Rheological behavior of aqueous suspensions containing cationic starch and aluminum magnesium hydrotalcite-like compound in the presence of different electrolytes

Abstract

The rheological properties of aqueous suspensions consisting of cationic starch (CS) and positively charged aluminum magnesium hydrotalcite-like compound (HTlc) in the presence of different electrolytes (NaCl, CaCl 2 and AlCl 3) were investigated. It is found that the network-like structure of pure CS solution is formed by the interaction between CS molecules. Both the equilibrium viscosities and the elastic response of CS solution decrease with the addition of NaCl, CaCl 2 and AlCl 3. Small amplitude sinusoidal oscillation tests show that a three-dimensional network of the HTlc/CS suspension can be formed through the bridge effect between CS molecules and HTlc particles due to the hydrogen bonding between the ether groups or hydroxyl groups of CS and the hydroxyl groups of HTlc. Both the equilibrium viscosity and dynamic property of the HTlc/CS suspensions indicate that the network-like structural strength of the suspensions increases firstly and then decreases with increasing HTlc content. The equilibrium viscosity and the elastic response of the HTlc/CS suspensions decrease gradually with the addition of NaCl or CaCl 2, but decrease firstly then increase and then decrease with increasing AlCl 3 concentration, i.e., the structural strength of the HTlc/CS suspensions can be strengthened by the addition of appropriate amount of AlCl 3 content.