Poly(vinyl alcohol) and poly(vinyl amine) blend membranes for isopropanol dehydration

Blended membranes of hydrophilic polymers poly(vinyl alcohol) (PVA) and poly(vinyl amine) (PVAm) were prepared and crosslinked with glutaraldehyde. The prepared membranes were characterized using infrared (attenuated total reflection mode) spectroscopy, differential scanning calorimetry, X‐ray diffractometry, and scanning electron microscopy measurements. Pervaporation performances of the membranes were evaluated for the separation of water‐isopropanol (IPA) mixtures. As the PVAm content increased from PVAm0 to PVAm1.5, the flux through a 70 μm film increased from 0.023 to 0.10 kg/m² h at an IPA/water feed ratio of 85/15 at 30 °C. The driving force for permeation of water increased due to the temperature but it has no effect on IPA permeation. Activation energies for the permeation of IPA and water were calculated to be 17.11 and 12.46 kJ/mol, respectively. Controlling the thickness of the blend membrane could improve the permeation flux with only a marginal reduction in the separation factor. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45572.     

Studies of chitosan. I. Preparation and characterization of chitosan/poly(vinyl alcohol) blend films

Various blending ratios of chitosan/poly (vinyl alcohol) (CS/PVA) blend films were prepared by solution blend method in this study. The thermal properties and chemical structure characterization of the CS/PVA blend films were examined by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), and Fourier transform infrared (FTIR). Based upon the observation on the DSC thermal analysis, the melting point of PVA is decreased when the amount of CS in the blend film is increased. The FTIR absorption characteristic is changed when the amount of CS in the blend film is varied. Results of X‐ray diffraction (XRD) analysis indicate that the intensity of diffraction peak at 19° of PVA becomes lower and broader with increasing the amount of CS in the CS/PVA blend film. This trend illustrates that the existence of CS decreases the crystallinity of PVA. Although both PVA and CS are hydrophilic biodegradable polymers, the results of water contact angle measurement are still shown as high as 68° and 83° for PVA and for CS films, respectively. A minimum water contact angle (56°) was observed when the blend film contains 50 wt % CS. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Preparation and characterization of conductive poly(vinyl alcohol)/polyaniline doped by dodecyl benzene sulfonic acid (PVA/PANDB) blend films

In this study a solution‐blend method is adopted to prepare conductive poly(vinyl alcohol)/polyaniline doped by dodecyl benzene sulfonic acid (PVA/PANDB) blend films. Emeraldine base (EB)‐type polyaniline (PANI) is dissolved in N‐methyl‐2‐pyrrolidinone (NMP) and then blended with PVA/dodecyl benzene sulfonic acid (DBSA) solution by various amounts. It is found that the electrical conductivity and the thermal degradation onset temperature of the PVA/PANDB blend film are increased as the amount of EB‐type PANI solution is increased. Fourier transform infrared (FTIR) spectra show that the intensity of the characteristic peak of the functional groups in the blend film is significantly changed as the amount of EB‐type PANI is changed. From optical microscopy examination, it indicates that the amount and size of green particles are increased with increasing the amount of EB‐type PANI solution. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3415–3422, 2007     

Preparation and characterization of chitosan/poly(vinyl alcohol) blend fibers

Chitosan and poly(vinyl alcohol) blend fibers were prepared by spinning their solution through a viscose‐type spinneret at 25°C into a coagulating bath containing aqueous NaOH and ethanol. The influence of coagulation solution composition on the spinning performance was discussed, and the intermolecular interactions of blend fibers were studied by infrared analysis (IR), X‐ray diffraction (XRD), and scanning electron micrograph (SEM) and by measurements of mechanical properties and water‐retention properties. The results demonstrated that the water‐retention properties and mechanical properties of the blend fibers increase due to the presence of PVA in the chitosan substract, and the mechanical strength of the blends is also related to PVA content and the degree of deacetylation of chitosan. The best mechanical strength values of the blend fibers, 1.82 cN/d (dry state) and 0.81 cN/d (wet state), were obtained when PVA content was 20 wt % and the degree of deacetylation of chitosan was 90.2%. The strength of the blend fibers, especially wet tenacity could be improved further by crosslinking with glutaraldehyde. The water‐retention values (WRV) of the blend fibers were between 170 and 241%, obviously higher than pure chitosan fiber (120%). The structure analysis indicated that there are strong interaction and good miscibility between chitosan and poly(vinyl alcohol) molecular resulted from intermolecular hydrogen bonds. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2558–2565, 2001     

聚乙烯醇膜的改性及应用研究进展

聚乙烯醇（PVA）的改性处理是其应用于膜分离过程必不可少的环节。本文对PVA膜常用的交联、接枝、共混、杂化和取代等改性方法进行了综述,比较了这几种改性方法的优缺点,针对这些改性方法存在的问题,提出了一些改进思路。论文也详细介绍了PVA改性膜在渗透汽化、超滤、纳滤及燃料电池等方面的应用,最后分别对保持良好亲水性PVA膜在渗透汽化脱水领域和高导电率、低甲醇渗透率PVA膜在燃料电池中的应用前景作了展望。     

Preparation and characterization of poly(vinyl alcohol)‐poly(vinyl pyrrolidone) blend: A biomaterial with latent medical applications

Aqueous solutions of poly(vinyl alcohol) and poly(vinyl pyrrolidone) are blended and films are produced by casting method with the further intention of being used as bio‐materials with latent medical application. Glutaraldehyde, 4,4′‐diazido‐2,2′‐stilbenedisulfonic acid disodium salt tetra‐hydrate are used as crosslinker agents, whereas lactic acid is the plasticizer in the blend. The obtained films are characterized by differential scanning calorimetry (DSC), mechanical properties, swelling and solubility behavior. DSC measurements show that the blends exhibit a single glass transition temperature indicating that they are miscible, even in the presence of the plasticizer and crosslinker agents. By the combination of all mentioned additives, a relevant enhancement of the swelling is observed, accompanied by a stabilization of the solubility during the tested time. Finally, mechanical properties show an appropriate performance in the studied parameters. As a consequence, the obtained films could be suitable for use as medium or long‐term implants. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Imidazolium functionalized poly(vinyl alcohol) membranes for direct methanol alkaline fuel cell applications

In this study, imidazolium functionalized poly(vinyl alcohol) (PVA) was synthesized by acetalization and direct quaternization reaction. Afterwards, composite anion exchange membranes based on imidazolium‐ and quaternary ammonium‐ functionalized PVA were used for direct methanol alkaline fuel cell applications. ¹H NMR and Fourier transform infrared spectroscopy data indicated that imidazole functionalized PVA was successfully synthesized. Inductively coupled plasma mass spectrometry data demonstrated that the imidazolium structure was efficiently obtained by direct quaternization of the imidazole group. Composite anion exchange membranes were fabricated by application of the functionalized PVA solution on the surface of porous polycarbonate (PC) membranes. Fuel cell related properties of all prepared membranes were investigated systematically. The imidazolium functionalized composite membrane (PVA‐Im/PC) exhibited higher ionic conductivity (7.8 mS cm^?1 at 30 °C) despite a lower water uptake and ion exchange capacity value compared to that of quaternary ammonium. In addition, PVA‐Im/PC showed the lowest methanol permeation rate and the highest membrane selectivity as well as high alkaline and oxidative stability. Dynamic mechanical analysis results reveal that both composite membranes were mechanically resistant up to 10⁷ Pa at 140 °C. The superior performance of imidazolium functionalized PVA composite membrane compared to quaternary ammonium functionalized membrane makes it a promising candidate for direct methanol alkaline fuel cell applications. © 2020 Society of Chemical Industry     

季铵化羟乙基纤维素/季铵化聚乙烯醇共混阴离子交换膜的制备与表征

阴离子交换膜是碱性直接甲醇燃料电池(ADMFC)的核心。本文将季铵化羟乙基纤维素(QHEC)和季铵化聚乙烯醇(QPVA)共混制备了一系列不同配比的QPVA/QHEC阴离子交换膜并对其进行热交联,对膜进行测试和分析,结果表明:膜表面均匀致密,低于300℃膜基本稳定;QPVA/QHEC共混膜的导电率随着QPVA量的增大而增大,在(2.0～7.8)×10-2 s/cm范围内,随着使用温度的升高逐渐升高;QHEC膜对甲醇有很好的阻隔效果,在20℃时,甲醇渗透率最低为2.49×10-6 cm2/s;随QPVA量的增加,共混膜的甲醇渗透率会略有增加。     

Development and characterization of poly(vinyl alcohol) and casein blend films

Blends of plasticized casein (CA) and poly(vinyl alcohol) (PVA) at various ratios were prepared using the solution‐casting method. The prepared blend solutions were cast onto polystyrene petri plates and bend films were obtained. The characterization of films was performed using Fourier transform infrared spectroscopy, tensile testing, thermogravimetric analysis, contact angle measurements and water vapour permeability. According to spectroscopic analysis, there were interactions between the CA and PVA molecules. The tensile test results showed that the tensile strength of CA increased with increasing PVA content. The flexibility of plasticized CA film increased with the incorporation of PVA. The thermal stability and water vapour barrier properties of plasticized CA improved on blending with PVA. As a result, it was seen that blend films were successfully produced using plasticized CA and PVA with potential for use in biodegradable packaging applications. © 2019 Society of Chemical Industry     

Structure and properties of hydrophobic cationic poly(vinyl alcohol)

A new class of derivatives of poly(vinyl alcohol) (PVA) was prepared through hydrophobic cationic modification. The structure and composition of PVA grafted with glycidyl‐N‐alkyl‐N,N‐dimethyl‐ammonium chloride (DA) (PVA‐ graft ‐DA) was confirmed with Fourier transform infrared spectral analysis and ¹H NMR spectral analysis. The stress‐strain curves of PVA‐ graft ‐DA samples all exhibited an elastic deformation stress plateau, and strain hardening behavior can be observed, indicating the transition of PVA from brittle fracture to ductile fracture. Compared with virgin PVA, the relaxation peak (T_g) of PVA‐ graft ‐DA shifted to a lower temperature. With increasing alkyl chain length and grafting ratio of DA, T_g decreased, and PVA‐ graft ‐DA exhibited a gradually decreasing storage modulus over the whole temperature range of testing due to the relatively weak intermolecular hydrogen bonding and increasing flexibility of molecular chains by introduction of long alkyl chains. PVA crystallites were not affected by grafting with DA, while the crystallization temperature and crystallinity of PVA were improved and the grain size decreased. On grafting with DA, the fracture surface of PVA changed from a smooth surface to regularly distanced striations, displaying much obvious character of tough fracture, indicating that appropriate intermolecular association of the hydrophobic groups facilitated the formation of physical entanglement of molecular chains to strengthen and toughen the PVA matrix. PVA‐ graft ‐DA showed a significant decreasing surface tension with polymer concentration, while the surface tension of PVA‐ graft ‐DA12 dropped most dramatically and declined with increasing grafting ratio of DA12, indicating improvement of the surface activity of PVA by introduction of hydrophobic alkyl chains and hydrophilic cationic groups. Copyright © 2011 Society of Chemical Industry     

Preparation and properties of chitosan/poly(vinyl alcohol) blend foams for copper adsorption

A new form of polymer blend, macroporous chitosan/poly(vinyl alcohol) (PVA) foams made by a starch expansion process, exhibits the functionalities of chitosan while avoiding its poor mechanical properties and chemical instabilities. The appropriate conditions for foaming are discussed using both insoluble and water‐soluble chitosan. The chitosan/PVA foams demonstrated interconnected and open‐cell structures with large pore size from tens to hundreds of micrometers and high porosities from 73.6 to 84.3%. Glutaraldehyde was employed to improve the retention of chitosan and copper adsorption of the chitosan/PVA foams. While it increased the retention of chitosan and the adsorption capacities, glutaraldehyde decreased the pore size and porosity. The macroporous structure of the chitosan/PVA foams indicates extensive application prospects in terms of the considerable adsorption of heavy metal ions. Copyright © 2006 Society of Chemical Industry     

Enhanced oxygen‐barrier and water‐resistance properties of poly(vinyl alcohol) blended with poly(acrylic acid) for packaging applications

To enhance the oxygen‐barrier and water‐resistance properties of poly(vinyl alcohol) (PVA) and expand its food packaging applicability, five crosslinked poly(vinyl alcohol)/poly(acrylic acid) (PVA/PAA) blend films were prepared via esterification reactions between hydroxyl groups in PVA and carboxylic acid groups in PAA. The physical characteristics of the blends, including the thermal, barrier, mechanical and optical properties, were investigated as a function of PAA ratio. With increasing PAA content, the crosslinking density was significantly increased, resulting in changes in the chemical structure, morphology and crystallinity of the films. The oxygen transmission rate of pure PVA decreased from 5.91 to 1.59 cc m^?1 day^?1 with increasing PAA ratio. The water resistance, too, increased remarkably. All the blend films showed good optical transparency. The physical properties of the blend films were strongly correlated with the chemical structure and morphology changes, which varied with the PAA content. © 2016 Society of Chemical Industry     

Electron beam synthesis and characterization of poly(vinyl alcohol)/montmorillonite nanocomposites

Poly(vinyl alcohol) (PVA)/montmorillonite clay (MMT) nanocomposites in the form of films were prepared under the effect of electron beam irradiation. The PVA/MMT nanocomposites gels were characterized by X‐ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and mechanical measurements. The study showed that the appropriate dose of electron beam irradiation to achieve homogeneous nanocomposites films and highest gel formation was 20 kGy. The introduction of MMT (up to 4 wt %) results in improvement in tensile strength, elongation at break, and thermal stability of the PVA matrix. In addition, the intercalation of PVA with the MMT clay leads to an impressive improved water resistance, indicating that the clay is well dispersed within the polymer matrix. Meanwhile, it was proved that the intercalation has no effect on the metal uptake capability of PVA as determined by a method based on the color measurements. XRD patterns and SEM micrographs suggest the coexistence of exfoliated intercalated MMT layers over the studied MMT contents. The DSC thermograms showed clearly that the intercalation of PVA polymer with these levels of MMT has no influence on the melting transitions; however, the glass transition temperature (T_g) for PVA was completely disappeared, even at low levels of MMT clay. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1129–1138, 2006     

Preparation and properties of keratin–poly(vinyl alcohol) blend fiber

Keratin–poly(vinyl alcohol) (PVA) blend fibers containing 13–46 wt % of –SSONa⁺ (S‐sulfo) keratin were prepared by the wet‐spinning technique. They were formed by dehydration of an aqueous solution of S‐sulfo keratin and PVA (spinning dope) in a coagulation bath of sodium sulfate–saturated solution and subsequently drawn. Keratin–PVA fibers showed higher tenacity than that of wool, presumably originating from the high mechanical strength of the PVA component. The heat treatment at about 200°C improved the waterproof characteristics such as shrinkage of keratin–PVA fibers more conspicuously than did PVA fibers. That is, after heat treatment at 195°C for 10 min, keratin–PVA blend fiber shrank 20% in water at 60°C, whereas PVA fiber shrank 56%. Differential thermal analysis suggested the crosslinking of disulfide bonds between keratin molecules during the heat treatment, whereas the additional crystallization of PVA component was not observed. Adsorption of heavy metal and toxic gas to keratin–PVA fibers was also investigated. Keratin–PVA fiber was found to adsorb Ag⁺ and formaldehyde gas more efficiently than PVA. Thus, blends of keratin and PVA were advantageous for both polymer fibers. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 756–762, 2004     

Preparation and structural characterization of nanocrystalline poly(vinyl chloride)

This article describes the development of novel nanocrystalline poly(vinyl chloride) (PVC) for potential applications in PVC processes and reports improvements in the mechanical properties and thermal resistance. Before the preparation of nanocrystalline PVC via jet milling, PVC was spray‐treated and heat‐treated to improve its crystallinity. The pulverization and degradation, morphology, crystalline structure, and melting‐point changes of postmodified PVC during jet milling and the relationship between the distributions of the particle size and processing temperature were investigated. X‐ray analysis and density testing indicated increased density and improved crystallinity. The crystalline region of nanocrystalline PVC was less than 80 nm, with a particle size distribution of 5–20 μm and a melting point of less than 128°C. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 563–569, 2004     

Thermal and spectroscopic studies of poly(N‐vinyl pyrrolidone)/poly(vinyl alcohol) blend films

Poly(N‐vinyl pyrrolidone) (PVP) and poly (vinyl alcohol) (PVA) homopolymers and their blended samples with different compositions were prepared using cast technique and subjected to X‐ray diffraction (XRD) measurements, infrared (IR) spectroscopy, ultraviolet/visible spectroscopy, and thermogravimetric analysis (TGA). XRD patterns of homopolymers and their blended samples indicated that blending amorphous materials, such as PVP, with semicrystalline polymer, such as PVA, gives rise to an amorphous structure with two halo peaks at positions identical to those found in pure PVP. Identification of structure and assignments of the most evident IR ‐ absorption bands of PVP and PVA as well as their blends in the range 400–2000 cm^?1 were studied. UV–vis spectra were used to study absorption spectra and estimate the values of absorption edge, E_g, and band tail, E_e, for all samples. Making use of Coats‐Redfern relation, thermogravimetric (TG) data allowed the calculation of the values of some thermodynamic parameters, such as activation energy E, entropy ΔS^#, enthalpy ΔH, and free energy of activation ΔG^# for different decomposition steps in the samples under investigation. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Glycerol-modified poly(vinyl alcohol)/poly(ethylene glycol) self-healing hydrogel for artificial cartilage

Poly(vinyl alcohol) (PVA) hydrogels have shown potential applications in bionic articular cartilage due to their tissue-like viscoelasticity, good biocompatibility and low friction. However, their lack of adequate mechanical properties is a key obstacle for PVA hydrogels to replace natural cartilage. In this study, poly(ethylene glycol) (PEG) and glycerol were introduced into PVA, and a PVA/PEG–glycerol composite hydrogel was synthesized using a mixing physical crosslinking method. The mechanical properties, hydrophilicity and tribological behavior of the PVA/PEG–glycerol hydrogel were investigated by changing the concentration of glycerol in PEG. The results showed that the tensile strength of the hydrogel reached 26.6 MPa at 270% elongation at break with 20 wt% of glycerol plasticizer, which satisfied the demand of natural cartilage. In addition, the excellent hydrophilicity of glycerol provides good lubricating properties for the composite gel under dry friction. Meanwhile, self-healing and cellular immunity assays demonstrated that the composite gel could have good self-healing ability and excellent biocompatibility even in the absence of external stimuli. This study provides a new candidate material for the design of articular cartilage, which has the potential to facilitate advances in artificial joint cartilage repair. © 2022 Society of Industrial Chemistry.     

Synthesis and characterization of an interpenetrating polymer network composed of poly(methacrylic acid) and poly(vinyl alcohol)

Temperature and pH‐responsive interpenetrating polymer network (IPN) hydrogels, constructed with poly(methacrylic acid) (PMAA) and poly(vinyl alcohol) (PVA), by a sequential IPN method, were studied. The characterization of IPN hydrogels was investigated by Fourier‐transform infrared spectroscopy, differential scanning calorimetry (DSC) and swelling under various conditions. The IPN hydrogels exhibited relatively high swelling ratios, in the range 230–380 %, at 25 °C. The swelling ratios of the PMAA/PVA IPN hydrogels were pH and temperature dependent. DSC was used for the quantitative determination of the amounts of freezing and non‐freezing water. The amount of free water increased with increasing PMAA content in the IPN hydrogels. Copyright © 2004 Society of Chemical Industry     

肝素化聚乙烯醇性能研究

用聚乙烯醇(PVA)缩醛化方法,共价键结合肝素。用Schiff试剂染色法、红外光谱分析、X射线光电子能谱法(ESCA)、元素分析等测试方法证明醛基和肝素的存在。力学性能测定表明,肝素化聚乙烯醇的拉伸强度达到12 25MPa,断裂伸长率为400%。生物学指标说明,在全血凝固时间实验(CT)中,肝素化聚乙烯醇的抗凝时间达3h,在活性部分凝血时间实验(APTT)中,缩醛化聚乙烯醇共价键结合肝素非常牢固,没有肝素脱落到血液中,证明肝素化聚乙烯醇具有显著的抗凝血性。     

Preparation and magnetometric characterization of iron oxide-containing alginate/poly(vinyl alcohol) networks

Alginate-based magnetic gels were prepared in a sequence of procedures for in situ synthesis of iron oxides: crosslinking of alginate in ferrous salt aqueous solution, immersion of the resulting gels into alkaline-earth metallic hydroxide solution, and treatment of the partially cation-exchanged gels with hydrogen peroxide. Magnetometry measurements revealed that the lyophilized gels showed superparamagnetism or ferromagnetism at room temperature, depending on the sort of the metallic cation employed in the alkali treatment. An interpenetrating network (IPN) type of alginate/poly(vinyl alcohol) (Alg/PVA) gels containing iron oxides was also designed and fabricated from mixed polymer solutions by a modified preparation method; the gelation and alkali treatment were carried out with the aid of a metallic borate. Viscoelasticity of the magnetic IPN composites in the gelatinous state was controllable by changing the mixing ratio of the compatible carbohydrate/viny polymer pair. Magnetization versus magnetic field curves were constructed at different temperatures for the IPNs freeze-dried. Their magnetic character was variable according to alterations of the Alg/PVA composition, alkaline reagent adopted, and measurement temperature.