SYNOPSISThe relationship between vulcanization reactivity and chemical structure was studied using a rheometer and DSC for natural rubber (SMR 5CV), butadiene rubber (BR Ol), styrenebutadiene 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.

The crystallinity and the disorder of crystallites were measured by X-ray diffraction method for ramie fibers treated with various concentrations of caustic soda with and without constraints.The crystallinity monotonously decreases with increasing concentration of caustic soda in the samples treated under constraint, whereas it decreases and again increases with the increases of concentration in the samples treated without constraint.In the case of sample treated under constraint, the order of crystallites increases remarkably with the concentration of caustic soda, while it remains unchanged for the samples treated without constraint.