Uncured Epoxy Resin--What to do?

[triton318]

So Friday evening I decided to continue work on the sea hood I had started about six months ago. I laid on two layers of fiberglass cloth over the wood, using West System epoxy. Afterwards, while cleaning up, I began to suspect something was wrong. The next morning, my suspicions were confirmed -- the resin hadn't kicked. I believe now that the pump on the hardener container wasn't dispensing the correct amount. (Although I primed -- or believed I had primed -- the pump.) Disgusted and thoroughly devastated, I blocked off the area to keep the kids off the uncured epoxy on the garage floor and left it. Later in the day, I peeled off the two layers of cloth.

This morning I went out and felt the resin -- it's not tacky. Will epoxy resin eventually cure given enough time even though not enough hardener was used (or will it forever remain uncured)? If it isn't completely cured, why is it no longer tacky? Has it just "dried?"

Thanks.

[bcooke]

Will epoxy resin eventually cure given enough time even though not enough hardener was used (or will it forever remain uncured)? If it isn't completely cured, why is it no longer tacky?

Epoxy works by combining the two compounds to form a new material. This is why the ratio is important. It doesn't 'dry' like paint and it isn't 'catalyzed' like polyester resin.

Epoxy won't cure eventually given enough time. It either does its thing or it doesn't. Perhaps the ratio was 'close enough' to achieve a tack free surface in your case. There is probably an excess of one part or the other in the final result. If you don't require the ultimate strength possible it might be okay. I think it depends on what you feel comfortable with.

[cmartin]

It's been pretty cold lately, at least in MD. Make sure you check the temp ranges for the system you are using. if you are using slow, you might want to check fast, depending on temps and work time needed.

[David]

I think you were just at the borderline temperature for curing. It can take a long time but eventually will cure. For West System epoxy, the ratio of hardener can be reduced from what is dispensed quite a lot and still get a hard cure, so I doubt that it was the fact that the ratio was off on the pump enough to affect curing.

David

[Idon84]

Here in the NW I'm seeing quite a difference in cure time with my MAS medium hardener from this summer to now. At about 30 degrees at night and 55-60 during the day it takes about 3 days to get to the point where I can sand the epoxy and do anything to it. Anything before then clogs up my sandpaper.

[CharlieJ]

I've found the two to one ratio epoxies to be MUCH slower curing than the 5-1 such as WEST Sys in cooler weather..

In temps to about 50 degrees, the MAS, SYS 3, RAKA, etc, can take up to three full days to reach a sandable cure, whereas WEST will do it in 24 to 36 hours usually.

Colder than that, they ALL are slow.

[bcooke]

Here is a good primer from the West System website.

http://www.westsystem.com/webpages/user ... /index.htm

Here is some specific cold weather epoxy tips.

http://www.westsystem.com/webpages/user ... 00-915.pdf

Here is a quote from the second link.

If the temperature is too low, the epoxy may eventually harden but may not reach a complete cure or achieve its designed physical properties

Note: For best results, its best not to simply go by the seat of your pants. Epoxy is a finely formulated material and should be treated as such. It isn't rocket science but it isn't Elmer's glue either.

[CharlieJ]

Note: For best results, its best not to simply go by the seat of your pants. Epoxy is a finely formulated material and should be treated as such. It isn't rocket science but it isn't Elmer's glue either.

Precisely!!! If it should be 5-1, make it 5-1. not 4-1 or 5-2. To do otherwise can compromise the strength, which none of us want in our boats.

[David]

<<Here in the NW I'm seeing quite a difference in cure time with my MAS medium hardener from this summer to now. At about 30 degrees at night and 55-60 during the day it takes about 3 days to get to the point where I can sand the epoxy and do anything to it. Anything before then clogs up my sandpaper. >>

West epoxy takes about 2 weeks to be considered fully cured and can take as long as 2 or 3 days to fully harden. I don't know much about MAS epoxy. In cool or cold weather West epoxy does not exotherm the way it can in hot weather or in warm weather when mixed in a small confined container. The exotherming to a point adds in the speed of the reaction so in cold weather it can take longer.

For some reason 45 degrees sticks in my mind as the minimum temp to be gluing with epoxy.

[Tim]

In the winter, I routinely work with West System epoxy at temperatures in the low to mid 50s, which is the temperature at which I keep the shop most of the time (except painting). I have never had it take longer than overnight (say, 16 hours) to become sandable at these temperatures.

Any cooler than this (45-50°), and I'd suggest one ought to seriously consider postponing the epoxy work till better temperatures can be guaranteed. Some things aren't worth pushing the envelope for.

[triton318]

It didn't get any colder than 50 deg in the garage that night, and when I started, it was probably about 65. I was also using the fast hardener. I'm sure I wasn't getting the correct amount from the hardener pump.

I suppose I'll sand off what's on the wood and start over (after getting new pumps). Oh well, at least I don't have to start over completely from scratch; at first I thought I was going to have to toss the sea hood and make another one!

[Ceasar Choppy]

One thing you might check is whether you have the correct pumps for the size cans of resin and hardener. They CAN be different (not always). But it bears mentioning. Good luck!

[Quetzalsailor]

Things I've done wrong and suffered using West System: mixing the old white pumps and the new yellow ones, loosing count of strokes.

Things I've done wrong and 'gotten away with it': low or high temperature; pumping issues: bubbles, priming, dirty-plugged spout, pump falling apart mid-stroke, not-a-full-slug from the pump; used old stuff; mixing the next batch in a still-uncured pot; too voluminous an application in an enclosed, insulated volume; insufficient stirring.

Bottom line is that the West is more tolerant of temperature, age, slight mis-pumps than they say it is. The stuff also goes off faster than advertised for the temperature if you've overstirred it, or added fillers, or over-stroked with the foam brush.

While West says that a temperature-retarded cure will never go off properly after 24 hours, it does not seem to be so. I've been conscious of continuing hardening through, maybe, 48 hours.

One should fret if you're working outside their parameters; they say the stuff may not be up to expectations for strength, etc. I haven't seen it, but that may be because I have not had high enough expectations.

Those few times when I've really screwed up, I wash them with lacquer thinner and grind clean and have another go. Clean, dry - not at all sticky.

[bcooke]

One should fret if you're working outside their parameters; they say the stuff may not be up to expectations for strength, etc. I haven't seen it, but that may be because I have not had high enough expectations.

The only way to really know how well the epoxy cured is to test it to its point of failure. Unless you lay down a test piece every time you mix up a batch you really can't know except by sticking within the general guidelines.

I realize that we have determined that temperature was not a factor but I thought I would add that the general practices link I posted earlier actually states that West epoxy resin with fast hardener will work down to 35 degrees. That was a surprise to me. The article also states that getting the epoxy to flow out correctly at that temperature requires a few tricks. Nonetheless, it will cure at 35 degrees. The slow and 'tropical' hardeners need more ambient heat.

[Idon84]

Great thread! I have another question at this point.

Tim Said,

Any cooler than this (45-50°), and I'd suggest one ought to seriously consider postponing the epoxy work till better temperatures can be guaranteed. Some things aren't worth pushing the envelope for.

I would defiantly agree to that. MAS says 45 degrees as well but why even start to push that envelope at 50 degrees.

PROBLEM. In the NW, while we typically will have 55 degrees during the day mid 30's are the norm overnight. I must continue working on some epoxy tasks during these times and wonder if a space heater would help with the process? I would, of course (mom always said no space heater when you're not around!), not leave it on during the evening unattended so here is the question...

If I were to work with the epoxy at say 55-60 degrees, keep that temp most of the day, remove the heat at night and then continue with the heat the next day do you think there could be curing problems when the temperature dips at night? My last layers of tabbing on my settees were done in 55 degrees with cool clear nights and have finally become sand-able as of last night, approx. 3 days.

Thoughts?

[kendall]

If the part's not too big, what I've often done is grab some cardboard and build a box around the part then place a light in the box. depending on wattage and size of the box you can easily keep it at 70 degrees.


Ken.

[CharlieJ]

500 watt Quartz shop lights give off a great deal of heat- you can aim them at the project from several feet away and warm things up nicely. If you can build a box or tent, so much the better.

I do recall Meade Gougeon at an Experimental Yacht Society meeting once- 1978 or 79, telling us about someone in the Pac NW who had trouble with WEST not curing- They found the cause to be a kerosene space heater giving off moisture in an enclosed space. Something to watch.

[Hirilondë]

If I were to work with the epoxy at say 55-60 degrees, keep that temp most of the day, remove the heat at night and then continue with the heat the next day do you think there could be curing problems when the temperature dips at night? My last layers of tabbing on my settees were done in 55 degrees with cool clear nights and have finally become sand-able as of last night, approx. 3 days.

That would probably work fine. I would add the heat lamp to the process as well (during the time you are there). Preheat the surfaces you are going to epoxy while you get ready. Keep the surface warm, not hot at least until the epoxy has solidified. Now the temperature drop at night will have a minimal effect other than extending the time for full cure. Heat is a catalyst for curing epoxy, it is also created by curing epoxy. The reaction feeds off of itself if you will. If it is too cold (the consensus seems to be below 45-50 F) then the reaction is slowed so much that the final result isn't the product as it was intended and will probably fail to meet the needs of the project. I find the first 4-5 hours after mixing to be the critical period for West, I can't speak of other brands in cool weather.

[Tim]

Bottom line is that the West is more tolerant of temperature, age, slight mis-pumps than they say it is.

Obviously they're going to err on the side of caution when determining the working conditions required for their product. That said, it's unhelpful to suggest to most of the users here that proper attention to the working conditions and mixing of epoxy is less than critical.

Little pumps and container mixing in a real-world environment will be necessarily less than perfectly accurate--hence the need for, and existence of, some tolerance in the mix ratios.

One should never use a batch of epoxy when it is known or even suspected that the mix ratio is off, such as during a mis-pump. Toss it, don't use it: discretion is the better part of valor. The occasional wasted batch is a lot less expensive than a poorly-cured laminate, or the removal of a non-cured batch of something.

While West says that a temperature-retarded cure will never go off properly after 24 hours, it does not seem to be so. I've been conscious of continuing hardening through, maybe, 48 hours.

What West actually says is that even though a temperature-retarded batch of epoxy might indeed harden and seem to properly cure over a longer period of time, it might fail to cure to its full, expected, and designed strength. There is a difference between hardening and properly curing: what becomes hard is not necessarily properly cured. Let's not confuse this issue with semi-truths.

With West System, fast hardener, and temperatures above 50°F, the laminate or filler should be hard, sandable, and effectively 90% cured (according to West System) in 24 hours. Any longer than this (within the reasonable bounds of environment and other conditions laid out here) and the batch is entirely suspect, in my opinion.

Most epoxy batch failures are the direct result of obvious sloppiness, lack of attention to proper and effective mixing (including proper ratios), and failure to follow the most basic working directions. It's a cinch to make epoxy work well for you, but one shouldn't think they are smarter than the product itself. It is important to use care and thoroughness when mixing epoxy. That doesn't mean you need beakers and a lab coat to do it effectively either.

Folks, mix your epoxy properly. Don't push the application envelopes. Doing so is just asking for trouble. That said, one need not be a fusspot about it--just intelligent and respectful of the product's directions and the admonitions of a very experienced manufacturer (speaking specifically of West System/Gougeon).

[David]

According to the Gougeon bible:

Page 32: "...The mixture will continue to cure for the next serval days to two weeks at room temerature, becoming an inert plastic solid..."

Page 33: "Although a residual reaction continues for up to two weeks, we consider epoxy to be fully cured three or four days after application, depending on ambient temperatures (Ed: so in lower temps, especially in a garage with a big cold concrete floor acting as a heat sink, full cure could easily take longer). Coatings of WEST SYSTEM epoxy should be sufficiently cured for subsequent operations after 12 to 24 hours--ususally overnight."

In my opinion I think this means that there is a much longer curing time than one might generally assume (since it gets hard and tack free relatively quickly). But as the document points out, full cure takes much longer "at room temeratures" meaning around 72 degress or more. If the boat is outside and the weather is colder, a full cure would therefore take longer.

Finally, also on page 33 are some special warnings about gluing in cold weather: "....Very cold weather can present greater problems. Resin viscosity increases and metering with dispenser pumps becomes almost impossible at very low termeratures. Thick epoxy is hard to handle and may not adequately penetrate wood for good adheasion. During slow cures coated surfaces may become contaminated, especially by moisture and carbon dioxide and become cloudy."

David

[Idon84]

Thanks guys!

Great stuff. During the last few weeks the temp around here has dropped so fast that it is quite easy to tell that the epoxy is working entirely differently.

CharlieJ said,

500 watt Quartz shop lights give off a great deal of heat-

We have been using this shop light to pre heat the epoxy for better flow and then we leave it below after we are finished, probably what saved my rear. I have been turning it off at night. We'll probably bring our electric heater aboard too. I'll take better care to watch the temp FOR SURE, I'm just happy to have learned this before any serious issues. MAS Says 50-55 degrees and less you should be using heat and the FAST hardener. Got 1.5 gallons of the stuff.

I was up late last night worrying about this and found the West manual, 002-915 Cold Temperature Bonding and Coating with Epoxy. Spelled it all out in just the manner we are discussing here.

Looks like time to work on the hatches, sanding the bulwarks, building the sampson posts, fitting the engine template as the NW runs through it's cold streak. February sees averages above 50's again!

Only 51 days until the beginning of the return of the sun! JOY!

Thanks!

[Idon84]

I wana have a shop like Tim's... sigh

[Idon84]

Problem Solved! Can maintain 57 degrees inside during 40 degrees outside. Gotta love those power bills! 1000W Shop Light and my radiant heater.

[Idon84]