In Part 1 of this series, we looked at a checklist for beginning a waterborne coating project. Once you have determined the technology type that best fits your needs, you find there are many different suppliers for this technology. What or how do you decide whom to use? I like to look at a lot of different suppliers and UL Prospector offers a way for members to receive samples of many of these.
I also like to see if the polymer supplier offers starting point formulations. Normally none of these are production ready; however the formulation they provide can sometimes guide you to proper film formation and what this takes in the way of additives. Let us now look at some of these additives.
Waterborne coating solvents
Depending on whether you have chosen a film-forming polymer may depend on the temperature in which a film is formed. You will probably have to use some sort of solvent to reach your desired temperature. If you do, look through the list of what solvents are compatible with the polymer. The supplier should be able to supply this information. If not, you will look to their starting point formulation and see what was used. If you really like this film and need a solvent, you may have to do a solvent ladder study to see which ones and at what level works best.
When choosing solvents in waterborne systems, always look at the overall type you wish to use. Many are now considered VHAP’s (volatile hazardous air pollutants) and will count on your VOC totals. I tend to go towards the propylene oxide glycol ether groups as opposed to the ethylene oxide glycol ether groups specifically for this reason.
Waterborne coating defoamers
Will you need a defoamer for your product? This is always a concern, as most defoamers have a silicone in their system. Silicone notoriously can cause film formation defects, commonly fisheyes, when over used, so carefully pay attention to the amounts recommended by the supplier. There are mineral oil types of defoamers as well that are sometimes work-arounds for a film imperfection problem.
Even after formulating for over 30 years (with most using water), I sometimes ask the supplier for their recommendations as they may offer 25 different types of defoamers and they all say the same thing on their data sheet. Take complete advantage of their knowledge in this area. You don’t have to tell them anything but the type of polymer you are using, and they should be able to help. Make sure you thoroughly test these products with your product.
Waterborne coating surface additives
You may want to use surface additives to modify the film for certain characteristics. These include slip, adhesion, & wetting, to name a few. Many of these are specific use additives and the usage rate is normally .01 to 5% based on total formulation weight.
With these types of ingredients, more is NOT BETTER. There are several companies that offer samples that allow you to pull from your stock and test as your research says to “try this”. Search the UL Prospector data base for these.
You can also add product additives for UV protection. When doing this, I like to use both the absorber as well as a stabilizer. Make sure to follow the supplier’s instruction, as they are rarely used in the same proportions. These are normally polymer system specific, so again make sure they are compatible with your system.
Waterboard coating biocides and preservatives
I am often asked if I need a biocide or in-can preservative in my product. If it is a clear coating, probably not; if a color, almost always. I know of only a few good suppliers for these types of products, so research the UL Prospector data base for these as well. Make sure they are compatible with your system.
Most of what I have covered is for clear products. Some formulators think that they can start with a clear base and then simply add some color. In some rare cases this can work, but normally not. In part 3 of this article, we’ll discuss the reasons, how to deal with making colors, and then the specific types of ingredients.
- Coating Film Defects, Part 1, by Jochum Beetsma
- Coating Film Defects, Part 2, by Marc Hirsch
- Adhesion Promoters 101, by Marc Hirsch
- A Primer on Antimicrobials, by Marc Hirsch
- Coatings Additives – Defoamers, Adhesion Promoters & UV Protection, by Marc Hirsch
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