Time-resolved XAFS Study on Crosslinking Reaction of Sulfur-based Rubber Compounds

Crosslinking reaction of sulfur-based rubber compounds with sulfur, accelerators and zinc oxide (ZnO) as crosslinking agents was studied by a time-resolved X-ray adsorption fine structure (XAFS) method. The Zn K-edge XANES (X-ray absorption near-edge structure) spectra obtained during the process were properly decomposed into two components, assigned to ZnO and zinc sulfide (ZnS). The [ZnO]/[Zn] ratio was found to decrease with the increased amounts of sulfur and accelerators, or by the addition of surface active-carbon black. It was confirmed that the decreasing behavior of the amount of ZnO gives a good indicator of the crosslinking reaction by changing of ZnO into ZnS through the chemical reactions with sulfur-containing reagents.