KR20000027315A - Method for producing light and strong carbon complex material of electronic shielding - Google Patents

Abstract

PURPOSE: A light strong carbon complex material is provided to have the excellent electronic shielding property by thermally processing and after-processing a reinforcing complex material of carbon fiber. CONSTITUTION: A light and strong carbon complex material is produced by hot pressing after making a prepreg of carbon fibrous complex fiber by drying after impregnating a single fiber or a fibrous mat formed by cutting a carbon fiber in a regular length in a high molecular resin. A material selected from a group formed by a filling agent, a hardening catalyst, a coloring agent, an inner release agent, and their compound into the resin after controlling the concentration of the resin using an acetone, an ethanol, or a methanol of 100-500% of the resin weight as a solvent to be the 45-90% content of the resin among the complex material of carbon fiber obtained finally.

Description

Manufacturing method of light weight high strength carbon composite material

The present invention relates to a method for manufacturing an electron shielding lightweight high strength carbon composite material, and more particularly, to develop a carbon alloy reinforced composite material by developing a polymer alloy material mixed with a resin, and to heat-treat and post-treat the same. It relates to a method for producing a high strength carbon composite material.

In general, shielding of electromagnetic waves means blocking external electromagnetic waves from entering the system, or blocking or absorbing electromagnetic waves from outside the system. In other words, it means to electromagnetically distinguish between the place where the electromagnetic wave is generated and the place where the obstacle is caused by the electromagnetic wave. To this end, it is to prevent inter-system interference that occurs with other systems.

One countermeasure against electromagnetic interference is the use of an electromagnetic shielding material. The main purpose of the electromagnetic shielding material is to prevent electromagnetic interference from passing therethrough. Since electromagnetic interference waves do not pass through the metal plate well, metal materials are used as a representative electromagnetic shielding material.

By the way, the metal material has a very good electromagnetic shielding effect, but there are problems such as weight, economic efficiency. Therefore, sheet metal, aluminum die casting, or the like, which has a capability of shielding electromagnetic waves from electronic device products, has been used as an electromagnetic shielding material to replace it. In recent years, plastic materials having advantages such as ease of molding, free design, and lightweight have been widely used in the main body of electronic devices as electromagnetic shielding materials. By the way, since the plastic material is generally low in conductivity and hardly shielding electromagnetic waves, a separate shielding treatment for electromagnetic waves is required when the plastic material is used for the main body of the electronic device.

Recently, plastic reinforced carbon composite material using carbon fiber used in aircraft and sporting goods, fiber reinforced plastic using glass fiber as reinforcement material and unsaturated polyester as matrix resin, and thermoplastics occupying more than 80% of resin molded products. Fibre-reinforced thermoplastic resins, which are improved resins, have been employed as electromagnetic shielding materials.

However, the plastic-reinforced carbon composite material has a disadvantage of high manufacturing cost and difficulty in mass production, and fiber-reinforced plastics have a low elastic modulus and a high specific gravity, which makes it difficult to use in thin and light materials. In addition, the fiber-reinforced thermoplastic resin is difficult to maintain the fiber length required for reinforcement because the fiber is cut by the viscosity of the resin during the injection molding process, there is a problem in reducing the reinforcement effect by the fiber and increase the elastic modulus.

The present invention has been made to solve the conventional problems as described above, an object of the present invention, by developing a polymer alloy material mixed with a resin to produce a carbon fiber reinforced composite material and heat treatment and post-treatment to the electron shielding properties The present invention provides a method for producing an excellent lightweight high strength carbon composite material.

1 is a flow chart of an experimental process according to a preferred embodiment of the present invention;

2 is a graph showing the electromagnetic wave absorption characteristics of the electromagnetic shielding material with BaTiO ₃ added to the carbon composite material,

3 is a graph showing the electromagnetic wave absorption characteristics of BaTiO ₃ and nickel (Ni) coated carbon fiber mat added to the carbon composite material,

4 is a graph showing the electromagnetic shielding characteristics of the carbon composite material, and

5 is a graph showing electromagnetic shielding characteristics of a material in which a nickel (Ni) coated carbon fiber mat is inserted into a carbon composite material.

In order to achieve the above object, the present invention,

Preparing a carbon fiber mat as a starting material (S1);

Cutting the prepared carbon fiber mat into a predetermined size (S2);

Pretreating the resin to impregnate the cut carbon fiber mat (S3);

Impregnating the cut carbon fiber mat in a pretreated resin (S4);

Drying the impregnated carbon fiber mat to make a prepreg (S5);

Stacking the prepreg into a mold (S6);

Hot pressing the stacked prepregs (S7); And

It provides a method for producing an electromagnetic shielding lightweight high strength carbon composite material comprising the step (S8) of cooling the high temperature pressurized prepreg.

Hereinafter, a method of manufacturing an electron shielding lightweight high strength carbon composite material according to a preferred embodiment of the present invention with reference to the accompanying drawings in more detail.

The present invention, impregnated with a short-fiber or fiber mat formed by cutting the carbon fiber to a predetermined length, and then dried to form a carbon fiber composite material prepreg by heating and pressurizing, thereby having a physical property as shown in Table 1 The company intends to develop lightweight, high strength carbon composites with excellent electron shielding properties.

Table 1.

Item Tensile strength (kgf / cm ² ) Flexural Strength (kgf / cm ² ) Volume resistivity (Ω.cm) EMI shielding Density (g / cm ³ ) Thickness (mm) Target 900 20.0 × 10 ² 3.2 × 10 ^-2 Good 1.35 0.9

1 is a flowchart of an experimental process according to a preferred embodiment of the present invention.

Referring to Figure 1, the experimental process of the present invention, first, as a starting material for making electron shielding lightweight high-strength carbon composite material, manufactured by British Technical Fiber Products (Optimat) 203 series). In addition, in order to check the shielding properties of the metal-coated fibers, a sheet of nickel (Ni) coated fiber paper manufactured by the company is inserted into the mat, and then a carbon composite material is manufactured to perform electromagnetic shielding characteristics analysis. .

Tables 2 and 3 show the physical properties of carbon fiber mat and nickel (Ni) coated fiber paper (Optimat 204 series) used in the experiment of the present invention.

Table 2. Properties of Carbon Fiber Mat (Optimat 203 series)

division Characteristics Fiber form PAN based carbon fiber, 250Gpa moduls Fiber length 1 inch Fiber diameter 6.8 μm weight 0.25-6.0 oz / yd ² Binder content 10% Binder form Epoxy The tensile strength 150 lbs / in Mat density 80kg / m ³ Surface resistance <10 Ω shape role

Table 3. Properties of Nickel Coated Fiber Paper (Optimat 204 series)

division Characteristics Fiber form PAN based carbon fiber, 250Gpa moduls, containing 42% Ni Fiber length 1 / 2inch Fiber diameter 10 μm weight 0.25-3.0 oz / yd ² Binder content 10% Binder form Epoxy The tensile strength 150 N / mm ² Mat density 120kg / m ³ Surface resistance <1 Ω shape Paper

After preparing the carbon fiber mat as described above, it is cut to a certain size and impregnated in the phenol resin. At this time, in the present invention, two types of phenol resins of GP-582D58 resin produced by Georgia Pacific Co., Ltd. and Resol type phenol resin (KRD-HM2) produced by Kolon Emulsification are used.

Commercially available resins, on the other hand, have high viscosity and are unsuitable for impregnating the carbon fiber mat directly into the resin, and thus require a pretreatment step depending on the intended use. That is, in order to perform a warm press molding, the fiber which mixed the filler, the hardening catalyst, etc. must be impregnated to a fiber. Pretreatment of the resin is performed by adjusting the concentration of the resin so that the content of the resin in the final carbon fiber composite material is about 60 to 80%, preferably about 75%, and then adding the filler, a curing catalyst, and an internal mold release agent into the resin to pretreat the resin. do. In order to control the concentration of the resin, acetone is used as a solvent and the resin is diluted. At this time, the amount of acetone is to be 100 to 500% by weight of the resin.

The resin produced in Georgia Pacific (Geogia pacific) was pretreated under the conditions shown in Table 4 below, and the resin produced in Kolon emulsified resin was produced for composites, so that the concentration was controlled by dissolving in methanol, ethanol or acetone. After that, only the internal mold release agent and the colorant were added to pretreat the resin. At this time, the amount of acetone, internal mold releasing agent and colorant was the same as in Georgia pacific resin.

Table 4. Pretreatment Conditions of Resin

ingredient part by weight (pbw) Remarks Resin (Phenol Resol) 100 Georgia pacific Filler (CaCO ₃ ) 60 Suwa Catalyst (CaO + Liquid Polyol) 6 to 8 Zinc starait 1.0 to 1.5 純正 Acetone 500 純正 coloring agent 2 HSC-5694

Table 5 below shows the characteristics of the internal mold release agent and the colorant added to the resin produced in Kolon Emulsion.

Table 5. Properties of Internal Release Agents

division standard Remarks Exterior Light brown liquid Solid content 25 ± 1 %, 1g × 135 ℃ × 1hr Acid 35 ± 2 mg KOH / g color 5 or less gradner pH 6.9 ± 0.1 pH meter

After the carbon fiber mat is impregnated with the pretreated phenol resin, the impregnated sample is dried at 70 ° C. for 30 minutes. As a result, prepreg is produced. Next, the thickness of the final specimen is first calculated to calculate the amount of sample to be laminated. Thereafter, the prepregs are laminated in a predetermined mold and hot pressed. At this time, the mold used in the present invention uses a mold manufactured in a size of 15cm × 5cm × 10cm (width, length, height) using a sus 304 material, and is a commercially available model manufactured by Carver in the USA as a press machine. Use the press of the M2089. After the high temperature pressurization is finished, the specimen is cooled to obtain the desired carbon composite material.

Example

In the present invention, a phenolic resin (KRD-HM2) commercially available from Kolon Emulsification is used as a starting material for producing an electron shielding lightweight high strength carbon composite material, and a PAN-based carbon fiber mat sold by Fibrite Co., Ltd. is used. Used as.

Before impregnating the PAN-based carbon fiber mat in the phenol resin (KRD-HM2), the phenol resin is pretreated. At this time, after adjusting the concentration of the resin so that the content of the phenol resin in the final carbon fiber composite material is about 75%, when the content of the phenol resin is 100, 3 to 15% of the internal mold release agent (RA 407), 5 ~ The phenol resin was pretreated by adding 15% colorant (HSC-5694) and 100-300% of solvent (acetone, ethanol or methanol) into the phenol resin.

After the pretreatment, the colorant is dissolved in the solvent. At this time, if the stirring is not sufficiently done, the colorant is left as it is, and after pressurizing, only the part where the chip is black is colored, and as a result, the stain appears to be dark. Therefore, the stirring speed is maximized and it is stirred until complete dissolution. When the colorant is completely dissolved, add the phenol resin and the internal release agent and stir again. The sample thus made is impregnated with a PAN fiber mat. At this time, for uniform impregnation, the resin is impregnated after the sample is poured into the dish, rather than being impregnated in the beaker under stirring. Next, the impregnated sample is dried at 70 ° C. for 30 to 50 minutes to prepare a prepreg.

Thereafter, the prepared prepreg is pressurized at high temperature to produce a lightweight electromagnetic shielding carbon composite material. To do this, first calculate the amount of sample to be laminated by first calculating the thickness of the final specimen. For example, when obtaining a 1 mm thick specimen, three to four sheets are laminated. After laminating the prepreg in the mold in this manner, the temperature was raised to 10 ° C./min at room temperature, dried at 50 to 100 ° C. for 5 to 10 minutes, the temperature was further increased to 120 to 130 ° C., and the pressure was slowly increased to 130 to 140 ° C. After the primary pressing, the pressure extraction step was performed, and then, the temperature was raised to a constant temperature, and the secondary pressing was performed at a pressure of 150 to 300 kg / cm ² . At this time, uniform pressure should be applied to the whole sample. After the pressing was finished, the specimen was cooled to obtain the desired carbon composite material.

Results and Discussion

<Mechanical and electrical property analysis>

① Mechanical Characteristic Analysis

The carbon composite material prepared according to the present invention was analyzed by requesting the Korea Testing Institute, a specialized test organization. The test was carried out according to the KSM 3006-93 method, and the distance between points of the test piece was measured at 40 mm, the test piece No. 1, and the test speed was 1.7 to 5 mm / min. The prepared specimens were analyzed for mechanical properties by measuring tensile strength, flexural strength and flexural modulus, respectively. Table 6 below shows the mechanical properties of the lightweight carbon composites prepared by using resins commercially available from Georgia Pacific, Inc., according to the final heat treatment temperature change.

As shown in Table 6, the tensile strength shows the best value of 1870Kgf / cm ² when the final heat treatment temperature is 180 ℃, the flexural strength and the modulus of elasticity of the final heat treatment at 160 ℃ 24.5Kgf / The best properties of mm ² and 2030Kgf / mm ² were shown. These values show better physical properties than the KPC-202 flame retardant grades developed in Japan and used in commercial PCs. This is believed to be the result of pretreatment conditions of the resin due to suitable blending and drying conditions that improve product properties.

Table 6.

Test Items Psalm Number Final curing temperature (℃) Result Test speed (mm / min) Resin Content (%) Thickness (mm) Tensile strength (kgf / cm ² ) One 170 1120 5 70.3 1.6 2 160 679 〃 73.0 1.6 3 150 954 〃 72.6 1.5 5 140 1280 〃 62.3 1.0 6 130 1260 〃 64.0 1.5 10 180 1870 〃 65.2 1.5 Flexural Strength (kgf / mm ² ) 4 150 19.6 1.7 73.2 1.6 7 130 18.8 1.7 73.9 1.5 8 160 24.5 2.7 60.3 1.0 9 140 20.6 1.8 72.4 1.5 11 180 16.6 1.8 70.4 1.5 Flexural modulus (kgf / mm ² ) 4 150 1390 1.7 73.2 1.6 7 130 1330 1.7 73.9 1.5 8 160 2030 2.7 60.3 1.0 9 140 1510 1.8 72.4 1.5 11 180 1390 1.8 70.4 1.6

Table 7.

Classification Psalm Retention time (minutes) Tensile Strength (Kgf / cm ² ) Elongation (%) Tensile Modulus (Kgf / cm ² ) Flexural Strength (Kgf / cm ² ) Flexural modulus (Kgf / cm ² ) Suzy(%) Thickness (mm) One One 1040 0.74 154000 1810 116000 77.3 1.9 2 2 944 0.75 151000 1660 111000 80.6 2.2 3 2 919 0.65 124000 1650 116000 77.9 1.9 4 3 706 0.80 92400 1310 93100 81.3 2.4 5 5 1020 0.87 133000 1550 116000 80.4 2.2 6 15 1080 0.90 129000 1680 115000 81.2 2.4 7 25 828 0.80 122000 1440 108000 82.2 2.2 8 45 970 0.69 120000 1630 117000 80.3 2.3 9 10 804 0.71 124000 1550 105000 82.5 2.5 10 10 1400 0.63 217000 2010 148000 72.6 1.6 11 10 1060 0.78 133000 1820 130000 75.4 1.7 12 10 1130 0.79 137000 1700 118000 76.4 1.8 Test Methods KSM 3006-93Test Speed: 5mm / min KSM 3008-93, Distance between points: 40mm, Test speed: 1.4mm / min

Table 7 shows the physical property values according to the holding time at the final curing temperature when the prepreg was prepared using a commercially available resin by Kolon emulsification and the final heat treatment at 150 ℃.

② Analysis of electrical resistance

Electrical characteristics of the electromagnetic shielding carbon composite material produced by the present invention were compared by measuring the volume resistivity (Ω.cm). The equipment used for the test was measured by the 4probe method using Hewlett Packard's 433A. The test pieces were measured by cutting the test pieces 7, 8, and 12 of Table 6 to a size of 3 mm in width and 24 mm in length, and the test pieces were manufactured by measuring 2 or 3 pieces to test the reliability of the test pieces. Table 8 summarizes the electrical resistance and density of the test piece used for the measurement.

Table 8.

Classification Test Piece Cross section area (cm ² ) Volume (cm ³ ) Weight (g) Density (g / cm ³ ) Resistance (mΩ) Volume specific resistance (Ωcm) 7 One 0.08109 0.20200 0.2577 1.2757 14.64 0.0365 2 0.08132 0.20299 0.2773 1.3661 16.75 0.0418 3 0.09109 0.22468 0.2881 1.2823 5.203 0.0128 8 One 0.06131 0.15298 0.1851 1.2093 5.50 0.0387 2 0.05596 0.13905 0.1717 1.2349 6.705 0.0167 3 0.06439 0.15938 0.2021 1.2681 6.923 0.0171 12 One 0.06486 0.14604 0.1864 1.2736 26.035 0.0646 2 0.06486 0.16078 0.2164 1.3460 22.25 0.0552

As shown in Table 8, except for specimen 12, the specific resistance was in the range of 1.3 to 4.2 x 10 ^-2 Ω.cm, and sufficient weight reduction was achieved in the density value range of 1.21 to 1.37 g / cm ³ . . In addition, it can be seen from the results of Tables 6 to 8 that the target value of Table 1 to be achieved through the present invention was sufficiently achieved.

<Electromagnetic Characteristic Analysis>

For the electromagnetic shielding test of the electromagnetic shielding carbon composite material prepared according to the present invention was prepared a test specimen as shown in Table 9.

Table 9.

Test piece number Prepreg manufacturing method One △ Fiber mat: Optima 203, △ Solvent: Acetone, △ Filler: CaO, △ Thickener: Zn-stearate, △ Shielding enhancer: BatiO ₂ (small amount) 2 △ Fiber mat: Optima 203, △ Solvent: Acetone, △ Filler: CaO, △ Thickener: Zn-stearate, △ Shielding enhancer: Nickel (Ni) coated carbon fiber mat + BaTiO ₃ (small amount) 3 △ Fiber mat: Optima 203, △ Solvent: Acetone, △ Filler: CaO, △ Thickener: Zn-stearate 4 Fiber Mat: Optima 203, Solvent: Acetone, Filler: CaO, Thickener: Zn-stearate, Shielding Enhancer: Nickel (Ni) Coated Carbon Fiber Mat

The electromagnetic shielding characteristics were analyzed using the test specimens prepared as described above, and the results are shown in the accompanying drawings of FIGS. 2 to 5.

2 is a graph showing the electromagnetic wave absorption characteristics of the electromagnetic shielding material added BaTiO ₃ to the carbon composite material, Figure 3 is the electromagnetic wave absorption of the material added BaTiO ₃ and nickel (Ni) coated carbon fiber mat to the carbon composite material A graph showing the characteristics. In addition, Figure 4 is a graph showing the electromagnetic shielding characteristics of the carbon composite material, Figure 5 is a graph showing the electromagnetic shielding characteristics of a material in which a carbon fiber mat coated with nickel (Ni) in the carbon composite material.

2 to 5, the electromagnetic shielding characteristics of the frequency band of 0 to 400MHz shows a high-performance shielding ability in all specimens of 40dB or more. As a result of analyzing the shielding effect of the four test specimens, the first specimen with the electromagnetic wave shield enhancer was the best, and the second specimen containing the nickel (Ni) coated carbon fiber mat was rather the electromagnetic shielding performance. Fell sharply. Specimen No. 3 is a generally manufactured specimen, but exhibits relatively good shielding ability although the electromagnetic shielding performance is lower than that of the BaTiO ₂ added specimen. Specimen No. 4 containing nickel (Ni) coated carbon fiber mat was slightly inferior in shielding ability to specimen No. 3 without nickel (Ni) coated carbon fiber mat. In conclusion, all specimens containing nickel (Ni) coated carbon fiber mat showed a tendency to be inferior to those without the addition of electromagnetic shielding ability. Therefore, it was found that BaTiO ₂ was added to produce a composite material as an optimum electromagnetic shielding material.

conclusion

As a result of manufacturing the electron shielding lightweight high strength carbon composite material according to the preferred embodiment of the present invention, the following conclusions were obtained.

First, test specimens and physical properties were analyzed using resins commercially available from Georgia Pacific, USA and resol type resins commercially available from Kolon Emulsion. A carbon fiber composite prepreg having similar or superior physical properties to the material could be prepared, wherein the resin content was 60 to 70%.

Second, the hot pressing showed good physical properties by applying pressure at 120 ~ 130 ℃ after sufficient drying time at 100 ℃ and pressurizing at 200Kgf / cm ² finally. .

Third, the mechanical properties showed somewhat different properties depending on the high temperature and pressurization conditions used, but were comparable to those of commercially available products such as Fibrite and Kobe steel. In case of using Georgia pacific resin, it showed the best tensile strength value of 1870Kgf / cm ² when the final heat treatment temperature was 180 ℃, and the flexural strength and elastic modulus were 24.5Kgf respectively at 160 ℃. / mm ² , 2030 Kgf / mm ² showed the best properties.

Fourth, the electrical characteristics were compared and analyzed by the volume resistivity value, and when the commercially available resin was used as a matrix by Kolon emulsification, the volume resistivity value was in the range of 1.3 to 4.2 x 10 &lt; ^-2 &gt; Is sufficiently achieved, and sufficient weight reduction is achieved in the density value at this time in the range of 1.21 to 1.37 g / cm ³ .

Fifth, as a result of comparing the electromagnetic wave absorptivity, all specimens containing nickel (Ni) coated carbon fiber mat showed a tendency to be inferior to the case where no electromagnetic shielding ability was added, and the optimum electromagnetic shielding material was BaTiO. It was found that the composite was prepared by adding ₂ . The electromagnetic shielding efficiency of these specimens is in the range of about 80% in the low frequency range below 10MHz compared to the products currently used as commercial products, and about 170% and 250% in comparison with nickel (Ni) based paints and conductive polymers, respectively. It was confirmed that excellent.

As mentioned above, in the method for producing an electromagnetic shielding lightweight high strength carbon composite material according to the present invention, a carbon fiber composite material is impregnated with a polymer resin and dried by impregnating short fibers or fiber mats formed by cutting carbon fibers to a predetermined length. After making the prepreg, a composite carbon fiber composite molding is made under heat and pressure. When the carbon composite material according to the present invention is used in a case of a notebook, it is possible to overcome the limitation of the weight reduction compared to a case made of synthetic resin such as ABS, and thus it is possible to reduce the weight by 50% or more compared to the existing ABS product. In addition, since the EMI coating process for electromagnetic shielding is not required, the process can be simplified, and it can be applied to structural materials and high-density precision parts that require lightweight, including notebook cases and office equipment. In addition, since the fiber cutting machine, resin impregnation machine, press machine, etc. required for carrying out the method of manufacturing the electron shielding light weight high strength carbon composite material according to the present invention can be automated and enlarged, mass production of the carbon composite material is possible.

Although described above with reference to a preferred embodiment of the present invention, those skilled in the art will be variously modified and changed within the scope of the invention without departing from the spirit and scope of the invention described in the claims below. I can understand that you can.

Claims (4)

Preparing a carbon fiber mat as a starting material (S1); Cutting the prepared carbon fiber mat into a predetermined size (S2); Pretreating the resin to impregnate the cut carbon fiber mat (S3); Impregnating the cut carbon fiber mat in a pretreated resin (S4); Drying the impregnated carbon fiber mat to make a prepreg (S5); Stacking the prepreg into a mold (S6); Hot pressing the stacked prepregs (S7); And Method for producing an electromagnetic shielding lightweight high-strength carbon composite material comprising the step (S8) of cooling the hot pressurized prepreg. The acetone, ethanol or methanol in an amount corresponding to 100 to 500% of the weight of the resin so that the content of the resin in the finally obtained carbon fiber composite material is 45 to 90% in the step (S3). After adjusting the concentration of the resin using a solvent, a material selected from the group consisting of a filler, a curing catalyst, a colorant, an internal mold release agent, and a compound thereof is added to the resin. Manufacturing method. The method according to claim 1, wherein in step S7, the temperature is raised to 10 ° C / min at room temperature, dried at 50 to 100 ° C for 5 to 10 minutes, and the temperature is further raised to 120 to 130 ° C. A method of producing an electromagnetic shielding lightweight high-strength carbon composite material, characterized in that the primary pressing is carried out by heating up to a second pressure, and then the pressing is carried out at a temperature of 150 to 300 kg / cm ² after heating to a constant temperature. The method for producing an electron shielding lightweight high strength carbon composite material according to any one of claims 1 to 3, wherein the carbon fiber is made of PAN-based carbon fiber, and the resin is a resol type phenol resin.