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On the pressure dependency of the viscosity of molten polymers
Author(s) -
Kadijk S. E.,
Van Den Brule B. H. A. A.
Publication year - 1994
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.760342004
Subject(s) - materials science , viscosity , polymer , dependency (uml) , thermodynamics , polymer science , inherent viscosity , chemical engineering , composite material , intrinsic viscosity , engineering , systems engineering , physics
A slit viscometer to measure the viscosity of polymer melts under processing conditions is described. Along the slit a pressure drop is generated by applying a pressure at both the entrance and the exit. In this way the pressure in the center can be controlled independently of the shear rate. The pressure gradient in the slit is measured by means of three pressure transducers which are mounted in the region of fully developed flow. Results of pressure‐dependent viscosity measurements on polystyrene, polyacrylonitrile‐butadiene‐styrene, and polypropylene are presented in a shear rate range of five decades. The flow curves obtained at different pressures and temperatures can be shifted onto a master curve. The shear thinning behavior of the three materials is adequately described with the generalized Cross‐Carreau equation, while the zero shear viscosity is modeled with a generalized Arrhenius‐W.L.F. relationship, incorporating a pressure dependency. Alternatively, it is possible to describe the zero shear viscosity in terms of the free volume fraction and the temperature.