Viscoelastic Properties of Some Industrial Pastes by Electro-magnetic Transducer Method

Abstract

Dynamic viscosity η′ and dynamic shear modulus G′ of aqueous solutions of carboxymethyl cellulose, methylcellulose, carboxymethylstarch, Na-alginate and Na-polyacrylate were measured by transducer method at 100c/s. The following results were obtained.
1) Shear thixotropy and non-linearity of η′ and G′ were not observed.
2) In the concentration range of 0-3%, dependences of η′ and G′ on the concentration are very characteristic for each paste. By the slope of linear part of log G′-log C plot, contributions of intermolecular secondary bondings and molecular orientation under shear to G′ were discussed. It was considered that intermolecular networks contribute to G' most strongly in the case of methylcellulose which is a non-electrolyte and orientation entropy contributes most strongly in the case of Na-polyacrylate which has no OH group and has comparatively flexible long molecular chain.
3) The variation of G′ with the temperature is most obvious in methylcellulose and almost negligible in Na-polyacrylate. These phenomena lead to the same conclusion as described in 2).
4) In carbxymethylstarch and Na-alginate, the variation of η′ and G′ with pH are not parallel with that of steady state viscosity in low pH range.
5) In general, it seems that dynamic measurement of viscoelasticity of pastes will be a very sensitive method for detecting the minute variation of the state of a paste.