SU808915A1 - Method of measuring liquid rheologic properties - Google Patents

Description

one

The invention relates to capillary viscometry and can be used in determining the rheological properties of Newtonian and non-Newtonian liquids, suspensions, emulsions, solutions and melts.

A device for studying the rheological properties of polymeric materials is known, in which a method is implemented which makes it possible to determine the flow velocity profile of a plastic by the deformation in the cylinder cavity of the tinted material 1.

The drawback of the device is the complexity of its design and the duration of measurements associated with stopping the flow, separating the deformed column of the subcreatable material from it, building a velocity profile and its numerical or graphical differentiation to determine the dependence of the velocity gradient on tangential stresses.

The closest technical solution is capillary viscometry of liquids, mainly. bath on measuring the dependence of the flow rate of a fluid passing through

the capillary pressure gradient and allowing the Berg – Rabinovich – Mooney formula by Weiss to go to the dependence of the velocity gradient on the capillary wall on the tangential stresses 1.2 J.

However, the determination of the rheological flow curve by this method is a laborious and time-consuming process.

0 since it requires numerous experiments to determine the dependence of the flow rate of the test liquid through the capillary at various pressure seals, to construct an intermediate graph of the dependence of the average velocity gradient on the tangential stresses on the capillary wall and its graphic or numerical differentiation.

The purpose of the invention is to increase the speed and simplify the measurement process.

This goal is achieved by the fact that in the method of determining the rheological properties of liquids, which consists in measuring the pressure gradient of the test liquid as it passes through the capillary, an indicator, is introduced into the inlet of the capillary. determine the dependence of the indicator concentration on the time of its stay in the capillary and, using the data obtained, determine the dependence of the velocity gradient on tangential stresses by formulas;

"(.Fcutdt) VjC tdt / Cut

ar

(Jcutdt

APR. ± H

-nr

Cutdt

tH is the velocity gradient, s; - the length of the capillary, m; - ra, capillary dius, m; - distribution function of the indicator residence time in the capillary, mm; the start and end time of the distribution function, s; tangential stress pressure gradient, n / m Decreasing the residence time distribution function and using it to determine the dependence of the velocity gradient on tangential stresses using the proposed formulas simplifies and speeds up the process of measuring rheological properties, since it significantly reduces the number of experiments, the time of experiments and processing of experimental data. The determination of the rheological properties of fluids according to the proposed method begins with the measurement of the gradient of laziness and the removal of the distribution function of the residence time. The method of removing the latter is to feed the indicator capillary inlet (salt solution, acid, radioactive isotopes, etc.) and automatically record its concentration from the capillary. Then, by the known pressure gradient and the distribution function of the stay, we plotted the dependence of the concentration of the indicator C on time t, determined by e1c the dependence of the velocity gradient on tangential stresses according to the formulas | l. (A: Jj1: utd7) / 7cutdt / cuti; a gt chn n

/ Jcutdt

flPR MM TL

J Cutc / t

iH

which, when integrated numerically, are converted to

(Q §f HV YzVucptcputj-VxCucptcpAt / Cut (1) X Cucp J. Cucp tepAt Example. According to the proposed method, the rheological properties of a 5% solution of carboxymethylcellulose in water are measured. with a diameter of 4 mm and a pressure drop of 65 mm of water, the residence time distribution function is removed (see the drawing) according to a known method. leaving the capillaries pa, the concentration of particles of the indicator is automatically measured and a graph of the residence time distribution function is plotted. The pressure gradient is calculated using the formula 64140 X 10 9.81, where H is the readings of the cup water differential pressure gauge, H 64 mm water; p 1000 kg / m - water density; "9.81 M / s - acceleration of free fall. The residence time distribution function is divided into intervals first after 2 s, then after 10 s and at each break point the corresponding concentration of Cu in millimeters is determined. The measurement results are shown in the table.

125 178 26 154 14870 14.25 0.263

227 140 28 122.5 20570 16.65 0.301

8000 9.7 0.189

 tcput 89430 n

de su - the function of residence time distribution;

Sisr is the mean value of the C function in the interval; average time

cp in the interval;

t is time;

at - time partitioning interval;

dv is the velocity gradient; dr.

 - tangential for example. The table presents the results.

dV speed gradient calculation - by

formula (1), as well as the tangential stresses f according to the formula (2).

Since L is 1 m, R 2d10 m,

tdV

XCucptcpAt 89430, then jp

h

 2.99 loVjCucptcpAt / Cut /

n in this example

-but

 628 n / m,

R 2 10 m;

  89430.

tH

then C- 2.1 loV CueptcpAt / M n

In the same capillary, a series of experiments was carried out to determine the dependence of the flow rate of a fluid on a pressure gradient, according to a method corresponding to a known method: the flow rate of a fluid is determined from a rotameter and its corresponding pressure H is determined from a cup diffan. 1 meter.

Table continuation

Using the proposed method as compared with the known with equal accuracy makes it possible to significantly reduce the number of necessary experiments, simplifies calculations, since it does not require the construction of an intermediate graph and its graphical or numerical differentiation, simplifies the determination of the viscometric flow curve and speeds up the process of conducting experiments and processing experimental data. data 4-5 times.

Claims (2)

1. The author's certificate of the USSR 399764, cl. G 01 N 1/02, 1972. 2. Mildman S. Polymer flow. M., Mir, 1971, with ... 24 (prototype).