Carbon Black-filled Styrene Butadiene Rubber Research Articles

Study of the Mullins Effect in Carbon Black-Filled Styrene–Butadiene Rubber by Atomic Force Microscopy Nanomechanics

Study of the Mullins Effect in Carbon Black-Filled Styrene–Butadiene Rubber by Atomic Force Microscopy Nanomechanics

Experimental identification of fracture toughness of a carbon black-filled styrene butadiene rubber undergoing energy dissipation by Mullins softening

The impact of the loading history on the resistance to break of a carbon-black filled styrene butadiene rubber is explored experimentally. Carbon-black filled rubberlike materials soften significantly upon the first loading due to the well known Mullins effect. The impact of this effect on the critical energy release rate at break, Gc, of the considered material is quantitatively estimated. For this purpose, the classical notched pure shear geometry is considered and the seminal global analysis from Rivlin and Thomas (1953) is adopted. Moreover, the same analysis is extended to non-elastic materials in order to account for the Mullins softening and define the critical energy release rate, Gc∗, characterizing the creation of new crack surfaces without including the energy dissipated by Mullins softening. Both global quantities, Gc and Gc∗, appear decreasing with the increase of softening already undergone by the material, stressing the difficulty of proposing a predictive criterion for the material resistance to failure. Finally, thanks to the local measures of the strain fields on the free surface of the pure shear specimen just before the crack propagation, it has been possible to evaluate the amount of Mullins dissipation upon the crack propagation and to explore the possible existence of an intrinsic value, G0, characterizing the crack propagation independently of any other source of dissipation.

Effect of mineral fillers on physico-mechanical properties and heat conductivity of carbon black-filled SBR/butadiene rubber composite

Heat conductivity, curing rate and fatigue crack growth properties of carbon black-filled styrene butadiene rubber (SBR)/butadiene rubber (BR) blend that is frequently used in passenger car tire treads were simultaneously improved by a hybrid filler system of carbon black, high dispersible precipitated silica, modified layered silicate and ultra-light mixed filler of alumina and aluminum sulfate. An optimum formulation was obtained and a study of mechanisms governing composite properties has been performed according to the filler variables through the designing of experiments and the regression and statistical analysis and with the aid of composite characterization techniques such as dynamic mechanical analysis (DMA) and FE-SEM/EDX. Alumina could improve thermal conductivity, DeMatia crack growth, and the tensile strength of the rubber composite, along with relative maintenance of hardness and modulus. The effects of statistically significant interactions between silica and alumina on the abrasion behavior and thermal conductivity were observed, which was attributed to the presence of the silane coupling agent and the effect of modifying the alumina surface with the ethoxysilanes groups. The partial substitution of carbon black by high dispersible silica resulted in an increase in thermal diffusion coefficient, the improvement of heat buildup, resilience and DeMatia crack growth, and relative maintaining of tensile properties as well as a slight loss in abrasion and aging behavior of the tire tread composite. Through the increase of thermal diffusivity coefficient and a slightly improvement in the aging behavior, modified layered silicate (organoclay) caused a significant reduction in the optimum curing time of the tire tread composite. Some evidence has been provided for the interactions between modified layered silicate and silane coupling agent. The improvement in crack growth and thermal conductivity of the elastomer composite was attributed to smaller interparticle distances of hybrid filler system compared to those of carbon black filler system.

Insights into the Payne Effect of Carbon Black Filled Styrene-butadiene Rubber Compounds

As a widely used reinforcing filler of rubber, carbon black (CB) often enhances the nonlinear Payne effect and its mechanism still remains controversial. We adopt simultaneous measurement of rheological and electrical behaviors for styrene-butadiene rubber (SBR)/CB compounds and CB gel (CBG) during large deformation/recovery to investigate the contribution of conductive CB network evolution to the Payne effect of the compounds. In the highly filled compounds, the frequency dependence of their strain softening behavior is much more remarkable than that of their CB network breakdown during loading, while during unloading the unrecoverable filler network hardly affects the complete recovery of modulus, both revealing that their Payne effect should be dominated by the disentanglement of SBR matrix. Furthermore, the bound rubber adjacent to CB particles can accelerate the reconstruction of continuous CB network and improve the reversibility of Payne effect. This may provide new insights into the effect of filler network, bound rubber, and free rubber on the Payne effect of CB filled SBR compounds.

Effects of tension fatigue on the structure and properties of carbon black filled-SBR and SBR/TPI blends

Abstract The aim of this study was to explore the impact of tension fatigue on the structure and properties of filled SBR and SBR/TPI blends. The effect of tension fatigue on the dynamic properties of carbon black-filled styrene-butadiene rubber (SBR) and SBR/trans-1,4-polyisoprene (SBR/TPI) blend vulcanizates were investigated by dynamic mechanical analysis (DMA). The Mooney-Rivlin analysis of tensile stress-strain data is used for the determination of a rubber network crosslink density. The fatigue fracture surface of SBR/TPI vulcanizates was observed with a scanning electron microscopy (SEM). The crystallinity of TPI in carbon black-filled SBR/TPI (80/20) was characterized by X-ray diffraction (XRD). The results showed that the incorporation of TPI into SBR vulcanizates influences the fatigue properties of the blend vulcanizates. The blend vulcanizates showed optimum fatigue properties with 20 phr TPI. With increasing fatigue cycles, the tensile properties and crosslink density of SBR vulcanizates were decreased substantially. Compared with that of SBR vulcanizates, the tensile properties and crosslink density of SBR/TPI (80/20) blend vulcanizates changed little with the increase in fatigue cycles, and tan δ and E′ decreased gradually with the fatigue cycles. There was a sharp decrease in the E′ and tan δ curve in the temperature range of 40 ~ 60°C. The XRD diffraction peak corresponding to 3.9 Å broadened when the fatigue cycles were increased to 1 million times, and a new peak with inter-planar spacing at 7.6 and 4.7 Å appeared.

A physically-based damage model for soft elastomeric materials with anisotropic Mullins effect

In this paper, we develop a new physically-based damage model to describe the anisotropic Mullins effect of elastomeric materials. The damage model is based on our previous hyperelastic model (Xiang et al., 2018), which has a strain energy density function composed of the crosslinked part and the entangled part. We describe the damage of the crosslinked network using a network alteration theory. Chains along various directions suffer from different degrees of damage and thus cause the anisotropy. The irreversible degradation on constraints for entanglement leads to the reduction of the entangled modulus with the increasing of historical maximal stretch. This model can well capture the stress-softening, anisotropy and residual deformation (permanent set) with only five parameters that have definite physical meanings. It also predicts the damage behaviors under various states of deformation, for both unfilled and filled elastomers. We use the model to fit the experiment data of VHB 4905, silicon rubber, carbon-black filled styrene butadiene rubber (SBR) and carbon-black filled nature rubber (NR). The damage induced anisotropy, which is validated by directional loading experiments of silicon rubber and carbon-black filled NR, can be characterized. We compare this model with other existing similar ones, and show its competitive advantages in characterizing the comprehensive Mullins effect with concise and explicit mathematical expression and physical meaning.

The degree of filler dispersion, rheometric and mechanical properties of carbon black-filled styrene-butadiene rubber composites in the presence of alkanolamide

The degree of filler dispersion, rheometric and mechanical properties of carbon black (CB)-filled styrene-butadiene rubber (SBR) composites in the presence of alkanolamide (ALK) were investigated using a semi-efficient sulphur accelerated vulcanisation system. The ALK was prepared from Refined Bleached Deodorized Palm Stearin and diethanolamine and added into the CB-filled SBR composites at1.0, 3.0, 5.0 and 7.0 parts per hundred rubber (phr). It was found that ALK decreased the scorch time, cure time and minimum torque of the CB-filled SBR composites. The ALK also increased the torque difference, tensile modulus, hardness, resilience and tensile strength; especially up to a 5.0 phr of loading. Due to its plasticising effect, ALK improved the degree of CB dispersion and increased the elongation at break of the CB-filled SBR composites. The crosslink density was increased by improving the degree of CB dispersion and rubber-filler interaction, respectively. The 5.0 phr of ALK was the optimum loading for CB-filled SBR composites which exhibited the highest values in tensile modulus, hardness, resilience and tensile strength.

Non―Gaussian-Type Tube-Based Entropy Model for Elastomeric Networks with Polymer Phase Influenced by Filler Loading: Data Analysis for Lightly to Highly Carbon-Black Filled Styrene-Butadiene Rubber Networks

ABSTRACTRecently the author proposed a new, non-Gaussian, tube-based entropy model for filled elastic networks, characterized by a filler-environmental parameter that was proposed to represent the extent of filler-agglomeration; it was specifically introduced for the polymer phase entropically affected by the presence of very irregularly structured fillers. In this report, the stress-strain relations derived from the above model were used together with the traditional and latest mechanisms of amplification of the strain due to the presence of a filler: namely, literature tensile data for styrene-butadiene rubber networks with a series of carbon-black loadings were systematically analyzed to understand the filler-loading dependence of the above parameter. As a consequence, it is proposed that this parameter is linked, from the static-mechanical standpoint, to a critical filler-loading coupled to the filler-networking. In addition, prior to commencing the examinations of the high-loading networks' tensile data, the data-fitting performance of the underlying elastic molecular model for non-filled networks was also examined using the unfilled and low-loading networks' tensile curves.

A coated inclusion-based homogenization scheme for viscoelastic composites with interphases

A coated inclusion-based homogenization scheme is developed for three-phase viscoelastic composites in the Laplace–Carson domain. The interphase between inclusion and matrix is considered as a coating in a composite-like inclusion and shows altered viscoelastic behavior compared to the matrix. The strain concentration equations between the viscoelastic inclusion and the viscoelastic coating are derived with two different models: the double inclusion (denoted DI) model, and the reconsidered double inclusion (RDI) model. Then, the homogenization scheme is based on a modified Mori–Tanaka scheme for three-phase viscoelastic composites, which is validated with the exact analytical formulation in the case of spherical composite inclusions and isotropic behaviors for all constituents. The comparison of the proposed coated inclusion-based homogenization scheme based on the RDI model with the exact analytical solution shows a significant improvement compared to the one based on the DI model in the prediction of effective properties for composites with interphases. Finally, considering experimental dynamic mechanical analyses (DMA) in the frequency domain for a carbon-black filled styrene butadiene rubber from the literature, the effective viscoelastic behavior is estimated with a good accuracy in terms of the storage and loss moduli for different volume fractions of composite inclusions.

Carbon Black–Filled Styrene Butadiene Rubber Masterbatch Based on Simple Mixing of Latex and Carbon Black Suspension: Preparation and Mechanical Properties

An improved process was developed for the production of carbon black (CB)–filled styrene butadiene rubber masterbatch (SBR-CB-MB) using a simple latex/CB mixing technology; the improvement comprised processing the CB as an emulsifier-free aqueous suspension by high-rate shearing. Tensile and tear strength, dynamic compression behaviors, the Payne effect, equilibrium swelling and bound rubber of the SBR-CB-MB and dry mixing CB filled SBR (SBR-CB-DM), covering a wide range of CB loading (45–70 phr), were investigated and compared. It was found that the tensile and tear strength, heat buildup and compression set, abrasion volume loss, and the Payne effect of the SBR-CB-MB were lower than those of the SBR-CB-DM, while the bound rubber content were higher, indicating good CB/rubber interaction in the SBR-CB-MB. SEM analysis showed that no free CB could be found on the surface or inside of the granular SBR-CB-MB particles, indicating good CB dispersion in the rubber matrix.

Physical interpretation of the Mullins softening in a carbon-black filled SBR

A 40 phr carbon-black filled styrene butadiene rubber has been submitted to several experiments in order to identify the physical damage responsible for the mechanical softening recorded upon first stretch. Damage in the rubber matrix was determined by swelling. The filler structure alteration was monitored by electrical conductivity measurements. Both damages are shown to be of minor importance compared to the substantial mechanical softening undergone by the material. Degradation at the rubber–filler interface may be recovered by exposing the material at high temperatures in vacuo. The chain mobility in such storage conditions promotes free chain adsorption at the filler surface. The existence of a layer of polymer whose movements are hindered adds to the filler reinforcement and its desorption creates Mullins softening.

Failure analysis of carbon black filled styrene butadiene rubber under fatigue loading conditions

The present paper deals with the fatigue crack growth in a carbon black-filled styrene butadiene rubber (CB-SBR) under fully relaxing loading conditions. More precisely, it is devoted to the determination of the scenario of crack growth. For that purpose, an original ‘microcutting’ technique, previously applied by the authors on natural rubber (NR), is used to observe microscopic phenomena involved in fatigue crack growth thanks to scanning electron microscopy (SEM). Results show that the crack tip grows following a tearing line by generating ligaments; it explains the differences between fatigue responses of crystallisable and non-crystallisable rubbers during crack propagation. So, contrary to crystallisable elastomers such as NR, the microstructure of SBR is similar at crack tip and in the bulk material, and the crack tip does not resist crack propagation. Moreover, the morphology of fracture surfaces only depends on particles encountered by the fatigue crack during its propagation.

Nanocavitation in Carbon Black Filled Styrene–Butadiene Rubber under Tension Detected by Real Time Small Angle X-ray Scattering

Nanocavitation was detected for the first time in carbon black filled styrene–butadiene rubber (CB-SBR) under uniaxial loading by real time small-angle X-ray scattering (SAXS) using synchrotron X-ray radiation. A three phase model was developed to calculate the void volume fraction from the scattering invariant Q determined from the observed SAXS patterns. The normalized scattering invariant Q/Q0, where Q0 is the invariant before deformation, greatly increased above a critical extension ratio λonset which we attribute to the formation of nanovoids. Analysis of the 2D scattering patterns show that voids formed are 20–40 nm in size and elongated along the tensile direction. Cavities formed beyond λonset are smaller as λ increases. Results from the scattering experiments are strongly supported by macroscopic volume change measurements on the samples under similar uniaxial strain. A nearly constant nanocavitation stress σonset (25 MPa) was observed when the filler volume fraction ϕCB was larger than 14%. This...

Morphology of ice wear from rubber–ice friction tests and its dependence on temperature and sliding velocity

Friction processes for ice on carbon-black filled styrene butadiene rubber have been investigated by observing wear and debris morphology on wear surfaces using low temperature scanning electron microscopy (LT-SEM) and correlating the features with sliding velocity and temperature. Friction experiments were carried out over a velocity range of 0.003 m s −1 to 2.6 m s −1 and a temperature range of −33 °C to −0.5 °C and the results used to form a friction map. Observation of worn surfaces at high velocity showed melt films that result from frictional heating. At low velocities and low temperatures morphologies indicative of much drier contact were seen. At higher temperatures and low velocity there is evidence of liquid films that we propose arise from the salt content of the ice. High friction ( μ ∼ 1) at low velocity and at temperatures around −25 °C was caused by the internal friction associated with the rubber glass transition.

High-Resolution Solid State NMR Investigation of the Filler-Rubber Interaction: Part III. Investigation on the Structure and Formation Mechanism of Carbon Gel in the Carbon Black-Filled Styrene—Butadiene Rubber

Abstract This investigation describes the elastomer—filler interaction and its formation mechanism using solid state high-resolution, high-speed 1H magic-angle spinning nuclear magnetic resonance (NMR) spectroscopy. Pulsed NMR measurements were carried out on pure styrene-butadiene rubber (SBR), and solvent extracted carbon gels from freshly prepared and storage matured master batches. The effects of filler loading, storage maturation, severity of extraction and experimental temperature on the elastomer-filler interaction were examined and discussed. High resolution in NMR was achieved by higher temperature/low spinning rate, room temperature/high spinning and combined rotation and multiple-pulse spectroscopy (CRAMPS) techniques. High-speed magic-angle spinning (MAS) was found to be the most suitable method to achieve high resolution. Proton spin—spin relaxation time, T2, was measured successfully for each of the principal resonance species present in the samples. These measurements reveal an insight into the site-specific nature of the polymer—filler interaction. The relative immobilization of the dynamics of different protons, due to the presence of carbon black filler, and their temperature dependence evidence that the main chain vinyl proton is the most significantly immobilized one compared to the aromatic and methylene species. The effects of storage maturation and severity of extraction on the dynamics of the conformational jump have also been discussed. This work clearly demonstrates the importance of unsaturation on the bound rubber formation. It also provides first direct physical evidence confirming the hypothesis that bound rubber variation during the storage maturation is due to slow progressive replacement of short rubber chains by larger ones.

Filler-polymer interactions in both silica and carbon black-filled styrene-butadiene rubber compounds

Bound rubber in a filled rubber compound is formed by physical adsorption and chemisorption between the rubber and the filler. Styrene–butadiene rubber (SBR) is composed of four components of styrene, cis-1,4-, trans-1,4-, and 1,2-units. Filler–polymer interactions in both silica and carbon black-filled SBR compounds were studied by analyzing microstructures of the bound rubbers with pyrolysis-gas chromatography. Differences in the filler–polymer interactions of the styrene, cis-1,4-, trans-1,4-, and 1,2-units were investigated. The filler–polymer interactions of the butadiene units were found to be stronger than that of the styrene unit. The interactions of the cis-1,4- and trans-1,4-units were stronger with carbon black than with silica, whereas the 1,2-unit interacted more strongly with silica than with carbon black. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 439–445, 2001

The influence of state-of-mix on the extrudate swell of a carbon black-filled styrene-butadiene rubber compound

The factors which govern the extrudate swell of a styrene–butadiene rubber compound filled with 30 phr of N330 carbon black at various states-of-mix were investigated. The state-of-mix is quantified by an effective filler volume fraction, based on an estimate of the amount of rubber immobilized in the carbon black agglomerates. The swell has been found to be dominated by recoverable strain and relaxation time, which are both controlled by the effective filler volume fraction. In contrast, shear rate, wall slip, and the rubber–carbon black network have not been found to have a significant effect on the extrudate swell. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:305–315, 1997

Relationship between the Cohesive Strength and Tack of Elastomers: Part IV, Carbon Black Filled Styrene-Butadiene Rubber

Abstract The autohesion and cohesion of uncrosslinked SBR (gum and black-filled) have been determined over a broad range of test temperatures and rates using a T-peel geometry. Peeling energies can be time-temperature superposed to form mastercurves using shift factors in accord with the WLF form. Universal constants are appropriate for the gum. While experimental constants were obtained for the black composition. Cohesion for the gum and filled SBR increase continuously with increasing test speed or reduced temperature. On the other hand, autohesion for the gum shows an abrupt transition by decreasing at a critical reduced rate, while autohesion of the filled SBR does not exhibit the transition. The transition is associated with a viscous-to-elastic response change with increasing RaT; filled SBR has reduced elasticity relative to the gum and hence the transition is not present. By examining relative autohesion, it is seen that the gum undergoes an interfacial-cohesive-interfacial transition response with increasing RaT. This is quite different than the behavior found when peeling apart elastomer/hard substrate bonds, such as the SBR/polyester bonds of Gent and Petrich; here, there is simply a cohesive-interfacial transition with increasing RaT. For elastomer-elastomer junctions there is interpenetration and chain mobility in the interphase formed. At sufficiently low RaT, interdiffused chains simply slide by one another giving interfacial failure. With increasing RaT entanglement couplings in the interphase become effective in preventing facile flow, and, at this point, failure becomes cohesive; finally, at even higher RaT, with a sufficiently elastic response, stresses apparently become concentrated at the interface and failure proceeds there. When an elastomer is bonded to a hard, immobile material, the mechanism of bonding is restricted to surface site adsorption. This reduces elastomeric chain mobility and produces more “glassy” dispersive interactions which resist separation relative to the chains which are held together by “rubbery” dispersive forces. Again at sufficiently high RaT, with increased elasticity, failure becomes interfacial.

Differential Dynamic Shear Moduli of Carbon Black-Filled Styrene-Butadiene Rubber Subjected to Large Shear Strain Histories

Abstract Combined measurements of shear-stress relaxation and differential dynamic storage and loss shear moduli G′ and G″ following a single-step shear strain of 0.4, as well as measurements of dynamic moduli in on-off strain and stress histories, have been made on styrene-butadiene rubber (type 1502) filled with carbon black (N299) at loadings of 40, 50, 60, and 70 phr, with 10 phr Sundex 790 oil. Both cured and uncured compounds were studied at temperatures of 25.0° and −0.5°C respectively. The maximum oscillatory shear strain was 0.005, and the frequency was from 0.4 to 1.8 Hz. The storage shear modulus G′(ω, 0) measured without imposition of static strain was approximately proportional to the fourth power of the volume fraction of black. With imposition of single-step strain, the differential storage modulus G′(ω, γ; t) fell 25% to 35% but slowly recovered somewhat while the strain was maintained for 4 to 5 h. During this period, the static stress relaxed continuously. At the highest content of black, the drop in log G′ was the least, and the final recovery was closest to the initial value of G′(ω, 0). In on-off experiments on uncured compounds, when the strain was “on” for 250 s and then “off” (either stress or strain returned to zero), G′ decreased when the strain was imposed as before and decreased further when it was removed. In the “off” state, G′ recovered partially but did not attain the initial value of G′(ω, 0) even after 7 d. In on-off experiments on cured compounds, removal of stress caused G′ to either increase or decrease depending on the content of black; in any case, in the “off” state, G′ recovered completely to its initial value. Other strain histories involved on-off sequences with different “on” periods and multiple on-off sequences with different “on” periods and multiple on-off sequences. The results are interpreted in terms of a network of black particle aggregates whose contacts can slowly rearrange even in the absence of stress as shown by stress relaxation at very small strains in earlier studies. In large strains, it is postulated that some contacts are broken but can partially reform, especially in the stress-free state; the rate of reformation is similar to that of small-strain stress relaxation. Only in cured compounds is the network fully recovered, presumably because in these the particles are imbedded in a crosslinked matrix and have crosslinked bridges that facilitate reestablishment of interparticle contacts, whereas in uncured compounds the matrix has no crosslinks and the bound rubber on adjacent particles may be merely entangled.

Stress Relaxation and Differential Dynamic Modulus of Carbon Black-Filled Styrene-Butadiene Rubber in Large Shearing Deformations

Abstract Combined measurements of shear stress relaxation and differential dynamic storage and loss shear moduli G′ and G″ have been made on styrene-butadiene rubber (type 1502) containing 50 phr N299 carbon black and 10 phr Sundex 790 oil, both cured and uncured, and compared with similar measurements on the cured and uncured gum rubber. The range of temperature was −22.5° to 63°C, and of static shear strain 0.01 to 0.40; the maximum oscillatory shear strain was about 0.005 and the frequency was usually 0.64 Hz. Dynamic measurements of G′ and G″ with no superposed static strain and stress relaxation measurements at small strains on the filled samples could be reduced by frequency-temperature superposition with αT shift factors that were somewhat larger than those that applied to the raw or crosslinked gum. At about 0.6 Hz, the filler increased the storage modulus by about a factor of 5 for the cured sample and about 10 for the uncured; the moduli for the cured and uncured filled samples were almost identical. The order of rates of relaxation was unfilled uncured > filled uncured > filled cured > unfilled cured. At small static strains, the stress relaxation of the filled samples (both uncured and cured) was substantial, but the differential dynamic moduli G′ and G″ remained nearly equal to their values with zero static strain throughout the relaxation process. With increasing static strain γ, the strain-dependent relaxation modulus G(γ;t) decreased by as much as a factor of 3 for the filled, cured sample and 4 for the filled, uncured sample. The modulus G(γ;t) could not be factored into a strain-dependent and a time-dependent function. During stress relaxation of the filled samples (both cured and uncured) at large strains, the differential storage modulus G′(ω,γ;t) experienced a drop followed by slow recovery toward its initial value at 25°C; the loss modulus G″(ω,γ;t) was unchanged. For the filled, cured sample, complete recovery to the initial value G′(ω,0) (where 0 refers to zero static strain) was accomplished by removing the shearing stress and heating for one day at 63° followed by return of the temperature to 25°C. The results are interpreted in terms of a structure which combines a crosslinked (or, in the case of uncured, an entangled) polymer network and a network of carbon black particles. At small strains, stress relaxation is thought to be accomplished primarily by rearrangements of carbon particles and/or polymer molecules bridging them, without structural damage in the sense that the rearranged structure has the same properties as the original. These rearrangements are impeded by crosslinking in the cured vis-a-vis the uncured filled rubber. The kinetics of rearrangement may be governed by configurational changes of the polymer molecules since the temperature shift factors do not differ greatly from those for the gum rubber. At large strains, the particle network can be damaged but can regain its structure by a healing process which is accelerated at higher temperatures. The conclusions apply to the particular compound studied here and not necessarily to other rubber-black compounds, which according to the literature show great diversity of properties.