The melt and polarization spectra of dotriacontane and polyethylene in the 750–1500 cm—1 region and of nylon 6 and nylon 11 in the 450–4000 cm—1 region are presented. In addition, the melt and crystal spectra of stearone are presented in the 650–3500 cm—1 region. The effect of crystallinity on the spectrum of polyethylene is discussed. With the aid of published Raman spectra of crystalline hydrocarbons, an assignment of frequencies for polyethylene is made. The effect of crystallization on the spectrum of stearone is discussed and unusual features pointed out. Orientations in films of nylon 6 and nylon 11 are shown to be in the extrusion direction. The effect of melting on the hydrogen bonding and on the CO and NH frequencies is discussed. A partial assignment and classification of frequencies is made. When the films are melted, certain peaks vanish. These are ascribed to splitting arising from crystal forces.

The problem of determining orientation distribution in polymer films from the measurement of infrared dichroism is treated from the theoretical point of view. It is shown that the distribution function cannot be determined from such measurements. However, if an elliptical distribution function is assumed, the axial ratio of the ellipse of planar components may be calculated. The curve for axial ratio as a function of measured dichroic ratio is given. The dichroisms of the 1300, 730, and 719 cm.−1 bands in polyethylene are discussed and interpreted. It is shown that, in extruded films, chain axes in the amorphous areas lie roughly in the extrusion direction. Chain axes in the crystalline areas lie roughly perpendicular to the extrusion direction. In stretched films, all chain axes line up in the stretch direction. The axial ratios calculated from the 730 and 719 cm.−1 bands are given for a cold‐stretched polyethylene film at different degrees of stretch. Axial ratios of over 100:1 may be attained for the crystalline regions of the film. Specific extinction coefficients for the crystalline band at 730 cm.−1 and the amorphous band at 1300 cm.−1 are determined from measurements on polyethylene films of different crystallinities. The latter values is compared with values measured in molten polyethylenes and normal hydrocarbons. The hydrocarbon values do not agree with the polyethylene values. The amorphous contents of a number of polyethylenes as measured by infrared, density, and x‐ray methods are given. Possible reasons for the disagreement between the results are briefly discussed.

The viscosity of molten polyethylenes at different temperatures and over a broad range of shear rates is of interest, not only because of the practical importance in extrusion and molding, but also because of the important relations that may exist between the molecular and flow properties of the polymer. The viscosity of polyethylenes has been studied by a number of technique^,'-^ but, except for the recent studies of Philippoff and Gaskins,' most of the measurements have been carried out over an insufficient range of shear rates. Especially notable is a lack of melt viscosity data at low rates of shear and on well characterized polyethylene fractions.In the characterization and evaluation of commercial polyethylenes, the criterion of melt index,s a measure of the flow properties of molten polyethylene, is commonly used. Whether the melt index values have any correlation with the melt viscosity of various polyethylenes at low shear rates has not been established. This paper describes studies on the melt viscosities of polyethylene by the use of capillary viscometers of simple design. The melt viscosities measured by these viscometers may be considered as having been obtained under Newtonian flow conditions, since very low shear rates were used. Results are given for unfractionated polyethylenes and for several carefully fractionated samples. The melt viscosities of unfractionated polyethylenes have been compared with the corresponding values of the melt index, and the melt index appears to be not an adequate measure of the melt viscosity determined under Newtonian flow conditions. The relationship between melt viscosity and the intrinsic viscosity of the fractions in toluene at 80°C. is discussed. Finally, from the determinations of melt viscosity at a number of temperatures, values of the activation energy of viscous flow were obtained.

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