Electrical conductivity and electromagnetic interference shielding of polyaniline/polyacrylate composite coatings

Lightweight and flexible composite coatings of p‐toluene sulfonic acid doped polyaniline (PANI–TSA) with various mass fractions and polyacrylate were prepared for electromagnetic interference (EMI) shielding. Both the volume and surface conductivities of the composite coatings increased with increasing PANI–TSA; furthermore, the volume conductivity showed a typical percolation behavior with a percolation threshold at about 0.21. The EMI shielding effectiveness (SE) of the PANI–TSA/polyacrylate coatings over the range of 14 kHz to 15 GHz increased with increasing PANI–TSA as the direct‐current conductivity did. EMI SE of the coatings at the low frequencies (14 kHz to 1 GHz) was around 30–80 dB, higher than that at the high frequencies (1–15 GHz); this indicated possible commercial application of the coatings for far‐field EMI shielding. The highest EMI SE value was 79 dB at 200 MHz with a coating thickness of 70 ± 5 μm. The moderate SE, light weight, and easy preparation of the coating are advantages for future applications for EMI shielding. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2149–2156, 2005     

Effect of swelling pretreatment on the deposition structure on electroless copper of polyacrylonitrile nanocomposites for electromagnetic interference shielding

In this investigation, the electroless copper method with various cupric sulfate concentrations (0.24, 0.36, 0.48, 0.60M) without sensitizing and activating is used to deposit electroless copper compounds (CuS) on the swelling pretreatment polyacrylonitrile(SPAN) surface for electromagnetic interference (EMI) shielding materials. The acetic acid can swell polyacrylonitrile (PAN) effectively which donot destroy the hexagonal structure of polyacrylonitrile, only looses the molecule chain of polyacrylonitrile then the hexagonal CuS crystal deposits on the SPAN easily, and increases the EMI shielding effectiveness (SE) of CuS‐SPAN composites. However, the nearly amorphous of CuS deposits on the surface of without swelling pretreatment PAN(CuS‐PAN). The EMI SE of CuS‐SPAN composites are better than those of CuS‐PAN, 10–15 dB larger from CuS‐PAN. In the study, the best EMI SE of CuS‐SPAN and CuS‐PAN composites are about 30–35 dB and 18–20 dB respectively, as the cupric ion concentration is 0.48M. From the high resolution transmission electron micrographs(HR‐TEM) analysis, there are two structures, face‐centered cubic(FCC) Cu_2‐xS crystal in the inner layer of CuS‐SPAN composite and hexagonal CuS crystal on the outer layer of CuS‐SPAN composite, in the SPAN as the cupric ion concentration is 0.48M. The particle size distribution of Cu_2‐xS in the inner layer of CuS‐SPAN is from 6 to 30 nm. However, the major particle size distribution of Cu_2‐xS in the inner layer of CuS‐SPAN is from 15 to 20 nm. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

5‐Sulfoisophthalic acid monolithium salt doped polypyrrole/multiwalled carbon nanotubes composites for EMI shielding application in X‐band (8.2–12.4 GHz)

This article describes the synthesis and characterization of highly conductive polypyrrole (PPy)/multiwalled carbon nanotube (MWCNT) composites prepared by in situ polymerization of pyrrole using 5‐sulfoisophthalic acid monolithium salt [lithio sulfoisophthalic acid (LiSiPA)] as dopant and ferric chloride as oxidant. Several samples were prepared by varying the amounts of MWCNTs ranging from 1 to 5 wt %. Scanning electron microscope and transmission electron microscope images clearly show a thick coating of PPy on surface of MWCNTs. The electrical conductivity of PPy increased with increasing amount of MWCNTs and maximum conductivity observed was 52 S/cm at a loading of 5 wt % of MWCNTs. Pure PPy prepared under similar conditions had a conductivity of 25 S/cm. Electromagnetic interference (EMI) shielding effectiveness (SE) also showed a similar trend and average EMI shielding of ?108 dB (3 mm) was observed for sample having 5 wt % MWCNT in the frequency range of 8.2–12.4 GHz (X‐band). The light weight and absorption dominated total SE of ?93 to ?108 dB of these composites indicate the usefulness of these materials for microwave shielding. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45370.     

Hybrid composites of ABS with carbonaceous fillers for electromagnetic shielding applications

This work evaluates the influence of two types of carbonaceous fillers, carbon black (CB) and carbon nanotubes (CNTs), on the electrical, electromagnetic, and rheological properties of composites based on poly(acrylonitrile‐co‐butadiene‐co‐styrene) (ABS) prepared by the melt mixing. Electrical conductivity, electromagnetic shielding efficiency (EMI SE) in the X‐band frequency range (8–12.4 GHz), and melt flow index (MFI) results showed that ABS/CNT composites exhibit higher electrical conductivity and EMI SE, but lower MFI when compared to ABS/CB composites. The electrical conductivity of the binary composites showed an increase of around 16 orders of magnitude, when compared to neat ABS, for both fillers. Binary composites with 5 and 15 wt % of filler showed an EMI SE of, respectively, ?44 and ?83 dB for ABS/CNT, and ?9 and ?34 dB for ABS/CB. MFI for binary composites with 5 wt % were 15.45 and 0.55 g/10 min for CB and CNT, respectively. Hybrid composites ABS/CNT.CB with 3 wt % total filler and fraction 50:50 and 75:25 showed good correlation between EMI SE and MFI. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46546.     

Synergistic effect of multiwalled carbon nanotubes and an intumescent flame retardant: Toward an ideal electromagnetic interference shielding material with excellent flame retardancy

To shield undesirable electromagnetic waves caused by electronic devices and simultaneously resolve the flame safety of the electronic components, an electromagnetic interference (EMI) shielding material with excellent flame‐retardant properties is urgently needed. The synergistic effect of the intumescent flame retardant (IFR) and multiwalled carbon nanotubes (MWCNTs) for polystyrene (PS) nanocomposites prepared by melt blending was investigated. The results show that addition of certain amounts of IFRs facilitated the dispersion of MWCNTs in the PS matrix, and the percolation threshold of the MWCNTs in the PS matrix also decreased from 1.67 ± 0.05 to 1.29 ± 0.04 wt %. Moreover, the EMI shielding efficiencies (SEs) of the PS–MWCNT–IFR composites were consistently higher than those of the PS–MWCNT composites without the addition of the IFRs at the same MWCNT content; this indicated that the synergistic effect of the MWCNTs and IFRs effectively improved the EMI SE of the PS–MWCNT–IFR composites. Furthermore, the limiting oxygen index (LOI) testing results show that the LOI values of the PS–MWCNT composites were consistently higher than 27%; this indicated that the PS–MWCNT composites effectively met the needs of flame safety; this indicated that the PS–MWCNT–IFR composite is a novel and promising candidate for an ideal EMI shielding material with excellent flame‐retardant properties for today's electronic devices. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45088.     

Comparison of polyelectrolyte and sodium dodecyl benzene sulfonate as dispersants for multiwalled carbon nanotubes on cotton fabrics for electromagnetic interference shielding

Cotton fabrics with multiwalled carbon nanotubes (MWCNTs) dispersed by Nafion, a polyelectrolyte, and sodium dodecyl benzene sulfonate (SDBS), a surfactant, were prepared for electromagnetic interference (EMI) shielding. The fabrics were characterized by scanning electron microscopy and vector network analysis. The fabrics with the Nafion–MWCNT coating possessed a better shielding efficiency (SE) than those with the SDBS–MWCNT coating because of a more uniform dispersion of MWCNTs, which improved the electrical conductivity and EMI shielding properties. The maximum SE value of the fabric reached 11.48 dB, and the specific SE was 39.6 dB cm³/g. The reflectivity and absorptivity were calculated separately to determine the main mechanism of EMI shielding. The absorptivity was 68.6% at 12 GHz for the Nafion–MWCNT‐coated fabric; this showed that the dominant mechanism of EMI shielding for the treated fabrics was absorption. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40588.     

Effect of weak reductant on properties of electroless copper polyacrylonitrile nanocomposites for electromagnetic interference shielding

In this work, the electroless copper method with different reductant compositions (NaHSO₃/Na₂ S₂O₃·5H₂O and Na₂S₂O₃·5H₂O) without sensitizing and activating, was used to deposit copper‐sulfide deposition on the polyacrylonitrile (PAN) surface for electromagnetic interference (EMI) shielding materials. The weak reductant, NaHSO₃, in the electroless copper method was used to control the phase of copper‐sulfide deposition. The Cu_x(x=1–1.8)S was deposited on the PAN (Cu_xS‐PAN) by reductant composition (NaHSO₃/Na₂S₂O₃·5H₂O) and the Cu_x(x=1–1.8)S deposition of Cu_xS‐PAN possesses three kinds of copper‐sulfide phases (CuS, Cu_1.75S and Cu_1.8S). However, the electroless copper with reductant was only Na₂S₂O₃·5H₂O (without weak reductant, NaHSO₃), the hexagonal CuS deposition was plated on the PAN (CuS‐PAN) and increased the EMI shielding effectiveness of CuS‐PAN composites about 10–15 dB. In this study, the best EMI SE of CuS‐PAN and Cu_xS‐PAN composites were about 27–30 dB and 15–17 dB respectively, as the cupric ion concentration was 0.24 M. The volume resistivity of CuS‐PAN composite was about 1000 times lower than that of Cu_xS‐PAN composite and lowest volume resistivity of CuS‐PAN composites was 0.012 Ω cm, as the cupric ion concentration was 0.24 M. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Electrical,rheological and electromagnetic interference shielding properties of thermoplastic polyurethane/carbon nanotube composites

Electrically conducting rubbery composites based on thermoplastic polyurethane (TPU) and carbon nanotubes (CNTs) were prepared through melt blending using a torque rheometer equipped with a mixing chamber. The electrical conductivity, morphology, rheological properties and electromagnetic interference shielding effectiveness (EMI SE) of the TPU/CNT composites were evaluated and also compared with those of carbon black (CB)‐filled TPU composites prepared under the same processing conditions. For both polymer systems, the insulator–conductor transition was very sharp and the electrical percolation threshold at room temperature was at CNT and CB contents of about 1.0 and 1.7 wt%, respectively. The EMI SE over the X‐band frequency range (8–12 GHz) for TPU/CNT and TPU/CB composites was investigated as a function of filler content. EMI SE and electrical conductivity increased with increasing amount of conductive filler, due to the formation of conductive pathways in the TPU matrix. TPU/CNT composites displayed higher electrical conductivity and EMI SE than TPU/CB composites with similar conductive filler content. EMI SE values found for TPU/CNT and TPU/CB composites containing 10 and 15 wt% conductive fillers, respectively, were in the range ?22 to ?20 dB, indicating that these composites are promising candidates for shielding applications. © 2013 Society of Chemical Industry     

Microwave absorption of poly‐N‐vinylcarbazole–polyaniline composites

Poly‐N‐vinylcarbazole–polyaniline (PANI) composites were synthesized using different loading concentration of aniline (0.025–0.1 M) for their microwave absorption characteristics. The obtained composites were studied by Fourier transform infrared spectroscopy, thermogravimetric analysis technique, and atomic force microscope for their chemical structure, thermal stability, and the surface modifications, respectively. The conductivity increased much with the increase of aniline concentration in the composites. The composite sheets exhibited a strong microwave absorption in the microwave range of 1–10 GHz and achieved a maximum absorption value of 33 dB. The position of absorbing peak shows a mixed trend moving from lower to higher and again to lower with an increasing the concentration of aniline in the poly‐N‐vinylcarbazole–PANI. The new polymer composite exhibited an appreciable electromagnetic interference shielding efficiency compared with the previously reported PANI composites. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers     

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     

Electrically conductive composites of polyurethane derived from castor oil with polypyrrole‐coated peach palm fibers

Electrically conducting fibers were prepared through in situ oxidative polymerization of pyrrole (Py) in the presence of peach palm fibers (PPF) using iron (III) chloride hexahydrate (FeCl₃·6H₂O) as oxidant. The polypyrrole (PPy) coated PPF displayed a PPy layer on the fibers surface, which was responsible for an electrical conductivity of (2.2 ± 0.3) × 10⁻¹ S cm⁻¹, similar to the neat PPy. Electrically conductive composites were prepared by dispersing various amounts of PPy‐coated PPF in a polyurethane matrix derived from castor oil. The polyurethane/PPy‐coated PPF composites (PU/PPF–PPy) exhibited an electrical conductivity higher than PU/PPy blends with similar filler content. This behavior is attributed to the higher aspect ratio of PPF–PPy when compared with PPy particles, inducing a denser conductive network formation in the PU matrix. Electromagnetic interference shielding effectiveness (EMI SE) value in the X‐band (8.2–12.4 GHz) found for PU/PPF–PPy composites containing 25 wt% of PPF–PPy were in the range −12 dB, which corresponds to 93.2% of attenuation, indicating that these composites are promising candidates for EMI shielding applications. POLYM. COMPOS., 38:2146–2155, 2017. © 2015 Society of Plastics Engineers     

Multiwalled carbon nanotube/cement composites with exceptional electromagnetic interference shielding properties

Multi-walled carbon nanotube (MWCNT)/portland cement(PC) composites have been fabricated to evaluate their electromagnetic interference (EMI) shielding effectiveness (SE). The results show that they can be used for the shielding of EMI in the microwave range. The incorporation of 15 wt.% MWCNTs in the PC matrix produces a SE more than 27 dB in X-band (8.2–12.4 GHz), and this SE is found to be dominated by absorption. Furthermore, the structural analysis, surface morphology and surface interaction of MWCNTs with PC matrix have been explored using XRD, SEM and X-ray photoelectron spectroscopy technique.     

Modification of sisal fiber by in situ coating steam explosion and electromagnetic interference shielding effectiveness of sisal fiber/PP composites

The technology of steam explosion was adopted to modify sisal fiber (SF) material and two different carbon particles, expanded graphite and conductive carbon black (CCB), were in situ coated on the surface of SF during steam explosion process. The DC conductivity and electromagnetic interference shielding effectiveness (SE) of the modified SF/polypropylene (PP) composites were studied and the measurement of electromagnetic interference (EMI) SE was conducted in two frequency ranges of 400–1,000 MHz and 1–18 GHz. The experimental results showed that this novel coating technology could improve the SE of the modified SF/PP composites significantly, which has a strong dependence on the loadings of the expanded graphite modified sisal fiber (SF‐EG) and conductive carbon black modified sisal fiber (SF‐CCB). When the loadings of SF‐EG and SF‐CCB reached 50 wt%, the maximum values of the SE were 33 dB and 51 dB, respectively. For the modified SF/PP composites, the experimental EMI SE values are in good correlation with the theoretical calculation values in far field of electromagnetic radiation. POLYM. COMPOS., 35:1038–1043, 2014. © 2013 Society of Plastics Engineers     

The influence of PVP on the synthesis and electromagnetic properties of PANI/PVP/CIP composites

Polyaniline/carbonyl iron powder (PANI/CIP) composites with core‐shell structure were synthesized via in situ polymerization in aqueous solution of polyvinylpyrrolidon (PVP). The micromorphology, structure, and microwave absorbing property of the PANI/PVP/CIP composites were characterized by scanning electron microscopy, fourier transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD), and vector network analysis. And, the modified mechanism of PVP on polymerization was discussed. The research showed that the presence of PVP was conducive to not only dispersion of CIP but also the formation coated well with PANI. PANI/CIP composites that were decorated by PVP have obviously improved on wave absorbing property compared with the composites which were synthesized without PVP. With the concentrations of 10 wt% PVP, the PANI/PVP/CIP composites show best microwave absorption, which the minimum reflection loss (RL) was −26.4 dB at 38.1 GHz and the corresponding thickness was 0.9 mm; for a thickness of 1.1 mm, an RL exceeding −10 dB was obtained in the frequency range of 27.6–39.0 GHz. POLYM. COMPOS., 36:1799–1806, 2015. © 2014 Society of Plastics Engineers     

Epoxy composite foams with excellent electromagnetic interference shielding and heat‐resistance performance

Epoxy composite foams with improved heat‐resistant property and efficient electromagnetic interference shielding effectiveness (EMI SE) were fabricated through a two‐step foaming technique. A sort of novel and untraditional expandable microspheres was adopted to reduce the density of prepared materials. A multiscale conductive network system composed of multiwalled carbon nanotubes (MWCNTs) and nickel‐plated carbon fibers (NiCFs) was introduced in these foams. Benefitting from the synergistic effect between NiCFs and MWCNTs, the multiscale epoxy foam with best comprehensive performance achieved a greatly enhanced T_g at 178.3 °C and an exceptional specific EMI SE ranging from 52.8 to 72.6 dB cm³ g^?1 in X band (8.2–12.4 GHz) at low filler loading. These properties are greatly better than original epoxy foam with a T_g of 157.8 °C and specific EMI SE of 1.0–6.4 dB cm³ g^?1. Their shielding mechanisms were discussed and the results showed that reflection is dominating. The effects of microspheres content, foaming temperature, NiCFs content, and length were investigated. In general, we provided a feasible, convenient and cost‐effective method to fabricate light‐weight, heat‐resistant thermosetting epoxy foams with sufficient EMI shielding performance which has a potential to be applied in aerospace or electronic devices. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46013.     

Synergistically improved thermal stability and electromagnetic interference shielding effectiveness (EMI SE) of in-situ synthesized polyaniline/sulphur doped reduced graphene oxide (PANI/S-RGO) nanocomposites

Polyaniline (PANI) and its composite with sulphur doped reduced graphene oxide (S-RGO) have been successively synthesized via in-situ chemical oxidative polymerization of aniline in presence of 10 wt. % S-RGO nanosheets. Physico-chemical analyses of the synthesized nanomaterial was performed with various characterization techniques such as X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDS), Atomic Force Microscopy (AFM) and Thermogravimetric analysis/Differential Scanning Calorimetry (TGA/DSC). The results interpreted from the various characterizations confirm the doping of RGO with sulphur as well as strong interaction of PANI nanofibers and S-RGO nanosheets. TG/DSC curves confirm the enhanced thermal stability of polyaniline/sulphur doped reduced graphene oxide (PANI/S-RGO) nanocomposites with heat resistance index (T_HRI) of 155.2 °C in comparision to pure PANI (T_HRI = 145.3 °C) at a filler loading of 10 wt. %. TGA validates that thermal stability of PANI/S-RGO nanocomposite improves by 6–7 °C than pure PANI in terms of weight loss percentage at a temperature of 1117 °C. However DSC analysis confirms that PANI/S-RGO retains its structural integrity and conformity to temperatures as high as 900 °C beyond which the polymer composite starts to degrade. The electromagnetic interference shielding effectiveness (EMI SE) of PANI and PANI/S-RGO nanocomposites were measured via open-ended coaxial probe set-up connected to a Vector Network Analyser (VNA) at a broadband frequency range of 1–20 GHz (1000–20000 MHz). For EMI SE measurements the various nanomaterials were incorporated into paraffin wax and made into composite pellets of thickness 5 mm by solution casting technique. The dielectric properties, electrical conductivity and EMI SE were all greatly enhanced for the PANI/S-RGO/Paraffin composite pellets. The as synthesized PANI/S-RGO/Paraffin composite pellets exhibited highest EMI SE of ?22.5 dB (>99%) as compared to ?15.89 dB of PANI/Paraffin composite pellets. The prepared composite pellets revealed an absorption dominant mechanism of shielding with highest SE_A of ?14.6 dB for PANI/S-RGO/Paraffin composite pellets.     

Preparation and investigation of structural,magnetic, and microwave absorption properties of aluminum‐doped strontium ferrite/MWCNT/polyaniline nanocomposite at KU‐band frequency

Aluminum‐doped strontium hexaferrite nanoparticle SrAl_1.3Fe_10.7O₁₉ was prepared by sol–gel method and polyaniline (PANi) multiphase magnetic nanocomposite SrAl_1.3Fe_10.7O₁₉/MWCNT/PANi was synthesized through a sonochemical method by in situ polymerization. The morphology, structure, and magnetic properties of the nanocomposites are investigated by field emission scanning electron microscopy, X‐ray powder diffraction, Fourier transform infrared spectroscopy, and vibrating sample magnetometer. The electromagnetic interference shielding efficiency was evaluated in the KU‐band (12.4–18 GHz). The reflection loss (RL) value showed that the composites have an excellent absorbing property in the KU‐band, minimum ?24.93 dB at 16.40 GHz with a bandwidth of 2.81 GHz (shielding effectiveness up to 10 dB) at a matching thickness 6.5 mm. The RL value of the SrAl_1.3Fe_10.7O₁₉/MWCNT nanocomposite was ?15.92 dB at 15.84 GHz with a bandwidth of 1.66 GHz (with a shielding effectiveness up to 10 dB). These results disclose the remarkable microwave shielding ability of SrAl_1.3Fe_10.7O₁₉/MWCNT/PANi in KU‐band due to the interactive effect of the three components. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45135.     

Enhanced Dielectric Constant for Efficient Electromagnetic Shielding Based on Carbon-Nanotube-Added Styrene Acrylic Emulsion Based Composite

An efficient electromagnetic shielding composite based on multiwalled carbon nanotubes (MWCNTs)-filled styrene acrylic emulsion-based polymer has been prepared in a water-based system. The MWCNTs were demonstrated to have an effect on the dielectric constants, which effectively enhance electromagnetic shielding efficiency (SE) of the composites. A low conductivity threshold of 0.23 wt% can be obtained. An EMI SE of ~28 dB was achieved for 20 wt% MWCNTs. The AC conductivity (σ _ac) of the composites, deduced from imaginary permittivity, was used to estimate the SE of the composites in X band (8.2–12.4 GHz), showing a good agreement with the measured results.     

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.     

Flexible poly(styrene-b-(ethylene-co-butylene)-b-styrene) nanocomposites for electromagnetic interference shielding

In this report, multiwalled carbon nanotubes (CNT) embedded poly(styrene-b-(ethylene-co-butylene)-b-styrene) (SEBS) microspheres (CNT/SEBS) were prepared by solvent evaporation method. Reduced graphene oxide (rGO) nanosheets were used to cover the surface of CNT/SEBS microspheres. The CNT/SEBS/rGO nanocomposites with special segregated conductive network were fabricated by hot pressing these as-prepared complex microspheres. The morphology, electrical percolation threshold, electrical conductivity, and electromagnetic interference (EMI) shielding effectiveness (SE) of CNT/SEBS/rGO composites were characterized. The shielding mechanisms were discussed in detail. Analysis of electrical conductive performance shows that the electrical percolation threshold of rGO is 0.22 vol %. Results of EMI shielding test confirmed the synergistic effect between CNT and rGO. The EMI SE of the composite filled by 2.1 vol % CNT and 3.35 vol % rGO can achieve 26 dB in 8.2− 12.4 GHz (X band), which exceeds the basic requirement for commercial application (20 dB). Its reflectance coefficient (19–41%) indicates that the most part of incident electromagnetic (EM) wave energy is attenuated through absorption mechanism. This kind of absorptive EMI shielding material can be applied without serious secondary EM radiation pollution problems. The effects of filler content, molding temperature on EMI SE, and shielding mechanism were also investigated. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48542.