KR100479739B1 - Synthesis and electrorheology of semiconducting polyaniline-coated polymethyl methacrylate microsphere suspensions - Google Patents

Abstract

The present invention relates to 10-30% by volume of PAPMMA particles dedoped with PAPMMA particle series coated with 100 parts by weight of PMMA micro spherical particles with 4 to 200 parts by weight of polyaniline to silicone oils, transformer oils, mineral oils, olive oils, corn oils and soybeans. It relates to a PAPMMA micro-particulate electrorheological fluid prepared by dispersing in at least one non-conductive solvent selected from the group consisting of oil and a method for producing the same.

Description

SYNTHESIS AND ELECTRORHEOLOGY OF SEMICONDUCTING POLYANILINE-COATED POLYMETHYL METHACRYLATE MICROSPHERE SUSPENSIONS

The present invention relates to an electrorheological fluid using polyaniline, which is a representative polymer material among conductive polymers. More specifically, in the present invention, 10 to 30% by volume of PAPMMA particles de-doped PAPMMA particle series coated with 100 parts by weight of PMMA micro spherical particles with 4 to 200 parts by weight of polyaniline may be used as silicone oil, transformer oil or mineral. The present invention relates to a PAPMMA micro-particulate electrorheological fluid prepared by dispersing in at least one non-conductive solvent selected from the group consisting of oil, olive oil, corn oil and soybean oil.

Electro-fluidic fluid is a generic term for fluids whose mechanical and physical properties change depending on the applied electric field, and are generally a solution in which electrically polarizable particles are dispersed in an electrically insulating solvent. In particular, the rheological fluid exhibits an increase in viscosity and yield stress behavior due to an electric field being loaded. The reaction is very fast and exhibits a reversible response to an electric field load. This is called an electrorheological effect (ER).

The first rheological fluids developed at the end of the 19th century consisted of liquids only, but they did not provide satisfactory results [Duff, A.W., Physical Review, Vol. 4, No. 1, 23 (1986)]. However, the first solid dispersion system proposed by Winslow has made significant progress compared to the past [see Winslow, W.H., J. of Applied Physics, Vol. 20, 1137 (1949), after which studies on systems containing conductive particles and nonconductive solvents continue. Most electrorheological fluids are aqueous fluids that induce polarization through water, such as corn starch or active silica gel particles dispersed in mineral oil, and zeolite particles dispersed in silicone oil. It was. In other words, the surface of the particles has hydrophilic properties, and the absorbed water plays a very important role in the ER effect.However, when the electrofluid is applied to a system requiring high temperature or high strain rate, the water is separated from the particles. As part of the water vaporizes, not only the ER effect is lowered, but also the risk of a short is generated. Therefore, it is urgent to develop a dry base electrofluidic fluid that does not basically require moisture. Development of particles (eg zeolites) that can limit the presence of moisture within the particles and development of dry-based electro-fluidic fluids in which polarization phenomena are caused by induced dipole moments caused by electron transport in the particles And the like.

Electrorheological fluids are fluids that exhibit solidification due to a sharp increase in viscosity under an electric field, and are generally present in a dispersed state of insulating oil and polarizable particles. Polyamines, well known as conductive polymers, have been studied for their excellent electrical properties. The polymerized polyamines, however, exhibit very irregular particle shapes, which makes them somewhat different compared to the theoretically proposed models. In the present invention, how to change the electrorheological properties by producing a full sphere (PMMA) of the core material to control the shape of the polyamine having such irregular particle shape.

The polyamine-coated PMMA particles were prepared by in-situ polymerization and characterized using FT-IR, TGA, SEM, picoammeter, and the like. The prepared particles can be classified into three categories. The first is a particle to see the effect on the coating thickness by varying the amount of amine, the second to change the size of core PMMA particles to examine the effect, and finally the pores of the PMMA particles are electrorheological effects. To see how this affects particles.

The rheological fluid shows the behavior of the Bingham fluid with yield stress, and the yield stress was obtained as a function of the electric field. Also, by measuring the dielectric spectra using an impedance analyzer, the polarization propensity of the dispersed particles themselves or the particle surface was observed and compared with the rheological properties.

Such characteristics can be applied to variable reduction mechanisms capable of controlling brakes, engine mounts, dampers, and the like, and power devices such as brakes and clutches, and are also extending to the robotics industry, including the automobile and aviation industries.

The role and application of polyaniline as an electrically conductive polymer is also important, but it is also important to use it as an electroconductive fluid by making it semi-conductive.

A good fluid must have a high yield stress under a low electric field, have a wide range of usable temperatures, and satisfy conditions without precipitation instability. Polyaniline, known as a conductive polymer, has been studied for its excellent electrical properties. However, the polymerized particles showed irregular particle shape, which was somewhat larger than the theoretically proposed models. The present invention provides a fluid which can determine how the electrorheological properties will be changed by controlling the shape of the polyaniline in a spherical form by coating the polyaniline, which is a conductive particle, on the polymethylmethacrylate particles. It is for that purpose.

The present invention relates to 10-30% by volume of PAPMMA particles dedoped with PAPMMA particle series coated with 100 parts by weight of PMMA micro spherical particles with 4 to 200 parts by weight of polyaniline to silicone oils, transformer oils, mineral oils, olive oils, corn oils and soybeans. It provides a PAPMMA micro-particulate electro-fluidic fluid prepared by dispersing in at least one non-conductive solvent selected from the group consisting of oil and a method for producing the same.

The present invention also removes oxygen by nitrogen purging a solution in which 10% by weight of PMMA monomer and 0.1% by weight of azobisisobutyronitrile are dissolved in 85.9% by weight of methanol in which 4% by weight of polyvinylpyrrolidone is dissolved at room temperature. Heating at 55 ° C. for 48 hours to wash the monodispersed particles in methanol to produce 2-10 μm PMMA particles; 10 g of the PMMA particles and 0.0095 M of sodium dodecyl sulfate were added to distilled water, followed by stirring. Then, 4 to 200 parts by weight of aniline was added per 100 parts by weight of PMMA and 0.002 M of hydroquinone solution. Acidified to 0.7 and under the solution (NH ₄ ) ₂ S ₂ O ₈ as an initiator to fix the molar ratio of the initial oxidizer / monomer to 1.25 was polymerized with stirring at 25 ℃ for 24 hours to coat polyaniline on the PMMA surface PAPMMA Preparing the particles; 10-30% by volume of PAPMMA particles dedoped with PAPMMA particles are dispersed in at least one nonconductive solvent selected from the group consisting of silicone oil, transformer oil, mineral oil, olive oil, corn oil and soybean oil It provides a method for producing a type electro-fluidic fluid.

Synthesis of the polymethylmethacrylate (PMMA) particles used in the present invention is one of the most useful methods of making monodispersed polymer particles, the dispersion polymerization method [Barthet, C., Armes]. , SP, Lascelles, SF, Luk, SY, Stanley, HM E, Langmuir, vol. 14, 2032 (1998). PMMA used in the present invention is preferably PMMA having a particle range of 2 ~ 10㎛.

PMMA micro spherical particles used in the present invention is proposed by Basset et al. [Reference: Barthet, C., Armes, SP, Lascelles, SF, Luk, SY, Stanley, HM E, Langmuir, vol. 14, 2032 (1998)]. Polyaniline, which has attracted much attention as a conductive polymer, has been studied as a non-aqueous ER fluid because it is easy to synthesize and has an advantage of controlling electrical properties by changing oxidation state. 3 is a Scanning Electron Microscopy (SEM) photograph of PMMA particles (10 μm). First, these PMMA particles and SDS (sodium dodecylsulfate) are added to distilled water and stirred, and aniline is added to 4 to 200 parts by weight and a small amount of hydroquinone (hydroquinone) solution per 100 parts by weight of PMMA. The mixed solution was acidified to pH about 0.7 in aqueous hydrochloric acid and polymerized by stirring at 25 ° C. for 24 hours with (NH ₄ ) ₂ S ₂ O ₈ (ammonium persulfate) as an initiator. In order to maintain a constant polymerization temperature, a prefabricated 2 liter reactor and a circulator are used (see FIG. 1). Since the polyamine produced in the present invention is polymerized in a strong acidic solution, the polyamine is doped with an acid and thus has high electrical conductivity. In order to be used in the rheological fluid, the electrical conductivity must be lowered and neutralized with NaOH to a desired pH of 7.5 to 10.0. The oligomers and residual monomers of the undoped polyamine-PMMA are removed and the precipitate is filtered, washed three to five times with 1.2 M HCl and filtered. The particles of this precipitated product are milled and then sieves are used to adjust the particle size. Figure 4 is a simple diagram showing in the form of a simple flow chart for this test method. The filtered polyamine-PMMA particles are placed in a vacuum oven at room temperature and dried until all of the moisture or other solvents are blown to obtain completely dried PAPMMA particles. The content of the polymerization of all particles is given in Table 1. FIG. 5 shows a scanning electron micrograph of PAPMMA particles completely dried by polymerization of polyaniline coated on PMMA particles. 5A is a scanning electron microscope of PAPMMA30-20 particles and FIG. 5B is a scanning electron microscope of PAPMMA100-20 particles.

      The electrorheological fluid of the present invention is prepared by dispersing the micro-sized particles in a non-conductive solvent as shown in FIG. The material which can be used as the non-conductive solvent of the present invention should not have a chemical reaction with other materials used in the electrofluidic fluid, have an appropriate stability within a normal operating temperature range, and preferably have a low viscosity under no electric field. Do. Therefore, the present invention mainly used silicone oil, in addition to transformer oil, mineral oil, olive oil, corn oil, soybean oil may be used.

      Electrorheological characterization of the motor fluid was performed using a physica rheometer with a high voltage generator. The measurement geometry used here is of the Couette cell type and the electric field is DC, applied to both sides of the cup and bob. Apply enough electric field to the sample for 3-5 minutes to allow the formation of chains to reach a steady state. The static yield stress is then obtained while adjusting the shear rate under the electric field. To ensure the accuracy of the test results, redistribute the transmission fluid each time and then proceed with the above procedure.

     Figure 6a is a result of measuring the shear stress in accordance with the change of the electric field by dispersing PAPMMA200-20 particles in silicon oil at a particle ratio of 10 vol%. It can be seen that the chain-shaped particle structure is well maintained even at high shear stress, and the shear stress at which the chain structure is broken depends on the size of the electric field. However, the electrorheological fluids of PAPMMA particles also show the behavior of Newtonian fluids at very high shear rates. When the electric field is not applied, the behavior of the Newtonian fluid is shown, but when the electric field is applied, the flow behavior is shown at a predetermined shear stress value. Figure 6b is a result of measuring the shear stress and shear viscosity of the electro-fluidic fluid prepared by dispersing the pH-controlled PAPMMA series particles (see Table 1) in silicone oil at a particle ratio of 10 vol%. 7 is a result of changing the static yield stress of the electric rheological fluid for the PAPMMA series particles and the electric field. Electro-fluidic fluids produce high shear stresses because the particles align in the direction of the electric field under the influence of an external electric field. When such a fluid flows through a continuous deformation caused by an external force, the particle chain is broken, but continues to form again as long as the electric field is maintained. The slower the flow rate, the more particles form the chain, and the rheological properties of the Bingham fluid are particularly high because a higher shear stress, or yield stress, is required to induce the initial flow in a well-developed static state. It follows the model of.

In the present invention, in order to study the mechanism of electrostatic interaction and polarization property of the electrofluidic fluid, the dielectric spectrum of the electrofluidic fluid was measured in the range of ²⁰ Hz to 10 ⁶ Hz using an impedance analyzer. 8A, 8B and 8C show Cole- for the PAPMMA series of ER fluids having a permittivity (ε ') and dielectric loss factor (ε ") and other polyaniline amounts as a function of electrical frequency, respectively. This is a Cole plot, a typical result from the interfacial polarization of suspensions, such as an electrorheological fluid consisting of a polarizable-dispersed phase and an insulating medium. .

Example 1 Preparation of PMMA Micro Spherical Particles

Polyvinylpyrrolidone (PVP), a high-purity methylmethacrylate (polyscience) monomer (2.5 g, 10 wt%) and a radical initiator (azobisisobutyronitrile (AIBN) (0.025 g, 0.1 wt%), stabilizer at room temperature (1 g, 4 wt%) in methanol (21.475 g, 85.9 wt%). The solution is deoxygenated by nitrogen purging and heated at 55 ° C. for 48 hours. The monodispersed particles were sufficiently washed out in methanol to prepare polymethyl methacrylate (PMMA) particles having a particle range of 2-10 μm.

Examples 2-6: Method of Coating Polyaniline on PMMA Surface

10 g of PMMA particles prepared in Example 1 and 0.0095 M of sodium dodecylsulfate (SDS) were added to distilled water and stirred, and aniline was added to 4, 20, 30, 100 and 200 g and 100 g of hydroquinone solution per 100 g of PMMA. 0.002M). The mixed solution was acidified to a pH of about 0.7 in an aqueous 1.2 M hydrochloric acid solution and (NH ₄ ) ₂ S ₂ O ₈ (ammonium persulfate) (fixed molar ratio of initial oxidant / monomer to 1.25) was used as an initiator. The polymerization was carried out by stirring at 25 ° C. for 24 hours. In order to maintain a constant polymerization temperature, a prefabricated 2 liter reactor and a circulator were used (see FIG. 1). The resulting polyamines are polymerized in a strong acidic solution and therefore doped with acid, so they have high electrical conductivity. In order to use the electro-fluidic fluid, the electrical conductivity must be lowered and neutralized to a desired pH of 7.5 to 10.0 with NaOH as a basic solution. Since pH and conductivity do not have a constant correlation, NaOH is added to the micropipette with constant stirring to establish a pH range in which the conductivity can be adjusted from 10 ^-9 to 10 ^-10 S / cm. The oligomer and residual monomers of the undoped polyaniline-PMMA were removed by washing with distilled water, and the precipitate was filtered using a depressurizer and washed three to five times with 1.2M HCl 3L and then filtered. The particles of this precipitated product were milled and then the particle size was adjusted using a 38 μm sieve. These particles are placed in a vacuum oven at room temperature and dried until all of the moisture or other solvents are blown to obtain completely dried PAPMMA particles (see Table 1). Polyaniline polymerisation is relatively stable in air, facilitates separation of the product and in particular at high yields of at least 60-70%. The aniline compound does not significantly reduce the yield as a result of increasing the amount of monomer for mass production purposes, and there is no significant difference in the properties of the particles.

Examples 7 to 9: Preparation of PAPMMA Micro Particle Electrorheological Fluid

Silicone oil having a viscosity of 50 cS was placed in a vacuum oven for a long time to remove moisture, and 10, 20 and 30 vol% of PAPMMA micro particles prepared and dried in the above Examples 2 to 6 were completely added to the silicone oil to be completely dehydrated. It was uniformly dispersed for about 2 hours to prepare a PAPMMA micro particle electrorheological fluid.

Determination of the electrorheological properties of the rheological fluid was made using a Fijika rheometer with a high voltage generator. The measurement geometry used here is of Coutte cell type and the electric field is applied to both sides of the cup and bob in DC. The electric field is applied to the sample sufficiently for 3 to 5 minutes to allow the formation of the chain to reach a steady state. After that, the discharge curve is obtained by adjusting the share ratio under the electric field, and the static yield stress is obtained by adjusting the share stress. To ensure the accuracy of the test results, redistribute the electrofluidic fluid each time and then proceed with the above procedure. All experiments were conducted at room temperature, and the electrical rheological properties of the electric field, the volume fraction, the conductivity, and the polymerization temperature were evaluated.

The synthesized product can be identified by composition analysis using Fourier transform infrared (FT-IR) spectroscopy using KBr pellets. Peak of 1740cm ^-1 in Fig. 9 represents a C = O peak in the PMMA 1600cm ^-1 is the peak caused by stretching the amine (amine streching) of polyaniline. The ratio of C = O peaks of PMMA to amine stretching peaks decreases as the amount of polyaniline loading increases. 10 shows the results of thermal analysis (TGA) of PMMA and PAPMMA series and PA. TGA is a measure of the change in weight of a sample over a period of time when the temperature is changed at a constant rate. The mass-temperature curve by TGA indicates the thermal stability and the composition of the material in the sample used, the thermal composition of the intermediates generated during heating, and the composition of the residue at the end of heating. In FIG. 10, PMMA almost thermally decomposes at 400 ° C., but polyaniline shows about 5% weight loss. The coating thickness of the PAPMMA series can be calculated from the secondary plateau region of the TGA data, assuming that all particles of the series have been completely coated with the same thickness (see Figure 11).

Sample The amount of aniline loaded per 100 g of PMMA Conductivity (S / cm) PMMA Particle Size PAPMMA4-20 4 g 3.22 × 10 ^-10 ~ 2㎛ PAPMMA20-20 20 g 8.02 × 10 ^-9 ～ 2㎛ PAPMMA30-20 30 g 8.59 × 10 ^-9 ～ 2㎛ PAPMMA100-20 100 g 9.65 × 10 ^-10 ～ 2㎛ PAPMMA200-20 200 g 1.53 × 10 ^-9 ～ 2㎛ PAPMMA20-45 20 g 2.54 × 10 ^-9 ˜4.5 μm PAPMMA20-90 20 g 5.14 × 10 ^-9 ～ 9㎛ PAPMMA20-pd 20 g 2.24 × 10 ^-9 ～ polydisperse PAPMMA20-pr 20 g 2.24 × 10 ^-9 ~ 10㎛ (porous)

An electrorheological fluid is a fluid with a characteristic of solidifying due to a rapid increase in viscosity under an electric field, and is generally present in a dispersed state of insulating oil and polarizable particles. Polyamines, well known as conductive polymers, have been studied for their excellent electrical properties. The polymerized polyamines, however, exhibit very irregular particle shapes, which makes them somewhat different compared to the theoretically proposed models. In the present invention, how to change the electrorheological properties by producing a fully spherical PMMA from the core material to control the shape of the polyamine having such irregular particle shape. As a result, there was no overall improvement in performance compared to polyaniline, but the agreement between the theoretical formulas was increased. In the future, if the particle size of PMMA, a core material, is changed at various angles, and the coating thickness of PAPMMA particles can be changed to maximize the polarization, there will be a big improvement in performance. The present invention is applicable to a variable damping mechanism that can control a suspension device, a vibration damper, an engine mount, and a power device such as a brake and a clutch based on the above characteristics, and is applicable to many fields including the automobile and aviation industries. This is a very useful invention possible.

1 is a photograph of an experimental reactor for the synthesis of PAPMMA particles.

Figure 2 shows the synthesis process of polymethyl methacrylate particles coated with polyaniline.

3 is a scanning electron micrograph of PMMA particles (10 μm).

Figure 4 is a flow chart illustrating a method for producing an electrorheological fluid of the present invention.

5 is a scanning electron micrograph of the PAPMMA30-20 and PAPMMA100-20 particles of the PAPMMA series particles.

6 is an experimental result of the shear stress and shear viscosity according to the electric field of the electric rheological fluid using PAPMMA series particles.

7 is an experimental result of the static yield stress according to the particle volume ratio and the electric field of the electric fluid using PAPMMA-based particles.

8 is an experimental result of the dielectric constant spectrum of PAPMMA series particles.

9 shows the FT-IR spectrum for the PAPMMA series.

10 shows a TGA diagram for the PAPMMA series.

11 shows the calculation of coating thickness from TGA data.

Claims (2)

delete A solution in which 10% by weight of PMMA monomer and 0.1% by weight of azobisisobutyronitrile was dissolved in 85.9% by weight of methanol in which 4% by weight of polyvinylpyrrolidone was dissolved was deoxygenated by nitrogen purging, followed by 48 at 55 ° C. Heating for a period of time and then rinsing the monodispersed particles in methanol to prepare 2-10 μm PMMA particles; 10 g of the PMMA particles and 0.0095 M of sodium dodecyl sulfate were added to distilled water, followed by stirring. Then, 4 to 200 parts by weight of aniline was added per 100 parts by weight of PMMA and 0.002 M of hydroquinone solution to acidify the mixed solution to pH 0.7 (NH ₄ ) preparing PAPMMA particles by coating polyaniline on the surface of PMMA by polymerizing with ₂ S ₂ O ₈ as an initiator while stirring at 25 ° C. for 24 hours; And After dedoping the PAPMMA particles, 10-30% by volume of the undoped PAPMMA particles are dispersed in at least one non-conductive solvent selected from the group consisting of silicone oil, transformer oil, mineral oil, olive oil, corn oil and soybean oil. PAPMMA micro-particulate electrofluidic fluid, characterized in that the step of making.