Carbon Black Agglomerates Research Articles

Morphology and properties of carbon black‐filled thermoplastic vulcanizate (TPV) composites based on hydrogenated acrylonitrile butadiene rubber and thermoplastic polyester elastomer

AbstractThe unique morphology of thermoplastic vulcanizates (TPVs) reveals a significant correlation between the microstructure and performance, and the development of high‐performance TPV composites for specialized applications has become a current research priority. This study is devoted to developing heat‐ and oil‐resistant TPV composites filled with carbon black (CB) based on hydrogenated acrylonitrile butadiene rubber (HNBR) and thermoplastic polyester elastomer (TPEE) following the masterbatch procedure of dynamic vulcanization. Herein, it focuses on the effects of CB content on the morphology, filler network structure, and properties of the TPV/CB composites. As observed by morphological studies, CB nanoparticles are interconnected and aggregated to form a dual network structure of rubber and CB particles in the composite. With the increasing CB content, it's demonstrated that dual networks have enhanced and shifted to rigid. Consequently, the hardness, thermal stability, and oil resistance of TPV/CB composites are improved, with a 104% elevation in the stress at 300% strain. The flowability in the molten state, toughness (the elongation at break decreased from 690% to 310%), and elasticity deteriorated by oversized (0.5 ~ 1.2 μm) CB agglomerates and rigid rubber particles. This study gives new insight into the microstructure‐properties relationship of TPVs, offering theoretical guidance for fabricating HNBR‐based TPV composites.

OLIVE PITS-BASED CARBON BLACK AGGLOMERATE AS AN ADSORBENT FOR PIPETTE-TIP SOLID-PHASE EXTRACTION FOR THE DETERMINATION OF CAFFEINE IN ENERGY DRINKS

Vegetal wastes are an interesting source for the synthesis of nanostructured carbon materials, which are potentially useful in various applications. Carbon black agglomerates (CBA) obtained from olive pits, synthesized in our previous research, had a low crystalline structure typical of this type of materials, with a pore size of 2.27 nm, confirming their micro/mesoporous structure, and with a high surface value of around 587 m2/g. These materials were used for the extraction of caffeine in energy drinks using a green-approach micro-sample technique called pipette-tip solid-phase extraction. This microextraction technique features reduced consumption of organic solvents, of the amount of sorbent and extraction time, thus making the whole sample pretreatment process faster and greener. In this work, we proposed an analytical method for the analysis of caffeine in commercial energy drinks, using CBA with a great extraction capacity due to its high porous surface area. The developed methodology has proven to be useful from a green chemistry point of view, using only one milligram of nanostructured sorbent, minimal solvent consumption, a reduced volume of sample, as well as easy and rapid automatization for the analysis of commercial energy drinks. For the quantification of the analyte in the energy drinks, a one-point standard addition calibration was applied to correct the matrix effect. Similar caffeine concentrations per milliliter were found in the three analyzed samples, likewise, the amounts of caffeine close to those reported by the manufacturers were established for two of the samples analyzed.

Microstructure effect analysis of carbon black-filled rubber composites

The unidirectional tensile stress-strain curves of four kinds of carbon black-filled rubbers with different volume contents were obtained by mechanical experiments, and the fine morphology maps of the carbon black-filled rubber composites were obtained by electron microscope experiments. Based on the hyperelastic constitutive model of rubber, an ellipsoidal carbon black particles randomly distributed finite element model was established using DIGIMAT and ABAQUS, and uniaxial tensile simulation was carried out on the established two-dimensional model. The effects of the volume fraction, distribution angle and number of agglomerates of carbon black particles on the stress-strain relationship curve and stress distribution of the composites were analyzed. The results show that: with the increasing volume fraction of carbon black particles, the stiffness value of the composite material becomes larger; when the particle direction is 0° to the load direction, the strength of the material is improved and the stress concentration phenomenon is less; with the increasing number of carbon black agglomerates, the strength of the composite material decreases and the stress concentration phenomenon is obvious in agglomerated area.

Non‐linear viscoelasticity of carbon black–fluoroether rubber mixture studied by large amplitude oscillatory shear tests

AbstractNon‐linear viscoelastic characteristics of carbon black (CB)‐filled fluoroether rubber mixture samples are investigated by large amplitude oscillatory shear (LAOS) tests. Three analysis approaches based on LAOS tests are then used to discuss correlations between rheological behavior and CB‐filling amount. Each non‐linear viscoelastic parameter of the mixture presents a three‐stage characteristic with increasing CB content, which are attributed to the alteration of CB–elastomer network structure, corresponding to the state where gum continuous phase, CB–elastomer mesophase, and excessive CB agglomerates predominate in the mixture compound, respectively. According to the findings in engineering experiments, a CB content of 35–40 phr is recommended, taking into account tensile, hardness, and aging properties. Excessive CB agglomerates are found to reinforce CB–elastomer networks at elevated temperatures. For cold‐resistance properties, structural changes in CB–elastomer network are proven to exert little effect on Tg, but a higher CB content was found to slightly enhance the cold‐resistance coefficient, probably due to the decrease in velocity fraction of gum rubber.Highlights LAOS tests were utilized to study the influences of CB on fluoroelastomer; Three‐stage alteration was observed in the mixture with increasing CB content; Correlation between CB content and the engineering properties was discussed.

Synthesis and characterization of seed-based Carbon Black Agglomerates: Application as sorbent material using a novel microextraction technique for dexamethasone in urine sample determination

The growing development of Nanotechnology has allowed the synthesis and characterization of nanomaterials with peculiar physicochemical properties. These nanomaterials have been applied in various scientific and industrial sectors. The present study established the synthesis of carbon black agglomerates (CBA) from waste vegetal materials as a source of renewable raw materials using a simple, fast, and effective procedure. Once this nanostructured material was obtained, several analytical techniques were applied to establish its main characteristics, including X-ray diffraction, Fourier transform infrared spectroscopy, Brunauer–Emmett–Teller (BET) theory analysis, and SEM imaging. The results of this characterization have made it possible to establish that these materials have properties that make them suitable for application as extracting sorbents in microextraction sample treatment techniques under the green analytical chemistry approach. In this study, we applied Pipette-tip SPE microextraction for pharmaceutical compound extraction studies, preparing extraction devices with less than five milligrams of the sorbent. The results showed high extraction percentages for compounds such as paracetamol, caffeine, diazepam, and dexamethasone. Finally, an application example of the last compound is presented, developing a procedure for its determination in urine samples by high-performance liquid chromatography with diode array detection (HPLC-DAD) chromatographic analysis with high merit figures in terms of simplicity, high extraction efficiency, and environmental friendliness. Keywords: carbon black; nanostructured material; olive seed; microextraction; biological samples

A review of the shear rheology of carbon black suspensions

The microstructural link to the rheology of carbon black suspensions has recently become clear as a result of advances in computational and experimental methods. This understanding reveals the important role of the restructuring, build-up, and break-up of carbon black agglomerates in simple shear, rationalized by a dimensionless balance of the hydrodynamic forces acting to break the agglomerates apart against the cohesive forces holding them together (i.e., the Mason number). The Mason number not only can predict the origin of reversible thixotropy seen in carbon black suspensions observed at higher shear intensities, but can also be used to rationalize the evolution of microstructure at lower shear intensities. This review focuses on carbon black suspension behavior, but the insights derived from carbon black suspensions are broadly applicable to a diverse class of soft matter including colloidal gels relevant to a variety of applications.

Study of the Cathode Pt-Electrocatalysts Based on Reduced Graphene Oxide with Pt-SnO2 Hetero-Clusters

A complex study of the structure, morphology, and electrochemical properties of the Pt20/SnO210/RGO electrocatalyst is presented. The advantage of the chemical synthesis of reduced graphene oxide (c-RGO) compared to thermal methods (t-RGO) is due to the formation of graphene plates with amorphous carbon black agglomerates and the chemical composition of the surface. The nature of the interaction between platinum and tin dioxide particles and a conclusion about the formation of heterostructures Pt-SnO2 with the surface interaction of lattices excluding the formation of hetero phases has been established. This achieves high dispersity during the formation of platinum particles without significant agglomeration and increases the electrochemical surface area (ESA) of platinum to 85 m2 g−1 vs. carbon black. In addition, the surface interaction of particles and the formation of hetero-clusters Pt-SnO2 can cause the improved activity and stability of the Pt20/SnO210/c-RGO electrocatalyst.

Process design for carbon black size and morphology

The structure (size and morphology) of carbon black (CB) largely determines its performance in tires, inks, batteries etc. Here, the impact of CB process synthesis variables, i.e. temperature, T, precursor (i.e. acetylene) flow rate, Q, and volume fraction, fv, on CB structure is elucidated by discrete element modeling (DEM) and compared to experimental data in the literature. The CB structure is quantified by the mobility, dm, and spherule or primary particle, dp, diameters, effective density, ρeff, and fractal dimension, Df. Decreasing Q or T enhances the CB yield, surface growth and agglomeration. This increases the mean dm and dp, consistent with experimental data from laminar flow ethylene pyrolysis reactors. The CB made at high Q or T is less compact than that made at low Q and T, having up to 50% smaller ρeff and 30% smaller Df, in excellent agreement with experimental data also. Increasing the fv (e.g. by increasing the precursor flow rate) results in CB aggregates (covalently-bonded CB primary particles) and increases the mean dm and dp, explaining commercial furnace black data. These CB aggregates are quite compact having up to 45% larger Df and larger ρeff than those of ethylene black. So process design diagrams generated by the present DEM simulations can be used to guide design and optimization of CB for various applications from first principles.

Quantitative measurements of changes in agglomerate size with oscillatory shear strain in polymer nanocomposites using online dielectric analysis

Shear strains during processing affect the agglomerate size of nanoparticles in nanocomposites and their final behavior in various applications. In this study, dielectric characterization technique as a novel and well-effective method is applied for quantitative measurement of average agglomerate size in polymer nanocomposites under shear strain sweep, combining with an existing analytical model. Examining how changes in filler content, surface energy and polarity of particles and the matrix control the strain-dependency of agglomerates size, two different nanoparticles, namely, titanium dioxide (TiO2) and carbon black (CB), with same average diameters and volumes were added to polystyrene (PS). It was found that larger agglomerates were present in the PS/CB nanocomposite prior to shearing and the CB agglomerates were less prone to deagglomeration under shear strain. This behavior was attributed to higher polarity of CB nanoparticles, leading to higher tendency for agglomeration and higher resistance to shear, in respect to TiO2 nanoparticles.

COMBINED TECHNIQUES AND RELEVANT IMAGE PROCESSING FOR QUANTITATIVE STATISTICAL CHARACTERIZATION OF INCLUSIONS IN ELASTOMERS

ABSTRACT The properties of elastomeric materials are strongly influenced by the inclusions resulting from the ingredients and the elaboration process. A methodology is proposed to differentiate the inclusions harmful for fatigue (larger than a few micrometers) in elastomers according to their chemical nature, and to characterize them quantitatively with sufficient statistics. Three techniques are used and compared: digital optical microscopy (OM), scanning electron microscopy (SEM) associated with energy dispersive X-ray spectroscopy, and X-ray micro-computed tomography (μ-CT). Six materials are used to challenge the methodology. In addition to the usual metal oxides and carbon black agglomerates, three atypical types of inclusions are highlighted, generating specific detection difficulties. A relevant image analysis procedure is developed to automatically detect the inclusions from the acquired images, more objectively and accurately than with the classical thresholding methods. The morphology and the spatial distribution of the different inclusions populations are then determined. μ-CT is the most comprehensive and accurate method for classification and statistical characterization of inclusions. Furthermore, relevant data on the size distribution of inclusions can be obtained using backscattered electrons (SEM-BSE) or digital OM. SEM-BSE provides more accurate results than digital OM.

In situ observation of microscopic damage and crack initiation mechanisms in a filled EPDM

The paper presents a precise 3D quantification of damage evolution and eventual crack initiation due to metallic oxide particles and filler agglomerates in a peroxide crosslinked filled EPDM during uniaxial solicitation, thanks to synchrotron radiation X-ray Tomography. An in-situ tensile study using this technique reveals polymer debonding at the poles of all metallic oxide particles upon stretching. The cavities caused by this decohesion do not lead to crack initiation since they grow parallel to the applied stress direction. Conversely, crack always initiates from carbon black agglomerates (CBaggl). The crack initiation mechanism is a three step process that begins with the nucleation of cavities inside the CBaggl upon stretching. This is followed by the growth of these cavities which brings about the fracture of the agglomerates. Finally, this fracture can lead to the creation of a matrix crack at the origin of the material rupture. It is also confirmed that CBaggl that initiate the critical crack in the material are the biggest sized CBaggl and are located close to the edges of the sample.

Crack propagation in filled elastomers: 3D study of mechanisms involving the filler agglomerates

This paper presents the impact of Carbon Blacks agglomerates, at different concentrations, on crack propagation mechanisms in a Carbon black (CB) filled Ethylene Propylene Diene Monomer (EPDM) elastomer. As shown by Transmission electron microscopy, these CB agglomerates (CBaggl) consist of aggregates clusters with interpenetrating elastomer, and for this reason, are soft and deformable. Crack tip observation using X-ray tomography demonstrates that these CBaggl can either undergo fracture or arrest/ deviate a crack during its propagation. This causes higher energy dissipation at the crack tip, which contributes to the dissipative component of the strain energy release rate G. For this reason, it is found that among the two materials tested with a significant amount of CBaggl (more than 3%), the material with the highest concentration has a slower crack propagation speed at high G.

Strain-induced irreversible change of the conductive network in a rubber/carbon-black composite revealed by polarization-resolved terahertz dielectric spectroscopy

The dielectric response during the deformation of a rubber composite filled with carbon black (CB) was studied by polarization-resolved terahertz spectroscopy, because the characterization of such responses can be used to reveal strain-induced irreversible changes in the electrical properties of a CB-filled rubber. During the first stretching-and-relaxation cycle, two characteristic behaviors were observed: strain-induced anisotropy and an irreversible reduction of the dielectric constants in the measured frequency range. To understand the origin of this result, we tried to reproduce the strain dependence of the dielectric function with a modified effective medium theory that accounts for the orientational distribution of the CB aggregates. From the dependence of the fitting parameters on the deformation condition, it was found that the reduction of the dielectric constants in the terahertz frequency range is mainly caused by the breakdown of the CB-based conductive network due to a dissociation of CB agglomerates. This finding indicates that polarization-resolved terahertz spectroscopy is a promising technique for the assessment of changes in the internal structure of CB fillers on the nanometer scale.

Analysing the Effects of High-Intensive Dry Mixing on the Calendering Process and Cell Performance of NMC622 Based Cathodes

A reliable design of production processes for the manufacturing of lithium-ion battery electrodes requires a deep understanding of the interdependency of processes, the resulting electrode microstructure and the influence on the cell performance indicators, like energy density, cycle life and aging. In the present study, the focus lays on the calendering process during which the electrode coating is compacted with the aim of adjusting uniform electrode properties such as mechanical, electrical and electrochemical behavior. Compaction of the electrode coating affects the pore structure and therefore has a crucial influence on the electrical and electrochemical behavior of the cell. Consequently, process and machine parameters have to be adapted in order to generate electrode structures optimized for a desired application. To meet this target, an in-depth understanding of how the calendering process affects the electrode structure beyond the simple reduction of porosity and further how the calendering process itself is affected by the preceding process steps like dry or wet mixing is mandatory.Thus, the focus of the presented work is to investigate the interdependency between the dry mixing process step and the subsequent calendering process by correlating powder properties adjusted via the dry mixing with the machine behavior during the calendering as well as the resulting coating density. The impact of the calendering process on the electrode microstructure and its correlation with electrode properties by developing process-product-property functions, regarding the above mentioned criteria, is an additional focus of the presented study.Therefore, powder mixtures of NMC622 with carbon black were created under varying the dry mixing intensity and thus adjusting the carbon black agglomerate size. The created powder mixtures were comprehensively characterized, e.g. particle size distribution and powder conductivity, and then used to build up electrodes which afterwards were compacted to different coating densities. The correlation between the powder properties and the calendering behavior shows a higher compaction resistance with decreasing carbon black agglomerate size. Whereas reducing the carbon black agglomerate size leads to lower electrical resistivity and therefore strongly impacts the C-rate capability.

Influence of operating temperature on the measured and predicted lifetime of carbon black-filled hydrogenated nitrile butadiene rubber

This work analyses the influence of the operating temperature on the lifetime of carbon black filled elastomers. The crack growth properties and the lifetime of elastomers are temperature dependent. The increase of temperature at the same nominal stress leads to an increase of crack growth rate and consequently to a decrease of the lifetime. The lifetime prediction is performed using the Monte Carlo principle. Carbon black agglomerate are randomly distributed in the investigated test volume. By combining the crack growth properties, agglomerate distribution and the local deformation in the component, the lifetime prediction can be performed. The prediction curves show good agreement with the measured lifetime at different operating temperatures and different loading levels.

Fabrication of porous Al2O3 ceramics using carbon black as a pore forming agent by spark plasma sintering

Fabrication of ceramic materials containing high amount of porosity with controlled size and structure is a critical factor for various applications. In this study, porous alumina ceramics were prepared by addition of 5–30 vol% carbon black (CB) powders with different specific surface area (SSA) into the alumina matrix as a pore forming agent and application of partial sintering via spark plasma sintering (SPS) technique. After removal of CB particles from the ceramic structures, physical, mechanical, and thermal properties of the porous alumina ceramics were investigated. The open porosity level was detected between 38.48 and 59.81% depending on the type and amount of CB removed. The compressive strength of the sintered samples was measured as ∼150 MPa, which is ∼3 times higher than that of the conventionally sintered samples thanks to the strong neck formation between grains. The large pores formed by removal of CB agglomerates in case of using CB powders with SSA of 107 and 254 m2/g resulted in a change in thermal conduction mechanism from lattice vibration to thermal convection.

Inner carbon black porosity as characteristic parameter for the microstructure of lithium-ion electrodes and its effect on physical and electrochemical properties

The conductive network within a lithium-ion battery electrode is mainly influenced by the process parameters chosen for the dry mixing and wet dispersing step during the production of a coatable electrode slurry, consisting of well-defined components. This conductive network, which results from the electrode's microstructure, plays a major role for the resulting battery cell performance, especially for high performance and power applications. Notable differences can be observed in the subsequently manufactured electrodes due to process-related modifications in the carbon black agglomerate size; mechanical, electrical, and, thus, electrochemical properties are significantly changing with the process parameters set. To allow for a direct correlation of these properties with the electrode structure, a characteristic parameter to describe the carbon black structure in electrode coatings is developed. Based on mercury intrusion measurements, the internal porosity of carbon black particles was determined as a characteristic parameter for the conductive microstructure. For a wide variety of lithium-ion battery cathode samples, the carbon black porosity can be well related to important electrode properties. This underscores the relevance of this carbon black-based microstructure parameter for a knowledge-based process and product optimization.

Elastic response of Carbon Black reinforced polyester based composites using micromechanical models: Role of interphase

Carbon-based reinforcements have been widely reported in improving mechanical properties of polymers. However, still few studies exist on the incorporation of the interphase as a result of the interfacial interactions into analytical prediction tools. To better understand the effect of interfacial interphase, this study compares and correlates the experimental mechanical response of polyester based composites filled with carbon black (CB) with the elastic behavior obtained from the micromechanical models. Mold cast composites of polyester reinforced with 0 wt%–10 wt% of CB were fabricated. To determine the length of cooperative rearranging region (CRR) as a measure of the interphase, thermal studies focusing on the variations in the specific heat capacity or the relaxation strength of the composites around the glass transition temperature ( Tg) range were performed using a thermodynamical model. Micromechanical models such as the Halpin-Tsai and Tandon-Weng were used to determine the Young’s modulus with respect to the CB wt% and diameter as well as the interphase thickness and modulus. The results exhibited the sensitivity of the models to the existence of the interphase as a secondary mechanism, which was correlated to the cross-link density and interfacial bonding. The impact results showed the decrease in the impact resistance upon the addition of higher filler loadings ascribed to the destroyed bonding at the interface and CBs agglomeration confirmed by morphological studies. The research results can be further utilized in the explanation of the changes in the elastic response of carbon-based reinforced thermosetting composites emphasizing the key role of interphase.

Investigation of Carbon Black/ Polyester Micro-composites: An Insight into Nano-size Interfacial Interactions

In the micro/nanomaterial reinforced composites, interfacial interactions at the interface of filler/polymer lead to the formation of a third layer called interphase as the secondary reinforcing mechanism. The interphase may be formed due to local adsorption of polymer chains at the interface, mechanical interlocking, and interdiffusion of polymer chains. Since the interactions govern the load transfer at the filler/polymer interface, they play a key role in the mechanical response of reinforced composites. However, there exist only a few well-established and validated studies in the description of the interfacial interactions presented in thermosetting composites. This research aims at the understanding of correlations amongst the mechanical properties of thermosetting polyester composites reinforced with 0-15 wt. % of carbon black (CB) focusing on the nano-size cooperative rearranging region (CRR). To estimate the length of CRR, thermal analysis of the variations in the specific heat capacity or the relaxation strength within the glass transition temperature (Tg) range was measured using a thermodynamic model. A nano-size CRR of 10 nm on average was estimated and correlated to the enhanced impact and toughness behavior of the specimens. The results suggested the presence of softer interphase based on the Tg values influenced by the CBs agglomeration level and cross-linking density, which in turn governs the mechanical response of the composites. The methodology introduced in this study can be used in the explanation of changes in mechanical and physical properties of reinforced composites with a focus on the underlying role of nano-size interfacial interactions.

Impact of the occurrence probability of carbon black agglomerates on the measured and predicted durability of filled elastomers

AbstractThis work analyses the impact of the sample geometry on the stress or strain concentration and the occurrence of big agglomerates in the investigated test volume. Although the three investigated dumbbell test specimens were loaded at the same stress level, there were significant differences in measured lifetime. These differences in the lifetime are due to the occurrence of the large agglomerates in the tested volume. The probability of occurrence of large agglomerates increases with increase in the investigated volume. In the lifetime prediction by Monte Carlo method, this effect is realized by changing the quantity of the distributed agglomerates in the mesh of the simulated model. The prediction of the different sample geometries shows a very good agreement with the measurement points. The numerical simulations illustrate the stress increase for the three used lifetime test samples.