High Structure Carbon Black Research Articles

Synergistic effect by high specific surface area carbon black as secondary filler in silica reinforced natural rubber tire tread compounds

The partial replacement of silica by high specific surface area and high structure Carbon Black (CB) N134 as secondary filler, keeping the same total filler content at 55 phr, shows a clear synergistic effect on overall performance. At low content of CB, i.e. in the range of 0–36 wt% of CB relative to total filler amount, the Payne effect and tan delta at both 0 °C and 60 °C change marginally, but thereafter gradually increase. Cure times are shortened in the presence of CB, facilitating an increase of productivity. Bound rubber content and mechanical properties show an optimum at 18 wt% of CB relative to total filler amount or at a ratio of silica/CB 45/10 phr. With regard to tire performance as indicated by the laboratory test results, the abrasion resistance, wet grip and ice traction can therefore be enhanced while maintaining the tire rolling resistance at the optimum level for this silica/CB ratio.

Effect of Hybrid Carbon Fillers on the Electrical and Morphological Properties of Polystyrene Nanocomposites in Microinjection Molding

The effect of hybrid carbon fillers of multi-walled carbon nanotubes (CNT) and carbon black (CB) on the electrical and morphological properties of polystyrene (PS) nanocomposites were systematically investigated in microinjection molding (μIM). The polymer nanocomposites with three different filler concentrations (i.e., 3, 5 and 10 wt %) at various weight ratios of CNT/CB (100/0, 30/70, 50/50, 70/30, 0/100) were prepared by melt blending, then followed by μIM under a defined set of processing conditions. A rectangular mold insert which has three consecutive zones with decreasing thickness along the flow direction was adopted to study abrupt changes in mold geometry on the properties of resultant microparts. The distribution of carbon fillers within microparts was observed by scanning electron microscopy, which was correlated with electrical conductivity measurements. Results indicated that there is a flow-induced orientation of incorporated carbon fillers and this orientation increased with increasing shearing effect along the flow direction. High structure CB is found to be more effective than CNT in terms of enhancing the electrical conductivity, which was attributed to the good dispersion of CB in PS and their ability to form conductive networks via self-assembly. Morphology observations indicated that there is a shear-induced depletion of CB particles in the shear layer, which is due to the marked difference of shear rates between the shear and core layers of the molded microparts. Moreover, an annealing treatment is beneficial to enhance the electrical conductivity of CNT-containing microparts.

A study of electric field-induced conductive aligned network formation in high structure carbon black/silicone oil fluids

An electric field-induced alignment characteristics of high structure carbon black (HSCB) nanoparticles in silicone oil base fluids with different viscosities were investigated in this work. Resistivity change versus time of HSCB/silicone oil fluids with different concentrations of HSCB filler and different silicone oil viscosities was determined at different electric field strengths. Measurement results were analyzed using percolation theory by calculating critical concentration at which rapid increase of conductivity appears. An analytic model based on tunneling percolation theory was developed and successfully applied to explain the experimental results. The obtained results potentially can be used in the development of polymer composites with aligned nanoparticle structure.

New understanding for the formation of conductive network in the nanocomposites during the crystallization of matrix

Crystallization behavior of conductive composite has a great effect on the formation of conductive network. But very few studies have exposited, specially on the micro level, the evolution of conductive network during the crystallization of matrix. In this study, the conductive network was found to be destroyed by crystallization behavior of isotactic polypropylene (iPP) matrix, and the carbon black (CB) particles were rejected to the amorphous region or the inter-lamellar of spherulite. By comparison, the low-structure carbon black (LCB) filled system was more sensitive to the crystallization of matrix than the high-structure carbon black (HCB) filled system because of the morphology and interaction force of the CB primary aggregate. A secondary increase in volume resistivity during terminal crystallization was observed in iPP/LCB composite when it isothermally crystallized at a certain temperature. In that case, an analysis of crystallization kinetics of composites through a modified Lauritzen-Hoffman model indicated that the transition from regime I→II in the isothermal crystallization process of iPP matrix showed significant influence on the network formation of LCB particles.

Reinforcing mechanisms of carbon nanotubes and high structure carbon black in natural rubber/styrene-butadiene rubber blend prepared by mechanical mixing − effect of bound rubber

The reinforcing effect of high structure carbon black (HSCB) and multi-walled carbon nanotubes (MWCNTs) on natural rubber/styrene-butadiene rubber blend processed using mechanical mixing was comparatively investigated. In-depth analysis by dynamic mechanical analysis, the Eggers − Schummer model and Medalia's relationship showed that HSCB aggregates provided large internal pores leading to significant immobilized macromolecules in filled rubber. Additionally, a tubular immobilized rubber layer with a thickness of 8 nm was estimated for the rubber/MWCNT system based on dynamic mechanical analysis data. The mechanical performance of the HSCB filled blend was higher than that of the MWCNT filled blend at the same loading which was correlated to its higher bound rubber content. Both bound rubber content and filler anisotropy were found to govern the overall mechanical properties of rubber/MWCNT composites. Stress softening was correlated with rupture energy suggesting hysteretic failure mechanisms in both MWCNT and HSCB filled rubbers. © 2015 Society of Chemical Industry

Research on Properties of CB/EVA Semiconductive Shielding Composites

In order to select suitable carbon black (CB) for manufacturing semiconductive shielding materials of XLPE insulated high voltage cable, the composites were prepared with the melt blending method by adding CB with different properties into ethylene/vinyl acetate copolymer (EVA). The volume resistivity, mechanical property and rheological property of the composites were measured. The effects of the properties and content of CB on the various properties of the composites were investigated and their mechanism was analyzed. The research results show that both structure and specific surface area of CB have great effects on the volume resistivity and rheological property of the composites. Because high structure CB usually has high specific surface area, the high structure CB/EVA composites have low percolation threshold and low rheological property. The EVA composites containing low structure CB with larger specific surface area exhibit low conductivity and high melt viscosity. When the mass fraction of CB with low structure and small specific surface area reaches 35%, the volume resistivity of the composites is approximately 100 Ω·cm and the rheological property of the composites is obviously superior to the composites filled with high structure CB. The CB with small specific surface area and low structure as conductive filler is beneficial for good conductivity and extrusion processability of the semiconductive shielding materials.

EMI shielding effectiveness of carbon based nanostructured polymeric materials: A comparative study

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.

X-band EMI shielding mechanisms and shielding effectiveness of high structure carbon black/polypropylene composites

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.

STUDY ON NANOMORPHOLOGY OF HIGH-STRUCTURE CARBON BLACK AND ITS BOUND RUBBER BY AFM

Bound rubber in carbon black (CB) filled rubber (natural rubber (NR) and styrene–butadiene rubber (SBS)) was prepared by the solvent method. The nanomorphology of CB and rubber/CB soluble rubber was observed by atomic force microscope. The results show that high-structure CB DZ13 has a "grape cluster" structure which consists of many original particles with the grain size of about 30–50 nm. Graphitizing process of CB decreases the amount of bound rubber. The NR/DZ13 soluble rubber with island–rim structure has been obtained, where the islands are DZ13 particles and the rims around the islands are occupied by NR film. But when the graphitized DZ13 particles were used as fillers of rubber, we have only observed that some graphitized DZ13 particles were deposited on the surface of the globular-like NR molecular chains, instead of the spreading of NR molecular chains along the surface of DZ13 particles, indicating that graphitized DZ13 has lower chemical activity than ungraphitized DZ13. Especially, we have already observed an interesting unusual bound rubber phenomenon, the blocked "bracelet" structure with the diameter of about 600 nm in which CB particles were blocked in ring-shaped SBS monomer.

Development of percolative electroconductive structure in piezoresistive polyisoprene–nanostructured carbon composite during vulcanization

In this work attention has been paid to polyisoprene–nanostructured carbon composites (PNCC) as prospective piezoresistive materials for use in pressure sensing applications as well as tactile elements for robotics. Our recent research approved that vulcanization process has an important role in the chain of processes when producing composite with necessary mechano-electric properties.In the current article we present an original attempt to investigate the development of the percolative electroconductive structure of PNCC during vulcanization. The “in-situ” measurements of electrical resistivity have been performed to evaluate the development of the percolative carbon black structure in PNCC directly during the vulcanization process. The measurements of the piezoresistive effect for samples with different durations of vulcanization time have been made. The samples have been studied using SEM and dielectric spectroscopy. To perform SEM analysis the samples were frozen in liquid nitrogen and then fractured. Four different processes that affect the formation of the percolation network of high-structure carbon black (HSCB) in PNCC during vulcanization phase have been identified.

Electromagnetic wave absorbing characteristics of carbon black cement-based composites

Abstract Electrical resistivity, compressive strength, and the electromagnetic absorbing effectiveness of carbon black (CB) cement-based composites (CBCC) with different contents of high-structure CB were studied in this paper. The results indicate that the resistivity of CBCC versus the concentration of CB curves has typical features of percolation phenomena: CBCC in the percolation threshold zone contains 0.36–1.34 vol.% of CB. Thus, the conductive network can be formed in CBCC by using small amount of high-structure CB. Compressive strength of CBCC decreases with CB content increasing. Especially, compressive strength decreases substantially when CB content is more than 3.0 wt.%. CBCC exhibits good performance of absorbing electromagnetic waves in the frequency range of 8–26.5 GHz. For CBCC containing 2.5 wt.% of CB, the minimum reflectivity reaches −20.30 dB. The frequency bandwidth in which the reflectivity is less than −10 dB was from 14.9 GHz to 26.5 GHz. The filling of CB has improved the dielectric constant and the loss factor of the cement material remarkably. The loss factor of CBCC increases with the CB content increasing.

Carbon/polyesterimide thick-film resistive composites – Experimental characterization and theoretical analysis of physicochemical, electrical and stability properties

This paper describes carbon/polyesterimide thick-film resistive composites. Polyesterimide (PEI) resin with high thermal durability served as an insulative matrix whereas medium structure carbon black (MSCB), blend of MSCB and graphite (G), and high structure carbon black (HSCB) have been used as an active phase. Chosen physicochemical investigations, electrical measurements (dependence of sheet resistance, hot temperature coefficient of resistance and 1/ f noise on kind and content of conductive filler and curing temperature) and various stability tests have been used for complete description of MSCB/PEI, (MSCB + G)/PEI and HSCB/PEI thick-film resistor series. Electrical properties have been analyzed based on continuum percolation model completed by Balberg concepts connected with excluded volume and assumption of power distribution of distances between conductive grains embedded in polyesterimide.

The Influence of Matrix Viscosity and Interfacial Properties on the Dispersion Kinetics of Carbon Black Agglomerates

Abstract The dispersion of carbon black agglomerates suspended in polydimethyl siloxane (PDMS) or polybutadiene (PBD) liquids has been studied. Agglomerates comprised of either a low-structure or a high-structure carbon-black were subjected to simple shear flow. Two characteristic length scales that affect the dispersion process are identified. One length scale (Lp) is a measure of the ease with which fluid can flow through the porous agglomerate structure. The second (δ) is a measure of the depth to which processing fluid has soaked into the agglomerate. Values of Lp were found to be independent of types or viscosity of the polymer but were sensitive to the structure and packing density within agglomerates. The parameter δ, which varies with time of immersion in the processing fluid, was found to be smaller at comparable immersion times for matrix fluids with high viscosity. Shearing experiments showed two kinetic regimes (fast and very slow dispersion). For each type of matrix liquid, there exists a critical packing density; agglomerates having a packing density lower than this critical value exhibit only fast erosion, but those with packing density higher than this critical value show dispersion kinetics that starts as fast but shifts to slow after a certain period of shearing. The critical packing density was higher in PBD than in PDMS for agglomerates of the low-structure carbon-black but was not significantly different for agglomerates of the high-structure carbon-black. The critical packing density was found to shift to higher values if higher viscosity PDMS was used. The dispersion kinetic regime for the different polymers liquids could be correlated with the value of δ/Lp. If δ/Lp remained less than a critical ratio, only fast erosion was observed. Measurement of fragment size distributions support the notion that fragments are produced primarily from the periphery of the agglomerate in the slow kinetic regime, but can be larger (up to the size of δ) for the fast kinetic regime.