Physical and Mechanical Properties of Cellulose Nanofibril Films from Bleached Eucalyptus Pulp by Endoglucanase Treatment and Microfluidization

A GH5 hyperthermostable endoglucanase (Ph-GH5) from the archaeon Pyrococcus horikoshii and a commercial endoglucanase (FR) were used to treat bleached eucalyptus pulp (BEP) fibers to produce cellulose nanofibrils (CNF) and subsequently to CNF films. TEM imaging indicated that Ph-GH5 produced longer and more entangled CNF than FR with the same number of microfluidization passes. Physical and mechanical properties of CNF films were characterized. Optical opacity of CNF films from FR (10 mg/g) at 40 passes through the microfluidizer can be as low as 3.7 %, compared with 18.2 % from untreated BEP at the same number of passes. CNF films exhibited similar thermal stability with untreated BEP. Highest specific modulus of CNF films was also obtained from FR (10 mg/g), reaching 56 MNm/kg, approximately 271 % of the CNF films from untreated BEP at 40 passes through the microfluidizer. CNF film from Ph-GH5 (1 mg/g) at 40 passes provided the highest specific maximum tensile strength at 120 kNm/kg.