Hmmm... seek the origin of vulcan. Heat?
The way I see it, this is not the accurate term at all. Contact cement is applied to the tube, and wherein the solvent evaporates, leaving a very thin layer of tacky rubber. The underside of a patch is a smooth *rubber* compound. It may merge or bond when applied, but not through the process of heat or vulcanisation.
You see, you are talking about a *chemical* process, not a process facilitated by heat.