Displacement processes on hydrophilic/hydrophobic surfaces in 1-propanol-water mixtures

Selective adsorption of 1-propanol-water mixtures was investigated on adsorbents of various surface character. The enthalpy of displacement of 1-propanol by water was studied on graphitized PRINTEX-80, K-60 silicagel, and n-alkylammonium vermiculites. The free enthalpy and entropy isotherms of displacement were derived. The adsorption between the silicate layers of hydrophobic vermiculites was followed by x-ray measurements, and thermodynamic functions were calculated for the structural changes in the adsorption layers. Formation of alcohol-water clusters on the surfaces plays an important role.     

Surface modified aluminium hydroxide in flame retarded noise damping sheets

Flame retarded polyethylene compounds were prepared using a series of aluminium hydroxide of different particle size applying a milling processes and special precipitation technologies. The processability and flame retardant efficiency of the flame retarded systems were compared. The effects of various surface modifications were analysed in case of one selected type of aluminium hydroxide. A silicone terminated reactive surfactant promoted not only the processability but also the flame retardant efficiency. Noise damping sheets were prepared by simultaneous application of aluminium hydroxide and barium sulphate in an elastomer blend matrix. V0 flame retardant grade could be achieved this way accompanied with improvement in the acoustic properties and maintenance of the mechanical properties.     

Effect of supercritical CO2 plasticization on the degradation and residual crystallinity of melt‐extruded spironolactone

Immediate‐release solid dispersions of a slowly dissolving active pharmaceutical ingredient, spironolactone, were prepared by supercritical‐CO₂‐assisted melt extrusion (a solvent‐free and continuous manufacturing technology) using Eudragit E as matrix. Through optimizing process parameters (i.e. temperature, melt throughput, pressure and CO₂ flow), stable foams with high porosity, homogeneous structure and thin (even submicronic) walls could be prepared, as revealed by scanning electron microscopy. The samples were found to be rigid enough to mill, enabling further processing, as is necessary to formulate tablets. The influence of extrusion temperature and melt throughput on residual drug crystallinity was measured using non‐invasive confocal Raman mapping coupled with chemometric analysis, while the influence on the degree of drug degradation was determined using high performance liquid chromatography. The plasticizing effect of supercritical CO₂ was shown to reasonably improve the purity of the prepared solid dispersions by enabling high‐yield production at lower temperature ranges. At the same time, shorter residence time and lower temperature slightly increased residual drug crystallinity. The obtained foamy structures ensured immediate drug dissolution in an acidic medium. Copyright © 2014 John Wiley & Sons, Ltd.     

Enhanced conductivity composites for aircraft applications: carbon nanotube inclusion both in epoxy matrix and in carbonized electrospun nanofibers

The potential of carbonized electrospun nanofiber mats to render epoxy resin composites for aircraft applications electrically and thermally more conductive was investigated. The effect of carbon nanotube inclusion both inside the carbon nanofiber and in the epoxy resin matrix material was studied, in order to reveal any synergistic effects of multilevel presence of nanosized reinforcements on the conductivity and mechanical properties. The carbon nanotube inclusion into the carbonized nanofibers increased the electrical conductivity of the samples by 20–50% and the thermal conductivity by approximately three times leading to a higher value than that of the conventional composites. The preparation of layered composites with a conductive upper layer containing nonwoven carbon nanofabric and a load bearing lower layer with conventional unidirectional carbon fiber reinforcement can offer a cost‐effective and weight‐saving solution for the replacement of metal meshes in structural aircraft composites. Copyright © 2014 John Wiley & Sons, Ltd.     

Thermal and spectroscopic analysis of inclusion complex of spironolactone prepared by evaporation and hot melt methods

Solvent and melt techniques were used to obtain molecular dispersion of the poorly soluble spironolactone (SPIR) model drug enhancing its dissolution rate. DSC study of the interaction between SPIR and hydroxypropyl-β-cyclodextrin confirmed the need for molecular dispersion if their complexation is required. Solvent-free twin-screw extrusion was suitable for forming inclusion complex significantly below the melting temperature of the SPIR. According to DSC, Raman and XRPD results fine dispersion of both components was achieved in a hydrophilic polymer. The molecules of the active ingredient are separated from each other in the polymer and the lack of the lattice energy causes faster dissolution.     

NMR assignments and the acid–base characterization of the pomegranate ellagitannin punicalagin in the acidic pH-range

In exploring the capability of nuclear magnetic resonance (NMR) spectroscopy for pomegranate juice analysis, the eight aromatic singlet resonances of α- and β-punicalagin were clearly identified in the ¹H NMR spectra of juice samples. The four downfield resonances were found to be sensitive to small pH changes around pH 3.50 where the NMR spectra of the juice samples were recorded. To understand this unusual behavior, the ¹H and ¹³C resonance assignments of the punicalagin anomers were determined in aqueous solution and pH titrations with UV and ¹H NMR detection carried out to characterize the acid–base properties of punicalagin over the pH range 2–8. Simultaneous fitting of all of the pH-sensitive ¹H NMR signals produced similar but significantly different pK _a values for the first two deprotonation equilibria of the gallagic acid moiety of the punicalagin α- (pK _a1?=?4.57?±?0.02, pK _a2?=?5.63?±?0.03) and β- (pK _a1?=?4.36?±?0.01, pK _a2?=?5.47?±?0.02) anomers. Equivalent pK _a values, (α?:?6.64?±?0.01, β?:?6.63±?0.01) were measured for the third deprotonation step involving the ellagic acid group, in good agreement with a prior literature report. The punicalagin anomer equilibrium readjusts in parallel with the proton dissociation steps as the pH is raised such that β-punicalagin becomes the most abundant anomer at neutral pH. The unusual upfield shifts observed for the glucose H3 and H5 resonances with increasing pH along with the shift in the α/β anomer equilibrium are likely the consequence of a conformational rearrangement.

Vergleichende Untersuchungen zur katalytischen Aktivität von Nickel und kristallinen Nickelboriden sowie RANEY-Nickel und borhaltigem RANEY-Nickel: Hydrierungs- und Dehydrierungsreaktionen,elektrochemische Methanoloxydation

The catalytic activation of the decomposition of gaseous formic acid with nickel powder and crystalline nickel borides is compared. Only after treatment with NH₃-solution the activity of the nickel borides has the same order as that of nickel powder. Ni₃B is the best of the catalysts used. The crystalline nickel borides cannot catalyze the anodic oxydation of methanol in alcaline solution at 80°C. — Nickel catalysts containing Boron can be prepared by the RANEY method from nickel boride and aluminum. These catalysts have the same activity as normal RANEY nickel with respect to the hydrogenation of the C?C? bond in crotonic acid; they are more active with respect to the C?O? bond of acetone. Methanol can be oxydised fastly in alcaline solution at 80°C on electrodes containing RANEY nickel. RANEY nickel containing boron is still better.     

Studies of thermally stimulated current in polypropylene/calcium carbonate/surfactant systems

Thermally stimulated polarization (TSP) and depolarization (TSD) experiments have been performed with two grades of polypropylene and some respective CaCO₃-filled composites containing small amounts of nonionic surfactant (0–2 wt%). The effects of electrode blocking, electrode materials on the thermally stimulated currents, and reproducibility of the measurements have been studied. The effect of water vapor adsorbed from the ambient air on the AC dielectric properties and on the thermally stimulated polarization behavior has been determined.The addition of either CaCO₃ or surfactant to PP decreases the intensity of the _c depolarization current peak in the pre-melting region, while the presence of both components increases the current. Partial discharges are present in poly propylene/CaCO₃ composites under high voltages if neither water vapor nor a coherent surfactant layer is present at the matrix/filler interface.A short literature survey is presented on the TSC studies of polyolefins and their composites, and various mechanisms responsible for the observed changes are discussed, including interfacial polarization, trap redistribution through nucleation, and oriented adsorption.     

Development of flame retarded self-reinforced composites from automotive shredder plastic waste

Multilayered self-reinforced composites were developed from a density-separated light fraction of automotive shredder waste of high polyolefin content, which can fulfil the current technical, safety and environmental requirements of structural materials. The significantly enhanced mechanical properties of the recycled composites were ensured by polypropylene fabric reinforcement; meanwhile, reduced flammability was obtained by modifying the matrix layers, made of secondary raw materials, with phosphorous-containing flame retardant additive. The results of the new flame retarded composite systems allowed the discussion of a novel mechanistic observation. The mechanical and flammability properties of the prepared self-reinforced composites are compared to conventional glass fabric reinforced composites and to compounds without reinforcement.