Abstract
The production of polymer blends increases at a rate of about 13 percent/y. Most of the commercial blends are multiphase systems of complex morphology, determined by the thermodynamic properties of the components and the rheology. Since the diffusion rates are relatively low, the blends are seldom at equilibrium. In most cases, the blend products have properties imposed by the morphology, created by a particular combination of the thermal and deformational history. There are three main reasons for studying the melt flow of blends: optimization of the processing conditions, search for the appropriate means to generate the desired morphology, and the interest in the basic study of the rheology of these complex systems.
In this paper the results published during the last five years are reviewed. The data for polymer blends are compared with those obtained for simpler model systems: liquid mixtures, emulsions, and polymer blends. From the rheological point of view, the blends are divided into three groups: those where viscosity shows positive deviation from the log‐additivity rule, PDB, those where the opposite effect is observed, NDB, and the remaining mixed‐behavior systems, PNDB. To PDB belong the miscible blends and those with strong inter‐domain interactions. To NDB belong those where the interactions are weak. To PNDB belong the blends in which there is a concentration‐dependent transition of structure. The shear dependent properties of blends are also discussed.