"Defective" Epoxy?

"Defective" Epoxy?
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All Forums >> RC Airplanes >> Questions and Answers >> "Defective" Epoxy?

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"Defective" Epoxy? - 7/2/2006 4:45:31 AM

ChuckW

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Anyone ever have any epoxy that just never wanted to fully harden? I have some 30 minute stuff I bought a few weeks ago. The first time I used it, it was still gummy the next day. I figured that I made a mixing mistake. I used it again today and it's still extremely soft after having the better part of the day to set up. I've never had any trouble with this stuff before, the same brand I always buy. Epoxy isn't rocket science to use so I figure there must be something wrong with it. It just doesn't have a very strong epoxy smell to me either.

RE: "Defective" Epoxy? - 7/2/2006 5:04:40 AM

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Hardening time has a lot to do with temp, and humidity. I just used some Epoxy 220 to glue the wings together on an ARF I'm building, and the next day the epoxy that was under the masking tape was sitll sticky on the surface. I've used this epoxy for years and sometimes it comes up rock hard in just a few hours and then other times it will be like the wing joint. It does finally harden though.

A 100 watt lamp in a desk lamp setup around 6" away from the joint will provide enough heat to fully harden the Epoxy 220 in just a couple hours. I've heard of guys putting their whole fuselage in a car with the windows rolled up in the sun to accelerate the hardening. Don't use to much heat though. around 130F is just about right.

Don

(in reply to ChuckW)

RE: "Defective" Epoxy? - 7/2/2006 7:57:18 AM

ChuckW

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Hopefully this stuff will harden up eventually. Every other time I've used this same brand, it has set up in 1/2-1 hour and fully cured overnight.

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RE: "Defective" Epoxy? - 7/2/2006 5:47:29 PM

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After hearing other comments about this, I mixed up a 'test batch' of 2 hour epoxy before fuel proofing a firewall. A week later and it still seems too spongy to use, and it's been plenty hot here in Texas. I've decided to throw this stuff out and try something else. Jim

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RE: "Defective" Epoxy? - 7/2/2006 7:27:32 PM

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Try a couple more things before you throw it out. Mix a bigger batch. Epoxy cures with heat, the hardner generates heat. Smaller batches sometimes don't kick off completely. Second, mix up another batch and put it under the light. 2 hour epoxy should be tack free after a couple hours under a light, After is has cooled back to room temp.

Don

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RE: "Defective" Epoxy? - 7/2/2006 7:55:08 PM

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How old was the epoxy? I bought a batch of 2-hour from my LHS a month or so ago, only to find out it was more like a two week curing time (and it still wasn't hard, despite the "leave it in the truck with the windows rolled up trick"

. I looked on the price sticker date from the original package, and it was dated '97. I took it back and got it replaced, but I'm still left with a float and glass that didn't cure right. I've since put some newer 30-minute on top of the glass, and that seemed to do the trick. I guess what I'm trying to say, just make sure your epoxy you purchase is relatively fresh.

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RE: "Defective" Epoxy? - 7/2/2006 9:09:11 PM

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I've had this epoxy for about a month. It had never been opened prior to my 'test'. Bought it from one of the major internet outfits, so I wouldn't think it had been on the shelf very long. The batch I made was equal to about 1/3-1/2 of one of those small paper epoxy cups- Jim

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RE: "Defective" Epoxy? - 7/3/2006 1:33:01 AM

Hurri

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I had some 12 min epoxy from Hanger 9 .I tried to use it over a couple of months & it would not go off . Tried several mixs over a couple of months to glue some plywood with cup hooks on in the floor of fuse , left it for 2 days---- 7 days , soon as i pulled on the rubber bands it would come apart. SO phoned to Ha nger 9 sid i had been building for 100's of years , so not a novice . They were good enough to send me some relacement bottles .

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RE: "Defective" Epoxy? - 7/3/2006 10:51:21 PM

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This don,t sound good. I just got my Hanger 9 brand 12 min epoxy a couple of days ago. I have not tried it yet. I looked for the cure date. Where do you find it? Thanks Capt,n

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RE: "Defective" Epoxy? - 7/4/2006 5:01:45 AM

ChuckW

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I was just pulling the engine out of my Somthin Extra ARF. The firewall came loose a few weeks ago. I cleaned it up and glued it with the epoxy in question. Well, tonight I noticed that it was still a little soft. The joint was very clean and it has been plenty hot in my garage. This glue is going in the trash and I'll buy more this weekend.

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RE: "Defective" Epoxy? - 7/4/2006 11:58:00 AM

RCPAUL

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I hope your not mixing the epoxy in a waxed paper cup or on waxed paper. The wax will keep epoxy from curing.

Paul

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RE: "Defective" Epoxy? - 7/4/2006 12:18:56 PM

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This is curious, I got some Hangar 9 30 min. epoxy last year, at half and half mix, it was like water, it really spread out. I have never used a thinner mix before. It took 2 - 3 days to set, but it would set alright. I thought it was just me...

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RE: "Defective" Epoxy? - 7/4/2006 5:16:37 PM

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If you have mixed the proper amounts of part A and Part B then it should harden according to the time it states on the mixing and curing section in the instructions. I have found out that many people guesstamate the amounts instead of measuring them very carfully. I my self use a scale and mix according to weight. Now I understand that not everybody has a scale that may be avaiable to them, but if you measure according to the directions then all should be O.K. The makers of Expoxy have spent many hours figuring out the ratios of how to mix their product in order to get it to work . Don't second guess these people, they know what they are doing. If you need to remove some soft expoxy that has not cured right use Acetone on a cloth and wipe it off, turning the cloth as much as needed.
Just in case you want to know what type of scale I use. It is designed for gunpowder and is very, very accurite ( I also re-load ammo) I have used this scale on all types of epoxy type adhesives and never had a problem of any thing curing, hell I even measure JB weld with it and that stuff is almost fool proof.

quote:

ORIGINAL: ChuckW

Anyone ever have any epoxy that just never wanted to fully harden? I have some 30 minute stuff I bought a few weeks ago. The first time I used it, it was still gummy the next day. I figured that I made a mixing mistake. I used it again today and it's still extremely soft after having the better part of the day to set up. I've never had any trouble with this stuff before, the same brand I always buy. Epoxy isn't rocket science to use so I figure there must be something wrong with it. It just doesn't have a very strong epoxy smell to me either.

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RE: "Defective" Epoxy? - 7/4/2006 5:41:59 PM

ChuckW

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Nope, I always use plastic cups.

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RE: "Defective" Epoxy? - 7/4/2006 5:45:54 PM

ChuckW

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I've never thought of using a scale; do you use a digital powder scale or a beam scale?. I normally just go by the graduations on the bottle. I've never had a problem for years until now. I think I just got a dud.

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RE: "Defective" Epoxy? - 7/4/2006 9:42:55 PM

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I don't think a slight mixing error would cause the problem you described. I mix by the markings on the plastic cups with good success. Getting a new batch, and measuring as you always have, will probably solve the problem.

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RE: "Defective" Epoxy? - 7/5/2006 2:16:31 AM

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I have always used the cups with the graduations in them. I had not had a problem until that batch of 30 min. You usually only have to be close to even to get good results. You can't believe the number of Navy aircraft I have used 2 part epoxy on with success. This stuff was just funny. Its' just 6 or 8 bucks worth of epoxy, I have 3 or 4 hundred worth of electronics and motor riding on it. I just pitched it as a freak thing.

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