THE A1 PROJECT - AN OVERVIEW

A test fluid of polyisobutylene in decalin was prepared and sent to a number of laboratories around the world. A workshop was held in France to compare the results of experiments on this fluid in shear and extension. In steady shear flow, excellent agreement on values of apparent viscosity and first normal stress difference as functions of shear rate was obtained between the laboratories. The data were fitted to a Carreau-Yasuda equation at each temperature. Shift factors relating the data at any particular temperature to that at the reference temperature of 20-degrees-C were fitted to the Williams-Landel-Ferry (WLF) equation. Further good agreement was obtained between the laboratories on values of eta' and G' with frequency. Data on combined steady and oscillatory shear flow are presented. The results of several different types of elongational experiments are given, and the methods are compared. Agreement within classes of experiment was fair, and most experiments showed a similar trend in the variation of transient elongational viscosity as a function of strain rate. A number of other types of flow were presented at the workshop, and are discussed.