High-stability PAO oil-based magnetorheological fluid as well as preparation method and application thereof

Abstract

The invention discloses high-stability PAO oil-based magnetorheological fluid as well as a preparation method and application thereof, and relates to the technical field of preparation of damping and vibration attenuation materials. The preparation method of the high-stability PAO oil-based magnetorheological fluid comprises the following steps: activating carbonyl iron powder with diluted hydrochloric acid to obtain activated particles; the activated particles are put into an alcohol-water solution, the pH value of the solution is adjusted, BTSE is dropwise added, and after heating and stirring treatment, a primary modified particle solution is obtained; adjusting the pH value of the modified particle solution, dropwise adding DTMS, heating, stirring, separating, washing with water, separating out secondary modified magnetic particles, cleaning the magnetic particles with absolute ethyl alcohol, and drying to obtain secondary modified particles; uniformly mixing PAO oil, hydrophilic fumed silica and a thixotropic synergist, and adding the secondary modified particles to obtain the PAO oil-based magnetorheological fluid. The problems of poor dispersion stability and sedimentation stability of the magnetorheological fluid are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of the preparation of damping and vibration reduction materials, and particularly relates to a high-stability PAO oil-based magnetorheological fluid and its preparation method and application. Background Art

[0002] Magnetorheological fluid is an intelligent material, mainly composed of a base carrier fluid, magnetic particles, and additives (such as stabilizers, surfactants, etc.). Magnetorheological fluid has strong magnetic response ability, excellent mechanical properties and plasticity, high reliability, easy control and operation, energy conservation and environmental protection, etc. It has great potential in manufacturing controllable fluid systems, can respond to external stimuli within a very short time, and achieve precise control and regulation functions; it can also be applied to mechanical transmission devices to play a buffering role and improve the operation efficiency of equipment; it is also widely used in fields such as automotive damping, aerospace, and medical.

[0003] Although magnetorheological fluid has the above-mentioned multiple advantages, there are still some deficiencies in its practical application. For example, the dispersion stability is poor (there is a large density difference between the magnetic particles and the base carrier fluid), the sedimentation stability is insufficient (the magnetic particles are prone to sedimentation under the action of gravity), and the preparation process is complex. These are all problems that need to be urgently solved in the current research on the preparation of magnetorheological fluid.

[0004] Patent CN116387007A discloses a preparation method of a highly dispersion-stable synthetic oil-based magnetorheological fluid. Specifically, 1) dilute hydrochloric acid is used to activate micron-scale carbonyl iron powder; 2) the carbonyl iron powder is coated with a first layer of surfactant BTES (bis-(γ-triethoxysilylpropyl)tetrasulfide); 3) the carbonyl iron powder is coated with a second layer of surfactant APTES (3-aminopropyltriethoxysilane); 4) the carbonyl iron powder is coated with a third layer of surfactant oleic acid; 5) the multi-coated carbonyl iron powder is dispersed in a high-temperature-resistant synthetic oil through mechanical stirring to prepare a magnetorheological fluid with high dispersion stability. This method prepares magnetorheological fluid by coating magnetic particles in three layers, and its preparation process is relatively complex and cannot meet the requirements for the preparation process of magnetorheological fluid in practical applications.

[0005] Therefore, the present invention proposes a preparation method of a high-stability PAO oil-based magnetorheological fluid, aiming to improve the dispersion stability and sedimentation stability of the magnetorheological fluid by optimizing the preparation process and formula, so as to meet the requirements in various application scenarios. Summary of the Invention

[0006] The technical problem to be solved by the present invention is that the existing magnetorheological fluid has poor dispersion stability and sedimentation stability. The purpose is to provide a high-stability PAO oil-based magnetorheological fluid and its preparation method and application, which solves the problem of poor dispersion stability and sedimentation stability of the magnetorheological fluid.

[0007] The present invention is achieved through the following technical solutions:

[0008] In a first aspect, the present invention provides a preparation method of a high-stability PAO oil-based magnetorheological fluid, comprising the following steps:

[0009] After activating carbonyl iron powder with dilute hydrochloric acid, washing with ultrapure water, separating magnetic iron powder particles, and then washing with absolute ethanol and drying, activated particles are obtained;

[0010] Put the activated particles into an alcohol aqueous solution, adjust the pH value of the solution, and then dropwise add 1,2-bis(triethoxysilyl)ethane (BTSE), and after heating and stirring treatment, a primary modified particle solution is obtained;

[0011] Adjust the pH value of the modified particle solution, dropwise add dodecyltrimethoxysilane (DTMS), heat and stir, separate and wash with water, then separate secondary modified magnetic particles, and then wash with absolute ethanol and dry to obtain secondary modified treatment particles;

[0012] Mix PAO oil, hydrophilic fumed silica and a thixotropy synergist evenly, add the secondary modified treatment particles, and stir and disperse to obtain a PAO oil-based magnetorheological fluid.

[0013] As a possible design, the concentration of the above-mentioned dilute hydrochloric acid is 0.01 - 5 mol / L;

[0014] The ratio of the dilute hydrochloric acid to the carbonyl iron powder is 10 - 1000 mL:5 - 400 g;

[0015] The specific activation of the carbonyl iron powder with dilute hydrochloric acid is to put the carbonyl iron powder into the dilute hydrochloric acid and stir at a rotation speed of 400 - 2000 rpm for 2 - 60 min.

[0016] As a possible design, the above-mentioned separation of magnetic iron powder is to place the activated carbonyl iron powder on a magnet to separate magnetic iron powder particles;

[0017] The magnetic iron powder particles are washed with water until the pH value of the solution is 6.5 - 7.5;

[0018] After the magnetic iron powder particles are washed with water, they are washed with absolute ethanol 2 - 10 times.

[0019] As a possible design, the volume ratio of alcohol to water in the above-mentioned alcohol aqueous solution is 10 - 100:1;

[0020] After the activated particles are put into the alcohol aqueous solution, the pH value is adjusted to 8 - 12.

[0021] As a possible design, the above-mentioned 1,2-bis(triethoxysilyl)ethane is 5 - 30 wt% of the content of the activated particles;

[0022] The temperature of the heat treatment after dropping 1,2-bis(triethoxysilyl)ethane is 30-80 °C, the stirring rate is 200-800 rpm, and the stirring time is 30-240 min.

[0023] As a possible design, adjusting the pH value of the modified particle solution specifically means adjusting the pH value to 8-12;

[0024] The dodecyltrimethoxysilane is 2-20 wt% of the content of the primary modified particles; the temperature of the heat treatment after dropping dodecyltrimethoxysilane is 30-80 °C, the stirring rate is 200-800 rpm, and the stirring time is 30-240 min;

[0025] The separation of the magnetic particles is to place the secondary modified particles on a magnet to separate the magnetic particles;

[0026] The washing of the secondary modified particles specifically means washing the magnetic particles with ultrapure water and then washing them with absolute ethanol 2-5 times.

[0027] As a possible design, the above thixotropic synergist is specifically thixotropic synergist R606;

[0028] The mass ratio of the secondary modified treatment particles to the PAO oil is 3-4:1-2;

[0029] The addition amount of the hydrophilic fumed silica is 0.05-3 wt% of the total amount of the PAO oil and the secondary modified treatment particles;

[0030] The addition amount of the thixotropic synergist is 0.05-5 wt% of the total amount of the PAO oil and the secondary modified treatment particles.

[0031] As a possible design, after adding the secondary modified treatment particles, the stirring rate for stirring and dispersing is 200-800 rpm, and the stirring time is 2-10 h.

[0032] In a second aspect, the present invention provides a highly stable PAO oil-based magnetorheological fluid prepared by the above preparation method.

[0033] In a third aspect, the present invention provides an application of the highly stable PAO oil-based magnetorheological fluid in brakes and shock absorbers.

[0034] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0035] The magnetic particles prepared by the present invention through the activation of dilute hydrochloric acid and the co-modification of carbonyl iron powder with BTSE and DTMS have the advantages of high saturation magnetization intensity, superparamagnetism, high stability, etc. The PAO oil-based magnetorheological fluid prepared by adding hydrophilic fumed silica and thixotropic synergist has a high saturation magnetization intensity and good stability performance.

[0036] The magnetorheological fluid prepared by the present invention has a high saturation magnetization intensity and can be applied to high-pressure differential sealing environments and the automotive damping field.

[0037] The magnetorheological fluid prepared by the present invention has high dispersion stability and sedimentation stability, and no obvious sedimentation phenomenon occurs after standing for 30 days.

[0038] The magnetorheological fluid prepared by the present invention has a simple preparation process, is easy to operate, has high efficiency, and has low requirements for equipment, and has good rheological properties, magnetic properties and stability performance. Description of the Drawings

[0039] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts. In the drawings:

[0040] Figure 1 It is the SEM image of the carbonyl iron powder particles without any treatment in Example 1 of the present invention.

[0041] Figure 2 It is the SEM image of the HCIP-BTSE-DTMS particles prepared in Example 1 of the present invention.

[0042] Figure 3 It is the VSM image of the PAO oil-based magnetorheological fluid prepared in Example 1 of the present invention.

[0043] Figure 4 It is the comparison diagram of the PAO oil-based magnetorheological fluid prepared in Example 1 of the present invention before and after sedimentation for 30 days. Detailed Embodiments

[0044] To make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and the drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention. For those conditions not specified in the embodiments, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. For the reagents or instruments not specified for the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0045] In the present invention, through surface activation treatment of carbonyl iron powder, a large number of -OH functional groups are attached to its surface; bis(triethoxysilyl)ethane (BTSE), a silane coupling agent with ethoxy groups at both ends, is selected as the surfactant. The hydroxyl groups generated after hydrolysis of the ethoxy groups at one end of it undergo dehydration condensation with the hydroxyl groups on the surface of carbonyl iron powder to generate Fe-O-Si bonds, and the hydroxyl groups generated after hydrolysis of the ethoxy groups at the other end of it condense with the hydroxyl groups generated after hydrolysis of the methoxy groups at one end of DTMS. Finally, double-layer chemical coating of carbonyl iron powder is realized; then hydrophilic fumed silica and thixotropic synergist R606 are added to PAO oil. After dispersing and stirring evenly, modified particles are added, and a magnetorheological fluid is prepared by dispersion. Among them, since PAO oil belongs to low-polarity substances, using hydrophilic fumed silica has a better anti-settling effect. And the thixotropic synergist R606 exhibits thixotropy by using fumed silica, which can enhance the hydrogen bond action of silica. By activating and modifying magnetic particles with surfactants to reduce the density of magnetic particles, and by adding hydrophilic fumed silica and thixotropic synergist to increase the viscosity of the base carrier fluid and form a good connection with magnetic particles (anti-settling), the problems of dispersion stability and sedimentation stability of the magnetorheological fluid are effectively solved. Therefore, a magnetorheological fluid with high dispersion stability and high sedimentation stability can be prepared.

[0046] A preparation method of a high-stability PAO oil-based magnetorheological fluid comprises the following steps:

[0047] S1. After activating carbonyl iron powder with dilute hydrochloric acid, washing it with ultrapure water, separating out magnetic iron powder particles, and then washing with absolute ethanol and drying, activated particles are obtained.

[0048] The concentration of the above-mentioned dilute hydrochloric acid is 0.01 - 5 mol / L.

[0049] The ratio of the above-mentioned dilute hydrochloric acid to carbonyl iron powder is 10 - 1000 mL:5 - 400 g.

[0050] The specific activation of the above-mentioned carbonyl iron powder with dilute hydrochloric acid is to put carbonyl iron powder into dilute hydrochloric acid and stir at a rotation speed of 400 - 2000 rpm for 2 - 60 min.

[0051] The separation of the above-mentioned magnetic iron powder is to place the activated carbonyl iron powder on a magnet to separate out magnetic iron powder particles.

[0052] The above-mentioned magnetic iron powder particles are washed with water until the pH value of the solution is 6.5 - 7.5.

[0053] The above-mentioned magnetic iron powder particles are washed with water and then washed with absolute ethanol 2 - 10 times.

[0054] S2. Put the activated particles into an alcohol aqueous solution, adjust the pH value of the solution, and then dropwise add 1,2-bis(triethoxysilyl)ethane (BTSE), and after heating and stirring treatment, a primary modified particle solution is obtained.

[0055] The volume ratio of alcohol to water in the above alcohol aqueous solution is 10 to 100:1.

[0056] The above alcohol includes methanol, absolute ethanol, and isopropanol.

[0057] After the above activation particles are put into the alcohol aqueous solution, the pH value is adjusted to 8 to 12.

[0058] The above 1,2-bis(triethoxysilyl)ethane is 5 to 30 wt% of the content of the activation particles.

[0059] The temperature of the above heat treatment after dropping 1,2-bis(triethoxysilyl)ethane is 30 to 80 °C, the stirring rate is 200 to 800 rpm, and the stirring time is 30 to 240 min.

[0060] S3. Adjust the pH value of the modified particle solution, drop dodecyltrimethoxysilane (DTMS), heat and stir, separate and wash, then separate the secondarily modified magnetic particles, wash with absolute ethanol again, and dry to obtain the secondarily modified treatment particles.

[0061] The above adjustment of the pH value of the modified particle solution is specifically to adjust the pH value to 8 to 12.

[0062] The above dodecyltrimethoxysilane is 2 to 20 wt% of the content of the primary modified particles;

[0063] The temperature of the above heat treatment after dropping dodecyltrimethoxysilane is 30 to 80 °C, the stirring rate is 200 to 800 rpm, and the stirring time is 30 to 240 min.

[0064] The above separation of the magnetic particles is to place the secondarily modified particles on a magnet to separate the magnetic particles.

[0065] The above washing of the secondarily modified particles is specifically to wash the magnetic particles with ultrapure water and then wash with absolute ethanol 2 to 5 times.

[0066] S4. Mix PAO oil, hydrophilic fumed silica, and thixotropic synergist evenly, add the secondarily modified treatment particles, and stir and disperse to obtain a PAO oil-based magnetorheological fluid.

[0067] The above thixotropic synergist is specifically thixotropic synergist R606.

[0068] The mass ratio of the above secondarily modified treatment particles to PAO oil is 3 to 4:1 to 2.

[0069] The addition amount of the above hydrophilic fumed silica is 0.05 to 3 wt% of the total amount of PAO oil and the secondarily modified treatment particles.

[0070] The addition amount of the thixotropic synergist is 0.05-5 wt% of the total amount of PAO oil and the secondarily modified particles.

[0071] After the addition of the above-mentioned secondarily modified particles, the stirring rate for stirring and dispersing is 200-800 rpm, and the stirring time is 2-10 h.

[0072] In a second aspect, the present invention also provides a highly stable PAO oil-based magnetorheological fluid prepared by the above method.

[0073] In a third aspect, the present invention also provides an application of the highly stable PAO oil-based magnetorheological fluid in brakes and shock absorbers.

[0074] Example 1

[0075] A preparation method of a highly stable PAO oil-based magnetorheological fluid includes the following steps:

[0076] S1. Prepare 0.3 mol / L dilute hydrochloric acid, measure 100 mL of dilute hydrochloric acid, and weigh 40 g of carbonyl iron powder (refer to Figure 1 ), then mix the two and carry out mechanical stirring at a stirring rate of 800 rpm for 30 min to activate the carbonyl iron powder. Wash the activated particles with ultrapure water, and place a magnet to separate the magnetic particles, wash until the pH value of the solution is 7, and then wash several times with absolute ethanol to remove other impurities in the particles. Then dry the particles in an oven for a certain time to obtain activated particles HCIP;

[0077] S2. Prepare an alcohol / water solution according to a volume ratio of 25:1, adjust the pH of the reaction solution to 9, then add the activated particles HCIP, and then uniformly dropwise add BTSE, the dosage of BTSE is 10 wt% of the magnetic particle content, carry out mechanical stirring at a stirring rate of 350 rpm, the reaction temperature is 40 °C, and the reaction time is 2 h to obtain a primary modified HCIP-BTSE particle solution.

[0078] After the reaction in step S2 is completed, adjust the pH of the reaction solution to 8.5, then uniformly dropwise add DTMS, the dosage of DTMS is 5 wt% of the magnetic particle content, carry out mechanical stirring at a stirring rate of 350 rpm, the reaction temperature is 40 °C, and the reaction time is 2 h to obtain HCIP-BTSE-DTMS particles. Wash the modified particles with ultrapure water, and place a magnet to separate the magnetic particles, wash until the pH value of the solution is 7, and then wash several times with absolute ethanol to remove other impurities in the particles. Then dry the particles in an oven for a certain time to obtain secondarily modified particles HCIP-BTSE-DTMS (refer to Figure 2 ).

[0079] S4. Weigh PAO oil, hydrophilic fumed silica and thixotropic synergist R606. The mass ratio of magnetic particles to PAO oil is 3:1. The dosage of hydrophilic fumed silica is 1 wt% of the magnetic particle content, and the dosage of thixotropic synergist R606 is 0.3 wt% of the magnetic particle content. Carry out mechanical stirring at a stirring rate of 800 rpm. After stirring evenly, add the modified particles HCIP-BTSE-DTMS, and carry out mechanical stirring at a stirring rate of 800 rpm for 6 h to obtain a PAO oil-based magnetorheological fluid by dispersion.

[0080] The saturation magnetization intensity of the prepared PAO oil-based magnetorheological fluid is 167.11 emu / g (refer to Figure 3 ). Observe Figure 4 , after the magnetorheological fluid is allowed to stand for 30 days, no obvious stratification occurs, indicating that the prepared magnetorheological fluid has a high saturation magnetization intensity and dispersion stability.

[0081] Example 2

[0082] A preparation method of a high-stability PAO oil-based magnetorheological fluid includes the following steps:

[0083] S1. Prepare 0.5 mol / L dilute hydrochloric acid, measure 800 mL of dilute hydrochloric acid, and weigh 200 g of carbonyl iron powder. Then mix the two and carry out mechanical stirring at a stirring rate of 1000 rpm for 20 min to activate the carbonyl iron powder. Wash the activated particles with ultrapure water, and place a magnet to separate the magnetic particles. Wash with water until the pH value of the solution is 7, and then wash several times with absolute ethanol to wash away other impurities in the particles. Then dry the particles in an oven for a certain period of time to obtain the activated particles HCIP;

[0084] S2. Prepare an alcohol / water solution according to a volume ratio of 50:1, adjust the pH of the reaction solution to 8.5, then add the activated particles HCIP, and evenly dropwise add BTSE to it. The dosage of BTSE is 15 wt% of the magnetic particle content. Carry out mechanical stirring at a stirring rate of 600 rpm, a reaction temperature of 30 °C, and a reaction time of 1 h to obtain a primary modified HCIP-BTSE particle solution.

[0085] S3. After the reaction in step S2 is completed, adjust the pH of the reaction solution to 8.5, and then uniformly dropwise add DTMS to it. The dosage of DTMS is 10 wt% of the magnetic particle content. Stir mechanically at a stirring rate of 600 rpm, with a reaction temperature of 30 °C and a reaction time of 1 h to obtain HCIP-BTSE-DTMS particles. Wash the modified particles with ultrapure water, and place a magnet to separate the magnetic particles. Wash with water until the pH value of the solution is 7, and then wash several times with absolute ethanol to remove other impurities in the particles. Then dry the particles in an oven for a certain period of time to obtain the secondarily modified particles HCIP-BTSE-DTMS.

[0086] S4. Weigh PAO oil, hydrophilic fumed silica and thixotropic synergist R606. The mass ratio of magnetic particles to PAO oil is 7:3. The dosage of hydrophilic fumed silica is 0.8 wt% of the magnetic particle content, and the dosage of thixotropic synergist R606 is 0.5 wt% of the magnetic particle content. Stir mechanically at a stirring rate of 700 rpm. After stirring evenly, add the modified particles HCIP-BTSE-DTMS and stir mechanically at a stirring rate of 700 rpm for 5 h to disperse and obtain a PAO oil-based magnetorheological fluid.

[0087] The saturation magnetization intensity of the prepared PAO oil-based magnetorheological fluid is 123.16 emu / g. After the magnetorheological fluid is left standing for 30 days, no obvious stratification occurs, indicating that the prepared magnetorheological fluid has a high saturation magnetization intensity and dispersion stability.

[0088] Example 3

[0089] A preparation method of a high-stability PAO oil-based magnetorheological fluid, comprising the following steps:

[0090] S1. Prepare 1 mol / L dilute hydrochloric acid, measure 200 mL of dilute hydrochloric acid, and weigh 50 g of carbonyl iron powder. Then mix the two and stir mechanically at a stirring rate of 1500 rpm for 10 min to activate the carbonyl iron powder. Wash the activated particles with ultrapure water, and place a magnet to separate the magnetic particles. Wash with water until the pH value of the solution is 7, and then wash several times with absolute ethanol to wash away other impurities in the particles. Then dry the particles in an oven for a certain period of time to obtain the activated particles HCIP;

[0091] S2. Prepare an alcohol / water solution according to a volume ratio of 40:1, adjust the pH of the reaction solution to 9, then add the activated particles HCIP, and then uniformly dropwise add BTSE to it. The dosage of BTSE is 8 wt% of the magnetic particle content. Stir mechanically at a stirring rate of 500 rpm, with a reaction temperature of 50 °C and a reaction time of 1.5 h to obtain a primary modified HCIP-BTSE particle solution.

[0092] S3. After the reaction in step S2 is completed, adjust the pH of the reaction solution to 9, then uniformly add DTMS dropwise thereto. The dosage of DTMS is 3 wt% of the magnetic particle content. Stir mechanically at a stirring rate of 500 rpm, with a reaction temperature of 50 °C and a reaction time of 1.5 h to obtain HCIP-BTSE-DTMS particles. Wash the modified particles with ultrapure water, and place a magnet to separate the magnetic particles. Wash with water until the pH value of the solution is 7, and then wash several times with absolute ethanol to remove other impurities in the particles. Then dry the particles in an oven for a certain period of time to obtain the secondarily modified particles HCIP-BTSE-DTMS.

[0093] S4. Weigh PAO oil, hydrophilic fumed silica and thixotropic synergist R606. The mass ratio of magnetic particles to PAO oil is 4:1. The dosage of hydrophilic fumed silica is 1.5 wt% of the magnetic particle content, and the dosage of thixotropic synergist R606 is 1 wt% of the magnetic particle content. Stir mechanically at a stirring rate of 500 rpm. After stirring evenly, add the modified particles HCIP-BTSE-DTMS, stir mechanically at a stirring rate of 500 rpm for 7 h to disperse and obtain a PAO oil-based magnetorheological fluid.

[0094] The saturation magnetization intensity of the prepared PAO oil-based magnetorheological fluid is 179.85 emu / g. After the magnetorheological fluid is left standing for 30 days, no obvious stratification occurs, indicating that the prepared magnetorheological fluid has a high saturation magnetization intensity and dispersion stability.

[0095] Example 4

[0096] A preparation method of a high-stability PAO oil-based magnetorheological fluid, comprising the following steps:

[0097] S1. Prepare 2 mol / L dilute hydrochloric acid, measure 500 mL of dilute hydrochloric acid, and weigh 150 g of carbonyl iron powder. Then mix the two and stir mechanically at a stirring rate of 1800 rpm for 40 min to activate the carbonyl iron powder. Wash the activated particles with ultrapure water, and place a magnet to separate the magnetic particles. Wash with water until the pH value of the solution is 7, and then wash several times with absolute ethanol to wash away other impurities in the particles. Then dry the particles in an oven for a certain period of time to obtain the activated particles HCIP;

[0098] S2. Prepare an alcohol / water solution according to a volume ratio of 30:1, adjust the pH of the reaction solution to 11, then add the activated particles HCIP, and then uniformly add BTSE dropwise thereto. The dosage of BTSE is 12 wt% of the magnetic particle content. Stir mechanically at a stirring rate of 450 rpm, with a reaction temperature of 80 °C and a reaction time of 3 h to obtain a solution of primary modified particles HCIP-BTSE particles.

[0099] S3. After the reaction in step S2 is completed, adjust the pH of the reaction solution to 11, and then uniformly dropwise add DTMS to it. The dosage of DTMS is 4 wt% of the magnetic particle content. Stir mechanically at a stirring rate of 450 rpm, with a reaction temperature of 80 °C and a reaction time of 3 h to obtain HCIP-BTSE-DTMS particles. Wash the modified particles with ultrapure water, and place a magnet to separate the magnetic particles. Wash with water until the pH value of the solution is 7, and then wash several times with absolute ethanol to remove other impurities in the particles. Then dry the particles in an oven for a certain period of time to obtain the secondarily modified particles HCIP-BTSE-DTMS.

[0100] S4. Weigh PAO oil, hydrophilic fumed silica and thixotropic synergist R606. The mass ratio of magnetic particles to PAO oil is 13:7. The dosage of hydrophilic fumed silica is 2 wt% of the magnetic particle content, and the dosage of thixotropic synergist R606 is 1.5 wt% of the magnetic particle content. Stir mechanically at a stirring rate of 400 rpm. After stirring evenly, add the modified particles HCIP-BTSE-DTMS, and stir mechanically at a stirring rate of 400 rpm for 8 h to disperse and obtain a PAO oil-based magnetorheological fluid.

[0101] The saturation magnetization intensity of the prepared PAO oil-based magnetorheological fluid is 117.73 emu / g. After the magnetorheological fluid is left standing for 30 days, no obvious stratification occurs, indicating that the prepared magnetorheological fluid has a high saturation magnetization intensity and dispersion stability.

[0102] Example 5

[0103] A preparation method of a high-stability PAO oil-based magnetorheological fluid, comprising the following steps:

[0104] S1. Prepare 5 mol / L dilute hydrochloric acid, measure 600 mL of dilute hydrochloric acid, and weigh 300 g of carbonyl iron powder. Then mix the two and stir mechanically at a stirring rate of 1200 rpm for 5 min to activate the carbonyl iron powder. Wash the activated particles with ultrapure water, and place a magnet to separate the magnetic particles. Wash with water until the pH value of the solution is 7, and then wash several times with absolute ethanol to wash away other impurities in the particles. Then dry the particles in an oven for a certain period of time to obtain the activated particles HCIP;

[0105] S2. Prepare an alcohol / water solution according to a volume ratio of 20:1, adjust the pH of the reaction solution to 9.5, then add the activated particles HCIP, and then uniformly dropwise add BTSE to it. The dosage of BTSE is 5 wt% of the magnetic particle content. Stir mechanically at a stirring rate of 300 rpm, with a reaction temperature of 60 °C and a reaction time of 4 h to obtain the primary modified particle solution HCIP-BTSE particles.

[0106] S3. After the reaction in step S2 is completed, adjust the pH of the reaction solution to 9.5, then uniformly dropwise add DTMS to it. The dosage of DTMS is 13 wt% of the magnetic particle content. Stir mechanically at a stirring rate of 300 rpm, with a reaction temperature of 60 °C and a reaction time of 4 h to obtain HCIP-BTSE-DTMS particles. Wash the modified particles with ultrapure water, and place a magnet to separate the magnetic particles. Wash with water until the pH value of the solution is 7, and then wash several times with absolute ethanol to remove other impurities in the particles. Then dry the particles in an oven for a certain period of time to obtain the secondarily modified particles HCIP-BTSE-DTMS.

[0107] S4. Weigh PAO oil, hydrophilic fumed silica and thixotropic synergist R606. The mass ratio of magnetic particles to PAO oil is 7:3. The dosage of hydrophilic fumed silica is 2.5 wt% of the magnetic particle content, and the dosage of thixotropic synergist R606 is 4 wt% of the magnetic particle content. Stir mechanically at a stirring rate of 350 rpm. After stirring evenly, add the modified particles HCIP-BTSE-DTMS, stir mechanically at a stirring rate of 350 rpm for 10 h to disperse and obtain a PAO oil-based magnetorheological fluid.

[0108] The saturation magnetization intensity of the prepared PAO oil-based magnetorheological fluid is 135.57 emu / g. After the magnetorheological fluid is left standing for 30 days, no obvious stratification occurs, indicating that the prepared magnetorheological fluid has a high saturation magnetization intensity and dispersion stability.

[0109] Example 6

[0110] A preparation method of a high-stability PAO oil-based magnetorheological fluid includes the following steps:

[0111] S1. Prepare 3 mol / L dilute hydrochloric acid, measure 150 mL of dilute hydrochloric acid, and weigh 80 g of carbonyl iron powder. Then mix the two and stir mechanically at a stirring rate of 600 rpm for 10 min to activate the carbonyl iron powder. Wash the activated particles with ultrapure water, and place a magnet to separate the magnetic particles. Wash with water until the pH value of the solution is 7, and then wash several times with absolute ethanol to wash away other impurities in the particles. Then dry the particles in an oven for a certain period of time to obtain the activated particles HCIP;

[0112] S2. Prepare an alcohol / water solution according to a volume ratio of 15:1, adjust the pH of the reaction solution to 10, then add the activated particles HCIP, and then uniformly dropwise add BTSE to it. The dosage of BTSE is 20 wt% of the magnetic particle content. Stir mechanically at a stirring rate of 400 rpm, with a reaction temperature of 70 °C and a reaction time of 2.5 h to obtain the primary modified particle solution HCIP-BTSE particles.

[0113] S3. After the reaction in step S2 is completed, adjust the pH of the reaction solution to 10, and then uniformly add DTMS dropwise thereto. The dosage of DTMS is 3 wt% of the magnetic particle content. Stir mechanically at a stirring rate of 400 rpm, with a reaction temperature of 70 °C and a reaction time of 2.5 h to obtain HCIP-BTSE-DTMS particles. Wash the modified particles with ultrapure water, and place a magnet to separate the magnetic particles. Wash with water until the pH value of the solution is 7, and then wash several times with absolute ethanol to remove other impurities in the particles. Then dry the particles in an oven for a certain period of time to obtain the secondarily modified particles HCIP-BTSE-DTMS.

[0114] S4. Weigh PAO oil, hydrophilic fumed silica, and thixotropic synergist R606. The mass ratio of magnetic particles to PAO oil is 3:1. The dosage of hydrophilic fumed silica is 1.2 wt% of the magnetic particle content, and the dosage of thixotropic synergist R606 is 0.8 wt% of the magnetic particle content. Stir mechanically at a stirring rate of 600 rpm. After stirring evenly, add the modified particles HCIP-BTSE-DTMS and stir mechanically at a stirring rate of 600 rpm for 9 h to disperse and obtain a PAO oil-based magnetorheological fluid.

[0115] The saturation magnetization intensity of the prepared PAO oil-based magnetorheological fluid is 142.34 emu / g. After the magnetorheological fluid is left standing for 30 days, no obvious stratification occurs, indicating that the prepared magnetorheological fluid has a high saturation magnetization intensity and dispersion stability.

[0116] Comparative Example 1

[0117] The preparation method of the magnetorheological fluid is the same as that in Example 1, except that hydrophilic fumed silica and thixotropic synergist R606 are not added, and the conditions of the remaining steps are the same.

[0118] After the prepared PAO oil-based magnetorheological fluid is left standing for 30 days, slight stratification occurs, and the sedimentation rate is 3.05%.

[0119] It can be seen that adding a certain amount of hydrophilic fumed silica and thixotropic synergist R606 can improve the dispersion stability and sedimentation stability of the magnetorheological fluid.

[0120] Comparative Example 2

[0121] The preparation method of the magnetorheological fluid is the same as that in Example 1, except that no BTSE and DTMS modification treatment is performed, and the conditions of the remaining steps are the same.

[0122] After the prepared PAO oil-based magnetorheological fluid is left standing for 30 days, slight stratification occurs, and the sedimentation rate is 7.33%.

[0123] It can be seen that modifying magnetic particles with BTSE and DTMS can improve the dispersion stability and sedimentation stability of magnetorheological fluids.

[0124] Comparative Example 3

[0125] The preparation method of the magnetorheological fluid was the same as that in Example 1, except that the carbonyl iron powder was not activated, and the conditions of the remaining steps were the same.

[0126] After the prepared PAO-based magnetorheological fluid was left standing for 30 days, slight stratification occurred, and the sedimentation rate was 1.87%.

[0127] It can be seen that activating carbonyl iron powder can improve the dispersion stability and sedimentation stability of magnetorheological fluids.

[0128] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above description is only the specific embodiments of the present invention and is not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A preparation method of a high-stability PAO oil-based magnetorheological fluid, characterized in that, It includes the following steps: After activating carbonyl iron powder with dilute hydrochloric acid, wash it with ultrapure water, separate the magnetic iron powder particles, then wash with absolute ethanol, and dry to obtain activated particles; Put the activated particles into an alcohol aqueous solution, adjust the pH value of the solution, then dropwise add 1,2-bis(triethoxysilyl)ethane (BTSE), and after heating and stirring treatment, obtain a primary modified particle solution; Adjust the pH value of the modified particle solution, dropwise add dodecyltrimethoxysilane (DTMS), heat and stir, separate and wash with water, then separate the secondary modified magnetic particles, and then wash with absolute ethanol and dry to obtain secondary modified treatment particles; Mix PAO oil, hydrophilic fumed silica and a thixotropic synergist evenly, add the secondary modified treatment particles, and stir and disperse to obtain a PAO oil-based magnetorheological fluid.

2. The preparation method of a highly stable PAO oil-based magnetorheological fluid according to claim 1, characterized in that, The concentration of the dilute hydrochloric acid is 0.01 - 5 mol / L; The ratio of the dilute hydrochloric acid to the carbonyl iron powder is 10 - 1000 mL:5 - 400 g; The activation of the carbonyl iron powder with dilute hydrochloric acid specifically means putting the carbonyl iron powder into dilute hydrochloric acid and stirring at a speed of 400 - 2000 rpm for 2 - 60 min.

3. The preparation method of a highly stable PAO oil-based magnetorheological fluid according to claim 1, characterized in that, The separation of the magnetic iron powder means placing the activated carbonyl iron powder on a magnet to separate the magnetic iron powder particles; The magnetic iron powder particles are washed with water until the pH value of the solution is 6.5 - 7.5; After the magnetic iron powder particles are washed with water, they are washed with absolute ethanol 2 - 10 times.

4. The preparation method of a highly stable PAO oil-based magnetorheological fluid according to claim 1, characterized in that, The volume ratio of alcohol to water in the alcohol aqueous solution is 10 - 100:1; After the activated particles are put into the alcohol aqueous solution, adjust the pH value to 8 - 12.

5. The preparation method of a highly stable PAO oil-based magnetorheological fluid according to claim 1, characterized in that, The 1,2-bis(triethoxysilyl)ethane is 5 - 30 wt% of the content of the activated particles; After dropwise adding 1,2-bis(triethoxysilyl)ethane, the heating treatment temperature is 30 - 80 °C, the stirring rate is 200 - 800 rpm, and the stirring time is 30 - 240 min.

6. The preparation method of a highly stable PAO oil-based magnetorheological fluid according to claim 1, characterized in that The adjustment of the pH value of the modified particle solution specifically means adjusting the pH value to 8 - 12; The dodecyltrimethoxysilane is 2 - 20 wt% of the content of the primary modified particles; the heating treatment temperature after dropwise adding dodecyltrimethoxysilane is 30 - 80 °C, the stirring rate is 200 - 800 rpm, and the stirring time is 30 - 240 min; The separation of the magnetic particles means placing the secondary modified particles on a magnet to separate the magnetic particles; The washing of the secondary modified particles specifically means washing the magnetic particles with ultrapure water, and after washing with water, washing with absolute ethanol 2 - 5 times.

7. The preparation method of a highly stable PAO oil-based magnetorheological fluid according to claim 1, characterized in that, The thixotropic synergist is specifically thixotropic synergist R606; The mass ratio of the secondary modified treatment particles to the PAO oil is 3 - 4:1 - 2; The addition amount of the hydrophilic fumed silica is 0.05 - 3 wt% of the total amount of the PAO oil and the secondary modified treatment particles; The addition amount of the thixotropic synergist is 0.05 - 5 wt% of the total amount of the PAO oil and the secondary modified treatment particles.

8. The preparation method of a highly stable PAO oil-based magnetorheological fluid according to claim 1, characterized in that, After adding the secondary modified treatment particles, the stirring rate for stirring and dispersing is 200 - 800 rpm, and the stirring time is 2 - 10 h.

9. A high-stability PAO oil-based magnetorheological fluid, characterized in that, It is prepared by using the preparation method described in any one of claims 1 - 8.

10. Use the preparation method described in any one of claims 1 to 8 to prepare a highly stable PAO oil-based magnetorheological fluid or the application of the highly stable PAO oil-based magnetorheological fluid described in claim 9 in brakes and shock absorbers.

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