Dr. Thomas Schweizer

Institute of Polymers, Department of Materials, ETH Zurich

Partitioned plate rheometry – do we make any progress?



Apart from Pollett’s early attempts in 1955, partitioned plate rheometry is now almost 30 years old. In this talk a brief history is sketched of the few instruments that have been built as stand-alone or as modifications of commercial rheometers. It is shown how N1 and N2 can be derived from the normal force signal(s), and which geometry is most favourable in terms of partial force weighting and shielding of the fracturing edge.
From the research at ETH Zurich, data for polystyrene melts and concentrated polystyrene solutions is shown in order to isolate the limits of the technique. Those limits are easier to see if experiments are faced to simulation data from a slip-link model (Jay Schieber, IIT) because the latter does not suffer from edge fracture and compliance. This model has been selected because of its ability to predict characteristic non-linear features (undershoot of the shear stress and N2 after the maximum, finite limit of N2/N1 at small shear rates) from a fit to LVE.
Nowadays partitioned plate geometries are commercialized by TA Instruments since 2013 for the ARES G2 and by Anton Paar since 2015 for the MCR702. In view of the experience with the prototype rheometers, a critical judgement is tried on how those devices can contribute to the advancement of the technique.

Date: 13/1/2016
Time:12:00 (coffee & cookies will be served at 00:00)
Place:FORTH Seminar Room 1