Epoxy Troubleshooting – amine blush.
Have you ever seen a waxy, often whitish haze form on your two pack epoxy coating?
Amine blush, as it is known, is a waxy substance that forms on the surface of some epoxies. In theory, being a soluble wax it can be removed by detergent washing, but it is not a condition you want to see.
So, what can happen if my floor shows amine blushing?
If your topcoat develops amine blush then you will obviously end up with visual defects and the surface will tend to pick up dirt more easily, so you will need to remove it if it occurs in your final coat. You cannot simply leave it there.
If you end up with amine blush in your basecoat, then you can expect crawling if you were to apply the second coat. You could also end up with large scale delamination as the amine blush essentially acts like a strong “mould release” across the affected surface.
Either way, it is a costly mistake that can be avoided by doing your homework on the resins and understanding why it happens (in the coaching classes I cover how to read data sheets and MSDS in order to understand the likelihood of amine blushing).
So, what causes amine blushing and how can I avoid it?…
Amine blushing is the result of the amine in the curing agent reacting with carbon dioxide and moisture to form the waxy substance. Some amines are more prone to the problem than others and fundamentally if your system is hydrophobic, or not miscible in water, then you have less risk of amine blushing.
A quick tech-talk side step, for those that are interested…in my experience, I have found isophorone diamine (IPD) based curing agents particularly susceptible to blushing and related surface defects. I mention IPD as it is a commonly used curing agent due to the fact it is highly reactive and cheap, so manufacturers tend to like it because they can use less of it. Being so reactive they tend to use a lot of diluent to boost the volume ratios, which further cheapens the product overall.
OK, so I mentioned that the amine blushing was a reaction with moisture and carbon dioxide. Therefore, a humid environment can be more prone to such problems, but it can also be quite inconsistent (happen one day and not the next) in hot, humid environments because the product crosslinks more quickly to begin with due to the higher ambient temperature.
The other extreme, is cold and wet conditions. In this case there is moisture in the air and the resin is slow curing giving the (blushing) reaction plenty of time to take place.
One scenario that many users do not consider is when they are looking to heat a room in order to speed up the curing process. They forget that a gas fired heater will be blowing carbon dioxide into the room, increasing the concentration of the gas compared to normal conditions and increasing the chance of amine blushing occurring (after all it is a reaction based on moisture and CO2).
So, how do I know if the resin is prone to blushing before I do a job?
Check the ideal curing conditions and product limitations supplied by the manufacturer. Pay particular attention to the humidity criteria and minimum temperatures stated on the data sheets. If in doubt, then simply ask the manufacturer.
Most applicators that have been doing floors for a while have seen some form of amine blushing. Have you seen the defect? What did you do?
Take care and talk to you later,