Structural characterization of polyolefins by pyrolysis—hydrogenation glass capillary gas chromatography

In order to obtain quantitatively specific and high-resolution pyrograms of high polymers, fundamental splitting conditions for pyrolysis—gas chromatography were studied using a vertical micro-furnace type of pyrolyzer attached to a glass capiliary separation column. High-resolution pyrograms were measured for polyolefins such as polyethylenes (PE), polypropylenes (PP) and various kinds of ethylen—propylene copolymers [P(E-co-P)] using a pyrolysis—hydrogenation device. Microstructures such as short branchings for PE, stereoregularities and chemical inversions for PP and sequence distributions for P(E-co-P) are discussed on the basis of the pyrograms.     

Electrokinetic phenomena in porous membranes: Determination of phenomenological coefficients and transport numbers

Electrokinetic phenomena in porous membranes were studied in the framework of the linear thermodynamics of irreversible processes. Phenomenological coefficients of two commercial porous membranes were determined. The variation of these coefficients with the different concentrations of NaCl used was also studied. Onsager's reciprocal relationship between cross-coefficients holds within the limits of experimental error.Membrane potentials were measured at concentrations ranging from 10^?3M to 75 X 10^?3M. The apparent transport number of the cation,

, was calculated from the diffusion potential expression. An electrometric method was used to obtain the true cation transport number,

, and the water transport number,

, for different solution concentrations, ranging from 15 x 10^?3M to 75 x 10^?3M. The true transport number of the cation,

, was also determined, taking into account water transport across the membrane. A good agreement was found between

and

values.     

Investigations on aromatic polyesters with polynaphthalene systems in the main chain—IX. Influence of the chain structure of aromatic copolyesters on their glass transition temperatures

Glass transition temperatures of terephthalic copolyesters of 4,4′dihydroxydinaphthyl 1,1′ and 2,2 bis(4-hydroxyphenyl)propane with various mole ratios of the comonomers and different chain structures have been measured. A relationship has been found between T_g and the chain structure of aromatic copolyesters with polynaphthalene rings in the chain.     

Verification of calorimetric models based on physical parameters by frequential characteristics

Quantitative criteria to ascertain the quality of calorimetric models based on physical parameters are presented. These include not only a comparison between model and experimental pulse responses, especially for the larger time constants, but also an analysis of their spectra up to the frequential limit brought about by the experimental noise.A calorimetric model based on the physical parameters of a Unipan 600 calorimeter is used to reconstruct a given power dissipation. The results are then compared to those given by other methods, i.e. dynamic optimization, inverse filtering and harmonic analysis.     

Photoassisted interfacial charge transfers at inhomogeneous semiconducting film-electrolyte junction in photoelectrochemical cells: Case of CdS and CdS(Al) sprayed films on to conductive glass

Photoassisted charge transfers at conductive glass based CdS and Al-doped CdS sprayed films only 0.5 μm thick in contact with an electrolyte are studied. Al is found to improve the photocurrent.     

Non-stoichiometric molybdenum oxides as cathodes for lithium cells: Part III. cells based on Mo18O52

The non-stoichiometric Mo₁₈O₅₂ oxide, based on the MoO₃ structure, was tested as a cathode material in both primary and secondary Li cells. It may intercalate reversibly in its layered structure up to 1.2 Li/Mo (at 0.5–1.0 mA cm^?2), so forming ternary phases.In the solid matrix Li⁺ ion diffusion is relatively fast (D≈10^?9 cm² s^?1) and gives rise to a structure in which Li⁺ is tetrahedrally coordinated by oxygen. This oxide shows a high rate capability and can also act as a cathode material for secondary batteries in the low-rate range. The resemblance to the parent oxide MoO₃ is obviously marked but differences were found with regard to the effect of additives and to the recharge efficiency, due to some structural differences.     

Mechanism of diffusion and sorption of carbon dioxide in poly(vinyl acetate) above and below the glass transition temperature

The pressure dependence below 1 atm of the apparent diffusion and permeation coefficients were observed by using the permeation time lag method for carbon dioxide in poly(vinyl acetate), which has a glass transition near room temperature, at temperatures ranging from 8 to 50°C. Above the glass transition temperature, pressure dependence of the diffusion and permeation coefficient has not been observed; hence, Fick's law with a concentration independent diffusion coefficient applies. On the other hand, in the glassy state, the apparent diffusion coefficient shows pressure dependence. Moreover, the behavior of the pressure dependence does not show a clear curve in the ranges between 30°C to 17°C. Above 17°C, the apparent diffusion coefficients show discontinuities, but below 17°C increase with pressure is regular. Using the theoretical prediction of Paul, a computer was used in the numerical calculation to determine the true diffusion coefficient and other dual sorption parameters. p]The compensated diffusion coefficients controlled only by Henry's law dissolution was described by three straight lines with two intersection in the form of Arrhenius plots, which give good agreement with both our results for He and Ar and those of Meares. It is assumed that beside the dual sorption mechanism, another effect, for instance some relaxation effect may also contribute to the diffusion for carbon dioxide in poly(vinyl acetate) near the glass transition temperature region.     

Application of a new catalyst based on molybdenum for the direct determination of oxygen by pyrolytic gas chromatography

Application of a new catalyst for the direct determination of oxygen by using a pyrolytic gas chromatographic technique is described. Achievement of the optimum experimental conditions depends upon numerous factors which have been examined. The results obtained with such a procedure indicate that the method is applicable for the determination of oxygen in a variety of organic and organometallic compounds.     

Evaluation of a chloramine-T-selective electrode for catalytic titration of silver and mercury(II) based on iodide-catalyzed chloramine-T reactions

Semiautomatic methods are described for the catalytic titrimetric determination of microamounts of silver and mercury(II) using a chloramine-T-selective electrode as monitor. The methods are based on the inhibitory effect of Ag(I) and Hg(II) on the iodide-catalyzed chloramine-T-arsenite and chloramine-T-H₂O₂ reactions. Microamounts of silver in the range 0.2–200 μg (1 × 10⁻⁷−1 × 10⁻⁴ M) and of mercury(II) in the range 0.1–200 μg (2.5 × 10⁻⁸−5 × 10⁻⁵ M) were determined using the chloramine-T-As(III) indicator reaction. Mercury(II) in the range 4–2000 μg (1 × 10⁻⁶−5 × 10⁻⁴ M) was also determined using the chloramine-T-H₂O₂ indicator reaction. The accuracy and precision were in the range 0.1–1%.     

Thermal studies on alkaline earth monomethyl violurates

Some alkaline earth monomethyl violurate hexahydrates were prepared in aqueous medium, and characterized on the basis of elemental analysis and IR spectral data. The thermal behaviour of these salts was studied with the aid of TG, DTG and DSC techniques. Heats of dehydration were calculated from DSC curves.     

Influence of ph on the reduction of thick anodic oxide films on gold

The reduction of thick oxide films, produced anodically on gold under constant potential conditions in the oxygen gas evolution region, was examined as a function of sweep-rate in both acid and base. Although peak maxima potential values for the reduction reactions were not totally independent of sweep-rate, even at very low values of the latter, the earlier assumption that the film is composed of at least two (and in some cases, according to the present results, as many as five) different oxygold species was shown to be a reasonable one. The other assumption, namely that the hydrous film in the case of gold is anionic (due to excess hydroxide-ion incorporation) was also shown to be a reasonable one by comparison with recent work with hydrous nickel oxide films for which structural data is available. In these systems counterbalancing cations (H⁺, Na⁺, etc.) are assumed to be present in water contained in pores or layers in the structure. Furthermore, the unusual potential-pH dependence of the hydrous film reduction process can easily be explained in terms of the excess hydroxide incorporation model.     

The influence of surface reactions on analytical thermogravimetric results

Two examples are given to show the influence of surface reactions on analytical thermogravimetric results. The first concerns the effect of the crucible material on the reduction of rhenium heptoxide by hydrogen. In the second, the effect of a strong metal-support interaction on the evaluation of the average oxidation number of rhodium present in small percentage in the system RhO_xTiO₂ is discussed.     

The influence of polymer morphology on polymer film electrochemistry

The electrochemical behavior of functionalized polystyrene-coated electrodes shows a marked dependence on the nature of the electrolyte ions. Scanning electron microscope and surface profile measurements are presented which show that changes in polymer film volume and morphology accompany electrochemical oxidation. Changing polymer morphology by doping the films with soluble monomers during preparation is shown to produce large changes in electrochemical response. Diffusion coefficients were determined for a neutral organic dye dopant in each of the polymer films investigated, and these correlate very well with the oxidation overpotentials observed electrochemically. The nature of polymer film/solvent interactions and the mechanism by which counter ions penetrate the polymer phase is discussed and is related to other physical properties of amorphous polymers in terms of free volume concepts.     

Thermal studies on metal dithiocarbamato complexes. A review

In the present review, the work done on thermal studies of metal dithiocarbamato complexes during the period 1969–1982 are given. The thermal studies include thermogravimetry, differential thermogravimetry, differential thermal analysis, differential scanning calorimetry and mass spectrometry. Fifty-two references are included.     

Molecularly adsorbed oxygen on metals: electron spectroscopic studies

Oxygen is shown to adsorb molecularly on gold as well as on Ag and Pt. UV and X-ray photoelectron spectroscopy and Auger electron spectroscopy have been employed to investigate electron states of molecularly adsorbed oxygen.     

Electrochemical adsorption and phase formation on mercury in sulphide ion solutions

Under electrochemical conditions, the formation of thin mercuric sulphide films on mercury proceeds in three distinct stages. In the first, mercuric sulphide adsorbs over a narrow range of potential to build up a monomolecular layer. This adsorbed layer subsequently rearranges in such a way that its packing density is increased. The rearrangement corresponds to a first order phase transformation, and clear evidence for the nucleation of the rearranged phase has been obtained. Finally the growth of subsequent monolayers of mercuric sulphide proceeds by the nucleation and expansion of two dimensional centres on the rearranged first layer. A variety of electrochemical techniques has been used in this study to characterise these three individual steps in detail.     

Exchange of metal carbonyl moieties on germanes

For R₃Ge = GeH₃, CH₃GeH₂ or (CH₃)₂GeH, R₃GeCo(CO)₄ reacts in an ether solvent with Mn(CO)₅^? to give R₃GeMn(CO)₅ while Mn(CO)₅^? displaces Fe(CO)₄^2? or (GeH₃)Fe(CO)₄^? and Fe(CO)₄^2? displaces Co(CO)₄^?.