The Visco-elastic Properties of Network Structure II. Structural Viscosity

Abstract

Viscosity behaviors of concentrated polymer solution are treated by making use of the model of weak Gaussian network. If chain-breakage coefficient, i.e. the probability of breakage of a chain in the network is independent of elongation of the chain, such system shows the Newtonian flow. Proper choice of chain-breakage coefficient, for example, that of square well type, yields a typical rate dependence of viscosity; the larger the rate of shearing flow, λ, the smaller the value of viscosity coefficient, μ. The tensile viscosity, μ^*, is also considered, which in general increases with the rate of stretching, λ^*, for small values of the rate. The so-called Trouton’s formula, μ^*=3μ is satisfied only in the limit of zero values of rates λ and λ^*.