Polystyrene impurities

There are at the present time many thousands of grades of commercial plastics materials offered for sale throughout the world. Only rarely are the properties of any two of these grades identical, for although the number of chemically distinct species (e.g. polyethylenes, polystyrenes) is limited, there are many variations within each group. Such variations can arise through differences in molecular structure, differences in physical form, the presence of impurities and also in the nature and amount of additives which may have been incorporated into the base polymer. One of the aims of this book is to show how the many different materials arise, to discuss their properties and to show how these properties can to a large extent be explained by consideration of the composition of a plastics material and in particular the molecular structure of the base polymer employed. 

Los Alamos is processing a wide variety of residues, including Pu-Be neutron sources, polystyrene-Pu02-U02 blocks, incinerator ash, Pu-U alloys and oxides, Pu-Zr alloys and oxides, Pu-Np alloys and oxides, Pu-Th alloys and oxides, etc. Processes have been developed for these scrap items (see Figure 2), but we need to know more about Pu-Np separations Pu-Th separations oxalate precipitations for both plus 3 and plus 4 valences valence stabilization dissolution methods for high-fired impure oxides in-line alpha monitors to measure extremely low concentrations of Pu and Am in HNO3 solutions and solubility of various mixtures of Pu02 and UO2 under a variety of conditions. 

For the large scale synthesis, the sodium salt of 2 formed in the NaCN-NaOH reaction could be purified by brominated polystyrene resin S P-207 chromatography to avoid acidic work-up which generates HCN. The SP-207 resin was first saturated with 1 M NaCl, and the crude reaction mixture was loaded onto the column. The column was then eluted with 1M NaCl to remove inorganic salts such as excess NaCN and NaOH and other polar impurities. Eluant switching to MeOH-H20 eluted the sodium salt of 2. Fractions containing >98.5 A% of... 

The physical properties of polystyrene depend upon the specific reaction components, the mass ratios of the components, and the conditions at which the reaction occurs. These will be discussed later. The impurities remaining in the polystyrene also affect the properties. For instance, the heat distortion temperature may be as low as 70°C if there is unreacted styrene present. It is normally between 90 and 95°C. Therefore the maximum percentage of styrene that will be allowed in the product is 0.01%. Careful drying is also necessary if the polystyrene is to be extruded. For this application the polystyrene must contain a maximum of 0.03-0.05% water. We will set 0.03% as the maximum amount of water allowed. The specifications for the polystyrene are given in Table 3E-1. Different types of rubbers may be used for making impact polystyrenes.12 We shall use polybutadiene. 

Before the polystyrene is separated from the water and impurities, the insoluble inorganics must be dissolved. This is done by adding enough dilute hydrochloric acid to react with the tricalcium phosphate and make a soluble product. The acid will also react with any remaining peroxide. However, nearly all the peroxide will have already reacted or decomposed, since its half-life is 2.1 hr at 85°C.27... 

Finely divided aluminium powder or dust forms highly explosive dispersions in air [1], and all aspects of prevention of aluminium dust explosions are covered in 2 recent US National Fire Codes [2], The effects on ignition properties of impurities introduced by recycled metal used to prepare dust were studied [3], Pyrophoricity is eliminated by surface coating aluminium powder with polystyrene [4], Explosion hazards involved in arc and flame spraying of the powder are analysed and discussed [5], and the effect of surface oxide layers on flammability was studied [6], The causes of a severe explosion in 1983 in a plant producing fine aluminium powder are analysed, and improvements in safety practices discussed... 

Polystyrene latices used as an adsorbent were prepared by the Kotera-Furusawa-Takeda method(8 to reduce the spurious effects of surface active substances. The average diameter(D) and the surface gharge density(ao) of the latex particles were determined D=2000 A and 0O = 1.5 uC/cm. A silica sample was prepared by the method described by Stttber et al.(9), and was composed of highly mono-disperse spherical particles of 1900 X in diameter. These colloids were used after dialyzing exhaustively against distilled water to remove the ionic impurities. 

In the early days of polymer science, when polystyrene became a commercial product, insolubility was sometimes observed which was not expected from the functionality of this monomer. Staudinger and Heuer [2] could show that this insolubility was due to small amounts of tetrafunctional divinylbenzene present in styrene as an impurity from its synthesis. As little as 0.02 mass % is sufficient to make polystyrene of a molecular mass of 2001000 insoluble [3]. This knowledge and the limitations of the technical processing of insoluble and non-fusible polymers as compared with linear or branched polymers explains why, over many years, research on the polymerization of crosslinking monomers alone or the copolymerization of bifunctional monomers with large fractions of crosslinking monomers was scarcely studied. 

MP borohydride catches one equivalent of the titanium catalyst, while the polystyrene-bound diethanolamine resin (PS-DEAM) can scavenge the remaining titanium catalyst. The borohydride reagent also assists in the reductive animation reaction. Final purification of the crude amine product is achieved with a polystyrene-bound toluene sulfonic acid resin scavenger that holds the amine through an ion exchange reaction, while impurities are washed off. The pure amine can be recovered with methanol containing 2M ammonium hydroxide. 

A pivotal step in the analytical process is sample preparation. Frequently liquid-liquid extractions (LLEs) are used. Solvents, pH, and multiple back extractions are all manipulated to increase selectivity and decrease unwanted contaminants before injection on the GC system. Solid phase extraction (SPE) is more convenient than it used to be because of an increase in commercially available SPE columns. SPE columns are packed with an inert material that binds the drug of interest, allowing impurities to pass through. As with LEE, solvent choices and pH affect retention and recovery. There are three commercially available types of SPE columns, diatomaceous earth (which uses the same principles as LLE), polystyrene-divinylbenzene copolymer, and mixed mode bonded silica (Franke and de Zeeuw, 1998). 

Berlin [69] also confirmed the importance of the presence of OH radicals in his investigation of the polymerisation of polystyrene in the presence of styrene monomer when he found the addition of water to the reaction solvent (benzene) greatly enhanced the yield of polymer. However, latterly it has been argued for these systems that the appearance ofwater decomposition products (e. g. H2O2) led to oxidation of the various impurities, which previously, may have acted as inhibitors in the polymerisation process. 

Based on this approach Schouten et al. [254] attached a silane-functionalized styrene derivative (4-trichlorosilylstyrene) on colloidal silica as well as on flat glass substrates and silicon wafers and added a five-fold excess BuLi to create the active surface sites for LASIP in toluene as the solvent. With THF as the reaction medium, the BuLi was found to react not only with the vinyl groups of the styrene derivative but also with the siloxane groups of the substrate. It was found that even under optimized reaction conditions, LASIP from silica and especially from flat surfaces could not be performed in a reproducible manner. Free silanol groups at the surface as well as the ever-present impurities adsorbed on silica, impaired the anionic polymerization. However, living anionic polymerization behavior was found and the polymer load increased linearly with the polymerization time. Polystyrene homopolymer brushes as well as block copolymers of poly(styrene-f)lock-MMA) and poly(styrene-block-isoprene) could be prepared. 

In the initial step, the first BOC-protected amino acid is bound to the polymer, e.g. polystyrene in which a proportion of the phenyl rings have chloromethyl substitution. Attachment to these residues is through the carboxyl via an ester linkage. This involves a simple nucleophilic substitution reaction, with the carboxylate as nucleophile and chloride as leaving group (see Section 6.3.2). After each stage, the insoluble polymer-product combination is washed free of impurities. 

The nonionic surfactant, nonylphenol deca(oxyethylene glycol) monoether, NP-EO10, supplied by Berol Kemi AB, Stenungsund, Sweden, was of technical grade and used without further purification. The main impurity is free polyethylene oxide. Analysis of the sample gave a polyethylene oxide content of = 3% (4). Note, that polyethylene oxide adsorbs on polystyrene latexes ( ), but a monolayer is reached at solution concentrations that are 10 times the concentration required to obtain a monolayer coverage with NP-EO q. The free polyethylene oxide, therefore, is expected to have negligible influence on the adsorption measurements. 

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