A Study of Thiocarbamyl Sulfenamide/Zinc Oxide and TMTD/Zinc Oxide Sulfurless Cure Systems

Abstract

Abstract In sulfurless cures of NR, soluble thiocarbamyl sulfenamides are found to produce the same state of cure as thiuram disulfides when compared on an equivalent dithiocarbamyl group basis. The addition of MBTS or benzothiazole sulfenamides to thiocarbamyl sulfenamides, or to thiurams, increases the modulus in proportion to the amount added. Adding sufficient benzothiazole sulfenamide appears to double the amount of sulfur donated by these thiocarbamyl accelerators and simultaneously increases monosulfide crosslink formation. The addition of zinc dibutyldithiocarbamate to thiocarbamyl sulfenamides significantly increases the modulus but has no effect on TMTD. Thiuram disulfides are generally reported to donate one sulfur per mole for crosslink formation. However, critical analysis of the literature and the above data indicates that two moles of TMTD are required to form one crosslink, i.e. donate one sulfur.