Materials Literature
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Abstract High molecular weight polyterephthalamides were synthesized from a homologous series of primary diamines (ethylenediamine to hexamethylenediamine) by the interfacial polycondensation method. These polymers were found to be extremely high‐melting (300–450°C). and difficult to dissolve. Fibers were prepared by…
It is widely recognized that electron tube failures may be classified into two types: sudden and delayed. A mixture of two Weibull distributions, each representing one type of tube failure, is proposed, and a simple graphical method for estimating the parameters of the mixed Weibull distribution described.
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPhotochromic Spiropyrans. I. The Effect of Substituents on the Rate of Ring ClosureElliot Berman, Richard E. Fox, and Francis D. ThomsonCite this: J. Am. Chem. Soc. 1959, 81, 21, 5605–5608Publication Date (Print):November 1, 1959Publication History Published online1 May 2002…
Abstract Heretofore, the master stress relaxation curves of amorphous polymers could only be resolved by approximation methods into a continuous distribution of relaxation times. This is obviously not entirely satisfactory in all cases, e.g., for Maxwellian stress decay or if the Rouse distribution for the rubbery flo…
Abstract Contrary to what has been thought before, polyesters containing meta phenylene groups can be crystallized. The entropies and enthalpies of melting of isomeric poly‐isophthalates and polyterephthalates have been determined. It is shown that the lower crystal melting points of the polyisophthalates are due main…
Abstract A compound between aluminum oxide and aluminum nitride can be produced in a reductive atmosphere above 1650°C. A new spinel formula AlN–Al2O3 should be adopted instead of the previous one Al2O–5Al2O3 or Al3O4. The physical constants of AlN-Al2O3 are as follows: crystal structure Fd3m, Z=8, a=7.940 Å; density…
A high temperature diffractometer has been used to determine the lattice spacing-temperature relations for both α- and β-titanium. For α-titanium, the mean coefficients of thermal expansion over the temperature range 0-600°C are 9.55 x 10 -6 deg -1 for the a spacing, and 10.65 x 10 -6 deg -1 for the c spacing; for β-t…
The thermal conductivity of clear fused silica was measured over the temperature range 300–2100°K in an experiment which minimized radiative energy transport. This was a steady-state experiment involving the measurement of the electric current and voltage drop through a fine tungsten wire which was embedded along the…
A high‐water‐pressure high‐temperature study has been conducted of the systems Y 2 O 3 ‐H 2 O, Sm 2 O 3 ‐H 2 O, Nd 2 O 3 ‐H 2 O, and La 2 O 3 ‐H 2 O. The trihydroxides La(OH) 3 , Nd(OH) 3 , and Sm(OH) 3 are isomorphous, but Y(OH) 3 does not belong to this group. On the other hand, the oxyhydroxides YOOH, SmOOH, and Nd…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTAssociation Reactions for Poly(alkylene Oxides) and Polymeric Poly(carboxylic Acids)K. L. Smith, A. E. Winslow, and D. E. PetersenCite this: Ind. Eng. Chem. 1959, 51, 11, 1361–1364Publication Date (Print):November 1, 1959Publication History Published online1 May 2002Publishe…
Abstract Deterioration in poly(vinyl chloride) is due primarily to zipperlike elimination of hydrogen chloride from the polymer chain, with formation of colored and easily oxidizable polyenes. Baum and Wartman have shown that elimination is initiated by rupture of certain particularly labile carbon‐chlorine bonds. The…
The dielectric constant, and the ferroelectric, pyroelectric, and piezoelectric properties of thiourea crystals have been measured in the temperature range 90°K to 300°K. At least three dielectric anomalies are found at 169°K, 177°K, and 202°K, the lowest of these corresponding to a pronounced discontinuity. The cryst…
The amount of 90° reorientation during poling was determined from mechanical strains measured during the poling process. With tetragonal lead titanate zirconate 53% of the possible 90° reorientation occurred during poling, but this figure dropped to 44% upon removal of the poling field. With barium titanate the figure…
The reflectance and fluorescent spectra of hexagonal CdS crystals have been measured at 77\ifmmode^\circ\else\textdegree\fi{} and 4.2\ifmmode^\circ\else\textdegree\fi{}K using polarized light in the region of 5000 A. Structure not previously reported has been found in the reflectivity curves which leads to the identif…
The static boundary problems of line currents and dipoles immersed in a perfectly conducting static fluid are considered first. The perturbing effect of moving fluid on the magnetostatic boundary about an isolated line current is then investigated. In this case, the initial circular boundary is distorted into an ellip…
It is widely recognized that electron tube failures may be classified into two types: sudden and delayed. A mixture of two Weibull distributions, each representing one type of tube failure, is proposed, and a simple graphical method for estimating the parameters of the mixed Weibull distribution described.
Abstract The phenomenon of ferroelectricity in pseudo-cubic crystals is discussed in terms of the normal modes of vibration. It is shown that the parameters which determine the lattice vibrations of a diatomic ionic crystal may be chosen in such a way that the crystal will exhibit ferroelectric properties, and that fe…
We have derived, by using simple considerations, a relation between the diffusion constant D in a liquid of hard spheres and the ``free volume'' vf. This derivation is based on the concept that statistical redistribution of the free volume occasionally opens up voids large enough for diffusive displacement. The relati…
The fuel element cans of most of the current gascooled graphite- moderated reactors are not bonded to the uranium fuel. Good contact between can and fuel is ensured by a pressurizing operation during the canning process. The temperature drop at the interface will be small compared to the can-to-gas temperature drop, b…
X-ray topographs of a new type have revealed fine fringes in the diffraction images of wedge-shaped parts of perfect and nearly perfect crystals. The fringes are analogous to those seen in electron microscope images of wedge-shaped parts of magnesium oxide crystals and can be interpreted according to the theory applic…