PHASE-CHANGE MATERIAL SUSPENSION FLUID COMPOSITION INCLUDING FUMED SILICA PARTICLES AND METHOD FOR PREPARING THE SAME

Abstract

Disclosed are a suspension fluid and a method for preparing the suspension fluid. Particularly, the suspension fluid is prepared by dispersing fumed silica particles in a solvent that includes one or more compounds selected from the group consisting of ethylene glycol and propylene glycol, and water. The phase-change suspension fluid obtained from the present invention is a shear thickening fluid that have a constant Newtonian behavior at a low rate of shear or a low frequency band, and further have a non-Newtonian behavior as a solid-like suspension at a high rate of shear or a high frequency band due to an increase in viscosity. In addition, the phase-change suspension fluid may reversibly change its phase with vibration of a vehicle, thereby providing advantages of both of the hydro bushes and the solid type bushes.

Claims

1-5. (canceled)

6. A method for preparing a phase-change suspension fluid, comprising: (i) preparing a suspension fluid by adding and dispersing fumed silica particles in a solvent including one or more compounds selected from the group consisting of ethylene glycol and propylene glycol, and water; (ii) sonicating the suspension fluid; and (iii) removing air from the sonicated suspension fluid by placing the sonicated suspension fluid in a vacuum chamber.

7. The method of claim 6, wherein the step of (ii) for sonicating the suspension fluid is performed for about 9 to 12 hours.

8. The method of claim 6, wherein the step of (iii) for removing air is performed for about 9 to 12 hours.

9-10. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The above and other behaviors of the present invention will now be described in detail with reference to certain exemplary embodiments thereof illustrated the accompanying drawings which are given hereinbelow by way of illustration only, and thus are not limitative of the present invention, and wherein:

[0026] FIG. 1 shows graphs from test results of shear viscosities in accordance with the shear rates of exemplary phase-change fluids prepared in Comparative Examples 1 and 2 and Examples 1 and 2 according to exemplary embodiments of the present invention, where I) shows the results of Comparative Example 1 and Example 1 using fumed silica having a particle size of about 7 nm and II) shows the results of Comparative Example 2 and Example 2 using fumed silica having a particle size of about 14 nm;

[0027] FIG. 2A shows graphs from test results of storage modulus and loss modulus in accordance with the strains of exemplary phase-change fluids prepared in Comparative Examples 1 and 2 and Examples 1 and 2 according to exemplary embodiments of the present invention, where FIG. 2A illustrates the storage modules, FIG. 2B illustrates the loss modulus, and particularly I) of FIG. 2A or FIG. 2B shows the results of Comparative Example 1 and Example 1 using fumed silica having a particle size of about 7 nm, and II) of FIG. 2A or FIG. 2B shows the results of Comparative Example 2 and Example 2 using fumed silica having a particle size of about 1.4 nm;

[0028] FIG. 3A shows graphs from test results of complex viscosities in accordance with the frequencies of exemplary phase-change fluids prepared in Comparative Examples 1 and 2 and Examples 1 and 2 according to exemplary embodiments of the present invention, where I) of FIG. 3A shows the results of Comparative Example 1 and Example 1 using fumed silica having a particle size of about 7 nm, and II) of FIG. 3A shows the results of Comparative Example 2 and Example 2 using fumed silica having a particle size of about 14 nm;

[0029] FIG. 3B shows graphs of storage modulus in accordance with the frequencies of exemplary phase-change fluids prepared in Comparative Examples 1 and 2 and Examples 1 and 2 according to exemplary embodiments of the present invention, where I) of FIG. 3B shows the results of Comparative Example 1 and Example 1 using fumed silica having a particle size of about 7 nm, and II) of FIG. 3B shows the results of Comparative Example 2 and Example 2 using fumed silica having a particle size of about 14 nm;

[0030] FIG. 3C shows graphs of loss modulus in accordance with the frequencies of exemplary phase-change fluids prepared in Comparative Examples 1 and 2 and Examples 1 and 2 according to exemplary embodiments of the present invention, where I) of FIG. 3C shows the results of Comparative Example 1 and Example 1 using fumed silica having a particle size of about 7 nm, and II) of FIG. 3C shows the results of Comparative Example 2 and Example 2 using fumed silica having a particle size of about 14 nm; and

[0031] FIG. 4 shows graphs from test results of damping factors in accordance with the frequencies of exemplary phase-change fluids prepared in Comparative Examples 1 and 2 and Examples 1 and 2 according to exemplary embodiments of the present invention, where I) of FIG. 4 shows the results of Comparative Example 1 and Example 1 using fumed silica having a particle size of about 7 nm, and II) of FIG. 4 shows the results of Comparative Example 2 and Example 2 using fumed silica having a particle size of about 14 nm.

[0032] It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various preferred behaviors illustrative of the basic principles of the invention. The specific design behaviors of the present invention as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes will be determined in part by the particular intended application and use environment. In the figures, reference numbers refer to the same or equivalent parts of the present invention throughout the several figures of the drawing.

DETAILED DESCRIPTION

[0033] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms a, an and the are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms comprises and/or comprising, when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term and/or includes any and all combinations of one or more of the associated listed items.

[0034] Unless specifically stated or obvious from context, as used herein, the term about is understood as within a range of normal tolerance in the art, for example within 2 standard deviations of the mean. About can be understood as within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the stated value. Unless otherwise clear from the context, all numerical values provided herein are modified by the term about.

[0035] Hereinafter reference will now be made in detail to various exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings and described below. While the invention will be described in conjunction with exemplary embodiments, it will be understood that present description is not intended to limit the invention to those exemplary embodiments. On the contrary, the invention is intended to cover not only the exemplary embodiments, but also various alternatives, modifications, equivalents and other embodiments, which may be included within the spirit and scope of the invention as defined by the appended claims.

[0036] Hereinafter, the present invention will be described in more detail with reference to one embodiment.

[0037] The phase-change suspension fluid composition may include: fumed silica particles; and a solvent including one or more compounds selected from the group consisting of ethylene glycol and propylene glycol and water.

[0038] In particular, the fumed silica particles used in the composition may be phase-change macromolecules and the phase-change fluids may be formed as suspension fluid (suspension) by dispersing the phase-change macromolecules in a solvent including one or more compounds selected from the group consisting of ethylene glycol and propylene glycol, and water.

[0039] The ethylene glycol represented by Formula I and the propylene glycol represented by Formula II in the solvent may have a number average molecular weight of about 50 to 100.

HOCH.sub.2CH.sub.2OH (I)

HOCH.sub.2CH.sub.2CH.sub.2OH (II)

[0040] When the number average molecular weight is less than about 50, the content of low molecular weight impurities may increase, and thus, the purity of ethylene glycol may be reduced. When the number average molecular weight is greater than about 100, the purity of propylene glycol may be reduced. Accordingly, the glycols in the above-described range may be used in the composition.

[0041] In addition, the fumed silica may be crystallized at a high temperature of about 1100 to 1180 C. The reaction thereof may be presented as follows.

[0042] [Reaction Formula]

SiCl.sub.4+H.sub.2+O.sub.4.fwdarw.SiO.sub.2+HCl

TABLE-US-00001 TABLE 1 Aerosil Aerosil Aerosil Aerosil Aerosil Aerosil Aerosil Carbosil 200 300 380 R812 R972 R104 R106 M-6 fumed Company Deguss-Hula Cabot Behavior hydrophilic hydrophobic hydro- toward water philic Surface treated HMDS Dimethyl Octamethyl dichloro- cyclo- silone tetrasiloxane SiO.sub.2 content (% w/w) >99.8 >99.8 >99.8 >99.8 >99.8 >99.8 >99.8 >99.8 Surface Area 200 300 380 280 110 150 260 200 BET(m.sup.2/g) Avarage Primary 12 7 7 7 16 12 7 Particle Size(nm) Tapped Density(g/l) 60 60 60 60 60 60 60 Standard Materrial Densified Material 120 120 120 90 90 (suffix v ) Loss on Drying <1.5 <1.5 <2.0 <0.5 <0.5 <1.6 (% w/w) Moisture content (2 hours at 106 C.) Igition Loss % <1 <2 <2.5 <0.6 <2 <2 (2 hours at 1000 C.) pH value 3.4~3.7 6.6~7.6 3.6~4.4 >4.0 >3.7 3.7~4.3 C-content 2.0~3.0 0.6~1.2 1~2 1.6~3.0 Sieve residue % <0.06 <0.06 <0.06 0.02 (W/W) (Mocker, >4 ) Oil absorption (ml/100 g) Carbosil HDK HDK HDK Reolosil Zeosil Nipsil TS-650 V 16 H2000 H3004 MT-10 132 LP fumed preciptated Company Cabot Wacker Tokuyama Rhodia Nippon Behavior hydro- hydro- hydrophobic hydro- hydro- toward water phobic philic phobic philic Surface treated silcone Methyltri- oil and chloro- HMDS silone SiO.sub.2 content (% w/w) >99.8 >99.8 >99.8 >99.8 Surface Area 215 150 140 200 120 170~220 BET(m.sup.2/g) Avarage Primary 9000 Particle Size(nm) Tapped Density(g/l) 60 220 80 60 60~80 Standard Materrial Densified Material 110 (suffix v ) Loss on Drying 0.6 <1.0 <0.6 <0.6 (% w/w) Moisture content (2 hours at 106 C.) Igition Loss % <1.6 <2.6 <2.6 (2 hours at 100 C.) pH value 4.8~7.6 3.8~4.3 6.7~7.7 6.0~8.0 4.0~6.6 6.6~8.6 C-content 4.2 <3.0 <6.0 Sieve residue % <0.01 (W/W) (Mocker, >4 ) Oil absorption 180~200 (ml/100 g) *Silica Properties indicates data missing or illegible when filed

[0043] The above-described Table 1 lists commercially produced fumed silica. In particular, the fumed silica having a hydrophilic particle and a particle size of 7 to 14 nm may be used in the present invention. When the particle size is less than about 7 nm, the fumed silica may not be suitably prepared in the composition, and when the particle size is greater than about 14 nm, t a shear thickening phenomenon may not be generated. Accordingly, the fumed silica having a particle size in the above-described range may be used.

[0044] In addition, the fumed silica having a specific surface area of about 200 to 400 m.sup.2/g may be used in the composition and the method of the invention. When the specific surface area is less than about 200 m.sup.2/g, t a particle size may not be distributed uniformly, and when the specific surface area is greater than about 400 m.sup.2/g, the particles may agglomerate together to form size thereof greater than about 14 nm. Accordingly, the fumed silica having a specific surface area in the above-described range may be used.

[0045] The fumed silica particles may be used in the amount of about 5 to 30 wt % or particularly in the amount of about 5 to 20 wt %, with respect to the total weight of phase-change suspension fluid composition. When the fumed silica particles are included in the amount of less than about 5 wt %, a Newtonian behavior without generating a shear thickening phenomenon may be dominant. When the fumed silica particles are included in the amount of greater than about 30 wt %, the viscosity thereof may be substantially increased, and thus, it may not be suitably used for applying the particles as a fluid in the hydro bushes. Accordingly, the particles may he used in the composition in the amount of the above-described range.

[0046] The method for preparing a phase-change suspension fluid may include: [0047] (i) preparing a suspension fluid by adding and dispersing fumed silica particles in a solvent including one or more compounds selected from the group consisting of ethylene glycol and propylene glycol, and water; [0048] (ii) sonicating the suspension fluid obtained in the step (i); and [0049] (iii) removing air from the sonicated suspension fluid.

[0050] Particularly, in step (iii), the air may be removed from the sonicated suspension fluid by placing the sonicated suspension fluid in a vacuum chamber, but the method of removing air may not be limited thereto.

[0051] In the step of (i), the suspension fluid may be prepared by adding and dispersing fumed silica particles in a solvent that may include one or more compounds selected from the group consisting of ethylene glycol and propylene glycol, and water. Particularly, the prepared suspension fluid may be in a state that fine solid particles are dispersed and floating in the liquid.

[0052] Next, in the step of (ii), the suspension fluid prepared in the step of (i) may be sonicated, such that the fumed silica particles may be dispersed uniformly. In particular, the sonication may be performed for about 9 to 12 hours. When the sonication is performed for less than about 9 hours, the dispersion of the particles and fluid in the suspension fluid may not be sufficiently performed. When the sonication is performed for greater than about 12 hours, the preparation time may be increased. Accordingly, the sonication or the preparing process may be performed during the above-described range of time.

[0053] In the step of (iii), air may be removed from the sonicated suspension fluid, particularly by placing the sonicated suspension fluid in a vacuum chamber to remove air bubbles included in the fluid. The removing air process may be performed for about 9 to 12 hours. When this process is performed for less than about 9 hours, the air bubbles may not be sufficiently removed, and when this process is performed for greater than about 12 hours, the preparing time may be increased. Accordingly, the process of removing air may be performed during the time in the above-described range.

[0054] The phase-change suspension fluid thus prepared may have a constant. Newtonian behavior at a low rate of shear or a low frequency band, and further may have a non-Newtonian behavior as a solid-like suspension by increasing its viscosity at a high rate of shear or a high frequency band. In particular, the phase-change suspension fluid may have a viscosity of about 0.01 to 20 Pa.s. When the phase-change suspension fluid has a viscosity of less than about 0.01 Pa.s, the difference of pure ethylene glycol or propylene glycol viscosity may not be generated. When the phase-change suspension fluid has a viscosity of greater than about 20 Pa.s, an injection may not be performed properly at the time of preparing a fluid to be filled. Accordingly, the phase-change suspension fluid may have the viscosity in the above-described range.

[0055] According to various exemplary embodiments of the present invention, the phase-change fluid may reversibly change the phase in accordance with vibration of a vehicle, and may be applied for controllable variable attenuators, such as, suspension systems, isolators, and engine mounts, or the power plant, such as, brakes and clutches.

[0056] Hereinafter, the present invention will be described in more detail with reference to Examples. However, these Examples are only for illustrating the present invention, but the present invention is not limited thereto.

EXAMPLES

[0057] The following examples illustrate the invention and are not intended to limit the same.

Example 1 and Comparative Example (Silica Particle Size of About 7 nm)

Examples 1-1 to 1-6 and Comparative Examples 1-1 to 1-4

[0058] According to the composition ratio of the constituents listed in Table 2, the fumed silica having a particle size of about 7 nm was mixed in a solvent that was prepared by mixing ethylene glycol and water, and then resulting mixture was mechanically mixed using a blender for about 1 hour to prepare a suspension fluid. The ultrasonication was performed for about 12 hours so as to uniformly disperse the polyethylene oxide particles in such a suspension fluid, and then, the suspension fluid was added in a vacuum chamber to remove air bubbles, thereby preparing the phase-change suspension fluid.

TABLE-US-00002 TABLE 2 Composition and content of phase-change suspension fluid (unit: g) Ethylene glycol Item Fumed silica (EG) Di-water Example 1-1 1.06 (5 wt %) 10 10 Example 1-2 0.87 (8 wt %) 10 10 Example 1-3 2.22 (10 wt %) 10 10 Example 1-4 3.52 (15 wt %) 10 10 Example 1-5 5 (20 wt %) 10 10 Example 1-6 8.6 (30 wt %) 10 10 Com. Example 1-1 0.02 (0.1 wt %) 10 10 Com. Example 1-2 0.2 (1 wt %) 10 10 Com. Example 1-3 13.3 (40 wt %) 10 10

Example 2 and Comparative Example 2 (Silica Particle Size of About 14 nm)

Examples 2-1 to 2-6 and Comparative Examples 2-1 to 2-4

[0059] The phase-change suspension fluids were prepared as described in Example 1 and Comparative Example 1, except that fumed silica having a particle size of about 14 nm was used.

TABLE-US-00003 TABLE 3 Composition and content of phase-change suspension fluid (unit: g) Ethylene glycol Item Fumed silica (EG) Di-water Example 2-1 1.06 (5 wt %) 10 10 Example 2-2 0.87 (8 wt %) 10 10 Example 2-3 2.22 (10 wt %) 10 10 Example 2-4 3.52 (15 wt %) 10 10 Example 2-5 5 (20 wt %) 10 10 Example 2-6 8.6 (30 wt %) 10 10 Com. Example 2-1 0.02 (0.1 wt %) 10 10 Com. Example 2-2 0.2 (1 wt %) 10 10 Com. Example 2-3 13.3 (40 wt %) 10 10

Experimental Example

[0060] In order to measure the rheological behaviors of the phase-change suspension fluids obtained by Examples 1-1 to 2-6 and Comparative Examples 1-1 to 2-2, the viscosities and damping factors were obtained while shear rates and frequencies were adjusted using an instrument. The measurement geometry used was a double gap cell type, and the cup and bob were not applied with any kinds of external forces. In addition, in order to obtain the accuracy of the test results, the above process was performed after re-dispersing vibration fluid all the time. The above measurement results are illustrated in FIGS. 1 to 4. Hereinafter, the test results will be described in detail.

[0061] FIG. 1 shows graphs from the test results of shear viscosities in accordance with the shear rates of exemplary phase-change fluids prepared in Comparative Examples 1 and 2 and Examples 1 and 2 according to exemplary embodiments of the present invention. As shown in FIGS. 1 I and II, the Newtonian behavior of constant viscosity may be shown at a low rate of shear, the non-Newtonian behavior may be shown at a high rate of shear because the viscosity of a shear thickening fluid (STY) increases so as to be solid-like suspension.

[0062] FIG. 2A shows graphs from the test results of storage modulus and loss modulus in accordance with the strains of exemplary phase-change fluids prepared in Comparative Examples 1 and 2 and Examples 1 and 2 according to exemplary embodiments of the present invention. The modulus in accordance with the strain to the frequency of 1Hz was shown. According to FIG. 2A, a linear viscoelastic region may be shown.

[0063] FIG. 3A shows graphs from the test results of complex viscosities in accordance with the frequencies of exemplary phase-change fluids prepared in Comparative Examples 1 and 2 and Examples 1 and 2 according to exemplary embodiments of the present invention. As shown in FIG. 3A, the complex viscosities show a constant behavior at a low frequency band, and further show a non-Newtonian behavior at a high frequency band because the complex viscosity of the shear thickening fluid (STF) increases to be solid-like suspension.

[0064] FIG. 3B shows the graphs of the storage modulus in accordance with the frequencies of exemplary phase-change fluids prepared in Comparative Examples 1 and 2 and Examples 1 and 2 and the spring characteristic of the phase-change fluid is shown.

[0065] FIG. 3C shows graphs of the loss modulus in accordance with the frequencies of exemplary phase-change fluids prepared in Comparative Examples 1 and 2 and Examples 1 and 2 according to exemplary embodiments of the present invention and the viscosity characteristic of the phase-change fluid is shown.

[0066] Finally, FIG. 4 shows graphs from the test results of damping factors in accordance with the frequencies of exemplary phase-change fluids prepared in Comparative Examples 1 and 2 and Examples 1 and 2 according to exemplary embodiments of the present invention. In detail, the viscosity characteristic is shown at greater than about 1 of a standard point, and the spring characteristic is shown at less than about 1 of a standard point.

[0067] Accordingly, the phase-change suspension fluid according to various exemplary embodiments of the present invention may have a constant Newtonian behavior at a low rate of shear or a low frequency band, and further may have a non-Newtonian behavior as a solid-like suspension at a high rate of shear or a high frequency band due to an increase in viscosity.

[0068] In other words, the present invention may provide an intelligent macromolecular dispersed fluid that has the advantages of a hydro bush in a low frequency band and the advantages of a solid type bush in a high frequency band, and may reversibly change the phase in accordance with vibration of a vehicle. Therefore, the fluid according to the present invention may be applied for controllable variable attenuators, such as, suspension systems, isolators, and engine mounts, or the power plant, such as, brakes and clutches, and may also be widely applied for the vehicle industry and the aircraft industry.

[0069] Accordingly, the phase-change suspension fluid obtained from the present invention may be a fluid with the shear thickening flowing behavior such that the phase may reversibly change according to vehicle vibration and the compatible effect of the advantage of hydro bush at a low frequency band and the advantage of solid type bush at a high frequency band can be provided.

[0070] Therefore, the phase-change suspension fluid may actively control a vehicle so as to improve riding quality and handling performance, and thus, can be applied for controllable variable attenuators, such as, suspension systems, isolators, and engine mounts, or the power plant, such as, brakes and clutches, and can be also widely applied for the robot industry as well as the automotive industry and aviation industry.

[0071] The invention has been described in detail with reference to exemplary embodiments thereof. However, it will be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.