KR102648777B1 - Manufacturing method of filament by LFT process and filament for 3D printing of Continuous carbon fiber reinforced thermoplastics manufactured thereby - Google Patents

Abstract

The present invention relates to a method for manufacturing filament for 3D printing by the LFT process, comprising: (a) extruding PA6 pellets containing a melt viscosity regulator with an extruder die; (b) drawing carbon fiber from one end of the die to the other end in a direction perpendicular to the die to produce a towpreg in which the carbon fiber is impregnated with PA6 resin; and (c) manufacturing a filament by cooling and drawing the tow preg. A method for producing a filament for 3D printing by the LFT process, and a 3D method for continuous carbon fiber-reinforced thermoplastic produced thereby. It's about filament for printing.

Description

Filament manufacturing method by LFT process and filament for 3D printing for continuous carbon fiber reinforced thermoplastics manufactured thereby}

The present invention relates to a method for manufacturing filament for 3D printing by the LFT process and to the filament for 3D printing manufactured thereby. Carbon fiber reinforced thermoplastic filament is manufactured according to the LFT process, and the efficiency of resin impregnation for carbon fiber is It relates to a method of manufacturing filament for 3D printing by the LFT process in which the physical properties are improved by sufficiently including carbon fiber in the filament, and the filament for 3D printing according to the method.

3D printing technology is a technology that shapes products in three dimensions by stacking specific materials in a layer-by-layer manner based on three-dimensional graphic design data. It is an existing process technology that produces products by manufacturing and assembling dozens of parts. Including manufacturing process technology that completes a finished product at once without designing or processing each part, it is used in various industries such as jewelry, toys, fashion and entertainment industries, and automobiles, aviation, space, defense industry and medical devices with high technological difficulty. The importance of 3D printing technology is growing.

Depending on the molding method, such 3D printers include solid-based extrusion lamination (FDM) (fused deposition modeling), powder-based SLS (selective laser sintering), 3DP (Powder bed and inkjet head printing), EBM (electron beam melting), and light-based 3D printers. It is largely divided into chemical liquid-based SLA (Stereolithography), DLP (Digital light processing), Polyjet (Photopolymer jetting), and laminated LOM (Laminated object manufacturing), and these printers are used for printing to expand the application field. Materials such as filament, powder, and liquid resin play a very important role.

Among the raw materials used in the 3D printer, liquid and powder raw materials are expensive in terms of equipment and materials, whereas in the FDM method, solid raw materials in the form of filaments are melted and extruded, and the solid fuel used at this time is mainly a thermoplastic polymer material. It is widely used because it is inexpensive and easy to print.

The thermoplastic polymers include Polylactic Acid (PLA), Acrylonitrile Butadiene Styrene (ABS), Polycarbonate (PC), Polyethylene Terephthalate (PET), Thermoplastic Elastomers (TPE), Thermoplastic Polyurethane (TPU), High Impact Polystyrene (HIPS), Polyamide- Nylon (PA), etc., among which PLA and ABS are especially widely used for FDM.

However, the strength of the thermoplastic polymer is weak, so there are limitations in realizing the high mechanical properties required in the 3D printing process, and there are also limitations in obtaining precise prints because sufficient pressure cannot be applied during the 3D printing process. Therefore, in order to improve this, a filament for 3D printing using carbon fiber-reinforced thermoplastic plastic with improved mechanical properties by adding carbon fiber to the thermoplastic resin matrix is being developed.

Korean Patent No. 10-1774941 (registration date: 2017.08.30.) and Korean Patent Publication No. 10-2022-0000876 (publication date: 2022.01.04.) relate to carbon fiber-reinforced thermoplastic resin filament compositions for 3D printers. It is disclosed that mechanical properties can be improved by including thermoplastic resin and carbon fiber.

However, in all of the prior literature, the 3D carbon fiber-reinforced thermoplastic resin filament composition is manufactured by melt-kneading thermoplastic resin and carbon fiber and then extruding it, and during the extrusion process, the fiber is cut or broken during the operation of the screw in the extruder barrel. , the fiber length is significantly reduced due to damage, and as a result, the physical properties of the composite material deteriorate, so the degree of improvement in the physical properties of the composite filament composition for a 3D printer is not significant.

In addition, when 3D printing using a thermoplastic resin, the thermoplastic resin has a relatively high melt viscosity, so there is a problem in that the wettability with carbon fiber is insufficient and it is difficult to impregnate the carbon fiber with the molten resin.

Therefore, the present invention improves the problems of manufacturing carbon fiber-reinforced thermoplastic plastic filaments applicable to the conventional 3D printing FDM method, prevents damage to carbon fibers, and improves the melt flow rate of thermoplastic resins for 3D printing with improved physical properties. A novel 3D printing filament manufacturing method capable of manufacturing filament and a 3D printing filament resulting therefrom are provided.

Korean Patent No. 10-1774941 (registration date: 2017.08.30.) Korean Patent Publication No. 10-2022-0000876 (Publication date: 2022.01.04.)

In the present invention, the conventional carbon fiber-reinforced thermoplastic filament for 3D printing is manufactured through an extrusion or injection process, so the carbon fiber is damaged, and the degree of impregnation between the resin and the carbon fiber is reduced due to the high melt viscosity of the thermoplastic resin, and the filament In order to improve the problem of deterioration in the physical properties of 3D printed composite materials, a method of manufacturing filament for 3D printing by the LFT process is provided.

In addition, the present invention provides a 3D printing filament manufactured according to the 3D printing filament manufacturing method by the LFT process.

Additionally, the present invention provides a carbon fiber reinforced thermoplastic filament containing PA6 resin and carbon fiber.

In order to solve the above problems, the present invention provides a method for manufacturing filament for 3D printing by the LFT process, including (a) extruding PA6 pellets containing a melt viscosity regulator with an extruder die; (b) drawing carbon fiber from one end of the die to the other end in a direction perpendicular to the die to produce a towpreg in which the carbon fiber is impregnated with PA6 resin; and (c) manufacturing a filament by cooling and drawing the tow preg.

In one embodiment, step (a) may be a step of extruding PA6 pellets containing 0.5 to 5 wt% of a melt viscosity regulator relative to the weight of pure PA6 with an extruder die, and the melt viscosity regulator is calcium stearate. ), polycaprolactone, or polyalkylene adipates.

In one embodiment, the content of carbon fiber impregnated in the filament in step (c) may be 30 to 60 wt%.

In addition, the present invention provides a 3D printing filament manufactured by the 3D printing filament manufacturing method using the LFT process.

In addition, the present invention is a carbon fiber reinforced thermoplastic plastic filament containing PA6 resin and carbon fiber. The content of carbon fiber impregnated in the filament may be 30 to 60 wt%, the pore content of the filament may be less than 10%, and the filament may be The tensile strength may be 600 to 910 MPa, and the tensile modulus may be 55 to 95 GPa.

The present invention improves the melt flow rate of PA6 resin in the production of filament for 3D printing and improves the impregnation efficiency of PA6 resin into continuous carbon fiber by applying the LFT process, while preventing damage to the carbon fiber and providing sufficient physical properties applicable to 3D printing. A filament having can be manufactured.

In addition, the filament manufactured according to the present invention increases the impregnated carbon fiber content in the filament as the carbon fiber is sufficiently impregnated with the resin, the pore content of the filament decreases, and has sufficient tensile strength and tensile modulus, thereby forming a 3D It can be manufactured as a carbon fiber-reinforced composite material through printing.

In addition, since the filament can contain a high content of carbon fiber by the above manufacturing method, a carbon fiber-reinforced composite material 3D printed using a filament containing a high content of carbon fiber can have excellent mechanical properties.

Figure 1 is a schematic diagram of a filament manufacturing process for 3D printing by the LFT process according to an embodiment of the present invention.
Figure 2 is a schematic diagram of a twin-screw extruder according to an embodiment of the present invention.
Figure 3 is a schematic diagram showing a cross-die according to an embodiment of the present invention.
Figure 4 is a cross-sectional photograph of CF/CaST-PA6 filament (Example 1) measured with an optical microscope according to an embodiment of the present invention.
Figure 5 is a cross-sectional photograph of CF/CaST-PA6 filament (Example 2) measured with an optical microscope according to an embodiment of the present invention.
Figure 6 is a photograph of CF/PA6 composite material 3D printed according to an embodiment of the present invention.

Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by a person skilled in the art to which the present invention pertains. In general, the nomenclature used herein is well known and commonly used in the art.

Throughout this specification, when a part "includes" a certain component, this does not exclude other components and may further include other components, unless specifically stated to the contrary.

The present invention relates to a method of manufacturing a carbon fiber-reinforced thermoplastic filament that can be applied to 3D printing technology. It not only improves the impregnability of carbon fiber by improving the relatively high melt viscosity of thermoplastic resin, but also improves the impregnation of carbon fiber through the LFT process. 3D using the LFT process, which reduces damage to carbon fiber during the carbon fiber drawing process and improves resin impregnation efficiency to show tensile strength, tensile modulus, carbon fiber content in the filament, and filament pore content applicable to 3D printing. This relates to a method of manufacturing filament for printing.

In one aspect, the present invention provides a method for manufacturing filament for 3D printing by the LFT process, comprising: (a) extruding PA6 pellets containing a melt viscosity regulator through an extruder die; (b) drawing carbon fiber from one end of the die to the other end in a direction perpendicular to the die to produce a towpreg in which the carbon fiber is impregnated with PA6 resin; and (c) manufacturing a filament by cooling and drawing the tow preg.

Figure 1 shows a schematic diagram of the manufacturing process of filament for 3D printing by the LFT process according to an embodiment of the present invention, and will be described in detail with reference to this.

In the present invention, step (a) is a step of extruding PA6 pellets containing a melt viscosity regulator through an extruder die.

Pure PA6 resin is a polyamide (PA) that has 6 carbon atoms in the repeating unit of the molecular chain structure containing the amide (-CONH-) group, and both the N-H bond and the C-O bond are polar. N and O have a negative charge. This polarity allows the formation of double bonds between PA6 molecules, and these double bonds are hydrogen bonds that limit the movement of PA6 molecules and increase tensile strength. In addition, the molecular chain of PA6 forms a planar layered structure through hydrogen bonds with surrounding molecular chains, resulting in high crystallinity. Therefore, PA6 not only has excellent properties such as high crystallinity, excellent physical properties, toughness, low gas permeability, fatigue resistance, weather resistance, and heat resistance, but also has excellent molding processability, so it is an engineering plastic that is very useful industrially. In particular, PA6 has excellent wear resistance, corrosion resistance, and low friction coefficient, so it can be used as a matrix for carbon fiber-reinforced composite materials.

On the other hand, PA6 is a thermoplastic resin and has a high melt viscosity, so its wettability with the fiber is reduced, making it difficult to impregnate the reinforcing fiber with the molten resin.

Therefore, in step (a) of the present invention, a melt viscosity regulator is compounded into pure PA6, and PA6 pellets containing 0.5 to 5 wt% of the melt viscosity regulator relative to the weight of pure PA6 are extruded using an extruder die as a matrix.

Figure 2 is a diagram showing a preferred embodiment of step (a). PA6 resin and a melt viscosity regulator are mixed through a twin-screw extruder at the main screw 640, and the extrudate is discharged through the extruder die 650. After the water is cooled, it can be made into PA6 pellets using a pelletizer.

At this time, the melt viscosity regulator acts as a lubricant to increase the melt flowability of the PA6 matrix and improve the resin impregnation of the carbon fiber. For example, the melt viscosity regulator may be a plasticizer such as calcium stearate, polycaprolactone, or polyalkylene adipates, and is added in an amount of 0.5 to 5 wt%. When added at less than 0.5 wt%, the melt viscosity of PA6 is not reduced or slightly reduced, and when added at more than 5 wt%, the melt viscosity of PA6 is lowered, but it forms an interface on the surface of the resin and is present inside the resin, creating a gap between molecules. This is because the problem of reducing the manpower and consequently deteriorating the physical properties of the resin may occur.

In addition, the present invention may further include a drying step of PA6 before step (a). PA6 is sensitive to polar solvents such as water due to the polarity of the amide group, and has a high moisture absorption rate of about 2.5% by weight, which can cause problems during processing or reduce the physical properties of the resin, so it must be completely dried before use.

In the present invention, step (b) is a step of continuously drawing carbon fiber from one end of the die to the other end in a direction perpendicular to the die to produce a towpreg in which the carbon fiber is impregnated with PA6 resin. am.

Specifically, the PA6 pellets supplied to the hopper 110 of the extruder 100 are melted through the screw 120 and continuously supplied through the die as molten resin, from one end of the die to the other end in a direction perpendicular to the extruder die. The continuous carbon fiber 200, which is continuously drawn, is manufactured by crossing the molten resin in a cross-die 130 and using a towpreg in which the carbon fiber is impregnated with PA6 resin.

More specifically, FIG. 3 is a view showing a portion of the cross-die 130. Carbon fibers drawn through the cross-die are impregnated with molten resin supplied perpendicular to the carbon fibers. At this time, By controlling the drawing speed, the impregnation time of the carbon fiber with the PA6 resin in the cross-die can be increased to make the surface of the manufactured filament uniform and smooth.

In step (b), the carbon fiber is continuously supplied to a resin impregnation die and is a tow made up of a bundle of untwisted continuous filaments. The tow size is not limited, but may be 1K to 60K, preferably 1K to 12K, where 'K' represents the number of filaments of the carbon fiber tow, and 1K tow consists of 1,000 thin fiber filaments. means.

Additionally, the carbon fiber may be PAN (polyacrylonitrile)-based, pitch-based, or rayon-based carbon fiber, and is preferably PAN-based carbon fiber.

In the present invention, step (c) is a step of manufacturing filament by cooling and drawing the tow prep, and the tow prep manufactured in step (b) is cooled and continuously applied to the pulling machine 300 and the pulling roll 310. ) This is the step of producing a filament with a significant length by drawing. The above process can be carried out by the generally known LFT process, so it is not described in detail. However, considering the high moisture absorption of PA6, the cooling is performed using a method such as a fan instead of cooling by a medium with moisture such as a water tank. Preferably, the pore content of the filament prepared in the above step is less than 10%, and if the pore content of the filament is more than 10%, the uniformity of the filament may decrease or the filament may break during 3D printing, and the printed composite material The mechanical properties also decrease.

The filament contains 30 to 60 wt% of carbon fiber. If carbon fiber is included in less than 30 wt%, the PA6 reinforcing effect by the fiber is low, so high physical properties of carbon fiber-reinforced thermoplastic plastic cannot be expected, and if it exceeds 60 wt%, carbon fiber is not sufficiently impregnated into the PA6 resin. This is because the effect of improving the physical properties of the filament cannot be expected. Preferably, 40 to 60 wt% of carbon fiber is contained in the filament.

If the carbon fiber content ratio is excessively high, the tensile strength decreases due to a lack of PA6 resin to be impregnated into the carbon fiber. As the tensile modulus improves as the carbon fiber content increases, it is manufactured using a 3D printer by adjusting the component ratio of the filament. The required mechanical properties of the composite material can be controlled.

The LFT series of processes (a) to (c) are carried out continuously by continuously supplying carbon fiber and molten PA resin by extrusion and drawing, and the filaments thus produced are spooled to prevent entanglement. ) (400) can be wrapped and stored, and can be sealed to prevent moisture absorption.

The filament manufactured by the above process can be used for 3D printing.

In addition, the present invention is a carbon fiber reinforced thermoplastic plastic filament containing PA6 resin and carbon fiber. The content of carbon fiber impregnated in the filament is 30 to 60 wt%, the pore content of the filament is less than 10%, and the tensile strength is Provided is a carbon fiber-reinforced thermoplastic plastic filament, characterized in that it has a tensile modulus of 600 to 910 MPa and a tensile modulus of 55 to 95 GPa.

In the case of the filament, sufficient carbon fiber is included in the PA resin to exhibit a reinforcing effect by carbon fiber, so the pore content is less than 10%, the tensile strength is 600 to 910 MPa, and the tensile modulus is 55 to 95 GPa, and these filaments are It can be manufactured as a composite material using a 3D printer.

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to the examples.

<Example>

1. Materials

PA6: KN11 Grade from KOLON PLASTIC

CaST (Calcium stearate): Product of Daejeong Chemical Co., Ltd.

Carbon fiber: T300, 1K PAN-based carbon fiber from Toray Advanced Materials Co., Ltd.

2. Manufacturing filament for 3D printing

<Example 1> CF/CaST-PA6 filament

(1) Preparation of PA6 pellets containing CaST

1 wt% of CaST was added to PA6 resin based on the above PA6 resin, and the extrusion process was performed at 180 ~ 250 ° C using a twin-screw extruder (BT-30-S2-421 model, LG Machinary (Korea)). The extrudate that came out through the extruder die was cooled through a water bath and then manufactured into PA6 pellets of 2-3 mm in size using a pelletizer.

At this time, the schematic diagram of the twin screw extruder and the temperature conditions of the barrel are shown in Figure 2 and Table 1 below.

barrel Feed Head die Zone1 Zone2 Zone3 Zone4 Zone5 Zone6 Zone7 Temperature (℃) 180 200 210 230 250 250 250 240 235

(2) CF/CaST-PA6 filament manufacturing

The prepared CaST-containing-PA6 pellets and 1K PAN-based carbon fiber (CF) were manufactured into filaments according to the LFT process.

Figure 1 shows a schematic diagram of the filament manufacturing process for 3D printing by the LFT process, and Figure 3 shows a drawing of a long T-type die in the LFT process, cross-die temperature 250 ℃, screw speed 5 rpm. and under the condition of puller speed of 10 rpm, the continuous 1K PAN-based carbon fiber passes through a nozzle with a cross-die inner diameter of 0.35 mm and intersects with PA6 resin in a T-type cross-die, forming a circular shape impregnated with the PA6 resin. A towpreg was manufactured, and a filament longer than about 500 m was manufactured by continuously moving it forward using a pulling machine.

However, during cooling during the LFT process, a fan was used to uniformly cool the continuous filament considering the high moisture absorption of PA6, and the manufactured continuous filament was used by Markforged so that it can be directly applied to Markforged's 3D printer. It was wound on a spool and stored in a zipper bag to prevent moisture absorption by the filament within the spool.

<Example 2> CF/CaST-PA6 filament

Filaments were manufactured in the same manner as Example 1, except that 1.5K PAN-based carbon fiber (CF) was used.

<Comparative Example 1> Markforged filament

A carbon fiber/Nylon filament (CF/PA6) product compared to a commercially available carbon fiber filament (50cc or 150cc) product from Markforged was used as Comparative Example 1.

3. Experiment

(1) Carbon fiber content of filament

The content (based on weight ratio) of carbon fiber impregnated in the CF/CaST-PA6 filament was determined using a chemical balance and the following equation. At this time, the lengths of the carbon fiber and filament were made the same and applied to the following equation.

Carbon fiber content = (carbon fiber mass/filament mass)

As a result of calculating the carbon fiber content in the filament using the above equation, it was about 53 wt% by weight and about 42 vol% by volume.

On the other hand, the carbon content of Comparative Example 1 is reported to be about 28 wt%.

(2) Pore content of filament

The pore content of the prepared CF/CaST-PA6 filament was calculated based on the ASTM D2734 standard.

(2-a) theoretical density

In the formula below, the density of carbon fiber is 1.76 g/cm ³ , the fiber content is 53 wt%, the density of PA6 resin (CaST-PA6) applied to the filament is 1.13 g/cm ³ , and the resin content is 47 wt%. did.

T = 100(R/D + r/d)

T = the theoretical density

R = the resin content in composite, weight %

D = the density of resin

r = the reinforcement content in composite, weight %

d = the density of reinforcement

As a result of calculation using the above equation, the theoretical density of the filament was 1.39 g/cm ³ .

(2-b) Experimental density

The experimental density of the prepared CF/CaST-PA6 filament was measured a total of 10 times by the following underwater substitution method (ASTM D792) and obtained from the average value.

<Underwater substitution method>

Fix the immersion vessel on a scale pan with a precision of 0.1 mg or better, measure the dry weight of the specimen in air, then completely immerse the specimen in the immersion vessel, and quickly measure the underwater weight to minimize water absorption of the specimen. do. At this time, the following formula is used, and the specimen is assumed to be a single material with a volume of 1 cm ³ or more, smooth surfaces and edges, and a size and shape suitable for the testing device.

Density = dry weight/(dry weight - underwater weight)

The experimental density of the filament measured by this underwater substitution method is shown in Table 2 below.

Number of experiments experimental density One 1.35 2 1.33 3 1.27 4 1.3 5 1.32 6 1.33 7 1.3 8 1.25 9 1.3 10 1.25 medium 1.3 g/cm ³

In Table 2, the average experimental density of the filament was 1.3 g/cm ³ and the standard deviation was 0.03 g/cm ³ .

(2-c) Porosity content

The formula for calculating the pore content through theoretical density and experimental density is as follows. The pore content of the filament obtained from this equation was 6.47% ± 2.34%.

= the void content, volume %

= the void content, volume %

= the theoretical composite density

= the theoretical composite density

= the measured composite density

= the measured composite density

Meanwhile, the pore content of Comparative Example 1 is known to be about 5% or more.

(3) Melt Flow Index (MFI)

In order to determine the melt flow index of PA6 pellets according to the addition of 1 wt% of CaST, the melt flow index of pure PA6 resin and PA6 resin with 1 wt% of CaST added to PA6 resin was measured using an MFI device. At this time, the temperature was 250°C and the load was 2.16 kg, and the cutting time was 10 seconds. A total of 10 measurements were made and the melt flow index was measured from the average value, which is shown in Table 3 below.

sample PA6 resin with 1wt% CaST added
MI (g/10 min) pure PA6 resin
MI (g/10 min) One 58.6 43.9 2 54.1 37.8 3 46.1 41.0 4 51.1 40.3 5 50.4 39.8 6 52.4 40.0 7 48.8 41.2 8 55.6 43.3 9 54.4 43.1 10 48.0 45.3 average 52.0 41.6

Through Table 3 above, it can be seen that when 1 wt% of CaST is added to PA6, the melt flow index increases compared to pure PA6 resin. This is because CaST acts as a lubricant and increases the flowability of the polymer matrix, and this improvement in melt flowability can improve resin impregnation.

(4) Tensile test

The tensile strength and tensile modulus of the CF/CaST-PA6 filament (Example 1) and the Markforged filament (Comparative Example 1) prepared above were measured using a universal testing machine (UTM).

According to ASTM D3039 standard, 30mm Tab was used for both RMx on filament with a length of 150mm. The load cell was set to 50 kN and the crosshead speed was set to 2 mm/min. Tensile strength and tensile modulus were measured from the average values by measuring 11 specimens for each filament sample.

Table 4 below shows the tensile strength and tensile modulus of Example 1 and Comparative Example 1.

tensile strength tensile modulus Psalter Example 1 (MPa) Comparative Example 1 (MPa) Example 1 (GPa) Comparative Example 1 (GPa) One 799.8 1272.5 71.95 60.95 2 900.4 1256.9 75.23 57.43 3 718.7 1293.1 81.55 62.70 4 812.7 1448.9 71.40 65.66 5 785.6 1193.6 62.06 57.96 6 837.3 1203.4 74.63 55.63 7 808.1 1109.6 65.65 55.73 8 836.9 1094.6 89.65 56.19 9 634.8 1185.8 60.01 56.84 10 864.6 1239.2 94.59 59.53 11 792.4 1192.7 59.88 56.12 average 799.2 1226.4 73.33 58.61

In Table 4, the tensile strength of Example 1 (CF/CaST-PA6 filament) was lower than that of Comparative Example 1, but the tensile modulus was 73.33 GPa, which was higher than the tensile modulus of Comparative Example 1 of 58.61 GPa.

In Example 1, the carbon fiber content was as high as 53 wt%, whereas in Comparative Example 1, it was about 28 wt%. From this, it can be seen that Comparative Example 1 has a relatively higher resin content than Example 1. Due to this high resin content, in Comparative Example 1, impregnation was better and the porosity was lowered, so the tensile strength was higher than that of Example 1. However, the tensile strength of Example 1 was also maintained at a level suitable for 3D printing, and the tensile modulus of Example 1 was higher than that of Comparative Example 1.

This is a result of the carbon fiber content of Example 1 being almost twice as high as that of Comparative Example 1, so the reinforcing effect of carbon fiber was higher, and the composite material manufactured with a 3D printer by introducing this also reflected the carbon fiber reinforcing effect. It has excellent mechanical properties.

(5) Optical microscope observation

In order to determine the degree of impregnation of PA6 in the prepared CF/CaST-PA6 filament, the cross-section of the filament was observed at ×600 magnification using an optical microscope, and all cross-sections of the samples used for microscopic observation were polished. It was used with any scratches or pores on the surface removed.

Figure 4 is a cross-sectional photograph of a CF/CaST-PA6 filament (Example 1) manufactured with 1K CF, and Figure 5 is a cross-sectional photograph of a CF/CaST-PA6 filament (Example 2) manufactured with 1.5K CF, showing a circular shape. The white dots on the inside are carbon fiber, and the thing wrapped around the outside is PA6.

Through Figures 4 and 5, the cross section of the CF/CaST-PA6 filament could be confirmed.

4. Manufacture of CF/CaST-PA6 composite material through 3D printing

Using the above-manufactured CF/CaST-PA6 filament using Markforged's MARK TWO model 3D printer, a fiber layer was printed on the three-layer Onyx plastic layer with the nozzle set to a constant temperature of 240 ℃, and Onyx was printed on top of the above-mentioned CF/CaST-PA6 filament. The plastic layer was printed to produce a composite material with a size of 63.5 mm × 12.5 mm × 3 mm with a total of 24 layers, as shown in Figure 6.

10: LFT process chart
100: single screw extruder
110: Hopper
120: single screw
130: die
200: Continuous carbon fiber bobbin
300: Pulling machine
310: Pulling roll
400: Spool
500: Cooling fan
600: Twin screw extruder
610: Hopper
620: Feeder screw
630: thermocouple
640: main screw
650: die

Claims (7)

In the method of manufacturing filament for 3D printing by the LFT process,
(a) extruding PA6 pellets containing 0.5 to 5 wt% of calcium stearate relative to the weight of pure PA6 with an extruder die;
(b) drawing carbon fiber from one end of the die to the other end in a direction perpendicular to the die to produce a towpreg in which the carbon fiber is impregnated with PA6 resin; and
(c) cooling and drawing the tow preg to produce a filament,
A method of manufacturing a filament for 3D printing by the LFT process, characterized in that the content of carbon fiber impregnated in the filament in step (c) is 30 to 60 wt%.
delete delete delete Filament for 3D printing, characterized in that manufactured by the method of claim 1.
According to claim 5,
The filament includes PA6 resin and carbon fiber, the content of carbon fiber impregnated in the filament is 30 to 60 wt%, and the pore content of the filament is less than 10%.
According to claim 5,
The filament is a filament for 3D printing, characterized in that the tensile strength is 600 to 910 MPa and the tensile modulus is 55 to 95 GPa.