Verification of the hypothesis of the existence of a potential with reference to teflon

In establishing the rheological relations describing the behavior of materials during deformation it is often very useful to employ a potential function. The hypothesis of the existence of a potential is verified in relation to the deformation of teflon in a complex state of stress.Scientific-Research Institute of Mathematics and Mechanics, Leningrad Zhdanov State University. Translated from Mekhanika Polimerov, No. 3, pp. 565–567, May–June, 1969.     

Effect of hydrostatic pressure combined with uniaxial tension on certain physical properties of polymers

The residual changes in the density and swelling properties of high-density polyethylene, teflon, PVC, and ebonite after extension under hydrostatic pressure have been investigated. It is shown that in this case the density of all the materials tested is higher and the swelling lower than in the case of uniaxial tension alone. This effect of hydrostatic pressure is attributable to the creation of favorable conditions for the healing of cracks formed in the deformation process.Mekhanika Polimerov, Vol. 3, No. 6, pp. 1018–1023, 1967     

Periodic deformation and viscous flow of polymer solutions and melts

The effect of nonlinear periodic deformation on the relaxation spectra and viscous-elastic characteristics of polymer melts and solutions is considered. The experimental and calculated relationships between the dynamic characteristics and effective viscosity and the amplitude of the rate of periodic deformation were compared.For Communication 1, see [6].Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Institute of Mechanics Problems, Academy of Sciences of the USSR, Moscow. Translated from Mekhanika Polimerov, No. 2, pp. 357–366, March–April, 1970.     

Dynamic properties of teflons obtained under various molding conditions

The natural frequencies and decrements, velocities of sound, dynamic moduli of elasticity, and Poisson's ratios of teflon specimens have been investigated in relation to the nature of the starting powder and molding conditions. The optimal dynamic characteristics are determined and it is shown that chey can be used to optimize the molding conditions and control the quality of teflon products.Mekhanika Polimerov, Vol. 2, No. 6, pp. 917–922, 1966     

Investigation of the Poisson's ratio of certain crystalline polymers under a constant compressive load

The results of an investigation of the Poisson's ratio in compression for two crystalline polymers, low-density polyethylene and teflon, are given. The effect of time under load and temperature on the value of the Poisson's ratio is examined.Mekhanika Polimerov, Vol. 1, No. 4, pp. 43–46, 1965     

Friction of polymeric materials

The case of contact of polymer and metallic surface has been examined. A formula is proposed for calculating the contact area as a function of time of holding the compression surface under load and for calculating the coefficient of friction, the dependence of Young's modulus and shear strength on temperature, deformation rate, and average force on the contact surface being taken into account. The nature of deformation of irregularities on the surfaces of polymeric materials under the action of normal and tangential loading has been examined.See [1] for Communication 1.Institute for Polymer Mechanics, Academy of Sciences of the Latvian SSSR, Riga. Translated from Mekhanika Polimerov, No. 5, pp. 809–815, September–October, 1972.     

Periodic deformation and viscous flow of polymer solutions and melts

The transition from the start of deformation to the establishing of a stationary state of nonlinear, periodic shear deformation and the kinetics of the change in the mechanical characteristics after deformation at finite amplitudes has ceased have been investigated. The calculated values have been compared with those obtained experimentally.For Communication 2 see [3].Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Institute of Mechanics Problems, Academy of Sciences of the USSR, Moscow. Translated from Mekhanika Polimerov, No. 3, pp. 521–529, May–June, 1970.     

Mechanical properties of polyethylene and teflon over a broad range of strain rates

Tensile load-extension diagrams have been obtained for low- and high-density polyethylene and teflon. Conventional notions concerning the effect of strain rate on the properties of solids are found not to apply. The unconventional distribution of the family of - curves plotted for different strain rates is caused by the combination of high-elastic and plastic deformation associated with the extension of crystalline polymers. An attempt is made to correlate the data on a narrow range of strain rates with the aid of a model of a viscoelastic solid with variable relaxation time, and on a broader range by means of an equation incorporating the limiting dynamic diagram.Mekhanika Polimerov, Vol. 4, No. 1, pp. 45–52, 1968     

Supermolecular structure of teflon and its role in the manufacture of metal-polymer antifriction materials

The question of the formation of supermolecular structures in teflon is considered. It is shown that during processing they become oriented, causing anisotropy of the material properties. The realtive rheological characteristics of the anisotropic materials are given as a function of the directionality of the force field. Specimens are obtained on the basis of the experimentally determined laws and certain properties of a polymer-metal antifriction material consisting of a high tin, porous bronze impregnated with teflon are investigated.Institute of the Chemistry of High Molecular Compounds, AS UkrSSR, Kiev. Translated from Mekhanika Polimerov, Vol. 4, No. 6, pp. 1122–1124, November–December, 1968.     

Virial expansions in problems of effective characteristics. 2. Antiplanar deformation of a fiber composite. analysis of self-consistent methods

Conclusion The virial expansion for the effective shear modulus (condition of antiplanar deformation) was constructed for an isotropic material with parallel cylindrical inclusions and the terms which are quadratic with respect to the concentration of inclusions were precisely calculated. A comparison of the results obtained with the results found with self-consistent methods showed that the differential (step) method gives a precise solution in the case of inclusions which strongly differ in size and a relatively small error (under 25% in the quadratic term) in the case of identical inclusions. The algebraic method and Lorentz method give more significant errors (up to 100 and 50%) in the quadratic term, respectively.See [1] for Communication 1.Translated from Mekhanika Kompozitnykh Materialov, Vol. 30, No. 2, pp. 329–342, March–April, 1994.     

Prediction of changes in the strength of filled thermoplastics upon aging in an oxidizing atmosphere

Problems related to analyzing specimens with damaged surface layers have been examined using polyamide, trioxane—dioxolane copolymer, and polycarbonate as source materials. A model was developed for the brittle fracture of block specimens with damaged surface layers, which provides an estimate of the restraints to plastic deformation in these layers. Three segments are seen in the strength—time curves featuring 1) increasing strength, 2) decreased strength with brittle fracture, and 3) constant low strength. The strength of filled specimens of a specific period permits us to evaluate the effect of the filler on the fracture resistance of the matrix. A method was proposed for predicting the strength of filled samples using the matrix aging data.Translated from Mekhanika Kompozitnykh Materialov, Vol. 29, No. 3, pp. 375–380, May–June, 1993.     

Anomalous deformation properties of carbon-black filled rubbers at low elongations

The behavior of carbon-black filled rubber based on SKMS-30 ARKM-15 during its extension at a constant rate has been studied. It has been established that under extension to a deformation of the order of 1% the first cycle stress-deformation dependence is located below the second cycle dependence; the rise in stiffness (antithixotropy) is explained by an orientation of the carbon-black structures upon extension.     

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.     

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.     

Creep of certain polymers under hydrostatic pressure

The problems of an experimental investigation of polymer creep under omnidirectional hydrostatic pressure are considered. The method of investigation is discussed, and the loading devices are described. The results of tests on low-pressure polyethylene and teflon are reported.Mekhanika Polimerov, Vol. 4, No. 2, pp. 232–236, 1968     

Characteristics of the creep and repeat creep deformation process for polymers in uniaxial tension. Part 2

Physical relations for approximating the creep deformation and recovery have been worked out for a material in the physically nonlinear state with a nonmonotonic θ (t) dependence. It has been shown experimentally that for filled low-density polyethylene and fluoroplastic there is no time similarity for the processes of longitudinal and transverse deformation, deformation under primary and repeat loading, and creep deformation and recovery.     

Effect of harmonic shear deformations on the viscosity of epoxy potting compounds

A method has been developed for experimentally determing the effect of harmonic shear deformation on the effective viscosity of pseudoplastic liquids. Harmonic deformation substantially reduces the effective viscosity of a filled composition based on epoxy resin ED-5.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, Vol. 5, No. 2, pp. 328–331, March–April, 1969.     

Positron annihilation in annealed and quenched teflon and in sulphur

The value (τ₂) and the intensity (I₂) of the delayed component in the lifetime spectra of positrons annihilating in annealed and quenched teflon and in sulphur and crystex (polymer sulphur), at room temperature and at 77° K are reported. These data and the X-ray diffraction patterns for these materials are discussed in terms of the free volume model for the formation and quenching of positronium atoms in molecular materials.     

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.     

Hardness of polymers

Hardness was measured on a Rockwell type instrument modified to measure the depth of the unrecovered indentation. The indentors were balls of various diameters and cones with various vertex angles. The hardness of the following materials was investigated: aminoplast (amino resin), K-17-2, FKP-1, polymethylmethacrylate (plexiglas), polyvinyl chloride (PVC), polyethylene, and teflon. The hardness is related to the strength and elastic characteristics.Mekhanika Polimerov, Vol. 2, No. 3, pp. 337–349, 1966