Comparison of the effect of ultraviolet radiation on polymer creep rate in a vacuum and in air

The effect of ultraviolet radiation on the creep rates of various polymers has been investigated in a vacuum and in air. It is shown that the ambient medium plays very little part in the processes leading to an increase in creep rate in the presence of ultraviolet radiation.Ioffe Physico-Technical Institute, Academy of Sciences of the USSR, Leningrad. Translated from Mekhanika Polimerov, No. 3, pp. 559–561, May–June, 1969.     

Effect of UV radiation and vacuum on the strength and failure of polymer films

The effect of UV radiation and vacuum on the strength and failure of polytetrafluorethylene (PTFE) films has been studied. After irradiation samples were extended in air. It was found that the strength and plasticity of the films is diminished by irradiation in vacuum or in air.Mekhanika Polimerov, Vol. 2, No. 3, pp. 359–364, 1966     

Effect of ultraviolet radiation on the lifetime of polymers under load in the low-stress region

In the low-stress region the lifetime of polymers placed under load in the presence of UV radiation is appreciably greater in a vacuum than in air. This indicates that the ambient medium plays an important part in the process of restoration of broken bonds and that the knee on the log =f() curve is at least partly due to recombination processes.Ioffe Physico-Technical Institute, Academy of Sciences of the USSR, Leningrad. Translated from Mekhanika Polimerov, No. 5, pp. 929–931, September–October, 1969.     

Effect of ultraviolet radiation on the creep rate of polymers

The effect of UV radiation on the creep rate of nine different polymers has been determined under load. A reversible increase in creep rate has been detected. This effect is attributable to radiation damage consisting in the breakage of bonds in the stressed polymer. The results obtained point to a close relationship between the processes of polymer fracture and deformation.Mekhanika Polimerov, Vol. 3, No. 3, pp. 404–408, 1967     

Mass-spectrometric investigation of solid lubricating coatings subjected to friction in a deep vacuum

The life of solid lubricating coatings of the VNII NP type, based on molybdenum disulfides and various binders, has been experimentally investigated under deep vacuum conditions (10^–8–5 · 10^–9 torr) together with the composition of the gas released in the friction process. It is shown that both under atmospheric conditions and in a deep vacuum the life of the coatings depends on the chemical nature of the film-former. The depth of the vacuum also has an important influence on the life of the coatings, both the mechanism and the end result of this effect depending to a large extent on the physicochemical properties of the bind. On the interval 10^–1–10^–2 torr there is a sudden change in the life of the coating.Physicotechnical Institute of Low Temperatures, Academy of Sciences of the Ukrainian SSR, Khar'kov. Translated from Mekhanika Polimerov, No. 6, pp. 1070–1075, November–December, 1970.     

Temperature — Time dependence of the strength of polymers exposed to UV radiation

Experiments on several polymers have shown that the dependence of the radiation lifetime under load on the intensity of the ultraviolet radiation and test temperature is governed by general empirical laws. An analysis of the results yields important information on the photodegradation of stressed polymers.Ioffe Physico-Technical Institute, Academy of Sciences of the USSR. Leningrad. Translated from Mekhanika Polimerov, No. 3, pp. 442–448, May–June, 1969.     

The effect of ultraviolet radiation on the stress relaxation rate of polymers

The effect of UV radiation on the stress relaxation rate for four different polymers was investigated. A reversible increase in the stress relaxation rate was noted: the rate increased during irradiation and declined after its termination. It is assumed that this effect involves the rupture of stressed polymer macromolecules by the action of UV rays.Mekhanika Polimerov, Vol. 3, No. 4, pp. 615–618, 1967     

Comparison of the lifetimes of polymers tested in a vacuum and in air

The temperature-time dependence of the strength of kapron (nylon 6) fibers has been studied in a vacuum and in air. In the vacuum tests a pole shift effect is observed, whereas in air no such effect is present. It is shown that the pole shift observed under vacuum conditions can be attributed to the inconstancy of the coefficient in the Zhurkov equation. In this case the activation energy of the fracture process U₀, calculated from the slopes of the log vs 1/T graphs, cannot be assigned the significance of a unit bond rupture energy.Ioffe Physico-Technical Institute, Academy of Sciences of the USSR, Leningrad. Translated from Mekhanika Polimerov, Voo. 5, No. 2, pp. 250–256, March–April, 1969.     

Effect of a vacuum on the adhesion of rubbers to metal

The effect of a vacuum on the adhesion of rubbers to metals has been investigated both when the joints are formed in the vacuum and when joints formed under normal conditions are transferred to a vacuum. A method of estimating the effect of the vacuum, independently of the duration of contact and the contact temperature and pressure used in forming the joint, is described. The results obtained (a sharp increase in adhesion under vacuum) correspond to the theoretical notions of Bikerman concerning weak boundary layers.Central Scientific-Research Laboratory of Chemical Packaging, Moscow. Translated from Mekhanika Polimerov, No. 6, pp. 1036–1041, November–December, 1973.     

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     

Global existence of strong solutions to the Cauchy problem for a 1D radiative gas

We consider a one-dimensional radiation hydrodynamics model in the case of the equilibrium diffusion approximation which is described by the compressible Navier-Stokes system with the additional terms in the pressure and internal energy respectively, which embody the effect of radiation. Under the physical growth conditions on the heat conductivity, we establish the existence and uniqueness of strong solutions to the Cauchy problem with large initial data, where the initial density and velocity may have differing constant states at infinity. Moreover, we show that if there is no vacuum in the initial density, then, the vacuum and concentration of the density will never occur in any finite time.     

Quantum statistical theory of radiation friction of a relativistic electron

We comprehensively investigate the effect of quantum space-time nonlocality that accounts for retardation of the electron interaction with both the electron’s own radiation field and the fluctuation field of the electromagnetic vacuum. We rigorously show that the quantum nonlocality effect eliminates the self-acceleration and the causality violation paradoxes that are inherent in the classical theory of radiation friction. __________ Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 158, No. 3, pp. 478–496, March, 2009.     

Effect of multiple extension on the thermal degradation of triacetate fiber

The effect of multiple extension on the vacuum thermal degradation of triacetate fiber, in the starting state and treated with hot air or saturated steam, has been experimentally investigated.Lithuanian Scientific-Research Institute of the Textile Industry, Kaunas. Translated from Mekhanika Polimerov, No. 6, pp. 1114–1116, November–December, 1971.     

Control of biopolymer poly-β-hydroxybutyrate characteristics by γ-irradiation

The influence of γ-irradiation on the structure and some mechanical properties of poly-β-hydroxybutyrate was studied. Specimens of PHB were γ-irradiated with various doses (1–20 Mrad) in air and vacuum. The molecular weight, structural characteristics of the crystalline and amorphous phases, characteristics of thermal degradation, and deformation of the polymer were determined. The crystallinity was found to increase with increase in the radiation dose and with the corresponding reduction in molecular weight. The increase of crystallinity was the greater the smaller the length of macromolecules (higher radiation dose). The melting temperature T _m , which characterizes the crystalline order, decreased with decrease in the molecular weight. The results of calorimetric studies suggest that radiation-caused degradation, which occurs at a temperature at which “cold” crystallization (60°C) is possible, might also affect the crystalline part of the polymer.     

Current state and prospects for development of the physical theory of brittle strength of polymers

Various mechanisms of brittle fracture and theories of the time dependence of the strength of rigid polymers are examined. The effect of various types of mechanical losses (deformation, dynamical, surface) on polymer strength and life is analyzed. The principal shortcomings of Griffith's theory of strength are pointed out. From an examination of the two basic mechanisms of brittle fracture of polymers-nonthermal and thermal (thermal fluctuation)-it is concluded that the latter is the more important. A comparison is made of the fluctuation theory of polymer strength with new experimental data on polymethyl methacrylate, and the causes of the transition from brittle to nonbrittle fracture are discussed. The effect of molecular orientation on the strength of polymers is examined on the basis of the fluctuation theory of strength.Mekhanika Polimerov, Vol. 2, No. 5, pp. 700–721, 1966     

External capacitive probes for the nondestructive determination of the dielectric properties of polymeric materials

The effect of the finite dimensions of the test object on the results of nondestructive determination of the dielectric properties of polymers with external capacitive probes has been investigated. Recommendations are made for eliminating the effect of the air gap between the electrodes and the surface of the test object.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 6, pp. 1098–1104, November–December, 1969.     

Friction properties of styrene-ε-caprolactam graft copolymers

The friction properties of styrene--caprolactam graft copolymers have been investigated in the atmosphere, in a vacuum, and in the presence of ionizing radiation.Mekhanika Polimerov, Vol. 4, No. 3, pp. 559–562, 1968     

Formation of singularities in solutions to the compressible radiation hydrodynamics equations with vacuum

We study the Cauchy problem for multi-dimensional compressible radiation hydrodynamics equations with vacuum. First, we present some sufficient conditions on the blow-up of smooth solutions in multi-dimensional space. Then, we obtain the invariance of the support of density for the smooth solutions with compactly supported initial mass density by the property of the system under the vacuum state. Based on the above-mentioned results, we prove that we cannot get a global classical solution, no matter how small the initial data are, as long as the initial mass density is of compact support. Finally, we will see that some of the results that we obtained are still valid for the isentropic flows with degenerate viscosity coefficients as well as for one-dimensional case.