Showing papers on "Styrene-butadiene published in 2000"

Morphology and mechanical properties of clay/styrene‐butadiene rubber nanocomposites

Abstract: Based on the character of a clay that could be separated into many 1-nm thickness monolayers, clay styrene-butadiene rubber (SBR) nanocomposites were acquired by mixing the SBR latex with a clay/water dispersion and coagulating the mixture. The structure of the dispersion of clay in the SBR was studied through TEM. The mechanical properties of clay/SBR nanocomposites with different filling amounts of clay were studied. The results showed that the main structure of the dispersion of clay in the SBR was a layer bundle whose thickness was 4–10 nm and its aggregation formed by several or many layer bundles. Compared with the other filler, some mechanical properties of clay/SBR nanocomposites exceeded those of carbon black/SBR composites and they were higher than those of clay/SBR composites produced by directly mixing clay with SBR through regular rubber processing means. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1873–1878, 2000

Styrene–butadiene rubber/natural rubber blends: Morphology, transport behavior, and dynamic mechanical and mechanical properties

Abstract: Blends of styrene–butadiene rubber (SBR) and natural rubber (NR) were prepared and their morphology, transport behavior, and dynamic mechanical and mechanical properties were studied. The transport behavior of SBR/NR blends was examined in an atmosphere of n-alkanes in the temperature range of 25–60°C. Transport parameters such as diffusivity, sorptivity, and permeability were estimated. Network characterization was done using phantom and affine models. The effect of the blend ratio on the dynamic mechanical properties of SBR/NR blends was investigated at different temperatures. The storage modulus of the blend decreased with increase of the temperature. Attempts were made to correlate the properties with the morphology of the blend. To understand the stability of the membranes, mechanical testing was carried out for unswollen, swollen, and deswollen samples. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1280–1303, 2000

transparent, impact-resistant polystyrene on a styrene-butadiene block copolymer basis

Abstract: The invention relates to block copolymers comprising at least two hard blocks S1 and S2 consisting of vinyl aromatic monomers and at least one random soft block B/S which is positioned between the hard blocks and consists of vinyl aromatic monomers and dienes. The proportion of hard blocks is more than 40 % by weight of the total block copolymer.

Pervaporative stripping of acetone, butanol and ethanol to improve ABE fermentation.

Abstract: Acetone-butanol-ethanol fermentation by anaerobic bacterium C. acetobutylicum is a potential source for feedstock chemicals. The problem of product induced inhibition makes this fermentation economically infeasible. Pervaporation is studied as an effective separation technique to remove the toxic inhibitory products. Various membranes like Styrene Butadiene Rubber (SBR), Ethylene Propylene Diene Rubber (EPDM), plain Poly Dimethyl Siloxane (PDMS) and silicalite filled PDMS were studied for the removal of acetone, butanol and ethanol, from binary aqueous mixtures and from a quaternary mixture. It was found that the overall performance of PDMS filled with 15% w/w of silicalite was the best for removal of butanol in binary mixture study. SBR performance was best for the quaternary mixture studied.

High-speed photocrosslinking of thermoplastic styrene–butadiene elastomers

Abstract: Photoinitiated thiol/ene polymerization was used to crosslink a triblock styrene/butadiene/styrene (SBS) polymer of low vinyl content (8%). The crosslinking process was followed by infrared spectroscopy (loss of unsaturation), insolubilization, swelling, and hardness measurements. The photogenerated thiyl radicals react with both the vinyl and the 2-butene double bonds of the copolymer. Concentrations of less than 1 wt % in the trifunctional thiol crosslinker and in the acylphosphine oxide photoinitiator proved to be sufficient to create, within 0.5 s, a permanent chemical network in the elastomeric phase. This UV-curing technology was successfully applied to crosslink rapidly commercial SBS–Kraton® thermoplastic elastomers. It proved also effective in the case of the much less reactive triblock styrene/isoprene/styrene (SIS) polymer which contains no vinyl double bonds. The thiol/ene polymerization was shown to be a much more efficient process to crosslink SBS and SIS thermoplastic elastomers than was the copolymerization of the rubber double bonds with a diacrylate monomer. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1902–1912, 2000

Syndiotactic styrene‐butadiene block copolymers synthesized with CpTiX3/MAO (Cp = C5H5, X = Cl, F; Cp = C5Me5, X = Me) and TiXn/MAO (n = 3, X = acac; n = 4, X = O‐tert‐Bu)

Abstract: Copolymers sPS-B consisting of blocks of syndiotactic polystyrene (sPS) and polybutadiene (B) have been prepared using CpTiX3 (Cp = C5H5, X = Cl, F; Cp = C5Me5, X = Me) and TiXn (n = 3, X = acetylacetonate (acac); n = 4, X = O-tert-Bu) activated with methylaluminoxane (MAO). If proper conditions are used, copolymers containing a range of styrene and butadiene molar fractions can be prepared. Structural analysis of these copolymers by means of 13C NMR spectroscopy allowed the assignment of different monomer diads (SS, SB, BB; S = styrene, B = butadiene) and the calculation of reactivity ratio products r1·r2. Differential scanning calorimetry (DSC) analysis further confirmed the block-like structure of these copolymers. The melting points (Tm) of syndiotactic styrene sequences decrease as the styrene molar fraction decreases, whereas the glass transition temperature (Tg) increases with decreasing butadiene molar fraction in the copolymer. The polydispersity values (Mw/Mn) determined by GPC suggest that these copolymers are produced by a single site catalyst.

Rubber toughened and optically transparent blends of cyclic olefin copolymers

Abstract: A study is presented of increasing the toughness of Cyclic Olefin Copolymer (COC) while maintaining its optical transparency. The COC consists of a random copolymer of ethylene and norbornene, and the impact modifiers consist of thermoplastic elastomers. It is shown that several requirements must be satisfied, namely: for toughening there is an optimum finite particle size, but in order to minimize light scattering the particles have to be as small as possible. In addition, the refractive index of the elastomer must be closely matched to COC over the visible wavelength range and use temperature. Also for toughening, there are additional requirements of the adhesion of the elastomer to COC and high molecular weight. It is found that styrene butadiene styrene (SBS) is the most effective elastomer in toughening COC while maintaining optical transparency. It is also found that the addition of an index matched styrene-ethylene-butylene-styrene (SEBS) copolymer as a compatibilizer to the SBS elastomer is beneficial in increasing the toughness and lowering the optical haze. Finally, light scattering calculations are presented based on the Rayleigh Debye model to calculate the optical haze and transmission of these blends. These calculations take into account the refractive index of COC and the elastomer, the particle size distribution and volume fraction of the elastomer. It is shown that there is reasonable agreement between calculation and experimental results. It is possible to increase the toughness of COC to greater than 50 J/m (Notched Izod) while keeping the optical haze to below 5% with an elastomer loading of 5% (w/w). We also identify opaque blends of COC with a toughness of greater than 500 J/m with an elastomer loading of 20% (w/w).

Thermal degradation of natural rubber/styrene butadiene rubber latex blends by thermogravimetric method

Abstract: Thermal properties of natural rubber (NR)/styrene butadiene rubber (SBR) latex blends made from latex blending have been investigated using thermogravimetric analysis. It was found that the initial degradation temperature of NR is lower than SBR, and on addition of SBR, the degradation temperature is increased, indicating increased thermal stability of the blend. The main degradation products of NR contain isoprene and dipentene and that of SBR contains a large number of products like 4-vinyl cyclohexene, styrene, methylbenzene, and so forth. In addition to that, the temperature at which 50% and 75% degradation of NR occurs is increased upon the addition of SBR. Vulcanization increased the thermal stability of NR/SBR blends slightly. The activation energies for the degradation of the blends are higher than that of the homopolymers.

Photodegradation and stabilization of styrene–butadiene–styrene rubber

Abstract: Photooxidative degradation and stabilization of a polystyrene–block–polybutadiene–block–polystyrene thermoplastic elastomer using a polychromatic UV light in air at 60°C has been studied by monitoring the appearance of the hydroxyl and carbonyl groups in Fourier transform infrared spectroscopy. The extent of photooxidative degradation in different samples has been compared. The rate of photooxidation was also estimated in the presence of different concentrations of 2,6-di-tert-butyl-4-methylphenol [BHT], 2-(2′-hydroxy-5′-methylphenyl)benzotriazole [Tinuvin P] and tris(nonylphenyl) phosphite [Irgafos TNPP], and 1,2,2,6,6-pentamethyl piperidinyl-4-acrylate was grafted onto the surface of the SBS film. The kinetic evolution of the oxidative reaction was determined. The morphological changes upon irradiation in the solution cast SBS films were studied by scanning electron microscopy. Based on the experimental data a suitable photooxidative degradation mechanism also has been proposed. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1097–1102, 2000

Functional MBS impact modifiers for PC/PBT alloy

Abstract: Functional group containing MBS impact modifiers for the poly carbonate/poly(butylene terephthalate (PC/PBT) alloy were synthesized and characterized in this study. The novel MBS consisted of three layers, in which the inner, middle, and outer layers were styrene butadiene rubber (SBR) latex, polystyrene, and a copolymer of the methacrylic acid (MMA) and the functional group containing vinyl monomer, respectively. Three different kinds of the functional monomers were used in this study, glycidyl methacrylate (GMA), acrylamide (AAM), and MAA. The functional group was used to improve the adhesion between the MBS and the PC/PBT alloy. Our results showed that the layer composition of the MBS exhibited a significant effect on the impact strength. A large variation of the impact strength from 14.1 to 23.6 ft-lb/in. was observed when the SBR content increased from 30 to 70%. An optimum amount (4–6%) of the functional monomer enhanced the adhesion between the MBS and the PC/PBT alloy and thus improved the impact strength. Furthermore, a much smaller amount of the functional group containing MBS in the PC/PBT alloy than the conventional MBS could obtain an impact strength as high as 25.2 ft-lb/in. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1280–1284, 2000

Chlorination of vulcanized styrene-butadiene rubber using solutions of trichloroisocyanuric acid in different solvents

Abstract: The chlorination of vulcanized styrene-butadiene rubbers (SBRs) with trichloroisocyanuric acid (TCI) has been studied. The solvent used to apply the TCI chlorinating solutions on the rubber plays an important role in the effectiveness of the treatment since the solvent determined the degree of penetration of TCI into the rubber and also different chlorinating species were produced depending on the nature of the solvent. Surface modifications produced on a synthetic sulfur-vulcanized SBR using TCI solutions in ethyl acetate (EA), methyl ethyl ketone (MEK), and EA + MEK mixtures have been compared. Furthermore, the effects of a solvent wipe with EA or MEK prior to the chlorination process were also considered. Surface modifications produced by the treatments were analyzed using ATR-IR spectroscopy, scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). Adhesion was obtained from the T-peel strength of treated rubber/polyurethane adhesive joints. TCI/MEK solutions produced a higher d...

Effective thermal conductivity of three-phase styrene butadiene composites

Abstract: Transient plane source technique was used for the simultaneous measurement of thermal conductivity and thermal diffisivity of three-phase styrene butadiene rubber composites. Two series of styrene butadiene rubber composites were studied, having natural rubber as a variable filler in both the composites along with 10 phr of silica and clay, respectively. The measurements were done at room temperature and normal pressure. The experimental results show that there is a small variation in the thermal conductivity of both the composites with the filler (NR) fraction. It is interesting to note that the thermal conductivity shows a sharp decrease at 10 phr filler loading and then increases. The comparative study of these composites shows that the conductivity as well as the diffusivity of the silica reinforced composites is larger than that of the clay composites. The thermal conductivity of the filler NR has been evaluated using the Agari model. It has also been found that the composite with 40 phr of NR has the maximum thermal conductivity. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1799–1803, 2000

Morphology and mechanical and viscoelastic properties of natural rubber and styrene butadiene rubber latex blends

Abstract: The morphology and mechanical and viscoelastic properties of a series of blends of natural rubber (NR) and styrene butadiene rubber (SBR) latex blends were studied in the uncrosslinked and crosslinked state. The morphology of the NR/SBR blends was analyzed using a scanning electron microscope. The morphology of the blends indicated a two phase structure in which SBR is dispersed as domains in the continuous NR matrix when its content is less than 50%. A cocontinuous morphology was obtained at a 50/50 NR/SBR ratio and phase inversion was seen beyond 50% SBR when NR formed the dispersed phase. The mechanical properties of the blends were studied with special reference to the effect of the blend ratio, surface active agents, vulcanizing system, and time for prevulcanization. As the NR content and time of prevulcanization increased, the mechanical properties such as the tensile strength, modulus, elongation at break, and hardness increased. This was due to the increased degree of crosslinking that leads to the strengthening of the 3-dimensional network. In most cases the tear strength values increased as the prevulcanization time increased. The mechanical data were compared with theoretical predictions. The effects of the blend ratio and prevulcanization on the dynamic mechanical properties of the blends were investigated at different temperatures and frequencies. All the blends showed two distinct glass-transition temperatures, indicating that the system is immiscible. It was also found that the glass-transition temperatures of vulcanized blends are higher than those of unvulcanized blends. The time-temperature superposition and Cole-Cole analysis were made to understand the phase behavior of the blends. The tensile and tear fracture surfaces were examined by a scanning electron microscope to gain an insight into the failure mechanism.

On the properties and processing of polyethylene terephthalate/styrene-butadiene rubber blend

Abstract: The mixing of incompatible polymers such as polyethylene terephthalate (PET) and styrene-butadiene rubber (SBR) produces a blend with poor mechanical and impact properties, because polymeric phases interact weakly with each other and segregate. The use of SBR grafted with maleic anhydride (MAH) increases the compatibility of the SBR-PET system by generating higher interactions and chemical links between the ingredients of the blend. The induced compatibility is reflected in the 2.5-fold increase in the impact resistance of the blend as compared to that of pure PET. The grafting reaction to produce SBR-g-MAH is carried out by reactive extrusion using a reaction initiator, benzoyl peroxide (BPO), and the extent of the reaction depends on the concentration of MAH and BPO. Results indicate the close relationship between processing conditions and microstructural parameters, such as particle diameter and interparticle distances of the dispersed rubber phase, necessary to achieve the optimum impact resistance.

Decabromobiphenyl oxide–aluminum hydroxide system as a flame retardant for styrene–butadiene rubber

Abstract: Styrene–butadiene rubber (SBR) was treated with decabromobiphenyl oxide (DBBO) and/or aluminum hydroxide [Al(OH)3] as a flame retardant. The flammability of the resulting system was determined by the limiting oxygen index method. The effect of the added flame retardants on the maximum torque (MH), curing rate, and tensile properties was also evaluated. The results showed, particularly, that DBBO was a more effective flame retardant than was Al(OH)3. On the other hand, this brominated compound reduced the modulus of elasticity while its effect on the maximum torque was insignificant. Moreover, the addition of DBBO was found to decrease the curing rate of SBR. In contrast, Al(OH)3 significantly increased the maximum torque and also markedly reduced the modulus of elasticity. Moreover, the effect of the treatment with Al(OH)3 on the curing rate was found to be insignificant. The flammability measurement of the SBR treated with different mixtures of the two flame retardants indicated that the two compounds reacted slightly antagonistically. The addition of Al(OH)3 to DBBO in a mixture that was applied to SBR remedied some negative impacts on the mechanical properties when DBBO was added separately to the rubber. The value of the maximum torque of SBR increased and the curing rate slightly increased as well. Meanwhile, the values of the modulus of elasticity were not affected. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 2134–2139, 2000

Some considerations concerning the dynamic mechanical properties of cured styrene–butadiene rubber/polybutadiene blends

Abstract: The dynamic mechanical response of several binary mixtures of a styrene–butadiene copolymer and high cis-polybutadiene has been studied. The loss tangent and shear modulus were measured with a free damping torsion pendulum at temperatures between 143 and 343 K in argon atmosphere. From the loss tangent data the glass transition temperature of each sample was evaluated. The results can be represented by the Fox equation that relates the glass transition temperature of the blend with that of constituent polymers. The influence in the loss tangent data of the crystallization of the high cis BR used in the blend is discussed. A study of the separation of the crystalline and amorphous parts in the polybutadiene using the storage modulus data is presented. Finally, the loss of crystallinity at different contents of SBR in the blend is analysed using the dynamic mechanical data. © 2000 Society of Chemical Industry

Styrene–butadiene copolymers: mechanical, swelling and orientational properties

Abstract: The results of equilibrium stress–strain and swelling experiments are reported for styrene–butadiene copolymers of varying crosslink density and varying butadiene microstructure. The orientation of polymer chains is investigated under uniaxial elongation by birefringence and infrared dichroism spectroscopies which probe orientation on a segmental scale. © 2000 Society of Chemical Industry

Stable liquid suspension compositions and suspending mediums for same

Abstract: Stable and environmentally friendly suspensions of solid particulates are provided through the addition of such solid particulates to a suspension medium which is comprised of a liquid carrier, a liquid carrier soluble resin, an organophyllic clay, and an activator wherein said liquid carrier is a carboxylic acid ester, preferably 2-ethylhexyl oleate, said liquid carrier soluble resin is selected from the group consisting of styrene-isoprene copolymers, styrene ethylene-propylene block copolymers, styrene isobutylene copolymers, styrene butadiene copolymers, polybutylene, polystyrene, polyethylene-propylene copolymers, methyl methacrylate and mixtures thereof, said organophyllic clay is one of kaolinite, halloysite, vermiculite, chlorite, attapullgite, smectite, montmorillonite, bentonite, hectorite, and mixtures thereof and said activator is an alcohol of the formula ROH wherein R is an alkyl group of 1 to 10 carbon atoms

Polymer/dispersed modifier compositions

Abstract: Polymer resin/dispersed modifier compositions are provided. The polymer resin/dispersed modifier compositions have improved melt processability and properties and may be used to thermally process films, fibers, and articles having improved properties. In one embodiment, the polymer resin/dispersed modifier compositions are further grafted with one or more monomers, which graft onto the polymer resin and/or the dispersed modifier. In a further embodiment, the polymer resin is a water-soluble or water-dispersible polymer, such as polyethylene oxide; the modifier is a styrene butadiene polymer, a carboxylated acrylonitrile-butadiene-styrene polymer, or a combination thereof; and the grafted monomer is poly(ethylene glycol) ethyl ether methacrylate, poly(ethylene glycol) ethyl ether acrylate, 2-hydroxyethyl methacrylate (HEMA), poly(ethylene glycol) methacrylate (PEG-MA), or a mixture thereof. The grafted PEO/dispersed modifier compositions have improved properties compared to unmodified polyethylene oxide compositions, and modified polyethylene oxide compositions.

Measurement of styrene-7,8-oxide and other oxidation products of styrene in air

Abstract: Styrene-7,8-oxide (SO) is generated at low concentrations from the oxidation of styrene during the processing of reinforced plastics. Since exposure to SO has important health implications, we developed air sampling and analytical methods to measure low levels of airborne SO in the presence of styrene and its other oxidation products, namely phenylacetaldehyde (PAA) and acetophenone (AP). Both active and passive air monitors were used. The active sampling method, which employed adsorption on Tenax, was suitable for measuring SO, PAA and AP but had limited capacity for styrene due to breakthrough. The passive monitor employed a carbon adsorbent and was suitable for measurement of styrene and SO but not PAA and AP due to poor recovery. After sampling, the analytes were extracted from the adsorbents with ethyl acetate and measured by gas chromatography with flame ionization detection or mass spectrometry. By maintaining the injection port at 70 degrees C, the thermal rearrangement of SO to PAA was minimized. Recovery of styrene and SO from the passive monitor depended upon loading and was corrected by linearization of the Freundlich isotherm. The limits of detection for SO, PAA, and AP were 0.2 ppb using the active monitor, and for SO was 1 ppb using the passive monitor. The sampling precision for SO (RSD from personal measurements) was 5.0% for the passive monitor and was 13.4% for the active monitor over a range of exposures from 5-150 ppb. The corresponding precision for styrene was 5.3% for the passive monitor for levels ranging from 1.2 to 104 ppm. Measurements of 235 personal exposures with the active monitor in 12 facilities manufacturing fiberglass-reinforced plastics (FRP) showed that levels of AP and PAA were below 7.8 ppb and 5 ppb, respectively. In contrast, SO averaged 30.4 ppb (SE=2.4) in these FRP facilities, ranging from below 0.2 ppb to 190 ppb. The active monitor was also used to detect airborne SO at levels of approximately equals 1 ppb in one facility manufacturing styrene butadiene rubber, suggesting that SO is generally present during the polymerization of styrene. Personal passive monitoring in the 12 FRP facilities (n = 657) revealed mean concentrations of styrene ranging between 1.8 and 55.4 ppm, and for SO between 1.7 and 62.6 ppb. The ratio of the mean styrene level to the mean SO level varied between 449:1 and 1,635:1 among the 12 FRP facilities.

A study of relationships between state‐of‐mix, rheological properties, dynamic properties, and bound rubber content

Abstract: The relationships between state-of-mix, rheologic properties, dynamic properties, and bound rubber content in N330 carbon black filled styrene butadiene rubber (SBR) were investigated. Shear viscosities measured from both Mooney viscometer and capillary rheometer decrease with increasing state-of-mix. By contrast, the stress relaxation determined from the Mooney relaxation viscometer (PR80) decreases with an increase in state-of-mix. In addition, glass transition temperature (Tg) is not strongly affected by a change in state-of-mix, whereas the magnitude of damping peak (tan δ) increases with state-of-mix. Bound rubber content appears to decrease as the state-of-mix increases. The concept of a change in an amount of immobilized rubber can be used to explain the results obtained. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1542–1548, 2000

Damping of shear vibrations in asphalt modified with styrene-butadiene-styrene polymer

Abstract: Shear vibrations in conventional and polymer-modified asphalt binders are examined. Using dynamic compliances instead of moduli, viscous deformation effects can be separated from total deformation and the modified dynamic loss compliance and modified loss tangent functions can be defined. These two material functions appear to be more sensitive than viscoelastic moduli to the rheological behavior of asphalt binders and to changes caused by polymer addition. The characteristic temperature of the transition from the viscoelastic to viscous behavior of asphalt binder (Tv) can be identified by using the viscous asymptote J". The damping of shear vibrations that likely relates to the internal structure of asphalt material can be described by the modified loss tangent. The rheological behavior of the base asphalt 200/300 penetration grade and its blends with different amounts of radial styrene-butadiene-styrene rubber is investigated. Using master curves of dynamic functions and the Williams-Landel-Ferry form o...