Aging of polymers
This paper provides background on the basic chemical processes which can occur during the exposure of polymers to typical end-use environments such as air, sunlight, water vapor, and various atmospheric pollutant gases.
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Revised phase diagram and X‐ray data of The Mn3O4Al2O3 System in air
Abstract The phase diagram of the quasi‐binary Mn 3 O 4 Al 2 O 3 system in air has been redetermined at temperatures from 850 to 1550°C with the help of the X‐ray powder diffraction technique including high‐temperature diffractometry. Lattice constants of manganese aluminates and the powder diffraction patterns of Mn…
Nickel-containing montmorillonites and chlorites from Brazil, with remarks on schuchardtite
Summary Clay-like, hydrous nickel silicates from Niquelandia, Goias, Brazil, and from Jacupiranga, São Paulo, Brazil, arc examined by X-ray diffraction, chemical analysis, and thermogravimetric methods. The nickel silicates from Niquelandia are ferric iron montmorillonites, with nickel in the octahedral positions and,…
Potassium perchromate as a source of singlet oxygen
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPotassium perchromate as a source of singlet oxygenJohn W. Peters, Paul J. Bekowies, Arthur M. Winer, and James N. Pitts Jr.Cite this: J. Am. Chem. Soc. 1975, 97, 12, 3299–3306Publication Date (Print):June 1, 1975Publication History Published online1 May 2002Published inissu…
High-temperature elastic moduli of polycrystalline silicon nitride
Elastic constants are reported for several polycrystalline silicon nitrides with densities between 2.37 and 3.18 g/cm3 in the temperature range 0–1000 °C. The density dependence of the elastic constants is in approximate agreement with the prediction of a theory of composites.
Neutron scattering study of human serum low density lipoprotein.
Regions of different proton density in the low density lipoprotein (LDL) particle from human serum have been determined by neutron scattering. From measurements in various H2O/D2O mixtures, the LDL particle appears to be quasi-spherical, with the centers of gravity of the hydrocarbon and polar regions coinciding. The…
Isotherms and energetics of carbon dioxide adsorption on .gamma.-alumina at 100-300.deg.
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTIsotherms and energetics of carbon dioxide adsorption on .gamma.-alumina at 100-300.deg.Michael P. RosynekCite this: J. Phys. Chem. 1975, 79, 13, 1280–1284Publication Date (Print):June 1, 1975Publication History Published online1 May 2002Published inissue 1 June 1975https://…
A MORPHOLOGICAL AND TAXONOMIC CONSIDERATION OF TABELLARIA (BACILLARIOPHYCEAE) FROM THE NORTHCENTRAL UNITED STATES1,2
SUMMARY The taxonomy, distribution, and ecology of the diatom genus Tabellaria Ehr. from a portion of the northcentral United States were studied from collections made from August 1968 to October 1971. Using the transmission electron microscope with carbon replicas of the frustule surfaces, taxonomically significant c…
Thermal properties of isotactic polypropylene quenched from the melt and annealed
Abstract DSC investigations on isotactic polypropylene ( it ‐PP) quenched from the melt and annealed over a range of temperatures are reported. The results confirm the existence of saturation levels of the ordered phase for different annealing temperatures, previously revealed by X‐ray diffraction methods. Thermal, X‐…
Microwave switching by picosecond photoconductivity
Bulk photoconductivity produced by the absorption of picosecond optical pulses in silicon transmission-line structures has been used to switch and gate microwave signals. The technique permits the generation of microwave and millimeter-wave pulses as short as a single cycle, and requires only a few microjoules of opti…
Effects of annealing and isothermal crystallization upon crystalline forms of poly(vinylidene fluoride)
Abstract Poly(vinylidene fluoride) exists in three crystalline forms. Optimum conditions for preparing form III were established by infrared spectroscopy, differential scanning calorimetry, and x‐ray diffraction measurements. Form III is easily obtained by annealing mats of solution‐grown crystals of form II at 175–18…
Thermal decomposition in the solid state
The foundation of solid state decomposition kinetics is based on the well known theory of nucleation and nucleus growth put forward by Jacobs and Tompkins. It has now been shown that all the kinetic equations thus derived can be represented by a general differential form:     &n…
Reflexion and transmission theorems for characteristic waves in stratified anisotropic absorbing media
The solutions of Maxwell's equations and of their adjoint equations, being essentially different in absorbing media, are written in terms of matrizants. A relation between these is established, utilizing the constancy of the bi-linear concomitant. With this, and with the concept of the conjugate field , introduced in…
Class E-A new class of high-efficiency tuned single-ended switching power amplifiers
The new class of amplifiers described is based on a load network synthesized to have a transient response which maximizes power efficiency even if the active device switching times are substantial fractions of the a.c. cycle. The new class of amplifiers, named `Class E,' is defined and is illustrated by a detailed des…
Triode optical gate: A new liquid crystal electro-optic device
A new liquid crystal field effect electro-optic device is described. Light transmission induced by voltage pulses across two electrodes is modulated or gated by voltage on a third electrode. The three-terminal gating characteristics are applicable to scanning and multiplexing arrays of devices for displays or light va…
Dissimilar Fabrics by Scan Electron Microscopy of Sedimentary Versus Hydrothermal Kaolins in Mexico
Abstract Dissimilar fabrics, observed by scan electron micrography (SEM) on freshly broken surfaces of kaolins from weathered, water-laid material vs hydrothermally altered material in Mexico are illustrated, contrasted, and tentatively related to their respective environments of genesis. Coarse, open-textured, well-p…
Optical and Electrical Properties of Boron
Optical constants of β-rhombohedral and amorphous boron were obtained by ellipsometry and by the measurements of transmissivity and reflectivity. The values of the refractive index were found between 3.00 and 3.35 for wavelengths between 0.35 µm and 1.20 µm. Absorption coefficient α of amorphous boron as a function of…
Anodic Polarization Behavior of High‐Purity 13 and 18% Cr Stainless Steels
Potentiodynamic polarization curves were obtained in and in for 13 and 18% Cr ferritic stainless steels containing 0–5% Mo. The critical current density for passivation was decreased by molybdenum additions in both acids, the decrease being more pronounced for the 18% Cr steels than for the 13% Cr steels. No complete…
Thermochemical Properties of Lanthanoid-Iron-Perovskite at High Temperatures
Abstract The standard Gibbs energy of formation of \barCFeO3(\barC=La, Nd, Sm, Eu, Gd, Tb, and Dy) from metallic iron, \barC2O3, and oxygen has been determined at temperatures from 1473 to 1673 K. Based on the free-energy data, the heat of reaction and the entropy change resulting from the reaction have been calculate…
Measured and calculated solubility of polymers in mixed solvents: Monotony and cosolvency
Abstract By a study of two ternary systems, 4‐heptanon–1‐chlorobutane–poly(methyl methacrylate) and 2‐butanol–1‐chlorobutane–poly(methyl methacrylate), differing only in one component of the mixed solvent, two types of demixing behavior are demonstrated: i.e., a monotone change with composition of the mixed solvent (m…