EP4184532A1 - Anisotropic magnetorheological elastomer article and manufacturing method of said article - Google Patents
Anisotropic magnetorheological elastomer article and manufacturing method of said article Download PDFInfo
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- EP4184532A1 EP4184532A1 EP21383051.6A EP21383051A EP4184532A1 EP 4184532 A1 EP4184532 A1 EP 4184532A1 EP 21383051 A EP21383051 A EP 21383051A EP 4184532 A1 EP4184532 A1 EP 4184532A1
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- Prior art keywords
- article
- magnetic particles
- elastomer
- layer
- magnetic field
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- 229920001971 elastomer Polymers 0.000 title claims abstract description 90
- 239000000806 elastomer Substances 0.000 title claims abstract description 90
- 238000004519 manufacturing process Methods 0.000 title claims description 19
- 239000006249 magnetic particle Substances 0.000 claims abstract description 67
- 230000005291 magnetic effect Effects 0.000 claims abstract description 54
- 239000011159 matrix material Substances 0.000 claims abstract description 40
- 239000007788 liquid Substances 0.000 claims description 28
- 238000007711 solidification Methods 0.000 claims description 15
- 230000008023 solidification Effects 0.000 claims description 15
- 238000009826 distribution Methods 0.000 claims description 14
- 238000000034 method Methods 0.000 claims description 14
- 239000000654 additive Substances 0.000 claims description 13
- 229920002379 silicone rubber Polymers 0.000 claims description 5
- 230000005294 ferromagnetic effect Effects 0.000 claims description 3
- 239000002245 particle Substances 0.000 claims description 3
- 229920000915 polyvinyl chloride Polymers 0.000 claims description 2
- 229920003051 synthetic elastomer Polymers 0.000 claims description 2
- 239000005061 synthetic rubber Substances 0.000 claims description 2
- 238000005452 bending Methods 0.000 description 4
- 239000012530 fluid Substances 0.000 description 3
- 230000003993 interaction Effects 0.000 description 3
- 230000002441 reversible effect Effects 0.000 description 3
- 239000007787 solid Substances 0.000 description 3
- 239000003795 chemical substances by application Substances 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 230000006355 external stress Effects 0.000 description 2
- 230000001174 ascending effect Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000001627 detrimental effect Effects 0.000 description 1
- 239000008240 homogeneous mixture Substances 0.000 description 1
- 230000001788 irregular Effects 0.000 description 1
- 238000012856 packing Methods 0.000 description 1
- 239000004800 polyvinyl chloride Substances 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
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Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
- H01F1/44—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of magnetic liquids, e.g. ferrofluids
- H01F1/447—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of magnetic liquids, e.g. ferrofluids characterised by magnetoviscosity, e.g. magnetorheological, magnetothixotropic, magnetodilatant liquids
Definitions
- the present invention relates to anisotropic magnetorheological elastomer articles and to methods of manufacturing said article.
- Magnetorheological elastomer (MRE) articles which comprise an elastomer matrix and magnetic particles distributed in the elastomer matrix and which, in the presence of a magnetic field, experience a change in rigidity and dimension due to the interaction between the magnetic particles which tend to be oriented in the direction of the external field applied, are known.
- the magnetic particles are distributed in a solid elastomer matrix, unlike magnetorheological fluids (MRF) in which the magnetic particles are suspended in a liquid fluid.
- Anisotropic magnetorheological elastomer articles comprising an internal anisotropic distribution of magnetic particles to achieve a greater change of properties in one of the directions of the article when a magnetic field is applied are also known.
- anisotropic magnetorheological elastomer articles in which the magnetic particles are oriented grouped into columnar or laminar structures by means of a magnetic field applied during the manufacturing thereof, are known.
- Anisotropic magnetorheological elastomer articles are more difficult to manufacture, although they are more effective than isotropic magnetorheological elastomer articles which, unlike anisotropic elastomers, exhibit a homogenous distribution of magnetic particles.
- CN110648815B discloses a manufacturing method of an anisotropic magnetorheological elastomer article which achieves a controlled axial distribution by separately solidifying magnetorheological elastomer blocks, each with a different content of magnetic particles, placing the solidified blocks in an organized manner according to the content of magnetic particles in the axial direction of the article, and attaching the different blocks to one another to give rise to the anisotropic magnetorheological elastomer article.
- the disclosed article comprises eight blocks which are arranged in an ascending or descending manner according to the content of magnetic particles, with the content of magnetic particles of each block being comprised between 10% and 80%.
- the object of the invention is to provide an anisotropic magnetorheological elastomer article, a manufacturing method of said article, and the use of said article, as defined in the claims.
- One aspect of the invention relates to an anisotropic magnetorheological elastomer article comprising an elastomer matrix and magnetic particles distributed in the elastomer matrix.
- the article is a plate formed by the elastomer matrix.
- the elastomer matrix comprises a first layer with magnetic particles and a second layer without magnetic particles, such that the article is bent if a magnetic field is applied in a direction perpendicular to said article.
- the article is therefore formed by a single elastomer matrix comprising two adjacent layers: a layer which is active with respect to the magnetic field, i.e., the first layer with the magnetic particles, and a layer which is inactive with respect to the magnetic field, i.e., the second layer without magnetic particles.
- the first layer and the second layer are not attached to one another, rather the article is formed by a single elastomer matrix, with the first layer and the second layer belonging to said single solidified elastomer matrix. Therefore, the article of the invention is an article that is free of attachment defects wherein external stresses, such as a magnetic field, do not weaken the integrity of the article. This fact, along with the first layer being active with respect to the magnetic field and the second layer being inactive with respect to the magnetic field, ensures a greater interaction between said layers than if each layer belongs to a separately solidified elastomer matrix.
- the article of the invention is a simpler and more effective alternative than anisotropic magnetorheological elastomer articles known in the state of the art because a significant change of properties is achieved with only two layers of a single elastomer matrix that are active and inactive with respect to the magnetic field.
- the way in which the article behaves in the presence of a magnetic field is different from that of the anisotropic magnetorheological elastomer articles of the state of the art.
- the dimension of the article changes in the direction of the applied magnetic field, as illustrated in Figure 1 .
- the article of the invention is bent if a magnetic field is applied in a direction perpendicular to the article.
- Another aspect of the invention relates to a method of manufacturing an article like the one defined above.
- the method comprises a first addition step of adding a liquid elastomer, the magnetic particles, and additives in a mold, and a second solidification and distribution step in which the additives solidify the liquid elastomer giving rise to the elastomer matrix, whereas an external force distributes the magnetic particles in the liquid elastomer before the solidification thereof ends, generating the first layer and the second layer.
- the method of manufacturing an article like the one defined above is simple and economical.
- Another aspect of the invention relates to the use of the article of the invention for flow control.
- the article 10 of the invention comprises an elastomer matrix 1 and magnetic particles 2 distributed in the elastomer matrix 1, as shown in Figure 2 .
- the article 10 of the invention is characterized in that it is a plate formed by the elastomer matrix 1.
- the elastomer matrix 1 comprises a first layer 3a with magnetic particles 2 and a second layer 3b without magnetic particles 2.
- the article 10 is formed by a single elastomer matrix 1 which comprises two adjacent layers: a layer which is active with respect to the magnetic field H, i.e., the first layer 3a with the magnetic particles 2, and a layer which is inactive with respect to the magnetic field H, i.e., the second layer 3b without magnetic particles 2. Therefore, the first layer 3a and the second layer 3b comprise a common interface S2.
- the elastomer matrix 1 is not a magnetorheological fluid but rather a solid matrix.
- the common interface S2 is an irregular longitudinal surface, as shown in Figure 2 .
- the article 10 further comprises side faces L and a first outer surface S1 which, together with the common interface S2 and the side faces L, demarcate the first layer 3a, and a second outer surface S3 which, together with the common interface S2 and the side faces L, demarcate the second layer 3b.
- the first layer 3a and the second layer 3b are not attached to one another, rather the article 10 is formed by a single solidified elastomer matrix 1, with the first layer 3a and the second layer 3b belonging to said single elastomer matrix 1. Therefore, the article 10 is an article that is free of attachment defects wherein external stresses, such as a magnetic field, do not weaken the integrity of the article 10. This, along with the first layer 3a being active with respect to magnetic field and the second layer 3b being inactive with respect to the magnetic field, ensures a greater interaction between said layers than if each layer belongs to a separately solidified elastomer matrix.
- the article 10 of the invention is a simpler and more effective alternative than anisotropic magnetorheological elastomer articles known in the state of the art because a significant change of properties is achieved with only two layers of a single elastomer matrix that are active and inactive with respect to the magnetic field.
- the article 10 behaves differently in the presence of a magnetic field as compared to anisotropic magnetorheological elastomer articles of the state of the art.
- the dimension of the article changes in the direction of the applied magnetic field, as illustrated in Figure 1 .
- the article 10 of the invention is bent if a magnetic field H is applied in a direction perpendicular to the article 10.
- the direction perpendicular to the article 10 is direction Z. If the magnetic field H is applied to the article 10 in direction Z, the article 10 is bent in said sense in direction Z.
- the shape into which the article 10 is bent depends on the geometry thereof. In the case of the article 10 with a geometry like the one shown in Figure 2 , if the magnetic field H is applied to the article 10 in a positive sense in direction Z, i.e., from the first layer 3a which is active with respect to magnetic field to the second layer 3b which is inactive with respect to the magnetic field, the article 10 and the outer surfaces S1 and S3 are bent in said positive sense in direction Z as shown in Figure 3 . If the magnetic field H is applied in the negative sense in direction Z, i.e., from the second layer 3b which is inactive with respect to the magnetic field to the first layer 3a which is active, the article 10 would be bent in said negative sense in direction Z.
- the article 10 is therefore more economical to manufacture than anisotropic magnetorheological elastomer articles of the state of the art because it does not require expensive equipment for arranging the magnetic particles 3 such that they are oriented with a specific orientation during the manufacturing thereof.
- the magnetic particles 2 of the article 10 are soft ferromagnetic particles.
- Soft ferromagnetic particles are characterized in that they return to their initial position and orientation on their own when the applied magnetic field H is eliminated, i.e., they are reversible. They have a high magnetic saturation, hardly any magnetic hysteresis, and can be readily magnetized and demagnetized.
- the article 10 is therefore reversible, i.e., it can acquire the initial curvature on its own after eliminating the applied magnetic field H as a result of the reversible characteristics of the magnetic particles 2 and of the elastomer matrix 1.
- the article 10 has a thickness t of less than 2 mm.
- the magnetic field H required for bending the article 10 is therefore lower.
- the first layer 3a has a thickness t1 of between 10 and 90% of the thickness t of the article 10. This thereby ensures that both layers 3a and 3b have a minimum thickness t1 of 10% of the thickness t of the article 10.
- the thickness t1 of the first layer 3a is the same as the thickness of the second layer 3b, i.e., the thickness t1 of the first layer 3a is 50% of the thickness t of the article 10.
- the content by weight of the magnetic particles 2 is between 10 and 70% of the content by weight of the article 10, preferably 60%. It has been proven that the article 10 must have at least 10% of the content by weight of the magnetic particles 2 for the article 10 to have sufficient bending capacity. The higher the content by weight of the magnetic particles 2 are, the greater the bending capacity of the article 10 in the presence of one and the same magnetic field H. However, it has been proven that, beyond 70% of the content by weight of the magnetic particles 2, the bending capacity of the article 10 does not increase, but only increasing the cost of the raw material.
- the elastomer matrix 1 is a synthetic rubber, polyvinyl chloride, or silicone elastomer.
- the elastomer matrix 1 is a silicone elastomer.
- the elastomer matrix 1 is therefore capable of being cured at low temperatures and it is also cured quickly at high temperatures.
- liquid silicone elastomer has a low viscosity, making it easier to form.
- the dynamic viscosity of the silicone elastomer used in one embodiment is 1.2 Pa.s.
- the magnetic particles 2 have a size greater than 50 ⁇ m. Therefore, the magnetic particles 2 can be more readily concentrated in the magnetically active layer 3a or 3b.
- the magnetic particles 2 can be in a spherical or amorphous shape. In comparison with the spherical shape, the amorphous shape may be beneficial to achieve high degrees of packing of the magnetic particles 2 and to thereby enable obtaining high concentrations of magnetic particles 2 in the magnetically active layer 3a or 3b of a certain thickness t1.
- Figure 4 shows a second embodiment of the article 10 according to the invention.
- This embodiment differs from the preferred embodiment described above in that two side faces L of the article 10 are attached such that the article 10 forms a tube.
- the article 10 is tubular, adopting said shape as a result of the hypothetical attachment of two side faces L of the plate shown in Figure 2 . Therefore, in this embodiment, a direction perpendicular to the article 10 is a direction perpendicular to the tube, i.e., a direction perpendicular to the direction of extension of the tube, and the article 10 is bent if the magnetic field H is applied in said direction.
- the rest of the features are identical to those described for the article 10 of the preferred embodiment, so they are not described again.
- the shape into which the article 10 is bent depends on the geometry thereof.
- the tubular article 10 extends in direction Z and has a circular section in the absence of a magnetic field.
- the article 10 is bent, adopting an elliptical section if a magnetic field H is applied in the direction perpendicular to direction Z.
- the greater the magnetic field H that is applied the smaller the length of the minor axis of the elliptical section, and therefore the smaller the passage cross-section through the tube will be, where the passage cross-section may even be non-existent or substantially non-existent.
- Another aspect of the invention relates to a manufacturing method of the article 10, the method comprising the following steps:
- the manufacturing method of the article 10 does not require expensive equipment or subsequent steps which increase the cost of and complicate the manufacturing method of the article 10 to achieve an anisotropic distribution of magnetic particles 2 such as, for example, a subsequent attachment step.
- Figure 5 and Figure 6 schematically show the addition step and the solidification and distribution step of an embodiment of the method of the invention.
- the mold 6 comprises a cavity in the shape of a plate having a thickness t in which the magnetic particles 2 and the liquid elastomer 4 are added together with the additives 5.
- the additives 5 mainly comprise vulcanizers which activate the curing and solidification of the liquid elastomer 4 in the mold 6.
- the additives 5 may also comprise other non-magnetic components, for example, plasticizing agents.
- the vulcanizers polymerize the liquid elastomer 4, forming increasingly more cross-linked bonds which hinder the movement of the magnetic particles 2 and give rise, at the end of the curing process, to the solid elastomer matrix 1, and on the other hand, the plasticizing agents increase the mobility of the magnetic particles 2 in the liquid elastomer 4, aiding to enable the suitable distribution of the magnetic particles 2 during the curing and solidification of the liquid elastomer 4.
- the magnetic particles 2 are suspended in the liquid elastomer 4 throughout the entire cavity of the mold 6, as shown in Figure 6A .
- the external force F is preferably a non-magnetic external force that does not require expensive equipment for generating said force.
- a magnetic force which orients the magnetic particles during the solidification of the elastomer matrix would increase the cost of the method significantly.
- the external force F is the gravitational force, such that the gravitational force causes the magnetic particles 2 to settle in the liquid elastomer 4, as shown in Figure 6B .
- the settling speed becomes slower as more cross-linked bonds are being formed in the liquid elastomer 4 during the curing process.
- the gravitational force allows the magnetic particles 2 to be concentrated in the lower portion of the mold 6 before the solidification of the liquid elastomer ends, the first layer 3a with the magnetic particles 2 being the layer of the article 10 which is arranged in the lower portion of the mold 6.
- the solidification and distribution step therefore does not require any equipment for generating the force F which distributes the magnetic particles 2.
- the mold 6 comprises a cavity in the shape of a tube and the external force F applied is a centrifugal force.
- the external force F can therefore be generated in a simple and inexpensive manner.
- the method comprises at least one mixing step before the addition step in which the liquid elastomer 4, the magnetic particles 2, and the additives 5 are mixed under pressure outside the mold 6. In this manner, when mixing is performed under pressure, air bubbles which are detrimental to the properties of the article 10 are eliminated and a homogenous mixture of the additives 5 and of the magnetic particles 2 in the liquid elastomer 4 which is ready to be introduced in the mold 6 is obtained.
- the liquid elastomer 4 has a dynamic viscosity of less than 5 Pa.s.
- the mobility of the magnetic particles 2 in the liquid elastomer 4 for their suitable distribution is thereby favored.
- Another aspect of the invention relates to the use of an article 10 described above for flow control, for example, as a part of a flow control valve or pump.
- the different behavior of the article 10 in the presence of a magnetic field enables said use in a particularly advantageous manner.
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Abstract
Description
- The present invention relates to anisotropic magnetorheological elastomer articles and to methods of manufacturing said article.
- Magnetorheological elastomer (MRE) articles which comprise an elastomer matrix and magnetic particles distributed in the elastomer matrix and which, in the presence of a magnetic field, experience a change in rigidity and dimension due to the interaction between the magnetic particles which tend to be oriented in the direction of the external field applied, are known. In magnetorheological elastomer articles, the magnetic particles are distributed in a solid elastomer matrix, unlike magnetorheological fluids (MRF) in which the magnetic particles are suspended in a liquid fluid.
- Anisotropic magnetorheological elastomer articles comprising an internal anisotropic distribution of magnetic particles to achieve a greater change of properties in one of the directions of the article when a magnetic field is applied are also known. For example, anisotropic magnetorheological elastomer articles in which the magnetic particles are oriented grouped into columnar or laminar structures by means of a magnetic field applied during the manufacturing thereof, are known.
- Anisotropic magnetorheological elastomer articles are more difficult to manufacture, although they are more effective than isotropic magnetorheological elastomer articles which, unlike anisotropic elastomers, exhibit a homogenous distribution of magnetic particles.
-
CN110648815B discloses a manufacturing method of an anisotropic magnetorheological elastomer article which achieves a controlled axial distribution by separately solidifying magnetorheological elastomer blocks, each with a different content of magnetic particles, placing the solidified blocks in an organized manner according to the content of magnetic particles in the axial direction of the article, and attaching the different blocks to one another to give rise to the anisotropic magnetorheological elastomer article. Specifically, the disclosed article comprises eight blocks which are arranged in an ascending or descending manner according to the content of magnetic particles, with the content of magnetic particles of each block being comprised between 10% and 80%. - The object of the invention is to provide an anisotropic magnetorheological elastomer article, a manufacturing method of said article, and the use of said article, as defined in the claims.
- One aspect of the invention relates to an anisotropic magnetorheological elastomer article comprising an elastomer matrix and magnetic particles distributed in the elastomer matrix. The article is a plate formed by the elastomer matrix. The elastomer matrix comprises a first layer with magnetic particles and a second layer without magnetic particles, such that the article is bent if a magnetic field is applied in a direction perpendicular to said article.
- The article is therefore formed by a single elastomer matrix comprising two adjacent layers: a layer which is active with respect to the magnetic field, i.e., the first layer with the magnetic particles, and a layer which is inactive with respect to the magnetic field, i.e., the second layer without magnetic particles.
- In the article of the invention, the first layer and the second layer are not attached to one another, rather the article is formed by a single elastomer matrix, with the first layer and the second layer belonging to said single solidified elastomer matrix. Therefore, the article of the invention is an article that is free of attachment defects wherein external stresses, such as a magnetic field, do not weaken the integrity of the article. This fact, along with the first layer being active with respect to the magnetic field and the second layer being inactive with respect to the magnetic field, ensures a greater interaction between said layers than if each layer belongs to a separately solidified elastomer matrix.
- The article of the invention is a simpler and more effective alternative than anisotropic magnetorheological elastomer articles known in the state of the art because a significant change of properties is achieved with only two layers of a single elastomer matrix that are active and inactive with respect to the magnetic field.
- The way in which the article behaves in the presence of a magnetic field is different from that of the anisotropic magnetorheological elastomer articles of the state of the art. In the articles of the state of the art, the dimension of the article changes in the direction of the applied magnetic field, as illustrated in
Figure 1 . However, the article of the invention is bent if a magnetic field is applied in a direction perpendicular to the article. - Another aspect of the invention relates to a method of manufacturing an article like the one defined above. The method comprises a first addition step of adding a liquid elastomer, the magnetic particles, and additives in a mold, and a second solidification and distribution step in which the additives solidify the liquid elastomer giving rise to the elastomer matrix, whereas an external force distributes the magnetic particles in the liquid elastomer before the solidification thereof ends, generating the first layer and the second layer.
- The method of manufacturing an article like the one defined above is simple and economical.
- Another aspect of the invention relates to the use of the article of the invention for flow control.
- These and other advantages and features of the invention will become apparent in view of the figures and the detailed description of the invention.
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Figure 1 shows an anisotropic magnetorheological elastomer article of the state of the art, in the absence of a magnetic field and when a magnetic field is applied. -
Figure 2 shows a perspective view of an anisotropic magnetorheological elastomer article of the invention according to a preferred embodiment, in the absence of a magnetic field. -
Figure 3 shows a perspective view of the article ofFigure 2 , when a magnetic field is applied in a direction perpendicular to the article. -
Figure 4 shows a perspective view of an anisotropic magnetorheological elastomer article of the invention according to another embodiment. -
Figure 5 shows a schematic depiction of the addition step of the manufacturing method of the invention according to one embodiment. -
Figure 6 shows a schematic depiction of the start and end of the solidification and distribution step of the manufacturing method of the invention according to one embodiment. - The
article 10 of the invention comprises anelastomer matrix 1 andmagnetic particles 2 distributed in theelastomer matrix 1, as shown inFigure 2 . Thearticle 10 of the invention is characterized in that it is a plate formed by theelastomer matrix 1. Theelastomer matrix 1 comprises afirst layer 3a withmagnetic particles 2 and asecond layer 3b withoutmagnetic particles 2. In other words, thearticle 10 is formed by asingle elastomer matrix 1 which comprises two adjacent layers: a layer which is active with respect to the magnetic field H, i.e., thefirst layer 3a with themagnetic particles 2, and a layer which is inactive with respect to the magnetic field H, i.e., thesecond layer 3b withoutmagnetic particles 2. Therefore, thefirst layer 3a and thesecond layer 3b comprise a common interface S2. - The
elastomer matrix 1 is not a magnetorheological fluid but rather a solid matrix. - In the preferred embodiment illustrated in
Figure 2 , thearticle 10 is a plate that is substantially planar in directions X and Y in the absence of a magnetic field H=0 and has a thickness t in direction Z, so thefirst layer 3a and thesecond layer 3b also extend along directions X and Y. The common interface S2 is an irregular longitudinal surface, as shown inFigure 2 . Thearticle 10 further comprises side faces L and a first outer surface S1 which, together with the common interface S2 and the side faces L, demarcate thefirst layer 3a, and a second outer surface S3 which, together with the common interface S2 and the side faces L, demarcate thesecond layer 3b. - In the
article 10 of the invention, thefirst layer 3a and thesecond layer 3b are not attached to one another, rather thearticle 10 is formed by a singlesolidified elastomer matrix 1, with thefirst layer 3a and thesecond layer 3b belonging to saidsingle elastomer matrix 1. Therefore, thearticle 10 is an article that is free of attachment defects wherein external stresses, such as a magnetic field, do not weaken the integrity of thearticle 10. This, along with thefirst layer 3a being active with respect to magnetic field and thesecond layer 3b being inactive with respect to the magnetic field, ensures a greater interaction between said layers than if each layer belongs to a separately solidified elastomer matrix. - The
article 10 of the invention is a simpler and more effective alternative than anisotropic magnetorheological elastomer articles known in the state of the art because a significant change of properties is achieved with only two layers of a single elastomer matrix that are active and inactive with respect to the magnetic field. - The
article 10 behaves differently in the presence of a magnetic field as compared to anisotropic magnetorheological elastomer articles of the state of the art. In the articles of the state of the art, the dimension of the article changes in the direction of the applied magnetic field, as illustrated inFigure 1 . However, thearticle 10 of the invention is bent if a magnetic field H is applied in a direction perpendicular to thearticle 10. - The applied magnetic field H having a component in said direction perpendicular to the
article 10 is enough for thearticle 10, which is substantially planar in the absence of a magnetic field H=0, to acquire a bent shape. However, the greater said component of the magnetic field H is in the direction perpendicular to thearticle 10, the more thearticle 10 will bend. - In the preferred embodiment shown in
Figures 2 and3 , the direction perpendicular to thearticle 10 is direction Z. If the magnetic field H is applied to thearticle 10 in direction Z, thearticle 10 is bent in said sense in direction Z. The shape into which thearticle 10 is bent depends on the geometry thereof. In the case of thearticle 10 with a geometry like the one shown inFigure 2 , if the magnetic field H is applied to thearticle 10 in a positive sense in direction Z, i.e., from thefirst layer 3a which is active with respect to magnetic field to thesecond layer 3b which is inactive with respect to the magnetic field, thearticle 10 and the outer surfaces S1 and S3 are bent in said positive sense in direction Z as shown inFigure 3 . If the magnetic field H is applied in the negative sense in direction Z, i.e., from thesecond layer 3b which is inactive with respect to the magnetic field to thefirst layer 3a which is active, thearticle 10 would be bent in said negative sense in direction Z. - In a preferred embodiment, the
magnetic particles 2 of thearticle 10 are arranged oriented arbitrarily in the absence of magnetic field H=0. Thearticle 10 is therefore more economical to manufacture than anisotropic magnetorheological elastomer articles of the state of the art because it does not require expensive equipment for arranging themagnetic particles 3 such that they are oriented with a specific orientation during the manufacturing thereof. - In a preferred embodiment, the
magnetic particles 2 of thearticle 10 are soft ferromagnetic particles. Soft ferromagnetic particles are characterized in that they return to their initial position and orientation on their own when the applied magnetic field H is eliminated, i.e., they are reversible. They have a high magnetic saturation, hardly any magnetic hysteresis, and can be readily magnetized and demagnetized. Thearticle 10 is therefore reversible, i.e., it can acquire the initial curvature on its own after eliminating the applied magnetic field H as a result of the reversible characteristics of themagnetic particles 2 and of theelastomer matrix 1. - In a preferred embodiment, the
article 10 has a thickness t of less than 2 mm. The magnetic field H required for bending thearticle 10 is therefore lower. - In a preferred embodiment, the
first layer 3a has a thickness t1 of between 10 and 90% of the thickness t of thearticle 10. This thereby ensures that bothlayers article 10. In the preferred embodiment shown inFigure 2 , the thickness t1 of thefirst layer 3a is the same as the thickness of thesecond layer 3b, i.e., the thickness t1 of thefirst layer 3a is 50% of the thickness t of thearticle 10. - In a preferred embodiment, the content by weight of the
magnetic particles 2 is between 10 and 70% of the content by weight of thearticle 10, preferably 60%. It has been proven that thearticle 10 must have at least 10% of the content by weight of themagnetic particles 2 for thearticle 10 to have sufficient bending capacity. The higher the content by weight of themagnetic particles 2 are, the greater the bending capacity of thearticle 10 in the presence of one and the same magnetic field H. However, it has been proven that, beyond 70% of the content by weight of themagnetic particles 2, the bending capacity of thearticle 10 does not increase, but only increasing the cost of the raw material. - In a preferred embodiment, the
elastomer matrix 1 is a synthetic rubber, polyvinyl chloride, or silicone elastomer. In the preferred embodiment shown inFigures 2 and3 , theelastomer matrix 1 is a silicone elastomer. Theelastomer matrix 1 is therefore capable of being cured at low temperatures and it is also cured quickly at high temperatures. Furthermore, liquid silicone elastomer has a low viscosity, making it easier to form. The dynamic viscosity of the silicone elastomer used in one embodiment is 1.2 Pa.s. - In a preferred embodiment, the
magnetic particles 2 have a size greater than 50 µm. Therefore, themagnetic particles 2 can be more readily concentrated in the magneticallyactive layer magnetic particles 2 can be in a spherical or amorphous shape. In comparison with the spherical shape, the amorphous shape may be beneficial to achieve high degrees of packing of themagnetic particles 2 and to thereby enable obtaining high concentrations ofmagnetic particles 2 in the magneticallyactive layer -
Figure 4 shows a second embodiment of thearticle 10 according to the invention. This embodiment differs from the preferred embodiment described above in that two side faces L of thearticle 10 are attached such that thearticle 10 forms a tube. In other words, thearticle 10 is tubular, adopting said shape as a result of the hypothetical attachment of two side faces L of the plate shown inFigure 2 . Therefore, in this embodiment, a direction perpendicular to thearticle 10 is a direction perpendicular to the tube, i.e., a direction perpendicular to the direction of extension of the tube, and thearticle 10 is bent if the magnetic field H is applied in said direction. The rest of the features are identical to those described for thearticle 10 of the preferred embodiment, so they are not described again. - As mentioned above, the shape into which the
article 10 is bent depends on the geometry thereof. In the case of a tubular geometry of thearticle 10 like the one shown inFigure 4 , thetubular article 10 extends in direction Z and has a circular section in the absence of a magnetic field. Thearticle 10 is bent, adopting an elliptical section if a magnetic field H is applied in the direction perpendicular to direction Z. The greater the magnetic field H that is applied, the smaller the length of the minor axis of the elliptical section, and therefore the smaller the passage cross-section through the tube will be, where the passage cross-section may even be non-existent or substantially non-existent. - Another aspect of the invention relates to a manufacturing method of the
article 10, the method comprising the following steps: - a first addition step of adding a liquid elastomer 4, the
magnetic particles 2, and additives 5 in amold 6, and - a second solidification and distribution step in which the additives 5 solidify the liquid elastomer 4 giving rise to the
elastomer matrix 1, whereas an external force F distributes themagnetic particles 2 in the liquid elastomer 4 before the solidification thereof ends, generating thefirst layer 3a and thesecond layer 3b. - The manufacturing method of the
article 10 does not require expensive equipment or subsequent steps which increase the cost of and complicate the manufacturing method of thearticle 10 to achieve an anisotropic distribution ofmagnetic particles 2 such as, for example, a subsequent attachment step. -
Figure 5 and Figure 6 schematically show the addition step and the solidification and distribution step of an embodiment of the method of the invention. Themold 6 comprises a cavity in the shape of a plate having a thickness t in which themagnetic particles 2 and the liquid elastomer 4 are added together with the additives 5. - Adding the elastomer 4 in liquid state increases the mobility of the
magnetic particles 2 for their suitable distribution. The additives 5 mainly comprise vulcanizers which activate the curing and solidification of the liquid elastomer 4 in themold 6. However, the additives 5 may also comprise other non-magnetic components, for example, plasticizing agents. On one hand, the vulcanizers polymerize the liquid elastomer 4, forming increasingly more cross-linked bonds which hinder the movement of themagnetic particles 2 and give rise, at the end of the curing process, to thesolid elastomer matrix 1, and on the other hand, the plasticizing agents increase the mobility of themagnetic particles 2 in the liquid elastomer 4, aiding to enable the suitable distribution of themagnetic particles 2 during the curing and solidification of the liquid elastomer 4. - At the start of the distribution and solidification step of this embodiment in which the additives 5 have yet to start the solidification of the liquid elastomer 4, the
magnetic particles 2 are suspended in the liquid elastomer 4 throughout the entire cavity of themold 6, as shown inFigure 6A . - The external force F is preferably a non-magnetic external force that does not require expensive equipment for generating said force. A magnetic force which orients the magnetic particles during the solidification of the elastomer matrix would increase the cost of the method significantly.
- In an embodiment of the method, the external force F is the gravitational force, such that the gravitational force causes the
magnetic particles 2 to settle in the liquid elastomer 4, as shown inFigure 6B . The settling speed becomes slower as more cross-linked bonds are being formed in the liquid elastomer 4 during the curing process. The gravitational force allows themagnetic particles 2 to be concentrated in the lower portion of themold 6 before the solidification of the liquid elastomer ends, thefirst layer 3a with themagnetic particles 2 being the layer of thearticle 10 which is arranged in the lower portion of themold 6. The solidification and distribution step therefore does not require any equipment for generating the force F which distributes themagnetic particles 2. - In another embodiment of the method not shown in the figures, the
mold 6 comprises a cavity in the shape of a tube and the external force F applied is a centrifugal force. The external force F can therefore be generated in a simple and inexpensive manner. - In an embodiment of the method, the method comprises at least one mixing step before the addition step in which the liquid elastomer 4, the
magnetic particles 2, and the additives 5 are mixed under pressure outside themold 6. In this manner, when mixing is performed under pressure, air bubbles which are detrimental to the properties of thearticle 10 are eliminated and a homogenous mixture of the additives 5 and of themagnetic particles 2 in the liquid elastomer 4 which is ready to be introduced in themold 6 is obtained. - In an embodiment of the method, the liquid elastomer 4 has a dynamic viscosity of less than 5 Pa.s. The mobility of the
magnetic particles 2 in the liquid elastomer 4 for their suitable distribution is thereby favored. - Another aspect of the invention relates to the use of an
article 10 described above for flow control, for example, as a part of a flow control valve or pump. The different behavior of thearticle 10 in the presence of a magnetic field enables said use in a particularly advantageous manner.
Claims (14)
- Anisotropic magnetorheological elastomer article comprising an elastomer matrix (1) and magnetic particles (2) distributed in the elastomer matrix (1), characterized in that the article (10) is a plate formed by the elastomer matrix (1) comprising a first layer (3a) with magnetic particles (2) and a second layer (3b) without magnetic particles (2), such that the article (10) is bent if a magnetic field (H) is applied in a direction perpendicular to said article (10).
- Article according to claim 1, wherein the magnetic particles (2) are arranged oriented arbitrarily in the absence of magnetic field.
- Article according to claim 1 or 2, wherein the magnetic particles (2) are soft ferromagnetic particles.
- Article according to any of the preceding claims, wherein the article (10) has a thickness (t) of less than 2 mm.
- Article according to any of the preceding claims, wherein the first layer (3a) has a thickness (t1) of between 10 and 90% of the thickness (t) of the article (10), preferably 50%.
- Article according to any of the preceding claims, wherein the content by weight of the magnetic particles (2) is between 10 and 70% of the content by weight of the article (10), preferably 60%.
- Article according to any of the preceding claims, wherein the elastomer matrix (1) is a synthetic rubber, PVC, or silicone elastomer.
- Article according to any of the preceding claims, wherein the magnetic particles (2) have a size greater than 50 µm.
- Article according to any of the preceding claims, wherein two side faces (L) of the article (10) are attached such that the article (10) forms a tube.
- Manufacturing method of an article according to any of the preceding claims, the method comprising- a first addition step of adding a liquid elastomer (4), the magnetic particles (2), and additives (5) in a mold (6), and- a second solidification and distribution step in which the additives (5) solidify the liquid elastomer (4) giving rise to the elastomer matrix (1), whereas an external force (F) distributes the magnetic particles (2) in the liquid elastomer (6) before the solidification thereof ends, generating the first layer (3a) and the second layer (3b).
- Manufacturing method according to claim 10, wherein the external force (F) is the gravitational force, such that the gravitational force causes the magnetic particles (2) to settle in the liquid elastomer (4).
- Manufacturing method according to claim 10 or 11, the method comprising at least one mixing step before the addition step in which the liquid elastomer (4), the magnetic particles (2), and the additives (5) are mixed under pressure outside the mold (6).
- Manufacturing method according to any of claims 10 to 12, wherein the liquid elastomer (4) has a dynamic viscosity of less than 5 Pa.s.
- Use of an article according to any of claims 1 to 9 for flow control.
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WO2002090105A1 (en) * | 2001-05-10 | 2002-11-14 | University Of Toledo | Actively controlled impact elements |
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US20110155945A1 (en) * | 2007-02-06 | 2011-06-30 | Rogers Corporation | Conductive polymer foams, method of manufacture, and uses thereof |
GB2548671A (en) * | 2016-03-25 | 2017-09-27 | Fuji Polymer Ind | Magneto-rheological elastomer composition, method for producing same, and vibration absorbing device including same |
CN110648815A (en) | 2019-09-29 | 2020-01-03 | 南京航空航天大学 | Magnetorheological elastomer capable of accurately controlling axial distribution of magnetic particles and preparation method thereof |
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WO2002090105A1 (en) * | 2001-05-10 | 2002-11-14 | University Of Toledo | Actively controlled impact elements |
US20050011710A1 (en) * | 2003-05-12 | 2005-01-20 | Hitchcock Gregory H. | Controllable magneto-rheological elastomer vibration isolator |
US20110155945A1 (en) * | 2007-02-06 | 2011-06-30 | Rogers Corporation | Conductive polymer foams, method of manufacture, and uses thereof |
GB2548671A (en) * | 2016-03-25 | 2017-09-27 | Fuji Polymer Ind | Magneto-rheological elastomer composition, method for producing same, and vibration absorbing device including same |
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