SILICA AND SILANE COUPLING AGENT FOR IN SITU REINFORCEMENT OF ACRYLONITRILE-BUTADIENE RUBBER

In situ silica reinforcernent for the acrylonotrile-butadiene rubber (NBR) vulcanizates, which were premixed with a cunventional silica (VN-3) and (gamma)-mercaptopropyltrimethoxysilaiie (gamma-MPSJ, was achieved by the sol-gel reaction of tetracihoxysilane (TEOS) using ethylenediamine. It was observed that the reinforcement efficiency tended to increase with the increase of mechanically premixed conventional silica. From the observations of transmission electron microscopy and scanning electron microscopy, the simultaneous use of VN-3 and gamma-MPS was found to promote the formation of large silica particles and clusters with a relatively good dispersion by the sol-gel reaction of TEOS mtheNBR vulcanizate. The results of hysteresis measurements supported this promotion. It was considered to he due to the surface modification of VN-3 by the sol-gel reaction of TEOS and the presence of gamma-MPS which worked as a dispersion agent for silica particles. The relationship between the mechanical properties and the morphology of the in situ silica tilled vulcanizaies is discussed.