5 Minute Epoxy?

[qquake]

I just noticed on the bottles of the Loctite epoxy I have, it says right on the front "5 Min Setting Time". So I don't know what to think. I did get some Devcon brand 5 minute epoxy to try, because a lot of the reviews said it set up quickly. It did seem to set faster, I was able to work with it after 10 minutes, although it was still a little bit soft.

 

[qquake]

There is nothing about set time on the Devcon.

 

[qquake]

Jim, I am a little surprised at this. Just about every Epoxy type I have ever purchased going back 40 - 50 years states in the instructions that the CURE time is xxx, which is longer than the set time. I say that, because I have always check a new brand (new to me) as to the cure time. It should be on the instructions of each.

As to a toaster oven, every person will use it differently and every person's milage might vary; That said, don't get it too hot. The cheaper toasters might not have an actual temp that will be below 175°, which can destroy epoxy's strength. It could be just me, but I have ruined a few glue-ups by heating them a little too high.

On the Walmart toaster oven, the temperature is marked as low as 200. But you can turn the knob below that. So I'm hoping it would go a lot lower than 200.

Robot or human?

 

[jrista]

I just noticed on the bottles of the Loctite epoxy I have, it says right on the front "5 Min Setting Time". So I don't know what to think. I did get some Devcon brand 5 minute epoxy to try, because a lot of the reviews said it set up quickly. It did seem to set faster, I was able to work with it after 10 minutes, although it was still a little bit soft.

There are three key times for any epoxy. The working time, the set time and the cure time. Set time is not cure time.

The working time is when the two halves are going through the initial phase of the reaction to create polymer chains. There is an Epoxoid group, the common chemical structure in all epoxies called Epichlorohydrin or ECH. ECH goes through a process that will convert it into a compound that can then be reacted into a polymer (or polymer subunit). This is generally what's happening during your working time.

Once there is enough of this hydroxylated Epichlorohydrin, then the next reaction begins which is what forms polymers subunits, and then longer chains of polymer. These polymer strands can get fairly long, BUT, they are NOT cross-linked... This intermediate phase of the process produces that semi-hard but still fluid-like substance. Once polymer chains start to form, you really don't want to be messing with your joints, because the final reactions have likely started to begin at this point, and continued fiddling will weaken your bond.

The final phase of reactions is where the hardener bonds with the polymer chains produced by the earlier reactions to CROSS-LINK the polymers into a three-dimensional web of structure. This is what creates the stronger, final, hardened bond that actually holds your parts together.

The 5 minutes, is the time you have before polymers, and not long after cross-linking, "sets in."

 

[jrista]

Jim, I am a little surprised at this. Just about every Epoxy type I have ever purchased going back 40 - 50 years states in the instructions that the CURE time is xxx, which is longer than the set time. I say that, because I have always check a new brand (new to me) as to the cure time. It should be on the instructions of each.

As to a toaster oven, every person will use it differently and every person's milage might vary; That said, don't get it too hot. The cheaper toasters might not have an actual temp that will be below 175°, which can destroy epoxy's strength. It could be just me, but I have ruined a few glue-ups by heating them a little too high.

I would like to see others experience in this area of overheating epoxy, and at what temp does that occur.

Jon Rista posted this: https://www.penturners.org/threads/t88-a-useful-paper.178952/#post-2197341

the paper has this in it:

Lap-Shear Strength vs. Temperature (Aluminum Tensile Shear)	67°F: 2,500 psi, 75°F: 2,000 psi, 150°F: 1,300 psi, 180°F: 1,000 psi
Heat Deflection Temperature	119°F (49°C)
Maximum Service Temperature	160°F (71°C)
Minimum Application Temperature	35°F (2°C)
Gel Time @ 77°F (25°C)	60 Minutes (100g mixture)

NOTICE the Temp variance in the Lap Shear Strength vx Temperature. Shear strength decreases with temp increase. Max service item is 160°. I mention this because an inexpensive toaster oven does not regulate the temp very well and the dial temp setting is an estimate at best.

Ooh. This is a good catch...I hadn't noticed the loss of shear strength with heat... It drops by nearly half at 150 degrees. Well, for one, despite that, I have not lost a bond with T-88 yet... But, I may have to reduce my temps. Might put a thermometer in my toaster oven, and see how warm it gets at the lowest setting.

 

[jttheclockman]

Man I am lost on this whole topic. Epoxy glue is what it says it is and works well when follow instructions. If you want faster set time switch to all CA. Can not get any faster than that stuff. Life is way too short. Slow down enjoy the ride.

 

[qquake]

Ooh. This is a good catch...I hadn't noticed the loss of shear strength with heat... It drops by nearly half at 150 degrees. Well, for one, despite that, I have not lost a bond with T-88 yet... But, I may have to reduce my temps. Might put a thermometer in my toaster oven, and see how warm it gets at the lowest setting.

How much strength does it really need? There's not a lot of pressure put on the tube. The bushings press against the tube and the blank.

 

[qquake]

If I decided to use a blow dryer or heat gun, how long does it take?

 

[jrista]

How much strength does it really need? There's not a lot of pressure put on the tube. The bushings press against the tube and the blank.

I am thinking more on the side of creating segmented blanks, then drilling them. I've started pre-drilling segmented parts, but that is not always possible. The main reason I moved to T-88 was the recommendations for it from other people who have had experience with segmenting. The main issue I have encountered with segmented blanks is them shearing off during the drilling process, and sometimes when I start turning. A shearing problem, and it looks like shear strength drops with the heat.

CA was the worst here, especially with metal layers. They just don't bond, even heavily scuffed up (which actually shows up as ridging along the edge of the metal layer in a finished blank, so I backed off the scuffing aggression there). JB Weld wasn't all that great. T-88 is just a different kind of epoxy, and however its chemistry works, it seems to work really well bonding disparate materials together. I haven't had a failure yet, but, knowing that the shear strength drops with heat, I may back off to say 100 degrees. I won't get those 30 minute cures, but at least it will still be less than 24-48 hours.

If you are mainly concerned about simple tube to blank bond, then, I don't think any of this matters. You could probably heat T-88 to 140C and be perfectly fine.

 

[qquake]

I wasn't thinking about segmenting. I've heard that T-88 is exceptionally strong, but can take days to cure. I used it once, on my son's Goonies pen. It was very old, very dry douglas fir, and it blew out on me twice with regular epoxy. So I got some T-88 and let it cure for two days before working with it. It was my last piece of doug fir, and I was VERY careful turning it. I was successful the third time. I don't know if it was the T-88 or my gentle touch, or a combination of the two. Probably the latter.

 

[jrista]

I wasn't thinking about segmenting. I've heard that T-88 is exceptionally strong, but can take days to cure. I used it once, on my son's Goonies pen. It was very old, very dry douglas fir, and it blew out on me twice with regular epoxy. So I got some T-88 and let it cure for two days before working with it. It was my last piece of doug fir, and I was VERY careful turning it. I was successful the third time. I don't know if it was the T-88 or my gentle touch, or a combination of the two. Probably the latter.

I remember this project, back when you first shared it. I think this was why I started using T-88! Or at least one of the reasons why. It was at least when T-88 first came to my attention, I remember that.

Anyway. You mentioned your garage was 105 degrees? That should speed up cure time. Its a curve, or a continuum...its not like cure time jumps from one time to another. At 70C, it cures in 24 hours. IIRC, back when you had this problem, it was pretty cold, and you were indeed looking at days to weeks for it to fully cure? If you glued up your blanks and just put em out where its warm/hit (105 degree shop should do!), then it should take less than a day to cure, maybe just a matter of hours, maybe half a day.

 

[qquake]

It gets really hot in my garage when it's really hot outside. I do my glue ups in the house where it's usually around 80. I'll try my heat gun on low and see if that helps. The Devcon epoxy did seem to set faster in the house.

 

[jrista]

It gets really hot in my garage when it's really hot outside. I do my glue ups in the house where it's usually around 80. I'll try my heat gun on low and see if that helps. The Devcon epoxy did seem to set faster in the house.

Is there some reason you couldn't do the glueups inside where its only 80, then when all the tubes are in, just move them out into the garage and leave them there to cure?

 

[qquake]

Is there some reason you couldn't do the glueups inside where its only 80, then when all the tubes are in, just move them out into the garage and leave them there to cure?

I usually glue in the mornings, when the garage is a lot cooler.

 

[jrista]

I usually glue in the mornings, when the garage is a lot cooler.

I see. Well, I don't see why a hand dryer or something like that wouldn't work. Thing is, you would probably have to sit there a good while to get any real benefit from that. A $20 new or even cheaper used toaster oven should do the trick with a lot less hassle. You can get down to just a couple hours cure time at around 150 degree, with 1300PSI sheer strength... If you want the fastest cure times you can get, I think that's it.

Oh, FWIW, I usually just leave the blanks in the toaster oven for the set time, which at ~150C is 30 minutes. I don't actually leave them in for a full 2 hours.

 

[qquake]

My oven goes down to 170F. Is that too warm?

 

[jrista]

My oven goes down to 170F. Is that too warm?

Yes, definitely. The maximum temp for T-88 is 160F, according to the data sheet. I would say, you don't even want to go to 150F...at that temp, at least up here in Colorado at 6000 feet, maybe its a pressure thing, I've gotten some bubbling of the glue, which I don't like.

Any chance you have a heat lamp?

You could also give the heat gun a try. I don't think you need to heat them for the full 2 hours...and maybe 10 minutes or so would do the job. I haven't experimented enough with it. I've come across a variety of techniques people use with T-88...sometimes it is recommended that you let the glue cure for a bit at room temp, then heat. Other times you would want to heat immediately. So, I would just experiment and see what helps.

 

[qquake]

I could always turn the oven off when it reached 120 or so.

 

[Curly]

Marla used to cure the sticky off her cast blanks by setting them on small sticks above an opened waffle/sandwich maker in a metal drawer. It was nice and warm inside on the lowest setting. Rather than putting the blanks in a toaster oven with their poor thermostats and heat control, you could heat a metal plate in the toaster oven (or in the kitchen oven). Put the plate in a small metal toolbox and then put the tubed blanks inside. That should be enough to warm them for a cure without exposing them to excessive heat.

 

[TonyL]

the bold printed times on the bottle are working-times, not full cure times. Also remember that there is an inverse relationship between curing times and strength. Some ask of strength is that important. It may or may not be. However, whether TBC or using bushings, any center or bushing contact with the brass tube may impose a shear force between the brass tube and blank material when apply resistance from a chisel.