Viscosity uniaxial

Unlike shear viscosity, extensional viscosity has no meaning unless the type of deformation is specified. The three types of extensional viscosity identified and measured are uniaxial or simple, biaxial, and pure shear. Uniaxial viscosity is the only one used to characterize fluids. It has been employed mainly in the study of polymer melts, but also for other fluids. For a Newtonian fluid, the uniaxial extensional viscosity is three times the shear viscosity ... 

Uniaxial viscosity, 21 718 Unicomponent metathesis initiators based on early transition metals,... 

Problem 6.8 (Worked Example) Estimate the steady-state uniaxial viscosity of a suspension of 0.1% by volume of rod-like particles L = 6 yum long and d = 10 nm in diameter in a Newtonian oil of viscosity 100 P at an extension rate of 1 sec . ... 

These relationships are known as Newton s Law of viscous flow a is termed the fluidity and -q the dynamical shear viscosity. Newton s Law is analogous to Hooke s Law, except shear strain has been replaced by shear strain rate and the shear modulus by shear viscosity. As shown later, this analogy is often very important in solving viscoelastic problems. In uniaxial tension, the viscous equivalent to Hooke s Law would be a=7] ds/dt), where q is the uniaxial viscosity. As v=0.5 for many fluids, this equation can be re-written as <7-=3Tj(de/dO using t7=t /[2(1+v)], the latter equation being the equivalent of the interrelationship between three engineering elastic constants, (fi=E/[2il + v)]). 

In Eqs. 196 and 197, Pq is the exit pressure which can be well approximated by the pressure drop through an orifice of the same radius as the die and n is the PL exponent which is obtained from capillary data (with die radius and length given by R and L, respectively). Cogswell s method, as well as other alternative methods for obtaining the uniaxial viscosity, have been compared against direct measurements in an extensional rheometer by Laun and Schuch [23]. 

Uniaxial viscosity of network (not viscosity, >i, of solid phase itself), F, and elastic shear modulus, G, versus time after gelation. From Scherer et al. [73],... 

Figure 7.4.4 shows data from the rotating clamp device for the transient equibiaxial viscosity at three different extension rates. For comparison, the linear viscoelastic viscosity and the uniaxial viscosity are shown. Results for the biaxial viscosity compare well to those measured in lubricated compression on the same polyisobutylene sample as in Figure 7.4.4 (Chatraei et al., 1981). So far, only results with the rotating clamp method have been reported for this sample. Maximum strains were 2.5 in the biaxial and multiax-ial tests and k < 0.1 s. Friction on the talcum powder may limit the total strain and the detectable stress values. Much larger, more homogeneous samples are required than were used in the lubricated squeezing experiments. However, because the rotating clamps can...

Transient equibiaxial viscosity (m = 1, open symbols), uniaxial viscosity (m = -0.5, solid symbols), and linear viscoelastic shear viscosity (lines) for polyisobutylene. Replotted from Meissner et al. (1982). 

Unlike shear viscosity, extensional viscosity has no meaning unless the type of deformation is specified. The three types of extensional viscosity identified aind measured are uniaxial or simple, biaxial, and pure shear. Uniaxial viscosity is the only one used to characterize fluids. It has been employed mainly in the study of polymer melts, but also for other fluids. For a Newtonian fluid, the uniaxial extensional viscosity is three times the shear viscosity ( fe)uni = 3/ . This is confirmed at very low shear rates in Figure 13, which provides a typical example of the extensional viscosity behavior of a polymer (129). The two other extensional viscosities are used to study elastomers in the form of films or sheets. Uniaxial and biaxial extensions are important in industry (118,125-128,130,132), the former for the spinning of textile fibers and roller spattering of paints, and the latter for blow molding, vacuum forming, film blowing, and foam processes. 

M. Cologna, V.M Sglavo, Vertical sintering to measure the uniaxial viscosity of thin ceramic layers. Acta Materialia 58(17), 5558-5564 (2010)... 

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