Isolation of Cellulose Nanowhiskers from Kenaf Fiber - Natural Polymers, Biopolymers, Biomaterials, and Their Composites, Blends, and IPNs - page 192

Figure 2. (a) Photo of raw fiber, (b) alkali treated fiber, and (c) bleached fiber.
Ftir spectroscopy
The efficiency of the chemical treatments on the fibers was studied by FTIR (Figure
3). The absorbance peak at 3,4003,300 cm -1 region and 1,6341,640 cm -1 were attrib-
uted to the stretching and bending vibrations, respectively, of the hydrogen bonding -
OH groups of cellulose, while those around 2,9002,800 cm -1 were due to the stretching
of C-H (Sain and Panthapulakkal, 2006). The prominent peak at 1,731 cm -1 that is seen
in the spectrum of raw fiber was assigned to the C=O stretching of the acetyl group
and uranic ester groups of the hemicelluloses or the ester linkage of carboxylic group
in the ferulic and p-coumeric acid of lignin and/or hemicelluloses (Rongji et al., 2009).
This peak disappeared completely in the spectrum of alkali treated fiber and bleached
fiber. Therefore, it showed that most of hemicelluloses and lignin were removed with
chemical treatment.
The peak at 1,250 cm -1 (Figure 3(a)) corresponds to the C-O stretching of the
aryl group in lignin which disappeared in other spectra due to the removal of lignin
after chemical treatment (Troedec et al., 2008). The peaks observed in the range of
1,4201,430 cm -1 and 1,3301,380 cm -1 in all spectra are attributed to the CH 2 symmetric
bending and the bending vibration of C-H and C-O groups of aromatic ring in polysac-
charides, respectively.
Figure 3. (a) FTIR spectra of raw kenaf fibre, (b) Alkali treated fiber, Bleached fiber (c), and cellulose
nano whiskers (d).