Showing papers on "Styrene-butadiene published in 2007"

Payne effect in silica-filled styrene–butadiene rubber: Influence of surface treatment

Abstract: The nonlinear effect at small strains (Payne effect) has been investigated in the case of silica-filled styrene-butadiene rubber. The originality of this study lies in the careful preparation of samples in order to fix all parameters except one, that is, the modification of the silica surface by grafting silane (introduced at different concentrations) via reactive mixing. The organosilane can be either a coupling or a covering surface treatment with an octyl alkyl chain. A careful morphological investigation has been performed prior to mechanical characterization and silica dispersion was found to be the same whatever the type and the amount of silane. The increasing amount of covering agents was found to reduce the amplitude of the Payne effect. A similar decrease is observed for low coupling agent concentration. At higher concentrations, the evolution turns through an increase due to the contribution of the covalent bonds between the matrix and the silica acting as additional crosslinking. The discussion of the initial modulus was done in the frame of both the filler-filler and filler-polymer models. It is unfortunately not possible to distinguish both scenarios, because filler-filler and filler-matrix interactions are modified in the same manner by the grafting covering agent. On the other hand, the reversible decrease of the modulus versus strain (Payne effect) is interpreted in terms of debonding of the polymeric chains from the filler surface.

Effect of montmorillonite on properties of styrene–butadiene–styrene copolymer modified bitumen

Abstract: Clay/styrene–butadiene–styrene (SBS) modified bitumen composites were prepared by melt blending with different contents of sodium montmorillonite (Na-MMT) and organophilic montmorillonite (OMMT). The structures of clay/SBS modified bitumen composites were characterized by XRD. The XRD results showed that Na-MMT/SBS modified bitumen composites may form an intercalated structure, whereas the OMMT/SBS modified bitumen composites may form an exfoliated structure. Effects of MMT on physical properties, dynamic rheological behaviors, and aging properties of SBS modified bitumen were investigated. The addition of Na-MMT and OMMT increases both the softening point and viscosity of SBS modified bitumens and the clay/SBS modified bitumens exhibited higher complex modulus, lower phase angle. The high-temperature storage stability can also be improved by clay with a proper amount added. Furthermore, clay/SBS modified bitumen composites showed better resistance to aging than SBS modified bitumen, which was ascribed to barrier of the intercalated or exfoliated structure to oxygen, reducing efficiently the oxidation of bitumen, and the degradation of SBS. POLYM. ENG. SCI., 47:1289–1295, 2007. © 2007 Society of Plastics Engineers

Stereoselective Polymerization of Conjugated Dienes and Styrene−Butadiene Copolymerization Promoted by Octahedral Titanium Catalyst

Abstract: The ability of the dichloro{1,4-dithiabutanediyl-2,2‘-bis(4,6-di-tert-butylphenoxy)}titanium complex (1) to catalyze homopolymerization of conjugated dienes and copolymerization of butadiene with styrene is reported. After proper activation with methylalumoxane, 1 resulted active in the trans-1,4 selective polymerization of butadiene and isoprene with good activity. The molecular weight distributions of the polymers are monomodal with the polydispersity indexes, consistent with a single site behavior of the catalyst. Isotactic polystyrene-co-trans-1,4-polybutadiene with an unprecedented architecture, covering a wide range of compositions (xS = 0.15−0.97), were also obtained. The chemo- and stereoselectivity of butadiene insertion and the isospecific styrene polymerization of the title catalyst are retained when the two monomers are copolymerized. The molecular weight distributions are consistent with the material being copolymeric in nature. The reactivity ratios values and the microstructure analysis (by...

Curing Behavior and Final Properties of Nanostructured Thermosetting Systems Modified with Epoxidized Styrene‐Butadiene Linear Diblock Copolymers

Abstract: Nanostructured thermosetting materials based on thermosetting matrices were prepared by modification of an epoxy system with linear PS-block-PB copolymers The nanostructured thermosets were obtained through PS block segregation Depending on the block-copolymer content in the thermosets and its epoxidation degree, the PS domains can display micellar, worm-like or hexagonally-packed cylinder structures, retaining the stiffness of the epoxy matrix, where the hexagonally cylindrical morphology lead to a significant increase in fracture toughness The rheokinetics of microphase separation during network formation was investigated Nanostructures are judged to be formed by polymerization-induced microphase separation, in marked contrast to equilibrium self-organized structures that are preformed, with the microphases fixed via a curing reaction

Effect of strain on the properties of a styrene–butadiene rubber filled with multiwall carbon nanotubes

Abstract: Multiwall carbon nanotubes were dispersed in a styrene–butadiene copolymer. The effect of nanotube concentration on the tensile characteristics of the composites was examined. Electrical properties carried out under uniaxial extension show an increase in resistivity upon gradual stretching. A second stretch performed after total release of the stress was shown to lead to a flat response in resistivity. Atomic force microscopy was used to examine orientational effects and changes in filler structure occurring upon application of an uniaxial deformation. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007

Effect of Nano CaCO3 on thermal properties of Styrene Butadiene Rubber (SBR)

Abstract: Styrene butadiene rubber (SBR) as matrix was reinforced separately with 9, 15 and 21 nm sizes of CaCO3, which were synthesized by matrix mediated growth technique. The mixing and compounding was done on two-roll mill and sheets were prepared in compression molding machine. The effect of nature and loading of nano CaCO3 on these rubber nanocomposites was investigated thoroughly by different characterizations such as DSC, TGA, XRD, and mechanical properties. An appreciable increase in glass transition temperature has been observed from DSC study. 9 nm sizes of CaCO3/SBR composites show more increment in Tg as compared to pristine SBR as well as different sizes of CaCO3 filled SBR. This increment in Tg is due to restricted mobility of nano CaCO3 filled SBR nanocomposites. XRD study of nanocomposites showed that nano CaCO3 dispersed uniformly throughout the matrix because of the small peak at lower 2θ. This uniform dispersion of nano CaCO3 contributes towards the higher mechanical properties of rubber composites. From TGA study, it was observed that as the size of CaCO3 reduces the thermal stability increases as compared to pristine SBR. The other results of these rubber nanocomposites were compared with commercial CaCO3 filled SBR.

Enhancing the mechanical properties of styrene–butadiene rubber by optimizing the chemical bonding between silanized silica nanofiller and the rubber

Abstract: The reinforcing effect of a large amount of synthetic precipitated amorphous white silica nanofiller on the mechanical properties of styrene–butadiene rubber was studied. The silica surfaces were pretreated with bis(3-triethoxysilylpropyl)tetrasulfane (TESPT). TESPT is a bifunctional organosilane that chemically adheres silica to rubber and also prevents silica from interfering with the reaction mechanism of sulfur cure in the rubber. The silica particles were fully dispersed in the rubber and the chemical bonding between the rubber and filler was optimized by the incorporation of accelerator and activator in the rubber. This study showed that the mechanical properties of the rubber vulcanizate improved substantially when the filler was added. The addition of elemental sulfur affected the rubber properties, although there was no overall advantage, as some properties improved and others deteriorated. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

Fly-ash particles and precipitated silica as fillers in rubbers. II. Effects of silica content and si69-treatment in natural rubber/styrene-butadiene rubber vulcanizates

Abstract: This article explored the possibility of using silica from fly-ash particles as reinforcement in natural rubber/styrene–butadiene rubber (NR/SBR) vulcanizates. For a given silica content, the NR : SBR blend ratio of 1 : 1 (or 50 : 50 phr) exhibited the optimum mechanical properties for fly-ash filled NR/SBR blend system. When using untreated silica from fly-ash, the cure time and mechanical properties of the NR/SBR vulcanizates decreased with increasing silica content. The improvement of the mechanical properties was achieved by addition of Si69, the recommended dosage being 2.0 wt % of silica content. The optimum tensile strength of the silica filled NR/SBR vulcanizates was peaked at 10–20 phr silica contents. Most mechanical properties increased with thermal ageing. The addition of silica from fly-ash in the NR/SBR vulcanizates was found to improve the elastic behavior, including compression set and resilience, as compared with that of commercial precipitated silica. Taking mechanical properties into account, the recommended dosage for the silica (FASi) content was 20 phr. For more effective reinforcement, the silica from fly-ash particles had to be chemically treated with 2.0 wt % Si69. It was convincing that silica from fly-ash particles could be used to replace commercial silica as reinforcement in NR/SBR vulcanizates for cost-saving and environment benefits. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007

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

Abstract: The 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

Styrene/Butadiene Gradient Block Copolymers: Molecular and Mesoscopic Structures

Abstract: Rubbery-glassy block copolymer dispersions are an attractive solution for toughening rigid thermoplastics like polystyrene without affecting optical transparency. An interesting facet of the copolymers used is molecular disorder, artificially introduced during anionic synthesis through composition gradients along the copolymer chain and/or blending and partial coupling of different copolymers. In particular, this level of disorder is apparently a key to achieve the desired PS/copolymer blend morphologies and properties in short processing times. In this work, we investigate the role of these "synthesis imperfections" on self-assembly of styrene-rich asymmetric gradient triblock copolymers, denoted S1-G-S2, where Si are pure polystyrene blocks and G is a gradient copolymer of styrene and butadiene. Kinetic modeling of conversion data is used to predict gradient composition profiles for the anionic copolymerization conditions used. Self-assembly, dynamic viscoelastic behavior, and experimentally determined mesoscopic composition profiles across microdomains are discussed in light of the particular copolymer structure.

Influence of Silica and its Different Surface Treatments on the Vulcanization Process of Silica Filled SBR

Abstract: The effect of different silica treatments on the vulcanization of silica filled Styrene Butadiene Rubber (SBR) is investigated. The concentration, the length and the functionality (coupling or non coupling) of the silane used for this treatment are the parameters studied. It is shown that the silane grafting, by covering the silica surface, modifies the adsorption and desorption on this surface of the accelerators used in the vulcanization system, which in turn modifies the crosslinking kinetic and therefore should influence the final crosslinking state of the matrix.

Multi‐Wall Carbon Nanotubes/Styrene Butadiene Rubber (SBR) Nanocomposite

Abstract: A floating catalyst chemical vapor deposition (FC‐CVD) method was designed and fabricated to produce high‐quality and ‐quantity carbon nanotubes. The design parameters like the hydrogen flow rate; ...

Organic interfacial tailoring of styrene butadiene rubber–clay nanocomposites prepared by latex compounding method

Abstract: The styrene butadiene rubber (SBR)–clay nanocompounds were prepared by the latex compounding method, and then hexadecyl trimethyl ammonium bromide (C16) and 3-aminopropyl triethoxy silane (KH550) were added into these nanocompounds on a two-roll mill to prepare nanocomposites with strong interfacial interaction. The structure and properties of SBR–clay nanocomposites were carefully studied by X-ray diffraction (XRD) studies, transmission electron microscopy (TEM), Rubber Process Analyzer (RPA), and mechanical testing. Compared with unmodified nanocomposites, the dispersion structure of modified SBR–clay nanocomposites is better with part rubber-intercalated or part modifier-intercalated structure. The tensile strength and the modulus at 300% elongation of modified SBR–clay nanocomposites are higher than three times of those of unmodified nanocomposites, respectively. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1826–1833, 2007

The Effect of Styrene-Butadiene-Styrene Modification on the Characteristics and Performance of Bitumen

Abstract: In order to cover the effect of styrene-butadiene-styrene (SBS) modification on the characteristics of bitumen, two types of bitumen, one plain bitumen, and one polymer modified bitumen produced with the plain bitumen as base material were characterized in terms of chemical composition, microstructure, micromechanical properties, and thermoanalytical behavior In order to determine the complex chemical composition of bitumen, elemental analysis, gel permeation chromatography, and the Iatroscan method were employed Microstructure and micromechanical properties were determined using an environmental scanning electron microscope and the nanoindentation technique Modulated differential scanning calorimetry was used to determine phase-change temperatures and endo/exotherms associated with molecular movement The addition of SBS leads to different rheological behavior over the whole service temperature range This is reflected in bitumen chemistry by differences in elemental composition and molecular weight distribution with much higher M w values for the modified bitumen Accordingly, the polymer leads to a shift in molecular fractions Electron microscopy reveals two distinct phases building up the bitumen microstructure The chosen mode of quantification leads to similar material parameters for both bitumens, which is explained by the use of the same base material In contrast, nanoindentation delivers viscosities in the micro-range corresponding to large-scale rheological properties Modulated differential scanning calorimetry indicates two glass transitions corresponding with two material phases also confirmed by other experiments Due to modification, these glass transitions depart from each other and the amount of the two material phases changes, correlating with the shift in molecular fractions observed in Iatroscan analyses

Thermal behaviour of styrene butadiene rubber/poly(ethylene-co-vinyl acetate) blends

Abstract: The thermal behaviour of styrene butadiene rubber (SBR)/poly (ethylene-co-vinyl acetate) (EVA) blends was studied by using thermogravimetry (TG) and differential scanning calorimetry (DSC). The effects of blend ratio, cross-linking systems and compatibilization on the thermal stability and phase transition of the blends were analyzed. It was found that the mass loss of the blends at any temperature was lower than that of the components, highlighting the advantage of blending SBR and EVA. The addition of compatibilizer was also found to improve the thermal stability. DSC studies indicated the thermodynamic immiscibility of SBR/EVA system even in the presence of the compatibilizer. This is evident from the presence of two different glass transition temperatures, corresponding to SBR and EVA phases in both compatibilized and uncompatibilized blends.

Dynamic reaction inside co‐rotating twin screw extruder. I. Truck tire model material/polypropylene blends

Abstract: Waste ground rubber tire (WGRT) is a complex composite containing various elastomers, carbon black, zinc oxide, stearic acid, processing oils, and other curatives. Most of the waste ground rubber tire is composed of mainly natural rubber (NR) and styrene butadiene rubber (SBR) in varying proportions. Blending it with other thermoplastic materials is difficult due to the inherent thermodynamic incompatibility. But, the compatibility can be increased by making the reactive sites in WGRT with suitable chemicals under optimum condition of shearing inside a twin screw extruder and it is said to undergo a dynamic reaction inside the extruder. To understand the mechanism of dynamic reaction process of a rubber/polyolefin blend, the blending of a truck tire model material rubber with polyolefin was first tried before it was applied to waste WGRT material. It was observed that the blends of a truck tire model rubber material and PP thermoplastic are physical mixture of two incompatible polymers in which a continuous plastic phase is largely responsible for the tensile properties. The rubber particles are the dispersed phase. The large particle size and the poor adhesion of these rubber particles are believed to be liable for the poor tensile properties. In case of blends of truck tire model material with isotactic polypropylene the tensile properties are found to be lower than that of its PP-g-MA counterpart which can be attributed to the reaction of the MA with the carbon black particles. A schematic representation of the possible interactions has been proposed. The effect of addition of compatibilizers such as SEBS and SEBS-g-MA has also been studied. The tensile and TGA studies indicate that the polarity of SEBS and SEBS-g-MA induces an increase in the performance characteristics for both types of polyolefins but the intensity of this increase is higher in the PP-g-MA based blends. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 106: 3193–3208, 2007

Biopolymers as fillers for rubber blends

Abstract: Polymeric materials from renewable resources have been tested as additives for rubber blends and vulcanisates. Their influence on the vulcanisation process, tensile strength properties and dynamical-mechanical properties has been studied and compared with silica. The corn starch, collagen hydrolysate, corn protein and various types of lignin have been added to natural and styrene butadiene rubber in order to find convenient fillers for rubber blends which are able to modify the properties of rubber products. Correlation between Wolf activity coefficient and mechanical properties of vulcanisates is discussed. Copyright © 2007 John Wiley & Sons, Ltd.