TETRAMETHYLTHIURAM DISULFIDE AND 2-MERCAPTOBENZOTHIAZOLE AS BINARY ACCELERATORS IN SULFUR VULCANIZATION .4. VULCANIZATION OF POLYISOPRENE IN THE PRESENCE OF ZNO

Polyisoprene was vulcanized with binary accelerator systems comprising mixtures of the zinc salts of tetramethylthiuram disulfide (TMTD) and 2-mercaptobenzothiazole (MBT). Samples were heated in a DSC at a prog rammed rate, the reaction was stopped at points along the thermal curv e, and the system was analyzed. Extractable curatives and reaction int ermediates were analyzed by HPLC and the crosslink density of samples measured by swelling. DSC curves for the different systems displayed s imilar characteristics and their similarity to the curve obtained with the zinc salt of TMTD rather than to the curve obtained with the zinc salt of MBT suggested that the reaction was dominated by the former a ccelerator. This conclusion was supported by HPLC analyses of extracta ble curatives. A reaction mechanism for the binary system is discussed . (C) 1996 John Wiley & Sons, Inc.