Carbon Black Reinforcement in Pre-Swollen Rubbers

1966 ◽  
Vol 39 (5) ◽  
pp. 1553-1564 ◽  
Author(s):  
G. R. Cotten
Keyword(s):  
Carbon Black ◽  
Elevated Temperatures ◽  
Polymer Network ◽  
Radioactive Tracer ◽  
Polymer Chains ◽  
Additional Information ◽  
Bound Rubber ◽  
Black Surface ◽  
Swollen Vulcanizates ◽  
Mobile Adsorption

Abstract The mechanism of carbon black reinforcement was studied by examining stress-strain properties in SBR 1500 vulcanizates cured while swollen, then de-swollen. Carbon black-polymer attachments started contributing to the modulus of rubber at much higher elongations (ca. 300 per cent for a swelling ratio of 4.0) than in normally cured, unswollen specimens. The modulus in pre-swollen rubbers is considerably lower than in normal vulcanizates but it can be increased by heating the same specimens 30 minutes at 155° C in their de-swollen state. The observed increase in modulus of vulcanizates containing graphitized and regular carbon blacks after such a treatment was found to be related to carbon black “activity” and loading. Bound rubber does not seem to function as a distinct phase contributing to reinforcement, but it can be used as a measure of the number of attachments of carbon black and polymer. Additional information on the molecular mechanism of the phenomenon was obtained through radioactive tracer analysis. It was also found that regular vulcanizates can be softened by heating swollen samples at elevated temperatures (150-170° C). This softening was related to carbon black “activity” and was fully reversible: the original modulus could be recovered by additional heating of de-swollen vulcanizates for a further thirty minutes at 155° C. The above observations are discussed in terms of mobile adsorption of polymer chains on carbon black surface and the steric effect of fixing carbon black particles into an already extended polymer network.

Immobilization of Elastomers at the Carbon Black Particle Surface

1970 ◽  
Vol 43 (5) ◽  
pp. 973-980 ◽  
Author(s):  
A. K. Sircar ◽  
A. Voet
Keyword(s):  
Carbon Black ◽  
Particle Surface ◽  
Carbon Black Particle ◽  
High Energy ◽  
Molecular Weights ◽  
Boiling Points ◽  
Furnace Black ◽  
Bound Rubber ◽  
Black Surface ◽  
Black Particle

Abstract Determinations have been made of the amount of elastomer unextractable from unvulcanized masticated mixes with carbon black by a given solvent at boil, expressed as immobilized elastomer. Saturated and unsaturated elastomers varying in molecular weights from 2000 to 325,000, were used, while solvents of greatly differing boiling points and solvent power were employed. It could be shown that the bonding between elastomers and carbon black is not a simple adsorption, but involves a higher energy interaction, defined as chemisorption. At successively higher temperatures elastomer is increasingly removed from the carbon black surface. The temperature Tm, obtained by extrapolation of the linear relationship between amounts immobilized and temperature of extraction, represents the temperature theoretically required to eliminate all bonds between carbon black and elastomer and is therefore indicative of the bond strength. Data suggest the existence of a bonding energy spectrum. Upon graphitization, blacks show a considerable decline in high energy bonding ability for elastomers. Saturated elastomers show less bonding than unsaturated elastomers with the same furnace black. “Bound rubber” represents the sum total of physically adsorbed, mechanically entangled, and chemisorbed elastomer. The actual values are greatly dependent upon the procedure used. “Immobilized rubber”, indicating chemisorbed elastomer, is easily determined, is not influenced by the method, and is more significant as an indicator of reinforcement.

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.

Characterization of Polymer Adsorption on Disordered Filler Surfaces by Transversal 1H NMR Relaxation

1997 ◽  
Vol 70 (5) ◽  
pp. 747-758 ◽  
Author(s):  
H. Lüchow ◽  
E. Breier ◽  
W. Gronski
Keyword(s):  
Surface Roughness ◽  
Carbon Black ◽  
1H Nmr ◽  
Nmr Relaxation ◽  
Rubber Matrix ◽  
Adsorption Sites ◽  
Bound Rubber ◽  
Carbon Black Surface ◽  
Black Surface ◽  
Tan Δ

Abstract The transversal 1H NMR relaxation of the bound rubber shell of carbon black loaded elastomers can be decomposed into three relaxation regimes corresponding to the loosely bound rubber, the rubber that is immobilized on the carbon black surface and a third component of intermediate mobility. The relaxation time T2 of the intermediate component is related to the end-to-end distance of polymer segments between adsorption sites on the carbon black surface, by converting the relaxation times to length scales on the basis of recent work on NMR relaxation of elastomeric networks. From measurements on SBR loaded with carbon black N 220, a distance of 2.3 nm was obtained in agreement with characteristic dimensions of crystallite sizes and surface roughness as determined by atomic force and scanning tunneling microscopy. The analysis was applied to novel inversion blacks which give lower tan δ/60°C, and rolling resistance without affecting tan δ/0°C and wet skid behavior. These blacks were found to possess a higher density of adsorption sites and a greater surface roughness as compared to standard carbon blacks. In addition to the surface characterization, the analysis of the mobile component of the compound allowed the estimation of the density of entanglement couplings between the rubber matrix and the bound rubber shell.

New Studies on the Surface Properties of Carbon Blacks

1990 ◽  
Vol 63 (5) ◽  
pp. 747-778 ◽  
Author(s):  
J. A. Ayala ◽  
W. M. Hess ◽  
A. O. Dotson ◽  
G. A. Joyce
Keyword(s):  
Carbon Black ◽  
Hydrogen Content ◽  
Surface Reactivity ◽  
Moisture Adsorption ◽  
Carbon Blacks ◽  
Surface Sites ◽  
Bound Rubber ◽  
Carbon Black Surface ◽  
Black Surface ◽  
Polymer Interaction

Abstract A series of carbon blacks of widely varying morphology and microstructure were analyzed for surface compositional properties employing SIMS, XPS/ESCA, and GC-MS. These studies were supported by bulk analyses for hydrogen and oxygen content. Surface reactivity was assessed by means of inverse gas chromatography, moisture adsorption, and oxidation in an oxygen plasma. To directly assess carbon-black-polymer interaction, the carbon blacks were evaluated in SBR and IIR compounds for stress-strain and dynamic properties as well as bound rubber. The major findings of these studies are: 1. The combined results of hydrogen content, SIMS, and pyrolysis-GC-MS suggest a complex hydrogen functionality at the carbon-black surface, which governs the level of interaction with elastomers. 2. SIMS analyses have shown that the hydrogen functionality at the carbon-black surface is preserved after an 1173 K heat treatment in an inert atmosphere. 3. Gas-solid chromatography results indicate that this technique may be very useful to determine the degree of heterogeneity of a carbon-black surface. It also provides a tool to characterize the nature of the surface sites which are responsible for such a heterogeneity. 4. Moisture-adsorption rates provides a means to explore the reactivity of carbon-black-surface sites. Initial rates of adsorption can be well explained by a second-order-rate mechanism. 5. Bound-rubber development (SBR) and oxygen content per square meter of carbon-black-surface area were directly proportional to the hydrogen content of the black. The hydrogen content is considered to be the primary compositional factor relating to carbon-black-surface activity, while bound rubber and oxygen levels are specific measures of surface reactivity. 6. The slope of the stress-strain curves (or the modulus value) in the λ=1 to 3 region divided by the black networking factor, η (E′ at 2% ptp ÷ at 25% ptp), is sensitive to changes in black-polymer interaction. This ratio (σ/η or M/η) shows an excellent correlation with black hydrogen content and bound rubber (SBR). 7. The σ/η values for SBR and IIR are highly correlated, although the values for SBR are two to three times higher, and there was no measurable bound rubber for any of the IIR compounds. 8. The σ/η values for IIR (λ=2−3) and the oxygen/m2 values were found to be the best discriminators for black-polymer interaction in explaining within-grade treadwear variations in SBR/BR multisection radial-passenger treads.

Chemical Interaction between Carbon Black and Elastomers — Crosslinking of Chlorosulfonated Polyethylene by Carbon Black

1994 ◽  
Vol 67 (4) ◽  
pp. 662-671 ◽  
Author(s):  
A. Roychoudhury ◽  
S. K. De ◽  
P. P. De ◽  
J. A. Ayala ◽  
G. A. Joyce
Keyword(s):  
Carbon Black ◽  
Elevated Temperatures ◽  
Chemical Interaction ◽  
Surface Oxidation ◽  
Rubber Content ◽  
Chlorosulfonated Polyethylene ◽  
Surface Sites ◽  
Bound Rubber ◽  
Thermometric Titration ◽  
Oxidized Carbon

Abstract Surface oxidation of a carbon black leads to an increased elastomer-filler bonding between the chlorosulfonated polyethylene and the carbon black. The increased interaction appears to be related to the increased concentration and reactivity of the oxygen containing sites in the oxidized carbon black, as deduced from the moisture adsorption and thermometric titration results. The bound rubber content is substantially higher for the oxidized carbon black. The reactive surface sites of the carbon black also promote the crosslinking of the elastomer at elevated temperatures.

Carbon-Black-Elastomer Interaction

1991 ◽  
Vol 64 (1) ◽  
pp. 19-39 ◽  
Author(s):  
J. A. Ayala ◽  
W. M. Hess ◽  
F. D. Kistler ◽  
G. A. Joyce
Keyword(s):  
Carbon Black ◽  
Surface Activity ◽  
Chemical Reactivity ◽  
Surface Reactivity ◽  
Moisture Adsorption ◽  
Carbon Blacks ◽  
Bound Rubber ◽  
Carbon Black Surface ◽  
Black Surface ◽  
Polymer Interaction

Abstract A number of different techniques were applied to measure carbon-black-surface reactivity and the level of black-polymer interaction in four different elastomer systems (SBR, IIR, NR, and NBR) representing differences in unsaturation, crystallinity and polarity. Known within-grade surface activity variations were based on partial graphitization of an N121-type carbon black. The surface activity of different black grades was studied as a function of variations in both surface area and DBPA. Direct measurements of carbon-black-surface reactivity were based on hydrogen analysis, SIMS, IGC, and moisture adsorption. In-rubber measurements included bound rubber, SIMS of cut surfaces, and an interaction parameter, σ/η, which is derived from the slope (σ) of the stress-strain curve at low elongations, and (η), the ratio of dynamic modulus (E′) at 1% and 25% DSA. The following trends were observed: 1. The σ/η values provided a good measure of black-polymer interaction in all four polymer systems for either the within-grade or across-grade comparisons. 2. Higher σ/η values were indicated for SBR and NBR, followed by NR and IIR in that order. 3. SBR indicated the greatest sensitivity for bound-rubber measurements in terms of distinguishing within-grade variations in black-polymer interaction, followed by IIR, NR, and NBR in that order. 4. Positive SIMS on dry carbon black indicates the presence of complex hydrocarbon structures suitable for chemical reactivity at the carbon-black surface. 5. SIMS analyses on the dry carbon blacks exhibited intensity variations in the negative hydrocarbon fragments which were in line with the within-grade variations in hydrogen content. 6. SIMS analyses on the cut-rubber compound surfaces showed overall variations in intensity which were proportional to the range and level of the bound-rubber measurements. The most meaningful variations were recorded for SBR and IIR. 7. Heats of adsorption derived from IGC measurements with different adsorbates showed an excellent correlation with black-polymer interaction for the within-grade studies. Measurements across grades did not correlate as well with the in-rubber measurements, but the best results were obtained using styrene as the adsorbate. 8. The within-grade moisture adsorption measurements showed excellent agreement with IGC and the other techniques for the N121 series of heat-treated carbon blacks.

Assignment of Effective Network Chains in Cured Rubbers Derived from Chemical Crosslinking, Entanglements, Polymer End Linking to Carbon Black and Filler Interaction: VII. Tensile Retraction Measurements

2006 ◽  
Vol 79 (2) ◽  
pp. 338-365
Author(s):  
William L. Hergenrother ◽  
J. D. Ulmer ◽  
Christopher G. Robertson
Keyword(s):  
Carbon Black ◽  
Volume Fraction ◽  
Polymer Network ◽  
Polymer Chains ◽  
Network Chain ◽  
End Groups ◽  
Individual Contributions ◽  
Cross Links ◽  
Effective Network ◽  
The Individual

Abstract The individual contributions to effective network chains from chemical cross-links and from trapped polymer chain entanglements were estimated for gum rubber compounds using Tensile Retraction (TR). In addition, the influences of carbon black and of polymers with functional end-groups, on the character of the polymer network in filled compounds were explored. The effective network chain contributions were established for gum vulcanizates through an entanglement model and an independent estimate of the polymer molecular weight between entanglements, Me. It was found that Me was related closely to the extrapolated γ intercepts obtained from the TR of cured gums. The gum compounds were used to further estimate the effects of fillers and functional end-groups on the total number of effective network chains. Comparing an α,ω-difunctional SBR with its non-functional counterpart enabled the assessment of the effects of functional end-groups. The comparison allowed for the determination of the probability, π, that a functional end group reacts with carbon black. The π was seen to increase as the volume fraction of filler increased, and π2 provided an estimate of the fraction of functional polymer chains that react with carbon black at both ends.

Interaction Between Rubber and Carbon Black Studied by ToF-SIMS

2002 ◽  
Vol 75 (4) ◽  
pp. 627-634 ◽  
Author(s):  
P. Bertrand ◽  
L.-T. Weng ◽  
W. Lauer ◽  
R. Zimmer
Keyword(s):  
Carbon Black ◽  
Thin Layer ◽  
Polymer Chain ◽  
Surface Concentration ◽  
Tof Sims ◽  
Bound Rubber ◽  
Polymer Chain Conformation ◽  
Carbon Black Surface ◽  
Black Surface ◽  
Styrene Butadiene

Abstract In order to study the rubber—carbon black filler interaction, different styrene-butadiene rubbers were adsorbed from solution on carbon black. Afterwards, the samples were washed to keep only the thin layer of bound rubber. The surface of these samples was characterized by ToF-SIMS. It was found that the carbon black surface was completely covered by the polymer, except for pure 1,4-polybutadiene where a non-uniform adsorption was seen. Moreover, the ToF-SIMS data showed that the parameters related to the polymer aromaticity and unsaturation decreased after adsorption. These results indicated a change in polymer chain conformation at the surface upon adsorption on carbon black. This was explained by a preferential interaction between phenyl (and in a weaker manner, 1,2-vinyl) groups with the carbon black surface. Indeed, when these groups tend to orientate toward the filler surface, their surface concentration seen by ToF-SIMS is expected to decrease.

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