KR20210004372A - Auxetic Porous Structure Based on Graphene and Method of Preparing the Same for Vibration and Shock Energy Dissipation - Google Patents

Abstract

The present invention relates to a three-dimensional auxetic porous structure based on two-dimensional corrugated graphene and a method for manufacturing the same. The graphene-based auxetic porous structure is obtained by forming auxetic polymer sponge through the tri-axial hot compressing of porous polymer sponge, and dipping the thus prepared auxetic polymer sponge in a graphene oxide solution, followed by drying, so that the inner part of the auxetic polymer sponge may be coated with a graphene oxide layer. The graphene-based auxetic porous structure has a structure characterized by a negative Poisson′s ratio, high porosity, high surface area and improved mechanical properties, and thus can be used as a vibration-, noise- and impact-absorbing material.

Description

Auxetic Porous Structure Based on Graphene and Method of Preparing the Same for Vibration and Shock Energy Dissipation for noise, vibration, and shock absorption

The present invention relates to a graphene-based augitive porous structure for absorbing noise, vibration and shock, and a method of manufacturing the same, and a method of manufacturing the same, and more particularly, a corrugated oxidized graphene layer having a negative Poisson's ratio. The present invention relates to a graphene-based porous structure for absorbing noise, vibration, and shock formed inside an augitive porous structure and a method of manufacturing the same.

In general, graphene is one of the carbon allotropes composed of carbon atoms. In general, graphene refers to a two-dimensional single sheet made of a sp2 hybrid of carbon. Graphene has a large surface area compared to other conventional nano additives (Na-MMT, LDH, CNT, CNF, EG, etc.), has excellent mechanical strength, thermal and electrical properties, and has the advantage of having flexibility and transparency. . Therefore, research is being actively conducted to develop a high-performance functional polymer composite material with excellent conductivity and mechanical strength by filling graphene in a polymer resin (Polymer Science and Technology Vol. 22, No. 5, October 2011).

The porous structure is mainly used as a material for damping noise and vibration. The vibration damping properties differ depending on the cell size or shape of this porous structure. In the case of using an augitive porous structure having a negative Poisson's ratio among the porous structures, the general circular unit cell structure is twisted and the wire is bent in an irregular shape. Accordingly, a structure characterized by a negative Poisson's ratio is formed, and shock and vibration damping properties are improved by an effective local compression strengthening effect of impact energy during tensile compression deformation. For this reason, research on practical engineering applications of the augitive porous structure is emerging. (ACS Appl. Mater. Interfaces, Vol. 10, No. 26, May 2018).

The augitive structure has been limited in practical engineering applications and uses, and has a porous structure that inevitably reduces mechanical performance. However, when a material has a negative Poisson's ratio, its physical and mechanical behavior tends to be reversed. That is, when compressing in the axial direction, it is also compressed in the lateral direction, so that it can be a material with isotropic and high compressibility. Such augmentative properties can be used as excellent properties in various applications by showing a local reinforcement effect due to an increase in the density of the compressed area.

However, the conventional manufacturing process for making a porous structure is a manufacturing process that is expensive and can only be produced in a small amount, and the materials are mechanically non-rigid, and it is difficult to accurately control the pore size and function.

Accordingly, as a result of the inventors' diligent efforts to solve the above problem, the first 3D auxetic foam having a property of negative Poisson's ratio wrapped with 2D wrinkled graphene oxide sheets Developed, and has a negative Poisson's ratio that gives augetic properties to polyurethane foam through a 3-axis thermal compression process, and a graphene oxide layer formed inside the augetic porous structure. It was confirmed that the graphene-based porous structure has high porosity, surface area, and mechanical properties, and at the same time has characteristics of absorbing material, sound-absorbing material, noise/vibration attenuation, and shock absorption, and the present invention was completed.

It is an object of the present invention to provide a graphene-based porous structure that has a structure characterized by a negative Poisson's ratio, a high porosity, a high surface area, and improved mechanical properties, and can be used as an absorbing material, a sound absorbing material, and an impact absorbing material, and a method of manufacturing the same.

Another object of the present invention is to provide a use of the graphene-based porous structure as an absorbent material, a sound absorbing material, or an impact absorbing material.

In order to achieve the above object, the present invention comprises the steps of: (a) triaxial thermal compression of a porous polymer sponge to prepare an augitive polymer sponge; And (b) immersing the prepared augmented polymer sponge in a graphene oxide solution and drying it to coat a graphene oxide layer inside the augitive polymer sponge. to provide.

The present invention also provides a graphene-based augitive porous structure, which is manufactured by the above method and has a Poisson ratio of -0.0 to -0.5.

The present invention also provides a damping material, a sound absorbing material or a vibration damping material including the graphene-based augetic porous structure.

The graphene-based augitive porous structure according to the present invention has high porosity, high surface area, and improved mechanical properties, and thus can be used as an absorbent material, a sound absorbing material, and an impact absorbing material. In particular, the augitive sponge technology in which the graphene oxide layer is formed according to the present invention can be applied to various fields such as conference rooms, general buildings, hotels, laboratories, various machinery and engine rooms that require various sound absorption and absorption facilities. Due to its advantages such as low installation cost and recyclability, it has a wide range of applications and excellent utility.

1 is an electron microscope (SEM) photograph of a graphene-based augetic porous structure according to the present invention. (a) represents a polyurethane foam, (b) represents an augitive polyurethane foam, and (c) represents an augitive polyurethane foam coated with graphene oxide.
2 is a SEM photograph of a graphene-based augitive porous structure (10% compression, 20% compression) according to the present invention.
3 is a compression test result of a graphene-based augitive porous structure sponge according to the present invention, and FIG. 3A is a view showing a compression deformation aspect of a general polyurethane foam, and FIG. 3B is a compression deformation aspect of an augitive polyurethane foam 3C is a graph of strain-stress, which is a result of a compression test.
4 is a result of a low-velocity impact test of the graphene-based augitive porous structure according to the present invention, FIG. 4 (a) is a graph of displacement-force, and (b) is a time-force (time- force).
5 is a result of measuring the Poisson's ratio of the graphene-based augitive porous structure sponge according to the present invention.
Figure 6 is a result of measuring the vibration damping performance of the graphene-based augetic porous structure sponge according to the present invention.
7 is a diagram showing a device for measuring the vibration damping performance of the graphene-based augitive porous structure sponge according to the present invention.
8 is a result of measuring the sound absorption performance of the graphene-based augetic porous structure sponge according to the present invention.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by an expert skilled in the art to which the present invention belongs. In general, the nomenclature used in this specification is well known and commonly used in the art.

In the present invention, the polyurethane foam is provided with augitive properties through a 3-axis thermal compression process, and the graphene-based porous structure in which the graphene oxide layer is formed inside the augetic porous structure has high porosity, surface area, and mechanical properties, and at the same time , It was confirmed that it can have the characteristics of a sound absorbing material and shock absorption.

Therefore, in one aspect, the present invention comprises the steps of: (a) triaxial thermal compression of a porous polymer sponge to prepare an augitive polymer sponge; And (b) immersing the prepared augitive polymer sponge in a graphene oxide solution and drying it to coat a graphene oxide layer inside the augitive polymer sponge. About.

In another aspect, the present invention relates to a graphene-based augitive porous structure, which is manufactured by the above method and has a Poisson's ratio of -0.0 to -0.5.

The present invention is the first to develop a 3D auxetic foam wrapped with 2D wrinkled graphene oxide sheets. The practical engineering application of the 3D carbon microstructure having the property of negative Poisson's ratio according to the present invention can be used for vibration damping and shock absorption.

Therefore, the 3D heterogeneous structure of graphene oxide-wrapped auxetic foam (3D heterogeneous structure of graphene oxide-wrapped auxetic foam) is (2D corrugated graphene oxide structure with negative Poisson's ratio and 3D with negative Poisson's ratio). The effective synergistic effect of the augitive foam provides improved mechanical properties capable of withstanding strong compressive forces, and significantly increases energy absorption.

In the present invention, oxidized graphene is prepared, an augetic shape is formed, and a graphene oxide layer is formed on the augitive polymer sponge in the sequence. First, oxidized graphene is prepared by modifying the Hummers method (Daniela C. Macrcano et al., ACS nano 2010, 4(8), 4806-4814.). The prepared polyurethane sponge is subjected to 3-axis thermal compression to impart augmentative properties. After immersing a polymer sponge, such as a polyurethane sponge with an augitive nature, in a certain concentration of graphene oxide solution, it is dried to form a graphene oxide layer to prepare an augitive graphene oxide sponge.

According to an embodiment of the present invention, the augitive polymer sponge is prepared as follows. Commercially available polyurethane foam is washed with ultrapure distilled water (D.I. Water) and ethanol and dried in an oven. Then, the polyurethane foam is placed in a frame box and heated at 150° C. for about 1 hour in a hot press. Cut clean augitive polyurethane foam according to the purpose and use it.

In addition, the three-axis thermal compression proceeds as follows.

For samples of 10x10x4 cm ³ , place the sample in a mold smaller than the sample before placing it in the hot press equipment. At this time, the mold is a mold with only an outer edge so that the sample size is 8x8x2 cm ³ . The sample is then compressed in the mold when pressed from above with a hot press machine. And if the temperature of the equipment is raised to 150℃ and left for about 1 hour, the softening temperature of polyurethane becomes soft and the structure is deformed.

In the present invention, the porous polymer sponge may be selected from the group consisting of a polyurethane sponge, a polyester sponge, a polyethylene sponge, and a vinyl acetate sponge, and preferably a polyurethane sponge, but is limited thereto. no.

The method of claim 1, wherein the step (a) may be thermally compressed under conditions of a temperature of 100 to 300°C. According to an embodiment of the invention, for example, when the size of the sample is 10cm x 10cm x 4cm, put it in a compression mold at a compression rate of 20% or 10% in the longitudinal direction, and a final result of 8cm x 8cm x 2cm will be produced. I can.

In the step (a), hot pressing or framing equipment may be used.

As described above, the graphene-based augitive porous structure according to the present invention is a new semi-open cell that was not seen in the existing cellular structure, and graphene oxide-based It can be said to be a cellular microstructure with a negative Poisson's ratio.

In the present invention, a polymer foam having large voids is three-dimensionally implemented by a three-dimensional thermal compression method (divided by 10% compression and 20% compression of the original length) to have a negative Poisson. Thereafter, structural strengthening (coating) is performed with graphene oxide containing an oxygen-functional group). Due to this structural reinforcement, a two-dimensional planar graphene oxide layer is created on a three-dimensional augetic structure. The SEM image of the structure according to the present invention is shown in FIG. 2. If you look at the SEM images of 20% GA-PUF and 10% GA-PUF, you can see the wrinkled graphene oxide surface, which is seen as a two-dimensional plane with negative Poisson ratio characteristics according to the previously reported literature. I can. (Advanced Materials, Vol.27, No. 8, February 2015) In other words, it has a three-dimensional augitive structure made of polymer foam with structurally negative Poisson's ratio and a coating layer with two-dimensional negative Poisson made of graphene oxide. It can be said that it is a feature of the present invention.

In addition, from the standpoint of technological commercialization, a synthesis method that allows small and mid-sized companies to rapidly mass-produce products in a short time was applied, and the 3-axis thermal compression method and the Hummer's method (Hummer's method, Daniela C. Macrcano et al., ACS nano 2010) were applied. , 4(8), 4806-4814) and coated with graphene oxide with large particles.

In the present invention, the graphene-based augmented porous structure manufactured by the above manufacturing method has higher porosity, surface area, and mechanical properties than the existing porous structure, and at the same time has the characteristics of absorption, sound absorption, and shock absorption. It was confirmed that a new engineering application is possible as an absorbent material.

Accordingly, in another aspect of the present invention, the present invention relates to an absorbent material, a sound absorbing material, or an impact absorbing material including the graphene-based augitive porous structure.

The measurement of the Poisson's ratio of a material is to take a negative value by dividing the transverse strain by the axial strain, which is well known (see Equation 1). Common materials have a positive Poisson ratio. Therefore, general materials shrink in the transverse direction when tensioned in the axial direction, and stretch in the transverse direction when compressed in the axial direction. The material was stretched and the specimen was photographed using a camera, and the degree of tension was measured by using Photoshop CS6 to measure the Poisson's ratio. In the case of negative Poisson's ratio, when the material is stretched in the axial direction, it is stretched in the transverse direction, and when compressed in the axial direction, it is reduced in the transverse direction.

[Equation 1]

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]

Preparation Example 1: Preparation of augetic porous structure

The polyurethane foam (PUF) was washed with ultrapure distilled water (D.I. Water) and ethanol and dried in an oven. Then, the polyurethane foam was placed in a frame box and heated in a press machine at 150° C. for 1 hour. The augitive polyurethane foam was cut to suit the purpose and used.

The GO solution was stirred at ambient temperature for 3 hours to obtain a homogeneous mixture. Then, the resulting mixture was poured into a dish with an augitive foam, and dried at 50° C. for 12 hours.

The result of the present invention was confirmed by the SEM of FIG. 1. 1(a) shows a polyurethane foam, FIG. 1(b) shows an augitive polyurethane foam, and FIG. 1(c) shows an augitive polyurethane foam coated with graphene oxide.

2 is a SEM photograph of a graphene-based augitive porous structure (10% compression, 20% compression) according to the present invention (10% A-PUF, 20% A-PUF, 10% GA-PUF, 20% GA- PUF).

If you look at the SEM images of 20% G-A-PUF and 10% G-A-PUF, you can see the wrinkled graphene oxide surface, which can be seen as a two-dimensional plane with negative Poisson ratio characteristics.

Example 1: Compression test of augetic porous structure

Fig. 3(a) is a diagram that is deformed during compression of a general polymer foam. Since a general foam has a positive Poisson's ratio, it expands in the transverse direction during vertical compression. However, as shown in Fig. 3(b), when compressed in the vertical direction, the augitive foam having a negative Poisson's ratio is also compressed in the horizontal direction.

3(c) is a graph showing the stress value at 50% strain, and it can be seen that the corrugated graphene oxide-coated augetic foam is the highest at 60 kPa, and the elasticity is considerably improved.

Existing polyurethane foam has a positive Poisson ratio (0.46), but the augitive foam according to the present invention has a negative Poisson ratio (-0.45). Due to this unique structural property, when 50% strain in the compression test , As shown in Fig. 3(c), the stress is 5.3kPa for the existing polyurethane and 60.67kPa for the GO-wrapped auxetic foam, which withstands a very large compressive force. In other words, a product in which the corrugated graphene oxide layer wraps the augetic structure than a product having an aggetic structure can withstand a significantly higher compressive force.

Therefore, the present invention can be used when applied to a harsh environment that endures high strain rates in the future. The present invention includes a technology capable of controlling a physical property called Poisson's ratio through control of a structure. In addition, it has a unique property of continuing flexibility while having the effect of strengthening the rigidity of graphene oxide. It is very advantageous for commercialization as it adjusts the Poisson's ratio of the material according to the target to be applied and the production cost is low.

Example 2: Measurement of the impact absorption rate of the augitive porous structure

The shock absorption rate of the prepared augitive porous structure was measured through a low-speed impact test.

The low-speed impact test was performed using CEAST 9350 (Instron) to test the performance as an impact absorbing material. A sandwich panel with a length and width of 60.0 mm was prepared for the impact test. The core (sample) thickness was 20 mm in all samples, and an Al plate having a thickness of 1T was placed on both the top and bottom of the sample to experiment with a sandwich structure. After placing an impactor of 2.13 kg on 40 cm of the sample, it was tested and dropped to 1.4 m/s.

A laser displacement sensor (Keyence, LK-031) and an NI-PXI data acquisition device (NI PXI 1042Q, PXI 6252 board) were used to measure the depression depth of the Al plate.

Fig. 4(a) is a graph of displacement-force, and Fig. 4(b) is a graph of time-force. Here, polyurethane foam (PUF), 10% compressed augetic foam (10% A-PUF), 20% compressed augetic foam (20% A-PUF), 10% compressed graphene oxide coated augetic Foam (10% GA-PUF), 20% compressed graphene oxide-organic foam (20% GA-PUF).

The conventional polyurethane foam used for shock absorption has the disadvantage of low durability and low shock absorption. However, it can be confirmed through the results of the low-speed impact test of FIG. 4 that the present invention overcomes such a disadvantage. Polyurethane showed an impact time of 9.62 seconds, and graphene oxide coated auxetic foam of 18.21 seconds. This shows a very high energy absorption capacity, as the shock absorption time has been increased by more than two times compared to the existing shock absorption foam. In addition, in the sandwich structure including the Al plate used in the low-speed impact test, the dent depth of the top Al plate affected by the impact was 0.6 mm, the polyurethane foam was 0.6 mm, and the graphene oxide-coated augitive foam (GO-wrapped). auxetic foam) is 0.15mm, and it can be seen that the core of the present invention is very excellent in shock absorption. Accordingly, durability is increased due to improved physical properties, and it has versatility because it can be easily cut, and it is possible to confirm the possibility of various application fields ranging from mechanical facilities, building structures, public facilities, and transportation means.

Example 3: Measurement of Poisson's ratio of augitive porous structure

For an experiment measuring Poisson's ratio, a sample of 80 mm length (80 mm x 20 mm x 20 mm) was uniformly pulled at a speed of 2 mm/s using a Zaber console.

5(a) and 5(b) are photographs of measuring Poisson's ratio of polyurethane foam and GO-wrapped auxetic foam (G-A-PUF). 5(c) is a graph showing the Poisson's ratio measurement result.

In the case of the polyurethane foam of FIG. 5(a), when a tensile load is applied in the axial direction and the length increases, the length in the lateral direction decreases, showing a positive Poisson value of about 0.46. And when pulling about 20% of the original length in the direction of the main axis, 20% A-PUF showed a negative Poisson value of about -0.5, and 10% A-PUF was about -0.3.

In the case of a sample coated with a graphene oxide layer, when tensile with a longitudinal strain of 20%, 20% GA-PUF has a Poisson's ratio, which is -0.45 and 10% GA-PUF is -0.3. . This is because the stiffness increases due to the graphene layer, and the twisted polyurethane wires are covered and connected by the graphene plate. As the strain ratio in the main axis direction increases, the Poisson's ratio decreases in all samples having augmentative structure, which can be seen that the augmentative properties vary depending on the tensile strength due to structural constraints.

Example 4: Measurement of vibration damping performance of an augitive porous structure

The vibration damping performance was measured using the apparatus as shown in FIG. 7.

The graphene-oxide coated augetic sponge shows very excellent performance as a vibration damping material. When the vibration damping material is attached to the cantilever beam and the frequency response function is viewed with an impact hammer, the density is increased compared to the existing polyurethane damping material and the natural frequency is lowered. In addition, it can be seen that the maximum amplitude is also somewhat reduced due to the effect of the corrugated graphene oxide layer.

FIG. 6(a) is a result of a frequency response function (FRF), and FIG. 6(b) is a graph showing a result of expanding the first resonant frequency among the results of (a).

Inertance = Accelerance = Acceleration/Force

Among the frequency response functions, inertance represents the motion as acceleration.

Comparing the damping ratio in FIG. 6(d), it can be seen that the polyurethane damping material is 2.34%, and the GO-wrapped auxetic foam is 4.89%, indicating that the energy dissipation capacity is also very improved. The above figure corresponds to a level that can replace the existing damping material.

Regarding the damping ratio, polyurethane foam was 2.34%, 10% A-PUF was 3.19%, 10% G-A-PUF was 4.16%, 20% A-PUF was 4.25%, and 20% G-A-PUF was 4.89%. The compression ratio increased by 10->20% to increase the density, or the graphene oxide coating layer acted as a constrained damping layer, resulting in a higher vibration damping ratio.

Example 5: Measurement of sound-absorbing performance of an augitive porous structure

In FIG. 8, samples (PUF, 10% A-PUF, 10% G-A-PUF, 20% A-PUF, 20% G-A-PUF) were measured for sound absorption coefficients by Bruel & Kjaer's impedance tube (type 4206). The closer the sound absorption coefficient is to 1, the better the sound absorption performance. Comparing the sound absorption coefficients of the samples with a thickness of 15 mm, the sound absorption performance of the augitive sound absorbing material from the low frequency band was far superior to that of the polyurethane foam. In particular, the sound absorption coefficient of 20% G-A-PUF at 2 kHz frequency is 0.984, which is the material absorbing 98.4% of the sound in the impedance tube.

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

110: impact hammer point
120: cantilever beam
130: sponge damper pad
140: FFT analyzer
150: portable computer (laptop)

Claims (8)

A method of manufacturing a graphene-based augitive porous structure comprising the following steps:
(a) triaxial thermal compression of the porous polymer sponge to prepare an augitive polymer sponge; And
(b) immersing the prepared augitive polymer sponge in a graphene oxide solution and drying it to coat a graphene oxide layer inside the augitive polymer sponge.
The method of claim 1, wherein the porous polymer sponge is selected from the group consisting of a polyurethane sponge, a polyester sponge, a polyethylene sponge, and a vinyl acetate sponge.
The method of claim 1, wherein the step (a) is thermally compressed at a temperature of 100 to 300°C.
The method of claim 1, wherein the step (a) uses hot pressing or frame equipment.
It is prepared by the method of claim 1 to claim 4, characterized in that the Poisson's ratio is -0.0 to -0,5 Graphene-based augmented porous structure.
An absorbent material comprising the graphene-based augetic porous structure of claim 5.
A sound-absorbing material comprising the graphene-based augetic porous structure of claim 5.
Vibration damping material comprising the graphene-based augetic porous structure of claim 5.

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