RU2157013C2 - Magnetic controllable flexible composite material - Google Patents

Abstract

FIELD: mechanical engineering; electrical engineering. SUBSTANCE: material is produced on the basis of caoutchouc and contains in mass parts: natural caoutchouc and/or synthetic rubber - 30-75, powder iron, its magnetic oxide or ferrite - 10-40, hydrocarbon oil, silicon oil or alkyl phthalate as plasticizer - 5-50, organic peroxide as cross- linking agent and/or sulfur-containing substance like tetraetoxyxylan or tri-isocyanate - 0.5-4.0. EFFECT: reversible changes of form and size under magnetic field action. 6 dwg, 1 tbl

Description

 The invention relates to the field of creating composite materials, in particular to the production of magnetically controlled elastic composites intended for the manufacture of elements controlled by a magnetic field, which can be used in machine and instrument-making, radio and electrical, chemical, textile and other industries.

 Composite materials are known which are a colloidal solution of magnetic particles stabilized by a surfactant in a carrier fluid.

(Pat. RF 1688752, publ. 1995, 6MKI H 01 P 1/28;
Pat. RF 2023317, publ. 1994, 6 MKI H 01 P 1/28;
Pat. RF 2056067, publ. 1996 6MKI H 01 F 1/28;
Pat. RF 2111572, publ. 1998 6MKI H 01 F 1/28;
EP 055065 publ. 1982, 6 MKI H 01 F 1/37;
EP 481670 publ. 1992, 6 MKI H 01 F 1/20;
Prince Berkovsky B.M., Medvedev V.F., Krakow M.S. Magnetic fluids. - M .: X., 1989).

 These composite materials interacting with an external magnetic field are called magnetic fluids and suspensions and are widely used in industry. It should be noted the variety of known compositions, including various carrier fluids (water, kerosene, organosilicon and fluorine fluids), various surfactants and magnetic powders (magnetite, transition metals of the iron group and their magnetic oxides).

The disadvantages of these materials are:
- the impossibility of their use outside the shape-setting vessel;
- limited application due to a change in the shape of only the open surface of the magnetic fluid when the external magnetic field is turned on. The inevitability of evaporation of toxic and corrosive components from the open surface of the magnetic fluid;
- difficulties in achieving uniformity and stability of magnetic properties due to aggregation of particles in a magnetic field.

 Composite materials are also known containing magnetic finely dispersed substances (magnetite powders, pure transition metals and their oxides), polymer binders, for example rubber and a crosslinking agent (vulcanizer), and in some cases plasticizing substances to improve mechanical properties.

(A. S. USSR 637879, publ. 1978, 6 MKI H 01 F 1/113;
A.S. USSR 1333109, publ. 1994, 6 MKI H 01 F 1/113;
A.S. USSR 1612893, publ. 1994, 6 MKI H 01 F 1/113;
Pat. RF 2015583, publ. 1994, 6 MKI H 01 F 1/113;
EP 0 289 799, publ. 1988, 6 MKI H 01 F I1 / 37;
EP 0558178, publ. 1993, 6 MKI H 01 F 1/37;
EP 0481670, publ. 1992, 6 MKI H 01 F 1/20;
Prince Alekseev A.G., Kornev A.E. Magnetic Elastomers. - M.: Chemistry, 1987, p. 143-144.)
Such materials, called magnetic elastomers, are highly technological, since they allow the manufacture of elements of any given shape. However, the latter can only be changed by significant mechanical influences and within small limits.

 The disadvantages of these materials are rather high hardness and low elasticity, requiring considerable mechanical forces for their deformation, which cannot be created by an external magnetic field.

 The closest chemical composition of the analogue of the proposed technical solution, we have chosen for the prototype (A.S. USSR N 1274010, publ. 1986, 6MKI H 01 F 1/113), is a magnetic composition consisting of natural rubber as a binder, oligodiene hydrocarbon - plasticizer, thiuram - vulcanizer, magnetic filler - barium ferrite and other additives to give the composite material the necessary physical and mechanical characteristics. The content of the magnetic filler in the composition is 82-90 wt. %, which prevents the achievement of the necessary elastic properties of the composite. Elements made of this material, when placed in a magnetic field, remain unchanged in their shape and size.

 Analysis of the above analogues and prototype allows us to conclude that the magnetically filled materials that we found in the technical literature and patent documentation practically do not change size and shape under the influence of an external magnetic field.

 The aim of the invention is the creation of an elastically deformable magnetically controlled material capable of substantially changing its size and shape in external uniform and inhomogeneous magnetic fields.

 The basis of the invention is the technical task to obtain a composite material with elastic and magnetic properties that are necessary to achieve this goal.

The problem was solved by developing the composition of a composite material containing a polymeric binder - natural and / or synthetic rubber, magnetic filler - ferrites, powdered iron or its magnetic oxides; plasticizer - hydrocarbon or silicone oil, alkyl phthalate; a crosslinking agent (vulcanizer) corresponding to the nature of the rubber is an organic peroxide, sulfur and / or sulfur-containing compound, triisocyanate or tetraethoxylan. The ratio of the proposed components is, in wt. hours:
Rubber - 30-75
Magnetic filler - 10-40
Softener - 5-50
Vulcanizer - 0.5-4.0
The rubber-based binder included in the proposed composition forms an elastic matrix containing magnetic particles, and mainly determines the elastic properties of the final composite. As experiments have shown, it is possible to use a number of rubbers, for example, natural (NK), isoprene (SKI), butadiene (SKD), styrene butadiene (SCS), butyl rubber (BK), ethylene propylene (SKEL), silicone (SKTN) and other synthetic rubbers. When using silicone rubber and silicone plasticizer increases the heat resistance of the material (up to 250 ^o C).

 The presence in the composition of hydrocarbon, silicone oil, alkyl phthalate, etc. as a plasticizer can significantly increase the ductility of the entire composition. When the content of plasticizer is less than 5 wt. parts - the composition is "hard", with an excess of more than 50 wt. parts - it loses its elastic properties.

 The magnetic powder introduced into the composition determines the magnetic properties of the resulting material, affecting in turn its elasticity. A decrease in the mass quantity of the magnetic component under the same test conditions reduces the elongation of the samples in a magnetic field. An increase in the mass fraction of the magnetic component in the composition also leads to a decrease in elongation due to the acquisition of a material with greater hardness. With a small amount of magnetic powder (<10 wt. Parts), a weakly magnetic material is obtained that is poorly stretched in a magnetic field. With a large content of the magnetic phase (> 40 wt. Parts), the magnetic properties of the material improve, but it becomes hard and poorly extensible in a magnetic field. A crosslinking agent (vulcanizer) completes the polymer formation process and determines the final elastic properties of the composition. In this case, the type and content of the vulcanizer must correspond to the nature of the rubber used.

(1), 300

(2) и 2 мкм (3), а также сферических частиц магнетита со средним размером 0,2 мкм (4). Изучение магнитомеханических свойств таких материалов проводилось в неоднородных и однородных магнитных полях. В неоднородных магнитных полях удлинение исследованных образцов достигает нескольких сотен % от первоначального размера. При этом после выключения магнитного поля образцы полностью восстанавливают свою первоначальную форму и линейный размер.As a result of the study of the obtained composite materials, it was found that their magnetic properties are mainly determined by the magnetic characteristics of the powders used and the fill factor of the composite material with magnetic particles. The use of various types of magnetic filler, the average particle size of which ranges from hundreds to tens of thousands of angstroms, made it possible to create magnetically controlled materials with a wide range of magnetic properties. Thus, materials were obtained whose coercive force varied from 2-3 to 300 Oe, and the specific magnetization reached 70 Ghcm ³ / g. As an example in FIG. Figure 1 shows the dependences of the specific magnetization ó on H for the magnetically controlled composite materials obtained by us based on iron particles with an average size of 110

(1), 300

(2) and 2 μm (3), as well as spherical particles of magnetite with an average size of 0.2 μm (4). The study of the magnetomechanical properties of such materials was carried out in inhomogeneous and uniform magnetic fields. In inhomogeneous magnetic fields, the elongation of the studied samples reaches several hundred% of the initial size. In this case, after turning off the magnetic field, the samples completely restore their original shape and linear size.

(1), 300

(2) и 2 мкм (3), а также сферических частиц магнетита со средним размером 0,2 мкм (4). Как видно на фиг. 2, все приведенные зависимости Δl от величины тока магнита I имеют нелинейный характер. При этом на некоторых зависимостях при достижении определенного значения тока наблюдается резкое увеличение длины образца на 200-300% от первоначального значения.As an example, figure 2 shows the dependence of the elongation Δl of tape samples of size 40x5x0.3 mm on the magnitude of the current I of the electromagnet. Here is a schematic diagram of the experience for testing the materials obtained. The material of the tape samples was obtained by dispersing in a polymer spherical iron particles with an average size of 110

(1), 300

(2) and 2 μm (3), as well as spherical particles of magnetite with an average size of 0.2 μm (4). As seen in FIG. 2, all the above dependences Δl on the magnitude of the magnet current I are nonlinear. Moreover, in some dependences, when a certain current value is reached, a sharp increase in the length of the sample by 200-300% from the initial value is observed.

 A study of spherical shaped samples in gradient magnetic fields showed that the samples also underwent deformation, elongating or contracting in the direction of the gradient of the external magnetic field, depending on the fixing conditions. In this case, the deformation reached 20-30% of the initial size.

 When placing samples made in the form of tapes in a uniform magnetic field of the order of 2-4 kOe, it was found that the tape oriented along the lines of force increases its length by 20-30% from the initial value. If the samples have a spherical shape, then a uniform magnetic field of the order of 2-4 kOe draws the sample along the lines of force. The size of the major axis of the resulting ellipsoid of revolution exceeds the diameter of the original spherical sample by 20-50%.

 To evaluate the magnetomechanical properties, we selected the Δl elongation of tape samples measuring 40x5x0.3 mm in an inhomogeneous magnetic field with a gradient of dH / dx = 200 E / cm and a magnetic field value at the specimen fixation point of H = 400 Oe (see Fig. 2).

 Example 1

The composition is prepared in a mechanical Z-type mixer by sequentially adding components. 40 g of SKU-3 rubber are introduced into the apparatus in the form of a 50% solution in methyl ethyl ketone, 30 g of magnetite powder with a particle size of 0.2 μm, 25 g of dioctyl phthalate plasticizer, 3.5 g of a cross-linking agent - triisocyanate (TT-75). The mixture is stirred for half an hour and poured into a mold for subsequent drying. Drying is carried out at 70 ^o C for 5 hours.

 Testing the sample: the tensile material under the above conditions for evaluating the magnetomechanical properties is 120%.

 Example 2

в количестве 20 г, дибутилфталат в количестве 40 г и вулканизатор - смесь серы (0,5 г), альтакса (0,3 г) и ДФГ - 1,3 г. После перемешивания в течение получаса смесь выливают в форму и сушат композицию при температуре 70^oC в течение 2 часов. Далее температуру поднимают до 140^oC с выдержкой 25 минут.40 g of isoprene rubber (SKI 3) is introduced into the mixer in the form of a 50% solution in hexane, an ultrafine iron powder with a particle size of 500

in an amount of 20 g, dibutyl phthalate in an amount of 40 g and a vulcanizer is a mixture of sulfur (0.5 g), altax (0.3 g) and DFG - 1.3 g. After stirring for half an hour, the mixture is poured into a mold and the composition is dried at temperature 70 ^o C for 2 hours. Then the temperature is raised to 140 ^o C with an exposure of 25 minutes.

 Tests of the sample showed: the tension of the material under the above conditions for evaluating the magnetomechanical properties is 150%.

 Example 3

50 g of SKTN-A silicone rubber, 20 g of carbonyl iron powder, 25 g of PMS-500 silicone oil and 2 g of tetraethylsiloxane are introduced into the mixer. After stirring for 15 minutes, the mixture was poured into a mold. Curing is carried out at room temperature of 20 - 25 ^o C for 12 hours.

 Testing of the sample: the tension of the material under the above conditions for evaluating the magnetomechanical properties was 220%.

 The following examples of developed magnetically controlled composite materials and their magnetomechanical properties are summarized in table. 1 and 2. Thus, for the first time, an elastic composite material is obtained that differs from the known ones by the property of directionally changing its dimensions and shape under the influence of a magnetic field and completely restoring them when turned off.

 Currently, the authors are not aware of technical solutions that would fulfill the task. Thus, our result can be considered new and consistent with other patentability criteria.

Claims (1)

Magnetically controlled elastic rubber-based composite material containing a magnetic filler, a plasticizer and a crosslinking agent, characterized in that it contains, by weight:
Natural and / or synthetic rubber - 30 - 75
Powdered iron, its magnetic oxide or ferrite - 10 - 40
Plasticizer - hydrocarbon, silicone oil or alkyl phthalate - 5 - 50
Crosslinking agent - organic peroxide and / or sulfur-containing compound, tetraethoxylan or triisocyanate - 0.5 - 4.0

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