In this report, a new nanocomposite based on chitosan/polyvinyl alcohol/nanocrystalline cellulose (Cts/PVA/NCC) was synthesized. The morphology and particle size of NCC and nanocomposites were studied by scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis and Fourier transform infrared (FT-IR) spectroscopy. According to XRD results, the size of NCC was found to be at the range of 15 - 17 nm. SEM images showed the rod-like shape of NCC whiskers. Finally, biodegradation and swelling studies were performed on Cts/PVA/NCC nanocomposites.
Nanostructures are produced from nanofillers which are dispersed in a polymer matrix. Incorporation of small amounts of nanometer-sized fillers can yield composites with enhanced properties earnestly required for many industrial and technological applications [
The materials used in this study, consist of Whatman No. 1 filter paper as a precourser for NCC, acetic acid (analytical purity), Sulfuric acid (98%) for acidic hydrolysis, PVA and low-molecular-weight Chitosan as matrices, which were obtained from Merk (Darmstadt, Germany) Company Inc.
The NCC was obtained via acidic hydrolysis using traditional method. A Whatman No. 1 filter paper (98% α-cellulose, 80% crystallinity) was chopped and transferred into 70 ml of deionized water and blended by a (10 Speed Osterizer) Blender to turn a pulp. The pulp was filtered by a Buchner Funnel under vaccume filtration. Then 40 ml Sulfuric acid (98%) was added dropwise to the solution under vigorous stirring at 45˚C until the slurry turned to a milky mixture for about 2 hours. After dilution with 200 ml of cold deionized water, the mixture was subjected to five washing/centrifugation cycles using a centrifuge apparatus (14,000 g, 15 min, Eppendorf, Germany). When pH was reached to about 4 - 5, the fine cellulose particles were dispersed into aqueous supernatant. The residue containing NCC, was then filtered.
Cts/PVA/NCC was prepared using traditional method. 1 g Cts was dissolved in 100 ml acetic acid (0.1 M) and stirred for 6 hours at room temperature. Then the solution was filtered in order to remove undissolved materials. PVA was dissolved in 20 ml of hot distilled water under constant stirring and then added to Cts solution followed by stirring for 2 hours. Various weight ratios of NCC (0, 5, 10 and 15% w/w) were added directly into Cts/PVA solution and then stirred for 24 hours. The mixtures were casted into petri dishes and placed in an air- convection oven at 60˚C for 12 hours. The average thickness of every prepared film was about 1 mm.
FT-IR spectroscopy was used to confirm that a reaction was occurred between PVA, Cts and NCC. The IR spectra of PVA/Cts/NCC films were recorded using a Bruker Optics Ft Tensor 27, Germany Instrument. FTIR spectra of cellulosic samples were recorded in the range of 400 - 4000 cm−1 by the resolution of 4 cm−1. The samples were grounded into powder, mixed with KBr and then converted into thin pellets.
An X-ray diffractometer (X Pert Prompd, Phillips, Netherlands) was used to investigate the crystallinity of nanocellulose. Milled sample powder was analyzed using a Cu-Kα (λ = 1.54 angstrom) analyser. The angle of incidence was varied from 4˚ to 80˚ by the step of 0.02˚ and at the rate of 3˚/min at 40 kV and 30 mA. The Segal method was used to calculate the sample crystallinity, using the height of the 2 0 0 peak (I2 0 0, 2θ = 22.93˚) and the lowest height between the 2 0 0 and 1 1 0 peaks (IAM, 2θ = 18˚). I2 0 0 represents both crystalline and amorphous regions while IAM represents amorphous material only.
Scanning electron microscopy (SEM) photographs of the samples were captured using (Hitachi S4160, Germany) electron microscope. The samples were coated with gold using sputtering technique. Scanning electron microscopy (SEM) was used to investigate the morphology of different types of films.
First the films were dried at 40˚C for 12 hours in an incubator and then weighed. Dried films were then immersed in distilled water for 1, 2, 4 and 8 hours. Wet weight of the films was measured after removing them from water and obliterating the surface adsorbed water. Then films were weighed immediately [
in which, S is the percentage of water adsorption of films at equilibrium state, ws and wd are the weights (in grams) of samples in swollen and dried states, respectively.
Biodegradation property of different PVA/Cts/NCC films was determined by exposing the samples to compost mud. In this study, the degradation of films was evaluated by measurement of their weight loss, which refers to erosion of the molecules from solid phase to aqueous phase. The dissolved components were easily degraded by micro organisms in a natural environment.
FT-IR spectra of NCC and the nanocomposites were shown in
The crystallinity of NCC was calculated to be 81.5% from Segal Method. This value was in the range of published values 86.7% for commercial microfibrillated cellulose (MFC). Pure Cts was shown two peaks at 2θ of 9.37˚, 19.56˚ and a broad peak appearing at 2θ values in the range 19˚ - 28˚ was generally pertinent to the polymeric PANi chains. The peaks at 2θ values of 7.12˚ for MMT and 6.09˚ for MMT/Cts were also observed. As shown in
where k = 0.94, λ = 0.154056 nm and β is the full width at half maximum (FWHM) in radians. The prepared NCC had rectangular shape with average dimensions of 15.7 nm. The above experimental observations were indicated that NCC belonged to semi-crystalline polymer, which were contained crystalline and amorphous regions. Accordingly, the above results were demonstrated that the hydrolysis was taken place in the amorphous region. This increase of crystallinity after acidic treatment has been reported by several authors [
The morphology of Cts/PVA/NCC nanocomposites was assigned using SEM. Scanning electron micrographs of the nanocomposite films with different contents of NCC were shown in
The weight loss in biodegradation of Cts/PVA and Cts/PVA/NCC films was shown in
Films | Weight loss (g) | |||
---|---|---|---|---|
1st day | 2nd day | 4th day | 5th day | |
Nanocomposite 0% | 0.16 | 0.12 | 0.11 | 0.09 |
Nanocomposite 5% | 0.21 | 0.23 | 0.13 | 0.07 |
Nanocomposite 10% | 0.32 | 0.30 | 0.15 | 0.03 |
Nanocomposite 15% | 0.40 | 0.33 | 0.19 | 0.02 |
In this research, NCC was synthesized from Whatmann No. 1 filter paper. Cts/PVA/NCC nanocomposites were prepared in different concentrations of NCC [5% (B), 10% (C) and 15% (D)]. Further studies should be focused on the investigation of other potential applications of NCC and its nanocomposites in combination with other polymers. NCCs which were isolated by sulfuric acid hydrolysis, were rod-like whiskers with an average size of about 15.7 nm observed by XRD analysis, and the crystallinity of NCC was about 81.5%. SEM images of NCC showed the dimensions of about 85 nm wide. NCC improved the barrier properties of Cts/PVA composite films via reduction of swelling property. Although, a comparison with related literature results showed that the nanocomposites which were investigated in this work were amongst the best materials reported so far, this approach appeared really promising for the design of a wide range of new related nanocomposites. Surface morphology of nanocomposite films revealed a homogeneous dispersion of NCC into the Cts/PVA matrix. The prepared Cts/ PVA/NCC films were biodegradable.
This research has been accomplished under financial support of the Department of Chemistry, Faculty of Science, and cordially laboratorial collaboration of our colleagues at the Department of Agronomy, Faculty of Agriculture, University of Zabol, which should be appreciated.
AlirezaSamzadeh-Kermani,NeginEsfandiary, (2016) Synthesis and Characterization of New Biodegradable Chitosan/Polyvinyl Alcohol/Cellulose Nanocomposite. Advances in Nanoparticles,05,18-26. doi: 10.4236/anp.2016.51003