KR102453290B1 - Carbon fiber composites with improved strength transfer rate and munufacturing method thereof and pressure vessel including the same - Google Patents

Abstract

The carbon fiber composite material with improved strength transfer rate according to an embodiment of the present invention is an epoxy resin composition including an epoxy resin, a curing agent mixture, and a catalyst impregnated in carbon fibers and cured, and has a strength transfer rate of 95% or more When applied to a container, it has high storage efficiency and can store the same amount of fuel even with a small amount of composite material, making it possible to reduce the weight and size of the pressure container, and is particularly suitable for a hydrogen pressure container that can store hydrogen.

Description

Carbon fiber composite material with improved strength transfer rate, manufacturing method thereof, and pressure vessel including the same

The present invention relates to a carbon fiber composite material comprising an epoxy resin composition, and more specifically, to a carbon fiber composite material comprising an epoxy resin composition having an improved strength transfer rate. It relates to a carbon fiber composite material having an improved strength transition rate capable of storing the same amount of fuel even with the amount of material, a method for manufacturing the same, and a pressure vessel including the same.

Recently, as the use of alternative fuel gas is gradually accelerated, the development of a pressure vessel for storing high-pressure gas continues, and accordingly, the field of application is also expanding. As such, according to the expansion of the field of application, alternative fuel gas is applied not only to the conventional large pressure vessel but also to a moving means such as an automobile, and the pressure vessel is mounted in various ways.

Such a pressure vessel is generally a structure that can contain a liquid, liquefied gas, condensed gas, etc. under a predetermined pressure, and may include a storage vessel, a pipe, a structure exposed to a temporary increase in pressure, and the like. The pressure vessel is composed of an outer composite layer that supports most of the internal pressure and a liner that provides an inner frame. Traditionally, the liner is made of metal. At the same time, there is a problem that the manufacturing cost is high. In particular, the pressure vessel generates a very high internal pressure when gas or liquid is filled inside, and when the filled gas or liquid is used, the internal pressure decreases and pressure changes occur continuously and repeatedly, so it has excellent durability against pressure changes. is required

In order to solve this problem, a technology for applying a reinforcing fiber such as carbon fiber or glass fiber to a pressure vessel is being developed. Fiber-reinforced composite materials composed of reinforcing fibers such as carbon fibers, glass fibers, and aramid fibers and thermosetting resins such as epoxy resins and phenolic resins are lightweight and have excellent mechanical properties such as strength and rigidity, heat resistance, and corrosion resistance. It is applied to numerous fields such as automobiles, ships, civil construction and sporting goods, and research on improving pressure vessels through the physical properties of these composite materials is in progress. As such, the use of a pressure vessel in which a reinforcing fiber such as carbon fiber or glass fiber is impregnated in a resin and then wound or laminated on the outside of a plastic liner is increasing. As an example, as an invention in which a composite material is applied to the structure of a pressure vessel, Korean Patent Application Laid-Open No. 10-2017-0140574 is an invention related to a hydrogen storage pressure vessel used as a fuel vessel for a vehicle, and a hydrogen storage pressure vessel using a composite material and carbon fiber Describes the technology to make it.

However, the pressure vessel manufactured using the fiber-reinforced composite material has a low productivity because the thickness of the composite layer is thick. In particular, the hydrogen pressure vessel (CHG Tank) mounted on a hydrogen fuel cell vehicle (FCEV) has a thick composite material layer, so it is easy to create voids in the composite material layer when manufacturing the pressure vessel, and has a higher curing temperature and longer curing than other pressure vessels. It may take time and reduce productivity. In addition, thermosetting resins such as epoxy resins and phenolic resins are used for the composite layer, and while mechanical properties such as strength and rigidity, heat resistance, and corrosion resistance are excellent, safety is prioritized due to brittleness and low toughness. It is a big disadvantage. In addition, the pressure vessel requires high hydrogen storage efficiency (ratio of the weight of hydrogen that can be stored to the total weight of the container) as well as low manufacturing cost, so a composite system that can store more hydrogen with a smaller amount of composite material than before is required. is increasing

Korean Patent Publication No. 10-2017-0140574

The present invention has been proposed to solve the problems of the prior art as described above, and the problem to be solved by the present invention is that it has high storage efficiency when applied to a pressure vessel, so that the same or larger amount of Carbon fiber composite material with improved strength transfer rate suitable for hydrogen pressure vessel and its manufacturing method and It is to provide a pressure vessel including this.

These and other objects and advantages of the present invention will become apparent from the following description of preferred embodiments.

The above object is a carbon fiber composite material obtained by hardening carbon fiber impregnated with an epoxy resin composition, which satisfies the following Equation 1,

(Equation 1)

STR(%) = F _A x 100/ (F _B x V _f )≥ 95%

Here, STR (%) is the strength transition rate, _{FA is the measured value of the tensile strength of the 0° unidirectional carbon fiber composite material, F B is} the measured value of the tensile strength of the carbon fiber strand, and V _f is the measured value of the _FA measurement specimen. It is achieved by the carbon fiber composite material, which is the carbon fiber volume ratio, and the strength transfer rate is improved.

Here, the epoxy resin composition may include an epoxy resin, a curing agent mixture, and a catalyst, and may be a cured product cured at 120° C. for 1 hour after raising the temperature from room temperature to 120° C. for 1 hour.

Preferably, the cured product of the epoxy resin composition may have an elongation of 4 to 8%.

Preferably, the cured product of the epoxy resin composition may have a glass transition temperature of 100 to 140°C.

Preferably, the carbon fiber has a specific gravity of 1,7 to 1.9, and may be composed of 1,000 to 300,000 filaments.

Preferably, the tensile strength of the carbon fiber composite material may be 2,500 to 3,500 MPa.

Preferably, the epoxy resin may include at least one of bisphenol A-type epoxy, bisphenol F-type epoxy, novolak epoxy, flame-retardant epoxy, cyclic aliphatic epoxy, and rubber-modified epoxy.

Preferably, the epoxy resin has two or more epoxy groups in one molecule and may have an equivalent weight of 150 to 340 g/eq.

Preferably, the curing agent mixture may include an aliphatic amine and an amine having two or more cyclic structures, and more preferably, the weight ratio of the aliphatic amine to the amine having two or more cyclic structures is 1:2 to 3 days. can

Preferably, the catalyst may be a low-temperature imidazole catalyst.

Preferably, the carbon fiber composite material may include 65 to 80% by weight of carbon fibers, 14 to 27% by weight of bisphenol A epoxy, 4 to 10% by weight of a curing agent mixture, and 0.1 to 1% by weight of a catalyst.

In addition, the above object, a first step of preparing an epoxy resin composition, a second step of impregnating the carbon fiber with the prepared epoxy resin composition, and a third step of curing the carbon fiber impregnated with the epoxy resin composition. The yield is achieved by a method for producing an improved carbon fiber composite material.

Preferably, the second step may be a step of impregnating the carbon fiber into the epoxy resin composition in a state in which tension is applied, and the third step may be a step of curing the epoxy resin composition in a state in which the carbon fiber tension is maintained.

Preferably, the third step may be a step of heating the carbon fiber impregnated with the epoxy resin composition from room temperature to 120° C. for 1 hour and then curing the carbon fiber at 120° C. for 1 hour.

In addition, the above object includes a liner (liner) including a fuel inlet and a fuel discharge port and capable of storing fuel, and an exterior material surrounding the outer circumferential surface of the liner, wherein the exterior material includes an epoxy resin, a curing agent mixture, a catalyst and carbon fiber and the curing agent mixture includes an aliphatic amine and an amine having two or more cyclic structures, and the catalyst is achieved by a pressure vessel which is a low-temperature imidazole catalyst.

Here, the exterior material satisfies the following Equation 1 after raising the temperature from room temperature to 120° C. for 1 hour and then curing at 120° C. for 1 hour,

(Equation 1)

STR(%) = F _A x 100/ (F _B x V _f )≥ 95%

Here, STR (%) is the strength transition rate, _{FA is the measured value of the tensile strength of the 0° unidirectional carbon fiber composite material, F B is} the measured value of the tensile strength of the carbon fiber strand, and V _f is the measured value of the _FA measurement specimen. It is preferable that it is a carbon fiber volume ratio.

Preferably, the exterior material contains 65 to 80% by weight of carbon fibers, 14 to 27% by weight of bisphenol A epoxy, 4 to 10% by weight of a curing agent mixture, and 0.1 to 1% by weight of a catalyst.

The above-described pressure vessel is preferably a pressure vessel for storing hydrogen as fuel.

According to the carbon fiber composite material with improved strength transfer rate and the manufacturing method thereof according to an embodiment of the present invention, the carbon fiber composite material has excellent strength transfer rate and has high storage efficiency when applied to a pressure vessel. There are effects such as being able to store the same or a larger amount of fuel even when using

In addition, according to the present invention, it is possible to reduce the size and weight of the pressure vessel, and there are effects such as being able to reduce the manufacturing cost.

In addition, according to the present invention, there are effects such as being suitable for a hydrogen pressure vessel capable of storing hydrogen.

However, the effects of the present invention are not limited to the above-mentioned effects, and other effects not mentioned will be clearly understood by those skilled in the art from the following description.

1 is a flowchart illustrating a method of manufacturing a carbon fiber composite material having an improved strength transfer rate according to another aspect of the present invention.
2 is a perspective view of a pressure vessel according to an embodiment of the present invention.
FIG. 3 is a cross-sectional view taken along the line II-II of FIG. 1 .

With reference to the accompanying drawings, embodiments of the present invention will be described in detail so that those of ordinary skill in the art to which the present invention pertains can easily implement them. However, the present invention may be embodied in several different forms and is not limited to the embodiments described herein.

In order to clearly express various layers and regions in the drawings, the thicknesses are enlarged. Throughout the specification, like reference numerals are assigned to similar parts. When a part of a layer, film, region, plate, etc. is said to be “on” another part, it includes not only cases where it is “directly on” another part, but also cases where there is another part in between. Conversely, when we say that a part is "just above" another part, we mean that there is no other part in the middle.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In case of conflict, the present specification, including definitions, will control. Also, although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described herein.

The carbon fiber composite material having an improved strength transfer rate according to an aspect of the present invention includes an epoxy resin composition and a carbon fiber, and has a form in which the carbon fiber is impregnated with the epoxy resin composition and cured.

In one embodiment, the epoxy resin composition impregnated into the carbon fiber and cured includes an epoxy resin, a curing agent mixture, and a catalyst.

In one embodiment, the epoxy resin is a liquid epoxy resin, and preferably includes at least one of bisphenol A-type epoxy, bisphenol F-type epoxy, novolak epoxy, flame retardant epoxy, cyclic aliphatic epoxy, and rubber-modified epoxy.

In addition, it is preferable that the epoxy resin has two or more epoxy groups in one molecule and has an equivalent weight of 150 to 340 g/eq. As such, when an epoxy resin having an equivalent weight of 150 to 340 g/eq and having two or more epoxy groups in one molecule is included, the viscosity of the final epoxy resin composition can be lowered, and handling and impregnation with carbon fiber bundles are easy, as well as The heat resistance of the cured product is also excellent. On the other hand, when the equivalent weight of the epoxy resin is less than 150 g / eq, there is a problem in that the brittleness of the cured product increases, and when it exceeds 340 g / eq, the viscosity of the resin composition is high and the handleability or impregnation property is poor.

In one embodiment, the epoxy resin preferably includes 14 to 27% by weight of the total 100% by weight of the carbon fiber composite material to be manufactured. This is because, when the epoxy resin content is less than 14% by weight, sufficient crosslinking is not made during curing, and when it is more than 27% by weight, the degree of curing is lowered and mechanical strength is lowered.

In one embodiment, the curing agent mixture is preferably a mixture of two or more amine-based curing agents selected from the group consisting of aliphatic polyamines, modified aliphatic polyamines, cyclic amines, and secondary or tertiary amines. More specifically, the curing agent mixture is more preferably a mixture of at least one aliphatic amine and at least one amine having two or more cyclic structures. The aliphatic amine has a chain structure to impart elongation to the cured product of the epoxy resin composition, and the amine having two or more cyclic structures improves the glass transition temperature of the cured product of the epoxy resin composition, and the elongation and the glass transition temperature of the epoxy resin composition Because it is possible to improve at the same time.

In one embodiment, the curing agent mixture preferably has a weight ratio of amines having two or more cyclic structures to aliphatic amines of 1:2 to 3. This means that when the weight ratio of the aliphatic amine and the amine having two or more cyclic structures is less than 1:2, that is, when the amine having two or more cyclic structures is insufficient, the glass transition temperature is lowered, and when it is more than 1:3, that is, two or more cyclic structures are insufficient. This is because when the amine having a cyclic structure is excessive, the elongation is lowered.

In one embodiment, the curing agent mixture preferably includes 4 to 10% by weight of the total 100% by weight of the carbon fiber composite material to be manufactured. This is because, when the content of the curing agent mixture is less than 4% by weight, the degree of curing is low and mechanical strength is lowered.

In one embodiment, the catalyst is for controlling the curing density of the cured product by improving the curing activity of the curing agent mixture, and preferably includes at least one of a phenol compound, imidazole, and a tertiary amine compound, and low-temperature imidazole More preferably, it is a catalyst.

In one embodiment, the catalyst preferably contains 0.1 to 1% by weight of the total 100% by weight of the carbon fiber composite material to be prepared. This is because, when the catalyst content is less than 0.1 wt %, the effect of curing activity is insignificant, and when the catalyst content is more than 1 wt %, storage stability may decrease or the brittleness of the cured product may increase.

The epoxy resin composition having the above configuration is preferably cured at 120° C. for 1 hour after raising the temperature from room temperature to 120° C. for 1 hour. This is because, when the time for which the epoxy resin composition is heated to 120 ° C. is less than 1 hour, the catalyst does not sufficiently improve curing activity, so that the curing density is lowered and the glass transition temperature (Tg) is lowered. to be. In addition, when the curing temperature is higher than 120° C., the plastic liner of the hydrogen pressure vessel becomes flexible by the curing heat, and thus there is a problem that the internal shape of the hydrogen pressure vessel cannot be maintained.

The carbon fiber composite material impregnated with the epoxy resin composition cured at 120 °C for 1 hour after raising the temperature from room temperature to 120 °C for 1 hour in the same manner as the curing conditions described above satisfies the following Equation (1). When the strength transition rate of the carbon fiber composite material is less than 95%, the hydrogen storage efficiency does not increase when the hydrogen pressure vessel is applied, so the effect of storing the same amount of hydrogen even with a small amount of the composite material is insufficient.

(Equation 1)

STR(%) = F _A x 100/ (F _B x V _f )≥ 95%

Here, STR (%) is the strength transfer rate, F _A is the measured value of the tensile strength of the 0° unidirectional carbon fiber composite material (ASTM D3039 standard), and F _B is the measured value of the tensile strength of the carbon fiber strand (ASTM D4018 standard) , and V _f is the carbon fiber volume ratio of the _FA measurement specimen. In addition, "0° unidirectional" in _FA means that each filament of the carbon fiber is aligned parallel to the reference axis direction.

In one embodiment, the cured product of the epoxy resin composition obtained by curing the epoxy resin composition under the curing conditions described above preferably has an elongation in the range of 4 to 8%. When the elongation of the cured product is less than 4%, there is a problem that cracks occur before carbon fibers in the composite material state, and stress transmission to carbon fibers is impossible, and when it exceeds 8%, there is a problem that the tensile strength is lowered.

In one embodiment, the cured product of the epoxy resin composition obtained by curing the epoxy resin composition under the above curing conditions preferably has a glass transition temperature (Tg) obtained by thermal analysis using a differential scanning calorimeter (DSC) of 100 to 140 ° C. do. When the glass transition temperature of the cured product is less than 100℃, it becomes flexible by the heat generated during charging and discharging of the hydrogen pressure vessel, and there is a problem in safety. Because.

In addition, the carbon fiber is impregnated in the above-mentioned epoxy resin composition, wound on the outside of the plastic liner, and then cured to form the outer shape of the hydrogen pressure vessel, and can withstand the stress of the hydrogen pressure vessel charged with high pressure.

In one embodiment, the carbon fiber preferably includes 65 to 80% by weight of the total 100% by weight of the carbon fiber composite material to be manufactured. This has a problem in that the area ratio of carbon fibers per volume is lowered when the content of carbon fibers is less than 65% by weight, and when the content of carbon fibers is more than 80% by weight, there is a problem in that voids are generated in the composite material.

In one embodiment, the specific gravity of the carbon fiber is preferably using a carbon fiber tow of 1.7 to 1.9, more preferably 1.75 to 1.85. When the specific gravity of the carbon fiber is less than 1.7, there are many voids in the filament forming the carbon fiber tow, or the compactness of the filament is lowered, and accordingly, the carbon fiber composite material made of such a carbon fiber filament has a low compressive strength. In addition, when the specific gravity of the carbon fiber exceeds 1.9, the weight reduction effect of the carbon fiber composite material is lowered.

In addition, the carbon fiber is preferably in the form of a filament bundle, and the number of filaments in the carbon fiber bundle is preferably 1,000 to 300,000. When the number of filaments in the carbon fiber bundle is less than 1,000, there is a disadvantage that the manufacturing cost is high due to the low area ratio per volume when manufacturing a large-area carbon fiber composite material. The disadvantage is that the tensile strength and compressive strength are lowered.

In one embodiment, the tensile strength of the carbon fiber composite material is preferably 2,500 to 3,500 MPa. When the tensile strength of the carbon fiber composite material is less than 2,500 MPa, the effect of storing the same amount of hydrogen even with a small amount of the composite material is insufficient. There is a problem in that the manufacturing cost increases.

1 is a flowchart illustrating a method of manufacturing a carbon fiber composite material having an improved strength transfer rate according to another aspect of the present invention.

Referring to Figure 1, the method of manufacturing a carbon fiber composite material with improved strength transfer rate according to an embodiment of the present invention includes a first step (S101) of preparing an epoxy resin composition, impregnating the carbon fiber with the prepared epoxy resin composition A second step (S102) and a third step (S103) of curing the carbon fiber impregnated with the epoxy resin composition is included.

First, in the first step (S101) of preparing an epoxy resin composition, an epoxy resin composition is prepared by mixing an epoxy resin, a curing agent mixture, and a catalyst. At this time, the epoxy resin is a liquid epoxy resin, and it is preferable to include at least one of bisphenol A epoxy, bisphenol F epoxy, novolak epoxy, flame retardant epoxy, cyclic aliphatic epoxy, and rubber-modified epoxy. In addition, the epoxy resin has two or more epoxy groups in one molecule and is preferably 150 to 340 g/eq equivalent, and the epoxy resin composition is preferably mixed with a curing agent mixture.

In the first step (S101) of preparing the epoxy resin composition, the curing agent mixture included in the epoxy resin composition preferably includes a mixture of one or more aliphatic amines and one or more amines having two or more cyclic structures, and aliphatic amines It is preferable that the weight ratio of the amine having two or more cyclic structures is 1:2 to 3. In addition, the epoxy resin composition preferably uses a low-temperature imidazole catalyst as a catalyst.

The epoxy resin composition prepared in the first step (S101) is impregnated with carbon fibers to form a carbon fiber composite material. When a pressure vessel capable of accommodating a hydrogen pressure vessel or another medium is manufactured using a carbon fiber composite material, it is required to withstand high pressure. Therefore, the cured product of the epoxy resin composition formed by heating the epoxy resin composition prepared in the first step (S101) from room temperature to 120°C for 1 hour and then curing the epoxy resin composition at 120°C for 1 hour has an elongation of 4 to 8% and free It is preferable that the transition temperature (Tg) is 100 to 140°C, and the strength transition rate of the carbon fiber composite material to be finally manufactured is preferably 95% or more.

In the second step (S102) of impregnating the carbon fiber with the prepared epoxy resin composition, the carbon fiber may be impregnated with the epoxy resin composition by various known processes. That is, by dissolving the epoxy resin composition in an organic solvent such as methyl ethyl ketone or methanol to lower the viscosity, impregnating the carbon fiber bundle, and then evaporating the organic solvent using an oven or the like, or without using an organic solvent. A liquid phase method of lowering the viscosity of the epoxy resin composition by heating and impregnating the carbon fiber bundle can be used, or the epoxy resin composition lowered in viscosity by heating is filmed on a roll or release paper and transferred to one or both sides of the carbon fiber bundle A hot-melt method or the like in which pressure is applied and impregnated by passing through a roll can be used. As an example, in the present invention, a liquid phase method capable of impregnating the epoxy resin composition with relatively simple equipment without using an organic solvent may be preferably used.

In one embodiment, in the second step (S102), when the carbon fiber is impregnated with the epoxy resin composition, the carbon fiber is preferably impregnated with the epoxy resin composition in a tension applied state. This is because the epoxy resin composition is not sufficiently impregnated in a state where no tension is applied to the carbon fiber.

Next, in the third step (S103) of curing the carbon fiber impregnated with the epoxy resin composition, the carbon fiber impregnated with the epoxy resin composition is subjected to a predetermined curing condition through various methods such as the method described above in the second step (S102). and hardened to produce a carbon fiber composite material.

Conditions for curing the carbon fiber impregnated with the epoxy resin composition in the third step (S103) are preferably cured at 120° C. for 1 hour after raising the temperature from room temperature to 120° C. for 1 hour. When the time for which the carbon fiber impregnated with the epoxy resin composition is heated to 120 ° C. is less than 1 hour, the catalyst does not sufficiently improve curing activity, so that the curing density is lowered and the glass transition temperature (Tg) is lowered, and when it exceeds 1 hour, the productivity is lowered because it can be In addition, when the curing temperature is higher than 120° C., the plastic liner of the hydrogen pressure vessel becomes flexible by the curing heat, and thus there is a problem that the internal shape of the hydrogen pressure vessel cannot be maintained.

In one embodiment, in the third step (S103), it is preferable to harden the epoxy resin composition in a state in which the tension of the carbon fiber is maintained. In a state where the tension is not maintained in the carbon fiber, the straightness of the carbon fiber filament is lowered during curing, resulting in a problem in that the tensile strength of the carbon fiber composite material is lowered.

The carbon fiber composite material prepared through the above-described first to third steps (S101 to S103) has a high strength transfer rate and can be used in a hydrogen pressure vessel, and has high hydrogen storage efficiency to reduce the weight and size of the hydrogen pressure vessel can make possible

In addition, it is natural that a pressure vessel manufactured by a method of impregnating the epoxy resin composition according to an embodiment of the present invention to carbon fiber, winding it on a liner, etc., and curing it by applying heat or a known method is included in the scope of the present invention.

More specifically, referring to FIGS. 2 and 3 , the pressure vessel according to an embodiment of the present invention includes a fuel inlet 10 and a fuel outlet 20 and a pressure vessel capable of storing gas (or fuel). It may include a liner 30 for use and an exterior material 40 surrounding the outer circumferential surface of the liner 30 .

Here, the pressure vessel may be a hydrogen pressure vessel storing hydrogen as a fuel, but is not limited thereto and may store various fuels such as methane, butane, propane, helium, nitrogen and oxygen. In the case of storing hydrogen as fuel, various types of pressure vessels such as a pressure vessel by compression by putting a hydrogen storage material such as a hydrogen storage alloy in the hydrogen pressure vessel, a fuel storage tank using a hydrogen storage material, or a pressure vessel storing hydrogen as a liquid are used. It can be manufactured in a pressure vessel. Also, the pressure vessel may be cylindrical or non-cylindrical having a hollow.

In one embodiment, the liner 30 may include a plastic material such as a synthetic resin.

In an embodiment, the exterior material 40 of the pressure vessel may be carbon fiber impregnated with the above-described epoxy resin composition, and the liner 30 may be wound and cured by applying heat to manufacture the pressure vessel. At this time, the curing temperature, curing time and conditions are the same as described above.

In the case of the pressure vessel manufactured in this way, not only the exterior material can have excellent tensile strength and bursting pressure, but also the strength transfer rate of the carbon fiber composite material is excellent. can be stored, thereby reducing the size and weight of the pressure vessel and reducing the manufacturing cost. In particular, according to the present invention, it is suitable for a hydrogen pressure vessel capable of storing hydrogen, but is not limited thereto.

Hereinafter, the configuration of the present invention and its effects will be described in more detail through Examples and Comparative Examples. However, these examples are for explaining the present invention in more detail, and the scope of the present invention is not limited to these examples.

[Example]

[Example 1]

Preparation Example 1: Preparation of an epoxy resin composition

Of the total 100% by weight of the carbon fiber composite material to be prepared, 14% by weight of a bifunctional epoxy resin, 4% by weight of a curing agent mixture, and 0.1% by weight of a low-temperature imidazole catalyst were added, using a vacuum rotary stirrer to revolve at 400 rpm and rotate at 200 rpm An epoxy resin composition was prepared by stirring under the conditions of 3 minutes. In this case, as the curing agent mixture, a weight ratio of an aliphatic amine to an amine having two or more cyclic structures was used in a weight ratio of 1:2.5.

Preparation Example 2: Preparation of carbon fiber impregnated with epoxy resin composition

The epoxy resin composition prepared in Preparation Example 1 was discharged and impregnated with 40 parts by weight of the total weight of the carbon fiber tow at a pressure of 20 kgf/cm ³ into the widely spread carbon fiber (TORAYCA T700S-24000-50C) tow, and the epoxy resin composition was impregnated. Carbon fiber was prepared. At this time, the impregnation process was performed in a state in which a tension of 500 gf was applied to the carbon fiber.

Preparation Example 3: Preparation of carbon fiber composite material

The carbon fiber impregnated with the epoxy resin composition prepared in Preparation Example 2 is wound in one direction on a bobbin, put in a mold designed to be cured to a thickness of 1 mm, heated from room temperature to 120° C. for 1 hour, and then press-molded at 120° C. for 1 hour. was cured to prepare a carbon fiber composite material. At this time, the press pressure was maintained at 1.2 N/mm ² . In addition, in Preparation Example 2, curing was performed while maintaining the tension applied to the carbon fiber.

[Example 2]

A carbon fiber composite material was prepared in the same manner as in Example 1, except that 1.0 wt% of the low-temperature imidazole catalyst was included.

[Example 3]

A carbon fiber composite material was prepared in the same manner as in Example 1, except that 22 wt% of the difunctional epoxy resin was included.

[Example 4]

A carbon fiber composite material was prepared in the same manner as in Example 1, except that 22 wt% of the difunctional epoxy resin was included and 10 wt% of the curing agent mixture was included.

[Example 5]

A carbon fiber composite material was prepared in the same manner as in Example 1, except that 27 wt% of the bifunctional epoxy resin was included.

[Comparative Example 1]

A carbon fiber composite material was prepared in the same manner as in Example 1, except that 13% by weight of the bifunctional epoxy resin was included.

[Comparative Example 2]

A carbon fiber composite material was prepared in the same manner as in Example 1, except that 28% by weight of the bifunctional epoxy resin was included.

[Comparative Example 3]

A carbon fiber composite material was prepared in the same manner as in Example 1, except that 3% by weight of the curing agent mixture was included.

[Comparative Example 4]

A carbon fiber composite material was prepared in the same manner as in Example 1, except that 22 wt% of the difunctional epoxy resin was included and 11 wt% of the curing agent mixture was included.

[Comparative Example 5]

A carbon fiber composite material was prepared in the same manner as in Example 1, except that the low-temperature imidazole catalyst was not included.

[Comparative Example 6]

A carbon fiber composite material was prepared in the same manner as in Example 1, except that 1.1 wt% of the low-temperature imidazole catalyst was included.

[Experimental example]

(1) Measurement of Elongation of Epoxy Resin Composition

The prepared epoxy resin composition was heated from room temperature to 120° C. for 1 hour, cured at 120° C. for 1 hour, and then cut into a dog-bone shape. Elongation was evaluated according to ASTM D638 standard using Instron Model 5985 UTM. At this time, a load cell having a maximum load of 10 tons was used, and the cross head speed was evaluated while maintaining a constant value of 5 mm/min.

(2) Measurement of Glass Transition Temperature (Tg) of Epoxy Resin Composition

The prepared epoxy resin composition was heated from room temperature to 120° C. for 1 hour and then cured at 120° C. for 1 hour. The glass transition temperature (Tg) of the specimen was measured at a temperature increase rate of 5° C./min using a differential scanning calorimetry (DSC).

(3) Measurement of tensile strength and strength transfer rate of carbon fiber composite materials

The tensile strength of the prepared carbon fiber composite material was evaluated according to ASTM D3039 standard using Instron Model 5985 UTM. At this time, a load cell with a maximum load of 10 tons was used, and the cross head speed was evaluated while maintaining a constant 2 mm/min.

In addition, using the measured value of the tensile strength of the carbon fiber composite material, the volume ratio of the carbon fiber of the measurement specimen, and the measured value of the tensile strength of the carbon fiber strand evaluated by the ASTM D4018 standard, the strength transfer rate (STR) was calculated according to Equation 1 below. .

(Equation 1)

STR(%) = F _A x 100/ (F _B x V _f )≥ 95%

F _A : Measurement of tensile strength of 0° unidirectional carbon fiber composite material, ASTM D3039

F _B : Measurement of tensile strength of carbon fiber strand, ASTM D4018

V _f :F _A Volume ratio of carbon fiber of the measurement specimen

Table 1 shows the composition ratio of the epoxy resin compositions of Examples 1 to 5 and Comparative Examples 1 to 6 and the results of evaluating physical properties through Experimental Examples.

division composition ratio Properties epoxy resin
(weight%) hardener mixture
(weight%) catalyst
(weight%) elongation
(%) glass transition temperature
(℃) strength transfer rate
(%) Example 1 14 4 0.1 4.2 103 95.1 Example 2 14 4 1.0 4.5 112 96.6 Example 3 22 4 0.1 6.6 126 99.2 Example 4 22 10 0.1 5.8 139 97.3 Example 5 27 4 0.1 7.8 124 96.3 Comparative Example 1 13 4 0.1 3.9 98 93.1 Comparative Example 2 28 4 0.1 8.1 121 94.2 Comparative Example 3 14 3 0.1 4.7 91 90.1 Comparative Example 4 22 11 0.1 4.9 138 94.8 Comparative Example 5 14 4 - 4.6 92 92.9 Comparative Example 6 14 4 1.1 3.9 114 94.4

As shown in Table 1 above, the carbon fiber composite materials according to Examples 1 to 5 of the present invention have excellent strength transfer rates, whereas the carbon fiber composite materials according to Comparative Examples 1 to 6 that do not satisfy the configuration of the present invention are It can be seen that the strength transfer rate decreases.

In addition, as in Examples 1, 3 and 5, the elongation increases as the epoxy resin content increases, which is understood to be because the epoxy chain length after curing increases as the epoxy resin content increases.

On the other hand, in the case of Comparative Example 1 in which the epoxy resin content is less than 14% by weight, it can be seen that the elongation and the glass transition temperature are low, and the strength transition rate is also lower than 95%.

In addition, in the case of Comparative Example 2, in which the epoxy resin content exceeds 27% by weight, the glass transition temperature is reduced, the elongation exceeds 8%, and the strength transition rate is also 95 compared to Example 5 containing 27% by weight of the epoxy resin. It can be seen that it is lower than %.

On the other hand, in the case of Examples 3 and 4 in which the curing agent mixture was added in 4% by weight and 10% by weight, respectively, high strength transfer rates were exhibited, whereas Comparative Example 3 in which 3% by weight of the curing agent mixture was added was 4% by weight of the curing agent mixture. It can be seen that the glass transition temperature is lower and the strength transition rate is lower than 95% compared to Example 1 containing It can be seen that the elongation is lower than that of , and the strength transfer rate is lower than 95%.

In addition, in the case of Examples 1 and 2 containing 0.1 and 1.0% by weight of the catalyst, the elongation is 4% or more, the glass transition temperature is 100°C or more, and the strength transition rate is 95% or more, whereas Comparative Example in which the catalyst is not included It can be seen that the glass transition temperature of 5 is less than 100° C. and the strength transition rate is also lower than 95%, and in the case of Comparative Example 6 in which 1.1% by weight of the catalyst was added, compared to Example 2 in which 1.0% by weight of the catalyst was added. It can be seen that the elongation is lowered and the strength transition rate is lower than 95%.

Although the preferred embodiment of the present invention has been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept of the present invention as defined in the following claims are also provided. is within the scope of the

10: fuel inlet
20: fuel outlet
30: liner
40: exterior material

Claims (19)

As a carbon fiber composite material obtained by curing carbon fibers impregnated with an epoxy resin composition,
It satisfies Equation 1 below,
(Equation 1)
STR(%) = FA x 100/ (FB x Vf)≥ 95%
Here, STR (%) is the strength transfer rate, FA is the measured value of the tensile strength of the 0° unidirectional carbon fiber composite material, FB is the measured value of the tensile strength of the carbon fiber strand, and Vf is the carbon fiber volume ratio of the FA measurement specimen. ,
The carbon fiber composite material is a carbon fiber composite material with an improved strength transfer rate, comprising 65 to 80% by weight of carbon fiber, 14 to 27% by weight of an epoxy resin, 4 to 10% by weight of a curing agent mixture, and 0.1 to 1% by weight of a catalyst. According to claim 1,
The epoxy resin composition includes an epoxy resin, a curing agent mixture, and a catalyst, and is a cured product cured at 120° C. for 1 hour after heating from room temperature to 120° C. for 1 hour. A carbon fiber composite material with improved strength transfer rate. 3. The method of claim 2,
The cured product of the epoxy resin composition has an elongation of 4 to 8%, a carbon fiber composite material having an improved strength transfer rate. 3. The method of claim 2,
The cured product of the epoxy resin composition has a glass transition temperature of 100 to 140° C., a carbon fiber composite material having an improved strength transition rate. According to claim 1,
The carbon fiber has a specific gravity of 1,7 to 1.9, and is composed of 1,000 to 300,000 filaments, a carbon fiber composite material having an improved strength transfer rate. According to claim 1,
The tensile strength of the carbon fiber composite material is 2,500 to 3,500 MPa, a carbon fiber composite material with an improved strength transfer rate. 3. The method of claim 2,
The epoxy resin comprises at least one of bisphenol A epoxy, bisphenol F epoxy, novolak epoxy, flame retardant epoxy, cyclic aliphatic epoxy, and rubber-modified epoxy, carbon fiber composite material with improved strength transfer rate. 3. The method of claim 2,
The epoxy resin has two or more epoxy groups in one molecule, and an equivalent weight of 150 to 340 g/eq, a carbon fiber composite material having an improved strength transfer rate. 3. The method of claim 2,
The curing agent mixture comprises an aliphatic amine and an amine having two or more cyclic structures, the carbon fiber composite material having an improved strength transfer rate. 10. The method of claim 9,
In the curing agent mixture, the weight ratio of the amine having the two or more cyclic structures to the aliphatic amine is 1:2 to 3, a carbon fiber composite material having an improved strength transfer rate. 3. The method of claim 2,
The catalyst is a low-temperature imidazole catalyst, a carbon fiber composite material having an improved strength transfer rate. delete A first step of preparing an epoxy resin composition;
a second step of impregnating the carbon fiber with the prepared epoxy resin composition; and
a third step of curing the carbon fiber impregnated with the epoxy resin composition to form a carbon fiber composite material;
includes,
The carbon fiber composite material contains 65 to 80% by weight of carbon fiber, 14 to 27% by weight of an epoxy resin, 4 to 10% by weight of a curing agent mixture, and 0.1 to 1% by weight of a catalyst. manufacturing method. 14. The method of claim 13,
The second step is a step of impregnating the carbon fiber in the epoxy resin composition in a state where tension is applied,
The third step is a step of hardening in a state in which the tension is maintained, a method for producing a carbon fiber composite material having an improved strength transfer rate. 14. The method of claim 13,
The third step is a step of curing the carbon fiber impregnated with the epoxy resin composition from room temperature to 120° C. for 1 hour and then curing the carbon fiber at 120° C. for 1 hour. a liner comprising a fuel inlet and a fuel outlet and capable of storing fuel; and
an exterior material surrounding the outer circumferential surface of the liner;
including,
The exterior material includes an epoxy resin, a curing agent mixture, a catalyst and carbon fiber,
The curing agent mixture comprises an aliphatic amine and an amine having two or more cyclic structures,
The catalyst is a low-temperature imidazole catalyst,
The exterior material is a pressure vessel comprising 65 to 80% by weight of carbon fiber, 14 to 27% by weight of an epoxy resin, 4 to 10% by weight of a curing agent mixture, and 0.1 to 1% by weight of a catalyst. 17. The method of claim 16,
The exterior material satisfies the following Equation 1 after raising the temperature from room temperature to 120° C. for 1 hour and then curing at 120° C. for 1 hour,
(Equation 1)
STR(%) = F _A x 100/ (F _B x V _f )≥ 95%
Here, STR (%) is the strength transition rate, _{FA is the measured value of the tensile strength of the 0° unidirectional carbon fiber composite material, F B is} the measured value of the tensile strength of the carbon fiber strand, and V _f is the measured value of the _FA measurement specimen. Carbon fiber volume ratio, pressure vessel. delete 18. The method of claim 16 or 17,
The pressure vessel is a pressure vessel for storing hydrogen as fuel.

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