Utility of Condenser Pick-Up in Some Rheometers

Abstract

Applications of condenser pick-up for rheometers in measuring displacement were studied.(1) By a condenser pick-up very large angular displacements (±70°) were easily measured and recorded. It was found that the amplitude dependence of logarithmic decrement of non-Newtonian polyelectrolyte solutions in free damping oscillation apparatus was very small. However, the samples which seemed to have very weak thixotropic structures evidently revealed the amplitude dependence of viscoelasticity, and the dependence, in general, became more and more obvious with decrease in frequency of oscillation.(2) The vertical oscillation of the rod in a so-called electromagnetic transducer were easily detected by a condenser pick-up, and the viscoelasticity of liquid materials in the audiofrequency range were measured electrically with no experimental difficulty as was often experienced in the transducer method. The viscoelasticity in this modified rheometer was calculated in the method as was described above.(3) A short comment on the creep and its recovery behaviors in concentrated polyelectrolyte solutions was described, where large shear deformations were also recorded by a condenser pick-up.