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Shear stress at polymer/metal interface during melting in extrusion
Author(s) -
McClelland D. E.,
Chung C. I.
Publication year - 1983
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.760230209
Subject(s) - materials science , rheology , shear thinning , composite material , polymer , extrusion , viscosity , shear (geology) , atmospheric temperature range , thermodynamics , physics
Prediction of the screw horsepower requirement involves, among many others, the calculation of the shear stress (τ s ) between the solid polymer and the barrel surface during melting. Prediction of the solid bed down‐channel velocity also requires the calculation of τ s . However, the pseudoplastic nature and strong temperature dependence of melt viscosity make the mathematics of calculating τ s extremely difficult. As a first step of developing a reasonable mathematical model for calculating τ s , experimental measurements of τ s were made over a wide range of metal temperature and sliding speed for five commercial polymers using molded, block samples. Although dependences of τ s on metal temperature and sliding speed were found to have similar functionality to those of the dependences of melt viscosity on melt temperature and shear rate, this study showed that τ s could not be expressed as a sole function of the melt rheological properties. Our subsequent study, to be reported in a follow up paper, will show that τ s must be expressed as a function of the thermodynamic properties and melt density of the polymer as well as the melt rheological properties and the melting conditions.