Characterization of Nanofibrillated Cellulose Produced by Different Methods from Cabbage Outer Leaves
2018
Khukutapan, Donnapa | Chiewchan, Naphaporn | Devahastin, Sakamon
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 °C 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 × 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 δ in the range of 0.12 to 0.13; the suspension exhibited a similar behavior to that prepared by the conventional chemical pretreatment method. PRACTICAL APPLICATION: NFC could be produced from cabbage outer leaves, which are an abundantly available by‐product of a vegetable processing plant, via the combined hydrothermal and mechanical pretreatment without the use of any chemicals. This chemical‐free preparation process is highly desirable as it leaves no residues in the product and causes no chemical waste that needs to be treated. Cabbage‐based NFC also exhibits similar characteristics to that prepared via a chemically treated route.
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