Viscoelastic behavior of polymer blends

There is a reciprocal relation between flow and structure in multiphase systems such as polymer blends or composites. For this reason characterization of these materials must be carried out under conditions which guarantee minimum modification of structure. Capillary rheometry is particularly ill suited as a test tool, but the small strain dynamic oscillatory method may provide the true material responses, Most frequently these are expressed as frequency, ω, dependent storage and loss shear moduli, G ′ and G ″, or real and imaginary viscosities, η′ = G ″/ω and η″ = G ′/ω. However, two other methods of data presentation seem to be more sensitive to melt structure. They are the Cole‐Cole plot of η″ vs. η′ and the relaxation spectrum. Frequently, both of them indicate a binomial response. Various mechanisms leading to such behavior will be discussed.