Epoxy didn't kick good

[cs]

I had mixed up a batch of epoxy the other day and coated my cheap canoe with it. Well it didn't kick off good and was still tacky after about 2 weeks. So I took and scraped off what I good and than sanded. After sanding I than rubbed it down with sawdust. Came back the next night and coated with epoxy again.

Do you think this will take care of it?

Chad

[Frank Hagan]

Has the new coat kicked off? My guess is that it will, since you removed as much of the uncured epoxy as you could (scraping and an abrasive rub are pretty effective.)

The Chemist may have to confirm this, but I suspect if the majority is wiped off, and the coat above hardens, you are out of the danger zone.

[PugetSound]

Epoxy needs two things to kick off: heat and fresh catalyst. The heat needs to be at least room temperature (70 degrees (F)). I recommend that, in the future, if you are unsure as to the shelf life of the chemicals that you mix up a test batch first. Just a small amount in a paper cup. If your shop is cold, then put a 100 watt light on the epoxied piece for about 5 minutes to start the reaction. After the reaction is started, no more heat is needed as epoxy reactions are exothermic. You should be suspicious of catalyst that is more than 2 or three years old. Also, acetone can be used as a solvent to clean away that uncured gunk.

[This message has been edited by PugetSound (edited 10-17-2001).]

[cs]

My shop is a basement and stays a comfortable 65-70 degrees. I had thought that maybe the cool temp and humidity might have cause the batch not to kick, so I fired up the kerosine heater and let it run for about 4 or 5 hours. The next day I took it outside to see if that would help. The resin and the hardner are both less than 3 months old.

Maybe, there is a slim possibility (real slim) that I might have mixed 1:3 instead of 3:1. I don't beleive that I did mix it wrong, but all the other batches have turned out fine.

I did go down this morning and run my hands over the new coat and it is tack free and has kicked off real good. So maybe I'm okay.

Chad

[Frank Wentzel]

I live in west-central Florida, so there is no "cool, dry" place for storage of epoxy supplies. I have used epoxy that has been stored under our ambient conditions for 10 years and more and never had the first problem with curing. (I will admit however that once or twice I may have had a problem when I reversed the ratios.) http://media5.hypernet.com/~dick/ubb/redface.gif

/// Frank ///

[Tom Dugan]

Chad,

I've had success with epoxy that was both older and colder than yours. Since your recoat seems to be fine, I'd suspect operator error in the previous attempt http://media5.hypernet.com/~dick/ubb/biggrin.gif and wouldn't worry about it now.

-T

[cs]

Tom are trying to say that maybe my headspace and timeing were off?

You know I always read the bottle and see wich part is 1 and which part is 3. I don't store that in my permant memoray space. I need that for important stuff like my name and where I live LOL.

The resin bottle don't say anything but the hardner bottle says it is a 3:1 hardner. So maybe just maybe I put in 3 parts hardner. Never mind the fact that it is obvious I have 3 times as much resin as I do hardner.

Chad

[Don Maurer]

The epoxy companies claim that 90% of curing problems are caused by improper mix ratios. I spoke with the MAS people about how far off the ratios can be and still cure. (I was worried about air bubbles in the pumps at the time) They said the ratio could be as much as 20% off and still cure. They mentioned it is better for the hardener to be the component on the short side.

[thechemist]

Yep.......pretty much what everybody else said, there.....

It is possible for some resin systems to separate upon cold storage, particularly the epoxy side [the clear one that does NOT smell of ammonia] , and then things do not cure. It is possible to have a big crystallized block of one of the epoxy resin components in the bottom of the oblong can, and for you to pour off a clear liquid containing epoxy-like additives but not really good, honest difunctional diglycidyl ether of bisphenol-A and other functional crosslinking materials, but rather the stuff with which they stepped on it, and you can mix that stuff with the hardener in any ratio and get Goo from Goo.

Shine a flashlight down into the neck of the can and satisfy yourself there is no big block of white crystals on the bottom of the can.

[ishmael]

Chad,

Hard to believe you got the ratios backward without noticing the difference in the mix. I think maybe the idea of out of date materials is a good one, but then you just built your boat in the last year right, so that shouldn't be the reason. Don't know. Did some fiberglass polyester resin work a number of years ago, and it didn't kick. PITA.

[NormMessinger]

So you mixed up a batch of epoxy and it didn't harden. You scraped it off and mixed up another batch (from the same containers?) which did harden? Can't be but one conclusion, eh?

What kinda goop you using? What sort of a metering system?

--Norm

[PugetSound]

Chemist,
Just curious about what you said regarding the epoxy components separating. If that happens, can the components be easily remixed? Or is it dead? If, dead then what is the best way to inert what is left (for safe disposal)?

[thechemist]

All pure compounds will crystallize. Some do it with more difficulty......and mixtures can separate , precipitating a component which crystallizes more readly than others.

The Diglycidyl ether of bisphenol-A [DGEBA] will sometimes crystallize out. Set the can [lid loosened]] in a pan of recently-brought-to-boiliing hot water, cover with a towel, and let sit overnight. In the morning the crystals should be melted. Shake the can to remix [heat it up again in another pot of water if it is too thick to shake] and it will be fine.

It is a violation of hazardous waste disposal laws to mix parts A and B of something for waste disposal purposes, so I suggest you think of useful experiments that can be done with any leftover resins ...... feel free to be really creative here.

[Ken Hall]

I've had pretty respectable results using white vinegar to clean up uncured resin, for anyone who's disinclined toward acetone.

Ken

[BrianCunningham]

Why am I glad I always measure my epoxy with pumps. Granted you need to be careful about priming them, and not letting the level get to low. But nothing beats 1 pump resin to 1 pump hardner.