Rheological properties of polymer melts

A new method of treating experimental data on the viscous and viscoelastic properties of various polymer melts is suggested. The dependence of the apparent viscosity on the molecular weight, temperature and shear stress can be represented as the product of three independent functions, each of them having a single argument. All three functions are universal, at least in first approximation, and the dependence of the apparent viscosity on the variables indicated is determined by two parameters (glass transition temperature and critical molecular weight), characteristic of each homologous polymer series. The viscoelastic characteristics (dynamic, relaxation, creep, as well as relaxation and retardation spectra) of polymer melts are universal in shape in the linear region and contain only one individual polymer parameter, viz., maximum Newtonian viscosity. It is shown that upon normalization of certain nonlinear characteristics with respect to the maximum Newtonian viscosity, they can also be represented in the universal form.     

Heavy oil as an emulsion: Composition,structure, and rheological properties

Recent works devoted to studying the structure and rheological properties of water/oil disperse systems have been reviewed. Contemporary understandings of crude heavy oil as a water-in-oil emulsion have been discussed. Data on the mechanism of the stabilizing effect of natural lipophilic surfactants and ultradispersed particles of different natures contained in oil have been presented. Methods that are used to improve the transport characteristics of heavy oil—in particular, the formation of low-viscosity oil-in-water emulsions—have been listed. Colloidal and rheological properties of heavy oil-in-water emulsions, which are increasingly applied for pipeline transportation of oil, have been considered.     

Invariants and nonequilibrium density matrices

A new method of calculating nonequilibrium density matrices with the aid of the quantum integrals of motion is proposed. The method is shown to be very effective in the case of systems described by means of quadratic Hamiltonians. The possibility of constructing phenomenological nonstationary Hamiltonians for a wide class of dissipative systems is discussed. The exact formulas for nonequilibrium density matrices of arbitrary quadratic systems are obtained. The quantum problem of the motion of a charged particle in uniform electric and magnetic fields in the presence of a frictional force proportional to the velocity is solved exactly by means of introducing the new phenomenological Hamiltonian.     

Kinetics of Curing of Epoxy Oligomer by Diaminodiphenyl Sulfone: Rheology and Calorimetry

Diaminodiphenyl sulfone is used as a curing agent to obtain an epoxy-resin-based binder with improved thermal stability. The kinetics of curing of this composition is studied by rheokinetic and calorimetric methods. It is shown that complete conversion is attained at a temperature of 200°С or higher. The rate of viscosity increase in the course of time in curing under flow conditions does not depend on the shear rate; the viscosity changes monotonically. The curing reaction occurs in the homogeneous mode without separation of a crosslinked polymer; it is described by a second-order equation with self-deceleration at low temperatures. The rheokinetic characteristics and temperature dependences of kinetic parameters of the process are determined.