Showing papers on "Styrene-butadiene published in 2004"

Styrene butadiene styrene polymer modification of road bitumens

Abstract: This paper describes the polymer modification of road bitumens with SBS. Six polymer modified bitumens (PMBs) were produced by mixing bitumen from two crude oil sources with an SBS copolymer at three polymer contents. The rheological characteristics of the SBS PMBs were analysed by means of dynamic mechanical analysis using a dynamic shear rheometer (DSR). The results of the investigation indicate that the degree of SBS modification is a function of bitumen source, bitumen-polymer compatibility and polymer concentration. When the polymer concentration and bitumen-polymer compatibility allow a continuous polymer network to be established, modification is provided by a highly elastic network which increases the viscosity, stiffness and elastic response of the PMB, particularly at high service temperatures. However, ageing of the SBS PMBs tends to result in a reduction of the molecular size of the SBS copolymer with a decrease in the elastic response of the modified road bitumen.

Preparation and properties of nanocomposites based on acrylonitrile-butadiene rubber, styrene-butadiene rubber, and polybutadiene rubber

Abstract: Nanocomposites were prepared with different grades of nitrile rubber with acrylonitrile contents of 19, 34, and 50%, with styrene–butadiene rubber (23% styrene content), and with polybutadiene rubber with Na-montmorillonite clay. The clay was modified with stearyl amine and was characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and transmission electron microscopy (TEM). The XRD studies showed an increase in the gallery gap upon the modification of the filler by stearyl amine. The intercalation of the amine chains into the clay gallery gap was confirmed by the presence of some extra peaks (2928, 2846, and 1553 cm−1) in the FTIR spectra. The clay–rubber nanocomposites were characterized by TEM and XRD. The mechanical properties were studied for all the compositions. An improvement in the mechanical properties with the degree of filler loading up to a certain level was observed. The changes in the mechanical properties, with changes in the nature and polarity of the rubbers, were explained with the help of XRD and TEM results. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1573–1585, 2004

Preparation and properties of styrene–butadiene rubber based nanocomposites: The influence of the structural and processing parameters

Abstract: Rubber-based nanocomposites were prepared with octadecyl amine modified sodium montmorillonite clay and styrene–butadiene rubber with different styrene contents (15, 23, and 40%). The solvent used to prepare the nanocomposites, the cure conditions, and the cure system were also varied to determine their effect on the properties of the nanocomposites. All the composites were characterized with X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and transmission electron microscopy (TEM). The XRD studies revealed exfoliation for the modified clay–rubber composites. The TEM photomicrographs showed a uniform distribution of the modified clay in the rubber matrix. The thickness of the particles in the exfoliated composites was around 10–15 nm. Although the FTIR study of the unmodified and modified clays showed extra peaks due to the intercalation of the amine chains into the gallery, the spectra for the rubber–clay nanocomposites were almost the same because of the presence of a very small amount of clay in the rubber matrix. All the modified clay–rubber nanocomposites displayed improved mechanical strength. The styrene content of the rubber had a pronounced effect on the properties of the nanocomposites. With increasing styrene content, the improvement in the properties was greater. Dicumyl peroxide and sulfur cure systems displayed similar strength, but higher elongation and slightly lower modulus values were obtained with the sulfur cure system. The curing of the samples at four different durations at 160°C showed that the cure time affected the properties. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 698–709, 2004

Fly ash particles and precipitated silica as fillers in rubbers. I. Untreated fillers in natural rubber and styrene–butadiene rubber compounds

Abstract: In this study, we investigated the effects of untreated precipitated silica (PSi) and fly ash silica (FASi) as fillers on the properties of natural rubber (NR) and styrene- butadiene rubber (SBR) compounds. The cure characteristics and the final properties of the NR and SBR compounds were considered separately and comparatively with regard to the effect of the loading of the fillers, which ranged from 0 to 80 phr. In the NR system, the cure time and minimum and maximum torques of the NR compounds progressively in- creased at PSi loadings of 30 -75 phr. A relatively low cure time and low viscosity of the NR compounds were achieved throughout the FASi loadings used. The vulcanizate prop- erties of the FASi-filled vulcanizates appeared to be very similar to those of the PSi-filled vulcanizates at silica con- tents of 0 -30 phr. Above these concentrations, the properties of the PSi-filled vulcanizates improved, whereas those of the FASi-filled compounds remained the same. In the SBR sys- tem, the changing trends of all of the properties of the filled SBR vulcanizates were very similar to those of the filled NR vulcanizates, except for the tensile and tear strengths. For a given rubber matrix and silica content, the discrepancies in the results between PSi and FASi were associated with filler- filler interactions, filler particle size, and the amount of nonrubber in the vulcanizates. With the effect of the FASi particles on the mechanical properties of the NR and SBR vulcanizates considered, we recommend fly ash particles as a filler in NR at silica concentrations of 0 -30 phr but not in SBR systems, except when improvement in the tensile and tear properties is required. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2119 -2130, 2004

Styrene−Butadiene−Styrene Triblock Copolymers Modified with Polyhedral Oligomeric Silsesquioxanes

Abstract: A novel hybrid organic/inorganic triblock copolymer of polystyrene−butadiene−polystyrene (SBS) containing grafted polyhedral oligomeric silsesquioxane (POSS) molecules was synthesized by a hydrosilation method. The POSS molecules were designed to contain a single silane functional group, which was used to graft onto the dangling 1,2-butadienes in the polybutadiene soft block. Unlike typical free radical copolymerizations commonly used for many other POSS incorporations investigated, this synthesis method allows us to make a series of polymers with varying amounts of POSS without any change to the overall degree of polymerization or structure of the main SBS backbone. This gives us a unique opportunity to study the POSS behavior in the matrix and know that all differences are solely due to the POSS grafted to the soft continuous butadiene phase. X-ray diffraction revealed that the grafted POSS are very well dispersed in the matrix of the hybrid polymer, which is compared to the strong phase segregation obs...

Styrene-butadiene-styrene Tri-block Copolymers Modified wit Polyhedral Oligomeric Silsesquioxanes

Abstract: : A novel hybrid organic/inorganic tri-block copolymer of polystyrene-butadiene-polystyrene (SBS) containing grafted polyhedral oligomeric silsesquioxane (POSS) molecules was synthesized by a hydrosilation method. The POSS molecules were designed to contain a single silane functional group, which was used to graft onto the dangling 1,2 butadienes in the polybutadiene soft block. Unlike typical free radical copolymerizations commonly used for many other POSS incorporations investigated, this synthesis method allows us to make a series of polymers with varying amounts of POSS without any change to the overall degree of polymerization or structure of the main SBS backbone. This gives us a unique opportunity to study the POSS behavior in the matrix and know that all differences are solely due to the POSS grafted to the soft continuous butadiene phase. X-ray diffraction revealed that the grafted POSS are very well dispersed in the matrix of the hybrid polymer, which is compared to the strong phase segregation observed in a POSS physical blend. Small-angle X-ray scattering indicates that although the cylindrical morphology attributed to the styrene component was not altered by the presence of POSS, but attachment of POSS to the continuous phase (polybutadiene block) causes the packing of discrete phase (polystyrene blocks) to lack long-range features. Results of dynamic mechanical analysis showed that the POSS has sterically hindered the motion of the polybutadiene blocks. More interestingly, the presence of POSS in the soft segments also resulted in a tapered tan peak associated with the glass transition of polystyrene and a higher tensile strength when deformed at temperature near Tg of polystyrene without affecting the elongational behavior of SBS at temperatures above Tg of polybutadiene.

Influence of filler type and content on properties of styrene-butadiene rubber (SBR) compound reinforced with carbon black or silica

Abstract: Rubber compounds are filled with reinforcing fillers to improve their physical properties. Carbon black and silica have different surface chemistries to each other. Differences in properties of carbon black- and silica-reinforced styrene-butadiene rubber (SBR) compounds were studied. Variation of properties of carbon black- or silica-filled compounds with the filler content was also investigated. The silica-filled compounds without any coupling agent and dispering agent were prepared to investigate the influence of polar materials-adsorption on the silica surface. Viscosity and crosslink density increased with increase of the filler content. Hardness, modulus, tensile strength, and wear property were improved more and more by increasing the filler content. Viscosity of the silica-filled compound was higher than that of the carbon black-filled one. Cure rate of the silica-filled compound became slower as the filler content increased, while that of the carbon black-filled one became faster. Difference in properties between the carbon black- and silica-filled compounds were explained by the poor silica dispersion and the adsorption of cure accelerator on the silica surface. Copyright © 2004 John Wiley & Sons, Ltd.

Organomodified montmorillonite as filler in natural and synthetic rubber

Abstract: The filler action of dodecylamine (12C) intercalated montmorillonite (MNT) referred to as organomodified montmorillonite (12C-MNT) up to 4 wt % on natural rubber (NR) and styrene butadiene rubber (SBR) was studied and findings were compared with respect to the unmodified Na-MNT. X-ray analysis was used to calculate the interchain separation (R and R′), degree of crystallinity (Xc), and distortion factor (k). It is noted that R and R′ showed the opposite trend, whereas Xc as well as k showed overall increasing trend with an increasing amount of 12C-MNT on both NR and SBR. For Na-MNT (1 wt %) filled NR and SBR, the corresponding magnitude of R and R ′ and Xc showed nearly no change, whereas kc increased significantly. The crosslinking density (vc) does not show any significant changes in NR, whereas for SBR, it increases with increasing 12C-MNT as filler. Interestingly, in the case of 1 wt % pure Na-MNT used as filler for both NR and SBR, vc was lower compared to the virgin rubbers. Both swelling index (si) and sol fraction (Q) do not show any significant variation for NR composites, whereas these decrease for SBR composites with increasing concentration of 12C-MNT filler. On the contrary, NR and SBR with 1 wt % of Na-MNT filler show greater magnitude of si and Q corresponding to the pure ones. Measurements of mechanical properties showed a significant increase in tensile strength and elongation at break for NR-12C-MNT (4 wt %) when compared with either virgin NR. In addition, modulus at the elongation at 100 and 200% in general increases with increasing loading of 12C-MNT filler in NR. Similar observations were also noted in the case of SBR. Interestingly, when only pure Na-MNT is used as filler, the strength of NR and SBR decreases drastically. Scanning electron microscopic studies were also to used support the mechanical behavior of NR-12MNT and SBR-12CMNT composites. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3583–3592, 2004

A Novel Approach to High Performance Elastomer by Using Clay

Abstract: A novel method was developed to prepare an exfoliated styrene butadiene rubber (SBR)/clay nanocomposite with a strong interface between the clay layers and the rubber. An exfoliation mechanism was proposed and verified based on X-ray diffraction (XRD)/transmission electron microscopy (TEM) analyses of the intercalation/exfoliation phenomena after each step of the process. The significant improvements of mechanical properties may give the first evidence that both exfoliation and a strong interface play critical roles in nanoreinforcement.

Improvement of properties of silica-filled styrene-butadiene rubber composites through plasma surface modification of silica

Abstract: The performance of plasma surface modified silica filler in styrene-butadiene rubber (SBR) matrix has been analyzed. The conditions of plasma modification have been optimized by taking secant modulus as a standard parameter and the occurrence of the modification has been confirmed by surface area determination and Fourier transform infrared spectroscopy. The plasma-modified surface of silica has been found to be composed of carbon–carbon double bonds and carbon–hydrogen bonds. Silane treatment also has been carried out on silica filler surface for a comparative assessment of its influence in the curing behavior and filler–rubber interaction. The cure reactions of all the rubber compounds have been found to be proceeded according to first-order kinetics. A reduction in the cure reaction rate constant has been observed with the loading of unmodified and surface modified silica, emphasizing the cure deactivation of the matrix rubber by the silica filler. The filler dispersion, as revealed by scanning electron microscopy, has been found to be greatly improved by the plasma as well as silane treatment. The filler–rubber interaction has been found to be greatly improved by both surface treatments, but the best balance of mechanical properties has been observed with plasma surface modification only. Copyright © 2004 John Wiley & Sons, Ltd.

Synthesis and Characterization of Epoxidized Styrene-Butadiene Block Copolymers as Templates for Nanostructured Thermosets

Abstract: Summary: A wide range of epoxidized styrene-block-butadiene block copolymers were synthesized using hydrogen peroxide in the presence of an in situ prepared methyltrioctylammoniumtetrakis(diperoxotungstate)phosphate as the catalyst system in a water/dichloroethane biphasic system. 1H NMR and FT-IR spectra revealed that the epoxidation procedure led mainly to 1,4-epoxidized butadiene units. GPC analysis showed that epoxidation changed the copolymer architecture into stars with fewer arms. The copolymers showed two glass transition temperatures in accordance with the phase separation for block copolymers and, as revealed in AFM images, the self-assembly takes place on a nanometer scale. Moreover, epoxidized styrene-butadiene (SB) copolymers showed improved miscibility with epoxy monomers leading to self-assembled nanostructures in the uncured state. This allows them to be used as templates for nanostructured resins. TM-AFM phase images for: a) 40 mol-% epoxidized copolymer (scale bar = 300 nm); b) uncured blend containing 50 wt.-% DGEBA in 50 mol-% epoxidized copolymer (scale bar = 1 μm), after annealing at 80 °C in vacuum for 3 h.

Free Volume of Montmorillonite/Styrene-Butadiene Rubber Nanocomposites Estimated by Positron Annihilation Lifetime Spectroscopy

Abstract: The size and comcentration of free-volume holes of two kinds of montmorillonite (MMT)/styrene-butadiene rubber (SBR) nanocomposites were investigated by positron annihilation lifetime spectroscopy (PALS). Strong interfacial interaction caused an apparent reduction of the free-volume fraction of rubber probaly by depressing the formation of free-volume holes in the interfacial region. Interfacial interaction in MMT/SBR nanocomposites was weaker than that in SBR filled with carbon black.

Effect of bound rubber on characteristics of highly filled styrene–butadiene rubber compounds with different types of carbon black

Abstract: Viscosity and cure time of a filled rubber compound having an accelerated sulfur cure system are affected by types and contents of the rubber and the filler as well as of the curatives. Bound rubber content is used as level of the reinforcement. Influence of bound rubber on viscosity and cure time of a rubber compound was studied using highly filled styrene–butadiene rubber compounds with carbon black having different structures. The bound rubber content increases with increase of the carbon black content and also increases as the carbon black structure is developed. The Mooney viscosity increases linearly with increase of the bound rubber content irrespective of the carbon black structure when the primary particle size of carbon black is nearly the same. The Mooney scorch time decreases linearly with increase of the bound rubber content irrespective of the carbon black structure. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1001–1006, 2004

Thermogravimetric analysis, flammability and oil resistance properties in natural rubber and dichlorocarbene modified styrene butadiene rubber blends

Abstract: Thermogravimetric analysis (TGA), flammability and oil resistance in natural rubber (NR) and dichlorocarbene modified styrene butadiene rubber (DCSBR) blends were investigated as a function of different composition. TGA plot confirms the better thermal stability and flame resistance of DCSBR as well as its blends with NR. The simultaneous difference temperature plot showed the energy requirement for the degradation pattern of the blends. The flammability of the blend was monitored by the limiting oxygen index (LOI) measurement of the rubber vulcanizate. The amount of DCSBR in the blend significantly affected the properties of blends. The mechanical properties investigated after the immersion in ASTM oil was tensile strength, modulus, tear strength and hardness. It was found that these properties were decreases progressively with increasing NR content in the blends.

Toughening of polypropylene–ethylene copolymer with nanosized CaCO3 and styrene–butadiene–styrene

Abstract: Nanocomposites of nanosized CaCO3/polypropylene–ethylene copolymer (PPE) and nanosized CaCO3/PPE/styrene–butadiene–styrene (SBS) were prepared by using a two-roll mill and a single-screw extruder. By adding CaCO3 nanoparticles into the PPE matrix, the toughness of the matrix substantially improved. At a nanosized CaCO3 content of 12 phr (parts per hundred PPE resin by weight), the impact strength of CaCO3/PPE at room temperature reached 61.6 kJ/m2, which is 3.02 times that of unfilled PPE matrix. In the nanosized CaCO3/PPE/SBS system, the rubbery phase and filler phase are independently dispersed in the PPE matrix. As a result of the addition of nanosized CaCO3, the viscosity of PPE matrix significantly increased. The increased shear force during compounding continuously breaks down SBS particles, resulting in the reduction of the SBS particle size and improving the dispersion of SBS in the polymer matrix. Thus the toughening effect of SBS on matrix was improved. Simultaneously, the existence of SBS provides the matrix with a good intrinsic toughness, satisfying the condition that nanosized inorganic particles of CaCO3 efficiently toughen the polymer matrix. The synergistic toughening function of nanosized CaCO3 and SBS on PPE matrix was exhibited. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 796–802, 2004

Rice husk powder–filled polystyrene/styrene butadiene rubber blends

Abstract: Natural fibers are rich in cellulose and they are a cheap, easily renewable source of fibers with the potential for polymer reinforcement. The presence of large amounts of hydroxyl groups makes natural fibers less attractive for reinforcement of polymeric materials. Composites made from polystyrene (PS)/styrene butadiene rubber (SBR) blend and treated rice husk powder (RHP) were prepared. The RHP was treated by esterification and acetylation. A similar series of composites was also prepared using maleic anhydride–polypropylene (MA–PP) as a coupling agent. The processing behavior, mechanical properties, effect of thermooxidative ageing, and surface morphology of untreated and chemically modified RHP were studied. There was a decrease in tensile strength (except MA–PP composites), elongation at break, and Young's modulus in chemically treated RHP composites. The postreaction process during thermooxidative ageing enhanced the tensile strength and Young's modulus of the esterified and MA–PP composites. Acetylation treatment was effective in reducing the percentage of water absorption in RHP/PS–SBR composites. In general chemically treated RHP/PS–SBR composites and MA–PP showed a better matrix phase and filler distribution. However, the degree of filler–matrix interaction was mainly responsible for the improvement of mechanical properties in the composites. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3320–3332, 2004

Double Yielding in a Styrene/Butadiene Star Block Copolymer

Abstract: The morphology and tensile deformation behaviour of a highly asymmetric styrene/butadiene star block copolymer (polystyrene (PS) content = 74%) containing random PS-co-PB (polybutadiene) copolymer as a rubbery phase were investigated. The existence of double yielding, similar to that observed in some semicrystalline polymers, was detected in this nanostructured amorphous polymer. The observed phenomenon may be correlated with two different micromechanical processes taking place at the initial stage of deformation.

Effects of the blend ratio and crosslinking systems on the curing behavior, morphology, and mechanical properties of styrene–butadiene rubber/poly(ethylene‐co‐vinyl acetate) blends

Abstract: Blends of styrene–butadiene rubber (SBR) and poly(ethylene-co-vinyl acetate) (EVA) with different ratios were prepared with a two-roll mixing mill and were vulcanized by three different crosslinking systems, namely, sulfur (S), dicumyl peroxide, and a mixture consisting of S and peroxide (mixed). The vulcanization behavior of the blends was analyzed from the rheographs. The mechanical properties, including stress–strain behavior, tensile strength, elongation at break, modulus, hardness, and abrasion resistance, of the blends were examined. The morphology of the prepared blends was studied with scanning electron microscopy with special reference to the effects of the blend ratio and crosslinking systems. A relatively cocontinuous morphology was observed for the 20/80 SBR/EVA composition. The mechanical properties increased with increasing EVA content up to 60–80%, for all of the vulcanizing modes. The tensile fracture surfaces were analyzed under a scanning electron microscope to understand the failure mechanism. Various theoretical models were applied to explain the properties of the blends. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 827–837, 2004

Mechanical and aging properties of cross-linked ethylene propylene diene rubber / styrene butadiene rubber blends

Abstract: The mechanical properties and aging characteristics of blends of ethylene propylene diene monomer (EPDM) rubber and styrene butadiene rubber (SBR) were investigated with special reference to the effect of blend ratio and cross-linking systems. Among the blends, the one with 80/20 EPDM/SBR has been found to exhibit the highest tensile, tear, and abrasion properties at ambient temperature. The observed changes in the mechanical properties of the blends have been correlated with the phase morphology, as attested by scanning electron micrographs (SEMs). The effects of three different cure systems, namely, sulfur (S), dicumyl peroxide (DCP), and a mixed system consisting of sulfur and peroxide (mixed) on the blend properties also were studied. The stress-strain behavior, tensile strength, elongation at break, and tear strength of the blends were found to be better for the mixed system. The influence of fillers such as high-abrasion furnace (HAF) black, general-purpose furnace (GPF) black, silica, and clay on the mechanical properties of 90/10 EPDM/SBR blend was examined. The ozone and water aging studies also were conducted on the sulfur cured blends, to supplement the results from the mechanical properties investigation. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2606–2621, 2004

Elastomer gum polymer systems

Abstract: Elastomer precursor gum (for any of fluoroelastomer, acrylic acid ester rubber/polyacrylate rubber, ethylene acrylic rubber, silicone, nitrile butyl rubber, hydrogenated nitrile rubber, natural rubber, polyurethane, and styrene butadiene rubber) and non-gum polymer are admixed with optional electrically conductive particulate and/or optional filler to provide either a continuous phase of polymer with dispersed gum portions, a continuous phase of elastomer precursor gum with dispersed polymer portions, or an interpenetrated structure of elastomer precursor gum and polymer. Curing is optionally enabled with techniques such as electron beam radiation.

“Living” radical graft polymerization of styrene to styrene butadiene rubber (SBR) with 2,2,6,6‐tetramethyl‐1‐piperidinyloxy (TEMPO)

Abstract: Well-defined graft copolymers with styrene butadiene rubber (SBR) backbones and polystyrene branches were synthesized by living free radical polymerization (LFRP) techniques. Thus 1- benzoyl-2-phenyl-2-(2′,2′,6′,6′-tetramethyl-piperidinyl-1′-oxy)ethane (BZ-TEMPO) was synthesized and hydrolyzed to the corresponding 1-hydroxyl derivative. This functional nitroxyl compound was coupled with brominated SBR (SBR-Br). The resulting macroinitiator (SBR-TEMPO) for “living” free radical polymerization was then heated in the presence of styrene for the formation of the controlled graft copolymer. 1H-NMR and IR spectroscopy were used to investigate the structure of the polymers. Copyright © 2004 John Wiley & Sons, Ltd.

High-speed testing and material modeling of unfilled styrene butadiene vulcanizates at impact rates

Abstract: High-speed tensile tests were performed on unfilled SBR strip and sheet specimens at room temperature. Uniaxial dynamic stress-extension ratio curves indicated three distinct regions of rate-dependent behavior when strain rates were below 180 s−1, between 180–280 s−1and above 280 s−1. With increasing strain rate, the toughness increased in the first region, remained roughly constant in the second region, and decreased in the third region. Time-temperature shift on SBR near the glass transition temperature used to obtain high strain rate tensile strength at room temperature did not give the same results as those found in the impact tensile test. The dynamic toughness was used to predict failure of rubber sheets under impact loads using ABAQUS Explicit. Predicted values of the sheet extension at the onset of failure were within 10% of experimental values.