Physical properties styrene/butadiene copolymers

This block copolymer has substantially different physical properties as compared to a random styrene-butadiene copolymer. 

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. ... 

Effects of Ozone Exposure on the Physical Properties of Butadiene and Styrene/Butadiene Copolymers... 

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. 

Physical property Physical units cis-1,4- Poly(isoprenes) Styrene/butadiene copolymers Poly(urethanes) ... 

Styrene- butadiene copolymer GRS, Buna S (SBR) 450-500 -60 to 120 (-75 to 250) Good physical properties excellent abrasion resistance not oil, ozone, or weather resistant electrical properties good, but not outstanding Same as natural rubber... 

Most polystyrene products are not homopolystyrene since the latter is relatively brittle with low impact and solvent resistance (Secs. 3-14b, 6-la). Various combinations of copolymerization and blending are used to improve the properties of polystyrene [Moore, 1989]. Copolymerization of styrene with 1,3-butadiene imparts sufficient flexibility to yield elastomeric products [styrene-1,3-butadiene rubbers (SBR)]. Most SBR rubbers (trade names Buna, GR-S, Philprene) are about 25% styrene-75% 1,3-butadiene copolymer produced by emulsion polymerization some are produced by anionic polymerization. About 2 billion pounds per year are produced in the United States. SBR is similar to natural rubber in tensile strength, has somewhat better ozone resistance and weatherability but has poorer resilience and greater heat buildup. SBR can be blended with oil (referred to as oil-extended SBR) to lower raw material costs without excessive loss of physical properties. SBR is also blended with other polymers to combine properties. The major use for SBR is in tires. Other uses include belting, hose, molded and extruded goods, flooring, shoe soles, coated fabrics, and electrical insulation. 

More than 800 million pounds of EPM and EPDM polymers were produced in the United States in 2001. Their volume ranks these materials fourth behind styrene-1,3-butadiene copolymers, poly( 1,4-butadiene), and butyl rubber as synthetic rubbers. EPM and EPDM polymers have good chemical resistance, especially toward ozone. They are very cost-effective products since physical properties are retained when blended with large amounts of fillers and oil. Applications include automobile radiator hose, weather stripping, and roofing membrane. 

The hydrogenation of the centre block of SBS copolymer produced oxidation stable thermoplastic elastomer. This product was commercialized by the Shell Development Company under the trade name of Kraton G. The field of thermoplastic elastomers based on styrene, 1-3-butadiene or isoprene has expanded so much in the last 10 years that the synthetic rubber chemist produced more of these polymers than the market could handle. However, the anionically prepared thermoplastic system is still the leader in this field, since it produced the best TPR s with the best physical properties. These TPR s can accommodate more filler, which reduces the cost. For example, the SBS Kraton type copolymer varies the monomer of the middle block to produce polyisoprene at various combinations, then, followed... 

The polymers described above have been chemically pure, although physically helerodisperse. It is oflen possible lo combine two or more of these monomers in the same molecule to form a copolymer. This process produces still further modification of molecular properties and, in turn, modification of the physical properties of file product. Many commercial polymers are copolymers because of the blending of properties achieved in this way. For example, one of the important new polymers of the past ten years has been the family of copolymers of acrylonitrile, butadiene and styrene, commonly called ABS resins. The production of these materials has grown rapidly in a short period of time because of their combination of dimensional stability and high impact resistance. These properties are related to the impact resistance of acrylonitrile-butadiene rubber and the dimensional stability of polystyrene, which are joined in the same molecule. 

Another widely used copolymer is high impact polystyrene (PS-HI), which is formed by grafting polystyrene to polybutadiene. Again, if styrene and butadiene are randomly copolymerized, the resulting material is an elastomer called styrene-butadiene-rubber (SBR). Another classic example of copolymerization is the terpolymer acrylonitrile-butadiene-styrene (ABS). Polymer blends belong to another family of polymeric materials which are made by mixing or blending two or more polymers to enhance the physical properties of each individual component. Common polymer blends include PP-PC, PVC-ABS, PE-PTFE and PC-ABS. 

In the present study, the effects of composition, molecular weight, and heat treatment on the relaxation behavior of styrene—butadiene-styrene (SBS) block polymers are investigated. There is evidence (e.g., 6,7,8) that these types of multicomponent multiphase systems exhibit unusual phenomena in their dynamic mechanical behavior and in other physical properties. These are apparently related to the presence of the so-called interphase mixing region between the elastomeric and glassy domains. Similar evidence has been obtained by gas diffusion and sorption studies on the copolymer samples used in this investigation (9). 

Incorporation of Ti02 into polystyrene(s), styrene-acrylonitrile, acrylonitrile-butadiene-styrene, and other associated copolymers and alloys is normally by way of concentrates prepared on equipment similar to that used for polyethylene. This concentration step is usually necessary to achieve high-quality dis-persion so color properties are fully developed and physical properties are not compromised. 

Blends of copolymers of styrene and acrylonitrile and butadiene and acrylonitrile called ABS plastics which are more ductile than polystyrene, are now used at an annual rate of almost 500 thousand tons. Terpoljrmers of styrene, acrylonitrile and maleic anhydride (Cadon) have heat deflection points above lOOOC.Q)While the physical properties of both ABS and the maleic anhydride terpolymers are superior to polystyrene, the improvements are not sufficient to classify them as high performance plastics. 

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