KR102185380B1 - Manufacturing method of basalt fiber-reinforced epoxy composites with natural graphite flakes intrduced - Google Patents

Abstract

The present invention relates to the production of a basalt fiber-reinforced epoxy composite material reinforced with natural graphite flakes, comprising: (1) mixing the natural graphite flakes with an epoxy resin using an organic solvent; (2) stabilizing the mixture prepared in step (1); (3) adding a curing agent to the mixture prepared in step (2); (4) stabilizing the mixture prepared in step (3) in a vacuum oven; (5) impregnating the mixture prepared in step (4) into basalt fiber and curing it.
According to the present invention as described above, by introducing natural graphite flakes to prepare a basalt fiber-reinforced epoxy composite material, a composite material having improved mechanical strength and thermal properties than the existing basalt fiber-reinforced epoxy composite material can be prepared.

Description

A method of manufacturing a basalt fiber-reinforced epoxy composite material with natural graphite flakes. {MANUFACTURING METHOD OF BASALT FIBER-REINFORCED EPOXY COMPOSITES WITH NATURAL GRAPHITE FLAKES INTRDUCED}

The present invention relates to the production of a basalt fiber-reinforced epoxy composite material into which natural graphite flakes (NGF) are introduced, and more particularly, by introducing natural graphite flakes, the interfacial bonding strength with the epoxy resin is improved, and the conventional The present invention relates to a method for producing a basalt fiber-reinforced epoxy composite material having stronger mechanical strength and improved thermal properties than the basalt fiber-reinforced epoxy composite material.

Epoxy, which has two or more epoxy groups (C-O-C) in its molecule, can be made of fiber-reinforced polymer composites (FRP) that are hard and insoluble when cured with basalt fibers. Due to the properties of epoxy's high tensile modulus, adhesion, chemical resistance, and structural stability, and the high strength, low specific gravity, and strong chemical resistance of the basalt fiber, it is emerging as a good alternative to polymer composites reinforced with E-glass fibers. It is applied to aerospace, ships, automobiles, coating materials, and electric and electronic industries. However, basalt fiber exhibits low interfacial adhesion within the epoxy matrix due to its chemically inert surface, which can degrade mechanical strength and thermal properties and be limited in various industries.

On the other hand, in order to improve the mechanical strength, recent studies have been confirmed that introduced methods such as combining other polymers, carbon materials, nano- or micro-sized particles.

Among various filler materials, carbon materials can be combined with an epoxy matrix to significantly improve mechanical strength and thermal properties. Among various carbon materials, natural graphite flakes are inherently abundant and are easy to process with high strength, low deformability at high temperature, low coefficient of thermal expansion, and low cost. Therefore, it is being studied very actively as a filler to improve mechanical strength and thermal properties by introducing natural graphite flakes into a basalt fiber-reinforced epoxy matrix.

Korean Patent Registration No. 10-1538032

An object of the present invention is to provide a basalt fiber-reinforced epoxy composite material with improved mechanical strength and thermal properties by manufacturing a basalt fiber-reinforced epoxy composite material into which natural graphite flakes are introduced.

In order to achieve the above object, the present invention comprises the steps of (1) mixing natural graphite flakes with an epoxy resin using an organic solvent; (2) stabilizing the mixture prepared in step (1); (3) adding a curing agent to the mixture prepared in step (2); (4) stabilizing the mixture prepared in step (3) in a vacuum oven; It provides a method for producing a basalt fiber-reinforced epoxy composite material reinforced with natural graphite flakes, including (5) impregnating and curing the mixture prepared in step (4) into basalt fibers.

The step (1) may include adding 10 to 40 g of natural graphite flakes to an organic solvent and then adding an epoxy resin to the ultrasonically treated mixture and stirring.

The step (2) may be heating the mixture prepared in the step (1) to remove the natural graphite flakes and the organic solvent in the epoxy resin.

The step (3) may be reacting by adding a curing agent to the mixture from which the organic solvent is removed in the step (2).

Step (4) may be to remove air bubbles by depressurizing the mixture prepared in step (3) in a vacuum oven.

In the step (5), the mixture from which the air bubbles have been removed in the step (4) may be impregnated with the basalt fiber and a mold and then cured in a hot press.

According to the present invention as described above, by using natural graphite flakes as a filler and adding them to the epoxy resin, many oxygen functional groups of the natural graphite flakes elicit strong interfacial bonding with the epoxy resin to reinforce basalt fiber with improved mechanical strength and thermal properties. There is an effect that can manufacture an epoxy composite material.

1 is a comparative graph of the thermal conductivity of a basalt fiber-reinforced epoxy composite material reinforced with natural graphite flakes and a comparative example
FIG. 2 is a comparative graph of surface energy of a basalt fiber-reinforced epoxy composite material reinforced with natural graphite flakes and a comparative example.
3 is a graph showing a comparison of fracture toughness of a basalt fiber-reinforced epoxy composite material reinforced with natural graphite flakes and a comparative example.
4 is a SEM photograph of a fracture surface after measuring the fracture toughness of Example 3 of a basalt fiber-reinforced epoxy composite material reinforced with natural graphite flakes.

Hereinafter, the present invention will be described in detail.

A method for producing a basalt fiber-reinforced epoxy composite material reinforced with natural graphite flakes according to an aspect of the present invention includes the steps of: (1) mixing the natural graphite flakes with an epoxy resin using an organic solvent; (2) stabilizing the mixture prepared in step (1); (3) adding a curing agent to the mixture prepared in step (2); (4) stabilizing the mixture prepared in step (3) in a vacuum oven; (5) impregnating the mixture prepared in step (4) into basalt fiber and curing it.

The step (1) may include adding 10 to 40 g of natural graphite flakes to an organic solvent, and then adding an epoxy resin to the ultrasonically treated mixture and stirring. More specifically, after adding 10 to 40 g of natural graphite flakes to 150 mL of acetone (C ₃ H ₆ O), ultrasonic treatment is performed at a temperature range of 10 to 40° for 1 to 2 hours. Add 100 g of epoxy resin to the mixture after the reaction, and stir for 1 to 4 hours while maintaining by heating at a temperature range of 30 to 60 ℃. If the ultrasonic treatment is performed for a long time exceeding 40°C and exceeding 2 hours, the inherent properties of natural graphite flakes may be damaged. Therefore, the ultrasonic treatment must be performed for 1 to 2 hours in the temperature range of 40°.

The step (2) may be heating the mixture prepared in the step (1) to remove the natural graphite flakes and the organic solvent in the epoxy resin. The mixture prepared in step (1) is preferably removed for 5 to 10 hours at a temperature range of 100° to 140° in order to evaporate the organic solvent.

The step (3) may be reacting by adding a curing agent to the mixture from which the organic solvent is removed in the step (2). More specifically, 34 to 36 g of a curing agent is added to the mixture from which the organic solvent has been removed in step (2), and reacted for 1 to 3 hours at a temperature in the range of 40 to 65° to dissolve the curing agent.

Step (4) may be to remove air bubbles by depressurizing the mixture prepared in step (3) in a vacuum oven. In the mixture prepared in step (3), when a curing agent is added to the epoxy resin, bubbles are generated due to a chemical reaction, so it is preferable to remove the bubbles for 1 to 2 hours at a temperature range of 40 to 60° under reduced pressure in a vacuum oven. When the air bubbles are removed as described above, the curing reaction may proceed. This is because the air bubbles generated in the mixing process may form pores in the finally manufactured epoxy composite material, thereby reducing the strength of the composite material.

In the step (5), the mixture from which the air bubbles have been removed in the step (4) may be impregnated with the basalt fiber and a mold and then cured in a hot press. The mold is manually impregnated with the mixture prepared in step (4) and 50 g of basalt fibers. Then, in the hot press, step 1 is 1 to 2 hours at a temperature range of 70 to 90°, step 2 is 1 to 2 hours at a temperature range of 90 to 120°, and step 3 is 1 to 2 hours at a temperature range of 150 to 170° By curing for 3 to 6 hours in a total of 3 steps, a basalt fiber-reinforced epoxy composite material reinforced with natural graphite flakes can be prepared. The reason why the curing process is carried out step by step as described above is that a total of three stages of stable curing are required: step 1 is a stabilization step, step 2 is a curing step, and step 3 is a final curing step for sufficient curing of the composite of the present invention. to be. If it exceeds 170°, it causes deterioration of properties, and if it is less than 110°, hardening does not occur properly, and this also causes deterioration of properties.

Hereinafter, the present invention will be described in more detail through examples. These examples are for illustrative purposes only, and it will be apparent to those of ordinary skill in the art that the scope of the present invention is not construed as being limited by these examples.

Example 1.

Natural graphite flakes were mixed with an epoxy resin using an organic solvent. After adding 10 g of natural graphite flakes to 150 mL of acetone (C ₃ H ₆ O), ultrasonic treatment was performed for 1 to 2 hours at a temperature range of 10 to 40°. After the reaction was completed, the epoxy resin was added to the mixture of natural graphite flakes, heated at a temperature of 30 to 60°, maintained, and stirred for 1 to 4 hours. Then, the organic solvent was removed for 5 to 10 hours in a temperature range of 100 to 140°. Then, 34 to 36 g of a curing agent was added to the remaining natural graphite flakes and the epoxy resin, and reacted for 1 to 3 hours at a temperature in the range of 40 to 65°. Thereafter, air bubbles were removed for 1 to 2 hours in a temperature range of 40 to 60° under reduced pressure in a vacuum oven. Then, after manually impregnating the above mixture and 50 g of basalt fibers in a mold, in a hot press, step 1 is 1 to 2 hours at a temperature range of 70 to 90°, and step 2 is 1 to 2 at a temperature range of 90 to 120°. Time, step 3 was cured for 3 to 6 hours in a total of 3 steps at 1 to 2 hours in a temperature range of 150 to 170 ° to prepare a basalt fiber-reinforced epoxy composite material reinforced with natural graphite flakes.

Example 2.

The procedure was carried out in the same manner as in Example 1, but a basalt fiber-reinforced epoxy composite material reinforced with natural graphite flakes was prepared by setting the content of natural graphite flakes to 20 g.

Example 3.

The procedure was carried out in the same manner as in Example 1, but a basalt fiber-reinforced epoxy composite material reinforced with natural graphite flakes was prepared by setting the content of natural graphite flakes to 30 g.

Example 4.

The procedure was carried out in the same manner as in Example 1, but a basalt fiber-reinforced epoxy composite material reinforced with natural graphite flakes was prepared with the content of natural graphite flakes being 40 g.

Comparative Example 1.

The process was carried out in the same manner as in Example 1, but the process of ultrasonic treatment after adding the natural graphite foil to 150 mL of acetone was omitted.

Measurement Example 1. Thermal conductivity test of basalt fiber-reinforced epoxy composite material reinforced with natural graphite foil prepared in the present invention

Thermal conductivity was measured at least three times after spray coating with graphite using a thermal conductivity analyzer (LFA 447 NanoFlash®Nederland, Germany). In addition, an infrared thermal imaging camera was used to see the heat absorption ability of the prepared basalt fiber-reinforced epoxy composite material, and the results are shown in FIG. 1.

Measurement Example 2. Surface energy test of basalt fiber-reinforced epoxy composite material reinforced with natural graphite foil prepared in the present invention

Surface energy was measured by measuring the contact angle of the basalt fiber-reinforced epoxy composite with 3 standard wetting liquids (distilled water, diiodomethane, ethylene glycol) using a Rame-Hart goniometer (Phoenix 300 Plus, SEO Co.). The surface energy was measured and the results are shown in FIG. 2.

Measurement Example 3. Fracture toughness test of basalt fiber-reinforced epoxy composite material reinforced with natural graphite foil prepared in the present invention

Fracture toughness test was measured using a universal testing machine (Lloyd LR5k) using a basalt fiber-reinforced epoxy composite material reinforced with natural graphite flakes according to ASTM E399, and then measured through a three-point bending test method. It is shown in 3.

Measurement Example 4. Observation of fracture surface after fracture toughness test of basalt fiber-reinforced epoxy composite material reinforced with natural graphite foil prepared in the present invention

In the present invention, after the fracture toughness test using scanning electron microscopy (SEM, SU 8010, Hitachi, Ltd., Japan), it was observed whether the structure of the basalt fiber-reinforced epoxy composite material reinforced with natural graphite flakes was changed, and the results are shown in FIG. 4 Shown in.

The following shows the manufacturing conditions of the basalt fiber-reinforced epoxy composite material reinforced with natural graphite according to the present invention in Table 1, and the thermal conductivity, surface energy, and fracture toughness of the basalt fiber-reinforced epoxy composite material reinforced with natural graphite according to the present invention. , And the degree of improvement, and numerical values are shown in Table 2.

Sample name Filler type content
(g) Dispersion time
(min) Stirring time
(min) Bubble removal time
(min) Curing temperature
( ^o C) Example 1 NGF 10 60 90 60 170 Example 2 NGF 15 60 90 60 170 Example 3 NGF 20 60 90 60 170 Example 4 NGF 25 60 90 60 170 Example 5 NGF 30 60 90 60 170 Example 6 NGF 35 60 90 60 170 Example 7 NGF 40 60 90 60 170 Comparative Example 1 - - - 90 60 170

Thermal conductivity
(W.mK ^-1 ) Surface energy
(mJ.m ^-2 ) Fracture toughness
(MPa.m ^1/2 ) Thermal stability
(kJ.mol ^-1 ) Example 1 0.39 ±0.01 40.10 87.40 ±4.01 147.03 Example 2 0.48 ±0.03 40.87 88.49 ±7.12 147.82 Example 3 0.63 ±0.01 41.76 91.56 ±6.58 148.96 Example 4 0.67 ±0.01 41.16 84.92 ±4.72 144.37 Example 5 0.75 ±0.01 40.01 81.82 ±2.07 142.69 Example 6 0.84 ±0.02 39.98 79.33 ±3.42 141.88 Example 7 0.95 ±0.02 39.94 77.30 ±3.30 141.23 Comparative Example 1 0.27 ±0.01 38.42 49.44 ±1.65 140.65

As described above, specific parts of the present invention have been described in detail, and for those of ordinary skill in the art, it is obvious that these specific techniques are only preferred embodiments, and the scope of the present invention is not limited thereby. something to do. Therefore, it will be said that the substantial scope of the present invention is defined by the appended claims and their equivalents.

Claims (6)

(1) mixing natural graphite flakes with an epoxy resin using an organic solvent;
(2) stabilizing the mixture prepared in step (1);
(3) adding a curing agent to the mixture prepared in step (2);
(4) stabilizing the mixture prepared in step (3) in a vacuum oven;
(5) a step of impregnating the mixture prepared in step (4) and curing it with basalt fibers, and the step (1) is a mixture obtained by ultrasonic treatment after adding 10 to 30 g of natural graphite flakes to an organic solvent A method for producing a basalt fiber-reinforced epoxy composite material reinforced with natural graphite flakes, characterized in that the epoxy resin is added and stirred.
delete The method of claim 1,
Step (2) is a method for producing a basalt fiber-reinforced epoxy composite material reinforced with natural graphite flakes, characterized in that the mixture prepared in step (1) is heated to remove the organic solvent in the natural graphite flakes and the epoxy resin. .
The method of claim 1,
The step (3) is a method of producing a basalt fiber-reinforced epoxy composite material reinforced with natural graphite flakes, characterized in that the reaction is performed by adding a curing agent to the mixture from which the organic solvent is removed in step (2).
The method of claim 1,
Step (4) is a method for producing a basalt fiber-reinforced epoxy composite material reinforced with natural graphite flakes, characterized in that the mixture prepared in step (3) is depressurized in a vacuum oven to remove air bubbles.
The method of claim 1,
The step (5) is a method for producing a basalt fiber-reinforced epoxy composite material reinforced with natural graphite flakes, characterized in that the mixture from which air bubbles are removed in the step (4) is impregnated with the basalt fiber and the mold and then cured in a hot press. .

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