Viktor Reim1, James P Eickhoff Jr.2, Gunther Arnold1, Jörg Läuger1 Anton Paar Germany GmbH, Ostfildern, Germany1, Anton Paar USA, Ashland, Virginia, USA2 Characterizing polymer melts at large deformations and/or high shear rates, is limited due to edge fracturing. This sample instability is characterized by a deformation of the sample surface at the free edges between upper and lower part of the geometry which propagates radially as a function of both time and applied deformation. Hence, edge fracture results in increasing measuring errors within standard cone-plate or plate-plate geometries when presetting large deformations and/or high shear rates. Consequently, the accuracy of start-up shear measurements and flow curves at high shear rates as well as for large-amplitude oscillatory shear (LAOS) measurements can be strongly influenced by edge fracture. In order to reduce the impact of edge fracture effects the use of a cone partitioned plate (CPP) has been recommended on several occasions [e.g.1-4]. Using this setup, the flow instabilities that arise at the edge of the CPP do not have an impact on the sample’s properties which are detected in the center of the sample only. Hence, the CPP reduces the effect of trimming and enables rotational and oscillatory measurements even at deformations which would result in an incomplete filling of the active measuring zone of conventional measuring geometries. The aim of the contribution is to highlight the difference in the measuring performance when using a CPP in comparison to conventional cone-plate or plate-plate geometries. [1] Meissner, J., Garbella, R.W., Hostettler, J. (1989). J Rheol 33, 843-864. [2] Schweizer, T. (2002). Rheol Acta 41, 337–344 [3] Schweizer, T. (2003). J Rheol 47, 1071-1085 [4] Snijkers, F., Vlassopoulos, D. (2011). J Rheol 55, 1167-1186.