Benzothiazole Sulfenamide Research Articles

Effect of Alkyl Group Structure on Cure Characteristics of N,N-Dialkylthio-Carbamyl-N′,N′-Dialkylsulfenamide Vulcanization Accelerators

Abstract Wide variations in scorch times and cure rates can be attained with tetraalkylthiocabamylsulfenamides through variation in alkyl groups. Substituent effects are substantial on either the carbamate nitrogen or on the sulfenamide nitrogen. Both inductive effects and steric effects influence the scorch times and cure rates. Positive inductive effects shorten scorch times and increase cure rates. Steric hindrance at the sulfenamide nitrogen increases the scorch time. Branching at the carbon atom beta to the nitrogen has a larger effect on scorch time than branching at the alpha carbon. Thiocarbamylsulfenamides can give appreciably higher cure rates and cure efficiencies than their benzothiazole sulfenamide analogs.

The Behavior of 2-Cyclohexyldithiobenzo-Thiazole and Related Unsymmetrical Disulfides in Rubber Vulcanization and Their Mass Spectral Fragmentation Patterns

Abstract The activities of the various cyclohexyldithio derivatives of thiazoles, benzoxazole and benzimidazole as accelerators may be correlated with their mass spectral fragmentation patterns. Present in the mass spectra are the molecular ions of 2-hydrodisulfides, 2-mereapto compounds, and cations corresponding to the molecular ions of 2-benzothiazolyl hydrodisulfide, 2-mercapto-benzothiazole, and their [M−1]+ ions, respectively. However, the cyclohexyl-dithiothiazoles are fairly strong accelerators, in contrast to the benzoxazole and benzimidazole derivatives which are weak accclerators. This shows that basically the compounds with thiazolylthio groups are superior as accclerators to those with the benzoxazolylthio or benzimidazolylthio group. Some of these cyclohexyldithio derivatives act as retarders when added to a benzothiazole sulfenamide accelerated stock. This property supports the postulate that one of the ways in which an addition of compounds which react with sulfur can inhibit vulcanization...

Synergism of free radical initiators with self‐extinguishing additives in vinyl aromatic polymers

AbstractVinyl aromatic polymers such as polystyrene can be made nonflammable by the addition of halogen compounds. The amount of halogen required to make such polymers nonflammable can now be greatly reduced by the addition of small amounts of certain free radical initiators. Normally about 5 phr of acetylene tetrabromide (parts of additive per hundred parts of polymer) must be added to polystyrene to obtain a self‐extinguishing polymer. Only 0.5 phr of acetylene tetrabromide is required if 0.5 phr dicumyl peroxide is added. This synergistic effect has been observed with a series of peroxides, hydroperoxides, azo compounds, quinone imines, benzothiazole sulfenamides, disulfides, and a bibenzyl compound. The synergistic mechanism seems to be based on a series of reactions involving attack of the polymer by the initiator and subsequent reaction between polymer fragments and the halogen compound. The result is a delay in the loss of halogen from the polymer mass and thus a more efficient use of the halogen additive for flame quenching. Known inhibitors of free radical reactions have a detrimental effect on the synergistic mechanism.