Formation of the adhesion bond between polyethylene and solids

When a coating of low-density polyethylene on steel or aluminum is heat-treated, the adhesion strength increases linearly from zero to values exceeding the strength of the film. This is caused by the metal-catalyzed oxidation of the polymer in the contact zone by oxygen diffusing through the film.Ural Scientific-Research Chemical Institute, Sverdlovsk. Translated from Mekhanika Polimerov, No. 5, pp. 932–934, September–October, 1970.     

Relation between the internal stresses and the structure of polyacrylonitrile fibers

The change in the structure of a polyacrylonitrile fiber after various stages of processing has been investigated. The existence of three relaxation processes in isometrically heated polyacrylonitrile fibers is demonstrated.Translated from Mekhanika Polimerov, Vol. 4, No. 5, pp. 943–945, September–October, 1968.     

Mechanism of the increase in strength and heat resistance of oriented polymeric materials modified by graft copolymerization with vinyl monomers

The mechanical properties and structures of oriented films and fibers composed of polyethylene, polymethyl methacrylate, and other amorphous and crystalline polymers modified by the synthesis of uniformly distributed graft and block copolymers of methyl methacrylate, acrylonitrile, vinylidene chloride and other monomers have been the subject of a comparative investigation. The effect of the grafted polymers on the molecular mobility, relaxation processes, and solubility of the materials is explained by reference to a universal physical "crosslinking" mechanism. A theory of the interrelation between the structure and physical properties of the materials, the nature of the polymers, and the grafting conditions is developed and used to analyze the experimental data on a broad range of systems.V. I. Lenin Belorussian State University, Minsk. Translated from Mekhanika Polimerov, No. 6, pp. 968–975, November–December, 1973.     

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.     

Temperature-time dependence of the adhesion strength for polymer — Polymer systems

The temperature — time dependence of the adhesion strength has been studied for polymer systems differing in the thermodynamic compatibility of the substrate and adhesive and in the rate of polymerization of the latter. The fracture-activation energies of these systems have been calculated. It is shown that the temperature — time dependence of the adhesion strength varies depending on whether chemical intermolecular forces are responsible for the strength of the joint.Perm Scientific-Research Institute of Polymer Materials. A. M. Gor'kii Ural State University. Translated from Mekhanika Polimerov, Vol. 4, No. 4, pp. 665–671, July–August, 1968.     

Stress on the interatomic bonds near the surface of a polymer

The stresses on the interatomic bonds in the interior and at the surface of polyethylene terephthalate film in uniaxial tension have been determined by means of infrared transmission and reflection spectroscopy. The stresses are found using the shift in the frequency of the atomic vibrations produced by the application of a mechanical load. It is shown that the stresses on some bonds in the specimen reach 700 kgf/mm², i.e., approach their theoretical strength. The concentration of these bonds in a surface layer 1 µ thick is approximately an order greater than the concentration in the interior of the specimen.A. F. Ioffe Physicotechnical Institute, Academy of Sciences of the USSR, Leningrad. Translated from Mekhanika Polimerov, No. 3, pp. 512–514, May–June, 1976.     

Impact strength of high-density polyethylene with various molecular weight distributions

The Charpy impact strength of high-density polyethylene specimens prepared under low pressure with average molecular weight from 60·10³ to 1.5·10⁶ and differing substantially in molecular weight distributions has been studied at room temperature and at –190°C. It is shown that, both at room temperature and at temperature considerably below the glass-formation temperature, the impact strength of polyethylene in the range of molecular weights mentioned is determined mainly by the content of fractions with molecular weights about 10⁵ and more and does not depend on the width of the molecular weight distribution."Plastpolimer" Scientific-Research Association, Leningrad. Translated from Mekhanika Polimerov, No. 5, pp. 919–921, September–October, 1973.     

Strength properties of polymer films subjected to continuous tearing

Using the principle of tearing at a constant velocity and applying this to samples with longitudinal notches, a method of recording the tearing strength as a continuous function of temperature, crystallization time, and other factors which continuously vary the state of a (polymer) film material is developed. The characteristic points of the temperature transitions are determined for a number of polymer films in relation to their mechanical (strength) properties. The crystallization kinetics of polyethylene terephthalate films are analyzed.Scientific-Research Institute of Plastics, Moscow. Translated from Mekhanika Polimerov, No. 2, pp. 257–261, March–April, 1972.     

Effect of supermolecular structure on deformation and strength properties of low-pressure polyethylene

The effect of the supermolecular structure on the mechanical properties of polyethylene was studied. A change in the structure of films was achieved by varying the isothermal crystallization conditions. Films have been prepared from low-pressure polyethylene (LPPE) which have fine spherulitic and lamellar structures. It has been demonstrated that the strength of unorientated films with a fine spherulitic structure is twice that of unorientated lamellar specimens. This difference in the strengths was also retained after orientational elongation to 20 times the length at a high temperature (102°C). The conclusion was reached that the casting of LPPE plays an important part in preparing high-strength orientated polyethylene films.A. F. Ioffe Physicotechnic Institute, Academy of Sciences of the USSR, Leningrad. Translated from Mekhanika Polimerov, No. 6, pp. 963–966, November–December, 1972.     

Study of a polyethylene terephthalate film by an acoustic method

The effect of orientation on the acoustic properties of a polyethylene terephthalate film is examined. In a crystallized, uniaxially oriented film the velocity of ultrasound measured along the orientation axis is lower than in an amorphous oriented film, while the velocity of ultrasound measured at angles of over 35° to the direction of orientation rises after crystallization. Evidently the supramolecular organization of the polyethylene terephthalate film before and after heat treatment is quite different.Scientific-Research Institute of Plastics, Moscow. Voronezh Branch of the Experimental Design Office of Automation. Translated from Mekhanika Polimerov, No. 4, pp. 759–761, July–August, 1972.     

Investigation of the dynamic fatigue of composite polymer materials

The dynamic fatigue of composite film materials has been studied as a function of the frequency and amplitude of deformation. The tests were carried out on a vibration apparatus with a frequency range from 10 to 600 cps. The test objects consisted of foil packaging with a polyethylene backing (foil-film).The dependence of the dynamic fatigue of foil-film on amplitude, frequency, and acceleration was studied. It has been shown that in all cases failure of the material is preceded by cracking of the foil and peeling of the foil from the polyethylene backing at the site of the cracks. The material fails as a result of puncture of the polyethylene backing by the broken edge of the cracked foil.Mekhanika Polimerov, Vol. 1, No. 5, pp. 90–94, 1965     

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 annealing temperature on the mechanical properties of polyethylene terephthalate fiber

The mechanical properties of polyethylene terephthalate fibers stretched at 45 and 110° C have been investigated in relation to annealing temperature. It is shown that for fibers with the maximum degree of stretch the annealing temperature has no effect on mechanical strength. Reduction in the stretch of the fibers leads to an increase in strength upon annealing, and this may be associated with densification of the amorphous zones due to the formation of a large number of intermolecular bonds between the links of the polymer chains.Mekhanika Polimerov, Vol. 3, No. 3, pp. 503–506, 1967     

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.     

Strength of polyethylene and capron as a function of stretch ratio

The relation between the strengths and stretch ratios of a capronmonofilament and a high-pressure polyethylene film has been investigated for various stretching temperatures and stretching rates. The strength, measured at –196°C (_–196), is directly proportional to the stretch ratio (). For a given , _-196 does not depend on stretching temperature and stretching rate. The breaking load at –196° C (for a given initial cross section of the starting unoriented specimen) does not vary with . A possible explanation is offered.Mekhanika Polimerov, Vol. 3, No. 4, pp. 591–595, 1967     

Effect of bond strength on the breaking strength of two-layer cellophane film materials

The effect of bond strength on over-all tensile strength has been investigated in relation to two-layer materials consisting of cellophane film cut in the longitudinal and transverse directions and bonded with polyisobutylene. It is shown that there is a linear correlation between the bond strength and the combination hardening effect. The breaking stress of two-layer materials is higher than that of the individual films. A possible explanation of this effect is proposed.Mekhanika Polimerov, Vol. 3, No. 1, pp. 89–94, 1967     

Residual stresses in glass-reinforced polyethylene

The variation of the axial and radial components of the residual stresses in fiber-reinforced polyethylene with distance from the fiber has been investigated. It is shown that, irrespective of the agent employed, coupling leads to an increase in stresses. The values obtained for the residual stresses are compared with the adhesion strength determined by the shearing method. The effect of a structure-forming agent on the residual stresses is investigated.Mendeleev Moscow Chemical Engineering Institute. Translated from Mekhanika Polimerov, No. 4, pp. 722–724, July–August, 1971.     

Long-term strength of thermoplastics in air and a physiological solution

The effect was examined of a physiological fluid on the long-term strength of P-12 polyamide CTD copolymer, fluorinated polymethylmethacrylate PMMAF and cast polyethylene terephthalate (PETP). It has been found that the durability curves for the thermoplastics in air and the physiological fluid are described by an exponential function which has an aberration in the region of low stresses.N. N. Priorov Central Scientific-Research Institute of Traumatology and Orthopedics, Moscow. Translated from Mekhanika Polimerov, No. 6, pp. 1044–1047, November–December, 1972.     

Two-dimensional extension of polyethylene and polypropylene film

The two-dimensional extension of polyethylene and polypropylene film has been investigated by optical microscopy. It has been established that there is no two-dimensional plastic flow (two-dimensional necking) and that failure is quasi-brittle in character. In a small region near the cracks that develop, uniaxial orientation of the polymer associated with stress concentrations near the crack tip is observed. Measurements show that the ultimate stress in two-dimensional extension is close to the necking stress in uniaxial tension.Mekhanika Polimerov, Vol. 3, No. 1, pp. 41–45, 1967     

Study of the supermolecular transitions associated with the reorientation of high-pressure polyethylene film

Small-angle optical and X-ray diffraction techniques have been used in a comparative study of the processes of orientation and reorientation of high-pressure polyethylene film. It is shown that at large stretch ratios both processes are governed by the same laws. In these supermolecular transitions it is possible to observe spherulite-macrofibril conversions during orientation and macrofibril-macrofibril conversions during reorientation, a direct genetic relationship being preserved between the dimensions of the starting spherulites or macrofibrils and the dimensions of the macrofibrils formed by stretching. However, the major period of the oriented film, the basic element of the microfibrils forming the macrofibril, is independent of the major period of the starting film and depends only on the temperature at which stretching is carried out.Institute of High-Molecular Compounds, Academy of Sciences of the USSR, Leningrad. Translated from Mekhanika Polimerov, No. 5, pp. 771–777, September–October, 1969.