الفهرس 
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Abstract
Poly(vinyl chloride) PVC, is one of the earliest industrial polymers, and its consumption of the total plastic product consumption is less than that of polyethylene but still ranks among the top five plastic products consumption rates. PVC is a thermoplastic material widely used in water pipes, medical equipment, food packaging, and toys because of its good mechanical properties as well as high chemical and abrasion resistance. PVC which presents in two basic forms, rigid (RPVC) and flexible one has also particular properties as easy modification, low production cost. So, it has become an important material in almost every aspect of modern-day life. PVC like other medical polymers are important in the treatment of diseases since they have a direct impact on patient’s health. Presence of medical polymers inside humans make these places for bacteria to adhere and breed. So, there is an increase interest to develop anti-infective medical polymers in the field of biomedical industry. Anti-infective properties of any medical polymer are usually attained by either impregnation or compounding with some well-known antimicrobial agents. In this work, chemical modification of PVC is mainly done to enhance its antimicrobial properties to be used in biomedical applications. The labile chlorine atoms present in the PVC polymeric chains were partially utilized for chemical modification through their reaction with some Schiff base derivatives through its addition on the imine group of the Schiff base. The chemical structure of the obtained Schiff base modified PVC samples was characterized their antimicrobial activity was evaluated. Some Schiff base derivatives modified PVC nanocomposites were prepared also for antimicrobial evaluation.
The present thesis comprises three chapters.
Chapter 1: Literature survey for PVC synthesis, properties and its various applications in some industrial and biomedical fields.
Chapter 2: Experimental involved materials, techniques, procedures, and characterization of the prepared compounds.
Chapter 3: Results and discussion included preparation of some Schiff base derivatives that resulting from the reaction of either aniline or its derivatives with some aromatic aldehydes. Furthermore, chemical modifications of PVC with the prepared Schiff base derivatives were performed, characterized and their antimicrobial properties have been investigated. Some Schiff base derivatives modified PVC silver nanocomposites have been prepared, their morphological investigation was performed in terms of scanning and transmission electron microscopic analysis and finally their antimicrobial activity was examined.
The experimental part can be summarized in terms of the following topics:
1- Preparation of Schiff base derivative
Schiff base derivatives were prepared by the reaction of aniline and/or its derivatives p-hydroxy aniline, p-chloroaniline and p-methoxyaniline with some aromatic aldehydes as salicylaldehyde, anisaldehyde, p-chlorobenzaldehyde, p-nitrobenzaldehyde, p-aminobenzaldehyde and 2,5-dimethoxybenzaldehyde. Chemical structures of the all prepared Schiff base derivatives were confirmed using elemental analysis as well as FTIR and 1HNMR spectroscopy. Antimicrobial activity of these derivatives was evaluated.
- Schiff base derivatives based on aniline
Schiff base derivatives of this series was obtained by the reaction of aniline with the previously named aromatic aldehydes to obtain derivatives SB1-SB6.
SB1: X=OH, Y, Z = H; SB2: X, Z = H, Y= OCH3; SB3: X, Z = H, Y=Cl; SB4: X, Z = H, Y=NO2; SB5: X, Z = H, Y=NH2; SB6: X, Z= OCH3, Y=H
- Schiff base derivatives based on p-hydroxyaniline
Schiff base derivatives of this series was obtained by the reaction of p-hydroxyaniline with the previously named aromatic aldehydes to obtain derivatives SB7-SB12.
SB7: X=OH, Y, Z = H; SB8: X, Z = H, Y= OCH3; SB9: X, Z = H, Y=Cl; SB10: X, Z = H, Y=NO2; SB11: X, Z = H, Y=NH2; SB12: X, Z= OCH3, Y=H
- Schiff base derivatives based on p-chloroaniline
This series of Schiff base derivatives are prepared by the reaction of p-chloroaniline and the applied aromatic aldehydes to get derivatives SB13-SB18
SB13: X=OH, Y, Z = H; SB14: X, Z = H, Y= OCH3; SB15: X, Z = H, Y=Cl; SB16: X, Z = H, Y=NO2; SB17: X, Z = H, Y=NH2, SB18: X, Z=OCH3;, Y= H
- Schiff base derivatives based on p-methoxyaniline
The last series of Schiff base derivatives are prepared by the reaction of p-methoxyaniline and the applied aromatic aldehydes to get derivatives SB19-SB24
SB19: X=OH, Y, Z = H; SB20: X, Z = H, Y= OCH3; SB21: X, Z = H, Y=Cl; SB22: X, Z = H, Y=NO2; SB23: X, Z = H, Y=NH2, SB24: X, Z=OCH3; Y= H
2- Preparation of Schiff bases modified PVC
1mol of each prepared Schiff base derivative was added to 4 mol of dissolved PVC in freshly distilled THF with stirring under reflux at 60°C for 6h. The reaction mixture was poured on cold methanol and the new modified polymeric solid material was filtered, washed with warm water and dried under vacuum to collect the Schiff-bases modified PVC.
Schiff bases modified PVC
3- Preparation of Schiff bases modified PVC/AgNPs
1 mol of each prepared Schiff base derivative was added to 4 mol of dissolved PVC in freshly distilled THF, refluxed for 2h, then 3% by weight of silver nitrate and an equimolar ratio of hydroxyl amine hydrochloride, as a reducing agent were added. The refluxing was continued at 60°C under stirring for another 6 h. The reaction mixture was poured on cold methanol; the new modified polymeric solid material containing AgNPs was collected, filtered, washed with warm water and dried under vacuum. Scanning and Transmission electron microscope (SEM and TEM) were applied to study the morphological structures of the prepared modified PVC nanocomposites and the investigation showed the homogeneity and the distribution of AgNPs in the polymeric substrate as well as the dimensions of the formed silver nanoparticles were determined. Antimicrobial activity of modified PVC loaded with AgNPs was evaluated against the microorganisms under investigation and the results showed improvement of the antimicrobial potential on incorporation of AgNPs into the polymeric substrate.
Concerning the original work, we can take the next summarized topics into consideration
1. Chemical modification of PVC using Schiff base derivatives based on aniline
This part concerns with the preparation and characterization of Schiff base derivatives to be used for PVC functionalization. Aniline and the previously mentioned aromatic aldehyde derivatives have been used to prepare Schiff bases (SB1-SB6) which in turn applied in chemical modifications of PVC to obtain the Schiff base modified PVC samples (PVC-SB1 to PVC-SB6) respectively.
• Elemental analysis, FTIR and 1HNMR were applied for both Schiff base derivatives and their corresponding modified PVC samples and the results are well matched and confirmed the chemical structures of the investigated compounds.
• Thermogravimetric analysis, TGA, were performed to illustrate the thermal stability of the prepared Schiff base derivatives modified PVC samples (PVC-SB1 to PVC-SB6) in comparison with that of the blank PVC sample and that stabilized with 2% by weight of the reference heat stabilizer (Ca-Zn stearate). It was found from the given theromograms that the investigated materials were characterized by high thermal stability when compared to the blank sample that stabilized with the reference heat stabilizer. It is observed also that the stabilizing efficiency of the investigated modified PVC samples was found to follow this order: PVC-SB6> PVC-SB2> PVC-SB5> PVC-SB1> PVC-SB4> PVC-SB3> PVC/A> PVC.
- Photostability of irradiated Schiff base modified PVC (PVC-SB1 to PVC-SB6)
- Weight loss of irradiated Schiff base modified PVC (PVC-SB1 to PVC-SB6)
Modified PVC samples of this part were subjected to UV irradiation and the results of the weight loss occurred upon UV exposure was taken as a function of the irradiation time. The results clearly show the low extent of weight loss of photodegraded Schiff base derivatives modified PVC in comparison with the weight loss of photodegraded blank PVC or PVC stabilized by the reference UV absorber used in this study, phenyl salicylate (salol). The stabilizing efficiency of the investigated modified PVC samples was found to follow this order: PVC-SB6> PVC-SB2> PVC-SB5> PVC-SB1> PVC-SB4> PVC-SB3> PVC/A> PVC. It was found that the modified PVC samples containing electron donating groups either in the aniline molecule or in the aldehyde one having higher photostability on UV exposure than that modified Schiff bases containing electron withdrawing substituent.
- Extent of discoloration of irradiated Schiff base modified PVC (PVC-SB1 to PVC-SB6)
The results showed that the degree of discoloration of modified PVC with Schiff bases is lower than that of both blank PVC and the stabilized sample with the reference UV absorber. The results also clarified that the extent of discoloration of modified PVC using SB6 Schiff base exhibited the lowest rate of color changes when compared to the other Schiff base modifiers and this agree well with obtained results of weight loss determinations.
- Antimicrobial activity of Schiff base modified PVC (PVC-SB1 to PVC-SB6)
Antimicrobial activities of the prepared Schiff base derivatives modified PVC were evaluated against four pathogenic bacteria, B. Subtilis and St. aureus as Gram +ve and two Gram –ve (E. coli and P. aeruginosa), in addition to C. albicans as a fungus using Ciprofloxacin and Nystatin as references antibacterial and antifungal drugs. The results showed that all the prepared compounds have good to high antibacterial activity against the two types of tested strains and the fungus under investigation in comparison with that nonmodified PVC and that of the standard antimicrobial agents. It is observed also that as well that the Schiff base derivatives modified PVC affected the Gram -ve bacterial strains more than that the Gram +ve ones. This may be due to the nature and the structure of the cell wall membranes of both types, since the Gram +ve bacteria is characterized by their thick wall than the other type. It was also found that the antibacterial activity is highly dependent on both physical and chemical properties of the substituents present in the Schiff base moiety that attached to PVC. Polarity and hence lipophilic nature, the power to donate or withdraw electrons of the substituent to the whole molecule are the main factors that affected the antibacterial potential of the compounds.
- Preparation of Schiff base derivative modified PVC silver nanoparticles (PVC-SB/AgNPs)
Chemical modification of PVC with the Schiff base derivatives (SB1 and SB6) that resulting from the reaction of aniline with salicylaldehyde and 2,5-dimethoxybenzaldehyde, in separate, in the presence of 3% by weight of AgNO3 and equimolar ratio of hydroxylamine hydrochloride as a reducing agent was carried out. Two modified samples of PVC silver nanocomposites (PVC-SB1/AgNPs and PVC-SB6/AgNPs) were performed for antimicrobial evaluation. SEM, TEM and EDX analysis were performed to study the morphology of the modified PVC silver nanocomposites. The SEM image for the surface of PVC-SB1/AgNPs shows a good degree of surface homogeneity for the polymeric matrix. Silver nanoparticles show a good distribution into the polymeric substrates without agglomeration. The TEM image of PVC-SB1/AgNPs showed that the AgNPs are formed in the polymeric substrate with intense dark colors with spherical shapes. The range of the determined diameters of the formed AgNPs are in the range of 8.06 and 12.23 nm. EDX spectrum of the PVC-SB1/AgNPs illustrates the presence of AgNPs that embedded in the polymeric substrate and the characteristic peak of AgNPs appeared at 3keV confirming the presence of the elemental silver in PVC substrate whereas the peak that related for the chlorine as a main constituent of PVC matrix appeared at 2.8 keV.
- Antimicrobial activity of Schiff base derivative modified PVC silver nanoparticles (PVC-SB/AgNPs)
The data of antibacterial efficiency of the examined modified PVC nanometal, PVC/SB1/AgNPs and PVC/SB6/AgNPs clearly showed that they have more inhibitory effect against the two types of the microorganisms under investigation than the corresponding modified PVC in absence of nanometal. This may be due to the role played by the AgNPs which is characterized by its high antibacterial activity. This antibacterial activity of silver may be due to its ability to entering the microbial cell, causing damage through its binding with the thiol groups (-SH) of the enzymes of microorganisms which can deactivate them or even causing microbial death.
2. Chemical modification of PVC using Schiff base derivatives based on p-hydroxyaniline
Some Schiff base derivatives, resulting from reaction of p-hydroxyaniline and the applied aromatic aldehydes, and their modified PVC samples (PVC-SB7 to PVC-SB12) were prepared.
- Elemental analysis, FTIR and 1HNMR were applied for Schiff base derivatives and their corresponding modified PVC samples and the results are well matched and confirmed the chemical structures of the investigated compounds.
- Thermal analysis of Schiff base derivatives modified PVC (PVC-SB7 to PVC-SB12)
Thermogravimetric analysis (TGA) of the Schiff base modified PVC samples (PVC-SB7-PVC-SB12) was carried out and the diagram showed the higher thermal stability of the prepared Schiff base derivatives modified PVC samples (PVC-SB7 to PVC-SB12) in comparison with that of the blank PVC sample and that stabilized with the reference heat stabilizer (Ca-Zn stearate).
- Photostability of irradiated Schiff base modified PVC (PVC-SB7 to PVC-SB12)
- Weight loss of irradiated Schiff base modified PVC (PVC-SB7 to PVC-SB12)
The results of weight loss of photodegraded Schiff base derivatives modified PVC (PVC-SB7 to PVC-SB12) in comparison with that of photodegraded blank PVC or PVC stabilized by the reference UV absorber indicated that the photostability of these investigated samples was found to follow this order: PVC-SB12> PVC-SB8> PVC-SB11> PVC-SB7> PVC-SB10> PVC-SB9> PVC/A> PVC. Again, the modified PVC samples containing electron donating groups either in the aniline molecule (the -OH group) or in the aldehyde one having higher photostability on UV exposure than that modified Schiff bases containing electron withdrawing substituent. So, these modified PVC samples are characterized by higher photostability than the previous series (PVC-SB1 to PVC-SB6) due to the presence of the electron donating hydroxy group of the aniline moiety of the Schiff base.
- Extent of discoloration of irradiated Schiff base modified PVC (PVC-SB7 to PVC-SB12)
The results showed that the degree of discoloration of modified PVC (PVC-SB7 to PVC-SB12) is lower than that of both blank PVC and the stabilized sample with the reference UV absorber. The results showed that the extent of discoloration of modified PVC using SB12 Schiff base exhibited the lowest rate of color changes when compared to the other Schiff base modifiers and this agree well with obtained results of weight loss determinations.
- Antimicrobial activity of Schiff base modified PVC (PVC-SB7 to PVC-SB12)
The results showed the higher antibacterial activity of all modified PVC samples against both types of bacteria with respect to the blank nonmodified one. Results of antifungal activity of the investigated samples are also indicated a relatively good activity for either the prepared Schiff bases or their modified PVC samples with respect to the reference drug. It is noticed that the antibacterial activity of the modified PVC samples of this series is relatively lower than that of series (PVC-SB1 to PVC-SB6). This may be due to the p-hydroxyaniline moiety of the Schiff base. The electron donation of the hydroxy group to the whole molecule may increase the electron density and then deactivate the antibacterial activity of the investigated series (PVC-SB7 to PVC-SB12).
- Preparation of Schiff base derivative modified PVC silver nanoparticles (PVC-SB/AgNPs)
Chemical modification of PVC with either of the prepared Schiff base derivatives that resulting from the reaction of p-hydroxyaniline with salicylaldehyde and 2,5-dimethoxybenzaldehyde separately, SB7 and SB12 respectively, in presence of 3% by weight of AgNO3 and equimolar ratio of hydroxylamine hydrochloride as a reducing agent to obtain (PVC-SB7/AgNPs and PVC-SB12/AgNPs). Morphological studies were carried out via SEM and TEM microscopy. SEM micrograph of PVC-SB7/AgNPs shows a good homogeneity for the polymeric matrix. Silver nanoparticles are shown to be uniformly distributed into the polymeric substrates with no agglomeration. TEM image of the same sample showed the presence of small spherical nanoparticles of Ag in the polymeric substrate with a slight intense in their colors. Diameters of the deposited nanoparticles are lying in the range of 1.74 and 2.80 nm. EDX spectrum of the PVC-SB7/AgNPs illustrates the presence of Ag that distributed and embedded in the polymeric matrix and the elemental silver appeared at 3keV. Antimicrobial investigation of the two modified PVC nanocomposite, PVC-SB7/AgNPs and PVC-SB12/AgNPs, samples was performed. These results exhibited higher antimicrobial efficiency of the formed modified PVC nanoparticles with respect to their samples in absence of AgNPs.
3. Chemical modification of PVC using Schiff base derivatives based on p-chloroaniline
Schiff bases based on p-chloroaniline that reacted with the aromatic aldehydes were prepared to use as modifiers for PVC and series of modified PVC (PVC-SB13 to PVC-SB18) were afforded.
- Elemental analysis, FTIR and 1HNMR were applied for Schiff base derivatives and their corresponding modified PVC samples and the results are well matched and confirmed the chemical structures of the investigated compounds.
- Thermal analysis of Schiff base derivatives modified PVC (PVC-SB13 to PVC-SB18)
Thermogravimetric analysis (TGA) of the Schiff base modified PVC samples (PVC-SB13-PVC-SB18) was carried out. The thermogram exhibited the higher thermal stability of the prepared Schiff base derivatives modified PVC samples (PVC-SB13 to PVC-SB18) in comparison with that of the blank PVC sample and that stabilized with the reference heat stabilizer (Ca-Zn stearate).
- Photostability of irradiated Schiff base modified PVC (PVC-SB13 to PVC-SB18)
- Weight loss of irradiated Schiff base modified PVC (PVC-SB13 to PVC-SB18)
The weight loss of photodegraded Schiff base derivatives modified PVC (PVC-SB13 to PVC-SB18) in comparison with that of photodegraded blank PVC or PVC stabilized by the reference UV absorber indicated that the photostability of these investigated samples was found to follow this order: PVC-SB18> PVC-SB14> PVC-SB17> PVC-SB13> PVC-SB16> PVC-SB15> PVC/A> PVC. Again, the modified PVC samples containing electron donating groups in the aldehyde moiety have higher photostability than that modified PVC containing electron withdrawing substituent. It is observed also that the photostability of modified PVC samples of this series are lower than that of the first one ((PVC-SB1 to PVC-SB6) due to the presence of the electron withdrawing chlorine atom of the aniline moiety of the Schiff base that may decrease the electron density on the whole molecule and then the stabilizing efficiency was decreased.
- Extent of discoloration of irradiated Schiff base modified PVC (PVC-SB13 to PVC-SB18)
It is noticed that the extent of discoloration of photodegraded Schiff-base modified PVC samples (PVC-SB13 to PVC-SB18) is lower than that of nonmodified sample and the stabilized with the reference UV absorber. The changes occurred in colors of photodegraded samples are agree well with the same direction of weight loss results.
- Antimicrobial activity of Schiff base modified PVC (PVC-SB13 to PVC-SB18)
The results of antibacterial activity of all modified PVC samples of this series showed the highest antibacterial activity among the other investigated series. The modified PVC samples PVC-SB15 and PVC-SB16 that containing chlorine atom and nitro-group in the para position of the aldehyde in addition to the p-chloroaniline molecule of the Schiff base showed a significant antibacterial activity among when compared to the other modified samples of this series. The presence of more than one of electron withdrawing substituents can easy decrease the electron density or in other words increase the net positive charge of the investigated compounds and this easily facilitates their attack of the negatively charged cell wall membrane of bacteria. This attack results in the damage of the DNA, disrupts the respiratory process and inhibits the growth or even death of the microorganism. The results also showed good antifungal activity of the examined modified PVC samples.
- Preparation of Schiff base derivative modified PVC silver nanoparticles (PVC/AgNPs)
Chemical modification of PVC with either of some prepared Schiff base derivatives that resulting from the reaction of p-chloroaniline with p-chlorobenzaldehyde (SB15) and aminobenzaldehyde (SB17), in separate, in the presence of 3% by weight of AgNO3 and equimolar ratio of hydroxylamine hydrochloride as a reducing agent to obtain (PVC-SB15/AgNPs and PVC-SB17/AgNPs). Morphological studies were carried out via SEM and TEM microscopy. The SEM micrograph for the surface of PVC-SB17/AgNPs showed a somewhat type of homogeneity for the polymeric matrix. Silver nanoparticles are shown to be distributed in a good way as light spots into the polymeric substrates, with a low extent of agglomeration. The TEM micrograph of the same sample demonstrated the formation of silver nanoparticles of in spherical forms with intense colors in the polymeric substrate and their diameters are in the range of 2.05 and 8.26 nm. EDX spectrum of the PVC-SB17/AgNPs confirmed the presence of Ag that embedded in the polymeric matrix and appeared at 3.1 keV. Antimicrobial investigation of the two modified PVC nanocomposite, PVC-SB15/AgNPs and PVC-SB17/AgNPs, samples was performed. The results exhibited higher antimicrobial efficiency of the formed modified PVC nanoparticles with respect to their samples in absence of AgNPs. This may be due to the role played by AgNPs with their high antibacterial activity.
4. Chemical modification of PVC using Schiff base derivatives based on p-methoxyaniline
Schiff bases based on p- methoxyaniline that reacted with the aromatic aldehydes were prepared to use as modifiers for PVC and series of modified PVC (PVC-SB19 to PVC-SB24) were afforded.
- Elemental analysis, FTIR and 1HNMR were applied for Schiff base derivatives and their corresponding modified PVC samples and the results are well matched and confirmed the chemical structures of the investigated compounds.
- Thermal analysis of Schiff base derivatives modified PVC (PVC-SB19 to PVC-SB24)
Thermogravimetric analysis (TGA) of the Schiff base modified PVC samples (PVC-SB19-PVC-SB24) was carried out. The results of TGA showed the higher thermal stability of the prepared Schiff base derivatives modified PVC samples in comparison with that of the blank PVC sample and that stabilized with the reference heat stabilizer (Ca-Zn stearate).
- Photostability of irradiated Schiff base modified PVC (PVC-SB19 to PVC-SB24)
- Weight loss of irradiated Schiff base modified PVC (PVC-SB19 to PVC-SB24)
The weight loss of photodegraded Schiff base derivatives modified PVC (PVC-SB19 to PVC-SB24) in comparison with that of photodegraded blank PVC or PVC stabilized by the reference UV absorber indicated that the photostability of these investigated samples was arranged as follows: PVC-SB24> PVC-SB20> PVC-SB23> PVC-SB19> PVC-SB21> PVC-SB22> PVC/A> PVC. The results showed that the modified PVC samples containing electron donating groups in the aldehyde moiety have higher photostability than that modified PVC containing electron withdrawing substituent. It is observed also that the photostability of modified PVC samples of this series have the highest photostability between the other three investigated series. this may be due to the increase of the electron donating power of the substituents by the presence of para methoxy group in aniline Schiff base molecule. This may lead to increase in the electron cloud or electron density which in turn can absorb more incident light which causes more protection for the polymeric substrate.
- Extent of discoloration of irradiated Schiff base modified PVC (PVC-SB19 to PVC-SB24)
It is noticed that this series is characterized with low extent of discoloration with respect to the other series and the changes occurred in colors of photodegraded modified PVC samples are matched well with the results of weight loss.
- Antimicrobial activity of Schiff base modified PVC (PVC-SB19 to PVC-SB24)
The results of antibacterial activity of all modified PVC samples of this series showed the lowest antibacterial activity among the other investigated series. The modified PVC samples PVC-SB24, PVC-SB20 and PVC-SB23 that containing electron donating substituents in addition to the para methoxy group of aniline have led to an increase to the net negative charge on the investigated molecules which consequently decrease the ability to attack the bacterial cell membrane. On contrary, the modified derivatives PVC-SB21 and PVC-SB22 showed higher antibacterial efficiency in this series.
- Preparation of Schiff base derivative modified PVC silver nanoparticles (PVC/AgNPs)
Chemical modification of PVC with either of some prepared Schiff base derivatives that resulting from the reaction of p-methoxyaniline with p-methoxybenzaldehyde (SB20) and aminobenzaldehyde (SB23), in separate, in the presence of 3% by weight of AgNO3 and equimolar ratio of hydroxylamine hydrochloride as a reducing agent to obtain the modified samples PVC-SB20/AgNPs and PVC-SB23/AgNPs. Regarding the morphological investigation of the PVC-SB23/AgNPs, the image of the SEM images showed silver metal nanoparticles as light spherical spots through the dark surface of PVC with a uniform distribution of AgNPs into the polymeric substrate. The TEM micrograph showed the AgNPs that are formed in spherical and regular shape with slightly different sizes. The particle sizes of the deposited nanoparticles are in the range of 2.83–9.37 nm. The data of EDX analysis of PVC-SB23/AgNPs showed that the characteristic peaks of Ag appeared around 3 keV with 5.09 % as an elemental composition or atomic percentage. Antibacterial of the two modified PVC nanocomposites was found to be higher than that in absence of AgNPs
- Mechanical properties of some Schiff base modified PVC samples
The mechanical properties of some Schiff base modified PVC samples were performed in presence of 20% by weight of the (DEHP) while these data of both blank rigid PVC (RPVC), PVC plasticized with 20% by weight of DEHP (PPVC) that industrially used for medical grade PVC were given for comparison. The results of the mechanical properties of the investigated samples showed that the elongation at break of Schiff-base modified PVC films was significantly higher than that of pure PVC which indicates that the presence of Schiff base derivatives as a main constituent of the PVC chains has good plasticizing properties for PVC. The results also showed the improved tensile strength and elongation at break on comparison with those of the blank one. Furthermore, the modulus of all samples increases as the % elongation increased from 50% to 200%, and this indicates the improvement of the mechanical properties of the investigated samples. This may be due to the presence of two phenyl rings in the Schiff base derivatives in addition to the functional group substituents in these rings. So, it could be concluded that the chemical structure can easily displace the polymeric chains far from each other and the larger the volume of the functional group substituents, the higher values of elongation and consequently the plasticity of the modified PVC samples. So, it can be said that the improvement of the mechanical properties of the modified PVC samples are dependent on nature and the chemical structure of the modifiers.
Finally, it could be said that the incorporation of some Schiff base derivatives as a main constituent of the PVC chains improved many of the desirable properties of this polymer. As shown from the given results that this modification gave rise to the enhancement of its thermal and photostability as well as mechanical properties. All modified PVC exhibited good antimicrobial efficiency against the microorganisms under investigations. So, Schiff base modified PVC is recommended to be used in some applications as packaging and some biomedical fields.