KR102100677B1 - Transparent composite and method of manufacturing the same - Google Patents

Abstract

A transparent composite material capable of replacing glass by securing transparent and excellent mechanical properties by matching the refractive index of the resin layer and the reinforcing fiber by applying the resin layer obtained by blending the polyester resin to the polycarbonate resin and the same. The manufacturing method is disclosed.
The transparent composite material according to the present invention includes a resin layer in which a polycarbonate resin and a polyester resin are mixed; And reinforcing fibers impregnated into the resin layer. Including, the reinforcing fiber has a first refractive index, the polycarbonate resin has a second refractive index greater than the first refractive index, the polyester resin has a third refractive index less than the first refractive index do.

Description

Transparent composite material and its manufacturing method {TRANSPARENT COMPOSITE AND METHOD OF MANUFACTURING THE SAME}

The present invention relates to a transparent composite material and a method for manufacturing the same, and more particularly, to a transparent composite material suitable for replacing glass by improving mechanical strength while ensuring transparency, and a method for manufacturing the same.

Recently, studies on plastics that can replace glass used in various fields have been actively conducted. In most cases, it is necessary to find a substitute material having excellent mechanical properties due to the inferior mechanical properties.

Currently, windowpanes used in automobiles have an area of approximately 3 to 4 m ² and a weight of approximately 30 to 35 kg.

In order to reduce the weight of automobile windowpanes, sunroofs, lamps, etc. in plastic materials, it is essential that the safety of passengers in the vehicle is guaranteed. Therefore, there is a need to improve the mechanical strength while using a plastic that can replace glass.

As a related prior document, Korean Patent Publication No. 10-2016-0107178 (published on September 13, 2016) discloses a fiber composite material and a manufacturing method thereof.

The object of the present invention is to replace the glass by ensuring excellent mechanical properties while being transparent by matching the refractive index of the resin layer and the reinforcing fibers by applying the resin layer obtained by blending the polyester resin to the polycarbonate resin, the same or similar. It is to provide a transparent composite material and a manufacturing method thereof.

A transparent composite material according to an embodiment of the present invention for achieving the above object is a resin layer in which a polycarbonate resin and a polyester resin are mixed; And reinforcing fibers impregnated into the resin layer. Including, the reinforcing fiber has a first refractive index, the polycarbonate resin has a second refractive index greater than the first refractive index, the polyester resin has a third refractive index less than the first refractive index do.

To achieve the above object, a method for manufacturing a transparent composite material according to an embodiment of the present invention includes: (a) dissolving a polycarbonate resin and a polyester resin in a solvent and drying to form a resin composition; (b) impregnating the reinforcing fiber with the resin composition; And (c) pressing the reinforcing fibers impregnated into the resin composition with a hot press; wherein the reinforcing fibers have a first refractive index, and the polycarbonate resin has a second refractive index greater than the first refractive index. , The polyester resin is characterized by having a third refractive index smaller than the first refractive index.

The transparent composite material according to the present invention and a method for manufacturing the same are obtained by manufacturing a resin layer through a blend of a polycarbonate resin and a polyester resin. While being secured, it is possible to improve mechanical strength by reinforcing fibers in a plate shape impregnated in the resin layer.

As a result, the transparent composite material according to the present invention and its manufacturing method have a structure in which a reinforcing fiber is impregnated in a resin layer, so that the weight is considerably lighter than that of glass, and yet it is possible to achieve lighter weight and transmittance of 75 to 90% and 100 to 300 MPa Since it has a tensile strength of, it is possible to secure mechanical strength while securing transparency, and it is possible to replace glass used in various fields, in addition to automotive glass applied to window glass, sunroof, and lamp.

1 is a cross-sectional view showing a transparent composite material according to an embodiment of the present invention.
Figure 2 is a process flow chart showing a transparent composite material manufacturing method according to an embodiment of the present invention.

Advantages and features of the present invention, and methods for achieving them will be clarified with reference to embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various different forms, and only the present embodiments allow the disclosure of the present invention to be complete, and common knowledge in the art to which the present invention pertains. It is provided to completely inform the person having the scope of the invention, and the present invention is only defined by the scope of the claims. The same reference numerals refer to the same components throughout the specification.

Hereinafter, a transparent composite material according to a preferred embodiment of the present invention and a method of manufacturing the same will be described in detail with reference to the accompanying drawings.

1 is a cross-sectional view showing a transparent composite material according to an embodiment of the present invention.

Referring to FIG. 1, the transparent composite material 100 according to an embodiment of the present invention includes a resin layer 120 and reinforcing fibers 140 impregnated in the resin layer 120.

Here, the resin layer 120 is a part forming the body of the transparent composite material 100, and a mixture of polycarbonate resin and polyester resin is used.

And, the reinforcing fiber 140 is impregnated in the resin layer 120, and has a structure that is inserted and disposed inside the resin layer 120.

Here, the reinforcing fiber 140 has a first refractive index of 1.54 ~ 1.58. At this time, the reinforcing fiber 140 is impregnated in the resin layer 120, and serves to reinforce mechanical strength. As the reinforcing fiber, at least one selected from glass fiber, basaltic fiber, and carbon fiber may be used, and it is preferable to use glass fiber. The glass fiber may be used without any particular limitation, such as a woven type, a nonwoven fabric, or a short fiber form, but it has a woven type sheet form, and it is more preferable that at least one is compressed by press compression.

In particular, the transparent composite material 100 according to an embodiment of the present invention by manufacturing the resin layer 120 through a blend of polycarbonate resin and polyester resin, the refractive index of the resin layer 120 is reinforced fiber 140 According to the same or similar matching of the refractive index of, it is possible to improve the mechanical strength by the reinforcement fibers 140 in the form of a plate impregnated in the resin layer 120 while ensuring transparency.

Here, the refractive index is an inherent value according to the polymer structure, and can be controlled by mixing unless phase separation between polymers occurs. Therefore, if the refractive index of the resin layer 120 manufactured by the blend of the polycarbonate resin and the polyester resin is matched to the refractive index of the reinforcing fiber 140, the refractive indexes are the same or similar to each other, so that they are different from each other. Although it is a material, it can lead to results that appear transparent like the same material.

As a result, as the transparent composite material 100 according to the embodiment of the present invention has a structure in which the reinforcing fibers 140 are impregnated in the resin layer 120, the weight is considerably lighter than that of glass, so that light weight can be achieved while transparency is achieved. It is possible to secure mechanical strength while securing it, and it is possible to replace glass used in various fields as well as automotive glass applied to window panes, sunroofs, lamps, and the like.

To this end, the polycarbonate resin has a second refractive index greater than the first refractive index, and more specifically, the second refractive index has 1.56 to 1.60.

In addition, the polyester resin has a third refractive index smaller than the first refractive index, and more specifically, the third refractive index has 1.52 to 1.56.

As a result, the resin layer 120 has a fourth refractive index by mixing a polycarbonate resin having a second refractive index and a polyester resin having a third refractive index, but the fourth refractive index is the same as the first refractive index, or the first refractive index The deviation from and may be less than 0.01.

At this time, the polycarbonate resin is excellent in heat resistance, impact resistance and transparency, and has the advantage of being easily processed. However, the polycarbonate resin has the disadvantages of poor glazing properties and susceptibility to scratch resistance. Therefore, when the resin layer is manufactured by using a polycarbonate resin, which is a thermoplastic resin that can be injection molded alone, there is a problem in that it is inadequate to replace with a windowpane, a sunroof, a lamp, etc. of a vehicle due to poor glazing properties and scratch resistance. .

On the other hand, in the present invention, in order to compensate for the disadvantages of using the polycarbonate resin alone, the resin layer 120 is a polyester resin having a refractive index smaller than the reinforcing fiber 140 in a polycarbonate resin having a refractive index larger than the reinforcing fiber 140. By using a mixture of the, by matching the refractive index of the resin layer 120 to the same or similar to the refractive index of the reinforcing fiber 140, it is possible to maintain transparency while securing mechanical strength by adding the reinforcing fiber 140. .

At this time, the polyester resin has good chemical resistance, weather resistance, high mechanical strength, and is resistant to thermal deformation and impact to such an extent that there is no deformation even at high temperature, and thus has excellent scratch resistance. Accordingly, when the polyester resin is blended with a polycarbonate resin, it is possible to supplement the glazing properties and scratch resistance.

These polycarbonate resins and polyester resins can be mixed in a manner that dissolves in a solvent. At this time, after the polycarbonate resin and the polyester resin are dissolved in a solvent and uniformly mixed, the solvent is volatilized and removed through a drying process.

At this time, it is preferable that the polycarbonate resin and the polyester resin are strictly controlled such that the polycarbonate resin and the polyester resin are mixed in a weight ratio of 40:60 to 60:40 in order to prevent phase separation between polymers.

That is, when mixing the polycarbonate resin and the polyester resin, when mixed uniformly like a polymer of the same kind, it is possible to realize transparent optical properties. If, when mixing the polycarbonate resin and the polyester resin is mixed outside the above weight ratio, due to phase separation occurs, the polymer may lose transparency and cause a problem that appears cloudy.

In other words, when the polycarbonate resin and the polyester resin are mixed in excess of or less than the weight ratio of 40:60 to 60:40, the matching between the refractive index of the resin layer 120 and the refractive index of the reinforcing fiber 140 is not achieved. By doing so, all of the reinforced fibers 140 impregnated in the resin layer 120 may cause a problem.

At this time, the resin layer 120 is preferably included in a content ratio of 30 to 70% by weight of the total weight of the transparent composite material (100). When the content of the resin layer 120 is less than 30% by weight of the total weight of the transparent composite material 100, mechanical strength increases due to an increase in the amount of the reinforcing fibers 140, but excessive addition of the reinforcing fibers 140 Due to this, the transmittance decreases sharply, which may lead to difficulties in securing transparency. Conversely, when the content of the resin layer 120 exceeds 70% by weight of the total weight of the transparent composite material 100, excellent transparency can be secured with an effect of improving transmittance, but the amount of reinforcement fiber 140 is relatively reduced. Difficulties in securing mechanical strength can be involved.

The transparent composite material according to the embodiment of the present invention described above, by manufacturing a resin layer through a blend of a polycarbonate resin and a polyester resin, the refractive index of the resin layer is matched to the refractive index of the reinforcing fiber is the same or similar, the transparency While it is possible to secure the mechanical strength by the plate-shaped reinforcing fibers impregnated in the resin layer.

As a result, the transparent composite material according to the embodiment of the present invention has a structure in which the reinforcing fibers are impregnated in the resin layer, so that the weight is considerably lighter than that of glass, and the light transmittance can be reduced to 75 to 90% and the transmittance of 100 to 300 MPa Since it has a tensile strength, it is possible to secure mechanical strength while ensuring transparency, and thus it is possible to replace glass used in various fields in addition to automotive glass applied to window glass, sunroof, lamp, and the like.

Hereinafter, a method of manufacturing a transparent composite material according to an embodiment of the present invention will be described with reference to the accompanying drawings.

3 is a process flow chart showing a method for manufacturing a transparent composite material according to an embodiment of the present invention.

Referring to FIG. 3, a method for manufacturing a transparent composite material according to an embodiment of the present invention includes a dissolving and drying step (S110), an impregnation step (S120) and a hot press step (S130).

Dissolving and drying

In the dissolving and drying step (S110), the polycarbonate resin and the polyester resin are dissolved in a solvent and dried to form a resin composition.

The polycarbonate resin has 1.56 to 1.60, and the polyester resin has 1.52 to 1.56.

At this time, the polycarbonate resin is excellent in heat resistance, impact resistance and transparency, and has the advantage of being easily processed, but has the disadvantages of poor glazing properties and susceptibility to scratch resistance.

On the other hand, the polyester resin has excellent chemical resistance, weather resistance, high mechanical strength, and has excellent scratch resistance because it is resistant to thermal deformation and impact to such an extent that there is no deformation even at high temperatures. Accordingly, when the polyester resin is blended with a polycarbonate resin, it is possible to supplement the glazing properties and scratch resistance.

As described above, in the present invention, in order to compensate for the disadvantages of using the polycarbonate resin alone, the polyester resin was dissolved in a solvent and dried to form a resin composition in a polycarbonate resin, which is a polyester resin having a refractive index smaller than that of the polycarbonate resin. It is to maintain the transparency while securing the mechanical strength by adding the reinforcing fibers by mixing the same or similar to the refractive index of the reinforcing fibers to be described later by mixing the resin composition.

In this step, the polycarbonate resin and the polyester resin can be mixed in a manner to dissolve in a solvent. At this time, after the polycarbonate resin and the polyester resin are dissolved in a solvent and uniformly mixed, the solvent is volatilized and removed through a drying process. At this time, the solvent is methylene chloride (methylene chloride), methyl ethyl ketone (Methyl ethyl ketone), N- methyl-2-pyrrolidone (N-Methyl-2-pyrrolidone), toluene (toluene), xylene (xylene) And one or more selected from acetone (acetone) may be used, of which methylene chloride (methylene chloride) is more preferable. Here, drying may be performed at 60 to 120 ° C. for 1 to 24 hours.

In particular, in this step, it is preferable that the polycarbonate resin and the polyester resin are strictly controlled such that the polycarbonate resin and the polyester resin are mixed in a weight ratio of 40:60 to 60:40 in order to prevent phase separation between polymers.

That is, when mixing the polycarbonate resin and the polyester resin, when mixed uniformly like a polymer of the same kind, it is possible to realize transparent optical properties. If the polycarbonate resin and the polyetherimide resin are mixed outside the above weight ratio when mixed, the phase separation may occur, causing the polymer to lose transparency and appear cloudy.

In other words, when the polycarbonate resin and the polyester resin are mixed in an amount exceeding or less than 40:60 to 60:40, the matching between the refractive index of the resin composition and the refractive index of the reinforcing fiber is not achieved, and thus the inside of the resin composition. All impregnated reinforcing fibers can cause problems.

Impregnation

In the impregnation step (S120), the reinforcing fibers are impregnated into the resin composition.

Reinforcing fibers are impregnated into the resin mixture, and serve to reinforce mechanical strength. As the reinforcing fiber, at least one selected from glass fiber, basaltic fiber, and carbon fiber may be used, and it is preferable to use glass fiber. The glass fiber may be used without any particular limitation, such as a woven type, a nonwoven fabric, or a short fiber form, but it has a woven type sheet form, and it is more preferable that at least one is compressed by press compression.

At this time, the reinforcing fiber has a refractive index of 1.54 ~ 1.58. Accordingly, the polycarbonate resin has a refractive index of 1.56 to 1.60 greater than the refractive index of the reinforcing fibers, and the polyester resin has a refractive index of 1.52 to 1.56 smaller than the refractive index of the reinforcing fibers.

In other words, as the resin composition is prepared by mixing a polycarbonate resin having a refractive index greater than the refractive index of the reinforcing fiber and a polyester resin having a refractive index smaller than the refractive index of the reinforcing fiber, the refractive index of the resin composition is adjusted to the refractive index of the reinforcing fiber. It can be matched with the same or similar, and as a result, it may be possible to maintain transparency while securing mechanical strength by adding reinforcing fibers.

Hot press

In the hot press step (S130), the reinforcing fibers impregnated with the resin composition are compressed with a hot press to form a transparent composite material.

Accordingly, the transparent composite material includes a resin layer made of a resin mixture and reinforcing fibers impregnated in the resin layer.

The resin layer is preferably included in a content ratio of 30 to 70% by weight of the total weight of the transparent composite material. When the content of the resin layer is less than 30% by weight of the total weight of the transparent composite material, the mechanical strength increases due to the relatively increase in the amount of reinforcing fibers, but due to the excessive addition of reinforcing fibers, the transmittance decreases rapidly, making it difficult to secure transparency. Can follow. Conversely, when the content of the resin layer exceeds 70% by weight of the total weight of the transparent composite material, excellent transparency can be secured by the effect of improving the transmittance, but it is relatively difficult to secure mechanical strength by reducing the amount of reinforcing fibers added. .

In addition, in this step, it is preferred that the hot press is performed at 140 to 200 ° C. for 10 to 60 minutes under a pressure of 10 to 30 MPa.

When the hot press temperature is less than 140 ° C or the hot press time is less than 10 minutes, there is a high possibility that sufficient curing is not achieved. Conversely, when the hot press temperature exceeds 200 ° C, or when the hot press time exceeds 60 minutes, not only does it act as a factor to increase only the manufacturing cost without a significant change in physical properties, there is a fear that the resin composition may be carbonized.

In addition, when the hot press pressure is less than 10 MPa, sufficient pressure may not be applied, and thus it may be difficult to secure mechanical strength. Conversely, when the hot press pressure exceeds 30 MPa, there is a concern that damage such as cracks may be applied to the resin layer due to excessive pressure.

The transparent composite material according to the embodiment of the present invention manufactured by the above process (S110 ~ S130) by manufacturing a resin layer through a blend of a polycarbonate resin and a polyester resin, the refractive index of the resin layer is the refractive index of the reinforcing fiber With the same or similar matching, it is possible to improve the mechanical strength by reinforcing fibers in a plate shape impregnated in the resin layer while ensuring transparency.

As a result, the transparent composite material produced by the method according to the embodiment of the present invention has a structure in which a reinforcing fiber is impregnated in a resin layer, so that the weight is considerably lighter than that of glass, and the light transmittance can be reduced to 75 to 90%. Since it has a tensile strength of 100 to 300 MPa, it is possible to secure mechanical strength while securing transparency, and it is possible to replace glass used in various fields, in addition to automotive glass applied to window panes, sunroofs, and lamps.

Example

Hereinafter, the configuration and operation of the present invention through a preferred embodiment of the present invention will be described in more detail. However, this is provided as a preferred example of the present invention and cannot be interpreted as limiting the present invention by any means.

The contents not described here will be sufficiently technically inferred by those skilled in the art, and thus the description thereof will be omitted.

1. Specimen preparation

Example  One

A polycarbonate resin having a refractive index of 1.586 and a polyester resin having a refractive index of 1.54 are mixed in a weight ratio of 51:49, dissolved in methylene chloride, and dried at 70 ° C. for 12 hours to obtain a resin mixture having a refractive index of 1.563. Was prepared.

Next, after impregnating the glass fiber at a ratio of 40 wt% of the glass fiber having a refractive index of 1.56 and 60 wt% of the resin mixture, a transparent composite was prepared by pressing with a hot press at a pressure of 20 MPa at 170 ° C. for 40 minutes. . Here, the glass fiber has a woven type sheet form, and four sheets are pressed by press bonding.

Example  2

A transparent composite specimen was prepared in the same manner as in Example 1, except that the glass fiber was impregnated into the resin mixture at a ratio of 60 wt% glass fiber and 40 wt% resin mixture.

Example  3

A transparent composite specimen was prepared in the same manner as in Example 1, except that the glass fiber was impregnated into the resin mixture at a ratio of 30 wt% glass fiber and 70 wt% resin mixture.

Example  4

The polycarbonate resin and the polyester resin were mixed in a weight ratio of 51:49, dissolved in methylene chloride, and dried at 70 ° C. for 12 hours to prepare a resin mixture having a refractive index of 1.564. A transparent composite specimen was prepared in the same manner as in Example 1.

Comparative example  One

After the polycarbonate resin having a refractive index of 1.585 was melted at 180 ° C., injection molding was performed to prepare a specimen of a transparent resin molded product.

Comparative example  2

A transparent composite material was impregnated with polycarbonate resin at a ratio of 40 wt% of glass fibers having a refractive index of 1.56 and 60 wt% of a polycarbonate resin having a refractive index of 1.585, followed by pressing with a hot press at 165 ° C for 25 minutes under a pressure of 25 MPa for a transparent composite material Specimens were prepared. Here, the glass fiber has a woven type sheet form, and four sheets are pressed by press bonding.

Comparative example  3

A transparent composite specimen was prepared in the same manner as in Example 1, except that the glass fiber was impregnated into the resin mixture at a ratio of 10 wt% glass fiber and 90 wt% resin mixture.

Comparative example  4

A transparent composite specimen was prepared in the same manner as in Example 1, except that the glass fiber was impregnated into the resin mixture at a ratio of 80 wt% glass fiber and 20 wt% resin mixture.

2. Property evaluation

Table 1 shows the results of evaluation of the physical properties of the specimens prepared according to Examples 1 to 4 and Comparative Examples 1 to 4.

1) Transmittance and haze

Transmittance and haze were measured using a spectrophotometer.

2) Tensile strength, tensile modulus and tensile elongation

Tensile strength, tensile modulus and tensile elongation were respectively measured according to ASTM D638 standard.

[Table 1]

As shown in Table 1, it can be seen that in the case of the specimens prepared according to Examples 1 to 4, 75 to 90% and transmittance corresponding to the target value, and tensile strengths of 100 to 300 MPa are all satisfied.

At this time, in the case of the specimens prepared according to Examples 1 to 4, as the content of the resin composition increases, the transmittance increases and the haze tends to decrease, which is advantageous for securing transparency, but the tensile strength and tensile modulus are lowered. have. Based on this, it was confirmed that the specimen prepared according to Example 2 was able to secure mechanical properties to the maximum while maintaining optical properties, and thus was most suitable for replacing glass.

On the other hand, in the case of the specimen prepared according to Comparative Example 1, the transmittance was found to be a fairly high value of 97%, but the tensile strength was only 65 MPa, confirming that the strength was too weak to replace the glass.

In addition, in the case of the specimen prepared according to Comparative Example 2 using a polycarbonate resin alone, the transmittance was considerably low, and the haze value was quite high, and thus it was confirmed that the transparency was poor, which was due to the use of the polycarbonate resin alone. It is believed that this is due to the inability to match the refractive index with the glass fiber.

In addition, in the case of the specimen prepared according to Comparative Example 3, the transmittance was high, the haze value was low, and the transparency was good, but it could be confirmed that the tensile strength was less than the target value.

In addition, in the case of the specimen prepared according to Comparative Example 4, the tensile strength was measured to the highest value, but it can be confirmed that the transparency is not good.

In the above, the embodiments of the present invention have been mainly described, but various changes or modifications can be made at the level of a person skilled in the art to which the present invention pertains. Such changes and modifications can be said to belong to the present invention without departing from the scope of the technical idea provided by the present invention. Therefore, the scope of the present invention should be judged by the claims set forth below.

100: transparent composite material
120: resin layer
140: reinforced fiber
S110: dissolution and drying step
S120: impregnation step
S130: hot press step

Claims (11)

A resin layer in which polycarbonate resin and polyester resin are mixed; And
Reinforced fibers impregnated into the resin layer; As a transparent composite material containing,
The reinforcing fiber has a first refractive index, the polycarbonate resin has a second refractive index greater than the first refractive index, the polyester resin has a third refractive index less than the first refractive index,
The resin layer contains 30 to 70% by weight of the total weight of the transparent composite, the polycarbonate resin and polyester resin are mixed in a weight ratio of 40:60 to 60:40,
The reinforcing fiber has a woven type sheet shape, and at least one or more transparent composite materials in which glass fibers compressed by press compression are used.
According to claim 1,
The resin layer
The polycarbonate resin having the second refractive index and the polyester resin having the third refractive index are mixed to have a fourth refractive index,
The fourth refractive index is the same as the first refractive index, or a deviation from the first refractive index is a transparent composite material of 0.01 or less.
According to claim 1,
The first refractive index is 1.54 ~ 1.58,
The second refractive index is 1.56 ~ 1.60,
The third refractive index is a transparent composite material of 1.52 ~ 1.56.
delete delete According to claim 1,
The transparent composite material
A transparent composite material with a transmittance of 75 to 90% and a tensile strength of 100 to 300 MPa.
(a) dissolving a polycarbonate resin and a polyester resin in a solvent and drying to form a resin composition;
(b) impregnating the reinforcing fiber with the resin composition; And
(c) forming a transparent composite material by compressing reinforcing fibers impregnated with the resin composition with a hot press;
The reinforcing fiber has a first refractive index, the polycarbonate resin has a second refractive index greater than the first refractive index, and the polyester resin has a third refractive index less than the first refractive index,
The resin composition contains 30 to 70% by weight of the total weight of the transparent composite, the polycarbonate resin and polyester resin are mixed in a weight ratio of 40:60 to 60:40,
The reinforcing fiber has a woven type sheet form, and at least one or more glass composites are used, which are compressed by press compression.
The method of claim 7,
The first refractive index is 1.54 ~ 1.58,
The second refractive index is 1.56 ~ 1.60,
The third refractive index is 1.52 ~ 1.56 method of manufacturing a transparent composite material.
The method of claim 7,
In step (a),
The solvent
Methylene chloride, methyl ethyl ketone, N-methyl-2-pyrrolidone, toluene, xylene and acetone Transparent composite material manufacturing method comprising at least one selected from.
delete The method of claim 7,
In step (c),
The hot press
A method of manufacturing a transparent composite material performed at 140 to 200 ° C. for 10 to 60 minutes under a pressure of 10 to 30 MPa.

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