyethylene Glycol Film-Forming Agent and Its Application in Chlorantraniliprole 5% Flowable Concentrate for Seed Coating. Industrial Crops and Products. V. 182. P 114877. August 2022.
10. Agriculture | Coating for Seeds, Fertilizers & FilmsPolyvinyl Alcohol. https://www.kuraray-poval.com/applications/agriculture (accessed September 10, 2024).
11. Chitosan. https://en.wikipedia.org/wiki/Chitosan (accessed September 10, 2024).
12. Hadwiger, L. A. Multiple Effects of Chitosan on Plant Systems: Solid Science or Hype. Plant Science. V. 208, 42-49. July 2013.
13. Electrolyte Tolerant Film Forming Agent for Seed Coatings. Borregaard https://www.borregaard.com/markets/agriculture/applications/seed-coating/products/film-forming-agent/ (accessed September 10, 2024).
14. Natural Alternatives to Microplastics Developed for the Seed Coating Industry. Environment Times. February 1, 2022. https://www.environmenttimes.co.uk/news/item/995-natural-alternatives-to-microplastics-developed-for-seed-coating-industry (accessed September 10, 2024).

By Kateryna Rudich, Yehor Polunin, Ayda Dadras, Mohiuddin Quadir, and Andriy Voronov

Introduction

The use of polymers as a seed coating is a prevalent agricultural practice because it helps to reduce the overall amount of chemicals needed, promoting more sustainable farming practices. Seed coating is the process of applying a protective layer, typically made of polymers, nutrients, or agrochemicals, to seeds before planting. The primary purposes of seed coatings are to enhance seed performance, protect against pathogens and pests, improve germination rates, and provide essential nutrients during early plant development, all while minimizing the risks associated with conventional seed treatment methods.¹ However, seed coatings mainly involve the use of petroleum-based, non-biodegradable polymers that significantly contribute to microplastic pollution.

This study explores the potential of biomass- and plant oil-based polymers recently developed by our group as a sustainable alternative to be applied in seed coatings. The resulting polymer, consisting of hemicellulose xylan modified by grafted chains made of babassu oil-based monomers (HX-g-BOBM), is designed as a sustainable film-forming material targeting advanced water barrier performance.² HX-g-BOBM is a highly biobased, tough, and processable bioplastic. Being biodegradable, it may offer a renewable alternative to applications of conventional petroleum-based polymers in food packaging. This study evaluates the feasibility of HX-g-BOBM as a seed coating by applying it to corn (Zea mays) seeds and assessing the effect on the seeds’ vigor and viability.

HX-g-BOBM Synthesis

Agricultural wastes such as some lignocellulosic materials and plant oils are excellent renewable resources for the production of sustainable coatings due to their chemical versatility, availability, and often low cost.3-6 HX-g-BOBM is synthesized from hemicellulose xylan and babassu oil, which are believed to be inherently biodegradable or compostable by nature. Babassu oil-based monomer (BOBM) and HX-g-BOBM were synthesized following the procedures described in earlier publications.^1,7,8 The structure of BBM is shown in Figure 1A. A schematic representation of HX-g-BOBM synthesis is presented in Figure 1B. Before polymerization, xylan was reacted with maleic anhydride through an esterification reaction. During this process, an ester bond is formed between the maleic anhydride and hydroxyl groups of xylan, while the vinyl group of maleic anhydride remains intact, providing a reactive site for the attachment of BOBM-based grafted chains. After successful maleinization, the modified xylan was added to the BOBM along with the AIBN initiator (1.5 wt %). Grafting polymerization reaction was conducted in bulk at 80 °C for 8 hours under a nitrogen atmosphere. After purification from unreacted xylan and BOBM, a homogeneous solution of highly branched HX-g-BOBM was obtained. Multiple xylan macromolecules are decorated by BOBM chains, and BOBM homopolymer is also present in the resulting material.

FIGURE 1 The chemical structure of babassu oil-based monomer (BOBM) used in this study. R (x:y) – the structure of the fatty acids (x – the number of carbon atoms in the fatty acid chain, y – the number of double bonds in the fatty acid) (A). Synthetic scheme of HX-g-BOBM grafted polymerization (B).

HX-g-BOBM Emulsification

To simulate an industrial approach, where seeds are typically covered by spraying a water-based slurry containing polymers and additives over the seeds in a rotating drum machine, HX-g-BOBM was emulsified in water. Dodecylbenzenesulfonic acid, which serves as an emulsifying agent, was first dissolved in water, vortexed for 5 min, and ultrasonicated for 20 min. The HX-g-BOBM dispersion was then added dropwise and was vortexed for an additional 5 min and ultrasonicated for 20 min until a stable emulsion with a final polymer content of 15 wt % was achieved. Particle size measurement was conducted using a Malvern Zetasizer Nano-ZS90 (Figure 2A).

The viscosity of the emulsion was measured using an ARES G2 rheometer with 25 mm parallel plate clamps, gap size 0.5 mm, strain 1%, frequency range 1-500 rad/s, and temperature 25 ÂşC. The viscosity of the HX-g-BOBM emulsion exhibits non-Newtonian behavior, with apparent viscosity decreasing as the shear rate increases, indicating shear-thinning behavior. At low shear rates (< 1 rad/s), the emulsion displays high viscosity, suggesting good stability and minimal settling of particles. The apparent viscosity decreased significantly at higher shear rates (> 10 rad/s), indicating that the emulsion would flow more easily during the seed coating process, which is beneficial for uniform coating application in industrial applications (Figure 2B).

FIGURE 2 Particle size (A) and rheological behavior (B) of 15 wt % HX-g-BOBM water emulsion.

Seed Coating Procedure

Seeds were coated manually using a plastic bag with a subsequent transfer of seeds to the sieve and drying at room temperature (25 ±1°C) for 24 hours. In each case, 100 corn seeds were incubated with 2 ml of water-based polymer slurry and manually shaken for 5 minutes to simulate the industrial rotating drum coating procedure. The weight of the seeds was compared before and after the coating procedure. The average weight increase was found to be 2.0 ± 0.3 wt % from the initial mass of seeds.

HX-g-BOBM Coating Water Absorption

The water absorption test was conducted to evaluate the coating’s interactions with water. Coating film samples were submerged in 20 ml of distilled water and kept at room temperature. After immersion, excess water was removed, and the samples were weighed at specific time intervals to quantify the changes in mass. To ensure accuracy and reliability, each test was performed in triplicate. The resulting plot shows the relationship between time and weight gain (Figure 3A). The ability of the coating to swell is advantageous for enhancing water retention, by helping to keep the seeds hydrated after planting.

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The paint and coatings industry gathered May 16–18 at Harrah’s Resort Atlantic City in New Jersey for the very successful 2023 edition of the Eastern Coatings Show. The technical conference and exhibit were hosted by three East Coast paint societies: the Philadelphia Society for Coatings Technology, the Metropolitan New York Coatings Association, and the New England Society for Coatings Technology. With more than 1,300 attendees, the conference had well-attended presentations and robust conversations on the exhibit floor.

The technical conference began on the first day with a coatings short course titled “Fundamentals of Coatings and Sustainable Materials in the Marketplace,” which was presented by James Rawlins and Robson Storey, both professors at the University of Southern Mississippi’s School of Polymer Science and Engineering. The second day started with a packed room for the keynote presentation on “Leading a Business through Challenging Times” by Dan Calkins, CEO and chairman of Benjamin Moore.

The afternoon of day two included an interesting panel discussion. Titled “Where Do We Go from Here? The Future of the Coatings Industry,” the panel included George Pilcher of the ChemQuest Group, Amanda Andrews of Michelman, Professor Dean Webster of North Dakota State University, and Professor Ray Fernando of the California Polytechnic State University. Each provided their unique view on what to watch for in the future and touched on topics such as sustainability, technical staffing, removing substances of concern from raw materials and formulations, raw material sourcing, recycling, and the role of artificial intelligence.

The technical program consisted of 42 technical presentations by industry scientists on a variety of topics, including advances in resins, pigments, additives, testing methods, and coatings formulation. This article examines some highlights and summaries of just a few of the presentations.

Sustainability

Sustainability is an important concern that is getting increased attention in the coatings industry. This includes the decades-long search for products with lower volatile organic content (VOC) and the more recent emphasis on biosourced raw materials, the industry has been interested in sustainable technologies for a long time. More than a buzzword, sustainability is becoming a way of life for the industry.

A full one-third of the presentations referred to sustainability in their abstracts and titles, and one of the concurrent tracks was titled “Driving Sustainable Coatings with Chemistry.” Even the short course presented on the first day of the technical program mentioned sustainable materials in its title.

In a presentation titled “Alkyd Emulsions and Their Contribution to More Sustainable Paint and Coatings Formulations,” Caroline Matthieson of Worlée-Chemie spoke about the use of biosourced raw materials in the production of alkyd resins. By introducing the 17 sustainable development goals set in the United Nations 2030 Agenda for Sustainable Development,^1,2 Matthieson first explained how Worlée is focusing on several of the goals in their own work, such as responsible consumption and production (#12), climate action (#13), and partnerships for goals (#17).

Figure 1. Typical structure of an alkyd resin, which is a polyester resin based on a polyacid (such as isophthalic acid, shown here) and a polyol (such as glycerol, shown here) and modified with a fatty acid.

The presentation then described the use of biosourced fatty acids in the production of alkyd resins. Alkyds are polyester resins, formed by the condensation reaction of polyacids and polyols and modified with fatty acids (Figure 1). The fatty acids used to make alkyds have biobased origins. For example, linseed oil is a common source of fatty acids used in alkyds and is produced from flax seeds. Matthieson explained that, although linseed oil is a great source of renewable and biobased raw materials, its use in coating resins competes with its use in the food supply, where it is employed as a source of alpha-linolenic acid (an omega-3 fatty acid).

Camelina oil was presented as a beneficial alternative to linseed. Table 1 shows a comparison of linseed and camelina oil compositions in terms of the fatty acids available in each. Matthieson explained how camelina oil is a more sustainable choice for Worlée because the camelina plant (Camelina sativa) is grown locally near their production sites in Germany, while flax is not. In addition to regional cultivation, camelina can be grown as a mixed crop with peas or as a secondary crop in temporarily fallow land, and thus, it does not compete with food production. Other advantages include that it provides a food source for pollinators, requires less fertilizer, has good resistance to pests such as aphids, and that the crop’s yield has a lower dependence on the weather.

Although there are limited choices of biobased polyacids for use in alkyd resins, some examples include furandicarboxylic acid and succinic acid. Many choices of biobased polyols exist, so depending on choice of raw materials, Matthieson explained that alkyds can be produced with 85% to almost 100% biobased raw materials. As an example, a waterborne alkyd emulsion with 85% renewable content and based on camelina oil was described as having very similar physical properties and performance compared to one prepared with linseed oil, and with the sustainability advantages of less competition with the food supply and use of regionally produced materials.

Table 1. Fatty Acid Distribution in the Composition of Oils

Another presentation on the topic of sustainable coatings was presented by George Daisey of Dow and was titled “Sustainable Coatings Technology That Works.” Daisey began with an introduction to Dow’s sustainability goals, which include combatting climate change, driving circular economy by designing for circularity, and innovating new materials that offer a more favorable health and environmental profile over their lifecycle. Dow has an ambitious goal of reducing carbon emissions and being carbon-neutral in its operations by 2050. In particular, Daisey described the sustainability benefits of roof coatings, which are defined as thick, white, monolithic, and solar-reflective elastomeric films.

The most important value proposition for maintenance with roof coatings is roof life extension, which lowers the lifecycle cost of the roof and decreases the amount of material associated with replacing a roof that is being sent to landfills. In addition, the use of solar-reflective roof coatings can help lower energy usage associated with air conditioning and reduce the “urban heat island” effect.² Daisey described how an effective roof coating must have both high reflectivity to prevent absorption of solar energy by the building, as well as high emissivity of the energy that is absorbed. According to Daisey, an uncoated roof can reach a surface temperature of approximately 180 °F on a hot summer day, with an effective roof coating dropping the temperature by 60 degrees to 120 °F. He emphasized that the drive for more sustainable roof coatings cannot ignore the other challenges that a roof coating must face, which include the need for resistance to biological growth and dirt pickup and adhesion issues on the varied roofing substrates.

According to Daisey, Dow is thinking about advancing roof coatings via multiple technologies, including delivering biological resistance without biocides, creating faster-setting acrylics to reduce labor and equipment time, enhancing durability, using biosourced raw materials, and developing hybrid technologies. He expanded on the hybrid technologies approach by describing new acrylic-urethane products for two global regions. One is a waterborne acrylic-urethane hybrid polymer designed for liquid-applied waterproofing membranes for flat roofs in the EMEAI markets (Europe, Middle East, Africa, and India). The hybrid polymer is designed to have a superior balance of cold temperature flexibility and traffic-ability at temperatures up to 90 °C. Roof coatings based on the acrylic-urethane hybrid can be formulated as a liquid-applied roofing membrane that meets European CE (ConformitĂ© EuropĂ©ene) marking requirements and passes the strict durability tests for an expected working life of 25 years, as set forth by the European Organisation for Technical Approvals (EOTA) in ETAG 005.³

Today, products meeting the ETAG 005 are mainly solventborne, with one-component (1K) polyurethanes being the most common. The hybrid offers a waterborne alternative in a market dominated by solventborne technology. Daisey presented data showing that the waterborne acrylic-urethane hybrid yields a coating with similar mechanical properties compared with a 1K polyurethane, while contributing to better durability. Tensile strength of the hybrid was close to that of a 1K polyurethane and higher than a standard waterborne acrylic coating. For elongation, after 14 days of thermal aging at 80 °C, the 1K polyurethane coating dropped to 137% from an initial value of 220%, while the hybrid started at 272% and only dropped to 245%, more in line with the performance of the waterborne elastomeric acrylic roof coating. The amount of water swelling exhibited by the hybrid coating (8.9%) was intermediate between the 1K polyurethane (1%) and the waterborne acrylic (16.4%). Accelerated and natural weathering data demonstrated that the hybrid maintains good mechanical properties on extended UV exposure and has improved durability versus the acrylic.

In an interesting presentation titled “Analytical methodologies and challenges for understanding paint emissions,” Michelle Gallagher, Ph.D., of Dow described some of the challenges facing the analytical chemist when attempting to quantify and identify volatile emissions. Emissions testing is becoming more important because health-conscious customers care about indoor air quality and emissions that originate from consumer products such as paint. In addition, Gallagher explained how the growth of green building certifications and their requirements for low VOC and low emission products has increased the industry’s need for such testing. Dow has been growing its emission testing capabilities to simulate the emission rate of paint VOCs after application, as well as to understand how its products affect emissions.

While bulk VOCs are measured on wet paints using ASTM D6886 and reported in units of g/L, emitted VOCs are measured on a paint after application using chamber methods and reported in units of ÎĽg/m³. There are several different certifications and standards dealing with emissions, such as the chamber method described in California Department of Public Health (CDPH) Standard Method v1.2, a widely used standard in North America for measuring emissions from building products such as paints.⁴ A typical chamber is made of stainless steel and has the ability to control humidity and airflow. The paint is applied to a plate and placed under constant airflow (e.g., 0.5 to 1 air exchange per hour). At various times, the emissions are sampled using an absorbent trap, which is then analyzed using GC-MS or HPLC methods.

Gallagher explained that one of the challenges in using these chamber methods is obtaining a clean background prior to testing for emissions. For example, each volatile should be under 2 ÎĽg/m³, and the total VOC should be under 25 ÎĽg/m³ in the CDPH Standard Method v1.2.⁴ Gallagher described how a robust cleaning procedure is required and how gloves should always be worn when working with the chamber and plates and holders. Even a single fingerprint can lead to the detection of volatiles (e.g., hexadecenoic acid) at a level above the threshold allowed for background emissions. Chambers must be cleaned and purged between each study, and the background emissions levels checked before taking a new series of measurements. In addition, Gallagher stressed that absorbent tubes should always be cleaned and background checked before collecting samples.

Other challenges include the choice of substrate specified by the method. While clean stainless steel and glass have very low background emissions, drywall or drywall with the edges taped is sometimes specified. Both the drywall and the edge tapes (such as foil or metallized polymer tape) can lead to contaminant emissions being measured that do not emanate from the coating. Calibration is also critical, and toluene is typically used for that purpose.

Identifying the source of the volatile emissions can also be challenging. Every material used in a paint formulation can have its own unique volatiles, so analyzing raw materials individually with GC-MS can help determine from where emissions originate. Understanding the source of emissions is necessary to better control them through both raw material and coating formulation design. ĚýFinally, it was stressed that it is difficult to predict emissions based on total VOC measurements, because ASTM D6886 measures the total VOC in the wet bulk paint, while emissions testing measures VOCs at various times as the coating dries.

Functional Coating

End-users are continuing to ask for more of their paints and coatings. In addition to their decorative and protective properties, there are numerous coatings that are also designed to provide other functions such as soft-feel haptics, sound damping, thermal insulation, or antimicrobial properties. For example, in a presentation titled “New Thermal Management Raw Materials Platform Gives Flexibility to Develop Next Generation Thermal Insulation Coatings (TIC) with Improved Performance,” Hrishikesh Bhide, Ph.D., of Evonik described new resin and filler materials for use in thermal insulation coatings. Thermal insulation coatings are a type of functional coating designed to provide personnel protection by reducing the surface temperature of hot surfaces and prevent skin burns, as well as to improve energy management. The coatings also provide direct protection of the substrate and lead to a reduced risk of corrosion under insulation (CUI).

Bhide described two new silica granules with low thermal conductivity that can be used in thermal insulation coatings. The first was described as a super-insulating granule (SIG) with a larger particle size (~300 μm) and high hydrophobicity. The SIG particles derive their insulation properties from a passivated amorphous silica composite core and have a thermal conductivity of 24 mW/m·K. The second granule material was described as a SIG synergist, having a particle size of ~30 m and thermal conductivity of 30 mW/m·K. The small particle size synergistic filler reduces the cracking tendency of highly filled insulation coatings and facilitates smoother coatings. When formulated with a waterborne acrylic binder, the combination of the SIG and SIG synergist granules provides a coating with lower thermal conductivity (about 5mW/m·K lower) than when either is used by itself and with little change in thermal conductivity after heat aging.

In addition to the insulating granules, Bhide also introduced a new waterborne silicone resin, which, along with the granules, can be utilized as the sole binder in thermal insulation coatings with higher heat resistance than standard binders such as acrylics. The combination of the silicone binder and the two insulating granules leads to coatings with good fire retardance and low thermal conductivity (57 mW/m·K at 25 °C). The silicone resin can also be blended with other waterborne binders such as acrylics to extend the heat resistance of insulation coatings based on traditional binders such as acrylics. Bhide also described the use of these materials in some field studies within chemical production facilities for condensation control, thermal management, and safe-touch properties.

In another paper titled “High-Touch Coatings with Bactericidal and Virucidal Properties,” Mark Langille, Ph.D., of Corning described a new copper-glass additive for use in antimicrobial coatings with high efficacy towards both bacteria and viruses. Langille began with a discussion of the expected performance of antimicrobial coatings that could be used to improve public health by killing microbes that come in contact with the coating surface. In contrast to liquid disinfecting agents, a dried coating would be expected to provide a surface that is continuously active, provides antimicrobial efficacy between regular cleaning cycles, and addresses a spectrum of real-world germs, including easier-to-kill bacteria and viruses (e.g., SARS-CoV-2) and harder-to-kill viruses such as non-enveloped viruses (e.g., norovirus).

In addition, Langille described how the U.S. Environmental Protection Agency (EPA) formalized guidance in 2022 for products claiming residual efficacy, including test methods for demonstrating both bactericidal and virucidal activity.^5,6 To better simulate real world contamination events, dry test conditions are utilized in which the surface is contaminated with bacteria or virus, allowed to dry, and then analyzed for how effectively it killed the microbes after only 2 hours. It is expected that at least a 3-log reduction occurs, or 99.9% of microbes are killed. In addition, durability of the antimicrobial properties is evaluated by putting the surface through simulated wear/cleaning cycles and then testing for efficacy.

Langille discussed how copper is a powerful, natural antimicrobial and is effective at killing both bacteria and viruses. Copper in the +1 oxidation state (Cu+1) is a particularly potent but less stable form of copper, and the innovation in the new additive is that Corning found a method of stabilizing Cu+1 in glass. Aluminoborosilicate glass and a copper source are melted together to form a glass, which is then milled to give the copper-glass additive, with an average particle size of 4 ÎĽm. The additive is a brown color but can be incorporated into a large variety of paint colors. A typical loading in a paint formulation is approximately 1% by weight of the copper-glass additive.

Data were presented showing results of antimicrobial activity (log kill) after dosing six commercial coating formulations with the copper-glass additive at various levels (0 to 40 g per gallon). Effectiveness at a particular dose varied amongst the coatings because of differences in formulation ingredients, but each coating demonstrated log-3 kill (99.9% kill) of Staphylococcus aureus at levels of approximately 1% additive, and all had log-5 kill (99.999% reduction) at a level of 40 g/gallon or below.

Langille also discussed how challenges in initial or long-term efficacy can occur for coatings that are high in polymer content due to their low porosity, which may prevent access of the Cu+1 in the coating to the microbe at the coating surface. An example presented was a waterborne direct-to-metal coating with 2% copper-glass additive, where efficacy dropped after 3 months. A study of compatibilizers to control the stability and availability of the copper-glass additive identified solutions that enabled long-term efficacy in the system. It was noted that compatibilizers can eliminate the need for significant formulation changes and thus make it easier for current commercial formulations to add antimicrobial functionality via the copper-glass additive.

Additive Technologies

Figure 2. Generic formula of alkyl aryl sulfonic acid salts used as corrosion inhibitors.

Coatings additives are always an important topic of discussion when the coatings industry gets together for technical conferences, and this year’s Eastern Coatings Show was no different, as multiple presentations covered new additives to enhance the performance of paints and coatings. In a presentation titled “Improving Corrosion Resistance of DTM Coatings Using Hydrophobic Alkyl Aryl Sulfonate Additives,” Matthew Gadman of King Industries talked about a class of easy-to-use liquid corrosion inhibitors that can be effective at low dosages of approximately 1 to 3%. Corrosion takes a large economic toll on the economy, to the tune of $2.5 trillion globally (about 3.5% of global gross domestic product), as Gadman described. The corrosion inhibitors he discussed have the generic structure shown in Figure 2 containing a hydrophobic naphthalene ring with alkyl substituents and a polar sulfonate salt group. The counterion can vary with both metal and amine cations being used.

The corrosion inhibitors can be used in both clear and pigmented coatings, including high gloss systems. They are compatible with a range of resins and can also act as catalysts for aminoplast coatings (for X = Zn and Ca). They can also aid in wet adhesion and pigment dispersion. In a coating on metal, the polar portion of the molecule orients toward the metal surface and passivates the surface, preventing the formation of anodic corrosion sites where oxidation reactions occur. The non-polar alkyl-substituted aryl group orients away from the metal surface and prevents water from reaching the surface.

Gadman shared the results of several experiments where the alkyl aryl sulfonate inhibitors were added to coating formulations and evaluated for corrosion resistance. For example, a barium sulfonate salt was incorporated at 1% on total formulation weight into a 1K solventborne acrylic/melamine clear baking finish and was found to aid in preventing blisters and rusting compared with the blank control, which had no inhibitor. In another set of experiments, the sulfonic acid salts were evaluated at 1% on total formulation weight in several pigmented formulations in combination with a variety of anticorrosive pigments. Thermoset and air-dry systems were evaluated, and all showed a synergistic effect on corrosion resistance when using the sulfonate salts with an inorganic anticorrosive pigment. Finally, in a third set of experiments, Gadman demonstrated that the addition of a barium sulfonate salt to aerosol paints improved the corrosion resistance and had no negative effect on appearance.

Helena Wassenius, Ph.D., of Nouryon presented an interesting paper covering a new type of cellulosic rheology modifier in a presentation titled “New Ultra-Low Viscous, Highly Associative Cellulose Ethers for Acrylic-Based Architectural Paints.” Wassenius explained how synthetic HEUR (hydrophobically modified ethoxylated urethane) rheology modifiers have low molecular weight and are highly associative, while HM-CE (hydrophobically modified cellulose ether) thickeners are cellulosic-based materials of high molecular weight and are typically moderately associative. HEUR thickeners provide excellent levelling, while HM-CE thickeners provide good sag resistance. The new cellulosic thickener falls between the two extremes and provides a high level of association.

Results of testing in 30% PVC semigloss architectural paints were detailed. Leveling performance of the formulation containing the new cellulosic ether was similar to one with HEUR thickener and much improved relative to those containing HM-CE thickener. Meanwhile, sag resistance was better than the HEUR and closer to that of an HM-CE thickener. In addition, viscosity loss on tinting, syneresis resistance, and color acceptance were much improved versus a HEUR thickened formulation. The new cellulose ether also shows excellent spatter resistance, and the hiding power, as measured by contrast ratio after roller application, was substantially better than HM-CE and close to that of a pure HEUR system. Finally, Wassenius alluded to significant sustainability benefits, as found in a lifecycle analysis that estimated the contribution of the thickener system to the carbon footprint of one ton of formulated paint is 40% lower for the new cellulose ether thickener compared to a synthetic HEUR thickener.

Perfluoroalkyl and polyfluoroalkyl substances (PFAS) offer many performance benefits to paints and coatings, but the industry is actively trying to replace these materials due to their link to serious health effects and persistence in the environment. In a presentation titled “Free of PTFE! New Micronized Wax Additives for Scratch & Scuff Resistance,” Smriti Arora of BYK discussed new wax additives that were developed as replacements for polytetrafluoroethylene (PTFE). PTFE, also known by the tradename Teflon, is a fluoropolymer and a well-known PFAS example. Wax additives based on PTFE are often used in coatings because they impart scuff, scratch, and abrasion resistance.

Figure 3. Orientation of wax additives in a dried coating film. Most wax additives orient to the surface of the film (a), while PTFE-based waxes orient more homogeneously throughout the film (b) due to their higher densities.

Most waxes orient to the paint surface but can be removed from the surface during abrasion. Arora explained that due to their higher density, PTFE-containing waxes orient more evenly throughout the coating film and have a more durable abrasion resistance (Figure 3). Three new PTFE-free additives, based on either polyethylene (PE) or modified PE alloy waxes, were introduced, and the presenter explained that they also provide a homogenous distribution in the coating film. The additives improve both abrasion resistance and scratch resistance and produce a medium-to-strong reduction in coefficient of friction (COF). Due to their small particle size, the additives have minimal impact on gloss. According to Arora, the new additives are also food-contact compliant.

Examples of their effectiveness in Taber and Wazau abrasion resistance was demonstrated for a 1K waterborne acrylic industrial coating, where the new PTFE-free additives showed similar performance to the PTFE-containing controls at 2% loading on total formulation weight. Evaluation in a BPA-free clear can coating showed abrasion results and COF reduction comparable to PE/PTFE controls at 1% loading. For systems with low COF requirements, a combination with a softer wax (e.g., carnuba) or polysiloxane additive was also recommended, and examples of the strategy were shown for an epoxy/phenolic gold lacquer. Results of testing at 4% loading in an architectural interior flat deep base were also shared, and the PTFE-free wax additives had a positive effect on both scuff resistance and scrub resistance. Arora stressed the wide compatibility of the PTFE-free wax additives across waterborne, solventborne, and UV coating systems and their comparable technical performance to PE/PTFE-based wax additives.

Resin Technologies

Several conference presentations covered new resin technologies for both architectural and industrial coatings. One such presentation was titled “New Polyester Dispersion for VOC-Compliant 2-Component Waterborne Coatings,” in which Ashish Zore, Ph.D., of Coim USA described the use of a new waterborne polyester polyol dispersion for use in two-component (2K) polyurethane floor coatings with good light stability and near-zero VOC content. Zore described some of the challenges facing the floor coating industry, including restrictive VOC limits that are under 50 g/L in some regions, the phasing out of exempt solvents, and the continuing demand for higher performance. Floor coating end-users are asking for better light stability, chemical resistance, wear resistance, and weatherability.

The polyester polyol dispersion is supplied at greater than 60% solids in water and contains no co-solvents or surfactants. It can be formulated into 2K waterborne polyurethane coatings utilizing standard hydrophobic polyisocyanates, rather than the hydrophilically-modified polyisocyanates that are often required for waterborne systems. According to Zore, it is suitable for use in various industrial coating applications, including general industrial finishing, protective coatings, and floor coatings.

Zore described testing results comparing a 2K polyurethane coating based on the waterborne polyester polyol dispersion with polyurethanes based on two waterborne acrylic polyols, as well as two high-solids polyaspartic coatings. The coating based on the polyester polyol dispersion had an ultra-low VOC level of under 25 g/L. The gloss of the polyester-based polyurethane was very high, with a 20°/60° gloss of 82/92, comparable to the polyaspartic coatings (88/94) and much higher than the two acrylic-based polyurethanes (8/40 and 39/71). Flexibility of the polyester-based coating was excellent, but both pencil and pendulum hardness were lower than the other systems. Zore noted that hardness could be improved by manipulating the polyol/isocyanate ratio toward more isocyanate and commented that stoichiometries with higher isocyanate also yield better chemical resistance. Finally, the estimated applied cost ($/sq ft) of the waterborne polyester-based formulation was only 75% of the cost of the waterborne acrylic-based polyurethane and approximately one-third of the cost of the high solids polyaspartic system.

In a presentation titled “Enhance Performance of Waterborne Coatings Using Functionalized Binders with Novel Monomers,” Tiffany Chen of Solvay described the use of a functional specialty monomer for acrylic and styrene-acrylic latex polymers. Added during the emulsion polymerization process, with recommended levels of 0.5 to 2% based on total weight of monomer, the monomer offers performance benefits in both architectural and industrial coatings. Chen first described its use in an architectural latex with a BA/MMA backbone. A control latex was made with 2% methacrylic acid (MAA) and compared with a latex containing 1% MAA and 2% specialty monomer. In a semigloss formulation (22% PVC), the functional monomer resulted in improvements in opacity and tint strength, as well as in metal adhesion and the removal of household stains.

In another study, a flat architectural coating (49% PVC) was prepared with a latex containing 1% specialty monomer. The functional latex demonstrated better color acceptance for both initial and heat aged paints compared to a control. Scrub resistance was also better, as was dry and particularly wet adhesion to various substrates (e.g., glass, steel, and aluminum).

The specialty monomer was also evaluated in a styrene-acrylic composition designed for light duty direct-to-metal (DTM) coatings. The control used 2% acrylic acid (AA), while the functional monomer replaced half of the acrylic acid in the experimental latex (1% AA and 1% specialty monomer). Formulated into a gloss DTM coating (18% PVC), the functional monomer led to improvements in corrosion resistance as measured by salt fog exposure (ASTM B117) and blister resistance upon immersion in water. Adhesion over cold-rolled steel was greatly improved versus the control, and in addition the initial gloss was much higher, with a 60° gloss of 63 units compared to the control with a gloss of only 17 units. Overall, the specialty monomer facilitates the improvement in several properties for both architectural and industrial latex coatings.

References

1. United Nations. 2030 Agenda for Sustainable Development. (accessed July 11, 2023).
2. United Nations. The Sustainable Development Goals Report 2022. (accessed July 11, 2023).
3. European Organisation for Technical Approvals. ETAG 005, Guideline for European Technical Approval of Liquid Applied Roof Waterproofing Kits, 2004.
4. California Department of Public Health. Standard Method for the Testing and Evaluation of Volatile Organic Chemical Emissions from Indoor Sources Using Environmental Chambers, Version 1.2, 2017.
5. US Environmental Protection Agency. Guidance for Products Adding Residual Efficacy Claims. (accessed July 11, 2023).
6. U.S. Environmental Protection Agency. Test Method for Evaluating the Efficacy of Antimicrobial Surface Coatings, SOP Number MB-40-00, revised September 2022.

About the Author

Leo J. Procopio, Ph.D., is president and owner of Paintology Coatings Research LLC. For more information, visitĚýĚýor emailĚýleo.procopio@scienceofpaint.com.

The past year marked a rebound in powder coating revenue as well as investment in R&D. In particular, both the North American and Latin American powder markets showed growth of 3.5% and 1.8%, respectively, in 2022.¹ These growth figures coincided with the introduction of several innovations in sustainability, low-temperature cure, corrosion resistance, outdoor durability, thin films, and thermoplastic application technology.

Sustainability

Sherwin-Williams recently introduced a powder coating product line based on post-consumer recycled plastic. Powdura® ECO powder coatings are formulated with polyester resins based on recycled polyethylene terephthalate plastic (rPET). Earlier versions of Powdura® ECO powder coatings were based on pre-consumer waste plastic that is generated in factories. This latest development will have an impact on recycling post-consumer plastic that comes mainly from beverage bottles.

According to the company, one pound of Powdura ECO TGIC/TGIC-free (triglycidyl isocyanurate) coatings contains the rPET equivalent of about sixteen 16-ounce water bottles, depending on the final product formulation Sherwin-Williams estimates that one pound of Powdura ECO hybrid coatings contains approximately the rPET of seven to ten 16-ounce water bottles, depending on the formulation.

Low-Temperature Cure

Pengchen (Simon) Yang, a senior researcher in allnex’s Corporate Innovation Group located in Wageningen, Netherlands, introduced a potentially game-changing powder technology at the 2023 European Coatings Conference. The breakthrough was described in his presentation, “Ultra Low Temperature Curing Powder Coating via Real Michael Addition.”

Yang’s work introduces a new chemistry to the low-temperature-cure powder coating universe. This fascinating technology is based on Real Michael Addition (RMA) chemistry that includes an innovative catalysis system that provides cure latency to this highly reactive chemistry. An RMA reaction relies on a combination of a “Michael donor” in the form of a nucleophile with an α,β-unsaturated carbonyl to create a Michael adduct. The allnex team, led by Yang, crafted this chemistry into solid polymers/oligomers that are extrudable and capable of film formation at relatively low temperatures, i.e., < 120 °C. In addition, these polymers/oligomers are reportedly stable at room temperature storage conditions.

This chemistry is comprised of two crosslinkable species: component A is a material containing C-H acidic moieties, and component B is an unsaturated polymer. The most preferred component A is a malonate functional polyester resin, and methacrylated polymers (polyester-, epoxy-, or urethane-based) are the most preferred B component.

The catalysis system is rather complex and is based on a catalyst precursor (P1) in combination with a catalyst activator (C1). P1 is a weak base (DABCO™ or tetramethyl guanidine) that reacts with C1, generally an epoxide compound, to produce a strong base catalyst. The epoxide compound can be TGIC, glycidyl methacrylate (GMA) acrylic resin, or Araldite™ PT-910/912. This catalyst technology is quite reactive; therefore, a retarder, typically a carboxylate, is used to introduce a degree of latency. Latency is critical to enable processing through the conventional extrusion techniques that are common in the powder coating industry.

Latency is further enhanced by macro-physically separating reactive species in independent compounded mixtures. For example, the C1 catalyst activator may be extruded into binder components independent of the P1 catalyst precursor/retarder blend. Two powder materials are generated that are then post-blended into a pseudo-2K powder mixture that is then applied to a substrate and cured at low temperatures, typically about 110–130 °C.

This groundbreaking technology is comprehensively detailed in the international patent application WO-2022/236519 A1, which was issued on November 17, 2022. It is the author’s hope that the powder coating world will take notice of Yang’s fascinating low-temperature RMA-curing technology and that this will open a spectrum of opportunities for growth into new markets and applications.

In other developments, AkzoNobel debuted Interpon W, a product group specially formulated for application to heat-sensitive substrates. Not only can these products be used to coat wood and engineered boards, but they can also be used on various plastics, gypsum, and plastic composites. Interpon W includes thermoset as well as UV-curable powder technologies. Allnex Resins is also supporting the development of low-temperature-cure powder coatings with the introduction of ultra-low-temperature-cure polyester resins. These include UVECOAT (UV cure) and Crylcoat (thermoset) resins specifically designed to cure at temperatures 80–135 °C.

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Through an open, collaborative, and consensus-based process, ACA staff and industry leaders seek to identify research needs that have the potential to advance industry sustainability and growth by informing manufacturers, raw materials suppliers, academic institutions, government research laboratories and other research organizations.

The first of these themes looks at the industry’s challenges in sustained use of critical materials for formulating both existing and emerging products.

The rigorous, multi-step analysis undertaken for this Technology Roadmap collected consensus-based input from a diverse set of industry experts using anonymous initial surveys followed by personal interviews to explore identified concepts for consideration. The resultant synthesis of potential consensus points was further refined by broader industry peer review. Key considerations included exploring the relevance and value of materials for coatings, the definition and communication of “safety,” the challenges of formulation and application, the importance of customer relationships, and the overall industry posture on emerging public policy with respect to product stewardship.

The key considerations offered in the findings of this Technology Roadmap include:

• The broad formulary required by an industry producing a diverse product line for an expanding group of end users (for both industrial and consumer products);
• The complicated “substitution process” for many unique raw materials;
• The role of the supply chain in supporting procurement and manufacturing use of new materials;
• End-user capacity for safe use and its relationship to product performance;
• Coatings industry collaboration and transparency on advancing policies and science requirements for safe materials; and
• Industry capacity for “proactive change,” and its acceptance by a diverse customer base.

A consensus vision statement was developed for the industry’s current and ongoing management of critical materials from consideration within this Technology Roadmap:

The coatings industry is recognized as a leader in supporting the underlying science and public policy for safe use of raw materials, accessing the most up-to-date information on product stewardship, and supporting established programs that both recognize and advance improvements in safe practices.

With this and future ACA Technology Roadmaps, the paint and coatings industry aims to build on its continued focus of offering paints and coatings that meet the needs of its customers without compromising their safety or endangering the environment.

Background on the ACA Technology Roadmap Project

For over two years, the ACA S&T Committee has developed a plan for producing a series of ACA Technology Roadmaps intended to spur research and development needed by the industry. The goal of the project is to support both near- and long-term needs of the coatings industry in an “open innovation” setting by identifying and communicating basic and applied research needs to manufacturers, raw materials suppliers, academic institutions, government research laboratories and other research organizations.

First and foremost, the Technology Roadmaps are not intended to promote or advance any product, practice, solution, or technology over or to the exclusion of others, nor restrain in any fashion the individual competitive effort of any company. Rather, the Technology Roadmaps are intended to drive innovation and competition by broadly sharing identified technological needs of the industry. Further, the process used to develop report content was carefully established to ensure contributors were cautioned not to disclose any confidential business information, research plans or competitively sensitive information. Where further collaborative action among companies is recommended herein, it is intended to be with the consultation of legal counsel to ensure compliance with antitrust rules and other applicable laws.