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Rheological properties of partially hydrolyzed ethylene–vinyl acetate copolymers

Authors

  • Mihailo Jacovic,

    1. Materials Research Laboratory, Polymer Science and Engineering, University of Massachusetts, Amherst, Massachusetts 01002
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    • On leave from the University of Beograd, Beograd, Yugoslavia.

  • Muneki Yamada,

    1. Materials Research Laboratory, Polymer Science and Engineering, University of Massachusetts, Amherst, Massachusetts 01002
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    • On leave from the Composite Research and Development Center of Toyo Seikan and Kohan Companies.

  • William J. Macknight,

    1. Materials Research Laboratory, Polymer Science and Engineering, University of Massachusetts, Amherst, Massachusetts 01002
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  • Roger S. Porter

    1. Materials Research Laboratory, Polymer Science and Engineering, University of Massachusetts, Amherst, Massachusetts 01002
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Abstract

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.

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