Barus

Naqvi, S.M., C.T. Flagge, and R.L. Hawkins. 1990. Arsenic uptake and depuration by red crayfish, Procam-barus clarkii, exposed to various concentrations of monosodium methanearsonate (MSMA) herbicide. Bull. Environ. Contam. Toxicol. 45 94-100. 

For convenience and simplicity, polymers have generally been considered to be isotropic in which the principle force is shear stress. While such assumptions are acceptable for polymers at low shear rates, they fail to account for stresses perpendicular to the plane of the shear stress, which are encountered at high shear rates. For example, an extrudate such as the formation of a pipe or filament expands when it emerges from the die in what is called the Barus or Weissenberg effect or die swell. This behavior is not explained by simple flow theories. 

Data on the vapor pressure of sulfur above the boiling point were reported by Barus,1,2 Greuner,1 Rassow,1 Regnault,6,7 Ruff and Graf,1 and Menzies.1... 

Barus Physics Laboratory, Brown University, Providence, R. I. 

The phenomenon of post-extrusion swelling or "ballooning" has been discussed in Chap. 15. It is related to the so-called Barus effect, according to which the diameter of polymer extrudates is larger than the capillary diameter when the melt is forced through an orifice. All materials with any degree of melt elasticity display this effect. The origin of the effect is related to the elastico-viscous nature of polymer melts, thus to Ni=Tu — T22. 

Barus suggests an alloy of platinum with 20 per cent, of iridium, instead of rhodium, as the e.m.f. of this couple is about 23 per cent, higher than that of Le Chateher s. 

The classic Barus equation describes the effects of pressure on viscosity 5... 

The negative first normal stress difference under a medium shear rate, characterized by liquid crystalline polymers, makes the material avoid the Barus effect—a typical property of conventional polymer melt or concentrated solution, i.e., when a polymer spins out from a hole, or capillary, or slit, their diameter or thickness will be greater than the mold size. The liquid crystalline polymers with the spin expansion effect have an advantage in material processing. This phenomenon is verified by the Ericksen-Leslie theory. On the contrary, the first normal stress difference for the normal polymers is always positive. 

H. E. Farnsworth, Barus Research Laboratory-, Brown University, Provi-... 

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