KR102515115B1 - Pet based continuous fiber complex and method of preparing same - Google Patents

Abstract

The present application relates to a PET-based continuous fiber composite material and a manufacturing method thereof, and relates to a PET-based continuous fiber composite material capable of dramatically reducing crack generation and a manufacturing method thereof.

Description

PET-based continuous fiber composite material and its manufacturing method {PET BASED CONTINUOUS FIBER COMPLEX AND METHOD OF PREPARING SAME}

The present application relates to a PET-based continuous fiber composite material and a method for manufacturing the same, and to a PET-based continuous fiber composite material and a method for manufacturing the same, which can significantly reduce cracking and increase mechanical properties of a composite sheet will be.

A fiber-reinforced composite material is a material made by combining two or more materials, and refers to a material manufactured with a structure in which a reinforcing material such as glass fiber or carbon fiber is impregnated into a base material such as a polymer resin.

The most important factor determining the physical properties of fiber-reinforced composite materials is that glass fibers or carbon fibers, which are reinforcing materials, are well mixed with the polymer base material. Here, the reinforcing material is in charge of mechanical properties including the strength or rigidity of the entire product, and the parent material serves as a binder that binds the reinforcing materials to each other and acts as a weathering resistance. It affects.

Among fiber-reinforced composites, continuous fiber-reinforced composites are composite materials manufactured by continuously impregnating fibers into a base material, unlike conventional short-fiber and long-fiber reinforced composites. Compared to conventional materials, continuous fiber-reinforced composite materials can use a higher ratio of reinforcing materials, and fibers can have a maximum aspect ratio. mechanical properties can be obtained.

In the case of continuous fiber-reinforced composites using the same reinforcing material, polypropylene (PP) or polyamide (PA) has been mainly used as a base material. However, recently, research on polyethylene terephthalate (PET), which has excellent mechanical properties, excellent price competitiveness, and even provides recyclability, has been expanded, and attempts to replace polypropylene or polyamide are continuing. .

In general, in the manufacturing process of continuous fiber-reinforced composite materials, unidirectional prepreg tape is manufactured through pultrusion, then laminated and compression molded. At this time, when polyethylene terephthalate is applied to the manufacturing process of such a general continuous fiber-reinforced composite material, compared to other resins, polyethylene terephthalate has a faster crystallization rate and a higher shrinkage rate, resulting in cracks in the fiber direction during the compression process. this has occurred

Therefore, it is the time when research to prevent or minimize the occurrence of such cracks is required.

Republic of Korea Patent Publication No. 10-2019-0107753 (published on September 20, 2019)

According to one embodiment of the present application, it is intended to provide a PET-based continuous fiber composite material and a manufacturing method thereof capable of dramatically reducing cracks generated in a compression process after unidirectional prepreg lamination.

One aspect of the present application relates to a method for manufacturing a continuous fiber composite material based on polyethylene terephthalate.

As an example, preparing a unidirectional prepreg including a polyethylene terephthalate (PET)-based thermoplastic resin and continuous fibers; Laminating a plurality of unidirectional prepregs to produce a composite sheet; heating and pressing the composite sheet followed by quenching; and annealing the composite sheet to prepare a continuous fiber composite material.

As an example, the component content ratio of the continuous fiber and the resin may be 40 to 70 parts by weight: 60 to 30 parts by weight.

As an example, the heating may be performed at a temperature condition of 255 to 320 °C.

As an example, the pressurization may be performed under a pressure condition of 5 to 10 MPa.

As an example, the rapid cooling may be performed at a rate of 100 °C/min or more.

As an example, the heat treatment may be performed at a temperature condition of 120 to 180 °C.

As an example, the heat treatment may be performed under a pressure condition of 0.5 to 3 MPa.

Another aspect of the present application relates to continuous fiber composites.

As an example, the tensile strength of the continuous fiber composite material may be 700 to 1100 MPa.

As an example, the flexural strength of the continuous fiber composite material may be 700 to 1100 MPa.

According to one embodiment of the present application, it is possible to provide a continuous fiber composite material based on polyethylene terephthalate.

According to one embodiment of the present application, it is possible to provide a continuous fiber composite material based on polyethylene terephthalate with minimized cracking.

According to one embodiment of the present application, it is possible to provide a polyethylene terephthalate-based continuous fiber composite material having excellent tensile strength.

According to one embodiment of the present application, it is possible to provide a continuous fiber composite material based on polyethylene terephthalate having excellent flexural strength.

1 is a flow chart for explaining a method for manufacturing a continuous fiber composite material based on polyethylene terephthalate according to an embodiment of the present application.
2 is a schematic diagram for explaining a method of manufacturing a unidirectional prepreg.
3 is a schematic diagram for explaining a conventional unidirectional prepreg lamination and bonding method.
4 is a schematic diagram for explaining a method of stacking and bonding unidirectional prepregs according to an embodiment of the present application.

Terms used in this application are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this application, terms such as "include" or "have" are intended to designate that the features, components, etc. described in the specification exist, but one or more other features or components may not exist or be added. That doesn't mean there aren't any.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the related art, and unless explicitly defined in this application, it should not be interpreted in an ideal or excessively formal meaning. don't

Hereinafter, the polyethylene terephthalate-based continuous fiber composite material of the present application and its manufacturing method will be described in detail with reference to the accompanying drawings. However, the accompanying drawings are illustrative, and the scope of the polyethylene terephthalate-based continuous fiber composite material of the present application and its manufacturing method is not limited by the accompanying drawings.

First, a method for manufacturing a continuous fiber composite material based on polyethylene terephthalate, which is an embodiment of the present application, will be described.

1 is a flow chart for explaining a method for manufacturing a continuous fiber composite material based on polyethylene terephthalate according to an embodiment of the present application.

As shown in FIG. 1, the method for manufacturing a polyethylene terephthalate-based continuous fiber composite material includes preparing a unidirectional prepreg including a polyethylene terephthalate (PET)-based thermoplastic resin and continuous fibers. (S10); Manufacturing a composite sheet by laminating a plurality of unidirectional prepregs (S20); Heating and pressing the composite sheet and then quenching it (S30); A step (S40) of preparing a continuous fiber composite material by annealing the composite sheet may be included.

Hereinafter, a method for manufacturing a continuous fiber composite material based on polyethylene terephthalate in each step will be described.

First, a unidirectional prepreg including a polyethylene terephthalate (PET)-based thermoplastic resin and continuous fibers is prepared (S10).

In particular, the resin may be polyethylene terephthalate. However, in some cases, it may be a resin containing short fibers or long fibers. It may also contain recycled resin. The component of the resin is not particularly limited, but as described above, it is preferable to apply polyethylene terephthalate.

Polyethylene terephthalate is a relatively dense polyester resin and is a crystalline or amorphous thermoplastic. The characteristics of amorphous polyethylene terephthalate are high transparency, but low tensile strength and low sliding properties. On the other hand, crystalline polyethylene terephthalate, which Ensinger uses as a semi-finished product for cutting, has high hardness, stiffness and strength and excellent It has the characteristics of sliding property and wear resistance. Due to its excellent creep strength, low water absorption, thermal properties and excellent dimensional stability, polyethylene terephthalate is suitable for complex parts and applications where dimensional accuracy and surface quality are demanding.

The prepreg of the present application includes such a thermoplastic resin as a matrix and continuous fibers as a reinforcing material. The continuous fibers are not particularly limited, but may be glass fibers or carbon fibers.

Here, the component content ratio of the continuous fiber and the resin is preferably 40 to 70 parts by weight: 60 to 30 parts by weight. When the content of the continuous fiber is less than 40 parts by weight, it is difficult to secure sufficient mechanical properties. On the other hand, when the content of the continuous fibers exceeds 70 parts by weight, there is a problem that is difficult to implement in the continuous fiber-reinforced composite material manufacturing process. Compared to general composite materials, the component content of continuous fibers is high, and through this, excellent mechanical properties can be provided. However, the content of the continuous fiber is preferably 50 parts by weight to 60 parts by weight, and most preferably 60 parts by weight.

In addition, the prepreg of the present application may include various additional components in addition to the continuous fibers and resins described above according to the user's intention. Any such additional component may be used as long as it can be applied in the technical field to which this application belongs. In addition, these additional components are components that are obvious to those skilled in the art to which this application belongs even without specifically providing an example.

Prepreg is an abbreviation of pre-impregnated materials, which means that reinforcement fibers are impregnated with resin in advance. In addition, as a combination of matrix and fiber, it means a product in a state that can be used directly in the production process of the product.

One-way prepreg is a prepreg formed by impregnating fibers into a resin, and means a tape-shaped product formed in one direction, and is one type of prepreg, but in this application, prepreg, prepreg tape and one-way tape, and one-way prepreg Pregs are used interchangeably.

2 is a schematic diagram for explaining a method of manufacturing a unidirectional prepreg (tape).

As shown in FIG. 2 , the unidirectional prepreg 17 may be manufactured by impregnating the continuous fibers 11 into the impregnation die 15 containing the resin 13, drawing them, and cutting them.

3 is a schematic diagram for explaining a conventional unidirectional prepreg lamination and bonding method. As shown in FIG. 3, conventionally, a unidirectional prepreg 21 is prepared, a plurality of prepared unidirectional prepregs (for example, 4 to 30 sheets) are laminated, and then thermally bonded by applying high temperature and high pressure to composite composite After forming the sheet 23, a cooling compression process was performed to manufacture a composite material 25 as a final product. However, as described above, in the case of polypropylene or polyimide, such a process can be performed without a major problem, but polyethylene terephthalate has a problem in that cracks occur when this process is applied.

In order to solve this problem, the present applicant has devised the following process.

4 is a schematic diagram for explaining a method of stacking and bonding unidirectional prepregs according to an embodiment of the present application. As shown in FIG. 4, a unidirectional prepreg 31 is prepared, a plurality of unidirectional prepregs are laminated, and then thermally bonded by applying high temperature and high pressure to form a composite sheet 33, followed by quenching ), a compression process and an annealing process were performed to manufacture a composite material 35 as a final product.

Hereinafter, this process will be described step by step.

Then, a plurality of unidirectional prepregs are laminated to manufacture a composite sheet (S20).

As described above, the unidirectional prepreg is a tape having a thickness of about 0.25 mm or less, and is not thick enough to be used alone in a product. Therefore, it is preferable to laminate and use such unidirectional prepregs.

Here, the number of unidirectional prepregs to be stacked is not particularly limited, and a composite sheet may be formed by stacking 4 to 30 sheets according to the user's intention.

Then, after heating and pressing the composite sheet, it is rapidly cooled (quenching) (S30).

The laminated composite sheet is heated, and at this time, it is preferably performed at a temperature condition of 255 to 320 °C. However, the temperature condition may be 270 to 310 °C or 280 to 290 °C.

In addition, the laminated composite sheet is pressurized, and at this time, it is preferably carried out under a pressure condition of 5 to 10 MPa. The pressure condition may be 6 to 9 MPa or 7 to 8 MPa.

In the above-described heating and pressing process, it is preferable to perform the pressing process after performing the heating process.

Through this heating and pressing process, the composite sheet is thermally bonded and can be maintained at a constant temperature.

And, by performing rapid cooling to room temperature, the degree of crystallinity is adjusted. The rapid cooling may be performed at a rate of 100 °C/min or more. The upper limit of the speed condition is not particularly limited, and may be appropriately limited according to the user's intention or the conditions of the working process. Through such rapid cooling, it is possible to prevent cracks from being formed in one fiber direction. Specifically, when rapid cooling is performed, fewer crystals are generated because the crystallization temperature range (~120 to 180 ° C.) is passed before crystallization proceeds. This prevents cracks from the crystallization process (based on shrinkage caused by the shrinkage of polymer chains to crystallize).

Then, by annealing the composite sheet, a continuous fiber composite material is prepared (S40).

The heat treatment may be performed at a temperature of 120 to 180 °C.

In addition, heat treatment may be performed while applying pressure. At this time, the pressure condition may be a pressure condition of 0.5 to 3 MPa.

As described above, since mechanical properties of polyethylene terephthalate resins that are not crystallized by rapid cooling are deteriorated, annealing may be performed in the above-described temperature range to increase crystallinity and improve mechanical properties. The method of manufacturing a continuous fiber composite material may further include steps, conditions, etc. of a method for manufacturing a thermoplastic resin-based composite material containing continuous fibers as a reinforcing material, configuration of a device for manufacturing the same, operating conditions, etc. . However, even if the steps, conditions, etc. of the manufacturing method, or the configuration, operating conditions, etc. of the apparatus for manufacturing the same are not specifically explained, those skilled in the art to which this application belongs will be advised of the steps, conditions, etc. of the manufacturing method, It is self-evident to add or limit the configuration and operating conditions of the device for manufacturing the same.

In addition, a continuous fiber composite material based on polyethylene terephthalate, which is an embodiment of the present application, will be described.

The polyethylene terephthalate-based continuous fiber composite material prepared by the above-described method may exhibit excellent mechanical properties due to minimized cracks.

In one example, the tensile strength of the continuous fiber composite material may be 700 to 1100 MPa.

In one example, the tensile stiffness of the continuous fiber composite material may be 27 to 35 GPa.

In one example, the flexural strength of the continuous fiber composite material may be 700 to 1100 MPa.

In one example, the flexural stiffness of the continuous fiber composite material may be 27 to 35 GPa.

In one example, the elongation at break of the continuous fiber composite material may be 1.8 to 3.5%.

In particular, the polyethylene terephthalate-based continuous fiber composite material of the present application has excellent physical properties, secures price competitiveness, and can replace conventional polypropylene-based fiber-reinforced composite materials or polyamide-based fiber-reinforced composite materials, , As described above, through a simple additional process (quenching + annealing), there is no crack, and it is possible to provide about 20% to 70% improvement in physical properties compared to the case of using the existing process.

Hereinafter, the present application will be described in more detail through experimental examples.

[ Experimental example One]

A unidirectional prepreg having a component content ratio of 40 parts by weight of polyethylene terephthalate resin and 60 parts by weight of continuous glass fiber was prepared.

Specifically, 3 to 5 guide bars were applied while roving the continuous glass fibers to spread the continuous glass fibers, and then the continuous glass fibers were impregnated while supplying polyethylene terephthalate resin to an impregnation mold at 255 to 320 ° C. While drawing it, it was cut using a cutter to prepare a unidirectional prepreg sample having a thickness of 0.25 mm.

[ Example One]

Four prepared unidirectional prepregs were laminated, heated to a temperature of 285° C., and then cooled at a cooling rate of 100° C./min or more under a pressure of 7 MPa for 3 minutes or more. After that, Example 1 was prepared by heat treatment at 150 ° C. for 1 hour after loading in a convention oven.

[ Example 2]

Four prepared unidirectional prepregs were laminated, heated to a temperature of 285° C., and then cooled at a cooling rate of 100° C./min or more under a pressure of 7 MPa for 3 minutes or more. Thereafter, after loading in a convention oven, Example 2 was prepared by heat treatment at 150 ° C. for 1 hour under a pressure of 0.5 MPa.

[ comparative example One]

Comparative Example 1 was prepared by stacking four prepared unidirectional prepregs, pressurizing at 7 MPa for more than 3 minutes, heating at a temperature of 285 ° C, and then cooling at a cooling rate of 5 to 10 ° C / min under the same pressure.

[evaluation]

Tensile properties of the samples of Examples 1 and 2 and Comparative Example 1 were measured. Tensile properties were performed based on ASTM D3039. The width x length x thickness of the sample was 15 x 250 x 1 mm, and the test speed was 5 mm/min. Tensile strength, tensile stiffness and elongation at break of each sample were measured and are shown in Table 1 below.

Example 1 Example 2 Comparative Example 1 Tensile strength (MPa) 854.9 929.7 743.9 Tensile Stiffness (GPa) 35.4 40.0 32.7 Elongation at break (%) 2.47 2.62 2.55

As shown in Table 1, it was confirmed that the tensile strength, tensile stiffness and elongation at break of Examples 1 and 2 were superior to those of Comparative Example 1.

[ Experimental example 2]

A unidirectional prepreg having a component content ratio of 40 parts by weight of polyethylene terephthalate resin and 60 parts by weight of continuous glass fiber was prepared.

Specifically, 3 to 5 guide bars were applied while roving the continuous glass fibers to spread the continuous glass fibers, and then the continuous glass fibers were impregnated while supplying polyethylene terephthalate resin to an impregnation mold at 255 to 320 ° C. While drawing it, it was cut using a cutter to prepare a unidirectional prepreg sample having a thickness of 0.25 mm.

[ Example 3]

16 prepared unidirectional prepregs were laminated, pressurized at 7 MPa for more than 3 minutes, heated to a temperature of 285 ° C, and cooled at a cooling rate of 100 ° C / min or more under the same pressure. After that, Example 3 was prepared by heat treatment at 150 ° C. for 1 hour after loading in a convention oven.

[ Example 4]

Sixteen prepared unidirectional prepregs were laminated, heated to a temperature of 285° C., and then cooled at a cooling rate of 100° C./min or more under a pressure of 7 MPa for 3 minutes or more. Thereafter, after loading in a convention oven, Example 4 was prepared by heat treatment at 150 ° C. for 1 hour under a pressure of 0.5 MPa.

[ comparative example 2]

Comparative Example 2 was prepared by stacking 16 prepared unidirectional prepregs, heating at a temperature of 285° C., and then cooling at a cooling rate of 10° C./min or more under a pressure of 7 MPa.

[evaluation]

The flexural properties of the samples of Examples 3 and 4 and Comparative Example 2 were performed based on ASTM D790. The width x length x thickness of the sample was 12.7 x 127 x 3.2 mm, and the test speed was 2 mm/min. The flexural strength, flexural stiffness and elongation at break of each sample were measured and are shown in Table 2 below.

Example 3 Example 4 Comparative Example 2 Flexural strength (MPa) 817.8 855.4 501.0 Flexural stiffness (GPa) 27.3 27.6 26.9 Elongation at break (%) 2.99 3.07 1.97

As shown in Table 2, it was confirmed that the flexural strength, flexural stiffness and elongation at break of Examples 3 and 4 were superior to those of Comparative Example 2.

Although the above has been described with reference to the preferred embodiments of the present application, those skilled in the art can variously modify and change the present application within the scope not departing from the spirit and scope of the present invention described in the claims below. You will understand that you can.

11: continuous fiber
13: Resin
15: impregnation die
17: one-way prepreg
21: one-way prepreg
23: composite sheet
25: composite material
31: one-way prepreg
33: composite sheet
35: composite material

Claims (10)

Preparing a unidirectional prepreg containing a polyethylene terephthalate (PET)-based thermoplastic resin and continuous fibers;
Laminating a plurality of unidirectional prepregs to produce a composite sheet;
heating the composite sheet at a temperature of 255 to 320° C. and pressing at a pressure of 5 to 10 MPa and then quenching the composite sheet at a rate of 100° C./min or more; and
Annealing the composite sheet under a temperature condition of 120 to 180 ° C. and a pressure condition of 0.5 to 3 MPa to prepare a continuous fiber composite material,
Component content ratio of continuous fiber and resin is 40 to 70 parts by weight: Method for producing a polyethylene terephthalate-based continuous fiber composite material of 60 to 30 parts by weight.
delete delete delete delete delete delete A continuous fiber composite material manufactured by the method of claim 1.
According to claim 8,
The continuous fiber composite material has a tensile strength of 700 to 1100 MPa.
According to claim 8,
The continuous fiber composite material has a flexural strength of 700 to 1100 MPa.

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