KR20220088284A - CFRP manufacturing method of in-mold type and hard case made using the same - Google Patents

Abstract

The present invention relates to an in-mold method of manufacturing carbon fiber reinforced plastic and a hard case manufactured using the same, and more particularly, by improving the bonding force between the carbon fiber composite and UV blocking clear, the UV blocking clear is peeled off during use. was done to prevent it from happening.
In particular, the present invention provides a method capable of significantly improving the bonding strength while significantly reducing the bonding process between the carbon fiber composite material and the UV blocking clear, thereby providing a high-quality surface coating method and improving the marketability and productivity of CFRP products. can do it
In addition, according to the present invention, by molding two carbon fiber composites by a pressurization method without bonding them, it is possible to easily manufacture a thin panel while sufficiently securing structural stability.
Therefore, it is possible to improve reliability and competitiveness in the field of CFRP, particularly the field of CFRP manufacturing and CFRP products, as well as similar or related fields.

Description

CFRP manufacturing method of in-mold type and hard case made using the same}

The present invention relates to an in-mold method for manufacturing carbon fiber reinforced plastic and a hard case manufactured using the same, and more particularly, by improving the bonding force between a carbon fiber composite and UV blocking clear, the UV blocking clear is peeled off during use. was done to prevent it from happening.

In particular, the present invention provides a method capable of significantly improving the bonding strength while significantly reducing the bonding process between the carbon fiber composite material and the UV blocking clear, thereby providing a high-quality surface coating method and, at the same time, improving the marketability and productivity of CFRP products. It relates to a method for manufacturing carbon fiber reinforced plastic in an in-mold method and a hard case manufactured using the same.

Carbon Fiber Reinforced Plastics (CFRP) is a composite material that is attracting attention as a lightweight structural material with high strength and high elasticity.

Such carbon fiber composites were high-quality materials mainly used in national-led industries including the aerospace field, but recently, due to the revitalization of economies of scale and demand for weight reduction, the scope of their use has expanded to include transportation equipment used in our daily life, such as automobiles and drones. It has been expanded and is widely used for exterior plates of various devices, facilities, and industrial structures.

On the other hand, the woven composite material using carbon fiber has the advantage of having a high elastic modulus and strong resistance to damage or breakage due to external impact because the structure of the fabric is a net (net) structure. Incomplete impregnation occurred during the impregnation process, and voids, pinholes, and peeling phenomena frequently occurred.

In particular, voids or pinholes may also occur in molding using a pressure (sterilization) processing machine (Autoclave), which may be a factor of lowering the structural strength of the manufactured CFRP (carbon fiber reinforced plastic).

In addition, in the case of synthetic resins used in carbon fiber composites (which constitute carbon fiber composites by impregnating and curing carbon fibers), the physical properties at the beginning of use are good, but during use, moisture, UV rays, ozone, nitrogen oxides and sulfur oxides in the atmosphere are good. etc. will be affected.

In particular, when energy such as ultraviolet light is absorbed, molecular chains may be cut or a part of the molecule may form an activated radical (unstable state with unpaired electron orbital), which may cause an oxidation reaction that is easily combined with oxygen. can

Therefore, in order to prevent deterioration, damage, and oxidation of the product, a separate coating is required to prevent external exposure of the product, and in particular, it is most important to block ultraviolet rays and the like.

However, when a surface coating agent for UV protection is used, due to the limitations of the paint spraying and the surface tension of the paint, the paint does not penetrate inside the voids or pinholes described above and there are many defects in which holes are drilled in the form of pores. .

In order to solve this problem, in the conventional method using a surface coating agent, the surface of the carbon fiber composite material manufactured by heat pressing using a mold is polished and degreased to remove the mold release agent on the surface, and a sealer with low viscosity is applied. It will fill the pinhole.

After that, it goes through a process such as curing, finishing the sealer surface, applying clear to block UV rays, curing, and polishing.

As such, a general manufacturing method using a surface coating agent may have a problem in that the productivity of the product is lowered because it undergoes a process of 10 or more steps.

In addition, in the case of the coating agent applied in the conventional way, since clear is applied to the surface of the carbon fiber composite material molded by the thermal pressure method, the carbon fiber composite material and clear cannot be sufficiently combined, which causes external impact, etc. In this case, peeling may occur at the interface with the fiber, and the peeling portion may become larger due to thermal expansion or penetration of moisture during subsequent use.

In other words, the conventional carbon fiber composite material composed of carbon fiber material and epoxy is vulnerable to ultraviolet light, and thus physical properties such as surface yellowing or reduced elasticity may occur. As a number of processes are added in this process, not only the productivity of the product is lowered, but there is a problem in that the bonding force between the carbon fiber composite material and the clear layer is insufficient, causing surface cracks or peeling phenomena.

Republic of Korea Patent Publication No. 10-1481143 'Plating method of carbon fiber reinforced plastic and its plating roller'

In order to solve the above problems, the present invention prevents the UV blocking clear from peeling off during use by improving the bonding strength between the carbon fiber composite and the UV blocking clear in the process of applying the UV blocking clear to the surface of the carbon fiber composite material. An object of the present invention is to provide an in-mold method for manufacturing carbon fiber reinforced plastics and a hard case manufactured using the same.

In particular, the present invention provides a method capable of significantly improving the bonding strength while significantly reducing the bonding process between the carbon fiber composite material and the UV blocking clear, thereby providing a high-quality surface coating method and, at the same time, improving the marketability and productivity of CFRP products. It relates to a method for manufacturing carbon fiber reinforced plastic in an in-mold method and a hard case manufactured using the same.

In addition, the present invention is widely applied to various devices, facilities, industrial structures, etc., as well as a case of a bag carried by a user or a protective equipment worn by a user, by enabling the product to be manufactured with a significantly improved adhesion strength and thin thickness compared to the conventional adhesive method. An object of the present invention is to provide an in-mold method for manufacturing carbon fiber reinforced plastics and a hard case manufactured using the same.

In order to achieve the above object, an in-mold method for manufacturing carbon fiber reinforced plastic according to the present invention includes an in-mold clear coating step of curing by coating UV blocking clear on the inner surface of a mold; and a molding and trimming step of forming a composite material including carbon fibers by layingup and thermal pressing, and finishing the molded workpiece.

In addition, the in-mold clear application step includes a primary application process of forming a primary clear layer by coating the inner surface of the mold with polyester UV blocking clear; a first clear layer gelling process of gelling the first clear layer; a secondary application process of applying a secondary clear layer of polyester UV blocking clear to the gelled primary clear layer in addition to forming the thickness of the entire clear layer to a set coating thickness; a room temperature aging process of waiting at room temperature so that the first clear layer and the second clear layer are completely combined; and a thermosetting process of curing the secondary clear layer by applying constant heat when the gelation of the secondary clear layer proceeds through the room temperature aging.

In addition, in the first application process, the protruding particles are formed in the first clear layer, and in the second application process, the polyester UV blocking clear is filled between the protruding particles of the first clear layer 2 A car clearing layer can be formed.

In addition, in the first application process, the temperature condition of the polyester UV blocking clear is 5° C. to 15° C., and the viscosity can be increased to 900 cps to 1000 cps.

In addition, in the first application process, the primary clear layer may be formed so that the protruding particle size of the polyester UV blocking clear is formed in a range of 150 μm to 250 μm.

In addition, the gelation process of the first clear layer may be performed at a temperature of 30° C. to 50° C. for 30 minutes to 90 minutes with the ratio of the curing agent in the first clear layer being 1% to 3%.

In addition, in the second application process, after the polyester UV blocking clear fills between the protruding particles of the primary clear layer, the entire thickness of the clear layer is repeatedly applied to form a set coating thickness of 350 μm to 450 μm. can do.

In addition, in the secondary application process, the injection pressure of the polyester UV blocking clear for forming the secondary clear layer maintains 10% to 30% of the injection pressure for forming the primary clear layer, and the secondary The injection amount for forming the clear layer maintains 120% to 140% of the injection amount for forming the first clear layer, and the protruding particles of the first clear layer are sprayed close to each other at a distance of 15 cm to 30 cm in the spot injection mode. After filling the gap, it can be applied repeatedly to form the set coating thickness by changing to the wide spray mode.

In addition, in the room temperature aging process, the aging temperature may be maintained at 21° C. to 25° C. and wait for 20 to 40 minutes.

In addition, in the thermal curing process, when the secondary clear layer is gelled in the room temperature aging step, it can be cured at a temperature of 35° C. to 40° C. until the stickiness of the secondary clear layer disappears.

In addition, the hard case manufactured using the carbon fiber reinforced plastic manufacturing method of the in-mold method according to the present invention includes a polyester UV blocking clear layer formed in an in-mold method; and a carbon fiber composite material layer molded by heat pressing on the polyester UV blocking clear layer; and, during the heat press molding, a part of the molten polyester UV blocking clear layer is filled between the fibers of the carbon fiber composite material layer and cured can be

In addition, the adhesive strength of the polyester UV blocking clear layer and the carbon fiber composite layer may be 2.5 MPa to 3.0 MPa.

In addition, the polyester UV blocking clear layer may have a thickness of 80 μm to 150 μm.

By means of the above solution, the present invention improves the bonding strength between the carbon fiber composite material and the UV blocking clear in the process of applying the UV blocking clear to the surface of the carbon fiber composite, thereby preventing the UV blocking clear from peeling off during use. There are advantages that can be

Through this, the present invention provides a continuous and stable UV blocking and protection function for the carbon fiber composite material, thereby greatly improving the resistance of external corrosion elements and increasing the durability, thereby enabling semi-permanent use.

In particular, the present invention provides a method capable of significantly improving the bonding strength while significantly reducing the bonding process between the carbon fiber composite material and the UV blocking clear, thereby providing a high-quality surface coating method and, at the same time, improving the marketability and productivity of CFRP products. There are advantages to doing it.

In addition, since the surface gloss of injection molding using a mold can be maintained at a high quality, there is an effect of improving the external aesthetics of the product even without a separate polishing operation.

In addition, the present invention is widely applied to various devices, facilities, industrial structures, etc., as well as a case of a bag carried by a user or a protective equipment worn by a user, by enabling the product to be manufactured with a significantly improved adhesion strength and thin thickness compared to the conventional adhesive method. There are advantages to doing.

In addition, the present invention has the advantage of being able to easily manufacture a thin panel while sufficiently securing structural stability by molding two carbon fiber composites by a pressurization method without bonding them together.

Therefore, it is possible to improve reliability and competitiveness in the field of CFRP, particularly the field of CFRP manufacturing and CFRP products, as well as similar or related fields.

1 is a flow chart showing an embodiment of the carbon fiber reinforced plastic manufacturing method of the in-mold method according to the present invention.
FIG. 2 is a flowchart showing an embodiment of a specific process of step 'S100' of FIG. 1 .
3 to 5 are diagrams illustrating a specific embodiment for explaining FIG. 2 .
6 is a diagram illustrating a specific embodiment of step 'S200' of FIG. 1 .
7 is a data showing the test results of the CFRP specimen prepared by FIG.
8 is data showing test results of specimens manufactured by a conventional method.

Examples of the carbon fiber reinforced plastic manufacturing method of the in-mold method according to the present invention and the hard case manufactured using the same can be applied in various ways. Hereinafter, the most preferred embodiment will be described with reference to the accompanying drawings. do.

1 is a flow chart showing an embodiment of the carbon fiber reinforced plastic manufacturing method of the in-mold method according to the present invention.

Referring to FIG. 1 , an in-mold method of manufacturing carbon fiber reinforced plastic includes an in-mold clear application step (S100) and a molding and trimming step (S200).

First, in the in-mold clear application step (S100), a UV blocking clear is applied to the inner surface of the mold and cured. Here, the UV blocking clear may include polyester.

If UV blocking clear is applied to the inner surface of the mold in this way in the in-mold method, a surface condition of constant quality can always be obtained for the CFRP produced later, so that a great effect can be obtained in product process management and quality control. do.

Thereafter, in the forming and trimming step (S200), the composite material including carbon fibers is laid up in the mold and formed by thermal pressure, and if necessary, the molded workpiece is finished.

As a result, compared to the conventional method described above, since the sealer process, the finishing process, and the degreasing process are unnecessary, the overall process can be significantly shortened, thereby greatly improving the productivity of the product.

On the other hand, in the conventional adhesive form as described above, a UV blocking clear layer of polyester is formed after a carbon fiber composite is made, and in the present invention, a carbon fiber composite is made after forming a UV blocking clear layer of polyester.

At this time, the carbon fiber composite material is composed of an epoxy and a carbon fiber material. As a result, the conventional technique is to bond a polyester layer to an epoxy layer, and the present invention is to bond an epoxy layer to a polyester layer.

And, comparing the bonding structures of the epoxy and polyester, the molecular chain of the epoxy is more densely bonded than the polyester.

In summary, in the case of bonding the polyester layer to the epoxy layer as in the prior art, the range of fusion is small because the layer of the weak bonding structure is applied to the layer of the strong bonding structure. In the case of bonding, since it is a method of applying a layer of a strong bonding structure to a layer of a weak bonding structure, as shown in FIGS. 7 and 8, the bonding force is 3 to 4 times stronger than that of the prior art. .

Hereinafter, each step will be described in more detail.

2 is a flowchart illustrating an embodiment of a specific process of step 'S100' of FIG. 1 .

Referring to FIG. 2 , the in-mold clear application step (S100) includes a primary application process (S110), a primary clear layer gelation process (S120), a secondary application process (S130), a room temperature aging process (S140), and thermal curing. It may include a process (S150).

First, in the first application process ( S110 ), as shown in FIG. 3 , a first clear layer 100 is formed by applying a polyester UV blocking clear to the inner surface of the mold 10 using the spray nozzle 20 . can do.

In general, the polyester material UV blocking clear has a low basic viscosity of 600 cps to 800 cps. form the same shape.

In this way, in order to prevent the clear from clumping in the same form as beading, the temperature condition of the polyester UV blocking clear is 5° C. to 15° C., and the viscosity is increased to 900 cps to 1000 cps, as shown in the enlarged part of FIG. As the surface tension effect of the applied clear is reduced as shown, the beaded sphere spreads in the direction of the arrow and becomes hemispherical, so that it can be effectively adhered to the inner surface of the mold 10 .

On the other hand, even if the initial adhesion of the clear becomes possible through the adjustment as described above, since the primary clear layer 100 is distributed in the form of dots as shown in the enlarged portion of FIG. 3 , the inner surface of the mold 10 . A lack of uniform application of the whole may occur.

Therefore, in the first application process (S110), preferentially, the size (D1) of the protruding particles 110 of the polyester UV blocking clear is 150 μm to 250 μm to form the first clear layer 100 . can

Then, the first clear layer formed through the first clear layer gelation process (S120) is gelled.

For example, if the primary clear layer 100 is maintained in a coated state, the bonding strength with the secondary clear layer 200 that is subsequently laminated may be weakened, and when the primary clear layer 100 is completely cured. In this case, there is a possibility that the secondary clear layer 200 to be laminated thereafter may be peeled off.

Accordingly, in the first clear layer gelation process (S120), the ratio of the curing agent in the first clear layer 100 is 1% to 3%, and it is preferably performed at a temperature of 30°C to 50°C for 30 minutes to 90 minutes. do.

Thereafter, a secondary application process ( S130 ) of laminating the secondary clear layer 200 on the semi-cured primary clear layer 100 is performed.

In the secondary application process (S130), the secondary clear layer 200 of polyester UV blocking clear is applied in addition to the gelled primary clear layer 100, and through this process, the thickness of the entire clear layer is set It can be formed by coating thickness.

More specifically, as shown in FIG. 4 , the polyester UV blocking clear sprayed through the spray nozzle 20 fills the space between the protruding particles 110 of the primary clear layer 100 , and the total thickness of the clear layer (D2) may be repeatedly applied to form a set coating thickness of 350㎛ to 450㎛.

At this time, in the secondary application process 130 , the injection pressure of the polyester UV blocking clear for forming the secondary clear layer 200 is 10% to 30% of the injection pressure for forming the primary clear layer 100 . % can be maintained.

And, the injection amount of the polyester UV blocking clear for forming the secondary clear layer 200 can be maintained at 120% to 140% of the injection amount for forming the primary clear layer.

In addition, the injection module 20 is operated in the spot injection mode, it may be operated to close injection at a distance of 15 cm to 30 cm based on the target surface.

At this time, the injection module 20 fills the space between the protruding particles 110 of the primary clear layer 100 in the spot spray mode, and then changes to the wide spray mode when the space between the protrusion particles 110 is sufficiently filled. The entire target surface can be uniformly applied to form a coating thickness.

In the room temperature aging process (S140), it is a process of waiting at room temperature so that the previously formed first clear layer 100 and the second clear layer 200 are completely combined. Orange peel and air bubbles can be minimized

For example, in the room temperature aging process ( S140 ), a process of waiting for 20 to 40 minutes while maintaining the aging temperature of 21° C. to 25° C. may be performed.

When the gelation of the secondary clear layer 200 proceeds through such room temperature aging, a thermosetting process (S150) of curing the primary clear layer 100 and the secondary clear layer 200 by applying a constant heat is performed. can

More specifically, in the thermal curing process (S150), when the gelation of the secondary clear layer proceeds in the room temperature aging step (S140), the secondary clear layer is cured at a temperature of 35°C to 40°C until the stickiness of the secondary clear layer disappears. It can be done, and this process usually takes more than 2 hours.

When such a thermal curing process (S150) is passed, the sticky (stickiness) of the surface can be removed, thereby enabling layup of carbon fibers without post-curing treatment.

In other words, in the present invention, in the first application process (S110), the protruding particles 110 can be formed on the primary clear layer 100, and then in the secondary application process (S130), the polyester UV blocking clear is performed. By forming the secondary clear layer 200 by filling the gaps between the protruding particles 110 of the primary clear layer 100, the quality deterioration caused by the mold release agent applied to the mold is prevented, and the bonding strength with the carbon fiber composite is improved. can be improved

When the in-mold clear application step (S100) is completed, as shown in FIG. 5, the molding and trimming step (S200) is performed.

Specifically, on top of the primary and secondary clear layers 100 and 200 that have been cured in the in-mold clear application step (S100), the carbon fiber composite material 300 is laid up as shown in the upper part of FIG. 5 . .

Thereafter, as shown in the lower part of FIG. 5 , molding is performed using a press 30 in a thermal press method.

For example, the carbon fiber composite material 300 may be laminated with various fiber materials such as carbon fiber and glass fiber, and the first to third fibers 310 to 330 are each of the first warp yarns 311 to the second The three warp yarns 331 and the first weft yarns 312 to the third weft yarns 332 may be formed in the form of a woven fabric.

When this carbon fiber composite material 300 is laid up on top of the primary and secondary clear layers 100 and 200 and pressurized while supplying constant heat by a thermal press method, 1 as shown in the lower part of FIG. As a part of the primary and secondary clear layers 100 and 200 is filled with the space between the weft and warp yarns of the carbon fiber composite material 300, the hard case according to the present invention can be manufactured.

The hard case manufactured in this way is then subjected to finishing the molded workpiece if necessary. For example, the finishing process may include a grinding process and a polishing process.

A look at these hard cases is as follows.

First, the hard case manufactured by the present invention may include a polyester UV blocking clear layer formed by an in-mold method, and a carbon fiber composite material layer molded by thermal pressurization on the polyester UV blocking clear layer.

In particular, during hot-press molding, a portion of the molten polyester UV blocking clear layer may be filled between the fibers of the carbon fiber composite material layer and cured.

In the hard case of the present invention manufactured in this way, the adhesive strength of the polyester UV blocking clear layer and the carbon fiber composite layer can be maintained at 2.5 MPa to 3.0 MPa, and the thickness (D3) of the polyester UV blocking clear layer is 80 It may be formed in a range of ㎛ to 150㎛.

Figure 7 is a test result report of the CFRP produced by the present invention, Figure 8 is a test result report of the CFRP produced by the conventional adhesive method.

Comparing the two reports, the CFRP of the present invention has a coating film thickness of 92㎛ and adhesion strength of 2.7MPa, compared to the adhesion method with a film thickness of 396㎛ and adhesive strength of 0.8MPa, the film thickness is 4.3 times thinner and the adhesion strength It can be seen that is 3.375 times stronger.

In the above, the carbon fiber reinforced plastic manufacturing method of the in-mold method according to the present invention and a hard case manufactured using the same have been described. Those skilled in the art to which the present invention pertains will understand that the technical configuration of the present invention may be implemented in other specific forms without changing the technical spirit or essential characteristics of the present invention.

Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive.

10: mold 20: spray nozzle
30: press
100: primary clear layer 110: protruding particles
200: 2nd clear layer
300: carbon fiber composite material
310: first fiber 311: first warp
312: first weft
320: second fiber 321: second warp
322: second weft
330: third fiber 331: third warp
332: third weft

Claims (13)

In-mold clear coating step of curing by applying UV blocking clear on the inner surface of the mold; and
In-mold method of carbon fiber reinforced plastic manufacturing method comprising a; molding and trimming step of performing layup (Layup) of a composite material containing carbon fibers and heat-pressing, and performing the finishing of the molded workpiece.
The method of claim 1,
The in-mold clear application step includes:
A primary application process of forming a primary clear layer by coating the inner surface of the mold with polyester UV blocking clear;
a first clear layer gelling process of gelling the first clear layer;
A secondary application process of applying a secondary clear layer of polyester UV blocking clear to the gelled primary clear layer in addition to forming the thickness of the entire clear layer to a set coating thickness;
a room temperature aging process of waiting at room temperature so that the first clear layer and the second clear layer are completely combined; and
In-mold method for manufacturing carbon fiber reinforced plastics, comprising: a thermosetting process of curing by applying constant heat when the secondary clear layer is gelled by the room temperature aging.
3. The method of claim 2,
In the first application process,
to form protruding particles in the first clear layer,
In the second application process,
An in-mold method of carbon fiber reinforced plastic manufacturing method, characterized in that the polyester UV blocking clear is filled between the protruding particles of the primary clear layer to form a secondary clear layer.
3. The method of claim 2,
The first application process is
In-mold method of carbon fiber reinforced plastic manufacturing method, characterized in that the temperature condition of the polyester UV blocking clear is 5°C to 15°C, and the viscosity is increased to 900cps to 1000cps.
5. The method of claim 4,
The first application process is
An in-mold method for manufacturing carbon fiber reinforced plastics, characterized in that the primary clear layer is formed so that the protruding particle size of the polyester UV blocking clear is 150 μm to 250 μm.
6. The method of claim 5,
The first clear layer gelation process,
An in-mold method for manufacturing carbon fiber reinforced plastics, characterized in that the ratio of the curing agent of the primary clear layer is 1% to 3%, and is performed at a temperature of 30°C to 50°C for 30 minutes to 90 minutes.
7. The method of claim 6,
The second application process is
In-mold method, characterized in that after the polyester UV blocking clear is filled between the protruding particles of the primary clear layer, the clear layer is repeatedly applied so that the total thickness of the clear layer is formed to a set coating thickness of 350 μm to 450 μm. A method for manufacturing carbon fiber reinforced plastics.
8. The method of claim 7,
The second application process is
The injection pressure of the polyester UV blocking clear for forming the secondary clear layer maintains 10% to 30% of the injection pressure for forming the primary clear layer,
The injection amount for forming the secondary clear layer maintains 120% to 140% of the injection amount for forming the first clear layer,
In-molding, characterized in that after close-spraying from a distance of 15 to 30 cm in spot spray mode to fill between the protruding particles of the first clear layer, change to wide spray mode and repeatedly apply to form a set coating thickness A method for manufacturing carbon fiber reinforced plastics in the de-method.
8. The method of claim 7,
The room temperature aging process,
An in-mold method of carbon fiber reinforced plastic manufacturing method, characterized in that standby for 20 to 40 minutes in a state of maintaining the aging temperature of 21 ℃ to 25 ℃.
10. The method of claim 9,
The thermosetting process is
In-mold type carbon fiber reinforced plastic, characterized in that when the secondary clear layer is gelled in the room temperature aging step, the secondary clear layer is cured at a temperature of 35°C to 40°C until the stickiness of the secondary clear layer disappears. manufacturing method.
A polyester UV blocking clear layer formed by an in-mold method; and
Including; a carbon fiber composite material layer molded by heat pressing on the polyester UV blocking clear layer;
A hard case manufactured by an in-mold method, characterized in that a part of the molten polyester UV-blocking clear layer is filled between the fibers of the carbon fiber composite material layer during the thermal press molding and is cured.
12. The method of claim 11,
The hard case manufactured by the in-mold method, characterized in that the adhesive strength of the polyester UV blocking clear layer and the carbon fiber composite layer is 2.5 MPa to 3.0 MPa.
12. The method of claim 11,
A hard case manufactured by an in-mold method, characterized in that the polyester UV blocking clear layer has a thickness of 80 μm to 150 μm.

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