NJTramcar

Devon issue - help with determining cause

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I have an issue that occurred with epoxy I have never seen before and trying to find a cause so I do not repeat it.

 

I tied a bunch of tail flags and hooks and sealed them with Devcon 2 ton epoxy.  I sweat the details and use a digital scale to make sure the mixes are correct.  Been doing this for years with no issue.

 

When I pack these in a clear bag, I check and the epoxy was hard and dry from letting sit all night.  Packed and shipped and the person who received them lets me know that the heads are soft and mushy.  The send me a couple of videos where he is squeezing them and it looks like they almost melted and were soft.

 

I had tied some before and one after before I found this had occurred and had no problem.  To be on the safe side, I tossed the bottles and started over with fresh ones.

 

What could have caused this?  I was told the package sat in the sun for a bit but that shouldn't cause it to soften.

 

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1 hour ago, NJTramcar said:

I have an issue that occurred with epoxy I have never seen before and trying to find a cause so I do not repeat it.

 

I tied a bunch of tail flags and hooks and sealed them with Devcon 2 ton epoxy.  I sweat the details and use a digital scale to make sure the mixes are correct.  Been doing this for years with no issue.

 

When I pack these in a clear bag, I check and the epoxy was hard and dry from letting sit all night.  Packed and shipped and the person who received them lets me know that the heads are soft and mushy.  The send me a couple of videos where he is squeezing them and it looks like they almost melted and were soft.

 

I had tied some before and one after before I found this had occurred and had no problem.  To be on the safe side, I tossed the bottles and started over with fresh ones.

 

What could have caused this?  I was told the package sat in the sun for a bit but that shouldn't cause it to soften.

 

Epoxy should be used by volume, not weight. There's always a little wiggle room in any mix and I suspect that's been the reason for past batches w/o issue. 

 

Don't overthink it, just mix equal volumes of each part.

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Thanks Drew.  I typically make sure there is a small bit of extra hardener but I see what you mean.  I guess I have just been lucky.  I will try what you said.

 

When I packed everything, it was dry and hard as usual but softened during shipping.  Head scratcher. 

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Posted (edited) · Report post

NJTramcar what is your ratio for mixing? I believe 1g hardner to 1.2g resin is the correct ratio. I think you had an incomplete cure. Occassionaly I get that esp. if I didn't mix enough and start scraping the sides of the mixing container for that last drop of epoxy. Not the stuff about turning mushy in a bag though. 

 

Mixing by weight is fine for epoxy. D2T provide the correct weight ratios on their technical data sheet. I write them on the bottles. 

 

I would hazard that mixing really small amounts of epoxy could have a higher risk of incomplete cure depending on how they are mixed, what container and stir stick used. 

 

Still I was reading the Bob Smith Industry's 30min epoxy tech data sheet and it says there is a 10% room for error on mixing. Probably similar room on the D2t. 

 

Maybe NJTramcar your final mix was off by just a bit more than that room this one time. 

 

Edited by TopStriperAngler

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Agree, it could be me and the mix.

 

It was hard when I shipped and soft on receipt.  Could it soften up due to a bad mix?  

 

Have made 3 batches with no epoxy and no issues.

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Surprising that it is 1.2 clear to 1 hardener ration by weight.  It is 1 to.1 ratio by volume.

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4 hours ago, NJTramcar said:

Surprising that it is 1.2 clear to 1 hardener ration by weight.  It is 1 to.1 ratio by volume.

Exactly 

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6 hours ago, NJTramcar said:

Surprising that it is 1.2 clear to 1 hardener ration by weight.  It is 1 to.1 ratio by volume.

I hear ya. Well, chalk it up to density, I guess. Take a look at the technical data sheet here and look in the table for "typical physical properties" in the uncured section. https://itwperformancepolymers.com/wp-content/uploads/umb/1008/2-ton-epoxy_041318.pdf

 

You mentioned above that you have been mixing using a scale. So you are doing 1:1 by weight?  

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6 hours ago, TopStriperAngler said:

I hear ya. Well, chalk it up to density, I guess. Take a look at the technical data sheet here and look in the table for "typical physical properties" in the uncured section. https://itwperformancepolymers.com/wp-content/uploads/umb/1008/2-ton-epoxy_041318.pdf

 

You mentioned above that you have been mixing using a scale. So you are doing 1:1 by weight?  

Yes, in a medicine cup on a digital scale.  I must have been very lucky because this has never happened before.

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Posted (edited) · Report post

I guess it just goes to show how generous this stuff is for errors in measuring. Like I said Bob Smith epoxy gives a 10% fudge room in their technical data sheet. 

 

Still your problem might have been to do with something else considering you haven't had problems in past. They say to make sure you have an angled tip on your stirring instrument and scrape the container really well while mixing to ensure full mixing. Get into the corner of bottom and sides. Scrape the stick off a few times and then mix that scraped stuff etc.  

Edited by TopStriperAngler

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Never thought you needed to be so exact with mixing the epoxy. I use 5 minute often with surf candies and crease flies and the heads on most of my flies,  I just put a dab of each on a post it , mix it and apply with little to no issues.

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23 hours ago, aneary said:

Never thought you needed to be so exact with mixing the epoxy. I use 5 minute often with surf candies and crease flies and the heads on most of my flies,  I just put a dab of each on a post it , mix it and apply with little to no issues.

 

My bet is that mixing on a flat surface makes for easier mixing than in a cup of some kind.

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It doesn't matter really. Cup, paper, it all works. Eyeball it on post-its, put it in a cup, etc. Just go by volume. If there's a problem a second, thin coat will fix it.

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Even though I don’t tie flies, I do tie and fix my own bucktails sometimes!

I use epoxy for other things also fixing rods,

etc, etc!

Even though I’m not using the same epoxy, they pretty much all work the same way!

I too recently have had problems with a couple different types of epoxies setting up beautifully only to come back and have them feel like they’re sticky and the epoxy is mushy like you’re explaining!

This did not start happening until heat/humidity showed up because of summer!

So, I did an experiment and went in the house where it was air-conditionined and the correct amount of humidity!

72 Fahrenheit and 40 to 50% humidity in the room that I used!

It was absolutely amazing the difference that it made going into a more controlled environment!

So I installed a 10,000 BTU AC unit in my garage  

and haven’t had a problem since!

The average temperature in there was 90° With a humidity reading of 75%!

Now I can maintain a temperature of 70 to 75° and keep the humidity around 50%!

 

EA

 

 

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