Electromagnetic interference shielding properties of graphene quantum-dots reinforced poly(vinyl alcohol)/polypyrrole blend nanocomposites

Graphene quantum dots (GQDs) reinforced poly(vinyl alcohol) (PVA)/polypyrrole (WPPy) nanocomposite films with various GQDs loadings were synthesized using the versatile solvent casting method. The structural and morphological properties of PVA/WPPy/GQDs nanocomposite films were investigated by employing Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy. The thermogravimetric analysis revealed enhanced thermal stability of synthesized nanocomposites while enhanced dielectric properties were also observed. The maximum dielectric constant value for PVA/WPPy/GQDs nanocomposite films was observed to be ε = 6,311.85 (50 Hz, 150°C). The electromagnetic interference (EMI) shielding effectiveness (SE) of nanocomposite films was determined in the X-band (8–12 GHz) and Ku-band (12–18 GHz) frequency region. The EMI SE was found to be increased from 0.8 dB for the pure PVA film to 9.8 dB for the PVA/WPPy/GQDs nanocomposite film containing 10 wt% GQDs loading. The enhanced EMI shielding efficiency of nanocomposite films has resulted from the homogenous dispersion of GQDs in PVA/WPPy blend nanocomposites. Thus, the prepared nanocomposites are envisioned to utilize as a lightweight, flexible, and low-cost material for EMI shielding applications.     

Efficient preparation of hybrid nanocomposite coatings based on poly(vinyl alcohol) and silane coupling agent modified TiO2 nanoparticles

In the present investigation, at first, the surface of titanium dioxide (TiO₂) nanoparticles was modified with γ-aminopropyltriethoxy silane as a coupling agent. Then a new kind of poly(vinyl alcohol)/titanium dioxide (PVA/TiO₂) nanocomposites coating with different modified TiO₂ loading were prepared under ultrasonic irradiation process. Finally, these nanocomposites coating were used for fabrication of PVA/TiO₂ films via solution casting method. The resulting nanocomposites were fully characterized by Fourier transform infrared spectroscopy (FT-IR), powder X-ray diffraction (XRD), thermogravimetric analysis/derivative thermal gravimetric (TGA/DTG), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The TEM and SEM results indicated that the surface modified nanoparticles were dispersed homogeneously in PVA matrix on nanoscale and based on obtained results a possible mechanism was proposed for ultrasonic induced nanocomposite fabrication. TGA confirmed that the heat stability of the nanocomposite was improved. UV–vis spectroscopy was employed to evaluate the absorbance and transmittance behavior of the PVA/TiO₂ nanocomposite films in the wavelength range of 200–800 nm. The results showed that this type of films could be used as a coating to shield against UV light.     

Dielectric properties and electromagnetic interference shielding studies of nickel oxide and tungsten oxide reinforced polyvinylchloride nanocomposites

ABSTRACT

Polyvinylchloride (PVC)/nickel oxide (NiO)/tungsten oxide (WO₃) nanocomposite films were prepared via solution casting technique. The crystallinity, morphology, and the analysis of dispersion state of PVC/NiO/WO₃ nanocomposite was carried out using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The dielectric studies of nanocomposite films were investigated and a maximum dielectric constant of 2.3 with dielectric loss (tan δ) of 2.4 was attained. The EMI shielding studies were carried out in the X and Ku-band frequency range (8 GHz-18 GHz). The maximum SE of 15.78 dB in X-band and 12.05 dB in Ku-band was achieved for 75/20/5 compositions of the PVC/NiO/WO₃ nanocomposite.     

Preparation of transparent PVA/TiO2 nanocomposite films with enhanced visible-light photocatalytic activity

Polymer/semiconductor oxide nanocomposite films have been intensively investigated for various applications. In this work, we reported a simple hydrothermal method to fabricate highly transparent poly(vinyl alcohol)/titanium dioxide (PVA/TiO₂) nanocomposite films with enhanced visible-light photocatalytic activity. The as-prepared PVA/TiO₂ nanocomposite films showed high optical transparency in the visible region even at a high TiO₂ content (up to 40 wt.%). The determination of photocatalytic activity by photodegradation of methyl orange (MO) and colorless phenol showed that PVA/TiO₂ nanocomposite films exhibited enhanced visible-light photocatalytic activity and excellent recycle stability. This work provided new insights into fabrication of polymer/TiO₂ nanocomposites as high performance photocatalysts in waste water treatment.     

Electrical and Electromagnetic Interference (EMI) shielding properties of hexagonal boron nitride nanoparticles reinforced polyvinylidene fluoride nanocomposite films

The hexagonal boron nitride nanoparticles (h-BNNPs) reinforced flexible polyvinylidene fluoride (PVDF) nanocomposite films were prepared via a simple and versatile solution casting method. The morphological, thermal and electrical properties of h-BNNPs/PVDF nanocomposite films were elucidated. The electromagnetic interference (EMI) shielding properties of prepared nanocomposite films were investigated in the X-band frequency regime (8–12 GHz). The EMI shielding effectiveness (SE) was increased from 1 dB for the PVDF film to 11.21 dB for the h-BNNPs/PVDF nanocomposite film containing 25 wt% h-BNNPs loading. The results suggest that h-BNNPs/PVDF nanocomposite films can be used as lightweight and low-cost EMI shielding materials.     

Roll-to-roll processable MXene-rGO-PVA composite films with enhanced mechanical properties and environmental stability for electromagnetic interference shielding

MXene films promise potential electromagnetic interference (EMI) shielding materials, but poor scalable processability, environmental instability, and weak mechanical properties severely restrict their applications. Herein, we engineer the large-area, high-performance, and compact nacre-like MXene-based composite films through cooperative co-assembly of Ti₃C₂T_X MXene and reduced graphene oxide (rGO) in the presence of polyvinyl alcohol (PVA). The resulting MXene-rGO-PVA composite films benefit from enhanced bonding strength and extra chain bridging effect of linear PVA molecules enriched with hydroxyl groups. Therefore, the composite film achieves high tensile strength (～238 MPa) and toughness (～1.72 MJ m^?3) while having high conductivity of ～32 S cm^?1. A significant EMI shielding effectiveness (41.35 dB) is also demonstrated, with an excellent absolute shielding effectiveness of ～20,200 dB cm² g^?1 at only 12-μm thickness. Moreover, due to the synergistic effect of multiple components, the composite films maintain a stable EMI shielding performance in harsh environments (sonication, hot/cold annealing, and acid solution) with mechanical properties that fluctuate only within 10% compared to the original film. More importantly, commercial polyethylene terephthalate release liner can be applied for the film coating, facilitating continuous roll-to-roll production of large-area films and future applications.     

Electrochemical Polymerization of Thiophene and Poly(3-hexyl)thiophene,Nanocomposites with TiO2, and Corrosion Protection Behaviors

Thiophene, 3-hexylthiophene, and their nanocomposites with TiO₂ were electropolymerized on Al1050 electrode by chronoamperometric technique. Different concentrations of thiophene and 3-hexylthiophene homopolymers and their nanocomposites with TiO₂ (2% in total content) were characterized by attenuated total reflection Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersion X-ray analysis, and electrochemical impedance spectroscopy. The anticorrosion tests for homopolymers and nanocomposite films were examined on Al1050 in 3.5% NaCl solution. Poly(3-hexylthiophene)/TiO₂ nanocomposite films gave the highest protection efficiency of 98% because the amount of defects was much lower than that for the poly(3-hexylthiophene), polythiophene, and polythiophene/TiO₂ films.     

ZrO2 functionalized graphene Oxide/SEBS‐Based nanocomposites for efficient electromagnetic interference shielding applications

ZrO₂‐coated graphene oxide (GO)/SEBS(styrene‐ethylene‐butylene‐styrene)‐based nanocomposites were prepared for use as an electromagnetic interference (EMI) shielding material. Transmission electron microscopy (TEM) reveals almost every individual GO is fully and homogeneously covered with uniform ZrO₂. X‐ray diffraction (XRD) patterns and Differential scanning calorimetry (DSC) revealed increased ordering of ‐(CH₂‐CH₂)n segments in the poly(ethylene‐co‐1‐butene) block of the SEBS matrix in the case of SEBS/ZrO₂‐coated graphene oxide composites than in the SEBS/pristine graphene oxide nanocomposite. Thermogravimetric analysis (TGA) proved better oxidation resistance of SEBS/ZrO₂‐coated GO nanocomposite compared to that of SEBS/pristine GO nanocomposite. The present nanocomposites exhibited excellent EMI shielding effectiveness (SE) over X‐band (8.2 GHz–12.4 GHz) with EMI SE of 37.9 dB. J. VINYL ADDIT. TECHNOL., 25:E130–E136, 2019. © 2018 Society of Plastics Engineers     

Exceptionally good,transparent and flexible FeS2/poly(vinyl pyrrolidone) and FeS2/poly(vinyl alcohol) nanocomposite thin films with excellent UV‐shielding properties

Composites of nanocrystalline iron disulfide (FeS₂) coated with poly(vinyl pyrrolidone) (PVP) or poly(vinyl alcohol) (PVA) have been successfully synthesized using a solvothermal process, in which PVP and PVA serve as soft templates. Transparent, flexible thin films of these nanocomposites were prepared from homogeneous solution using a solution‐casting approach. X‐ray diffraction and thermogravimetric analysis and energy‐dispersive X‐ray, Fourier transform infrared and UV‐visible absorption spectroscopic techniques were employed to study the structural and optical properties of these nanocomposite films. UV‐visible spectra in transmission mode reveal the UV‐shielding efficiency of these nanocomposite films and the films are found to be exceptionally good for UV‐shielding applications in the wavelength range 200 to 400 nm. The present work aims at developing transparent and flexible UV‐shielding materials and colour filters using cost‐effective and non‐toxic inorganic–polymer nanocomposites. © 2012 Society of Chemical Industry     

Nanocomposites based on transition metal oxides in polyvinyl alcohol for EMI shielding application

In the present work, the nanocomposites based on different transition metal oxides like iron oxide (Fe₂O₃), zinc oxide (ZnO), silicon dioxide (SiO₂), zirconium dioxide (ZrO₂), and titanium dioxide (TiO₂) in PVA matrix have been studied for their suitability as electromagnetic interference (EMI) shielding materials in the frequency range of 4–8 GHz (C-band) and 8–12 GHz (X-band). The nanocomposites containing 0.1, 0.5, 1.0, 5.0, and 10.0 wt% of oxides in the matrix were synthesised by solvent casting method. The EMI attenuation studies in 4–12 GHz frequency range were carried out using the Vector Network Analyzer R & S: ZVA40 method by measuring the loss due to reflection. The minimum reflectivity values for the composites containing Fe₂O₃, ZnO, SiO_2, ZrO₂, and TiO₂ in PVA matrix at 10 wt% concentration level in the matrix were found to be ?38.85 dB (10.4 GHz), ?33.65 dB (10.4 GHz), ?41.90 dB (10.4 GHz), ?24.90 dB (11.0 GHz), and ?32.90 dB (9.76 GHz), respectively. Based on these results, the SiO₂- and Fe₂O₃-based composites, which also exhibit high thermal stability and mechanical strength, are found to be low-cost and efficient EMI shielding materials.     

Electromagnetic interference shielding properties of PEDOT/PSS–halloysite nanotube (HNTs) hybrid films

Poly(3,4‐ethylenedioxythiophene)/poly(4‐styrene sulfonate) (PEDOT/PSS) films hybridized with halloysite nanotubes (HNTs) were for the first time investigated for electromagnetic interference (EMI) shielding. The hybridization of the HNTs induced EMI properties for the pristine PEDOT/PSS films, and the content of the HNTs in the hybrid films significantly influenced the EMI properties of the hybrid films. The highest EMI shielding effectiveness of the hybrid film is ?16.3 dB in the measured frequency range from 2 to 13 GHz for the PEDOT/PSS film hybridized with 75% HNTs, using a sample with 4.5 mm thick. The contribution of EMI shielding effectiveness in the hybrid films is mainly due to dielectric loss rather than magnetic loss. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44242.     

Electromagnetic interference shielding behavior of chemically and thermally reduced graphene based multifunctional polyurethane nanocomposites: A comparative study

This article presents the effect of exfoliation, dispersion, and electrical conductivity of graphene sheets onto the electrical, electromagnetic interference (EMI) shielding, and gas barrier properties of thermoplastic polyurethane (TPU) based nanocomposite films. The chemically reduced graphene (CRG) and thermally reduced/annealed graphene (TRG) having Brunauer–Emmett–Teller surface areas of 18.2 and 159.6 m²/g, respectively, when solution blended with TPU matrix using N,N-dimethylformamide as a solvent. Graphene sheets based TPU nanocomposites have been evaluated and compared for EMI shielding in Ku band, electrical conductivity, and gas barrier property. TRG/TPU nanocomposite films showed excellent gas barrier against N₂ gas as compared to CRG/TPU. The EMI shielding effectiveness for neat CRG and TRG graphene sheets is found to be −80, −45 dB, respectively, at 2 mm thickness. The EMI shielding data revealed that TRG/TPU nanocomposites showed better shielding at lower concentration (10 wt %), while CRG displayed better attenuation at higher concentrations. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47666.     

Employment of ultrasonic waves for the preparation of PVA/TiO2‐BSA nanocomposites: Mechanical,thermal, and optical properties

The goal of this project is to obtain poly(vinyl alcohol) (PVA)/TiO₂‐bovine serum albumin (BSA) nanocomposite (NC) films in different weight percentages of modified TiO₂. For this purpose, to prevent the accumulation of nanoparticles (NPs) in the PVA matrix, the surface of the TiO₂ NPs was treated with the BSA molecules. To achieve this aim, ultrasonic waves were used as an environmentally friendly and green process that decrease the time of reactions, help better spreading of TiO₂ NPs and maintain dimensions of TiO₂ NPs in the nanoscale range. In the end, the features of the PVA/TiO₂‐BSA NC films were considered with a variety of techniques. The Fourier transform infrared spectroscopy, energy dispersive X‐ray, and X‐ray diffraction showed that the BSA was well placed on the surface of TiO₂ NPs. The thermal gravimetric analysis and UV‐visible results demonstrated that all the PVA/TiO₂‐BSA NC films have better thermal and optical properties than the pure PVA. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46558.     

Synthesis and photocatalytic performance of PVA/TiO2/graphene‐MWCNT nanocomposites for dye removal

TiO₂/graphene‐MWCNT nanocomposite was prepared using solvothermal reaction for the effective distribution of TiO₂ nanoparticles on carbonaceous materials. TiO₂/graphene‐MWCNT nanocomposite was immobilized in poly(vinyl alcohol) (PVA) matrix for a convenient recovery after wastewater purification. MWCNT was incorporated in a nanocomposite not only to prevent the restacking of graphene but also to increase the electron transfer from TiO₂. The detailed characterization of the nanocomposite was performed using SEM, EDX, XRD, XPS, and FTIR. The photocatalytic performance of PVA/TiO₂/graphene‐MWCNT nanocomposite was investigated by UV spectroscopy on the basis of degradation of organic pollutants. PVA/TiO₂/graphene‐MWCNT nanocomposite showed improved photocatalytic decomposition of more than 70% of residual dye left in case of using PVA/TiO₂/graphene nanocomposite due to the improved electron transfer and the higher adsorption of organic pollutants. PVA/TiO₂/graphene‐MWCNT nanocomposite was suitable as a promising material for the recyclable photocatalytic wastewater purification system. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40715.     

Anomalous behavior of the dielectric and electrical properties of polymeric nanodielectric poly(vinyl alcohol)–titanium dioxide films

The complex dielectric permittivity, alternating‐current electrical conductivity, electric modulus, and impedance spectra of polymeric nanocomposite (PNC) films consisting of a poly(vinyl alcohol) (PVA) matrix dispersed with nanosize particles of titanium dioxide (TiO₂); (i.e., PVA–x wt % TiO₂, where x is 0, 1, 3, or 5) were investigated in the frequency range 20 Hz to 1 MHz at ambient temperature. A detailed analysis of the results showed that the values of the dielectric and electrical parameters of these PNC‐based nanodielectric films varied anomalously with increasing TiO₂ concentration. The temperature‐dependent dielectric characterization of the PVA–3 wt % TiO₂ film revealed that the dielectric polarization at a fixed frequency increased nonlinearly with increasing temperature. The temperature‐dependent electric modulus relaxation time values of the nanodielectric film obeyed Arrhenius behavior. The X‐ray diffraction study confirmed that the crystalline phase of the PVA matrix decreased with increasing TiO₂ concentration; this suggested that the interaction of the TiO₂ nanoparticles caused some destruction of the hydroxyl group dipolar ordering in the hydrogen‐bonded crystalline structure of the pristine PVA matrix. The intensities of the diffraction peaks of the TiO₂ nanofiller were enhanced as its concentration increased in these nanodielectrics; this confirmed the existence of TiO₂ nanoparticles inside the crystalline phases of the PVA matrix. The surface morphology of the films was examined by the study of their scanning electron micrographs. The feasibility of using these flexible polymeric nanodielectric films as electrical insulators and dielectric substrates in low‐power microelectronic devices operated at audio‐ and radio‐frequency electric fields was explored. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44568.     

Structure,electrical and optical properties of (PVA/LiAsF6) polymer composite electrolyte films

In this work, Li⁺ ion conducting polymer composite electrolyte films (PECs) were prepared based on poly (vinyl alcohol) (PVA), lithium hexafluoro arsenate (LiAsF₆), and ceramic filler TiO₂ using solution cast technique. The XRD and FTIR spectra were used to determine the complexation of the PVA polymer with LiAsF₆ salt. The ionic conductivities of the (PVA + LiAsF₆) and (PVA + LiAsF₆ + TiO₂) films have been determined by the A.C. impedance measurements in the temperature range 320–440 K. The maximum conductivity was found to be 5.10 × 10^?4 S cm^?1 for PVA:LiAsF₆ (75:25) + 5 wt% TiO₂ polymer composite film at 320 K. The calculation of Li⁺ ion transference number was carried out by the combination of A.C. impedance and D.C. polarization methods and is found to be 0.52 for PVA:LiAsF₆ (75:25) + 5 wt% TiO₂ film. Optical properties such as direct energy gap, indirect energy gap, and optical absorption edge values were investigated in pure PVA and salt complexed PVA films from their optical absorption spectra in the wavelength range of 200–600 nm. The absorption edge was found at 5.76 eV for undoped film, while it is observed at 4.87 and 4.70 eV for 20 and 25 wt% LiAsF₆ doped films, respectively. The direct band gaps for these undoped and salt doped PVA films were found to be 5.40, 5.12, and 4.87 eV, respectively, whereas the indirect band gaps were determined as 4.75, 4.45, and 4.30 eV. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers     

Enhanced Solid‐Phase Photocatalytic Degradation Activity of a Poly(vinyl chloride)‐TiO2 Nanocomposite Film with Bismuth Oxyiodide

A new type of photodegradable poly(vinyl chloride)‐bismuth oxyiodide/TiO₂ (PVC‐BiOI/TiO₂) nanocomposite film was prepared by embedding a nano‐TiO₂ photocatalyst modified by BiOI into the commercial PVC plastic. The solid‐phase photocatalytic degradation behavior of the as‐prepared film was investigated in ambient air at room temperature under UV light irradiation, with the aid of UV‐Vis spectroscopy, weight loss monitoring, scanning electron microscopy, and FT‐IR spectroscopy. Compared to the PVC‐TiO₂ nanocomposite film, the PVC‐BiOI nanocomposite film and the pure PVC film, the PVC‐BiOI/TiO₂ nanocomposite film exhibited a higher photocatalytic degradation activity. The optimal mass ratio of BiOI to TiO₂ was found to be 0.75 %. The weight loss rate of the PVC‐BiOI/TiO₂ nanocomposite film reached 30.8 % after 336 h of irradiation, which is 1.5 times higher than that of the PVC‐TiO₂ nanocomposite film under identical conditions. The solid‐phase photocatalytic degradation mechanism of the nanocomposite films was briefly discussed.     

Preparation of poly(vinyl alcohol)/poly(acrylic acid)/TiO2/carbon nanotube composite nanofibers and their photobleaching properties

The composite nanofibers of poly(vinyl alcohol) (PVA)/poly(acrylic acid) (PAAc)/titanium(IV) oxide (TiO₂) were prepared by electrospinning for a novel photocatalytic treatment of waste water. To improve the photoelectronic properties of PVA/PAAc/TiO₂ composite nanofibers, carbon nanotubes (CNTs) were used as an additive. The TiO₂ and CNTs were immobilized in the PVA/PAAc hydrogels as electrospun nanofibers for an easier recovery after the wastewater treatment. The improved efficiency of pollutant dye removal was observed at pH 10 due to the pH-sensitive swelling behavior of the PVA/PAAc/TiO₂/CNTs composite nanofibers. The photocatalytic activity of TiO₂ was improved noticeably by applying electric field to the CNTs-embedded composite nanofibers.     

Polymer Nanocomposites based on Modified ZrO2 NPs and Poly(vinyl alcohol)/Poly(vinyl pyrrolidone) Blend: Optical,Morphological, and Thermal Properties

Nanocomposite films were prepared successfully by simple solution casting method from the blend of poly(vinyl alcohol) and poly(vinyl pyrrolidone) as the polymer matrix and functionalized ZrO₂ nanoparticles as nanofiller. To prevent aggregation and improve the dispersion of nanoparticles into the matrix, ZrO₂ nanoparticles were functionalized with citric acid and ascorbic acid. Then, nanocomposites were fabricated by adding different contents of modified nanoparticles into the poly(vinyl alcohol)–poly(vinyl pyrrolidone) matrix. Thermal stability of the obtained nanocomposite films was improved in comparison to the pure blend. Furthermore, optical property of nanocomposites makes them a potential candidate for ultraviolet shielding material.     

The utilization of poly(amide-imide)/SiO2 nanocomposite as nanofiller for strengthening of mechanical and thermal properties of poly(vinyl alcohol) nanocomposite films

The present investigation reports the preparation and characterization of the thermally stable poly(vinyl alcohol)/(poly(amide-imide)-SiO₂) nanocomposite (PVA/PAI-SiO₂ NC) films. For this reason, the surface of SiO₂ nanoparticles (NPs) was modified with N-trimellitylimido-l-methionine and subsequently, 5 wt.% of modified SiO₂ NPs were dispersed in the PAI matrix via sonochemical reaction. The resulting NC was studied by different techniques. Finally, the PAI-SiO₂ NC was employed as nanofiller and was incorporated into the PVA matrix for the enhancement of its mechanical and thermal properties. The synthesized NCs were studied by Fourier transform infrared and X-ray diffraction spectroscopy analysis. The surface topography and morphology of the NCs were studied by atomic force microscopy techniques, field emission scanning electron microscopy and transmission electron microscopy. The micrographs demonstrated that the nanofillers were homogeneously dispersed in the PVA matrix. The thermo gravimetric analysis curves indicated that the thermal decomposition of the PVA/PAI-SiO₂ NC films shifted toward higher temperature in comparison with the pure PVA. The effect of nanofiller on the mechanical properties of NC films was also explored.