Styrene-butadiene copolymers commercial

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). 

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. 

SEC, which is mainly used for high-molecular weight compounds like polymers and proteins, has been coupled to FTIR. Using SEC-FTIR, liu and Dwyer [100] examined the types of branching in styrene-butadiene copolymers and Jordan and Taylor [101] measured the additives in several commercial polymers. 

Commercially available synthetic latex with a 50 % solid content was used. The latex is an anionic water dispersion of a styrene-butadiene copolymer with an antifoam agent. This latex is produced in Portugal. 

Waterborne dispersed polymers include both synthetic polymer dispersions and natural rubber. Synthetic polymer dispersions are produced by emulsion polymerization. A substantial part of the synthetic polymer dispersions is commercialized as dry products these include SBR for tires, nitrile rubbers, about 10% of the total PVC production, 75% of the total ABS and redispersable powders for construction materials. Carboxylated styrene-butadiene copolymers, acrylic and styrene-acrylic latexes and vinyl acetate homopolymer and copolymers are the main polymer classes commercialized as dispersions. The main markets for these dispersions are paints and coatings, paper coating, adhesives and carpet backing. 

Atactic polystyrene is sometimes known as general-purpose polystyrene (GPPS). There are other commercial grades of polystyrene, such as medium-impact polystyrene (MIPS) and high-impact polystyrene (HIPS). These impact-resistant forms of polystyrene are specially formulated by grafting to a rubber, such as polybutadiene or a styrene-butadiene copolymer, and dispersed in the base polystyrene. The inclusion and detection of small amounts of butadiene-based materials into the base polystyrene has been discussed. 

The reason for this change in with composition is that the glass transitions of the two components, as homopolymers, are — 87 C for polybutadiene and 106 °C for polyacrylonitrile. The glass transitions of the copolymers lie in between these two extremes. This is both the anticipated and the observed behaviour. The glass transition of a copolymer poly AB will lie at a temperature between the glass temperatures of the two homopolymers poly A, and poly B. For example, the dependence of on composition for the styrene-butadiene copolymers is shown in Fig. 3.9 the styrene contents of the commercial SBR rubbers fall in the range 10 to 40 per cent. 

Block copolymers can be prepared by several techniques, of which anionic polymerization offers the best possibilities for controlling the product. In this method the first step is to polymerize a single monomer, allowing reaction to proceed until the monomer is exhausted. To the living polymer is added a second monomer which then forms the second block. When the second monomer is exhausted a third monomer may be added, and so on. Many combinations of monomers have been investigated and a few block copolymers are now commercially available, e.g., the styrene-butadiene copolymer described in Chapter 18. 

Methyl-5-vinylpyiidine-butadiene copolymers (usually about 20 80 molar) are now commercially available. These copolymers are compounded and vulcanized in much the same way as styrene-butadiene copolymers and the vulcanizates have broadly similar properties the vinylpyridine rubbers show improved low temperature flexibility, abrasion resistance and oil resistance. 

Synthetic polymers that are commercially manufactured in the quantity of billions of pounds may be classified in three categories (1) plastics, which include thermosetting resins (e.g., urea resins, polyesters, epoxides) and thermoplastic resins (e.g., low-density as well as high-density polyethylene, polystyrene, polypropylene) (2) synthetic fibers, which include cellulosics (such as rayon and acetate) and noncellulose (such as polyester and nylon) and (3) synthetic rubber (e.g., styrene-butadiene copolymer, polybutadiene, ethylene-propylene copolymer). 

With the onset of World War II, immediate work was started to find a commercial substitute for natural rubber because of the restrictions on world movement of goods and likelihood of the loss of rubbergrowing areas in the Far East to the Japanese. Some commercial quantities of GRS, a styrene-butadiene copolymer, became available and modern forms of this make up the rubber type in most popular use, especially in car tyres. After World War II renewed interest in the field of fundamental polymerization technology soon produced a number of new synthetic rubbers, many of which required special additives to assist their processing, whilst others such as ethylene-propylene terpolymer allowed very large volumes of petroleum oil to be used as extenders rather than in limited quantities as plasticizers. Work in the field of natural rubber also enabled large volumes of oil to be used with this polymer. 

Emulsion polymerization is the leading technique to produce colloidal polymer dispersions. Carboxylated styrene-butadiene copolymers, acrylic and styrene-acrylic latexes, and vinyl acetate homopolymer and copolymers are the main polymer classes produced by this technique. These products are commercialized as dispersions and as dry products. 

Copolymers often have glass transition temperatures intermediate between the associated homopolymers. For commercially important copolymers, such as styrene-butadiene copolymers, this has been carefully studied. For butadiene-styrene copolymers, Henderson [35] gives... 

The SAN and ABS cxjpolymers aantain approximately 25 wt% of acrylonitrile and polybutadiene rubber in amounts up to 20 wt%. Other styrene copolymers of industrial importance include styrene—maleic anhydride copolymer (SMA), styrene-divinylbenzene copolymer, acrylic—styrene-acrylonitrile terpolymer, and styrene-butadiene copolymer. Recently, metallocene catalysts have been developed to synthesize syndiotactic polystyrene (sPS). The polymerization process and process conditions have major effects on polymer properties and process economy. For styrene homopolymerization and copolymerization, various types of polymerization reactors are used commercially. 

Acrylonitrile—Butadiene—Styrene. ABS is an important commercial polymer, with numerous apphcations. In the late 1950s, ABS was produced by emulsion grafting of styrene-acrylonitrile copolymers onto polybutadiene latex particles. This method continues to be the basis for a considerable volume of ABS manufacture. More recently, ABS has also been produced by continuous mass and mass-suspension processes (237). The various products may be mechanically blended for optimizing properties and cost. Brittle SAN, toughened by SAN-grafted ethylene—propylene and acrylate mbbets, is used in outdoor apphcations. Flame retardancy of ABS is improved by chlorinated PE and other flame-retarding additives (237). 

Styrene [100-42-5] (phenylethene, viaylben2ene, phenylethylene, styrol, cinnamene), CgH5CH=CH2, is the simplest and by far the most important member of a series of aromatic monomers. Also known commercially as styrene monomer (SM), styrene is produced in large quantities for polymerization. It is a versatile monomer extensively used for the manufacture of plastics, including crystalline polystyrene, mbber-modifted impact polystyrene, expandable polystyrene, acrylonitrile—butadiene—styrene copolymer (ABS), styrene—acrylonitrile resins (SAN), styrene—butadiene latex, styrene—butadiene mbber (qv) (SBR), and unsaturated polyester resins (see Acrylonithile polya rs Styrene plastics). 

Styrene Copolymers. Acrylonitrile, butadiene, a-methylstyrene, acryUc acid, and maleic anhydride have been copolymerized with styrene to yield commercially significant copolymers. Acrylonitrile copolymer with styrene (SAN), the largest-volume styrenic copolymer, is used in appHcations requiring increased strength and chemical resistance over PS. Most of these polymers have been prepared at the cross-over or azeotropic composition, which is ca 24 wt % acrylonitrile (see Acrylonithile polya rs Copolyp rs). 

Anionic polymerization, if carried out properly, can be truly a living polymerization (160). Addition of a second monomer to polystyryl anion results in the formation of a block polymer with no detectable free PS. This technique is of considerable importance in the commercial preparation of styrene—butadiene block copolymers, which are used either alone or blended with PS as thermoplastics. 

Commercially, anionic polymerization is limited to three monomers styrene, butadiene, and isoprene [78-79-5], therefore only two useful A—B—A block copolymers, S—B—S and S—I—S, can be produced direcdy. In both cases, the elastomer segments contain double bonds which are reactive and limit the stabhity of the product. To improve stabhity, the polybutadiene mid-segment can be polymerized as a random mixture of two stmctural forms, the 1,4 and 1,2 isomers, by addition of an inert polar material to the polymerization solvent ethers and amines have been suggested for this purpose (46). Upon hydrogenation, these isomers give a copolymer of ethylene and butylene. 

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