Effect of squeeze, homogenization, and freezing treatments on particle diameter and rheological properties of palygorskite

• Effect of mechanical treatment on rheological properties of palygorskite was studied.
• Squeeze, homogenization and freezing methods were employed to disperse palygorskite.
• Yield stress, shear modulus and association degree of suspensions were evaluated.
• Colloidal properties are related to dispersion and disruption of palygorskite rods.
• Strongly associated system is got by squeeze for 3 times and homogenization at 30 MPa.

The natural palygorskite exist as aggregates or bundles via weak electrostatic and van der Waals interactions. A new method for effective disaggregation of bundles was developed via freezing combined with squeeze and homogenization processes. In this work, the effects of squeeze, homogenization, and freezing treatments on particle size and rheological properties of palygorskite were investigated systematically by particle diameter distribution, steady shear, and linear oscillatory measurements. The influences of squeezing times, homogenization pressure, and freezing time on shear stress and shear modulus were studied in detail. The association capacity of rods in the obtained suspensions was discussed according to a power law of the form Y=kyCnY=kyCn. The correlation among the dispersion of palygorskite, the aspect ratio of the rods, and the rheological properties was discussed. The diameter distribution changed from 4.3 to 3.0 μm of natural palygorskite to 1.8 μm of sample squeezed for two times, frozen at −18 °C for 4 h, and homogenized at 10 MPa. The suspension with higher shear stress and shear modulus was obtained after squeezed for three times and homogenized at 30 MPa.

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