IN-SITU FORMED SILICA PARTICLES IN RUBBER VULCANIZATE BY THE SOL-GEL METHOD

In situ silica filling of butadiene rubber (BR) was carried out by the sol-gel process using tetraethoxysilane (TEOS). BR was sulfur-cured, and the resultant crosslinked BR was subjected to soaking in TEOS at 3 0 degrees C for 48 h. The swollen vulcanizates were kept in the aqueou s solution of n-butylamine at 30 degrees C for 24 h, followed by stand ing at 50 degrees C for 72 h to conduct the in situ sol-gel reaction o f TEOS. The resultant vulcanizates contained silica particles which we re prepared by the in situ filling technique. They were subjected to t ensile and dynamic mechanical measurements, differential scanning calo rimetry and transmission electron microscopic observation. The in situ formed silica was dispersed homogeneously in the rubbery matrix. The size of in situ silica was influenced by the crosslinking density, pro bably because it was formed in the crosslinked rubber networks. Compar ed to the conventional silica-filled BR vulcanizate, which was prepare d by mechanical mixing of the silica particles, the new vulcanizates w ith the in situ formed silica showed better mechanical properties. (C) 1997 Elsevier Science Ltd.