Originally Posted by
Polaris OBark
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?
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.
If I had to guess, 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.
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.
(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.)
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.