Viscoelastic properties of hydrophilic polymers in aqueous dispersions

Rheological characterization of polymer solutions and polymer dispersions d eals with wide range of mechanical responses. Flow behaviour and especially the viscoelastic properties of aqueous dispersions of hydrophilic bio-poly mers: welan, gellan, and carboxymethyl cellulose were examined at low polym er concentrations. Different types of rheological responses were achieved b y varying polymer concentration and by preparing different mixtures of the polymers at various mutual ratios. Dispersions of polymer blends were prepa red at constant overall polymer concentration. These systems were prepared in order to study the influence of different structural conditions of the s amples on rheological properties. The transition from sol-to-gel behaviour was achieved by changing the polymer concentration, or by changing the comp osition at constant polymer concentration. The viscoelastic properties of t he systems were measured under non-destructive shear conditions of oscillat ory shear, by using the controlled stress rheometer. The analysis of experi mental data was performed by using the generalized Maxwell model and the Fr iedrich - Braun model for describing the mechanical spectra in linear visco elastic regime.