Effect of polyethylene oxide (PEO) and shear rate on rheological properties of bentonite clay

In this paper, the influence of polyethylene oxide (PEO) and shear rate on rheological properties of bentonite suspensions is studied. The model of Herschel–Bulkley which is used to fit the flow curves of the mixture which based on the bentonite-polyethylene oxide and the Generalized Kelvin–Voigt model has been successfully applied to fit the creep and recovery data and to analyze the viscoelastic properties of mixture. The addition of polyethylene oxide (PEO) in a concentration range between 0 and 2% in 4% of bentonite induces not only an increase of the yield stress and the consistency index of bentonite but also a decrease of the flow index of bentonite. It is also the addition of PEO between 0 and 2% to 4% that may cause an increase in the viscoelastic properties of bentonite. For constant shear rate applied on the 4% bentonite at the 20 °C in which a thixotropic behavior was observed and analyzed by using a modified model of Herschel–Bulkley a structural parameter λ is included in order to account for time dependent effect.