WO2008098714A1

WO2008098714A1 - Conductivity measurement/device

Info

Publication number: WO2008098714A1
Application number: PCT/EP2008/000996
Authority: WO
Inventors: Jens Hepperle; Dirk Jacques Dijkstra; Thomas CÜPER; Reiner Rudolf
Original assignee: Bayer Technology Services Gmbh
Priority date: 2007-02-15
Filing date: 2008-02-09
Publication date: 2008-08-21
Also published as: DE202007018634U1; DE102007007461A1

Abstract

The invention relates to a rheometric measuring piece (2), comprising at least one electrically insulated measuring cell with an actuator and a stator side, wherein the measuring cell has at least one electrical connector (11) on the actuator side and at least one electrical connector (12) on the stator side and the electrical connectors are electrically connected to a device (13) for measuring at least one electrical property of a medium (5) in the measuring cell, a rheometer, comprising such a measuring cell, a method for the simultaneous measurement of rheological and electrical properties of a medium and the use of such a measuring piece for the simultaneous measurement of rheological and at least one electrical property of a medium.

Description

Conductivity measurement / device

The present invention relates to a rheometric measuring part for measuring rheological properties of a medium, a rheometer containing this measuring part, a method for the simultaneous measurement of theological and electrical properties of a medium and the use of the measuring part according to the invention for the simultaneous measurement of theological and electrical properties of a medium.

Rheometers with measuring parts designed to generate mechanical stresses are already known from the prior art.

Macosko, Christopher W., Rheology: Principles, Measurements and Applications, ISBN 1-56081-579-5, pages 181 to 191 and 285 to 305 and M. Pahl, W. Gleißle and HM Laun, Practical Rheology of Plastics and Elastomers, VDI Verlag, 1996, pages 56 to 59, 82 to 83 and 88 to 89 disclose rheometers which are suitable for measuring flow properties of fabrics. For this purpose, the sample to be examined must be deformed at a predeterminable speed and the force required for deformation measured. From the speed, the shear rate can be calculated with the corresponding device dimensions and the associated stresses from the measured forces. In principle, the procedure can also be reversed, ie. the forces or stresses are specified, and the resulting speeds or deformations are measured.

With pressure-driven flows, the viscosity data are determined from the capillary dimensions and the measured pressure loss. The procedure is known to the person skilled in the art and disclosed, for example, in M. Pahl, W. Gleißle and H. M. Laun, Practical Rheology of Plastics and Elastomers, VDI Verlag, 1996, pages 167-215.

Three of the common rotary rheometer types are the coaxial cylinder rheometer, also called the Couette rheometer, the cone-plate rheometer, and the plate-plate rheometer. In the cylinder rheometer, a liquid sample is deformed between two juxtaposed cylinders by rotating one of the cylinders. In a plate-plate rheometer, the substance to be examined is between two mutually rotatable discs. By turning one of the discs, the sample is deformed. From a plate-plate rheometer, a cone-plate rheometer differs in that a rotatable disc is replaced by a cone on the tip.

With the above-mentioned rheometers different basic theological experiments can be carried out on a material to characterize its flow behavior. A selection of these experiments is in M. Pahl, W. Gleißle and HM Laun, Practical Rheology of Plastics - -

and elastomers, VDI Verlag, 1996, pages 56 to 59, 82 to 83 and 88 to 89 and includes clamping test, creep test, relaxation test, vibration test (oscillation) and ramp test.

J. Appl. Polym. Be. 79 (2001), 108 to 114 discloses an electrorheological measuring cell. In this measuring cell, a dispersion of doped with dodecylbenzenesulfonic acid polyaniline particles was rheologically examined while a high-voltage field at the same time

Sample acts. The measuring cell disclosed in said document makes it possible to study electroviscous properties of liquids and dispersions, i. the

Changes in theological properties under the action of an electric field. Measurements of electrical properties with simultaneous action of defined

Forces / deformations on the sample to be examined are described in J. Appl. Polym. Be. 79 (2001),

108 to 114 not disclosed.

So far it has not been disclosed to carry out a simultaneous measurement of theological and electrical properties. This possibility is useful for studying the electrical properties of technical liquid media, e.g. of paints, additives or conductive composites of thermoplastics and solids, under the influence of a defined mechanical stress or a defined flow, for example in production or processing processes.

Therefore, it is an object of the present invention to provide a simple and robust measuring part, which allows the observation and investigation of electrical properties of fluids, e.g. of paints, additives or conductive composites of thermoplastics and solids, under the influence of a defined mechanical tension. It is another object of the present invention to provide for monitoring changes in electrical conductivity due to processing, e.g. Painting, injection molding, to allow the medium occurring forces.

This object is achieved by a rheometric measuring part (1, 2) comprising at least one electrically isolated measuring cell (2) with an actuator and a stator side, the measuring cell having at least one electrical connection (11) on the actuator side and at least one electrical connection ( 12) on the stator side, wherein the electrical connections to a device (13) for measuring at least one electrical property of a medium present in the measuring cell (5) are electrically connected.

The measuring part according to the invention for measuring theological properties is generally contained in a rheometer known to those skilled in the art. In a preferred embodiment, this is a shear rheometer, a capillary rheometer or a Extensional rheometer. The measuring part according to the invention can be tempered in a preferred form, for example by an oven. Thus, with the device according to the invention measurements at a temperature of -200 to 600 ⁰ C, preferably 25 to 400 ⁰ C, more preferably 150 to 350 ⁰ C are performed.

Suitable shear rheometers and extensometers are known to those skilled in the art and are disclosed, for example, in Macosko, Christopher W., Rheology: Principles, Measurements and Applications, ISBN 1-56081-579-5, pages 181 to 191 and 285 to 305.

Shear rheometers are rheometers in which a shearing motion is generated by flowing the liquid medium to be tested between a fixed and a movable surface. Examples of shear rheometers are the Couette rheometer, the plate-plate rheometer or the cone-plate rheometer.

In strain rheometers, deformation of the specimen to be examined is produced by stretching it in various ways, for example by deformation of a polymer melt between two clamps which rotate, or by pulling the melt by means of holders fixed at the ends. So that the melt does not flow away, a tempered support medium, for example silicone oil or the like, with comparable density is used. These rheometers are disclosed in Macosko, Christopher W., Rheology: Principles, Measurements and Applications, ISBN 1-56081-579-5, 285-305.

In capillary rheometers, a flow movement is initiated by pressure, for example, in an embodiment in which the sample to be examined is forced through a slot (slit flow) or in the axial direction through a pipe or a channel. At the same time via corresponding, known to those skilled devices, such as pressure sensors, the

Pressure conditions in the pipe or channel determined, and from the measurements obtained the

Shear viscosities determined. The tube or the channel can have any cross-sectional shape known to those skilled in the art, preferably round or angular.

As a medium which can be investigated in the device according to the invention are generally all media usable, the rheological and electrical properties of interest. In a preferred embodiment, the medium is a fluid medium. Examples of fluid media are liquid substances or mixtures of liquid substances, solutions of solids in corresponding solvents, substances or mixtures of various substances in the molten state, mixtures of at least one liquid substance with at least one solid substance (dispersion, compound), mixtures of at least one liquid substance with at least one other liquid (emulsion). Particularly preferred liquid media are - -

Lacquers, additives, molten polymers or conductive composites of polymers and solids, for example polymers and carbonaceous solids.

In the context of the present invention, the term actuator side (3, 7) is understood to mean the side of the measuring part which is formed by corresponding devices known to the person skilled in the art, e.g. a motor, which performs rotational or oscillating movements, a corresponding movement on the sample to be examined exercises. The term stator side (4, 6) is understood to mean the side of the measuring part which is not moved, but remains rigid and absorbs the forces to be measured. Actuator side (7) and stator side (4) are separated by the sample to be examined.

The measuring part according to the invention has at least one, preferably one, electrical connection (11) on the actuator side. The electrical connection (11) on the actuator side can be done by any of the skilled man known types, for example by a fixed or a movable contact. Furthermore, the measuring part according to the invention has at least one, preferably one, electrical connection (12) on the stator side. The electrical connection (12) on the stator side can be made by any of the known to the expert types, for example by a fixed or a movable contact.

The present in the inventive measuring part actuator (3) is connected via an electrical connection of the actuator side (11). The stator (6) present in the measuring part according to the invention is connected to the at least one electrical connection of the stator side (12) via an electrically insulating material, for example plastic or coated conductor, for example metal with plastic coating.

The measuring cell (2) present in the measuring part (1, 2) according to the invention is generally constructed from two measuring plates (4) arranged opposite one another, between which the medium (5) to be examined is located.

The measuring part (1, 2) is designed to be tempered in a preferred embodiment. It is possible that the entire measuring cell (2) is formed temperable, but it is also possible that one or both measuring plates (4) and / or the medium to be examined (5) are tempered. In the context of the present invention, tempering can be understood as meaning both heating and cooling. For heating, in a preferred embodiment, the measuring part (2), preferably one or both measuring plates (4) and / or the medium (5) can be irradiated with an IR radiator. In a further embodiment, the measuring cell (2) via the supply of heated gases, such as air or nitrogen, are heated. In a further embodiment, the measuring part (2), preferably one or both measuring plates (4), with a heating bath, which with a heat transfer medium, For example, oil, particularly preferably silicone oil, or water is filled, are heated. For cooling the measuring part (2), preferably one or both measuring plates (4), this can be provided with cooling devices known to the person skilled in the art, for example a water cooling or a cryostat. The measuring part (2) can also be cooled with a liquid gas, for example liquid nitrogen.

The two electrical connections (11, 12) of the measuring cell according to the invention are connected to a device for measuring at least one electrical property.

In a preferred embodiment, in the measuring part according to the invention, the electrical connection (11) on the actuator side via a movable contact with the device (13) for measuring at least one electrical property and the electrical connection (12) on the stator side via a fixed contact with the Device (13) for measuring at least one electrical property. In a preferred embodiment, the measuring plates (4), which are remote from the medium, are connected to cylinders of electrically conductive material, for example steel, copper or aluminum, to which the electrical connections (11, 12) are respectively attached. In a further preferred embodiment, one or both electrical connections are integrated in the housing of the device (1) according to the invention. In this case, the connections can be attached to any suitable location, as long as care is taken that they are protected against a short circuit. A person skilled in the art knows suitable locations.

In a further preferred embodiment, both the electrical connection (11) on the actuator side and the electrical connection (12) on the stator side in each case via a fixed contact with the device for measuring electrical properties (13).

As device (13) for measuring at least one electrical property, all devices known to those skilled in the art can be used. In a preferred embodiment, a device is used to measure exactly one electrical property. In a particularly preferred embodiment according to the invention, the device for measuring at least one electrical property (13) is a resistance measuring device. In a further preferred embodiment, the device (13) is an impedance measuring device.

The following theological properties can be measured with the measuring part according to the invention: shear stress as a function of the imposed deformation and time, from which other theological characteristics such as viscosity or modulus can be calculated. In the same way, the expansion stresses and extensional viscosities can be determined with the extensometer according to the invention, and the pressure losses and shear viscosities thereof in the case of the capillary rheometer. - -

At the same time, the following electrical properties can be measured: resistance, dielectric constant or AC resistance.

With the measuring part according to the invention the following advantages are achieved:

With the aid of the measuring part according to the invention, a defined flow can be set in the measuring cell, while simultaneously impressing a defined deformation on the liquid medium to be examined and measuring the forces absorbed by the medium, wherein the electrical conductivity of the medium is simultaneously recorded. In particular, a time-resolved conductivity measurement is thus made possible as a function of the deformation imposed on the liquid medium and the deformation history. Another advantage is that existing devices or industrially available rheometer can be easily retrofitted with the additional components for resistance measurement.

The present invention also relates to a rheometer which contains a measuring part according to the invention. In a preferred embodiment, the rheometer is a shear rheometer. In a further preferred embodiment, the rheometer is a stretch rheometer. In a further preferred embodiment, the rheometer is a capillary rheometer, particularly preferably with a round capillary or an angular channel.

The present invention also relates to a method for the simultaneous measurement of theological and electrical properties of a, preferably liquid, medium. In this method, a sample to be examined is introduced into the device according to the invention. Then, by the actuator (3, 7) a movement, for example, a translational or oscillatory movement, is exerted on the sample. The force received by the sample can be measured by the stator (4, 6) while at the same time at least one electrical property, preferably the resistance or the impedance, is measured by the device (13). The method allows the measurement of the theological properties of a sample as a function of at least one electrical property, and vice versa. With respect to the device according to the invention, electrical and rheological properties and the samples to be examined, the above applies.

The present invention also relates to the use of the device according to the invention for the simultaneous measurement of rheological and at least one electrical property of a, preferably liquid, medium.

Hereinafter, an embodiment of the present invention with reference to Figures 1 to 3 will be explained in more detail. - -

Figure 1 shows the basic structure of the device according to the invention using the example of a shear rheometer provided with electrical connections. The reference numbers in Figure 1 have the following meanings:

I housing with control and measuring devices

2 measuring part

3 actuator

4 measuring devices

5 the medium to be examined

6 Measuring transducer holder, stator

7 cylinders 1

8 cylinders 2

9 insulating disc 1

10 insulating washer 2

I 1 electrical connection on the actuator side

12 electrical connection on the stator side

13 device for measuring at least one electrical property

The shear rheometer according to FIG. 1 is constructed from a housing (1) with a drive and measuring unit and the actual rheometer measuring part (2), which can also be made temperature-controllable as described above. It comprises an actuator (3), which is in communication with the drive unit and generates an oscillatory or translatory rotational movement, a Messaufhehmer (4) with the liquid medium to be examined (5) and a Messaumehmer-holder (6) connected to the measuring unit connected to the rheometer. The actuator (3) via a cylinder (7) and the Meßaufhehmer holder (6) via the cylinder (8) with the Meßaufhehmer (4) mechanically connected. The Messaumehmer-holder acts as a stator, as it, in contrast to the actuator, is not moved. The Messaumehmer-holder (6) detects the force that is transmitted from the actuator (3) through the liquid (5) on the upper plate (4). The two cylinders (7) and (8) are made of an electrically conductive material, for example of a metal selected from copper, steel, iron or aluminum. To the measurers - -

(4, 7, 8) electrically isolate from the housing (1) and the pickups (6, 3), the rods (7) and (8) via insulating discs (9) and (10) with the actuator (3) or the Messaumehmer- holder (6) connected. On one side of the measuring cell (4) the rod (7) is provided with an electrical connection (11) and on the opposite side the rod (8) with a second electrical connection (12). The terminal (12) is designed as a solid contact. The terminal (11) can be made as a fixed or movable contact and consists in the case of a movable contact, e.g. from a brush or sliding contact. For measuring the electrical resistance, the terminals (11) and (12) are connected to a resistance measuring device (13). Instead of an ohmmeter but can also be another meter, for. an impedance meter can be connected so that the dielectric constant of the liquid medium can be measured. In this way it is possible to simultaneously examine rheometric and at least one electrical property of a sample (5) within the sensor.

Figure 2 shows a capillary rheometer according to the invention with a rectangular channel. The reference numerals 1 and 9 - 13 have the same meanings as in Figure 1. In addition, reference numeral 14 sensor for pressure measurement. The shear viscosity can be determined via the measured pressure difference. The arrows describe the flow direction of the medium to be examined. However, this can also flow in the other direction. The capillary rheometer according to Figure 2 can thus be operated in both directions. It can be the pressure loss between the sensors 14 and at the same time, for example, the electrical resistance across the sensors 11 and 12 are measured. The sensors 11 and 12 are electrically non-conductive via insulating pieces on the pipe or channel. In the housing of the capillary rheometer according to Figure 2 usually tempering devices are integrated.

Figure 3 shows a measuring example, which is carried out with the apparatus of Figure 1. The diagram shows the electrical resistance R (y-) registered as a function of time t (x-axis).

Axis) of a conductive polymer-solid composite under the action of an oscillatory

Shear (shear flow) at a frequency of 1 Hz and an amplitude of 200%. Beginning and end of the deformation, i. the action of the shear force are also in the diagram

Arrows drawn. In the range between 50 and 60 seconds, the corresponding part of the graph has been copied out and enlarged. It can be seen that the electric

Resistance as a result of the oscillatory shear flow also shows an oscillatory behavior (see enlarged detail). From such measurement results can important

Conclusions can be drawn regarding the optimization of the conductivity of polymers with the aid of the formulation or with regard to the flow forms used in the further processing of the polymers.

Claims

- Patent claims

1. Rheometric measuring part (1, 2), comprising at least one electrically insulated measuring cell with an actuator and a stator side, characterized in that the measuring cell at least one electrical connection (11) on the actuator side and at least one electrical connection (12) on the Stator side, wherein the electrical connections with a device (13) for measuring at least one electrical property of a medium present in the measuring cell (5) are electrically connected.

2. Measuring part according to claim 1, characterized in that the electrical connection (11) on the actuator side via a movable contact with the device (13) for measuring at least one electrical property and the electrical connection (12) on the

Stator side via a fixed contact with the device (13) for measuring at least one electrical property.

3. Measuring part according to claim 1, characterized in that both the electrical connection (11) on the actuator side and the electrical connection (12) on the stator side in each case via a fixed contact with the device (13) for measuring at least one electrical

Property done.

4. measuring part according to one of claims 1 to 3, characterized in that the device (13) for measuring at least one electrical property is a resistance measuring device.

5. measuring part according to one of claims 1 to 4, characterized in that it can be tempered.

6. rheometer, comprising a measuring part according to one of claims 1 to 5.

7. Rheometer according to claim 6, characterized in that it is a shear rheometer.

8. Rheometer according to claim 6, characterized in that it is a Dehnrheometer.

9. Rheometer according to claim 6, characterized in that it is a capillary rheometer.

10. Rheometer according to claim 9, characterized in that the channel has a round or rectangular cross-sectional shape.

11. Method for the simultaneous measurement of theological and electrical properties of a medium.

12. Use of a measuring part according to one of claims 1 to 5 for the simultaneous measurement of theological and at least one electrical property of a medium.