Enzymatic modification of cellulose nanofibers to enhance thermal resistance and hydrophobicity

Cellulose nanofibers (CNFs), which is crystalline cellulosic fibers of 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 has 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, the contact angles of their sheets increased. These results indicate that the hydrophobicity of the surfaces of the CNFs was slightly increased by biomass-degrading enzymatic treatment.