Styrene-butadiene copolymers blends

K-Resin Styrene-Butadiene Copolymer Blends, Technical Service Memorandum 316, Chevron Phillips Chemical Co., Bartlesville, OK. 

Luranyl PPE/styrene-butadiene copolymer blend, reinforced with up to 30 wt% glass fiber or not BASF Plastics... 

Butadiene copolymers are mainly prepared to yield mbbers (see Styrene-butadiene rubber). Many commercially significant latex paints are based on styrene—butadiene copolymers (see Coatings Paint). In latex paint the weight ratio S B is usually 60 40 with high conversion. Most of the block copolymers prepared by anionic catalysts, eg, butyUithium, are also elastomers. However, some of these block copolymers are thermoplastic mbbers, which behave like cross-linked mbbers at room temperature but show regular thermoplastic flow at elevated temperatures (45,46). Diblock (styrene—butadiene (SB)) and triblock (styrene—butadiene—styrene (SBS)) copolymers are commercially available. Typically, they are blended with PS to achieve a desirable property, eg, improved clarity/flexibiHty (see Polymerblends) (46). These block copolymers represent a class of new and interesting polymeric materials (47,48). Of particular interest are their morphologies (49—52), solution properties (53,54), and mechanical behavior (55,56). 

FIGURE 20.14 (a) Height image of a cluster of carbon black (CB) particles. The sample was prepared by pressing the particles into a pellet, (b) Optical micrograph of a cryo-ultramicrotome cut of a mbbery composite loaded with silica, (c, d) Phase images of a nanocomposite of polyurethane (PU) loaded with silica and a mbber blend based on natural mbber (NR) and styrene-butadiene copolymer (SBR) loaded with siUca, respectively. The samples were prepared with a cryo-ultramicrotome. 

H.P. Siebel and H.-W. Otto, Styrene- acrylonitrile copolymers blended with graft copolymers of styrene onto butadiene-alkyl acrylate-vinyl alkyl ether terpolymers, US Patent 3280219, assigned to BASF AG, October 18,1966. 

Figure 3.6 Variation of retention with the composition of the stationary phase in GLC. Stationary phase styrene-butadiene polymer blends and copolymers, the butadiene fraction is plotted on the horizontal axis, (a) Specific retention volumes for three n-alkanes and benzene. V is proportional to the capacity factor, (b) the retention index for benzene. The solid line is calculated from the straight lines in figure 3.6a. The circles (polymer blends) and triangles (copolymers) represent experimental data. Figure taken from ref. [310], Reprinted with permission.

Figure 12.6. Volume resistivity against filler loading for SBR composites filled with MWNTs and mixtures (10 phr CB + x phr (MWNTs) (A) and TEM image of a styrene-butadiene copolymer (SBR) containing a dual filling (5 phr CB + 5 phr MWNTs) (B). [Reprinted from L. Bokobza, M. Rahmani, C. Belin, J.-L. Bruneel, N.-E. El Bounia "Blends of carbon blacks and multwall carbon nanotubes as reinforcing fillers for hydrocarbon rubbers", Journal of Polymer Science Part B Polymer Physics, 46,1939,2008, permission from John Wiley and Sons].

When only spectroscopic methods are used, they are able to identify polymer components with respect to their chemical nature. However, in many cases, they are unable to answer the question whether two chemical structures are combined to yield a copolymer or a blend or both. For example, analyzing a rubber mixture one is able to identify styrene and butadiene as the monomer units. However, using FTIR or NMR it is impossible to decide if the sample is a mixture of polystyrene (PS) and polybutadiene (PB),or a copolymer of styrene and butadiene, or a blend of a styrene-butadiene copolymer and PB. For the latter case, even the copolymer composition cannot be determined just by running a FTIR or NMR spectrum. 

Selected blends of styrene-acrylonitrile copolymer (30 to 55%), a styrene-butadiene copolymer grafted with styrene and acrylonitrile (45 to 70%), and a coal-tar pitch (0 to 25%), were prepared. Physical properties of the experimental blends were determined and statistical techniques were used to develop empirical equations relating these properties to blend composition. Scheff canonical polynominal models and response surfaces provided a thorough understanding of the mixture system. These models were used to determine the amount of coal-tar pitch that could be incorporated into ABS compounds that would still meet ASTM requirements for various pipe-material designations. ... 

These properties determine how carbon black will be distributed within the blend. These properties are not those of the filler but are the essential properties of the matrix. The matrix thus has strong influence on particle distribution. SEM studies showed that high vinyl polybutadiene and styrene-butadiene copolymers had morphologically identical carbon black distribution. However, their mechanical properties were very different. NMR analysis indicated that the difference in mechanical behavior is related to the interaction and more precisely to the molecular motions in rubbery matrix. 

Styrene butadiene copolymers come in a wide variety of types, with a similar wide variety of properties. As discussed in Section 4.6, HIPS (High Impact PS), is partially a graft copolymer and partially a physical blend of polystyrene and polybutadiene. HIPS, which is opaque, typically contains 2 to 15 weight % polybutadiene. In addition to significantly decreased brittleness, it has a broad processing window and is easy to thermoform, either as sheet or as extruded foam. 

Styrene-butadiene copolymers are often blended with other polymers. Transparent blends can be made with styrene, styrene-acrylonltrlle copolymers, or styrene-methyl methacrylate copolymers. Blends with styrene have low impact strength even at low styrene levels, while blends with styrene-methyl methacrylate copolymers can have greatly Improved impact strength. Blends with high impact polystyrene, polypropylene, and polycarbonate are opaque. 

Figure 15.7 Results demonstrating that much more polymeric material can be extract by suitable organic solvents bom vulcanizates derived from polystyrene-polybutadie blends than from vulcanizates from styrene-butadiene copolymers (Shundo et al. [19 ( ) peroxide-vulcanized copolymers (O) sulfur-vulcanized copolymers (O) radi don-vulcanized copolymers (A) peroxide-vulcanized latex blends (A) sulfiir-vulcaniz< latex blends (A) radiation-vulcanized latex blends ( ) peroxide-vulcanized roll blenr ( ) sulfur-vulcanized roll blends (Qf) radiation-vulcanized roll blends. The compoun for peroxide vulcanizates and sulfur vulcanizates were as given in the cation Figure 15.6. The compound for radiation vulcanization was (parts by mass) polymer 10 calcium caibonate ICIO. Roll blending was done at 110°C. Peroxide and sulfur vulca-izatkxis were carried out at 150°C. Radiation vulcanization was achieved using 10 n from a cobaIt-60 source in air at normal ambient temperature...

Miscible blends are most commonly formed from elastomers with similar three-dimensional (Hansen, 1967a,b Hansen and Beerbower, 1971) solubility parameters. An example of this is blends from copolymer elastomers (e.g., ethylene-propylene or styrene-butadiene copolymers) of slightly different composition, or microstructure. When the forces between the components of the polymer blend are mostly dispersive, miscibility is only achieved in neat polymers with a very close match in Hansen s three-dimensional solubility parameter (Hansen, 1967a,b Hansen and Beerbower, 1971), such that small combinatorial entropy for high molecular weight elastomers can drive miscibility. 

Figure 10-19 illustrates with unpublished data of Hashimoto and Takenaka for a critical blend of styrene-butadiene copolymer (SBR) and polybutadiene (PB) that master curves can be obtained for X and Y, i.e., the scaling laws for km and (eq 2.39 and 2.40) hold. This result is somewhat surprising, because these data were obtained at veiy deep quench depths (Tc for the blend was estimated to be about 400°C [31]). The solid curves in Figure 10-20 give T ) and log/m(t,T ) as functions of log t calculated from the smooth curves in Figure 10-19. In the range of timescales shown, the slope for qm...

Common examples of miscible blends are ethylene-propylene copolymers of different composition that result in an elastomer comprising a semicrystalline, higher ethylene content and an amorphous, lower ethylene content components. These blends combine the higher tensile strength of the semicrystaUine polymers and the favorable low temperature properties of amorphous polymers. Chemical differences in miscible blends of ethylene-propylene and styrene-butadiene copolymers can also arise from differences in the distribution and the type of vulcanization site on the elastomer. The uneven distribution of diene, which is the site for vulcanization in blends of ethylene-propylene-diene elastomers, can lead to the formation of two distinct, intermingled vulcanization networks. 

Styrene-butadiene copolymers are extremely important to the rubber industry. They are particularly important in tire manufacture. Styrene-butadiene polymer is produced by emulsion polymerization and solution polymerization. Most of the volume is by emulsion polymerization. This affords the opportunity to prepare polymer nanocomposites by several avenues. One can blend an aqueous dispersion of the nanoparticles with the styrene-butadiene latex before flocculation to produce the rubber crumb, disperse an organically treated nanoparticle in the styrene-butadiene solution polymer before the solvent is stripped from the polymer, disperse the organically treated nanoparticles into the monomers, or prepare the rubber nanocomposite in the traditional compounding approach. One finds all of these approaches in the literature. One also finds functional modifications of the styrene-butadiene polymer in the literature designed to improve the efficiency of the dispersion and interaction of the nanoparticles with the polymer. 

PA-6 (80 parts)/hydrogenated styrene-butadiene copolymer-g-MA (20 parts 0.5-2.3 wt% MA) TSE/mechanical properties vs. blend with unfunctionalized copolymer/ also used PA-66 or hydrogenated styrene-butadiene copolymer-g-AA Shiraki et al. 1986, 1987a, b... 

In a series of papers by Soares and coworkers (see, e.g., Soares et al. 2001), compatibilized blends have been prepared through copolymer formation between a thiol-functionalized polymer (also termed a mercapto-functionalized polymer) and a second polymer comprising a double bond (alkene). In a specific example, styrene-butadiene copolymer/EVAc blends with different ratios of components were compatibilized through addition of mercapto-modified EVAc. Evidence for copolymer formation came from FTIR and DMA. Morphology, mechanical properties, and DSC results were also reported. 

Fig. 19.9 (a) Schematic representation of the weatherability of ASA ASA-PC vs ABS (b) Effect styrene-butadiene copolymer (SBC) in polystyrene/SBC blends on the transparency and tensile elongation at break (Anonymons 2006)... 

Cavanaugh and co-workers (166) have studied the compatibilization efficiency of various styrene-butadiene copolymers in polystyrene (PS, Mw = 202,000)/polybutadiene (PB, Mw = 320,000) blends. The most effective compat-ibilizer proved to be a long, asymmetric diblock (M = 182,000 PS content 30%), which could entangle in both homopolymer phases. Short diblock copolymers and most of the random copolymers were inadequate as interfacial agents. Moderate improvement in impact strength was observed for a S-B multiblock. 

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