摘要:

The orientation of the crystallites when polyethylene is stretched at 96°C is normal in that, from the onset of stretching, the preferred orientation is that wherein the long chain axis is parallel to the direction of stretch. At low extensions the preference for this orientation is weak, but it progressively becomes stronger as stretching proceeds.When polyethylene is stretched at room temperature, the crystallite behavior is more complicated. The first 20 percent extension produces no preferred orientation of the crystallites. From 30 percent to 200 percent extension the preferred orientation is that wherein the 011 ``axis'' is parallel to the direction of stretch, and the long chain axis therefore inclined to this direction at an angle of 64°. From 200 percent extension to the break (about 600 percent extension), the tilt of the crystallites in the preferred orientation progressively lessens and almost vanishes at the break. The stress‐strain diagram of polyethylene is interpreted in the light of these findings. The preferred orientation of the crystallites in the region of the shoulder in necked‐down polyethylene is also that wherein the 011 ``axis'' aligns with the stretching direction.When stretched polyethylene is relaxed by shrinking at elevated temperatures, the crystallites become disoriented but in a non‐random manner. This behavior is described qualitatively.

ISSN:0021-8979    

DOI:10.1063/1.1698424

出版商:AIP    

年代:1949

数据来源: AIP

摘要:

Infra‐red absorption spectra of polythene, rubber, polystyrene and polyvinyl chloride have been obtained at 4° absolute, in the rocksalt region, in a specially designed transmission cell containing liquid helium. No unusual changes occur on cooling which considerably alter the absorption. Some sharpening and improvement in resolution occurs, but the widths of most bands in polymers remain wide.In polythene one component of the doublet at 720 cm−1becomes very sharp (possibly even less than the experimental value of the slit width, 1 cm−1). Its companion remains broad, about 4 cm−1. The two components are interpreted as CH2wagging intrans‐ andcis‐configurations of the hydro‐carbon chain.

ISSN:0021-8979    

DOI:10.1063/1.1698425

出版商:AIP    

年代:1949

数据来源: AIP

摘要:

By means of a density balance, the relationship between intrinsic viscosity and dilatometric properties is established for polyethylene terephthalate. The most pronounced property change associated with increasing intrinsic viscosity was observed to be the second‐order transition temperature. The relationship between crystallinity and dilatometric properties is presented for 3 aromatic polyesters. In every case, increased crystallinity in the polymers is associated with higher second‐order transition temperatures, larger transition range, higher density, and lower volume coefficients of expansion. Second‐order transition temperatures, densities at 0°C, and volume of coefficients of expansion are presented for a number of polyesters and vinyl polymers to illustrate the effects of chemical structure as well as physical state on these dilatometric properties. Illustration of the effect of copolymerization on second‐order transition temperatures is made with a copolyester system.

ISSN:0021-8979    

DOI:10.1063/1.1698426

出版商:AIP    

年代:1949

数据来源: AIP

摘要:

By means of both a density balance and gradient tube, experimental density data are obtained to illustrate the thermal crystallization behavior of 3 aromatic polyesters at temperatures from 90°C to 150°C. The data are discussed with reference to both amount and rate of crystallization and density curves are presented to show qualitative similarity between kinetics of polymer crystallization and the kinetics of chemical reactions. From the experimental data, a temperature, for convenience labeled the minimum crystallization temperature, is described and is shown to be 30° to 50° above the second‐order transition temperature for the polyesters. In addition to thermal crystallization, data are presented to show that immersion media may initiate crystallization below the minimum temperature associated with thermal crystallization of polymers. Liquids used as immersion media for polyethylene terephthalate were water, methyl alcohol, acetone, benzene, nitromethane, and nitric acid. The last four liquids initiate crystallization of the polymer at room temperature.

ISSN:0021-8979    

DOI:10.1063/1.1698427

出版商:AIP    

年代:1949

数据来源: AIP

摘要:

In this paper very simple formulas are deduced for calculating the amplitude of modes produced in a cylindrical guide when the currents distribution is known. One example is included.

ISSN:0021-8979    

DOI:10.1063/1.1698428

出版商:AIP    

年代:1949

数据来源: AIP

摘要:

A mechanical method is described for graphing the effect of the variation with frequency of the series reactance (X1) and the shunt reactance (X2) of a filter section. This method permits the quantitiesX1/−4X2,X1X2{(X1/−4X2)−1} andX1X2/{(X1/−4X2)−1}, from which the characteristics of an electric wave filter are calculated, to be graphed easily as a function of frequency. The cut‐off frequencies are located directly from the graphs ofNandD(whereN/Dis either the ratioX1/−4X2or (X1/−4X2)) as functions of frequency, and the calculation of the attenuation and phase shift at any frequency is readily made from the ratio of corresponding ordinates of theNandDcurves. The image impedance is determined from the ratio of corresponding ordinates from two additional curves which are mechanical plots of the numerator and the denominator of the expression for the square of the image impedance,X1X2{(X1/−4X2)−1} for the mid‐series image impedance, andX1X2/{(X1/−4X2)−1} for the mid‐shunt image impedance.

ISSN:0021-8979    

DOI:10.1063/1.1698429

出版商:AIP    

年代:1949

数据来源: AIP

摘要:

The Barkhausen noise is calculated for ferromagnetic cores used in magnetic amplifiers. The method of analysis follows that used in the analysis of the shot effect. The signal‐to‐noise ratio for a typical magnetic amplifier circuit is calculated and compared with experiment.

ISSN:0021-8979    

DOI:10.1063/1.1698430

出版商:AIP    

年代:1949

数据来源: AIP

摘要:

Young's modulus,E, has been measured by dynamic and static methods for 25 zinc single crystals. The results fit a parabolic curve when 1/Eis plotted against the square of the cosine of the orientation. From the constants of this curve and earlier data on linear compressibility by Bridgman, are derived numerical values for the coefficients of compliance of the zinc crystal, as follows:S11=8.38,S12=0.5,S13=−7.31,S33=28.4,S44=26.1, all ×10−13cm2/dyne.Data on three crystals were taken from room temperature to 375°C. From these may be computed Young's modulus for any orientation and any temperature in the range given. Young's modulus decreases for all orientations with increasing temperature.

ISSN:0021-8979    

DOI:10.1063/1.1698431

出版商:AIP    

年代:1949

数据来源: AIP

摘要:

An experiment is performed to determine whether the presence of a periodic transverse electric field produces modulation, either of amplitude or of phase, of a continuous progressive ultrasonic wave train passing through the liquid. One object of the experiment is to ascertain whether the application of an electric field to a polar liquid influences either the compressibility or the viscosity of the liquid through molecular orientation. The results of a related investigation in which an electric field was applied in the direction of wave travel, published in 1945 by Barone and Giacomini, were inconclusive. The present experiments reveal phase modulation in a number of conducting liquids. This is explained as a thermal effect involving the temperature dependence of velocity of sound. No evidence is found of phase modulation resulting from dipole orientation in non‐conducting polar liquids. Amplitude modulation, which would result from change of attenuation, is not found in any liquid. A variety of organic liquids is investigated. Limits of sensitivity of the apparatus are given.

ISSN:0021-8979    

DOI:10.1063/1.1698432

出版商:AIP    

年代:1949

数据来源: AIP

摘要:

Simple formulas for calculating the small angle x‐ray scattering from aggregates of identical spherical particles, taking into account the interference between different particles, are given. The case of independent clumps of particles and the case of a more general arrangement describable by a radial density function are considered. Calculated curves of scattered intensityvs.angle for likely arrangements of both types are presented. The assumption that each particle scatters independently is seen to be a poor approximation whenever there is a significant amount of clumping or whenever the average density of the sample is as much as one third of the density corresponding to close packing. Estimates of particle size from the small angle scattering are shown to be seriously affected.

ISSN:0021-8979    

DOI:10.1063/1.1698433

出版商:AIP    

年代:1949

数据来源: AIP