@#%!*** Sticky Epoxy

[Tom Robb]

Speaking of The Chemist, I miss the patient erudition. Oh well...

My epoxy problem, other than the smell, the need to cover myself in a hazmat suit and the chemestry experiment aspect, is it's still sticky.

Two days ago I trowled on a thin coat of System 3 and wood flower to fill the weave in the FG on the outside of the plywood pram I never got around to finishing (not good enough work to be proud of it). Two days later it's still slightly sticky. It was getting warm in the cup I mixed it (full 2 minutes) in so I'm supposing the ratio was ok. Power sanding (palm sander) yesterday afternoon (been in the 80s the last 2 days) only sort of smeared it around. Swell.

Now what sports fans? Any advice - other than stick to traditional construction methods?

[P.L.Lenihan]

Hi,
Never heard of System2 but have heard lots of good things about System3.

With most retail "marine" epoxies on the market today,about the only way to get them not to cure is by improper ratio. Perhaps you got the hardener mixed up with the resin? As warm as it was/is when you mixed it for a full two minutes, the heat you felt may have been your own.

About the only other issue I can think of which may cause your problem to occur would be a heavily contaminated surface or mixing cup or mixing stick.

Perhaps better minds will help out soon.

Peter

[P.L.Lenihan]

one more thought.......immediately after pouring the two parts together,did you then directly add the filler powder then mix or was the epoxy well mixed BEFORE you added the thickening agent? This may explain why it is still sticky as some of the hardener may have been soaked up in the thickening agent and/or the resin got soaked up making for perhaps a touchy bit of cross-linking of the two parts.That is, the two components should be well blended before adding fillers.
Good luck!

Peter

[JimD]

My very un-Chemist hunch is still a mixing ratio problem. BTW, for those who would like to improve their chemical vocabular regarding epoxy, there are a number of very interesting explanations using plenty of big words at Paul Oman's Progressive Epoxy Polymers, Inc., site http://www.epoxyproducts.com/chemistry.html , http://www.epoxyproducts.com/ . 'The Chemist' even gets acknowledgement for his guru-like status:


Cycloaliphatic chemistry explained by "The Chemist" - the hands-down expert on epoxies - in a 2/18/03 post on the Wooden Boat Forum --
"The cycloaliphatic structure refers to a six-member carbon-atom ring in the backbone of the curing agent instead of carbon-carbon linkages between amines in some other curing agents such as West or Sys. 3. The cycloaliphatic curing agents have the amine groups connected to the rings. Both use Diglycidyl ether of Bisphenol-A as the major component of the epoxide curing agent, and both contain benzyl alcohol, a volatile plasticizer which acts as a molecular lubricant and facilitates curing [although systems with cycloaliphatic curing agents contain much more, typically 20-30%, as they simply do not cure more than about half-way at room temperature without it.]

While the cycloaliphatic ring is resistant somewhat to Uv degradation, more that the carbon-carbon linkages between amines in some other types of curing agents, both contain the aromatic ring structure of diglycidyl ether of Bisphenol-A, which breaks down fairly readily on UV exposure, and both contain amines; these give both molecular breakdown and yellowing all by themselves.

None of these structures should be considered UV-stable, even though the cycloaliphatic structures are better than the aliphatic amine-structures in that regard."

[Tom Robb]

Well mixed before adding the filler.
It got rather warm well after mixing, not from intense effort.
Ratio was what the pumps gave me as usual.
Cured just fine previously w/ the same ratio and mix/stir time.
Advice for next time is apreciated, of course,
but the given problem remains:
What now? That is, what to do with the residual stickiness....

[JimD]

What now? That is, what to do with the residual stickiness....

Remove it. Pick a test area. If its blush (but it doesn't sound like it) it should just wash off. I use soapy warm water. If its uncured epoxy common vinegar should disolve it. If it turns out to be sticky all the way down, boy, what a mess. Acetone, maybe. I once had to scrub an entire hull with acetone due to uncured epoxy. It worked but it wasn't a very enjoyable afternoon. I don't trust pumps. I'm not saying that was it but I don't use them anymore.

[Jim Ledger]

I don't know about System 3 but with West Epoxy if you want to do a thin top coat you should use the special coating hardener.The fast or slow hardener works if you're filling the weave of the cloth but takes forever to harden if you put on a thin coat. Maybe System 3 has a similar hardener.

[Tom Robb]

I'll try those tomorrow.
Thanks Jim & Jim.
BTW, how do you guys measure?

[The Bigfella]

Ratio was what the pumps gave me as usual.



JimD beat me to it. I had too many burping / farting experiences with my West System pumps to ever want to try one again (epoxy pump that is).

I mix in parallel-sided cups (a particular local brand of yoghurt container, actually) - and measure against a pencil-marked ice cream stick. Hundreds (more likely thousands) of mixes later (thats a lot of yoghurt and a lot of epoxy) - nary a problem in the seven years since throwing the pumps away.

[JimD]

I use graduated paper cups like these. Of course the company shows the logo side instead of the side with the measurements marked on them but they are marked in mililitres and ounces and are plenty accurate for measuring epoxy. Cost about ten or 15 cents each:

Mixing Containers

http://www.ippnet.com/assets/Product~Images/7ozMixCupIPP.jpg Perfect for measuring, storing or mixing resin and catalysts as the containers will not dissolve in contact with the products. They are available in 30cc, 200ml, 500ml, 1 liter, 2liter, 4 liter, 10 liter and 20 liter sizes. The 30cc to 3.8 liter containers are graduated for easy measuring. The 200 ml cup is a wax coated paper container.

[Lewisboats]

Is the area humid? can you tent the area and add a heater to see if it will kick? I had the same problem and it only finally got hard after 3 days and the application of some local heat...and this was summer.

Steve

[JimConlin]

Put a heatlamp on a spot and heat it to maybe 120 degrees. If it doesn't harden in half an hour, you have an off-ratio mix and it should all be removed.
The things that might work are vinegar, acetone or other nasty organic solvent, coarse sandpaper, Scotchbrite grill scrubbers or scrapers. Good luck.

[sdowney717]

I just mixed up some DOW 331 resin and versamid 140 hardener and it was not curing on the backside of the plywood panel as it got rained on. So I took a 500 watt worklight and placed it 4 inches away and moved it every few hours. It cured it very well. The light got it very hot, hot enough to burn my fingers.

All I can attribute my problem to was the rain. I know I mixed it well enough. However my versamid hardener is old and I also thinks it absorbs moisture from the air over time.

I have had trouble with epoxy not setting before and the worklight has been a great help.

A test for sticky epoxy to see if heat will cure it, is to scrape off some epoxy, roll it into a marble shaped ball and put it on a light bulb for a few hours. If it sets up you can then use a hot lamp to cure the sticky mess.

[Tom Lathrop]

Properly mixed two part epoxy of proper ratio will, in my experience, always set up. Ratio is most important and most epoxies are more tolerant of mixing than ratio imbalance. All epoxies (all of the major ones and some others) I have used will eventually set up even in a freezer where I keep the tailings of a batch temporarily to avoid some waste in case I can use it later. Left over a day or so, it is always set up hard.

Not to say that there have not been failures but they can be traced to loss of concentration in mixing ratios. If one batch works well and the next one does not, it's practically an impossibility that the chemistry is at fault. Low ratio epoxies are much more forgiving of a little carelessness than high ones like WEST. Heck any hardener will work with any resin as long as you use the proper ratio for the hardener.

All glues are messy to some extent although epoxy is usually more problematic if you don't practice cleaning up along the way and let runs and drips set up. Working a piece of wood with a plane, chisel or drawknife may be more pleasurable but epoxy has an enviable record in boatbuilding whether many want to admit it or not.

Give up on epoxy because one batch came out sticky? Would a traditional builder never make another that way because a garboard plank ruptures in the bending? Of course not. They would chalk it up to a bad plank or slip in handling and be more careful next time.

Use heat lamps very carefully or you will wind up with a mess to clean up from bubbling or boiling epoxy. Never use a lot of heat on surface coatings on wood since the wood will outgas and cause bubbles.

[Rick Starr]

I've found the proprietary special ratio pumps to be quite unreliable. Raka, which I used for sheathing the handybilly in xynole, uses standard mustard pumps which seem quite simple and capable of measuring out consistent quantities of goop. The key is Raka is mixed in 2-1 ratio so two squirts of resin to one squirt of hardener works every time.

[Tom Lathrop]

I've found the proprietary special ratio pumps to be quite unreliable. Raka, which I used for sheathing the handybilly in xynole, uses standard mustard pumps which seem quite simple and capable of measuring out consistent quantities of goop. The key is Raka is mixed in 2-1 ratio so two squirts of resin to one squirt of hardener works every time.

That's what I use Rick although many swear at them. When they start burping is the time to put in new ones. Also learned not to pump more that once from each at a time. Alternating between resin and hardener keeps from losing count which is the main source of unbalanced ratios. Keeping resin warm enough so that it does not crystallize is also necessary. Maybe that was the source of the problem.

[pcford]

I typically use System Three, which is a 2 to 1 ratio. Pumps are nice but I don't like to use them when doing small quantities.

Anywayssss, I was once measuring out some epoxy. I measured out the resin very carefully. I then meticulously measured out half that amount in resin.

Did not work worth a darn. Had to scrape off some expensive goo.

It is easy, at least for me, to space out and use only one component.

[Bob Perkins]

I use a digital kitchen scale (inside a gallon sized plastic baggie) to measure epoxy now.

The pumps quickly get out of calibration. a +- 10% on epoxy will leave a not fully cured mess :(

Good Luck,
Bob

[pipefitter]

When using the pumps,if they have been sitting awhile,I always burped them. And when pumping used ones ,I make sure they are always pulled up to the top of their stroke.I don't just let them rise to the top on their own but instead,pull them upwards to top them out after they have stopped before proceeding with the next stroke.If I get a burp,it's not a hard guess of how much of a drop of resin or hardener it was missing.You have to make sure the pumps are assembled tightly before installing them to the bottle.

[Tom Robb]

I disliked chemistry class (except for Millie Stein who was my lab partner) and thought I'd never have to suffer the likes of it again. Sigh...
I'll try the heat. The leftovers in the cup seemed to kick ok. It has been very humid. The weight/volume mix ratio ideas sound like they'd be more idiot proof.

You guys are great in a pinch. Thanks.

[pcford]

I use a digital kitchen scale (inside a gallon sized plastic baggie) to measure epoxy now.



I was told by the owner of a major epoxy company that this may be risky because of difference in volume/weight measurements. (or specific gravity.)

[pipefitter]

I disliked chemistry class (except for Millie Stein who was my lab partner) and thought I'd never have to suffer the likes of it again. Sigh...
I'll try the heat. The leftovers in the cup seemed to kick ok. It has been very humid. The weight/volume mix ratio ideas sound like they'd be more idiot proof.

You guys are great in a pinch. Thanks.

If the leftovers in the cup kicked,what you put on the boat should as well. Epoxy cures faster in mass amounts. When you thin them out,the thermal factor is minimized. When you add fillers,the epoxy is dilluted further yet. If the coating just feels tacky but is not moldable or that you can't leave a deep fingernail print in it after a weeks time,the tackiness would be most likely superficial. You could then break the sticky glaze with amonia/warm water and a scotchbrite pad to help from clogging the sandpaper until you break the glaze entirely.

In some cases,when using a filler rich mix,it is good to let the epoxy sit for a few minutes mixed before adding the filler to assure the chemical reaction is on it's way and less affected by the addition of inert ingredients. I had the tackiness happen when using the phenolic microballoons but hardly ever when using wood flour or glass powder.

[johnnyv]

I was told by the owner of a major epoxy company that this may be risky because of difference in volume/weight measurements. (or specific gravity.)

Epoxy will most likely have different mix ratios by weight or volume.
Many brands only show the volume mix ratio on the label although you may be able to find the weight ratio on a data sheet.
I use an epoxy with a 4:1 R:H by volume and 4.55:1 R:H by weight for example.

[JimConlin]

I was told by the owner of a major epoxy company that this may be risky because of difference in volume/weight measurements. (or specific gravity.)

The West System directions say 5:1 by weight OR volume. If you dig a bit deeper in their site, you'll find that that the specific gravity of the resin and the hardeners are about equal, so that's OK.

I also use a digital kitchen scale, but only for batches over a pint (500 g.) or so. My scale has a resolution of 4g. (1/8 oz.) and therefore isn't useful for smaller batches. For those, I use the pumps.

I've only had one failure of the Gougeon mustard pumps in about 100 gallons of epoxy. That was with the old style of pump (white top). All such pumps are sensitive to the viscosity of the resin. If it's too thick, they 'burp'. So, if it's at all cool, I keep a heatlamp on my epoxy jugs.

[donald branscom]

I understand just what you mean.
I mixed my epoxy perfectly and followed all instructions too.
But when i try to sand it, it clogs my sandpaper right away.
I have tried wiping it down with vinegar and it helps a little.
I think I am going to try the warm soap and water next.

It did go off and the surface is hard but I hate the slight tackiness that is still present. After you get it sanded it seems ok.

[DDan]

I don't know where you're building, but basements can be cold, even this time of year. I've had some take days to fully cure when it's cold - even with tenting and a light bulb from warmth, after I noticed the slow curing. As stated above, pot concentrates heat of reaction & gets warm; thin coats are basically at ambient temperature.

[donald branscom]

Yes- I am working in a basement like setting.

[Matt J.]

Anywayssss, I was once measuring out some epoxy. I measured out the resin very carefully. I then meticulously measured out half that amount in resin.

Did not work worth a darn. Had to scrape off some expensive goo.

It is easy, at least for me, to space out and use only one component.

:D

I did that on the prams we built a few years ago. Ugh.

I am personally not a System3 fan. I got this with the CLC kayak and I really miss MAS epoxies (well, as much as one can miss "any" epoxy).

[Tom Robb]

Yes, a tacky surface.
(I read the label on the can that I thought was wood flower - the color was right - it turns out to be microbaloons.
Didn't someone say, "When all else fails, read the directions.")
Clogs the sandpaper and leaves little bits of crud lightly stuck to the surface. Then, on a whim, I tried a scraper. et Viola! The scraper seems to be doing the trick and it doesn't clog.

[Thorne]

Additional heat and time should harden it up -- are you in a hurry?

;0 )

I've learned that epoxy requires a lot of patience -- which is why I'll often use PL Premium for quick jobs in certain applications rather than epoxy. If the epoxy isn't dry when I check on it, I walk away for a day or so and check it again...and again.

[Tom Robb]

In a hurry? Well, no.
I started the pram (Bolger Ruben's Nymph) 15 years ago:rolleyes: to keep busy and on a whim. Later when I decided that the thing wasn't something to be proud of (my workmanship - not the design) it got put off over and over for more pressing tasks. Number Two Son decided that I ought to finish it and be done with it, and has been bugging me about it so it got dusted off and restarted.
So, no, I'm obviously not in that much of a hurry.
But it does take up too limited shop space.