Union Carbide (United States)

At low overvoltage values, deviations from Tafel behavior for a noncorroding electrode are due primarily to the reverse reaction of the oxidation‐reduction system, and at high overvoltages to concentration and/or resistance polarization. It is shown further that the practice of placing straight lines through a few experimental points is extremely hazardous, while the indiscriminate introduction of "breaks" is contrary to the electrode kinetics described.

In this paper it is shown that the viscosity of the liquid normal paraffins can be accurately defined as a simple function of relative free-space except for values in the neighborhood of the freezing points of each compound. A novel method of extrapolating the specific volumes of this family of compounds to absolute zero is described which permits the calculation of reliable values of the relative free-space from density data. An expression of the same form as the author's function, but in which temperature rather than free-space is the primary variable (the so-called Andrade equation), fails to reproduce the viscosity of n-heptadecane over the same range of temperatures within the limits of the known accuracy of the measurements.

Silicon–oxygen and aluminum–oxygen compounds exhibit significant XPS Auger and photoelectron chemical shifts that are accurately measurable. Chemical state plots of KLL Auger kinetic energy versus 2p photoelectron energy permit identification of chemical species from the locations of their points on the plots. The KLL Auger electrons of Al and Si were generated by the bremsstrahlung component of the radiation, with conventional instrumentation. The location of points on the plots can be understood on the basis of polarizability of the environment (on the Auger parameter grid of lines, slope +1) and on the basis of the factors contributing to the energy of the final state ion in the Auger transition (a grid of line, slope −1). Tetrahedral aluminum has a significantly smaller Auger parameter than octahedral aluminum, and this difference is repeated, but with reduced magnitude on the similar plots for silicon and oxygen lines for the same compounds. Otherwise, the Auger parameters for this class of compounds are remarkably uniform. The Auger parameter values for oxygen and sodium in these compounds, using the 1s and KLL lines, are relatively small compared to those of other compounds of oxygen and sodium. For compounds of similar Auger parameter, differences in Auger final state ion energy are interpretable on the basis of electron density on aluminum and silicon atoms in the initial state, due to extent of bonding to oxygen, or to amount of negative formal charge on the silicate structure. Inclusion of tetrahedral aluminum enhances the negative charge and decreases the final state ion energy in high alumina zeolites. The difference between the energies of the O1s and Si2p lines in the inorganic silicon compounds is almost invariant, 429.0 to 429.6 eV. The three silicon polymers examined have a significantly larger line difference, 429.8 to 430.1 eV, making possible a differentiation between silicones and silicates. The oxygen KVV lines, with Auger transition final vacancies in valence levels, have shapes characteristic of chemical structure. The uncharged Si–O–Si structure exhibits a well-defined shoulder; in Al–O–Si the shoulder is so close in energy it merely gives rise to asymmetry in the peak; Al–O–Al and charged Si–O–Si give oxygen KVV lines as single sharp peaks.

Graphite whiskers have been grown in a dc arc under a pressure of 92 atmospheres of argon and at 3900°K. They are embedded in a solid matrix of graphite which builds up by diffusion of carbon vapor from the positive to the negative electrode. Diameters range from a fraction of a micron to over five microns, with recoverable lengths up to 3 cm. They consist of one or more concentric tubes, each tube being in the form of a scroll, or rolled-up sheet of graphite layers, extending continuously along the length of the whisker, with the c axis exactly perpendicular to the whisker axis. They exhibit a high degree of flexibility, tensile strengths up to 2000 kg-mm−2, Young's modulus in excess of 7×1012 dyne-cm−2, and values of room-temperature resistivity of around 65 μohm-cm, which approximates the single crystal value.

Abstract A new, general synthetic route to poly‐ p ‐xylylene and substituted poly‐ p ‐xylylenes is described. The key intermediate in the new process is di‐ p ‐xylylene [(2,2) p ‐cyclophane]. It has been found that di‐ p ‐xylylene is quantitatively cleaved by vacuum vapor‐phase pyrolysis at 600°C. to two molecules of p ‐xylylene. p ‐Xylylene spontaneously polymerizes on condensation to form high molecular weight, linear poly‐ p ‐xylylene. The conversion of di‐ p ‐xylylene to poly‐ p ‐xylylene is quantitative. The process is adaptable to the preparation of a wide variety of substituted poly‐ p ‐xylylenes by pyrolysis of ring‐substituted di‐ p ‐xylylenes and polymerization of the resultant substituted p ‐xylylenes. Many of these polymers are not attainable by any other route. All are linear and free of crosslinking. Evidence supporting the proposed mechanism of pyrolytic cleavage of every molecule of di‐ p ‐xylylene to two molecules of p ‐xylylene is presented. Tough, transparent polymeric films are obtained from the process when the polymerization of the p ‐xylylenes is conducted on glass or metal surfaces. Outstanding combinations of physical, electrical, and chemical properties are displayed by poly‐ p ‐xylylene, polychloro‐ p ‐xylylene, and other substituted polymers. A comparison of the relative merits of the original Szwarc route and the new di‐ p ‐xylylene route to poly‐p‐xylylenes is presented.

Abstract A series of new aromatic polyethers have been prepared by solution condensation polymerization. The synthesis involves the condensation of a dialkali metal salt of a dihydric phenol with an “activated” or negatively substituted aromatic dihalide in an anhydrous dipolar aprotic solvent at elevated temperatures. The reaction is rapid, free of side reactions, and yields polymers of excellent color. Bakelite polysulfone can be prepared in this manner by reaction of the disodium salt of bisphenol A with 4,4′‐dichlorodiphenyl sulfone in dimethyl sulfoxide (DMSO). Only dipolar aprotic solvents are useful for conducting the polymerization. Of these, DMSO and Sulfolane (tetrahydrothiophene 1,1‐dioxide) are the most effective. Water or other competing nucleophiles must be absent if high molecular weight is to be obtained. Besides providing the necessary solubility, this highly polar solvent is believed to be essential in providing the rapid polymerization rates observed. The rates are further found to depend on the basicity of the bisphenol salt and upon the electron‐withdrawing power of the activating group in the dihalide. As is usual for this type of reaction, the difluorides are found to be more reactive than the corresponding dichlorides. Most of the polyethers are amorphous, rigid, tough thermoplastics with high second‐order transitions ( T g ). Thermal stability and electrical properties are noteworthy. These and other properties are described for polysulfone, and glass transitions are given for a selected list of the other polyethers.

A method is described for simulating the dynamical behavior of a linear polymer in dilute solution, subject to random collision with solvent molecules. Equilibrium distributions of various chain dimensions may be obtained by periodic inspection of the chain. Relaxation phenomena in such chains may also be studied. Results are given for equilibrium distribution and relaxation behavior of the end-to-end length, for chains of 8, 16, 32, and 64 beads. The equilibrium chain dimensions are in satisfactory accord with the calculations of Wall and his collaborators, while the relaxation times are close to those predicted with the aid of the hydrodynamic theory of Rouse and Zimm.

This paper presenm the algorithm “DETMAX” whose purpose is to construct experimental designs that are “D-optimal.” These are designs for which the determinant of X'X is maximum, where X is the “matrix of independent variables” in the usual linear model y = Xβ + e. Although the algorithm does not guarantee D-optimality, it has performed well in many cases where D-optimal designs are known. Five examples are given, illustrating the use of DETMAX to construct designs “from scratch” and to augment existing data. A FORTRAN listing is available on request.

Abstract Increased awareness of the problems caused by air pollution and the decrease of fossil fuel reserves have resulted in great interest in combustion techniques that reduce pollutant emission levels from combustors while simultaneously increasing combustion efficiency. The development of catalytic combustors has two primary objectives: to attain levels of NOX emissions substantially below those possible with conventional ones, and/or to carry out stable combustion for low concentrations of fuel in air.

Efficient spectral narrowing, and tunability over a wide spectral range, has been demonstrated in solid and liquid organic dye lasers using diffraction gratings as cavity reflectors.

Electron energy-loss spectra (ELS) have been obtained from polycrystalline Ag metal, AgO powder, and ${\mathrm{Ag}}_{2}\mathrm{O}$ powder using primary electron-beam energies ranging from 100 to 2000 eV. These samples were characterized using x-ray photoelectron spectroscopy (XPS) to determine the compositions and chemical species in their near-surface regions. The ELS spectra obtained from these three materials are significantly different, implying that ELS is a useful technique for distinguishing between Ag metal, AgO, and ${\mathrm{Ag}}_{2}\mathrm{O}$ or analyzing mixtures of these species. Such an analysis is difficult using techniques including XPS or Auger-electron spectroscopy because spectral features of these species are quite similar and closely spaced. The ELS spectral features consist of losses due to the formation of surface and bulk plasmons and interband transitions. An attempt has been made in this study to assign the processes responsible for the ELS features observed in the spectra. This interpretation will be improved as the electronic structures of Ag metal, AgO, and ${\mathrm{Ag}}_{2}\mathrm{O}$ are better understood.

Polysulfone has been sulfonated to varying degrees using a sulfur trioxide–triethyl phosphate complex as the sulfonating agent. These conditions are suitable for surface sulfonation as well as solution sulfonation. The neutralized, sodium salt form is much more stable than the free acid form. The glass transition temperature of polysulfone is increased by as much as 130°C (i.e., to 310°C) by the introduction of SO3Na groups. Sulfonation also causes a major shift in the low-temperature (−100°C) transition of polysulfone. Compositions of intermediate degree of sulfonation, containing 0.5 SO3Na groups per polysulfone repeat unit, are melt processable. This composition also displays the best balance of properties. Water absorption, which exerts a large influence on mechanical properties, ranges from 1% to 61%, depending upon degree of sulfonation and sorption conditions. Water absorption and desorption curves show non-Fickian behavior. Compositions of intermediate degree of sulfonation display optimum reverse osmosis desalination behavior. Gas permeability is significantly reduced by sulfonation. Overall behavior is consistent with an ionomer-type structure.

The conduction-electron diamagnetism has been calculated for the three-dimensional band structure of graphite. The magnetic energy levels are found and the susceptibility calculated by analytically carrying out the free energy sum. Agreement with experiment is found for values of the band parameters nearly equal to those which give agreement with the de Haas-van Alphen effect and other phenomena. The value of ${\ensuremath{\gamma}}_{0}$ is found to be 2.8\ifmmode\pm\else\textpm\fi{}0.1 ev. The results indicate the ${\ensuremath{\gamma}}_{1}$ is about 0.27 ev and $\ensuremath{\Delta}$ is about 0.025. The other band parameters do not have an important influence upon the value of the susceptibility. The relation to the general treatments of conduction-electron diamagnetism is also discussed.

Abstract

Abstract Various α‐halo‐ p ‐xylenes have been polymerized with base yielding p ‐xylylene polymers. The reaction involves a 1,6‐dehydrohalogenation to give a xylylene which then polymerizes. α,α′‐Dichloro‐ p ‐xylene forms poly‐α‐chloro‐ p ‐xylylene and polymers containing stilbene units; α,α,α′,α′‐tetrachloro‐ p ‐xylene gives poly‐α,α,α′‐trichloro‐ p ‐xylylene; alkyl, aryl, and halogen ring‐substituted α‐chloro‐ p ‐xylenes give the corresponding ring‐substituted poly‐ p ‐xylylenes. The more halogens in the α positions (up to five), the weaker the base necessary for dehydrohalogenation. Sodium hydroxide in methanol will polymerize tetrachloro‐ p ‐xylene, while potassium tert ‐butoxide in refluxing p ‐xylene is necessary to polymerize α‐chloro‐ p ‐xylenes. Stilbenes are formed when α‐halo‐ p ‐xylenes are reacted with potassium tert ‐butoxide in polar solvents such as dimethyl sulfoxide.

Electron spin resonance of acceptors due to substitutional Li, and the resonance of certain donors previously reported at $g\ensuremath{\cong}1.96$ were examined using polycrystalline samples of ZnO. It was found that the latter signal could actually be a superposition of two independent signals, one arising from the oxygen vacancy and the other from the substitutional halogen. The analysis of the resonance spectra gave for the Li acceptor ${g}_{\mathrm{II}}=2.0026\ifmmode\pm\else\textpm\fi{}0.0005$, ${g}_{\ensuremath{\perp}}=2.0254\ifmmode\pm\else\textpm\fi{}0.0005$, ${A}_{\mathrm{II}} (\mathrm{with} {\mathrm{Li}}^{7} \mathrm{nucleus})\ensuremath{\leqq}0.1\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$ ${\mathrm{cm}}^{\ensuremath{-}1}$ and ${A}_{\ensuremath{\perp}} (\mathrm{with} {\mathrm{Li}}^{7} \mathrm{nucleus})=(1.73\ifmmode\pm\else\textpm\fi{}0.02)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$ ${\mathrm{cm}}^{\ensuremath{-}1}$; for the donor due to oxygen vacancy ${g}_{\mathrm{II}}=1.957\ifmmode\pm\else\textpm\fi{}0.001$, and ${g}_{\ensuremath{\perp}}=1.956\ifmmode\pm\else\textpm\fi{}0.001$; and for the halogen donor $g=1.960\ifmmode\pm\else\textpm\fi{}0.001$. These $g$ values are interpreted in terms of a picture in which a hole associated with the Li acceptor is localized in the valence orbital of one of the four adjacent oxygen, while the electrons trapped by the donor levels due to oxygen vacancies or substitutional halogen are shared more or less equally among the valence orbitals of the surrounding zinc ions.

The free-space concept, previously applied to variation resulting from a change in temperature only, is here adapted to a case where both temperature and molecular weight vary. The molecular weight range of the n-paraffins illustrative of this case is limited to m=100 through m=240. Over this range of molecular weights the family of lines represented by lnη=B(ν0/νf)+lnA intersects the vertical axis at very nearly a common point. By assuming a common intercept and representing the slopes of this family of lines in terms of molecular weight, an expression defining viscosity as a function of molecular weight and free space is deduced. This expression reproduces the ``selected data'' satisfactorily over the molecular weight range mentioned. Its greater significance as a step in the development of a far more useful function will become apparent in the succeeding paper.

Abstract The polymerization of lactones provides a facile route to polyesters that is unimpeded by the long reaction cycles and elevated temperatures inherent in the condensation of hydroxyl and acid functional groups. Depending on the structure of the lactone monomer, catalyst/initiator systems are known which allow preparation of extremely high molecular weight polyesters of low polydispersity. In addition to obtaining high molecular weight polyesters in relatively short reaction cycles and at moderate temperature, lactone polymerization allows careful control of polymer end groups through proper selection of the initiating species. The type of end group plays an important role in both the thermal stability and hydrolytic stability of the resulting polyester. This study reviews and updates the field of lactone polymerization with specific emphasis on the chemistry and Theological

Abstract Chromocene deposited on silica supports of high surface area forms a highly active catalyst for polymerization of ethylene. Polymerization is believed to occur by a coordinated anionic mechanism previously outlined. The catalyst formation step liberates cyclopentadiene and leads to a new divalent chromium species containing a cyclopentadienyl ligand. The catalyst has a very high chain‐transfer response to hydrogen which permits facile preparation of a full range of molecular weights. Catalyst activity increases with an increase in silica dehydration temperature, chromium content on silica, and ethylene reaction pressure. The temperature‐activity profile is characterized by a maximum near 60°C, presumably caused by a deactivation mechanism involving silica hydroxyl groups. A value of 72 was estimated for the ethylene–propylene reactivity ratio ( r 1 ). Linear, highly saturated polymers are normally prepared below 100°C. By contrast with other commercial polyethylenes, the chromocene catalyst produces polyethylenes of relatively narrow molecular weight distribution. Above 100°C, unsaturated, branched polymers or oligomers are formed by a simultaneous polymerization–isomerization process.

Several forms of biological treatment can be used to treat contaminated aquifers. In situ treatment increases the activity of the indigenous organisms by the addition of nutrients and electron acceptor. Withdrawal and treatment technologies rely on removal of the ground water and any of several wastewater treatment processes to biodegrade the organics. Addition of acclimated or genetically engineered organisms may overcome the time necessary for acclimation to the contaminants, but requires that the added population establish itself in the environment and be able to locate and continue to degrade the compounds of interest at what are often very low concentrations. Most of these techniques utilize aerobic organisms, but the potential for treatment with anaerobic organisms exists. Mathematical models that include biological decay terms are useful tools in the design and evaluation of biological treatment options. Biological treatment techniques are a valuable tool for the restoration of contaminated aquifers.