Journal of Materials Science and Chemical Engineering, 2013, 1, 49-52
http://dx.doi.org/10.4236/msce.2013.15010 Published Online October 2013 (http://www.scirp.org/journal/msce)
Homogeneous Isolation of Nanocellulos e from Cotton
Cellulose by High Pressure Homogenization
Yihong Wang1,2, Xiaoyi Wei1, Jihua Li1,3*, Fei Wang1, Qinghuang Wang1,3*, Lingxue Kong4
1Agriculture Products Processing Research Institute, Chinese Academy of
Tropical Agricultural Sciences, Zhanjiang, China
2College of Food Science and Technology of Huazhong Agricultural University, Wuhan, China
3National Center of Important Tropical Crops Engineering and Technology Research, Haikou, China
4Institute for Frontier Materials, Deakin University, Waurn Ponds, Vic, Australia
Received July 2013
ABSTRACT
Nano-cellulose materials are widely believed to have the potential to push polymer mechanical properties. The cotton
cellulose was dissolved in ionic liquid (1-butyl-3-methylimidazolium chloride ([Bmim]Cl)), and then was isolated by
high pressure homogenization in a homogeneous media. The nano-cellulose was obtained at 80 MPa for 30 cycles. The
geometry and microstructure of the cellulose nano-fibres were observed by SEM and their particle size analysis. FTIR,
XRD and TGA were used to characterize changes to chemical functionality. Particular emphasis is given to the physical
and chemical characterization of these nano-fibres together w ith their thermal stability and crystallinity, in order to de-
velop their suitability.
Keywords: Ionic Liquid; Particle Size; High Pressure Homogenization; Thermal Stability; Crystallin ity
1. Introduction
Science and technology continue to move toward re-
newable raw materials and more env ironmentally friend-
ly and sustainable resources and processes [2]. Cellulose,
as a whole is of growing importance in the development
and application of polymer materials, represents a pote n-
tially sustainable source to create fuels, chemicals, com-
posites, and a host of other products to replace fossil-
based products [8]. The nanomaterial landscape is vast,
which is widely believed to have the potential to push
polymer mechanical properties to extreme values [6].
Production of nanocellulose has different methods, such
as acid hydrolysis [9] alkali hydrolysis ball milling and
so on. And the weakness of these methods limit the de-
velopment.
Homogeneous isolation of nanocellulose by high pres-
sure homogenization is a new and comparatively green
method due to without pretreatment by adding catalytic
amount of sulfuric acid and cellulose solution under mild
condition [5].
We report the structural and physicochemical proper-
ties of the nanocellulose caused by the whole process,
using Four ier transform infrared (FT-IR) spectroscopy,
transmission electron microscopy, and XPS measure-
ments.
2. Experimental
2.1. Materials
Cotton cellulose was purchased by local factory in Zhan-
jiang, China. The ionic liquid 1-butyl-3-methylimidazo-
lium chloride ([Bmim]Cl) was synthesized according to
the previous work [4]. All other chemicals were of ana-
lytical grade, come from Guangzhou Chemical Reagent
Factory (Guangzhou, China).
2.2. Preparation of Nanocellulose
Cotton cellulose was pretreated by 1% (w/v) sodium hy-
droxyl solution to remove hemicellulose and lignin, re-
spectively. It was washed with distilled water until the
solution was neutral, and then air dried. Pretreated cotton
cellulose was dissolved in [Bmim]Cl by microwave
(Qpro-M, Questron Inc., Canada) heating until it formed
a clear and viscous solution after completely dissolved in
ILs. Then it was homogenized by a high pressure homo-
genizer (AH100D, ATS Engineering Inc., Canada) at
pressure levels ranging from 40 to 120 MPa and for up to
50 HPH cycles. Fin a lly, the regenerated SBC was dried
in a vacuum freeze drying equipment.
*Corresponding a uthor.

Y. H. WANG ET AL.
50
2.3. Characterization
2.3.1. TEM Analysis
The morphology of the nanocellulose was studied by
TEM (JEM-100, JEOL, Tokyo, Japan), operated at 100
keV.
2.3.2. Infrar ed Spectroscopy (IR) Analysis
The FTIR spectra of original cellulose, IL pretreated cel-
lulose and nanocellulose was measured in the range from
4000 to 400 cm−1 (Spectrum GX-1, PerkinElmer, USA).
2.3.3. Thermal Analysis
Thermal analysis measurements (TG) were carried out
with a Synchronous Thermal Analysis (STA449C/4/G,
Netzsch, Germany). Original cellulose, IL treated cellu-
lose, and nanocellulose were heated from 50˚C to 700˚C
at a heating rate of 10˚C min−1. Under a nitrogen atmos-
phere with a gas flow of 20 ml·min−1.
2.3.4. X-Ray Diffraction (XRD) Analysis
X-ray diffractometry in reflection mode was carried out
using a diffractometer (DLMAX-2550, Japan), with mo-
nochromatic Cu Kα radiation (λ = 0.15418 nm), gener-
ated at 40 kV and 40 mA , at room temperature. The
samples were scanned within 5.00 - 45.00˚ 2θ in step
mode with a step of 0.01˚ and a rate of 1 min−1. The
crystallite index of cellulose was calculated using the
kim’s empirical method [1].
3. Results and Discussion
Dissolution process was performed at 110˚C, 120˚C,
130˚C, 140˚C and 150˚C. As expected, the dissolution
time of cellulose decreased with increasing temperature.
However, the yield of cellulose always increased with
increasing temperature. Finally, we found experimentally
that the best solub ilisation could be achieved in 1% (g/g)
cellulose/[Bmim]Cl during 150˚C for 6mins at 400 W of
microwave.
The pretreated cotton cellulose was dissolved in
[Bmim] Cl to form a homogeneous solution. And the
mixed solution was passed through high pressure homo-
genizer to gain the nanocellulose. Considered the par ticle
sizes and economical factor, the optimum of HPH
process condition was at a pressure of 80MPa with 30
cycles.
3.1. TEM Analysis
The TEM micrograph of a dilute suspension of nanocel-
lulose was shown in Figure 1. The particles of nanocel-
lulose was about 20 nm. This result indicates that the
diameter of cellulose treated by HPH could be reached
on the scale of a nanometer.
3.2. Infrared S pectroscopy (IR) Anal ysis
FT-IR spectra of original cellulose, IL treated cellulose
and nanocellulose was carried out in Figure 2. We ob-
served between 3700 cm−1 and 3000 cm−1 corresponding
to O-H stretching, decrease and become broader after
treated with ILs, which can be correlated with a disrup-
tion of int ra-molecular and intermolecular hydrogen
bonds. The absorption band at 1452 cm−1 in cotton cel-
lulose, assigned to CH2 motion [11], became very weak
and shifted to a low wave number after treated with ILs
in different temperature , resp onding to the breaking of an
intra-molecular hydrogen bond involving O6 [13]. The
band at 880 cm−1 belongs to β-glucosidic bond, and the
absorption peak in regeneration cotton cellulose shifted
to a high wave number than the corresponding one in the
cotton cellulose, which is a characteristic of transition
from cellulose I to cellulose II [3].
Significantly, no difference was found between the
spectrum of nanocellulose and IL treated cellulose. The
result indicates that no other derivational reaction oc-
curred during the processes of dissolutio n and refining.
3.3. Thermal Analysis
The TGA and DTG curves of three kinds of cellulose
were shown in Figure 3. The onset decomposition tem-
perature of original cellulose was about 339˚C. Whereas
IL treated cellulose and homogenized cellulose was
Figure 1. TEM of nanocellulose.
5001000 1500 2000 2500 3000 3500
0
c
b
Transmittan ce(%)
Wavenumber(cm-1)
a
Figure 2. IR spectra of original cellulose (a), IL treated cel-
lulose (b) an d nan ocellulose (c).

Y. H. WANG ET AL.
51
326˚C and 286˚C respectively. It implied that the nano-
cellulose exhibited the lowest thermal stability. Possible
explain was that crystal region between cellulose were
destroyed in the process.
3.4. X-Ray Diffraction (XRD) Analysis
The X-ray diffraction patterns of original cellulose, IL
treated cellulose as well as nanocellulose was shown in
Figure 4. shown in ˚C. The diffraction peaks on about
10 20 30 40
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
c
b
Inst ensi ty
2θ
a
Figure 3. X-ray diffraction patterns of original cellulose (a),
IL treated cellulose (b) and nanocellulose (c).
100 200 300 400 500 600 700
0
20
40
60
80
100
c
b
Ma ss(%)
Temperature(°C)
a
100 200 300 400 500 600 700
- 25
- 20
- 15
- 10
-5
0
5
c
b
DTG(%min )
Temperature(°C)
a
Figure 4. TG and DTG curves of original cellulose (a), IL
treated cellulose (b) and nanocellulose (c).
15.1˚ (11̅0), 16.9˚ (110), and 23.0˚ (200), confirmed that
only cellulose I was present in it [12]. During the disso-
lution process, the cellulose chains are separated and
became random [7], which are indicated by the crystal-
line form of regenerated cotton cellulose II [10]. The
crystallinity index of original cellulose, IL treated cellu-
lose and homogenized cellulose was 4 3.1%, 15 .8% and
14.66% respectively. The crystallinity index decreased
because the intermolecular and intra-molecular h ydrogen
bonds of cellulose were broken by ionic liquids and HPH
[7]. It was suggested that the hydrogen bonds of cellulose
were broken, which cause the collapse of crystal struc-
ture duri n g the whole process .
4. Conclusion
The present work has demonstrated that nano-cellulose
could be prepared by high pressure homogenization.
Nanocellulose with dimension s o f 20 nm in diameter was
served under TEM. The FTIR spectra confirmed that the
basic structure of cellulose nanocrystals was maintained
and no derivative was formed. The nanocellulose had a
lower thermal stability and crystallinity index. These
results showed significant modifications in the structure
and the texture treated by HPH. A possible explanation
was that numbers of hydrogen bonds decreased by HPH.
The applications of n ano -ellulose will be explored .
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