الفهرس 
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Abstract
In the recent year’s significant progress has been achieved in the field of blending some natural polymers with and without synthetic polymers for various industrial applications from the environmental, health and safety points of view.
The blending process is one of the various methods which are used for improving physico-chemical and physico-mechanical properties and thermal stability of the blend from environmental and economic aspects.
In the present study we reported the preparation of a new series based on blending chitosan (CS) with poly vinyl alcohol (PVA) or with polyethylene glycol (PEG) in presence of nano-montmorillonite (MMT) or nano silica in different concentrations to get hybrid organic/inorganic nanocomposites of enhanced physico-mechanical and thermal properties and having biodegradable properties.
1. Preparation of chitosan / poly vinyl alcohol casted films (AB)
Chitosan solution (A) was added to PVA solution (B) in different ratios [70:30, 50:50, 30:70], the casted dry films of the different ratios of polymers blend named AB1, AB2 and AB3 respectively.
2. Preparation of hybrid chitosan-PVA/montmorillonite (MMT) nanocomposite films (C)
To a blends of (10 ml) chitosan solution (A) and (10ml) of PVA solution (B) was added different ratios [4%, 5% and 6%] ofnano MMT respectively, the three composite films named (C4, C5 and C6) were prepared for various testing and characterization experiments.
3. Preparation of hybrid chitosan -PVA / silica nanocomposite films (D):
To a blends of (10 ml) chitosan solution (A) and (10ml) of PVA solution (B) were added different ratios [4% and 6%] of nano silica respectively, the two composite films named (D4 and D6) were obtained.
4. Preparation of chitosan / poly ethylene glycol (PEG) films (AE):
Add from prepared chitosan solution (A) to PEG solution (E) in different ratios [70:30, 80:20, 90:10], the three hydrogel ratios are obtained AE1, AE2 and AE3.
5. Preparation of chitosan - polyethylene glycol /nano montmorillonite (nano MMT) blended films (F):
To (10 ml) of chitosan solution (A) add PEG solution (E) (10ml) then add nano MMT in different ratios [4%, 5% and 6%] respectively, the three blended films (F4, F5 and F6) are obtained respectively.
6. Preparation of chitosan -polyethylene glycol /nano silica blended films (G):
To solution of a mixture of chitosan solution (A) (10 ml) and PEG solution (E) (10 ml) add nano silica in different ratios [4%and 6%]. the two blended films (G4 and G6)are obtained respectively.
The casted films of chitosan, PVA, PEG and their hybrid composites with either nano montmorillonite or withnano silica were subjected for investigation using spectroscopic methods of analysis FT-IR, XRD and morphological properties using transmition electron microscope (TEM) in addition to thermal analysis via TGA and DSC. The mechanical properties were measured using tensile testing machine (tensile strength, elongation) and investigating the degradation properties of the hybrid composite films.
X-Ray diffraction
• The x-ray diffraction patterns are expressed as simply mixed patterns of chitosan and PVA with the same ratios as these for mechanical blending.
• The diffraction intensities of chitosan decreased with adding PVA and began to increase with increasing the content of PVA in the blends, however the crystal intensities of chitosan/PVA blends increased as the ratio of PVA increased.
• By adding nano MMT to chitosan/PVA blend, the intensity of chitosan decreased by increasing the content of nano MMT while the crystal intensity increase by decreasing nano MMT. The more crystallinity blend be;(chitosan/PVA (30:70)) and (chitosan -PVA /nano MMT 4%).
• By adding nano silica to chitosan/PVA, the intensity of chitosan decreased by increasing the content of nano silica while the crystal intensity increase by increasing nano silica so (CS- PVA/ nano silica 6%) is more crystal than CS itself.
• In case of adding PEG, the crystal peaks appear at intensity which decrease with increase PEG content in blends and the crystal intensity increase by decrease PEG content in blends so; (chitosan /PEG (70:30)) has a little bit crystallinity than CS itself.
• In cases of adding nano-MMT to chitosan/PEG blends, crystallinity decrease by increasing the content of nano MMT and the intensity decrease then began to increase by increasing nano MMT content in the blends so; (chitosan-PEG/nano-MMT4%) is more crystalline than CS itself.
• In case adding nano silica to chitosan/PEG, the intensity decrease by increasing the nano silica content and the crystal intensity decrease with increasing the nano silica content so; (chitosan -PEG/ nano silica 4%) is more crystalline than CS itself.
TEM analysis:
TEM analysis was carried out as a characterization method to evaluate the morphology of the nano MMT and nano silica. This technique can provide a representative perception of the morphology being analyzed. Therefore, the present study aims to take advantage of this technique to better understand the dispersion mechanisms of layered clays in polymer blend.
SEM analysis:
• The SEM micrographs of surfaces of chitosan, PVA and chitosan/PVA blended show that, chitosan film is smooth and homogeneous surface and also the pure PVA is homogeneous surface too. The surfaces of the blended films of chitosan and PVA are flat smooth homogeneous surface with no pores and have no interface layer. That homogeneous blends are due to the uniform distribution of CS and PVA molecules throughout the films and mostly the interactions of hydrogen bonds between the functional groups of the blended component (–OH and –NH2 groups in chitosan and –OH groups in PVA).
• By adding nano MMT, the SEM micrographs shows some straps, spherical and needles shapes by increasing the content of nano-MMT which due to the rearrangement of the elements in MMT with the blended films.
• Finally, by adding nano silica, the SEM micrographs shows that there was no evidence of any micro cracks on the surface of the CS/PVA blended films although the pores appeared to be larger in size and more numerous in presence of nano silica.
• With the addition of PEG, the surface structure changed markedly. When the PEG contents become higher, such as the case of the film with blend ratio of (70:30), besides the chitosan crystal structure, PEG spherulites could be also resolved. When the content of PEG decrease as in Figure 3.29 C, D and E and Figure 3.30 F, G and H became more spherical and spread out the surface. By adding nano MMT, that spherical shapes as shells which covered by nano MMT and became bigger than without adding nano MMT and ingatherings each other.
Thermal Analysis
Thermal stability for blends shows;(CS/PVA (50:50)) is more stable than CS itself, while, (CS- PVA/ nano MMT 4%) is more stable than CS itself and (CS- PVA/ nano silica 6%) increasing the content of nano silica lead to an increase in thermal stability more than CS itself.
DSC shows that; the enthalpy of the glass transition peak irregularly changed with increasing the concentration of PVA, adding nano MMT to CS/PVA decreases ΔH value with increasing the content of nano MMT and the glass transition is irregularly changed with the change of the content of nano MMT. In addition, the enthalpy change ΔH increases with increasing the content of Nano silica.
The thermograph of the Figures (3.33-3.42) shows the effect of the PVA, MMT and silica nanocomposites content on the stability of CS.
The TGA thermogram Figure (3.33) shows the thermal stability of different hydrogels 1- 5. is increased with increasing chitosan content so, the casted films(chitosan/ PVA (50:50) show higher thermal stability than chitosan itself.
Figure (3.34) shows the thermal stability of different hydrogels of chitosan, PVA and nano montmorillonite: The data show that addition of nano MMT decrease the thermal stability of the chitosan so, (chitosan-PVA/nano MMT 4%) is more stable than that of chitosan itself.
Figure (3.35) show that the addition of nano silica decrease the thermal stability of the chitosan casted film so, (CS-PVA/nano silica 4%) is more stable than that of chitosan itself.
Figure (3.36) the DSC for CS/PVA shows the intensity and enthalpy associated with exothermic crystalline peak increased with decreasing the PVA content in blended films, while its position is approximately unaffected. In addition, the glass transition peak irregularly changed with increasing the concentration of PVA in samples. These observations indicate that the compatibility between CS and PVA because of the presence of –OH, -NH2 in chitosan and –OH in PVA capable of forming hydrogen bond.
Figure (3.37) the DSC for CS/PVA hydrogel in presence of nano MMT shows the intensity and enthalpy associated with endothermic crystalline peak decrease by increasing the content of nano MMT and the glass transition is irregularly changed with the change of the content of nano MMT in samples.
Figure (3.38) show the DSC of the hydrogels of Chitosan-PVA/nano silica with different ratios.
the intensity and enthalpy associated with endothermic crystalline peak increase by increasing the content of nano silica and the glass transition is irregularly changed with the change of the content of nano MMT in samples.
In case of adding PEG, with the increase in the concentration of PEG, thermal stability increase more than chitosan itself CS/PEG (70:30) is more stable than chitosan itself and with the increase in the concentration of nano MMT, thermal stability decrease so CS-PEG/nano MMT 4% is more stable than chitosan itself.
DSC in case adding PEG shows that;All CS/PEG in ratios are possess Tg that is near to each other, the intensity and enthalpy associated with exothermic crystalline peak increased with decreasing the PEG content in blended films. In addition, the glass transition peak irregularly changed with increasing the concentration of PEG in samples.The thermograph of the Figures (3.39-3.42) shows the effect of the PEG, MMT and silica nanocomposites content on the stability of CS.
In Figure (3.39) TGA for CS/PEG shows by increasing the concentration of PEG, thermal stability increase more than chitosan itself.In Figure (3.40) TGA of CS- PEG/ nano MMT in different ratios show that with increasing the concentration of nano MMT the thermal stability decrease more than chitosan itself,Figure (3.41) DSC for CS/PEG shows by increasing the content of PEG, for CS/PEG (70:30) an exothermic glass transition peak observed irregularly changed while the intensity and enthalpy increased with decreasing the PEG content in blended films. These observations indicate that the compatibility between CS and PEG because of the presence of –OH, -NH2 in chitosan and –OH in PEG capable of forming hydrogen bond.
Figure (3.42) show the DSC for CS/PEG blends in presence of nano MMT 4% found that the glass transition is endothermic peak which irregularly changed while the intensity and enthalpy decrease with increasing the PEG content in blended films.
Mechanical Analysis
• The casted film of the blend of (CS/PVA (30:70) has high elongation and low strength,
• Adding nano MMT, the casted film of the hybrid composite (CS- PVA/ nano MMT 6%) has high elongation and low strength, while
• Adding nano Silica, the casted film of the hybrid composite (CS - PVA/ nano Silica 4%) has high values in both elongation and strength.
• With increasing MMT, an increase in elongation and decrease in the strength was obtained, while increasing of nano silica a decrease of both elongation and strength was occurred.
In case of casted films containing PEG, the mechanical properties showed that:
• The casted film of the blend of (CS/PEG (70:30) has high in both elongation and low strength,
• Adding nano MMT, the casted film of the hybrid composite (CS- PEG/ nano MMT 6%) has high elongation and high strength.
Degradation test:
from the data of biodegradability of chitosan and its blends and composites which were performed under soil burial for 3 weeks, as a possible solution to waste disposal problems through biological means because biodegradation offers an efficient or ‘green’ solution to tackle waste management. The results showed that all the samples are easy to get rid of in a secure manner and preserve the environment.