Oriented Polymer Films Research Articles

Physical interpretation of the anisotropy and temperature dependence of the piezoelectric constant of polyvinylidene fluoride

The anisotropy and the anomalous temperature dependence of the piezoelectric constants of polyvinylidene fluoride can be quantitatively explained in a simple model. As a result the transverse piezoelectric effect originates in the large Poisson ratio of the highly oriented polymer film.

The role of surface in the atomic mechanism of fracture of polymers

Highly oriented polymer films were stretched along the axis of orientation. Using i.r. transmission and reflection spectroscopy, the scission of polymer molecules under stress in the volume and in the surface layer ~ lμm thick was studied. The accumulation of scissions of chemical bonds in the surface layer was found to be at least an order more intense than that in the volume. It is shown that this phenomenon is due to considerable heterogeneity of external load distribution over chemical bonds near the surface. It is inferred that the surface plays a leading role in the fracture mechanism of polymers. The intensity of the intermolecular interactions in the volume and on the surface of polymers was studied and was found to be lower in the surface layer. It is proposed that the role of surface in the fracture process results from weakening of the intermolecular interactions.

An infrared spectroscopic study of the breakdown of polymers under load

It has been found that when a uniaxial tension is applied to highly oriented polymer films of polypropylene, polyvinyl alcohol, or polyethylene, an increase in the intensity of the absorption bands corresponding to the vibrations of the C=O carbonyl groups is observed. These groups are produced by the oxidation of the free radicals formed on the rupture of the chemical bonds under the influence of mechanical stress. The composition of the products has been studied, and their concentration has been estimated. Curves giving the accumulation of C=O groups with time at constant load and with increase in stress for a fixed period of time under load have been studied. It is suggested that the rate of accumulation of C=O groups in both cases is determined chiefly by the rate of rupture of the molecular chains under load.

Scattering of light from oriented polymer films. II

AbstractA statistical theory for the scattering of light from oriented polymer films is developed in terms of angularly dependent generalized correlation functions. Numerical calculations of scattering patterns are carried out for special cases. The scattering depends upon two types of distributions describing (1) the orientation distribution of optical axes of scattering elements and (2) the angular dependence of correlation in orientation between pairs of optic axes. These distributions are expanded in Fourier series (in a two‐dimensional treatment), the coefficients of which are functions of elongation and describe the elongation dependence of the scattering patterns.

Equipment for the uniaxial orientation of polymer films

Equipment for the uniaxial orientation of polymer films

Effect of birefringence on low‐angle light‐scattering patterns from oriented polymer films. II

AbstractA quantitative theoretical calculation is made of the effect of birefringence of the surrounding medium on the light‐scattering pattern from a two‐dimensional anisotropic spherulite. The calculated modification of the light‐scattering pattern is in accord with the prediction previously made on the basis of qualitative considerations and model experiments.

Effect of certain working media on spontaneous orientation of polymer films

A study was carried out of the tensile strength of plane-oriented amorphous and crystalline polymer films previously acted on by water and aqueous solutions of salts and organic acids. The dependence of strength on the time of exposure to the action of liquids was found to be extremal in character. X-ray diffraction analysis and optical measurements established that the increase in strength is accompanied by an increase in the optical anisotropy of polymers and is associated with supplementary spontaneous orientation of a part of their structural elements.

Effect of birefringence on low‐angle light‐scattering patterns from oriented polymer films

AbstractThe effect of birefringence of a polymer film upon its photographic light‐scattering pattern is considered for the case of a single, anisotropic, two‐dimensional spherulite imbedded in a birefringent matrix. It is shown that for the case of a polarizer and analyzer crossed at +45° and −45° to the analyzer, the scattering pattern is modified in a manner agreeing with experimental observation.

Light Scattering by Oriented Dipoles

Soleillet's theory of light scattering by a random aggregation of dipoles has been extended through Mueller matrix algebra to formulate a matrix for light scattering by an array of oriented dipoles. The proposed matrix reveals certain interesting characteristics of dipolar scattering. Linear relations between the parameters of the Stokes' vectors of incident and scattered beams have been obtained for the case of oriented dipoles. The applicability of the matrix has been indicated in the case of radiations in the horizontal plane from an ungrounded antenna or an array of antennas oriented in the vertical plane, and in polarization studies of light scattering by oriented polymer films and fibers which have completely aligned long-chain molecules.

Effect of birefringence on light scattering from oriented systems

AbstractThe effect of birefringence on the intensity of polarized scattered light from an oriented polymer film is analyzed on the basis of a model in which the scattering element is imbedded in a homogeneous birefringent matrix. The scattering intensity is shown to depend upon the polarizer and analyzer angles, the scattering angles, the sample birefringence and thickness, and the scattering coefficients for the four polarization combinations. Computer calculations for reasonable values of these parameters indicate that these corrections can be quite appreciable.

Heat conductivity anisotropy of oriented polymer films

Heat conductivity anisotropy of oriented polymer films

Light Scattering from Oriented Polymer Films

A theory of scattering of light by oriented films of crystalline high polymers is developed. This describes the variation in the dependence of scattering upon the angle between the incident and scattered beam, the film tilt and azimuthal angles, and the orientation directions of polarizers in the incident and scattered beams upon sample parameters. These are the sizes of the density and orientation fluctuations, correlation distances for each, and parameters describing the average orientation of the optic axes of the scattering elements of the film. Methods for experimentally evaluating these parameters are proposed and are illustrated for polyethylene films of differing degree of biaxial orientation.

Anisotropy of the mechanical properties of uniaxially oriented polymer films

Anisotropy of the mechanical properties of uniaxially oriented polymer films

Determination of molecular orientation in polymer films by infrared spectrophotometry

Determination of molecular orientation in polymer films by infrared spectrophotometry

X‐Ray determination of the crystallite orientation distributions of polyethylene terephthalate films

AbstractA set of definitions is proposed to describe uniquely the six types of orientation possible in semicrystalline polymeric films. Oriented polymer films were studied by a new x‐ray diffraction technique which permits rotation of a sample about a number of independent axes yielding orientation distributions of the crystalline regions. The definitions and the method of measuring the crystallite‐orientation distributions have been applied to polyethylene terephthalate films.

Diffusion and swelling of high polymers. Part III.—anisotropic swelling in oriented polymer film

Diffusion and swelling of high polymers. Part III.—anisotropic swelling in oriented polymer film