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.     

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     

Homogeneous uniaxial tension of polyethylenes. Temperature effect

Mechanics of Composite Materials - The effect of temperature on the process of homogeneous uniaxial tension of polyethylenes of different crystallinity is analyzed by means of an analytic formula...     

An analytical description of the creep behavior of polymers in a flowing state in the linear deformation region

The methods available for the estimation of the parameters, which determine the steady state conditions for the slow shear flow of polymers, under indifferent creep conditions have been considered, and the results of experiments carried out using a shear plastometer have been compared with calculations in which Boltzmann-Volterra equations with a memory characteristic have been used. The resolvent previously suggested in [3] has been employed in these latter equations. It has been shown that the equilibrium values for the modulus of rubber-like elasticity can be calculated from the results of experiments on unsteady creep states.     

Strength of orthogonally reinforced plastics in uniaxial tension

Failure conditions are proposed for an orthogonally reinforced plastic in uniaxial tension at an arbitrary angle to the directions of reinforcement. The failure conditions are formulated for the case when the strength of the bond between the resin and the reinforcement is greater than the strength of the resin. The strength of the resin, which is in a volume state of stress, is determined by an energy criterion.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 4, pp. 629–633, July–August, 1973.     

Deformation of thin polycaprolactam film in uniaxial tension

The individual stages of deformation of spherulitic specimens of polycaprolactam have been studied by a microscopic method. An empirical relation between the total deformation of the specimen and the deformation of the individual spherulite is obtained.     

Effect of uniaxial tension on the density distribution in polycaproamide

The effect of uniaxial tension on the density of polycaproamide has been studied in the temperature region from +20 to +150°C. The density measurements were made by the flotation method. It is shown that the relative change of density increases with temperature. An empirical formula for the density distribution along the stretched specimen is proposed.Severodonetsk Glass-Reinforced Plastics Plant. Lugansk Mechanical Engineering Institute. Translated from Mekhanika Polimerov, Vol. 4, No. 4, pp. 760–761, July–August, 1968.     

Creep of reinforced plastics in uniaxial tension along the fibers

Relations are proposed for determining at any moment of time the strains in a reinforced plastic stressed in the resin and the reinforcement by a constant tensile load as a function of the reinforcement ratio and the rheological properties of the reinforcement and resin. The proposed relations agree quite well with the experimental data.Mekhanika Polimerov, Vol. 1, No. 6, pp. 69–77, 1965     

Development of slits in polyethylene and polypropylene films stressed in uniaxial tension

Optical microscopy has been used to investigate the development of a slit in polyethylene and polypropylene films with spherulites of different types and sizes stressed in uniaxial tension. The angle between the slit and the direction of extension was 0, 45, or 90°. Slits at 45 and 90° initially develop through localization of slits by a stronger oriented polymer and subsequently as a result of failure of the oriented polymer at the tip of the slit. A longitudinal slit does not develop and does not affect the deformation of the film.Mekhanika Polimerov, Vol. 3, No. 1, pp. 95–98, 1967     

Predicting the deformation properties of polymers

Physically well-founded relations, following from a consideration of the molecular-kinetic nature of the relaxation processes, are proposed for the time-temperature superposition principle. It is shown that the well-known Williams—Landel—Ferry relation is a particular case of more general formulas.V. I. Lenin Moscow State Pedagogical Institute, Problem Laboratory of Polymer Plastics. Translated from Mekhanika Polimerov, No. 6, pp. 1106–1109, November–December, 1971.