Solution-polymerized Styrene Butadiene Research Articles

Modeling of dynamic-mechanical behavior of reinforced elastomers using a multiscale approach

The investigation of the molecular mobility of polymer chains and networks in the presence of active fillers such as carbon black or silica presents a big interest for the physics of reinforced rubbers. A better understanding of the physical characteristics of the filler–rubber interface is necessary to improve the overall macroscopic properties of these elastomers. The main goal of our work is to develop a physically based multi-scale approach for description of the viscoelastic properties of reinforced elastomers. Rubber compounds, based on a solution-polymerized styrene butadiene rubber filled with precipitated silica, were investigated. Dynamic-mechanical experiments were carried out in a wide range of temperatures to construct master curves for the small strain storage E′(ω) and loss E″(ω) moduli for nearly 20 decades of frequencies at a chosen reference temperature. The developed multiscale theoretical approach allows to analyze the master curves across the 20 decades of frequencies and to investigate the effects of the filler particles on the relaxation processes in simple rubber compounds at different time scales.

CORRELATION OF FILLER NETWORKING WITH REINFORCEMENT AND DYNAMIC PROPERTIES OF SSBR/CARBON BLACK/SILICA COMPOSITES

ABSTRACTThe use of silica to partially replace carbon black is a common practice in the fabrication of “green tires.” Although some degree of consensus has been approached concerning the improved performance conferred by silica substitution, such as the improved dispersion of carbon black, a quantitative understanding of the relationship between filler networking and the performance of rubber composites has not been established. Thus, an investigation focusing on filler network structure and the correlation between the network structure and the reinforcement of rubber composites was conducted. We prepared solution-polymerized styrene–butadiene rubber (SSBR) reinforced by carbon black and carbon black/silica in different ratios. To exclude as much of the effect from changed crosslinking, and figure out how filler blending influences filler dispersion and filler network structure, the silane generally used in the tire industry was not adopted. The quantitative predictor, the mass fractal dimension df, was derived from the Kraus model and the Huber–Vilgis model. We found that when the amount of substituted silica increases, the filler cluster branching decreases, accompanied by increased reinforcement efficiency. The depressed filler networking induced by silica substitution at an appropriate proportion leads to improved dynamic properties, including lower rolling resistance and better wet skid. When the silica proportion in the filler is too high, severe filler networking is observed, resulting in decreased reinforcing efficiency and impaired dynamic properties.

The Influence of the Styrene Content and Features of the Molecular Structure of Solution-Polymerised Styrene Butadiene Rubber on the Service Properties of Tread Rubbers

The Influence of the Styrene Content and Features of the Molecular Structure of Solution-Polymerised Styrene Butadiene Rubber on the Service Properties of Tread Rubbers

The Influence of the Molecular Weights and Viscosity of Solution-Polymerised Styrene Butadiene Rubber on the Properties of Rubber Mixes and Silica-Filled Vulcanisates

The Influence of the Molecular Weights and Viscosity of Solution-Polymerised Styrene Butadiene Rubber on the Properties of Rubber Mixes and Silica-Filled Vulcanisates

Preparation and performance of silica/SBR masterbatches with high silica loading by latex compounding method

With the help of a new coupling agent Si747, silica water slurry and styrene–butadiene rubber (SBR) latex were successfully co-coagulated by the latex compounding method, even silica/SBR masterbatches with silica loading as high as 200 phr could be prepared by such method. Compared to the traditional dry blending method, the latex compounding method had lower energy consumption during mixing and better silica dispersion in rubber matrix. Meanwhile, the effect of the amount of silica in the SBR latex on the properties of silica/SBR composites was investigated, and the results showed that the larger the amount of silica in the rubber matrix, the stronger the filler network. The performance of these composites was good and the dispersion of silica was relatively homogeneous. Furthermore, the masterbatches with high silica loading were mixed with emulsion polymerized styrene–butadiene rubber (ESBR) or solution polymerized styrene–butadiene rubber (SSBR). The silica dispersed better in ESBR than in SSBR.

The Influence of the Molecular Weight and Viscosity of Solution-Polymerised Styrene Butadiene Rubber on the Properties of Rubber Mixes and Vulcanisates

The Influence of the Molecular Weight and Viscosity of Solution-Polymerised Styrene Butadiene Rubber on the Properties of Rubber Mixes and Vulcanisates

Influence of network structure on the viscoelastic properties of dynamically vulcanized rubber/plastic blends: An alternative approach to understand the microstructure evolution

The formation of finely dispersed micron-sized cross-linked rubber agglomerates in the thermoplastic matrix during dynamic vulcanization is now a well accepted theory to explicate the final properties of thermoplastic vulcanizates (TPVs). Based on our previous results, we have investigated further in the present work on the most influential and essential parameters which controls the ultimate properties of the TPVs. Three TPVs based on poly[styrene-b-(ethylene-co-butylene)-b-styrene] triblock copolymer (S-EB-S) and solution polymerized styrene butadiene rubber (S-SBR) have been prepared containing different proportions of rubber fraction. A semi-efficient (SEV) sulphur based curing system has been adopted to cross-link the rubber phase and advanced microscopic techniques viz. transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) have been used for the microstructure analysis. Thereafter, dynamic experiments have been performed to correlate the morphological observations with viscoelastic properties. The experimental results and the morphological images confirm that the network structure formation during dynamic vulcanization and its integrity is the most influential parameter to cause the utmost properties of the TPVs. The finely dispersed cross-linked rubber particles obtained during dynamic vulcanization are actually the disintegrated and agglomerated rubber nano-particles having average particle size between 80 and 85nm. It has also been confirmed that the integrated rubber network structure has an inverse relationship with the proportion of rubber fraction present in the TPVs. Mechanical properties, melt rheology and dynamic viscoelastic measurements also support the network structure disruption and disintegration observed in the morphological images and thus, nullifies the supremacy of dispersed phase morphology theory behind the superior properties obtained from the TPVs. This work elucidates the necessity and importance of integrated network structure formation over the morphology evolution during dynamic vulcanization and leads to a new avenue to understand morphology–mechanical–rheological–viscoelastic property correlation in TPVs.

Meticulous analysis and consequences of microstructure changes on melt rheology and dynamic viscoelasticity of thermoplastic vulcanizates upon reprocessing

ABSTRACTThermoplastic vulcanizates (TPVs), which are a special class of elastomer alloy, prepared by dynamic vulcanization possess unique morphology of finely dispersed micron‐size cross‐linked elastomeric particles in a continuous thermoplastic matrix. The present study investigates the microstructure formation of elastomeric phase and its associated morphological changes during reprocessing of TPVs based on poly[styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene] triblock co‐polymer (S‐EB‐S) and solution polymerized styrene butadiene elastomer (S‐SBR) by scanning electron microscopy and atomic force microscopy. Semi‐efficient and efficient sulfur‐based curing systems have been adopted to cure the elastomeric phase and a comparative study has been made to demonstrate and explain the effect of reprocessing on the melt rheology and dynamic viscoelasticity of the TPVs. The present work also provides a better insight and guidance to control the microstructure of the cross‐linked elastomeric phase to prepare selectively co‐continuous or dispersed phase morphology. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 41182.

Nano-scale morphological analysis of graphene–rubber composites using 3D transmission electron microscopy

In this work three-dimensional transmission electron microscopy (3D-TEM) is exploited to characterize a soft graphene based nano-composites structure and the constituted morphology in a qualitative way. The reconstruction of the two dimensional slides into a three dimensional tomographic image is a powerful tool, when the images of the nano-object are reflected into a quasi-distinguishable object due to superposition effect. By using this technique it is possible to mark the contour area of the nano-sized object inside the soft rubber matrix. To extract information about the filler network, the clustering process of the fillers or the existence of single or multiple graphene sheets, a solution polymerised styrene butadiene rubber was selected as a soft matrix which was filled with carbon black (CB) and graphene nano-platelets (GnP). The dispersion/exfoliation of the stacked graphene sheets into individual single sheets was facilitated by the presence of carbon black in the system as understood from TEM, X-ray diffraction and Raman spectroscopic studies. The existence of oligo-layer graphene sheets was detected by this 3D-TEM, especially when the rubber matrix exists in a complex morphology arisen from filler–filler networks in all spatial dimensions.

Contribution of silica–rubber interactions on the viscoelastic behaviors of modified solution polymerized styrene butadiene rubbers (M-S-SBRs) filled with silica

Dynamic mechanical analysis of M-S-SBR filled with silica: the temperature dependence of loss factor, tan δ.

The Research on the Rheological Properties of SSBR-Based Composites Filled with CB/Silica

The dynamic viscoelastic properties of solution polymerized styrene-butadiene (SSBR) filled with different proportion of carbon black and silica were studied by using the rubber processing analyzer (RPA2000) and DMA under different scanning conditions. The results indicated that in the first strain sweeping process, the storage modulus (G) reduced gradually with the increase of ratio of carbon black, and the function of coupling agent (Si69) decreased. During the secondary strain sweeping process, it was found that with the increase of sweeping time interval, the stress softening phenomenon abates. On the other hand, through three strain sweeping, it was considered that the effect of Payne was not caused only by the factor of filler-net.

Development of modified expanded graphite-filled solution polymerized styrene butadiene rubber vulcanizates in the presence and absence of carbon black

Expanded graphite (EG) consists of a huge number of partially exfoliated graphite sheets with the thickness of most of the sheets in the nanometer range. This study analyses the effect of EG and modified EG (MEG) on the mechanical, thermal, and dynamic mechanical properties of solution styrene butadiene rubber (SSBR) with and without carbon black (CB). The surface of the EG was modified to enhance its dispersion in the SSBR matrix. In addition, oil-extended carboxylated styrene butadiene rubber (XSBR) was used as a compatibilizer to disperse MEG in the base nonpolar SSBR matrix. XSBR/MEG nanocomposites have been prepared by solution mixing. The obtained nanocomposites were incorporated into the SSBR matrix in the presence of CB by melt blending. Morphological properties of the nanocomposites revealed intercalation of MEG sheets in the SSBR matrix. Nanocomposites containing MEG in the presence of CB show improvement in mechanical, thermal, and dynamic mechanical properties. POLYM. ENG. SCI., 54:33–41, 2014. © 2013 Society of Plastics Engineers

Study on the structure, morphology, and properties of end‐functionalized star‐shaped solution‐polymerized styrene–butadiene rubber

AbstractThree kinds of star‐shaped solution‐polymerized styrene–butadiene rubber (S‐SSBR) were synthesized by living anionic polymerization using a self‐made multifunctional organic lithium initiator. One was S‐SSBR with 100% coupling degree. Others were the functionalized S‐SSBR which had macromolecular chain‐free ends terminated directly (ES‐SSBR‐1), and macromolecular chain terminated after dissociation in the polymerization solution (ES‐SSBR‐2) by 3‐chloropropyl trimethoxy siloxane. The molecular structure parameters of three kinds of SSBR were determined and the end‐functionalized efficiency was calculated. The rheological properties, mechanical properties, and dynamic mechanical properties of ES‐SSBR and S‐SSBR composites filled with silica (SiO2)–carbon black (CB) were investigated. The morphology was observed by transmission electron microscopy and high‐resolution transmission electron microscopy, and the dispersion of the two kinds of filler in the composites was distinguished by X‐ray energy spectrometry. The results showed that the mixing speed of hydrophilic SiO2 powder in the ES‐SSBR was higher than that in the S‐SSBR. SiO2‐CB/ES‐SSBR composites presented excellent mechanical properties, high wet‐skid resistance, and low rolling resistance. Two kinds of nanofiller in the ES‐SSBR exhibited outstanding doping nanometer dispersion and good distribution, which indicated that after being coupled and end‐functionalized, the two free ends of the macromolecular chains formed chemical bonding with the surface chemical groups of CB and SiO2, respectively. Accordingly, ES‐SSBR was a remarkable energy‐saving elastomer. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Effects of Carbon Black on Chain Mobility and Dynamic Mechanical Properties of Solution Polymerized Styrene-Butadiene Rubber

The structure of the bound rubber, the 1H NMR (nuclear magnetic resonance) relaxation time, and the crosslink density of the physical network and the glass transition, were studied for solution polymerized styrene-butadiene rubber (SSBR) filled by carbon black, to investigate the effects of carbon black on the chain mobility and dynamic mechanical properties. It was found by 1H NMR analysis that the rubber chains were adsorbed on the surface of carbon black to form physical crosslinks and restrict the mobility of the chains, especially for some high-mobility units such as chain ends. It was calculated, according to the molecular weight between adjacent crosslinks, that the main motion units of the tightly adsorbed chains appeared to be similar in size to the chain segments. The glass transition temperature (T g) obtained by differential scanning calorimetry (DSC) could not be used to judge the effect of carbon black on chain mobility, while the appearance and change of the loss-tangent (tan δ) peak at high temperature in dynamic mechanical thermal spectrometry (DMTS) test showed that there were three chain states: free chains, loosely adsorbed chains, and tightly adsorbed chains. The dynamic rheology test showed that the unfilled SSBR compound had the rheological characteristics of entangled chain networks; however the nonlinear viscoelasticities of the filled SSBR were related to the gradual disentanglement of adsorbed chains and free chains. The peaks in tan δ vs. temperature curves implied that the motion unit size decreased with the increase of bound rubber content, and the modulus vs. temperature curve showed an apparently lower mobility of adsorbed chains than that of free chains through the very low dependence of modulus on temperature for the highly filled compounds. The extremely high tensile modulus of the vulcanizate with 63.6% carbon black at room temperature also implied that the adsorbed chains were in the glass state due to their restriction by the carbon black.

Study on Dynamic Fatigue Properties of Solution-Polymerized Styrene Butadiene Rubber T2000R

Dynamic fatigue properties of solution-polymerized styrene butadiene rubber with the trade name T2000R were studied. The influence of different cure systems, reinforcing agents, anti-degradants, and plasticizers on the flex-cracking property of T2000R vulcanizates was investigated. The results showed that T2000R cured with an effective vulcanization system had relatively high fatigue life. Vulcanizate filled with carbon black N330 with a load of 15 phr had better fatigue resistance. Then, a combination of aging resisters 6PPD and RD prolonged the fatigue life of T2000R significantly. T2000R extended with aromatic oil had a fatigue life higher than those extended with mineral oil, naphthenic oil, and courmarone. Among all the factors, aging resister and the load of carbon black contributed more to the flex-cracking properties of T2000R than other additives.

EFFECT OF SILANE COUPLING AGENTS ON DYNAMIC RHEOLOGICAL PROPERTIES FOR UNVULCANIZED SSBR/SILICA COMPOUNDS

Effects of silane coupling agent on the dynamic properties for unvulcanized solution-polymerized styrene butadiene rubber(SSBR)/silica(SiO_2)compounds were investigated on an advanced rheometric expansion system(ARES).It is found that the molecular structure of silane coupling agent significantly influences the dynamic storage modulus(G')in the temperature range from 100℃ to 180℃ and also the strain(γ)and frequency(ω)dependence of G' at 100℃.The highest G' appears for the compound containing bis-(3-triethoxysilylpropyl)-tetraslufide(TESPT),and the lowest for the compound containing 3-octanoylthio-1-propyltriethoxysilane(NXT),indicating different reaction degrees of silane with SiO_2 and SSBR during mixing at 160℃.The molecular structure of silane coupling agents also influences the γ and ω dependence of G' at 100℃.The critical strains(γ_c)for the onset of nonlinear viscoelasticity are 1.00%,0.36% and 0.57%,and the slopes of plotting lgG' versus lgω in the low ω_s range(terminal range)are 0.14,0.17 and 0.20,for the compounds containing TESPT,TESPD and NXT,respectively.It is suggested that the increase of both γ_c value and the slopes of those plots are responsible for surface-modification of SiO_2 particles and enhancement of interaction between the particle and SSBR.

The mechanical and viscoelastic properties of SSBR vulcanizates filled with organically modified montmorillonite and silica

The mechanical and the dynamic rheological behavior of solution-polymerized styrene butadiene rubber (SSBR) filled with compounding fillers organic montmorillonite (OMMT)/silica (SiO2) were studied. The mechanical properties of the vulcanizates could be improved by incorporation of low OMMT contents, and the best reinforcement effect appeared when 7 phr (parts per hundred rubber) OMMT was added. Moreover, due to the formation of the exfoliated silicate platelet in the matrix, a strong cooperative reinforcement effect to the vulcanizate could be gained for the vulcanizate containing 7 phr OMMT and 20 phr SiO2. Incorporation of SiO2 up to 50 phr to the vulcanizates with or without OMMT resulted in marked reinforcement effect, and the best mechanical properties were obtained for 7 phr OMMT filled composites. On the other hand, compounding fillers OMMT/SiO2 significantly influences the dynamic mechanical behavior of the vulcanizates. It was found that the compounding filler with a certain composition facilitated preparing SSBR vulcanizates with optimized wet traction, rolling resistance, and strength properties.

EFFECT OF INCORPORATING STARCH/SILICA COMPOUND FILLERS INTO UNCURED SSBR ON ITS DYNAMIC RHEOLOGICAL PROPERTIES

The dynamic rheological properties of a composite composed of solution-polymerized styrene butadiene rubber (SSBR) filled with starch/silica (SiO2) compound fillers were studied by means of temperature, frequency and strain sweeps, respectively, and the influence of the starch content in the compound fillers (SCCF) on the rheological behaviors was discussed. It is found from frequency sweeps that a maximum of loss tangent (tanδ) appears at 20 rad/s, which is independent of SCCF. G′ of the composites decreases whereas tanδ and critical strain (γc) of Payne effect increase with increasing SCCF. The reasons for these are believed to be that both SiO2 and starch could form filler networks due to interaction of hydrogen bounding between them, and the interactions between SiO2 and SSBR are stronger than those between starch and SSBR. Moreover, increasing SCCF in the compound fillers is in favor of improving the stability of the filler networks. Furthermore, tanδ values at 0°C and 60°C representing the properties for the wet traction and the rolling resistance of SSBR composites respectively can be improved by partial replacing SiO2 with starch. However, the reinforcement effect of starch to SSBR is weaker than that of SiO2 due to starch agglomeration.

Nonlinear rheological behavior of silica filled solution‐polymerized styrene butadiene rubber

AbstractThe reinforcement and nonlinear viscoelastic behavior have been investigated for silica (SiO2) filled solution‐polymerized styrene butadiene rubber (SSBR). Experimental results reveal that the nonlinear viscoelastic behavior of the filled rubber is similar to that of unfilled SSBR, which is inconsistent with the general concept that this characteristic comes from the breakdown and reformation of the filler network. It is interesting that the curves of either dynamic storage modulus (G′) or loss tangent (tan δ) versus strain amplitude (γ) for the filled rubber can be superposed, respectively, on those for the unfilled one, suggesting that the primary mechanism for the Payne effect is mainly involved in the nature of the entanglement network in rubbery matrix. It is believed there exists a cooperation between the breakdown and reformation of the filler network and the molecular disentanglement, resulting in enhancing the Payne effect and improving the mechanical hysteresis at high strain amplitudes. Moreover, the vertical and the horizontal shift factors for constructing the master curves could be well understood on the basis of the reinforcement factor f(φ) and the strain amplification factor A(φ), respectively. The surface modification of SiO2 causes a decrease in f(φ), which is ascribed to weakeness of the filler–filler interaction and improvement of the filler dispersion. However, the surface nature of SiO2 hardly affects A(φ). © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2594‐2602, 2007