Rubber–pristine clay nanocomposites prepared by co-coagulating rubber latex and clay aqueous suspension

Abstract

The structure of several rubber–clay nanocomposites, including styrene butadiene rubber (SBR)–clay, natural rubber (NR)–clay, nitrile butadiene rubber (NBR)–clay, carboxylated acrylonitrile butadiene rubber (CNBR)–clay nanocomposites, prepared by directly co-coagulating the rubber latex and clay aqueous suspension, were investigated. X-ray diffraction (XRD) patterns and transmission electron microscopy (TEM) micrographs showed that these nanocomposites possessed a unique structure, in which the rubber molecules “separated” the clay particles into either individual layers or just silicate layer aggregates of nanometer thickness without the intercalation of rubber molecules into clay galleries, different from intercalated and exfoliated clay nanocomposites. Such a structure resulted from the competition between separation of rubber latex particles and re-aggregation of single silicate layers during the co-coagulating process. The content of bound rubber of SBR–clay nanocompound is more than that of the corresponding rubber filled with micrometer clay or silica because of the increased networking of silicate layers with the nano-meter dispersion and the high aspect ratio. The glass transition temperature of SBR–clay nanocomposites increased as compared with that of the pure SBR. The tensile strength of SBR–clay nanocomposite loading 20 phr clay was 6.0 times higher than that of the conventional SBR–clay composite. The gas permeability of separated rubber–clay nanocomposites containing 20 phr decreased 50% as compared with the corresponding gum vulcanizates.