FREQUENTLY ASKED QUESTIONS
What is Epoxy?
Epoxy is a type of thermoset resin system that includes an epoxy resin and a hardener that, in the case of Resin Research, is a cycloaliphatic curing agent.
Most epoxy resins are what is called an addition reaction which is a reaction of two different chemicals when mixed. Some other thermoset resins are catalytic reactions which are one chemical that is initiated by adding a catalyst.
Why are epoxies generally considered superior?
In most high tech applications whether it’s racing boats, high performance automobiles, aerospace, etc. epoxies are used because they offer the best strength to weight results of any polymer product. Also with the myriad of resins and curing agents available the availability of a wide range of manufacturing processes are applicable.
What is Pot Life?
Pot life is an industry-wide standardized test that indicates how use much time you have after mixing. It is based on a 77F (25C) standard temperature. This means that the resin, hardener and ambient temperature must all be 77F and the mix total is 100 ml. So here’s what’s tricky about this:
1. For every 10 degrees F the temperature is increased the pot life goes down by 50%. So let’s say your resin/hardener mix has a 40 minute pot life at 77F. at 87F your pot life is 20 minutes. At 97F it’s 10 minutes. And so on.
2. For every 10 degrees F the temperature is decreased the pot life doubles. So let’s say your resin/hardener mix has again a 40 minute pot life at 77F. At 67F your pot life is 80 minutes. At 57F it’s 160 minutes. And so on.
3. This ultimately means that ambient temperature is going to dictate which hardener you going to use as much or more than that pot life number on the label.
4. Quantity also has an effect on pot life. The bigger the batch size, the shorter your pot life will become. On very small batches your pot life with be extended.
Doesn't that make epoxy hard to work with?
Not at all. Unlike some other thermoset resins, epoxy does not have a hard “gel” time. It gradually gets thicker and thicker on your surface until it finally sets rather than gelling all at once. This gives you ample time to get the part finished and even some extra time to fix issues.
To make it easier, here are some tricks:
1. Once you’re done mixing, get all the resin out of your cup/bucket as quickly as possible and on to the project. This will double or even triple your available work time.
2. Use smaller batches of resin and work on smaller areas of your project instead of trying to mix one batch for the entire thing. Since epoxy has no hard gel time it’s easy to do this and there is no disadvantage to it. I’ve seen entire boat hulls laminated in this way using quart buckets.
How important is the mix ratio? Doesn't adding more hardener make reaction time faster?
Mix ratio in epoxy systems must be adhered to at least reasonable close. Adding more hardener is not an effective way to quicken drying times, we have an accelerator for that, X-55, if needed. The reason for the adherence to mix ratio is the structure of the epoxy itself. It is an addition reaction and the correct number of molecules exist in each of the components.Adding more hardener will only result in making your finished project weaker since there will be unreacted hardener floating around in your finished project.
Do you provide pumps for measuring ratio?
We do not. Available today at all hardware stores and home improvement centers are metered mixing buckets available in the paint isle. These are far more accurate, faster to use and cleaner to work with than any bottle top pump system out there. For production there are some excellent pump systems. We like some of these from Micheal Engineering.
What about HDT, Should I be concerned with a failure if my product goes over that temperature?
HDT or Tg is another standardized test.
HDT measures a 10% deflection in an epoxy rod. The temperature is slowly increased in the test until there is the 10% result. This measures the stability of the cured resin to heat and cold.
Tg is another similar test. Neither of these tests are for service temperature. Service temperatures are much higher and in everyday use this is rarely a problem. But there are cases where higher service temperatures are required. In these cases the resin will need to be heat cure at an elevated temperature. Generally speaking HDT is about 50 degrees F higher that the temperature it was cured at. So if cured at 75F it’s HDT would be 125. But if it’s cured at 150F the HDT would be around 200F. Generally, we see engine compartments, unpainted carbon fiber automobile panels, exhaust systems and other similar applications that require this.
What is crystallization? If this happens is my resin ruined?
Crystallization is something we see occasionally, usually in winter. Epoxy resins almost all have this tendency and it first appears as white crystals in the bottom of the bottle (we have never seen this in drums). This is caused by changes in temperature and is exactly the same thing as crystallization in honey. If this happens here are some solutions:
1. In honey, the solution is to place the jar in hot water. The solution for epoxy is the same but usually requires a bucket.
2. We’ve also melted crystals in a microwave by placing the bottle in and nuking it for 2 minutes. Then pull the bottle out loosen the cap letting out expanded air. If there are still crystals, put it back for another two minutes then release the expanded air again. Continue this until the crystals disappear.
3. Once the crystals are melted the resin is good as new and can once again be used.