Properties of multicomponent polymers systems

In order to design materials having different mechanical properties combined with a permittivity of 2.2–2.6 and tg =2·10^–4-4.10^–4 at 20±1° C and 10⁶ Hz, it is possible to use compositions consisting of polystyrene, polyisobutylene and polyethylene. Projections of the three-dimensional triangular composition-property diagrams are presented for selecting the composition corresponding to spcified properties (hardness at 20 and 50° C and breaking stress and elongation).Central Scientific-Research Institute of Communications, Moscow. Moscow Krupskaya Regional Pedagogical Institute. Translated from Mekhanika Polimerov, Vol. 4, No. 6, pp. 133–1135, November–December, 1968.     

Effect of steady-state flow of a polyisobutylene solution on its dynamic characteristics measured in the direction of flow

The effect of steady-state flow on the linear dynamic characteristics of a 10% solution of polyisobutylene in cetane, measured in the direction of flow, is investigated. The material characteristics in steady-state flow quantitatively describe the dynamic viscosity and elasticity at deformation frequencies small as compared with the steady-state shear rate.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 5, pp. 913–919, September–October, 1970.     

Method of investigating the extension of high-elastic polymers

A method has been developed for studying the deformation of polymers in a field with a longitudinal velocity gradient. The changes in the longitudinal viscosity and modulus of high elasticity of polyisobutylene in uniaxial tension at constant extension and strain rates are compared.Mekhanika Polimerov, Vol. 4, No. 2, pp. 343–348, 1968     

Large deformations of thermorheologically simple bodies

The relation between the true stresses and true strains associated with the simple finite deformation of a viscoelastic body is modified for the case in which the properties of the material depend on temperature and the body is located in an inhomogeneous nonstationary temperature field. This modification is based on the time-temperature equivalence principle. The validity of this principle for the case in question is confirmed by the experimental data of Andrews, Hofman-Bang, and Tobolsky on the true stress relaxation at large deformations of a polyisobutylene specimen. The modified relations are used to solve the problem of the large deformations of a heated cylinder, made of a viscoelastic material whose properties depend on temperature, under the action of internal and external pressures that are functions of time. The case of polyisobutylene is analyzed as an example of a specific viscoelastic material. The analogous problem in the presence of a reinforcing cylindrical shell is also considered. In the latter problem the solution of the solving nonlinear integrodifferential equation is unique and is obtained in the form of an infinite convergent series.Mekhanika Polimerov, Vol. 3, No. 3, pp. 436–447, 1967     

Variation of the elasticoviscous characteristics of a heavily filled rubber after periodic shear deformation

The results of an investigation of the recovery of the elasticoviscous characteristics after thixotropic reduction by periodic deformation in the nonlinear zone are reported. The rate of recovery of the mechanical properties depends on the deformation frequency and the previous history of dynamic deformation is shown to affect the dependence of the elasticoviscous characteristics on the shear rate gradient. The effects of stationary and dynamic deformation regimes on the relaxation spectrum of the material are compared.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 3, pp. 528–533, May–June, 1969.     

Rheological Properties of Nanosized AlN Powder Suspensions for Advanced Ceramics

The rheological properties (flow curves and viscoelastic behavior) of injection molding suspensions of a plasma-processed AlN nanosized powder (nanopowder) in paraffin are investigated over a broad range of shear rates (0.07–1350 s^–1). Two viscosity plateaux are observed on the flow curves and two values of the yield stress are obtained. The lower value of the strain amplitude (0.66%), exceeding the linearity limit of periodic shear, is restricted by the rheometer resolution. The ultrasound treatment and shear deformation of suspensions affect the structure of particle packing, which is responsible for the dependence of their rheological properties on the prehistory of mechanical actions.     

Dependence of the acoustic and mechanical properties of polyethylene on temperature and cyclic cooling and heating

The low-temperature stability of polyethylene is confirmed by acoustic and mechanical investigations. Data are given on the dependence of the acoustic and mechanical properties of polyethylene on temperature and repeated cyclic cooling to –50° and heating to +60°C, together with information on the change in Poisson's ratio and volume during deformation.Mekhanika Polimerov, Vol. 1, No. 3, pp. 145–150, 1965     

Thixotropy of filled-polyethylene melts subjected to periodic shear deformation

As a result of the action of periodic finite-amplitude shear deformations filled high-pressure polyethylene melts exhibit thixotropic properties. The effect of the previous deformation history on the frequency dependence of the complex dynamic shear modulus is investigated.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR Riga. Translated from Mekhanika Polimerov, Vol. 4, No. 5, pp. 927–931, September–October, 1968.     

Deformation of elastic polyurethanes with a bimodal cellular structure

This article examines the cellular structure and mechanical properties of elastic foamed polyurethanes with a bimodal cellular structure (BFPUs). It is shown that the sizes of the oval cells (3–12 mm) in the elastic foamed polyurethenes that are studied are a tenth of an order greater than the sizes of the polyhedral cells (0.1–0.6 mm). Conversely, for rigid foamed polyurethanes, the polyhedral cells are more than a tenth of an order larger than the oval cells (microcells). The equations of the compression curve of BFFUs are found, and it is established that the deformation of BFPUs is determined by the deformation function of the cellular structure and the viscoelastic properties of the polymer matrix. The deformation functions of the cellular structure and the relaxation properties of BFPUs are determined. It is shown that choosing BFPUs with a cellular structure improves the comfort properties of the foamed material: the softness coefficient increased by 8–19% in the investigated case, while the support coefficient increased by 15–35%.Paper presented at the IX International Conference on the Mechanics of Composite Materials (Riga, 1995).Translated from Mekhanika Kompozitnykh Materialov, Vol. 32, No. 3, pp. 330–339, May–June, 1996.     

Elasticity and strength of nonoriented partially crystalline polymers

The dependence of the elastic modulus and strength on the crystallinity and temperature was studied. During the analysis of the strength data, the nonoriented crystalline polymers can be regarded as compositions consisting of a compliant matrix (amorphous phase) and a more rigid reinforcement (crystalline phase).The A. F. Ioffe Physicotechnical Institute, Academy of Sciences of the USSR, Leningrad. Translated from Mekhanika Polimerov, No. 6, pp. 964–968, November–December, 1975.     

Stability of a transversely isotropic cylindrical shell in axial compression

The problem of the stability of a transversely isotropic cylindrical shell subjected to axial compression is considered with the aid of three-dimensional linearized equations for small subcritical strains. Transcendental equations are obtained for the critical loads corresponding to axisymmetric and nonaxisymmetric deformation. It is shown that in the case of the axisymmetric buckling mode the Kirchhoff-Love hypothesis is asymptotically exact irrespective of the properties of the material. The dependence of the critical load on the properties of the shell material is investigated numerically. Graphs of the variation of the critical load with relative shear modulus are presented.Institute of Mechanics, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Mekhanika Polimerov, No. 6, pp. 1064–1068, November–December, 1969.     

Estimation of the molecular characteristics of polymers by the SPRT method and study of their influence on the properties of compositions

Pressure relaxation was examined in the cylinder of an MPT Monsanto processability tester after stopping the piston. The experimental function of the pressure drop F(t) was smoothed over and approximated by cubic splines. The spectra of pressure relaxation times (SPRT) were obtained according to the method of Schwarzl-Staverman. The SPRT method served well for estimating the spectra of the molecular-mass distribution (MMD) of polymers close in their physical sense to the SPRT. The correlation of the characteristic relaxation times and average molecular mass of ethylene-propylene rubbers and polyethylenes obtained by gel permeation chromatography was approximated by optimum models used for calculating the the molecular mass of rubbers according to the measurement results of the relaxation pressure of melts. The SPRT and characteristic relaxation times were used to analyze the significant technical properties of compositions based on polyethylene and rubber. The SPRT method was used to examine the failure of the cure network of butyl rubber and the dependence of the mechanical properties of thermoplastic elastomers on the molecular features of the decomposite.Presented at the 10th International Conference on the Mechanics of Composite Materials (Riga, April 20–23, 1998).Kazan State Technological University, Tatarstan, Russia. Translated from Mekhanika Kompozitnykh Materialov, Vol. 34, No. 5, pp. 691–698, September–October, 1998.     

Region of linearity of the deformation properties of contact-molded glass-reinforced plastic

A study was made of the creep and recovery of contact-molded glass-reinforced plastic in different directions in the plane of the sheet in uniaxial tension. On the basis of experimental data, the region of linearity of the deformation properties of the material under investigation was established. The influence functions in the relations of the theory of viscoelasticity were taken in the form proposed by Bronskii. The dependence of the parameters which determine these functions on direction was investigated. It is shown that, in practice, this dependence is inherent in only one of the parameters, and a relationship which is in satisfactory agreement with the experimental results is proposed to describe it.Moscow Institute of Chemical Machine Building. Scientific-Research Institute for Mechanics, M. V. Lomonosov State University, Moscow. Translated from Mekhanika Polimerov, No. 3, pp. 404–410, May–June, 1970.     

Antifriction and mechanical properties of polymer compositions based on silicone adhesives

A comparative investigation has been made of the antifriction and mechanical properties of polymer compositions based on K-400 silicone adhesive and fillers in the form of finely dispersed powdered polymers (tetrafluoroethylene, Kapron, polyethylene), graphite, sawdust, B-83 babbitt, and a lubricant^–US-2 grease. The antifriction properties of these materials are not inferior to those of some common nonferrous metals (B-83 babbitt, TsAM9-1.5 zinc alloy, OTsS5-5-5 bronze). The rational range of application of the compositions investigated is indicated.Rostov-on-Don Institute of Railroad Transport Engineers. Translated from Mekhanika Polimerov, No. 5, pp. 937–940, September–October, 1969.     

Dynamic properties of certain unvulcanized rubbers in the high-elastic and fluid states

The dynamic properties of a series of unvulcanized rubbers (cis-polybutadienes, Na-polybutadiene, cis-polyisoprene, butyl rubber, polyisobutylene, and ethylene-propylene copolymer) have been investigated in a low-frequency dynamic testing machine and a frequency rheometer on the frequency range from 5 · 10^–2 to 4.5 · 10³ Hz at temperatures of 25 and 60°C. At these temperatures the mechanical loss factor is the most sensitive criterion of transitions from one physical state of the polymer to another. For all the specimens investigated on the experimental range of angular frequencies the modulus of the complex dynamic viscosity and the effective viscosity determined under static conditions coincide, assuming the equivalence of angular frequencies and shear rates.A. V. Topchiev Institute of Petrochemical Synthesis, Academy of Sciences of the USSR, Moscow. Translated from Mekhanika Polimerov, No. 4, pp. 698–703, July–August, 1969.     

Nonautonomous Integrable Systems Associated with Hurwitz Spaces in Genuses Zero and One

Briefly outlining our recent work, we construct a family of nonautonomous integrable systems (deformations of the principal chiral model) in connection with the Hurwitz spaces of meromorphic functions on the Riemann sphere, cylinder, and torus. We give differential equations describing the dependence of the critical points of the rational, elliptic, and trigonometric functions on the critical values. We outline a relation to the deformation framework of Burtzev–Mikhailov–Zakharov.     

Effect of monoaxial stretching on molecular motion in Kapron

The effect of cold drawing on molecular motion in Kapron has been studied by the mechanical-loss method at a frequency of 1 Hz. A specially adopted procedure for carrying out experiments made it possible to evaluate the contribution to losses from amorphous bands and crystallites selectively. The decrease (recovery) of logarithmic decrement with time in freshly deformed Kapron samples has been observed — a phenomenon analogous to the known Köster effect, which is characteristic of low-molecular-weight crystalline solids. It has been shown that just as in conventional crystalline substances, the time dependence of damping in Kapron can be explained within the framework of the Granato-Hikata-Lücke theory, in conformity with which the recovery is caused by gripping of dislocations by point defects induced by the deformation. The dependence of the rate of recovery on the degree of deformation and the conditions of deformation (in the loaded or relieved state of the sample) is discussed.S. Ordzhonikidze Siberian Metallurgical Institute, Novosibirsk. Translated from Mekhanika Polimerov, No. 2, pp. 202–208, March–April, 1972.     

Solid-state extrusion of polymerization-filled polymer compositions

The mechanical properties of ultra-high molecular polyethylene and filled compositions based on it produced by solid-state extrusion of powder semifabricates have been investigated. It is shown that high-level properties are obtained by extrudates with fillers possessing high disposition to adhesive interaction with the polymer matrix. A mathematical model of solid-state extrusion of the compositions is derived considering the possibility of compaction and loosening of the material in the process of deformation. Satisfactory agreement of the calculated and experimental data is obtained.Translated from Mekhanika Kompozitnykh Materialov, Vol. 35, No. 1, pp. 101–108, January–February, 1999.     

Effect of the rate of deformation on the mechanical properties of compact bone tissue

Conclusions The results of this study show that the ultimate stress increases with increasing deformation rate from 10^–5 to 1 sec^–1 but the initial elasticity modulus remains virtually constant. A characteristic feature of bone tissue is the significant increase or even maximum in specific deformation energy for destruction in the range of deformation rates corresponding to normal physiological conditions for bone function. The deformation diagrams of human bone tissue for the same values of moisture content and deformation rate in tensile testing do not differ from the analogous curves for the bone tissue of cattle. Quantitatively, the ultimate stress ₁₁ and the initial elasticity modulus E₁ are 5–10% and 15–25% greater, respectively, than for cattle bone tissue, while the ultimate deformation eu is virtually the same. An increase in the moisture content of bone tissue leads to a more pronounced dependence of the mechanical parameters on the deformation rate.Translated from Mekhanika Kompozitnykh Materialov, No. 3, pp. 512–517, May–June, 1982.     

Thermofrictional properties of self-lubricating antifriction plastics

New thermally stable polymers (polyimides, polyarylates, and phenolphthalein-phenolformaldehyde copolymers) were used in a study of the thermofrictional properties of their compositions with molybdenum disulfide. We established the existence of several temperature zones of friction and demonstrated their connection with the changes in the relaxation and autohesion properties of the polymers in these same temperature zones.Institute of Organoelement Compounds, Academy of Sciences of the USSR, Moscow. Translated from Mekhanika Polimerov, No. 3, pp. 481–485, May–June, 1970.