Filler dispersion is a critical factor in determining the properties of filled rubber composites. Silica has a high density of silanol groups on the surface, which lead to strong filler–filler interactions and a poor filler dispersions. A cure accelerator, N-tert-butyl-2-benzothiazole sulfenamide (TBBS), was found to improve filler dispersion in silica-filled natural rubber (NR) compounds. For the silica-filled NR compounds without the silane coupling agent, the reversion ratio generally increased with increase in TBBS content, whereas those of the silica-filled NR compounds containing the silane coupling agent and carbon black-filled NR compounds decreased linearly. The tensile strength of the silica-filled NR vulcanizate without the silane coupling agent increased as the TBBS content increased, whereas carbon black-filled samples did not show a specific trend. The experimental results were explained by TBBS adsorption on the silica surface and the improvement of silica dispersion with the aid of TBBS. Copyright © 2003 Society of Chemical Industry

Properties of natural rubber composites reinforced with silica or carbon black: influence of cure accelerator content and filler dispersion

Since silica has strong filler-filler interactions and adsorbs polar materials, a silica-filled rubber compound has a poor dispersion of the filler and poor cure characteristics. Improvement of the properties of silica-filled styrene-butadiene rubber (SBR) compounds was studied using acrylonitrile-butadiene rubber (NBR). Viscosities and bound rubber contents of the compounds became lower by adding NBR to the compound. Cure characteristics of the compounds were improved by adding NBR. Physical properties such as modulus, tensile strength, heat buildup, abrasion, and crack resistance were also improved by adding NBR. Both wet traction and rolling resistance of the vulcanizates containing NBR were better than were those of the vulcanizate without NBR. The NBR effects in the silica-filled SBR compounds were compared with the carbon black-filled compounds.

Improvement of properties of silica‐filled styrene–butadiene rubber compounds using acrylonitrile–butadiene rubber

High temperature vulcanization of elastomers: 2. Network structures in conventional sulphenamide-sulphur natural rubber vulcanizates

Gas chromatographic-mass spectrometric identification of volatiles released from a rubber stock during simulated vulcanization

Device for thermally-induced vapor phase transfer of adsorbed organics directly from an adsorbent to a gas chromatograph-mass spectrometer

Changes in the value of [η], [ηm], K′, (M) and μ of SBR masticated in the cold at 25.0 ± 5.0° C in presence of oxygen with the times of mastication are reported. An empirical relation has been developed between the intrinsic viscosity [η] and Mooney viscosity [ηm] which permits molecular weight of the rubber to be determined directly from Mooney viscosity. The value of g which appears in the Flory equation connecting true crosslink density with the physically determined one has been calculated for unfilled SBR.

Viscosity and Molecular Weight of Masticated Styrene-Butadiene Rubber

Sulfenamide type of accelerators are well known for their outstanding processing safety combined with ultra-strong accelerating activity resulting in superior quality vulcanizates. Sulfenamides derived from different amines afford varying degrees of scorch delay and accelerating activity. Since there is no unanimity on the chemistry involved in this type of accelerated vulcanization, a preliminary study has been carried out to gain some insight into the mechanistic scheme. The present paper contains reports on the effects of varying concentrations of N-cyclohexyl-benzothiazole-2-sulfenamide (CBS) on the rate of free sulfur decrease and cross-link formation as well as zinc sulfide formation—whenever it occurs—both in the absence and presence of zinc oxide and of zinc oxide and stearic acid. The influence of temperature has also been investigated.

S. K. Bhatnagar

Papers

Viscosity and Molecular Weight of Masticated Styrene-Butadiene Rubber

Kinetics of Accelerated Vulcanization—III N-Cyclohexyl-Benzothiazole-2-Sulfenamide Accelerated Sulfur Vulcanization of Rubbers