Preparation of resistant starch/poly(vinyl alcohol) blend films with added plasticizer and crosslinking agents

We report on the physical properties of films synthesized with native corn starch (NCS) and resistant starch (RS4) prepared with NCS. NCS and RS4/poly(vinyl alcohol) (PVA) blend films were synthesized with a mixing process and casting method. Glycerol (GL) and citric acid (CA) were used as additives. Glutaraldehyde (GLU) was used as a crosslinking agent of the films. RS4 was synthesized with sodium trimetaphosphate and sodium tripolyphosphate as a crosslinker. Then, the RS4 thus synthesized was confirmed by the pancreatin–gravimetry method, swelling power, differential scanning calorimetry, and X‐ray diffraction. The tensile strength, elongation, swelling behavior, and solubility of the films were measured. The results of the measurements indicated that the RS4‐added film was better than the NCS‐added film. In particular, the RS4/PVA blend film with CA as an additive showed physical properties superior to those of the other films. Also, the physical properties with GLU added as a crosslinking agent to the films were investigated. With increasing GLU contents, the tensile strength increased but the elongation, swelling behavior, and solubility values of the GL‐added and CA‐added films decreased. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Effect of graphene loading on thermomechanical properties of poly(vinyl alcohol)/starch blend

Polymer nanocomposites based on poly(vinyl alcohol) (PVA)/starch blend and graphene were prepared by solution mixing and casting. Glycerol was used as a plasticizer and added in the starch dispersion. The uniform dispersion of graphene in water was achieved by using an Ultrasonicator Probe. The composites were characterized by FTIR, tensile properties, X‐ray diffraction (XRD), thermal analysis, and FE‐SEM studies. FTIR studies indicated probable hydrogen bonding interaction between the oxygen containing groups on graphene surface and the –OH groups in PVA and starch. Mechanical properties results showed that the optimum loading of graphene was 0.5 wt % in the blend. XRD studies indicated uniform dispersion of graphene in PVA/starch matrix upto 0.5 wt % loadings and further increase caused agglomeration. Thermal studies showed that the thermal stability of PVA increased and the crystallinity decreased in the presence of starch and graphene. FE‐SEM studies showed that incorporation of graphene increased the ductility of the composites. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41827.     

Influence of the molecular weight of chitosan on the spinnability of chitosan/poly(vinyl alcohol) blend nanofibers

The electrospinning of the biopolymer chitosan (CS) and poly(vinyl alcohol) (PVA) was investigated with 90% acetic acid as the solvent and with different CS/PVA ratios. The long chains of high‐molecular‐weight CS prevented it from forming nanofibers in a high‐voltage field. The treatment of CS under high‐temperature alkali conditions reduced its molecular weight exponentially with the treatment time and caused a reduction of the viscosity consequently. PVA, acting as a plasticizer and accompanied by the alkali‐treated CS of lower viscosity, made the electrospinning of CS/PVA blends possible. The effects of the duration of the alkali treatment on the molecular weight of CS and its viscosity were investigated and optimized. The diameter of the bicomponent nanofiber decreased proportionally with the increase in the CS portion, whereas the surface porosity increased inversely. Fourier transform infrared studies illustrated that the alkali treatment or blending of CS with PVA had no effect on its chemical nature. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Self-crosslinkable hydroxylated natural rubber/carboxymethyl starch blend and its properties

Self-crosslinkable hydroxylated natural rubber (HNR) and carboxymethyl starch (CMS) was successfully prepared via in situ mixing of CMS slurry in HNR latex. The purpose of this work was to study the crosslinking of HNR using CMS as a novel crosslinker in order to reduce the use of sulfur vulcanizing agent and other toxic chemicals such as accelerator. Two systems with different HNR:formic acid:hydrogen peroxide ratios were prepared: 1:0.25:0.25, designated as HNR025, and 1:0.35:0.35, designated as HNR035. Well dispersion and distribution of CMS in the HNR025 matrix were obvious as imaged in scanning electron microscope micrographs. The resulting interfacial combination and ester bonding between HNR and CMS molecules were believed to enhance the mechanical properties and thermal stability of the HNR/CMS blends. It was remarkable that the determined crosslink densities of the HNR/CMS blends increased with the CMS loading and were corresponding to the improved mechanical properties. This self-crosslinkable blend between HNR and CMS without using any vulcanizing agents would be of interest for the preparation of the green biodegradable rubber products in the future. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47271.     

Effect of oxidation level on the dual modification of banana starch: The mechanical and barrier properties of its films

Banana starch was oxidized at three different levels and then acetylated. The double‐modified starch was used for film preparation. The physical, mechanical, and barrier properties were tested. The oxidation level increased the whiteness of the film, and the second modification (acetylation) did not affect this parameter. The solubility increased with temperature and oxidation level. However, acetylation decreased the solubility value. At the longest storage times, the solubility decreased because of starch reorganization inside the polymeric matrix. In general, oxidation increased the tensile strength of the films, and a slight increase was observed when the oxidized starch was acetylated. This effect was more noticeable at the longest storage time. The oxidation level decreased the percentage elongation at break, and a slight effect due to acetylation was observed. The film of oxidized–acetylated starch showed a higher elastic modulus value than its oxidized counterpart. The water vapor permeability increased with oxidation level, but the acetylation decreased this parameter. The oxidation increased the hydrophilic character of the starch because of the formation of carbonyl and carboxyl groups that showed more affinity for water molecules. When the oxidized banana starch was acetylated, a decrease in the water vapor permeability was found because the acetylation increased the hydrophobic character of the starch due to the ester group. Films prepared with the double‐modified banana starch had some improved physical, mechanical, and barrier properties, and they may be used in specific applications. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Preparation and characterization of poly(vinyl alcohol) and gelatin blend films

Poly(vinyl alcohol) (PVA) is a water-soluble polymer that has been studied intensively because of several interesting physical properties that are useful in technical applications, including biochemical and medical applications. In this article, we report the effects of the addition of gelatin on the optical, microstructural, thermal, and electrical properties of PVA. Pure and PVA/gelatin blend films were prepared with the solution-casting method. These films were further investigated with Fourier transform infrared (FTIR), differential scanning calorimetry (DSC), X-ray diffraction (XRD), ultraviolet–visible (UV–vis) spectroscopy, and dielectric measurements. The FTIR spectrum shows a strong chemical interaction between PVA and gelatin molecules with the formation of new peaks. These peaks are due to the presence of gelatin in the blend films. The DSC results indicate that the addition of gelatin to PVA changes the thermal behavior, such as the melting temperature of PVA, and this shows that the blends are compatible with each other. This also shows that the interaction of gelatin and PVA molecules changes the crystallite parameters and the degree of crystallinity, and this supports the XRD results. The UV–vis optical study also reflects the formation of the complex and its effect on the microstructure of the blend film. Moreover, the addition of gelatin also gives rise to changes in the electrical properties of PVA/gelatin blend films. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Water‐absorptive blend fibers of copoly(acrylic acid–acrylamide) and poly(vinyl alcohol)

Through the addition of N‐hydroxymethyl acrylamide as a potential crosslinker, water‐absorptive blend fibers of copoly(acrylic acid–acrylamide) and poly(vinyl alcohol) with three‐dimensional network structures were prepared with heat‐crosslinking technology after fiber formation. Fourier transform infrared, scanning electron microscopy, dynamic mechanical analysis, and thermogravimetry were used to analyze the structures and properties of the fibers. The tensile behavior and absorbent capacities of the fibers were also studied. The results showed that there were lots of chemical crosslinking points in the fibers, the compatibility of copoly(acrylic acid–acrylamide) and poly(vinyl alcohol) was perfect, and the tensile properties of the fibers could be improved effectively through stretching in a vapor bath. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3353–3357, 2006     

Morphology and mechanical properties of pullulan/poly(vinyl alcohol) blends crosslinked with glyoxal

We prepared pullulan/poly(vinyl alcohol) (PVA) blend films by casting the polymer solution in dimethyl sulfoxide. Their morphology and mechanical properties were investigated. Scanning electron micrographs revealed that the pullulan was immiscible with PVA over the entire composition range. The tensile strength and modulus of the blend films were lower than those predicted by the upper bound composite equation. To improve the mechanical properties, we investigated the reaction of the 40/60 blend with glyoxal. The infrared spectral change and the increase in the glass‐transition temperature (corresponding to the PVA component) accompanying the reaction indicated that crosslinking with glyoxal had proceeded. The crosslinked films were homogeneous and had higher tensile strengths and moduli than the simple blend. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2273–2280, 2001     

Modified cassava starch/poly(vinyl alcohol) blend films plasticized by glycerol: Structure and properties

We report a systematic investigation on the structure–property relationships in glycerol-plasticized poly(vinyl alcohol) (PVA)/cassava starch blends prepared via solution casting. In particular, PVA mixed with native, low-oxidized, high-oxidized, and pregelatinized cassava starches were characterized by means of SEM, XRD, FTIR, thermal analysis and mechanical testing and the immiscible systems were received. Burial tests over a period of several days suggested the preferential degradation of the starch and glycerol component (as indicated by the absence of FTIR signatures of those components) and the amorphous phase of PVA (as indicated by the enhanced crystallinity index of the degraded samples). The rheological properties of the blends seem to dictate their morphological characteristics that, in turn, have a profound impact on their mechanical properties. In that sense, the study highlights promising strategies for the development of a new family of polymeric materials that combine their biodegradable nature within superior mechanical properties. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48848.     

Structure and properties of starch/poly(ethylene-co-vinyl alcohol) blown films

Blends of native corn starch and poly(ethylene-co-vinyl alcohol) (EVOH), with starch: EVOH ratios of 1 : 1 (SE-50) and 2 : 1 (SE-67A, SE-67B), were processed into blown films. SE-67A had a higher glycerol and water content and was processed at 5°C higher than was SE-67B. The films were conditioned to various moisture contents by equilibrating at a constant relative humidity and by oven drying at 41°C. Equilibrium moisture content, which ranged from 2 to 11%, increased with increasing starch content at a given relative humidity. Mechanical properties depended strongly on starch and moisture content as well as on processing history. The extension to break of SE-50 was only about one-third that of EVOH, while that of the 2 : 1 blends was even lower. SE-67A exhibited a higher extension to break, lower tensile strength and modulus, and greater moisture sensitivity than those of SE-67B. Differential scanning calorimetry and dynamic mechanical analysis revealed evidence of interactions between starch and EVOH, probably indicative of extensive intermixing but not necessarily miscibility. Scanning electron micrographs of fracture surfaces revealed extensive differences in texture with microcracking in SE-50 and SE-67A. The combination of the analytical results provide a basis for explaining many aspects of the mechanical behavior including the marked difference in properties between SE-67A and SE-67B. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 2613–2622, 1997     

Use of poly(ethylene‐co‐vinyl alcohol) as compatibilizer in LDPE/thermoplastic tapioca starch blends

Poly(ethylene‐co‐vinyl alcohol) (EVOH) was used as a compatibilizer to make blends of low‐density polyethylene (LDPE) and plasticized starch (TS). The tensile properties and impact strength were measured and compared with those of neat LDPE. The morphology of the blend specimens, both fractured and unfractured, was observed by scanning electron microscopy. Comparison of the properties showed that the impact strength of the blend improves significantly by the addition of a compatibilizer even with a high TS loading of 40 and 50% (by weight). A high elongation at break almost matching that of neat polyethylene was also obtained. The blend morphology of the etched specimens revealed fine dispersion of the starch in the polyethylene matrix, while the fracture surface morphology clearly indicate that the failure of compatibilized blends occurs mainly by the ductile mode. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3126–3134, 2002     

Antibacterial films with enhanced physical properties based on poly (vinyl alcohol) and halogen aminated-graphene oxide

Graphene oxide (GO) nanosheets as great nanofiller have been utilized for the enhancement of a polymer matrix. In this work, polymeric N-halamine poly[5,5-dimethyl-3-(3′-triethoxysilylpropyl)hydantoin] (PSPH) was covalently grafted onto GO, which was denoted as GO-PSPH. The chlorinated GO-PSPH (GP-Cl) was then mixed with poly (vinyl alcohol) (PVA) solution to obtain the PVA/GP-Cl hybrid films. The as-prepared hybrid films were characterized by scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) spectra. Compared with PVA film, the addition of GP-Cl into PVA matrix endowed the film with enhanced thermal and mechanical properties, and the crystallinity, tensile strength, and Young's modulus increased by 45, 21, and 246%, respectively. It can be deduced that the interfacial interaction between PVA matrix and GP-Cl nanosheets was the crucial factor for the physical enhancement. Furthermore, the synergistic effect between GO and polymeric N-halamine greatly improved the antibacterial activities of the hybrid films with 3.95 logs reduction of Staphylococcus aureus and 4.53 logs reduction of Escherichia coli O157:H7 with 30 min of contact time, respectively. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48176.     

Heat‐sealing properties of soy protein isolate/poly(vinyl alcohol) blend films: Effect of the heat‐sealing temperature

To promote the heat‐sealing properties of soy protein isolate (SPI) films applied in the packaging field, we mixed a synthetic polymer of poly(vinyl alcohol) (PVA) with SPI to fabricate blend films by a solution‐casting method in this study. To clarify the relationship between the heat‐sealing properties and the heat‐sealing temperature, strength, melting process, crystalline structure, and microstructure, variations of the heat‐sealing parts of the films were evaluated by means of differential scanning calorimetry, tensile testing, scanning electron microscopy, X‐ray diffraction, and Fourier transform infrared spectroscopy, respectively. The test results showed that both the PVA and glycerol contents greatly affected the melting behavior and heat of fusion of the SPI/PVA blends; these blend films had a higher melting temperature than the pure SPI films. The peel strength and tensile strength tests indicated that the long molecular chain of PVA had a main function of enhancing the mechanical properties above the melting temperature. With increasing heat‐sealing temperature, all of the mechanical properties were affected by the microstructure of the interface between the laminated films including the chain entanglement, crystallization, and recrystallization. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Poly(vinyl alcohol) films crosslinked by glutaraldehyde under mild conditions

The use of mild conditions to perform the entrapment of biomolecules in polymeric matrices is a crucial step in a broad range of applications as biosensors, biocarrier‐mediated facilitated transport membranes, and drug‐controlled release devices. In this study, we investigated the crosslinking of poly(vinyl alcohol) (PVA) by glutaraldehyde in the absence of an acid catalyst and organic solvents to improve the water resistance of the hydrophilic biocompatible polymer. Glutaraldehyde was chosen as the crosslinking agent because it favors the intermolecular reaction with PVA and is able to bind nonspecifically to proteins. The effects of the temperature and glutaraldehyde content on the thermal and structural properties of the PVA films were examined. Membranes prepared at 40°C showed a maximum crosslinking density for low glutaraldehyde content namely, 0.04 wt % in the spreading solution. Higher amounts of the crosslinker led to the branching of PVA. The increase in membrane thermal properties and reduction in crystallinity were ascribed to the crosslinking treatment, which was confirmed by Fourier transform infrared analysis. The oxygen permeability of the films was reduced up to 2.7 times, which indicated that the crosslinking of the polymer was successfully accomplished. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Physical and mechanical properties of plasticized butenediol vinyl alcohol copolymer/thermoplastic starch blend

The poly(vinyl alcohol) (PVOH) is an eco‐friend polymer and has an excellent oxygen barrier property due to its strong intermolecular force, but difficulty in processing with conventional extrusion process gives it a limitation for various industrial applications, especially packaging industry. Many studies have attempted to plasticize PVOH to improve its processability, but high cost of PVOH is still drawback for a variety of industrial applications. Therefore, PVOH often blended with other biodegradable polymers such as starch to acquire the cost benefit. Nowadays, the butenediol vinyl alcohol copolymer (BVOH) is getting a great attention due to its melt processability and bio‐degradability, but its high cost is barrier to the industrial application as well. In this study, thermoplastic starch (TPS)/plasticized BVOH (P‐BVOH) were prepared by melt mixing technique, and the plasticization effect of glycerol on starch and BVOH with different composition was observed for optimized processing condition. Based on our preliminary study, TPS was blended with varying amount of P‐BVOH (100:0, 90:10, 80:20, 70:30, 60:40, and 50:50 weight ratio). Physical, oxygen barrier, and mechanical properties of the TPS/P‐BVOH blends were evaluated by various analytical instruments to achieve balanced property and performance. J. VINYL ADDIT. TECHNOL., 25:109–116, 2019. © 2018 Society of Plastics Engineers     

Controlled release of naproxen from sodium alginate and poly(vinyl alcohol)/sodium alginate blend beads crosslinked with glutaraldehyde

In this study, polymeric beads of sodium alginate (NaAlg) and its blend with poly(vinyl alcohol) (PVA) were prepared by crosslinking with glutaraldehyde (2.5% v/v) and hydrochloric acid (3% v/v) for the release of naproxen sodium (NS). The prepared beads were characterized with Fourier transform infrared spectroscopy, and pictures of the beads were determined with an optic microscope. The release studies were carried out at three pH values (1.2, 6.8, and 7.4) for 2 h. The effects of the preparation conditions, including the PVA/NaAlg (w/w) ratio, drug/polymer (w/w) ratio, and time of exposure to the crosslinker, on the release of NS were investigated for 10 h at 37°C. The release of NS decreased with the PVA/NaAlg (w/w) ratio and drug/polymer ratio increasing. At the end of 10 h, the highest release of NS was found to be 84% for the 1/2 PVA/NaAlg (w/w) ratio. The swelling measurements of the beads supported the release results. The release kinetics were described with Fickian and non‐Fickian approaches. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

On the viscoelastic properties of poly(vinyl alcohol) and chemically crosslinked poly(vinyl alcohol)

Poly(vinyl alcohol)(PVA) films chemically crosslinked with glutaraldehyde(GA) in the presence of HCl were prepared by casting from aqueous solutions. The PVA and PVA gels were investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA); their swelling characteristics and tensile strength were also determined. The DSC results for the gels displayed depressions of the melting and crystallization temperatures, as well as a decrease of the heat of fusion, when compared to those of PVA free of crosslinker. The DMA analysis revealed that: (1) The glass transition temperature of the wet PVA was lower than that of the dry one, indicating that the water had a plasticizing effect. (2) The gels had a lower glass transition temperature than PVA. (3) The glass transition temperature of the wet gels increased with increasing crosslink density. Possible explanations are provided for these observations. Whereas the thermogravimetric curves of PVA exhibited a single degradation peak, two degradation peaks were detected for the crosslinked PVA. The wet PVA and PVA gels displayed lower tensile strengths and higher elongations than the dried ones. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1816–1823, 2001     

Oleophilic modification of poly(vinyl alcohol) films by functionalized soybean oil triglycerides

In this study, maleinized (SOMAP) and isocyanated soybean oil (SONCO) triglycerides have been successfully grafted onto one surface of poly(vinyl alcohol)(PVA) films to give films that are hydrophilic on one side and hydrophobic on the other. The surface grafting was accomplished by the reaction of succinic anhydride or isocyanate functionalities of soybean oil derivatives and the hydroxyl groups of PVA films. The reaction was run in toluene, using PVA films on glass slides so that only one side of the film was accessible. After grafting, the films were rinsed with hot toluene to remove ungrafted triglycerides from the surface. The reaction on the surface was confirmed by ATR‐FTIR and ¹H‐NMR spectroscopic techniques. A series of films were prepared at different concentrations of SOMAP or SONCO in toluene. The increase in hydrophobicity with an increase in SOMAP or SONCO concentrations was observed by water contact angle measurements. The contact angles on the grafted side of the film reach their maximum value of 88° and 94° for 26 and 2.5% SOMAP and SONCO concentrations in toluene, respectively, while the ungrafted side gives contact angle of 48°. Surface morphologies of PVA‐g‐SOMAP and PVA‐g‐SONCO films were investigated by atomic force microscopy, whereas optical microscopy and staining was used to determine the homogeneity of the films. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Phase structure in the blend of atactic poly(vinyl alcohol) with atactic poly(vinyl alcohol‐block‐vinyl acetate)

An almost fully saponified atactic poly(vinyl alcohol) and an atactic poly(vinyl alcohol‐block‐vinyl acetate) of which degree of saponification is 89 mol % were blended by a solution casting method. The phase structure of the blend film was analyzed by optical microscopy, ¹³C‐NMR, and differential scanning calorimetry. The most remarkable structure of the blend was composed of cylindrical domains penetrating the film. The swelling behavior of the blend films was also investigated in the dimethylsulfoxide and water mixed solvents to find differences in solubility and diffusion behavior between the matrix and the domain. The cylindrical domains could be selectively dissolved away in water and the film became porous. We tried to change the size of the cylindrical domain with various film preparation conditions. This aimed to turn the film into the useful filter membrane. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1807–1815, 2002     

Effects of different porous fillers on interfacial properties of poly (vinyl alcohol) hybrid films

Poly(vinyl alcohol) (PVA)-based hybrids have demonstrated broad liquid separation applications but separation performances are constrained by the compatibility between fillers and polymer, and thus it is essential to study the interfacial properties of these hybrids. In this work, PVA hybrids with four different porous fillers have been fabricated and characterized with Fourier transform infrared, X-ray diffraction, Scanning electron microscope, swelling and contact angle tests. Swelling results show that PVA has a degree of swelling (DS) of 79% in water but the swelling is compressed after adding fillers and the DS for PVA hybrids has decreased by 19%, 17%, 15%, and 9% for 30 wt% loading of ZIF-8, UiO-66, Hβ and ZSM-5, respectively. For methanol and its 10 wt% aqueous solution, similar swelling results are obtained due to mutual interactions among the filler, polymer and test liquids. Based on water and glycerol contact angle results, the surface energy of PVA is estimated to be 40.56 Nm⁻¹ and it drops to 27.39 Nm⁻¹ after adding less hydrophilic ZIF-8 or rise to 48.56 Nm⁻¹ after introducing more hydrophilic ZSM-5. The high-film hydrophilicity and then large surface energy have rendered methanol/water sorption selectivity of PVA hybrids decrease to some extent or vice versa.