In situ silica filled natural rubber with a high silica content was prepared by using a solgel reaction of tetraethoxysilane in the rubber matrix. Uncross-linked in situ silica filled NR showed a high reinforcement effect and low hysteresis loss and residual strain comparing with those of uncross-linked carbon black or commercial silica VN-3 filled NR samples. Sulfur cross-linked in situ silica filled natural rubber with a high silica content was also prepared and its tensile properties and coefficient of kinetic friction were compared with those of sulfur cross-linked VN-3 silica filled natural rubber. The former showed a very unique tensile properties and slip behavior and it can be one of the candidates for an excellent sport rubbery material.

DESCENTE SPORTS SCIENCE Vol.30/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE