Despite the original meaning of Vulcan and the fact that most vulcanization IS done at elevated temperature, heating is not necessary for "vulcanization" of rubber as we now know it. The most basic curing of rubber used only heat. Results were fairly poor. Bye and bye chemical curatives and accelerators were discovered which improved the process and allowed it to be carrier out at lower and lower temperatures and faster and faster. The term is now used interchangeably with "curing" and "crosslinking" to mean a chemical process which creates three dimensional structures from the previously linear rubber polymer chains. The three dimensional structures are what give "vulcanized" rubber its permanent elasticity, resistance to softening at elevated temperature, tensile strength, high elongation without breaking, resistance to oxidation, etc. The requirement for heat is usually desirable since it gives the processor a "knob" to turn to control the process and plenty of time to arrange the rubber parts in their desired configurations in the molds before the reaction starts to take place and makes it impossible to further change the shape of the rubber. Since patching a tube on the road or at home necessarily can't involve heat very conveniently, the chemistry for that is chosen to not require added heat. But it can still be properly called vulcanization.