Advances Enabled by Water-Based Coatings

By Diane M. Calabrese / Published July 2023

Birds and butterflies are lovely creatures, as all would agree. ‘Volatiles’ is a name given to them in Middle English.

     Volatile, which derives from the Latin word volare (to fly), now applies far outside the realm of winged beauties. Not only does it encompass unpredictable personalities, but it also describes unwieldy chemicals.

     Volatile organic compounds (VOCs) cause so much consternation that they get their own acronym, one that penetrates the everyday lexicon. A VOC has one or more of several characteristics (in addition to being organic). 

     In the atmosphere, a VOC may take part in photochemical reactions (some of which contribute to the formation of ozone in the troposphere). A VOC generally vaporizes at low temperatures, and it has a boiling point below 100°C (212°F). (That is not the full list of attributes that might land a compound in the VOC category.)

     [A word about the ozone: In the stratosphere—the outer atmosphere—it is a naturally forming and protective molecule (O3), but in the troposphere—the lower atmosphere—it’s a byproduct of chemical oxidation involving many airborne compounds released by processes like combustion and manufacture and use of petroleum products. Because of its negative impact on respiratory health, ozone reduction has been one of the main goals of the Clean Air Act.] 

     It’s the petroleum-based products that interest us here. The good they do when used as coatings to enhance the longevity of surfaces of varied compositions cannot be overstated. Bridges, homes, and pipelines—all the conveniences and comforts of modern life—stand up better to the vagaries of the environment over time because of protective coatings.

     Can protective coatings be manufactured and applied without the use of solvents that fall into the category of VOCs? Not entirely yet. But there’s a great deal of interest in moving in the direction of water-based coatings as fast as possible.

     “When a coating is water-based, it means water is used in your formulation to emulsify your finished coating,” says Dan Thompson, a sales representative with Deco Products Inc. in Denver CO. “Water-based chemistry has significantly made leaps and bounds in the manufacturing process.”

     The move toward water-based chemistry in the manufacturing process is welcomed by all of us who have our eyes on the balance between industrial innovation and environmental stewardship. Balance depends on many factors, including generating the least amount of waste possible. 

     “Waste material has been almost completely eliminated, and the carbon footprint has been minimized by not emitting harmful [VOCs] into the atmosphere,” says Thompson. Deploying water-based technological methods, his company has been able to manufacture single component water-based coatings with no waste.

     A prudent use of coatings—another facet of waste reduction—is facilitated by having water-based coatings in hand. “If you have coating left over at a jobsite, you put the top back on the container and use the rest of it for your next job,” says Thompson.

     Producing a high-quality, high-utility product while simultaneously minimizing waste and treating our environment gently is possible. “A good-quality, water-based coating will provide excellent durability, easily clean up with water, and lower VOC emissions, meaning less harmful impact on the environment and therefore being environmentally friendly,” explains Thompson.

     Everything becomes a bit easier with a high-functioning water-based coating. Protocols for storage of coatings with low-VOC content may not be as stringent as for those with high-VOC content. Of course, always follow the manufacturer’s instructions. 

     Water-based coatings also help provide a safer workplace for those who use them as employees or as contracting professionals. Exterior coatings in the paint category usually are alkyd or oil based. They should not be used indoors because the confined space increases exposure to their higher level of VOCs.

     Latex, or water-based, paints still emit VOCs, but not at the same volume or intensity as alkyds. Again, achieving the safest application begins with following the manufacturer’s instructions.

     Initiatives such as Prop 65 in California, which have a reach to all manufacturers who sell products in the state, also give impetus to water-based coatings. With fewer VOCs in a product, there are potentially fewer chemicals that meet disclosure requirements as possible carcinogens. Outside of minimizing reporting requirements, there is the knowledge there are fewer carcinogens—a good outcome.

Durable and Doable

     Advances sometimes come when an old method is made new again. Limewash has verified antiseptic and antifungal properties. It also acts as a fire retardant. 

     Once used to coat fences and wooden structures (usually outbuildings), limewash (aka whitewash) has enthusiasts. Roughly 80 percent water and 20 percent limestone, limewash is brushed on a surface. When the application dries, the surface is coated in calcium carbonate.

     The chemical process for getting to the coating involves burning limestone or shells, resulting in calcium oxide. When mixed with water, the calcium oxide becomes calcium hydroxide, or what’s brushed on a surface. 

     The Environmental Protection Agency (EPA) advocates programs looking for sustainable alternatives to coatings with VOC, and limewash is in the mix. The National Park Service (NPS) National Center for Preservation Technology and Training (NCPTT) has used limewash to protect the trunk bases of historic trees. 

     The NCPTT method for protecting trees might be a viable alternative for electric utility companies that use coatings with VOCs and chemical injection to protect their poles. The use of coatings extends well beyond buildings and bridges.

     EPA and NCPTT both have interest in the historically tried (and proven) methods for making limewash more waterproof. Among biodegradables that have been added are molasses, casein, pine rosin, and tallow. 

     Biodegradables are also renewable and sustainable components. We can expect much more innovation from looking back and looking forward at the same time.

Photo courtesy of Deco Products.

     Meanwhile, EPA’s focus on VOCs is intense, both outdoors and indoors. The EPA uses a condensed definition of VOC, and here’s the essential part: “…organic chemical compounds whose composition makes it possible for them to evaporate under normal indoor conditions of temperature and pressure.”

     That short definition highlights the importance of water-based coatings. Water does not contain carbon and is not an organic compound, so its evaporation is not a health hazard.  And water-laden air (e.g., high humidity) does not pose the equivalent health risks of air permeated by VOCs.

     EPA cites the World Health Organization (WHO) classification of VOCs as useful. WHO designates
them as very volatile, volatile, and semi-volatile categories. Very volatile fit the traditional definition of VOC (see first section) because they have a boiling point below 100°C (212°F). Propane, butane, and methyl chloride are examples.

     Volatile organic compounds in the second category of the WHO classification include, for example, formaldehyde, toluene, and ethanol. In the third WHO category are semi-volatile organic compounds, which include compounds such as pesticides, plasticizers, and fire retardants likely to be used indoors. 

     The EPA now endeavors to give indoor air quality as much attention as it has always given to outdoor air quality. And the EPA points to the WHO designations as much more useful for delineating and understanding risks.

     As a parallel effort, the EPA and other groups want to establish standardization in labeling and in certification of products. Certification has become an issue because products certified as “green” or “environmentally friendly” may still contain VOCs. 

     Backing up a bit, the CFR [Code of Federal Regulations] definition of VOCs should be kept in mind, too. It begins “[VOC] means any compound of carbon, excluding carbon monoxide, carbon dioxide, carbonic acid, metallic carbides or carbonates, and ammonium carbonate, which participates in atmospheric photochemical reactions…” (from 40 CFR Part 51.100). (Readers will notice the compounds not regulated as VOCs are still regulated or are the subjects of intense regulator interest.)

     Obviously, using a compound as ubiquitous and harmless as water as a base for coatings will only become more popular. Water-based coatings are extremely popular now. According to the Paint Quality Institute, 80 percent of household paints sold today are water based. 

     Yet until water based becomes synonymous with zero VOCs, we can expect regulation—and innovation to keep pace with or outpace the regulation—to continue. There’s much more to motivate innovators in coatings, however, than regulations.

     The positives in water-based paints go well beyond lower VOC content. True, too, most of them are tied to the lower content.

     For instance, lower VOC content equates with less odor and less flammability. On the practical side, disposal (tipping) fees for VOCs are likely to be less. 

     Combining the optimal qualities of a high VOC coating (e.g., more resistant to environmental conditions and better lifetime wear) with the positives of water-based coatings is more than a goal. It’s the future. 

     How far in the future? That we can’t predict. But consider that research and development in water-based coatings engages researchers in medical, electronics, space, and technology fields.

     Water-based coatings with low VOC interest all sectors of commerce and industry. They make the workplace safer, keep the environment healthier, and at the same time lower costs, thanks to simpler storage and disposal requirements.

     There’s imaginative research and development all around us. One day we may return to “volatiles” referring to butterflies and birds  with only good thoughts about them.