Non-Newtonian Flow and Fluid Elasticity of Pastes

Abstract

Non-Newtonian flow and fluid elasticity of Na-carboxymethyl cellulose, Na-alginate, methyl cellulose, hydroxyethyl cellulose and Na-carboxymethyl starch solutions were studied with the apparatus (double cylinder viscometer) described in the previous paper.
The experimental results are plotted as logσ_i-logγ_ia, logθ_e-logγ_ia, and logθ_e-logσ_irelationship, where σ_i and γ_ia are the shearing stress and the shearing rate at the inner cylinder surface respectively and θ_e is the angular displacement of the inner cylinder after the cessation of steady flow.
The slopes of the curves described above are employed to evaluate the non-linearity in viscoelastic properties of samples. In general, the slopes varies continuously or discontinuously with shearing rate or stress. These phenomena may be interpretted as a result of continuous or discontinuous shear break-down of secondary structures.
In Na-alginate which seemed to form little secondary structures, and in high consistency Na-carboxymethyl starch and gelatinized methylcellulose which seemed to contain a great deal of secondary structures, θ_e were comparatively small. Hence, it is plausible that there should be an optimum condition secondary structures in these fluids.
In carboxymethyl cellulose and carboxymethyl starch, non-linearity of viscoelasticity and the amount of elastic recovery (θ_e) were influenced profoundly by preparative conditions.