The differential viscometer. I. A new approach to the measurement of specific viscosities of polymer solutions

Abstract

SynopsisA new type of solution viscometer is described that measures the specific viscosity directly. This is accomplished with a balanced network of four capillaries arranged in a manner analogous to a Wheatstone bridge. A differential pressure transducer measures the increase in pressure across the bridge when a solution is injected into one of the capillaries while solvent flows continuously in the other three capillaries. The differential pressure is proportional to the specific viscosity of the solution. The differential viscometer is about 10 times more sensitive than a conventional glass tube viscometer, permitting precise measurements of specific viscosities of 0.01 or less. The measurements are also inherently fast, averaging about 3 min per sample. Precision is about 1% RSD. Accuracy was investigated by running standard solutions of sucrose in water, polystyrenes in toluene, and polyethylenes in decalin. The agreement was within 2-3% of the standard values in most cases.

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“…As shown in the figure, this configuration is a fluid flow analog of the Wheatstone bridge electrical circuit. [11,12] The differential pressure transducer measures the change in pressure across the bridge (DP), while the inlet pressure transducer measures the pressure change through the bridge (IP). The polymer 2008 STRIEGEL AND ALWARD ©2002 Marcel Dekker, Inc. All rights reserved.…”

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