AN OVERVIEW OF THE PROJECT Ml
The scope of the program was widened while the focus on extensional viscosity measurements was retained, and attempts were made to have the same measurements repeated using different techniques and instruments.
Abstract
One of the outstanding and well-recognized problems in the rheology of mobile systems is the measurement of extensional viscosity. Over the last two decades various techniques have been described to measure this property and specialist workshops have been conducted such as the recent one at Chamonix [l]. At this meeting it was soon apparent that the data from various instruments were significantly different partly because different fluids were utilized, and a pressing need for a cooperative measurement exercise on a single fluid was articulated. The response to this idea was encouraging, and it was decided that the program needed to be widened to allow as complete a characterization of a single fluid as possible. The importance of such data for the proper evaluation of extensional viscosity measurements hardly needs amplification. Furthermore, many constitutive equations have been proposed but less than adequately tested owing to the lack of such data. A proper evaluation of these theoretical approaches also requires a comprehensive collection of data on a single fluid. Parenthetically, we also note the utility of such data for teaching purposes. As a result of these considerations the scope of the program was widened while the focus on extensional viscosity measurements was retained. Additionally, attempts were made to have the same measurements repeated using different techniques and instruments. The comprehensive nature of the exercise immediately set constraints on the selection of the test fluid owing to widely different capabilities and limitations of different equipment [2]. A test fluid which could satisfy these sometimes conflicting constraints was prepared at Monash University (which, incidentally, led to the fluid’s being called Ml). It needs to be emphasized that Ml is a compromise and a different set of constraints could well allow a “better’ fluid to be chosen. The fluid was despatched to the participants during 1988. A preliminary meeting of some of the participants was held during the International Rheology Congress at Sydney. The program culminated in a workshop held at Combloux, France, during March 1989.