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Rheological properties of partially hydrolyzed ethylene–vinyl acetate copolymers
Author(s) -
Jacovic Mihailo,
Yamada Muneki,
Macknight William J.,
Porter Roger S.
Publication year - 1976
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/app.1976.070200515
Subject(s) - activation energy , rheology , copolymer , materials science , hydrolysis , polymer chemistry , shear rate , vinyl acetate , chemical engineering , ethylene , ethylene vinyl acetate , viscosity , vinyl alcohol , chemistry , organic chemistry , composite material , catalysis , engineering , polymer
Studies have been made of steady‐shear and dynamic viscosities for melts of two ethylene–vinyl acetate copolymers and their partially hydrolyzed derivatives using a Weissenberg rheogoniometer over the temperature range of 123–150°C with some tests at 160°C. The flow activation energy of all samples studied was essentially independent of shear stress. The introduction of hydroxyl groups in controlled concentrations, however, produced a complicated flow behavior. At low concentrations, there is a marked increase in Newtonian viscosity, flow activation energy, and shear dependence of viscosity. In contrast to previous reports, a further increase in all three functions was not observed with increasing vinyl alcohol concentration. Dynamic viscosities, in contrast, show monotonic increases with increasing hydroxyl group content, as do activation energies derived from the temperature dependence of the dynamic viscosity. These data may result from an increased chain cohesion due to hydrogen bonding of hydroxyl groups.