Dependence of the acoustic and mechanical properties of polyethylene on temperature and cyclic cooling and heating

The low-temperature stability of polyethylene is confirmed by acoustic and mechanical investigations. Data are given on the dependence of the acoustic and mechanical properties of polyethylene on temperature and repeated cyclic cooling to –50° and heating to +60°C, together with information on the change in Poisson's ratio and volume during deformation.Mekhanika Polimerov, Vol. 1, No. 3, pp. 145–150, 1965     

Polyethylene autohesion under simultaneous deformation

The strength of polyethylene autohesion joints obtained by simultaneous deformation is compared with that of compressed specimens of monolithic LPP. The probable mechanisms of polyethylene autohesion under these conditions are discussed.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, Vol. 4, No. 4, pp. 656–660, July–August, 1968.     

Temperature dependence of the deformation properties of compositions based on polyethylene and polyisobutylene

The temperature dependence of the deformation properties (deformability and recoverability) of compositions based on low-density polyethylene and polyisobutylene has been investigated. For two-component polyethylene—polyisobutylene systems this dependence varies with the component ratio. Introducing a filler (talc) reduces the recoverability of the compositions owing to increases in both the delayed high-elastic deformation and the flowability. The deformation properties of compositions plasticized with paraffin change abruptly at the melting point of the latter.Moldavian Scientific-Research Institute of the Food Industry, Kishinev. Translated from Mekhanika Polimerov, No. 4, pp. 758–760, July–August, 1971.     

Adhesion of polyethylene in simultaneous deformation

The strength of the joints arising as a result of the mutual deformation of polyethylene specimens is studied, and it is shown that mutual deformation can lead to the formation of a strong joint.Mekhanika Polimerov, Vol. 2, No. 4, 574–579, 1966     

Conformational transitions associated with the deformation of oriented polyethylene fibers

It is shown that, as the elastic deformation of the polymer increases, the number of gauche isomers in oriented polyethylene fibers decreases linearly.A. F. Ioffe Physicotechnical Institute, Academy of Sciences of the USSR, Leningrad. Translated from Mekhanika Polimerov, No. 1, pp. 170–172, January–February, 1970.     

Thixotropy of filled-polyethylene melts subjected to periodic shear deformation

As a result of the action of periodic finite-amplitude shear deformations filled high-pressure polyethylene melts exhibit thixotropic properties. The effect of the previous deformation history on the frequency dependence of the complex dynamic shear modulus is investigated.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR Riga. Translated from Mekhanika Polimerov, Vol. 4, No. 5, pp. 927–931, September–October, 1968.     

The optico-deformation effect in irradiated polyethylene

The absorption of light by polyethylene film subjected to extension and electron bombardment has been investigated on the wavelength interval 220–800 nm. It is shown that irradiation and illumination by a xenon lamp during extension reduce the stresses corresponding to the beginning of high-elastic deformation of the polyethylene. It is established that deformation and electron bombardment lead to an increase in the light absorption of the polyethylene film with absorption maxima at 245 and 290 nm. It is assumed that the nature of the effect is associated with reorientation of the macromolecule chains under the influence of mechanical stress and the appearance of allyl radicals-CH₂-CH CH-H-CH₂-.Institute of Physical Chemistry, Academy of Sciences of the USSR, Moscow. Translated from Mekhanika Polimerov, No. 3, pp. 451–455, May–June, 1972.     

Effect of the size of the specimen cross section on the long-term strength of polyethylene

The scale effect has been investigated in relation to the long-term strength of specimens of high-density polyethylene. Time dependences of the tensile strength at ordinary temperatures have been obtained. It is shown that the long-term strength depends on the dimensions of the specimen cross section. The deformation of the specimens depends on their size and the shape of the gage cross section.Higher Chemical Technology Institute, Sofia. Translated from Mekhanika Polimerov, No. 4, pp. 741–743, July–August, 1973.     

Relation between deformation and rotational isomerism

In uniaxially oriented polyethylene and polyethylene terephthalate films conformational transitions were studied by the absorption IR-spectroscopy method during deformation of the specimens carried to rupture in a wide range of temperatures and with different loading methods. It is shown that upon elongation of the polymers the concentration of trans isomers increases and that of gauche isomers decreases. A linear unique relation is obtained between the number of rotational isomers and magnitude of deformation in the amorphous parts of the investigated polymers. It is hypothesized that the conformational transitions determine the magnitude of deformation of amorphous-crystal-line polymers.A. F. Ioffe Physicotechnical Institute, Academy of Sciences of the USSR, Leningrad. Translated from Mekhanika Polimerov, No. 6, pp. 1077–1080, November–December, 1975.     

Bulk deformation during linear extension of certain solid polymers

This article describes an experimental study of the bulk deformation in a forward-and-reverse creep cycle of low-density polyethylene and plasticized acetyl celluloses under stresses beyond the linearity region of the viscoelastic properties.All-Union Scientific-Research Institute of Synthetic Resins, Vladimir. Translated from Mekhanika Polimerov, No. 2, pp. 352–354, March–April, 1974.     

The vibration-time analogy

The vibrocreep of low-density polyethylene has been investigated in nonisothermal deformation regimes on the frequency range 150–400 Hz at variable stress amplitudes from 3.1 to 5.8 kgf/cm². The validity of the time-vibration superposition principle has been tested.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, Vol. 4, No. 5, pp. 793–798, September–October, 1968.     

Effect of tensile deformation on the melting point,specific volume,and volume coefficient of expansion of polyethylene

Disks of polyethylene of different density were subjected to plane tensile deformation along eight axes. It was established by volume dilatometry that the melting interval of the deformed plates had been shifted into the region of higher temperatures. It follows from the behavior of the specific volume increment associated with melting that deformation leads to the destruction of some of the low-melting structures and increases the content of higher-melting structures.Lugansk Machine-Building Institute. Translated from Mekhanika Polimerov, No. 6, pp. 1102–1104, November–December, 1970.     

Breakdown of high-pressure polyethylene in bulk

The mechanism of polyethylene breakdown in bulk at low initial stresses, relaxing during the breakdown process, is discussed. Optical, electron, and scanning microscopy were used to investigate the surface of disintegrating polyethylene for cable insulation. It was found that in prolonged tests the breakdown surface has an appearance typical for the brittle breakdown of glass polymers. It was also established that in the case of brittle breakdown with clearly expressed mirror-like and rough zones, the disintegration process passess passes through an evident deformation of the surface layer and the formation of micronecks prior to rupture.Translated from Mekhanika Polimerov, No. 5, pp. 935–936, September–October, 1972.     

Effect of surface-active agents on the friction properties of polymers

The effect of surface-active agents on the friction properties of plastics has been investigated in relation to the example of an aqueous solution of alkyl phenol polyethylene glycol ether (OP-10) and polymethyl methacrylate. In the presence of a surface-active agent, as a result of adsorption plasticization, the deformation is localized in a thin plasticized layer without affecting the underlying layers of plastic.Moscow Lenin State Pedagogical Institute, Problem Laboratory of Polymer Physics. Translated from Mekhanika Polimerov, No. 5, pp. 927–929, September–October, 1970.     

Harmonic distrotions under nonlinear periodic deformation of fluid polymers

Conclusions 1. It has been shown for a number of viscoelastic fluid systems that under nonlinear periodic deformation, the contribution of the third harmonic of the stress to the fundamental does not exceed 20% of the amplitude.2. In the case of clay soil and melt of filled polyethylene, the shape of the stress waves is essentially definable by the relative phase angle of the third harmonic of the stress and is practically independent of the deformation amplitude in a growing nonlinear range of deformation.3. In the case of the polyethylene melt, the amplitude dependence of the phase angles of the stress harmonics is in satisfactory agreement with the analysis of model I. With increasing deformation amplitude, the modulus vector of the first harmonic rotates counterclockwise and remains in the first trigonometric quadrant; the modulus vector of the third harmonic passes from the second to the third quadrant, and the modulus vector of the fifth harmonic passes from the second to the fourth quadrant via the third.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 5, pp. 893–898, September–October, 1978.     

Variation of the frequency and amplitude of periodic deformation in a Weissenberg rheogoniometer

The stresses that develop in the material due to changes in the frequency or amplitude of periodic deformation in a Weissenberg rheogoniometer are described. Examples of stress buildup and relaxation are presented for a filled low-density polyethylene melt.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 5, pp. 936–938, September–October, 1970.     

Molecular mechanism of oriented crystalline polymers

It is shown with reference to linear polyethylene that the deformation of an oriented crystalline polymer takes place as a result of elongation of the coiled parts of the macromolecules in the amorphous zones owing to conversion of gauche into extended trans isomers. The decrease in coiled isomer content when the specimen is deformed by approximately 5% is accompanied by a small number of chemical bond breakages. Repeat deformation by the same amount does not result in any additional breakage of polymer chains.A. F. Ioffe Physicotechnical Institute, Academy of Sciences of The USSR, Leningrad. Translated from Mekhanika Polimerov, No. 4, pp. 584–588, July–August, 1973.     

Study of the prefracture states of rigid polymers 1. Forced high-elastic deformation

It is shown that in the process of extension specimens of a rigid unoriented polymer — polyethylene terephthalate — go over into the oriented state before failure. Various cases of transition to the oriented state are considered: with the formation of a neck and deformation bands, with and without loss of continuity. The degree of molecular orientation of the specimens and their fracture conditions are estimated.A. F. Ioffe Physicotechnical Institute, Academy of Sciences of the USSR, Leningrad. Translated from Mekhanika Polimerov, No. 1, pp. 8–14, January–February, 1976.     

Rheology and molecular structure of polyethylene melts 1. Melt identification from mechanical properties

It is proposed to use periodic deformation for the identification of the molecular structure of polyethylenes. By comparing the dependence of the complex and apparent viscosities on frequency and shear rate, respectively, it is shown that these functions are not equivalent for low-density polyethylene melts. The need for a numerical characteristic of the rheological functions, which should be related to the numerical characteristics of the molecular structure of the polymer, is established. The possibilities of using generalized relations for investigating the molecular structure are discussed. It is shown that the dynamic viscosity of polyethylene melts, described by a three-parameter equation, quite accurately reflects the viscoelastic properties of polyethylene melts and makes it possible, with the aid of the calculated function of the relaxation spectrum, to construct a frequency dependence of the modulus corresponding to the experimental data. Three numbers characterizing the viscoelasticity of polyethylene, which must be related with three molecular characteristics, are established.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 3, pp. 523–532, May–June, 1975.     

Characteristic features of the deformation process on creep and secondary creep of polymers under conditions of monaxial tensioning. Part I

Experiments carried out in the field of linear and nonlinear creep of a filled polyethylene and Teflon resin, including two complete cycles of creep and deformation recovery at monaxial tensioning, show that the bulk deformations (t) change nonmonotonically, and relationships computed by summation of terms containing a function of time cannot be used to approximate the deformation.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 3, pp. 399–405, May–June, 1974.