Puncture alloplasty of the tendon-capsule part of the external rotators of the shoulder and subacromial bursa by fast-setting polyurethane SKU-PFL in tendonitis and chronic lacerations of the tendon of the musculus supraspinatus (clinical-biomechanical investigation)

A method is proposed for alloplastic restoration of the dynamic stability of the shoulder joint with the use of fast-setting polyurethane SKU-PFL in the most common injuries of the tendoncapsule apparatus of the shoulder joint — tendonitis and lacerations of the musculus supraspinatus. A biomechanical substantiation of the proposed method of treatment is given.     

Effect of liquid media on the weight,hardness, volume,and deformation of polyurethane

The resistance of polyurethane to aviation fluids and water has been investigated. The deformation of polyurethane directly exposed to these fluids has been determined. It is shown that polyurethane is insoluble in aviation fluids and sensitive to the action of acids and RDV liquid; it has good resistance to water and atmospheric conditions. The deformation that develops in the first hours of exposure subsequently shows little change.Kiev Institute of Civil Aviation Engineers. Translated from Mekhanika Polimerov, Vol. 5, No. 2, pp. 342–344, March–April, 1969.     

Deformation and sliding friction of polyurethane in the presence of a lubricant

The relation between coefficient of friction and elastic and high-elastic strains is investigated with reference to polyurethane subjected to friction in various liquid media. It is shown that a definite relationship between these parameters does exist. The effect of various liquids on the elastic and high-elastic deformation of polyurethane is studied.Kiev Institute of Civil Aviation Engineers. Translated from Mekhanika Polimerov, Vol. 5, No. 2. pp. 357–359, March–April, 1969.     

Investigation of fatigue damage in polymer films by the method of light scattering

Conclusions In cyclic loading of the investigated polyurethane there originates a polydisperse system of microdefects with nonspherical shape, in consequence of which the light scattering increases irreversibly. The method of light scattering is sufficiently sensitive for determining the relative concentrations and dimensions of microdefects that are smaller than the wavelength of light. It was shown that the predominant mechanism of failure of polyurethane is the increased concentration of microdefects whereas their dimensions change only imperceptibly.Translated from Mekhanika Kompozitnykh Materialov, No. 5, pp. 910–917, September–October, 1984.     

Thermomechanical properties of fibrous nonfabric materials of the adhesive type with polyurethane binders

The thermomechanical properties of nonfabric materials of the adhesive type with polyurethane binders were studied in relation to the nature of the fibers, the interaction between the polymers of the binder and the fiber, and the amount of polyurethane in the sample material. The thermomechanical properties were considerably influenced by the manner in which the polymers of the fiber and the binder interacted; this depended on the nature of the fiber and its capacity to swell in an aqueous medium. This latter (swelling capacity) leads to a considerable penetration of polyurethane into viscose fiber, on which the polyurethane has a considerable plasticizing effect.Moscow Textile Institute. Translated from Mekhanika Polimerov, No. 3, pp. 550–552, May–June, 1970.     

Fatigue strength at subzero temperature of films made of polymer mixtures based on thermoplastic polyurethane

Conclusions The investigations show that the flexing resistance of the films of thermoplastic polyurethane at the subzero temperatures can be increased several times by mixing polyurethane with rubber with a low glass transition temperature. As a result of the heterogeneity of the structure in the mixtures containing the optimum or almost optimum amount of rubber, cyclic bending is accompanied by the formation of a large number of microdefects but the conditions for formation of a macrocrack are less favorable, whilst in pure polyurethane the main crack can form and propagate in the presence of far less extensive volume damage. The design of the small-angle light diffractometer proposed in this work can be used successfully for examining fatigue damage in nonuniformly loaded specimens. The quality of the resultant mixtures can be inspected by measuring the integral optical properties or light scattering indicatrices.Translated from Mekhanika Kompozitnykh Materialov, No. 6, pp. 977–984, November–December, 1987.     

Effect of liquid media on the deformation of the surface layers of a polymer-metal pair in sliding friction

The relation between the high-elastic component of polyurethane deformation and the deformation of the surface layers of metals has been investigated for sliding friction in various media. The surface layers of polymer and metal are plastically deformed. There is a certain correlation between the coefficient of friction and the amount of deformation.Kiev Institute of Civil Aviation Engineers. Translated from Mekhanika Polimerov, No. 1, pp. 147–149, January–February, 1970.     

Tensile behavior of plastic foams

The tensile stress-strain diagram of plastic foams is calculated on the basis of a previously proposed 14-faced cell model. An S-shaped inflection due to the flexural deformations of the ties is detected on the initial section of the diagram. It is shown that for closed-celled foams this inflection may degenerate. The results of testing PVC and polyurethane foams (volume content of polymer base about 3–6%) prove to be in satisfactory agreement with the calculations.Vladimir Scientific-Research Institute of Synthetic Resins. Translated from Mekhanika Polimerov, No. 4, pp. 670–675, July–August, 1971.     

Rate of resorption of polymeric implants in relation to biological fluid hydrodynamics

The dissociation of water-insoluble macromolecular complexes dissociating with the formation of soluble macromolecules is theoretically examined. The dissociation dynamics in static and open systems are compared (model media and the living organism, respectively). The effect of the rate of metabolic processes and the water-salt balance on the dissociation-association equilibrium in the organism is predicted. The effect of the tension in thread formed from a polycomplex on its life is analyzed for constant and relaxing stress. The use of the theory for predicting the resorption times of polymeric implants (sutures) in the living organism is demonstrated.Paper presented at the First All-Union Conference on Engineering and Medical Biomechanics, Riga, October, 1975.All-Union Scientific-Research Institute of Medical Polymers, Moscow. Translated from Mekhanika Polimerov, No. 4, pp. 740–743, July–August, 1975.     

Effect of the medium of a living organism on the vulcanization of silicone rubber

Conclusions The vulcanization process of SKTN silicone rubber in a living organism significantly depends on the chemical nature of the catalyst. The organism accelerates this process if cross-linking of the rubber occurs in the presence of tin dioctyldilaurate (Sn⁴⁺) and may retard this process if tin octoate (Sn²⁺) serves as the catalyst.Presented to the Second All-Union Conference on Biomechanics, Riga, April 1979.Translated from Mekhanika Kompozitnykh Materialov, No. 2, pp. 345–349, March–April, 1980.     

Properties of polyurethanes SKU-10 under pulsed and static loads

Conclusion The investigations of the optical and mechanical properties of modifications of polyurethane SKU-10 under static and pulsed loads and the results of solving the model problem of the nonstationary stressed state permit concluding the possibility of using these materials for solving by the photoelasticity method engineering problems of the stressed state of structural elements and structures under static and pulsed loads?Translated from Mekhanika Kompozitnykh Materialov, No. 1, pp. 121–128, January–February, 1981.     

Model analysis of the cellular structure of plastic foams of the polyurethane type

A mathematical analysis of the mechanical properties of foam materials at the cellular structure level is given on the basis of a proposed 14-faced model of the cell of an opencelled plastic foam of the polyurethane type. The results obtained are shown to be in good agreement with the experimental data even without the introduction of arbitrary constants.Vladimir Scientific Research Institute of Synthetic Resins. Translated from Mekhanika Polimerov, No. 5, pp. 859–865, September–October, 1970.     

Vibrocreep of polymeric materials

The recovery of rigid porous polyurethane after preliminary static and vibrational creep has been experimentally investigated. The effect of a small additional vibrational load on the recovery process is discussed. The results of describing the recovery with the aid of an expression in the form of a Volterra multiple-integral series and a relation of the Leaderman-Rozovskii type are examined.For Communication 6 see [17].Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 5, pp. 818–824, September–October, 1970.     

Effect of the crosslink density of elastic polyurethane fibers on their mechanical properties

The effect of the nature of the bonds and the degree of crosslinking on the properties of elastic polyurethane fibers has been investigated in relation to various fiber treatments. The fiber properties are mainly determined by the chemical bonds, the proportion of which should be not less than 40%.Leningrad Branch, All-Union Scientific-Research Institute of Artificial Fibers. Kaunas Artificial Fiber Plant. Translated from Mekhanika Polimerov, No. 3, pp. 515–516, May–June, 1976.     

Some properties of rigid polyurethane foam obtained from oligoglycerooxalate

The dependence of the modulus of elasticity and compressive strength on the apparent density has been found for polyurethane foam based on oligoglycerooxalate.Institute of Wood Chemistry, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 4, p. 739, July–August, 1973.     

Experimental investigation of compression waves in polyurethane foam

The behavior of porous foam plastics under impact loading has been experimentally investigated with reference to the example of polyurethane foam. The specially designed loading mechanism made it possible to measure the propagation velocity of the compression wave, its dependence on the impact velocity, and the absorption. The impact loading velocities varied from 2.5 to 13 m/sec. The results obtained are discussed from the standpoint of nonlinear acoustics.Leningrad Zhdanov State University. Translated from Mekhanika Polimerov, No. 1, pp. 160–162, January–February, 1970.     

Multiparameter prediction of polymer creep

An investigation of the thermocreep of low-density polyethylene (LDP) and the vibrocreep of porous polyurethane (PPU) in complex states of stress has shown that multiparameter creep prediction based on the combined application of the time-stress, time-temperature, and time-vibration superposition principles can be used for rapid analysis of the nonlinear viscoelasticity and thermovibrocreep of polymeric materials under complex loading.For communication 1 see [1].Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 3, pp. 416–420, May–June, 1971.     

Effect of elastic filler on the fatigue failure of thermoplastic polyurethane film at low temperature

Conclusion It was established by mathematical modeling of the curves of spectral transmissivity and by comparing them with experiments that in the mixture of polyurethane with caoutchouc an increase of the volume fraction of filler entails changes of the characteristic dimensions of its particles. With small volume fractions of filler (less than 10%), in consequence of the predominantly small size of the impurities, the mechanism of quasibrittle failure is realized without development of bulk damage to the mixture. When the mixture contains 20–30% filler, satisfactory static elastic and strength properties are retained, and in case of fatigue a considerable amount of damage accumulates and the mechanism of inhibiting macrocracks on the boundaries of impurities begins to act. When the proportion of filler increases further, the elastic and strength properties of the mixture are rapidly impaired, and as a consequence the material becomes practically unusable in operation.Translated from Mekhanika Kompozitnykh Materialov, No. 6, pp. 1040–1044, November–December, 1988.     

Vibrational creep of polymeric materials

An experimental study of the effect of vibration on the creep process has been carried out in the case of the rigid porous polyurethane PPU-3, as a function of the magnitude of the vibrational loading and the level of basic static stresses. It has been shown that with increase in the velocity amplitude of the dynamic stresses, the creep process is accelerated, without being accompanied thereupon by vibrational heating of the material. The possibility has been established of approximating vibrational creep curves by the integral equation of Volterra, using a discrete series of relaxation times transformed by the vibro-time analogy method.For Communication No. 3, see [1].Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 2, pp. 223–232, March–April, 1970.     

Polymer morphology and strength characteristics in the presence of large and small deformations

An investigation of the strength characteristics of polychloroprene under the action of a chemically active agent and of polypropylene under the action of a physically active agent, as well as of polychloroprene and polyurethane in both the brittle and highly elastic states in the absence of an aggressivemedium showed that the strength properties of polymers in the small-deformation region are a function of the degree of crystallinity or spherolite size and do not depend on these parameters in the high-deformation region. The influence of the degree of crystallinity on strength characteristics at small deformations and the absence of this effect at large deformations were also demonstrated with pressed specimens having the granular structure typical of real rubbers.Scientific-Research Institute of the Rubber Industry, Moscow. Translated from Mekhanika Polimerov No. 2, pp. 222–225, March–April, 1972.