Novel fabrication of high-modulus cellulose-based films by nanofibrillation under alkaline conditions

摘要

We herein propose a novel continuous process for fabricating high-modulus films based on cellulose nanofibers. In place of a dissolution process, the pulps were mechanically disintegrated into nanofibers by ball-milling in an 8% NaOH solution. NaOH treatment loosened the hydrogen bonding between the cellulose microfibrils in the pulps, and a highly concentrated suspension (8%) of cellulose nanofibers with a uniform diameter of approximately 20-50 nm was prepared after ball-milling for 90 min. The resulting nanofiber suspensions prepared in the NaOH solution exhibited the crystal forms of both Cellulose I and Cellulose II, although the Cellulose II content gradually increased upon increasing the milling time. Finally, hydrogels were formed following neutralization of the suspensions, and the hydrogel sheets were hot-pressed into thin films at 120 degrees C. The Young's moduli of the films were significantly higher than those of typical regenerated cellulose films due to the presence of some remaining Cellulose I and a high crystallinity.