Effect of Pulp Concentration during Cellulase Pretreatment on Microfibrillated Cellulose and Its Film Properties

Pulp concentration was increased, during preparation of microfibrillated cellulose (MFC), in an effort to improve the efficiency of cellulase pretreatment. It was hypothesized that increased pulp concentration could possibly increase the interactions between cellulase and cellulose, therefore improving the cellulase pretreatment efficiency and benefiting MFC and its film properties. Results showed that higher pulp concentration enhanced the cellulase adsorption ratio from 70% to 90% for pulp concentrations of 2% and 10%, during the pretreatment process. While pulp concentration was changed from 2% to 10% during cellulase pretreatment, the specific area rose from 30.1 m/g to 35.5 m/g. Compared with the original eucalyptus pulp, the crystallinity degree of different pulp concentration was increased, presumably due to the enzymatic breakdown of amorphous cellulose. In addition, the aspect ratio of MFC rose from 19.1 to 35.5. Concurrently, MFC film properties showed better performance, as the elongation at break increased from 0.75% to 1.95%, tensile strength increased from 15.3 MPa to 33.5 MPa, and oxygen permeability coefficient decreased from 111×10 cm·cm/cm·s·Pa to 89.7×10 cm·cm/cm·s·Pa, reflecting the oxygen barrier properties of MFC film.