Electrical conductivity and electromagnetic interference shielding effectiveness of carbon black/sisal fiber/polyamide/polypropylene composites

The effects of hybrid fillers on the electrical conductivity and electromagnetic interference (EMI) shielding effectiveness (SE) of polyamide 6 (PA6)/polypropylene (PP) immiscible polymer blends were investigated. Carbon black (CB) and steam exploded sisal fiber (SF) were used as fillers. CB was coated on the surface of SF, and this was exploded by water steam to form carbon black modified sisal fiber (CBMSF). CB/SF/PA6/PP composites were prepared by melt compounding, and its electromagnetic SE was tested in low‐frequency and high‐frequency ranges. We observed that SF greatly contributed to the effective decrease in the percolation threshold of CB in the PA6/PP matrix and adsorbed carbon particles to form a conductive network. Furthermore, an appropriate CB/SF ratio was important for achieving the best shielding performance. The results indicate that CBMSF was suitable for use as electronic conductive fillers and the CB/SF/PA6/PP composites could be used for the purpose of EMI shielding. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42801.     

Fabrication and electromagnetic interference shielding effectiveness of carbon nanotube reinforced carbon fiber/pyrolytic carbon composites

Carbon nanotube reinforced carbon fiber/pyrolytic carbon composites were fabricated by precursor infiltration and pyrolysis method and their electromagnetic interference shielding effectiveness (EMI SE) was investigated over the frequency range of 8.2–12.4 GHz (X-band). Carbon nanotubes (CNTs) were in situ formed through catalyzing hydrocarbon gases evaporating out of phenolic resin with nano-scaled Ni particles. The content of CNTs increased with the increase of Ni loadings (0.00, 0.50, 0.75 and 1.25 wt.%) in phenolic resin. Thermal gravimetrical analysis results showed that the carbon yield of phenolic resin increased with the addition of Ni catalyst. With the formation of CNTs, the EMI SE increased from 28.3 to 75.2 dB in X-band. The composite containing 5.0 wt.% CNTs showed an SE higher than 70 dB in the whole X-band.     

The effects of MWCNT length on the mechanical,crystallization and electromagnetic interference shielding effectiveness of PP/MWCNT composites

The length of multi-walled carbon nanotubes (MWCNT) has an important influence on the properties of polymer/MWCNT composites. This study aims to examine the influence of the length of MWCNT on the mechanical properties, distribution, melting and crystallization behavior, and electromagnetic interference shielding effectiveness (EMI SE) of PP/MWCNT composites. The test results show that MWCNT of a short length contribute to better mechanical properties and have a better dispersion in the matrix. MWCNT also serve as a nucleating agent for PP, thereby increasing the crystallization temperature (T_c). In particular, short MWCNT provide PP/MWCNT composites with a greater degree of cyrstallinity. The conjunction of 8 wt% long MWCNT in PP/MWCNT composites results in an optimal electrical resistivity of 65.02 Ω-cm, and an average EMI SE of ?29.47 dB. The polymer/MWCNT composites have properties that can be adjusted by using different lengths of MWCNT, which is advantageous for application in diverse products.     

High electromagnetic interference shielding effectiveness in MgO composites reinforced by aligned graphene platelets

Graphene has been considered as an excellent filler to reinforce ceramics with enhanced properties. However, the uniform dispersion and controlled orientation of graphene sheets in a ceramic matrix have become major challenges toward higher performance. In this paper, we prepared MgO matrix composites with parallel graphene layers through the intercalation of the precursor into expandable graphite. We obtained a high electromagnetic interference (EMI) shielding effectiveness of ~30 dB, due to the multiple reflections and absorptance of electromagnetic waves between the parallel graphene layers. The hardness and strength of the MgO composite were also increased by introducing parallel graphene layers. All these properties suggest that the graphene/MgO composite represents a promising electromagnetic shielding material.     

Morphological,mechanical, and electromagnetic interference shielding effectiveness characteristics of glass fiber/epoxy resin/MWCNT buckypaper composites

Glass fiber/epoxy resin composites (GF/EP) using one and three multi-walled carbon nanotube buckypapers (BP) were obtained and their complex parameters, reflectivity, and electromagnetic interference (EMI) shielding effectiveness (SE) at X-band (8.2–12.4 GHz) and Ku-band (12.4–18 GHz) were evaluated. The preparation of BP used polyacrylonitrile (PAN) nanofibers (PF These composites show both large storage and energy loss capacity in both bands revealing promising results related to EMI SE applications. Besides, a high attenuation of around 67% and 72% were achieved for BP based composites. The cross-section view of the buckypaper and the laminates was analyzed by scanning electron microscopy (SEM). The incorporation of the CNT film into the laminates showed no improvements in the elastic properties through dynamic mechanical analyses (DMA). Nevertheless, a decrease in the shear properties by the compression shear test (CST) and interlaminar shear strength (ILSS) has been observed. GF/EP/BP/PF composite presented a reduction of 29 and 39% in its ILSS properties compared to the base laminate (GF/EP). Also, the decrease was even more significant, revealing a steep reduction in its CST properties. On the other hand, the removal of the pan nanofiber (PF) led to better mechanical properties for GF/EP/BP/RPF composites. Results have shown ILSS values of 47.4 ± 2.2 MPa which are close to the base laminate (52.4 ± 3.1 MPa). The removal of the PF provided larger porous in the CNT network, making the impregnation by epoxy easier in the BP/RPF which resulted in improved shear properties compared to GF/EP/BP/PF samples.     

Fabrication of novel polyaniline/flowerlike copper monosulfide composites with enhanced electromagnetic interference shielding effectiveness

Novel polyaniline (PANI)/flowerlike CuS composites with improved electromagnetic interference (EMI) shielding effectiveness (SE) were prepared through the in situ polymerization of PANI into the flowerlike CuS microspheres. X‐ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, ultraviolet–visible optical absorption spectroscopy, thermogravimetric analysis, electrical conductivity testing, and EMI SE testing were used to characterize the as‐obtained products. The results reveal that the flowerlike CuS was uniformly coated by a PANI shell. Most importantly, compared with the original CuS and pure PANI, the novel PANI/flowerlike CuS composites exhibited a remarkably enhanced SE. With a thickness of 3 mm, the optimal EMI SE of the PANI–CuS composites reached ?45.2 dB at 2.78 GHz, and an improved shielding efficiency below ?18 dB was also obtained over the frequency range from 300 kHz to 3 GHz. This suggested that these novel PANI/flowerlike CuS composites have promising applications in the field of shielding materials. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45232.     

Processing conditions for electromagnetic interference shielding effectiveness and mechanical properties of acrylonitrile-butadiene-styrene based composites

A conductive plastic was compounded in a twin screw extruder by incorporating conductive carbon fiber (CF) into an acrylonitrile-butadience-styrene (ABS) copolymer. The effects of various processing parameters prior to injection molding were investigated; then, the electromagnetic interference shielding effectiveness (EMI SE), fiber length, processability, and mechanical properties of the composite were studied. Results showed that the EMI SE of the composite increased as the final fiber length increased. The longer final fiber was produced by feeding fibers into the ABS melt at 240°C and 60 rpm. A more conductive network was formed by adding lubricants to the composite to reduce fiber damage and increase fiber dispersion. The increase of the fiber content affected processability. When the fiber content was higher than 40 phr (parts per hundred resin) in the composite, the average fiber length shortened. This study shows that better shielding can be obtained by adding a fiber at a rate higher than 30 phr. The best shielding obtained is about 30 decibels (dB).     

微孔发泡PP/PET/CNTs复合材料的制备及其电磁屏蔽效能研究

采用聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、碳纳米管(CNTs)制备了具有纤维结构的微孔发泡复合材料,借助层叠器内部流道的变化,实现了造粒阶段PET的连续化原位成纤.通过差示扫描量热仪(DSC)、扫描电子显微镜(SEM)、矢量网络分析仪和万能试验机对复合材料的结晶性能、表观形态、电磁屏蔽效能(EMI SE)和拉...     

Electrical conductivity and electromagnetic interference shielding effectiveness of polyaniline–ethylene vinyl acetate composites

Electrical conductivity and electromagnetic interference (EMI) shielding effectiveness at microwave (200–2000 MHz) and X‐band (8–12 GHz) frequency range of polyaniline (PAni) composites were studied. It has been observed that EMI shielding of conductive polyaniline (PAni)–ethylene vinyl acetate composites increases with the increase in the loading levels of the conductive polymer doped with dodecylbenzene sulfonic acid. The result indicates that the composites having higher PAni loading (>23%) can be used for EMI shielding materials and those with lower PAni loading can be used for the dissipation of electrostatic charge. Copyright © 2004 Society of Chemical Industry     

Carbon fiber reinforced composites from industrial waste for microwave absorption and electromagnetic interference shielding applications

Lightweight materials with hybrid microstructures are getting great attention in the area of electromagnetic wave absorption. In the present study, carbon fiber and fly ash reinforced composites are prepared by mixing them with ground granulated blast furnace slag, followed by compaction and sintering at 1000 °C under an argon atmosphere. Akermanite-gehlenite was observed to be the primary crystalline phase present in the prepared samples. Porous composites are obtained with the addition of fly ash and carbon fiber as they inhibit densification. The resultant microstructure has homogeneous carbon fiber dispersion and uniform fly ash anchoring on the matrix phase. This enhanced interface polarization, defect polarization, electron transportation, and impedance matching characteristics of the composites. Hence, the developed composites' microwave absorption and electromagnetic interference shielding properties exhibited an outstanding performance at low thickness with a reflection loss value of ?41.24 dB and total shielding effectiveness of 42.29 dB at the X-band.     

Preparation of polyaniline/polyacrylate composites and their application for electromagnetic interference shielding

Polyaniline (PANI) deposited polyacrylate (PA) powders were prepared by chemical polymerization of aniline in hydrochloric acid with dispersed PA powders. The powders, after dedoped with ammonia water, were re‐doped with camphorsulfonic acid (CSA) to render them conductive, and conductive PANI/polyacrylate composite coatings (PANI/PA) were prepared by bead milling of these CSA‐doped PANI (PANI–CSA) deposited polyacrylate powders (PANI–CSA/PA). It was found that aniline was polymerized preferentially at the surfaces of the powders and PANI deposited powders were obtained as indicated by the scanning electronic microscopy images. The amount of deposited PANI increased with the aniline/polyacrylate weight ratio in feed, and no isolated PANI particles was found. UV–Vis and Fourier transformed infrared spectra indicated that the PANI layer was physically adhered to the PA powders, and not chemically. Conductivities of the PANI–CSA/PA powders and the PANI/PA coatings increased with the amounts of PANI–CSA and a percolation threshold of 0.2 and 0.3 was demonstrated, respectively. Electromagnetic interference shielding measurements showed that the shielding effectiveness of the PANI/PA coatings increased with PANI–CSA loadings, and shielding effectiveness as high as 60 dB can be achieved with the coatings. POLYM. COMPOS., 27:627–632, 2006. © 2006 Society of Plastics Engineers     

Electromagnetic interference shielding behavior of polyaniline/graphite composites prepared by in situ emulsion pathway

Polyaniline–graphite composites were prepared via in situ emulsion pathway, using different weight ratios of aniline to graphite. These composites were characterized for thermal, electrical, and spectral attributes. The thermal stability (～ 230°C) and electrical conductivity (67.9 S/cm) were improved significantly as compared with polyaniline doped with conventional inorganic dopants such as HCl (140°C and 10 S/cm). Scanning electron micrographs indicated a systematic change in morphology from globular to flaky with increasing amounts of graphite. The relative shifting of UV–visible bands indicates that some interactions exist between doped polyaniline and graphite. Absorption‐dominated total electromagnetic interference shielding effectiveness of the order of ?33.6 dB suggests that these materials can be used as futuristic microwave shielding materials. The good electrical conductivity and thermal stability make them ideal candidates for preparing conducting composites by melt blending with conventional thermoplastics such as polyethylene, polypropylene, and polystyrene, etc. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

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.     

Anticorrosion and electromagnetic interference shielding behavior of candle soot-based epoxy coating

This article presents candle soot (CS) as anticorrosion coating material for mild steel (MS) in 3.5 wt % of NaCl solution using potentiodynamic polarization and electrochemical impedance spectroscopy. CS is easily available, low-cost material, and characterized by using X-Ray diffraction (XRD), Raman spectroscopy, UV–vis spectroscopy, Fourier-transform infrared (FTIR), and scanning electron microscopy (SEM). CS is superhydrobhobic in nature that helps to prevent corrosion by repelling water molecules from MS surface. The electrochemical results confirmed the prevention in corrosion process for MS using candle soot-epoxy (CS-EP) based anticorrosion coatings. The CS-based coatings displayed outstanding barrier properties in 3.5 wt % of NaCl solution in comparison to the neat EP coating. Different candle CS-EP coating combinations were tested that exhibited excellent corrosion inhibition performance with highest protection increased up to 98.45% at 0.2 wt % of CS. The surface morphological studies were used to analyze the MS surface conditions in absence and presence of CS-EP coating in 3.5 wt % of NaCl solution. CS-EP admixtures were also tested for their shielding effectiveness in the frequency range of 8.2–12.4 GHz and it has been found that on incorporation of 0.2 wt % of CS in EP resin total shielding effectiveness (SE_T) increased to −5.3 dB as compared to −0.33 dB for neat EP. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 137, 48675.     

Toughening strategies of carbon nanotube/polycarbonate composites with electromagnetic interference shielding properties

The effect of different toughening strategies on the mechanical properties of multiwalled carbon nanotube/polycarbonate composite (PC/MWNT) for electromagnetic interference shielding was analyzed from the mechanical and fracture tests using linear elastic fracture mechanics. The effect of processing (injection and compression molding) and manufacturing (annealing) conditions in the mechanical properties and electrical conductivity has been studied. The classic electromagnetic theory predicts a shielding effectiveness around 40 dB for nanocomposites with 5 wt% of MWNT in the frequency range studied. These values make these compounds to be very interesting materials for potential applications as electronic housings. Therefore, a combination of cyclic form of polybutylene terephthalate addition and annealing strategies let to optimize flexural parameters and improve the flexural modulus of PC composites. The rheology results showed that the dynamic moduli and the viscosity grew with increasing MWNT content. A significant change in frequency dependence of the moduli was observed, with respect to pure PC, which indicates a transition from a liquid‐like to a solid‐like behavior. Finally, the morphological study proves that the composites display different toughening mechanisms as function of carbon nanotube quantity. This fact could explain the different fracture behaviors of materials. In summary, it has been proved that it is possible to obtain PC/MWNT nanocomposites with relatively high conductivity, minimizing the loss of mechanical properties, using processing techniques easily scalable at industrial level. POLYM. COMPOS., 34:1938–1949, 2013. © 2013 Society of Plastics Engineers     

The electromagnetic interference shielding of polypyrrole impregnated conducting polymer composites

A lightweight conducting polymer composite was prepared by the incorporation of conducting polypyrrole in the pores of a host polymer to form a conductive network. The inclusion of polypyrrole in a porous cross-linked polystyrene host polymer, prepared by the concentrated emulsion polymerization method, was carried out by imbibing the host polymer with a pyrrole solution (or oxidant solution), partially drying the saturated host polymer, and imbibing it again with the oxidant solution (or pyrrole solution) for 2 h. The conductivity of the polymer composite is as high as 0.5 S/cm and the shielding effectiveness of the composite reaches 26 dB in the frequency range from 1.0 to 2.0 GHz.     

High electromagnetic interference shielding effectiveness achieved by multiple internal reflection and absorption in polybenzoxazine/graphene foams

Electromagnetic interference (EMI) is an increasingly severe issue in modern life and high-performance EMI shielding materials are in desperate need. To achieve high EMI shielding effectiveness (EMI SE), a series of polybenzoxazine/graphene composites foams are developed using a simple sol–gel method. When the graphene loading increases from 1 to 20 wt%, the density of the composites foams drops from 0.4143 g/cm³ to 0.1654 g/cm³. Meanwhile, an electrically conductive path is formed at around 7 wt% of graphene. Below the percolation threshold, the dielectric constant increases with graphene content and composite foam with 5 wt% graphene shows dielectric constant of 10.8 (1 MHz). At the highest graphene content of 20 wt%, the electric conductivity reaches 0.02 S/cm, 10 orders of magnitude higher than pure polybenzoxazine foam. Benefiting from the high electrical conductivity and lightweight porous structure, the composite foam PF/20G delivers an EMI SE of 85 dB and a specific SE of 513.9 dB·cm³/g. Importantly, the EMI shielding is dominated by absorption attenuation, with PF/20G shows absorption ratio higher than 98% in the range of 8.4–11.0 GHz, which is believed to be caused by multiple internal reflection and absorption inside the conductive foam.     

Mechanical and electromagnetic interference shielding properties of carbon fiber/graphene nanosheets/epoxy composite

Graphene oxide (GO) was introduced into carbon fiber/epoxy composite using a wet process for impregnating carbon fiber by epoxy added with GO, which resulted in an enhancement in the interfacial performance and electromagnetic interference shielding effectiveness (SE) of composite. To investigate the reinforcing mechanism, we compared the reinforcing effect between graphene oxide and reduced graphene oxide through interlaminar shear strength test, microdrop test, scanning electron microscopy, and transmission electron microscopy. The results indicate that toughening effect plays the key role for the interfacial improvement of carbon fiber/graphene nanosheets/epoxy composite. By adding only 0.1 wt% GO, the composite achieved an 11% enhancement of interlaminar shear strength at the maximum of 117.45 MPa and a SE improvement about 10 dB in the range of 5–20 GHz in the meantime, giving rise to a highly practicable potential for industrial utilization. POLYM. COMPOS., 37:2494–2502, 2016. © 2015 Society of Plastics Engineers