Showing papers on "Styrene-butadiene published in 2009"

Synergistic effect of carbon black and nanoclay fillers in styrene butadiene rubber matrix: Development of dual structure

Abstract: Styrene butadiene rubber (SBR) based hybrid nanocomposites containing carbon black (CB) and organo-modified nanoclay (NC) was prepared. X-ray diffraction (XRD) and transmission electron microscopy (TEM) revealed the presence of intercalated, aggregated, and partially exfoliated structures. Incorporating 10 phr NC to the control SBR containing 20 phr CB resulted 153% increase in tensile strength, 157% increase in elongation at break and 144% stress improvement at 100% strain, which showed synergistic effect between the fillers. The dynamic modulus reinforcement of nanocomposites was examined by the Guth, Modified Guth, and Halpin–Tsai equations. For predicting CB filled nanocomposite modulus, the contribution of modified intercalated structure of clay and the ‘nano-unit’ (dual structure) comprising CB–NC should be considered.

Practical Use of Multiple Stress Creep and Recovery Test: Characterization of Styrene–Butadiene–Styrene Dispersion and Other Additives in Polymer-Modified Asphalt Binders

Abstract: The rheological properties of asphalt binders modified by styrene-butadiene-styrene (SBS) depend on formulation variables. The most sensitive of them may be listed as polymer amount, cross-linking agent amount (percentage), and other additives such as polyphosphoric acid (PPA). The dispersion of SBS in an asphalt binder depends on the time and temperature of blending and the base asphalt binder compatibility. In this study an incompatible binder and a compatible base asphalt binder were selected and modified with various amounts of SBS. Elemental sulfur was used as a cross-linking agent in different proportions. Other additives, such as PPA at 0.5% concentration, were also used. High shear blends of SBS-modified asphalt binders were made in the laboratory by varying blending time until an optimum dispersion of polymer was obtained. The dispersion of the polymer was studied with a fluorescence microscope. A multiple stress creep and recovery (MSCR) test was used to study creep and recovery behavior of thes...

Fundamental Understanding of the Thermal Degradation Mechanisms of Waste Tires and Their Air Pollutant Generation in a N2 Atmosphere

Abstract: The thermal decomposition of waste tires has been characterized via thermo-gravimetric analysis (TGA) tests, and significant mass loss has been observed between 300 and 500 degrees C. A series of gas chromatography-mass spectrometer (GC-MS) measurements, in which the instrument was coupled to a TGA unit, have been carried out to investigate the thermal degradation mechanisms as well as the air pollutant generation including volatile organic carbons (VOCs) and polycyclic aromatic hydrocarbons (PAHs) in a nitrogen atmosphere. In order to understand fundamental information on the thermal degradation mechanisms of waste tires, the main constituents of tires, poly-isoprene rubber (IR) and styrene butadiene rubber (SBR), have been studied under the same conditions. All of the experimental work indicated that the bond scission on each monomer of the main constituents of tires was followed by hydrogenation and gas phase reactions. This helped to clarify the independent pathways and species attributable to IR and SBR during the pyrolysis process. To extend that understanding to a more practical level, a flow-through reactor was used to test waste tire, SBR and IR samples in the temperature range of 500-800 degrees C at a heating rate of approximately 200 degrees C. Lastly, the formation of VOCs (approximately 1-50 PPMV/10 mg of sample) and PAHs (approximately 0.2-7 PPMV/10 mg of sample) was observed at relatively low temperatures compared to conventional fuels, and its quantified concentration was significantly high due to the chemical structure of SBR and IR. The measurement of chemicals released during pyrolysis suggests not only a methodology for reducing the air pollutants but also the feasibility of petrochemical recovery during thermal treatment.

Tailoring properties of styrene butadiene rubber nanocomposite by various nanofillers and their dispersion

Abstract: Organic–inorganic nanocomposite hybrids of styrene butadiene rubber were prepared with various nanofillers like modified and unmodified montmorillonite, sepiolite (SP), hectorite, carbon nanofiber (F), and expanded graphite. Comparison of the nanocomposites against the gum on the basis of mechanical properties illustrates that Cloisite15A (15A) produced an increment of 230% in the tensile strength (TS), at 8 phr loading. At 6 phr loading, F increased the modulus by 101%, while tear strength increased by 79%. Once optimized for loading, these nanocomposites were subjected to various compatibilization and dispersion techniques to achieve enhanced dispersion of the nanofillers. On modification, 15A registered 146% increase in modulus and 303% in TS, while F illustrated 150% increment in modulus and 113% in TS of the nanocomposite, over the gum control. Thorough dynamic mechanical and swelling studies were also performed. X-ray diffraction, atomic force microscopy and transmission electron microscopy were used to study the morphology. The London dispersive forces explained the enhanced properties on using carbon nanofiber, while the wider gallery gap and increased compatibility because of high organo-modifier content explicated the efficacy of 15A. Adsorption followed by shearing as well as intercalation of the rubber into clay layers were suggested as the probable mechanisms. POLYM. ENG. SCI., 2009. © 2008 Society of Plastics Engineers

The use of styrene-butadiene rubber waste as a potential filler in nitrile rubber: order of addition and size of waste particles

Abstract: Styrene-butadiene rubber (SBR) has large applications in the shoe industry, especially as expanded sheets used to produce insoles and inner soles. According to TG analysis, the rubber content in SBR residues (SBR-r) was found to be around 26-wt%. Based on that data, a cost-effective technique for the reuse of SBR-r in Nitrile rubber (NBR) was developed. Later, the effect of SBR-r on the cure behavior, mechanical performance, swelling, and crosslink density of reused rubber was investigated, with more emphasis placed on the effect of both particle size and loading of waste filler. Cure characteristics such as optimum cure time and scorch time were then reduced by the increasing amount of SBR-r filler. Owing to the reinforced nature of the largest particle size SBR-r, the best results for the mechanical properties of NBR were those in which SBR-r was added at the end of the cure process. The study has thus shown that SBR residue (SBR-r) can be used as an economical alternative filler in NBR.

Conductivity and mechanical properties of composites based on MWCNTs and styrene‐butadiene‐styrene block™ copolymers

Abstract: Composites based on multiwall carbon nanotubes (MWCNTs) and the block copolymer styrene-butadiene-styrene with two different contents of styrene have been investigated and their electrical conductivity and mechanical properties have been evaluated. The composites were prepared by a solution casting procedure, using a dispersant agent for the MWCNTs. Conductivity values of 10−4 and 1.6 S cm−1 have been obtained for samples containing 1 and 12 wt % of MWCNTs, respectively. The percolation threshold achieved for these systems was ∼0.25 wt %. According to dynamic mechanical analysis, the MWCNTs interact with both phases of the copolymers, acting as a reinforcement filler, whereas the dispersant agent acts as a plasticizer. However, it was shown that the reinforcing effect of the MWCNTs overcomes the latter, resulting in an overall improvement of mechanical properties of the composites. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Dynamic mechanical analysis of ethylene–propylene–diene monomer rubber and styrene–butadiene rubber blends

Abstract: The effects of blend ratio, crosslinking systems, and fillers on the viscoelastic response of ethylene–propylene–diene monomer (EPDM)/styrene–butadiene rubber (SBR) blends were studied as functions of frequency, temperature, and cure systems. The storage modulus decreased with increasing SBR content. The loss modulus and loss tangent results showed that the EPDM/SBR blend vulcanizate containing 80 wt % EPDM had the highest compatibility. Among the different cure systems studied, the dicumyl peroxide cured blends exhibited the highest storage modulus. The reinforcing fillers were found to reduce the loss tangent peak height. The blend containing 40 wt % EPDM showed partial miscibility. The dispersed EPDM phase suppressed the glass-transition temperature of the matrix phase. The dynamic mechanical response of rubbery region was dominated by SBR in the EPDM–SBR blend. The morphology of the blend was studied by means of scanning electron microscopy. The blend containing 80 wt % EPDM had small domains of SBR particles dispersed uniformly throughout the EPDM matrix, which helped to toughen the matrix and prevent crack propagation; this led to enhanced blend compatibility. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Improving the aging resistance of styrene-butadiene-styrene tri-block copolymer and application in polymer-modified asphalt

Abstract: Thermal oxidation process of styrene-butadiene-styrene (SBS) copolymer was studied by using a variety of analytical and spectroscopic methods including thermal analysis, dynamic mechanical analysis and FTIR spectroscopy. The experimental results indicate that the thermal oxidation process of SBS is a free radical self-catalyzed reaction containing four steps (initiation, growth, transfer, and termination of the chain) with both crosslinking and scission and the latter is confirmed to be the main process. The antioxidants 1010 as scavenger of free radicals and 168 acting decomposition of hydroperoxides were used to improve the oxidation aging resistance of SBS copolymer. It has been found that synergic effect of 1010 and 168 may be the best in practice and 0.2 wt % 1010 + 0.4 wt % 168 can effectively prevent SBS from the thermal oxidation at certain temperature. Furthermore, the aging resistance of the SBS-modified asphalt was improved by addition of complex antioxidants. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 116: 754-761, 2010

Preferential Media for Abrasive Flow Machining

Abstract: The abrasive flow machining (AFM) is used to deburr, radius, polish and remove recast layer of components in a wide range of applications. Material is removed from the workpiece by a flowing semisolid mass across the surface to be finished. In this study a medium for AFM has been developed from the various viscoelastic carriers and has been contrasted through experimental investigation. The viscoelastic media are selected on the basis of existing media through the studies of thermogravimetric analysis and are characterized by mechanical, as well as rheological, properties with the help of a universal testing machine and a rheometer. The performance of the medium is evaluated through the finishing criteria on a two-way AFM setup. The investigation reveals that the styrene butadiene rubber (SBR) medium gives a good improvement in surface finish. The surface improvement through SBR media is 88%. It is also found that the strain, temperature, shear rate, time of applied constant stress, cyclic loading, etc. have an impact on the mechanical and rheological properties of the newly developed medium, which are ultimately governed by the performance of the medium in the target applications.

Accelerator adsorption onto carbon nanotubes surface affects the vulcanization process of styrene–butadiene rubber composites

Abstract: The multiwalled carbon nanotubes (MWCNT) filled styrene–butadiene rubber (SBR) composites were prepared by incorporating MWCNT in a SBR/toluene solution and subsequently evaporating the solvent. These composites have shown a significant improvement in Young's modulus and tensile strength with respect to SBR gum without sacrificing high elongation at break. However, this improvement is less than expected at the higher filler content. Then, the influence of low concentrations of MWCNT on the vulcanization process of the SBR composites was studied by means of rheometer torque curves, swelling measurements, differential scanning calorimeter (DSC) analysis, and Fourier transform infrared (FTIR) spectroscopy. Also, their thermal degradation was studied by thermogravimetric analysis (TGA). It has been noticed that MWCNT affects the cure kinetics of SBR gum matrix reducing all parameters, i.e., the total heat rate and order of the reaction, scorch delay, maximum torque, and crosslink density. This effect increases as MWCNT content does, and it was attributed to the adsorption of the accelerator employed in the vulcanization (N-tert-butyl-benzothiazole-2-sulfenamide) onto the MWCNT surface. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Nanostructured fly ash–styrene butadiene rubber hybrid nanocomposites

Abstract: Hybrid nanocomposites of styrene butadiene rubber (SBR) with nanostructured fly-ash (NFA) were prepared in the laboratory by melt blending technique in an internal mixer. Curatives were added on a laboratory two-roll mill. Curing characteristics as well as physicomechanical properties of the composites were evaluated. A comparison on SBR composites filled with fresh fly-ash (FFA); carbon black (CB) and precipitated silica (PS) has been reported. In general, SBR-NFA composites exhibit higher state of cure and higher strength properties as compared with HAF black-filled and fresh fly-ash-filled SBR composites at equivalent loadings. This may be attributed to the higher reinforcing ability of NFA. This fact has also been supported by the swelling studies and Kraus’ plot. Tear strength and abrasion resistance of the SBR-NFA composites were superior to FFA-filled and precipitated silica-filled vulcanizates, but were inferior to carbon black- filled SBR vulcanizates. The SBR-NFA composites showed lower hardness as compared with both the carbon blackfilled and silica-filled composites. Transmission electron microscopy and scanning probe microscopy studies revealed that the NFA particles are well dispersed in the SBR matrix. These results were further supported by fracture surface analysis under the SEM, which revealed the role of NFA in the prevention of fracture propagation. POLYM. COMPOS., 30:1647–1656, 2009. a 2008 Society of Plastics Engineers

Morphology, interfacial interaction and properties of styrene-butadiene rubber/modified halloysite nanotube nanocomposites

Abstract: A natural nanotubular material, halloysite nanotubes (HNTs), was introduced to prepare styrene-butadiene rubber/modified halloysite nanotube (SBR/m-HNT) nanocomposites. Complex of resorcinol and hexamethylenetetramine (RH) was used as the interfacial modifier. The structure, morphology and mechanical properties of SBR/m-HNT nanocomposites, especially the interfacial interactions, were investigated. SEM and TEM observations showed that RH can not only facilitate the dispersion and orientation of HNTs in SBR matrix at nanometer scale, but also enhance the interfacial combination between HNTs and rubber matrix. FTIR and XPS investigations confirmed that a number of hydrogen bonds were formed between the phenol hydroxyl groups in resorcinol-formaldehyde resin derived from RH and the oxygen atoms in Si–O bonds or hydroxyl groups on HNTs surfaces. The m-HNTs modified with RH have significant reinforcing effect on SBR vulcanizates. RH as a good interfacial modifier can remarkably improve mechanical properties of...

Thermal degradation behavior of styrene‐butadiene‐styrene tri‐block copolymer/multiwalled carbon nanotubes composites

Abstract: The thermal degradation behavior of styrene-butadiene-styrene triblock copolymer (SBS) and SBS/multiwalled carbon nanotubes (MWCNTs) composites prepared by solution processing and melt mixing, respectively, was investigated using nonisothermal thermogravimetric analysis (TGA). The kinetic parameters of the activation energy (Ea) for degradation, preexponential factor A, and the reaction order (n) were evaluated by the Flynn-Wall-Ozawa, Kissinger, and Coats-Redfern methods, respectively. Ea increased and n decreased after the incorporation of 3 wt % of MWCNTs into the SBS. The Ea of SBS/MWCNTs composite prepared by melt mixing was higher than that by solution processing, which was attributed to the good dispersion of MWCNTs in SBS and the interactions between MWCNTs and SBS. The gases evolved during thermal degradation at a nitrogen atmosphere were studied by Fourier transform infrared spectroscopy (FTIR) coupled with the TGA. Aliphatic and aromatic CH peaks appeared simultaneously in FTIR spectra, indicating the thermal degradation of SBS proceeds by a random chain scission process. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Wear characteristics of styrene butadiene rubber/natural rubber blends with varying carbon blacks by DIN abrader and mining rock surfaces

Abstract: In this study, nine rubber compounds were produced by varying the proportions of natural rubber (NR), styrene butadiene rubber (SBR), and four different carbon blacks. Tensile and tear properties are enhanced by the addition of intermediate super abrasion furnace (ISAF) N231, and modulus increases for the compounds containing N234 carbon blacks. The wear behavior of the prepared rubber vulcanizates against various rocks, such as, granite, shale, schist, sandstone, coal, and concrete, at 4.4 N normal load and 0.8 m/s relative sliding speed were studied in a specially fabricated experimental setup. The DIN abrasion testing results show good abrasion resistant properties of 70 phr NR and 30 phr SBR with N231 grade ISAF type carbon black. Also, moderate abrasion resistance is found in rubber compound containing 80 phr NR and 20 phr SBR with N234 grade ISAF type of carbon black. Out of the various rock types, the schist and sandstone are observed to be highly abrasive against the prepared rubber compounds. The microscopic examination of the abraded rubber surfaces has indicated the formation of longitudinal grooves against harder rocks and transverse ridges against softer rocks. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Synthesis and characterization of styrene butadiene rubber—Bentonite clay nanocomposites

Abstract: In the present study, naturally occurring unfractionated bentonite clay was used to prepare styrene butadiene rubber/bentonite clay nanocomposite by latex stage blending. The bentonite clay was organo-modified by in situ resol formation by the reaction of resorcinol and formaldehyde. The latex clay mixture was co-coagulated with acid. The resulting clay masterbatch was compounded and evaluated by Fourier Transform Infrared spectroscopy, X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), Energy Dispersive X-ray spectroscopy (EDS), Scanning Electron Microscopy, Thermogravimetric analysis, and Differential Scanning Calorimetry. XRD showed that the interplanar distance of the in situ resol-modified bentonite clay increased from 1.23 to 1.41 nm for the unmodified bentonite. TEM analysis indicated partial exfoliation and/or intercalation. EDS (Si and Al mapping) of the clay revealed the nature of the dispersion in the nanocomposites vis-a-vis the conventional styrene-butadiene rubber (SBR)/bentonite clay composite. Thermogravimetric analysis was used to compare the decomposition trends of the SBR/clay nanocomposites with the SBR/clay composite. The glass transition temperature of SBR/clay nanocomposites increased as compared with that of neat SBR. Substantial improvement in most of the other mechanical properties was also observed in case of the nanocomposites. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers