Polymerized Styrenes

Copolymers of polystyrene with acrylonitrile (SAN), a-methylstyrene (SMS), acryl-styrene-acrylester (ASA), or acrylonitrile-ethylene-propylene styrene (AES) exhibit better weathering stability than homo-polystyrenes, Table 5.3. All polymerized styrenes will yellow under long-term weathering conditions, however, and their 

Impact modified polystyrene and ABS are prone to oxidation because of their polybutadiene content. Under weathering conditions degradation begins at the surface and is seen in yellowing and rapid decline of mechanical properties such as impact strength. The development of sterically hindered amines allowed, albeit to a limited extent, the use of SB and ABS in outdoor applications [86]. 

SB Impact resistant Highly impact resistant Embrittles and yellows, more sensitive than PS Embrittles and yellows, more sensitive than PS 

AES More resistant than ABS, more sensitive than ASA 

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Impact polystyrene (IPS) is one of a class of materials that contains mbber grafted with polystyrene. This composition is usually produced by polymerizing styrene (by mass or solution free-radical polymerization) in the presence of a small amount (ca 5%) of dissolved elastomer. Some of the important producers of impact-resistant polystyrenes are BASE (Polystyrol), Dow (Styron), and Monsanto (Lustrex). The 1988 U.S. production of impact polystyrene was more than 1 million t (92). 

This product is a difunctional initiator and can polymerize styrene monomer ... 

Block copolymer chemistry and architecture is well described in polymer textbooks and monographs [40]. The block copolymers of PSA interest consist of anionically polymerized styrene-isoprene or styrene-butadiene diblocks usually terminating with a second styrene block to form an SIS or SBS triblock, or terminating at a central nucleus to form a radial or star polymer (SI) . Representative structures are shown in Fig. 5. For most PSA formulations the softer SIS is preferred over SBS. In many respects, SIS may be treated as a thermoplastic, thermoprocessible natural rubber with a somewhat higher modulus due to filler effect of the polystyrene fraction. Two longer reviews [41,42] of styrenic block copolymer PSAs have been published. 

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. 

The most important use of polystyrene is in packaging. Molded polystyrene is used in items such as automobile interior parts, furniture, and home appliances. Packaging uses plus specialized food uses such as containers for carryout food are growth areas. Expanded polystyrene foams, which are produced by polymerizing styrene with a volatile solvent such as pentane, have low densities. They are used extensively in insulation and flotation (lifejackets). 

Another family of polyols is the filled polyols.llb There are several types, but die polymer polyols are die most common. These are standard polyether polyols in which have been polymerized styrene, acrylonitrile, or a copolymer thereof. The resultant colloidal dispersions of micrometer-size particles are phase stable and usually contain 20-50% solids by weight. The primary application for these polyols is in dexible foams where the polymer filler serves to increase foam hardness and load-bearing capacity. Other filled polyol types diat have been developed and used commercially (mainly to compete with die preeminent polymer polyols) include the polyurea-based PEID (polyhamstoff dispersion) polyols and the urethane-based PIPA (poly isocyanate polyaddition) polyols. 

Indeed, cumyl carbocations are known to be effective initiators of IB polymerization, while the p-substituted benzyl cation is expected to react effectively with IB (p-methylstyrene and IB form a nearly ideal copolymerization system ). Severe disparity between the reactivities of the vinyl and cumyl ether groups of the inimer would result in either linear polymers or branched polymers with much lower MW than predicted for an in/mcr-mediated living polymerization. Styrene was subsequently blocked from the tert-chloride chain ends of high-MW DIB, activated by excess TiCU (Scheme 7.2). 

Polystyrene is made by polymerizing styrene. In the suspension process the styrene is broken up into small droplets which are suspended in water. Various additives aid in controlling this and the reaction rate. These additives amount to about 1% of the styrene added. For high-impact styrene up to 0.15 lb rubber/lb styrene is included. The two major materials needed are water and styrene. 

Block copolymers of polystyrene with rubbery polymers are made by polymerizing styrene in the presence of an unsaturated rubber such as 1,4 polybutadiene or polystyrene co-butadiene. Some of the growing polystyrene chains incorporate vinyl groups from the rubbers to create block copolymers of the type shown in Fig. 21.4. The combination of incompatible hard polystyrene blocks and soft rubber blocks creates a material in which the different molecular blocks segregate into discrete phases. The chemical composition and lengths of the block controls the phase morphology. When polystyrene dominates, the rubber particles form... 

We can readily polymerize styrene by a variety of methods including solution, emulsion, suspension, and bulk processes. Historically, bulk polymerization was the first commercial process, but it has now largely been superseded by solution and suspension polymerization. 

Several rhodium(I) complexes have also been employed as ATRP catalysts, including Wilkinson s catalyst, (177),391 421 422 ancj complex (178).423 However, polymerizations with both compounds are not as well-controlled as the examples discussed above. In conjunction with an alkyl iodide initiator, the rhenium(V) complex (179) has been used to polymerize styrene in a living manner (Mw/Mn< 1.2).389 At 100 °C this catalyst is significantly faster than (160), and remains active even at 30 °C. A rhenium(I) catalyst has also been reported (180) which polymerizes MM A and styrene at 50 °C in 1,2-dichloroethane.424... 

Hazardous when exposed to oxygen due to peroxide formation and subsequent peroxide initiation of polymerization Styrene Butadiene Tetrafluoroethylene Chlorotrifluoroethylene Vinyl acetylene Vinyl acetate Vinyl chloride Vinyl pyridine Chloroprene... 

GRS A process for making a synthetic rubber by co-polymerizing styrene and butadiene. 

SDS [Sulzer Dainippon Sumitomo] A continuous process for polymerizing styrene. The reactants are mixed in a static mixer, which gives a very uniform time/temperature history for the polymer. Developed jointly by Sulzer, Dainippon Ink Chemicals, and Sumotomo Heavy Industries. Offered for license in 1990. 

The suspension process, developed in the U.S.A. ( 1 7 ) and also tested during the war in Ludwigshafen for polymerizing styrene (18), did not fully come into its own until after 1945. 

With conventional techniques and electrolytes, it was not possible to obtain living anions because they are rapidly protonated by tetraalkylammonium salts and residual water. The first report of the production of living polymers by an electrolytic method has to be attributed to Yamazald et al. [247], who used tetrahydrofuran as solvent, and LiAlH4 or NaAl(C2H5)4 as electrolyte for the polymerization of a-methylstyrene. A similar technique was used to polymerize styrene as well as derivatives [248-252]. 

In 1981 we reported (2, 3) the first examples of free radical polymerizations under phase transfer conditions. Utilizing potassium persulfate and a phase transfer catalyst (e.g. a crown ether or quaternary ammonium salt), we found the solution polymerization of acrylic monomers to be much more facile than when common organic-soluble initiators were used. Somewhat earlier, Voronkov and coworkers had reported (4) that the 1 2 potassium persulfate/18-crown-6 complex could be used to polymerize styrene and methyl methacrylate in methanol. These relatively inefficient polymerizations were apparently conducted under homogeneous conditions, although exact details were somewhat unclear. We subsequently described (5) the... 

About 25% of polymerized styrene is in the copolyrner form. The largest volume copolymer is SBR (25% styrene, 75% butadiene-rubber), used for making tires, hoses, belts, footwear, foam rubber, rubber-coated fabrics, and adhesives. ... 

Another type of copolymer is a block copolymer. Here a low molecular weight polymer may be extended by reaction with a new monomer. Recall that we talked about living polymers in this Chapter, Section 2.3. If, for example, we polymerized styrene alone first, then added some butadiene and polymerized it further, we would have a number of styrene units bundled together and a number of butadienes also together. 

If one obtained a yield of 10% polymer after 10 min of polymerizing styrene by a free radical mechanism, what would be the composition of the other 90% ... 

Would it be safe to polymerize styrene by bulk polymerization in a 55 gal drum ... 

Emulsion polymerization is one of the major examples where detergents are applied to create microreactions. For instance, to polymerize styrene (which is insoluble in water), an initiator is added to the aqueous phase. The polymer (polystyrene [PS]) is formed, and the suspension is stabilized by using suitable emulsifiers. The latex thus formed is used in various industrial applications. 

Alkyl derivatives of the alkaline-earth metals have also been used to initiate anionic polymerization. Organomagnesium compounds are considerably less active than organolithiums, as a result of the much less polarized metal-carbon bond. They can only initiate polymerization of monomers more reactive than styrene and 1,3-dienes, such as 2- and 4-vinylpyridines, and acrylic and methacrylic esters. Organostrontium and organobarium compounds, possessing more polar metal-carbon bonds, are able to polymerize styrene and 1,3-dienes as well as the more reactive monomers. 

Matyjaszewski, K., Carbocationic Polymerization Styrene and Substituted Styrenes, Chap. 41 in Comprehensive Polymer Science, Vol. 3, G. C. Eastmond, A. Ledwith, S. Russo, and P. Sigwalt, eds., Pergamon Press, Oxford, 1989 Macromol. Symp., 174, 51 (2001). 

High-impact polystyrene (HIPS) is produced by polymerizing styrene in the presence of a rubber, usually poly(l,3-butadiene). HIPS has improved impact resistance compared to polystyrene and competes with ABS products at low-cost end applications such as fast-food cups, lids, takeout containers, toys, kitchen appliances, and personal-care product containers. HIPS as well as ABS and SMA are used in physical blends with other polymers, such as polycarbonates, polyesters, and polyamides, to improve impact resistance (Sec. 2-13c-3). 

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