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Improving the Characterisation of Samples Showing Edge Fracture - .PDF file.

Improving the characterisation of samples showing edge fracture

When characterising the rheological properties of a sample, a number of external influences need to be taken into consideration, such as temperature and pressure. Furthermore, sample-specific properties must be taken into account when choosing a suitable measuring geometry and defining a measuring regime, in order to avoid any misinterpretation of the measuring results. For example wall-slip effects and shear banding but also turbulent flow may result in erroneous measuring results.

A main limitation for characterising polymer melts and concentrated polymer solutions at large deformation and/or high shear rates is known as edge fracture. This kind of sample instability is characterised by a deformation of the sample’s surface at the free edges between the upper and lower part of the geometry.

Furthermore, secondary flow effects may develop within the sample at the edge. Deformation of the surface and secondary flow propagate 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 pre-setting large deformations 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.

How to reduce the influence of edge fracture in measurements?
In an experiment from Anton Paar, a measuring system consisting of a cone and a partitioned plate has been recommended.

Click on the link above to download the Application Report and to learn about the results of this experiment.

Anton Paar Ltd

Anton Paar develops, produces and distributes highly accurate laboratory instruments and process measuring systems, and provides custom-tailored automation and robotic solutions.

Anton Paar develops, produces and distributes highly accurate laboratory instruments and process measuring systems, and provides custom-tailored automation and robotic solutions.

It is the world leader in the measurement of density, concentration and CO2 and in the field of Rheometry. Other areas of specialty are: Viscometry, Polarimetry, Refractometry, Microwave Sample Preparation & Synthesis, Chemical and Mechanical Surface and Nanostructure Analysis.

With over 2200 employees at the headquarters in Graz (Austria) and the 25 sales subsidiaries worldwide, Anton Paar ensure that their products live up to their excellent reputation. The core competence of the company – high-precision production – and close contact to the scientific community form the basis for the quality of Anton Paar’s instruments.

A strong sales network in more than 110 countries guarantees customers rapid support and answers to their application and service queries.

Innovation is the basis for progress and every year Anton Paar invests more than 20 percent of the annual turnover in R&D.

Anton Paar Limited, a subsidiary of Anton Paar GmbH, provides sales, application support and service to users across the UK and Ireland.

With an office in St Albans (UK) and Dublin (Ireland) and a team of over 30 dedicated employees, Anton Paar Limited aims to provide first-class service at every stage in the customer relationship, ensuring our products live up to their excellent reputation.

Anton Paar Ltd
Unit F, The Courtyard
St Albans
AL4 0LA
UK

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