A Healthier Dose of Protection: The Environmental Concerns on the Use of Waterborne Coatings
Everything we do is going to come back to bite us some day and that day might be much sooner than we think. Last month, the World Health Organization (WHO) released a report that states that more and more microplastics are found in the water we drink. It's still somewhat inconclusive on how they might impact our health but it's still a point of concern that we've now arrived at a point where we regularly consume plastics every day through water.
It's not just with plastics, from the greater prominence given to Sweden's Greta Thunberg and the recently concluded global climate strike, we're now more aware than ever on the destructive environmental impacts of our actions. This awareness has also seeped in to the coating industry where the use of waterborne coatings has slowly and steadily replaced other more environmentally harmful coatings. Coatings are one of the main sources for volatile organic compound (VOCs) emission and hazardous air pollutants (HAPs) and the use of waterborne coatings go a long way on fixing that problem.
How coating impacts the environment
If you've ever tried house painting, you must've noticed how the average house paint carries a certain scent. That scent you smell is actually VOC emissions, gas emissions that are expelled from certain materials. VOCs are named so because they can easily vaporize even under normal temperature thanks to their high vapor pressure and are commonly found in the majority of solvent-based coatings available in the market although the amount of VOC emissions vary from one type of coating to another.
VOC emissions are most prominently found during the curing process which is why paints smell the strongest when they're still fresh. Once the paint has completely dried, the paint no longer emits VOC and is also the reason why you should always leave the window open when the painting is still wet. VOC emissions can cause dizziness in humans and they're also pegged as one of the causes for the depleting ozone layer which is why the use of coatings are heavily regulated by the government.
The only thing that separates VOCs and HAPs is that HAPs do not pose a risk to the ozone layer. HAPs still pose a risk to both humans and the environment but they're not as strictly regulated as VOCs. Other than emissions, coatings that regularly come into contact with water, ship coatings for example, also have to be designed in such a way that they possess no environmental dangers to the water. It's because of the above reasons that the industry needed a better alternative in the form of waterborne coatings.
An overview of waterborne coatings
Coatings are typically defined by the type of resin they're made of which is why it's common to see the word urethanes and epoxies be used to categorize a coating. While it's true that these resins have a sizable effect on deciding the properties and characteristics of a coating, the solvent used to give the coating its liquid properties also has a similar effect. In terms of solvent used, coatings can be broadly categorized into water-based solvents and chemical-based solvents and for this discussion; we'll be mostly focusing on the former.
Waterborne coatings, as their name implies, are coating that relies on water-based solvent as their liquifying agent. Technically, both water-based solvents and chemical-based solvents both contain water but with vastly different amounts. Water-based solvents typically contain water by as much as 80% in terms of volume with the rest consisting of chemicals such as alcohol. As a result, coatings with water-based solvents typically have less viscosity than coatings with chemical-based solvents. This means that coating thickness might be more of an issue with waterborne coatings, requiring the use of gauges such as Elcometer 480 during the application process.
The benefits and challenges of waterborne coatings
The main advantage of using waterborne coatings is that because of their chemical composition, they emit considerably less emissions. With stricter environmental restrictions placed by the government on businesses all over the world, waterborne coatings have turned into something that's nice to have into an essential need. The small amount of emissions also mean that businesses don't need to prepare as many health and safety precautions as usual, reducing operational costs and difficulties across the board.
However, waterborne coatings also raise some difficulties as water-based solvents are considerably more sensitive to the environment during the application process. Factors such as temperature and humidity can easily affect the curing time for waterborne coatings, making them somewhat less versatile than chemical-based solvents. This can be remedied by reducing the amount of water in the solvent or by adding additives but that would lessen the benefits of waterborne coatings. It should also be noted that water is actually one of the main catalysts for corrosion, requiring the use of a primer coat to prevent direct contact with metallic substrates or by using a formulation that ensures the water would be pulled to the top of the coating.