Interpretation of Viscosity Data for Concentrated Polymer Solutions

An empirical viscosity vs concentration relation for concentrated polymer solutions is derived in terms of a simple free volume theory, and its applicability is tested with some available data for amorphous polymer+solvent systems. It is found that the derived relation fits well those data over the range of polymer concentrations so concentrated that interchain entanglements occur to form a weak network structure throughout the solution. In the region of relative low polymer concentrations, however, it shows deviation of a common feature from the experimental results. Two temperature-dependent parameters are contained in the viscosity equation derived; one is characteristic of the polymer species and the other is dependent upon the particular combination of polymer and diluent. These parameters are evaluated from comparisons with experimental data, and their variations with temperature are discussed.