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.     

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.     

Experimental determination of the influence of periodic shear deformation and filling on the effective viscosity of solutions of synthetic rubber

The influence of periodic shear deformation on the effective viscosity of filled solutions of synthetic rubber has been studied. The study was carried out on an amplitude-frequency viscosimeter developed by the authors. It has been established that during periodic deformation a linear region exists in which the effective viscosity is independent of the vibration rate, and a nonlinear region where the effective viscosity of the solutions decreases with increase in amplitude of the speed of relative deformation.Presented at the IV Symposium on Rheology of Polymers at the A. V. Topchiev Institute for Petrochemical Synthesis, Academy of Sciences of the USSR, Moscow, May 27–30, 1969.Institute for Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 3, 514–520, May–June, 1970.     

Theory of flow of concentrated polymer solutions and melts

Starting from the concept of a polymer system as a collection of macromolecules forming an effective network, an expression is obtained for the stress tensor of a flowing concentrated polymer solution or melt. It is shown that the variation of the effective viscosity of polymer systems is associated with the orientation of the macromolecules and changes in the equilibrium number of nodes during flow. A system of equations describing the flow of polymer systems characterized by a gradient dependence of the effective viscosity and normal stresses in shear is written in the single relaxation time approximation.Institute of Chemical Physics, Moscow Region, Academy of Sciences of the USSR. Translated from Mekhanika Polimerov, Vol. 4, No. 4, pp. 724–730, July–August, 1968.     

Some relationships between the specific functions and constants of visoelastic media

It is proved that the shear, lateral creep, and relaxation functions can be expressed in an elementary way by the longitudinal creep and relaxation functions and the elasticity modulus of the bulk.I. M. Gubkin Moscow Institute of Petrochemical and Gas Industry. Translated from Mekhanika Polimerov, No. 5, pp. 810–814, September–October, 1973.     

Periodic shear deformation of a curing epoxy composition

The curing of an epoxy resin with amines is investigated in relation to the changes in the viscoelastic shear characteristics. The effect of the shear deformation amplitude on the curing kinetics is considered.Presented at the Symposium on Polymer Rheology, Institute of Petrochemical Synthesis, Academy of Sciences of the USSR, Moscow, May, 1970.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 2, pp. 301–306, March–April, 1971.     

Optimal rigidity of a thin-walled orthotropic cylinder in combined tension and torsion

The problem of optimizing the reinforcement of an orthotropic cylinder in combined torsion and tension is considered in relation to the condition of minimum displacement. A numerical example is given. It is shown that the stiffness depends on the ratio of the normal and shear stresses, the elastic moduli, and the parameters.Moscow Aviation Technological Institute. Translated from Mekhanika Polimerov, No. 6, pp. 1121–1123, November–December, 1973.     

Rheological properties of rubbery polymers at low shear stresses

The rheological behavior of the rubbery amorphous polymers SKB-35 (sodium-butadiene rubber), SKN-26M(butadiene-nitrile rubber), and PIB-85 (polyisobutylene) has been investigated in relation to the creep process. The tests were conducted at low shear stresses, in the constant shear stress regime, on the temperature interval from 0 to 100°C using a parallel-plate viscometer. We have shown, for the first time, by a viscometric method that in the high-elastic state rubbery polymers have a particular equilibrium structure corresponding to each temperature. A reduction in temperature leads to molecular ordering processes associated with an increase in the viscosity of the polymer. A temperature rise leads to molecular disordering and a gradual fall in viscosity. At a given temperature the two processes converge to the same value of the equilibrium viscosity. The rate of the process of equilibrium structure formation is determined not only by the temperature but also by the nature of the polymer. The higher the polarity, the more slowly the equilibrium structure is established.Moscow Lenin State Pedagogical Institute, Problem Laboratory of Polymer Physics. Translated from Mekhanika Polimerov, No. 6, pp. 970–974, November–December, 1969.     

Barus effect in polymer flows through cylindrical and flat dies

The determination of the swell factor of a polymer jet extruded from a cylindrical or flat die is examined. Relations are obtained for the dependence of the swell factor on shear rate and shear stress, expressed in terms of the constants of the rheological model.Scientific Research Institute of Plastics, Moscow. Kiev Polytechnic Institute. Translated from Mekhanika Polimerov, No. 3, pp. 487–492, May–June, 1976.     

Effect of ultrasonic vibrations on the flow of a viscoelastic liquid

The rheological characteristics of a viscoelastic liquid flow, on which finite-amplitude ultrasonic shear vibrations have been superimposed, are investigated. It is shown that at periodic deformation amplitudes of 5 µ or more there is a thixotropic reduction of the viscosity and elasticity of the system owing to the destruction of certain types of structural bonds. The experimental apparatus is described.Moscow Institute of Chemical Machine Building. Translated from Mekhanika Polimerov, No. 6, pp. 1097–1099, November–December, 1971.     

Normal stresses in non-Newtonian polymer flows

The calculation of the normal stresses from the flow curve is considered on the basis of the method of correlation of the frequency and stationary characteristics of flowing polymer systems. Simple expressions are given for finding the initial normal stress coefficient and the high-elastic modulus from the point corresponding to the beginning of non-Newtonian flow. A necessary condition for the appearance of normal stresses is a viscosity anomaly. It is shown that for a bounded value of the initial normal stress coefficient to exist the derivative of the effective viscosity with respect to shear rate must be zero at the initial point.Topchiev Institute of Petrochemical Synthesis, Academy of Sciences of the USSR, Moscow. Translated from Mekhanika Polimerov, No. 3, pp. 506–514, May–June, 1971.     

Periodic deformation and viscous flow of polymer melts and solutions (communication 1)

The principles of the theory of thixotropy are formulated. The basic relations are obtained for cases of periodic vibration superimposed on shear flow. The effect of stationary shear flow on the linear dynamic characteristics of an elastic liquid is investigated. The calculated values are compared with the experimental data.Institute of Problems of Mechanics, Academy of Sciences of the USSR, Moscow. Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 3, pp. 519–527, May–June, 1969.     

Effect of relaxation parameters on the behavior of rigid polymers in pure shear

The authors have investigated the effect of the relaxation parameters of a rigid polymer corresponding to the individual terms of the relaxation spectrum on the nature of the theoretical curves calculated for creep, strain relaxation and loading at constant strain rate in pure shear on the assumption that the stress-strain relation is described by the generalized Maxwell equation.Institute of Chemical Physics, Academy of Sciences of the USSR, Moscow. Translated from Mekhanika Polimerov, No. 3, pp. 431–436, May–June, 1969.     

Viscosity,rubber elasticity,and viscoelasticity of concentrated polymer solutions

The results of a comparative investigation of the effect of the nature of the polymer and the solvent on the viscosity, rubber elasticity, and viscoelasticity of concentrated polymer solutions in the region of linear mechanical behavior are presented. It is established that in the case of nonpolar polymers the solvent affects only the free volume of the solution, whereas for polar polymers it also affects the entanglement network. This leads to the equality of the viscosities of solutions of nonpolar polymers in different solvents when compared in corresponding states (relative to the glass transition temperature) and to the dependence of the shear modulus of solutions of polar polymers on the nature of the solvent and temperature. It is shown that there is a universal relaxation spectrum in the flow zone for solutions of different polydisperse polymers after normalization with the shear modulus and the natural relaxation time determined as the ratio of the viscosity to the shear modulus.A. M. Gor'kii Ural State University, Sverdlovsk, A. V. Topchiev Institute of Petrochemical Synthesis, Academy of Sciences of the USSR, Moscow. Translated from Mekhanika Polimerov, No. 4, pp. 729–736, July–August, 1973.     

Normal stresses associated with the flow of non-Newtonian polymer systems

It has been experimentally confirmed that the method of calculating the shear rate dependence of the normal stresses from the flow curve, proposed in [1], gives good results consistent with the experimental data. A series of simple relations proposed for estimating the initial normal stress coefficient are compared with the experimental results and it is shown that there is good agreement between calculation and experiment. In the linear region the Lodge relation, which equates the high-elastic strains to half the ratio of the normal to the shear stresses is satisfied.For communication 1 see [1].Topchiev Institute of Petrochemical Synthesis, Academy of Sciences of the USSR, Moscow. Translated from Mekhanika Polimerov, No. 4, pp. 714–721, July–August, 1971.     

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.     

Experimental study of the effect of the technological factor of rolling-in (packing) on the physicomechanical properties of glass plastic

Conclusions 1. The rolling-in (packing) of wound glass-plastic objects is a favorable technological factor, improving the homogeneity of the material, increasing the elastic and strength characteristics of the glass plastic, and reducing the thermal expansion coefficients and macroscopic residual stresses due to the thermal shrinkage of the objects.2. However, extremely large packing forces may reduce certain of the mechanical characteristics of the material, chiefly the strength and modulus relating to interlayer shear.Moscow Power Institute. Translated from Mekhanika Polimerov, No. 6, pp. 1043–1047, November–December, 1976.     

Application of the technical theory to sandwich shells with a solid polymeric core

The possibilities of using the technical theory for analyzing cylindrical sandwich shells with a core of low-modulus polymeric material are considered. It is shown to be necessary to make assumptions concerning the distribution of the deformations over the elements of the three-layer section and to take account of the shear strains in the core, the flexural rigidity in the longitudinal direction, and the Poisson ratio in determining the forces and moments. The theoretical conclusions have been experimentally confirmed by static tests on a model.All-Union Structural Engineering Correspondence Institute, Moscow. Translated from Mekhanika Polimerov, No. 2, pp. 298–304, March–April, 1973.     

Determination of the shear strength of the metal-plastic adhesion bond and its response to lubrication

A new method of determining the shear strength of the metal-plastic adhesion bond is considered. Experimental data on its dependence on load and indenter dimensions are presented for various types of plastics under different conditions.State Scientific Research Institute of Machine Science, Moscow. Translated from Mekhanika Polimerov, No. 5, pp. 854–858, September–October, 1970.     

Mechanical characteristics of oriented glass-reinforced plastics in shear

The mechanical characteristics of oriented glass-reinforced plastics stressed in shear are considered. Various methods of determining them are compared. The dispersion of the shear strength is characterized and the possibility of glass-reinforced plastics elements failing as a result of low interlaminar shear strength is discussed.Moscow Aviation Technological Institute. Translated from Mekhanika Polimerov, No. 6, pp. 1008–1013, November–December, 1969.