Showing papers on "Polystyrene published in 1976"

Flow-Field-Flow Fractionation: A Versatile New Separation Method

Abstract: Flow-field-fractionation is a new separation technique that seems likely to have broad applicability. Its theoretical scope includes any solute for which one can find a solvent and a semipermeable membrane. The principles on which the technique is based are presented. Some experiments with polystyrene beads, viruses, and proteins verify that retention depends solely on diffusion coefficients.

A comparison of the adsorbed layer thickness obtained by several techniques of various molecular weight fractions of poly(vinyl alcohol) on aqueous polystyrene latex particles

Abstract: The thickness of the adsorbed layer of various molecular weight fractions of poly(vinyl alcohol) on polystyrene latex particles was measured at the plateau region of the isotherm using three hydrodynamic methods, namely, ultracentrifugation, diffusion (using intensity fluctuation spectroscopy, IFS), and electrophoresis. The thickness was also measured from the volume of the close-packed sediment of particles obtained by slow speed centrifugation. In all the experiments, electroviscous effects were nullified by addition of sufficient electrolyte. The thickness values obtained from the diffusion coefficients, using particles of 330 nm diameter, were considerably higher (50–100%) than those obtained from sedimentation coefficient measurements on a smaller particle size (71.7 nm) latex. However, if one assumes that both the surface area and the volume occupied by each adsorbed polymer molecule is independent of particle radius, then the adsorbed layer thickness should increase with increase in particle radius. This proved to be the case when the thickness, using polystyrene latices of various particle sizes (100–523 nm diameter) was measured using IFS. Taking this effect into account, reasonable agreement was obtained between the two sets of values, for the medium and high molecular weight fractions. The values obtained from diffusion measurements were also in agreement with those obtained from measurement of sediment volume with particles of the same size. The electrophoresis results, however, on the same latex, gave values that were invariably higher than those obtained by the other methods. Moreover, the values obtained were not independent of the electrolyte concentration employed, suggesting that the assumptions that are generally made in using the electrophoresis method are invalid.

Studies on the preparation and characterisation of monodisperse polystyrene latices

Abstract: A series of polystyrene latices prepared by emulsion polymerisation have been characterised by electrophoresis. Dodecanoic acid, dodecylamine hydrochloride and dodecylphosphoric acid were used as emulsifying agents and hydrogen peroxide and potassium persulphate as initiators. After a preliminary dialysis to remove oxidation products formed in the polymerisation the mobility against pH curves showed regions which were characteristic of the adsorbed surface active agent. After extensive dialysis these regions were no longer present and the curves were characteristic of a carboxylic acid with a surface pK of 4.64. The experiments indicated that the carboxyl groups were an integral part of the polymer. This was confirmed by the preparation, using suspension polymerisation, of a dispersion of polystyrene particles in the complete absence of surface active agent. For this material the mobility — pH behaviour was very similar to that of the extensively dialysed latices. A detailed discussion is given of the problem of obtaining pK values from electrokinetic data.

Switching in polystyrene films: Transition from on to off state

Abstract: Experiments on polystyrene films formed by a glow‐discharge technique shows a reproducible bistable switching. Various interpretations are briefly reviewed. It is shown that the resistance of the on state is strictly related to the energy needed by the on‐off transition. From the value of this energy it is concluded that the most probable explanation is that the on current takes place along a filamentary path constituted by carbon atoms. A quantitative analysis is made on the basis of the heat balance equation. Formation of carbonated chains is confirmed by a chromatography analysis in vapor phase which shows an hydrogen release.

Charge transfer in metal/atactic polystyrene contacts

Abstract: Contact charge‐exchange experiments between various metals and atactic polystyrene are utilized to elucidate the electronic structure of the polystyrene Bulk states present at approximately 1014/cm3 within a 4‐μ‐thick boundary layer, as well as surface states of approximate density 1010/cm2, govern the charge‐exchange characteristics of polystyrene in the metal contacts It is argued that the carriers are electrons injected from the region of the Fermi level of the metal into the polymer, and that the metal/polymer junction remains indefinitely in a nonequilibrium state A steady‐state injection level is reached because of differences in injection and transport properties of the surface boundary layer and the deeper bulk material A significant effect of the substrate metal on the populations of the electronic states at the free surface of the polystyrene films is identified and shown to be long range (at least 15 μ)

Quantitative analysis of styrene monomer in polystyrene and foods including some preliminary studies of the uptake and pharmacodynamics of the monomer in rats.

Abstract: A variety of food containers, drinking cups and cutlery, fabricated from polystyrene (PS) or polystyrene-related plastic, were analyzed for their styrene monomer content. Samples of yogurt, package...

Application of ESCA to polymer chemistry. VIII. Surface structures of AB block copolymers of polydimethylsiloxane and polystyrene

Abstract: The surface morphology of a number of films of AB block copolymers of polydimethylsiloxane and polystyrene was examined by ESCA and contact angle measurements. In all cases the immediate surface is shown to consist of an essentially pure polydimethylsiloxane component. By comparing the intensities of elastic peaks corresponding to photoionizations from core levels without energy loss for polydimethylsiloxane and polystyrene with those for the block copolymers and by consideration of shake-up phenomena specific to the polystyrene component, an estimate of the thickness of the polydimethylsiloxane outer layer of the latter may be obtained. This is shown to vary between ∼13 and 40 A, depending on the method of formation of copolymer film.

Characterization of polystyrene networks by small‐angle neutron scattering

Abstract: Polystyrene networks prepared by anionic polymerization have been characterized by small-angle neutron scattering. Two kinds of systems have been examined: (A) networks with labelled branch points allowing characterization of the spatial distribution of crosslinking points; (B) networks containing a low proportion of chains labelled with perdeuterated polystyrene in order to characterize the conformation of individual elastic chains of the polymeric network. The dependence of the results on swelling and uniaxial extension is discussed.

Solubility of gases and liquids in molten polystyrene

Abstract: Experimental solubility data have been obtained for sixteen organic solutes in molten polystyrene by a gas chromatographic procedure for temperatures from 408° to 503°K and pressures to 4 atm. The effects of diffusion and adsorption of the solute on the substrate were considered. The Henry's law constants resulting from this study and those obtained by other investigators were related to the reduced temperature. The effect of pressure on the Henry's law constants is also discussed, and a relationship is presented for the heat of solution.

Gradient polymers by diffusion polymerization

Abstract: Gradient polymers are multicomponent polymers whose structures or compositions are not macroscopically homogeneous, but vary as a function of position in the sample One method to prepare such polymers is by diffusing a guest monomer into a host polymer and then polymerizing the monomer in position to retain the concentration gradient created by the diffusion One series of such type of materials was prepared by diffusing acrylonitrile into polystyrene The gradient profile was determined by analyzing the nitrogen content in succeeding layers of the sample These gradient polymers exhibit improved resistance to hydrocarbon solvents The second series of gradient polymers was made by diffusion of methyl acrylate into poly(methyl methacrylate) These materials are shown to possess substantially increased fracture strain Eyring's stress-biased activated rate theory of yielding was used to rationalize the observed toughening effect in gradient polymers

Polyreaktionen an Pigmentoberflächen. VII. Mitteilung: Reaktionen von Polymeren mit endständigen Chlorsilangruppen an Siliciumdioxidoberflächen

Abstract: Chlorsilanmodifizierte Polymere wie Polystyrol und Polymethylmethacrylat mit Chlorsilanendgruppen, reagieren mit oberflachenstandigen Hydroxylgruppen von Siliciumdioxiden unter Ausbildung von Siloxanbindungen und kovalenter Verknupfung der Makromolekulemit der Feststoffoberflache. Die reaktiven Polymeren werden durch Ubertragung bei der radikalischen Polymerisation der Monomeren und durch Abbruch anionisch lebender Polymerer mit Chlorsilanen (Siliciumtetrachlorid, Trichlormethylsilan, Dichlordimethylsilan) dargestellt. Die Menge des an die Siliciumdioxidoberflache kovalent gebundenen Polymeren betragt, abhangig vom Molekulargewicht der Makromolekule, von den Reaktionsparametern Zeit, Temperatur, Losungsmittel, Konzentration an Festkorper und Polymeren sowie von der spezifischen Oberflache der Siliciumdioxide, bis zu 500 mg Polymeres pro Gramm Siliciumdioxid. Durch einfache Adsorption und anschliesende Desorption werden maximal 30 mg Polymeres pro Gramm Siliciumdioxid irreversibel adsorptiv gebunden. Die mit Polystyrol oder Polymethylmethacrylat modifizierten Siliciumdioxide sind hydrophob und zeigen ein gegenuber unmodifiziertem Siliciumdioxid verandertes Sedimentationsverhalten. Polymers with chlorosilane endgroups, such as polystyrene and polymethyl methacrylate, react with superficial hydroxyl groups of silicon dioxides by formation of siloxane bonds and covalent binding of the macromolecules to the surface. The active polymers are prepared either by a radical polymerisation of the monomers in presence of chlorosilanes or by a terminating reaction of the anionically living polymers with chlorosilanes (tetrachlorosilane, trichloro methylsilane, dichloro dimethylsilane). The amount of polymer coverage depends on the molecular weight of the macromolecules, on the reaction parameters (time, temperature, solvent, concentration of silicon dioxide and polymers) and on the specific surface of the silicon dioxides. According to varying reaction conditions, the amount of polymer coverage ranges up to 500mg of polymer per gram of silicon dioxide, whereas only 30 mg of polymer per gram of silicon dioxide is bonded irreversibly by adsorption of the polymer from solution and subsequent desorption. The polymeric modification of the silicon dioxides effects changed properties, such as a hydrophobic character and a different sedimentation behaviour.

Filled-polystyrene laminates

Abstract: Thermoplastic polystyrene laminates are disclosed, one of the layers of which comprises a filled polystyrene composition containing from about 5 to about 50 of filler, such as calcium carbonate, clay, asbestos, etc. The filled polystyrene composition is prepared from a filled polystyrene masterbatch of impact polystyrene, filler, rubber and mineral oil, cut back by mixing with other polystyrene, either crystal or impact polystyrene. Laminates may be prepared by coextrusion. The filled polystyrene layer may be foamed. The laminates may be used for making formed articles such as cups, containers, trays, plates, sheets, etc.

ESCA studies of polymers. VII. Shake‐up phenomena in some alkane–styrene copolymers

Abstract: Shake-up satellites corresponding to π* π transitions accompanying C1s core ionizations have been studied for polystyrene and a series of alkane–styrene copolymers. It is shown that the shake-up intensities are additive in nature and give a direct measure of copolymer compositions.

Epoxidized copolymers of styrene, butadiene and isoprene

Abstract: Epoxidized polymers having the structure S-D/S-S or D/S-S-D/S-S in which S represents a polystyrene block and D/S represents a tapered block of styrene and butadiene and/or isoprene, with the further provision that 5-95% of the olefinic unsaturation of the polymer has been epoxidized, exhibit good oil and ozone resistance.

Surface properties of styrene–ethylene oxide block copolymers

Abstract: Hydrophobic–hydrophilic block copolymers were prepared by “living” anionic polymerization. They consist of polystyrene and poly(ethylene oxide) blocks, and are soluble in water. Their interfacial properties were investigated, employing aqueous solutions. The block copolymers lowered the surface tension of water in analogy with the low molecular weight surfactants such as sodium lauryl sulfate and heptaethylene oxide n-dodecyl ether. Their aqueous solutions exhibited solubilization properties differing from those of polyethylene glycol. Therefore, it is thought that the polystyrene blocks produce solubilization phenomena. In samples of the same styrene content, the precipitation temperature of a high molecular weight copolymer in water was lower than that of a low molecular weight copolymer at the same concentration in the same solvent. The surface tension and precipitation temperature of aqueous solutions seem to be influenced by molecular weight and composition.

A generalized melt viscosity-temperature dependence for styrene and styrene-acrylonitrile based polymers

Abstract: The dependence of the melt flow of polymers on temperature is of both theoretical and commercial importance. A useful representation of the temperature dependence of the shear-dependent viscosity, based on superposition of flow curves at various temperatures, has previously been presented by the author for several olefin polymers. This method is extended in the current work to styrene and styrene-acrylonitrile based polymers. The melt viscosity-temperature dependence of a broad range of styrenic polymers and copolymers, ranging from polystyrene to 82 percent AN styrene-acrylonitrile copolymer, with and without rubber inclusions, was investigated. Flow curves at the various temperatures were found to be superimposable, as had earlier been found to be the case for olefin polymers, and a unique quantitative relationship between the superposition shift factors and temperature was found applicable to the entire family of polymers. The resultant energy of activation for viscous flow is in excellent agreement with previously published results for polystyrene Newtonian viscosities, and the magnitude of the shift factors is consistent with a limited set reported for ABS polymers. Independent tests of the derived relationships provided excellent prediction of measured viscosities. Thus, it is considered that a general viscosity-temperature relationship has been defined for this family of polymers, independent of molecular structural detail.