摘要:

AbstractThe infrared absorption spectra of selected crystalline and noncrystalline bands were studied in bulk‐crystallized specimens of linear polyethylene which encompassed the extremely wide density range of 0.92–0.99 g./cm.3. The analysis of the data obtained at room temperature yield degrees of crystallinity by infrared methods which are in very good accord with the values deduced from the density measurements. Studies of the infrared spectra as a function of temperature give fusion curves which are in agreement with those obtained by thermodynamic methods. However, in order to obtain these latter results cognizance must be taken of the large negative temperature coefficient of the specific extinction coefficients of the crystalline bands from room temperature to the melting point. The necessary data to account for this phenomena were obtained from studies of the spectra of then‐paraffin, C94H190, where molecular crystals are formed. Analysis of the twogauchebands, at 1352 and 1303 cm.−1, which are assigned to the noncrystalline regions demonstrate that for bulk‐crystallized samples of lowest densities the intensity ratio at room temperature is identical to that expected from the pure melt at this temperature. The conclusion is thus reached that the noncrystalline regions in these cases and the pure melt are structurally very similar. For samples of higher density, where the crystallite size is comparable to the extended chain length, the intensity ratio of the twogauchebands is altered. This change could reflect a change in the sequential distribution ofgauchebonds. This intensity ratio for crystals formed from dilute solution is very similar to that for the high‐density bulk‐crystallized material and indicates a similarity in structure of the noncrystalline regions in

ISSN:0449-2978    

DOI:10.1002/pol.1967.160050201

出版商:John Wiley&Sons, Inc.    

年代:1967

数据来源: WILEY

摘要:

AbstractThe adsorption of iodine by rayon tire yarn samples from aqueous solutions in which the concentration of iodide and triiodide ions is suppressed was studied. Fowler and Guggenheim's model of adsorption on regular localized monolayers appeared to be applicable to the adsorption phenomena considered. It is concluded that adsorption takes place on patches of sites in the cellulose–water ge

ISSN:0449-2978    

DOI:10.1002/pol.1967.160050202

出版商:John Wiley&Sons, Inc.    

年代:1967

数据来源: WILEY

摘要:

AbstractNMR linewidth studies of molecular motion in several polyacrylonitrile samples have been carried out. The motional transition temperature is found in the 105–124°C. range and depends upon polymerization conditions. In addition, the thermal activation energy for the motional process underlying this transition was evaluated at 16.4 kcal./mole. Finally, measurement of the transition temperature for one of the specimens in three different physical states (bulk, spun only, and spun and drawn with a ratio of 3:1), revealed that no change in the transition temperature was effected by either spinning or drawi

ISSN:0449-2978    

DOI:10.1002/pol.1967.160050203

出版商:John Wiley&Sons, Inc.    

年代:1967

数据来源: WILEY

摘要:

AbstractTo investigate the solution properties of polyethylene, which has the simplest structure of the vinyl polymers, experiments were made with a magnetically suspended equilibrium ultracentrifuge. Preliminary studies were carried out with a polystyrene–chloroform system at 25°C. and a polystyrene–methylcyclohexane system at 68°C. (which is close to the theta temperature) in order to check the difficulties involved in the flotation equilibrium in the former case and the high temperature measurement in the latter. However, no trouble was encountered in either system, and the results were discussed and compared with earlier results for polystyrene solutions. It was found that chloroform is a good solvent for polystyrene, and the measured weight‐average molecular weight is somewhat smaller than the value obtained in a theta solvent. After overcoming some technical difficulties involved in studies at higher temperatures, we carried out experiments on polyethylene in α‐chloronaphthalene at 130°C. The results are considered reasonable by comparison with results obtained by other methods. The sample employed, Marlex 50 of melt index 0.7, has a wide molecular weight distribution: i.e.,Mz/Mw= 5.2 andM

ISSN:0449-2978    

DOI:10.1002/pol.1967.160050204

出版商:John Wiley&Sons, Inc.    

年代:1967

数据来源: WILEY

摘要:

AbstractAccurate measurements of stress relaxation after steady‐state flow have been carried out, in the Newtonian flow region, for a polystyrene and a poly(methyl methacrylate) melt, with a cone‐and‐plate rotational rheometer. From the stress relaxation σ(t) versustcurves the relaxation spectraHwere calculated by means of the first approximation equation:\documentclass{article}\pagestyle{empty}\begin{document}$ H = - ({1 \mathord{\left/ {\vphantom {1 {\dot \gamma t)d\sigma {{(t)} \mathord{\left/ {\vphantom {{(t)} d}} \right. \kern-\nulldelimiterspace} d}}}} \right. \kern-\nulldelimiterspace} {\dot \gamma t)d\sigma {{(t)} \mathord{\left/ {\vphantom {{(t)} d}} \right. \kern-\nulldelimiterspace} d}}}\ln t $\end{document}. The shear stress–shear rate curves, σ versus\documentclass{article}\pagestyle{empty}\begin{document}$ {\dot \gamma } $\end{document}were also measured, in large ranges of shear rates, for the same melts, and from these data the relaxation spectraHwere obtained by means of equations given by Faucher and Ferry. The Faucher equation,\documentclass{article}\pagestyle{empty}\begin{document}$ H = - \dot \gamma ^2 d{\sigma \mathord{\left/ {\vphantom {\sigma d}} \right. \kern-\nulldelimiterspace} d}\dot \gamma ^2 $\end{document}, has been found to give results which compare satisfactorily with those obtained from the first approximation equation. It has been found that the Ferry equation has to be modified for comparable

ISSN:0449-2978    

DOI:10.1002/pol.1967.160050205

出版商:John Wiley&Sons, Inc.    

年代:1967

数据来源: WILEY

摘要:

AbstractPolarized infrared measurements were made on polymer samples to obtain the structural changes occurring during the orientation process. The absorbances of the infrared bands were measured by determining the three components of the absorbance. Two components were obtained directly with plane‐polarized light while the third is obtained by tilting the sample and extrapolating. Corrections were made for machine optics polarization, sample birefringence, polarizer inefficiency, anisotropy of the index of refraction, and scattering from the film surface. Data are reported for polyethylene obtained from cold‐drawn specimens as a function of draw temperature. Polyethylene exhibits no strain‐induced crystallization as a result of the chain‐alignment process. Annealing of the drawn samples reperfects the distorted c

ISSN:0449-2978    

DOI:10.1002/pol.1967.160050206

出版商:John Wiley&Sons, Inc.    

年代:1967

数据来源: WILEY

摘要:

AbstractThe effect of polydispersity on liquid–liquid phase equilibrium in systems containing polymer, solvent, and nonsolvent is investigated numerically in the Flory‐Huggins approximation for several special cases. The resulting phase diagrams indicate that, except in the immediate vicinity of the critical region, the degree of swelling of a polymer precipitate phase with a given number‐average molecular weight is essentially independent of polydispe

ISSN:0449-2978    

DOI:10.1002/pol.1967.160050207

出版商:John Wiley&Sons, Inc.    

年代:1967

数据来源: WILEY

摘要:

AbstractThe diffusion coefficient of 1,1,2‐trichlorotrifluoroethane (TTE) in a liquid polybutene was determined at 25°C. as a function of concentration over the range 1.0–19.5 g. TTE/100 cc. The diffusion coefficient increase with increasing TTE concentration, rising continuously from 3 × 10−8cm.2/sec. at the lowest concentration to 15 × 10−8cm.2/sec. at the highest. The magnitudes of the diffusion coefficients indicate that the diffusion mechanism for small molecules in polymeric media must afford vastly greater opportunities for diffusion than the Stokes‐Einstein relation allows. Similarly, self‐diffusion coefficients for the liquid polymer are much lower than the observed mutual diffusion coefficients. An explanation for this behavio

ISSN:0449-2978    

DOI:10.1002/pol.1967.160050208

出版商:John Wiley&Sons, Inc.    

年代:1967

数据来源: WILEY

摘要:

AbstractThe effect of long‐chain branching must be considered in gel permeation chromatography to evaluate the molecular weight polydispersity of branched polyethylenes. Osmotic molecular weights of fractions of branched polyethylene were correlated with elution volumes; weight‐average and number‐average molecular weights of a branched polyethylene were determined. Molecular weight changes on crosslinking polyethylene by ionizing radiation are accompanied by branching and cannot be simply interpreted by gel permeation chromatog

ISSN:0449-2978    

DOI:10.1002/pol.1967.160050209

出版商:John Wiley&Sons, Inc.    

年代:1967

数据来源: WILEY

摘要:

AbstractThe results of detailed measurements of osmotic pressure, light scattering, and viscosity of poly(vinyl chloride) solutions are used to establish the molecular weight dependence of [η] and A2, to estimate the unperturbed dimensions of the poly(vinyl chloride) molecule, and to analyze critically the [η]–Mcorrelations published hithe

ISSN:0449-2978    

DOI:10.1002/pol.1967.160050210

出版商:John Wiley&Sons, Inc.    

年代:1967

数据来源: WILEY