Search results for "Polystyrene"

DIMENSIONAL STABILITY OF REINFORCED MATRICES.

1983

Particulate fillers are often used to improve the dimensional stability of polymeric items obtained through processing techniques such as injection molding, deep drawing, hot stamping, etc. In these operations the material undergoes large multiaxial deformations which result in molecular orientation and remain as frozen-in stresses during cooling of the material. Once the formed objects are exposed to sufficiently high temperatures, various degrees of spring-back take place and subsequent changes in shape and dimension occur (1).

HPS-based catalysts: a computational study

2012

How the POSS molecules improve the UV stability of polystyrene based nanocomposites?

2012

1978

Theoretical relations for the dependence of the z-average radius of gyration Rz as a function of the mass average molar mass Mw are derived for expanded coils, persistence coils with persistence of direction, persistence coils with persistence of direction and curvature, and for needles, all exhibiting a Schulz-distribution of their molar masses. These relations are applied to experimental data from light scattering of polystyrene in toluene and DNA-Na in aqueous NaCl-solution of 200 mol NaCl per m3 at room temperature. In the case of DNA it becomes evident that the double helix shows no important persistence of curvature and that the experimental data can be described adequately by a persi…

Efecto in vitro de la adición de resinas de intercambio iónico sobre la biodisponibilidad de electrolitos en fórmulas de nutrición enteral artificial

2008

The in vitro effect of the addition of ion exchange resins on the bioavailability of electrolytes in artificial enteral feeding formulas Objective: To determine in vitro free ion concentration in three standard artificial enteral feeding formulas following the addition of ion exchange resins. Method: Three standard types of AEF were chosen: Osmolite HN®, Nutrison Standard® and Isosource Standard®. The ion exchange resins used were: Sodium Polystyrene Sulfonate and Calcium Polystyrene Sulfonate. 100 ml of AEF were mixed in a beaker with 1.5 g or 3 g of ion exchange resins for 48 hours at 37oC. Subsequently, the samples were precipitated and the supernatant obtained was used for determining t…

Interdiffusion in blends of polystyrene and polymethylstyrene studied by light scattering after temperature jumps across the phase boundary

1992

Abstract We describe a simple light scattering set-up for measuring interdiffusion coefficients D in polymer blends by generating spinodal decomposition and subsequent dissolution after temperature jumps across the phase boundary. In blends of polystyrene and polymethylstyrene (random copolymer of 60% m-methylstyrene and 40% p-methylstyrene) D values were obtained between 10−11 and 10−15 cm2s−1 at temperatures up to 50 K above the upper critical solution temperature. The results are discussed in relation to tracer diffusion in the same system.

Orientation and Dynamics of ZnO Nanorod Liquid Crystals in Electric Fields.

2010

ZnO nanorod polymer hybrids (i.e., ZnO nanorods coated with a block copolymer with a short anchor block (dopamine) and a longer solubilizing block of polystyrene (PS)) form liquid crystalline (LC) phases if they are dispersed at high concentration e.g., in a PS oligomer matrix. Due to the high mobility of the low T(g)-matrix the nanorod polymer hybrids show a switching behavior under an applied AC electric field. Hence, the orientation of the nanorod mesogens can be changed from planar (parallel to the substrate) to homeotropic (perpendicular) in full analogy to the switching of low molecular liquid crystals in an electric field. Dielectric measurements show that such a switching is mainly …

Photo-oxidation behaviour of polystyrene-block-polybutadiene-block-polystyrene /CNTs nanocomposites

2014

Highly robust and selective system for water pollutants removal: How to transform a traditional photocatalyst into a highly robust and selective syst…

2019

Highly porous monolithic aerogels based on ZnO photocatalyst and syndiotactic polystyrene (s-PS) were obtained by supercritical CO2 treatment of ZnO/s-PS gels. The prepared aerogels were characterized and their photocatalytic activity was evaluated using phenol and toluene as water pollutant models. The s-PS nanoporous crystalline phase, able to absorb pollutant molecules, was proven to be necessary to ensure high photocatalytic efficiency as the aerogel acts not only as a support, but also as pollutant pre-concentrator. The reusability of ZnO/s-PS aerogels is also strong showing no decrease in photocatalytic activity after six consecutive degradation trials. Finally, the aerogel matrix pre…

Syndiospecific polymerization of styrene using methylaluminoxane-activated bis(phenolato)titanium complexes

1998

Styrene was polymerized using a series of methylaluminoxane-activated bis(phenolato)titanium complexes of the type ((OC 6 H 2 -4-Me-6- 1 Bu) 2 Z)TiX 2 (X = Cl, O 1 Pr, η 5 -C 5 Me 5 ) to give syndiotactic polystyrene. Catalyst activity was found to depend on the nature of the bridging group Z, where Z = CH 2 , CH 2 CH 2 , S, S=O. Activity was found to be highest for Z = S.