Study of the process of unstable flow of elastomers in open and closed channels and its connection with mechanical characteristics of the material

The unstable flow process has been studied for examples of a series of unvulcanized rubbers of different structures by a complex of methods — capillary, tribometric, and dynamic methods. A connection has been found between the critical parameters which characterize the onset of this process and the dynamic mechanical characteristics. The possibility of modeling the unstable flow process in open channels is shown.A. V. Topchiev Institute for Petrochemical Synthesis, Academy of Sciences of the USSR, Moscow. Translated from Mekhanika Polimerov, No. 3, pp. 530–536, May–June, 1970.     

Hydrodynamic analysis of the flow of a liquid with an exponential rheological equation in the cylindrical channel of an extruder screw

Equations are obtained for the angular velocity profile and flow rate in the case of integral and nonintegral exponents n when a non-Newtonian liquid with an exponential rheological equation moves between two rotating cylinders in the presence of a tangential pressure gradient.Branch Institute of Chemical Physics, AS USSR, Moscow. Translated from Mekhanika Polimerov, Vol. 4, No. 6, pp. 1094–1102, November–December, 1968.     

Propagation of large-amplitude low-frequency vibrations in polymer melt flows

The propagation of low-frequency periodic pressure pulses along an isothermal stationary flow of various polymer melts in a flat channel of finite length has been experimentally and theoretically investigated. It is shown that as a result of the wave character of the process there is a phase shift between the pressure vibrations at various points along the length of the channel, while the amplitudes of the pressure vibrations decrease along the flow in accordance with a nonlinear law. Analysis of the problem leads to the establishment of a relation between the characteristics of the wave process, the properties of the medium, and the channel geometry.Moscow Institute of Chemical Machine Building. Institute of Problems of Mechanics, Academy of Sciences of the USSR, Moscow. Translated from Mekhanika Polimerov, No. 3, pp. 493–500, May–June, 1976.     

Friction and wear of certain thermoplastic materials in physiological solution

The wear resistance of certain thermoplastics has been subjected to comparative investigation together with the velocity dependence of the coefficients of friction at various pressures and after various periods of contact with a model physiological solution.Priorov Central Scientific-Research Institute of Traumatology and Orthopedics. Moscow Technological Institute of the Food Industry. Second Moscow Pirogov State Medical Institute. Translated from Mekhanika Polimerov, No. 6, pp. 1116–1119, November–December, 1971.     

Effect of lubricating greases on rubber-metal sliding friction at high temperatures

The effect of sliding velocity and temperature on the lubricating action of greases has been investigated under constant and variable temperature conditions. The most important factor is the friction temperature. Two different temperature regions, separated by a change in the type of friction, have been detected. A method has been developed for evaluating the lubricating effect of greases.Scientific-Research Institute of the Rubber Industry, Moscow. Translated from Mekhanika Polimerov, Vol. 4, No. 5, pp. 876–880, September–October, 1968.     

Effect of loading on the roughness set in run-in metal - rubber surfaces

A study has been made on the effect of loading on the roughness set of a metal surface run-in with rubber containing an SKN-18 + SKN-26 nitrile rubber blend in conditions of friction without lubrication. The experimental results are compared with those calculated.State Scientific-Research Institute of Mechanical Engineering, Moscow. Scientific-Research Institute of the Rubber Industry, Moscow. Translated from Mekhanika Polimerov, No. 4, pp. 737–740, July–August, 1972.     

Correlation of the effective and complex dynamic viscosities of viscose

The results of comparative measurements of viscosity of viscose in the steady-state flow and harmonic vibration regimes are presented. It is shown that in order to describe the dependence of the effective viscosity on the velocity gradients in the steady-state flow regime it is possible to employ the mathematical apparatus of the phenomenological theory used in dynamic investigations. The operating regimes of automatic viscometers intended for measuring the maximum Newtonian viscosity of viscose are determined.All-Union Scientific-Research Institute of Synthetic Fiber, Moscow Region. Translated from Mekhanika Polimerov, No. 4, pp. 756–759, July–August, 1973.     

Variation of the deformation resistance of phenol-formaldehyde thermosets during cure

The dependence of the viscosity of phenol-formaldehyde thermosets on the previous thermal history has been investigated at a fixed shear rate.Moscow Institute of Chemical Machine Building. Institute of Problems of Mechanics, Academy of Sciences of the USSR, Moscow. Translated from Mekhanika Polimerov, No. 4, pp. 619–623, July–August, 1971.     

Calculation of the resistance to the flow of polymeric systems through short channels

A method is proposed for calculating the pressure drop associated with the flow of polymeric systems (solutions, melts, and rubber blends) through short capillaries in which the steady-state flow regime is not established. The method is based on the assumption that the duration of deformation in the prestationary stage plays a decisive role. The results of the calculations are in good agreement with the experimental data.All-Union Scientific-Research and Design-Engineering Institute of the Rubber Industry, Volzhskii. Topchiev Institute of Petrochemical Synthesis, Academy of Sciences of the USSR, Moscow. Volgograd Polytechnic Institute. Translated from Mekhanika Polimerov, No. 1, pp. 171–174, January–February, 1973.     

Viscoelastic properties and unstable flow of monodisperse polybutadiene solutions

The conditions governing the onset of unstable flow when concentrated solutions of monodisperse polybutadiene in -methylnaphthalene are extruded through a capillary have been investigated. The critical values of the parameters corresponding to these conditions have been found. It is shown that unstable flow of the "elastic turbulence" type is associated with transition of the system to the forced high-elastic state.Topchiev Institute of Petrochemical Synthesis, Academy of Sciences of the USSR, Moscow. Translated from Mekhanika Polimerov, No. 1, pp. 132–137, January–February, 1973.     

Variation of the deformation resistance of phenol-formaldehyde thermosets during cure communication 2

The effect of the previous thermal and strain history on the viscosity properties and curing reaction kinetics of composition K18-2 has been investigated. Flow curves have been obtained for the composition over a broad range of shear rates and temperatures. The viscosity super-anomaly effect has been studied. A general functional dependence of the viscosity of composition K18-2 on degree of cure, temperature, and shear rate has been obtained.For communication 1 see [1].Moscow Institute of Chemical Machine Building. Institute of Problems of Mechanics, Academy of Sciences of the USSR, Moscow. Translated from Mekhanika Polimerov, No. 5, pp. 820–826, September–October, 1971.     

Relation between the shear and longitudinal viscosity coefficients for concentrated polymer solutions

A relation between the shear and longitudinal viscosity coefficients is obtained on the basis of the theory of flow of polymeric systems in the single relaxation time approximation. A comparison of the shear and longitudinal viscosity coefficients for polymer melts and solutions shows that the relation obtained is valid over a broad stress region.Institute of Chemical Physics, Academy of Sciences of the USSR, Moscow. Scientific-Research Institute of Synthetic Fibers, Moscow. Translated from Mekhanika Polimerov, No. 1, pp. 124–131, January–February, 1973.     

Dynamic mechanical properties of multicomponent polymeric compositions

The mechanical relaxation processes in rubber-polymer compositions have been investigated by the forced nonresonance vibration method. A method of evaluating black-filled polymer mixtures with advantages over microscopic methods is proposed.Scientific-Research Institute of the Tire Industry, Moscow. V. I. Lenin Moscow State Pedagogical Institute, Laboratory of Problems in Polymer Physics. Translated from Mekhanika Polimerov, No. 1, pp. 138–141, January–February, 1970.     

Effect of structural changes in amorphous polymer films on the mechanical properties of coatings

The effect of structure formation on the mechanical properties of amorphous paint films has been investigated. It is shown that the organization of the supermolecular formations affects the internal stresses and adhesion of the film and, moreover, their tensile and impact strengths over a broad temperature interval. Fibrillar and "reticulate" structures give the best mechanical properties.State Scientific-Research and Planning Institute of the Paint Industry, Moscow. L. Ya. Karpov Physicochemical Institute, Moscow. Translated from Mekhanika Polimerov, Vol. 4, No. 5, pp. 771–775, September–October, 1968.     

Fracture under cubic compression of polymethylmethacrylate subject to laser radiation

It has been established that samples of PMMA under cubic compression retain their fracture characteristics when subjected to laser radiation. Only the length of the fracture region is altered. The dimensions of the microdefects and the pressure within them causing the growth of discoidal fracture cracks have been determined.Institute of Problems in Mechanics, Academy of Sciences of the USSR, Moscow. Translated from Mekhanika Polimerov, No. 3, pp. 449–452, May–June, 1970.     

Mechanism of occurrence of microcirculatory phenomena in a constant magnetic field

A motion-picture study of the capillary network of the interdigital membranes of frogs has been carried out in order to clarify a number of effects observed after individual parts of the body and the whole organism are placed in a constant magnetic field. A constant magnetic field is observed to have three principal effects on the blood flow. The intensified blood flow following exposure to the field is explained as a complex reflex response mechanism, in which a definite part is played by a change in blood particle potentials and by processes of aggregation with subsequent disaggregation.Paper presented at the First All-Union Conference on Engineering and Medical Biomechanics on the topic: Problems of Microcirculation and Mass Transfer, Riga, October, 1975.Riga Scientific-Research Institute of Traumatology and Orthopedics. Translated from Mekhanika Polimerov, No. 5, pp. 891–894, September–October, 1975.     

Energy dissipation from an extrudate in the gap between the screw rib and the extruder shell

A dimensionless equation is derived for determining the energy dissipation between the screw rib and the sleeve of an extruder for a Newtonian model extrudate. The parameter ranges, within which the pressure at the exit from the screw and some geometrical parameters do not affect the dissipation, are indicated.Moscow Institute of Chemical Engineering. Translated from Mekhanika Polimerov, No. 4, pp. 746–749, July–August, 1972.     

Design of two-way glass-reinforced plastics with high compressive strength

The conditions determining the design of two-way glass-reinforced plastics with high compressive strength are investigated. The relations between the physicomechanical and geometric parameters of the composite are obtained in the form of a system of inequalities, satisfaction of which ensures the obtaining of a high-strength material with a given utilization factor. It has been shown experimentally that these inequalities can be used as a first approximation for the optimal design of a two-way reinforced composite with high compressive strength.All-Union Scientific-Research Institute of Glass-Reinforced Plastics and Glass Fiber, Moscow. Moscow Institute of Electronic Machine Building. Translated from Mekhanika Polimerov, No. 4, pp. 655–660, July–August, 1973.     

The acoustic properties of polymers with an asymmetric potential barrier at liquid-helium temperatures

The pulse-phase compensation method has been used to measure the propagation velocities of longitudinal and shear waves in polyvinyl chloride, polyvinyl fluoride, and polystyrene at frequencies of 1 and 5 MHz on the temperature interval 2.1–240°K. It has been established that as the temperature falls to 2.1°K the speed of ultrasound in these polymers monotonically increases, the dispersion (frequency dependence) of the speed of sound being preserved over the entire temperature interval. Two possible causes of the viscoelastic relaxation observed in the investigated polymers in the region of helium temperatures are considered.Scientific-Research Institute of Plastics, Moscow. Translated from Mekhanika Polimerov, No. 4, pp. 749–751, July–August, 1973.     

Investigation of the adhesion strength of carbamide resins

The adhesion of carbamide resin to clean or treated fiber glass surfaces has been determined. The effect of this adhesion on the strength of glass-reinforced plastics is examined.Moscow Mendeleev Chemical Engineering Institute. Translated from Mekhanika Polimerov, Vol. 4, No. 6, pp. 1119–1121, November–December, 1968.