Characterization of Nanofibrillated Cellulose Produced by Different Methods from Cabbage Outer Leaves

摘要

The potential use of cabbage outer leaves as a starting material for the production of nanofibrillated cellulose (NFC) was investigated. Chemical-free pretreatment methods, namely, autoclaving, ultrasonication (US), and high-shear homogenization (HS), were applied to remove noncellulosic components from cabbage cell walls prior to defibrillation, which was conducted by subjecting a pretreated sample to HS and then high-pressure homogenization. The sample undergone autoclaving at 130 ℃ for 2 hr was noted to contain a significantly higher cellulose content (36.5% dry mass) compared with the fresh leaves (12.48% dry mass). This led to an increase in the crystallinity index (CI) of the autoclaved cabbages from 30.8% to 50.7%. Further increase in the cellulose content (47.0% to 49.2% dry mass) was observed when subjecting the autoclaved sample to either US at 37 kHz for 1 hr, HS at 3800 x g for 15 min or HS followed by US at the aforementioned conditions. After pretreatment and defibrilllation, a suspension of NFC with the diameters of 4 to 50 nm was obtained, with the CI of 59.1% to 66.7%. Such a suspension exhibited a gel-like behavior with tan 8 in the range of 0.12 to 0.13; the suspension exhibited a similar behavior to that prepared by the conventional chemical pretreatment method.