Gradient structure of polypropylene composites filled with carbon black

Russian Chemical Bulletin - Gradient polymer composites were prepared by melt-mixing of carbon black and polypropylene in a compounder and subsequent hot pressing of pellets. The thermally treated...     

Aggregation of clay platelets in nematic liquid crystal, 5CB: microstructure,electrical conductivity and rheological investigations

The microstructure, electrical conductivity and rheological properties of a nematic liquid crystal (5CB) doped at concentrations up to 4.5 wt% of montmorillonite (MMT) or organomontmorillonite (OMMT) clay nanoplatelets, were investigated at temperatures between 293 and 310 K. Microscopy and electrical conductivity assessment revealed noticeable differences in aggregation in MMT and OMMT suspensions, MMT nanoplatelets showing a strong tendency to aggregation. The incubation of 5CB in the presence of MMT initially produced loose aggregation, followed by the formation of compact aggregates. The latter had practically no influence on the surrounding inter-aggregate regions. In the case of OMMT, a greater degree of integration of the nanoplatelets was observed within the liquid crystal structure of 5CB, resulting in a noticeable effect on electrical conductivity and activation energy of the composite material. Thixotropy was observed in suspensions of 5CB composites formed with either MMT or OMMT. A composite of 5CB with OMMT also exhibited anomalous viscous thinning at shear rates below 100 s^?1. A structural model is suggested to explain this behaviour.     

Electron-electron correlations in Raman spectra of VO2

Physics of the Solid State - It has been shown that, in single crystals and films of a strongly correlated material, namely, vanadium dioxide, upon a thermally stimulated phase transition from the...     

Ionic mobility,structure, and conductivity of 45ZrF<Subscript>4</Subscript>-35BiF<Subscript>3</Subscript>-20CsF glass according to <Superscript>19</Superscript>F NMR,IR, Raman,and impedance spectroscopy

¹⁹F NMR, IR, Raman and impedance spectroscopy are used to study the ionic mobility, structure, and conductivity of 45ZrF₄-35BiF₃-20CsF bismuth fluorozirconate glass. With the increase in temperature from 150 K to 500 K the fluorine-containing groups pass from the rigid lattice to local movements (reorientations), and then to diffusion. According to the results of IR and Raman spectroscopy, the lattice of this glass consists of ZrF₈ polyhedra linked by their vertices into chains. The glass has high ionic conductivity: σ ≈ 1.8×10⁻⁴ S/cm in a temperature range of 480–485 K.     

Electron spectra of Hammett dye-indicators sorbed by montmorillonite

Theoretical and Experimental Chemistry -     

The effect of temperature on the stress-strain behavior of composites based on high-density polyethylene and rubber particles

The failure behavior of composites based on HDPE, which breaks down at the necking stage, and dispersed rubber particles is studied. In was shown that the materials containing at most 8 vol % filler experience the brittle-to-ductile transition with increasing temperature. It was assumed that the ductility retained at elevated temperatures by the composites based on a polymer with unstable neck propagation is due to the interplay of two factors, the decrease in the upper yield point of the matrix polymer and the increase in the polymer draw ratio in the neck. These factors markedly reduce the sensitivity of the materials to the presence of defects and facilitate neck formation and propagation, as well as change the form of the defects from cracks to slitlike pores.     

Hydrogen Bonds at Silica – Polyvinylpyrrolidone – Water Interfaces

The effect of the adsorption of polyvinylpyrrolidone on the surface of highly dispersed silica on the state of interfacial water was studied by ¹H NMR spectroscopy and thermally stimulated depolarization with freezing out of the bulk water.     

Ionic Mobility in Glasses in the ZrF4-BiF3-MF Systems (M = Li,Na, K) as Probed by 7Li, 19F,and 23Na NMR

The ion mobility in new fluoride glasses (mol %) 45ZrF₄ · 25BiF₃ · 30MF (I) (M = Li, Na, K), (70 - x)ZrF₄ · xBiF₃ · 30LiF (II) (15 ≤ x ≤ 35), and 45ZrF₄ · (55-x)BiF₃ · xMF (III) (M = Li, Na; 10 ≤ x ≤ 30) has been studied by ⁷Li, ¹9F, and ²³Na NMR in the temperature range 250–500 K. The character of ion motion in bismuth fluorozirconate glasses I and III is determined by temperature and the nature and concentration of an alkali-metal cation. Major type of ion mobility in glasses I–III at temperature 400–440 K are local motions of fluorine-containing moieties and diffusion of lithium ions (except for the glass with x = 10). The factors responsible for diffusion in the fluoride sublattice of glasses I have been determined. Sodium ions in glasses I and III are not involved in ion transport.