Carbon Black Dispersion and Reinforcement

1952 ◽  
Vol 25 (4) ◽  
pp. 843-857 ◽  
Author(s):  
E. M. Dannenberg
Keyword(s):  
Electrical Resistivity ◽  
Carbon Black ◽  
Aggregate Size ◽  
Surface Oxidation ◽  
Light Transmittance ◽  
Rubber Matrix ◽  
Carbon Blacks ◽  
Improved Technique ◽  
High Degree ◽  
Carbon Black Dispersion

Abstract Different mixing conditions were employed to obtain vulcanizates, varying only in degree of carbon black dispersion, with natural and synthetic rubbers, using a single sample of a commercial grade HAF black. Light transmittance measurements on dilute solutions of dissolved unvulcanized stocks prepared by an improved technique were used to evaluate the size of carbon black aggregates in cold GR-S and natural rubber stocks. Electron micrographs of films show the high degree of carbon black aggregation, even after prolonged mixing. A limiting degree of dispersion or a minimum aggregate size is obtained very rapidly as mixing is increased. Black incorporation and dispersion appear to take place simultaneously; a high degree of abrasion reinforcement was noted in most rubbers with mixing (less than 75 seconds) barely sufficient to incorporate the black. Carbon blacks in general respond rapidly to mixing, and the chainlike aggregates characteristic of reinforcing carbon blacks observed under the electron microscope are practically unchanged after mixing with rubber. Dispersion of carbon blacks during mixing depends on the packing and coherence of their agglomerates resulting from such factors as surface oxidation and extent of mechanical bulk densification. There is some evidence that oil-type furnace blacks disperse more easily than channel blacks. A major cause of the disappointing abrasion reinforcement with most noncarbon pigments possessing extreme fineness may be the tendency for excessively strong aggregate binding and resulting large aggregates in rubber. A striking rise in electrical resistivity was observed as the amount of mixing was increased. As the size of the aggregates did not change, the higher electrical resistivity cannot be explained by assuming better dispersion and breakdown of conductive carbon paths. Increased mixing might provide better distribution of the carbon aggregates in in the rubber matrix without change in size of aggregates.

CARBON BLACK FOR RACING AND MOTORCYCLE TIRE TREADS. PERFORMANCE MODEL DEVELOPMENT

2011 ◽  
Vol 84 (4) ◽  
pp. 493-506
Author(s):  
Irene S. Yurovska ◽  
Michael D. Morris ◽  
Theo Al
Keyword(s):  
Carbon Black ◽  
Critical Role ◽  
Model Development ◽  
Aggregate Size ◽  
Rolling Resistance ◽  
Performance Model ◽  
Average Life ◽  
Carbon Blacks ◽  
Truck Tires ◽  
And Performance

Abstract Racing tires and motorcycle tires present individual segments of the tire market. For instance, while the average life of car and truck tires is 50 000 miles, the average life of race tires is 100 miles. Because tires play a critical role in a race, technical demands to assure safety and performance are growing. Similarly, tires have a large influence on safety, handling/grip, and performance of the rapidly growing world fleet of motorcycles, due to the fact of only two wheels being in contact with the ground. Thus, the common feature of both market segments is that the typical tire compromise of wear, rolling resistance, and traction is strongly weighted toward traction. Most of the recent efforts of rubber scientists have been directed toward lowering rolling resistance of the tread compounds, which left a certain void in the science of compounding for racing and motorcycle treads. Particularly, the industrial assortment of polymers and fillers used for motorcycle treads is commonly different from that used for car or truck treads, but it is not known how the filler properties affect the hysteresis–stiffness compromise. The objective of this study is to evaluate the effects of the carbon black characteristics on the important properties of a typical racing and motorcycle tire tread compound. More than 50 individual carbon blacks were mixed in a SBR formulation. The acquired data were statistically analyzed, and a linear multiple regression model was developed to relate rubber properties (responses), such as static modulus, complex dynamic modulus, hysteresis, and viscosity to the key carbon black characteristics (variables) of surface area, structure, aggregate size distribution, and surface activity. Prediction profiles created from the model demonstrate rubber performance limits for the range of carbon blacks tested, and indicate the niches to provide required combinations of the rubber properties.

The Effect of Structure Breakdown of Carbon Black on Rubber Properties

1974 ◽  
Vol 47 (5) ◽  
pp. 1082-1093 ◽  
Author(s):  
B. B. Boonstra ◽  
E. M. Dannenberg ◽  
F. A. Heckman
Keyword(s):  
Carbon Black ◽  
New Technology ◽  
Aggregate Size ◽  
Void Volume ◽  
Diameter Distribution ◽  
Sphere Diameter ◽  
Projected Image ◽  
Carbon Blacks ◽  
Normal Carbon ◽  
First Time

Abstract Mechanical processing of carbon blacks by a novel pressure-milling technique provides a controlled breakdown of primary carbon-black aggregates. In contrast, direct compression has a much smaller effect on aggregate size. In rubber vulcanizates, the pressure-milled carbon blacks give about the same vulcanizate properties as normal carbon blacks with the same void volume or DBP absorption value. Breakdown of aggregates occurs during the process of incorporating and dispersing carbon black in rubber. The retention of average aggregate size after mixing in rubber is in the range of 60–70 per cent for Vulcan M (N339), a new technology tread black. We have shown that the DBP absorption method cannot distinguish between loss in void volume by compaction of aggregates versus the actual breakdown of aggregates. The sedimentation method by centrifuging provides a means for measuring aggregate size independent of the original packing of the dry black. In order to carry out these studies, a number of new experimental techniques were used. These include: a) controlled aggregate size breakdown by pressure-milling. b) Stokes diameter distribution measurements by centrifuging aqueous dispersions in a Joyce Loebl apparatus. c) Quantimet analysis of projected aggregate areas from electron micrographs from specially prepared solvent dispersions of rubber-carbon black samples where the aggregates are clear of interference from adhering rubber. It has been shown for the first time that for both Vulcan M (N339) and Vulcan 6 (N220) the median Stokes diameters, DSt, obtained by the centrifuge method and the equivalent sphere diameter, De, from Quantimet projected image analysis are in the range of 123–153.

Online Electrical Conductivity as a Measure to Characterize the Carbon Black Dispersion in Oil Containing Rubber Compounds with a Different Polarity of Rubber

2004 ◽  
Vol 77 (5) ◽  
pp. 815-829 ◽  
Author(s):  
H. H. Le ◽  
I. Prodanova ◽  
S. Ilisch ◽  
H.-J. Radusch
Keyword(s):  
Electrical Conductivity ◽  
Carbon Black ◽  
Conductivity Measurement ◽  
Infiltration Rate ◽  
Rubber Matrix ◽  
Electrical Conductivity Measurement ◽  
Infiltration Process ◽  
The Matrix ◽  
Polar Oil ◽  
Carbon Black Dispersion

Abstract The influence of viscosity, polarity of the rubber matrix and the types and contents of extender oil on the carbon black dispersion has been characterized using the online electrical conductivity measurement. A corresponding change of the online conductivity with the rubber infiltration and extent of carbon black dispersion has been observed. The infiltration rate increases with increasing polarity and decreasing viscosity of the rubber matrix, whereby the matrix polarity shows a stronger effect than the viscosity. The oil addition accelerates the infiltration process. This is caused by the reduction of the matrix viscosity and the intensification of the filler-matrix interaction. Oil addition affects the carbon black dispersion in non-polar rubber much more than in polar rubber. Furthermore, in non-polar rubber, polar oil shows a stronger effect than non-polar oil.

Electrical Resistivity of Carbon-Black-Loaded Rubbers

1990 ◽  
Vol 63 (3) ◽  
pp. 451-471 ◽  
Author(s):  
Tejraj M. Aminabhavi ◽  
Patrick E. Cassidy ◽  
Corley M. Thompson
Keyword(s):  
Electrical Resistivity ◽  
Electrical Properties ◽  
Carbon Black ◽  
High Surface ◽  
Self Regulation ◽  
Physicochemical Characteristics ◽  
Rubber Matrix ◽  
High Resistivity ◽  
High Electrical Resistivity ◽  
Materials Research

Abstract Uses are growing for rubbers with varying levels of resistivity. High electrical resistivity is very much essential in wire and cable insulation applications. Low levels of resistivity are needed for electrostatic discharge in phonograph records and many medical, industrial, and military products and for semiconductive cable compounds. The level of resistivity depends upon the number of contacts or near contacts between conductive particles in the rubber matrix. Loading level is obviously a major determinant in addition to physicochemical characteristics of the black. In the latter regard, the highly conductive grades are characterized by small particle size, high structure, high surface porosity, and low volatile content. One would, therefore, seek the reverse of those factors for high-resistivity rubbers. One of the goals of materials research now is to create new materials with physicomechanical properties tailored to a particular application and to understand the physical processes which determine the end properties. In this review, an attempt has been made to discuss the electrical properties of carbon-black-loaded rubber composites, a class of materials which covers the range from insulators to conductors. The carbon-black-loaded rubbers are formed by dispersing carbon black into the rubber. The compounding is done by adding the carbon black to the rubber, mixing at temperatures above Tg and subjecting the mixtures to high shears until a uniform blend is obtained. The carbon-black particles may be as small as 14 nm in diameter or as large as 300 nm, and they may be individually dispersed or agglomerated in micron-sized clusters. Morphology of the rubber has a profound effect on its electrical properties. High electrically resistive rubbers are becoming increasingly important. Their wide array of applications include antistatic products, shielding materials, insulating membranes, resistors, etc. In the vicinity of the crystalline transition region the rubber shows a dramatic resistivity increase which can be utilized for self-regulation processes. Compounds suitable for such various applications differ appreciably in the nature of their components and composition depending on the specific performance required.

Effect of Heat Treatment on Reinforcing Properties of Carbon Black

1956 ◽  
Vol 29 (1) ◽  
pp. 286-295
Author(s):  
W. D. Schaeffer ◽  
W. R. Smith
Keyword(s):  
Carbon Black ◽  
Volatile Matter ◽  
Graphitized Carbon Black ◽  
Carbon Surface ◽  
Minor Effect ◽  
Carbon Blacks ◽  
Carbon Black Surface ◽  
Black Surface ◽  
High Degree ◽  
Degree Of Graphitization

Abstract The high degree of stiffness or modulus which reinforcing carbon blacks impart to rubber has often been associated with reinforcement. Modulus appears to be associated with the chemical nature of the carbon black surface ; when the carbon black surface is cleaned of combined oxygen and hydrogen, a drastic drop in modulus occurs, and this is not accompanied by an equally drastic decrease in tire road wear. Reinforcing and semireinforcing carbon blacks have been heat-treated at successive increments through a temperature range of 1000° to 2700° C. Treatment up to 1500° results in removal of all combined oxygen and hydrogen, followed by an increasing degree of graphitization at higher temperatures. These carbon blacks have been compounded in a standard natural-rubber compound and properties evaluated. Modulus is profoundly altered by the chemistry of the carbon surface. Electrical resistivity passes through a minimum at 1500° C. Scorchiness or premature vulcanization improves with removal of volatile matter. The degree of graphitization of the carbon has only a minor effect on rubber properties. A highly graphitized carbon black still imparts a high degree of resistance to abrasive wear to tire treads.

Mixing of Carbon Black with Rubber I. Measurement of Dispersion Rate by Changes in Mixing Torque

1984 ◽  
Vol 57 (1) ◽  
pp. 118-133 ◽  
Author(s):  
George R. Cotten
Keyword(s):  
Carbon Black ◽  
Volume Fraction ◽  
Small Samples ◽  
Butadiene Rubber ◽  
Mixing Process ◽  
Carbon Blacks ◽  
Bound Rubber ◽  
Power Peak ◽  
Dispersive Mixing ◽  
Carbon Black Dispersion

Abstract Analysis of the torque data obtained for a large range of carbon blacks in an oil-extended butadiene rubber (CB-441) shows that the rate of decrease of torque (after the second power peak) follows first order kinetics. The rate of decrease represents the rate of reduction in effective filled volume fraction through dispersion of carbon black agglomerates, and thus, a reduction in the volume of rubber occluded between individual aggregates within the agglomerates. The assumption that the rate of torque reduction is proportional to the rate of carbon black dispersion was tested by examining the responses to various factors influencing the mixing process. In general, the conclusions reached from the analysis of torque data were in agreement with the common industrial experience and predictions based on the mathematical analysis of dispersive mixing. Tadmor's analysis of dispersive mixing predicts that the rate of agglomerate rupture depends on the number of particle-particle contacts and thus is related to the size of individual aggregates, but is independent of agglomerate size. Thus, it is in agreement with the present findings that the rate of dispersive mixing increases with decreasing surface area and increasing structure of aggregates. Increasing polymer-filler interaction gives rise to a faster rate of dispersive mixing, possibly by increasing the effective radii of aggregates through bound rubber formation. Increasing the batch temperature increases the rate of dispersive mixing due to reduced cohesion between the aggregates and a more favorable balance between cohesive and shearing forces. Increasing carbon black loading increases the rate of dispersive mixing by increasing the viscosity and, thus, shearing forces generated during the mixing process. The technique developed in this work may provide a better means for measuring dispersibility of carbon blacks, since other available methods suffer certain disadvantages. For instance, the resistivity measurements are not only dependent on carbon black dispersion, but also on the chemical nature of its surface, while microscopic methods depend on the examination of very small samples that may not be representative of the whole batch.

Carbon Black Structure Effects in Synthetic Rubbers

1961 ◽  
Vol 34 (4) ◽  
pp. 1141-1161
Author(s):  
T. D. Bolt ◽  
E. M. Dannenberg ◽  
R. E. Dobbin ◽  
R. P. Rossman
Keyword(s):  
Carbon Black ◽  
Term Structure ◽  
Primary Structure ◽  
Mechanical Strain ◽  
Secondary Structures ◽  
Spherical Particles ◽  
Carbon Blacks ◽  
Carbon Particles ◽  
Particle Association ◽  
High Degree

Abstract Carbon blacks are composed of spherical particles which are to varying degrees arranged in chainlike structures. This type of particle association, which is readily seen in electron photomicrographs of most carbon blacks, can be termed “primary structure”. The use of the term “structure” to describe interparticle association must not be confused with the basic intraparticle structure of an atomic crystallographic nature. There is strong evidence that primary structure units, and possibly individual particles, can further associate or flocculate in fluid or elastomeric systems. This is a secondary type of structure formation which can be readily disrupted under the influence of mechanical strain. Some investigators have used the term “structure” to describe this strain-sensitive flocculation behavior. It is suggested here that carbon blacks possess both primary structure features and the ability to form secondary structures by flocculation in dispersed systems. The tendency to form secondary structures is probably greater with carbon blacks possessing a high degree of primary structure. Unless otherwise specified, the term “structure” in this paper will be used in the sense of primary structure. The structure of carbon blacks is thought to originate in the flame by the agglomeration of growing carbon nuclei and particles. The appearance of electron micrographs of carbon blacks lends some support to the assumption of simultaneous agglomeration and growth processes. Carbon blacks having a broad particle size distribution are characterized by carbon black chains, where each chain is composed of particles of the same size, rather than a randomized distribution of various sized carbon black particles. Thus, these chainlike structures must result from the continued growth of agglomerates formed from neighboring carbon particles at the same stage of their growth history. This process results in a chemical fusing of these particles as layers of new carbon are deposited on the surfaces of actively growing agglomerates.

Reinforcement of Elastomers by Carbon Black

1978 ◽  
Vol 51 (2) ◽  
pp. 297-321 ◽  
Author(s):  
Gerard Kraus
Keyword(s):  
Carbon Black ◽  
Size Distribution ◽  
Viscoelastic Behavior ◽  
Aggregate Size ◽  
Surface Oxidation ◽  
Spatial Arrangement ◽  
Indirect Measure ◽  
Dominant Characteristic ◽  
Average Size ◽  
Physical And Chemical

Abstract The reinforcement of elastomers by carbon black is governed by the morphology of the black and its physical and chemical interactions with the polymer. The latter are strongly affected by graphitization and surface oxidation. In modern rubber-grade carbon blacks strong bonding of the polymer to the carbon black surface is effected by several mechanisms, but surface chemical differences between blacks are relatively small, so that the dominant characteristic becomes the morphology. This is determined by the average size and size distribution of the particles which are fused together to form primary aggregates resembling branched random coils, the spatial arrangement of the particles in these aggregates, and the number of particles per aggregate and its distribution. This highly complex morphology can, to a first approximation, be represented by the specific surface area accessible to rubber and some, usually indirect, measure of the volume pervaded by the primary aggregates (“structure”). Important mechanical properties of reinforced rubbers depend to different degrees on these two characteristics, often in rather complex manner. Their effects on viscoelastic and failure properties are described. Additionally, some very recent observations on the effects of carbon black on network structure and the influence of the breadth of the aggregate size distribution on viscoelastic behavior are discussed.

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