Styrene butadiene compounds

Degassing Solvents from Synthetic Rubber (Styrene-Butadiene Compounds)... 

This type of adhesive is generally useful in the temperature range where the material is either leathery or mbbery, ie, between the glass-transition temperature and the melt temperature. Hot-melt adhesives are based on thermoplastic polymers that may be compounded or uncompounded ethylene—vinyl acetate copolymers, paraffin waxes, polypropylene, phenoxy resins, styrene—butadiene copolymers, ethylene—ethyl acrylate copolymers, and low, and low density polypropylene are used in the compounded state polyesters, polyamides, and polyurethanes are used in the mosdy uncompounded state. 

Tire Cord. Melamine resins are also used to improve the adhesion of mbber to reinforcing cord in tires. Textile cord is normally coated with a latex dip solution composed of a vinylpyridine—styrene—butadiene latex mbber containing resorcinol—formaldehyde resin.. The dip coat is cured prior to use. The dip coat improves the adhesion of the textile cord to mbber. Further improvement in adhesion is provided by adding resorcinol and hexa(methoxymethyl) melamine [3089-11 -0] (HMMM) to the mbber compound which is in contact with the textile cord. The HMMM resin and resorcinol cross-link during mbber vulcanization and cure to form an interpenetrating polymer within the mbber matrix which strengthens or reinforces the mbber and increases adhesion to the textile cord. Brass-coated steel cord is also widely used in tires for reinforcement. Steel belts and bead wire are common apphcations. Again, HMMM resins and resorcinol [108-46-3] are used in the mbber compound which is in contact with the steel cord to reinforce the mbber and increase the adhesion of the mbber to the steel cord. This use of melamine resins is described in the patent Hterature (49). 

Styrene—butadiene latexes generally are quite stable mechanically because of the presence of relatively large amounts of emulsifying and stabilizing agents, and therefore require addition of less stabilizer in compounding. The apphcations of SBR latex are classified in Table 21. This classification indicates the scope of the industry and illustrates the large number of diverse applications in which synthetic latices are employed. The latex types previously found most suitable for particular applications are also listed. 

Styrene—butadiene, acrylonitrile—butadiene, and butyl latices have also been prevulcanised, but this usually results in a lower wet gel strength. Where the mbber is to be deposited onto a fabric substrate, as in manufacture of fabric-lined gloves, the lower gel strength is not a problem. For unsupported dipped synthetic mbber products, however, the use of post-vulcanised compounds is more common. 

Natural mbber was also used extensively in its oil-extended form in winter tires in the 1970s (57). Use of oil-extended natural mbber treads, found to have excellent traction on ice and snow, superseded studded synthetic mbber treads when studs were banned in certain countries and states owing to the damage they cause to partially cleared roads. This concept has been extended into aH-season tires, which account for over 75% of original equipment and replacement tires in the United States. It has been shown (58) that part replacement of styrene—butadiene mbber (SBR) in the formulation of aH-season tire tread compounds with oil-extended natural mbber increases ice and snow traction, reduces rolling resistance, and has no effect on normal wet grip. Also, there is only a minor trade-off in wear performance, because below a tire surface temperature of approximately 32°C, the wear of natural mbber is superior to SBR, whereas above this temperature the reverse is tme (59). Thus, wear of an aH-season tire ultimately depends on the surface temperature of the tread over its annual cycle of temperatures. 

Rubber. The mbber industry consumes finely ground metallic selenium and Selenac (selenium diethyl dithiocarbamate, R. T. Vanderbilt). Both are used with natural mbber and styrene—butadiene mbber (SBR) to increase the rate of vulcanization and improve the aging and mechanical properties of sulfudess and low sulfur stocks. Selenac is also used as an accelerator in butyl mbber and as an activator for other types of accelerators, eg, thiazoles (see Rubber chemicals). Selenium compounds are useflil as antioxidants (qv), uv stabilizers, (qv), bonding agents, carbon black activators, and polymerization additives. Selenac improves the adhesion of polyester fibers to mbber. 

Between the 1920s when the initial commercial development of mbbery elastomers based on 1,3-dienes began (5—7), and 1955 when transition metal catalysts were fkst used to prepare synthetic polyisoprene, researchers in the U.S. and Europe developed emulsion polybutadiene and styrene—butadiene copolymers as substitutes for natural mbber. However, the tire properties of these polymers were inferior to natural mbber compounds. In seeking to improve the synthetic material properties, research was conducted in many laboratories worldwide, especially in the U.S. under the Rubber Reserve Program. 

Other polymers used in the PSA industry include synthetic polyisoprenes and polybutadienes, styrene-butadiene rubbers, butadiene-acrylonitrile rubbers, polychloroprenes, and some polyisobutylenes. With the exception of pure polyisobutylenes, these polymer backbones retain some unsaturation, which makes them susceptible to oxidation and UV degradation. The rubbers require compounding with tackifiers and, if desired, plasticizers or oils to make them tacky. To improve performance and to make them more processible, diene-based polymers are typically compounded with additional stabilizers, chemical crosslinkers, and solvents for coating. Emulsion polymerized styrene butadiene rubbers (SBRs) are a common basis for PSA formulation [121]. The tackified SBR PSAs show improved cohesive strength as the Mooney viscosity and percent bound styrene in the rubber increases. The peel performance typically is best with 24—40% bound styrene in the rubber. To increase adhesion to polar surfaces, carboxylated SBRs have been used for PSA formulation. Blends of SBR and natural rubber are commonly used to improve long-term stability of the adhesives. 

BR is incompatible with CR because of the large difference in polarity. Mingyi et al. have studied their compatibUization in the presence of a styrene-butadiene-styrene block (SBS) copolymer [30]. The blends were prepared by blending the two mbbers separately at approximately 75°C. The master batch of the BR compound contained 1 part of sulfur, 2 parts of copolymer, 1.5 parts of TMTD, 5 parts... 

FIGURE 26.19 Log ajv values as function of speed for a natural rubber (NR) and a styrene-butadiene rubber (SBR) compound on wet and icy track surfaces. 

FIGURE 26.20 The log a v speed function of the previous chart is combined with the friction master curves for a natural rubber (NR) and a styrene-butadiene rubber (SBR) gum compound on glass showing the limited range of friction values (and their position on the log a-iv axis for different testing conditions) which are obtained when the sliding speed is increased. 

FIGURE 26.52 Sliding abrasion of three different tread compounds as function of temperature at a sliding speed of 0.01 m/s (a) styrene-butadiene rubber (SBR), (b) ANR, (c) NR,-tread compound, —gum compound. 

FIGURE 26.56 Log Abrasion loss by a blade (solid lines) and log cut growth rate (dashed hnes) of noncrystallizing rubber compounds as function of log frictional and log tearing energy, respectively isomerized natural rubber (NR), 2 styrene-butadiene rubber (SBR), and 3 acrylate-butadiene rubber (ABR). (From Champ, D.H., Southern, E., and Thomas, A.G., Advances in Polymer Friction and Wear, Lieng Huang Lee (ed.), Plenum, New York/London, 1974, p. 134.)... 

FIGURE 26.64 Log (abrasion) for two tread compounds natural rubber (NR) + black and styrene-butadiene rubber (SBR) + black on two surfaces of different sharpness Alumina 60 and Alumina 180 blunt as function of log (energy dissipation). (From Grosch, K.A. and Heinz, M., Proc. IRC 2000, Helsinki, 2000, paper 48.)... 

The effect of the mixing behavior on the rheological properties of styrene-butadiene mbber (SBR) compounds has been reported by Leblanc. ... 

FIGURE 35.11 Typical energy balance of one batch-mixing process on a GK320E mixer (styrene-butadiene rubber/carbon black [SBR/CB] compound). 

---