System Three Epoxy - T88 - questions

[Brian Tymchak]

Morning all, I'm going to be using epoxy on some large M&T joints. I'm looking at the System Three T88 epoxy, and specifically the 8.4 oz cartridge that fits in a standard caulk gun. This is a 2-part epoxy and needs mixed. I have 24 of these joints to glue up, but will be done 1 at a time over the span of several weeks. Does anyone have experience using the cartridges? Is the tip a mixing tip so that I don't have to mix the parts? If so, is the tip a single-use tip? The description doesn't provide any detail about this. I don't see extra tips for sale on the System Three site.

https://www.systemthree.com/products/t-88-structural-epoxy-adhesive

Thanks for your help, Brian

[Steve Eure]

Brian, I have not used the T88 epoxy, but have use several of their other products. I had questions also that their website did not address so I emailed them my queation and they were quick to reply with an answer. I would suggest that you contact them via emaila or maybe try calling them. You may get a slow response right now because of the Christmas holiday.

[Eric Schmid]

Although you can clean up T88 with lacquer thinners I’ve always considered the mixing nozzles as single use. In the shop I use a mixing cup and a scale. Pour out equal parts and mix. This epoxy has a long working time so mix small batches until you get a feel for how much you need for each session.

[Prashun Patel]

The website description says it’s a dual chamber that eliminates the need for mixing.

That being said, the normal t88 requires a good deal or mixing to get it well mixed. I mix an oz for maybe 45 seconds.

It is slow setting - and will remain workable for about 45 minutes. So, you may be better served mixing 4 oz in a yogurt cup by hand and brushing your joints. The caulk gun won’t save you any time on the actual glue up.

[Mike Cutler]

Morning all, I'm going to be using epoxy on some large M&T joints. I'm looking at the System Three T88 epoxy, and specifically the 8.4 oz cartridge that fits in a standard caulk gun. This is a 2-part epoxy and needs mixed. I have 24 of these joints to glue up, but will be done 1 at a time over the span of several weeks.
Why one at time? With epoxy you could easily assemble all of the joints at the same time.

Does anyone have experience using the cartridges?
Yes, I have used T-88 for many years. Both the cartridges and the single bottles.

Is the tip a mixing tip so that I don't have to mix the parts?
No. Unless something has changed, the tip is to meter out a 50/50 ratio. You will need to mix it after you squirt it in a cup. I know they say it mixes it in that tip, but I didn't find that to be the case.
If so, is the tip a single-use tip?
No, the tip can be cleaned with a rag and acetone after use, and the cap(s) placed back on.
The description doesn't provide any detail about this. I don't see extra tips for sale on the System Three site.

https://www.systemthree.com/products/t-88-structural-epoxy-adhesive

Thanks for your help, Brian

Brian
You might be better served by buying the individual bottles. You need to spread the product out on the joint, not caulk it.
It takes epoxy years to go bad,and the resin can be reheated to liquify itself if to goes solid in the bottle. I've never had the hardners go solid, only the resin.
T-88 is a very forgiving epoxy. T-88 is also a "gap filling" epoxy, meaning that it has it's own thixotropic agent in it. If you have really tight fitting joints, T-88 may not be the correct epoxy.
You have a long working time with T-88. 20 minutes or so easily in the cup. Close to an hour or more if it's spread out on the joint(s). If you let the epoxy mix sit for a few minutes, it begins to "thicken" a little bit and will stay in place easier that as soon as you're done mixing.
You need a 24 hour cure "in the clamps" to reach about 80% of strength. It will continue to strengthen for the next day or so to 100%.
You clamp only enough to bring the parts together and into alignment. Squeeze out is not the goal with epoxy, and will leave you with a "starved joint" if you clamp epoxy to tight.
When mixed, T-88 has a whitish color. It doesn't cure that color though. It will be a sort of opaque whitish color if it is a blob. Other wise it will cure clear.

[Brian Tymchak]

Thanks all. I think your input has me leaning to mixing my own.

Really appreciate the tips on mixing. The pieces I'm joining are large and heavy, so the long open time was a key factor for going with epoxy. It will take some time to glue up the joint (with wedged tenons) and clamp against a jig to assure it cures at a specific angle.


The website description says it’s a dual chamber that eliminates the need for mixing.

I missed this Prashun, and I thought I reviewed the site pretty thoroughly.. :o Thanks for pointing that out.

[Mike Cutler]

Brian

Unless something has changed dramatically with the dual chamber mixing tip, I did not find that it mixed it adequately for me. I've mixed a lot of by hand and know what it looks like mixed. We actually threw the tip away and shot it straight out of the cartridge.
Maybe they improved it though. The would be nice.

[Mike Hollingsworth]

I find T88 very forgiving on the mixing ratio, unlike the other brand. I always mix thoroughly.

[Brian Tymchak]

Hi Mike,

Thanks for the reply and the tips. You mentioned a few things I'll follow up on.



Why one at time? With epoxy you could easily assemble all of the joints at the same time.

Well, primarily because I work slow and I'm limited to a couple hrs a day on the weekends in the shop. The project is a timber-frame inspired lumber rack. There are 3 arms and a foot for each upright standard. There are 6 standards. The arms will sit up 3* from perpendicular to the standard. Each joint will require a clamping jig to hold the joint at an 87* angle while the epoxy cures. Having thought a little about it, I might build 3 jigs so I can glue up 1 full standard in a single session.



T-88 is a very forgiving epoxy. T-88 is also a "gap filling" epoxy, meaning that it has it's own thixotropic agent in it. If you have really tight fitting joints, T-88 may not be the correct epoxy.

These are the first large M&T joints I've done and the first few I've done are not as tight fitting as I would like. I will be relying a bit on the gap filling.