Abstract
N, N'-polythiobis (dimethylamine), N, N'-polythiobis (diethylamine) and heptasulfuryl imide were found to be effective curing agenst for natural rubber. These agents were characteeized by apparent non-blooming and delayed scorching. Only 1.5 phr of these agents is enough to cure natural rubber tightly without accelerators under usual vulcanization condition. The scorch time of the compounds is longer than that of Ncyclohexylbenzothiazyl-2-sulfenamide and sulfur system (I). The tensile properties of the vulcanizates seem to vary with sulfur content of N, N'-polythiobis (dimethylamine) (II). The highest tensile strength of te vulcanizates was attained by the use of (II), sulfur content of which was about four atoms of sulfur per molecule. The strength was found to be higher than that of the vulcanizate cured with (I). The valcanizates cured with these organic polysulfides possessed poor resistance to heat aging, but this defects was improved by using common vulcanization accelerators together with antioxidant.
