Error amplification in capillary viscometry of power law fluids with slip

Abstract Rheological characterization through capillary viscometry of molten polymers that slip at solid walls is quite a challenging task. In fact, it is based on an indirect measurement that introduces remarkable error amplifications, mainly because of the Mooney procedure. Sometimes these are so large that unphysical results are obtained. In this paper we study these issues analytically, using a particular power law fluid as a test model. Interestingly, it is found that there is dependence on the fluid characteristics, such as the shear thinning behavior. Two software programs are provided in the Mendeley Data Repository. One quantifies the error amplification, the other one can be used by interested researchers for properly designing the testing setup (e.g. the most convenient choice for the capillary diameters). In order to use the programs, though, the material constants of the fluid that is intended to be characterized must be known at least approximately.