Enzymatic modification of cellulose nanofibers to enhance thermal resistance and to decrease hydrophilicity

Cellulose nanofibers (CNFs), which are crystalline cellulosic fibers 3–100 nm in width, are promising advanced materials. CNFs have attractive considerable attention due to their light weight, high strength, and large surface area. However, increasing thermal stability is a challenge in the application of CNFs. Generally, CNFs contain trace substances such as hemicellulose, which have a lower thermal degradation temperature than cellulose. Therefore, hemicellulose may decrease the thermal degradation temperature of CNFs. To increase the thermal stability of CNFs by removing hemicellulose, commercial CNFs were subjected to several cellulases and hemicellulases, and evaluated by thermogravimetric analysis. Our results showed that xylanase treatment for 1 h increased the pyrolysis temperature of the CNFs. Next, the basic sheet properties of enzyme-treated CNFs were investigated. The tensile strength of the CNF sheets decreased after enzymatic treatment, however, their contact angles increased. These results indicate that the hydrophilicity of the surfaces of the CNFs was decreased by biomass-degrading enzymatic treatment.