Effect of processing conditions on the supramolecular structure and strength properties of polycaprolactam

The formation of supramolecular structures in block polycaprolactam is considered. It is shown that technological factors have a considerable effect on the nature of the supramolecular structure. Two of these factors are the temperature gradient of the polymer melt and the nature of its motion in the cylinder of the injection molding machine up to the moment of injection into the mold. It is shown that the nonuniformity of deformation and the considerable number of defects associated with large supraspherulitic formations lead to a deterioration in the strength and deformation properties of polymers.Mekhanika Polimerov, Vol. 2, No. 5, pp. 659–663, 1966     

Influence of hydrostatic pressure on the lifetimes of polymers

Under uniaxial tension, the lifetimes of polymers under hydrostatic pressure are longer than under atmospheric pressure. This effect is attributed to a change in the failure mechanism under pressure owing to retardation of the free-radical chain reaction of breakage of the macromolecules under omnidirectional compression.A. F. Ioffe Physicotechnical Institute, Academy of Sciences of the USSR, Leningrad. Translated from Mekhanika Polimerov, No. 2, pp. 207–213, March–April, 1976.     

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     

Effect of hydrostatic pressure on the density of various plastics

It is shown that application of hydrostatic pressure causes an increase in the density of ebonite but practically no change in the density of polyethylene, kapron (nylon-6), PVC, plexiglas, and FKP-1. Uniaxial compression of some materials first increases their mean density, then, at fairly high strain, causes the density to decrease. For the majority of the materials examined, the rate of this reduction in density decreases in the simultaneous presence of hydrostatic pressure.Mekhanika Polimerov, Vol. 2, No. 3, pp. 355–358, 1966     

On the dynamics of fine structure

Summary We investigate models for the dynamical behavior of mechanical systems that dissipate energy as timet increases. We focus on models whose underlying potential energy functions do not attain a minimum, possessing minimizing sequences with finer and finer structure that converge weakly to nonminimizing states. In Model 1 the evolution is governed by a nonlinear partial differential equation closely related to that of one-dimensional viscoelasticity, the underlying static problem being of mixed type. In Model 2 the equation of motion is an integro—partial differential equation obtained from that in Model 1 by an averaging of the nonlinear term; the corresponding potential energy is nonlocal.After establishing global existence and uniqueness results, we consider the longtime behavior of the systems. We find that the two systems differ dramatically. In Model 1, for no solution does the energy tend to its global minimum ast . In Model 2, however, a large, dense set of solutions realize global minimizing sequences; in this case we are able to characterize, asymptotically, how energy escapes to infinity in wavenumber space in a manner that depends upon the smoothness of initial data. We also briefly discuss a third model that shares the stationary solutions of the second but is a gradient dynamical system.The models were designed to provide insight into the dynamical development of finer and finer microstructure that is observed in certain material phase transformations. They are also of interest as examples of strongly dissipative, infinite-dimensional dynamical systems with infinitely many unstable modes, the asymptotic fate of solutions exhibiting in the case of Model 2 an extreme sensitivity with respect to the initial data.     

Creep of fluoroplastic in shear with application of hydrostatic pressure

Conclusions 1. It has been shown that under a deformation regime with Vxy = const, with an increase in shear deformation the effect of the action of hydrostatic pressure rises. A considerable effect of pressure on the character of the shear diagram is observed in the pressure region above 500 kgf/cm².Paper presented at the Third All-Union Conference on Polymer Mechanics in Riga, 1976.Leningrad Technological Institute of the Refrigeration Industry. Okhtinsk Scientific-Manufacturing Union Plastpolimer Leningrad. Translated from Mekhanika Polimerov, No. 5, pp. 812–818, September–October, 1977.     

Effect of hydrostatic pressure on submicrocrack formation in oriented polymers

Small-angle x-ray scattering has been used to obtain a quantitative estimate of the concentration and size of the submicrocracks in Kapron and polypropylene equally extended at 1 and 1500 atm. Direct evidence of the retarding effect of pressure on fracture development has been obtained.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga: Ioffe Physicotechnical Institute, Academy of Sciences of the USSR, Leningrad. Translated from Mekhanika Polimerov, No. 5, pp. 917–921, September–October, 1971.     

Effect of hydrostatic pressure on the water absorption of epoxy polymers

The water absorption of epoxy polymers at hydrostatic pressures up to 1000 kgf/cm² has been studied. It has been shown that pressure very definitely reduces the water absorption value but essentially does not change the diffusion coefficient of water into the polymers under study. An explanation of the data obtained is given.     

Effect of hydrostatic pressure on the deformation properties of polymer materials

It is suggested that the bulk modulus of homogeneous polymer materials is a function of the specific volume only. The dependence of the bulk modulus and Young's modulus on temperature and hydrostatic pressure is determined on the basis of this assumption. It is shown that the Young's modulus must be higher in compression than in tension. The experimental data are confirmed by the relations obtained. The effect of hydrostatic pressure on the relaxation properties of materials is discussed.Institute of Polymer Mechanics, ASLatSSR, Riga. Translated from Mekhanika Polimerov, Vol. 4, No. 6, pp. 986–991, November–December, 1968.     

Effect of gamma radiation on the mechanical properties and structure of oriented polycaprolactam (kapron)

Mechanical tests and x-ray diffraction measurements at large and small angles indicate that when oriented polycaprolactam is exposed to gamma radiation the "damage" is chiefly concentrated in the amorphous intercrystallite regions.Mekhanika Polimerov, Vol. 4, No. 1, pp. 173–177, 1968     

Effect of hydrostatic pressure on the strength properties of polymer materials

On the assumption that the strength characteristics of homogeneous polymer materials depend on the specific volume, equations are derived for the dependence of the strength or high-elastic limit on the hydrostatic component of the stress tensor and temperature. The ultimate strengths in simple tension, compression and shear are considered in relation to brittle and plastic fracture.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 3, pp. 449–454, May–June, 1969.     

Effect of hydrostatic pressure on the tensile strength of polymer materials

The effect of hydrostatic pressure on the tensile strength of amorphous, crystalline, and thermosetting polymers has been investigated. The maximum hydrostatic pressure was 2000 kgf/cm². The surfaces of some specimens were protected from the ambient medium (oil). The tests showed that hydrostatic pressure improves the strength or high-elastic limit and Young's modulus of all the materials investigated. In the case of brittle materials, the increase in strength is greater if the surface is protected, whereupon the plasticity is also improved. Hydrostatic pressure produces important changes in the deformation behavior of crystalline polymers.Mekhanika Polimerov, Vol. 3, No. 6, pp. 1043–1047, 1967     

Effect of hydrostatic pressure on mechanical properties of plastics

The effect of hydrostatic pressure on the elastic and strength properties of plastics is investigated. Hydrostatic pressure is found to raise the modulus of elasticity, the tensile strength, and the elastic limit. Approximate equations for calculating the strength and elastic properties under various amounts of hydrostatic presure are proposed.Mekhanika polimerov, Vol. 1, No. 1, pp. 65–75, 1965     

The equilibrium of a flexible membrane under hydrostatic pressure

In the construction industry it is often necessary to drain a section of a canal. This may be done after the insertion of flexible membranes made of PVC‐coated polyester. This paper discusses a simple mathematical model to examine the equilibrium of such a membrane under hydrostatic pressure. The model predicts that the maximum displacement of a membrane from the vertical occurs at a depth which varies between l/‐√3 and l/‐√2 , where l is the depth of the canal.     

Generic relativizations of fine structure

It is shown how certain generic extensions of a fine structural model in the sense of Mitchell and Steel [MiSt] can be reorganized as relativizations of the model to the generic object. This is then applied to the construction of Steel's core model for one Woodin cardinal [St] and its generalizations. Received: 28 March 1997