Note: Initial Results of a Flow Birefringence Study of the Hole Pressure for Polymer Melts

Pike, D C; Baird, Donald G.

doi:10.1122/1.549776

Cited by 7 publications

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“…Even though a number of the assumptions made during the derivation of Equation ( 7) were later proved to be invalid [110,111], Yao and Malkus [112] showed that the errors due to violated assumptions exactly canceled each other, and they concluded that the final equation to calculate N 1 from P h derived by Higashitani and Pritchard [108] should be representative. For Newtonian and inelastic liquids under laminar conditions, P h is zero.…”

Section: The First Normal Stress Differencementioning

confidence: 99%

Principles and Guidelines for In-Line Viscometry in Cereal Extrusion

et al. 2022

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In the food industry, extrusion cooking finds numerous applications thanks to its high productivity and nutrient retention. More specifically, cereal extrusion, e.g., for savory snacks and breakfast products has an important market share. For such applications, rheology, which addresses viscous and elastic contributions, plays an important role in developing, optimizing, and controlling the extrusion manufacturing technique. In this context, conventional off-line rheometers are not ideal for providing data, as the goal is to replicate the exact thermomechanical history to which the food is subjected in the extrusion process. Hence, to achieve reliable analyses, in-line viscometers that have mostly been tested using oil-based polymers were introduced. Biopolymers (e.g., starch), however, are highly sensitive to both heat and mechanical degradation, and the viscometer design has to be adapted accordingly to produce an accurate measurement. Alongside a discussion of the different designs available, this review will address the most common methodologies for measuring the steady shear viscosity, extensional viscosity, and the first normal stress difference for food applications, providing researchers in the biopolymer and food engineering fields with a general introduction to this emerging topic.

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