Conductive Carbon Black Research Articles

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

Electrical and Mechanical Properties of Conductive Carbon Black Filled Epoxidized Natural Rubber

Electrical and mechanical properties of epoxidized natural rubber (ENR-25) filled with conductive carbon black (CCB) have been investigated. SEM was used to analyze dispersion of CCB particles in rubber matrix. The results indicated that the AC conductivity increase with increasing volume fraction of carbon black as well as frequency. The percolation thresholds of the electrical conductivity was found at 0.10 volume fraction of CCB. Furthermore, addition of CCB at volume fraction 0.05 caused the highest tensile strength of the composites. The tensile strength and elongation at break were decreased with increasing content of CCB greater than 0.05 volume fraction. However, the volume fraction of CCB at 0.10 demonstrated the most suitable proportion for the ENR composites with superior electrical and mechanical properties.

Electrically conductive CB/PA6/HDPE composite with a CB particles coated electrospun PA6 fibrous network

Electrically conductive carbon black (CB)/polyamide 6 (PA6)/high density polyethylene (HDPE) composite with a low percolation threshold was fabricated by embedding conductive CB/PA6 membrane into the HDPE matrix. The CB/PA6 membrane was prepared by localizing CB particles on the surfaces of the electrospun PA6 fibrous membrane by a dip-coating method. Percolation threshold of this CB/PA6/HDPE composite was only ca. 4.3vol%, showing a considerable reduction compared to that of the common CB/HDPE (8.5vol%). Through the present method, a conductive polymer composite with enhanced processability and lowered cost has been achieved with extremely low loading of PA6 (1.5vol%).

Tuning of liquid sensing performance of conductive carbon black (CB)/polypropylene (PP) composite utilizing a segregated structure

Carbon black (CB)/polypropylene (PP) with a novel segregated structure was fabricated. For this composite, CB particles were selectively distributed on the interfaces between PP polyhedrons, leading to a lower percolation threshold (2.34vol%). Liquid sensing behaviors of the composite were studied. Nice selectivity, high response rate and high response intensity have been achieved. The designed interfaces, which accelerate the penetration of solvents under the action of the capillary effect, are responsible for the nice performances. A fine reproducibility has also been obtained. This study offers an approach for manufacturing high performance liquid sensor by tailoring the microstructure of a composite.

Correlation between rheological and dielectric percolation of conductive carbon black-filled ethylene acrylic elastomer

Conductive rubber composites based on ethylene acrylic elastomer (AEM) and conductive carbon black (CCB) were prepared by a two-roll mixing mill. From the transmission electron microscope photomicrographs, the uniform distribution of CCB aggregates and the interconnected CCB aggregates in the AEM matrix were observed. The bound rubber content of unvulcanized rubber was found to increase significantly with increasing CCB content. The effect of CCB concentration on the dynamic viscoelastic properties of AEM matrix was determined using a Rubber Process Analyzer (RPA 2000) in terms of strain sweep and frequency sweep of both uncured and cured AEM/CCB systems. The storage modulus ( G′) increased with an increase in CCB loading. In the case of strain sweep, the G′ values decreased with strain amplitude for both the systems, but the G′ was more for cross-linked AEM/CCB systems. The strain dependency of G′ for CCB-filled AEM systems can be explained on the basis of the Payne effect. The complex viscosity ( η*) of these systems increased with CCB loading, and it decreased with strain amplitude, which is due to the shear thinning effect. The tan δ for unvulcanized and vulcanized systems increased with the strain; however, the value of tan δ was <1 throughout the experimental strain range, which explains the elastic nature of the cured systems. The G′ increased with angular frequency for both the systems and the tan δ became independent upon the angular frequency after 10 Hz. The alternating current conductivity ( σAC) increased with an increase in CCB loading at all frequencies and the system achieves the percolation at 20 phr CCB loading, which is in accordance with the rheological percolation. The direct current conductivity (σDC) also increased with an increase in CCB concentration.

The Synthesis of Different Forms of Electrically Conductive Carbon Black by the Thermo-Oxidative Pyrolysis of Hydrocarbons. Phenomenological and Mathematical Models of the Synthesis Process

The Synthesis of Different Forms of Electrically Conductive Carbon Black by the Thermo-Oxidative Pyrolysis of Hydrocarbons. Phenomenological and Mathematical Models of the Synthesis Process

Influence of matrices chemical nature on the dynamic mechanical and dielectric properties of rubber composites comprising conductive carbon black

The study presents the effect that elastomeric matrices different in their chemical nature (a non-polar and crystallizing natural rubber and a polar and non-crystallizing acrylonitrile-butadiene rubber) have upon the dynamic mechanical and dielectric properties of the composites comprising different amounts of conductive carbon black. Dynamic mechanical thermal analysis (DMTA) and Dielectric thermal analysis (DETA) are the techniques used for studying the structure-properties relationships of the composites. The experimental results show that the matrices studied and their specific properties have a great impact upon both the dynamic mechanical and dielectric parameters of the composites based on them. The chemical nature, structure and specific characteristics of the matrix affect the storage modulus, glass transition temperature, elasticity behavior, high-elasticity, energy dispersion, dielectric permittivity and DETA tan δ of the composites investigated. The matrix effect dominates at lower filler amounts and determines the properties of the composites.

Characterization of deformation induced changes to conductivity in an electrically triggered shape memory polymer

Transforming a shape memory polymer (SMP) based part into a new configuration is typically achieved by increasing the temperature of the material to just above the glass transition temperature (Tg). This paper describes the preparation and testing of an electrically conductive SMP based composite which can be heated beyond Tg through the passage of an electric current at low power levels and with good temperature-time response characteristics. Conductivity was achieved by impregnating the resin with conductive carbon black (CB) using two dispersion techniques. Samples were subjected to tensile deformation tests to assess the effects of strain on the carbon black based conductive networks within the matrix. A series of these tests were performed on each sample to further assess recovery behavior from repeated loading cycles and any ensuing effect on electrical properties. The SMP showed similar strain recovery in repeated loading cycles. The electrical nature of the filled materials, as measured by the resistivity, was found to change, registering an increase and/or decrease, in response to the magnitude of the strain. Three distinct regions could be identified in the resistivity versus strain plots which are explained vis-à-vis filler chain interaction and rearrangement. The data endorses the technique of using electrical actuation as a means of triggering SMPs which can then be an enabling technology in myriad applications in the aerospace, automotive and biomedical fields. Furthermore, the resistivity change data can be used in the design process to predict the response of components manufactured using reconfigurable composites.

Study and modeling of an electrostrictive polyurethane diaphragm loaded with conductive carbon black

Electroactive polymers (EAPs) have been shown to have great potentials as actuators in micro-systems due to their light weight, low cost and large electrical field-induced strains. In this article, a diaphragm type actuator comprising an electrostrictive carbon black (CB) loaded polyurethane (Pu) membrane is described. First, equations are derived for such a system, taking into account its resonant nature. Then, equations for a diaphragm actuator in plate-like and membrane like behavior are written. A resonance frequencies study has been done in order to confirm the membrane-like behavior of the proposed system. Thus, a large deflection model was applied and showed good fitting between experimental and calculated data. To completely model the system, electrodes clamping effect term and a quality factor term are added. The effect of CB loading on the deflection is thoroughly discussed. It was found that a CB concentration of 1.25wt% gave a deflection at the center of a 50μm-thick diaphragm of 12μm under a 9V/μm electric field at 700Hz whereas a 50μm pure Pu membrane gave a deflection of 3μm at the same electric field. An increase of 4-fold is therefore achieved, allowing significant enhancement in using such devices in MEMS systems.

Improved stability of volume resistivity in carbon black/ethylene-vinyl acetate copolymer composites by employing multi-walled carbon nanotubes as second filler

Semiconductive polymer shielding layers of power cable require stable volume resistivity to protect the insulation layer from stress enhancements when carbon black (CB)/polymer composite undergoes thermal cycles. For the CB-filled polymer composites, CB would often re-aggregate when temperature is close to the melting point of polymer matrix, so that the conductive network would be destroyed. Re-distribution of CB and re-formation of conductive CB network under thermal cycles might be the main reason for the instability of volume resistivity. In this work, the re-aggregation of CB in the CB/polymer composites was disclosed. Besides, a small amount of multi-walled carbon nanotubes (MWNTs) was employed as cofiller with CB to improve the stability of volume resistivity of the polymer composites under thermal cycles. The total weight fraction of conductive fillers (CB or CB cofilled with MWNTs) was set as 35 wt%. Compared with the polymer composites loaded with CB solely, the volume resistivity of the composites filled with CB-MWNTs was much more stable with changing temperature. This can be attributed to the enhancement of conductive networks when the MWNTs are employed as second conductive filler.

Study of dielectric relaxation behavior of electron beam-cured conductive carbon black-filled ethylene acrylic elastomer

Composites based on ethylene acrylic elastomer (AEM) filled with a special type of conductive carbon black (CCB) have been prepared by two-roll mixing mill. The compression-molded sheet of the prepared composites have been subjected to electron beam (EB) radiation dose up to 400 kGy to induce radiation crosslinked composites. The crosslinked density has been calculated according to Flory–Rehner equation and is found to increase with increasing EB dose and CCB loading. Chain scission-to-crosslink density has been calculated by Charlesby–Pinner equation, which shows decreasing trend with increasing radiation dose. The dielectric relaxation behaviors of different doses of EB-treated AEM/CCB composites have been extensively studied as a function of frequency of applied electric field (101–106 Hz), CCB loading [0–30 phr (parts per hundred)], temperature (25–120 °C), and EB dose (50–400 kGy). It is observed that the dielectric permittivity (e′) increases with CCB loading and temperature, but decreases with increasing EB dose. This can be explained on the basis of interfacial polarization. Based on dielectric loss tangent (tan δ) values, it is observed that the dielectric relaxation time decreases with increases in the filler loading and temperature. However, it increases with increase in the radiation doses. Both the real and imaginary parts of the impedance (Z′ and Z″) have been found to decrease with increase in conductive filler loading. The AC conductivity (σac) increases with increase in the CCB concentration, test temperature, and radiation doses, which is attributed to the more pronounced hopping and tunneling mechanism. The percolation threshold (φcrit) occurred in the range of 16 phr CCB loading. The dispersions of CCB phase in AEM matrix below and above percolation have been captured by the transmission electron microscope photomicrographs.

A Study on the Effective Permittivity of Carbon/PI Honeycomb Composites for Radar Absorbing Design

Radar absorbing honeycomb composites with different coating thicknesses are prepared by impregnation of aramid paper frame with solutions containing conductive carbon blacks (non-magnetic) and PI (polyimide). Expressions for the effective permittivity of the composites are studied and validated both in theory and experiment. It is found that a theoretical equivalent panel with given permittivity can be obtained to represent the honeycomb structure in the quasistatic approximation, which provides a feasible way to optimize the design of radar absorbing honeycomb structure by connecting the effective electromagnetic parameters with the unit cell dimensions. The effective permittivity is measured by a network analyzer system in the frequency range of 8-12 GHz and compared with the theoretical result.

Electronic conduction and microstructure in polymer composites filled with carbonaceous particles

Physical and physico-chemical properties of polymer filled with carbon black (CB) particles, namely, the microstructure dependence of these properties, are not only interesting on their own but are particularly important for electronic applications as they can impose limits on the sensitivity of a device. With this purpose, we report on an experimental study of the structural and electrical properties of semi-crystalline ethylene-co-butyl acrylate polymer filled with conductive CB nano-particles. We found that the value of the direct current conductivity exhibits a jump of 12 orders of magnitude over a small change in CB concentration and is due to a percolation-like behavior. To assess the temperature evolution of supercolative samples, we present measurements of the conductivity as function of temperature. Above the glass transition temperature of the polymer, the CB network restricts the motions of the polymer chains. This behavior was ascribed to the change in CB mesostructure in the polymer matrix as probed by scanning electron microscopy and atomic force microscopy as well as to the difference in the thermal expansion between the two phases. In addition to the observed conductivity increase, the effect of adding CB particles in the polymer matrix is to increase the thermal stability as is probed by thermogravimetric analysis tests. The room temperature alternating current conductivity, studied over the frequency range from 100 Hz to 15 MHz, is interpreted as arising mainly from inter-aggregate polarization effects. By considering carefully the CB content of the alternating current conductivity, we found that our experimental data agree well with the Sheng’s model of fluctuation-induced tunnelling of charge carriers over nanometric gaps between adjacent CB aggregates. For studying the filler content dependence of the effective permittivity, several mixing laws and effective medium theories have been used. The observed discrepancies between our experimental data and these theoretical predictions may be occur partly because these analysis contain an inaccurate knowledge of the physicochemical properties of the carbonaceous phase, give a poor description of the interfaces in these complex heterostructures, or both. As part of the present investigation, present results are compared to transport properties of polystyrene-cobutyl acrylate latex and epoxy resin matrices filled with different loadings of multiwalled carbon nanotubes (MWCNT) and over wide temperature and frequency ranges. It is remarkable that the MWCNT’s anisotropy (length-to-diameter ratio close to 100) manifests itself in percolation-like behavior with lower threshold volume fraction and different mesostructure than that evidenced for CB filled samples.

Investigation of carbon black/silicone elastomer/dimethylsilicone oil composites for flexible strain sensors

Conductive carbon black (CB) nano-particle filled silicone elastomer (SE) composites with dimethyl silicone oil (SO) as a diluting agent and plasticizer were fabricated for potential strain sensing applications. Heat treatment was used to stabilize the composites, and thermal gravimetric analysis confirmed the good stability of the composites after heat treatment. Effect of CB loading on electrical properties of the composites was studied and a percolation transition range of 0.5–2.5 wt% was observed. I–V characteristics and impedance analysis were used to reveal the conductive mechanisms of the composites. The presence of SO reduced the Young's modulus of the composites without lowering the elongation at break. Characterization of coupled electromechanical properties of the composites demonstrates that, in the post-percolation range, the 9.0CB composite possesses suitable strain sensitivity, good repeatability and linearity as well as slight strain rate dependence, so that it can be used in flexible strain sensors for measuring repeated large deformations.

Production of Super Conductive Carbon Black by High-Pressure Steam Activation

Production of Super Conductive Carbon Black by High-Pressure Steam Activation

Three-dimensional nano MnO2/CB composite and its application for electrochemical capacitor

A three-dimensional nanostructure composed of birnessite MnO2 and carbon black (CB) was built via a quite simple co-precipitation method at room temperature. The natural porous construction of conductive CB granules provided enough sites for MnO2 deposition. The as-prepared composite showed that dispersive MnO2 nanowires were directly crystallized on the surface of CB matrix, which was believed to be beneficial to its electrochemical performance. The further investigation of cyclic voltammetry (CV) in 1M Na2SO4 confirmed the inference, which showed good symmetrical rectangular shape, and the specific capacitance was calculated about 186F/g at a scan rate of 2mV/s. After 1000cycles of CV at 10mV/s, the initial capacitance was maintained at about 91%, indicating that the designed structure had benefit to high electrochemical stability.

Electrical, thermal, and rheological properties of carbon black and carbon nanotube dual filler-incorporated poly(dimethylsiloxane) nanocomposites

Conductive nano-sized carbon black (CB) and carbon nanotube (CNT) are widely used in the polymer industry due to their excellent electrical and thermal conduction behavior and reinforcing ability. Herein, poly(dimethylsiloxane) (PDMS) nanocomposites filled with both conductive CB and CNT were fabricated using a planetary mixer and two-roll mill. Due to excellent thermal, electrical, and physical properties of CB and CNT, both the thermal and electrical properties of the composites and the dynamic mechanical properties were improved by the incorporation of CB and CNT into PDMS. The thermal conductivities of the composites linearly increased with filler concentration, and the electrical threshold was determined to be low. The rheological properties of the PDMS/CB and PDMS/CB/CNT nanocomposites were significantly influenced by filler incorporation.

Electromagnetic characteristic and microwave absorbing performance of different carbon-based hydrogenated acrylonitrile–butadiene rubber composites

Hydrogenated acrylonitrile–butadiene rubber (HNBR) was mixed with carbon fiber (CF), conductive carbon black (CCB) and multi-walled carbon nanotubes (MWCNT) to prepare microwave absorbing composites, their complex permittivity was measured in microwave frequencies (2–18GHz), and their electromagnetic characteristics and microwave absorbing performance were studied. The real part and imaginary part of permittivity of the composites increased with increasing carbon filler loading, showing dependency on filler type. The microwave reflection loss of the composites also depended on the loading and type of fillers. The matching thickness of the absorber layer decreased with increasing permittivity, while the matching frequency decreased with increasing layer thickness. The minimum reflection loss was −49.3dB for HNBR/MWCNT (100/10) composite, while −13.1dB for HNBR/CCB (100/15) composite and −7.1dB for HNBR/CF (100/30) composite. The efficient microwave absorption of HNBR/MWCNT composites is accounted from high conduction loss and dielectric relaxation of MWCNT, and strong interface scattering.

Mechanical, Dynamic Mechanical and Electrical Properties of Conductive Carbon Black/Piezoelectric Ceramic/Chlorobutyl Rubber Composites

The composites based on conductive carbon black (CCB) and piezoelectric ceramic particles, PMN, and chlorobutyl rubber (CCB/PMN/IIR) were prepared by compounding and vulcanizing process. Microstructure, mechanical, dynamic mechanical and electrical properties of CCB/PMN/IIR with various CCB and PMN loading were measured by SEM, mechanical tests, and electrical analysis. The results show tensile properties decrease with increasing PMN loading, while showed a maximum value with CCB loading. Tanδmax increased and the glass transition broadened for composites with 50 wt% PMN and 25 wt% CCB. The electric resistance decreased with CCB loading. The piezoelectric damping theory was used to explain the experimental results. The three-phase composites with proper composition can be used as high damping polymer materials.

Conductive carbon black-filled ethylene acrylic elastomer vulcanizates: physico-mechanical, thermal, and electrical properties

The effect of conductive carbon black (CCB) on the physico-mechanical, thermal, and electrical properties have been investigated by various characterization techniques. Physico-mechanical properties of the vulcanizates were studied with variation of filler loading, which revealed that the tensile strength increased up to 20 phr (parts per hundred rubber) CCB loading, whereas at higher filler loading it decreased marginally. Furthermore, tensile modulus, tear strength, and hardness gradually increased with increase in filler loading. The compression set and abrasion loss decreased with increasing CCB loading. The bound rubber content (Bdr) of unvulcanized rubber was found to increase significantly with increasing CCB content. The crosslink density increased, whereas the swelling decreased with CCB loading. The thermal stability of the vulcanizates evaluated by thermogravimetric analysis (TGA) showed a minor increment with increase in CCB content. It is observed from the dynamic mechanical thermal analysis (DMTA) that the storage modulus (E′), loss modulus (E″), and glass transition temperature (T g) of ethylene acrylic elastomer (AEM) matrix increased by incorporation of CCB. The dielectric relaxation characteristics of AEM vulcanizates such as dielectric permittivity (e′), electrical conductivity (σ ac), and electric moduli (M′ and M″) have been studied as a function of frequency (101 to 106 Hz) at different filler loading. The variation of e′ with frequency and filler loading was explained based on the interfacial polarization of the fillers within a heterogeneous system. The e′ increased with increasing the CCB loading and it decreased with applied frequency. The frequency dependency of σ ac was investigated using conduction path theory and percolation threshold limit. The σ ac increased with increase in both CCB concentration and applied frequency. The M′ increased with applied frequency, however, it decreased above 30 phr filler. The M″ peak shifted towards higher frequency region and above 20 phr filler loading the peaks were not observed within the tested frequency region. The electromagnetic interference shielding effectiveness (EMISE) was studied in the X-band frequency region (8–12 GHz), which significantly improved with increase in CCB loading.