Vulcanization kinetics of butyl rubber–clay nanocomposites and its dependence on clay microstructure

Properties of rubber articles are very much influenced by their vulcanization characteristics. Vulcanization kinetics of isobutylene isoprene rubber (IIR) or butyl rubber, filled with three organically modified montmorillonites, having different degrees of hydrophilic nature, was investigated by oscillating disc rheometer (ODR). Microstructures of the nanocomposites were characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), gas permeation, and uniaxial tension. It was shown that structure of clay ranged from moderately or highly intercalated to agglomerated structure for different organoclays. Microstructure of nanocomposites was used to explain opposite trends observed in vulcanization kinetics of them. It was shown that not only the chemical nature of the clay modifier, but also physical effects such as diffusion of vulcanizing agents in butyl rubber, limited by filler network, can alter vulcanization kinetics of this rubber. For less hydrophilic organoclays, dispersion is better, and formation of filler network structure limits diffusion and accessibility of curing agents to vulcanization sites. Two empirical models of Isayev and Ghoreishy were also employed and compared in explaining the results quantitatively.