The rheological state of suspensions in varying the surface area of nano-silica particles and molecular weight of the poly(ethylene oxide) matrix
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The combined superimposing influences of the surface area of silica nano-particles and molecular weight of polyethylene oxide matrix on the rheological properties of suspensions have been studied. The parameters of both components varied over a wide range: the surface area of silica from 100 to 390 m2/g, molecular weight of poly(ethylene oxide) from 200 to 2 × 105 Da, and concentration of silica from 1 to 13 vol%. In all cases, silica formed aggregates in suspension with apparent diameters of 50 to 230 nm; the higher values were observed for particles with larger surface area. Low-concentration suspensions in an oligomer matrix showed a slight non-Newtonian behavior; the size of silica particles was a determining parameter. Increasing the silica concentration led to dilatancy at high shear stresses. There was a threshold in the concentration dependence of viscosity, beyond which gelation of suspensions occurred. Depending on the silica concentration and molecular weight of the polymeric matrix, the dispersions behaved more like typical colloidal suspensions in a low molecular weight matrix or viscoelastic polymer melts containing an amount of solid filler. An increase in molecular weight of the polymeric matrix resulted in competition between increase in viscosity, appearance of viscoelasticity, and finally the transition from the gel state of a suspension in viscous medium to an elastic fluid.
KeywordsSilica Poly(ethylene oxide) Yield stress Dilatancy Viscoelasticity Rheology Viscosity
This research was partially supported by the Council for Grants of the President of the Russian Federation (project no. MK-545.2017.3).
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Conflict of interest
The authors declare that they have no conflict of interest.
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