Altering the Mix Ratios with Industrial Epoxy Systems
by Erik Steinbring
There appears to be a lot of confusion between the differences between Polyester based systems and Industrial Epoxy Adhesive systems. The reason I say this is because nine times out of ten, people in my seminars answer the following question incorrectly. How do you accelerate the cure time in a EPOXY system, neglecting changing the base resin materials? Ninety percent answer add more catalyst or "B" side.
If you read the previous two BLOG posts, you would know the correct answer would be: In a epoxy system, the adjustment of temperature and the amount of mass. The answer the ninety percentile give is absolutely correct if we were discussing Polyester based systems but the question was for an Epoxy based system. The biggest problem with this misunderstanding is that it could lead to failures and call backs to job sites.
Bottom line, the systems are two different animals when is comes to mix ratios. So let's take a look at how altering the mix ratio of an epoxy changes the dynamics. First let me explain what a 1:1 mix ratio is, that would be where one part of "A" (resin) is mixed with one part of "B" (catalyst). A 2:1 would be two parts "A" mixed with one part "B".
To explain the effects of changing the mix ratio I would like to use the Epo-Grip Clear Paste to illustrate. In this paragraph we will discuss the results by altering the mix by adding more "A" side. The Epo-Grip Clear Paste is a 1:1 mix and it provides a cured result that has superior adhesion, is hard but not so hard that it will not take abuse, vibration and shock. If we take that same material and mix it 2:1 we end up with a harder cure that has good adhesion but is a much harder cure and not as apt to take much abuse or shock. Last if we mix the material 3:1 it will yield a very hard cure, where adhesion is compromised, will not take any shock or abuse and will often shatter like glass upon impact.
On the flip side what happens when we add more "B" side or catalyst. We already discussed what results occur with a 1:1 mix above. Now if we change that to a 1:2 mix ratio the end result is a softer cure, one that will readily take fingernail impressions, adhesion has been compromised, and is often sticky to the touch on the surface. A 1:3 will often yield a cure that can be peeled up with fingernail, with little to no adhesion, is very sticky and will often never cure beyond that. I think we can stop there as a 1:4 is nothing but a pile goo.
To summarize, the addition of more "B" side will not accelerate the cure time, but rather compromise the strength of the bond. The addition of more "A" side will make a harder curing product, but adjust the ratio too far and failures can occur. If you are in business, calls backs and redos are not an option and cannot be afforded. Mixing industrial epoxy adhesive products to the specified manufacturer ratios is very important in order to achieve reliable consistent results. .