THE MULTIPASS RHEOMETER

This article describes the technical performance and initial results f or a new, two-piston, ''multipass rheometer.'' Fluid is contained with in a capillary by two servo-hydraulically controlled pistons. Both ste ady flow and oscillatory data can be obtained from the device with mea n pressure as an independent adjustable variable. Steady and oscillato ry data are presented for a silicone oil and a viscoelastic solution a nd certain data are compared with results obtained from a Rheometrics RDS-II mechanical spectrometer or with literature data. The results sh ow that the multipass rheometer is capable of extending the experiment al ranges of many conventional rheometers, particularly in terms of pr essure control, high shear rates, and multiple, successive flow measur ements. (C) 1995 Society of Rheology.