Pure PVA Film Research Articles

Artificial Nacre-Like Gold Nanoparticles–Layered Double Hydroxide–Poly(vinyl alcohol) Hybrid Film with Multifunctional Properties

Gold nanoparticles–layered double hydroxide–poly(vinyl alcohol) (Au NPs–LDH–PVA) hybrid films have been successfully prepared for the first time by bottom-up assembly of pretreated Au NPs–LDH nanosheets and subsequent spin-coating of PVA. The cross sections of the as-prepared hybrid films resemble the brick-and-mortar structure of nacre. The tensile strength of the Au NPs–LDH–PVA hybrid film reaches a high value of 122 MPa, which is higher than that of a pure PVA film and surpasses the strength of natural nacre. Furthermore, we demonstrate that Au NPs–LDH–PVA hybrid films possess surface-enhanced Raman scattering and catalytic properties. Therefore, our report on the fabrication of multifunctional Au NPs–LDH–PVA hybrid films not only shows a feasible route to functionalizing artificial nacre-inspired materials but also potentially broadens applications of these nacre-like materials.

Composite Films of Poly(vinyl alcohol) and Bifunctional Cross-linking Cellulose Nanocrystals.

Long and flexible cellulose nanofibrils or stiff and short cellulose nanocrystals (CNCs) are both promising lightweight materials with high strength and the potential to serve as reinforcing agents in many polymeric materials. In this study, bifunctional reactive cellulose nanocrystals (RCNCs) with carboxyl and aldehyde functionalities were used as reinforcements to prepare acetal-bonding cross-linked poly(vinyl alcohol) (PVA) films. Two RCNCs were obtained through the mechanical homogenization of partially carboxylated dialdehyde cellulose (DAC) with a residual aldehyde content of 0.55 and 1.93 mmol/g and a carboxyl content of 1.65 and 1.93 mmol/g, respectively. The mechanical, thermal, and barrier properties of PVA-RCNC films with a variable mass ratio of RCNCs (0.5-10%) were determined. Reference CNCs without reactive aldehydes were obtained through the reduction of aldehyde functionalities to primary hydroxide groups, and their reinforcing effect was compared to RCNCs. With the addition of 10% acetal-bonding RCNCs with respect to PVA weight, the tensile strength and Young's modulus were up to 2-fold greater than those of pure PVA film. An addition of only 0.5% RCNCs improved the tensile strength of the PVA film by 66% and the modulus by 61%. In comparison, a significantly lower reinforcing effect (19% with CNC loading of 0.5%) was found using reference CNCs. PVA's effective oxygen barrier and thermal properties were preserved when RCNCs were introduced into the films.

The plasticizing effect of properties of manganous chloride and glycerin on poly(vinyl alcohol)

Abstract Poly(vinyl alcohol) films were prepared with manganous chloride (MnCl2 · 4H2O) and glycerin as complex plasticizer. The micro morphology of pure PVA film and complex plasticizer plasticized PVA films was observed by scanning electron microscope (SEM). The interaction between complex plasticizer and PVA molecules was investigated by Fourier transform infrared spectroscopy (FT-IR). The influence of complex plasticizer on crystalline, thermal and mechanical properties of PVA films was studied by X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TG), and tensile testing, respectively. The results showed that the complex plasticizer of MnCl2 · 4H2O/glycerin could interacted with PVA molecular and then effectively destroy the crystals of PVA. PVA films plasticized with complex plasticizer of MnCl2 · 4H2O/glycerin became soft and ductile, with lower tensile strength and higher elongation at break compared with PVA films. This is an important cause of plasticization of the complex plasticizer of MnCl2 · 4H2O/glycerin on PVA films.

Highly-enhanced water resistant and oxygen barrier properties of cross-linked poly(vinyl alcohol) hybrid films for packaging applications

Abstract To enhance the thermal stability and barrier properties of pure poly(vinyl alcohol) (PVA), five different cross-linked poly(vinyl alcohol)/boric acid (PVA/BA) hybrid films were prepared via a solution blending method, and their properties including barrier properties, thermal stability, transparency, and mechanical properties were investigated as a function of the BA content. The physical properties of the PVA/BA hybrid films were strongly dependent upon the chemical structure and morphology of the films originating from the amount of BA and change in degree of cross-linking. With increasing BA content, the size and amount of PVA crystallites decreased, whereas the cross-linking density increased, resulting in more compact packing of the molecules and lower free volume in the amorphous regions. The glass transition temperature and thermal stability were highly enhanced with increasing BA content. The oxygen transmission rate (OTR) of pure PVA decreased from 5.96 to 0.15 cc/m 2 day with increasing BA content and were greatly suppressed by 22.8% for 1% BA, 7.7% for 3% BA, and 2.5% for 3% BA, respectively, relative to pure PVA film. With increasing BA content, their water-resistant pressure and tensile strength increased with BA loading. All the hybrid films showed good transparency. These properties of the cross-linked PVA/BA hybrid films make them potential candidates for versatile applications as coatings, films, and packaging materials.

Studies on AC Electrical Conductivity and Dielectric Properties of PVA/NH<sub>4</sub>NO<sub>3</sub> Solid Polymer Electrolyte Films

Solid polymer electrolytes have been extensively studied due to wide applications in various elec- trochemical devices (1)-(3). Most of the solid polymer electrolytes consist of polymer as a host material to provide strength and good mechanical stability and an inorganic salt that supplies io- nic carriers to cause electrical conductivity. In our studies, we prepared PVA/NH4NO3 polymer electrolyte films by solution casting method. The prepared films with varied Ammonium Nitrate concentration from 0 - 20 wt% are characterized by XRD & FTIR spectroscopy. XRD results show that amorphous nature increases as the amount of the Ammonium Nitrate salt in PVA is increased. IR-spectra confirm the polymer salt complexes in the range of 3700 - 712 cm −1 . Conductance anal- ysis reveals that polymer electrolyte films containing 20 wt% of NH4NO3 exhibit the highest ionic conductivity of 1.01 × 10 −7 S/cm while pure PVA films give the lowest ionic conductivity of 2.10 × 10−11 S/cm. It was evident from this study that the increase of ionic conductivity depended on the Ammonium Nitrate salt concentration. The dielectric constant exponentially decreases with in- crease of frequency for pure PVA and NH4NO3 doped PVA film composites. The temperature de- pendent studies of AC conductivity and dielectric constant also included to understand the con- ducting property. The results obtained by these studies are reported in this work.

Preparation and properties of poly(vinyl alcohol)/vinyltrimethoxysilane (PVA/VTMS) hybrid films with enhanced thermal stability and oxygen barrier properties

To enhance the thermal stability and barrier properties of pure poly(vinyl alcohol) (PVA), a series of poly(vinyl alcohol)/vinyltrimethoxysilane (PVA/VTMS) hybrid films were prepared via a sol-gel process, and their physical properties were investigated as a function of VTMS content. During the sol-gel process, simultaneous reactions between hydroxyl groups of PVA and silanol groups of hydrolyzed VTMS and self-condensation of VTMS occurred, inducing a cross-linked network structure and greatly enhanced thermal stability and oxygen barrier properties. The glass transition temperature and thermal decomposition temperature (T 5%) of the PVA/VTMS hybrid films increased from 72.6 to 84.3 °C and 273.6 to 342.2 °C, respectively, with increasing VTMS content from 0 to 20%. Oxygen transmission rates of the hybrid films decreased from 6.12 to 0.17 cm3/m2×day, and those of the hybrid films incorporating 5%, 10%, and 20% VTMS were suppressed by 65.7%, 95.6%, and 97.2%, respectively, versus a pure PVA film. These are dependent on the chemical structure and morphology of the films with differing initial amounts of VTMS. The chemical affinity for water, intermolecular packing, and rigidity in polymer chains increased with increasing cross-linking by VTMS, leading to enhanced oxygen barrier properties and thermal stability in the PVA/VTMS hybrid films.

Bioinspired design and assembly of layered double hydroxide/poly(vinyl alcohol) film with high mechanical performance.

Inspired by the hierarchical structure and excellent mechanical performance of nacre, LDH nanosheets with an appropriate aspect ratio to withstand significant loads and at the same time allow for rupture under the pull-out mode were synthesized as artificial building blocks for the fabrication of nacre-like films. Multilayered PVA/LDH films with a high tensile strength and ductility were prepared for the first time by bottom-up layer-by-layer assembly of pretreated LDH nanosheets and spin-coating of PVA. The weight fraction of inorganic LDH platelets in the hybrid PVA/LDH films (wp) was controlled by changing the concentration of PVA solution applied in the spin-coating process. The resulting films revealed that the PVA/LDH hybrid films were piled close together to form a well-defined stratified structure resembling the brick-and-mortar structure of natural nacre. In the hybrid films, the content of inorganic LDH platelets was comparable to the value in nacre, up to 96.9 wt %. It could be clearly seen that the mechanical performance of the as-prepared PVA/LDH films was greatly improved by increasing the rigid building-block LDHs. The tensile strength of the 2 wt % PVA/LDH hybrid film reached a value of 169.36 MPa, thus exceeding the strength of natural nacre and reaching 4 times that of a pure PVA film. Meanwhile, its elastic modulus was comparable to that of lamellar bone.

Antioxidant, antifungal, water binding, and mechanical properties of poly(vinyl alcohol) film incorporated with essential oil as a potential wound dressing material

ABSTRACTIn this study, the properties of poly (vinyl alcohol) (PVA) films incorporated with Zataria multiflora essential oil (ZMO) as a potential antioxidant/antibacterial material was investigated. PVA films were prepared from PVA solutions (2% w/v) containing different concentrations of ZMO. Water solubility, moisture absorption, water swelling, and water vapor permeability for pure PVA films were 57 ± 1.1, 99 ± 3.2%, 337 ± 8%, and 0.453 ± 0.015 g mm/m2 h, respectively. Incorporation of ZMO into PVA films caused a significant decrease in water swelling and moisture absorption and increase in solubility and water vapor permeability. Tensile strength, elastic modulus, and elongation at break for pure PVA films were 13.5 ± 0.61 MPa, 15.2 ± 0.8 MPa, and 216 ± 4%, respectively. Incorporation of ZMO into the PVA films caused a significant decrease in tensile strength and elastic modulus and increase in elongation at break of the films. Pure PVA film showed UV‐visible light absorbance ranging from 280 to 440 nm with maximum absorbance at 320 nm. Addition of ZMO caused a significant increase in light absorbance and opacity. PVA films exhibited no antioxidant and antifungal activities, whereas PVA/ZMO films exhibited excellent antioxidant and antifungal properties. Although the bioactivity PVA films were improved by the addition of ZMO, however, the mechanical properties and water binding capacity of the films were weaken slightly. Thus, ZMO emulsified in the ethanol not compatible with PVA matrix and more suitable emulsifier was needed in order to obtain strong film with higher mechanical properties. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40937.

Mechanical Properties Research and Structural Characterization of Alkali Lignin / Poly(vinyl alcohol) Reaction Films

With alkali lignin and PVA as the primary materials, glutaraldehyde as the cross-linker, and glycerin as the plasticizer, alkali lignin/PVA cross-linking reaction film was prepared by casting. The process conditions were evaluated one at a time for different variables. Mechanical properties of the composite film were tested. The performance of the reaction film was analysed by XRD, TG, SEM, and FT-IR. The results showed that when the mass ratio of alkali lignin/PVA was 1/5, glutaraldehyde content 1.67%, and glycerol content 7.1% (w/w) of the dry matter, respectively, the reaction film had satisfactory mechanical properties. Under the best conditions, the mechanical properties of the reaction film were better than that of pure PVA film. The thermal stability of the reaction film was higher than the stability of PVA film. Compared with pure PVA film, the crystallinity of the reaction film decreased a little. SEM images indicated that compatibility of alkali lignin and PVA was good. The FT-IR analysis showed that a cross-linking reaction occurred between alkali lignin and PVA(1788). But the aldol reaction between the lignin and PVA(1788) was weak.

Understanding the relationship of performance with nanofiller content in the biomimetic layered nanocomposites

Montmorillonite/poly(vinyl alcohol) (MMT/PVA) nanocomposites spanning the complete range of MMT content (0-100 wt%) are prepared by simple evaporation-induced assembly. Effects of MMT content on the structure and mechanical properties of nanocomposites are systematically investigated and exhibit two important transitions at MMT contents of 30 wt% and 70 wt%. In the range of 0-30 wt%, the nanocomposites show a random structure. With the content of PVA increasing, the mechanical properties of the resultant nanocomposites were dramatically enhanced and were higher than that by prediction according to the conventional composite model. In the range of 30-70 wt%, the nanocomposites show a nacre-like layered structure with alternating MMT platelets and PVA layers, and all PVA is completely restricted by MMT platelets. The mechanical properties of nanocomposites were further improved by increasing the content of MMT, and reached the maximum value at the MMT content of 70 wt%. The 70 wt% MMT/PVA nanocomposite has a tensile strength of 219 ± 19 MPa, which is 5.5 times higher than that of a pure PVA film and surpasses nacre and reported biomimetic layered clay/PVA composites. When the MMT content is higher than 70 wt%, the layered structure is transformed to tactoids, which deteriorate mechanical properties. These results offer comprehensive understanding for developing high-performance biomimetic layered nanocomposite materials with high nanofiller loading.

Anisotropic silver nanoparticles as filler for the formation of hybrid nanocomposites

Prismatic and plate-like silver nanoparticles (Ag NPs) were synthesized according to the seed-mediated method. These particles were used as precursors for preparation of homogenous, transparent and colored Ag/poly(vinyl alcohol) (PVA) nanocomposite films with different concentrations of Ag by solution-casting technique. Optical and structural characterization of these nanocomposites includes UV–visible spectroscopy, X-ray diffraction (XRD), FTIR spectroscopy and SEM measurements. Further, the effect of embedded nanoparticles on the thermal properties of the PVA matrix was studied. The value of the glass transition temperature of polymer is found to increase after embedding Ag NPs. Comparison of thermal properties of pure PVA and nanocomposite films showed that the thermo-oxidative stability of polymer slightly increased in the presence of Ag NPs. Furthermore, the effect of the Ag NPs on the crystallinity of polymer was also observed.

Slow-Release Antibacterial and Physical Properties of PVA Antibacterial Film

The antifungal PVA film was fabricated by addition of the clove oil/β-cyclodextrin inclusion complex into PVA, which is acted as the basic packaging material. The mechanical properties, oxygen permeability and the bacteriostatic action of the film varied with the additional amount of inclusion complex. The tensile strength of PVA film decreased with the addition of inclusion complex and the effect is little when the amount was less than 25%. Adding less than 25% had no obviously effect on oxygen permeability of the film. It proved that pure PVA films have no antibacterial property and the growth of aspergillus was inhibited in different degrees when the content was different. The growth range of aspergillus is smaller and the bacteriostatic action to aspergillus is increased with the increase of inclusion complex amount of agent. The inhibitory zone appeared when the inclusion complex amount was more than 20%.

폴리비닐알콜/폴리아크릴로니트릴 블렌드 필름의 제조 및 특성

A poly(vinyl alcohol)(PVA)/poly(acrylonitrile)(PAN) blend film was prepared and its properties were characterized to investigate the possibility of improving PVA as a reinforcing materials. From the wide-angle X-ray diffraction patterns of the blend films it can be seen that the diffraction peaks from each polymer's crystal were not changed by blending, this implies there is no mutual influence in crystallization. The water contact angle of the blend film increased with increasing PAN content. The decrease rate of the water contact angle of the blend film with time was smaller than the rate for pure PVA film. The melting temperatures of the PVA/PAN blend film only at the ratios of 99/1 and 97/3 were higher than that of pure PVA film. The thermal decomposition temperature and residual weight of the blend films were increased with increasing PAN content, indicating improved thermal stability after blending with PAN. The tensile strength and Young's modulus of the film increased after blending and the PVA/PAN blend film containing 3wt% of PAN showed the best mechanical properties.

Effect of gamma irradiation on biopolymer composite films of poly(vinyl alcohol) and bacterial cellulose

Composite materials containing in different ratios poly(vinyl alcohol) (PVA), bacterial cellulose (BC) and glycerol (G) as plasticizer were obtained and exposed to different γ radiation doses using an irradiator GAMMATOR provided with 137Cs source. These films successively received up to 50kGy absorbed doses at a dose rate of 0.4kGy/h at room temperature. In order to study the chemical and structural changes during γ irradiation, Fourier-transformed infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and UV–Vis spectroscopy were used. Water vapour permeability (WVP), Hunter colour parameters and hardness were also measured for the irradiated samples. Investigation revealed that WVP was not significantly affected by the irradiation. Colour measurements indicated a slight decrease of pure PVA films transparency and it made clear that all samples became more reddish and yellowish after irradiation. The samples hardness was not affected by the irradiation doses used. However, the results showed no drastic structural or chemical changes of the irradiated samples, which prove, in consequence, a good durability. These composite materials could be used as packaging materials for γ irradiated products.

Preparation of nanocrystalline cellulose via ultrasound and its reinforcement capability for poly(vinyl alcohol) composites

Rod-shaped nanocrystalline cellulose (NCC) was prepared from microcrystalline cellulose (MCC) using the purely physical method of high-intensity ultrasonication. Scanning electron microscopy, transmission electron microscopy, and X-ray diffraction was used for the characterization of the morphology and crystal structure of the material. The thermal properties were investigated using thermogravimetric analysis. The reinforcement capabilities of the obtained NCC were investigated by adding it to poly(vinyl alcohol) (PVA) via the solution casting method. The results revealed that the prepared NCC had a rod-shaped structure, with diameters between 10 and 20 nm and lengths between 50 and 250 nm. X-ray diffraction results indicated that the NCC had the cellulose I crystal structure similar to that of MCC. The crystallinity of the NCC decreased with increasing ultrasonication time. The ultrasonic effect was non-selective, which means it can remove amorphous cellulose and crystalline cellulose. Because of the nanoscale size and large number of free-end chains, the NCC degraded at a slightly lower temperature, which resulted in increased char residue (9.6–16.1%), compared with that of the MCC (6.2%). The storage modulus of the nanocomposite films were significantly improved compared with that of pure PVA films. The modulus of PVA with 8 wt.% NCC was 2.40× larger than that of pure PVA.

Optical, structural and thermal characterization of gold nanoparticles – poly(vinylalcohol) composite films

We report synthesis and characterization of gold NPs/PVA composite films. Gold colloidal NPs were introduced into a PVA matrix by simple solution-casting method to obtain homogenous, transparent, and colored films. NPs and NC films with different contents of inorganic phase (0.7, 1.4, and 2.1 wt %) were characterized by UV/Vis and FTIR spectrophotometry. Dimensions of the colloidal NPs were obtained by TEM (d ∼ 15±3 nm) and compared with results obtained by AFM of NC films. Comparison of thermal properties of the pure PVA and NC films showed that thermal stability is slightly reduced. DSC measurements revealed that Tg and melting temperatures of NCs are higher compared to pure PVA films.

Preparation, characterization, and photoluminescence study of PVA/ZnO nanocomposite films

ZnO nanoparticles with average diameter of 25 nm were synthesized by a modified sol–gel method and used in the preparation of (in wt.%) (100 − x) poly(vinyl alcohol) (PVA)/ x ZnO nanocomposite films, with x = 0, 1, 2, 3, 4, and 5. The PVA/ZnO films were exposed to UV radiation for 96 h and their thermal, morphological, and spectroscopic properties were investigated. In inert atmosphere, the nanocomposite films showed lower thermal stability than the pure PVA film, and the calorimetric data suggest an interaction between PVA and ZnO in the nanocomposite films. Some crystalline phases could be seen in the films with ZnO, and a direct dependence on the ZnO concentration was also observed. The original structure of ZnO nanoparticles remained unaltered in the PVA matrix and they were uniformly distributed on the film surface. The roughness of the PVA film was not modified by the addition of ZnO; however, it increased after 96 h of UV irradiation, more significantly in the nanocomposite films. The films showed an absorption band centered at 370 nm and a broad emission band in the UV–vis region when excited at 325 nm.

Use of l-tyrosine amino acid as biomodifier of Cloisite Na+ for preparation of novel poly(vinyl alcohol)/organoclay bionanocomposites film

Cloisite Na+ was modified via cation exchange reaction using natural l-tyrosine amino acid. This novel chiral organo-modified Cloisite Na+ was characterized using fourier transform infrared spectroscopy (FT–IR), X-ray diffraction (XRD), and thermogravimetric analysis/derivative thermal gravimetric (TGA/DTG). Then, polymer bionanocomposites were prepared by dispersing chiral organo-modified Cloisite Na+ in poly(vinyl alcohol) (PVA) via ultrasonic irradiation. The novel bionanocomposites were characterized by FT–IR, UV–Visible, TGA, and XRD. Scanning electron microscopy and transmission electron microscopy were used to obtain the information about morphological structure of PVA/Cloisite Na+/Tyr bionanocomposites. The results showed that a mixture of intercalated and exfoliated Cloisite Na+ dispersion in PVA matrix. The TGA data was compared with the pure PVA and the results showed that the introduction of a small amount of Cloisite Na+/Tyr led to improvement in thermal stability of the obtained new bionanocomposites. UV–Visible transmission spectra of pure PVA and new bionanocomposites film in the visible light region (400–800 nm) showed that they are rather transparent.

The role of hydrogen-bonding interaction in poly(vinyl alcohol)/poly(acrylic acid) blending solutions and their films

The aim of this work is to investigate the hydrogen-bonding interaction in poly(vinyl alcohol) (PVA)/poly(acrylic acid) (PAA) blending system and its influence on rheological properties in solution and the physical properties in solid state. Introducing PAA into PVA solutions resulted in a thickening behavior of blend solutions. The viscosity of the solutions increased with PAA content increasing, and a maximum viscosity could be obtained when the ratio of PVA/PAA was 70/30. The intermolecular hydrogen-bonding and miscibility between PVA and PAA in solid state were investigated by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and mechanical measurements. The results displayed the great influence of introducing PAA on the properties of blending films. The tensile strength increased from 89.31 MPa to 119.8 MPa and Young’s modulus improved by over 300% with increasing PAA concentration compared with those of pure PVA films. By systematically studying the rheological behaviors of solutions and the physical properties of films, the influence of hydrogen-bonding in solutions and solid states were discussed.

Electrochemically modified graphite nanosheets and their nanocomposite films with poly(vinyl alcohol)

AbstractA novel, facile, and environment friendly approach based on electrochemical oxidation and ultrasonication was presented to prepare electrically conductive graphite nanosheets (GNs). The as‐prepared GNs with a large aspect ratio were then incorporated into poly (vinyl alcohol) (PVA) by solution compounding. The GNs can be well and stably dispersed in water medium without the need for polymeric or surfactant stabilizers because of the electrochemical modification and their PVA nanocomposite films exhibit enhanced electrical, thermal, and mechanical properties compared with pure PVA film. Electrical resistivity decreases by 4 orders of magnitude with a percolation threshold of ca. 6 wt%. A significant improvement in thermal stability of 45°C and a large shift in glass transition temperature of 14°C are obtained, together with improved mechanical strength and toughness with the optimal GNs loading. POLYM. COMPOS., 31:1770–1775, 2010. © 2010 Society of Plastics Engineers.