Effects of rubber/filler interactions on the structural development and mechanical properties of NBR/silica composites

Abstract

AbstractA study was carried out on the effects of interactions between nitrile–butadiene rubber (NBR) and silica on the developments of agglomerates by silica particles and of bound rubber in NBR/silica composites. The mechanical properties of the composites were also investigated in relation to the structure development. Transmission infrared spectra revealed the existence of hydrogen bonding between nitrile groups in NBR and silanol groups on the silica surface. The number of hydrogen bonds increased with the increasing nitrile group content of NBR. Transmission electron microscopy observations and thermal analysis revealed that the averaged size of agglomerates in composites decreased, and simultaneously the amount of filler–gel in silica‐filled NBR decreased with increasing nitrile group content of NBR. These results suggest that the hydrogen bonding between nitrile groups and silanol groups suppresses the development of agglomerates by silica particles, that is, the dispersion of silica is improved by the hydrogen bonding. At a given nitrile group content of NBR, the storage modulus and the initial slope of stress–strain curves for vulcanized composites increased with increasing the amount of filler–gel. Further, at a larger strain, the composites showed a clear pseudo‐yielding point on the stress–strain curves, with this tendency more prominent in the larger agglomerate size. These results suggest that the mechanical properties for NBR/silica composites are affected by the content of filler–gel. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 74–81, 2005