While we are talking epoxy, let me ask this.
A couple of recent epoxy jobs have resulted in the epoxy remaining tacky. This was a name brand, longer setting epoxy in the double plunger type container. I’ve used this kind of epoxy in the past, but maybe not the slower setting variety. I’m I not getting proper mixing? Cool damp weather a problem?
Slower setting epoxy prone to this?
Also, what do I do now? If a glued joint stays tacky is it likely to fail?
poor mixing
or improper ratio. You can dipsense an improper ratio and mix it well,resulting in partial cure, or dispense the proper amounts and mix insufficiently leaving partial cure.
If it doesn’t cure up with extra heat it’s never going to cure hard.
Yep.
Sometimes getting an accurate 1:1 ratio out of a double-plunger syringe is difficult.
And insufficient mixing can be a problem. Years age when I was selling XC skiis I had an employee who habitually under-mixed two part epoxy for the binding holes in foam core skiis. Epoxy would often not set properly.
Jim
Cold has a definite effect.
Slows reaction time down considerably.
Virgin package?
Was this a virgin, never used double-barrel pack, or had you used some before, tossed it in a drawer and used more later thing? The hardener side can tend to get crusty, partially clogging the hole and resulting in an improper ratio.
Both resin and harder have long, but not infinite shelf life. It may simply be past its time.
If it is not cured, the joint will be weak. Scrape the sticky stuff off and get down to bare whatever, and try again.
Skip the plunger in the future
I don’t use the plungers based on the same problems you are having.
Try mixing using some plastic measuring spoons for accuracy, or a mark a plastic cup with three equal measures. Then add 2 part resin - 1 part hardener, then mix thoroughly.
Plungers are fine IF …
– Last Updated: Feb-12-08 1:01 PM EST –
... you avoid squirting air bubbles. There's usually air in each chamber (at least there is for me, since I "back off" the plungers prior to re-sealing to keep the cap from getting glued on), and letting the air bubble rise up away from the spout prior to squirting is the only precaution I've worried about. Before the days of plungers, when the tubes of epoxy and hardener came in two separate "toothpaste tubes", I'd just squirt two roughly equal size puddles side-by-side onto a piece of cardboard and mix with a nail. I do the same thing now with the plunger containers. I've never had a problem in all this time, so I don't believe that lack of measuring precision is the problem here. Lack of thorough mixing seems possible, but the proportions need not be that exact. I might point out that by squirting the two nozzles onto a flat surface, you can eyeball the quantity of each componant just as well as everyone used to do when the stuff came in two separate tubes. This way, you can alter the flow of one plunger compared to the other easily enough if one of them is tending to stick. I would use measuring cups for working with much larger quanities, but that doesn't seem to be the situation here.
I’ll Second That
When I started my first S&G VOLKSKAYAK, I was strongly cautioned against using pumps - accurate when new, but they can get gummy over time.
We, being cheap by nature, use those carbdboard frozen juice cans, cut to match the resin:hardener ratio. In our case, 3:1 - so 1.5 inch resin can can needs .5 inch hardner can, 3" resin can needs 1" hardener can, etc. Simple, foolproof (well, I can use it!) and very, very inexpensive.
Brand New…
Tubes and different tubes and days. Even with the sometimes uneven flow from the plungers I can eyeball pretty close (never have had trouble with JB weld in the “toothpaset” tubes. Based on these responses I’m thinking maybe the mixing. Maybe I’m absent mindedly not mixing well enough.
Thanks for the help.
same here
the ratios have to be pretty bad for it to be sticky. With heat even a 3:2 ratio with 1:1 will harden up if mixed well, at least to a rubbery state. For it to be sticky means there’s a smear of totally unmixed resin/hardner through it. All this assuming it’s already in the middle of the ideal temp range of 70degrees and you’re not applying it at 45degrees expecting a cure rate at 70.
There is a fix for this
If you feel most of the epoxy has set, scrape off all the tacky epoxy you can. Mix up a batch of epoxy making sure it is very well mixed. Put just a dab extra hardener in it and recoat. The new epoxy will help the unhardened epoxy kick.
If it is tacky all the way through… you will have to remove it and start over…
maybe it is the damp
I’ve had problems with epoxy in high humidity in the 90’s and solved them by covering the epoxy with saran wrap. epoxy doesn’t work well in temps under 60 F either.
I’d try covering it and putting a lamp on it.
Blush?
Is the epoxy hard, but feels sticky. If you press a thumbnail into it does dent easily? If you can not make a significant mark in the epoxy the mix ratio is probably fine but the damp weather has caused it to blush. Blush can make the epoxy feel sticky. If it is blush you should be able to wash it off with water. When the water dries the epoxy should no longer feel sticky.
If the epoxy is soft and gooey after several days you probably have a mix problem, but I suspect blush is your problem.
Bad tube?
I had a problem with a new tube of quick set epoxy last year. Had to toss it and start over with another new tube different brand. I dont remember the brand, bought it at Ace Hardware, but it would not set. I tried several batches with no luck. The other tube worked fine. I was on the road or I would have sent it back to the mfg.
Heat it good
Nick might be right - blush.
But my first choice would be to hang a lightbulb over it for a day. Many times the difference of a few degrees can really slow down a cure to a stall.
vk1nf and others … double check your
epoxy to make sure whatever ratio it needs to be mixed @ is by VOLUME when using the above mixing technique. Some epoxys go by weight for ratio.