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

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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.