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.     

Evidence for a Phase Transition in Three-Dimensional Lattice Models

It was recently discovered that an eigenvector structure of commutative families of layer-to-layer matrices in three-dimensional lattice models is described by a two-dimensional spin lattice generalizing the notion of one-dimensional spin chains. We conjecture the relations between the two-dimensional spin lattice in the thermodynamic limit and the phase structure of three-dimensional lattice models. We consider two simplest cases: the homogeneous spin lattice related to the Zamolodchikov–Bazhanov–Baxter model and a chess spin lattice related to the Stroganov–Mangazeev elliptic solution of the modified tetrahedron equation. Evidence for the phase transition is obtained in the second case.     

The half-widths of the bands due to the skeletal vibrations of polyethylene molecules,free and under an applied load

The third-order phonon interactions in free polyethylene chains and polyethylene chains under load have been analyzed to obtain the theoretical temperature dependence of the half-widths of the bands due to the skeletal vibrations potentially active in the absorption and Raman spectra. The problems of the harmonic and anharmonic vibrational analysis of polymers under load are discussed.A. F. Ioffe Order of Lenin Physicotechnical Institute, Academy of Sciences of the USSR, Leningrad. Translated from Mekhanika Polimerov, No. 1, pp. 3–11, January–February, 1972.     

Effect of γ radiation on the long-term strength of polyethylene terephthalate

By analyzing the results of a study of the long-term strength and isometric heating diagrams of polyethylene terephthalate exposed to radiation it has been established that irradiation leads to a decrease in the short-time and long-term strength of the polymer and to the misorientation of its structural elements. The coefficient in the long-term strength equation increases with the radiation dose, while U₀ varies along a curve with a maximum at small doses.Lenin Tadzhik State University. Translated from Mekhanika Polimerov, No. 2, pp. 239–243, March–April, 1973.     

Effect of electron irradiation on the mechanical and thermal properties of some polymer materials

The effect of electron irradiation on the mechanical properties (deformability) of polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE), polyimide (PI), and Fenilon (Fe) films, as well as the thermal properties (heat conductivity and capacity) of PTFE is studied experimentally. The thickness of the films was 40–50 m. Mechanical tests showed that polyimide films were more resistant to radiation than the other films. The investigation of the changes in the thermal properties of PTFE due to electron irradiation revealed that the phase transitions observed at temperatures of 293 and 303 K in unirradiated PTFE were shifted to lower temperature regions.Abai Alma-Ata State University, Kazakhstan. Translated from Mekhanika Kompozitnykh Materialov, Vol. 34, No. 5, pp. 683–689, 1998.     

Applicability of the superposition principle to periodically loaded polyethylene

The lifetime of isotropic specimens of high-density polyethylene subjected to periodic tensile loading and "recovery" has been investigated. The lifetime determined without allowance for the time for "recovery" of the polymer is greater than the lifetime under constant load; under periodic application of a constant stress the lifetime increases exponentially with increase in the length of the "recovery" interval; at the same "recovery" time the life-time decreases exponentially with increase in the time under load during each cycle.Higher Chemical Engineering Institute, Sofia. Translated from Mekhanika Polimerov, No. 6, pp. 1009–1013, November–December, 1970.     

Generalization of the Goryachev-Chaplygin gyrostat in quantum mechanics

A generalization of the Goryachev-Chaplygin top, which admits the application of the quantum method of the inverse scattering problem, is constructed. The additional parameter introduced plays the same role as the spin of a node in spin chains.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova AN SSSR, Vol. 164, pp. 134–141 (1987).The authors thank E. K. Skylanin for helpful discussions of the quantum method of the inverse problem.     

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.     

Experimental study of the effect of laser beams on transparent dielectrics

The destruction of transparent polymer blocks by laser action is investigated. It is established that microscopic breakdown regions, whose size remains constant in time, are formed in the zone of action of the laser pulse. The intensity of the radiation from these microregions varies with time and corresponds to a temperature of (2–4) · 10³°K. The microregions are located near, but not at the centers of the cracks. The previously irradiated region of the polymer is shown to be in a state of stress. The possibility of thermal explosion with subsequent crack formation is evaluated. The continued development of the cracks as a result of repeated irradiation is studied. The temperature of the gas in the large cracks has been measured and found to exceed room temperature by 15°. The molecular weight has been measured before and after irradiation and found to decrease. The effect of laser beams of various wavelengths is considered. The rate of growth of the disk-shaped cracks has been measured.Institute of Problems of Mechanics, Academy of Sciences of the USSR, Moscow. Translated from Mekhanika Polimerov, No. 5, pp. 827–835, September–October, 1969.     

The life of loaded rubbers

It has been demonstrated experimentally that the dependence of failure time on stress (in the coordinates log –log and log –) for loaded rubbers based on SKN-26 and SKN-40, elastomers, natural rubber, polychloroprene rubber and SKMS-30 ARKM-15 with channel and lamp blacks, fine colloidal silica, "Aerosil," and whiting has a discontinuity. The assumption has been made that the discontinuity is the result of a change in the nature of the failure, associated with greater or smaller rupture of chemical bonds. This is corroborated by the difference in the values of the apparent activation energy and its dependence on the stress in the two parts of the curve, as well as the displacement of the discontinuity into the shorter failure times region with an increase in the test temperature and a reduction in the amount or activity of the filler.Scientific-Research Institute of the Rubber Institute, Moscow. Translated from Mekhanika Polimerov No. 3, pp. 539–541, May–June, 1970.     

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.A. F. Ioffe Physicotechnical Institute, Academy of Sciences of the USSR, Leningrad. Translated from Mekhanika Polimerov, No. 3, pp. 433–436, May–June 1970.     

Equations of motion of rotating bodies in general relativity in the post-Newtonian approximation

Equations of the translational and rotational motion of two bodies possessing intrinsic angular momentum are obtained by the Einstein—Infeld—Hoffmann method in the post-Newtonian approximation. The results agree with the Kerr metric expressed in a harmonic system of coordinates with symmetry of the spatial components of the metric with respect to its indices and with a conservation law for the total angular momentum that is the sum of the orbital and spin angular momenta, and they give the correct passage to the limit to the equation of motion of a test particle with spin.All-Russia Institute of Experimental Physics. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 101, No. 1, pp. 123–135, October, 1994.     

Effect of γ radiation on the distribution of stresses in polymers

Infrared spectroscopy has been used to study the effect of -radiation on the distribution of an applied stress over the individual polymer chains. It has been shown that, as the irradiation dose is increased, the maximum stress on the bonds which are ruptured is attained at a lower value for the mean stress applied to the sample.V. I. Lenin Tadzhik State University, Dushanbe. Translated from Mekhanika Polimerov, No. 2, pp. 214–217, March–April, 1975.     

Influence of prestressing on the service lives of polymers

The authors have investigated changes in the lifetimes of polymethylmethacrylate, polyethylene, and polystyrene resulting from prestressing. They show that, according to the temperature, stressing can cause either an increase or a decrease in the lifetime.A. F. Ioffe Physicotechnical Institute, Academy of Sciences of the USSR, Leningrad. Translated from Mekhanika Polimerov, No. 1, pp. 176–178, January–February, 1972.     

Elasticity of the crystal lattice of polyethylene terephthalate

The elasticity of the crystal lattice of polyethylene terephthalate was studied along and across the axes of the polymer molecules. The elastic modulus across the chains depended on the degree of crystallinity and the interplane distances in the directions of thea and b parameters of the unit cell. The nature of the elastic deformation in the crystal lattice was analyzed, and its elastic modulus along and across the axes of the chains was calculated. On loading biaxially oriented amorphous-crystalline polymers with a tensile stress applied in the direction of one of the orientation axes of the polymer, the stresses in the crystallites oriented along and across the external applied force and the amorphous regions in series with them were equal to the stress in the sample averaged over the cross section.Deceased.Translated from Mekhanika Polimerov, No. 6, pp. 982–986, November–December, 1972.     

Behavior of singularities of a nonsteady wave field near a caustic in a medium with a variable velocity

The Cauchy problem for the wave equation is considered. A discontinuity in the form of a homogeneous generalized function of degree is given at the initial front. An asymptotic solution is found in the vicinity of the space-time caustic in the interaction of the discontinuity surface with the caustic. The solution is represented in the form of a certain combination of the generalized function with associated Legendre polynomials.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova AN SSSR, Vol. 156, pp. 98–108, 1986.     

Spin chains and gauge-string duality

We discuss the string picture behind the integrable spin chains governing the evolution equations in the Yang—Mills theory. We show that the one-loop correction to the dilatation operator in the N=4 theory can be expressed in terms of two-point correlation functions on the two-dimensional worldsheet. Using the relation between the Neumann integrable system and spin chains, we argue that the transition to the finite gauge-theory coupling implies discretization of the worldsheet. We conjecture that the string-bit model for the discretized worldsheet corresponds to the representation of the integrable spin chains in terms of the separated variables.Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 142, No. 2, pp. 179–196, February, 2005.     

Infrared spectroscopic study of the prefracture state of rigid polymers

A correspondence has been established between the effects of stress and temperature on the half-width and the position of the maximum of the 972-cm^–1 absorption band for polyethylene terephthalate. It is shown that the prefracture state of polyethylene terephthalate is a softened state.A. F. Ioffe Physicotechnical Institute, Academy of Sciences of the USSR, Leningrad. Translated from Mekhanika Polimerov, No. 3, pp. 520–523, May–June, 1976.     

Improvement of the deformative characteristics of poly-β-hydroxybutyrate by plasticization

Plasticized systems of poly--hydroxybutyrate (PHB) are studied, where low-molecular compounds traditionally used for this purpose for various systems, i.e., dioctyl sebacate, dibutyl sebacate, polyethylene glycol, Laprol 503, and Laprol 5003, are used as plasticizers. All of them are nontoxic and biodegradable compounds with a similar molecular weight and comparable polarity of molecules. The main purpose of this study is to improve the deformability of PHB taking into account the structural changes in plasticized PHBs. The plasticizers chosen are completely compatible with the polymer and form a monophase system up to a plasticizer content of 15–20%. An increase in the plasticizer content allows us to increase efficiently the deformability of the polymer (the relative breaking elongation of PHB at room temperature grows up to 250–300%). At the same time, the system becomes considerably weaker and therefore there is no point in increasing the concentration of plasticizers by more than 20 wt.%. According to the data obtained from DSC measurements, the ratio between the amorphous and crystalline regions of PHB in the presence of plasticizers mentioned remains practically constant. The changes in the elastic properties of PHB/low-molecular plasticizer systems are mainly due to efficient weakening of intermolecular interactions in the amorphous regions of the polymer. A slight decrease in the crystalline order of PHB is of secondary importance.Institute of Polymer Materials, Riga Technical University, Riga, LV-1048, Latvia. Translated from Mekhanika Kompozitnykh Materialov, Vol. 35, No. 4, pp. 527–538, July–August, 1999.     

Effect of aging on the lifetime of industrial polyimide film

Results are given of a study of the thermomechanical properties of industrial polyimide film at constant mechanical-stress values and on nonlinear change in temperature with time. The effect of thermal aging and of irradiation with neutrons on polyimide (PM) film is examined. From the experimental data obtained, the possibility is presented of predicting the "service life" of material over a wide range of mechanical loads and temperatures.S. M. Kirov Polytechnic Institute, Tomsk. Translated from Mekhanika Polimerov, No. 6, pp. 1046–1049, November–December, 1974.