Flow properties of microcrystalline cellulose suspension prepared by acid treatment of native cellulose

• Published in: Colloids and surfaces. A, Physicochemical and engineering aspects Vol. 142; no. 1; pp. 75 - 82
• Main Authors: Araki, Jun, Wada, Masahisa, Kuga, Shigenori, Okano, Takeshi
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 30.11.1998
• Subjects: Acid treatment; Cellulose microcrystals; Rod-like particles; Surface charge; Thixotropy/anti-thixotropy; Acid treatment; Thixotropy/anti-thixotropy; Surface charge; Cellulose microcrystals; Rod-like particles
• ISSN: 0927-7757; 1873-4359
• DOI: 10.1016/S0927-7757(98)00404-X

The properties of cellulose microcrystals and their colloidal suspensions obtained by acid treatments of native cellulose have been investigated. Bleached softwood kraft pulp was treated with 65% (w/w) sulfuric acid or 4 N hydrochloric acid and the resulting particle morphology and flow properties of the aqueous suspensions were studied. Colloidal dispersion of the HCl-treated sample was obtained by more thorough removal of acid from the hydrolysate than in the case of H 2SO 4 treatment. The H 2SO 4-treated and HCl-treated samples had similar particle sizes and shapes when observed by electron microscopy. Conductometric titration of suspensions revealed that the H 2SO 4-treated sample had a surface charge of 84 m-equiv kg −1 dry material due to the introduction of sulfate groups, while that of the HCl-treated sample was undetectable. The H 2SO 4-treated suspension showed no time dependence in viscosity, while the HCl-treated suspension was thixotropic at concentrations >0.5% (w/v) and anti-thixotropic <0.3%. The inclination of the relative viscosity–concentration plot (Einstein coefficient) for the H 2SO 4- and HCl-treated suspensions were 135 and 1380, respectively. The former value, when used in Simha's equation for rod-like particle suspension, roughly corresponds to an axis ratio of 50 estimated from the micrographs.