RCU Forums - Epoxy cure problem

RCU Forums (https://www.rcuniverse.com/forum/)

- Questions and Answers (https://www.rcuniverse.com/forum/questions-answers-154/)

- - Epoxy cure problem (https://www.rcuniverse.com/forum/questions-answers-154/6649072-epoxy-cure-problem.html)

RE: Epoxy cure problem

I use paper plates ,,,then count the seconds out of each bottle ,,mix well then apply. Nver had a problem in 10 years. Simple ,maybe crude,,but it works for me just fine. Go to walmart and get a giant bag of craft sticks.. they are about 1/8 flat on one end and pointed on the other end ..Stick is 31/2 inches long. You can go right from mixing using the same stick for applying---simple

JIM

RE: Epoxy cure problem

Before you try to remove the epoxy, try some heat from a covering air gun. Get it warm for 10 to 15 minutes and let it cool. It may be enough to finalize the cure.

RE: Epoxy cure problem

Thank you guys for all hints.
I have learned a lot about epoxy handling by posting my question....:)

Andrzej

RE: Epoxy cure problem

Catflyer,

The best solvent for epoxies is probably acetone. Be aware that acetone is an extremely flammable solvent with a flashpoint of -7 degrees F if my memory serves me right DANGEROUS if not handled correctly. You could also use Xylol or Toluol for thinning. Once the solvent flashes out of the mixture curing will occur.

RE: Epoxy cure problem

Steve:
I have been working with 30min slow cure epoxy but find my workable or useable application time to be quite a bit shorter. I have been mixing in a small 1oz medicine cup quantities of 1/2 oz max or less. I did not time it, but I must be getting less than 5 -10 minutes of application time before it gets too thick to spread. I have been applying with a cheap 1/2 brush like plumbers use for spreading flux, etc. The brushes were labeled "acid brush". I got them cheap like the mixing cups and I have no complaints about the epoxy not curing, but curing so fast, faster than I would expect.
John

RE: Epoxy cure problem

John,

I understand what you are saying. There are only two things that generally effect the cure time of epoxies other than the resin and its respective hardner which are temperature and mass. If you mix up a fair amount of material even a half ounce in a mixing cup it will cure faster vs being mixed on a flat surface where it can be spread out. More mass, more heat generated in the reaction. If your working enviroment is warm your material will cure faster than if its cold. Below about 55 degrees F most epoxies go almost into remission taking practically forever to cure until the temperature comes backup. About 75-80 degrees is a good working temperature for most applications.

Another thing we don't know is what the potlife benchmark is based upon for your brand of 30 minute epoxy. Is it a 30 minute cure or or a 30 minute potlife(working time)? We generally base our times on a 100 gram mass at 77 degrees F. Anything different than those parameters the potlife and cure time changes.

Hope that helps :)

Steve

RE: Epoxy cure problem

Quote:

ORIGINAL: Steve Steinbring

ARB,

Now I think we have the answer to what really happened. Epoxies don't work like fiberglass where if you add more hardner you will get it harder and hotter even to the point of catching fire.

With epoxies the more hardner you add the softer the cured material will be to the point where its gummy and won't really cure. The less hardner you add the harder the cured epoxy will be to the point where its too hard. What we do as manufacturers is to give you a mix ratio that provides a very strong bond, but is not so hard that it will shatter if shocked or stressed.

We get alot of home chemists that we have to deal with. Most of our product is supplied to the furniture repair industry. Some of these folks insist on second guessing us and often get failures.

Its also possible that you got mixed up and mixed two portions of A or B together it does happen. :(

Have a great Thanksgiving! PM me if you have other questions I'll be out of touch for a day or so but will get back with you.

Steve

I'm assuming when you mention fiberglass and adding more hardener to get it harder and hotter above that you are referencing polyester resin. Polyester resin uses a catalyst, usually MEKP, to cure the resin. And yes the more catalyst you add, the faster it will cure. There are exceptions such as Bondo which actually uses Benzoyl Peroxide as a catalyst. Don't try using the MEKP with Bondo or the Bondo catalyst with normal polyester resin or you will have one really horrible mess to clean up. Also, there's a difference in the stuff you find at an auto store or home center and the finishing resin you should use.

Epoxies on the other hand do use hardeners and they do generate some heat as do polyesters when they cure. Usually it's pretty difficult to use 2 portions of the same in the hobby type epoxies because the majority of the time, one part is usually tinted and the other is usually clear. Most of the hobby mixes are 1:1 to simplify things for the user. I remember one of the older Hobby Poxy brands, I think it was their #4 which had something like a 2:1 mix but that was a long time ago. I have some professional finishing epoxy that uses a 2:1 mix and both parts are crystal clear. And one other thing, epoxys and polyesters do have a shelf life. So if this stuff is pretty old, like over a year or two, especially the quicker curing types, I'd trash it and buy new.