Carbon Black Filled Rubber Compounds Research Articles

Elongational flow mixing: A novel innovative approach to elaborate high-performance SBR-based elastomer compounds

Abstract A dominant extensional flow mixing device (Reactor/Elongational Flow MiXer; RMX) was used to prepare styrene-butadiene rubber (SBR)/silica nanocomposites with high physical performances. First, the processing parameters such as the temperature, number of mixing cycles, and sequenced mixing protocol have been optimized. Thereafter, the morphological structure of different compounds was probed using scanning and transmission electron microscopy. The prediction of the flow properties during processing of uncured materials were modeled using the dynamic and capillary rheometry. The thermo-mechanical sweep behavior of the as-prepared silica-filled SBR specimens was also investigated. By comparing with SBR/silica compounds prepared by the internal mixer, it was proven that elongational flow mixing process can not only reduce mixing energy consumption but also make the manufactured parts to have high state of dispersion, excellent viscoelastic properties, high extensional and yield stresses, and high elastic and rubbery moduli. This study highlights the potential of the elongational flow mixing as an innovative processing approach which is compatible with the industrial expectations for the fast manufacturing of high-performance silica and carbon black filled rubber compounds.

Reduction of filler-filler interaction and hysteresis loss of carbon black filled rubber compound by using modified carbon Black

The carbon black, used in rubber compound as reinforcing filler, improves the strength, durability, and wear resistance of the rubber compound. However, it causes filler-filler interaction and results in extensive hysteresis energy losses on deformation. This research aims to reduce hysteresis energy loss of rubber compound by reducing filler-filler interaction and by improving the filler dispersion in rubber matrix. In this study, the effect of carbon black treated with benzyl tri-ethyl ammonium chloride (BTEAC) on solution styrene butadiene rubber and butadiene rubber (SSBR-BR) system was studied. Microscopic study of dispersion and distribution of carbon black in rubber matrix was performed and a significant improvement in dispersion of BTEAC treated carbon black in SSBR-BR rubber matrix was observed. As a result of increased interaction of BTEAC treated carbon black with rubber, the filler - filler interaction was significantly reduced, resulting lower hysteresis energy loss of the compound as expressed by loss tangent (tanδ) value and it has been observed that an extent of around 15% reduction in tanδ value was achieved in rubber compound consisting of BTEAC treated carbon black. In this research, the carbon black was treated with different concentration of BTEAC, such as 0.5%, 1% and 1.5% and the best balance of rubber properties was observed for 1% and 1.5% BTEAC treated carbon black.

Enhancement of the properties of carbon-black-filled natural rubber compounds containing soybean oil cured with peroxide through the addition of coagents

Due to the hazard of the commercial rubber processing oil such as distillate aromatic extract (DAE), many rubber researchers play attention to find the green alternatives. Vegetable oils seem to gain a lot of attraction for this. It is not just only due to their environmentally friendly nature but also their abundance and affordable cost. The use of soybean oil (SBO) for the carbon black-filled rubber compounds was focused here and comparatively discussed with the use of DAE. Furthermore, this work also proposed the way to improve the mechanical properties and environmental endurance of the rubber compounds containing SBO by adding coagents. There were two types of coagent including trimethylolpropane trimethacrylate (TMPTMA) and triallyl isocyanurate (TAIC) used here. It was found that the cure time, cure rate index, and cure reaction rate constant of SBO-added rubber compounds with and without coagents were higher than those of DAE-added rubber compounds, whereas the activation energy of SBO-added rubber compounds was lower than the one with DAE. Without coagent, the mechanical properties of rubber compounds with DAE and SBO are equal. However, the addition of coagents improved the mechanical properties of rubber compounds containing SBO. The modulus at 100% strain, modulus at 200% strain, and tensile strength of TMPTMA-added rubber compounds increased by 41%, 48%, and 15%, respectively, whereas the rubber compounds with TAIC increased by 7%, 8%, and 20%, respectively, when compared to the one with SBO alone. Interesting, the SBO-added rubber compounds with and without coagents showed better thermal aging and ozone resistances than the DAE-added rubber compounds. All results showed that the presence of coagents especially TMPTMA gave the SBO-added rubber compound with the superior performance to the DAE-added rubber compound and the SBO-added rubber compound without coagent.

Screening of mixing parameters based on their significance on the extent of silanization and energy consumption of silica‐filled S‐SBR elastomer compounds for fuel‐saving tyre application

AbstractIncreasingly stringent in demand for a fuel‐saving tyre with low rolling resistance, the application of silica filler is governing the tyre industry day by day. Unlike carbon black filled rubber compound, silica compound is rather complicated as it demands, a reactive mixing where, mixing parameters of internal mixer play a vital role in the degree of silanization reaction. In this paper, a design of experiments (DOE) is carried out to screen the factors that significantly affect the silanization reaction during mixing. Taguchi method with L18 orthogonal array is employed to determine the significance of mixing parameters on the degree of silanization reaction. To quantify the significance of each mixing parameter on silanization, such as mixing temperature, mixing time, fill factor, feed door condition, ram pressure, and temperature control unit of Banbury mixer are explored. Key properties like Tan δ at 60°C, reinforcement index, and Payne effect (∆G') are considered responses for the DOE. It was observed that the silanization temperature and time were the most influencing factor in silanization using the contribution plot. In contrast, ram pressure and feed door condition have the least significance on the degree of silanization.

Development of a New Model Based on Ogden-Roxburgh Model for the Prediction of the Stress-Softening Behavior of Carbon Black-Filled Rubber Compounds

Development of a New Model Based on Ogden-Roxburgh Model for the Prediction of the Stress-Softening Behavior of Carbon Black-Filled Rubber Compounds

A Self-Healing System Based on Ester Crosslinks for Carbon Black-Filled Rubber Compounds

Carbon black-reinforced rubber compounds based on the blends of natural rubber (NR) and butadiene rubber (BR) for tire sidewall applications were formulated to investigate the self-healing efficacy of a modifier called EMZ. This modifier is based on epoxidized natural rubber (ENR) modified with hydrolyzed maleic anhydride (HMA) as the ester crosslinking agent plus zinc acetate dihydrate (ZAD) as the transesterification catalyst. The influence of EMZ modifier content in sidewall compounds on processing characteristics, reinforcement, mechanical and fatigue properties, as well as property retentions, was investigated. Increasing the content of EMZ, the dump temperatures and Mooney viscosities of the compounds slightly increase, attributed to the presence of extra polymer networks and filler–rubber interactions. The bound rubber content and Payne effect show a good correction that essentially supports that the EMZ modifier gives enhanced filler–rubber interaction and reduced filler–filler interaction, reflecting the improved homogeneity of the composites. This is the key contribution to a better flex cracking resistance and a high fatigue-to-failure resistance when utilizing the EMZ modifier. To validate the property retentions, molecular damages were introduced to vulcanizates using a tensile stress–strain cyclic test following the Mullins effect concept. The property retentions are significantly enhanced with increasing EMZ content because the EMZ self-healing modifier provides reversible or dynamic ester linkages that potentially enable a bond-interchange mechanism of the crosslinks, leading to the intermolecular reparation of the rubber network.

Understanding fracture of a carbon black filled rubber compound using material force theory

This paper is based on the determination of important fracture parameters for commercially important rubber blends through experimental and finite element modeling methods. Properties of NR/BR blends, which are mainly suitable for tire applications, of various compositions have been tested under tensile load and the result is utilized to determine the suitable hyperelastic material model. A model proposed by Yeoh has been found to be more relevant to the test materials and is used to represent them in simulation. Single Edge Notched Tensile samples (SENT) are ued for the fracture analysis. The samples are tested for uniaxial Mode I fracture (Tensile), which is the most commonly observed among the three modes of fracture, and crack growth was studied using the Virtual Crack Closure Technique (VCCT). A finite-element replica of the test specimen has been created using in-house code, which uses an implicit mesh adaptive method to study the strain potential around the crack tip. The code for each specimen is executed using the commercially available third-party software ANSYS Parametric Design Language (APDL). The stress–strain behaviors from experimental and simulation responses were compared. The energy release rate otherwise known as tearing energy has been derived for both experimental and numerical tests.

Contraction and capillary flow of a carbon black filled rubber compound

Highly filled rubber compounds exhibit a unique rheological behavior, which is affected by its filler–filler and filler–matrix interactions leading to pronounced nonlinear viscoelasticity. The necessity to consider these characteristics in rheological testing and modeling, adds further complexity providing universally valid numerical descriptions. In the present study, the pressure driven contraction and capillary flow of a carbon black filled hydrogenated acrylonitrile–butadiene rubber compound is studied both experimentally and numerically. Rheological testing indicates no pronounced slippage at the wall but a shear sensitive plug flow at the centerline. The viscoelastic Kaye‐Bernstein–Kearsley–Zapas/Wagner, the viscoplastic Herschel–Bulkley and the viscous power‐law models are used in computational fluid dynamic simulations aiming to predict measured pressure drops in an orifice and various capillary dies. Viscoelastic modeling is found of particular importance describing contraction flow dominated areas, whereas viscous models are able to predict pressure drops of capillary flows well. POLYM. ENG. SCI., 60:32–43, 2020. © 2019 The Authors. Polymer Engineering & Science published by Wiley Periodicals, Inc. on behalf of Society of Plastics Engineers.

RUBBER BLEND AND FILLER EFFECTS ON DAMAGE MECHANISMS UNDER MONOTONIC AND FATIGUE LOADING

ABSTRACT To appreciate the nature and failure mode of elastomers, it is important to understand their fracture behavior. There are various factors that influence the fracture characteristics of rubber vulcanizates, namely, temperature, strain rate, and type of loading. In this research, fracture behavior of gum and carbon black filled rubber compounds having 100 parts natural rubber (NR), polybutadiene rubber (BR), and 60–40 NR/BR blend is reported. The effect of strain rate, temperature, and carbon black on tensile strength, fracture/tearing energy, and crack growth is detailed. Based on our investigation, we have determined BR to be more sensitive to temperature change than NR. Also, contrasting behavior is observed for gum and filled polymer blends. Tensile and fatigue tests were performed on a universal testing machine and tear and fatigue analyzer, respectively. The tested samples were also examined in the scanning electron microscope to obtain high-resolution imaging of fracture surfaces. The samples tested under monotonic loading provide smoother surfaces by showing the phase separation in comparison with fatigue loading.

Development of a new combined numerical/experimental approach for the modeling of the nonlinear hyper-viscoelastic behavior of highly carbon black filled rubber compound

In this work, a new approach was developed for the determination of the parameters of a complex constitutive model for a highly filled rubber compound. A SSBR sulfur-vulcanized rubber sheet reinforced by carbon black was prepared. Three test specimens in the form of two rubber strips and dumbbell were cut from it. The Arruda-Boyce equation was selected to describe the hyperelastic behavior of the rubber. A parallel rheological framework (PRF) model and a new equation using a sigmoid function were selected to describe the nonlinear viscoelastic and stress softening effects. The model parameters were determined via a novel methodology based on the solution of the inverse problem comprising of the finite element models of the tests. Two multi-objective optimization loops based on the Nelder–Mead simplex method were designed. The accuracy of the predicted parameters was checked via the comparison of the model predictions with their corresponding data obtained from uniaxial and stress relaxation tests. A thorough analysis was made on the predicted results.

CRACK GROWTH BEHAVIOR OF STYRENE-BUTADIENE RUBBER, NATURAL RUBBER, AND POLYBUTADIENE RUBBER COMPOUNDS: COMPARISON OF PURE-SHEAR VERSUS STRIP TENSILE TEST

ABSTRACT Fatigue crack growth experiments on different carbon black–filled rubber compounds have been carried out to evaluate the influence of pure-shear and strip tensile testing mode by using sine and pulse as waveforms. In a previous set of experimental investigations regarding the influence of both waveform and tested material, it was found that the mode I of crack opening sometimes propagates too quickly to be properly monitored in tests involving strip-tensile specimens. An alternative test methodology based on pure-shear test mode has been investigated, optimizing both the shape of the specimen and the test equipment. Data obtained from the different compound formulations were consistent with the theoretical background and resulted in similar ranking of compound crack growth resistance for the two testing modes; in addition, pure-shear mode showed a higher sensitivity to formula variations.

Viscoelastic properties of short aramid fibers‐reinforced rubbers

AbstractAmong short fiber‐reinforced composites, those with rubber matrices have gained great importance due to the advantages they have in processing and low cost, coupled with high strength. These composites combine the elastic behavior of rubbers with strength and stiffness of fibers. Reinforcement with short fibers offers attractive features such as design flexibility, high modulus, tear strength, etc. The degree of reinforcement depends upon many factors such as: the nature of the rubber matrix, the type of fiber, the concentration and orientation of the fibers, the fiber to rubber adhesion and fiber length. One of the main features related to this class of composites is their hysteretic properties which are of great importance especially in dynamic applications such as tire treads. In this research, short aramid fibers with different kinds of surface treatments: Standard finish and resorcinol formaldehyde latex (RFL)‐coating, have been applied in two different carbon black filled rubber compounds based on natural rubber (NR) and ethylene propylene diene rubber (EPDM). The dynamic properties of the compounds have been measured as influenced by the different kinds of fiber treatments on rubber‐fiber interaction. Finally, the contribution of the interfaces and/or interphase layers to the loss properties is characterized. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2013

Simplified modeling calculations to enlighten the mechanical properties (modulus) of carbon black filled diene rubber compounds

AbstractA simplified model is developed to calculate the modulus of carbon black filled rubber compounds by using standard characterization data of the filler, its volume fraction and only one fitting parameter: the number of junctions between neighboring carbon black aggregates. The model is based on three hypotheses with respect to (1) the optimal dispersion of aggregate, (2) the pure physical nature of rubber—carbon black interactions, and (3) the possibility to describe aggregates essentially in terms of specific surface area and structure, both accessible through standard characterization methods. Average rubber—filler interactions are introduced through micromechanical considerations. The model is probed by using dynamic strain sweep test results on two series of carbon filled compounds, one on the basis of SBR1500 Emulsion Styrene‐Butadiene Rubber, the other on RSS3 Natural Rubber. It is found that the number of junctions is decreasing with increasing strain amplitude, thus, offering a clear explanation for the well known dynamic strain softening effect. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

COMPARISON OF SINE VERSUS PULSE WAVEFORM EFFECTS ON FATIGUE CRACK GROWTH BEHAVIOR OF NR, SBR, AND BR COMPOUNDS

Abstract Fatigue crack growth experiments on carbon black-filled rubber compounds have been carried out to evaluate the influence of testing conditions over different compound formulations. Investigations on the influence of waveform, data acquisition, and compound formulation have been performed on strip-tensile specimens reproducing the mode I of crack opening. The response of three different compound formulations (based on either natural rubber, butadiene rubber, or styrene-butadiene rubber) to the application of two different waveforms, pulse and sine, has been analyzed, showing significant differences in fatigue behavior and ranking of the various compounds. Compared to the sinusoidal waveform, the use of a pulse waveform provided an improved correlation of the tearing energy with the crack propagation speed. This difference was particularly evident in the case of natural rubber and butadiene rubber, while it resulted negligible in the case of styrene-butadiene rubber. Such a different behavior could be attributed to differences in macromolecular chains orientation. Fine-tuning of video acquisition parameters provided an accurate observation of the crack growth process, as confirmed by the low standard deviation of the estimated tearing energy and crack growth rate.

A Comparative Study on the Reinforcing Effect of Aramide and PET Short Fibers in a Natural Rubber-Based Composite

Four types of chopped fibers have been studied as reinforcement additives in a standard natural rubber based, carbon black filled formulation. The fibers studied were aramide (2 types) and polyester (2 types). The chopped fibers were added on top of the carbon black filled rubber compound at 2, 4, and 8 phr levels. The extra reinforcing effect in the modulus, especially at low elongation, the increase in hardness, the anisotropic properties, and the stiffening effects have been studied together with the evaluation of the mechanical hysteresis in strain and in compression. The permanent set of the resulting rubber compounds have been evaluated as well. The best compromise in performances and price was found for a certain type of polyester fiber.

Modelling of frequency- and amplitude-dependent material properties of filler-reinforced rubber

Filler-reinforced elastomers are extremely complicated materials with pronounced deformation and temperature history-dependent material properties. In the current paper, the dynamic material behaviour is investigated and modelled. To this end, a carbon black-filled rubber compound is loaded with harmonic deformations under different frequencies and amplitudes and the stationary stress response is evaluated in terms of the storage and the loss modulus or, equivalently, in terms of the dynamic modulus and the loss angle. In this essay, detailed experimental investigations of the dynamic material properties of carbon black-filled elastomers are provided and a new three-dimensional constitutive approach of finite nonlinear viscoelasticity to represent the observed material behaviour is developed.

A Nonlinear Rubber Material Model Combining Fractional Order Viscoelasticity and Amplitude Dependent Effects

A nonlinear rubber material model is presented, where influences of frequency and dynamic amplitude are taken into account through fractional order viscoelasticity and plasticity, respectively. The problem of simultaneously modeling elastic, viscoelastic, and friction contributions is removed by additively splitting them. Due to the fractional order representation mainly, the number of parameters of the model remains low, rendering an easy fitting of the values from tests on material samples. The proposed model is implemented in a general-purpose finite element (FE) code. Since commercial FE codes do not contain any suitable constitutive model that represents the full dynamic behavior of rubber compounds (including frequency and amplitude dependent effects), a simple approach is used based on the idea of adding stress contributions from simple constitutive models: a mesh overlay technique, whose basic idea is to create a different FE model for each material definition (fractional derivative viscoelastic and elastoplastic), all with identical meshes but with different material definition, and sharing the same nodes. Fractional-derivative viscoelasticity is implemented through user routines and the algorithm for that purpose is described, while available von Mises’ elastoplastic models are adopted to take rate-independent effects into account. Satisfactory results are obtained when comparing the model results with tests carried out in two rubber bushings at a frequency range up to 500 Hz, showing the ability of the material model to accurately describe the complex dynamic behavior of carbon-black filled rubber compounds.

Filler Phase Distribution in Rubber Blends Characterized by Thermogravimetric Analysis of the Rubber-Filler Gel

Abstract The analysis of the rubber-filler gel of carbon black filled rubber compounds and blends provides useful information about the mixing process taking place inside the internal mixer. A new measure technique named wetting rate was introduced to describe the wetting behavior of the rubber onto the filler. Natural rubber (NR)/styrene-butadiene rubber (SBR) blends has been used for experimental investigation. NR shows a significantly higher wetting rate than SBR. The wetting rate does not only depend on the viscosity of rubber but strongly on the functionalization of it. Using the data determined from the thermogravimetric analysis (TGA) of rubber-filler gel, a new method was developed to characterize the kinetics of carbon black (CB) localization in the phases of heterogeneous rubber blends. During the first mixing stage, the CB localization is affected strongly by the wetting rate ratio of the blend components. In the second mixing stage, the rubber-filler interaction dominantly influences the distribution kinetics of the filler to the phases. Because of the higher wetting rate of the NR component, in the investigated NR/SBR blends more CB is found in the NR phase than in the SBR phase. The effect of the matrix viscosity and polarity on the phase specific CB distribution was systematically investigated.

Radiation-Cured Nanocomposites Based on Diene Rubber and Nanoclay

SBR/BR-based rubber nanocomposites filled with carbon black (65 phr) and nanoclay (1 and 3 phr) were radiation-cured at 100, 200, 389 and 800 kGy from a 60Co γ radiation source and tested against a reference compound without nanoclay. For reference the same compounds where also sulfur cured. The nanoclay consisted of a layered silicate, a montmorillonite, treated with an alkylammonium salt. The nanoclay was added on top to a conventional carbon black-filled rubber compound during the first masterbatch preparation. The spectacular reinforcement effect derived from the nanoclay addition to the composite has been observed both in the radiation-cured compounds and in the sulfur-cured compound. Although the sulfur-cured composite show a reduction in hysteresis after the nanoclay addition, the radiation-cured compounds show an opposite trend.

Characterisation of carbon black filled rubber compounds by the Microwave Coaxial Method

Abstract The open-ended Coaxial Line Resonator Microwave method is employed for the characterisation of rubber compounds of different concentration and activity of carbon black filler. The method is sensitive to both the concentration and activity of carbon black. There is evidence that it also detects small changes of dielectric parameters during vulcanisation. The method is also effective for the study and testing of the inhomogeneities of rubber compounds. As for its sensitivity and reliability in combination with simplicity, the method can be recommended for practical use in research and development, as well as in the production of rubber compounds and generally for filled polymers.