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** Activation energy, viscous flow **

Figure 4.1 Dependence of activation energy for viscous flow on melting point for normal metals and semi-metals. Reprinted, by permission, from T. lida and R. I. L. Guthrie, The Physical Properties of Liquid Metals, p. 187. Copyright 1988 by Oxford University Press. |

Walter, R. H., and Sherman, R. M. (1981). Apparent activation energy of viscous flow in pectin jellies, f. Food Sci. 46 1223-1225. [Pg.219]

Figure I. Effect of phosphoric acid concentration in additive on the activation energy of viscous flow of casting solutions |

A variation of Equation 4-9 is to approximate the many terms in it by viscosity Tj (Kirkpatrick, 1975). Assuming that the activation energy for viscous flow is the same as that for nucleation, then p =A exp[E/(RT)] where A is a constant. Substituting it into Equation 4-9 leads to [Pg.337]

Under stress conditions similar to those arising in the extrusion or pressure molding processes, the activation energy for viscous flow of systems with PMF is little different from that for the matrix [163, 164,209, 344, 345], This means that the secondary network of the materia has been destroyed [69]. [Pg.55]

Recently, contribution of dimethylsiloxane unit in the series of cyclic (D3 - Ds) and linear (D2 - Du) oligodimethylsiloxanes with various end groups was studied [1-4], It is indicated that absolute values of the activation energy of viscous flow of each cyclic compound are higher, compared with linear ones possessing the same number of dimethylsiloxane units in the molecule. [Pg.167]

Caustic Waterflooding. In caustic waterflooding, the interfacial rheologic properties of a model crude oil-water system were studied in the presence of sodium hydroxide. The interfacial viscosity, the non-Newtonian flow behavior, and the activation energy of viscous flow were determined as a function of shear rate, alkali concentration, and aging time. The interfacial viscosity drastically [Pg.224]

In connection with the earlier consideration of diffusion in liquids using the Stokes-Einstein equation, it can be concluded that the temperature dependence of the diffusion coefficient on the temperature should be T(exp(—Qvls/RT)) according to this equation, if the activation energy for viscous flow is included. [Pg.295]

The viscosities of the same two series of methylpolysiloxanes have been measured at several temperatures,11 and the logarithm of the absolute viscosity at any one temperature has been found to be a linear function of the logarithm of the number of units in either series. The activation energy of viscous flow may be expressed by an equation very similar to those just given for heat of vaporization [Pg.67]

Accordingly the increase in excimer/molecular fluorescence yield ratio with temperature in this region (Fig. 9) reflects the corresponding increase in encounter frequency dm[M] of excited and unexcited molecules if t/([M]rP)/ dT 0, and the temperature coefficient is related to the activation energy for viscous flow of the solvent Ed. [Pg.182]

The viscosity of liquid silicates such as drose containing barium oxide and silica show a rapid fall between pure silica and 20 mole per cent of metal oxide of nearly an order of magnitude at 2000 K, followed by a slower decrease as more metal oxide is added. The viscosity then decreases by a factor of two between 20 and 40 mole per cent. The activation energy for viscous flow decreases from 560 kJ in pure silica to 160-180kJmol as the network is broken up by metal oxide addition. The introduction of CaFa into a silicate melt reduces the viscosity markedly, typically by about a factor of drree. There is a rapid increase in the thermal expansivity coefficient as the network is dispersed, from practically zero in solid silica to around 40 cm moP in a typical soda-lime glass. [Pg.309]

The results of the calculations shown in Fig. 2.32 represent a complete quantitative solution of the problem, because they show the decrease in the induction period in non-isothermal curing when there is a temperature increase due to heat dissipation in the flow of the reactive mass. The case where = 0 is of particular interest. It is related to the experimental observation that shear stress is almost constant in the range t < t. In this situation the temperature dependence of the viscosity of the reactive mass can be neglected because of low values of the apparent activation energy of viscous flow E, and Eq. (2.73) leads to a linear time dependence of temperature [Pg.75]

Melt Viscosity. As shown in Tables 2 and 3, the melt viscosity of an acid copolymer increases dramatically as the fraction of neutralization is increased. The relationship for sodium ionomers is shown in Figure 4 (6). Melt viscosities for a series of sodium ionomers derived from an ethylene—3.5 mol % methacrylic acid polymer show that the increase is most pronounced at low shear rates and that the ionomers become increasingly non-Newtonian with increasing neutralization (9). The activation energy for viscous flow has been reported to be somewhat higher in ionomers than in related acidic [Pg.406]

** Activation energy, viscous flow **

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