Mechanical properties of clay coating films containing styrene–butadiene copolymers

The mechanical properties of clay-based pigmented coating films bonded with a series of carboxylated styrene–butadiene latex binders have been investigated. The in-plane tensile strength and the elongation at rupture increased with increasing amount of polymeric binder. It is suggested that this is due to an improvement in stress transfer through the structure. The mechanical behavior of the films was furthermore found to be strongly related to the properties of the polymeric binder at the usage temperature. In torsional pendulum experiments an increase in the glass transition temperature of the polymeric binder was observed when it was incorporated in the coating film. This is interpreted as being the result of a decrease in the segmental mobility of the polymer molecules due to the presence of the clay particles, i.e., due to the interaction between the clay pigments and the binder. The interaction was, however, less noticeable in experiments using an NMR (nuclear magnetic resonance) technique. If the clay was replaced by calcium carbonate, a strong interaction, as measured using NMR, was observed between CaCO₃ and the styrene–butadiene polymer, although the in-plane mechanical strength and ductility were reduced. A structural model accounting for some of the observed differences in mechanical behavior between clay-based and CaCO₃-based coating films is suggested.     

Studies of interaction in silica/styrene–butadiene copolymers

Adsorption, bound rubber, mechanical properties, and electron microscopy determinations were carried out in silica/styrene–butadiene copolymers. These studies reveal equivalent trends with varying copolymer composition. Thus, when the copolymer is richer in styrene, adsorbance and bound rubber increase, the stress softening effect becomes more remarkable, and silica is more uniformly dispersed in the elastomeric matrix. These results indicate that polymer–filler interaction becomes stronger when the content of styrene in the elastomer is increased. This interaction does not appear to be explicitly reflected in the other mechanical properties studied.     

Structural morphology and properties of star styrene–isoprene–butadiene rubber and natural rubber/star styrene–butadiene rubber blends

Star styrene–isoprene–butadiene rubber (SIBR) was synthesized with a new kind of star anionic initiator made from naphthalene lithium and an SnCl₄ coupled agent. The relationship between the structure and properties of star SIBR was studied. Star block styrene–isoprene–butadiene rubber (SB‐SIBR), having low hysteresis, high road‐hugging, and excellent mechanical properties, was closer to meeting the overall performance requirements of ideal tire‐tread rubber according to a comparison of the morphology and various properties of SB‐SIBR with those of star random SIBR and natural rubber/star styrene–butadiene rubber blends. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 336–341, 2004     

Evaluation of the properties of bitumen modified by SBS copolymers with different styrene–butadiene structure

Four styrene–butadiene–styrene(SBS) modified bitumens had been prepared by a base bitumen, a crosslinking agent and four SBS copolymers which differ in styrene blocks content and molecular configuration (radial or linear) under the same experimental conditions. Conventional properties, morphology, thermal behavior and microstructure were investigated by means of conventional tests, fluorescence microscopy, differential scanning calorimetry (DSC), and Fourier transform infrared (FT‐IR) spectroscopy. In terms of linear SBS polymers, the SBS molecule with the styrene content of 30% has a perfect dispersion and complete stretching in bitumen matrix, and in this case, the conventional properties and thermal stability of bitumen are enhanced substantially. However, the star SBS polymer due to long branched chains forming the preferable steric hindrance to enhance the intensity of base bitumen, plays a more important role in improving the conventional properties of base bitumen than linear SBS polymers. Furthermore, the FT‐IR spectra indicate that, the main bands assignations of four modified bitumens are identical and the significant variation is the peak intensity. And a noncomplete crosslinking reaction happens between the bitumen and each SBS polymer, which can efficiently prevent excessive cross‐linking from affecting the intrinsic bitumen characteristics. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40398.     

Stress–strain optical study of styrene–butadiene and ethylene–propylene rubbery copolymers

Birefringence–temperature behavior at constant stress during cooling and heating of styrene–butadiene and ethylene–propylene copolymers between ?120°C and +60°C was investigated. Copolymer composition, thermal treatment, and stress levels were shown to have a pronounced effect on the photoelastic properties.     

Morphology and mechanical properties of polypropylene/polystyrene blends compatibilized with styrene–butadiene block copolymers

The effect of molecular structure of styrene–butadiene block (SB) copolymers on the morphology, tensile properties, impact strength, and microhardness of polypropylene/polystyrene (PP/PS) (80/20) blends was studied. The addition of SB copolymers substantially reduces the size of dispersed PS particles formed at mixing. The distribution of SB copolymers between the interface and bulk phases is controlled by the length of styrene blocks in SB, but a decrease in the size of PS particles at mixing correlates with total molecular weight of SB copolymers. For a substantial part of compatibilized blends, PS particles aggregate rapidly during compression molding and form honeycomb‐like particles split by SB partitions, which persist at further annealing. Aggregation of PS particles continues slowly at further annealing. Blends containing PS particles with well‐developed honeycomb structure show lower yield stress, higher plasticity, and lower tensile impact strength than the blends having PS particles with simple or undeveloped honeycomb structure. Microhardness of PP/PS blends is additive and of PP/PS/SB blends is lower than the additive due to the effect of SB copolymers on crystalline structure of PP matrix. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers     

Anisotropy of styrene–butadiene rubber

Anisotropy of styrene–butadiene rubber (SBR) was investigated. The anisotropy of the copolymer varies linearly with the styrene content and the ultimate value coincides with that of polystyrene at elevated temperature. From these facts, the transverse configuration of the pendant phenyl group is estimated irrespective of the styrene content of SBR.     

Short-fiber-reinforced styrene–butadiene rubber composites

Processing characteristics, anistropic swelling, and mechanical properties of short-jute-fiber-and short-glass-fiber-reinforced styrene–butadiene rubber (SBR) composites have been studied both in the presence and absence of carbon black. Tensile and tear fracture surfaces of the composites have been studied using scanning electron microscopy (SEM) in order to assess the failure criteria. The effects of bonding agent. carbon black, jute fiber, and glass fiber on the fracture mode of the composites have also been studied. It has been found that jute fiber offers good reinforcement to SBR as compared to glass fibers. The poor performance of glass fibers as reinforcing agent is found to be mainly due to fiber breakage and poor bonding between fiber and rubber. Tensile strength of the fiber–SBR composites increases with the increase in fiber loading in the absence of carbon black. However, in the presence of carbon black a minimum was observed in the variation of strength against fiber loading. SEM studies indicate that fracture mode depends not on the nature of the fiber but on the adhesion between the fiber and the matrix.     

Compatibilization efficiency of styrene–butadiene triblock copolymers in polystyrene–polypropylene blends with varying compositions

The compatibilization efficiency of two styrene‐butadiene‐styrene triblock copolymers with short (SB1) and long (SB2) styrene blocks was studied in polystyrene (PS)–polypropylene (PP) blends of composition 20, 50, and 80 wt % PS. The supramolecular structure of the blends was determined by small‐angle X‐ray scattering, and the morphology was studied with transmission electron microscopy and scanning electron microscopy. Structural changes in both the uncompatibilized and compatibilized blends were correlated with the values of tensile impact strength of these blends. Even though the compatibilization mechanisms were different in blends with SB1 and SB2, the addition of the block copolymers to the PS–PP 4/1 and PS–PP 1/4 blends led to similar structures and improved the mechanical properties in the same way. These block copolymers had a very slight effect on the impact strength in PS–PP 1/1 blends, exhibiting a nearly cocontinuous phase morphology. The strong migration of SB2 copolymers to the interface and of SB1 copolymers away from the interface were detected during the annealing of compatibilized PS–PP 4/1 blends. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2431–2441, 2004     

Improvement of properties of silica‐filled styrene–butadiene rubber compounds using acrylonitrile–butadiene rubber

Since silica has strong filler–filler interactions and adsorbs polar materials, a silica‐filled rubber compound has a poor dispersion of the filler and poor cure characteristics. Improvement of the properties of silica‐filled styrene–butadiene rubber (SBR) compounds was studied using acrylonitrile–butadiene rubber (NBR). Viscosities and bound rubber contents of the compounds became lower by adding NBR to the compound. Cure characteristics of the compounds were improved by adding NBR. Physical properties such as modulus, tensile strength, heat buildup, abrasion, and crack resistance were also improved by adding NBR. Both wet traction and rolling resistance of the vulcanizates containing NBR were better than were those of the vulcanizate without NBR. The NBR effects in the silica‐filled SBR compounds were compared with the carbon black‐filled compounds. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1127–1133, 2001     

Relaxation properties of styrene–butadiene block copolymers. A comparative study of thermally stimulated currents and thermoluminescence

The thermoluminescence (TL) and thermally stimulated current (TSC) curves observed in styrene—butadiene block copolymers, undoped and doped with different dyes, have been compared in order to test to what extent the thermoluminescence phenomenon can be correlated with intrinsic relaxation properties of the macromolecular chains. Generally, good agreement has been found between the two types of curves. However, the observance of a significant shifting of TL peaks as a function of the nature of the added dye shows that strict correspondence between the kinetics of the two phenomena is unlikely. Consequently, it seems actually dangerous to deduce the characteristic relaxation parameters of the polymer from TL curves.     

Overall properties of fibrillar silicate/styrene–butadiene rubber nanocomposites

The mechanical properties, heat aging resistance, dynamic properties, and abrasion resistance of fibrillar silicate (FS)/styrene butadiene rubber (SBR) nanocomposites are discussed in detail. Compared with white carbon black (WCB)/SBR composites, FS/SBR composites exhibit higher tensile stress at definite strain, higher tear strength, and lower elongation at break but poor abrasion resistance and tensile strength. Surprisingly, FS/SBR compounds have better flow properties. This is because by rubber melt blending modified FS can be separated into numerous nanosized fibrils under mechanical shear. Moreover, the composites show visible anisotropy due to the orientation of nanofibrils. There is potential for FS to be used to some extent as a reinforcing agent for rubber instead of short microfibers or white carbon black. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2725–2731, 2006     

Viscoelastic properties and film morphology of heterogeneous styrene–butadiene latexes

Heterogeneous carboxylated styrene–butadiene (S/Bu) latexes were prepared by a twostage emulsion polymerization process, using three PS seeds with different molecular weights. The second-stage polymer was a copolymer with a fixed S/Bu ratio of 1 : 1 and a methacrylic acid (MAA) content of either 1 or 10 wt %. Morphological studies by transmission electron microscopy (TEM) as well as studies of the viscoelastic properties by mechanical spectroscopy have been performed on films prepared from the latexes. The studies showed that the glass transition temperature, T_g, of the second-stage polymer was considerably affected by copolymerization with MAA. An increase in the MAA content in the second-stage polymer increased the T_g of this phase significantly. Addition of DVB as a crosslinking agent in the preparation of the PS seed phase substantially increased the rubbery moduli of the films, whereas the glass transition temperature of the second-stage polymer was unaffected. On the other hand, the presence of a chain transfer agent reduced the glass transition of the second-stage copolymer containing 1 wt % MAA dramatically, whereas the rubbery modulus was unaffected. When the MAA content was increased to 10 wt % the influence of the MAA monomer had a dominating effect on T_g. Latexes containing 10 wt % MAA had T_g values close to each other, regardless of chain transfer agent present in the second-stage polymerization. It was found that the morphology of the latex particles influenced the rubbery modulus of the films. The presence of irregularly shaped seed particles in samples prepared from a crosslinked PS seed had a considerable reinforcing effect on the films, whereas spherical seed particles originating from core–shell particles had a less reinforcing effect. © 1996 John Wiley & Sons, Inc.     

Dichlorocarbene modification of styrene–butadiene rubber

Dichlorocarbene-modified styrene–butadiene rubber (SBR) prepared by the alkaline hydrolysis of chloroform using cetyltrimethylammonium bromide as a phase-transfer agent resulted in a product that showed good mechanical properties, excellent flame resistance, solvent resistance, and good thermal stability. The activation energy for this chemical reaction calculated from the time–temperature data on the chemical reaction by the measurement of the percentage of chlorine indicated that the reaction proceeded according to first-order kinetics. The molecular weight of the polymers, determined by gel permeation chromatography, showed that chemical modification was accompanied by an increase in molecular weight. The chemical modification was characterized by proton NMR, FTIR studies, thermogravimetric analysis, and flammability measurement. Proton NMR and FTIR studies revealed the attachment of chlorine through cyclopropyl rings to the double bond of butadiene. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 153–160, 1998     

The influence of styrene–butadiene diblock copolymer on styrene–butadiene–styrene triblock copolymer viscoelastic properties and product performance

The effects of the styrene–butadiene (SB) diblock copolymer on the viscoelastic properties of styrene–butadiene–styrene (SBS) triblock copolymers were examined in both in the the neat state and within specific product applications. The addition of the SB diblock copolymer into a pure SBS triblock copolymer resulted in a significant decrease in the plateau storage modulus and a quantitative linear rise in tan delta. In a pure triblock, in which all endblocks are anchored in polystyrene domains, all entanglements are physically trapped. The SB diblock embodies untrapped polybutadiene endblocks that are able to relax stress by chain reptation through the rubbery polybutadiene matrix. The SB diblock copolymer quantitatively lowered the microphase separation temperature (MST) of the SBS triblock copolymer. These changes in linear viscoelastic behavior manifest themselves into a reduction in the efficiency and performance of the SBS triblock copolymer in asphalt pavement binders and hot-melt adhesive blends. Specifically, the SB diblock diminished the complex shear modulus and elasticity of a polymer-modified asphalt, which translated into lower predicted rutting specification values. The increase in diblock content altered the viscoelastic response of the hot-melt adhesive blend, translating into a reduction in the shear holding power and shear adhesion failure temperature. The lack of network participation, coupled with the relaxation of the polybutadiene endblocks, accounts for the lower strength and greater temperature susceptibility of the diblock-containing systems. © 1995 John Wiley & Sons, Inc.     

Microstructure analysis of brominated styrene–butadiene rubber

The bromine addition to the SBR double bonds in chloroform at 0°C has been investigated by FTIR, ¹H NMR and DSC techniques. In this case, bromine molecules react exclusively with the polydiene double bonds and the polystyrene units are unaffected. The bromine reacts preferentially with 1,4‐trans double bonds of the polybutadiene segment of SBR. At low bromination level (below 15%) the bromine reacts mainly with the 1,4‐trans double bonds of SBR, while at higher bromination level (up to 30%) the bromine shows the most reactivity toward the vinylic double bond. Above 30%, the addition reaction occurs on 1,4‐trans double bonds. The microstructure of modified and unmodified styrene–butadiene copolymers were fully characterized by ¹H NMR technique. Expanded regions have been utilized to resolve the complex ¹H NMR spectrum and establish the compositional and configurational sequences of styrene–butadiene copolymers. POLYM. ENG. SCI., 47:87–94, 2007. © 2007 Society of Plastics Engineers     

Synthesis,characterization and properties of functionalized styrene–maleimide copolymers

New functionalized styrene–maleimide copolymers were prepared by free radical copolymerization of styrene (St) and N‐4‐carboxybutylmaleimide (NBMI) in chloroform, using 2,2′‐azobisisobutyronitrile (AIBN) as initiator. Monomer and copolymer characterization was carried out by ¹H‐ and ¹³C‐NMR. Copolymer composition was determined by elemental analysis and Fourier‐transform infrared (FTIR) spectroscopy. The glass transition temperature (from DSC) and the thermogravimetric analysis (TGA) of the copolymers were consistent with the thermal behavior and stability observed for alternating St–maleimide copolymers. St–NBMI copolymers crosslinked with divinylbenzene (DVB) were also synthesized and their cation exchange properties evaluated in order to assess the capacity of the new copolymers to bind metallic ions. Copyright © 2005 Society of Chemical Industry     

Use of mid‐ and near‐infrared techniques as tools for characterizing blends of copolymers of styrene–butadiene and acrylonitrile–butadiene

There is increased technological interest in using blends of various dissimilar elastomers in applications for which service, material availability, or cost of a single elastomer do not provide the necessary processing, vulcanizate, or economic properties. The properties of these polyblends are sensitive to small variations in the amounts of the individual polymers used. Accurately estimating the elastomer composition of blends is of vital importance to the elastomer industry. This study illustrates the feasibility of using mid-infrared (MIR) and near-infrared (NIR) spectroscopy to estimate the amount of styrene–butadiene and acrylonitrile–butadiene copolymers in blends composed of varying ratios of the two elastomers. Sometimes it is difficult to obtain a film of an elastomer amenable to IR analysis; to address this problem, several techniques were developed in this study [MIR transmission of a film, attenuated total internal reflection (ATR)-FTIR of a chunk, and NIR using a fiber-optic probe]. A plot of the absorbance ratio (absorbance of the characteristic peak for styrene–butadiene rubber or acrylonitrile–butadiene rubber/absorbance of the CC stretching vibration of polybutadiene) versus the amount of each elastomer in the blend was used to predict the blend composition. In addition, the blends were also characterized by ATR-FTIR using a plot of the characteristic peak absorbance versus the polymeric content for a series of standards. A partial least-squares algorithm was used to develop a calibration curve for the NIR region. Finally, the accuracy of the test methods developed in this work is compared to results obtained by pyrolysis-GC/MS and thermogravimetric analysis. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88:1653–1658, 2003     

Oil absorbents based on styrene–butadiene rubber

Four oil absorbents based on styrene–butadiene (SBR)—pure SBR (PS), 4‐tert‐butylstyrene–SBR (PBS), EPDM–SBR network (PES), and 4‐tert‐butylstyrene‐EPDM‐SBR (PBES)—were produced from crosslinking polymerization of uncured styrene–butadiene rubber (SBR), 4‐tert‐butylstyrene (tBS), and ethylene–propylene–diene terpolymer (EPDM). The reaction took place in toluene using benzoyl peroxide (BPO) as an initiator. Uncured SBR was used as both a prepolymer and a crosslink agent in this work, and the crosslinked polymer was identified by IR spectroscopy. The oil absorbency of the crosslinked polymer was evaluated with ASTM method F726‐81. The order of maximum oil absorbency was PBES > PBS > PES > PS. The maximum values of oil absorbency of PBES and PBS were 74.0 and 69.5 g/g, respectively. Gel fractions and swelling kinetic constants, however, had opposite sequences. The swelling kinetic constant of PS evaluated by an experimental equation was 49.97 × 10^?2 h^?1. The gel strength parameter, S, the relaxation exponent, n, and the fractal dimension, d_f, of the crosslinked polymer at the pseudo‐critical gel state were determined from oscillatory shear measurements by a dynamic rheometer. The morphologies and light resistance properties of the crosslinked polymers were observed, respectively, with a scanning electron microscope (SEM) and a color difference meter.