Dispersibility in Water of Dried Nanocrystalline Cellulose

Abstract

Dispersibility is important for nanocrystalline cellulose (NCC) because recovering the unique suspension and particle properties is essential after the product has been dried for storage or transport. It is our goal to produce dried NCC that redisperses in water to yield colloidal suspensions without the use of additives or a large energy input. In contrast with the as-prepared acidic form of NCC (H-NCC), suspensions of neutral sodium-form NCC (Na-NCC) dried by evaporation, lyophilization, or spray-drying are readily dispersible in water. Suspension properties and NCC particle size determined by light scattering were used as indicators of dispersion quality. The neutral counterion content, drying technique, freezing action, drying and redispersion concentrations, and moisture content in the dried NCC were all found to influence dispersibility. When a minimum of 94% of the H⁺ counterion is exchanged for Na⁺, the neutral salt form is fully dispersible in water even when fully dried. Mild sonication is generally sufficient to recover measured particle sizes identical to those in the never-dried Na-NCC sample. A threshold moisture content of 4 wt % was found, above which dried H-NCC is fully dispersible in water.