Estimates of apparent elongational viscosity using the fibre spinning and “pure” methods

A comparison is made between elongational properties predicted by the FENE-P dumbbell rheological equation of state for fibre spinning and true values obtained from pure elongation. True values are found by using a constant elongation rate in the model and calculating the steady state values of the stresses. Two new averaging procedures are suggested for extracting elongational properties from fibre spinning experiments. It is suggested that a variety of flow conditions be used and care be taken when determining these properties. The rheological model is found to predict adequately shear and elongational flow properties of the polyacrylamide-type of Boger or ideal elastic fluid.