Showing papers on "Polystyrene published in 1984"

Characterization of Optical Diffraction and Crystal Structure in Monodisperse Polystyrene Colloids

Abstract: Bragg diffraction of laser light from crystalline aqueous colloids of polystyrene spheres is examined to determine crystal structure, orientation, and elasticity. A new technique using Kossel rings is described which simultaneously measures structure, lattice spacings, and crystallite orientation. The monodisperse polystyrene sphere latex dispersions crystallize into large single crystals, which, depending on sphere concentration, are either face-centered or body-centered cubic. The interparticle spacings in the crystals are many times larger than the sphere diameter (0.109 μm). The use of tunable lasers to easily determine crystal structure is described, and the technique is further illustrated by the experimental determination of the bulk modulus. The bulk modulus is a macroscopic physical constant which can be used to monitor intersphere potentials and the screening of the particle charges by electrolytes in the solution. Data are presented which suggest that crystallite orientation occurs with the closest packed sphere layers parallel to the sample cell quartz walls.

Forces between two layers of adsorbed polystyrene immersed in cyclohexane below and above the θ temperature

Abstract: Forces entre couches de polymere (de masse moleculaire 6.10 5 et 9.10 5 ) absorbe sur du mica et immerge dans du cyclohexane, a 26 et 37°C

Polymer Compatibilization Through Hydrogen Bonding

Abstract: Partially modified polystyrene containing vinyl phenyl hexafluorodimethyl carbinol was mixed with a number of counterpolymers containing poly(vinyl-acetate), poly(methyl methacry1 ate), poly(ethy] methacrylate, poly (n-butyl methacry late), poly(viny] methyl ether), poly(2,6 dimethyl-1,4 phenylene oxide), bisphenol A polycarbonate poly(styrene-co-acryloni-trile), poly (dimethyl siloxane), a crystallizable polyester, an amorphous polyamide and two amorphous polyamides. Hydrogen bonding interactions to effect miscibility were related to the number of proton donating groups in the modified polystyrene, and these were studied in regard to lower critical solution temperatures and the glass transition temperatures of the hydrogen bonded blends.

High density polyethylene/polystyrene blends: Phase distribution morphology, rheological measurements, extrusion, and melt spinning behavior

Abstract: An experimental study of the development of phase morphology, rheological properties, and processing behavior of mechanical blends of a polystyrene (PS) and a high density polyethylene (PE) is presented. Phase morphologies were determined by scanning electron microscopy for (i) products prepared in a screw extruder/static mixer system, (ii) samples removed from a cone-plate viscometer, (iii) extrudates, and (iv) melt spun fibers. Disperse phase dimensions were measured. The values varied from 1–5 μm in the products from static mixers. The dimensions of the dispersed phase in the blend products from the cone plate and capillary die were of the same order. The melt-spun fibers exhibited disperse phase dimensions as low as 0.35 μm. Polystyrene was extracted from the blend fibers producing small diameter, PE fibrils, or minifibers. Both the initial melts and the blends were rheologically characterized. The shear viscosity and principal normal stress difference N1 exhibit maxima and minima when plotted as a function of composition. The characteristics of extrudates and melt spinning behavior of the blends were investigated. The shrinkage of extrudates of PE is much greater than PS. Additional small amounts of PE to PS greatly increase its shrinkage. Addition of PE to PS initially increases extrudate swell, though the swell shows maxima and minima when considered as a function of composition. The positions of the maxima and minima correspond to those of N1. The onset of draw resonance has been investigated in isothermal melt spinning. Wide angle X-ray diffraction studies have been carried out on blend fibers and the orientation of the crystalline polyethylene regions has been determined as a function of process conditions. This orientation decreases rapidly with the addition of polystyrene when the melt-spun filaments are compared at the same spinline stress or drawdown ratio.

Miscibility enhancement via ion-dipole interactions. 1. Polystyrene ionomer/poly(alkylene oxide) systems

Abstract: : It is shown that ion-dipole interactions can lead t miscibility enhancement in polymer blends. While polystyrene is not miscible with poly(ethylene oxide) or poly(propylene oxide), styrene ionomers show very high miscibility with these materials at low alkylene oxide contents (10 wt %) and high, though not complete, miscibility at higher loading levels. For these systems it is seen that the glass transition temperature (from G' peak positions) of the styrene ionomer is depressed dramatically with increasing alkylene oxide contents and that the glass transition of the alkylene oxide rises appreciably (in most cases) with increasing styrene ionomer content. Increases in ion content at constant styrene levels increase the miscibility. The degree of miscibility enhancement is comparable to that achieved in hydrogen-bonded system. Finally, molecular weight effects observed here are quite similar to those seen in other blend systems.

Phase Equilibria and Transition in Mixtures of a Homopolymer and a Block Copolymer. I. Small-Angle X-Ray Scattering Study.

Abstract: : The small-angle X-ray scattering technique is utilized to study the phase separation and phase transition occurring in the mixtures of a styrene butadiene diblock copolymer with a low molecular weight polystyrene. At low temperatures the scattering curve shows a main peak and a secondary peak indicating the presence of well-developed microdomains. As the temperature is raised the peaks gradually lose intensity. The binodal and spinodal temperatures for the transition between the ordered structure at low temperature and the disordered, homogeneous structure at high temperature are determined and found to increase with increasing amount of the added polystyrene. With increasing amount of polystyrene the main peak at first shifts toward lower angles, indicating an increased distance between microdomains. However, at concentrations beyond about 50% polystyrene, which evidently corresponds to the solubility limit of the latter in the microdomains, the peak position remains constant. The observed shift in the relative position of the secondary peak suggests that the morphology of the microdomains changes gradually from spherical to lamellar as the proportion of polystyrene is increased. With all the mixtures no evidence is found for an increase in the microdomain boundary thickness with increasing temperature.

Quantitative headspace analysis of solid samples; a classification of various sample types

Abstract: Volatile compounds in various solid samples have been analyzed quantitatively by equilibrium headspace gas chromatography with the technique of multiple headspace extraction (MHE). Solid samples can represent either a partition system, such as certain polymers, or an adsorption system, particularly when present as porous material. It has been found that the humidity of the sample has a strong influence on the equilibration in an adsorption system with a hydrophilic matrix and that the addition of water increases the volatility and speeds up the equilibration time. The influence of various important parameters, such as temperature, time, size and structure of the solid samples on the equilibration is demonstrated on the examples of the quantitative determination of vinyl chloride monomer in PVC, styrene in polystyrene, ethylene in polyethylene, ethylene oxide in a contact lens, halogenated hydrocarbons in coffee and residual solvents in drugs.

Control of ionic interactions in sulfonated polystyrene ionomers by the use of alkyl‐substituted ammonium counterions

Abstract: Polystyrenes containing up to about 20 mol % sulfonic acid are reproducibly and readily prepared by the sulfonation of polystyrene at 50°C with acetyl sulfate in 1,2-dichloroethane solution. The metal salts of sulfonated polystyrene possess extremely high melt viscosities and are soluble in single solvents such as toluene and THF only at very low sulfonate levels. Such properties are the result of the very strong ion-dipole interactions among the metal sulfonate groups. Such strong interactions can be substantially reduced through the neutralization of the sulfonic acid with ammonia and, most especially, relatively simple low molecular weight amines. Sulfonated polystyrenes varying in sulfonic acid content from about 1 mol % to about 20 mol % were neutralized with various mono-, di-, and tri-substituted alkyl amines ranging in alkyl chain length from H (ammonia) to C20, and their rheological and thermal properties were measured. As the number of substituents on the nitrogen increased, the glass transition temperature and the melt viscosity decreased. The tributylamine sulfonates possessed viscosities almost as low as unsulfonated polystyrene and the longer chain amines behaved as if internally plasticized. The properties of amine neutralized sulfonated polystyrenes are concluded to be primarily a function of amine size. Increasing the size of the amine reduces the strength of the ion-dipole interaction by preventing close approach of the amine sulfonate groups.

Electrospray mass spectroscopy of macromolecules: application of an ion-drift spectrometer

Abstract: Macroions of lysozyme and polystyrene produced by the electrospraying of dilute solutions of these macromolecules into nitrogen gas at atmospheric pressure have been studied by means of the measurement of their mobilities in nitrogen by means of an ion-drift spectrometer. In the case of polystyrene mainly clusters of negative macroions have been detected and studied, but in the case of lysozyme macroions containing one, two or three positive charges can be identified. The effect of change of solution concentration, temperature and pressure in the ion-drift tube on the data obtained in the case of polystyrene has been observed.

Core‐shell emulsion copolymerization of styrene and acrylonitrile on polystyrene seed particles

Abstract: Seeded emulsion copolymerization of an azeotropic composition of styrene (St) and an acrylinitrile (AN) comonomer mixture in polystyrene (PS) seed at different polymerization temperature of 55–75°C were investigated. The kinetic data showed a transition temperature at 65°C, above which the activation energy of polymerization is low, 6.1 Kcal/mol, compared with 9.8 Kcal/mol below it. The particle-size results and thin layer chromatographic (TLC) data showed two types of particle of different composition and morphology in the final latex system: a smaller size of (St–AN) copolymer and a larger size of core-PS and (St–AN) copolymer shell, with a zone of PS grafted (St–AN) copolymer in between. Various polymerization parameters, that is emulsifier concentration, type of seed particle and its size, and monomer/polymer ratio, were studied and their effects on particle size and particle morphology were examined. The percent of grafted core-PS was 10% below a polymerization temperature of 65°C and 40% above that temperature. By adjusting the size and number of the seed particles, monomer-polymer ratio, and emulsifier concentration conditions were established in which a final copolymer latex with “perfect” core-shell morphology was achieved.

Graft polymers with macromonomers. II. Copolymerization kinetics of methacrylate‐terminated polystyrene and predicted graft copolymer structures

Abstract: La copolymerisation de macromeres polystyrene a groupe terminal methacrylate avec plusieurs comonomeres verifie le schema cinetique propose et permet des previsions de compositions et structures des copolymeres greffes

Study of cryostructurization of polymer systems

Abstract: The influence of freezing on reaction systems consisting of a polymer and suitable cross-linking agent in organic media has been studied. It was shown that the cryostructurization in organic medium displays mainly the same regularities as the processes of gelation at the freezing of aqueous polymer solutions in the presence of cross-agent. The study of two reaction systems was carried out: A — alternative N-viniylpyrrolidone — maleic anhydride and 4,4′-diaminodiphenyloxide in dimethylsulphoxide; B — polystyrene and p-xylylene dichloride in the presence of SnCl4 in nitrobenzene medium.

Processing of composites with titanate coupling agents—a review

Abstract: It is proposed that titanium-derived coupling agents react with free protons at the inorganic interface to form organic monomolecular layers on the inorganic surface, which causes inorganic/organic phase compatibilization resulting in new composite property, catalysis, adhesion, and rheology performance standards. Processing techniques and rheology effects using titanates are discussed. The injection pressures of CaCO3, carbon black filled polystyrene, and glass-fiber, talc-filled poly(phenylene sulfide) are shown to be reduced 50 percent by use of cumyl phenyl type titanate. Adhesion effects are discussed in many composites such as epoxy/aluminum, acrylic/slate, carbon fiber/polyester, etc., followed by data showing significant property improvements in 1/16 inch milled glass fiber and Wollastonite RRIM urethane, printed circuit boards and amide and anhydride cured aramid fiber-reinforced epoxy.

Temperature dependence of self diffusion of polystyrene and polyethylene in the melt. An interpretation in terms of the free volume theory

Abstract: The temperatur dependence of the self diffusion coefficients of polystyrene and polyethylene in the melt was measured with the pulsed field gradient nmr technique. The temperature and molar mass dependences of the self diffusion coefficients can be described by the free volume model. Taking into account the matrix effect we detected the beginning of the break of the reptation process for polystyrene at low molar masses. The activation energies of the self diffusion process are comparable with those observed for viscosity.

Rubber.reinforced polymers of monovinylidene aromatic compounds having a unique balance of gloss and physical strength properties and a method for their preparation

Abstract: A rubber-reinforced polymer comprising a continuous matrix phase of a polymer derived from one or more polymerizable monovinylidene aromatic compounds and having discrete rubber particles dispersed throughout the polymer matrix with a shell/ core morphology and volume average particle size of from 0.1 to 0.25 microns exhibit an excellent balance of gloss and physical strength properties. Specifically, the polymer product exhibits a gloss of 80 percent or greater over a wide range of molding conditions and a impact strength of at least 2 to 3 times that of polystyrene.

Impact-resistant thermoplastic molding material

Abstract: An impact-resistant thermoplastic molding material, containing polystyrene as the matrix, and, dispersed therein, two elastomeric polymers or copolymers I and II composed entirely or predominantly of 1,3-dienes and containing particles of different mean size, namely, in I, particles from 0.2 to 0.6 μm in size and having capsule particle morphology, and, in II, particles from 2 to 8 μm in size, having cell particle or coil particle morphology.

Equilibrium melting point depression for blends of isotactic polystyrene with poly(2,6-dimethylphenylene oxide)

Abstract: Interaction entre les composants du melange. Relation entre la composition et la temperature de transition vitreuse

Controlled degradation of polystyrene

Abstract: For the purpose of efficient utilization of waste polystyrene, the recovery method of a styrene oligomer having a molecular weight of 1000–3000 was studied. Thermal and catalytic degradations were carried out. It was impossible to obtain a styrene oligomer with a molecular weight less than 5000 by thermal degradation in the temperature range of 300–500°C. Catalytic degradation in the presence of silica–alumina catalyst in the temperature range of 190–230°C made it possible to control the decrease in molecular weight and to obtain a styrene oligomer having a molecular weight of 500–3000. Simultaneously, the molecular structures of the reaction products from thermal and catalytic degradations were determined by NMR analysis.

Cationic grafting from carbon black. II. Polymerization of styrene initiated by COClO4 group on the surface of carbon black

Abstract: The cationic grafting of polystyrene initiated by carbon black containing the CO+ClO group was investigated. The introduction of CO+ClO groups onto a carbon black surface was achieved by the reaction of AgClO4 with carbon black that contained a COCI group. The latter was introduced by the reaction of carboxyl groups with SOCl2. It was found that polystyrene chains could be grown from CO+ClO groups on the surface of carbon black. Moreover, polystyrene was effectively grafted from carbon black: the grafting ratio at 20°C increased to 58% as conversion increased. Furthermore, the grafting ratio and molecular weight of ungrafted polystyrene decreased with an increase in polymerization temperature. These results were explained by the fact that the increasing temperature of the polymerization caused an increase in the rate of chain transfer reaction of the growing polymer chain to the monomer. The carbon black obtained from the reaction produced a stable colloidal dispersion in a good solvent for polystyrene.

Characteristics of microemulsion polymerized styrene with water‐soluble versus oil‐soluble initiators

Abstract: The effect of oil-soluble versus water-soluble free-radical generators in the polymerization of styrene in oil-in-water (O/W) micromulsions were investigated by photon correlation spectroscopy. The microemulsions were formed by styrene, brine, sodium dodecyl sulfate (SDS), and pentanol. The polymerizations were carried out in two microemulsions that contained droplets differing by a factor of 2.4 in volume. Under the conditions of ϕ = 0.019 and NaCl/SDS > 2 the microemulsions were stable and the droplets were independent of one another. Both oil-soluble and water-soluble initiators produced polystyrene that contained fractions of two different sizes. In the case of the oil-soluble initiator the droplet size in the microemulsion seemed to be correlated to the size of the product whereas in the case of the water-soluble initiator, there seemed to be little relation.

On the CO2 permeation of uniaxially drawn polymers

Abstract: The CO2 permeation coefficient and the difficient were measured using the permeation time-lag method for films of atactic polystyrene and high-density polyethylene, each as a function of uniaxial draw ratio. The reduction of permeability with draw ratio is observed for polystyrene and for polyethylene. In the latter it is associated with an increase in crystallinity. In both cases the premeability decreases and the solubility constant remains unchanged. The reduction of permeability is thus caused only by the reduction in diffusion of CO2 in the drawn polymers. The mechainism is different for the two polymers, as is confirmed by measurements of birefringence, glass transition temperature, and crystallinity.