Influence of surface charge on viscosity behavior of cellulose microcrystal suspension

Abstract

Microcrystalline cellulose with minimal surface charge was prepared from softwood kraft pulp via hydrolysis by 4 N hydrochloric acid instead of sulfuric acid. To this material, sulfate ester groups as surface charge were introduced by treating with 55% (w/w) sulfuric acid. A treatment at 60°C for 2 h gave nearly the same level of surface charge as that of the H2SO4-hydrolyzed microcrystal. The number of sulfate groups were controlled by changing the H2SO4 treatment conditions. Although the microscopic size and shape of the microcrystalline particles were the same irrespective of the preparation method, the introduction of surface charge drastically reduced the viscosity and removed its time dependence. These changes in viscosity behavior are considered to result from charge-induced dispersion of loose aggregates existing in the initial charge-free microcrystals prepared by HCl hydrolysis. © The Japan Wood Research Society 1999.