Biomedical Engineering Reference
In-Depth Information
out to bleach the fibers. The solution used in this treatment consisted of equal parts of
acetate buffer (a mix solution of 2.7g NaOH and 7.5 ml glacial acetic acid in 100 ml
distilled water), aqueous chlorite (1.7% w/v) and distilled water. The bleaching treat-
ment was performed at 130°C for 4 hr and 3 times, under mechanical stirring. The
bleached fiber were washed respectively by distilled water and subsequently air-dried.
Preparation of Cellulose Nanowhiskers
Colloidal suspension of cellulose whiskers in water prepared as described elsewhere
(Azizi Samir et al., 2004). Acid hydrolysis was done at 45°C with 65 wt% H 2 SO 4
(pre-heated), for 40 min, under mechanical stirring. The suspension was diluted with
ice cubes to stop the reaction and washed with water until neutrality before succes-
sive centrifugation at 10,000 rpm at 10°C for 10 min each step and dialyzed against
distilled water in the sequence. The dispersion of whiskers was completed by an ul-
trasonic treatment. The resulting suspension was subsequently stored in a refrigerator
after adding several drops of chloroform in order to avoid bacterial growth.
Characterization
Chemical Composition
Chemical compositions of fibers were estimated after various stages of chemical treat-
ment. α-cellulose content was calculated by further treating the cellulose fibers with
NaOH after the holocellulose content determination (ASTM D1103-55T and ASTM
D1104-56). The difference between the values of holocellulose and α-cellulose gives
the hemicelluloses content of the fiber. The lignin content was measured according to
ASTM D1106-56.
Fourier Transform Infrared (FTIR) Spectroscopy
The Fourier transform infrared (FT-IR) spectroscopy (Perkin-Elmer, GX Model) was
used to examine the changes in functional groups that may have been caused by the
treatments. The samples were ground and mixed with KBr. The resultant powder was
pressed into transparent pellets and analyzed in transmittance mode within the range
of 4000600 cm -1 .
Field Emission Scanning Electron Microscope (FESEM)
The morphology of fibers after each treatment was investigated by using field emis-
sion scanning electron microscopy (FESEM) Zeiss Supra 55VP model with the magni-
fication of 400x and all samples had been sputter-coated with gold to avoid changing.
X-Ray Diffraction Analysis (XRD)
The X-ray diffraction (XRD) measurements were performed on a Bruker AXS-D8
Advance model system. The diffracted intensity of Cu Kα radiation (0.154 nm, 40 kV
and 40 mA) was measured in a 2θ range between 10º and 70º. Ground kenaf fibers and
hydrolyzed cellulose sample were subjected to crystallinity analysis.
Termogravimetric Analysis (TGA)
The thermal stability of kenaf fibers after each treatment was characteraized using
Mettler Toledo, SDTA 851e model TGA under linear temperature conditions. The
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