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Epoxy Glue Aggain

Old 11-01-2015, 08:25 PM
  #1  
dereckbc
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Default Epoxy Glue Aggain

OK I have been using Robert Shaw 30-minute Epoxy and not happy with it as it is too brittle when dried and cured. It is somewhat pliable at room temps and higher. But today is our first cool day down here in TX. It is a very chilly 58 degrees this morning. I went out to the garage this morning to work on my plane when I made a shocking discovery. A few days ago I mixed up some Epoxy for a model I am working on, and still had the wax paper I used to mix the last batch. So to tidy up I went to throw it away, and as soon as I picked up the paper to wad it up, the glue literally exploded and shattered into a hundred pieces with almost no effort, It is as fragile as very thin glass like glass used to make Xmas tree globes.

So does anyone know where one can find some good pliable epoxy that does not turn to glass in cool weather?
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Old 11-01-2015, 08:43 PM
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Originally Posted by dereckbc View Post
OK I have been using Robert Shaw 30-minute Epoxy and not happy with it as it is too brittle when dried and cured. It is somewhat pliable at room temps and higher. But today is our first cool day down here in TX. It is a very chilly 58 degrees this morning. I went out to the garage this morning to work on my plane when I made a shocking discovery. A few days ago I mixed up some Epoxy for a model I am working on, and still had the wax paper I used to mix the last batch. So to tidy up I went to throw it away, and as soon as I picked up the paper to wad it up, the glue literally exploded and shattered into a hundred pieces with almost no effort, It is as fragile as very thin glass like glass used to make Xmas tree globes.

So does anyone know where one can find some good pliable epoxy that does not turn to glass in cool weather?
The only time i have seen this happen if its old epoxy . I have used different brands from local hobby shops and craft stores with a good succes so far. joe
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Old 11-01-2015, 09:23 PM
  #3  
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I use Bob Smith epoxy also WEST resin for larger jobs i.e. laminating doublers, glassing wing joints, and balsa sheeting foam core wings. Bob Smith in 15 and 30 minute for small jobs - I avoid any 5 minute epoxy
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Old 11-01-2015, 11:43 PM
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fhhuber
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Faster epoxy tends to cure more brittle.

temperature you are working in when mixing and applying the epoxy can affect how fast it cures and how brittle the result.

Larger batches tend to "cook off" and cure early due to the chemical reaction heating the epoxy. This also tends to make it more brittle. This effect can be extreme, causing 2 hr epoxy to harden in under 20 minutes.

"Slow cure" epoxy will be labeled for WORKING TIME. It will have a tacky surface for a long time after that, possibly 2 DAYS for 30 minute "slow cure"
Slow cure tends to not be as brittle, but it does tend to have everything possible that you don't want end up stuck to the surface.

There are hundreds of epoxy formulas and each has its own characteristics... and thus places where it is good and other places where its not appropriate at all.
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Old 11-02-2015, 12:13 AM
  #5  
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I've had real good luck with the Atlanta Hobby Mercury adhesive brand.
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Old 11-02-2015, 01:55 AM
  #6  
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Originally Posted by fhhuber View Post
Faster epoxy tends to cure more brittle.
Yep thus why I used Robert Shaw 30-minute

Originally Posted by fhhuber View Post
temperature you are working in when mixing and applying the epoxy can affect how fast it cures and how brittle the result.
Mixed at room temp at 72 degrees, applied, cured, and dried at room temp.

Originally Posted by fhhuber View Post
Larger batches tend to "cook off" and cure early due to the chemical reaction heating the epoxy. This also tends to make it more brittle. This effect can be extreme, causing 2 hr epoxy to harden in under 20 minutes.
Very small batch about pea sized. Thus thought I did everything right.
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Old 11-02-2015, 01:57 AM
  #7  
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Default Ca remover

Works great to remove unwanted ca from planes.
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Old 11-02-2015, 03:25 AM
  #8  
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Devcon ... is my favourite but sadly I cannot get it in Latvia ... so I use Bison from local hardware shop.

I use 5 min for nearly everything if epoxy called for. The difference of 5 min to slow cure is minimal when you use a reputable brand. My Bison 5 min Epoxy is fine even in -10C and lower in use. OK - there's no way I would mix and apply in such temps ... it's just unworkable for any such two part. But once cured .. it survives excellently all temps I fly in.

If your epoxy is shattering ... then I suggest it's either faulty compound or the mix is unbalanced ... too much catalyst will create a brittle unreliable mix. Too much adhesive will just create a half cured mess, that takes forever to cure.

Nigel
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Old 11-02-2015, 05:04 AM
  #9  
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Originally Posted by dereckbc View Post
OK I have been using Robert Shaw 30-minute Epoxy and not happy with it as it is too brittle when dried and cured. It is somewhat pliable at room temps and higher. But today is our first cool day down here in TX. It is a very chilly 58 degrees this morning. I went out to the garage this morning to work on my plane when I made a shocking discovery. A few days ago I mixed up some Epoxy for a model I am working on, and still had the wax paper I used to mix the last batch. So to tidy up I went to throw it away, and as soon as I picked up the paper to wad it up, the glue literally exploded and shattered into a hundred pieces with almost no effort, It is as fragile as very thin glass like glass used to make Xmas tree globes.

So does anyone know where one can find some good pliable epoxy that does not turn to glass in cool weather?
Hi I use the Harbor freight epoxy, It works great, never a problem with it.

http://www.harborfreight.com/quick-s...oxy-68386.html

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Old 11-02-2015, 05:29 PM
  #10  
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Originally Posted by dereckbc View Post
OK I have been using Robert Shaw 30-minute Epoxy and not happy with it as it is too brittle when dried and cured. It is somewhat pliable at room temps and higher. But today is our first cool day down here in TX. It is a very chilly 58 degrees this morning. I went out to the garage this morning to work on my plane when I made a shocking discovery. A few days ago I mixed up some Epoxy for a model I am working on, and still had the wax paper I used to mix the last batch. So to tidy up I went to throw it away, and as soon as I picked up the paper to wad it up, the glue literally exploded and shattered into a hundred pieces with almost no effort, It is as fragile as very thin glass like glass used to make Xmas tree globes.

So does anyone know where one can find some good pliable epoxy that does not turn to glass in cool weather?
You caused this by using wax paper to mix the epoxy on. Any wax coated container can cause this problem; always mix on a material that will not contaminate the mix. Use glass, clear plastic, wood, most types of paper etc. to mix the epoxy in. Also, if you did not pay close attention to the ratio of the two parts, you can get poor cure results. Usually, to much hardner will cause a brittle result, to little gives you slow cure or low strength results.
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Old 11-02-2015, 05:37 PM
  #11  
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I have been using many brands of epoxy for years and I have never found any difference in hardness caused by temperature variation on cureing. Now this means within most environmental temperatures. Get it to hot (where it bubbles or boils and you can have problems, to cold and it will not cure). Brittleness is almost always caused by an improper proportion during mix. Heat , within reason, will only effect the rate of cure with hotter curing faster.
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Old 11-02-2015, 05:53 PM
  #12  
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Faster means shorter molecular chains which is weaker and more brittle.
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Old 11-02-2015, 06:00 PM
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Originally Posted by CHELLIE View Post
Hi I use the Harbor freight epoxy, It works great, never a problem with it.

http://www.harborfreight.com/quick-s...oxy-68386.html


I've used the above on a variety of materials.......just be careful of blend ratios and do mix on glass or other non-porous solid smooth surface. If let set to long, it will stick to plastic mixing surfaces.......been there, done that........
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Old 11-02-2015, 10:45 PM
  #14  
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If I may chime in too, some previous posts have answered the question. I only wanted to reinforce the consensus and relate personal experience. I've used lots of epoxies for lots of years, and also R.I.M. processes with epoxy resins to make parts.

Proportions are really important; The ratio of hardener/resin will affect the relative hardness as already stated in other posts. I once used a product that would mold rigid or flexible parts depending on the A/B ratio. It was engineered that way. It's actually pretty hard to judge amounts when mixing up small batches by hand, and a thorough blending is necessary too. I also question the specified ratios the hobby grade products use; it always seems to be 50/50.

Proportioning dispensers can mess you up.

Exothermic reaction (heat) in curing is dependent on mass to a degree, and product-by-product differences can sometimes be established only by trial and error.

The product itself; may be crap. Or you may have mixed it wrong.

Just voting here; the other guys have said it already.

Tom

edit: p.s. I also like Devcon products a lot.

Last edited by tr4252; 11-02-2015 at 11:04 PM.
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Old 11-02-2015, 11:08 PM
  #15  
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Originally Posted by Rodneh View Post
You caused this by using wax paper to mix the epoxy on. Any wax coated container can cause this problem; always mix on a material that will not contaminate the mix. Use glass, clear plastic, wood, most types of paper etc. to mix the epoxy in. Also, if you did not pay close attention to the ratio of the two parts, you can get poor cure results. Usually, to much hardner will cause a brittle result, to little gives you slow cure or low strength results.
I think this is the most likely answer, the mix was contaminated. I always use appropriate mixing components to mix epoxy in, such as mixing cups and mixing sticks. I also only use BSI Adhesives, I've found over the years that their adhesives are always the freshest and most consistent from batch to batch.
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Old 11-03-2015, 12:56 AM
  #16  
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Originally Posted by Xpress.. View Post
I think this is the most likely answer, the mix was contaminated. I always use appropriate mixing components to mix epoxy in, such as mixing cups and mixing sticks. I also only use BSI Adhesives, I've found over the years that their adhesives are always the freshest and most consistent from batch to batch.
HEY HEY we have a winner ! Its hard yo tell how much he mixed of either one and how cold it was . I have bought the cheapest stuff you could think of and always worked out good. I have a friend named Merlyn Graves and he uses epoxy that NASA uses with great results . joe
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Old 11-03-2015, 04:16 AM
  #17  
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Originally Posted by road king 97 View Post
Its hard yo tell how much he mixed of either one and how cold it was.
Joe I did say what the temps were when mixed, applied and cured. It was room temps @ 72 F or 23 C. I do know epoxy should be mixed, applied, and cured at room temps or slightly warmer but not hot. Cold is a No-No so I got that part down.

I did not say how it was measured, I knew that was not the problem. It was accurate as you can get , I used two syringes and used equal amounts by volume. I do know epoxy should be mixed, applied, and cured at room temps of slightly warmer but not hot. Cold is a No-No so I got that part down.

As for the wax paper being the problem, I was unaware of and never heard that before. However I am 50+ years old and using epoxy for more years than some of have been around. Never seen this happen before. All my other glue joints using epoxy DO NOT have the brittleness problem. I even painted the Motor Box with epoxy as directed in the instructions and it is flexible and that was a large amount O mixed up with 10 ml of each. However I have taken note and give all of you the benefit of a doubt and will not use wax paper ever again.

What I am having trouble with is with every batch of epoxy I used on this project, I keep the batch with the plane for at least 24 hours so I can test the epoxy once cured to make sure it is not tacky or brittle. It was a very small batch, just enough to glue two clevis onto carbon fiber 2mm rods. I am no chemist, just a engineer (electrical), and having trouble that the glue interacts and contaminated the mix. Not saying it does not, that is just not what I have witnessed. Every batch I have tested after curing, the glue comes right off the paper because the glue cannot bond to it and it releases very easily.

But before any of you bite my head off, NO MORE WAX PAPER in the future. My only issue right now is the other glue joints and the uncertainty. Fortunately very little gluing was required on my ARF. Most of it is the Vortex generators. The bad news is the control horns and motor box used epoxy. I have tested the control horns and they seem to be flexible. No way to test the motor box to firewall joints.

THX guys.
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Old 11-03-2015, 04:30 AM
  #18  
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Originally Posted by Rodneh View Post
You caused this by using wax paper to mix the epoxy on. Any wax coated container can cause this problem; always mix on a material that will not contaminate the mix. Use glass, clear plastic, wood, most types of paper etc. to mix the epoxy in. Also, if you did not pay close attention to the ratio of the two parts, you can get poor cure results. Usually, to much hardner will cause a brittle result, to little gives you slow cure or low strength results.
Sorry cannot agree about the Wax paper .......... I've used it many times and never had any ill effects from it.

Only time I had bad Epoxy joints is when dust or particles contaminated the mix either on mixing surface or the joints to be made.

Another item that can create 'brittle Epoxy' ... but you would notice instantly ... is if CA contacts the epoxy mix. It instantly goes hard ... turns white ...
It's an old trick to dab ends of an epoxy run to hold the joint while rest of the epoxy cures.

Nigel
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Old 11-03-2015, 05:05 AM
  #19  
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I rarely use the stuff now but when I did I always had better results with 5 min Araldite. Some Epoxys go soft after a year or so but I never had a problem with Araldite.
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Old 11-03-2015, 05:43 AM
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Originally Posted by Panther View Post
I rarely use the stuff now but when I did I always had better results with 5 min Araldite. Some Epoxys go soft after a year or so but I never had a problem with Araldite.
Many years ago ... Araldite name was used literally universally ... bit like people say Hoover when they mean Vacuum Cleaner.

It was literally an industry standard epoxy. For years in UK - Araldite Standard was the recc'd jointing for aquarium glass as example...

One of the problems is that resins like many liquid products can be made up of either Virgin new stock or reconstituted / old stock. This can lead to performance variations, especially when enhancing agents are used.

Nigel
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Old 11-03-2015, 06:56 AM
  #21  
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Originally Posted by Panther View Post
I rarely use the stuff now but when I did I always had better results with 5 min Araldite. Some Epoxys go soft after a year or so but I never had a problem with Araldite.
"Today, Araldite is the registered trademark name (one of many) adhesive products proprietorially manufactured by the publicly traded Huntsman Advanced Materials Corporation. Corporately located in Salt Lake City, Utah, U.S.A......with over 80 international manufacturing/distribution facilities globally."

Info courtesy of.......:

http://www.huntsman.com/advanced_materials/a/Brands
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Old 11-03-2015, 06:44 PM
  #22  
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Originally Posted by dereckbc View Post
Joe I did say what the temps were when mixed, applied and cured. It was room temps @ 72 F or 23 C. I do know epoxy should be mixed, applied, and cured at room temps or slightly warmer but not hot. Cold is a No-No so I got that part down.

I did not say how it was measured, I knew that was not the problem. It was accurate as you can get , I used two syringes and used equal amounts by volume. I do know epoxy should be mixed, applied, and cured at room temps of slightly warmer but not hot. Cold is a No-No so I got that part down.

As for the wax paper being the problem, I was unaware of and never heard that before. However I am 50+ years old and using epoxy for more years than some of have been around. Never seen this happen before. All my other glue joints using epoxy DO NOT have the brittleness problem. I even painted the Motor Box with epoxy as directed in the instructions and it is flexible and that was a large amount O mixed up with 10 ml of each. However I have taken note and give all of you the benefit of a doubt and will not use wax paper ever again.

What I am having trouble with is with every batch of epoxy I used on this project, I keep the batch with the plane for at least 24 hours so I can test the epoxy once cured to make sure it is not tacky or brittle. It was a very small batch, just enough to glue two clevis onto carbon fiber 2mm rods. I am no chemist, just a engineer (electrical), and having trouble that the glue interacts and contaminated the mix. Not saying it does not, that is just not what I have witnessed. Every batch I have tested after curing, the glue comes right off the paper because the glue cannot bond to it and it releases very easily.

But before any of you bite my head off, NO MORE WAX PAPER in the future. My only issue right now is the other glue joints and the uncertainty. Fortunately very little gluing was required on my ARF. Most of it is the Vortex generators. The bad news is the control horns and motor box used epoxy. I have tested the control horns and they seem to be flexible. No way to test the motor box to firewall joints.

THX guys.
Not biting off your head Dereck and you measure it better than my method of eyeballing it. lol I use Devcon too and have never had a problem . Hard to say what caused it but thow it out and try a different brand its not worth using it on a expencive plane. joe
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Old 11-03-2015, 10:23 PM
  #23  
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I have doubts about contamination, though I believe it could happen if certain chemicals were transferred to the mix. But I don't think waxed paper would do it.

I've mixed lots of different things into epoxy, mostly pigments, but other stuff as well; metal dust, sawdust, embedded things like brass and aluminum tubing, etc. Never had a bad reaction in epoxies I'd previously used and trusted. Mixed on numerous surfaces too, including waxed paper.

Maybe this is just a freak "accident" or a bad batch or something.

Tom
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Old 11-03-2015, 11:24 PM
  #24  
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…...

Last edited by Turner; 11-04-2015 at 02:35 PM.
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Old 11-04-2015, 12:30 AM
  #25  
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it helps prevent bubble build-up and makes for a faster and easier clean-up.
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