i typically patch my tubes 2-5 times before i toss them. vulcanizing fluids and rubber cement are typically volatile organic solvents with dissolved vulcanized rubber. the dissolved rubber is not necessary for vulcanization since both inner tubes and patches are already vulcanized. the chemistry typically involves sulphur linkages but this may depend on the patch. pressure and/or heat speed up vulcanization reactions. this is why its important to pump up that tire and ride it as soon as its patched. high pressure tires are easier to patch than low pressure tires.