Plastics rheology

The model includes a dynamic thermodynamic sea ice model. The dynamics of sea ice are formulated using viscous-plastic rheology [Hibler (1979)]. The thermodynamics relate changes in sea ice thickness to a balance of radiant, turbulent, and oceanic heat fluxes. The effect of snow accumulation on sea ice is included, along... 

At h h polymer concentrations, polymer molecules entangle, producing pseudo-plastic rheological behavior. This occurs at a polymer concentration, cf = comparable to that in the polymer... 

These t3 pes of floccs give rise to a plastic rheology with a yield stress. 

These velocity profiles for Newtonian and Bingham plastic rheology follow. The velocity profile for Crossian rheology has not yet been developed for this geometry. ... 

Vehicles that exhibit the unusual property of Bingham-type plastic rheological flow are characterized by the need to overcome a finite yield stress before flow is initiated. Permanent suspension of most pharmaceutical systems requires yield-stress values of at least 2-5 Pa (20-50 dyn/cm ). Bingham plastic flow is rarely produced by pharmaceutical gums and hydrophilic colloids. National Formulary (NF) carbomers exhibit a sufficiently high yield value at low solution concentration and low viscosity to produce permanent suspensions. The carbomers, however, require a pH value between 6 and 8 for maximum suspension performance. The polymer is essentially incompatible... 

ALMOST UNCHARTED AREAS OF COMPOSITE AND PLASTIC RHEOLOGY... 

Creaming is the separation of dispersed droplets from the continuous phase under the action of gravity. The droplets do not coalesce when they touch. If the dispersed medium is less dense than the continuous phase, the emulsion will cream upwards. Conversely, for a more dense dispersed phase, the emulsion will cream downwards or sediment. Creaming will inevitably occur in any dilute emulsion in accordance with Stokes s law if the phases are not exactly equal in density. Creaming is, therefore, a trivial form of instability that can be avoided by addition of thickeners that confer plastic rheology, and, therefore, yield value to the aqueous phase. 

In their article on Test methods for plasticity and extrusion behaviour , Katrin Gohlert and Maren Ubel focus attention on methods of particular importance for the characterization and registration of rheological data. The paper concentrates mainly on the various instruments used for determining plasticity / rheological indicators. 

Uses Phenoxy resin for hot-melt prepregs, epoxy prepreg additives, hot-melt and structural adhesives, pipe coatings, polymer alloys modifier for plastics rheology control agent for epoxies modifier for phenolic and melamine resins... 

A carbopol solution p = lOOOkg/m ), with Bingham plastic rheology (Tq = 8Pa and plastic viscosity of 50 m Pa-s), is flowing through a 25 mm diameter pipeline. Estimate the pressure drop per metre of pipe when the mean velocity is 1 m/s. Also, estimate the radius of the unsheared plug in the core region. 

R. S. Lenk, Plastics Rheology, Appl. Sci. Publishers, London, 1978. 

Sobhanie, M., Isayev, A.I., and Fan, Y. (1997) Viscoelastic plastic rheological model for particle filled polymer melts. Shed. Acta, 36 (1), 66-81. 

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