STUDY OF THE MECHANICAL PROPERTIES OF CELLULOSE/ ZrO2.nH2O
COMPOSITES
a
Daniella Regina Mulinari, b Herman Jacobus Cornelis Voorwals
c
Maria Lúcia Caetano Pinto da Silva, dMaria Odila Hilário Cioffi
a,b,d
Fatigue and Aeronautic Materials Research Group, Department of Materials and Technology
State University of São Paulo – UNESP. Av. Ariberto Pereira da Cunha, 333 CEP 12516-410
Guaratinguetá/ SP- Brazil
c
News Materials Group, Department of Chemical Engineering- /EEL/USP. Rodovia Lorena-Itajubá, Km
74,5 CEP 12600-000 Lorena/ SP- Brazil
danimulinari@dequi.faenquil.br
ABSTRACT
This work describe the preparation and characterization of cellulose/ hydrous zirconium oxide composites by conventional
precipitation method (PC) using cellulose from the sugarcane bagasse. The composites were prepared using an aqueous
ammonium solution as precipitating agent. The amount of zirconium oxychloride (2 grams and 3 grams) in the reactional
system was studied, to determine which cellulose/ hydrous zirconium oxide composite shows better incorporation of metallic
oxide on the surface cellulose. Furthermore, were characterized by X-ray diffractometry (XRD), surface area measurements
(BET) and scanning electron microscopy (SEM). The results showed that conventional precipitation method (PC) is a good
method to prepared and that these materials can be used as reinforce fibers for polymer matrix.
Keywords: sugarcane bagasse, hydrous zirconium oxide, composites, hybrid materials.
Introduction
Cellulose and its derivatives are frequently used to prepare composite materials since present many intrinsic
advantages, such as low cost, availability, biodegradability, and easy handling [1]. However, the polymer is relatively inert
because hydrous groups, which are responsible for the majority of the reactions with organic and inorganic reagents, are
involved in inter and intramolecular hydrogen bonding [2]. In the recent years, many procedures for the preparation of metal
oxide- coated cellulose fibers, Cell/ MxOy, have been described [3-6]. Depending on the nature of the metal oxide, have been
used for specific applications: TiO2 for enzyme immobilization [7], and retention and analysis of Cr(VI) [8], Al2O3 for
immobilization of ion- exchange polymer [9] and organofunctional groups for metal adsorption from ethanol solutions [10], and
Nb2O5 for cobalt(II) porphyrin immobilization and use as oxygen sensor [11].
The experimental methodology of the fiber- coating process varies depending on which form cellulose is used obtained:
as fiber or as membrane. In the fiber form, the treatment of cellulose with a precursor reagent can be made in aqueous or nonaqueous solvent. To prepare the membranes, cellulose acetate is normally used because it is very soluble in most of the
common organic solvents. Generally, two procedures are also used to coat the fibers in the membrane form: (a) Acetate
cellulose and the precursor reagents are dissolved in a non-aqueous solvent, molded as a membrane, and followed by the
phase- inversion process and (b) the previously prepared membrane is immersed in a solution of the precursor reagent
followed by its hydrolysis [12].
Borgo et al. [13] have shown that the modification of the cellulose with metallic oxide particles presented excellent
degree tack of oxides on the surface of the cellulose, becoming these attractive materials in diverse applications, such as:
adsorption of chemical species in solution.
Oxides structural transformations are related of the form as interact with the cellulose. Gushikem and Da Silva [14]
affirm that the interaction of the zirconium occurs by means of hydroxyl groups of the cellulose, which attribute to a character
covalent.
Gushikem and Da Silva [14] also affirm that the cellulose presents thermal stability up to 473 K, with a loss mass of 3%
until this temperature, due to absorbed humidity. It was noticed an alteration in the interval of the temperature 673 of 573 K,
resulted from heterolitics splits of the cellulosic chain linkings, in positions C (2,6), that are susceptible to the attack of metallic
oxide.
The zirconium oxide dispersed on cellulose acetate has been used to immobilize urease and glucose oxidase enzymes
[15]. Highly dispersed oxide in the membrane is an efficient phosphate adsorvent [16].
The literature reports the preparation of this type of composite using ammonia flow and commercial cellulose [13].
However, in this work some adaptations will be made to describe the method of literature, that was called conventional
precipitation (PC).
In the conventional precipitation method, the precipitating (ammoniac solution) is added to an acid solution of the
zirconium oxychoride, generating hydrous zirconium oxide.
Some techniques of analyses supply information about the modified materials as well as the pure materials. The
morphology of dispersed metallic oxide on the cellulose can be studied by x-ray diffractometry (XRD) and scanning electron
microscopy (SEM). The thermal stability of the composites can be studied by thermogravimetry (TG/ DTG) to determine the
loss mass in a certain interval of temperature.
The objective of this work is prepare and characterize modified cellulose from sugarcane bagasse coated hydrous
zirconium oxide, since this residue have been used as fiber reinforce of polymer matrix, it is possible use the composite in
structural application [17-19].
Experimental
2.1. Preparation of the bleached cellulose
The bleached cellulose was obtained by following way: the sugarcane bagasse was pretrated with 10% sulfuric acid
solution (reactor of 350 L at 120 ºC, 10 min), followed by centrifugation with the purpose of separating the rich pentosanes
solution. Extracted lignocellulosic fraction was deslignificated with 1% NaOH solution (reactor of 350 L at 100 ºC, 1 hour) being
obtained the crude pulpe and bleached with sodium chloride. Since the bleached cellulose dry in a store at 50 ºC, 12 hours
[20].
2.2. Preparation of the Hydrous Zirconium Oxide by Conventional Precipitation Method (PC)
-1
Five grams of zirconium oxychloride were dissolved in 100 mL of aqueous hydrochloric acid solution (0.5 mol.L ). The
precipitate was obtained adding an ammonium solution (1:3) at pH 10.0, under stirring, which was filtered , rinsed several
times with distilled water for the complete removal of chloride ions (negative silver nitrate test). Finally, the product was dried at
50 ºC for 20 hours.
2.3. Preparation of the Cellulose/ Hydrous Zirconium Oxide Composite by Conventional Precipitation Method (PC)
-1
Two grams of zirconium oxychloride were dissolved in 100 mL of aqueous hydrochloric acid solution (0.5 mol.L ) and
mixed with 5 g of bleached cellulose. This material was precipitate with ammonium solution (1:3) at pH 10.0 and under stirring.
The solid was filtered under vaccum, rinsed several times in distilled water for the complete removal of chloride ions (negative
test to silver nitrate). The product was dried at 50 ºC for 24 hours. The resulting composite was designated as Cell/ ZrO2.nH2O
(2 g) PC. The procedure was repeated using a variated amount of oxychloride in the reational system (3 g), and as a resulted
the composite was designated as Cell/ ZrO2.nH2O (3 g) PC.
2.4.Characterization of materials
Prepared materials were characterized by x-ray diffractometry (XRD), scanning electron microscopy (SEM) and surface
area measurements (BET).
X-ray diffractograms were obtained in a Rich Seifert diffractometer model ISO- DEBYFEX1001. The following
conditions were used to obtained the spectra: radiation CuKα, tension of 30 kV, current of 40 mA and 0.05 (2θ/ 5 s) scanning
from values of 2θ it enters 10 to 70 ºC.
Surface area measurements were obtained in a Quantachrome instrument model NOVA 1000 in nitrogen atmosphere,
followed by pre-treatment at 50 ºC for 3 hours of samples.
Micrographs were obtained in a scanning electron microscope LEO1450V using low vacuum, in backscattered
electrons for the cellulose and composites and secondary electrons for oxide. Samples were dispersed on a brass support and
fixed with a double face 3M tape.
Results
The hydrous zirconium oxide incorporated on the cellulose surface can be seen through of the analysis XDR. The x-ray
diffractogram of the cellulose shows characteristics of crystalline material, with intense peak (Figura 1A). Instead of the
hydrous zirconium oxide x-ray diffactogram shows characteristics amorphous material, without definited peaks (Figure 1B). As
expected, it was observed that coating cellulose with hydrous zirconium oxide, present a gradual reduction of the cristallinily,
which is attributed to the amorphous character of the hydrous zirconium oxide (Figure 1C). It also can be observed that
increasing the amount of ZrOCl2.8H2O in the reactional system decreasing the cristallinily (Figure 1D).
Figure 1. X-ray: (A) Bleached cellulose; (B) ZrO2.nH2O; (C) Cell/ ZrO2.nH2O (2g); (D) Cell/ ZrO2.nH2O (3g).
This results were confirmed by scanning electron microscope (SEM). The bleached cellulose micrograph (Figure 2A)
shows a great amount of fibres presents forms flattened, while the hydrous zirconium oxide (Figure 2B) presents as a little
porous agglomerate. The Figure 2C and 2D shows the hydrous zirconium oxide dispersed on the surface of the fibres
cellulose, however, it notices that the oxide was not deposited of form uniform on the surface fibres cellulose. As expected, it
was observed that an increase the oxide in the Cell/ZrO2.nH2O (3g) composite.
Figure 2. Micrographs: (A) Bleached cellulose; (B) ZrO2.nH2O; (C) Cell/ ZrO2.nH2O (2g); (D) Cell/ ZrO2.nH2O (3g).
This effect was confirmed from surface area measurements (BET). Comparing the analyses data of specific superficial
area of the ZrO2.nH2O with the Cell/ ZrO2.nH2O composites, it is observed that the ZrO2.nH2O presented higher superficial
areas that the materials indicated in Table 1. It was observed also an increase of the area measurement related to increasing
the amount of ZrOCl2.8H2O in the reactional system.
Table 1. Surface area measurements.
Material
Cellulose
ZrO2.nH2O
Cell/ ZrO2.nH2O (2g).
Cell/ ZrO2.nH2O (3g).
2
-1
Surface area (m .g )
0.6
253.7
36.1
57.2
For the future test, it is expected a higher mechanics strength material, which could be used as reinforce fibers for
polymer matrix [21-24].
Conclusions
The surface area measurements (BET) showed a best result for Cell/ ZrO2.nH2O (3g). This can be confirmed by
scanning electron microscope (SEM).
The X-ray diffractogram show that the Cell/ ZrO2.nH2O (2 and 3g) have a lesser cristallinity than the pure cellulose,
confirming presence of oxide in the cellulose surface.
We can say that the conventional precipitation method (PC) is a good method to prepared and that these materials can
be used as reinforcing fibres in polymer matrix polymers.
Acknowledgements
The authors express their acknowledgements to CNPq 310015/2006-5 process nº for the financial support.
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