Influence of storage time and temperature and silane coupling agent on bound rubber formation in filled styrene–butadiene rubber compounds

Abstract

Bound rubber reflects the filler–polymer interactions involving physical adsorption, chemisorption, and mechanical interaction. For silica-filled rubber compounds, silane coupling agent is used to improve the filler dispersion. In the present work, variation of the bound rubber content with the storage time was studied using styrene–butadiene rubber (SBR) compounds filled with silica or carbon black. Influence of the silane content on the bound rubber formation was also investigated. The bound rubber content increases with increased storage time. The bound rubber content also increases with increase of the silane content. For the silica-filled compounds containing the silane, the bound rubber content increases dramatically at the beginning of storage. For the carbon black-filled compounds containing the silane, the bound rubber content increases notably over 20 days after the storage when the silane content is high. The bound rubber content also increases as the storage temperature increases. Increase of the bound rubber content by storage is explained by the formation of chemical bonds between the filler and rubber through the silane.