EP-4735864-A1 - RHEOMETER FOR SIMULTANEOUS RHEOLOGICAL AND ELECTRICAL MEASUREMENTS

Abstract

Described is an apparatus for measuring rheological and electrical properties of a sample. The apparatus includes a first geometry comprising a first and a second stationary element each being electrically conductive and having a surface disposed to face the surface of the other stationary element across a gap. The first and second stationary elements are electrically isolated from each other. The apparatus further includes a second geometry comprising a rotatable element disposed in the gap and configured to rotate between the first and second stationary elements. The rotatable element is electrically conductive such that a first electric field is generated between the first stationary element and the rotatable element and a second electric field is generated between the rotatable element and the second stationary element in response to application of a voltage difference applied across the first and second stationary elements.

Inventors

• MERRULLO, Scott
• WHITCOMB, KEVIN
• MAY, Jeremy

Assignees

• TA Instruments-Waters LLC

Dates

Publication Date

20260506

Application Date

20240308

Claims (15)

1. 1. An apparatus for measuring rheological and electrical properties of a sample comprising: a stationary geometry comprising a double wall concentric cylinder having a cylinder axis, an outer wall, an inner wall and a gap defined between the outer wall and the inner wall, the outer and inner walls being electrically conductive and being electrically isolated from each other; and a moving geometry comprising a cylindrical bob disposed in the gap and rotatable about the cylinder axis, wherein the cylindrical bob is electrically conductive and wherein an outer sample gap is defined between the cylindrical bob and the outer wall and an inner sample gap is defined between the cylindrical bob and the inner wall.
2. 2. The apparatus of claim 1, further comprising a motor shaft coupled to the cylindrical bob through an electrically insulating element.
3. 3. The apparatus of claim 1, wherein the outer and inner walls are secured to an electrically insulating base.
4. 4. The apparatus of claim 3, wherein the electrically insulating base comprises a thermally conductive material.
5. 5. The apparatus of claim 2, further comprising a motor coupled to the motor shaft and a voltage source in communication with the outer wall through a first electrically conductive path and in communication with the inner wall through a second electrically conducive path.
6. 6. The apparatus of claim 3, further comprising at least one electrode disposed inside the electrically insulating base.
7. 7. The apparatus of claim 4, further comprising a temperature controller in thermal communication with the electrically insulating base.
8. 8. The apparatus of claim 4, further comprising a fluid channel that passes through the electrically insulating base and the inner wall and configured to conduct a flow of a heat transfer fluid.
9. 9. The apparatus of claim 4, further comprising a fluid channel that passes through the stationary geometry.
10. 10. An apparatus for measuring rheological and electrical properties of a sample comprising: a moving geometry comprising a rotatable plate formed of an electrically conductive material and having an electrically insulating hub; a shaft extending from the electrically insulating hub along an axis of rotation and configured to rotate the rotatable plate about the axis of rotation; and a stationary geometry comprising a first stationary plate and a second stationary plate each formed of an electrically conductive material and spaced apart from each other to define a gap therebetween in which the rotatable plate is disposed, the first stationary plate having a central opening to pass the shaft and the second stationary plate having an electrically insulating hub arranged opposite to the electrically insulating hub of the rotatable plate.
11. 11. The apparatus of claim 10, further comprising an electrically insulating side wall disposed circumferentially about the gap and about an outer edge of each of the first and second stationary plates.
12. 12. The apparatus of claim 11, wherein the electrically insulating side wall is configured to rotate about the axis of rotation at a wall angular velocity that is substantially equal to an angular velocity of the rotatable plate.
13. 13. The apparatus of claim 10 wherein a radius of the rotatable plate is less than a radius of the first stationary plate and less than a radius of the second stationary plate.
14. 14. An apparatus for measuring rheological and electrical properties of a sample comprising: a first geometry comprising a first and a second stationary element each being electrically conductive and having a surface disposed to face the surface of the other across a gap, the first and second stationary elements being electrically isolated from each other; and a second geometry comprising a rotatable element disposed in the gap and configured to rotate between the first and second stationary elements, the rotatable element being electrically conductive, wherein a first electric field is generated between the first stationary element and the rotatable element and a second electric field is generated between the rotatable element and the second stationary element in response to application of a voltage applied across the first and second stationary elements.
15. 15. An apparatus for measuring rheological and electrical properties of a sample comprising: a first geometry comprising a stationary element having a first electrically conductive region and a first surface; and a second geometry comprising a rotatable element having an electrically conductive region and a second surface, the second geometry being separated from the first geometry across a gap defined between the first and second surfaces, wherein the first and second electrically conductive regions are arranged opposite to each other across the gap and wherein an electric field is generated between the first and second electrically conductive regions across the gap in response to an application of a voltage applied between the first and second electrically conductive regions.

Description

RHEOMETER FOR SIMULTANEOUS RHEOLOGICAL AND ELECTRICAL MEASUREMENTS RELATED APPLICATION This application is a non-provisional patent application claiming priority to U.S. Provisional Patent Application No. 63/523,858, filed June 27, 2023, titled “Rheometer for Simultaneous Rheological and Electrical Measurements,” which is incorporated herein by reference. FIELD OF THE INVENTION The disclosed technology relates generally to rheological and electrical characterization of materials. More particularly, the technology relates to an apparatus for performing simultaneous electrical and rheological measurements of test samples. BACKGROUND Simultaneously measuring electrical and rheological properties of a material sample enable correlation of changes in the electrical and rheological properties. To enable such measurements, an electric field is established in the sample and electrical properties are measured across the stress/strain gradient during rheological measurements. Current state of the art systems achieve concurrent electrical and rheological measurements by using the moving and stationary geometries of a rheological instrument as electrodes of opposite polarity such that electrical current flows from one electrode through the sample to the other electrode. Liquid or sliding friction contacts are employed to conduct current between the continuously moving geometry and the stationary geometry. Potassium chloride solution and liquid metal alloys are examples of conductive liquids that are sometimes used to make electrical contact with the moving geometry. Spring brushes may be used as sliding friction contacts. The liquid or sliding friction contacts add undesirable friction torque to the rheological measurement and undesirable electrical impedance to the electrical impedance measurement. Consequently, the resolution of both types of measurements is decreased due to a degradation in the signal to noise ratio. In combined motor transducer rheometers the undesirable friction is particularly problematic. More specifically, the torque required to rotate the moving geometry is also used to determine sample material property data, therefore the instrument measurement sensitivity is limited by additional sources of torque that are independent of torque imparted by the sample. SUMMARY In one aspect, an apparatus for measuring rheological and electrical properties of a sample includes a stationary geometry that includes a double wall concentric cylinder having a cylinder axis, an outer wall, an inner wall and a gap defined between the outer wall and the inner wall. The outer and inner walls are electrically conductive and are electrically isolated from each other. The apparatus further includes a moving geometry that includes a cylindrical bob disposed in the gap and rotatable about the cylinder axis. The cylindrical bob is electrically conductive. An outer sample gap is defined between the cylindrical bob and the outer wall and an inner sample gap is defined between the cylindrical bob and the inner wall. The apparatus may further include a motor shaft coupled to the cylindrical bob through an electrically insulating element. The apparatus may additionally include a motor coupled to the motor shaft and a voltage source in communication with the outer wall through a first electrically conductive path and in communication with the inner wall through a second electrically conducive path. The outer and inner walls may be secured to an electrically insulating base and the electrically insulating base may include a thermally conductive material. One or more electrodes may be disposed inside the electrically insulating base. A temperature controller may be in thermal communication with the electrically insulating base. A fluid channel that passes through the electrically insulating base and the inner wall may be included to conduct a flow of a heat transfer fluid. A fluid channel that passes through the stationary geometry may be included. In another aspect, an apparatus for measuring rheological and electrical properties of a sample includes a moving geometry, a shaft and a stationary geometry. The moving geometry includes a rotatable plate formed of an electrically conductive material and having an electrically insulating hub. The shaft extends from the electrically insulating hub along an axis of rotation and is configured to rotate the rotatable plate about the axis of rotation. The stationary geometry includes a first stationary plate and a second stationary plate each formed of an electrically conductive material and spaced apart from each other to define a gap. The rotatable plate is disposed in the gap. The first stationary plate has a central opening to pass the shaft and the second stationary plate has an electrically insulating hub arranged opposite to the electrically insulating hub of the rotatable plate. The apparatus may further include an electrically insulating side wall disposed circumferentially about