Silica Rubber Research Articles

Study of Styrene Butadiene Rubber Reinforced by Polybutadiene Liquid Rubber-Modified Silica.

The dispersion of silica in rubber systems and its interaction with rubber are two key factors in the preparation of rubber composites with excellent properties. In view of this, silica modified with terminal isocyanate-based polybutadiene liquid rubber (ITPB) is used to improve the dispersion effect of silica in rubber and enhance its interaction with the rubber matrix to improve the rubber's performance. The impact of different modification conditions on the dispersion of silica and the properties of modified silica-filled rubber composites were studied by changing the amount of ITPB and the modification method of silica, including blending and chemical grafting. The experimental results show that ITPB is successfully grafted onto silica, and the use of modified silica improves the cross-linking density of rubber, promotes the rate of rubber vulcanization, and overcomes the shortcomings of the delayed vulcanization of silica itself. When the ratio of ITPB liquid rubber to silica equals 1:20, the comprehensive performance of rubber is the best, the ITPB-modified silica has a better dispersion effect in rubber, and the rolling resistance is slightly improved, with tensile strength reaching 12.6 MPa. The material demonstrates excellent overall performance and holds promise for applications in the rail, automotive, and electrical fields.

A novel in-situ dynamic mechanical analysis for human plantar soft tissue: The device design, definition of characteristics, test protocol, and preliminary results

The in-situ mechanical characterization of elastomers is not highly regarded due to the existence of a well-established set of sample-based standard tests for research and industry. However, there are certain situations or materials, like biological soft tissue, where an in-situ approach is necessary due to the impossibility of sampling from a living body. We have developed a dynamic mechanical analysis (DMA)-like device to approach in-vivo and in-situ multidimensional stress-strain properties of human plantar soft tissues. This work elucidates the operational mechanism of the novel measurement, with the definition of a new set of moduli, test standardization and protocol. Exploratory results of a volunteer's living plantar, silica rubber samples are presented with well preciseness and consistence as expected.

The Effect of Composition and Type of Metal Filler on Heat Resistance of Silica Rubber Matric Composites

Thermal Tensioning is one of the methods use to minimise the occurrence of residual stress and unwanted distorsion during welding. One of the thermal tensioning methods is Static Thermal Tensioning (STT), which involves countering thermal stress during welding. The STT method requires an active cooling behind the welding line. Several properties are required for the coolant material, such as thermal conductivity, heat resistance, and good flexibility. To achieve the desired properties, a mixture of different materials was used, commonly called a composite. The purpose of this study is to know the effect of filler metal composition and type on the heat resistance of silica rubber matric composites. This study used 2 independent variables: the filler composition in composites with variations of K1 (60%) and K2 (70%), and the type of filler metal, aluminium and copper powder with variation J1 (100%-0%), J2 (75%-25%), J3 (50%-50%), J4 (25%-75%), and J5 (0-100%). The testing process used Thermogravimetry Analysis (TGA) method with replication 2 times. The results of this study showed the specimens with K1;J1 composition,containing 60% pure aluminium filler metal, showed the best heat resistance with a final weight of 88,25%. While specimens with K2;J5 composition, containing 70% pure copper filler metal, showed the worst heat resistance with a final weight of 74,25%.

Durability Assessment of Sustainable Mortar by Incorporating the Combination of Solid Wastes: An Experimental Study

The excessive mining of high-quality river sand for cement sand mortar resulted in environmental impacts and ecological imbalances. The present study aims to produce sustainable mortar by combining solid waste such as desert sand, stone dust, and crumb rubber to fully replace river sand. In addition, replacing cement with silica fume helps reduce the environmental carbon footprint. The present research prepared three types of mortar mixes: natural dune sand mortar (M1), natural dune sand stone dust crumb rubber mortar (M2), and natural dune sand stone dust crumb rubber silica fume mortar (M3). The developed mortar samples were examined at ambient and elevated temperatures of 100°C, 200°C, and 300°C for 120 minutes. Furthermore, 3 cycles of 12 hours each at freezing temperature (-10° ± 2°C) and crushed ice cooling (0° to -5°C) were also tested. Results of the study showed an increment in compressive strength values in M1, M2, and M3 mortar mixes (up to 200°C). Later, an abrupt drop in the compressive strength was noticed at 300°C in all mixes M1, M2, and M3, respectively. The mix M3 combinations resist heating impacts and perform significantly better than other mixes M1 and M2. Also, M3 combinations resist the cooling effect better than M1 and M2. It can be concluded that the mortar mix M3 with desert sand, stone dust, crumb rubber, and silica fume combination is considered the best mix for both heating and cooling resistance. Hence, the developed sustainable mortar M3 combination can be utilized in all adverse weather conditions. Doi: 10.28991/CEJ-2023-09-11-09 Full Text: PDF

GLYCIDYL METHACRYLATE AS A NON-SILANE MODIFIER IN RUBBER/SILICA COMPOSITES

ABSTRACT Glycidyl methacrylate (GMA) was grafted onto styrene butadiene rubber (SBR) and silica by a solution grafting process. Successful grafting onto rubber and silica was confirmed by Fourier-transform infrared (FTIR) spectrometry, with the peaks at 1149, 842, and 1729 cm−1 attributed to the C–O stretching, the epoxy group, and the C=O stretching vibration of the GMA monomer, respectively. After grafting onto the silica surface, the peak at 842 cm−1 in the spectra disappeared, confirming the grafting reaction through the epoxy group. Grafting onto SBR was also confirmed by proton nuclear magnetic resonance (1H NMR) spectroscopy, and the SBR-GMA interaction was shown using two-dimensional 1H NMR spectroscopy. The grafted products were further characterized by thermogravimetric analysis (TGA) and differencial scanning calorimetry. Grafting density and grafting weight percentage of GMA-grafted silica were calculated using TGA: 10 and 20% GMA-grafted SBR and 20% GMA-grafted silica compounds and their vulcanizates were prepared. Rubber–silica interaction through grafted GMA was shown using FTIR spectroscopy for both types of vulcanizates. Dispersion of pristine and GMA-modified silica onto the SBR matrix was quantified using scanning electron microscopy and atomic force microscopy. Mechanical and dynamic mechanical properties of these GMA-modified vulcanizates were studied and compared with those of previously reported 3-octanoylthio-1-propyltriethoxysilane–modified vulcanizates. The effect of the state of dispersion of silica onto the physico-mechanical properties of the vulcanizates was investigated. The properties of the non-silane–modified systems were comparable with, and in some cases superior to, that of the new mercapto silane-modified systems in the energy-efficient tire application.

Based on mussel-inspired modified BN fillers and their application in thermally conductive silica rubber

Nowadays, with electronics becoming more refined and integrated, the heat transfer problem between devices is becoming increasingly problematic, so thermal interface materials with good thermal conductivity are becoming more critical. In this paper, thermally conductive composites are prepared based on silicone rubber (SR), and boron nitride coated with tannic acid and grafted with hexamethyldisilazane ([email protected]). After modification with TA-HMDS, [email protected] and silicone rubber has excellent compatibility and can be well dispersed within the silicone rubber matrix. It can be found that when the mass part1 of [email protected] is 50, the thermal conductivity of the composites reaches 0.735 W/m·K, which is about 6 times that of pure SR. In addition, the viscosity of the composite before cured is significantly reduced. When the mass part of [email protected] is 50, the system's viscosity is only 1/50 of the BN/SR at the same ratio. This work provides a good guideline for the mass filling to build a better thermal pathway to improve the material's thermal conductivity.

Highly adhesive chitosan/poly(vinyl alcohol) hydrogels via the synergy of phytic acid and boric acid and their application as highly sensitive and widely linear strain sensors.

In recent years, flexible strain sensors have attracted increasing interest, and accurate sensing and comfortable wearables are highly demanded. However, current flexible strain sensors fail to have wide linearity and high sensitivity simultaneously, and their adhesion is insufficient for convenient wear and precise motion monitoring. Herein, chitosan/poly(vinyl alcohol) hydrogels with phytic acid (PA) and boric acid (BA) as crosslinkers (CS/PVA-PA-BA hydrogels) were fabricated. The synergy of phytic acid and boric acid not only improved the mechanical properties of the obtained hydrogels (1070% of fracture strain and 0.83 MPa of fracture stress), but also provided them with outstandingly strong adhesion. Their adhesive strength was up to 527 kPa for a variety of materials, including glass, silica rubber, steel, polytetrafluoroethylene (PTFE), and skin. In addition, the hydrogel-based strain sensor demonstrated high sensitivity (gauge factor = 4.61), a wide linear strain range (up to 1000%, R2 = 0.996), fast response time (90 ms), and good stability. A flexible strain sensor with such high sensitivity and wide linear range simultaneously, to the best of our knowledge, has never been reported before. The development of CS/PVA-PA-BA hydrogels is expected to inspire a novel method for high-adhesive and high-sensing-performance wearable electronics.

Effect of Activation Modes on the Property Characterization of Crumb Rubber Powder from Waste Tires and Performance Analysis of Activated Rubber-Modified Asphalt Binder.

The rubber molecular chain in waste vulcanized tire rubber will be crosslinked to form a network structure that would be difficult to degrade in asphalt. Crumb rubber treated by desulfurization activation could form active groups on the surface by interrupting the crosslinking bond to improve the compatibility between crumb rubber powder and asphalt. To explore the influence of activation modes on crumb rubber powder and the corresponding rubber-modified asphalt binder, crumb rubber powder was firstly activated through three commonly used activation methods and asphalt binder samples modified by activated crumb rubber powder were also prepared. The basic properties of activated crumb rubber powder were characterized by infrared spectroscopy, and conventional tests were used to study the conventional physical properties of the asphalt binder. The infrared spectroscopy and elemental analysis showed that the crumb rubber powder was mainly composed of alkanes, alkenes, sulfonic acids, aromatics, and a little silica rubber and antioxidant zinc oxide, which is suitable for asphalt modification. The simple heat activation treatment method is not enough to greatly destroy the cross-linking structure of crumb rubber powder, but the “C=C” bond was destroyed more seriously. Under the action of adjuvants, the polysulfide cross-linking bond could be broken in crumb rubber powder. The heat treatment and chemical treatment could not achieve the purpose of reducing the viscosity and improving the compatibility of rubber asphalt binder through desulfurization activation. The mechanochemical treatment would help to improve the performance of crumb-rubber-powder-modified asphalt binder. The data correlation analysis based on the grey relational degree can provide a reference for the selection of activated crumb rubber powder for different application requirements in the asphalt modification procedure.

Dual-Silane Premodified Silica Nanoparticles-Synthesis and Interplay between Chemical, Mechanical, and Curing Properties of Silica-Rubber Nanocomposites: Application to Tire Tread Compounds.

In silica–rubber based nanocomposites, a single organo-silicon is often used to compatibilize and covalently link silica to rubber. In this work, we have investigated the impact, at micro- and macroscales, of the decoupling of the hydrophobization and the coupling activity of silane by pretreating silica with two different silane chemistries. The first one, a mercaptosilane, is the coupling agent that promotes a covalent link between silica and rubber during the sulfur-mediated vulcanization reaction. The second one, an alkylsilane, aims to improve the silica dispersion. For both kind of silanes, we have varied the chain length and studied at macroscale the dynamic mechanical properties through the key indicators that are E′′ as loss modulus, E′ as storage modulus, and their respective ratio tan δ. The shorter silanes combination yielded an improvement in terms of wet grip indicators with tan δ at 0 °C increasing from 0.205 to 0.237 while maintaining rolling resistance indicators at the same level. We have evaluated the impact of the silane chemistry onto the cross-linking reactivity within the fabricated rubber-based nanocomposites by using moving-dye rheometer measurements (MDR). By purposely using atomic force microscopy (AFM), we have studied the silica dispersion in the matrix and the rubber/silica interface and provided the rationale explanation of the mechanical properties observed at the macroscale. AFM observation pointed out the existence of a soft interface around silica fillers when long alkylsilanes were used. We infer that this interface impacts the polymer–filler dynamic and subsequently affects the mechanical properties of the composite material.

Rubber Rail Pad Reinforced by Modified Silica Using GPTMS and Sulfenamide Accelerator

The interaction between silica and rubber is very important for the production of high performance rubber. Silica surface modification with silane is a general method that aims to enhance the reinforcement efficiency of silica. In this study, a new surface modification of silica with silane and the chemical reaction with sulfenamide accelerator were investigated. The (gamma-glycidoxypropyl) trimethoxysilane (GPTMS) was used as a silane. The N-cyclohexyl-2-benzothiazole sulfenamide (CBS) and N-tert-butyl-2-benzothiazole sulfenamide (TBBS) were used as sulfenamide accelerators. The FTIR spectra results indicate that the GPTMS and sulfenamide accelerators (CBS and TBBS) could successfully form on the silica surface. The new modification is capable of significantly enhancing the reinforcement efficiency; more than the conventional silica surface modification by GPTMS (m-silica). In particular, modifying silica with GPTMS and TBBS (m-silica-TBBS) is capable of increasing the crosslink density and mechanical properties more efficiently than modified silica with GPTMS and CBS (m-silica-CBS), m-silica, silica (unmodified), and unfilled natural rubber. This is due to the presence of GPTMS, which plays an important role in increasing the chemical cross-linking in the rubber chain, while TBBS, as a sulfenamide accelerator, provides a high accelerator to sulfur ratio, which is able to give a more efficient vulcanization. With the reinforcement of a rubber rail pad with silica surface modification, the results indicate that the increment of m-silica-TBBS loading could reduce the deformation percentage of the rubber rail pad more than m-silica and m-silica loading. This is mainly due to the static spring improvement, which results in a stiffer material.

Effect of rubber reinforcement with filler on extrusion flow and extrudate swell

Abstract The extrusion process of silica rubber through a chemical reaction is unstable, and the flow mechanism in the extruder is still unclear. In this study, styrene-butadiene rubber (SBR) has been chosen as the matrix and the reinforcing effects of two different kinds of fillers, silica and titanium dioxide, have been investigated on SBR. Additionally, the effect of the properties of the SBR/filler composites on extrudate swelling has been examined. The reinforcing effect of the filler was confirmed by dynamic viscoelasticity, and the swell ratio was measured using a capillary rheometer. The results suggest that titanium dioxide has no reinforcing effect, as there is no interaction between titanium dioxide and the molecular structure of SBR. In contrast, there was a significant interaction between silica and SBR. It was found that the bound rubber, which is an SBR gel with restricted molecular chains, causes a reduction in the swell ratio, and this reduction effect is larger than that caused by filling the filler in the matrix. Furthermore, it was observed that this bound rubber deforms during flow and affects the extrudate swell phenomenon.

Preparation of Natural Rubber Composites with High Silica Contents Using a Wet Mixing Process.

A wet mixing process is proposed for filled rubber composites with a high silica loading to overcome the drawbacks of high energy consumption and workplace contamination of the conventional dry mixing process. Ball milling was adopted for preparing the silica dispersion because it has a simple structure, is easy to operate, and is a low-cost process that can be easily scaled up for industrial production. The response surface methodology was used to optimize the making of the silica dispersion. The optimum conditions for a well-dispersed silica suspension with the smallest silica particle size of 4.9 mm were an about 22% silica content and 62 h of ball milling. The effects of dry and wet mixing methods on the properties of silica-filled rubber composites were investigated in a broad range of silica levels from low to high loadings. The mixing method choice had little impact on the properties of rubber composites with low silica loadings. The silica-filled rubber demonstrated in this study, however, shows superior characteristics over the rubber composite prepared with conventional dry mixing, particularly with high silica loadings. When compared to silica-filled natural rubbers prepared by dry mixing (dry silica rubber, DSR), the wet mixing (for WSR) produced smaller silica aggregates with better dispersion. Due to the shorter heat history, the WSR exhibits superior curing characteristics such as a longer scorch time (2.2–3.3 min for WSR and 1.0–2.1 min for DSR) and curing time (4.1–4.5 min for WSR and 2.2–3.1 min for DSR). Additionally, the WSR has superior mechanical properties (hardness, modulus, tensile strength, and especially the elongation at break (420–680% for WSR and 360–620% DSR)) over the DSR. The rolling resistance of WSR is lower than that of DSR. However, the reversed trend on the wet skid resistance is observed.

Functionalized Nanosilica for Vulcanization Efficiency and Mechanical Properties of Natural Rubber Composites

Accelerator functional character was introduced on nanosilica by chemical reaction of sodium isopropyl xanthate (SIPX) with nanosilica (NS). Functional characteristics of nanosilica were confirmed by elemental analysis, thermogravimetric analysis, and infrared spectroscopy. This SIPX functionalized nanosilica (SIPX-NS) incorporated natural rubber (NR) composites were used to evaluate the dispersion of silica in rubber and also the interaction between rubber and filler. The finely dispersed SIPX-NS particles in the NR matrix are revealed from the morphological analysis. Subtle changes in the surface chemistry of silica had a profound influence on dispersibility in the NR matrix. NR 4SIPX-NS composite showed an increase in tensile strength by 10%, flex crack initiation resistance by 13%, tensile strength retention by 16% and cure time reduced by 2 min relative to those of NR 3NS composite. This simple, efficient and cost-effective surface modification of silica improved the vulcanization efficiency and mechanical performance of NR composites and has great potential in the fabrication of high-performance polymer composites.Graphical abstract

Effect of Sulfur Variation on the Vulcanizate Structure of Silica-Filled Styrene-Butadiene Rubber Compounds with a Sulfide-Silane Coupling Agent.

The vulcanizate structure of filled compounds is affected by filler–rubber interactions (FRI) and the chemical crosslink density (CCD) of the matrix rubber. In particular, in filled compounds using a silica–silane system, FRIs due to silica–rubber coupling are a major influencing factor for the vulcanizate structure and physical properties. In this study, the effect of sulfur variation on the vulcanizate structure of silica-filled solution styrene–butadiene rubber compounds using a sulfide–silane coupling agent was studied. The vulcanizate structure according to sulfur variation was quantitatively analyzed using the swelling test and Flory–Rehner and Kraus equations. As the sulfur content increased, both FRI and the CCD increased, and it was confirmed that sulfur variation influenced the silica–rubber coupling efficiency through increased FRI. In addition, field emission scanning electron microscope images showed that increased FRI contributed to improvements in silica dispersion, abrasion resistance, and energy loss characteristics.

VELCRO-INSPIRED SUPRAMOLECULAR SYSTEM FOR SILICA–RUBBER COUPLING

ABSTRACT The state-of-the-art silica–rubber coupling is based on forming chemical links between a silica surface and rubber macromolecules. However, the chemical links are relatively short and stiff, thus in case of a chemical breakage they are highly unlikely to recombine. This could result in a potential deterioration of the interphase properties over time. To overcome this drawback, a new approach to silica–rubber coupling was investigated in the current study. The new approach is inspired by the Velcro hook-and-loop system from nature that facilitates a re-connectability, thus re-formation of the interphase properties in case of a breakage. For this, various long oligomeric brushes were grafted onto silica surfaces considered to act as supramolecular hooks. Such modified silica were dispersed in rubber and vulcanized. The resulting cross-linked rubber matrix is considered to act as supramolecular loops. The prepared vulcanizates were compared with reference samples containing common coupling or covering agents. The reinforcing potential provided by the newly developed system is lower than the chemical coupling system but considerably higher than the covering system. The new system also provides better mechanical properties, recovery after cycling stretching, and heat treatment than the references. A new reinforcing mechanism is proposed for the silica grafted with oligomeric brushes that exhibits a good chemical compatibility to the rubber matrix.

The correlation of tear deviation and resistance with the bound rubber content in rubber-silica composites

The tear strength (TS) of rubber-silica composites is inevitably lowered by the reduction of viscoelastic dissipation imparted by the use of bifunctional silanes. It is of interest to find out whether promoting crack tip deviation represented by a slip-stick tearing can compensate for such a loss in the tear strength. Here, the phenomenon of crack growth in terms of the TS and also the tearing type is considered for both the untreated and silane-treated silica rubber composites to figure out the microstructure parameters affecting the slip-stick tearing. It was realized that within a certain volume fraction of the reinforcing filler, deviation whether in the form of slip-stick or knotty tearing can be found for both cases. Tearing for silane-treated silica is more similar to a slip-stick tearing with an ordered pattern of deviation and re-initiation; whereas tearing in the composites with untreated silica is like a knotty one with random deviation and re-initiation. Interestingly, a dual role was identified between the bound rubber content and the tearing: on one hand, increasing the bound rubber directly augments the viscoelastic dissipation and the value of TS, and on the other, it inversely suppresses the crack tip deviation. The second part of this work deals with applying strategies to promote crack tip deviation in treated silica systems. By increasing the degree of bonding at the rubber-silica interface and reducing the bound rubber, the tear deviation was successfully promoted. With a slip-stick type of tearing the crack had to proceed through a tortuous path, thereby enhancing the effective tear diameter and the subsequent tear strength. This roughening role of bound rubber is however insufficient to fully compete with the impact of bound rubber on the viscoelastic dissipation, and thus the decreased TS of composites with treated silica cannot be totally compensated by this strategy.

A Coarse-Grained Force Field for Silica-Polybutadiene Interfaces and Nanocomposites.

We present a coarse-grained force field for modelling silica–polybutadiene interfaces and nanocomposites. The polymer, poly(cis-1,4-butadiene), is treated with a previously published united-atom model. Silica is treated as a rigid body, using one Si-centered superatom for each SiO unit. The parameters for the cross-interaction between silica and the polymer are derived by Boltzmann inversion of the density oscillations at model interfaces, obtained from atomistic simulations of silica surfaces containing both (hydrophobic) and (silanol-containing, hydrophilic) silicon atoms. The performance of the model is tested in both equilibrium and non-equilibrium molecular dynamics simulations. We expect the present model to be useful for future large-scale simulations of rubber–silica nanocomposites.

Devulcanization of Waste Rubber and Generation of Active Sites for Silica Reinforcement.

Each year, hundreds of millions of tires are produced and ultimately disposed into nature. To address this serious environmental issue, devulcanization could be one of the sustainable solutions that still remains as one of the biggest challenges across the globe. In this work, sulfur-vulcanized natural rubber (NR) is mechanochemically devulcanized utilizing a silane-based tetrasulfide as a devulcanizing agent, and subsequently, silica (SiO2)-based rubber composites are prepared. This method not only breaks the sulfur–sulfur cross-links but also produces reactive poly(isoprene) chains to interact with silica. The silica natural rubber composites are prepared by replacing 30% fresh NR by devulcanized NR with varying contents of silica. The composites exhibit excellent mechanical properties, tear strength, abrasion resistance, and dynamic mechanical properties as compared with the fresh natural rubber silica composites. The tensile strength of devulcanized rubber-based silica composites is ∼20 MPa, and the maximum elongation strain is ∼921%. The devulcanized composites are studied in detail by chemical, mechanical, and morphological analyses. Thus, the value added by the devulcanized rubber could attract the attention of recycling community for its sustainable applications.

INFLUENCES OF THE COMPATIBILITY OF NR/SSBR AND PHASE-SELECTIVE DISTRIBUTION OF SILICA ON ITS STATIC AND DYNAMIC PROPERTIES

ABSTRACT The compatibility between solution polymerized styrene–butadiene rubber (SSBR 2466) and natural rubber (NR) is characterized by differential scanning calorimetry and dynamic mechanical thermal analysis. The single glass transition in the entire temperature range of all NR/SSBR blends and good correlation between Tg and SSBR fraction prove the excellent compatibility between SSBR 2466 and NR. With increasing SSBR content, a reduced Payne effect, more homogeneous dispersion of silica, stronger rubber–filler interaction, and more silica selectively distributed in the SSBR phase were determined via rubber-processing analysis, transmission electron microscopy, bound rubber, and thermogravimetric analysis, respectively. The high vinyl content, low styrene content, and end-functionalized structure of SSBR play vital roles in promoting its compatibility with NR and a stronger rubber–silica linkage. The resulting increased tan δ at 0 °C and low tan δ at 60 °C indicates good wet-skid resistance and low rolling resistance by blending SSBR 2466, and 70/30 NR/SSBR is the best balance for producing a “green tire” tread.

Evolution of Payne effect of silica-filled natural rubber in curing process

Vulcanisation is the key process for determining the final properties of elastomers due to the relationship between curing condition and viscoelastic behaviour. This study focuses on the variations in the dynamic behaviour of silica-filled natural rubber caused by crosslinking. The rubber samples with different degrees of curing (DOC) are prepared by thermal quenching during the crosslinking process. The strain sweep mode is used to study the Payne effect. The Kraus model is used to fit the test data. The relationship between the parameters of Kraus model and DOC is obtained at small strain (< 10%). The storage modulus at small strain amplitudes (usually < 0.01%) $$ G^{\prime}_{ 0} $$ is proportional to DOC; however, the storage modulus at large strain amplitudes $$ G^{\prime}_{\infty } $$ has small changes with DOC. The characteristic value of the strain amplitude $$ \gamma_{\text{C}} $$ shifts to large strain and the maximum loss modulus $$ G^{\prime\prime}_{\text{m}} $$ decreases with the increase of DOC. In addition, a deviation between Kraus model and experiment is observed when the strain is larger than 10%, and the loss modulus increases with the increase of strain amplitude. The deviation decreases when DOC increases. The mechanism for this deviation is discussed and the interaction between silica filler and rubber chain might be responsible for the observed deviation.