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Resin Not curing

RVG8tor

Well Known Member
10 day ago I mixed up slow hardener and resin (West systems) and rolled it onto my canopy skirt (inside). Due to snow and ice storm and power outages I am just now getting to sanding this coat down to do another. Three days after the coat the power went out for 3 days so the temperature in the garage dropped from the normal 58-60 but not by much, maybe down to 45. I did bring the skirt inside the house for two days after the first 24 hours in hopes of getting it to set, but I took it back to the garage.

Well now 10 days later it is still slightly tacky and gums up when I try to sand it down. Normally I just get dust when sanding. So I am guessing I messed up the mixture of resin and hardener (West pump system) and there is not enough hardener or is this all temperature related? Hard to believe the pump system failed me but I did read having the product at a cold temperature can effect how much comes out of the pump. :confused:

Now what to do, can I re-coat as is and if not how to get the gummy stuff off. This is the inside of my skirt so I am not concerned about looks as the plan is to have cloth cover over the visible part of the inside skirt. I am basically using the inside to practice technique, and a good thing too. I know warmer temperatures will help. I have a propane heater going in the garage now and I can get it close to 68 in a few hours.

Cheers
 
10 day ago I mixed up slow hardener and resin (West systems) and rolled it onto my canopy skirt (inside). Due to snow and ice storm and power outages I am just now getting to sanding this coat down to do another. Three days after the coat the power went out for 3 days so the temperature in the garage dropped from the normal 58-60 but not by much, maybe down to 45. I did bring the skirt inside the house for two days after the first 24 hours in hopes of getting it to set, but I took it back to the garage.

Well now 10 days later it is still slightly tacky and gums up when I try to sand it down. Normally I just get dust when sanding. So I am guessing I messed up the mixture of resin and hardener (West pump system) and there is not enough hardener or is this all temperature related? Hard to believe the pump system failed me but I did read having the product at a cold temperature can effect how much comes out of the pump. :confused:

Now what to do, can I re-coat as is and if not how to get the gummy stuff off. This is the inside of my skirt so I am not concerned about looks as the plan is to have cloth cover over the visible part of the inside skirt. I am basically using the inside to practice technique, and a good thing too. I know warmer temperatures will help. I have a propane heater going in the garage now and I can get it close to 68 in a few hours.

Cheers

THe slow hardner really likes 70+ degree temps. If you are going to work in the cold, you'll need to get the fast hardner. I don't have the numbers or the temp ranges handy, but they are on the West Systems site.

I would probably bring the parts (if you can) into a warm area to finish curing, then sand as appropriate.
 
Scrape old stuff

That gummy mass need to go Mike. Remove it completely don't even try to cover it or heat to cure. It will stay soft even when temps are higher. Scrape off take your time on it. Use utility knife razors or similar. Do it again in proper temps with right mix. I had that experience. Chemistry gurus may explain the process.
 
I Agree with just waiting in a warm environment for it to cure

I typically use EZ-Poxy brand wirh 24 hour cure hardner but I have mixed some off nominal combinations and they have always hardened eventually. I would bring it inside and let it warm for a few days and I think it will harden and sand normally. When McDonnell was first getting into composites with the skins on the F-15 tail surfaces and speed brake I had to do the initial certification of the new the facility. It has been a long time but I remember that one of the refrigeration temperatures that was used for storage of the prepreg material to prevent it from starting to cure was 40 F deg.

Bob Axsom

P. S. I just read Vlad's post and he obviously had a different experience. I would suggest both approaches may be tried - try to let it cure in 70 F minimum temperature and if it doesn't cure follow his remove and replace procedure. Since you have used the material and process before I doubt that you can be uncureably far off but he has experienced this failure.

BA
 
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I took it off

I called a local guy who had built sail planes and he recommended taking it off with acetone or MEK. It actually did not take long. I took it off with the acetone I had on hand, gave a an additional wipe with denatured alcohol and then sanded it down real good, no more gummy bits.

I have not had any issues with the West systems curing in my 60 degree garage up to now, so I am guessing I mixed the batch up wrong and that is what caused the problem. I just put on another coat and the garage is nearing 69 with the heater going so time will tell. I do have some of the fast cure on hand I guess I should try that next.

Can you put a mixture with fast hardener on top of a partially cured slow hardener? I want to do a second coat after this one is partially cured in a few hours and wondered if I should use the fast cure hardener for the second coat.

Cheers

BTW thanks for the advice and inputs
 
Why Not....

Why not ask the Gougeon Brothers? I prefer going to the source for tech questions... but hey, what do I know....!

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One thing I find is if you are working with cooler temps is to have the resin kept in a warm place before use.
Ron
 
Thin layers of epoxy take much longer to cure, especially when cool.

Unvented kerosene or propane heaters can inhibit the cure of epoxy and contaminate epoxy surfaces with unburned hydrocarbons. I use a heat pump or portable electric heater with fast hardener.
 
don't cover it up

I have built several sail boats with West Systems epoxy. One think i know for sure is, do not cover up sticky - poor mixed or cured epoxy. Scrape, scratch, grind, or sand it off. It will come back to haunt you once sun hits it, cold, pressures, whatever, it will pop or something. Just my 2cents, but an hour or two now could save you many hours later.
 
Once you realized that the ratio of the mixture wasn't per spec then you did the right thing by removing the epoxy.

Rockwoodrv9 and Vlad gave you good advice.
 
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Never...use denatured alcohol.

gave a an additional wipe with denatured alcohol and then sanded it down real good, no more gummy bits.

This is posted as a composite aircraft builder not an avionics company tech rep. :)

IMHO, using denatured alcohol as a "cleaner" should never be used with composites. Denatured alcohol is "denatured" to make the alcohol undrinkable.

Typically, wood naphtha or petroleum oil is used to denature the alcohol. These additives may adversely affect the adhesion properties of the epoxy causing the composite part to delaminate under load.

I suggest mechanical removal. For what it's worth.

Regards,

Carlos Fernandez
 
Learned a few things today!

This is posted as a composite aircraft builder not an avionics company tech rep. :)

IMHO, using denatured alcohol as a "cleaner" should never be used with composites. Denatured alcohol is "denatured" to make the alcohol undrinkable.

Typically, wood naphtha or petroleum oil is used to denature the alcohol. These additives may adversely affect the adhesion properties of the epoxy causing the composite part to delaminate under load.

I suggest mechanical removal. For what it's worth.

Regards,

Carlos Fernandez

Carlos,

Thank you for that little tidbit, I guess I will have to watch my laid up seam on the canopy skirt. I used the alcohol to final clean it before doing the next layer. So far it holds but if what you say is true I guess I might have some delamination possible at this joint. I knew I was going slow and was intimidated by the glass work, this just proves Is should worry. Time to do more reading!

Thanks again everyone.
 
One tip I did during fiberglass was always leave some resin in the bottom of the mixing cup and save the cup as a test. First thing I always looked at is the stick in the cup to see if it is cured. I used the fast West Systems and did all my fiberglass in the winter here in STL. Worked in a heated hanger but turned off the heat when leaving. I used halogen lamps pointed at the fiberglass parts to help then cure while the heat was off. Before using the resin and hardner each day did warm it in front of the furnace for a few minutes to get it to room temperture. All worked great.
 
I actually ran into this problem a couple of months ago. The tech support guy at Gudgeon told me that hardener lean mixture is better than hardener rich.In the hardener rich, There simply isn't enough epoxy molecules to mix with the extra hardener molecules and it would never harden. He also told me that on occasion the pumps could be out of calibration. I bought new pumps and haven't had any more issues. Canopy, skirt and windshield done. Tim
 
Adding to this issue

We have heard about West epoxy not curing and it seemed the consensus is it can not happen. Well, it can and it was not mix ratio or temperatures. My factual experience is added to this thread for the rare possibility that it happens to you.

I did the layup on the plexi to canopy recently. West systems slow harder and 105 resin was used. A black tint was added, a non-west product.

After a hard day of layups I waited,

-Checked in 24 hrs, room temps 70F all. Still sticky.
-Checked in 48 hrs, same temps, still sticky - even had a 100 watt bulb in the cabin for the last 24 hrs, surface temps at 89F.
-Checked the garbage can, the last batch of resin was like heavy tar, still stir-able. (music of dread here)
-Called West - never had that happen . . . Suggested using a heat gun and scrape it off. Did that, worked like a charm, got down to the hard layers. then Sanded.

But -what happened??

Experiment: My friend mixed a batch and used 5% tint, I made one and did the same. Room temps both the same similar batch size, similar depth in the cup bottom. His had an exotherm 15F higher than mine. His exotherm lasted longer than mine. His was hard in 24 hrs, mine was still gooey. Bad - expired product? I conclude it was, and that the tint pushed it over the edge. I left the sample in the house for a couple of months and it eventually did fully cure. You can tap on each sample his and mine and hear a tick, not a dull tack sound.

Conclusion(s)
1. West product can get old and result in an very extended cure time.
2. Tint additives (or micro balloons) will slow the process significantly.
3. Heat did not help greatly after the first 24 hrs.
4. The product can, and should be, removed with a heat gun within a few days, no solvent needed.
5. The cause was not mixing ratios, although the hardner was near the bottom and poured into a clear container - no separation.

If you have stumbled on this, I hope it was not the whole layup and on the bottom. You can wait a few months, or take it all off, right now. The glass peeled off like sticky tape. The resin like, well, goo with a scraper. Good luck, may it never happen to you. If your product is old and using tint or micro, do a test with a higher % additive than expected in a shallow cup (1/4") to test it. Compare to a non additive sample to be sure. Weigh the mix components. If the additive sample exotherm is low and hardening is slower, get new product. It is likely just the hardener, not the resin. I had no issues with the same resin and fast hardener, but have replaced them both for additive uses.
 
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Slow curing-paint also

Had a friend spray all his plastic airplane control surfaces with a incorrect paint mix ratio and they never cured. They just hung there like giant flypaper.

He had to scrape carefully to remove all and do over.

Lesson for RVers: make sure you get your paint AND epoxy expirations, mix ratios, and temps within specs, or else......
 
This may or may not have been an issue, but when you use tint, you add it and mix it into the resin before hardener is added, and then when you add the hardener, make sure you add it in proportion to the resin only. If you weigh the resin/tint mixture and add hardener in proportion to that total weight, you're either going to get a fast exotherm or resin that won't cure correctly. Of course, fresh resin/hardener etc goes without saying. I used tint from Fibreglast.com and had no problems.
 
This may or may not have been an issue, but when you use tint, you add it and mix it into the resin before hardener is added, and then when you add the hardener, make sure you add it in proportion to the resin only. If you weigh the resin/tint mixture and add hardener in proportion to that total weight, you're either going to get a fast exotherm or resin that won't cure correctly. Of course, fresh resin/hardener etc goes without saying. I used tint from Fibreglast.com and had no problems.

Good point, Mark, but lets not cloud the issue here, West Systems does not have an infinite life nor an expiration date. This, for sure, was not a mixing or resin/hardener issue, it was age weakened and pushed past it's limit by additives. People should not fear critical mix ratios, but using 9 yr old product with additives, beware. While I am convinced, you may not, so test ahead of time. Based on these tests, life limits are reached earlier with additives.

The post-issue test was at 5% tint (or total wt), but the mix for the work was less than 2%. The fact that fresh resin/hardener with the same tint ratio was rock hard in 24hrs vs old resin/hardener at the same temps and ratios took two months was definitive for me. 60X longer seems extreme for a simple mix order issue. A neat (no tint) sample (old) is rock hard in 24 hrs. The conclusion remains, at least for West Systems.
 
Adding to the database, I had the experience of West 105 plus 206 hardener, mixed with microballoons fail to cure fully a few weeks ago while finishing the front of a canopy. Overnight low temps were down in the 40s but daytime high was 60+ degrees. I was concerned about it not curing so I built tent with stools and a tarp over the canopy and put an electric space heater inside. 4 days later it was still soft.

I had a couple of cans of 206 hardener and a can of 205 hardener in the shop, so after that messy experience I mixed up 3 batches, each one using a different hardener. One of the 206 batches and the 205 batch cured fine in 24 hours, the other not so much. Clearly the one can of 206 had gone bad.

As an aside, West Systems epoxy will form amine blush in cool, humid conditions. If you haven't experienced it, the waxy layer could be confused with not-fully cured resin as it will rather thoroughly clog sandpaper in a hurry. It comes off easily with soap and water. I've been dealing with that a lot here lately due to the weather conditions. It's obvious when that's the problem. Before washing the sandpaper clogs, afterward, it sands nicely.
 
Good point, Mark, but lets not cloud the issue here, West Systems does not have an infinite life nor an expiration date. This, for sure, was not a mixing or resin/hardener issue, it was age weakened and pushed past it's limit by additives. People should not fear critical mix ratios, but using 9 yr old product with additives, beware. While I am convinced, you may not, so test ahead of time. Based on these tests, life limits are reached earlier with additives.

The post-issue test was at 5% tint (or total wt), but the mix for the work was less than 2%. The fact that fresh resin/hardener with the same tint ratio was rock hard in 24hrs vs old resin/hardener at the same temps and ratios took two months was definitive for me. 60X longer seems extreme for a simple mix order issue. A neat (no tint) sample (old) is rock hard in 24 hrs. The conclusion remains, at least for West Systems.
Didn't mean to cloud the issue...I missed the part where the resin was 9 years old. I would have thought that obvious. :rolleyes:
 
Maybe not that obvious . . .

Didn't mean to cloud the issue...I missed the part where the resin was 9 years old. I would have thought that obvious. :rolleyes:

Maybe not that obvious ( I should have stated the age in the post)- I have some Aeropoxy that is much older and it is just fine. I was concerned about it so I purchased the West. I use it for bucks and molds etc as it's color is dark but it sets up nicely with flox & micro. I have always used the West for the plane. I had called West last year (summer) when some micro mix was slow to cure and they said " there is no expiration date" - "that should not happen". I took them at their word and continued using it until this event. Now we know better, at least with additives. Oddly, the fast hardener still seems to be unchanged, but no definitive tests to be sure.
 
Bill, how about another experiment? I wonder if something evaporates with age and/or exposure.

You have fresh resin and hardener? Pour some of the hardener into a perfectly clean open-topped container, and allow it to sit exposed to air for a week or so. Then mix two small test batches, one with the exposed hardener, the other with hardener from a capped can.
 
Maybe not that obvious ( I should have stated the age in the post)- I have some Aeropoxy that is much older and it is just fine. I was concerned about it so I purchased the West. I use it for bucks and molds etc as it's color is dark but it sets up nicely with flox & micro. I have always used the West for the plane. I had called West last year (summer) when some micro mix was slow to cure and they said " there is no expiration date" - "that should not happen". I took them at their word and continued using it until this event. Now we know better, at least with additives. Oddly, the fast hardener still seems to be unchanged, but no definitive tests to be sure.

Interestingly my WEST Fast Hardener turned to quite a dark brown over the span of a year or so.

It still seemed to work but I replaced it anyway...:)
 
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