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The use of plastics in automobiles is increasing dramatically due to their advantages of low weight and cost-effectiveness. Various products can be manufactured by recycling end-of-life vehicle (ELV) plastic waste, enhancing sustainability within this sector. This study presents the development of an electromagnetic interference (EMI) shield that can be used for protecting electronic devices in vehicles by recycling waste bumpers of ethylene propylene diene monomer (EPDM) rubber from ELVs. EPDM waste was added to a unique combination of  40 / 60 : PP/CaCO 3  master batch and conductive nanofiller of carbon nanotubes using an internal melt mixing process. This nanocomposite was highly conductive, with an electrical conductivity of  5.2 × 10 − 1 S · cm − 1  for 5 vol% CNT in a 30 wt% EPDM/70 wt% PP/CaCO 3  master batch and showed a high EMI shielding effectiveness of 30.4 dB. An ultra-low percolation threshold was achieved for the nanocomposite at 0.25 vol% CNT. Waste material in the composite improved the yield strain by about 46% and strain at break by 54% in comparison with the same composition without waste. Low cost and light-weight fabricated composite from ELV waste shows high EMI SE for application in electronic vehicles and opens a new path to convert waste to wealth. [ABSTRACT FROM AUTHOR]

Hybrid polymer nanocomposites based on polyvinylidene fluoride (PVDF) as the matrix, carbon nanotubes (CNTs) as the primary conductive filler, and metal nanoparticles as secondary fillers were fabricated by melt mixing. Secondary nanofillers with different geometry and properties (nickel nanowire (NiNW), silver nanowire (AgNW), nickel nanoparticle (NiNP), and silver nanoparticle (AgNP) were selected to investigate the effect of geometry and properties of secondary filler on the hybrid polymer nanocomposites' properties. Electrical conductivity, electromagnetic interference (EMI) shielding effectiveness, and complex microwave properties of the fabricated hybrid nanocomposites were studied in X‐band frequency (8.2–12.4 GHz). The hybrid nanocomposites containing CNT/AgNW demonstrated superior conductivity and EMI shielding compared to individual fillers such as CNT, AgNW, NiNW, AgNP, NiNP, or hybrid system such as CNT/NiNW. The novelty of the present study lies in the unique synergy arising from the combination of nanofillers with similar geometry and high electrical conductivity, which resulted EMI shielding effectiveness as high as 27 dB for a shield with only 1.1 mm thickness. The EMI shielding mechanisms, including negative permittivity were studied and explained in details in the manuscript. [ABSTRACT FROM AUTHOR]

In this work, we have used a single-step pyrolysis method in synthesizing carbonaceous materials at 800 °C and 1000 °C, using metal (Ni- or Mn-) acetylacetonate and toluene as precursors. We demonstrated that the pyrolysis synthesis temperature (TP) and the choice of organometallic precursors affect the morphology and the microstructure of the carbonaceous materials. Namely, at low temperature (800 °C), the Ni(acac)2 precursor leads to the formation of metallic-Ni catalysts for the growth of carbon nanotubes (CNTs), but at high temperature (1000 °C) this favors the growth of carbon globules (CG). In contrast, the Mn-(acac)2 precursor leads to the formation of MnO-particles, and associated carbon globules at both the temperatures used. The electromagnetic interference (EMI) shielding effectiveness (SE) of the PVDF polymer based composite specimens prepared with the carbonaceous samples having a metallic Ni-core is found to be far superior than that obtained using the specimen with particles of the MnO-core. The observed contrast in SE behavior is shown to originate due to the size and metallic nature of the Ni-nanoparticles and the Ohmic conduction loss in these metallic particles over the loss due to interfacial polarization-based scattering of the insulating MnO nanoparticles present in the PVDF-based composite films. Hence, our study highlights the necessary synthesis parameters, and the importance of graphite coated metallic nanoparticles in designing highly efficient EMI shields. [ABSTRACT FROM AUTHOR]

Lightweight and flexible materials with high conductivity and low thickness are highly desirable for electromagnetic interference (EMI) shielding applications. Developing hybrid nanostructured materials, which combine the properties of their constituents, is an excellent strategy to create highly effective EMI shields. In this study, we report a hybrid polymer nanocomposite composed of carbon nanotube (CNT) and ZnO nanowire (ZnONW) for EMI shielding applications. We found that the combination of a conductive filler (CNT) and a dielectric filler (ZnONW) with a similar geometry is an effective method to fabricate nanocomposites with enhanced EMI shielding. We achieved high average shielding effectiveness of 27.3 dB (with a maximum of 41 dB at 10.2 GHz) for a sample of CNT:ZnONW (5.0:2.5 wt%) with only 1.1 mm thickness, which is among the best‐reported values in the literature for polymer nanocomposites with similar filler loading and thickness. This performance originates from the excellent electrical conductivity and dielectric properties of hybrid nanocomposites, combined with the geometry of ZnO nanowire. A comparison of the shielding properties of the developed hybrid nanocomposites with the literature implies that they are promising functional materials in the world of EMI shielding applications. [ABSTRACT FROM AUTHOR]

In this study, we achieved almost 99% (i.e., 19 dB) electromagnetic interference shielding effectiveness (EMI SE), at a much lower cost than poly(vinylidene fluoride) (PVDF)/multi-walled carbon nanotube (MWCNT) nanocomposite, by selectively localizing MWCNT in the polystyrene (PS) phase of PS/PVDF (70:30) blend nanocomposite. This study demonstrates that we can tune MWCNT dispersion, nano localization, electrical conductivity, EMI SE and rheological properties of PS/PVDF/MWCNT nanocomposites by manipulating the mixing order of blend components. Premixing MWCNT with PS phase of PS/PVDF (50:50) blend reduces the agglomeration of MWCNT by 6% (via optical micrograph analysis), compared to the one-step mixing technique. Transmission electron microscope images of PS/PVDF blend nanocomposite show that MWCNT is located in the phase with which MWCNT is premixed. However, for the one-step mixing technique, the MWCNT mostly locates in PVDF with some agglomerates in PS phase. Scanning electron microscope images demonstrate the alteration of blend morphology (e.g., from droplet to co-continuous) depending upon the mixing technique and blend composition. In this context, the PVDF/MWCNT nanocomposite depicts higher EMI SE (19 dB) than PS/MWCNT nanocomposite (12 dB). However, using a specific sequential mixing approach, equal EMI SE to PVDF/MWCNT is achieved in PS/PVDF (70:30) immiscible blend nanocomposite through multiple scattering at significantly low cost. Another key finding is the complex permittivity of hetero-dielectric media demonstrates a linear relation with EMI SE of the blend nanocomposite. Taken together, this study provides a method to design a high-performance microwave absorber by sequential addition of microwave active fillers in the immiscible polymer blends. [ABSTRACT FROM AUTHOR]

This paper investigated the effect of carbon nanotubes (CNTs) on the electromagnetic interference shielding of carbon fiber reinforced polymer (CFRP) composites. The CNT/CFRP composites were fabricated by dry spray deposition of CNT on surfaces of carbon fiber prepregs and then out‐of‐autoclave curing process. The interlaminate shear strength of CNT/CFRP composites was first examined. It was found that the shear strength was strengthened if the CNT loading between prepregs was below 3.0 g/m2. Then, the electromagnetic interference shielding effectiveness (EMI SE) of CNT/CFRP composites was characterized as a function of CNT loadings over the X‐band frequency range (8.2–12.4 GHz). The tests revealed that the maximum and minimum EMI SE of CNT/CFRP composites increased by approximately 20%, from 62 to 74 dB and from 45 to 53 dB, respectively, by adding 2.5 g/m2 CNT at the interlaminate surfaces. The results unveiled that the shielding by absorption dominates in the overall EMI SE of CNT/CFRP composites, while the shielding by reflection is almost independent of CNT loadings. It was also observed that the overall EMI SE increased linearly with CNT loading. This study shows that the spray deposition of CNT is an efficient technique to improve the EMI shielding performance of CFRP composites. POLYM. COMPOS., 39:E655–E663, 2018. © 2016 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Nitrogen-doped and Undoped carbon nanotubes (CNTs) were synthesized by selective transmission of source and carrier gases (ethane, ammonia, hydrogen, and argon) over an alumina-supported iron catalyst in a quartz tubular reactor at 650 °C. Conductive nanocomposites were prepared by mixing CNTs and a polyvinylidene fluoride (PVDF) matrix using a small scale melt mixer (APAM mixer) at 240 °C and 235 rpm. Various characterization techniques, such as X-ray photoelectron spectroscopy, transmission electron microscopy, and Raman spectroscopy revealed that nitrogen doping altered the structure of CNTs, reduced the aspect ratio, deteriorated the crystalline structure, and changed the electronic properties of CNTs. It was also observed that the Undoped CNT/PVDF nanocomposites presented better state of dispersion, higher electrical conductivity, lower percolation threshold, and significantly higher electromagnetic interference shielding than their Nitrogen-doped counterparts. For instance, at 3.5wt% the Undoped CNT/PVDF nanocomposites shielded the incident electromagnetic wave 16 times more than the Nitrogen-doped ones. The enhanced electrical properties of the Undoped CNT/PVDF nanocomposites were attributed to enhanced dispersion, superior crystalline structure, and higher aspect ratio of Undoped CNTs. [ABSTRACT FROM AUTHOR]

Nanocomposites using copper nanowires (CuNWs) or carbon nanotubes (CNTs) as fillers with polypropylene (PP) as matrix were prepared by miscible solution mixing and precipitation method. Comparative studies on electrical conductivity and electromagnetic interference shielding properties were reported. On the conductivity curve, a plateau was found for both CuNW/PP composite and CNT/PP composite. The plateaus are located at a different concentration range for each composite type: for CuNW/PP composite, it is between 0.8 and 1.7 vol %, while for CNT/PP composite the plateau occurs in a narrower range between 0.4 and 0.6 vol %. The shielding effectiveness (SE) increases with increased concentration of fillers. CNT/PP composite has higher SE at concentrations less than 2 vol %; the two curves cross near 10 dB at this point and at concentrations higher than 2 vol %, CuNW/PP composite has higher SE. © 2014 American Institute of Chemical Engineers AIChE J, 61: 296-303, 2015 [ABSTRACT FROM AUTHOR]

The influence of melt mixing conditions on the level of dispersion and the aspect ratio of vapor grown carbon nanofibers (VGCNFs) in a polystyrene (PS) matrix was studied. Final electrical and electromagnetic shielding capabilities in the 0.05-1.5 GHz frequency range are reported and discussed in the light of the composites' microstructure. The morphological study was based on analyzing scanning electron microscopy and optical microscopy micrographs and measuring the VGCNF length as a function of shear mixing conditions. The influence of mixing conditions on the microstructure was also indirectly studied by analyzing the dynamic mechanical behavior of the composites via rheology. Degradation of the VGCNF aspect ratio was found to be a function of the mixing energy. VGCNFs lost one-third of their aspect ratio under gentle (low shear stress and mixing energy) mixing conditions. After VGCNFs had lost 40% of their aspect ratio, they had more resistance to breakage with increase in mixing energy. The dispersion of the VGCNFs was remarkably enhanced with increase in mixing energy. The percentage of area taken up by big agglomerates in the micrographs decreased from 14.1% to 5.5% when the mixing energy was increased from 100 J mL−1 to 453 J mL−1. The electrical and electromagnetic shielding properties of the 7.5 vol% VGCNF/PS composites were not affected by changing the processing energy because the enhancement of VGCNF dispersion with increasing mixing energy was accompanied by a loss in nanofiber aspect ratio. © 2012 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The electromagnetic interference (EMI) shielding effectiveness (SE) and EMI shielding mechanisms of high structure carbon black (HS-CB)/polypropylene (PP) composites in the X-band frequency range were studied. Composite plates with three different thicknesses and five different electrical conductivities were studied. The reflection loss and absorption loss of the composites were quantified based on the electromagnetic radiation power balance. The results showed that for HS-CB/PP composites, absorption loss contribution to the overall attenuation is more than the contribution of the reflection loss. The ability of the theoretical model to predict the EMI shielding by reflection and absorption was found to be a function of the shielding plate thickness and conductivity. [ABSTRACT FROM AUTHOR]

Processing, electrical, and electromagnetic interference (EMI) shielding behaviors of carbon nanotube (CNT)/acrylonitrile-butadiene-styrene (ABS) nanocomposites were studied as function of CNT concentration. The nanocomposites were prepared by melt mixing followed by compression molding. The selective and good level of dispersion of CNT in the styrene-acrylonitrile section of the ABS polymer was found to create conductive networks in the ABS matrix at a nanofiller loading of 0.75 wt %. At this nanofiller loading, the nanocomposite electrical conductivity was 10−5 S/m. This conductivity makes the nanocomposite suitable for electrostatic discharge protection applications. The EMI shielding effectiveness of the nanocomposites increased with the increase in nanofiller concentration. In the 100-1500 MHz frequency range, 1.1 mm thick plates made of ABS nanocomposite filled with 5 wt % CNT exhibit an EMI shielding effectiveness of 24 dB. At this shielding level, the nanocomposite is suitable for a broad range of applications. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012 [ABSTRACT FROM AUTHOR]

The effect of melt mixing conditions on the morphological, rheological, electrical, electromagnetic interference (EMI) shielding effectiveness (SE), and tensile properties of 7.5 vol% vapor grown carbon nanofiber (VGCNF)/polyethylene composites were investigated. 7.5 vol% VGCNF was used because such loading is required to obtain a composite with satisfactory EMI SE. The composites were compounded by melt mixing and the parts were prepared by hot-compression molding. The dispersion and distribution of nanofibers were enhanced by increasing the mixing energy, i.e. mixing time and/or rotation speed. The influence of mixing energy on the electrical and EMI SE properties was found to be a function of rotation speed, i.e. shear stress. For composites compounded at 20 rpm, increasing the mixing energy from 70 to 2300 J/ml decreased the EMI SE from 29.5 to 23.9 dB. However, for composites prepared at 100 rpm, increasing the mixing energy from 600 to 1700 J/ml decreased the EMI SE from 25.4 to 18.6 dB. No considerable influence on the yield stress, Young's modulus, and strain at break were found for different processing conditions. Copyright © 2009 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: The electromagnetic interference (EMI) shielding mechanisms of multi-walled carbon nanotube (MWCNT)/polymer composites were analyzed experimentally and theoretically. For the experimental analysis, EMI shielding effectiveness (SE) of MWCNT/polypropylene (PP) composite plates made in three different thicknesses and at four different concentrations were studied. A model based on the shielding of electromagnetic plane wave was used to theoretically study the EMI shielding mechanisms. The experimental results showed that absorption is the major shielding mechanism and reflection is the secondary shielding mechanism. The modeling results demonstrated that multiple-reflection within MWCNT internal surfaces and between MWCNT external surfaces decrease the overall EMI SE. The EMI SE of MWCNT/PP composites increased with increase in MWCNT content and shielding plate thickness. [Copyright &y& Elsevier]

Abstract: Vapor grown carbon nanofiber (VGCNF)/polymer conductive composites are elegant materials that exhibit superior electrical, electromagnetic interference (EMI) shielding effectiveness (SE) and thermal properties compared to conventional conductive polymer composites. This article reviews recent developments in VGCNF/polymer conductive composites. The article starts with a concise and general background about VGCNF production, applications, structure, dimension, and electrical, thermal and mechanical properties. Next composites of VGCNF/polymer are discussed. Composite electrical, EMI SE and thermal properties are elaborated in terms of nanofibers dispersion, distribution and aspect ratio. Special emphasis is paid to dispersion of nanofibers by melt mixing. Influence of other processing methods such as in-situ polymerization, spinning, and solution processing on final properties of VGCNF/polymer composite is also reviewed. We present properties of CNTs and CFs, which are competitive fillers to VGCNFs, and the most significant properties of their composites compared to those of VGCNF/polymer composites. At the conclusion of the article, we summarize the most significant achievements and address the future challenges and tasks in the area related to characterizing VGCNF aspect ratio and dispersion, determining the influence of processing methods and conditions on VGCNF/polymer composites and understanding the structure/property relationship in VGCNF/polymer composites. [Copyright &y& Elsevier]

The similar molecular structure but different geometries of the carbon nanotube (CNT) and graphene nanoribbon (GNR) create a genuine opportunity to assess the impact of nanofiller geometry (tube vs. ribbon) on the electromagnetic interference (EMI) shielding of polymer nanocomposites. In this regard, GNR and its parent CNT were melt mixed with a polyvinylidene fluoride (PVDF) matrix using a miniature melt mixer at various nanofiller loadings, i.e., 0.3, 0.5, 1.0 and 2.0 wt%, and then compression molded. Molecular simulations showed that CNT would have a better interaction with the PVDF matrix in any configuration. Rheological results validated that CNTs feature a far stronger network (mechanical interlocking) than GNRs. Despite lower powder conductivity and a comparable dispersion state, it was interestingly observed that CNT nanocomposites indicated a highly superior electrical conductivity and EMI shielding at higher nanofiller loadings. For instance, at 2.0 wt%, CNT/PVDF nanocomposites showed an electrical conductivity of 0.77 S·m−1 and an EMI shielding effectiveness of 11.60 dB, which are eight orders of magnitude and twofold higher than their GNR counterparts, respectively. This observation was attributed to their superior conductive network formation and the interlocking ability of the tubular nanostructure to the ribbon-like nanostructure, verified by molecular simulations and rheological assays. [ABSTRACT FROM AUTHOR]

Abstract: The microstructure, electromagnetic interference (EMI) shielding effectiveness (SE), DC electrical conductivity, AC electrical conductivity and complex permittivity of nanostructured polymeric materials filled with three different carbon nanofillers of different structures and intrinsic electrical properties were investigated. The nanofillers were multiwall carbon nanotubes (MWCNT), carbon nanofibers (CNF) and high structure carbon black (HS-CB) nanoparticles and the polymer was acrylonitrile-butadiene-styrene (ABS). In addition, the EMI SE mechanisms and the relation between the AC electrical conductivity in the X-band frequency range and the DC electrical conductivity were studied. The nanocomposites were fabricated by solution mixing and characterized by uniform dispersion of the nanofillers within the polymer matrix. It was found that, at the same nanofiller loading, the EMI SE, permittivity and electrical conductivity of the nanocomposites decreased in the following order: MWCNT>CNF>CB. MWCNT based nanocomposites exhibited the lowest electrical percolation threshold and the highest EMI SE owning to the higher aspect ratio and electrical conductivity of MWCNT compared to CNF and HS-CB. The AC conductivity in the X-band frequency range was found to be independent of frequency. [Copyright &y& Elsevier]

Abstract: Multi-walled carbon nanotube (MWCNT)/polystyrene (PS) composites were injection molded into a mold equipped with three different cavities. A high alignment of MWCNTs in PS was achieved by applying high shear force to the melt. The effects of gate and runner designs and processing conditions, i.e., mold temperature, melt temperature, injection/holding pressure and injection velocity, on the volume resistivity of the composites were investigated in both the thickness and in-flow directions. The experiments showed that volume resistivity could be varied up to 7 orders of magnitude by changing the processing conditions in the injection molded samples. The electromagnetic interference shielding effectiveness (EMI SE) of the molded composites was studied by considering the alignment of the MWCNTs. The EMI SE decreased with an increase in the alignment of the injection-molded MWCNTs in the PS matrix. This study shows that mold designs and processing conditions significantly influence the electrical conductivity and shielding behavior of injection molded CNT-filled composites. [Copyright &y& Elsevier]

In this work, EMI shielding behaviors in the X-band frequency have been investigated for flexible polyvinylidene fluoride (PVDF) composites containing globular- and tubular-shaped carbonaceous nanostructures embedded with mono-metallic (Ni) and bi-metallic (FeNi, CoNi, MnNi) alloy nanoparticles. Pyrolysis was carried out at two different temperatures (800 °C and 1000 °C) to synthesize carbonaceous materials with two different morphologies. Carbon nanotubes (CNTs) are predominantly seen in the samples synthesized at lower temperature (800 °C), whereas carbon globules (CGs) are observed for the samples synthesized at higher temperature (1000 °C). The PVDF-CNT composites show superior microwave shielding behavior than the PVDF-CG composites, which is attributed to the enhanced absorption of the microwave through Ohmic conduction and interfacial polarization loss. The 1-D structure of CNTs provides the required conduction path for the electrons and forms a network to trap the microwave within them via multiple scattering. The microwave absorption behavior of the composites predominantly results from the metallic nature of the embedded nanoparticles, the graphitic layer encapsulating them and the graphitic walls of the CNTs. We further demonstrate the direct correlation of the EMI shielding behavior of the nanocomposites with the morphology of carbonaceous nanomaterials and the conductivity of the embedded metallic nanoparticles. Image 1 [ABSTRACT FROM AUTHOR]

Abstract This study provides critical insight into the design of nanocomposites and presents both enhanced mechanical and electromagnetic interference (EMI) shielding performance. Polypropylene nanocomposites reinforced with carbon nanotube (CNT) alone, stainless steel fiber (SSF) alone, and a hybrid filler system of SSF and CNT, with 50/50 filler volume ratio but different total filler loadings, were developed via melt-mixing. It was revealed that the hybrid nanocomposites depicted simultaneous enhanced EMI shielding and mechanical performance over single filler composites. The enhanced mechanical and EMI shielding performance of the hybrid nanocomposite was attributed to the bridging of rigid SSFs with flexible CNTs, leading to a robust conductive hierarchical filler network. To characterize and assess the network, standard morphological analysis was performed. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Employing chemical vapor deposition technique, multi-walled carbon nanotubes (CNTs) were synthesized over Fe catalyst at a broad range of temperatures, i.e. 550° C to 950° C (at 100° C intervals). CNTs were melt-mixed into a polyvinylidene fluoride (PVDF) matrix at various loadings, and then compression molded. Surprisingly, despite the ascending trend of CNT powder conductivity with the synthesis temperature, the nanocomposites made with CNT synthesized at 650° C had significantly lower percolation threshold (around 0.4 wt%) and higher electromagnetic interference shielding effectiveness (EMI SE) (20.3 dB over the X-band for 3.5 wt% CNT and 1.1 mm thickness) than the other temperatures. Exhaustive characterization studies were conducted on both CNTs and composites to unveil their morphological and electrical characteristics. Superior EMI shielding of CNT 650° C was attributed to a combination of high carbon purity, aspect ratio, crystallinity, and moderate powder conductivity along with decent state of dispersion within the PVDF matrix. [ABSTRACT FROM AUTHOR]

[Display omitted] • Innovation of an 80 nm heater electrode/EMI shield with 91% optical transparency. • De-icing a 2 mm ice layer in less than a minute under – 10 °C temperature condition. • Achieving a superior figure-of-merit of 610 and a sheet resistance of 6.4 Ω sq–1. • Attenuation of electromagnetic waves by 99.5% using a specific layering design. • Fabrication of an oxidation-free electrode/shield using a sandwich assembly. An unprecedented highly transparent glass heater and electromagnetic interference (EMI) shield is fabricated, using a layer-by-layer assembly of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and silver nanowires (AgNWs) to replace both the conventional indium tin oxide (ITO) and other metal- and carbon-based electrodes proposed to date. The novel simple fabrication of the electrode, unlike many other reported technologies, does not require any vacuum or chemical vapor deposition, hot pressing, pulsed laser irradiation, UV-lithography, and electroplating. The ∼ 80 nm layered thin film offers an exceptionally high figure-of-merit of 610 with a low sheet resistance of 6.4 Ω sq–1 and a total EMI shielding of 23 dB, attenuating 99.5% of the incident electromagnetic waves in the X-band frequency range at high optical transparency of 91%. The transparent heater, sandwiched between two ∼ 2.5 mm glass substrates, shows promising Joule heating performance when successfully de-ices a 2 mm ice in less than a minute while maintained under a sub-zero temperature of – 10 °C. A numerical heat transfer model is also developed to assess the temperature profile distribution and confirm the de-icing time. [ABSTRACT FROM AUTHOR]

Abstract: This study compares electromagnetic interference (EMI) shielding properties of injection molded versus compression molded multi-walled carbon nanotube/polystyrene (MWCNT/PS) composites, i.e., properties such as EMI shielding effectiveness (EMI SE), electrical conductivity, real permittivity and imaginary permittivity. The injection molded (MWCNT-aligned) samples showed lower EMI shielding properties than compression molded (randomly distributed MWCNT) samples that was attributed to lower probability of MWCNTs contacting each other due to MWCNT alignment. The compression molded samples showed higher electrical conductivity and lower electrical percolation threshold than the injection molded samples. The compression molded samples at MWCNT concentrations of 5.00 and 20.0wt.% showed real permittivity two times and imaginary permittivity five times greater than the injection molded samples. The EMI SE for the compression molded samples at MWCNT concentrations of 5.00 and 20.0wt.% was 15.0 and 30.0dB, respectively, significantly greater than EMI SE for the injection molded samples. Lower EMI SE for the injection molded samples was ascribed to lower electrical conductivity, real permittivity (polarization loss) and imaginary permittivity (Ohmic loss). Comparison of the EMI shielding properties of the compression molded versus injection molded samples confirmed that EMI shielding does not require filler connectivity; however it increases with filler connectivity. [Copyright &y& Elsevier]

Abstract: The electrical and electromagnetic interference shielding effectiveness (EMI SE) properties of multi-walled carbon nanotubes/polycarbonate (MWCNT/PC) composites are investigated. The composites were prepared by diluting masterbatch (15wt.% MWCNT) using a Haake mixer and then injection-molded into a dog-bone mold. Various MWCNT alignments were created by changing operating conditions. Electrical resistivity measurements were carried out at three different areas at both parallel and perpendicular to the flow direction. The results showed higher resistivity and percolation threshold at higher alignments in both parallel and perpendicular to the flow direction. By applying Ohm’s law it was seen that after percolation, the field emission mechanisms are more important at higher orientations. Higher MWCNT alignments were observed in areas with higher resistivities, and this was verified using SEM, TEM and Raman spectroscopy techniques. Additionally, EMI SE measurements were done on compression-molded samples at different concentrations and thicknesses. The results showed that both EMI SE by reflection and absorption increased with increase in MWCNT loading and shielding material thickness. [Copyright &y& Elsevier]