Carbon Black Distribution Research Articles

The role of carbon black distribution in cathodes for Li ion batteries

The influence of carbon black distribution/arrangement in cathode composite on cathode performance is studied using three types of active materials: LiMn 2O 2-spinel, LiCoO 2, and LiFePO 4. To the active materials, carbon black is added in two different ways: (a) using a conventional mixing procedure and (b) using a novel coating technology (NCT) invented in our laboratory. Different technologies yield different arrangement (distribution) of carbon black around active particles. It is shown that the uniformity of carbon black distribution affects significantly the cathode kinetics, regardless of the type of active particles used. A simple model explaining the influence of carbon black distribution on cathode kinetics is presented.

Characterization of Rubber Micro-Morphology by Atomic Force Microscopy(AFM)

Abstract Micro-morphology of the rubber compounds, such as polymer compatibility and carbon black distribution, is one of the most important parameters affecting compound performance. Transmission Electron Microscopy (TEM) technique enables us to examine this micro-morphology, but has many difficulties. It requires high skill for sample preparation, high cost and a long time. Atomic Force Microscopy (AFM) technique is a relatively easy way for detecting these images. Through TM-AFM (Tapping Mode Atomic Force Microscopy) technique, two different polymer domains were distinguished in the unfilled rubber blend (natural rubber/ synthetic rubber blend). In order to verify the images, analogue signal (voltage) histograms for those images were analyzed by Gaussian multi-peak analysis method. Filler morphology was also examined in the filled natural rubber and filled rubber blend compounds. Silica and carbon black showed different behavior in the rubber blend. Carbon black lies predominantly in the polybutadiene rubber domain whereas silica exists in the natural rubber domain.

Size analysis of industrial carbon blacks by sedimentation and flow field-flow fractionation

Carbon black is one of the most useful particulate materials in the industrial field. Among the various physical properties of carbon black, size and size distribution are the most important properties to affect the quality of a final product. However, it is difficult to measure the exact particle size of carbon black since it suffers unavoidable interference from flocculation. In this study, the effects of various factors on the dispersion of industrial carbon blacks were investigated for the determination of size and size distribution of carbon black particles. Sedimentation and flow field-flow fractionations (FIFFF) were used to determine the size of carbon black, and their optimum analytical conditions were tested by changing surfactant, pH, ionic strength, and method of dispersion. The results showed that surfactant structure and its concentration played significant roles in dispersion stability. Carbon black was dispersed well with a nonionic surfactant with a pH of around 8 and an ionic strength of 0.003 M. The mean diameters measured from two types of FFF and photon correlation spectroscopy are in good agreement. This study demonstrates the potential of sedimentation and flow FFF for analyzing highly adsorptive industrial particles and guides for sample preparation.

The conduction mechanism of carbon black-filled poly(vinylidene fluoride) composite

The positive temperature coefficient (PTC) effect of carbon black (CB)-filled poly(vinylidene fluoride) (PVDF) composite and the changes in resistivity under different conditions were studied. It was found that there were some coherence between the volume expansion and the crystallite melting of PVDF. It is believed that the homogenization diffusion of CB particles results in increasing resistivity during volume expansion and crystallite melting. At high temperature, the resistivity decrease is due to the agglomeration of CB particles or aggregates, which results in a new CB distribution of better conductivity. On the base of the experimental evidence, it is concluded that the PTC effect of PVDF/CB composite is dominated by the volume expansion of composite matrix, the diffusion of CB particles from amorphous region to melted crystalline region and the agglomeration of CB particles.

Carbon black filled conducting polymers and polymer blends

AbstractThe objective of this article was to review the use of carbon black (CB) as a conductive filler in polymers and polymer blends. Important properties of CB related to its use in conducting polymers are discussed. The effects of polymer structure, molecular weight, surface tension, and processing conditions on electrical resistivity and physical properties of composites are discussed. Several percolation models applicable to CB/polymer blends are reviewed. Emphasis is placed on recent trends using polymer blends as the matrix to obtain conducting composites at a lower CB loading. A criterion for the distribution of CB in polymer blends is discussed. © 2002 Wiley Periodicals, Inc. Adv Polym Techn 21: 299–313, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.10025

A STUDY OF CARBON BLACK DISTRIBUTION AND PROPERTIES IN BR/NBR BLENDS: ROLES OF COMMERCIAL HOMOGENIZER AND SLIPPING AGENT

Effects of commercial processing aids, Struktol NS60 (hydrocarbon resin) homogenizer and Struktol WB16 (a mixture of metal salt and a fatty acid amide) slipping agent on the distribution of carbon black and physical properties in BR/NBR blends have been investigated. It was found that Struktol 60NS and Struktol WB16 in blend systems migrate preferentially to BR phase due to the strong interaction between Struktol and BR phase, leading to a decrease in viscosity of BR phase and thus an increase in carbon black residing in BR phase. Mechanical properties of unfilled compounds are strongly affected by blend ratio and loading of processing aids. However, in the case of filled compounds, the influence of carbon black distribution in each phase of the blends override those blend ratio and additive loading effects.

Study of carbon black distribution in BR/NBR blends based on damping properties: Influences of carbon black particle size, filler, and rubber polarity

AbstractEffects of filler and rubber polarity on the distribution of filler in butadiene/nitrile rubber (BR/NBR) blends were investigated, using the dynamic mechanical thermal analysis technique. As 30‐phr filler is added, the reduction in heights of damping peaks (tan δmax), attributed to the dilution effect, was observed. It was also found that the BR phase in the blends, compared to the NBR phase, is more preferential for small‐ and large‐particle size carbon blacks to reside, probably because of the lower viscosity and lower polarity of the BR phase. The addition of silica instead of carbon black leads to an increase in filler migration to the NBR in the 20/80 BR/NBR blend, which is attributed to the strong silica–NBR interaction. In addition, an increase in NBR polarity promotes carbon black migration to the BR phase. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3198–3203, 2001

Electrical behavior and structure of polypropylene/ultrahigh molecular weight polyethylene/carbon black immiscible blends

AbstractThis study investigates the electrical behavior, which is the positive temperature coefficient/negative temperature coefficient (PTC/NTC), and structure of polypropylene (PP)/ultrahigh molecular weight polyethylene (UHMWPE)/carbon black (CB) and PP/γ irradiated UHMWPE (XL‐UHMWPE)/CB blends. As‐received UHMWPE or XL‐UHMWPE particles are chosen as the dispersed phase because of their unusual structural and rheological properties (extremely high viscosity), which practically prevent CB particles penetration. Because of their stronger affinity to PE, CB particles initially form conductive networks in the UHMWPE phase, followed by distribution in the PP matrix, thus interconnecting the CB‐covered UHMWPE particles. This unusual CB distribution results in a reduced electrical percolation threshold and also a double‐PTC effect. The blends are also investigated as filaments for the effect of shear rate and processing temperature on their electrical properties using a capillary rheometer. Because of the different morphologies of the as‐received and XL‐UHMWPE particles in the filaments, the UHMWPE containing blends exhibit unpredictable resistivities with increasing shear rates, while their XL‐UHMWPE containing counterparts depict more stable trends. The different electrical properties of the produced filaments are also related to differences in the rheological behavior of PP/UHMWPE/CB and PP/XL‐UHMWPE/CB blends. Although the flow mechanism of the former blend is attributed to polymer viscous flow, the latter is attributed to particle slippage effects. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 104–115, 2001

Properties influenced by addition of copoly (ethylene/octene) in BR–NBR blends

The effects of copoly (ethylene/octene) (EOM) on rheological, mechanical, and cure properties and on carbon black distribution in each phase of butadiene rubber–nitrile/butadiene rubber (BR–NBR) blends have been investigated. It was found that EOM added to the blends is able to function as a plasticising agent for BR and NBR, and the plasticising efficiency of EOM is more significant in NBR than BR. With increasing EOM content, the deviation of Mooney viscosity from the additive line (interpolated values) reduces markedly. In pure components (i.e. 100 : 0 and 0 : 100), cure rate reduces and cure time increases with addition of EOM. In contrast in the blend systems, cure rate increases and cure time decreases when EOM is added. The distribution of carbon black in each phase of the blends is strongly controlled by the viscosity of each phase in the blend. The lower the phase viscosity, the greater the residual carbon black. Accordingly, dynamic mechanical thermal analysis reveals a slight shift in the glass transition temperature of the BR phase to higher temperature, compared with the NBR phase, as EOM is added. From the results obtained, it is proposed that EOM exists in the interfacial area between the two phases. However, at higher amounts of EOM, saturation of EOM at the interfacial area occurs and the excess EOM starts to migrate to the BR phase. Further increase in EOM concentration leads to saturation of EOM in the BR phase and EOM then migrates to the NBR phase.

A numerical simulation of the electrical resistivity of carbon black filled rubber

A simple model is proposed and a numerical simulation is carried out to calculate the electrical resistivity of a composite of carbon black in an insulating matrix. From load of carbon black and aggregate size and distribution, it is possible to know the resistivity of the compound assuming a random lattice where the resistance between sites (aggregates) varies exponentially with the gap. A computer program was developed and several samples were prepared and measured to obtain the model parameters. Numerical results are compared with experimental data.

Carbon black-reinforced dynamically cured EPDM/PP thermoplastic elastomers. I. Morphology, rheology, and dynamic mechanical properties

The structure development, rheological behavior, and viscoelastic properties of carbon black-filled dynamically vulcanized thermoplastic elastomers based on the ethylene–propylene–diene terpolymer (EPDM) and polypropylene (PP) with the ratio range of 50/50 to 80/20 were studied and compared with similar but unfilled samples. Two-phase morphology was observed at all ratios for the dynamically cured samples in which rubber particles are dispersed in the thermoplastic matrix. Carbon black distribution in each phase and damping behavior was found to be dependent upon the mixing condition and route of carbon black feeding. However, carbon black tends to stay mainly in the rubber phase, which leads to increase in the viscosity difference and, therefore, increase in the rubber particle size. Tensile strength and rupture energy increased with carbon black loading. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1127–1137, 2000

Effect of incorporating ethylene‐ethylacrylate copolymer on the positive temperature coefficient characteristics of carbon black filled HDPE systems

AbstractIn order to study the effect of introducing ethylene‐ethylacrylate copolymer (EEA) in carbon black‐HDPE composite systems, two HDPE‐EEA composites prepared by pre‐blending and masterbatch‐blending processes were compared with HDPE and EEA composites in terms of positive temperature coefficient (PTC) characteristics and percolation threshold. The percolation threshold of masterbatch‐blended composites occurred at the lowest carbon black concentration among four kinds of composites. The conduction path in the masterbatch‐blended composite is effectively formed as a result of the localization of carbon black distribution predominantly in the EEA phase, resulting in an increase of conductivity. Ipeak values, the resistivity ratio of the peak to 25°C, of two blend composites were lower than those of HDPE composites. The I85 values, the resistivity ratio of 85°C to 25°C, of masterbatch‐blended composites were higher than those of pre‐blended as well as HDPE composites. It is evident that since most carbon black is dispersed in the EEA phase of the masterbatch‐blended composites, the conduction networks are mainly broken by the crystal melting of EEA before the temperature reaches the crystal melting temperature of HDPE.

Effect of filler treatment on temperature dependence of resistivity of carbon-black-filled polymer blends

Polyblends prove to be able to provide more possibilities for tailoring conductive polymer composites in comparison with individual polymer systems. Accordingly, ethylene–vinyl acetate—low-density polyethylene (EVA–LDPE) filled with carbon black (CB) was prepared in this study as a candidate for positive temperature coefficient (PTC) material. In consideration of the fact that CB distribution plays the leading role in controlling a composite's conduction behavior, chemical treatment of CB was applied to reveal its influence on percolation and the PTC effect. It was found that titanate coupling agent treatment facilitated sufficient distribution of CB in LDPE phase, leading to lower resistivity and a squarer PTC curve. Composites filled with nitric-acid-treated CB exhibited specific temperature dependence of resistivity as a result of the heterogeneous dispersion of CB at the interface of EVA–LDPE, which might provide the materials with a new function. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 489–494, 1999

Effect of filler treatment on temperature dependence of resistivity of carbon‐black‐filled polymer blends

Polyblends prove to be able to provide more possibilities for tailoring conductive polymer composites in comparison with individual polymer systems. Accordingly, ethylene–vinyl acetate—low-density polyethylene (EVA–LDPE) filled with carbon black (CB) was prepared in this study as a candidate for positive temperature coefficient (PTC) material. In consideration of the fact that CB distribution plays the leading role in controlling a composite's conduction behavior, chemical treatment of CB was applied to reveal its influence on percolation and the PTC effect. It was found that titanate coupling agent treatment facilitated sufficient distribution of CB in LDPE phase, leading to lower resistivity and a squarer PTC curve. Composites filled with nitric-acid-treated CB exhibited specific temperature dependence of resistivity as a result of the heterogeneous dispersion of CB at the interface of EVA–LDPE, which might provide the materials with a new function. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 489–494, 1999

Carbon Black Distribution in Rubber Blends: A Dynamic-Mechanical Analysis

Abstract The influence of phase morphology and carbon black distribution on energy storage and dissipation during dynamic excitations of rubber blends is discussed. It is shown that differences in the local stiffness of the phases in the glass transition regime of unfilled blends lead to characteristic deviations of the local strain from the external strain amplitude. These deviations are governed by a critical phenomenon due to the formation of a phase network above a critical blend ratio. As a result, a strongly nonlinear dependence of the glass transition maxima of the loss modulus on the volume fraction of the phases is observed. By counting the elastically effective bonds of the phase network, the local strain amplitude is estimated by purely geometrical arguments. Based on a consideration of the phase network, the distribution of carbon black in the different phases of filled blends is estimated from the height of the local maxima of the loss modulus in the glass transition regime. Thereby, a linear increase of the maximum value of the loss modulus with rising carbon black concentration is exploited that relates the enhanced energy dissipation of filled rubbers to the internal friction of the filler particles. Results on EPDM/BR/N550 blends indicate that carbon black is preferably located in the BR phase. A somewhat higher concentration of carbon black in the SBR phase is found in the case of NR/SBR(40% Styrene)/N330 blends.

The effect of a new type of pin mixing section on the performance of a single‐screw extruder

AbstractThe effect of a holed‐pin mixing section on the performance of a single screw extruder was investigated and compared with a free flight and a normal pin mixing section, using a practical single‐screw extruder. The effect of axial distance between two pins in a holed‐pin mixing section on performance was also studied. Mixing ability was quantified using the statistical approach of carbon black concentration distribution in the extruded film mixed with a carbon black masterbatch. The results indicate that a free flight gives the lowest melt temperature rise, pressure drop, and driver power, but the worst mixing; a holed‐pin mixing section has better mixing ability, lower melt temperature rise, and lower driver power than a normal pin mixing section does; the value of the pressure drop of the two types of pin mixing sections is approximately identical. A longer axial distance between the two pins in a holed‐pin mixing section gives better mixing and lower melt temperature rise than a shorter one; however, when the distance is longer than a critical value, the improvement of mixing is not so outstanding; for different axial distances between two pins, no great change in pressure drop was found and the extrusion throughput has almost no great relation to the axial distance.

Characterization of Immiscible Elastomer Blends

Abstract Considerable improvements have been made in the analysis of elastomer blends for composition, morphology and filler inter-phase distribution. GC, IR, NMR and thermal analysis (DTG, DSC, TG) techniques can provide quantitative information on composition. The latter three methods, along with SAXS, SANS, DMTA and microscopy (LM phase contrast, TEM, SEM, AFM) are also useful for resolving differences in blend homogeneity. The microscopical techniques are the most useful for characterizing morphology. TEM, in conjunction with cryosectioning and staining techniques, has provided the best means of resolving filler distribution to date. However, new AFM scanning modes may provide improved analyses in the future. Carbon black inter-phase distribution in blends of NR, SBR and BR can be controlled reasonably well by blending Banbury mixed masterbatches containing the desired carbon black loading in each polymer. Transfer of carbon black from one elastomer to another is favored by low unsaturation for the polymer originally containing the black, or a low heat history (e.g. solution and latex mixing) during preparation of the masterbatch. The overall polymer interaction with carbon black increases in the order: IIR, EPDM, NR, BR, SBR, the latter two being fairly close. Commercial carbon blacks will transfer extensively from an IIR Banbury masterbatch to NR, but not from EPDM to NR. Significant transfer to SBR occurs from both IIR and EPDM. Inert (partially graphitized) carbon blacks tend to distribute more evenly between the blend components regardless of which polymer contained them initially. Carbon black phase distributional variations can cause significant changes in unvulcanized and vulcanized rubber properties. For NR/BR and NR/SBR blends, reduced hysteresis generally occurs with a higher carbon black loading in the NR phase. Tear strength and cut growth tend to be maximized with higher carbon black in the continuous polymer phase, particularly when that phase is the higher strength polymer. The smaller the carbon black particle size, the greater the improvement in tear strength as a function of phase distribution. NR/BR fatigue life was maximized with about an equal distribution of carbon black in each polymer. This type of carbon black distribution also produced the greatest resistance to ozone cracking for NR/EPDM blends, which were further improved with very small domain size for the EPDM (disperse) phase. The abrasion resistance of NR/BR blends has indicated some improvement in the direction of higher carbon black in the BR. These results have been variable, however, and further study is needed for clarification.

Carbon Black Distribution in NR/Polybutadiene Blends

Abstract The distribution of carbon black between the phases of a NR/cis-1,4-polybutatdiene (BR) blend was studied. An N550 carbon black was added to the blend using different mixing techniques. The carbon-black distribution was determined using a variety of analytical techniques. The crystallization temperature of the BR was measured by differential scanning calorimetry. This temperature is related to the carbon-black level in the BR phase. Samples were dissolved in toluene to separate the bound and soluble rubber portions and the fractions were analysed for polymer type and amount by solid stale 13C MAS nuclear magnetic resonance. Results indicated that the N550 black has no preference for either the NH or the BR. In phase mixed samples, the majority of the black remains in tho polymer to which it is initially udded. When black and polymers are mixed simultaneously, the black tends to distribute itself uniformly between the polymers. Physical test results on a typical sidewall compound indicated that the location of the carbon black has a significant effect on physical properties, especially cut-growth resistance.

Quantitative Estimation of Filler Distribution in Immiscible Rubber Blends by Mechanical Damping Studies

Abstract The peak value of tan δ at the glass-transition temperature (Tg) in the plot of tan δ versus temperature is lowered on addition of filler to a rubber. This relative lowering of tan δ at Tg can be used to estimate the filler distribution in an immiscible rubber blend. In the present investigation, distribution of silica filler and carbon black was studied in blends of natural rubber (NR) and epoxidized natural rubber (ENR). It was observed that silica migrated preferentially to the ENR phase. The magnitude of the distribution depends on filler loading and the epoxy content of ENR. The amount of carbon black migrated to the NR phase is higher than that of silica at a similar loading in blends of NR and ENR.

Effect of Interfacial Free Energy on the Heterogeneous Distribution of Oxidized Carbon Black in Polymer Blends

The effect of oxidation of carbon black (CB) on the heterogeneous distribution in polymer blends was examined. In three kinds of polymer blends, i.e., high density polyethylene (HDPE)/isotactic polypropylene (PP), PP/atactic poly(methyl methacrylate) (PMMA), and HDPE/PMMA, the heterogeneous distribution of CB and oxidized CB were observed. The heterogeneous distribution of fillers in a polymer blend matrix was mainly due to the difference in affinity of CB particles to each component of the polymer blend. In HDPE/PP blend, the dispersion state of oxidized CB was different from that of unoxidized CB. The dispersion states of the fillers in these samples were predicted qualitatively from the values of the wetting coefficient which were calculated from the interfacial free energies, and they were coincident with the observations by scanning (SEM) and transmission (TEM) electron microscopies.