Migration Styrene

PS Meat trays, take-out food containers and cups Possible contaminant migrating styrene (accumulates in body fat)... 

About half of the styrene produced is polymerized to polystyrene, an easily molded, low-cost thermoplastic that is somewhat brittle. Foamed polystyrene can be made by polymerizing it in the presence of low-boiling hydrocarbons, which cause bubbles of gas in the solid polymer after which it migrates out and evaporates. Modification and property enhancement of polystyrene-based plastics can be readily accomplished by copolymerization with other substituted ethylenes (vinyl monomers) for example, copolymerization with butadiene produces a widely used synthetic rubber. 

Styrene hydrozirconation led to a ratio for terminal and benzylic zirconocene products of around 85 15 [97]. Experimental evidence on alkyl-substituted styrene suggested that both electronic [98,99] and steric effects [41,86] are important for the formation of the benzyhc and terminal zirconium isomers. Migration of the metal fragment during the reaction of the zirconocene moiety might occur, perturbing the terminal/benzyl regioisomer ratio of the isolated products (Scheme 8-11) [67, 83, 98-102]. 

Gilsonite is active as a fluid loss additive because the permeability of cement is reduced. Latex additives also act as fluid loss additives. They also act as bonding aids, gas migration preventers, and matrix intensifiers. They improve the elasticity of the cement and the resistance to corrosive fluids [921]. A styrene-butadiene latex in combination with nonionic and anionic surfactants shows less fluid loss. The styrene-butadiene latex is added in an amount up to 30% by weight of the dry cement. The ratio of styrene to butadiene in the latex is typically 2 1. In addition, a nonionic surfactant (octylphenol ethoxylate and polyethylene oxide) or an anionic surfactant, a copolymer of maleic anhydride, and 2-hydroxypropyl acrylate [719] can be added in amounts up to 2%. 

Applications Radiotracer measurements, which combine high sensitivity and specificity with poor spatial resolution, have been used for migration testing. For example, studies have been made on HDPE, PP and HIPS to determine effects of manufacturing conditions on migration of AOs from plastic products into a test fat [443]. Labelled antioxidant was determined radio-analytically after 10 days at 40 °C. Acosta and Sas-tre [444] have used radioactive tracer methods for the determination of styrene ethyl acrylate in a styrene ethyl acrylate copolymer. 

The amination of styrene, however, led to two products (1-phenyl-1-ethylamine and 2-phenyl-l-ethylamine) in a 1 3 ratio [113], indicating that the hydrozirconation was not completely regioselective [114,115]. Since it is well known that hydrozirconation of trisubsti-tuted alkenes places zirconium at the least hindered carbon of the chain by a process involving zirconium migration, this class of alkenes was not investigated [5,116], On the other hand, hydrozirconation/amination of 3-methyl-l,2-butadiene gave an allylic amine. Reaction of the latter could either occur at the terminal carbon or proceed with... 

It can be seen from Table I that the oil phase viscosity increases at a much slower rate than the polystyrene phase due to its lower reactivity at 80°C. Also, the volume of the polystyrene-rich phase is increasing at the expense of the oil-rich phase as styrene and polystyrene migrate to the polystyrene-rich phase. 

Pines and Herling 83) dehydrated the title alcohols over alumina B (Footnotes, Table V). The dehydration was made at 350° and the contact time was adjusted in order to obtain 50-60% styrenes. The dehydration was accompanied by a 6% of the phenyl and 9% of the tolyl migration from carbon atom 2 to carbon atom 1 and can be explained as follows ... 

Brunelli, N., Nocci, R. and Magno, F. (2002). Global migration from styrenics to liquid food simulants, Ann. Chim., 92, 7-8, 637-648. 

Tawfik, M.S. and Huyghebaert, A. (1998). Polystyrene cups and containers styrene migration, Food Addit Contam., 15, 5, 592-599. 

Varner, S.L., Breder, C.V. and Fazio, T. (1983). Determination of styrene migration from food-contact polymers into margarine, using azeotropic distillation and headspace gas chromatography, J. Assoc. Ojf. Anal. Chem., 66, 5, 1067-1073. 

In the preceding cyclization, one concern is the behavior of intermediate 24 if its benzyl cation is replaced with a tertiary cation to avoid forming a tertiary carbon, the 1,2-aryl migration of this intermediate would be unlikely to occur. When this cyclization was extended to 2,2-dimethyl(o-ethynyl)styrene 26, the 2-alkenyl-lH-indene product 28 [16] was obtained in 76% yield, as depicted in Scheme 6.14. In this transformation, the alkenyl double bond of the 3,5-dien-l-ynes is cleaved and a... 

Hosokawa, Murahashi, and coworkers demonstrated the ability of Pd" to catalyze the oxidative conjugate addition of amide and carbamate nucleophiles to electron-deficient alkenes (Eq. 42) [177]. Approximately 10 years later, Stahl and coworkers discovered that Pd-catalyzed oxidative amination of styrene proceeds with either Markovnikov or anti-Markovnikov regioselectivity. The preferred isomer is dictated by the presence or absence of a Bronsted base (e.g., triethylamine or acetate), respectively (Scheme 12) [178,179]. Both of these reaction classes employ O2 as the stoichiometric oxidant, but optimal conditions include a copper cocatalyst. More recently, Stahl and coworkers found that the oxidative amination of unactivated alkyl olefins proceeds most effectively in the absence of a copper cocatalyst (Eq. 43) [180]. In the presence of 5mol% CUCI2, significant alkene amination is observed, but the product consists of a complicated isomeric mixture arising from migration of the double bond into thermodynamically more stable internal positions. 

In contrast, 1-phenylethylidene (74), which can undergo 1,2-hydrogen migration to form styrene (75), was found to be thermally stable in argon or xenon matrix at 10 K. The carbene decay to give styrene only when warming to 65 K in xenon matrix (Scheme 9.18). From the disappearance rate constant for 74, a energy barrier... 

Ehret-Henry, J., Ducruet, V, Luciani, A. Feigenbatrm, A. (1994) Styrene and ethylberrzene migration from polystyrene into dairy products by dynamic prrrge-and-trap gas chromatography. J. Food Sci., 59, 990-1001... 

In the original investigation of the Pd- or Ni-catalyzed alkenyl-benzyl and benzyl-alkenyl coupling reactions168, both Pd- and Ni-phosphine catalysts were shown to be effective. In some Ni-catalyzed reactions, however, double-bond migration to produce styrene derivatives was observed as a side reaction169. Nonetheless, both Pd- and Ni-catalyzed procedures have been successfully applied to the synthesis of various coenzymes Q , where n is < 10, and related menaquinones (Scheme 63)171,172. 

It is evident from the structures that the distance between the crosslinking sites increases from NUP (I) to NUP (III) leading to increase in elongation [303, 304, 354] which is in accordance with the data given in Table 4.16. The lower value of NG absorption or migration of NUP (III) compared with NUP (II) may be explained on the basis of the presence of double-bonds in the polyester backbones of NUP (III) which are terminal and provide crosslinking sites for styrene monomer. This... 

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