Waterborne coatings use water as a solvent to disperse a resin, thus making these coatings eco-friendly and easy to apply. In most cases, waterborne coatings contain up to 80% water with small quantities of other solvents, such as glycol ethers. These coatings are also known to be environment-friendly as US and European regulations require waterborne coatings to have a VOC content of less than 3.5 pounds per gallon of water.
Types of Waterborne Coatings
Below are some of the various types of waterborne coatings that are available in the market today:
- Water-soluble paints – contain water-soluble resins whose individual molecules dissolve completely in water. The resins are usually produced via polycondensation or polymerization reactions in an organic medium, hence they mostly contain organic co-solvents like alcohols, glycol ethers or other oxygen-containing solvents that are soluble or miscible with water. The resins used include polyesters, polyacrylates, alkyds, epoxies and epoxy esters. These paints provide high gloss, a high level of corrosion protection, good pigment, wetting and stabilization.
- Water-dispersible paints or colloidal coatings – contain small clusters of insoluble resin particles that are suspended in water using mechanical agitation. Small quantities of organic solvents are used as coalescing agents, which evaporate on drying. The resins used in these types of dispersion paints include vinyl propionate copolymers, vinyl acetate copolymers, acrylate-methacrylate copolymers, and styrene-butadiene copolymers and polymers. Colloidal dispersions are used mainly to coat porous materials.
- Emulsions/latex paints - are quite similar to water-dispersible paints. The main difference is that the resin clusters in emulsions tend to be larger, and an emulsifier is required to keep the clusters in suspension. The resins used include styrene-butadiene copolymers, acrylics, alkyds, polyvinyl acetate, and polystyrene. These paints posses increased permeability which allows them to "breathe," thus reducing blistering or peeling.
- Water-based alkyds – These coatings tend to take longer to dry than solvent-borne coatings; however the end result has similar gloss, flow and levelling properties. They are very versatile as they can be thinned with water to almost any viscosity. Water-based alkyds can be applied with spray or dip applications, and are one of the cheaper VOC-compliant coatings.
Advantages of Waterborne Coatings
The key advantages to using waterborne coatings are listed below:
- They are ideal primers as they posses good resistance to heat and abrasion
- Provide excellent adhesion
- Low toxicity and flammability due to low VOC levels and HAP emissions
- Help reducing air emissions
- In most cases, these coatings cost less than solvent-borne coatings and require no additives, thinners, or hardeners
- compared to solvent-borne coatings, less coating is required to cover the same surface area
- The pot life of waterborne products is relatively long and unused coatings can be preserved in a sealed container for future use
- Waterborne primer is ideal for use where solvent primer would react with existing substrate materials or coatings
- The paint guns can be cleaned easily with water or water-based solutions and do not require paint thinner, acetone, or methyl acetate
- Can use conventional application techniques
Applying the Coating
To use a waterborne coating, a spray application equipment designed for waterborne coatings is required. The spray guns have to be designed with corrosion resistant materials, such as plastic or stainless steel.
The curing time for waterborne coatings is comparatively long compared to that for solvent-borne coatings. Consumers have to take that point into consideration before embarking on the coating process, as specialized drying equipment might be required. In the case of coating a car for instance, the primer can be applied to all cars and allowed to dry overnight before applying the color and finish coatings the following day.
The binders that are generally used for water-borne coatings are polyvinyl ethers, polyacrylate, or polyurethane resins. Epoxy and alkyd resins can also be formulated for waterborne coating applications.
Many large-scale coating factories have installed spray booths with heating and air movement devices to increase production by reducing curing time. Waterborne coatings have different a viscosity than solvent-borne coatings; hence painters would need to be given adequate training to understand the different application techniques to get optimal results.
Companies Involved in Waterborne Coatings
The following is a list of some of the major companies manufacturing a variety of water-borne coatings with a brief introduction for each:
- Williams-Hayward Protective Coatings Inc. produces coatings for industry and consumers. The company is located in Illinois, USA. Their unique line of coatings include Thermalbond I, II, & III, which is an acrylic-vinyl-rubber latex coating, Aqua-Epoxy, Aqua-Lust/Aqua-Lust Epoxy Ester, Safe-T-Coat containing aklyd, acrylic, and ester primer copolymers, Acrylem coatings are acrylic latex-based, Aqua-Slip Coatings, No-Voc Acrylic-Vinyl-Rubber Latex Coatings, and Aqua-Thane, which is waterborne urethanes
- Chemical company, BASF's Intermediates division operates in several locations around the world such as Germany, Belgium, USA, Japan, Korea, China, and Malaysia. BASF's range of solvents and additives provide synergistic enhancement in shelf-life stability, processability and performance properties in waterborne coating systems.
- Junair is a British company involved in the manufacture of innovative spray booth equipment that provides solutions to reduce energy, increase productivity, enhance performance and ultimately increased profitability for customers
- Precision for Collision (PFC) is located in California and provides spray booth, UV curing lamps, infrared, and curtain enclosures.
- Ohio-based DeVilbiss provides paint drying system for waterborne coatings consumers
Uses of Waterborne Coatings
Waterborne coatings are available for various applications. The following is a list of prominent uses for waterborne coatings:
- Applied on copiers, fax machines, printers, , typewriters, and computers
- Automotive OEM sector
- As a quick release coating for interiors of coal cars, fly ash hoppers, plastic pellet hoppers, refuse containers and trucks, filled with PE or Teflon extenders
- To coat porous materials such as paper or leather
- Emulsion waterborne paints are widely used in the architectural market sector
- Printing Inks