Method and rheometer for determining the density of an at least flowable, in particular liquid, specimen

Patent metadata

Field	Value
Publication number	US-11921022-B2
Application number	US-202117366700-A
Country	US
Kind code	B2
Filing date	Jul 2, 2021
Priority date	Jul 7, 2020
Publication date	Mar 5, 2024
Grant date	Mar 5, 2024

Abstract

A method for determining the density of an at least flowable, in particular liquid, specimen with a rheometer, in particular a rotational rheometer, includes providing the rheometer with a first measurement component for receiving the at least flowable, in particular liquid, specimen, and a second measurement component with a known volume to be immersed into the specimen. The first and second measurement components are movable relative to one another. The perpendicular force between the two measurement components is measured after the immersion of the second measurement component into the specimen. The measured perpendicular force corresponds to the buoyancy force acting between the specimen and the second measurement component. The density of the specimen is calculated based on Archimedes' principle by reference to the known volume of the second measurement component and the measured perpendicular force. A rheometer for carrying out the method is also provided.

First claim

The invention claimed is:

1. A method for determining the density of an at least flowable or liquid specimen, the method comprising:
providing a rotational rheometer including a first measurement component for receiving the at least flowable or liquid specimen, and a second measurement component to be immersed into the specimen, the first measurement component and the second measurement component each having a bottom surface, the components being movable relative to one another and the second measurement component having a known volume;
measuring a normal force acting in a direction normal to the rheometer between the bottom surfaces of each of the first and second measurement components after an immersion of the second measurement component into the specimen, the measured normal force corresponding to a buoyancy force acting between the specimen and the second measurement component; and
calculating the density of the specimen based on Archimedes' principle by reference to the known volume of the second measurement component and to the measured normal force.

2. The method according to claim 1 , which further comprises controlling a temperature of the specimen during the measurement of the normal force, and repeating a determination of the density of the specimen at different temperatures.

3. The method according to claim 2 , which further comprises controlling the temperature of the specimen by at least one of heating up to a temperature of 1730° C. or cooling.

4. The method according to claim 1 , which further comprises:
before a determination of the density, determining a thermal expansion of the second measurement component at various reference temperatures and storing the thermal expansion; and
during a following determination of the density of the specimen, at least one of correcting or taking into account an influence of temperature on the volume of the second measurement component at a respective measurement temperature by reference to stored values.

5. The method according to claim 4 , which further comprises storing the thermal expansion as a volume-correction curve or volume-correction table.

6. The method according to claim 1 , which further comprises:
before the measurement of the density of the specimen, carrying out test measurements at various reference temperatures with reference liquids having a known density at prescribed reference temperatures, determining an influence of temperature on the volume of the second measurement component and on the normal-force measurement in combination and storing the influence; and
during a following determination of the density of the specimen, correcting the influence of temperature on the volume of the second measurement component and on the measured normal force in combination at a respective measurement temperature by reference to stored values.

7. The method according to claim 6 , which further comprises storing the influence as a normal-force-correction curve or normal-force-correction table.

8. The method according to claim 1 , which further comprises:
before a determination of the density of the specimen:
calculating a geometric density at least of one reference liquid from a mass of a reference liquid introduced into the first measurement component and from a position, determined during an approach of the second measurement component, of a surface of the reference liquid, and from a known geometry of the first measurement component;
determining a density of the reference liquid, and determining a correction factor by a comparison of a determined value of the density of the reference liquid with a determined value of the geometric density of the reference liquid; and

during a following determination of the density of the specimen, correcting an effect of an immersion depth of the second measurement component into the specimen by reference to the determined correction factor.

9. The method according to claim 8 , which further comprises calculating the geometric density of the at least one reference liquid at prescribed reference temperatures, determining the density of the reference liquid at the prescribed reference temperatures, storing the correction factor in an evaluation unit, and correcting the effect of the immersion depth at the respective measurement temperature.

10. The method according to claim 1 , which further comprises:
keeping the first measurement component or the second measurement component stationary during the measurement of the normal force, or
at least one of rotationally oscillating or rotating the first measurement component or the second measurement component during the measurement of the normal force.

11. The method according to claim 1 , which further comprises determining rheological parameters or viscosity of the specimen in addition to or simultaneously with a determination of the density of the specimen.

12. The method according to claim 1 , which further comprises measuring a temperature of at least one of the specimen or the first measurement component or of the second measurement component, and not determining the density until the temperature of at least one of the specimen or the first measurement component or the second measurement component reaches a prescribed temperature-threshold value.

13. The method according to claim 1 , which further comprises keeping a vertical distance between the first and second measurement components constant during the measurement of the normal force.

14. A rotational rheometer for determining the density of an at least flowable or liquid specimen, the rotational rheometer comprising:
a first measurement component for receiving the specimen and a second measurement component with a known volume, each of said components having a bottom surface, said second measurement component being disposed in said first measurement component for immersion into the specimen, and said first measurement component and said second measurement component being disposed in the rheometer for movement relative to one another;
a normal-force-measurement unit disposed and configured in the rheometer for measuring a force acting in a direction normal to the rheometer and acting on said bottom surface of each of said first and second measurement components before, during and after the immersion of said second measurement component into the specimen, the measured normal force of said immersed second measurement component corresponding to a buoyancy force acting between the specimen and said second measurement component; and
a control and processing unit configured to calculate the density of the specimen based on Archimedes' principle.

15. The rheometer according to claim 14 , wherein:
said first measurement component is configured as a measurement cup with a cylindrical cross section;
said second measurement component is configured as a measurement body with a cylindrical cross section or as a rheological measurement spindle, said second measurement component has an external diameter being smaller than an internal diameter of said first measurement component; and
said first measurement component and said second measurement component are disposed coaxially in the rheometer for providing a measurement gap with a width between concentric walls of said first measurement component and of said second measurement component.

16. The rheometer according to claim 14 , which further comprises at least one of a heating or cooling device for controlling a temperature of the flowable or liquid specimen, said at least one of a heating or cooling device being at least one of:
disposed in said first

Assignees

• Anton Paar Gmbh

Inventors

• Schuetz Denis
• Giehl Chistopher
• Ehgartner Daniela

Classifications

• G01N11/14 Primary

  by using rotary bodies, e.g. vane (G01N11/16 takes precedence) · CPC title

• G01N11/162

  Oscillations being torsional, e.g. produced by rotating bodies · CPC title

• G01N11/142 Primary

  Sample held between two members substantially perpendicular to axis of rotation, e.g. parallel plate viscometer · CPC title

• G01N9/34 Primary

  by using elements moving through the fluid, e.g. vane · CPC title

• G01N9/10

  by observing bodies wholly or partially immersed in fluid materials · CPC title