SHEAR AND BIAXIAL EXTENSION MEASUREMENTS OF REINFORCEMENT FROM INSITU PRECIPITATED SILICA

Elastomeric networks were prepared by tetrafunctionally end-linking hydroxyl-terminated polydimethylsiloxane (PDMS) chains and were then filled by the in-situ precipitation of silica. The resulting networks were investigated in shear and biaxial extension. The method employed to produce large shears was to stretch a short, wide strip between two clamps. The deformation produced in this way is pure shear; simple shear was calculated directly from the pure-shear data. Biaxial extension measurements were carried out by inflation of circular sheets of the networks. Compared to the unfilled networks, the silica-filled samples showed large reinforcing effects. Specifically, their values of the modulus, ultimate strength, and rupture energy increase significantly. The results thus indicate that the PDMS networks filled by the in-situ precipitation of silica have good mechanical properties, not only in uniaxial clongation, but in shear and biaxial extension as well.