A comparative study on viscosity behavior of water-soluble chemically modified guar gum derivatives with different functional lateral groups

A comparative study was carried out on the viscosity behavior of three new water-soluble chemically modified guar gum derivatives with different functional lateral groups, including O-carboxymethyl-O-hydroxypropyl guar gum (CMHPG), with anionic character, O-2-hydroxy-3(trimethylammonio)propyl guar gum (HTPG), with cationic character, and O-carboxymethyl-O-2hydroxy-3-(trirnethylammonio)propyl guar (CMHTPG), with amphoteric character. It was found that the shear rate, concentration, temperature, added salt and surfactant affected the viscosity properties of these new guar gum derivatives in aqueous solutions. Regardless of the functional lateral groups, all sample solutions behaved as non-Newtonian shear-thinning fluids, and their viscosity increased with the increase in their concentration but decreased with the increase in temperature. Aqueous CMHTPG solution had the strongest shear-thinning property, and aqueous CMHPG solution investigated had the greatest viscous flow activation energy. In contrast to cationic HTPG or anionic CMHPG, amphoteric CMHTPG had an enhanced viscosity property in aqueous salt solutions, exhibiting an unusual anti-polyelectrolyte viscosity behavior. The addition of sodium dodecylsulfate was found to result in a decrease in the viscosity of aqueous HTPG solution and an increase in the viscosity of aqueous CMHPG solution or CMHTPG solution. (c) 2005 Society of Chemical Industry.