Expired Glues - observations

With the caveat these are single data points. I found a few random tubes of expired “glue” in the gear stash today. 1 used but re-sealed tube of A7+. Another unused but expired  A7+ and an unused but expired re 500 sausage. All are at least 2 years past their “use by” date. Out of curiosity I pumped samples (way more than one bolt worth) into sand which bags, kneaded the crap of of each to mix and waited. The old used A7 failed to harden at all and was mush hours later. The expired, unopened A7 had bits of the bag get hot and harden but other spots were much. The RE 500 hardened up consistently and was impressively hard. Usually I can snap dried A7 like peanut brittle. Th e Re500 in the bag , at most 1/4” thick, did not break in my hands even after some effort.   Curious if anyone knows more about the chemistry that may be going on here?  Is the epoxy acrylate (a7) prone to degradation or perhaps mix sensitivity? (This was by hand, not nozzle). The pure epoxy seems unaffected in casual observation.

Calling jim titt for a really intriguing question

Very interested in this thread.

I've noticed that all the epoxy acrylates I've used are very mix sensitive. I got some shorter mixing nozzles as spares for A7+/AC100 tubes and found that with fewer mixing elements both products were finicky on cure. That being said I used a 2 year expired tube of A7+ to reinforce a couple of shaky holds this spring. I used the full sized nozzle that is provided and the product cured perfectly. As for the RE 500 I'm usually more concerned about the stupid foul packs breaking than the glue setting, regardless of age.

C Williams wrote: I've noticed that all the epoxy acrylates I've used are very mix sensitive. I got some shorter mixing nozzles as spares for A7+/AC100 tubes and found that with fewer mixing elements both products were finicky on cure. That being said I used a 2 year expired tube of A7+ to reinforce a couple of shaky holds this spring. I used the full sized nozzle that is provided and the product cured perfectly. As for the RE 500 I'm usually more concerned about the stupid foul packs breaking than the glue setting, regardless of age.

I did some testing for a caving association who had varied results with one of the US produced resins and we also got erratic results using the standard nozzles, mixed by hand and using the longer nozzles no problems. There are two lengths of nozzles, only the longer ones with more mixing chambers get ETA (European Technical Approval). In the UK the suppliers then changed the nozzles they delivered with the resin.

Jim Titt wrote:

I did some testing for a caving association who had varied results with one of the US produced resins and we also got erratic results using the standard nozzles, mixed by hand and using the longer nozzles no problems. There are two lengths of nozzles, only the longer ones with more mixing chambers get ETA (European Technical Approval). In the UK the suppliers then changed the nozzles they delivered with the resin.

So the "varied results" was more from the lack of mixing than the fact that it was expired?  Or was this test based solely on the effects of the different nozzles, with unexpired glue? And would you speculate, please, on using expired glue?

Ma Ja wrote:

So the "varied results" was more from the lack of mixing than the fact that it was expired?  Or was this test based solely on the effects of the different nozzles, with unexpired glue? And would you speculate, please, on using expired glue?

What were storage conditions like for the epoxy/glue/resin? Stored in a temperature controlled environment? Temps continuosly between 40 and 95 degrees F?

Ted Vandell wrote:

What were storage conditions like for the epoxy/glue/resin? Stored in a temperature controlled environment? Temps continuosly between 40 and 95 degrees F?

I dont have any, but I know someone who has some and wont use it.

If it was ever stored at or near freezing temperatures, or in 100 + degree temperatures, it's toast.
If it was in a temperature controlled environment and the container was properly sealed, simply apply a test glue up to assess the efficacy.

Social Distancing and morning coffee "lab work"...  
So I pulled the Expired but only opened yesterday A7+ and decided to mess around some more with it. EDIT: This was stored in my TX garage.  It gets warm in there in the summer but never north of mid 80s.   This time I got two nozzles out as well. 1 is an OLD STYLE A7 nozzle from years ago - translucent with the mixing element nearly to the tip.  The other is the A24s clear nozzle that comes on current A7+.  I attached the tube and squeezed out multiple lines using both nozzles AND put a bunch more into a bag and hand mixed the remaining stuff.  Pic below...

The lower beads are with the old style nozzle.  Middle clump is new nozzle as well as upper beads.  There was no set up at all with the older nozzle (which seems to have more mixing elements) and minimal and varied setup with the new style.  You can clearly see how inconsistent the color is on top.  The hand mixed bag (very thorough mix) completely set up.  Casual observation while hand mixing tells me something is off with the black component.  It seems to have hard crystals in it that I don't recall seeing in a fresh tube which always mixed to smooth, uniform grey.  The hand mixed stuff still shows "Grit".  Pure speculation but I think this is probably a combination of expired elements crystallizing combined with minimal mixing from the tubes.   Really grinding the mix by hand seems to have overcome that issue.Either way, no expired epoxy acrylates for me...  

Ma Ja wrote:

So the "varied results" was more from the lack of mixing than the fact that it was expired?  Or was this test based solely on the effects of the different nozzles, with unexpired glue? And would you speculate, please, on using expired glue?

Of course it was unexpired, I'd have said so otherwise (and wouldn't have been testing it anyway). And no I won't speculate on using expired glue, I've used hundreds of tons of resin of various kinds over my life and know plenty about the effects of age and storage conditions but I'm certainly not going to tell people it's safe to use old stock. In boat building/composite engineering we know what we are doing and correct something if it goes wrong, not someone bolting.

mattm wrote: Social Distancing and morning coffee "lab work"...  
So I pulled the Expired but only opened yesterday A7+ and decided to mess around some more with it. EDIT: This was stored in my TX garage.  It gets warm in there in the summer but never north of mid 80s.   This time I got two nozzles out as well. 1 is an OLD STYLE A7 nozzle from years ago - translucent with the mixing element nearly to the tip.  The other is the A24s clear nozzle that comes on current A7+.  I attached the tube and squeezed out multiple lines using both nozzles AND put a bunch more into a bag and hand mixed the remaining stuff.  Pic below...

The lower beads are with the old style nozzle.  Middle clump is new nozzle as well as upper beads.  There was no set up at all with the older nozzle (which seems to have more mixing elements) and minimal and varied setup with the new style.  You can clearly see how inconsistent the color is on top.  The hand mixed bag (very thorough mix) completely set up.  Casual observation while hand mixing tells me something is off with the black component.  It seems to have hard crystals in it that I don't recall seeing in a fresh tube which always mixed to smooth, uniform grey.  The hand mixed stuff still shows "Grit".  Pure speculation but I think this is probably a combination of expired elements crystallizing combined with minimal mixing from the tubes.   Really grinding the mix by hand seems to have overcome that issue.Either way, no expired epoxy acrylates for me...  

Well mid 80's is over the storage temp for the resins I sell........  

The hardeners do tend to dry out and go a bit crunchy, I've seen the dispenser pump nozzles get blocked in spray plants and with old cartridges that's the one that blocks as well. Store it cooler and sealed in vacuum bags.

Jim Titt wrote:

Of course it was unexpired, I'd have said so otherwise (and wouldn't have been testing it anyway). And no I won't speculate on using expired glue, I've used hundreds of tons of resin of various kinds over my life and know plenty about the effects of age and storage conditions but I'm certainly not going to tell people it's safe to use old stock. In boat building/composite engineering we know what we are doing and correct something if it goes wrong, not someone bolting.

Speculate may have been the wrong word to use. I'm asking about your knowledge of the effects of age and storage of glue. I'm not asking for you to approve it's use, I would just like to understand why there is an expiration date to begin with, and what is actually happening to the components when it is going bad. Just curious.

Jim Titt wrote:

Well mid 80's is over the storage temp for the resins I sell........  

The hardeners do tend to dry out and go a bit crunchy, I've seen the dispenser pump nozzles get blocked in spray plants and with old cartridges that's the one that blocks as well. Store it cooler and sealed in vacuum bags.

Double checked - A7+ storage is 32-95F but I'm pretty close to max.  This wasn't really meant to be re-used but I'll certainly be better with storage on the next batch with summer approaching here.

mattm wrote:  The RE 500 hardened up consistently and was impressively hard. Usually I can snap dried A7 like peanut brittle. Th e Re500 in the bag , at most 1/4” thick, did not break in my hands even after some effort.   Curious if anyone knows more about the chemistry that may be going on here?  Is the epoxy acrylate (a7) prone to degradation or perhaps mix sensitivity? (This was by hand, not nozzle). The pure epoxy seems unaffected in casual observation.

I don't have any experience with expired A7, but I've had several similar experiences with the RE-500.   The only obvious difference I've seen is that it hardens more slowly.  I haven't actually tested the hardened strength, but it seems to be very high.  I had a 2"x2"x 1/8" piece I couldn't break except with a hammer.

Five or six years ago I had some "2.5 years past the expiry date" RE-500 that I didn't use for bolting but for house maintenance.  I sealed up a half-dozen cracks/leaks (it sticks beautifully to wet concrete) in my cistern and septic tank and years later they still look perfect and don't leak.   There was a large spall in the cistern (6"x6") that I filled with it.  Still perfect.

But the most impressive thing was repairing several stepping stones.  These were a foot square and only 2" thick, unreinforced, concrete squares that had broken in two.    I glued them back together with the expired RE-500 on a whim, because I didn't think anything would actually hold them together.  It's been 6 years of people walking on them and the stones are still solid.

Ma Ja wrote:

Speculate may have been the wrong word to use. I'm asking about your knowledge of the effects of age and storage of glue. I'm not asking for you to approve it's use, I would just like to understand why there is an expiration date to begin with, and what is actually happening to the components when it is going bad. Just curious.

Well the polyester/vinylester resins inexorably go hard with age because they are thermosetting and slowly but surely the molecular chains join together, industrially it's a pain because the viscosity changes which makes laminating difficult, then you send it back and the polymer engineers do something magic and send it back ( you can buy it as re- processed resin). This doesn't really effect us as the stuff is already thickened anyway. Except that especially at higher temperatures the resin falls out from the morter mixture and you end up with a sticky mess oozing from the bottom of the cartridge and a more solid lump at the top. The cartridges should be regularly rotated if you store them a long time, maybe every six months. 

The hardener is a hassle as dibenzoylperoxide is normally a white crystaline powder and to make it into a paste it's dissolved in something, for us this is normally styrol (forget that the label says styrol free) to be compatible with the resin and it evaporates and you get back to the crystalline clumps which either block the outlet from the tube or the mixer. Mixed by hand the peroxide again dissolves, this time in the resin and it all goes hard like it should. You can actually dissolve the peroxide in almost anything, we had a plant which used just the crystals and we dissolved it ourselves, we even tested using beer! (The most used acne treatment is dibenzoylporoxide in water as it's a very effective bacteriocide).  

Pure epoxies (epoxyacrylates are vinylester resin with some epoxy mixed in) Have other problems, the usual one being the hardener component gradually crystalises, particularly if if gets cold and these don't dissolve in the base resin so don't mix and the stuff never, ever goes hard. The solution to this is put it in a water-bath and cook it slowly until the crystals dissapear, easy enough with a drum of the stuff but not really something with a cartridge system!  
Store it carefully, look after it and it will look after you!

Jim Titt wrote:

Well the polyester/vinylester resins inexorably go hard with age because they are thermosetting and slowly but surely the molecular chains join together, industrially it's a pain because the viscosity changes which makes laminating difficult, then you send it back and the polymer engineers do something magic and send it back ( you can buy it as re- processed resin). This doesn't really effect us as the stuff is already thickened anyway. Except that especially at higher temperatures the resin falls out from the morter mixture and you end up with a sticky mess oozing from the bottom of the cartridge and a more solid lump at the top. The cartridges should be regularly rotated if you store them a long time, maybe every six months. 

The hardener is a hassle as dibenzoylperoxide is normally a white crystaline powder and to make it into a paste it's dissolved in something, for us this is normally styrol (forget that the label says styrol free) to be compatible with the resin and it evaporates and you get back to the crystalline clumps which either block the outlet from the tube or the mixer. Mixed by hand the peroxide again dissolves, this time in the resin and it all goes hard like it should. You can actually dissolve the peroxide in almost anything, we had a plant which used just the crystals and we dissolved it ourselves, we even tested using beer! (The most used acne treatment is dibenzoylporoxide in water as it's a very effective bacteriocide).  

Pure epoxies (epoxyacrylates are vinylester resin with some epoxy mixed in) Have other problems, the usual one being the hardener component gradually crystalises, particularly if if gets cold and these don't dissolve in the base resin so don't mix and the stuff never, ever goes hard. The solution to this is put it in a water-bath and cook it slowly until the crystals dissapear, easy enough with a drum of the stuff but not really something with a cartridge system!  
Store it carefully, look after it and it will look after you!

Thank you, sir!

I always check that both materials are flowing before putting the nozzel on the cartridge. Especially for a second use on a cartridge. Culking gun has a probe built in to clear the plug if you have no flow.

Matt clearly the black component was not flowing well in some of your tests.