A RHEOMETER FOR THE MEASUREMENT OF A HIGH-SHEAR MODULUS COVERING MORE THAN 7 DECADES OF FREQUENCY BELOW 50 KHZ

A new rheometer is described. It consists of a transducer unit supplied with an electric impedance analyzing unit. The transducer unit converts a mechanical impedance into an electrical impedance by the piezoelectric effect. A detailed quantitative analysis of the interaction between the sample and the transducer is given. The real and imaginary parts of the shear modulus of a viscoelastic sample can be found in the frequency range of 1 mHz-50 kHz, modulus range of 0.1 MPa-10 GPa, and the temperature range of 150-300 K. The sample volume is 0.3 cm(3) and the strain amplitude is exceedingly small. The small size of the transducer allows for good temperature control and equilibration. It has a simple construction based on inexpensive components. Results on the supercooled liquid 2-metyl-2,4-pentandiol at the glass transition obtained by the method are included. (C) 1995 American Institute of Physics.