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Capillary and slit flow behavior of concentrated solutions of a rod‐like polymer
Author(s) -
Kao C. H.,
Baird D. G.
Publication year - 1982
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.760220902
Subject(s) - materials science , rheometer , composite material , capillary action , rheology , shear rate , polymer , isotropy , newtonian fluid , shear flow , mechanics , optics , physics
This paper is concerned with the flow behavior of isotropic solutions of the rod‐like polymer, poly(p‐phenyleneterephthalamide) (PPT), in 100 percent sulfuric acid. Studies include entry flow visualization in a slit die and solution fracture, and die swell in capillaries and a slit die. It was observed that solutions of PPT exhibit nearly negligible die swell, a slip‐stick type of fracture that disappears at high shear rates, and radial entry flow patterns similar to Newtonian fluids. Fracture was associated with the plateau in the shear stress vs shear rate curve. Because values of the wall shear stress (τ w .) obtained from capillary measurements were in good agreement with those obtained from a cone‐and‐plate rheometer and values of the loss modulus ( G ″) obtained from small‐strain dynamic oscillatory measurements, it is believed that the rheological properties lead to the flow instability. These results are in agreement with the predictions of a recent theory by Doi and Edwards for concentrated solutions of rod‐like molecules. Data are also presented for a flexible chain polyamide, nylon 6,6, in 100 percent H 2 SO 4 for the purpose of comparing the flow characteristics of rigid and flexible chain polymers.