TETRAMETHYLTHIURAM DISULFIDE AND 2-MERCAPTOBENZOTHIAZOLE AS BINARY ACCELERATORS IN SULFUR VULCANIZATION .3. VULCANIZATION OF POLYISOPRENE IN THE ABSENCE OF ZNO

Polyisoprene was vulcanized with the binary accelerator system tetrame thylthiuram di-sulfide-2-mercaptobenzothiazole (TMTD-MBT) in the absen ce of ZnO. Samples were heated in a DSC at a programmed rate, the reac tion was stopped at points along the thermal curve, and the system was analyzed. Extractable curatives and reaction intermediates were analy zed by HPLC and the crosslink density of samples measured by swelling. Two crosslinking reaction sequences were identified, the first being initiated by polysulfides of the mixed accelerator N,N-dimethyldithioc arbamylbenzothiazole disulfide, and the second by MET. All the TMTD is consumed in the first reaction sequence. Synergism of the reaction is discussed in terms of recent work detailing a reaction mechanism for TMTD-accelerated vulcanization. (C) 1996 John Wiley & Sons, Inc.