The relationship between vulcanization reactivity and chemical structure was studied using a rheometer and DSC for natural rubber (SMR 5CV), butadiene rubber (BR 01), styrene-butadiene rubber (SBR 1501), and their blends. The overall rate of the vulcanization was SBR > BR > NR. This was the same trend as the number of allylic hydrogens in the statistical repeat unit of the rubber used. Because the corresponding rate constant for an allylic hydrogen was very similar regardless of the rubbers, it was found that the vulcanization condition for a compounded rubber could be predicted by comparing the number of allylic hydrogens. The activation energy of the vulcanization was calculated for each rubber also. © 1996 John Wiley & Sons, Inc.