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The dependence of shear and elongational viscosity on the molecular weight of poly(vinylidene fluoride)
Author(s) -
Koizumi T.,
Usui S.
Publication year - 1999
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/(sici)1097-4628(19990404)71:14<2381::aid-app9>3.0.co;2-6
Subject(s) - capillary action , materials science , viscosity , shear (geology) , shear rate , shear flow , rheometer , polymer chemistry , thermodynamics , composite material , shear viscosity , rheology , physics
The dependence of shear and elongational viscosity on the molecular weight of poly(vinylidene fluoride) has been studied using a capillary rheometer. The elongational viscosity was evaluated based on Cogswell's method with two types of capillaries: capillary length ( L )/capillary diameter ( D ) = 10 mm/1 mm and L / D = 0 mm/1 mm. We used the ratio P 0 / P L that indicates the contribution of elongational flow to the total flow involving both the shear and elongational flows. P L and P 0 are the pressure losses in the capillary and the converging flows, respectively. P 0 / P L increased with molecular weight and shear rate. This corresponds to decreasing the number of entanglements of molecular chain under a large displacement, especially high shear. Thus, we suggest using P 0 / P L as the parameter of the entanglement interaction on the molecular chain under a large displacement. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 2381–2384, 1999