There continues to be a growing emphasis in the coatings industry for sustainable and environmentally friendly raw materials and coatings. Providing continuous improvement in sustainability requires the development and implementation of new science and technologies to minimize waste, save energy, lower VOC, reduce hazardous waste, use renewable raw materials and minimize water and air pollution. Advances in Smart coatings, Nano coatings and heavy metal free alternatives to Chrome has fueled many of these advances along with the development and implementation of biobased renewable materials. In multiple cases, new technologies provide a triad of economic, environmental and social benefits.
Economic Sustainability
Examples of economic sustainability possible through the use of innovative coatings and materials that provide energy savings, and/or improve the life expectancy of the coated object include:
- Energy savings through the use of cool roof coatings that utilize solar reflective doped ceramic pigments to reflect sunlight and thus reduce solar absorption and reduce air conditioning costs by as much as 15%.
- Marine coatings utilizing silicone hydrogel demonstrate average fuel savings of 6% along with reducing the level of biocide. Traditional marine antifouling paints contain metals such as copper, zinc and lead. Antifouling coatings can provide enormous eco-efficiency when used on cargo ships and tanker vessels, can reduce drag and lower greenhouse gases and other emissions by an average of 9%.
- New Drag reducing aerospace coatings provide improved fuel efficiency and extend aircraft range by improving laminar flow over the surface of an aircraft.
- Icephobic coatings utilizing nano materials on windmill blades reduce the resistance to erosion and improve operating efficiency.
- Long Life Coatings (automotive, building products) provide longer lasting film integrity and thus material and labor savings over the lifetime of the product or building.
- Anti-reflective coatings for solar cells (for example using silicate, titanium dioxide, silicon and boron nitrides) increase energy output by up to 3%, while hydrophobic self-cleaning coatings increase light transfer through the glass.
- Hydrophobic and Superhydrophobic coatings using nanomaterials for application on structural steel, and oil rigs to delay the onset of corrosion by limiting the migration of moisture and soluble salts to the metal surface. These coatings reduce the need for more frequent repainting which in turn reduces volatile emissions.
- Coatings which cure when exposed to light energy (LED, UV, etc.), moisture or air (oxygen). The cure of these coatings is less dependent on the use of fossil fuels.
- Self-Healing coatings – Increase the service life of a coating as well as the surface it is applied to especially if applied to an oxidizable metal surface. Self-healing technology is based on capsules or fibers. Once the coating is scratched, micro or nano-capsules containing catalyzed liquid polymerizable materials (e.g. drying oils, dicyclopentadiene) are released into the scratch. Figure 2 illustrates Self-Healing technology based on capsules or fibers. Once the capsules are ruptured, polymerization takes place filling the void and functions to reduce moisture ingress and thus improve corrosion resistance as well as the appearance of the coating. Fibers based on thermoplastic poly(e-caprolactone) distributed in an epoxy matrix is one example of self-healing technology to restore film integrity when exposed to heat.
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Figure 1- Self Healing Coatings based on Capsules or Fibers
Environmental Sustainability
Environmental sustainability involves the reduction in emissions, recyclability of paint/materials, use of renewable energy, conservation of water and alternatives to the dependency on fossil fuels that minimize global warming, Lastly the use of Eco-friendly paints as well as bio-based renewable materials together provide a sustainable environment. Some of these initiatives are described below.
- Reduction in emissions is obtained through the conversion to lower or zero VOC paints such as waterborne, powder, UV/LED and EB, higher solids and 100% solids coatings, along with incineration of volatiles. The sum of all these measures contributed to the dramatic reduction in TRI (Toxic Release Inventory Materials) despite doubling the gallons of paint sold from 1980 to 2015. Other measures to reduce emissions include the incorporation of VOC exempt solvents including t-butyl acetate, acetone, propylene carbonate, methyl acetate, dimethyl carbonate and parachlorobenzotrifluoride have contributed to the reduction of air pollutants as Figure 2 indicates. For waterborne formulations, Eastman Optifilm Enhancer 300 or 400 contribute little or no VOC as a coalescent solvent. Their low VOC is attributed to a very low volatility (low vapor pressure and a boiling point >700° F for Optifilm Enhancer 400 and 537.8° F for Optifilm Enhancer 300). These materials can be used in multiple applications including Architectural finishes, Can and Coil coatings, General Industrial, Maintenance and wood coatings.
Fig. 2 EPA Reduction in Toxic Release (TRI) Inventory materials
- Replacement of PFAS (per- and poly fluoroalkyl chemicals) with suitable replacements that provide many of the same benefits without the accompanying hazards to the environment through long lasting contamination and the potential for their effect on human health due to their chemical inertness and longevity. Multiple states have issued legislation that go into effect in 2024 restricting the use of PFAS for multiple applications along with a requirement for record keeping and reporting per the Toxic Substances Control Act’s PFAS Recordkeeping and Reporting Rule on Nov. 12, 2024. Canada is expected to release their final version of their PFAS report concerning the prohibition of certain toxic substances in the summer of 2024. Under REACH, the EU is also considering a proposal to restrict PFAS within 12 months of the initial consultation date. PFAS chemicals are utilized in a number of coating applications such as polymers, wetting agents and surfactants. Per and poly fluoroalkyl chemicals are used extensively as they provide low surface tension, chemical inertness and durability. Depending on the application several alternatives have been proposed such as the use of silicones as well as other substances derived from naturally occurring substances.
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- Examples of biobased materials derived from multiple renewable plant-based sources can provide solvent, oil and other building blocks for utility as biobased solvent or monomer and polymer synthesis.
- Renewable Materials – Fibrillated cellulose can provide a renewable raw material that improves mechanical, surface and rheological performance in coatings for Elastomeric Roof Coatings (SAPPI-Valida). Another example is the use of the waste material from Rice Husks which is used to synthesize silica nanoparticles, graphene nanosheets and graphene oxide nanosheets.
Social Sustainability – Implementing responsible Environmental and Economic sustainable processes ensures prolonged availability of our natural resources, less emissions, cleaner water, improved health, slowing climate change, fewer and less severe natural disasters and less loss of biodiversity.
Resources
- UL Prospector – Sustainability Our Goals as a Society
- UL Prospector – Smart Coatings, The intelligent Choice
- ACA 2020 Sustainability Report
- PCI – Biobased Polymers for Sustainable Coatings
- GOOGLE and AI Internet Search for Sustainability and Biobased Materials
- EPA – Cool Roofs to Reduce Heat Islands
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