The instron rheometer
The rheometer is based on an original design by the Monsanto Chemical Co., for the study of flow properties of polymer melts. Shear rates over the range 101 to 106 reciprocal seconds are obtained by driving a plunger at constant rates through a barrel with interchangeable capillary tubes at the exit. The resulting shear stress is measured by the accurate load measuring system of the basic instrument.
Errors due to the length to diameter ratio of the capillaries, plunger friction, polymer compressibility, temperature rise due to friction and pressure drop in the barrel, are discussed and correction methods suggested.
Standard and special applications of the rheometer are discussed indicating that it can be used to determine factors other than apparent viscosity.