The rheological properties of aqueous suspensions containing cationic starch (CS) and positively charged aluminum magnesium hydrotalcite-like compound (Mg-Al HTlc) were investigated by steady shear and oscillatory shear experiments. In the range of pH tested, all of the suspensions exhibit shear-thinning behavior. The rheological fluctuation behavior was discovered in the suspensions, i.e., the apparent viscosity of the suspensions oscillated with time at a constant low shear rate after pre-shearing. The fluctuation mechanism is proposed in terms of the periodic transformation of CS molecular (chain) conformation. Because pH, interaction between HTlc and CS molecule and shear rate can affect the energy and frequency of transformation of CS molecular conformation, the oscillation amplitude and period can change with pH, HTlc content and shear rate.

Key words: aluminum magnesium hydrotalcite-like compound, cationic starch, suspensions, rheology, fluctuation