Characterization of the viscoelastic behavior of complex fluids using the piezoelastic axial vibrator

The piezoelectric axial vibrator (PAV) is a squeeze-flow rheometer working at frequencies f between 1 and 4000 Hz. It can be used to measure the storage modulus G' and the loss modulus G '' of complex fluids in this frequency range. Using polymer solutions with known G' and G '' it is shown that the PAV gives reliable mechanical spectra for frequencies between 10 and 3000 Hz. The measurements done with the PAV are combined with a conventional mechanical rheometer (10(-3) <= f <= 15 Hz) and a set of torsional resonators (f = 13, 25, and 77 kHz) to obtain G' and G '' between 10(-3) Hz and 77 kHz. Using this combination we present the first analysis of the viscoelasticity of an aqueous suspension of thermosensitive latex particles in this range of frequency. It is demonstrated that the combination of the three devices gives the entire mechanical spectra without resort to the time-temperature superposition principle. (C) 2005 The Society of Rheology.