TETRAMETHYLTHIURAM DISULFIDE AND 2-MERCAPTOBENZOTHIAZOLE AS BINARY ACCELERATORS IN SULFUR VULCANIZATION .2. EXCHANGE-REACTIONS BETWEEN THE ACCELERATORS AND THEIR ZINC SALTS IN THE ABSENCE OF RUBBER

Exchange reactions between tetramethylthiuram disulfide, 2-mercaptoben zothiazole, and sulfur in the presence of ZnO were studied by heating powdered mixes to vulcanization temperatures at a preprogrammed rate i n a DSC. The reaction was stopped at points along the thermal curve an d the mixture was analyzed. Sulfide exchange reactions between the acc elerators leads to a mixed accelerator and dimethyldithiocarbamic acid that is trapped by ZnO to give the zinc accelerator complex bis(dimet hyldithiocarbamato)zinc (II). Exchange also occurs between the acceler ators and ligands on both the thiuram and benzothiazole zinc accelerat or complexes. Zinc complexes containing ligands of both accelerators w ere synthesized. These showed little interaction on being heated with sulfur, but on dissolution yielded a spectrum of products similar to t hat obtained in the other system containing zinc. Reactions to account for changes in the spectrum of products on heating different mixes of these curatives to different temperatures are discussed. (C) 1995 Joh n Wiley & Sons, Inc.