Dynamic Testing and Reinforcement of Rubber

1988 ◽  
Vol 61 (5) ◽  
pp. 842-865 ◽  
Author(s):  
J. M. Funt
Keyword(s):  
Molecular Weight ◽  
Carbon Black ◽  
Hydrodynamic Interaction ◽  
Dynamic Testing ◽  
Large Strain ◽  
Aggregate Size ◽  
Effective Volume ◽  
Bound Rubber ◽  
Rubber Forming ◽  
Entanglement Network

Abstract A series of experiments have been run to determine which mechanisms dominate carbon black reinforcement of rubber. A broad range of compounds using oil-extended and non-oil-extended rubbers and carbon blacks covering the spectrum of tread blacks have been tested. The results for measurements made in an all-SBR formulation are reported here. The primary experiment consisted of measurement of the dynamic modulus and hysteresis of the cured and uncured compounds over a broad range of frequencies, temperatures, and strains. Ternperatures ranged from −70°C to +90°C; frequencies varied from 0.01 to 10 Hz; double strain amplitudes varied from 0.5% to 35%. From a discussion of the literature and evaluation of the experimental results, two mechanisms have been found to control the primary effects of carbon black on rubber reinforcement, where reinforcement refers to a general enhancement of properties, such as modulus, as well as the tensile strength of the compound. Hydrodynamic interaction, which is the increase in properties caused by the modification of strain fields in the region of an aggregate, dominates the large-strain dynamic and tensile properties of the compound. The primary carbon black variable in this mechanism is the effective aggregate size, such as measured by tint, which controls the effective volume loading of the carbon black at a given weight loading of carbon black. At low strains, the modulus is even higher than that predicted from the hydrodynamic-interaction/effective-volume model. This additional reinforcement is caused by the entanglement network formed between the tightly absorbed bound rubber on the carbon black surface and the bulk rubber far removed from the surface. The main carbon black variables in this mechanism are surface area and surface chemistry. The strain dependence of modulus is caused by the breaking and reforming of effective crosslinks in the rubber forming a transition zone between the bound rubber and the bulk rubber. To a large extent, this mechanism is dominated by the rubber properties, such as molecular weight and molecular-weight distribution. However, the dynamics of the entanglement network may be modified by altering specific interactions between carbon black and rubber.

Sorption of GR-S Type of Polymer on Carbon Black. III. Sorption by Commercial Blacks

1953 ◽  
Vol 26 (1) ◽  
pp. 102-114 ◽  
Author(s):  
I. M. Kolthoff ◽  
R. G. Gutmacher
Keyword(s):  
Molecular Weight ◽  
Carbon Black ◽  
Intrinsic Viscosity ◽  
Benzene Solution ◽  
Weight Fraction ◽  
High Molecular Weight Fraction ◽  
Molecular Weights ◽  
Bound Rubber ◽  
Flow Through ◽  
Peculiar Behavior

Abstract The sorption capacities toward GR-S five commercial carbon blacks are in decreasing order: Spheron-6, Vulcan-1, Philblack-0, Sterling-105, Philblack-A. Apparently, the sorption is not related to surface area. The sorption on Vulcan-1 of GR-S from its solutions in seven different solvents or mixtures of solvents increases with decreasing solvent power for the rubber. The sorption curves of two “cold rubbers,” polymerized at −10 and +5° respectively, showed little difference from that of 50° GR-S. Previous heating of carbon black in nitrogen at 500 or 1100° increased the sorption by about 20 per cent over unheated carbon. Air-heating of carbon black at 425° did not cause a difference in the sorption from benzene solution, but produced an increase in the sorption of rubber from n-heptane solution. In the range 75% butadiene-25% styrene to 5% butadiene-95% styrene, there is practically no effect of the degree of unsaturation on the sorption. Polystyrene of high intrinsic viscosity exhibits a peculiar behavior with furnace blacks. Vulcan-1 sorbed microgel as well as the sol fraction from n-heptane solutions of GR-S containing microgel (conversion 74.7 and 81.5 per cent). There was no appreciable difference in the amount of sorption of rubber fractions having average molecular weights varying from 433,000 to 85,000. There is little change in the amount sorbed after two hours of shaking, but the intrinsic viscosity of the residual rubber decreases with time. The low molecular-weight rubber is sorbed more rapidly, but is slowly replaced by the more tightly sorbed high molecular weight fraction. Partial fractionation of a rubber sample can be achieved by allowing the rubber solution to flow through a column of weakly sorbing carbon black. A large portion of the sorbed rubber can be recovered from the column by washing it with a good solvent such as xylene. Bound rubber is produced by intimate mixing of equal parts of carbon black and rubber swollen in chloroform, when the mixture is dried in vacuum at 80° or at room temperature. Milling is not essential to get bound rubber.

Mixing of Carbon Black with Rubber. VI. Analysis of NR/SBR Blends

1988 ◽  
Vol 61 (4) ◽  
pp. 609-618 ◽  
Author(s):  
George R. Cotten ◽  
Lawrence J. Murphy
Keyword(s):  
Molecular Weight ◽  
Carbon Black ◽  
High Molecular Weight ◽  
Surface Area ◽  
Bound Rubber ◽  
Very High

Abstract The distribution of carbon black in NR/SBR blends was determined through the analysis of bound rubber. The NR/SBR blends were found to be very different from the previously studied SBR/BR compounds: these differences were assigned to mutual insolubility of the two polymers and a very high molecular weight of NR. In NR/SBR blends, it was found that changes in molecular weight of the polymer has no effect on the carbon black distribution in the blend. While the “activity” of carbon black did not affect the distribution, the loading of the black in NR decreased linearly with increasing surface area of the black. Approximately 35% of normal tread blacks (surface area 80–100 m2/g) was found in the NR phase. However, the bond between NR and carbon black is quite weak, and black continues to migrate into the SBR phase on prolonged mixing or during blending of NR and SBR masterbatches.

Studies on Carbon Black. III. Theory of Bound Rubber

1957 ◽  
Vol 30 (1) ◽  
pp. 157-169
Author(s):  
D. S. Villars
Keyword(s):  
Molecular Weight ◽  
Carbon Black ◽  
Selective Adsorption ◽  
General Sense ◽  
Polymer Molecules ◽  
Naturally Occurring ◽  
High Molecular Weight Material ◽  
Chemical Type ◽  
Bound Rubber ◽  
Set Up

Abstract Theories of reinforcement may be grouped into two general classes, mechanical and chemical. The mechanical type of theory attempts to explain reinforcement by alteration of direction of tear or by mechanieal entrainment. The chemical type of theory invokes the formation of bonds between the filler and rubber. Because of its implication with respect to the latter, Fielding of Goodyear developed a “bound rubber” test. The amount of rubber bound to carbon black was defined as that unextractable from the raw masterbatch by benzene. Some ten years ago, Baker and Walker reported an insolubilization of GR-S, on mixing with carbon black, over and above the amount of naturally occurring gel. The amount of insolubilized polymer increases with increasing molecular weight of the GR-S, and a selective adsorption of the high molecular weight material was found. Since this phenomenon was obtained also in polymers where they believed chemical gelation to be impossible, the conclusion was drawn by them that it is purely physical—this notwithstanding the fact that they found that extractions at higher temperatures failed to remove the insolubilized polymer. Because the method of analysis for insolubilized polymer used by Baker and Walker was essentially a bound-rubber analysis, interest in the latter was revived and it became desirable to set up a hypothesis to explain the mechanism of bound-rubber formation. (Let us understand the term “rubber” as applying in its more general sense as synonymous with “elastomer”.) The present paper reports a theory developed by the writer about ten years ago to explain various observations on the hypothesis that bound rubber is a gel of carbon black particles, the bonding agent of which consists of the longer polymer molecules. The theory interprets the observed linear dependence of bound rubber on loading in terms of an elemental area associated with the segmental adsorption of elastomer molecules, the molecular weight of these segments, and the functionality of the carbon black particles.

Molecular Weight Effects in Adsorption of Rubbers on Carbon Black

1968 ◽  
Vol 41 (5) ◽  
pp. 1256-1270 ◽  
Author(s):  
Gerard Kraus ◽  
J. T. Gruver
Keyword(s):  
Molecular Weight ◽  
Carbon Black ◽  
Large Particle ◽  
Molecular Weights ◽  
Molecular Weight Dependence ◽  
Bound Rubber ◽  
Sieve Effect ◽  
High Structure ◽  
Very High ◽  
Poor Solvent

Abstract The molecular weight dependence of the adsorption of polybutadiene on carbon black from a poor solvent, n-heptane, and bulk, i.e., the phenomenon of “bound rubber”, was investigated. For narrow distribution polymers the adsorption is proportional to Mn, where n = 0.14 for adsorption from n-heptane solution; n = 0.5 for adsorption from bulk. Anomalously low solution adsorption was observed for polymers of very high molecular weight (> 500,000). This is ascribed to a sieve effect by aggregates of carbon black particles which cannot be penetrated by the large molecular coils. In high structure blacks, which pack more loosely, and in large particle blacks, which form larger interstices between particles, onset of anomalous adsorption is shifted toward higher molecular weights.

Characterization of New Technology Carbon Blacks

1973 ◽  
Vol 46 (5) ◽  
pp. 1239-1255 ◽  
Author(s):  
A. I. Medalia ◽  
E. M. Dannenberg ◽  
F. A. Heckman ◽  
G. R. Cotten
Keyword(s):  
Carbon Black ◽  
Iodine Number ◽  
Surface Activity ◽  
New Technology ◽  
Aggregate Size ◽  
Nitrogen Adsorption ◽  
Solid Sphere ◽  
Sphere Diameter ◽  
Bound Rubber ◽  
Morphological Differences

Abstract In this paper we have examined a limited number of conventional and new technology blacks, using the “t” method of nitrogen adsorption for comparison of surface area and dibutyl phthalate adsorption (DBPA) for comparison of structure. At a given “t” area the new technology blacks are of lower iodine number; conversely, at a given iodine number, the new technology blacks are of higher “t” area. This is not due to porosity, but rather to differences in carbon black-iodine surface interaction. The DBPA tests gives a fairly consistent measure of carbon black structure in rubber, for both types of blacks. An important difference between the two classes of black is in the higher tinting strength of new technology blacks, at a given “solid sphere” diameter (which depends primarily on the “t” area and to a lesser extent on the DBPA). We have introduced the use of a disk photosedimentometer for studying carbon black aggregate size distributions and have found that at a given “t” area, the distribution curves for the new technology blacks are shifted in the direction of smaller Stokes diameters. This can account, at least qualitatively, for their higher tinting strength. Electron microscopy supports the shift in Stokes diameters, at least qualitatively, and also indicates a more open aggregate morphology for the new technology blacks. The new technology blacks impart a higher level of reinforcement, at the same “t” area, as shown by tensile strength and roadwear. This is accompanied by a higher loss tangent or lower rebound. These properties may be due in part to a higher surface activity, as shown by a higher moisture adsorption and higher bound rubber, and partly to morphological differences, as shown by the smaller Stokes diameters and higher tinting strength. In summary, the higher bound rubber and higher tinting strength of the new technology blacks reflect differences in surface activity and aggregate size, which are responsible for the superior reinforcement shown by these blacks at a given “t” area.

The Effects of Carbon Black and Other Compounding Variables on Tire Rolling Resistance and Traction

1983 ◽  
Vol 56 (2) ◽  
pp. 390-417 ◽  
Author(s):  
W. M. Hess ◽  
W. K. Klamp
Keyword(s):  
Carbon Black ◽  
High Speed ◽  
Dynamic Testing ◽  
Aggregate Size ◽  
Rolling Resistance ◽  
High Viscosity ◽  
High Positive Correlation ◽  
Wide Range ◽  
Tan Δ ◽  
High Viscosity Oil

Abstract The rolling resistance of SBR/BR radial passenger tire treads was varied as a function of carbon black type and loading, as well as other compounding variables, such as oil content, high-viscosity oil and resin addition, and NR substitution. In all instances, the rolling loss variations showed a good correlation with either tan δ or resilience. The tan δ response was valid for a wide range of test temperatures, frequencies, and strain amplitudes. Wet (32 km/h) and dry (64 km/h) traction indicated a high positive correlation with loss compliance (D″). Here, the best correlations were obtained at lower dynamic testing temperatures (0–25°C.) and higher strain amplitudes. High-speed wet traction (97 km/h) appeared to be relatively independent of the tread compounding variables but did show a slight correlation with tan δ measured at ™25°C. The following patterns were observed relative to tread rolling resistance, traction, and wear as a function of compounding variables: 1. Black loading.—Reduced black loading lowers rolling resistance without much effect on traction. About 4% less black in the tread compound lowers rolling resistance by about 5–6% in the formulations which were evaluated. 2. Oil loading.—At a fixed black level, increased oil raises both rolling resistance and traction. About 2% higher rolling resistance was found for a 10 phr increase in oil loading, but the effect on wet traction appeared to be much greater (7–8%). 3. Black type.—Increasing black fineness raises both rolling resistance and traction, the latter effect being considerably less. Increased DBPA has very little effect on rolling resistance but reduces traction. At reduced black loadings, the finer and higher DBPA blacks show the least loss in treadwear resistance. Blacks with broad aggregate size distribution give lower rolling resistance at the same surface area and DBPA. For extreme blends (carcass and tread grades), however, the loss in treadwear resistance is quite severe (∼30%). 4. Curatives.—Increased sulfur and accelerator levels produced a significant reduction in tan δ, with a similar but lesser drop in D″. The same reduction in tan δ with increased accelerator (OBTS) level produced less effect on D″ than the sulfur increase. 5. Natural rubber substitution.—Compounds in which 30 phr of NR were substituted for 25 phr of SBR and 5 phr of BR indicated slightly better performance in terms of both rolling resistance and traction. 6. High-viscosity oil or resin substitution.—Replacing conventional extender oil with high-viscosity oil or resin appears to improve traction but has a greater adverse effect on rolling resistance. 7. Compound optimization.—N299 black gives the best overall balance of performance in terms of rolling resistance, traction, and treadwear at reduced black loadings. N121 confers about 10% better treadwear and equal traction in the same compound, but at about 4% higher rolling resistance.

Relationship between Molecular Structure and Mixing Mechanism

1987 ◽  
Vol 60 (1) ◽  
pp. 14-24 ◽  
Author(s):  
S. Shiga
Keyword(s):  
Molecular Structure ◽  
Molecular Weight ◽  
Carbon Black ◽  
Mixing Time ◽  
Molecular Size ◽  
Rubber Compounds ◽  
Bound Rubber ◽  
Strong Linear Correlation ◽  
Black Surface ◽  
The Relationship

Abstract The relationship between the molecular weight, the bound rubber, and the PI value was studied for EPR, of which the molecular structure was measured with GPC-LALLS. A strong linear correlation is found between the bound rubber and the PI value. The Meissner theorem, modified to express a severer dependence of the bound rubber on the molecular weight than the original theorem expects and the use of a molecular size instead of the molecular weight, can explain the relationship between the molecular weight and the bound rubber, accordingly the PI value. They indicate not only the dependence of mixing processability on polymer adsorption, but also strongly suggest the mechanism of carbon black dispersion that aggregates are scraped out from the surface of agglomerates as illustrated by the onion model. A pulsed NMR was used to measure the spin-spin relaxation time T2 of EPR in rubber compounds of different mixing time to study the rubber phase structure and its time change. It can be imagined from the T2-time curves that till tmin, polymer molecules are rapidly bound on the carbon black surface to become thick gradually, while adsorbed segments per a molecule increase with time. After tmin, gradual rearrangement of molecules on the surface and the biphasic structure of the bound rubber may proceed. The whole thickness of the bound rubber increases gradually even after tmin. The resistance against the dispersion of carbon black seems to be strengthened with mixing time.

Formation of Bound Rubber of GR-S Type Polymers with Carbon Blacks

1952 ◽  
Vol 25 (3) ◽  
pp. 500-516 ◽  
Author(s):  
June Duke ◽  
W. K. Taft ◽  
I. M. Kolthoff
Keyword(s):  
Molecular Weight ◽  
Carbon Black ◽  
High Molecular Weight ◽  
Lower Molecular Weight ◽  
Carbon Blacks ◽  
Bound Rubber ◽  
Temperature Levels ◽  
Black Other ◽  
Lower Carbon

Abstract The bound rubber-black complex formed by milling various GR-S polymers and carbon blacks at several temperature levels was studied. The amount of bound polymer increased with greater loadings of black, but per unit of carbon black, it decreased at the higher black loadings. The temperature of mixing likewise has a large effect—at lower carbon black loadings, higher temperatures increase the amount of binding; the effect ia minimized as the loading is increased until at high loadings (100 to 125 parts of black per 100 parts of rubber) this effect is eliminated. By fractionation of the sol portion, it has been shown that polymer of progressively lower molecular weight is bound as the black loading is increased. Polymer of high molecular weight does not replace bound polymer of lower molecular weight; the polymer of higher molecular weight is preferentially bound during mill mixing. Although more polymer appears to be bound as the conversion is increased from 50 to 72 per cent at a loading of 50 parts of black, other factors besides conversion may be determinative. No differences in relationship were found for polymers made at 122° or 41° F.

Influence of Carbon Black on Process-Ability of Rubber Stocks. I. Bound Rubber Formation

1975 ◽  
Vol 48 (4) ◽  
pp. 548-557 ◽  
Author(s):  
G. R. Cotten
Keyword(s):  
Molecular Weight ◽  
Carbon Black ◽  
Polymer Degradation ◽  
Processing Conditions ◽  
Rubber Content ◽  
High Molecular Weight Polymer ◽  
Molecular Weight Polymer ◽  
Bound Rubber ◽  
Wide Range ◽  
Process Ability

Abstract 1. A direct correlation between bound rubber content and molecular weight of soluble polymer was found for a wide range of carbon black samples and processing conditions in SBR. 2. No significant polymer degradation occurred during the ineorporation of carbon black into SBR rubber. 3. A theory was proposed to explain the observed changes in viscosity and extrusion shrinkage of rubber stocks. This theory is based on the concept of occluded rubber which is rich in high molecular weight polymer and behaves as a part of filler volume during viscous flow.

Bound Rubber and Carbon Black Reinforcement

1986 ◽  
Vol 59 (3) ◽  
pp. 512-524 ◽  
Author(s):  
E. M. Dannenberg
Keyword(s):  
Molecular Weight ◽  
Carbon Black ◽  
Selective Adsorption ◽  
Three Dimensional ◽  
Polymer Molecules ◽  
Chemical Bond Formation ◽  
Synthetic Rubber ◽  
High Molecular Weight Material ◽  
Bound Rubber ◽  
Physical And Chemical

Abstract The first description of the bound rubber phenomenon was by Twiss in 1925, who made the observation that the resistance of carbon black-natural rubber mixes to solvents was related to improved mechanical properties. Boiry studied many of the factors influencing the insolubilization of NR by fillers including type and amount of fillers, and mixing and testing variables. In 1937 J. H. Fielding of Goodyear developed a so-called “bound rubber” test because of his interest in the possibility of chemical bond formation between fillers and rubber. During the start of the U.S. synthetic rubber program, Baker and Walker reported in 1945 an insolubilization of SBR when mixed with carbon black significantly greater than the amount of normal gel in the unfilled elastomer. They were also the first to report that the amount of gel increased with increasing molecular weight and that a selective adsorption of high molecular weight material occurred. Since that time, many investigations have confirmed these findings with other elastomers, and theories of “bound rubber” formation have been based on these observations. The early concept that “bound rubber” is a gel of carbon black particles held together in a three-dimensional lattice by longer interparticle polymer molecules is still valid. The nature of the segmental attachments of the polymer molecules to the filler surfaces now appears to be both physical and chemical, depending upon filler surface activity and chemical functionality, and the chemical composition and functionality of the elastomer. Regardless of the type of interaction, the bonding is essentially permanent and can only be disrupted by extraction with good solvents at high temperatures.

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