Measurements of the Mechanical Properties of Polymer Solutions by Electromagnetic Transducers

A concentrated polymer solution is sheared by a rod oscillating axially with a very small amplitude in a closed tube. The rod is driven by a coil in a magnetic field; from electrical measurements on the coil, the mechanical resistance and reactance of the system are calculated by transducer relationships. Equations are given for obtaining the dynamic viscosity, η′, and rigidity, G′, of the solution. In the case of some polymer solutions, the audiofrequency range covered by the present apparatus falls in the dispersion zone where η′ and G′ change rapidly with frequency. In other cases the frequency range covered appears to be at the upper end of the dispersion zone; η′ is far smaller than the viscosity in steady flow, and G′ changes very little with frequency. The advantages and limitations of the method are discussed.