Effect of the molecular weight of the polystyrene matrix on the physicomechanical properties of impact polystyrene

The effect of the molecular weight of the polystyrene on the properties of impact polystyrene obtained by mechanical mixing of polystyrene and rubber has been investigated. As the molecular weight of the polystyrene increases, the physicomechanical properties of the impact polystyrene improve and its rheological properties deteriorate. There is a definite correlation between the physicomechanical properties of the polystyrene and those of the impact polystyrene.Scientific-Research Institute of Synthetic Rubber, Kralupy-on-Vltava, Czechoslovakia. Translated from Mekhanika Polimerov, No. 3, pp. 545–546, May–June, 1971.     

Generalized concentration dependence of the viscosity of concentrated polymer solutions

The construction of a generalized concentration dependence of the viscosity of concentrated solutions is analyzed. It is shown that there should be a single dependence for different polymers in different solvents of the form: (/_o)^1–2k=1+(1–2k)c[], where k is the Huggins-Martin constant, and [] is the intrinsic viscosity. Deviations from this relation may be observed in the presence of structure formation in the solution or when the experimental temperature is close to the glass-transition temperature of the system."Plastpolimer" Okhtinsk Research-Production Association, Leningrad. Translated from Mekhanika Polimerov, No. 1, pp. 172–175, January–February, 1976.     

Effect of electrical discharges on the mechanical strength and molecular weight of polystyrene film

Electrically aged polystyrene film was examined to determine the effect of voltage, aging time, and nature of the medium on the mechanical strength and molecular weight. It was established that the changes in the mechanical strength and molecular weight of the film always correspond.Mekhanika Polimerov, Vol. 4, No. 1, pp. 59–63, 1968     

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.     

Effect of orientation and molecular weight on the modulus of elasticity of polymer materials

The modulus of elasticity of a perfectly crystalline polymer is calculated as a function of the orientation of the crystallites. The calculations are based on the mechanics of a micro-inhomogeneous continuum. The dependence of the modulus of elasticity on crystallite orientation and molecular weight is calculated with reference to the example of crystalline kapron.Moscow-Lenin Pedagogical Institute. Problem Laboratory of Polymer Physics. Translated from Mekhanika Polimerov, Vol. 4, No. 6, pp. 1002–1007, November–December, 1968.     

Parabolic Harnack inequality of viscosity solutions on Riemannian manifolds

We consider viscosity solutions to nonlinear uniformly parabolic equations in nondivergence form on a Riemannian manifold M with the sectional curvature bounded from below by −κ   for κ≥0$\kappa \ge 0$. In the elliptic case, Wang and Zhang [24] recently extended the results of [5] to nonlinear elliptic equations in nondivergence form on such M, where they obtained the Harnack inequality for classical solutions. We establish the Harnack inequality for nonnegative viscosity solutions to nonlinear uniformly parabolic equations in nondivergence form on M. The Harnack inequality of nonnegative viscosity solutions to the elliptic equations is also proved.     

NMR relaxation and micro-imaging study of polystyrene in concentrated cyclohexane solution

¹³C-relaxation times of polystyrene (PS) in its θ solvent, cyclohexane, are measured at different temperatures. A two-step model for the dissolution is proposed. Swelling of the polymer below the θ temperature is eventually the dispersion of the side group phenyl rings only. While above the θ temperature, complete dissolution is the dispersion of the main chain at a molecular level. The results of T₁(C) are confirmed by¹H-NMR imaging. NMR and its imaging are powerful twls to study the dynamic behavior of dissolution process of polymers in their θ solvents. Project supported by the National Key Projects for Fundamental Research “Macromolecular condensed state”, the State Science and Technology Commission of China.     

Influence of viscosity on the smoothness of solutions of incompletely parabolic systems

A study of the smoothness of two groups of solution components of systems whose space-variable operator splits into two operators, one parabolic and the other hyperbolic.Translated from Matematicheskie Zametki, Vol. 10, No. 1, pp. 93–99, July, 1971.     

Global solutions of the Navier-Stokes equation with strong viscosity

Following Ebin and Marsden the Navier-Stokes equation is viewed as a perturbation of a geodesic flow on the group of volume preserving diffeomorphisms on a compact Riemannian manifold. Existence and uniqueness of bounded solutions for all position time is shown by taking a higher order diffusion term.Partial y supported by Alexander von Humboldt Foundation     

On the definition of viscosity solutions for parabolic equations

In this short note we suggest a refinement for the definition of viscosity solutions for parabolic equations. The new version of the definition is equivalent to the usual one and it better adapts to the properties of parabolic equations. The basic idea is to determine the admissibility of a test function based on its behavior prior to the given moment of time and ignore what happens at times after that.

     

On viscosity solutions of irregular Hamilton-Jacobi equations

It is proved that the initial-value problem for admits a unique continuous viscosity solution under certain conditions which do not exclude that H(x, p) is discontinuous in x. Particular attention is devoted to the linear transport equation , where a may be discontinuous. Received: 21 October 2002     

Regularity of viscosity solutions near KAM torus

In this paper, we give weak regularity theorems on P of u~ε(x, P), where u~ε(x, P)is the viscosity solution of the cell problem H_ε(P D_xu~ε, x)=H_ε(P).     

Effect of molecular weight on strength and deformation characteristics of oriented amorphous polymers

Tensile tests were carried out on uniaxially oriented films of several amorphous linear polymers (polymethyl methacrylate, polystyrene, and poly-2,2-octamethylene-5,5-dibenzimidazol) of various molecular weights. It was shown that molecular weight has no direct effect on polymer strength, which is determined by structure. However, when polymer fibers and films are formed and stretched, the molecular weight of a given material affects the orientation of macromolecules and so predetermines the structure of the products obtained and, consequently, their strength.Mekhanika Polimerov, Vol. 3, No. 4, pp. 579–585, 1967     

Effect of polymer molecular weight on its reaction with nonporous and porous fillers

The effect of polymer molecular weight (using polyethylene and polyisobutylene) on the formation of polymer contact with the surface of porous and nonporous fillers has been studied. It has been shown that the extent of coating of a nonporous surface by polymer does not depend on polymer molecular weight, but the extent of coating of a porous surface is larger, the lower the molecular weight of the polymer; this is explained by a selective adsorption of macromolecules of lower molecular weight on the porous filler from the polymer melt.     

Effect of the molecular weight of monodisperse specimens of high-density polyethylene on the dynamic modulus of elasticity

The effect of the molecular weight on the instantaneous dynamic modulus of elasticity of monodisperse specimens of linear polyethylene has been studied. It is shown that above a critical value of the molecular weight the modulus of elasticity is constant and equal to 4·10⁹ N/m², while below that value it increases to 7.28·10⁹ N/m².M. Azizbekov Azerbaidzhan Institute of Petroleum and Chemistry, Baku. Translated from Mekhanika Polimerov, No. 3, pp. 531–533, May–June, 1976.