Vulcanization. Part V. The Formation of Crosslinks in the System: Natural Rubber-Sulfur-MBT-Zinc Ion

Abstract

Abstract The response of the delay time and specific rate of vulcanization (treated as first order) to changes in starting concentrations of accelerator, sulfur and activator in the system: natural rubber-sulfur-MBT-Zn++ was defined by empirically derived relationships. The effects of compounding variables on the number and types of crosslinks formed in the vulcanizate were also studied. A reaction scheme was proposed to explain the role of soluble Zn++. The scheme is consistent with the fact that increases in the concentration of soluble Zn++ give slower specific rates of crosslink formation but more crosslinks. In the scheme, it was proposed that Zn++ chelates certain crosslink presursors.