I seem to remember from childhood a type of patch a neighbor kid had that you had to light on fire to get it to adhere properly.

No, because we're talking about cold vulcanization here.

OK.

Is cold vulcanization glue the same as rubber cement?

No. Rubber cement is just a rubbery glue. It can work pretty well, but the Rema stuff forms a much stronger chemical bond. It's nearly impossible to remove a Rema patch if you've done it right.

No. Proper cold vulcanization creates permanent bonds between the patch and the tube.

OK, it is the trichloroethylene solvent that is different.

cf: MSDS

Canonical rubber cement uses n-heptane, a solvent that has the merit of not being a carcinogen.

The MSDS calls out the solvent because it's potentially harmful. That doesn't mean the TCE is what's doing the bonding. Quite the opposite -- we wait for the fluid to dry (solvent has evaporated) before applying the patch.

There have been a lot of threads about this already, and [MENTION=21724]cyccommute[/MENTION] could give a much better explanation of the chemistry if he's not tired of it by now. ;)

I'm also a chemist.

I remain skeptical that there is any difference apart from the solvent.

If the solvent isn't the critical difference, why would they use a carcinogenic one?

If I had to guess, [this is wrong; see below] trichloroethylene dissolves the surface layer of the butyl tube a little bit better than n-heptane. It works as a contact cement, so the solvent essentially enables the rubber contact glue to bond to the tube surface as it evaporates. Then the little bit of adhesive on the patch sticks to the tacky surface created on the tube as the solvent evaporates, and the patch bonds to the tube as you apply pressure.

(I've used the little tubes primarily because the solvent dries up after you open it, not because I think it is magically different from rubber cement, which would probably be more than adequate. I found out the hard way the patch works reasonably well even in the absence of any cement.)

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Maybe it evaporates faster? My experience with rubber cement is that it stays tacky for a really long time, even when you expose it to dry air for days. That's not what we generally want in a tube patch. We want it to stick firmly from the get-go and be completely done curing ASAP.

(The theory you added to your post on edit sounds plausible, too. I just have two semesters of chemistry and a passing interest in how it works. :) )

For the record, I don't know anything about adhesives.

An older version of the SDS (Revision 4, 2018), lists n-ethylcyclohexylamine as one of the ingredients. The amine is an accelerator for the process. There’s another SDS for the patch that I can’t seem to locate now but it lists a sulfur compound in the patch material. My understanding of the chemistry is that the accelerator promotes the cross linking process so that it can be carried out at room temperature instead of having to be heated.

Yes. My father still had some in the '70s. The back side had a pad of what seemed like cardboard made with gunpowder, that you could not put out once lit. Vulcan was the God of Fire, right? Real Vulcanizing involved real fire, that melted the patch material onto the tube. My friend did not believe my warning not to try lighting one, and filled the workshop with smoke minutes before my father came home. What are friends for?

Probably to speed up evaporation. I’ve seen SDS versions that use naphtha or tricholorethylene. Revision 4 that I linked to lists naphtha as the solvent.

The solvent has no effect on the bonding. The solvent has completely evaporate for the bond to form. In fact, the bond will form even if the adhesive patch is allowed to stand even for weeks at a time. I’ve forgotten about patch jobs and applied the patch two to three weeks later without problems.

The tubes drying out is usually due to improper closure or to cracked tubes…they are aluminum after all. I resist rolling the tube when using it unless there is very little fluid left. A can of fluid with a tightly fitted cap will last for a very long time. Leave the cap off and the solvent goes away very quickly.

I’m not clear on how you can apply a patch without cement.

By the way, I’m not an adhesive chemist either. Did a little bit of work on replacing phenol in phenol/formaldehyde plywood adhesives with wood pyrolysis oils long ago but that’s not this kid of adhesive. I have done a whole lot of studying of Rema’s patch chemistry as part of these kinds of discussions., however.

Vulcanization is the curing of an elastomer. The original method invented by Goodyear involved heat but we have progressed since 1839. Cold vulcanizing is a whole lot easier, just as strong, and you don’t need to carry a fire source, a clamp, and a rather bulky patch kit. Hot patching isn’t something that is easily done on the road and, as you found out, it makes some rather nasty smoke.

This thread started to get some insults going. I deleted a couple posts. Let’s stop. If you don’t like a post, how about ignoring and move on rather than insulting?

I apologize. I shouldn’t have responded the way I did.

Thank you, as always. I've learned quite a bit.

+1 Tubes properly patched with Rema brand patches and cement and properly "stitched" to the tube will be fine. The tube should be good as new. Just make sure you sprinkle talc around the patched area so that it doesn't stick to the inside of the tire.

I remember my GranPa adding a little Gasoline to and old can of Monkey Grip vulcanizing cement to reconstitute it. He told me you can only do this once because the gasoline will dry it out faster. It worked just fine. Vulcanizing Cement and Gasoline in the 50s had allot of Heptaine in it. Naphtha in modern day vulcanizing cements would be much safer. I am sure he would have used Naphtha if he had had it around.

https://cimg6.ibsrv.net/gimg/bikefor...c4aa2ae255.png
https://media.napaonline.com/is/cont...y/113869197pdf

A little OMS seemed to do the trick. I mixed a bit an a baby food jar, and it mixed up ok so I added some directly to the can. Kept adding ~10ml at a time until it reached what seemed like a good working consistency. I'll try to remember to report back how it holds up over time.

Another pro patch tip. A DE razor with an aggressive head works great for shaving down the seams before sanding. I used a cheap Merkur Futur knockoff.

I'm between jobs for a few weeks right now. This must be what Tuesday in retirement will be like for me someday.

https://cimg8.ibsrv.net/gimg/bikefor...4091c3dafd.jpg

Not sure why anyone is messing with old school style patches and cement. These work just as good and no mess...

https://www.parktool.com/product/super-patch-kit-gp-2

What's the most number of years you've gotten out of a glueless patch? Par is decades.