Relaxation behavior of conductive carbon black reinforced chlorosulfonated polyethylene composites

Dynamic mechanical analysis and dielectric relaxation spectra of conductive carbon black reinforced chlorosulfonated polyethylene (CSM) composites were used to study their relaxation behavior as a function of temperature and frequency, respectively. A marginal increase in glass transition temperature has been observed upto 30 phr carbon black filled polymer composite, beyond which it decreases, which has been explained on the basis of aggregation of filler particles in the polymer matrix. The strain dependent dynamical parameters were evaluated at dynamic strain amplitudes of 0.1–200%. The nonlinearity in storage modulus increases with increase in filler loading. It can be explained on the basis of filler–polymer interaction and aggregation of the filler particulates. The frequency dependent dynamical mechanical analysis has also been studied at frequency range of 0.1–100 Hz. The variation in real and complex part of impedance with frequency has been studied as a function of filler loading. The effect of filler loading on ac conductivity has been observed as a function of frequency. An increase in conductivity value has been observed with increase in filler loading. This can be explained on the basis of formation of conducting paths between filler particulates. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Improvement of polyimide/polysulfone composites filled with conductive carbon black as positive temperature coefficient materials

In this study, polyimide (PI)/polysulfone (PSF) blends filled with carbon black (CB) were developed for the use as positive temperature coefficient (PTC) materials in order to achieve the volume resistivity as lower than 10⁴ Ω.cm at room temperature. The weight ratios of PI/PSF were various from 100/0 to 10/90 with CB varied from 0 to 20 wt%. The use of conductive filler was reduced when PSF was blended with PI; the blends clearly possessed a percolation threshold decreased by 90%. The electrical conductivity of the CB-filled blends was higher than those of CB-filled pure PI. The transition temperature for PTC material was reported in the range of 180 to 210 °C. The preferential location of CB filler in PI domains could be observed using the optical microscope. In addition, the composites met the standards for the obtained mechanical and thermal properties, exhibiting the potential use as PTC materials. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48482.     

Electrical and thermal phenomena in low-density polyethylene/carbon black composites near the percolation threshold

Low-density polyethylene (LDPE)/carbon black (CB) composites were fabricated via melt-compounding technique. The percolation threshold was found to be around 20 wt % CB, and an electrical network formed by conductive CB was proven by scanning electron microscopy investigation. Dielectric responses depicted an interfacial relaxation peak at 20 wt % CB content. LDPE/CB composites showed an electric field-dependent conductivity as and a hysteresis behavior around the percolation threshold region. The CB particles with high thermal conductivity increased the heat conductance of the LDPE/CB20 up to 56%. The dynamic mechanical analysis of the LDPE/CB composites exhibited a noticeable contribution of CB throughout the composites, increasing the storage and loss modulus. The physical interactions between CB particles in the filler network enhanced the thermal degradation of the LDPE/CB25 composite for more than 76°C. The maximum breakdown strength of the LDPE/CB composites appeared with an approximately 10% improvement for LDPE/CB5 than pure LDPE. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47043.     

Effect of different carbon fillers on the properties of PP composites: Comparison of carbon black with multiwalled carbon nanotubes

Polypropylene (PP)/carbon composites were prepared via melt blending PP with carbon fillers, including multiwalled carbon nanotubes (MWNTs) and carbon black (CB). Field‐emission scanning electron microscopy was used to research the morphology and dispersion of fillers in the PP matrix. The electrical properties, mechanical properties, and crystallization behaviors of PP/carbon composites were also investigated. The results show that the influence of MWNTs on the properties of PP composites is different with CB, which can be ascribed to the structure and aspect ratio difference between MWNTs and CB. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:4823–4830, 2006     

Design of sandwich structure conductive polypropylene/styrene-butadiene-styrene triblock copolymer/carbon black composites with inherent morphological tunability

The insulator-conductor transition of conductive polymer composites (CPCs) can be ascribed to the fabrication of conductive networks, and the morphology of conductive networks plays a significant role in the electrical conductivity. This study presents CPCs with inherent morphology tunability which can be controlled by kinetic methods (i.e., mixing procedures and sequences, and polymer melt viscosity). Polypropylene (PP)/styrene-butadiene-styrene block copolymer (SBS) (50/50, in volume)/10 phr (parts per hundred of the polymer matrix) conductive carbon black (CB) composites prepared by different compounding sequences (PP/CB composites mixed with SBS, SBS/CB composites mixed with PP, and PP/SBS blend mixed with CB) are named as PC₁₀S, SC₁₀P, and PSC₁₀. With the difference between the phase morphologies, distribution, and dispersion of CB, the PP/SBS/CB composites realize seven orders of magnitude difference in resistivity. The volume resistivity (ρ_v) of PC₁₀S SC₁₀P and PSC₁₀ are 1.57 × 10¹, 1.68 × 10², and 4.88 × 10⁸ Ω m, respectively.     

Effect of a carbon black surface treatment on the microwave properties of poly(ethylene terephthalate)/carbon black composites

A surface treatment was applied to carbon black to improve the electrical and microwave properties of poly(ethylene terephthalate) (PET)-based composites. Three different formamide solutions with 1, 2, and 3 wt % concentrations were prepared to modify the surface chemistry of carbon black. Microwave properties such as the absorption loss, return loss, insertion loss, and dielectric constant were measured in the frequency range of 8–12 GHz (X-band range). Composites containing formamide-treated carbon black exhibited enhancements in the electrical conductivity, electromagnetic interference (EMI) shielding effectiveness, and dielectric constant values when compared to composites with untreated carbon black. In addition, increases in the formamide solution concentration and carbon black content of composites resulted in an increase in the electrical conductivity, EMI shielding effectiveness, and dielectric constant values. The percolation threshold concentration of PET composites shifted from a 3 to 1.5 wt % carbon black composition with the surface treatment. The best EMI shielding effectiveness was around 27 dB, which was obtained with the composite containing 8 wt % carbon black treated with a 3 wt % formamide solution. Moreover, this composition gave the lowest electrical resistivity and the highest dielectric constant among the produced composites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Development of HDPE/EPDM‐g‐TMEVS nanocomposites with enhanced electrical and flame properties

Nanoclay reinforced HDPE/silane grafted EPDM composites have been developed using an epoxy functionalized HDPE as compatibilizer.The nanoclay has been varied from 0% to 10% in the composites along with the incorporation of compatibilizer and without compatibilizer in a brabender plasticorder.The dielectric and fire retardant properties of these nanocomposites have been examined. Addition of nanoclay enhanced char formation with increased values of limiting oxygen index. Electrical properties such as volume and surface Resistivity improved with addition of nanoclay and compatibilizer. The values of tan δ increased with increase in grafted EPDM and silanated nanoclay loading. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Structural variations and morphological features of polyethylene/carbon black conductive composites after processing in an internal mixer

Polyethylene (PE) composites filled with carbon black (CB) were prepared using an internal mixer. Several analytical techniques, including rheometry, gel permeation chromatography, electrical conductivity measurements, differential scanning calorimetry, wide‐angle X‐ray diffraction, and transmission electron microscopy (TEM), were used to reveal the structural variations, thermal degradation, morphological features, and crystallization of the PE/CB conductive composites. It was found that the PE polymer chains were degraded, forming long‐chain branching structures after over 30 min of internal mixing. The electrical conduction of the PE/CB composites was determined by the filler content and distribution. The electrical percolation threshold of the PE/CB composites was determined to be between 20 and 30 wt %. The addition of CB had no significant influence on the crystallinity of the PE/CB composites. In contrast, the electron‐beam radiation dose had a significant effect on crystallinity. TEM micrographs of the PE/CB composites exhibit a random four‐phase morphology, including PE lamellae, PE amorphous, CB particles, and voids at the PE/CB interface. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1038‐1046, 2013     

Effect of carbon black on the mechanical and dielectric properties of rubber ferrite composites containing barium ferrite

Fine particles of barium ferrite (BaFe₁₂O₁₉) were synthesized by the conventional ceramic technique. These materials were then characterized by the X‐ray diffraction method and incorporated in the natural rubber matrix according to a specific receipe for various loadings of ferrite. The rubber ferrite composites (RFC) thus obtained have several applications, and have the advantage of molding into complex shapes. For applications such as microwave absorbers, these composites should have an appropriate dielectric strength with the required mechanical and magnetic properties. The N330 (HAF) carbon black has been added to these RFCs for various loadings to modify the dielectric and mechanical properties. In this article we report the effect of carbon black on the mechanical and dielectric properties of these RFCs. Both the mechanical and dielectric properties can be enhanced by the addition of an appropriate amount of carbon black. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 769–778, 2003     

Developing electrically conductive polypropylene/polyamide6/carbon black composites with microfibrillar morphology

We have established that the PP/PA6/CB composite with 3D microfibrillar conducting network can be prepared in situ using melt spinning process. CB particles preferably were localized at the interface between polypropylene as the matrix and PA6 microfibrils, which act as the conducting paths inside the matrix. The percolation threshold of the system reduced when aspect ratio of the conducting phase was increased by developing microfibrillar morphology. The effect of annealing process on the conductivity of PP/PA6/CB composite with co‐ continuous and microfibrillar morphologies was studied. It was observed that, annealing process forces CB particles towards the interface (2D space) of PP and PA6 co‐continuous phases, and percolation threshold and critical exponent of classical percolation theory will be decreased, while the conductivity of conducting composite with microfibrillar morphology was not affected considerably by annealing process at temperatures either higher or lower than the melting point of the PA6 microfibrils. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Supercritical carbon dioxide assisted preparation of conductive polypyrrole/cellulose diacetate composites

Supercritical carbon dioxide (SC‐CO₂) has been used to assist the preparation of conductive polypyrrole/cellulose diacetate (PPy/CDa) composites by in situ chemical oxidative polymerization. The morphology and conductivity of resulted composites were investigated with scanning electron microscopy and four‐probe method, respectively. With the assistance of strong swelling effect of SC‐CO₂, composite films were obtained with a macroscopically homogeneous structure and conductivity up to 10^?1 S cm^?1 order of magnitude. Increasing the pressure of SC‐CO₂ increased conductivity, while increasing the temperature decreased conductivity. For comparison, PPy/CDa composite was also prepared with conventional oxidative method in aqueous solution. From the viewpoint of conductivity and environmental protection, the SC‐CO₂ method showed its superiority over the conventional one. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4575–4580, 2006     

In situ melt grafting in carbon black/polyolefin composites and its influence on conductive performance

To improve the conductive properties of carbon‐black‐filled low‐density polyethylene, in situ grafting of certain monomers was applied during the melt compounding process. The experimental data obtained demonstrated that chemical bonding could thus be established between the fillers and the matrix polymer. The degree of enhancement of the filler/matrix interfacial interactions in the composites prepared in this way depends on the species of the grafting monomers being employed. When compared with the untreated carbon black composites, the composites manufactured through in situ melt grafting exhibited reduced room temperature resistivities and greatly increased positive temperature coefficient intensities, as well as favorable performance reproducibility. This proposed technical route has several advantages, including simplicity, low cost and easy control. Copyright © 2004 Society of Chemical Industry     

Effects of thermal ageing treatment and antioxidants on the positive temperature coefficient characteristics of carbon black/polyethylene conductive composites

Polyethylene (PE)‐filled with carbon black (CB) is a prototypical composite that displays resistance switching. These materials can exhibit either a positive temperature coefficient (PTC) or negative temperature coefficient (NTC). The CB‐filled semicrystalline polymer composites ideally need antioxidants, which stabilize the composites against thermooxidative degradation, because they should be resistant to the severe conditions of high temperature. The characterization of PTC materials is affected by the crystallinity of the polymer, and the crystallinity of the polymer is changed with thermal ageing treatment. Thermal ageing of PTC samples was conducted in an oven in the range 50–140°C, in air. The composites, containing 0.5–3% (by weight) Irganox 1076 (Ciba‐Geigy), were irradiated under nitrogen at room temperature with different doses of gamma rays from a ⁶⁰Co source. The resulting composites were analyzed by differential scanning calorimetry, gel fractionation, X‐ray diffraction, and dynamic mechanical analysis. The conductivity of the composites depended on the amounts of antioxidants and the duration of the thermal ageing treatment. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2316–2322, 2003     

Dielectric and microwave properties of carbon nanotubes/carbon black filled natural rubber composites

Abstract

Natural rubber (NR) based nanocomposites containing a constant amount (50 phr) of standard furnace carbon black and carbon nanotube (CNT) at a concentration from 1 to 5 phr have been prepared. Their dielectric (dielectric permittivity and dielectric loss) and microwave properties (coefficients of absorption and reflection of the electromagnetic waves and electromagnetic interference shielding effectiveness) have been investigated in the 1–12 GHz frequency range. The results achieved allow recommending CNTs as second filler for NR based composites to afford specific absorbing properties.     

Electrical properties and morphology of polypropylene/epoxy/glass fiber composites filled with carbon black

The volume resistivity and percolation thresholds of carbon black (CB) filled polypropylene (PP), PP/epoxy, and PP/epoxy/glass fiber (GF) composites were measured. The morphology of these conductive polymer composites was studied with scanning electron microscopy (SEM). The effects of the GF and epoxy contents on the volume resistivity were also investigated. The PP/epoxy/GF/CB composite exhibited a reduced percolation threshold, in comparison with that of the PP/CB and PP/epoxy/CB composites. At a given CB content, the PP/epoxy/GF/CB composite had a lower volume resistivity than the PP/CB and PP/epoxy/CB composites. SEM micrographs showed that CB aggregates formed chainlike structures and dispersed homogeneously within the PP matrix. The addition of the epoxy resin to PP resulted in the preferential location of CB in epoxy, whereas in the PP/epoxy/GF multiphase blends, because of the good affinity of CB to epoxy and of epoxy to GF, CB particles were located in the epoxy phase coated on GF. The decreased percolation threshold and volume resistivity indicated that conductive paths existed in the PP/epoxy/GF/CB composite. The conductive paths were probably formed through the interconnection of GF. Appropriate amounts of GF and epoxy should be used to decrease the volume resistivity and provide sufficient epoxy coating. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1142–1149, 2005     

Study on PET/PP microfibrillar composites. I. Morphological development in melt extrusion

Poly(ethylene terephthalate)/polypropylene (PET/PP) blends of different compositions were extruded through a 2‐mm capillary die using a corotating twin‐screw extruder. The extrudates were cryogenically fractured and examined using scanning electron microscopy. The viscosity ratio of the constituent polymers alone was found not suitable for explaining the polymer blend morphology. At a PET concentration of 20%, the extrudate consists of three regions: The skin layer, about 10 μm thick, has a lower concentration of the dispersed PET phase than that of the overall concentration. The intermediate region, about 400 μm thick, has profuse PET fibers and some small PET particles. The central region, approximately 800 μm in diameter, contains mainly PET particles that are generally bigger. A low barrel temperature, low die temperature, and fast cooling rate helped to retain the fibers near the extrudate skin. Meanwhile, variation of the barrel temperature, die temperature, and cooling media did not affect the PET particle‐size distribution significantly in the central region of the extrudate. A high screw speed and a high postextrusion drawing speed were very effective in producing fibers in the extrudates through elongation of the particles. At a PET concentration of 30%, coalescence of the PET phase was prevalent, leading to the formation of PET platelets near the extrudate skin and irregular PET networks in the central region of the extrudate. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 3100–3109, 2003     

Effect of nanosized carbon black on the morphology,transport, and mechanical properties of rubbery epoxy and silicone composites

Three different types of nanosized carbon black (CB), Printex XE2 (CBP), Vulcan XC72, and Printex 140 U (CBU), were dispersed by mechanical mixing in rubbery epoxy (RE) and silicone to produce composites. It was found that the maximum possible loading of CB in the polymers depended on the surface area of CB. For a given loading, all three CBs produced similar improvements in the thermal conductivity of the resulting composites, but their effects on the electrical conductivity varied and ranged from insulating composites with CBU to conducting composites with CBP. CBP produced a greater improvement in the electrical conductivity than the thermal conductivity of the polymers compared to the other CBs. This was attributed to the high structure of CBP, which led to the formation of a concatenated structure within the matrix. The CB/silicone composites had a similar thermal conductivity to that of the CB/RE composites, but only the CBP/silicone composite produced at 8 wt % loading was electrically conducting. The compression and hardness properties of RE were also significantly improved with the addition of CB. However, in the case of silicone, only CBP had a considerable effect on the compression properties. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Enhanced dielectric properties of polyamide 11/multi‐walled carbon nanotubes composites

Composites with multi‐walled carbon nanotubes (MWNTs) involved in polyamide 11 (PA11) were prepared via a conventional melt blending method. The structure, morphology, crystallization behavior, electrical, and dielectric properties of composites were investigated. The results demonstrated that the dispersed uniformly MWNTs favored the formation of α crystal of PA11 when the composites were quenched from melt. The dielectric constant of composites was dependent on the electric field frequency and MWNTs content, and the highest value of dielectric constant was as high as 350 for the composite with 1.21 vol % MWNTs at 10³ Hz, accompanied by a low dielectric loss. The enhanced dielectric properties could be interpreted by the formation of abundant nanocapacitors within the composites and the interfacial polarization effect resulting from accumulation of charge carriers at the internal interfaces between MWNTs and PA11. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42642.     

Morphology,thermal expansion,and electrical conductivity of multiwalled carbon nanotube/epoxy composites

Multiwalled carbon nanotube/epoxy composites loaded with up to 0.5 wt % multiwalled carbon nanotubes were prepared and characterized. Infrared microscopy, scanning electron microscopy, thermogravimetry, differential scanning calorimetry, thermomechanical analysis, and electrical conductivity measurements of the composites were performed. Infrared microscopy and scanning electron microscopy images showed that the debundled nanotubes were well dispersed. The thermal expansion coefficients, before and after the glass transition, remained approximately constant with the addition of nanotubes, whereas the electrical conductivity at room temperature increased approximately 5 orders of magnitude. This result was attributed to the thermal expansion coefficients of the intertube gap on the carbon nanotube bundles, which were in the same range as that of the epoxy resin. Therefore, nanocomposites capable of electrostatic dissipation can be processed as neat epoxy materials with respect to the volume changes with temperature. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008