Showing papers on "Styrene-butadiene published in 2018"

Effect of ageing on the morphology and creep and recovery of polymer-modified bitumens

Abstract: Polymer additives are used to improve the properties of road bitumens including their oxidative resistance. However, their usage as anti-oxidative materials remains relatively unclear. This study aims to investigate the changes in the morphology and the rheological response of polymer modified bitumens used in road pavement construction caused by ageing. An elastomer (radial styrene butadiene styrene, SBS) and a plastomer (ethyl vinyl acetate, EVA) polymer were mixed with one base bitumen at three polymer concentrations. The bitumens were RTFO and PAV aged. The morphology of the bitumens was captured by fluorescence microscopy while the rheological properties were measured by means of the multiple stress creep and recovery (MSCR) test. The results show that the morphology of the SBS modified bitumen degrades with ageing as a function of polymer concentration and dispersion, with higher dispersion being more resistant. The morphology of the EVA modified bitumen has a low ageing susceptibility irrespective of polymer concentration. The MSCR response of EVA modified bitumens does not differ from that found for unmodified bitumen, where the hardening produces a decrease in the non-recoverable compliance. In the case of SBS modified bitumen, the degradation of the polymer backbone affects the bitumen hardening as much as the polymer phase dispersed and networked in the bitumen phase. Furthermore, in the case of the elastomer, the average percent recovery is in agreement with the variation of the morphology with ageing. Therefore, the use of the average percent recovery as a valuable rheological index of the integrity of the polymer network can be advocated.

Microstructures, thermal and mechanical properties of epoxy asphalt binder modified by SBS containing various styrene-butadiene structures

Abstract: As the most important thermoplastic and thermosetting modifiers, styrene–butadiene–styrene triblock copolymer (SBS) and epoxy resin have been widely applied in asphalt modifications. In this paper, epoxy SBS-modified asphalts (ESBAs) were prepared with epoxy monomer, curing agent and SBS-modified asphalts (SBAs) with various styrene–butadiene structures, which in turn were subjected to laser scanning confocal microscopy (LSCM), viscous measurements, thermal analysis and tensile tests. The LSCM results revealed that both polymer-rich phase and fluorescent particle-rich phase were observed in the asphalt matrix. Moreover, the number of SBS particles in SBAs increased with the increase of styrene contents. The presence of SBS decreased the size of dispersed domains in the continuous epoxy phase of the neat epoxy asphalt binder (EAB). For ESBAs, a double phase separation occurred between SBA and epoxy in the continuous epoxy phase and between asphalt and SBS in the dispersed SBA phase. Both number and size of SBS domains in the dispersed SBA phase of ESBAs increased with the increase of styrene contents. The inclusion of styrenic polymers increased the viscosity of the neat EAB. The viscosity of ESBAs increased with the increase of average molecular weights of the styrenic polymers. The addition of styrenic polymers increased the glass transition temperature (Tg) and storage modulus (E′) of the neat EAB. Meanwhile, the inclusion of styrenic polymers weakened the damping properties of the neat EAB. The styrene-butadiene structures had little effect on the Tg and damping properties of ESBAs. The E′ of ESBAs decreased with the increase of styrene contents. The presence of SBS enhanced the thermal stability of the neat EAB. Tensile results showed that the addition of SBS increased the tensile strength of the neat EAB.

Intrinsic Tuning of Poly(styrene-butadiene-styrene)-Based Self-Healing Dielectric Elastomer Actuators with Enhanced Electromechanical Properties.

Abstract: The electromechanical properties of a thermoplastic styrene-butadiene-styrene (SBS) dielectric elastomer was intrinsically tuned by chemical grafting with polar organic groups. Methyl thioglycolate (MG) reacted with the butadiene block via a one-step thiol-ene "click" reaction under UV at 25 °C. The MG grafting ratio reached 98.5 mol % (with respect to the butadiene alkenes present) within 20 min and increased the relative permittivity to 11.4 at 103 Hz, with a low tan δ. The actuation strain of the MG-grafted SBS dielectric elastomer actuator was 10 times larger than the SBS-based actuator, and the actuation force was 4 times greater than SBS. The MG-grafted SBS demonstrated an ability to achieve both mechanical and electrical self-healing. The electrical breakdown strength recovered to 15% of its original value, and the strength and elongation at break recovered by 25 and 21%, respectively, after 3 days. The self-healing behavior was explained by the introduction of polar MG groups that reduce viscous loss and strain relaxation. The weak CH/π bonds through the partially charged (δ+) groups adjacent to the ester of MG and the δ- center of styrene enable polymer chains to reunite and recover properties. Intrinsic tuning can therefore enhance the electromechanical properties of dielectric elastomers and provides new actuator materials with self-healing mechanical and dielectric properties.

Catalytic and networking effects of carbon black on the kinetics and conversion of sulfur vulcanization in styrene butadiene rubber

Abstract: The present work discusses the effects of carbon-black (CB) on the kinetics and conversion of sulfur vulcanization in styrene butadiene rubber (SBR) compounds. Kinetic studies revealed that the onset of the vulcanization reaction shortens monotonically by incorporation of CB, but the rate of vulcanization goes through a maximum at a critical loading of CB. It was demonstrated that CB has two roles in the kinetics of vulcanization: a catalytic effect on accelerating the initial reactions among vulcanization agents and a networking effect on retarding the crosslinking of macro-radicals. It was shown that the latter effect dominates the former one at high concentrations of CB where the rubber-mediated network of CB is formed and a large portion of rubber is immobilized as bound rubber. By using two types of CBs with very different specific surface areas, it was discussed that the critical loading at which the retarding effect begins coincides with the rheological percolation threshold of CBs. Moreover, conversion of vulcanization under isothermal conditions was continuously reduced as the concentration of CBs increased. This was correlated to the magnitude of the physical restrictions exerted by CBs, depending on the specific surface area of each CB. However, it was also shown that this restriction could be alleviated at higher temperatures during non-isothermal vulcanization, which enhances the degree of conversion in crosslinking.

Design of a High-Strength XSBR/Fe3O4/ZDMA Shape-Memory Composite with Dual Responses

Abstract: In this paper, dual-response shape-memory polymers (SMPs) based on carboxylic styrene butadiene rubber (XSBR)/ferriferrous oxide (Fe3O4)/zinc dimethacrylate (ZDMA) were designed. Fe3O4 was incorpor...

The aggregation structure regulation of lignin by chemical modification and its effect on the property of lignin/styrene–butadiene rubber composites

Abstract: The aggregation structure of lignin in aqueous solution had an important effect on the dispersion of lignin and the properties of lignin/styrene–butadiene rubber (SBR) composites. This article revealed the relationship between aggregation structure and chemical structure of modified lignin. Unmodified lignin was amorphous; however, our results showed that aldehyde-modified lignin was transformed into spherical aggregates, while propylene-oxide-modified lignin self-aggregated into supramolecular domains. The relationships between aggregation structure, filler dispersion, filler–rubber interaction, and performance were also studied by investigating the microstructure, viscoelastic behavior, and mechanical properties of lignin/SBR composites. Meanwhile, a solution to improve the coprecipitation efficiency of lignin and SBR latex was proposed. In this article, epoxidized natural rubber (ENR) was also used as compatibilizer to improve the interfacial adhesion between polar lignin and nonpolar SBR. The results showed better lignin dispersion for the ENR-containing rubber composites, as well as superior wet skid resistance and lower rolling resistance. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 135, 45759.

The role of devulcanizing agent for mechanochemical devulcanization of styrene butadiene rubber vulcanizate

Abstract: More or less universally, bis(3-triethoxysilyl propyl) tetrasulfide (TESPT) has been used as a coupling agent during dispersion of silica filler in a virgin nonpolar rubber compound. It is for the first time that TESPT has been used as a devulcanizing agent and as-grown devulcanized rubber facilitates the silica dispersion in nonpolar rubber compound without any coupling agent. Dual functionalities of TESPT have been modeled and validated in this work. Various factors like the role of sol-gel content, inherent viscosity of sol rubber, crosslink density, and degree of devulcanization were investigated as a function of devulcanization time and amount of TESPT to optimize devulcanization time and TESPT amount. To study the silica reinforcement, revulcanization of devulcanized SBR was carried out with silica filler and the curing characteristics of the material were evaluated. From the mechanical properties and thermogravimetry analysis the optimum time for devulcanization is determined. Further, scanning electron microscopy (SEM) studies were undertaken to check the coherency and homogeneity of the material. POLYM. ENG. SCI., 2017. © 2017 Society of Plastics Engineers

A molecular dynamics study on efficient nanocomposite formation of styrene–butadiene rubber by incorporation of graphene

Abstract: A molecular level study has been made on enhanced mechanical and tribological properties of graphene-reinforced styrene butadiene rubber (SBR) composites using molecular dynamics simulation technique. Constant strain method is applied to calculate the mechanical properties of developed structures. Two molecular level layer model one with SBR and another with graphene-reinforced SBR composites were developed, and shear loading was applied on the top and bottom Fe layers to study tribological properties, i.e., abrasion rate, and friction coefficient. The Young’s and shear modulus of composites with different graphene oxide volume fractions have been developed and studied. The 5 vol% addition of graphene into SBR matrix shows a significant increase in Young’s and shear modulus and hardness. By incorporation of the GO, 48 and 56% decrease in friction coefficient and abrasion rates of SBR polymer was observed, respectively. About 15% reduction in the RDF values of GO/SBR composites was obtained. The interaction energy between graphene oxide sheet and SBR matrix during the shear process has been obtained and discussed.

A molecular dynamics study on Young’s modulus and tribology of carbon nanotube reinforced styrene-butadiene rubber

Abstract: Styrene-butadiene rubber is a copolymer widely used in making car tires and has excellent abrasion resistance. The Young's modulus and tribology of pure styrene butadiene rubber (SBR) polymer and carbon nanotube reinforced polymer composites have been investigated using molecular dynamics simulations. The mechanism of enhanced tribology properties using carbon nanotube has been studied and discussed. The obtained Young's modulus shows the enhancement in mechanical properties of SBR polymer when carbon nanotubes are used as reinforcement. The concentration, temperature and velocity profiles, radial distribution function, frictional stresses, and cohesive energy density are calculated and analyzed in detail. The Young's modulus of SBR matrix increases about 29.16% in the presence of the 5% CNT. The atom movement velocity and average cohesive energy density in the friction area of pure SBR matrix was found to be more than that of the CNT/SBR composite. Graphical abstract Initial and final conditions of (a) pure SBR matrix and (b) CNT/SBR matrix subjected toshear loading and frictional stresses of top Fe layers of both pure SBR and CNT/SBR composite.

Dopamine-grafted heparin as an additive to the commercialized carboxymethyl cellulose/styrene-butadiene rubber binder for practical use of SiO x /graphite composite anode

Abstract: Graphite is used commercially as the active material in lithium ion batteries, frequently as part of a graphite/SiOx composite. Graphite is used in conjunction with SiOx to overcome the limited energy density of graphite, and to lessen the adverse effects of volume expansion of Si. However, electrodes based on graphite/SiOx composites can be made with only 3–5 wt % SiOx because of the increased failure of electrodes with higher SiOx contents. Here, we developed a new polymer binder, by combining dopamine-grafted heparin with the commercial binder carboxymethyl cellulose (CMC)/styrene butadiene rubber (SBR), in order to more effectively hold the SiOx particles together and prevent disintegration of the electrode during charging and discharging. The crosslinking using acid-base interactions between heparin and CMC and the ion-conducting sulfonate group in heparin, together with the strong adhesion properties of dopamine, yielded better physical properties for the dopamine-heparin-containing CMC/SBR-based electrodes than for the commercial CMC/SBR-based electrodes, and hence yielded excellent cell performance with a retention of 73.5% of the original capacity, a Coulombic efficiency of 99.7% at 150 cycles, and a high capacity of 200 mAh g−1 even at 20 C. Furthermore, a full cell test using the proposed electrode material showed stable cell performance with 89% retention at the 150th cycle.

Thermoplastic–elastomer composition based on an interpenetrating polymeric network of styrene butadiene rubber–poly(methyl methacrylate) as an efficient vibrational damper

Abstract: A new series of interpenetrating polymer networks (IPNs) and semi-IPNs based on styrene butadiene rubber (SBR) and poly[methyl methacrylate] (PMMA) have been synthesized by sequential polymerization. The synthesized IPNs show promise for application as vibrational dampers. Raman spectroscopy and imaging were successfully utilized to establish IPN formation for the first time. The different viscoelastic properties of the IPNs were investigated in detail. Rigidity, entanglement density and phase mixing at the interface were enhancing by increasing the PMMA loading. The significant inward shifts of the glass transition temperatures of the SBR and PMMA phases proved their mixing in the IPNs. The cross-linking of the SBR and PMMA phases contributed to the viscoelastic behavior of the IPNs. The semi-IPN with the same composition possessed a slightly higher storage modulus and damping property compared to the corresponding IPN. The experimental values of area under the linear loss modulus were larger than those obtained by group contribution analysis. Five different composite models were employed for theoretical predictions. Among them, the Davies model most accurately reproduced the experimental data. The homogeneity of the system was further studied with Cole–Cole analysis. Morphological analyses using SEM, AFM, and TEM provided clear insights into the component distributions in the IPNs. The co-continuous morphology of IPN predicted by DMA analysis, particularly at high PMMA concentration, is in good agreement with the morphological analyses and theoretical predictions. This protocol for IPN characterization can serve as a platform for designing new vibrational dampers and their chemistries.

Investigation on performance of polyphosphoric acid (PPA)/SBR compound-modified asphalt mixture at high and low temperatures

Abstract: With the aim of improving the asphalt and asphalt mixture performance at high and low temperatures, polyphosphoric acid (PPA) and styrene butadiene rubber (SBR) were added to achieve a modification...