Published in Applied Rheology Nov/Dec 2000

MEASURING THE RHEOLOGY OF DIFFICULT MATERIALS

1. INTRODUCTION
An innovative rheometer capable of evaluating a wide range of materials was launched in 1999 following 3 years of development and field trials. This paper describes the instrument known as the FT3 Powder Rheometer from Freeman Technology and some of the potential applications.

The FT3 was designed to test complex semi-solids and particularly powders and granulated materials in order to meet the material characterising needs of many industrial processors. The design objectives were to consider methods of establishing flow patterns in materials that were not confined to a thin shear plane such as is commonly used in cone and disc viscometers or shear cells for evaluating powder characteristics. It was felt that the more complex flow patterns commonly found in materials processing, needed to be reproduced in a repeatable way whilst allowing the forces associated with this to be sensitively measured.

The usual definition of rheology includes the measurement of the forces needed to cause deformation and flow of a material. The FT3 principle establishes a particular flow pattern at a prescribed flow rate whilst measuring the forces necessary to do this