JPH04266970A - Elastic modulus-variable material - Google Patents

Abstract

PURPOSE:To provide a flexible polymer material changing its elastic modulus by the action of a magnetic field having higher safety than that of an electric field. CONSTITUTION:An elastic modulus-variable material is characterized by dispersing particles magnetically polarized by the action of a magnetic field in a flexible polymer material. The polymer material is a rubber or a gel, and the dispersing particles are the particles of one kind or more of metals, organic components and organic.inorganic composite materials which are magnetically polarized by the action of a magnetic field. The elastic modulus of the material is rapidly and reversibly changed by the application of the magnetic field, thereby permitting to safely apply the material to energy-transmitting or absorbing parts such as automotive clutches and dampers.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a material with variable elastic modulus,
More specifically, the elastic modulus of a material (dynamic elastic modulus reflecting the material's stiffness and loss elastic modulus representing viscosity) changes reversibly under the action of an external magnetic field, and the elastic modulus changes depending on the strength of the magnetic field. The present invention relates to a variable elastic modulus material whose degree of change changes continuously, and which can therefore be applied to automobile parts for transmitting and absorbing energy and for vibration isolation, such as clutches, dampers, shock absorbers, and engine mounts.

0002

BACKGROUND OF THE INVENTION In recent years, polymeric materials having the function of converting energy such as light, heat, electricity, etc. into mechanical energy have been applied to various fields. S. P. 32
No. 15572 and Japanese Unexamined Patent Publication No. 132303/1988 disclose magnetic fluids whose viscosity is changed by a magnetic field. on the other hand,
The applicant has proposed a particle-dispersed polymer material (patent application No. 1-227817) whose elastic modulus changes under the action of an electric field.
) has already been applied for.

However, since the magnetic fluid described above is a fluid that does not have a specific shape, it is difficult to apply it to automobile parts and the like. In addition, the polymer material disclosed in Japanese Patent Application No. 1-227817 is an excellent material that does not have such drawbacks, but there is a restriction that the matrix must be electrically insulating, which makes it difficult to apply a high voltage electric field. Safety considerations also need to be taken into account.

0004

[Problems to be Solved by the Invention] Therefore, the present invention provides a flexible material that has formability because the matrix is solid, regardless of whether the matrix is electrically insulating; The object of the present invention is to provide a material whose elastic modulus changes under the action of a highly safe magnetic field.

[0005]

[Means for solving the problem] (Point of view) The present inventors
The present invention was completed by focusing on the fact that the above problems can be solved by utilizing the interaction of fine particles that are magnetically polarized in a magnetic field.

(Structure of the present invention) The structure of the present invention for solving the above-mentioned problems is a flexible polymer material having a variable elastic modulus material in which particles that are magnetically polarized by the action of a magnetic field are dispersed. It is.

[0007]

[Function] The variable elastic modulus material of the present invention is originally a flexible material with a constant elastic modulus, but when a magnetic field is applied to it, the magnetic moment existing within the dispersed particles is shifted in the direction of the magnetic field lines. Since the dispersed particles are magnetically polarized in a certain direction along , a chain of magnetic bonds is formed between the dispersed particles, for example, in the form of a network. The binding force of this chain of magnetic coupling increases the dynamic elastic modulus and loss modulus of the material, increasing its elastic modulus. Conversely, when the magnetic field is removed, the magnetic coupling between the dispersed particles is dissolved and the elastic modulus of the material decreases to its original level. This effect occurs regardless of whether or not the matrix polymeric material is electrically insulating.

[0008] The response of the change in elastic modulus to the application of a magnetic field is extremely good. Furthermore, since the degree of change in the elastic modulus corresponds to the strength of the magnetic field, when the strength of the magnetic field is continuously changed, the elastic modulus also changes continuously. The relationship between such good responsiveness and the amount of change in elastic modulus corresponding to the strength of the magnetic field is
Due to the above mechanism, it is always constant, and is unlikely to deteriorate due to continuous application of a magnetic field or over time.

[0009]

Effects of the Invention The variable elastic modulus material of the present invention is a flexible material that can be processed into a specific shape suitable for use, and the elastic modulus changes due to the action of a magnetic field, so it can be used in clutches, dampers, shock absorbers, etc. It can be applied to automobile parts such as engine mounts that transmit and absorb energy and provide vibration isolation. At this time, the amount of change in the elastic modulus can be continuously and arbitrarily controlled by adjusting the strength of the magnetic field. Furthermore, it is safe because there is no need to apply a high-voltage electric field to change the elastic modulus. Furthermore, parts using the variable elastic modulus material of the present invention have excellent responsiveness and durability.

0010

[Embodiments] [Embodiments] The present invention can be carried out, for example, in the following embodiments.

[0011] As the flexible polymer material used as the matrix, a rubber-like or gel-like polymer material is used. For example, ethylene-propylene rubber, butadiene rubber, isoprene rubber, silicone rubber, and gels obtained by swelling these rubbers with a solvent or the like are flexible at room temperature. Polymer gels other than rubber, such as polyvinyl alcohol, polyacrylamide, polystyrene, and polyalkylthiophene, can also be used. Furthermore, ethylene-vinyl acetate copolymers, polyurethane, polypropylene, etc. exhibit a rubber-like or gel-like state at expected operating temperatures.

The dispersed particles may be any material as long as it has the property of being magnetically polarized by the action of a magnetic field, such as pure iron, electromagnetic soft iron, grain-oriented silicon steel, Mn-Zn ferrite, Ni-Z
Particles made using metals such as n-ferrite, magnetite, cobalt, and nickel, organic substances such as 4-methoxybenzylidene-4-acetoxyaniline and triaminobenzene polymers, and organic/inorganic composites such as ferrite-dispersed anisotropic plastics. , or particles using two or more of these are used.

[0013] The shape of the dispersed particles is not limited to regular shapes such as spherical, acicular, and tabular shapes, but may also be irregular shapes. There is no restriction on the particle size of the dispersed particles, but particularly desirable ones are those that are generally considered to be fine particles (for example, particles with a particle size of about 0.01 to 500 microns).

[0014] The dispersed particles may have their surfaces treated with a surfactant or a water repellent, and furthermore, they can be used in the form of either solid particles or hollow particles.

Regarding the dispersion state of the dispersed particles in the flexible polymeric material that is the matrix, there are not only states in which the dispersed particles are in contact with each other and are connected, but also states in which the dispersed particles are not in contact with each other. Alternatively, they may be in a dispersed state in which they are substantially in contact with each other when a magnetic field is applied. In short, any dispersion state is sufficient as long as a magnetic bond is formed between the dispersed particles in a chain manner when a magnetic field is applied.

In order to realize the above-described dispersed state of the dispersed particles and to avoid deterioration of the physical properties of the material due to an excess of dispersed particles, the dispersion concentration of the dispersed particles in the elastic modulus variable material should be set at a volume fraction of 5. It is desirable that it be in the range of ~60%. Note that the dispersed particles can be uniformly dispersed in the polymeric material that is the matrix, or can be intentionally dispersed non-uniformly. In the latter case, for example, by making the dispersion density different between certain parts of the matrix and other parts, or by setting the dispersion density in a gradient shape over the entire matrix or in a part, the elastic modulus change of the matrix is unique. It can be made to occur under a certain pattern.

[Example] Next, an example of the present invention will be described. The performance of the variable elastic modulus material of each Example was evaluated using a viscoelastic spectrometer (manufactured by Iwamoto Seisakusho). In the evaluation, the variable elastic modulus material of the present invention was placed between parallel flat plates of a sandwich structure, and then a magnetic field was applied in a direction perpendicular to the flat plates to vibrate the inner flat plate at a frequency of 10 Hz. In this state, the torque applied to the outer flat plate was measured. Then, the dynamic shear modulus and the loss shear modulus were determined from the measured torque, and evaluated by the ratio before and after the application of the magnetic field.

(Example 1) 60 g of electrolytic iron powder with a particle size of 150 μm is added to 20 g of a reaction solution of a fast-curing two-component reactive silicone rubber.
were simply mixed and rubberized at room temperature. The elastic modulus variable material of the present invention thus obtained as a particle-dispersed flexible polymeric material quickly exhibits a dynamic shear modulus of 50% and a loss shear modulus of 65% at room temperature in a 320 G magnetic field. increased to

(Example 2) 41 g of carbonyl iron powder with a particle size of 50 μm was mixed with 20 g of a heating type two-component reactive silicone gel reaction solution, and after transferring this to a Petri dish, the iron powder was placed on a permanent magnet. Combined. 70°C in this state
The elastic modulus variable material of the present invention, which is a particle-dispersed silicone gel, was obtained by heating to . When a 740G magnetic field is applied to this, the dynamic shear modulus changes from 7.8kPa to 21kPa at 50°C.
．． The loss shear modulus was improved by about 2.8 times from 5.3 kPa to 18.2 kPa, and about 3.4 times from 5.3 kPa to 18.2 kPa. These changes occurred rapidly, and the values quickly returned to their initial values when the magnetic field was removed.

(Evaluation of Examples) As described above, the modulus of elasticity of the variable elastic modulus materials of Examples 1 and 2 according to the present invention changed reversibly and rapidly under the action of a magnetic field, and to a satisfactory degree. .

Claims (1)

[Claims] 1. A material with variable elastic modulus, characterized in that particles that are magnetically polarized by the action of a magnetic field are dispersed in a flexible polymeric material.