Comparison of tetraethyl- and tetramethylthiuram disulfide vulcanization. I. Reactions in the absence of rubber

The reactions of tetraethylthiuram di- and monosulfide (TETD and TETM, resp ectively) were investigated in the absence of rubber and compared with thos e reported previously for tetramethylthiuram compounds. The reactions of TE TM, TETD, and zinc diethyldithiocarbamic acid with zinc oxide and sulfur we re investigated by differential scanning calorimetry, and the reaction prod ucts analyzed by high performance liquid chromatography. TETM was shown to be more stable at vulcanization temperatures (+/-150 degreesC), but also le ss reactive with sulfur than tetramethylthiuram disulfide (TMTD). The react ions of TETD are very similar to those of TMTD, the TETD reacting slower th an the TMTD to form analogous products. In the presence of zinc oxide, the formation of the zinc compound of TETD, zinc diethyldithiocarbamic acid, oc curred readily. TMTD does not react readily with zinc oxide. The reaction o f TETD with sulfur lead to the formation of polysulfidic accelerator specie s, although the concentrations formed in the absence of rubber were conside rably less than that formed by the corresponding TMTD system. These differe nces in reactivity would affect the vulcanization reactions that take place in the rubber. (C) 2001 John Wiley & Sons, Inc.