STUDIES OF GEL VISCOELASTICITY BY A WAVE INTERFERENCE TECHNIQUE

A new technique involving high-frequency shear wave interferometry has been used to investigate the viscoelastic properties of gels formed f rom aqueous dispersions of a synthetic hectorite-type clay colloid. Th e technique facilitates studies of stress relaxation phenomena under a range of strains and strain rates, in both linear and nonlinear defor mation regimes. Measurements of the group and phase velocities of freq uency-multiplexed shear waves, conducted in the presence and absence o f steady shear fields, provide visco elastic-solid-like relaxation spe ctra. Under shear, the relaxation spectra indicate a trend to fluidiza tion of the system as shear rate increases. A viscoelastic solid model is used to interpret the wave dispersion and the results, which const itute the first rheometrical exploitation of the 'beat' phenomenon, su pport conclusions drawn from light scattering and small-angle neutron scattering studies concerning the origin of viscoelasticity in this sy stem.