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Time of Solubility as a Function of PVA Content in PVA/S Blend Films at Different Temperatures in Water (A& B); and in Water/Ethanol (70/30, V/V) Mixture (C & D).
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Polyvinyl alcohol (PVA) was blended with starch (S) in presence of glacial acetic acid as crosslinking agent. The effect of blend ratio and molecular weight of PVA on the physical, thermal and mechanical properties of PVA/S blends were investigated using various techniques such as DSC, TGA, SEM, tensile strength, and solubility tests. Furthermore,...
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Context 1
... Glass transition temperature ( T g ) of samples were measured using differential scanning calorimetry (DSC) (NETZSCH DSC200PC), using aluminum crimped pans under N 2 -1 o o atmosphere at flow rate 20 mL min . The measurements were carried out between 25 C and 210 C at a heating rate of 10 o C.min -1 . Thermogravimetric analyses were performed using a Perkin – Elmer TG-7 analyzer. Film samples ranging o from 3-7 mg were placed in a platinum sample pan and heated from 25 to 900 C under N 2 atmosphere at a heating rate o -1 of 10 C.min . During the heating period, the weight loss and temperature difference were recorded as a function of temperature. The microstructure and miscibility of the prepared blends were also investigated by using scanning electron microscopy (SEM) (Carl-Ziess SMT, Oberkochen). The degree of solubility of the PVA/S blend films samples was carried out by measuring the weight of the films after o immersion in either water or in water/ethanol (v/v: 70/30) at different temperatures (20, 25, 30, 37, and 40 C) and compared with the weight of the dry films prior to immersion. The degree of solubility of the blend films was determined according to the following formula: % Solubility = [(m - m 0 ) / m] x 100 Where m and m 0 represent the weight of the films prior and after immersion, respectively. Biodegradation experiments of PVA/S blend films were carried out in a conventional soil placed in a plastic container. Two types of soils were used, a moist soil and a dry soil taken from the courtyard of the Faculty of Chemistry and Chemical Technology. The biodegradability of polymeric films was examined after burying them in moist and dry soils for 30 days. The reaction between PVA with and S was confirmed by FT-IR spectroscopy, as shown in Fig. 1. In Fig. 1a, the peaks appearing at 2955, 1264 and 668 and 1096 cm - 1 is attributed to the C – H stretching, C – H bending and C – O stretching - 1 bands of PVA, respectively. The broad absorption peak appearing at 3406 cm is related to the O-H stretching - 1 frequencies of PVA and water hydroxyl groups. The characteristic carbonyl group (C=O) band at 1708 cm is related to the residual acetate groups, remaining after the manufacture of PVA from the hydrolysis of polyvinyl acetate [26]. -1 After blending of PVA with S, the prepared PVA/S blend films showed a broad band around 3500-3100 cm which is attributed to the O – H stretching. The bands at 1240 and 1082 cm - 1 are attributed to the stretching vibration of C – O in C – O – H groups, and the band at 1020 cm - 1 is related to the C – O stretching vibration of C – O – C groups of the glucose unit in starch (Fig. 1, M1-M4). In addition, the characteristic absorption peak of the carbonyl group of acetic acid is observed at 1732 cm -1 , and the aliphatic C – H stretching vibration band appeared at 2937 cm -1 . Since the films were thoroughly washed with water to remove the unbound acetic acid, the presence of the carbonyl peak confirms the chemical linkages between PVA and starch in the presence of acetic acid, which promotes the -1 interaction between PVA and starch, as previously reported [27]. As shown in Figs. 1, the band around 1425 cm (C-H stretch) belongs to the spectrum of PVA. On the other hand, the absorption peaks appearing at 1425, 1373, and 845 cm are due to the starch only and this is an ideal reference frequency to monitor starch content in the films. As expected and in agreement with previously reported results by other authors [28], [29], PVA/S blend films showed a broad band -1 between 3550 and 3200 cm , which is related to the stretching band arising from the intermolecular hydrogen bonds between O-H groups of PVA and starch. The same behavior was reported by authors [30], when they studied FTIR spectroscopy of PVA, which chemically crosslinked with glutaraldehyde. The effect of PVA content on the transparency and appearance of the PVA/starch blend films was investigated. It was observed that the transparency and flexibility of PVA/S blend films increase by increasing PVA content in the blend. As previously reported [31], [32], the amylose and amylopectin ratio in the starch may affect the properties of starch-based products, forming brittle films due to the extensive interactions between starch chains through hydrogen bonding, electrostatic and hydrophobic interactions. Accordingly, the usual approach to enhance film-forming properties is to add a plasticizer. PVA is considered as a hydrophilic plasticizer that reduces starch chain-to-chain interaction. As a result, the increase of PVA ratio lowers the glass transition temperature of the starch, forming more flexible and soft films. Furthermore, it was found that glacial acetic acid breaks down the amylopectin and changes the structure and properties of the polymer [33]. The effect of molecular weight and content of PVA on solubility of the PVA/S blend films in either water or ethanol/water solution as a function of time is shown in (Fig. 2 A-D). It is obvious that the time of solubility of PVA/S blend films decreases as PVA ratio increase, which can be attributed to the hydroxyl groups present in PVA [34-38]. However, inter- and intra-molecular hydrogen bonds between the hydroxyl groups of PVA and starch enhance the solubility of PVA/S blend films in water. In addition, the residual acetate groups present in the partially hydrolyzed PVA have hydrophobic character, which hinder the inter- and intra-molecular hydrogen bonding between the adjacent hydroxyl groups, leading to higher solubility of blend films in water. Similar results were obtained, as expected, in a previously reported study [39], since water solubility increases in parallel with citric acid content in the blend. Generally, solubility of a material often can be predicted based on components of interactive energy, including dispersion force (van der Waals) and acid – base components, as well as hydrogen bonding characteristics [40, 34, 35]. On another hand, the solubility of a polymer in aqueous solution is dependent on various factors such as molecular weight, temperature or addition of a co-solvent or additive [41-44]. The solubility of PVA/S blend films decreases as Mw of PVA in the blends increases as a result of the interaction between the segments of the blends. For instance, PVA (31 10 3 g/mole)/S films containing 95 wt% of PVA (Fig. 2A) showed shortest time of solubility in water as compared to its counterpart containing the high molecular weight PVA (205 10 3 g/mole) (Fig. 2B). The blend films dipped in water at 20 o C showed longer time of solubility confirming the o formation of three-dimensional crosslinks [45]. However, the blends films that dipped in water at 40 C showed shorter time of solubility could be briefly explained by the crosslinks break when the films are heated to higher temperature [46], [47]. Furthermore, the higher the temperature, the shorter time of solubility of the film either in water or ethanol/water solution. However, the PVA/S blends had longer time of solubility in aqueous solution containing 30% alcohol as compared to that soluble in water, probably due to the more interaction between the starch and PVA in alcoholic solution than that in aqueous solution as shown in Fig. 2 C&D. DSC thermograms of the PVA/S blend films with different blend ratios of (PVA & S) and Mw of PVA (31x 10 & 3 205x 10 g/mole) is shown in (Fig. 3 A&B), and a summary of the DSC features is given in Table 1. It can be seen, there is only one T g in the DSC curves due the miscibility of blends. Such miscibility is attributed to the hydrogen bonding between PVA and S in the blends. The T g results agree well with the FT-IR data. The FT-IR data showed that the miscibility of the blends is associated with hydrogen bonding interactions between the hydroxyl groups of PVA and o o S. The DSC curves in Fig. 3A shows eutectic melt between an onset of 175 C and midpoint of 195.5 C of PVA (31x 3 o o 3 10 g/mole)/S blends and an onset of 182.5 C and midpoint of 197.5 C of PVA (205x 10 g/mole)/S blend films (Fig. 3 3 3B). It can be observed in Table 1 that the glass transition temperature ( T g ) of PVA (31x 10 g/mole and 205x 10 o g/mole) was 65.80 and 64.89 C respectively. In PVA/S blend films; T g was shifted to higher temperature with an increase of S content from 5% to 30%. This is attributed to the strong interaction among hydroxyl groups on PVA and starch chains. Similar results were reported when PVA was blended with S in presence of urea [21]. It should be noted that T g is independent on molecular weight of PVA, T g of the endothermic peaks from DSC of PVA 3 3 (31x 10 g/mole)/S blend films were found to be lower than that of PVA (205x 10 g/mole)/S blend films. These endothermic peaks were related to the dissolving of PVA crystals, which demonstrate solubility of blend films in water by increasing temperature. Thermal properties of the PVA/S blend films containing 70, 80, 90 and 95 wt % of PVA were studied by thermogravimetric analysis (TGA) and differential thermal analyses (DTA). The analyses were performed from 20oC to 850oC at 20oC/min heating rate in air oxygen atmosphere. Fig. 4 and Table 1, summarize the TGA results of the PVA/S blend films with different molecular weight of PVA. From Fig 4, it was not observed that the variations in weight loss o of pure PVA and different blend films occurred until 271 C. These results are in contrast with what is generally o reported in the literature [48], [49], where the weight losses of PVA/starch blend was observed at 120 C. This can be attributed to the role of acetic acid in the cross-linking reaction between PVA and S. Two weight losses are observed in the TGA curve as shown in Fig 4. The first weight loss (from 8.2 to 12.7%) occurs ◦ 3 3 between 271.77 and 278.72 C for PVA 31x10 g/mole, and PVA (31x10 g/mole)/S blend films, and (from 2.6 o 3 3 to11.1%) occurs between 275 and 296.01 C for PVA 205x 10 g/mole and ...
Context 2
... After blending of PVA with S, the prepared PVA/S blend films showed a broad band around 3500-3100 cm which is attributed to the O – H stretching. The bands at 1240 and 1082 cm - 1 are attributed to the stretching vibration of C – O in C – O – H groups, and the band at 1020 cm - 1 is related to the C – O stretching vibration of C – O – C groups of the glucose unit in starch (Fig. 1, M1-M4). In addition, the characteristic absorption peak of the carbonyl group of acetic acid is observed at 1732 cm -1 , and the aliphatic C – H stretching vibration band appeared at 2937 cm -1 . Since the films were thoroughly washed with water to remove the unbound acetic acid, the presence of the carbonyl peak confirms the chemical linkages between PVA and starch in the presence of acetic acid, which promotes the -1 interaction between PVA and starch, as previously reported [27]. As shown in Figs. 1, the band around 1425 cm (C-H stretch) belongs to the spectrum of PVA. On the other hand, the absorption peaks appearing at 1425, 1373, and 845 cm are due to the starch only and this is an ideal reference frequency to monitor starch content in the films. As expected and in agreement with previously reported results by other authors [28], [29], PVA/S blend films showed a broad band -1 between 3550 and 3200 cm , which is related to the stretching band arising from the intermolecular hydrogen bonds between O-H groups of PVA and starch. The same behavior was reported by authors [30], when they studied FTIR spectroscopy of PVA, which chemically crosslinked with glutaraldehyde. The effect of PVA content on the transparency and appearance of the PVA/starch blend films was investigated. It was observed that the transparency and flexibility of PVA/S blend films increase by increasing PVA content in the blend. As previously reported [31], [32], the amylose and amylopectin ratio in the starch may affect the properties of starch-based products, forming brittle films due to the extensive interactions between starch chains through hydrogen bonding, electrostatic and hydrophobic interactions. Accordingly, the usual approach to enhance film-forming properties is to add a plasticizer. PVA is considered as a hydrophilic plasticizer that reduces starch chain-to-chain interaction. As a result, the increase of PVA ratio lowers the glass transition temperature of the starch, forming more flexible and soft films. Furthermore, it was found that glacial acetic acid breaks down the amylopectin and changes the structure and properties of the polymer [33]. The effect of molecular weight and content of PVA on solubility of the PVA/S blend films in either water or ethanol/water solution as a function of time is shown in (Fig. 2 A-D). It is obvious that the time of solubility of PVA/S blend films decreases as PVA ratio increase, which can be attributed to the hydroxyl groups present in PVA [34-38]. However, inter- and intra-molecular hydrogen bonds between the hydroxyl groups of PVA and starch enhance the solubility of PVA/S blend films in water. In addition, the residual acetate groups present in the partially hydrolyzed PVA have hydrophobic character, which hinder the inter- and intra-molecular hydrogen bonding between the adjacent hydroxyl groups, leading to higher solubility of blend films in water. Similar results were obtained, as expected, in a previously reported study [39], since water solubility increases in parallel with citric acid content in the blend. Generally, solubility of a material often can be predicted based on components of interactive energy, including dispersion force (van der Waals) and acid – base components, as well as hydrogen bonding characteristics [40, 34, 35]. On another hand, the solubility of a polymer in aqueous solution is dependent on various factors such as molecular weight, temperature or addition of a co-solvent or additive [41-44]. The solubility of PVA/S blend films decreases as Mw of PVA in the blends increases as a result of the interaction between the segments of the blends. For instance, PVA (31 10 3 g/mole)/S films containing 95 wt% of PVA (Fig. 2A) showed shortest time of solubility in water as compared to its counterpart containing the high molecular weight PVA (205 10 3 g/mole) (Fig. 2B). The blend films dipped in water at 20 o C showed longer time of solubility confirming the o formation of three-dimensional crosslinks [45]. However, the blends films that dipped in water at 40 C showed shorter time of solubility could be briefly explained by the crosslinks break when the films are heated to higher temperature [46], [47]. Furthermore, the higher the temperature, the shorter time of solubility of the film either in water or ethanol/water solution. However, the PVA/S blends had longer time of solubility in aqueous solution containing 30% alcohol as compared to that soluble in water, probably due to the more interaction between the starch and PVA in alcoholic solution than that in aqueous solution as shown in Fig. 2 C&D. DSC thermograms of the PVA/S blend films with different blend ratios of (PVA & S) and Mw of PVA (31x 10 & 3 205x 10 g/mole) is shown in (Fig. 3 A&B), and a summary of the DSC features is given in Table 1. It can be seen, there is only one T g in the DSC curves due the miscibility of blends. Such miscibility is attributed to the hydrogen bonding between PVA and S in the blends. The T g results agree well with the FT-IR data. The FT-IR data showed that the miscibility of the blends is associated with hydrogen bonding interactions between the hydroxyl groups of PVA and o o S. The DSC curves in Fig. 3A shows eutectic melt between an onset of 175 C and midpoint of 195.5 C of PVA (31x 3 o o 3 10 g/mole)/S blends and an onset of 182.5 C and midpoint of 197.5 C of PVA (205x 10 g/mole)/S blend films (Fig. 3 3 3B). It can be observed in Table 1 that the glass transition temperature ( T g ) of PVA (31x 10 g/mole and 205x 10 o g/mole) was 65.80 and 64.89 C respectively. In PVA/S blend films; T g was shifted to higher temperature with an increase of S content from 5% to 30%. This is attributed to the strong interaction among hydroxyl groups on PVA and starch chains. Similar results were reported when PVA was blended with S in presence of urea [21]. It should be noted that T g is independent on molecular weight of PVA, T g of the endothermic peaks from DSC of PVA 3 3 (31x 10 g/mole)/S blend films were found to be lower than that of PVA (205x 10 g/mole)/S blend films. These endothermic peaks were related to the dissolving of PVA crystals, which demonstrate solubility of blend films in water by increasing temperature. Thermal properties of the PVA/S blend films containing 70, 80, 90 and 95 wt % of PVA were studied by thermogravimetric analysis (TGA) and differential thermal analyses (DTA). The analyses were performed from 20oC to 850oC at 20oC/min heating rate in air oxygen atmosphere. Fig. 4 and Table 1, summarize the TGA results of the PVA/S blend films with different molecular weight of PVA. From Fig 4, it was not observed that the variations in weight loss o of pure PVA and different blend films occurred until 271 C. These results are in contrast with what is generally o reported in the literature [48], [49], where the weight losses of PVA/starch blend was observed at 120 C. This can be attributed to the role of acetic acid in the cross-linking reaction between PVA and S. Two weight losses are observed in the TGA curve as shown in Fig 4. The first weight loss (from 8.2 to 12.7%) occurs ◦ 3 3 between 271.77 and 278.72 C for PVA 31x10 g/mole, and PVA (31x10 g/mole)/S blend films, and (from 2.6 o 3 3 to11.1%) occurs between 275 and 296.01 C for PVA 205x 10 g/mole and PVA (205x 10 g/mole)/S blend films, which is related to the evaporation of residual moisture. The second weight loss (from 79.82 to 87.8%) occurs between 425.05 and 432.41 ◦C for PVA (31x10 3 g/mole)/S blends and (from 71.14 to 79.7%) occurs between 420.81 and 431 o C 3 for PVA (205x 10 g/mole)/S blends, which corresponds to the side chain decomposition of PVA and the main chain of the starch molecule due to broken inter- and intra-molecular hydrogen bonds between PVA and starch. The weight loss of degradation depends upon many factors such as the surrounding atmosphere, temperature and molecular weight of the polymer. For example, weight loss of PVA/S blend films decreases with increasing number average weight of PVA in the blend as shown in the Table 1. The initial decomposition temperature (IDT) corresponds to the temperature at which the initial degradation may occur [50], [12]. It was observed that IDT is higher than 306 °C, which is above the highest rheological measurements employed in this study and decomposition temperature of starch [39], as shown in the 3 3 Table 1. However IDT of PVA (205x 10 g/mole)/S blend films is higher than that of (31x10 g/mole)/S blends films. On the other hand the maximum polymer degradation temperature (PDT max ) corresponds to the temperature at which the 3 maximum rate of weight loss occurred, appeared in the range from 431.7 to 444.97 oC for the PVA (31x10 g/mole)/S 3 blend films and in the range from 441.01 to 450.29 oC for PVA (205x 10 g/mole)/S blend films. The PDT max increases 3 as molecular weight of the PVA increases. The PVA (205x 10 g/mole)/S blend films containing 80% PVA (M2) shows o the highest PDT max at a temperature of 450 C. Consistently, thermal stability of blend film depends on the composition of the two components, molecular weight and the residual weight of blend films The mechanical properties of PVA/S blend films as a function of molecular weight of PVA and its ratio in blend films were studied and shown in Fig. 5. It can be seen that tensile strength decreased and elongation increased with increasing 3 PVA content in the blends. However, PVA (31x 10 g/mole)/S blend films showed the largest tensile as compared with 3 PVA (205x 10 g/mole)/S blend films. This is presumably due to ...
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Citations
... Figure S2a shows the FTIR spectra of the PVA powders used for the preparation of the hydrogel samples. Five characteristic regions were identified [38,39]. The strong large absorption peak at around 3300 cm −1 is related to the O-H stretching from the intramolecular and intermolecular hydrogen bonds and, consequently, it is more intense in PVA 20:98, which has a higher HD (thus more free -OH groups). ...
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... It showed that the interaction of starch with PVA is not significantly visible during FTIR analysis. However, it shows that all samples with different proportions of PVA shared the same characteristics of broad band ranging from 3264 to 3268cm -1 that shows the frequencies of hydroxyl groups of PVA and starch in the bioplastic films [16,28]. All the bioplastic samples show that there is presence of C-H stretching ranging on 2926 to 2928cm -1 . ...
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... The reason for this can be attributed to the changes of microscopic structure, as mentioned in the electron microscope section. In fact, the addition of the extract causes irregularities in the structure of the cellulose acetate film, and this accelerates the rate of decomposition of the cellulose acetate film with F. vulgaris extract, which is consistent with the results of other researchers who investigated the biodegradability of polyvinyl alcohol and starch composite films (Negim et al. 2014). In another study, the biodegradability of cellulose acetate, carrageenan and alginate composite film was investigated within 70 days, and its biodegradability was reported in three months (Rajeswari et al. 2020). ...
... Negim et al. [24] used glacial acetic acid as a crosslinking agent, which improved the biodegradability of PVA/starch blend films. The physical, thermal, and mechanical properties of PVA/S mixtures were analyzed with a change in the ratio of the mixtures and the molecular weight of the PVA. ...
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... The reason for this can be attributed to the changes of microscopic structure, as mentioned in the electron microscope section. In fact, the addition of the extract causes irregularities in the structure of the cellulose acetate film, and this accelerates the rate of decomposition of the cellulose acetate film with F. vulgaris extract, which is consistent with the results of other researchers who investigated the biodegradability of polyvinyl alcohol and starch composite films (Negim et al. 2014). In another study, the biodegradability of cellulose acetate, carrageenan and alginate composite film was investigated within 70 days, and its biodegradability was reported in three months (Rajeswari et al. 2020). ...
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... The findings were consistent with previous studies. 12,21 Moreover, the increase of pregelatinized starch on PVOH system from 10% to 40% hindered the crystallization of PVOH, which was reduced from 15% (P-St 10) to 9% (P-St 40). The enthalpy of DSC thermograms did not change because the amorphous structure of starch could not give sufficient signal to the degree of gelatinization of starch; however, XRD pattern was the alternative method of identifying the degree Figure 1 of gelatinization, as reported by Baks et al. and Van et al. 15,22 The degrees of gelatinization are shown in Figure 2 and summarized in Table 3. ...
... This is consistent with previously published data. 9,21,27 Increases in pregelatinized starch content from 10% to 30%, led to a significant decrease in starch domain size significantly. Interestingly, a co-continuous phase between PVOH and pregelatinized starch with small coalescence was seen when the sample had 30% of pregelatinized starch, while the addition of pregelatinized starch at 40% tended to enlarge the domain size and a continuous phase with large coalescence appeared. ...
This research was focused on the properties of poly (vinyl alcohol) (PVOH) blended with pregelatinized starch (PSt) as a suitable material to make laundry bags for infected clothes application. PVOH and PSt (0, 10, 20, 30, and 40 wt.%) with glycerol 20 phr were melt-blended by twin-screw extruders. The samples were processed into the film by single layer-blown film extrusion. From the results, it was found that PVOH, glycerol, and pregelatinized starch had intermolecular interactions with each other, forming hydrogen bonding interactions between PVOH/pregelatinized starch and glycerol. The glass transition temperature (T g ) of a blend was shifted to a higher temperature by increasing the pregelatinized starch content leading to a reduction in the percent crystallinity. The presence of pregelatinized starch slightly increased the melt flow rate (MFI)/melt volume rate (MVR), apparent viscosity, and viscosity average molecular weight (M v ) of the blends due to the chain entanglement but it decreased the water solubility time and the moisture content. A co-continuous phase with small coalescence was found when 30% pregelatinized starch was added, increasing the elongation at break to 171%. On the other hand, the pregelatinized starch content was 40%, the elongation at break reduced to 154%.
... In this regards, different workings has been proposed by various researchers for either synthetic-to-natural [11,12], natural-to-natural [13,14], synthetic-to-synthetic [7,15] polymer blends. Among various reported synthetic-to-natural, the blends of starch and PVA is most widely studied [1,[16][17][18]. Sreekumar et al. [19] studied the structure and physical properties of different blends of corn starch and PVA, by analyzing X-ray diffraction and thermal and mechanical response. ...
... This acetyl (C = O) peak observed in the PVA film was due to intermolecular hydrogen bonding of C = O with the adjacent OH group. The OH groups bending vbrations appeared at 1437 cm −1 [7,16,17]. The peak at 1653 cm −1 also reveals the semi-crystalline nature of the PVA film. ...
... It indicates that BRS attaches to CH and methylene CH 2 in the side chain of PVA molecules. [1,6,16,17]. Figure 14 represents the FTIR spectrum plot of PVA/ MBRS blend films with varying compositions (70/30, 50/50, 30/70). The vibrational peaks appeared in FTIR spectrum of PVA/MBRS blend films were almost same as PVA/BRS. ...
Polymeric flms of Poly(vinyl alcohol) (PVA) to produce a lower band gap by blending it with native basmati rice starch
(BRS) and Octenyl Succinic Anhydride (OSA) modifed basmati rice starch (MBRS) were generated in the current study.
The recorded UV–visible spectra in the wavelength range 190–1100 nm specifed a redshift in the UV region from 190 to
220 nm, which attributed to the π→π* transitions. The UV–visible absorbance data was utilized to evaluate the optical
constants such as band gap, extinction coefcient, refractive index, carbon atoms in conjugation, Urbach’s energy, and opti-
cal conductivity. The Eg of PVA signifcantly decreased from 6.36 to 5.77 eV with BRS and MBRS addition. The shifts and
alteration in the OH band intensity in the FTIR spectrum confrmed the hydrogen bonding among the blended flms. The
XRD analysis specifed blending of PVA with BRS or MBRS reduced the crystallinity of the blended films
... In this regards, different workings has been proposed by various researchers for either synthetic-to-natural [11,12], natural-to-natural [13,14], synthetic-to-synthetic [7,15] polymer blends. Among various reported synthetic-to-natural, the blends of starch and PVA is most widely studied [1,[16][17][18]. Sreekumar et al. [19] studied the structure and physical properties of different blends of corn starch and PVA, by analyzing X-ray diffraction and thermal and mechanical response. ...
... This acetyl (C = O) peak observed in the PVA film was due to intermolecular hydrogen bonding of C = O with the adjacent OH group. The OH groups bending vbrations appeared at 1437 cm −1 [7,16,17]. The peak at 1653 cm −1 also reveals the semi-crystalline nature of the PVA film. ...
... It indicates that BRS attaches to CH and methylene CH 2 in the side chain of PVA molecules. [1,6,16,17]. Figure 14 represents the FTIR spectrum plot of PVA/ MBRS blend films with varying compositions (70/30, 50/50, 30/70). The vibrational peaks appeared in FTIR spectrum of PVA/MBRS blend films were almost same as PVA/BRS. ...
Polymeric films of Poly(vinyl alcohol) (PVA) to produce a lower band gap by blending it with native basmati rice starch (BRS) and Octenyl Succinic Anhydride (OSA) modified basmati rice starch (MBRS) were generated in the current study. The recorded UV-visible spectra in the wavelength range 190-1100 nm specified a redshift in the UV region from 190 to 220 nm, which attributed to the π → π* transitions. The UV-visible absorbance data was utilized to evaluate the optical constants such as band gap, extinction coefficient, refractive index, carbon atoms in conjugation, Urbach's energy, and optical conductivity. The E g of PVA significantly decreased from 6.36 to 5.77 eV with BRS and MBRS addition. The shifts and alteration in the OH band intensity in the FTIR spectrum confirmed the hydrogen bonding among the blended films. The XRD analysis specified blending of PVA with BRS or MBRS reduced the crystallinity of the blended films.
... The FTIR spectra of E0_1 and E0_2 show a broad band with the peak between 3250 cm −1 and 3275 cm −1 , corresponding to stretching vibrations of the OH hydroxyl groups, which formed intermolecular hydrogen bonds [128], and the peaks at around 2925 cm −1 can be assigned to asymmetric stretching vibrations of the -CH2 methylene groups from the PVA [129]. Peaks in the range of 1745-1680 cm −1 are assigned to symmetric stretching vibrations of the C = O groups [130], peaks at 1085 cm −1 are assigned to C-N stretching vibrations [131], and bending vibrations of CH from PVP are revealed at around 1428 cm −1 , 1285 cm −1 , and 920 cm −1 . The changes that occurred in the PVA/PVP matrices during crosslinking were highlighted in the FTIR spectra by peaks of 1234.22 cm −1 , assigned to the secondary stretching of C = O from GTA, which was present only in E0_2. Figure 9 presents the FTIR spectra of the control sample E1 and compositions loaded with essential oils in the polymeric matrices. ...
Wound dressings for skin lesions, such as bedsores or pressure ulcers, are widely used for many patients, both during hospitalization and in subsequent treatment at home. To improve the treatment and shorten the healing time and, therefore, the cost, numerous types of wound dressings have been developed by manufacturers. Considering certain inconveniences related to the intolerance of some patients to antibiotics and the antimicrobial, antioxidant, and curative properties of certain essential oils, we conducted research by incorporating these oils, based on polyvinyl alcohol/ polyvinyl pyrrolidone (PVA/PVP) biopolymers, into dressings. The objective of this study was to study the potential of a polymeric matrix for wound healing, with polyvinyl alcohol as the main material and polyvinyl pyrrolidone and hydroxypropyl methylcellulose (HPMC) as secondary materials, together with additives (plasticizers poly(ethylene glycol) (PEG) and glycerol), stabilizers (Zn stearate), antioxidants (vitamin A and vitamin E), and four types of essential oils (fennel, peppermint, pine, and thyme essential oils). For all the studied samples, the combining compatibility, antimicrobial, and cytotoxicity properties were investigated. The obtained results demonstrated a uniform morphology for almost all the samples and adequate barrier properties for contact with suppurating wounds. The results show that the obtained samples containing essential oils have a good inhibitory effect on, or antimicrobial properties against, Staphylococcus aureus ATCC 25923, Enterococcus faecalis ATCC 29212, Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, and Candida albicans ATCC 10231. The MTT assay showed that the tested samples were not toxic and did not lead to cell death. The results showed that the essential oils used provide an effective solution as active substances in wound dressings.
... Thermograms in Figure 17 show that untreated PVA/DBDMA undergoes two principal steps of thermal decomposition. The first occurs at a temperature range of 95−160°C revealing a weight loss of 4.42% which refers to the removal of moisture and residual solvent, 52 whereas the temperature range at which the second decomposition step occurs is 270−436°C with a weight loss of 87.15% which represents more significant weight loss due to the degradation of side group (−OH) to give polyene 53 and also the cleavage of (C−C) in the main chain of PVA (leading to carbocation). 54 In addition, these thermal findings showed more enhanced thermal properties of the casted and blended PVA/DBDMA film compared to a pure PVA film reported in the literature. ...
Currently, particular attention is paid to public health related to the field of γ-ray dosimetry, which is becoming increasingly important in medical diagnostic processes. Incorporating sensitive dyes as radiation dose sensors in different material hosts has shown promising radiation dosimetry application routes. In this perspective, the current study proposes a new fluorescent dye based on boron difluoride complex, the pyridomethene-BF2 named 2-(1-(difluoroboraneyl)-1,2-dihydroquinolin-2-yl)-2-(1-methylquinoxalin-2-ylidene) acetonitrile (DBDMA) as an indicator for low γ-ray doses. The different optical and quantum chemical parameters and the spectral behavior of the selected fluorescent dye were first studied. Then, PVP/DBDMA electrospun nanofibers and PVA/DBDMA thin films were prepared. The different UV-vis spectrophotometric and fluorescence studies revealed a clear change after exposure to different γ-ray doses. Thermogravimetric analysis exhibited excellent thermal stability of the prepared nanocomposite films, showing altered thermal behavior after γ-ray treatment. Furthermore, the SEM evaluation displayed a significant modification in the surface morphology of the two designed nanomaterials with increased radiation dose intensity. These novel forms of dosimeter designed in nanoscale composites could therefore constitute a promising and efficient alternative for rapid and accurate detection of low doses of γ-rays in various medical applications.
