Aqueous Solution Of Polyvinyl Alcohol Research Articles

3D printable carbon nanotubes-based composites with reconfigurable shapes and properties

In this work, we developed an efficient approach to fabricating composites of carbon nanotubes (CNT) with shape reconfiguration ability and Joule heating behavior by incorporating the direct ink writing (DIW) technique. Our 3D printable ink consisted of a high concentration of CNT stabilized by polyvinylpyrrolidone (PVP) in an aqueous polyvinyl alcohol (PVA) solution. The rheology of the ink was tuned by the amounts of CNT and PVP. The printed objects underwent the freeze-thaw process to form weak hydrogels induced by the crystallization of PVA. Subsequently, the hydrogels were immersed in a deep eutectic solvent (DES) bath consisting of choline chloride and glycerol. This process replaced the water in the hydrogels with DES and led to mechanically tough DES/CNT gels. We utilized the high stretchability of DES/CNT gel to achieve complex geometries that would be challenging to accomplish solely with DIW. After reshaping the DES/CNT gels, the target shape was fixed by further solvent exchange with ethanol and drying. The final CNT composites showed a high electric conductivity of up to 33.94 S/m and exhibited remarkable Joule heating performance using a low applied voltage (5 V). Additionally, we successfully achieved a spatial variation of mechanical stiffness, electrical conductivity, and Joule heating across the printed objects by a selective solvent removal process. In short, this work expands the scope of possible shapes and properties of CNT-based composites.

Synthesis and Evaluation of Plugging Gel Resistant to 140 °C for Lost Circulation Control: Effective Reduction in Leakage Rate in Drilling Process.

Gel plugging agents have become one of the preferred methods for plugging in complex and severe loss conditions during drilling due to their good adaptability to loss channels. To address the common issue of poor temperature resistance in gel-based plugging agents, high-temperature-resistant gel plugging materials were synthesized through the molecular design of polymers, modifying existing agents. Based on the temperature and salt resistance of the aqueous solution of an acrylamide (AM)/N-vinylpyrrolidone (NVP) binary copolymer, temperature-resistant monomer sodium styrene sulfonate (SSS) was introduced and reacted in a polyvinyl alcohol (PVA) aqueous solution. Using ammonium persulfate (APS) as an initiator and crosslinking with N,N-methylenebisacrylamide (MBA), a gel plugging material resistant to 140 °C was synthesized. The structure, thermal stability, water absorption and expansion, and plugging performance of the gel were studied through hot rolling aging, thermogravimetric analysis, infrared spectroscopy, electron microscopy scanning, sand bed experiments, and drag reduction experiments. The results show that the gel material has good thermal stability and water absorption and expansion at 140 °C, and its temperature-resistant plugging performance is excellent, significantly slowing down the loss rate of drilling fluid. This provides a basis for the further development of gel materials.

Q-switched Er-doped fiber laser using an aqueous solution of gold nanorods and polyvinyl alcohol

Authors reported the generation of Q - Switched pulses in an erbium-ytterbium co-doped fiber laser using an aqueous solution of colloidal gold nanorods (GNRs) and Polyvinyl Alcohol (PVA) as a saturable absorber (SA). The effect of the GNRs and PVA concentrations on the pulses has been explored. Passive Q-Switching is achieved at 1.1 W (1.8 A). Pulses with a minimum width of 9.6 µs having a repetition rate of 21.5 kHz and a maximum energy of 0.15 µJ at 1.56 μm are obtained for a pump current of 2.195 W (3.12 A).

Preparation of CeO2-PVA composite film based on in-situ generation of nano CeO2 particles

In order to prepare nano CeO2-Polyvinyl alcohol (PVA) composites, obtaining composite materials with specific performance generated by the synergistic effect of organic and inorganic component, and to simplify the composite process and improve the dispersion uniformity of inorganic particles in the polymer matrix, a cerium-triethanolamine complex was used as a precursor whose aqueous solution was mixed with 10 wt% polyvinyl alcohol (PVA) aqueous solution, hydrolyzed at room temperature, in-situ generated CeO2 nanoparticles, and achieved a nano CeO2- PVA composite coating solution. The CeO2- PVA composite film was obtained by casting the coating solution onto a watch glass at room temperature. The composite coating solution and the film was respectively characterized by TEM, XRD, UV, IR, TG-DTG and PL. The thin composite film presents slight yellow colour and remains highly transparent even when the CeO2 content reaches 2.0 wt%. The optical bandgap Eg value of the film is 3.55eV, exhibiting excellent ultraviolet absorption ability and blue fluorescence characteristics. It is a highly valuable anti ultraviolet material with potential applications in fluorescent lamps and displays. The characterization results indicate that CeO2 nanoparticles in the composite film are encapsulated by polymer molecular chains and there is interaction between them, which increases the glass transition temperature of the polymer. The incorporation of inorganic particles and the residue of hydrolysis by-products do not put a obvious negative impact on the thermal stability of the composite film.

An ultra‐tough, creep‐resistant, wear‐resistant hydrogel for cartilage replacement

AbstractAs a load‐bearing tissue, natural cartilages possess a compressive stress above 50 MPa, a water content around 60%, and a friction coefficient (FC) less than 0.1, which remains difficult for synthetic materials to realize. Herein, a facile strategy was reported to achieve this goal. The hydrogel was obtained through a three‐step strategy from polyvinyl alcohol (PVA), chitosan (CS), sodium carboxymethyl cellulose (CMC‐Na), lecithin (LS), and deionized water. First, freezing–thawing the aqueous solution of PVA and CS three times generated the precursor gel. Second, immersing it in aqueous solution of CMC‐Na to form multiple linkages (hydrogen bonds, ionic interactions, and crystallize domains). Third, it was coated with LS to form a lubrication layer. Due to the synergy of dynamic interactions, the compressive stress was 115 MPa, superior to most tough hydrogels. Owing to existence of LS, the FC was 0.03, better than the requirement for artificial cartilage. Remarkably, the FC remained stable within 50,000 wear cycles. On account of the reversible break/reformation of physical linkages, the creep recovery efficiency was 93%. The raw materials are all biocompatible and the fabrication process exclude the adoption of toxic additives. All of these features make it an ideal material for cartilage replacement.

The preparation of cellulose acetate capsules using emulsification techniques: high-shear bulk mixing and microfluidics

Abstract This work describes an emulsification-solvent-evaporation method for the preparation of liquid-filled capsules made from cellulose acetate. Two different emulsification techniques were applied: bulk emulsification by high-shear mixing, and droplet generation using microfluidics. The bulk emulsification method resulted in the formation of oil-in-water emulsions composed of an organic mixture of isooctane and cellulose acetate in methyl acetate, and an aqueous phase of high-molecular-weight polyvinyl alcohol (PVA). Upon the solvent evaporation, the emulsion droplets evolved into isooctane-filled cellulose acetate capsules. In contrast, microfluidics led to the formation of monodisperse droplets composed of the aqueous PVA solution dispersed in the organic phase. Upon the solvent evaporation, the emulsion droplets evolved into water-filled cellulose acetate capsules. Owing to the thermoplastic properties of the cellulose acetate, the capsules formed with the bulk mixing demonstrated a significant expansion when exposed to an increased temperature. Such expanded capsules hold great promise as building blocks in lightweight materials.

Design of PVA/PF/CL-20 explosive ink with small critical size and research on micro-sized detonation performance

ABSTRACT Using 3D direct writing technology, a small critical size explosive ink formula was designed using polyvinyl alcohol (PVA) aqueous solution and phenolic resin (PF) ethanol solution as a two-component bonding system, and CL-20 as the main explosive. In particular, we investigated the influence of the CL-20 solid content on the micro-size detonation performance. Preliminary research shows that when the content of the main explosive in the explosive ink is less than 92%, the detonation velocity increases with the increase of the content, and the detonation critical size decreases with the increase of the content. The micromorphology, molding density, explosive crystal form, mechanical sensitivity, thermal stability and detonation corner of the molded samples were tested and characterized. The results show that the internal particle distribution of the printed molded sample is uniform, without cracks and fractures, the crystal form remains ε-type, the mechanical sensitivity and thermal stability are reduced, and the detonation velocity after molding with 92% explosive ink reaches 7281m·s-1, which is critical The detonation size is 1×0.027mm, and the detonation angle can reach up to 160°, showing excellent micro-size detonation performance.

High-strength, water-resistant polyvinyl alcohol films reinforced with regenerated cellulose fibers for food packaging

Polyvinyl alcohol (PVA) film, a promising biodegradable packaging film material, shows low water resistance and mechanical properties, which hinder its application in the packaging field, particularly in humid or aqueous environments. Herein, PVA/regenerated cellulose fibers (RC) blend films (PVA/RC films) were fabricated by a simple controllable regeneration of cellulose fibers in an aqueous solution of PVA. The potentiation formed by the uniformly distributed RC in PVA/RC films and the competitive advantage of hydrogen bond (N···H-O) formation between urea and PVA afforded superior water resistance and mechanical characteristics to PVA/RC films. In particular, PVA/RC films displayed good tensile strength and elongation at break under dry and humid conditions (75.97 and 35.37 MPa; 281.17% and 624.83%, respectively). The shelf life of fresh strawberries packed in these blend films was extended by an additional 4 days. The present study revealed a simple and economical approach to manufacture PVA-based packaging film materials for use in humid and aqueous environments.

Ln-MOF and its hydrogel composite Ln-MOF@PVA for dual-luminescence ratiometric temperature sensing

In this study, we synthesized a solid solution of MOF, Eu0.05Y0.95-PTC (H3PTC represents 2, 4, 6-pyridine tricarboxylic acid) by hydrothermal reaction, which showed exceptional stability under both weakly acidic and alkaline conditions and multiband luminescence. We further prepared Eu0.05Y0.95-PTC@PVA hydrogels by immobilizing Eu0.05Y0.95-PTC into a polyvinyl alcohol (PVA) aqueous solution, which exhibited both the integrity and temperature sensing behavior of the MOF solid solution, alongside excellent mechanical performance. Both Eu0.05Y0.95-PTC and Eu0.05Y0.95-PTC@PVA-8 hydrogel displayed temperature sensing capabilities over the range from 303 to 383 K, with relative sensitivities (Sr) reaching a maximum value of 1.94 %•K−1 and 0.65 %•K−1 at 383 K, respectively, and good recyclability as well.

Preparation of flexible and binder-free lignin-based carbon nanofiber electrode materials by electrospinning in aqueous system

Abstract Lignin, as a widely distributed, renewable and environmentally friendly source of carbon, could been utilized for carbon nanofibers to not only maximize the usage of resources, but also expand the energy-related opportunities. In this research, flexible lignin-based carbon nanofibers are prepared by electrospinning lignin nanofibers in a new green aqueous solution of lignin and polyvinyl alcohol (PVA), which is then characterized by physical and chemical characterizations. The results reveal that optimal carbonization temperature of 800 °C shows great improvements on the structural properties of lignin-based carbon nanofibers, which can be applied as binder-free electric double layer capacitor (EDLC) electrodes with good flexibility. The 2032 type button battery has a superior electrochemical performance with a large specific capacitance of 217.2 F g−1 at a 0.2 A g−1 current density, and remarkable cyclic stability of 94.9 % capacitance retention even after 10,000 charge and discharge cycles, due to the abundance of mesoporous volume and large microporous surface area of lignin-based carbon nanofiber electrodes carbonized in 800 °C.

Polyvinyl alcohol composite gel membrane modified by natural polysaccharide and waterborne polyurethane

AbstractA new composite gel material was obtained by blending polyvinyl alcohol (PVA) aqueous solution with sodium alginate (SA), sodium carboxymethyl cellulose (CMC‐Na), waterborne polyurethane (WPU), and polyvinylpyrrolidone (PVP). Titanium dioxide nanoparticles (nTiO2) were doped as an antibacterial agent. The liquid composite could to form a transparent protective gel membrane. The microstructure of the gel membrane was observed via scanning electron microscopy, and the intermolecular interaction was investigated by total reflection infrared spectroscopy. The results demonstrated a homogeneous phase and significant hydrogen bonding between chain segments. The best results indicated that the equilibrium swelling rate increased from 147% to 170%, the 3‐h water vapor transmission rate increased from 279.41 g/m2∙day to 374.75 g/m2∙day, and the water contact angle increased from 16.8° to 60.7°, relative to the PVA substrate. The properties of this composite gel material suggest possible biomedical usage, particularly in skin and wound protection scenarios.Highlights A novel gel film‐forming material consisting of a viscous liquid is prepared. Adding polysaccharides modifiers resulted in significant improvements of the performance. The bacteriostatic and antihemorrhagic properties are introduced to the material. Low‐irritating materials were used to prepare the gel material.

Photocuring-assisted emulsion of ceramic suspensions containing phase-separable camphene/photopolymer vehicle for porous ceramic spheres

We herein describe photocuring-assisted emulsion of a ceramic suspension prepared using a thermo-regulated phase-separable camphene/photopolymer vehicle for synthesis of porous hydroxyapatite (HA) spheres with unique porous structures. HA suspensions with different camphene contents (60 vol %, 70 vol %, and 80 vol %) were prepared by dispersing HA particles in various camphene/hexanediol diacrylate (HDDA) solutions at room temperature and then emulsified in an aqueous polyvinyl alcohol (PVA) solution via magnetic stirring. Emulsions were frozen at −20 °C for phase separation of camphene/HDDA solutions and then photocured for polymerization of HDDA enclosing HA particles. Synthesized spheres were freeze-dried to remove the camphene-rich crystals. All spheres sintered at 1250 °C for 3 h had well-defined spherical shape with three-dimensionally interconnected pores. The porosity of individual HA spheres increased from ∼ 56.5 vol % to ∼ 78.7 vol % with an increase in camphene content from 60 vol % to 80 vol %.

A facile method to fabricate multifunctional polyvinyl alcohol mineralized hydrogels with high strength and adaptable shape

AbstractHydrogel‐based materials are widely used in many fields, but most of them compared to tendons with the same water content do not exhibit high toughness, strength or fatigue resistance, which limits their application. The Hofmeister effect can adjust the mechanical properties of hydrogels by ions affecting the aggregation of polymer chains. Herein, we prepared a bioactivated hydrogel through simply mixing polyvinyl alcohol (PVA) and Na2CO3 aqueous solutions. PVA chains are aggregated by strong hydrogen bonds between CO32− and OH, at which stage the hydrogel is soft and easy to shape. Further salting out promotes the formation of crystal microphase of PVA chain, resulting in high mechanical strength and excellent toughness. The existence of Na2CO3 endow the hydrogel with conductivity, exhibits high and stable sensitivity in strain sensing, and could be used to monitor human actions. On the basis of this method, Ca2+ was added to prepare mineralized PVA hydrogels, which had high stability and long‐term swelling resistance in different ionic solutions. In vitro cell experiment, hydrogel had obvious effect of promoting bone cell proliferation and calcium deposition. This work provides a facile and feasible method for preparing bionic hydrogels with high strength, toughness, and adaptable shape.

Vapor phase-grown TiO2 and ZnO nanoparticles inside electrospun polymer fibers and their calcination-induced organization

The spatial organization of metal oxide nanoparticles represents an important factor in the chemical utilization of resulting structures. For the production of networks that are composed of metal oxide nanoparticle chains, we dispersed vapor phase-grown TiO2 and ZnO nanoparticles homogeneously in an aqueous polyvinyl alcohol solution. After electrospinning, we analyzed the sizes and diameters of the compositionally homogeneous electrospun fibers and discussed the size distribution and morphology of the nanoparticles inside. Calcination-induced polymer removal gives rise to self-supported nanoparticle-based nanofibers. Particle coarsening by a factor of ~ 2 for TiO2 and ~ 3 for ZnO nanoparticles is observed.Graphical abstract

Synthesis of copolymer nanocomposite by in situ intercalative polymerization for batch and fixed bed adsorption

AbstractPartially neutralized acrylic acid (AA)/sodium acrylate (NaAA) and N, N′‐methylenebisacrylamide (MBA) were subjected to intercalative copolymerization in aqueous solution of polyvinyl alcohol (PVA) in the presence of sodium montmorillonite (NaMMT) nano clay to prepare filled semi‐interpenetrating network (FSIPN) type composite polymer networks. Filled Full IPN (FFIPN) composites were prepared in a similar way by additional crosslinking of PVA with maleic acid (MA) crosslinker. The polymers were characterized with FTIR, NMR, XRD, TGA, SEM, EDAX, TEM, XPS, DLS, PZC, and pH reversibility test. The synthesis variables were optimized with respect to batch adsorption of 100 mg/L each of methyl violet (MV) and congo red (CR) dye as response using the central composite design (CCD) of response surface methodology (RSM). The FFIPN prepared from polyacrylic acid (PAA)/sodium polyacrylate containing PVA/Clay/MBA/MA of optimized composition of 4/1.5/0.75/4 (wt.% of AA/NaAA), respectively, showed an optimized adsorption (mg/g adsorbent) of 459.16/417.31 of MV/CR as single dye and 438.01/417.31 of MV/CR in 1:1 binary mixtures of 100 mg/L feed concentration. The FFIPN showed an adsorption (mg/g) of 41.54/37.61 and removal% of 88.5/80.12 at a feed flow rate, bed height, and feed inlet concentration of 20 mL/min, 20 mm, and 50 mg/L, respectively.

Design of TDI modified oil‐in‐water emulsion and its application in explosive ink

AbstractIn order to solve the short stabilization time of the water‐in‐oil emulsion binder system and the shortcomings of the critical blast size of the explosive ink molding sample, a water‐in‐oil emulsion binder was designed with polyvinyl alcohol (PVA) aqueous solution as the aqueous phase, fluorocarbon resin (FEVE) ethyl acetate solution as the oil phase, and toluene diisocyanate (TDI) added to modify the water‐in‐oil emulsion binder. The hexanitrohexaazaisowurtzitane(CL‐20)based explosive ink was made by incorporating submicron CL‐20 into the binder system, and the print‐formed samples were tested for microscopic morphology, crystallographic analysis, mechanical susceptibility, and detonation transmission performance. The results showed that the explosive ink‘s viscosity was moderate and suitable for direct printing, and the formed sample‘s surface particles were uniformly dispersed and had a honeycomb structure. The crystal form of CL‐20 explosive in the explosive ink did not change, the molded sample‘s impact and frictional sensitivities were 1 J and 32 N lower than those of submicron CL‐20, respectively, and the detonation velocity of the molded sample was 6655 m/s. The critical detonation size and critical detonation thickness were 1×0.0078 mm and 0.1 mm, respectively, and a critical detonation corner turning of 90°–160° could be achieved. The results show that the prepared binder system is stable for a long time, and the explosive ink molding samples have excellent blast transmission performance.

Performance of alkali and Cu-modified ZSM-5 during catalytic ozonation of polyvinyl alcohol in aqueous solution.

A novel hierarchical Cu/ZSM-5 was prepared over alkaline treatment and incipient wet impregnation method for the catalytic ozonation of polyvinyl alcohol (PVA). Under the optimum preparation conditions, hierarchical Cu/ZSM-5 exhibited an excellent mineralization performance during the PVA degradation process, and the removal rate of TOC after 60min of reaction was 47.86%, much higher than that of ozonation alone (5.40%). Its high catalytic activity could attribute to the large pore volume (0.27 cm3/g) and pore size (6.51nm) which are beneficial for the distribution of loaded copper and adsorption performance for PVA. Compared to ·OH, 1O2 (2.66 times in 10min) contributed more to the removal of PVA. The degradation of PVA was a combined process of direct ozone oxidation, catalytic ozonation and adsorption. With its high catalytic performance and stability, hierarchical Cu/ZSM-5 has a very broad application prospect in the process of catalytic ozonation of refractory pollutants.

Enhancing moisture-electric power generation through in situ incorporation of carbon dots into polyelectrolyte membrane

The electric generation performance of traditional polyelectrolyte membrane with moisture usually fall far behind expectations due to its limited hydrophilic groups and poor directional transport capacity of protons. To this end, we introduce the suspension of carbon dots (CDs) prepared by selective oxidation etching of coal pitch with the mixture of formic acid and H2O2 under ambient temperature into the aqueous solution of polyvinyl alcohol (PVA) and poly(4-styrensulfonic acid) (PSS) to fabricate a novel hybrid membrane. This membrane (1.00 cm2) continuously delivers a voltage output of 0.83 V with a short-circuit current of 5.20 μA under proper moist conditions over a prolonged period, outperforming the power generation performance of the pristine membrane and many current moisture-enabled electric generation (MEG) devices. Moreover, CDs endow the polymer membrane with more superior mechanical properties, in favor of processing and scale integration for higher power output. With excess hydrophilic groups provided by as-prepared CDs’ suspension, the denser hydrogen-bond network can be formed in the membrane and facilitates water adsorption and the formation of a higher proton concentration gradient. CDs-induced bridging interactions between PSS chains pave a fast directional transport pathway for moveable protons, resulting in a remarkable power output. Accordingly, this work offers a facile and economic method for remoulding traditional polyelectrolyte membrane to conduct highly efficient MEG for practical applications.

Visible-light photocatalytic degradation of water-soluble polyvinyl alcohol in aqueous solution by Cu2O@TiO2: Optimization of conditions, mechanisms and toxicity analysis

Polyvinyl alcohol (PVA), a water-soluble synthetic polymer, is one of the most prevalent non-native polyvinyl alcohols found in the environment. Due to its inherent invisibility, its potential for causing severe environmental pollution is often underestimated. To achieve efficient degradation of PVA in wastewater, a Cu2O@TiO2 composite was synthesized through the modification of titanium dioxide with cuprous oxide, and its photocatalytic degradation of PVA was investigated. The Cu2O@TiO2 composite, supported by titanium dioxide, facilitated photocarrier separation and demonstrated high photocatalytic efficiency. Under alkaline conditions, the composite exhibited a 98% degradation efficiency for PVA solutions and a 58.7% PVA mineralization efficiency. Radical capture experiments and electron paramagnetic resonance (EPR) analyses revealed that superoxide radicals primarily drive the degradation process within the reaction system. Throughout the degradation process, PVA macromolecules are broken down into smaller molecules, including ethanol, and compounds containing aldehyde, ketone, and carboxylic acid functional groups. Although the intermediate products exhibit reduced toxicity compared to PVA, they still pose certain toxic hazards. Consequently, further research is necessary to minimize the environmental impact of these degradation products.

Heavy metal ions incorporated within strippable PVA-TTA polymeric matrix detected by colorimetry and vibrational spectroscopies

We report the synthesis and characterization of a novel strippable polymeric matrix of polyvinyl alcohol (PVA) aqueous solutions embedded with 2-thenoyl trifluoroacetone (TTA) organic ligand for decontamination of heavy metal ions. The TTA-containing polymeric matrix was applied to several contaminated surfaces comprising various concentrations of UO22+, Cu2+, Fe3+ and Cs+ contaminants. Except for Cs+, the contaminants were found to interact with the ligand contained in the polymeric matrix, accompanied by a consequent indicative strong color change, specific to the metal contaminant. The dried coating is easily exfoliated leaving the surface decontaminated. ATR-IR and Raman spectroscopies were also applied, showing a clear spectroscopic signature of each metal contaminant, in particular when contained in a mixed ion solution. All in all, the utilization of vibrational spectroscopies is shown to provide important complementary detection signatures that are otherwise vague when surfaces comprising trace amounts of contaminants, lacking color responsive behavior, are involved.