Driving Sustainability in High-Performance Polyurethane Coatings
By Steven Reinstadtler and Corey Fowler, Covestro LLC
There are certain iconic sports cars synonymous with high performance, fast speeds, and enhanced styling. Whether a classic version or the newest model featuring the latest technology, the car’s reputation precedes it. Similarly, certain coating types, such as polyurethanes and polyaspartics, are associated with high performance as well as, interestingly enough, three of the leading sustainability drivers for coatings: in-use performance, environmental impact, and extended lifecycle. In some cases, traditional polyurethane coatings continue to be the stalwart of a particular market segment even 40 years later, while some younger upstarts have been making their mark in other market segments due to their ability to satisfy modern sustainability targets.
Let’s consider how polyurethane coating developments have affected the sustainability of this class of coatings by taking a quick lap around several market segments.
Protective and Marine
Polyurethane-based coatings in the protective and marine segment are like the 1970s muscle car. Introduced as a sustainable replacement for vinyl/zinc and lead/alkyd systems, site-applied structural steel polyurethane topcoats revolutionized the industry.
Compared to previous technologies, polyurethane topcoats eliminated lead and reduced volatile organic compound (VOC) content. Asset owners soon found that a system based on polyurethane protected against corrosion and provided long-term aesthetics. Now, over 40 years later, engineers continue to specify polyurethane topcoats because the durability of the asset is the top priority. The proven performance of polyurethane is well-known to seasoned professionals who depend on its excellent chemical and UV resistance to extend the life cycle of the asset, as well as the repaint cycle.
A newer entrant in the race, polyaspartic coatings, is proving its mettle as a fast-curing alternative to epoxy and polyurethane in site-applied and fabrication shop applications. Polyaspartics can be applied in a thicker coat, which may allow the reduction from three coats to two. They also meet VOC guidelines and can greatly reduce hazardous air pollutants (HAPS), which many local municipalities restrict. Whether site-applied or fabrication shop, it is all about deadlines and detours; so a fast-curing, thicker coating can eliminate a coat in the process, reducing the painting cycle labor by 30%.
A specifier once said, “If you think it costs a lot to use a high-performance coating, you should see how much it costs to use a lower-performing coating.” In the architectural world, specifiers familiar with coatings used in other applications sought to incorporate them into their buildings. The result is the use of several newer technologies in the building environment that address sustainability trends, such as lower VOC, in-use durability, and long-term aesthetics. For architectural coatings, think of the teenage tuner looking to trick out a two-seater. The trend has been to lower VOCs and odor without sacrificing performance. One area where performance and sustainability intersect is concrete floor coatings where, like that teenager modifying the first car, contractors are looking for performance and aesthetic attributes that unknowingly support sustainability goals. One example would be the rise of decorative polished concrete used in public spaces like lobbies, retail stores, and restaurants. Although the polishing technique offers sustainability advantages such as using the existing floor substrate rather than tile or carpeting, there are sustainable options for protecting the substrate when stain and chemical resistance are needed. Two-component waterborne polyurethanes are being used as an aesthetic enhancement but with the added sustainability benefits of low VOC, low odor, and increased service life. Contractors also reach for the turbo upgrade in the form of a polyaspartic floor coating, which offers a fast-curing, low-VOC, labor-reducing, decorative concrete option.
For manufacturers, sustainability preferences look more like an all-electric sports coupe. For them, efficiencies in production speed and power consumption are not just good for sustainability reasons; they are good for the bottom line. For example, topcoat finishes for factory applications such as tractors, trailers, and utility boxes can now be efficiently coated with a DTM (direct-to-metal) polyurethane or polyaspartic monocoat for 15- to 20- year durability. In the case of the newer polyaspartic technology, the coating can be formulated to be low VOC, ultra-low HAPS, and cured at ambient temperatures allowing the manufacturer to shut off expensive CO2– producing ovens. For plastic or composite parts, a growing trend is the use of coatings to add a haptic feel. In the past, solventborne soft-touch coatings were used with the disadvantage of high VOC and possible substrate attack. With new waterborne polyurethane technology, the haptic performance of plastic composites can be accomplished while greatly reducing VOC and HAPS levels as well as enhancing the compatibility with the substrate.
Transportation preferences are changing rapidly and this creates an exciting challenge for automotive designers. Coatings continue to be an important consideration in the future of mobility, and while performance and appearance always make the top of the list of requirements, sustainability continues to be a top consideration. Automotive manufacturers are constantly looking for more ways to improve sustainability. Polyurethane is uniquely capable of helping to meet those desires while still achieving high performance and appearance standards. A very important value of polyurethane is its high durability; with the increase in ride-sharing, these vehicles are seeing an increase in their use rate and thus the durability of automotive coatings continues to be a vital quality. Another ongoing trend is the desire for renewable content. Bio-based polyurethane, in particular, is able to create coatings that offer high performance solutions while utilizing polymers made from natural building blocks.
Responsible for one of the largest industries in the United States, automotive manufacturers have very robust sustainability strategies driven by consumer demands, economics, and regulations. Polyurethanes can help meet their sustainability goals now and in the future by offering the durability, processing flexibility, and formulation versatility that automakers desire.
Although the majority of the textile industry has moved overseas, the more specialty applications are still made in the United States. Like the high-end sports car, these elegant textiles have particular performance needs that require an aesthetically pleasing, functional coating. In this space, the drive toward more sustainable materials starts with consumers and non-governmental organizations that want footwear and apparel brands to move towards more sustainable materials and processes. New polyurethane textile coatings are starting to make a dent in this large, $21 billion industry1 by offering synthetic textile solutions that eliminate the use of solvents. One coating example not only creates a more sustainable synthetic material that gives the appearance of leather, it can also be processed in such a way that reduces water consumption by up to 95%, energy usage by up to 50%, and the carbon used by up to 50% when compared to traditional methods. Overall, polyurethane synthetic textile coatings provide a uniquely sustainable solution that brands and consumers value. These innovative coatings are used in a variety of applications and industries including automotive interiors, specialty apparel, and footwear.
The next big trends on the drive to sustainability for this industry are bio-based materials and incorporating CO2 as a feedstock. Polyurethane solutions with renewable content are already available and seeing increased demand from textile brands. However, there is still room for innovation in this space that can increase the performance and cost efficiency of the materials. In the future, bio-based materials and CO2 feedstock appear to be the next step toward more-sustainable business practices in the textile coating market.
Sustainability is not a new concept, but its drivers are having increasingly greater influence on manufacturers up and down the value chain. This provides an opportunity for coatings suppliers to showcase key attributes that contribute to creating more sustainable products including better in-use performance, lower environmental impact, and extended product lifecycles. “People, planet, profit” is a timeless principle of many sustainable business initiatives because it highlights the importance of creating solutions that contribute and do not sacrifice one component for a gain in another. Although certain principles have been applied for years, continuous improvement has led to the adoption of the 17 United Nation’s sustainable development goals. These goals, which touch on various social and environmental issues, are becoming the basis for many companies’ long-term goals and are filtering down to decision makers in all the major coatings market segments.
CoatingsTech | Vol. 14, No. 5