INSTRUMENT FOR MEASURING VISCOSITY AND SHEAR MODULUS UNDER STEADY SHEAR-STRESS

An instrument which can measure both shear modulus and viscosity under very low steady shear stress is described. Applicable shear stress fo r a torsion wire used was 1.02 X 10(-4) to 3.4 X 10(-3) N/m2. The meas urable ranges of the shear rate and viscosity are from 7 x 10(-1) to 6 x 10(-7) s-1 and 1.4 X 10(-4) to 6.0 X 10(3) Pa.s, respectively. By e xchanging the torsion wire, maximum shear stress can be increased to 1 .6 X 10(6) N/m2 and the measurable viscosity range is extended to 16 d ecades. Applicability of the instrument was tested for the thermo-reve rsible sol-gel transition of agarose solution, and the usefulness was confirmed. The minimum shear modulus measured here was 1.46 X 10(-5) N /m2.