Effect of storage conditions on cellulose nanocrystal stability
Cellulose nanocrystals (CNCs) have evolved from a laboratory curiosity to an industrial material manufactured at a scale of up to 1 ton/day. Such large quantities of CNCs will inevitably be stored for different lengths of time before shipping and use. The chemical and physical stability of CNCs during long-term storage under various conditions was monitored. As-produced acidic H-CNCs and neutral salt form Na-CNCs were stored at ambient temperature and at 4°C as never-dried suspensions, and as a freeze-dried solid in the case of Na-CNCs. A variety of parameters were measured at intervals during the storage period. The CNC sulfate half-ester content, the cellulose chain length, and the unique optical properties of CNC films were of particular interest. Changes in these parameters were analyzed to determine the kinetics of long-term CNC degradation and establish the shelf-life of CNCs under different storage conditions.