MXPA05000737A

MXPA05000737A - Methodology based on the adaptation of a bicone geometry and a measurement cell into a commercial rheometer for detecting interfacial rheological properties.

Info

Publication number: MXPA05000737A
Authority: MX
Inventors: Orozco Juan Pablo Perez
Original assignee: Univ Autonoma Metropolitana
Priority date: 2005-01-18
Filing date: 2005-01-18
Publication date: 2006-07-17

Abstract

The present invention is related to the manufacturing industry of laboratory and industry equipment, and to a method for measuring physical properties of different materials, including food, in different phases using said equipment. More particularly, the invention refers to a modified equipment and a method for measuring cut interfacial properties. Unlike the method and equipment of the prior art, the present invention has the advantage of being easily installed in current conventional rheometers, thereby providing a sophisticated equipment which allows a higher sensibility to be obtained during measurements. The inventive equipment and method are also useful for determining the minimum parameters, along with the development of equations and models showed in literature, required to be applied in the evaluation of the interfacial rheological properties. The process is characterized in that it comprises the following steps: First, forming an interface; and second, determining the diffe rent parameters. The first step is carried out by pouring an aqueous solution into a refrigerating bath, lowering the bicone, and finally verifying the location of the bicone in the interface.

Description

METHODOLOGY BASED ON THE ADAPTATION OF A BICONOUS GEOMETRY AND A MEASUREMENT CELL TO A COMMERCIAL REOMMETER FOR THE DETERMINATION OF RHEOLOGICAL PROPERTIES I N T E R F I I S FIELD OF THE INVENTION The present invention is related to the manufacturing industry of equipment for laboratory and industry, and to the methodology for the measurement of physical properties of various materials, using these equipment, in different phases and even for food. More specifically, it is a modified equipment and a methodology for measuring cutting properties.

BACKGROUND OF THE INVENTION Currently there are several devices for determining the rheological properties of cutting films adsorbed in water-oil and / or water-air interfaces, based on the concept of the Couette rheometer, in which a biconical geometry is suspended by a torsion wire, whose diameter can vary between 0.03-0.13 mm, on a container in which the system to be analyzed is placed. The container rotates at a constant speed and the The force transmitted by this to the interface is evaluated by determining the torsion suffered by the wire, and this force is used to determine the interfering parameters such as the shear stress, the interfacial deformation and the apparent internal viscosity.

With the equipments and the methodologies of the state of the art, the comparison and reproducibility of the spatial properties is limited, due to many reasons among which is the fact that there is no standardization in the determination of said properties, besides that the sensitivity of the devices is low due to the difficulty encountered in determining the wire twist.

In order to standardize these measurements and to generate new alternatives that allow to have a greater sensitivity and reproducibility in them, we thought about the development of a practical methodology that uses the use of a conventional rheometer, in the determination of interfacial rheological properties of biopolymer films absorbed in water-oil and / or water-air interfaces.

We define as a conventional rheometer, that rheometer of controlled effort and / or controlled speed, ideal for Theological measurements in homogeneous liquid systems. In design, this equipment is not used to measure the theological properties.

OBJECTIVES OF THE INVENTION One of the objectives of the invention is the adaptation of a device easy to implement in the current conventional rheometers that have a sophisticated data capture equipment, which allows you to have greater sensitivity during measurements Another objective is to make it possible to determine the minimum required parameters that can be used together with the development of the existing equations and models in the literature, in the evaluation of interfacial rheological properties.

Other objects and advantages of the present invention may be apparent from the study of the following description and the accompanying drawings for illustrative purposes only and not limitation.

BRIEF DESCRIPTION OF THE INVENTION In short, the present invention consists of two aspects, on the one hand in a modification of the rheometers of the state of the art and on the other in a very specific methodology for using this modified equipment.

The properties that can be determined, with the methodology and equipment proposed here, are interfacial apparent viscosity and interfacial creep-capacitance properties.

In the side of the equipment, the adaptation consists in that a conventional rheometer that works under control of stress and / or deformation, adapts a bicono type geometry of radius Rb of double angle (2a) and an acrylic cooling bath with radio Re and a depth H that allows to have a control on the temperature. The cooling bath is seated on the Peltier plate and / or the rheometer.

The insertion of the geometry to the software of the rheometer is established according to the procedures of each team, taking into consideration the following points: • The bicone type geometry is inserted as if it were a cone-plate geometry of the same radius.

• Half of the magnitude of the bicone angle is inserted.

In its methodological aspect, this consists in the formation of the interface in the first instance, and in the determination of the different parameters at once.

The interphase formation is carried out by pouring the aqueous solution over a cooling bath, then lowering the bicone, then, in one of the modalities, carefully adding the oil phase, and finally, verifying the location of the bicone at the interface.

The methodology of determining the parameters will depend on which is the parameter to be determined.

In order to better understand the characteristics of the invention, the present description, as an integral part thereof, is accompanied by the drawings, which are illustrative but not limitative, which are described below.

BRIEF DESCRIPTION OF THE FIGURES Figure 1 shows a photograph of the adaptations mounted on a compact modular rheometer type PaarPhysica (MCR 300).

Figure 2 shows the operating scheme of the adapted device.

For a better understanding of the invention, a detailed description will be made of some of the modalities thereof, shown in the drawings that are attached to the present description for non-limiting illustrative purposes.

DETAILED DESCRIPTION OF THE INVENTION To a conventional rheometer that works under control of stress and / or deformation, it adapts a twin-cone geometry of radius Rb of double angle (2a) and an acrylic cooling bath with radius Re and a depth H that allows to have a control over temperature. The bath sits on the peltier plate and / or plate of the rheometer.

Figure 1 shows a photograph of the adaptations mounted on a PaarPhysica MCR 300 rheometer with dimensions Rb = 15 mm, Re = 27 mm, H = 34 mm and 2a = 10 °. In this figure, the coolant bath is indicated with 1; Element 2 consists of bicone geometry; 3 points to the rheometer sensor and 4 indicates the peltier plate or rheometer plate.

• Half of the magnitude of the bicone angle is inserted.

Figure 2 shows the operating scheme of the adapted device. As can be seen, the rheometer sensor allows us to determine the minimum parameters necessary for the calculation of interfacial theological properties, which are: angular velocity, moment of force or torque and the angle of displacement of the geometry.

For the formation of the interface: The aqueous solution is poured on the cooling bath, taking care that it only occupies half of it (at a depth H1), for the case of our device this is achieved with 30 ml and H1 of 17 mm.

The bicone is lowered slowly until it is located at the water-air interface.

If you want to form a water-oil interface, after the biconical is placed in the water-air interface, the oil phase is carefully added until reaching the total depth of the container (H2 = 17 mm in our device and covered with 30 ml). of the oil phase).

It is verified that the bicone is located in the interface, passing an ace of light through it and verifying that there is no formation of rings around the bicone.

The properties that can be determined, with the methodology proposed here, are interfacial apparent viscosity and properties of interfacial creep-capacitance.

For the measurement of interfacial apparent viscosity 1) The water-air or water-oil interface is formed with the solutions to be analyzed. 2) The bicono is rotated at a constant angular velocity (O), which can vary between 0.63-2.54 x 10- 3 rad / s. 3) The displacement angle is measured as a function of time (^) and the moment of force (A /) necessary to maintain said velocity. «'"' 4) The apparent interfacial viscosity ('), the deformation of the interface, is determined. { ') and the interfacial shear stress (s "') by the following expressions: mi _ M 1 1_ 7 '4pO v¾2 Re M 2p £ where or? is the displacement angle of the bicone determined by the equipment.

Note. The critical parameter of this measurement is the angular momentum, the rheometer must have a measurement reading minimum of 0.7 μ ???. This value makes it possible to evaluate a minimum interfacial apparent iscosity of approximately 100 mNm-1, which corresponds to the formation of films of synthetic or natural polymers adsorbed in fluid interfaces, or to any molecule and / or adsorbed compound that provides this resistance.

For the measurement of interfacial creep-capacitance properties. 1) The water-air or water-oil interface is formed with the solutions to be analyzed. 2) A moment of constant force is applied for a time followed by a moment of force of magnitude zero.

The displacement angle is measured and interfacial shear stress and strain is evaluated The capacitance of the interface is calculated by means of expression: Note: The rheometer must control the application of force moment of 0.2 μ ?? t? at least, if one wants to determine the creep-capacitance parameters of adsorbed films that have a low visco-elasticity (instantaneous elastic moduli less than 10 mN / m).

The invention has been sufficiently described so that a person with average skill in the art can reproduce and obtain the results that we mentioned in the present invention. However, any person skilled in the field of the art that is competent in the present invention may be able to make modifications not described in the present application, however, if for the application of these modifications in a certain structure or in the methodology of application of the same, it is required of the matter claimed in the following claims, said structures should be included within the scope of the invention.

Claims

R E I V I N D I C A C I O N S Having sufficiently described the invention, it is considered as a novelty and therefore it is claimed as property what is expressed and contained in the following claim clauses.

1. Determination of physical rheological properties characterized by the formation of the interface in the first instance, and in the determination of the different parameters immediately; said interphase formation is carried out by pouring the aqueous solution over a cooling bath, then lowering the bicone, and finally, verifying the location of the bicone at the interface.

2. Determination of interfacial rheological properties as claimed in the previous indication, also characterized by including the addition of the oil phase between the descent of the bicone and the verification of the location thereof.

3. Determination of interfacial rheological properties as claimed in claim 1, characterized in that the property to be determined is the viscosity apparent interfacial taking place in the following way: > The water-air or water-oil interface is formed with the solutions to be analyzed. The bicone is rotated at a constant angular velocity (O), which can vary between 0.63-2.54 x 10-3 rad / s. > The displacement angle is measured as a function of time (^ '- *) and the moment of force (M) necessary to maintain that speed. The apparent interfacial viscosity (^), the interface deformation (') and the interfacial shear stress are determined by the following expressions: M 4pO V Rb Rc J 2R¡ -Ri) Determination of interfacial rheological properties as claimed in claim 1, characterized in that the property to be determined is the interfacial creep-capacitance taking place in the following manner: > The water-air or water-oil interface is formed with the solutions to be analyzed. > A moment of constant force is applied for a time followed by a force moment of zero magnitude. > The displacement angle is measured and the interfacial shear stress and strain is evaluated > The capacitance of the interface is calculated by the expression: Equipment for the determination of interfacial rheological properties characterized in that it consists of a conventional rheometer that works under stress and / or deformation control comprising a bicone type geometry of double angle Rb radius (2a) and an acrylic cooling bath with radius Re and a depth H that allows to have a control on the temperature. SUMMARIZES The present invention is related to the manufacturing industry of equipment for laboratory and industry, and to the methodology for the measurement of physical properties of various materials, using these equipment, in different phases and even for food. More specifically, it is a modified equipment and a methodology for measuring cutting properties. In contrast to the methodology and equipment of the state of the art, those who understand the teachings of the present invention have the advantage of being easy to implement in the current conventional rheometers that have a sophisticated equipment that allows them to have greater sensitivity during the measurements and makes it possible to determine the minimum parameters required that can be applied together with the development of the existing equations and models in the literature, in the evaluation of interfacial rheological properties. The process is characterized by the steps consisting in the formation of the interface in the first instance, and in the determination of the different parameters immediately; said interphase formation is carried out by pouring the aqueous solution over a cooling bath, then lowering the bicone, and finally, verifying the location of the bicone at the interface.