SQUALENE, A MODEL-COMPOUND FOR VULCANIZATION - A STUDY WITH SFC

Vulcanization of NR was simulated by reaction of squalene. The mass of the products were determined by Supercritical Fluid Chromatography (SFC): squalene, sulfur bound monomers and dimers. Especially the reaction of ''pendent groups'' or ''pending groups'' was of greater interest. These were formed by accelerators, N,N'-tetramethylthiuram disulfide (TMTD), monosulfide (TMTM), N,N'-di-(methyl-phenyl)-thiuram disulfide with sulfur or selenium. - The main yield of an efficient vulcanization was monomeric squalene with a different number of added groups, e.g. (CH3)2NC(= S)-S(x)with up to three sulfidic sulfur atoms (x less-than-or-equal-to 3). Dimers with sulfur bridges or monomers with internal sulfur bonds were produced in less extent. After addition of sulfur and zinc oxide and a following second vulcanization dimeric squalenes and cyclic monomers with a different number of sulfur atoms resulted. Heating of squalene with TMTM and zinc oxide lead to a small number of ''pendent groups'' attached to squalene with at most of one bridging sulfur atom (x less-than-or-equal-to 0; 1). After adding sulfur and zinc oxide and repeated heating a normal non-accelerated vulcanization took place. These two step reactions showed that a formation of TMT-polysulfides is necessary for accelerated curing. This can be shown when TMTM, sulfur and zinc oxide were heated in decaline and the resulting mixture of polysulfides were analyzed by SFC. - Vulcanization of squalene with TMTM, zinc oxide and selenium formed ''pendent groups'' with selenium atoms in the bridge.