KR101436371B1 - Method by using interface for preparing aerogel reinforced composite material - Google Patents

Abstract

The hydrophobic airgel is formed at an interface with the hydrophilic aqueous solution and then stirred at an appropriate temperature and speed to prevent the pores in the airgel from being impregnated with the resin and to minimize the material content other than the airgel to maintain a high porosity and low thermal conductivity And a method of manufacturing the same. Accordingly, the pores of the aerogels mixed in the aerogel composite material, which may be generated when the aerogel composite material is produced by the conventional melt compounding method in which particles to be mixed are injected after heating at a temperature higher than the melting temperature of the resin, It is possible to prevent the porosity from being impaired by the impregnation with the resin to obtain the airgel composite material with low thermal conductivity.

Description

TECHNICAL FIELD [0001] The present invention relates to a method for manufacturing an aerogel composite material using an interface,

The present invention relates to a method of manufacturing an aerogel using an interface, and more particularly, to a method of manufacturing an aerogel reinforced plastic by preventing deterioration of the porosity of an incorporated airgel, The present invention relates to a method of manufacturing an airgel composite material and an airgel composite material produced thereby.

Energy conservation can solve global environmental problems such as global warming, oil price increase and carbon dioxide regulation, and insulating material is an important factor for realizing efficient energy saving. Therefore, interest in aerogels having the lowest thermal conductivity in human history has increased. .

Aerogels were found in the early 1930s by Kistler as dried gels with high air porosity. Silica aerogels were first synthesized by low temperature sol-gel chemistry, and aerogels have received great interest because of their potential for commercialization in the last 20 years.

Aerogels composed of open pores with nanoparticles of 1 to 100 nm have a high specific surface area of 500-1200 m ² / g, a low dielectric constant of 1.1 to 2.0 and a thermal conductivity of 0.013 to 0.14 W / m · K. Because of its excellent heat insulation performance, aerogels can be applied to heat insulation materials such as space heat protection, nuclear reactors, and steam pipes. Accordingly, there is a demand in the industry for a technique for making various composite materials having an insulating performance using aerogels, utilizing such performance of aerogels.

Meanwhile, in connection with the technology for producing a composite material, generally, a particle-containing composite material can be manufactured by various methods depending on the characteristics of the raw material and the intended use, size and shape of the composite material. Among them, The method is a typical method of molding various types of particle-incorporated composites. In the melt compounding method, the resin is heated and melted at a temperature higher than the melting temperature, and particles to be mixed with the resin are injected and molded.

However, aerogels in the form of particles or granules are easily broken due to their high porosity, so that it is not easy to composite them. When the aerogel composite is manufactured, the pores inside the aerogels must be preserved to maintain the low thermal conductivity of the aerogels. Therefore, the aerogel composite material needs a proper molding method different from the general melt-mixing manufacturing method.

10-2010-0036104 10-2009-0078357

D. Ge, L. Yang, Y. Li, J. Zhao. Journal of Non-Crystalline Solids, 355, 2610 (2009) N. Gupta, W. Ricci. Journal of Materials Processing Technology, 198, 178 (2008)

The present invention relates to a method for producing a composite material by mixing an aerogel and other materials, which prevents particles of an aerogel from being destroyed by not using a conventional method for melting and mixing particles, And to maintain a heat insulating performance of the airgel.

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-described technical problems, and it is an object of the present invention to provide a method of manufacturing an aerogel composite material by forming an interface in a state of phase separation from each other by using a hydrophilic material capable of forming an interface with an aerogel, The air porosity of the airgel can be prevented from being lowered even after the material is produced, so that the heat insulating performance can be maintained.

More specifically, the present invention relates to a method for producing an aerogel composite material using a hydrophobic aerogel and other materials, comprising the steps of: using a hydrophilic aqueous solution as the another material to form an interface between the hydrophobic aerogel and a hydrophilic aqueous solution; A method for manufacturing an aerogel composite material is provided.

At this time, the method further includes a step of stirring after the formation of the interface, whereby the water in the aqueous solution is evaporated.

As the hydrophobic aerogels, silica airgel or carbon aerogels can be used. As the hydrophilic aqueous solution, for example, polyvinyl alcohol (PVA) aqueous solution can be used. The internal porosity of the aerogels used is preferably at least 90 vol%, more preferably at least 99 vol%.

The aqueous solution of polyvinyl alcohol (PVA) can be adjusted to an appropriate concentration in consideration of the characteristics of the interfacial formation with the airgel and the subsequent stirring step. The concentration of the polyvinyl alcohol is not particularly limited, but can be adjusted in the range of approximately 0.1 wt% to 50 wt%.

Polyvinyl alcohol (PVA) resin is deposited at the interface with the airgel by the evaporation of water as a solvent in an aqueous solution of polyvinyl alcohol (PVA). The porosity of the airgel mixed into the airgel composite and the porosity of the airgel composite The content of polyvinyl alcohol (PVA) resin and the like are taken into account and the stirring temperature and speed are appropriately controlled. The stirring temperature is preferably selected from room temperature to 350 DEG C, and the stirring speed is preferably greater than 1 rpm and less than 50000 rpm, but is not particularly limited.

The volume fraction of the airgel (airgel / polyvinyl alcohol) can be appropriately adjusted. In order to exert some performance of the airgel, the volume fraction of the airgel is preferably selected within the range of 5 vol% to 99 vol% More preferably greater than 10 vol.%.

The aerogel composite material produced by the above method substantially retains the characteristics of the airgel before being formed into a composite material, that is, the porosity and the low thermal conductivity. Accordingly, the aerogel composite material produced by the above-described method provided by the present invention can have a low thermal conductivity of about 0.04 W / m · K or less, more preferably 0.01 W / m · K or less.

According to the present invention, when the aerogel composite material is manufactured by a method of appropriately stirring using an interface formed between an airgel and an aqueous solution, a melt compounding method of injecting particles to be mixed by heating at a temperature higher than the melting temperature of the resin There is a disadvantage that may occur when the airgel composite material is impregnated with the airgel composite material, that is, the pores of the aerogel composite material are impregnated with the resin to lower the porosity and the thermal conductivity of the airgel composite material is lowered, .

That is, according to the present invention, by forming an interface between a hydrophobic aerogel and a hydrophilic aqueous solution, for example, an aqueous solution of polyvinyl alcohol (PVA), the aerogel composite material is appropriately stirred to form an interface of 0.001-0.04 W / m · An airgel composite material with a low thermal conductivity of about K can be produced.

FIG. 1 shows the interface formation of an aqueous solution of an aerogel and a polyvinyl alcohol (PVA) in an embodiment of the present invention. FIG. 1 shows that the aqueous solution of aerogels and polyvinyl alcohol (PVA) It is a photograph.
2 is a photograph showing the shape of the aerogel composite material produced in the embodiment of the present invention.
Figure 3 is a photograph showing the presence of pores in the aerogels incorporated into the manufactured aerogel composite material in an embodiment of the present invention.

Hereinafter, the present invention will be described in more detail with reference to embodiments of the present invention.

1. Examples of the aerogel composite material of the present invention

a. material

To prepare the airgel composite, a silica airgel purchased from Empower was prepared. A polyvinyl alcohol (PVA, molecular weight: 22,000) powder purchased from Daejung Chemical (PVA 500) was prepared.

The physical properties of the aerogels used are shown in the following table.

Thermal conductivity
(thermal conductivity)
0.02 W / m · K
Density
0.05 g / cm ³
Thermal stability
(thermal stability)
-200 to 450 ° C
Porosity
90% Particle distribution 1 to 10 m (> 95%) Pore distribution ≪ 20 nm (average 9 nm)

b. Preparation of aqueous solution of polyvinyl alcohol (PVA)

Polyvinyl alcohol (PVA) powder prepared by dissolving prepared polyvinyl alcohol (PVA) powders in distilled water at 60 ℃ in distilled water at a stirring speed of 200 rpm was used to prepare 5 wt% aqueous solution of polyvinyl alcohol (PVA).

c. Interfacial formation of aerogels and polyvinyl alcohol (PVA)

Under the normal temperature and normal pressure conditions, 500 ml of an aqueous solution of polyvinyl alcohol (PVA) prepared in a beaker was loaded with the same volume of silica airgel particles. At this time, an interface was formed between a hydrophilic aqueous solution of polyvinyl alcohol (PVA) and a hydrophobic silica airgel, and phase-separated. A picture of the phase-separated state is shown in Fig.

FIG. 1 shows the interfacial formation of an aqueous solution of an aerogel and a polyvinyl alcohol (PVA) in an embodiment of the present invention, and shows that the aqueous solution of aerogels and polyvinyl alcohol (PVA) are clearly phase-separated .

d. Aerogel composite manufacturing

Polyvinyl alcohol (PVA) aqueous solution and silica airgel having an interface were stirred at a speed of 200 rpm while being heated at 60 ° C on a hot plate. The mixture was stirred for 48 hours to prepare an aerogel composite material containing silica airgel in polyvinyl alcohol (PVA) resin.

2 is a photograph showing the shape of the aerogel composite material produced. It can be seen that a suitable polyvinyl alcohol (PVA) concentration is maintained, and an appropriate stirring temperature and speed are applied, thereby making the produced airgel composite while maintaining a desired airgel content and a high air porosity of the airgel.

e. Analysis of pore characteristics

The microstructure of the prepared aerogel composite material was confirmed by scanning electron microscope (JEOL, scanning electron microscope, FE-SEM JSM-6390LV model). As shown in FIG. 3, it can be seen that pores in the aerogels mixed in the manufactured aerogel composite material are well preserved.

f. Thermal conductivity measurement

The thermal conductivity of the manufactured airgel composite material was measured using a thermal conductivity analyzer (Thermal analyzer, Thermo Labo II-KES-F7 model, KATO TECH Co., Ltd., Japan).

The measurement was made according to the following method.

Heat is generated in a thermal plate (solid copper plate) with an area of 9 cm ² and a mass of 9.79 g with a heat capacity of 4.186 × 10 ³ JK ^-1 m ^-2 . By contacting the top surface of the sample with a thermal plate, the stored calories are transferred to the cold sample. The measured value is the peak value of heat transfer q max after 0.2 seconds of contact.

* q max is proportional to the temperature deviation between the thermal plate temperature and the sample temperature, and also to the contact pressure. When the plate is 90 g and the contact area is 9 cm ² , a condition of 10 gf / cm ³ is used as a standard test condition.

* Thus, the measurement proceeded as follows.

i) Set the water box temperature to room temperature.

ii) Place a 5 x 5 cm sample on the water box and place the thermal plate on top of the sample.

iii) After reaching a constant value, read the heat flow loss W of the thermal plate.

iv) The thermal conductivity K is calculated from the above equation

At this time, the contact pressure is set to 6 g / cm < ² >, and the temperature of the thermal plate is adjusted in an error range smaller than 0.1 DEG C.

As a result of measurement by the above method, the thermal conductivity of the aerogel composite material produced in the above example was 0.02 W / m · K.

g. Results analysis of the example

It was confirmed that the thermal conductivity of the airgel was the same as the value of the thermal conductivity of the airgel before forming the composite material.

This is because it does not follow the rule of mixture and the thermal conductivity is mixed with PVA which is 10 times larger than that of aerogels. However, maintaining low thermal conductivity maintains the pores inside the airgel, This is because the transfer of the phonon, the main mediator of heat transfer, is delayed by the thermal interface resistance that occurs when it is put in.

In addition, when composites including the above-mentioned interface forming step, by adjusting the ratio of the use of the airgel and the PVA and the reaction conditions (pressure, temperature, stirring speed, etc.), the volume fraction of the airgel and the The porosity can be controlled and it is possible to maintain the effect of the low thermal conductivity of the aerogels used as much as possible even after the composite material is formed. For example, when the stirring temperature is 80 ° C and the stirring speed is 200 rpm, the volume fraction of the airgel is 99 vol% and the porosity of the inside of the airgel is 99 vol%, which is preferable in order to maintain the thermal conductivity of the airgel composite .

2. Comparative Example

In general, studies on the production of aerogel composites using epoxy, which is a resin capable of maximizing the incorporation rate of filler as compared with melting compounding, have been carried out. As a control for the present invention, aerogels / epoxy (Kukdo Chemical, YD 128, IPDA) composite material, and the results are summarized in Table 1.

As can be seen in Table 1, the thermal conductivity of the aerogel / epoxy composites was less than 0.27 W / m · K, the thermal conductivity of the epoxy resin used at 0.112 W / m · K at 0.123 W / m · K, Which is much larger than 0.02 W / m · K. This is because the epoxy resin penetrates into the airgel pores and the porosity of the composite material is lowered.

The thermal conductivity of the plasma-treated aerogel / epoxy composite material is 0.085 W / m < 2 >. As shown in Table 1, the thermal conductivity of the plasma- K of 0.11 W / mK. These results have been mentioned in the study of Ge et al.

Journal of Non-Crystalline Solids 355 2610-2615 (2009)

Aerogel (Vol%) Epoxy (Vol%) Plasma treatment of aerogels Composite Thermal Conductivity (W / m · K) 25 75 X 0.112 50 50 X 0.123 75 25 X 0.113 25 75 O 0.085 50 50 O 0.087 75 25 O 0.110

Claims (9)

A method for producing an aerogel composite material using a hydrophobic aerogel and other materials, comprising the step of using a hydrophilic aqueous solution as said another material and forming an interface between said hydrophobic aerogel and a hydrophilic aqueous solution . 2. The method of claim 1, comprising the step of stirring after the interface is formed. The method of claim 1 or 2, wherein the hydrophobic aerogels are silica airgel or carbon aerogels. [Claim 5] The method according to claim 3, wherein the hydrophilic aqueous solution is an aqueous solution of polyvinyl alcohol (PVA). [6] The method of claim 4, wherein the concentration of the polyvinyl alcohol is controlled at 0.1 wt% to 50 wt%. The method of claim 1, wherein the volume fraction between the aerogels and the hydrophilic aqueous solution during the interfacial formation is controlled to within 5 vol% to 99 vol%. The method of claim 2,
Wherein the volume fraction of the aerogels in the aerogel composite material and the porosity of the inside of the aerogels are adjusted by changing the stirring temperature and the stirring speed in the stirring step. The method according to claim 7, wherein the stirring temperature is from room temperature to 350 ° C, and the stirring speed is from 1 rpm to 50,000 rpm. An aerogel composite material produced by the method of claim 1.

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