Relationship between structures and rheological properties of plate-like particle suspensions

The structures and rheological properties of three different plate-like particle suspensions, i.e., organically-modified montmorillonite (OMMT), graphene oxide (GO) and Kaolinite (Kaolin) in silicone oil (SO), are explored. Since the interactions between plate-like particle and SO are different, the dispersion states of these particles in SO are different. OMMT particles disperse relatively well in SO, and small clusters exist in GO/SO suspensions, but larger aggregates are found in Kaolin/SO suspensions. Moreover, liquid-crystalline ordering structure is found in both OMMT/SO and GO/SO suspensions, while it is absent in Kaolin/SO suspensions. Negative normal stress differences (Delta N) are observed during shear in all three plate-like particle suspensions, however, the mechanisms of the negative Delta N might be different. It can be further inferred that the negative Delta N in OMMT/SO suspensions results from the tumbling and rotating motions of OMMT sheets, while for GO/SO or Kaolin/SO suspensions, the negative Delta N results from the vorticity alignment of large GO clusters and Kaolin aggregates. (C) 2015 Elsevier B.V. All rights reserved.