Properties of ZnO/SiO2 cross-linked butadiene-acrylonitrile rubber

Properties of novel core-shell elastomer filler were investigated. The filler comprised precipitated silica with zinc oxide surface modification (ZnO/SiO2) and was characterized by different surface properties, rheological properties on suspending in paraffin oil and oil number (dibutyl phthalate adsorption) as compared with unmodified silica. The ZnO/SiO2 systems (containing up to 20% ZnO) were used to fill and cross-link a carboxylated butadiene-acrylonitrile rubber (XNBR). Zinc oxide alone proved to be a less effective crosslinking agent as compared with ZnO modified silica. Vulcanizates received using the ZnO/SiO2 systems contained unconventional crosslink nodes disintegrating under ethylenediamine, chloroform and acetic acid treatment. IR spectra confirmed presence of interactions between rubber carboxyl groups and the crosslinking/filler systems investigated. Physical relaxation at ambient temperature confirmed influence of non-covalent crosslinks on stress dissipation in the vulcanizate. DMTA showed existence of a second maximum related with presence of ion cross-links in vulcanizates containing the modified silica. Elastomers cross-linked with the ZnO/SiO2 System had better mechanical properties than those cross-linked with dicumyl peroxide (Table 5).