摘要:

AbstractAnisotropic growth of β‐form crystals of isotactic polypropylene in type III and type IV spherulites has made possible microanalysis of the unit cell structure, optical properties, and crystal arrangement within the spherulites. Micro x‐ray studies of the type III and type IV spherulites show that interspherulitic β‐form crystals have a hexagonal unit cell with dimensions;a= 19.08 Å andc= 6.49 Å. The intrinsic refractive indices of these β‐form crystals are 1.506 along theaaxis and 1.536 along thecaxis. The organization of the crystals within the spherulites and the optical properties of the spherulites are also quantitatively evaluated. Both the type III and type IV spherulites have theaaxis of the crystal radial while the crystals rotate randomly around the type III spherulite radii and periodically around the type IV spherulite radii. The radial refractive index for both the type III and type IV spherulites has the same value of 1.496. The tangential refractive index of the type III spherulite has a constant value of 1.509; it varies periodically between a minimum of 1.496 and a maximum of 1.519 in the type IV spherulite. Microtechniques such as micro x‐ray diffraction, interference microscopy, birefringence, and optical microscopy were required for acquisiti

ISSN:0449-2978    

DOI:10.1002/pol.1972.160100301

出版商:John Wiley&Sons, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractMeasurements are reported for the dielectric loss factor of the SCMC solutions over the frequency range 2 MHz to 50 MHz as a function of concentration of SCMC, concentration of added sodium chloride, molecular weight, and temperature. The results are in general agreement with those of other workers and are interpreted in terms of ionic theories in which motion of the diffuse counterions is the dominant feature.

ISSN:0449-2978    

DOI:10.1002/pol.1972.160100302

出版商:John Wiley&Sons, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractThe kinetics of the polycondensation of 3,3′‐diaminobenzidine with 1,4,5,8‐naphthalenetetracarboxylic acid (NTC) have been investigated. Polymerizations were carried out in solution in either polyphosphoric acid (PPA) or in PPA mixed with some sulfuric acid. The reaction is heterogeneous in PPA owing to partial solubility of NTC, whereas it is homogeneous in the mixed solvent. The rate of disappearance of NTC and of dicarboxylic endgroups on oligomers was followed as a function of time at several reaction temperatures. The results show that NTC is more reactive than oligomers, so that the principle of equal reactivity is not valid for the initial steps in the polycondensation rea

ISSN:0449-2978    

DOI:10.1002/pol.1972.160100303

出版商:John Wiley&Sons, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractThe structure of granular polytetrafluoroethylene has been studied by electron microscopy. On the basis of the texture of surfaces resulting from fracture a model of the structure is proposed which suggests that PTFE consists of extended chain crystals with both inter‐ and intra‐lamellar noncrystalline regions. The effects of γ‐radiation on the structure have been investigated by examining the texture of irradiated fracture surfaces and also the texture produced by post‐irradiation fracture. The irradiations have been performedin vacuoand in oxygen. In both atmospheres PTFE undergoes degradation with a concurrent increase in crystallinity. However, the texture of the surfaces of high crystallinity PTFE, prepared by radiation, differs markedly to the texture of fracture surfaces of high crystallinity PTFE prepared by thermal annealing. It is proposed that radiation causes rupture of bonds in the interlamellar (chain fold) and intralamellar regions, resulting in the production of chain ends and interlamellar links. Due to scavenging of the free radicals, interlamellar linking is pobably a minor process with irradiation in oxygen. These chemical changes cause modifications to the extended chain lamellar crystals and consequently alterations to the physical properties of the

ISSN:0449-2978    

DOI:10.1002/pol.1972.160100304

出版商:John Wiley&Sons, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractProton spin‐lattice relaxation times of solvent molecules were measured on ternary mixtures of a polymer and two solvents by the adiabatic rapid‐passage method. The selective adsorption of a good solvent was verified by this experimental technique for the systems benzene—cyclohexane—polystyrene(PS), benzene—carbon tetrachloride—poly(methyl methacrylate)(PMMA), and chloroform—carbon tetrachloride—PMMA. The number of molecules of adsorbed benzene per monomeric unit of PS was estimated to be about four, which is almost identical with that determined previously by thermodynamic measurements. The number of molecules of benzene and chloroform adsorbed on PMMA were also determined to be about five and four, respectively. It was found that the interaction between chloroform and PMMA has the greatest effect on the molecular motion of the solvent, whereas the benzene—PS in

ISSN:0449-2978    

DOI:10.1002/pol.1972.160100305

出版商:John Wiley&Sons, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractThe healing of scratches on the surface of vitreous selenium was observed over a period of nine weeks, and from the data the solid surface tension of vitreous Se is estimated to be (100 ± 20) dyne/cm at 38.8°C, about the same as that of the liquid at the melting point. This value is three times as large as the critical surface tension determined from contact angle measurements, which indicates that for vitreous Se in contact with organic liquids, the solid—liquid interfacial tension is about two‐thirds as much as the solid surface tension. The present method of measurement can probably be used to determine the solid surface tension of other polymers, and by measuring the healing of scratches on a solid immersed in a liquid the method could be used to determine the solid—liquid interfacial

ISSN:0449-2978    

DOI:10.1002/pol.1972.160100306

出版商:John Wiley&Sons, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractA new typical orientation pattern of polyethylene has been observed in extruded, melt‐drawn composites containing 10% polyethylene and 90% polystyrene. In these composites, the polyethylene phase is dispersed in the polystyrene matrix as thin, long ribbons (width 1000 Å, thickness 500 Å). Thebaxis of the crystallites is found oriented preferentially along the long dimension of the ribbons, i.e., in the extrusion direction. Theaandcaxes of the crystallites show no preferred orientation. This texture pattern is attributed to the fact that, in view of the small cross section of the polyethylene phase, crystallization can proceed only along the long axis of the ribbons. Since thebaxis is the direction of fastest growth in polyethylene (and the radial direction in a spherulite), most polyethylene unit cells are oriented with theirbaxes in the long dimension of the ribb

ISSN:0449-2978    

DOI:10.1002/pol.1972.160100307

出版商:John Wiley&Sons, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractStarting from the Lorentz‐Lorenz equation, Heller, a few years ago, advanced a method for calculating the partial specific volume of a substance in a dilute solution from the refractive index increment of the solution and the specific refraction of the solute. It is shown that this method, based on graphical extrapolation, can be considerably simplified. Further, a method is indicated by which the partial specific volume of a substance over the whole range of concentrations can be calculated in an analogous manner. The method is checked and elucidated with reference to some experimental example

ISSN:0449-2978    

DOI:10.1002/pol.1972.160100308

出版商:John Wiley&Sons, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractThe extrema in the unpolarized and the horizontally polarized angular scattering patterns are used as a basis for size‐distribution analysis of polymer latex systems composed of single, spherical, optically isotropic particles. The method of analysis is similar to that recently proposed for vertically polarized scattered light and the polarization ratio, where the modal diameter and a distribution width parameter are determined from the experimental angular scattering pattern and prepared theoretical diagrams obtained by Mie theory calculations. The method of analysis, based on all four scattering functions, is illustrated by use of a Dow polystyrene latex sampl

ISSN:0449-2978    

DOI:10.1002/pol.1972.160100309

出版商:John Wiley&Sons, Inc.    

年代:1972

数据来源: WILEY

摘要:

AbstractThe tack ofcis‐polybutadiene was measured by means of a Skewis tackmeter, and the results, which showed considerable variability, could be represented by a double exponential cumulative distribution function of Gumbel. It was concluded that there exists a linear relationship between the applied forces (contact and break) and the time that these forces are applied in the tack test. The mechanism of tack is considered in terms of two distinct processes: (a) the development of a bond and (b) the strength of the bond thus formed. The latter is rationalized by applying Eyring's absolute rate theory. A simple equation is derived which predicts an inverse linear relation between the breaking time and breaking force, which is in agreement with the experiment. The theory also suggests that the area of actual interpenetration of polymer interfaces depends largely on the contact pressure, whereas the depth of penetration appears to depend to a similar degree on both contact pressure and contact tim

ISSN:0449-2978    

DOI:10.1002/pol.1972.160100310

出版商:John Wiley&Sons, Inc.    

年代:1972

数据来源: WILEY