Styrene-butadiene rubber stability

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. 

Latexes are usually copolymer systems of two or more monomers, and their total solids content, including polymers, emulsifiers, stabilizers etc. is 40-50% by mass. Most commercially available polymer latexes are based on elastomeric and thermoplastic polymers which form continuous polymer films when dried [88]. The major types of latexes include styrene-butadiene rubber (SBR), ethylene vinyl acetate (EVA), polyacrylic ester (PAE) and epoxy resin (EP) which are available both as emulsions and redispersible powders. They are widely used for bridge deck overlays and patching, as adhesives, and integral waterproofers. A brief description of the main types in current use is as follows [87]. 

Styrene-butadiene rubber (SBR) latexes which are compatible with cementitious compounds are copolymers. They show good stability in the presence of multivalent cations such as calcium (Ca++) and aluminum (A1+++) and are unaffected by the addition of relatively large amounts of electrolytes (e.g., CaCl2). Outdoor exposure to... 

The major general purpose rubbers are natural rubber, styrene-butadiene rubber, butadiene rubber, isoprene rubber, and ethylene-propylene rubber. These rubbers are used in tires, mechanical goods, and similar applications. Specialty elastomers provide unique properties such as oil resistance or extreme heat stability. Although this differentiation is rather arbitrary, it tends also to classify the polymers according to volumes used. Styrene-butadiene rubber, butadiene rubber, and ethylene-propylene rubber account for 78 percent of all synthetic rubber consumed. 

Used as a secondary accelerator with antioxidant, antiozonant, and stabilizing function in synthetic rubber and high polymer materials in the plastics and rubber industries. Mainly used in styrene-butadiene rubber (SBR), chloroprene rubber (CR), epichlorohydrin, and chlorosulfonated polyethylene rubber. Promotes heat-resistance of chlorosulfonated polyethylene rubber, EPDM and CSM and sunshine resistance of CR. 

The uses of mercaptans in polymers fall into three major categories chain transfer agents, additives such as stabilizers against heat or UV light, and monomers that incorporate an alkylmercapto group into their structure. Mercaptans r-dodecyl, n-dododecyl, etc. are excellent chain transfer agents used to control molecular weight of several different kinds of polymers, styrene butadiene rubber, acrylonitrile-butadiene-styrene, polyacrylates, to name a few. " " ... 

A proposed expansion of the company s styrene-butadiene rubber production will require an additional 10,000 tons/yr of butadiene as a raw material. For many years, butadiene has been manufactured by dehydrogenating butene or butane over a catalyst at appropriate combinations of temperature and pressure. It is customary to dilute the butene feed with steam (10 to 20 mol HjO/mol butene) to stabilize the temperature during the endothermic reaction and to help shift the equilibrium conversion in the desired direction by reducing the partial pressures of hydrogen and butadiene. The current processes suffer from two major disadvantages ... 

Radhakrishnan, C., Alex, R., Unnikrishnan, G., Thermal, ozone and gamma ageing of styrene butadiene rubber and poly(ethylene-co-vinyl acetate) blends. Polymer Degradation and Stability 2006,91,902-910. 

Poly butadiene having a high content of cis 1,4 groups is difficult to process and also has a low coefficient of friction. Blending with an oil-extended styrene-butadiene rubber (SBR) overcomes these disadvantages, without adversely affecting resilience or chemical stability. 

Mixtures, formulated blends, or copolymers usually provide distinctive pyrolysis fragments that enable qualitative and quantitative analysis of the components to be undertaken, e.g., natural rubber (isoprene, dipentene), butadiene rubber (butadiene, vinylcyclo-hexene), styrene-butadiene rubber (butadiene, vinyl-cyclohexene, styrene). Pyrolyses are performed at a temperature that maximizes the production of a characteristic fragment, perhaps following stepped pyrolysis for unknown samples, and components are quantified by comparison with a calibration graph from pure standards. Different yields of products from mixed homopolymers and from copolymers of similar constitution may be found owing to different thermal stabilities. Appropriate copolymers should thus be used as standards and mass balance should be assessed to allow for nonvolatile additives. The amount of polymer within a matrix (e.g., 0.5%... 

Shojaei, A, Faghihi, M. Physico-mechanical properties and thermal stability of thermoset nanocomposites based on styrene-butadiene rubber/phenolic resin blend. Mat. Sci. Eng. A. 527, 917-926 (2010)... 

Shojaei and Faghihi [20] studied the effect of different concentrations of organoclay on styrene-butadiene mbber and phenolic resin blends prepared by two-roll mill. Thermogravimetric studies indicated that the organoclay enhanced the thermal stability of styrene-butadiene rubber vulcanizate, whilst manifesting a catalytic behavior in presence of the phenolic resin. 

The group of Gu Z. in the 2009, reported the behavior of styrene butadiene/ rubber/organo-bentonite nanocomposite prepared from latex dispersion, content was lower than 12 mass%. The results showed were that presence of organo-bentonite in the nanocoposite affects direct in the thermo stability, mechanical properties and swelling behavior, which was attribute to the good barrier properties of the dispersed nanoparticles. The dispersion is an important factor that can affect various properties such as thermal stability [81]. 

First, the stability of these polymer materials is very important for their practical use and processing. Assessment of surface chemical modification of rubber after aging treatment is, by example, primordial for pneumatic manufacturing. Similar to conventional methods, LA-MS is allowed to evaluate and follow the oxidation effects on model polymers such as polybutadiene (PB), polystyrene (PS), and styrene butadiene rubber (SBR) by both detection and identification of the degradation products. The thermooxidative stability of SBR has been then investigated. 

Kalf et al. studied the effect of grafting cellulose acetate and methylmethacrylate as compatibilizers on acrylonitrile butadiene rubber (NBR) and styrene-butadiene rubber (SBR) blends. Morphology studies of the samples show an improvement in interfacial adhesion between the NBR and SBR phases in the presence of the prepared compatibilizing agents. The authors also reported the samples with grafted compatibilizers showed superior crosslink density and thermal stability, as compared to the blends without graft copolymers. ... 

The reaction of carbenes with olefins to form cyclopropyl derivatives has been used to modify elastomers. Pinazzi and Levesque and Berentsvich et al. found that carbene addition had a significant influence on the properties of polydienes. Thermogravimetric analysis (TGA), flammability and oil resistance in NR and dichlorocarbene modified styrene butadiene rubber (DCSBR) blends were investigated by thermogravimetrie analysis as a funetion of different composition. The TGA plots confirmed the better thermal stability and flame resistance of DCSBR as well as its blends with NR. The amount of DCSBR in the blend significantly affected the properties of blends. 

The thermal stability of NR and carboxylated styrene butadiene rubber (XSBR) lattices and their blends were studied by thermogravimetric methods by Stephen et The thermal degradation and ageing properties of these individual lattices and their blends were investigated with special reference to blend ratio and vulcanization techniques. As already described, as the XSBR content in the blends increased, their thermal stability was also found to increase. Among sulphur and radiation-vulcanized samples, radiation cured possessed higher thermal stability due to the higher thermal stability of carbon carbon crosslinks. 

R. Stephen et al. also studied the effect of microfillers on the thermal stability of NR, carboxylated styrene-butadiene rubber (XSBR) lattices and their 70/30 NR/XSBR blend. Microcomposites of XSBR and their blend were found to be thermally more stable than unfilled samples. ... 

The copolymerization of a,p-unsaturated ketones has been studied extensively in order to improve the poor chemical and thermal stability exhibited by the homopolymers. The vinyl ketones have been copolymerized with most of the common vinyl and diene monomers. The data are given in Ref. [326]. For initiation, the same reagents could be used as for free-radical homopolymerization. Copolymerization was carried out in bulk [371] and in emulsion systems [372]. In copolymerization with methyl methacrylate, vinyl acetate [373], and styrene [371] it was concluded that the relative reactivities of the vinyl ketones increase with the increasing electron-withdrawing nature of the vinyl ketone substituent. Polar and steric effects are not observed. Most of the work has been directed toward the preparation of oil- and solvent-resistant rubbers to replaee styrene-butadiene rubber. Emulsion eopolymerization of butadiene with methyl isopropenyl ketone yielded rubbers with good solvent resistance and low temperature flexibility, but the products tended to harden on storage and were not compatible with natural rubber [374]. The reactive earbonyl function caused sensitivity to alkine reagents. Copolymers of butylacrylate and methyl vinyl ketone, for example, can be erosslinked by treatment with hydrazine [375]. 

Zhang Y, Zhang Q, Liu Q, Cheng H, Frost RL (2014) Thermal stability of styrene butadiene rubber (SBR) composites filled with kaolinite/silica hybrid filler. J Therm Anal Calorim 115 1013... 

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