KR20100046557A - The multi-walled carbon nanotube/cellulose composites and their manufacturing method - Google Patents

Abstract

PURPOSE: A multi-walled carbon nano tube/cellulose composite and a manufacturing method thereof are provided to uniformly disperse and combine a multi-walled carbon nano tube with cellulose for improving conductivity, tensile strength and others. CONSTITUTION: A multi-walled carbon nano tube/cellulose composite contains 0.01~70wt% of multi-walled carbon nano tube and cellulose. A manufacturing method of the multi-walled carbon nano tube/cellulose composite comprises the following steps: preparing the multi-walled carbon nano tube; obtaining a mixed solution containing N-methylmorpholine-N-oxide solution and the multi-walled carbon nano tube; sonicating the mixed solution; and mixing the cellulose with the mixed solution.

Description

Composite of multi-walled carbon nanotubes / cellulose and its manufacturing method {THE MULTI-WALLED CARBON NANOTUBE / CELLULOSE COMPOSITES AND THEIR MANUFACTURING METHOD}

The present invention relates to a composite of multi-walled carbon nanotubes / cellulose and a method of manufacturing the same, and more particularly, multi-walled carbon nanotubes in cellulose using N-methyl morpholine-N-oxide (NMMO) as a dispersion solvent The present invention relates to a composite of multi-walled carbon nanotubes / cellulose having improved mechanical, thermal and electrical properties by uniformly dispersing and compounding the same, and a method of manufacturing the same.

In general, fibers have been produced from petroleum based polymers. However, petroleum fiber (synthetic fiber) causes serious environmental problems. In addition, cellulose-based rayon has been developed to replace synthetic fibers. However, the rayon fiber manufacturing process uses very harsh chemicals, which are also harmful to the human body as well as environmental problems. Accordingly, in recent years, biodegradable and environmentally friendly materials have been developed and put into practical use. Representative is lyocell fiber (cellulose fiber) which is a natural fiber.

Cellulose has a very high affinity with other materials, but due to the crystal structure made of strong hydrogen bonds in the molecular chain or chains, it is difficult to dissolve it as a general solvent. N-methylmorpholine-N-oxide (hereinafter referred to as "NMMO") is widely used among solvents that can break down the structure of cellulose and make it into a solution. The process of melting cellulose using such NMMO is commonly referred to as a "Lyocell" process. The manufacturing process of lyocell fiber (cellulose fiber) using NMMO solvent has the advantage of being harmless to the human body while being pollution-free according to the recovery and reuse of the whole amount of the solvent. The lyocell fiber has characteristics such as low cost, low density, biodegradability, and specific properties compared to glass fiber and carbon fiber. In addition, the lyocell fibers have a simpler process compared to the rayon process, are manufactured by an environmentally friendly method, and have excellent heat resistance and form stability.

Currently, many cellulose application technologies using the lyocell process as described above have been proposed. For example, U.S. Patent Nos. 4,142,913 and 4,144,080 disclose distillation under reduced pressure of cellulose swelling dispersed in NMMO hydrate to obtain a solution in which cellulose is dissolved, which is cooled to prepare a solid phase (a kind of chipping), and then to an extruder. A method for preparing a cellulose solution by dissolving at is provided. U. S. Patent No. 5,584, 919 discloses a process for preparing solid NMMO with a water content of 5 to 17%, stirring in powdered cellulose and a horizontal cylindrical high speed mixer to make a granule precursor and then dissolving it in an extruder. In addition, U.S. Patent No. 5,948,905 discloses a method of instantaneous vacuum evaporation while passing a nozzle of 1.5 to 6.0 mm in diameter to produce a cellulose solution by evaporating water in a cellulose mixture with NMMO hydrate having a water content of about 23%. Presented.

In addition, Korean Patent Laid-Open Publication No. 10-2002-0024689 discloses a method in which a cellulose pulp powder is swelled using a liquid NMMO hydrate solvent supercooled using cooling air, and then dissolved to prepare a highly homogeneous cellulose solution. Doing. And the Republic of Korea Patent No. 0755377 is a method for producing cellulose fibers, by dissolving cellulose powder in liquid concentrated NMMO to prepare an NMMO solution, by dispersing silicon dioxide in the NMMO solution to prepare an NMMO additive solution, the NMMO After mixing, swelling and dissolving the additive solution and the cellulose powder, a cellulose solution having an appropriate viscosity is prepared, and the cellulose solution is extruded through a spinning nozzle having an orifice number of 500 to 2,000, and then passed through an air layer to reach a coagulation bath. Then, it is solidified to obtain a multifilament, and thereafter, a method for producing a cellulose fiber is shown in which the obtained multifilament is wound by washing, drying and emulsion treatment.

However, the lyocell product according to the prior art including the prior patent document, that is, a product (fiber or film) manufactured from a mixed solution of cellulose and NMMO, is inferior in thermal stability to mechanical properties such as tensile strain and tensile stress. There is a problem. In addition, there is a problem that does not have the electrical characteristics and its application range is limited.

The present invention is to solve the problems of the prior art as described above, by uniformly dispersing and compounding multi-walled carbon nanotubes in lyocells (a mixed solution of cellulose and NMMO) to improve the mechanical, thermal and electrical properties An object of the present invention is to provide a composite of multi-walled carbon nanotubes / cellulose and a method of manufacturing the same.

The present invention to achieve the above object,

Multi-walled carbon nanotubes; And it provides a multi-walled carbon nanotube / cellulose composite containing cellulose.

In this case, the multi-walled carbon nanotubes may be included in an amount of 0.01 to 70.0% by weight based on the mixed weight of the multi-walled carbon nanotubes and cellulose. The multi-walled carbon nanotubes, preferably contained in 0.1 to 70.0% by weight based on the mixed weight of the multi-walled carbon nanotubes and cellulose, more preferably contained in 0.1 to 12.0% by weight, more More preferably included 0.2 to 5.0% by weight.

In addition, the present invention,

Preparing a multi-walled carbon nanotube;

Obtaining a mixed solution containing an N-methylmorpholine-N-oxide (NMMO) solution and the multi-walled carbon nanotubes;

Ultrasonically grinding the mixed solution; And

It provides a method for producing a multi-walled carbon nanotube / cellulose composite comprising the step of mixing cellulose in the ultrasonically pulverized mixed solution.

In addition, the present invention,

Preparing a multi-walled carbon nanotube;

Mixing an N-methylmorpholine-N-oxide (NMMO) solution, the multi-walled carbon nanotubes and cellulose; And

It provides a method for producing a multi-walled carbon nanotube / cellulose composite comprising the step of ultrasonic grinding the mixed solution.

According to a preferred embodiment, the method for producing a composite according to the present invention may further comprise the step of modifying the surface of the prepared multi-walled carbon nanotubes. More preferably, the surface of the multi-walled carbon nanotubes are modified by introducing functional groups or coating polar compounds on the prepared multi-walled carbon nanotubes, and then, N-methylmorpholine-N-oxide (NMMO) solution. It is good to mix with (and cellulose).

At this time, the step of modifying the surface of the multi-walled carbon nanotubes, may preferably include one or two or more processes selected from the following (1) to (7) process.

(1) Acid-treatment of Multi-Walled Carbon Nanotubes

(2) Ultrasonic irradiation process on multi-walled carbon nanotubes

(3) Process of irradiating microwaves to multi-walled carbon nanotubes

(4) A process of irradiating radiation on multi-walled carbon nanotubes

(5) Corona discharge treatment of multi-walled carbon nanotubes

(6) A step of irradiating ion beams to multi-walled carbon nanotubes

(7) coating polar compound on the surface of multi-walled carbon nanotubes

According to the present invention, the multi-walled carbon nanotubes are uniformly dispersed and compounded in cellulose, thereby improving mechanical properties (tensile strength, fracture strength, etc.), thermal properties (pyrolysis temperature) and electrical properties (electric conductivity, etc.). Has

Hereinafter, the present invention will be described in more detail.

Carbon nanotube / cellulose composite according to the present invention (hereinafter abbreviated as "composite") is a multi-walled carbon nanotube (MWNT; CNT having a double or triple wall or more; And cellulose. Specifically, the composite according to the present invention is a nanocomposite, in which cellulose and multi-walled carbon nanotubes are uniformly dispersed and complexed using N-methylmorpholine-N-oxide (hereinafter referred to as "NMMO") as a dispersion solvent, It may have a high viscosity dope, or may have a solid state (powder phase, etc.) by removing the solvent (NMMO).

In this case, the multi-walled carbon nanotubes are preferably a functional group introduced (active) or a polar compound coated on the surface through a pretreatment process (surface modification). The introduction (coating) of such functional groups and / or polar compounds improves the bonding strength (bonding by hydrogen bonding or the like), dispersibility, and the like with cellulose, and more preferably combines them.

The NMMO acts as a solvent of cellulose as well as a dispersant of multi-walled carbon nanotubes. The NMMO is not particularly limited, but, for example, a hydrate synthesized through oxidation of tertiary amine N-methylmorpholine and hydrogen peroxide (H ₂ O ₂ ) may be used. (Tertiary amine N-methylmorpholine + H ₂ O ₂ / C0 _2- > N-methylmorpholine-N-oxide + H ₂ O; NMMO monohydrate synthesis) At this time, the hydration of one water molecule and NMMO in the synthesis process produces monohydrate NMMO. NMMO has a 4.38mD dipole moment and a high NO polar group. At this time, the multi-walled carbon nanotubes are introduced with functional groups of the hydroxyl group and the carboxylic acid group by pretreatment (surface modification), thereby allowing hydrogen bonding with the NO group of the NMMO. That is, O in the NO high polar group of the NMMO may be one or two hydrogen bonds in the hydroxyl group or carboxylic acid group introduced into the multi-walled carbon nanotubes. By such hydrogen bonding, multi-walled carbon nanotubes are dispersed and complexed with cellulose in NMMO.

In addition, the multi-walled carbon nanotubes are mixed with NMMO solution, and then ultrasonically pulverized. By such ultrasonic pulverization, the multi-walled carbon nanotubes can achieve uniform dispersibility.

According to the present invention, the mechanical properties (tensile strength, fracture strength, etc.), thermal properties (pyrolysis temperature) and electrical properties (electric conductivity, etc.) are improved by the composite of the multi-walled carbon nanotubes as described above. Multi-walled carbon nanotubes have excellent physical properties even in small amounts. However, when too much multi-walled carbon nanotubes are added, transparency is poor and uniform dispersion is difficult.

On the other hand, the method for producing a composite according to the present invention includes the following steps (a) to (d) according to the first aspect of the present invention.

(a) preparing a multi-walled carbon nanotube;

(b) obtaining a mixed solution comprising an NMMO solution and the multi-walled carbon nanotubes prepared in step (a);

(c) ultrasonic grinding the mixed solution obtained in step (b); And

(d) mixing cellulose with the ultrasonically pulverized mixed solution through step (c):

At this time, it is preferable to further include the step of ultrasonic grinding (again ultrasonic grinding) of the solution obtained by mixing the cellulose in the step (d).

In addition, in mixing the raw materials, NMMO solution, multi-walled carbon nanotubes and cellulose can be mixed in one step. Specifically, the composite may be prepared including the following steps (iii) to (iii) according to the second aspect of the present invention.

(Iii) preparing multi-walled carbon nanotubes;

(Ii) mixing an N-methylmorpholine-N-oxide (NMMO) solution, the multi-walled carbon nanotubes prepared in step (iii) and cellulose; And

(Iii) ultrasonically grinding the mixed solution obtained in step (ii):

At this time, according to a preferred embodiment, the method for producing a composite according to the present invention (the first and second forms) is preferably further comprising the step of modifying the surface of the multi-walled carbon nanotubes. Specifically, it is preferable to modify (pretreat) the surface of the multi-walled carbon nanotubes prepared in steps (a) and (iii) and then use them for mixing (mixing with NMMO solution). By such a surface modification step, the multi-walled carbon nanotubes have more improved dispersibility and are uniformly combined with cellulose. The surface modification step can be any method as long as it can improve the dispersibility of the multi-walled carbon nanotubes, for example, a physical method, a chemical method and can be performed in parallel. Preferably, a functional group may be introduced (active) on the surface of the multi-walled carbon nanotube or a polar compound is coated (or introduced).

As described above, the multi-walled carbon nanotubes undergo a pretreatment (surface modification) prior to mixing in the NMMO solution for surface modification for dispersibility, wherein the pretreatment (surface modification) is preferably ( 1) acid-treatment the multi-walled carbon nanotubes; (2) irradiating ultrasonic (Ultra-sonic) to the multi-walled carbon nanotubes; (3) irradiating microwaves to the multi-walled carbon nanotubes; (4) irradiating radiation to the multi-walled carbon nanotubes; (5) corona discharge treatment of the multi-walled carbon nanotubes; (6) irradiating an ion beam to the multi-walled carbon nanotubes; And (7) coating a polar compound on the surface of the multi-walled carbon nanotube, or the like. Although pretreatment (surface modification) is not specifically limited, It is preferable to advance to the process containing at least the process (1) performed by acid treatment among the said (1) process-(7) process. Specifically, the surface modification of the multi-walled carbon nanotubes may be performed by the step (1) alone, or by continuing one or more steps selected from (2) to (7) following the step (1). . In the case of acid treatment of multi-walled carbon nanotubes, there is an advantage that the purity is increased at the same time the functional group is introduced.

The step (1), namely, acid treatment, may be performed by treating the multi-walled carbon nanotubes with an acid in a reflux or by dipping the multi-walled carbon nanotubes in an acid aqueous solution. By this acid treatment, the carbon nanotubes remove the metal catalyst contained in the preparation thereof by the strong acid, thereby increasing the purity and introducing functional groups on the surface of the carbon nanotubes having hydrophobicity. The introduction of such functional groups makes it hydrophilic and easily dispersed in the NMMO solution, and at the same time, it is complexed through cellulose and hydrogen bonding. Although the said acid treatment is not specifically limited, It is good to process with 60-200 degreeC acid. For example, an appropriate amount of carbon nanotube powder is added to an aqueous acid solution, and heat is applied to maintain the temperature at a temperature of about 60 to 200 ° C. to immerse the powder. In this case, when the acid temperature is less than 60 ℃, it is difficult to introduce functional groups (improve hydrophilicity) to the chemically stable carbon nanotubes, and when the temperature exceeds 200 ℃, the acid boils explosively and may affect the surrounding environment and an accident may occur. Not desirable Therefore, the acid treatment is preferably carried out in an acid in the above temperature range. In addition, the acid treatment time is not particularly limited, but is preferably treated for 2 hours or more. If the treatment time is less than 2 hours, the carbon nanotubes do not cause sufficient chemical deformation, it may be difficult to introduce the functional group. At this time, even if the processing time is more than 36 hours, it is difficult to show the increased effect of the increase in time. Thus, the acid treatment is preferably, but not particularly limited, proceed by reflux or immersion method for 2 to 36 hours. In addition, the acid used for the acid treatment includes an inorganic acid and an organic acid, for example, sulfuric acid, nitric acid, hydrochloric acid or a mixture thereof may be used as the inorganic acid.

In the pretreatment (surface modification), the steps (2) to (6) can be carried out using various commercially available devices (ultrasound generator, microwave generator, etc.).

In addition, the step (7), that is, the process of coating a polar compound on the surface of the multi-walled carbon nanotubes to be a polar factor is coated on the surface of the multi-walled carbon nanotubes, for example, a surfactant having a polar group It can be proceeded by diluting the surfactant in a solvent and coating it. At this time, the dispersibility of the multi-walled carbon nanotubes is improved by the polarity effect. Polar compounds that can be used in this process include, but are not limited to, for example, sodium dodecyl sulfate (SDS; Sodium dodecyl sulfate), polyvinylpyrrolidone (PVP; Polyvinylpyrrolidone), cetyltrimethylammonium bromide (CTAB; Cetyltrimethylammonium) One or two or more kinds of surfactants selected from the group consisting of bromide) and sodium carboxymethyl cellulose (Na-CMC) may be used. At this time, for example, when sodium dodecyl sulfate (SDS) is used as a polar compound, a polarity factor is introduced (coated) on the surface of the multi-walled carbon nanotubes through the following reaction mechanism. In the following reaction mechanism, (a) is a schematic diagram of carbon nanotubes before coating, and (b) is a photograph of carbon nanotubes having a polarity factor introduced on the surface thereof.

Reaction Mechanism

On the other hand, the ultrasonic grinding is to ensure uniform dispersion of multi-walled carbon nanotubes and cellulose in the NMMO solution, the ultrasonic grinding is preferably performed for 20 minutes to 14 hours through an ultrasonic mill. At this time, if the ultrasonic grinding time is less than 20 minutes, it is difficult to achieve uniform dispersion. If the ultrasonic grinding time is longer than 14 hours, the synergistic effect due to the excessive grinding is not so great, and the carbon nanotubes are subjected to the strong energy of the ultrasonic wave and the surface or appearance is destroyed. It is undesirable because the function may be lost. However, the ultrasonic grinding time is not limited to the above range. Depending on the intensity of the ultrasonic waves, the grinding time can be appropriately added or subtracted. Carbon nanotubes have C = C and C-C bonds in their structure. At this time, the C = C bond is broken by the strong energy of the ultrasonic wave and converted into CC- (O, OH, etc.) in the NMMO solution, which is effectively dispersed in the solution. Evenly distributed and compounded throughout.

In addition, the multi-walled carbon nanotubes may be mixed so as to include 0.01 to 70.0% by weight of the multi-walled carbon nanotubes and cellulose based on the mixed weight (that is, the mixture of the multi-walled carbon nanotubes + cellulose is 100). As described above, multi-walled carbon nanotubes improve the physical properties even when added in a small amount, but when added in a small amount of less than 0.01% by weight, it is difficult to have good physical properties (mechanical, thermal, electrical properties, etc.) and exceeds 70.0% by weight. If a large amount is added, it has excellent thermal properties (such as an increase in pyrolysis temperature) and electrical properties (such as an increase in electrical conductivity), but mechanical properties such as tensile strength and transparency may be lowered, thereby limiting application fields. Preferably it is mixed to be included in 0.1 to 70.0% by weight, more preferably mixed to be included in 0.1 to 12.0% by weight, even more preferably contained (mixed) in 0.2 to 5.0% by weight It is good. In this case, according to the present invention, when the multi-walled carbon nanotubes are included in an amount of 0.2 to 5.0 wt%, they have good properties in terms of all physical properties such as mechanical, thermal, electrical properties, and transparency.

In addition, although not particularly limited, the cellulose may be included in an amount of 2.0 to 25.0 wt% based on the mixed weight of NMMO and cellulose (that is, 100 of NMMO + cellulose mixed). In addition, the NMMO is a hydrate having a water content of 5 to 60 wt%, for example, a monohydrate is not particularly limited, but is 60.0 based on the total weight of the composite (multi-walled carbon nanotubes + cellulose + NMMO hydrate 100). ~ 98.0% by weight may be included.

The composite according to the present invention described above may be manufactured and commercialized by a film by a casting method or a fiber by a spinning method. In addition, as the composite according to the present invention has electrical conductivity and transparency, it can be utilized for various purposes such as optical components and electrical / electronic components (for example, transparent electrodes). Specifically, the composite according to the present invention, as well as mechanical and thermal properties as well as transparency and electrical conductivity ensures the electrode (electrode of capacitor), photodiode, antistatic coating of the capacitor by spin coating (spin-coat) It can be used for a wide range of applications such as antistatic coating, electrochromic windows using light transmittance, field effect transistors, and hole transport materials.

Hereinafter, the Example of this invention is illustrated. The following examples are provided as illustrative examples of the present invention and are provided only to assist in understanding the present invention, and the technical scope of the present invention is not limited thereto.

EXAMPLE

<Composite manufacturing>

Multi-walled carbon nanotubes (hereinafter referred to as "MWNT") are 95% pure, manufactured by chemical vapor deposition (CVD), and purchased from Nanomirae ^ⓒ . MWNTs were acid-treatment using reflux for 24 hours at 110 ° C. with a mixed solution of 68 wt% nitric acid and 98 wt% sulfuric acid to increase the purity and introduce functional groups. Hereinafter, the acid treated MWNT is referred to as "A-MWNT". NMMO was used as a monohydrate purified from 50 wt% hydrated NMMO solution of BASF ^ⓒ provided by Kolon ^ⓒ . Cellulose powder is Buckeye Co. The V-81 grade (polymerization degree 1200) of the product was used and used.

As described above, after preparing the material, first, the NMMO was heated in an oil-bath at 95 ° C. to make a liquid, and A-MWNT was added differently to the NMMO solution. That is, A-MWNT was added to be 0.0wt%, 0.2wt%, 0.4wt%, 0.6wt%, 0.8wt%, 1.0wt%, 3.0wt%, 5.0wt%, 9.0wt%, 12.0wt% and the like. In this case, the content of A-MWNT (wt%) is based on the mixture of A-MWNT and cellulose.

The mixed solution of A-MWNT and NMMO was ultrasonically ground for 7 hours with a tip-type ultrasonic mill (Vibracell, VCX-750 700W / 60Hz). Thereafter, 5.0 wt% of cellulose powder was added to the mixed solution of A-MWNT and NMMO, and dispersed by stirring with a mechanical stirrer for 2 hours. At this time, the content of cellulose (5.0wt%) is based on the mixture of cellulose and NMMO solution. The dispersed complex dope was again ultrasonically pulverized and mixed for 4 hours using an ultrasonic mill again, and then further mixed for 2 hours with an agitator. Then, the air was removed for 2 hours to remove the air contained in the dope.

In this case, FT-IR spectroscopy was performed on the untreated acid (pure MWNT), acid treated MWNT (A-MWNT), pure cellulose, and acid treated A-MWNT / cellulose complexed with cellulose. 1 is shown. In Figure 1, (a) is the result of untreated acid MWNT, (b) is the result of acid treated MWNT (A-MWNT), (c) is pure cellulose, acid treated to A complexed with cellulose FT-IR spectroscopy results of -MWNT / cellulose. The FT-IR spectrometer was measured under vacuum using Jasco's FT / IR-620 model. The sample was used by mixing KBr, and the diameter of the sample was prepared to be 10mm pellets (round shape). And spectroscopic measurement was measured with the resolution of 1 cm <^-1> .

As shown in FIG. 1, A-MWNT shows peaks of hydroxyl (-OH group) bands at 1700 and 1000 to 1200 cm ^-1 , and carboxylic (-COO-) acid bands at 1720 to 1650 cm ^-1 . These results indicate that hydroxyl and carboxylic acid groups are present in A-MWNT.

Figure 2 shows a photograph of the dispersed solution. In FIG. 2, the leftmost photograph is a photograph after adding 12.0 wt% of A-MWNT to NMMO, followed by ultrasonic grinding (for 7 hours), and the middle photograph of FIG. 2 shows 0.2 wt% of A-MWNT in NMMO. Addition, but only after the mechanical stirring without ultrasonic grinding. And the rightmost picture in Figure 2 is a picture of a solution (A-MWNT content of 0.0wt%) does not contain A-MWNT. As can be seen in the left picture of Figure 2, even when the ultrasonic grinding is carried out it can be seen that the uniformity was made even though a lot of A-MWNT was included. And when the ultrasonic grinding is not performed as shown in the center of Figure 2 it can be seen that even though a small amount of A-MWNT is added A-MWNT particles are agglomerated enough to visually confirm.

Composite Specimen Preparation

The composite dope obtained as described above was poured into a glass plate, and then milled with a glass rod to prepare a flat film. At this time, a tape was wound at both ends of the glass rod to form a gap between the glass plate and the glass rod, so as to have a thickness corresponding to the tape thickness. In order to remove and solidify NMMO, the film was immersed in water for 24 hours while attached to a glass plate. Then, taken out in water, and dried at room temperature for 24 hours to prepare a composite film (sample). At this time, in order to prevent shrinkage of the film (sample), it was fixed by drying on a sample holder.

<Property Evaluation>

Mechanical properties, thermal properties, permeability and electrical properties of the composite film (sample) prepared were measured.

Mechanical properties (tensile strength, fracture strength, toughness, etc.) were used in the Instron Instron 5564 model, and the load was measured at room temperature with 5kgf and speed of 10mm / min. The length, width and thickness of the composite fill were used as 30mm, 10mm and 20㎛, respectively, the results are shown in Figures 3a and 3b.

Thermal properties (thermal stability) were measured using a TGA-50 model of Shimadzu, using the composite film completely dried in a vacuum oven as a specimen. At this time, it was measured at a rate of 10 ℃ / min (TGA temperature measurement) under a nitrogen stream from 150 ℃ to 400 ℃, the results are shown in Figure 5a and 5b.

The transmittance was measured using a V-650 model of Jasco, a UV / visible spectrometer, and the results are shown in FIG. 6.

The electrical properties (electric conductivity) were measured by a four point probe at room temperature using the HMS-3000 model. At this time, the size of the composite film (test piece) was 1cm in width, 1cm in length, the thickness was used was 0.02mm, it was measured after fixing the indium (indium) metal is not impeded to the conductivity at each corner end of the specimen. Conductivity measuring range of the measuring instrument 10 is ³ - 10 ^-6 was used as the S / cm of the results are shown in Fig.

First, FIG. 3A is a strain-stress curve of a composite film having A-MWNT contents of 3.0 wt% (a), 10.0 wt% (b), and 12.0 wt% (c), and as the content of A-MWNT increases. It can be seen that the strain increases until the break point and the stress increases linearly together. In addition, Figure 3b shows a tensile strainer and Young's modulus according to the content of A-MWNT (0.0wt%, 0.2wt%, 0.4wt%, 0.6wt%, 0.8wt%, 1.0wt%). As shown in FIG. 3B, the tensile strain rapidly increased to 0.8 wt% of A-MWNT, and then decreased. In addition, as shown in Figure 3b, tensile strain (at break) and Young's modulus (tensile strength at break) is when the content of A-MWNT is 0.8wt%, when A-MWNT is not added as 0.0wt% ( Compared to the pure lyocell film), it can be seen that 5 and 2 times increased, respectively. This is a result of the well-dispersed A-MWNT in cellulose, and this increase in tensile strength and strain means an increase in toughness. And toughness can be seen in the result of FIG. 4D. Therefore, pure lyocell (A-MWNT content of 0.0wt%) can be easily broken compared to conventional synthetic fiber Rayon (Rayon), it can be seen that the mechanical properties are increased by the addition of A-MWNT. This increase in mechanical properties is thought to be the hydrogen bonding action between A-MWNT and cellulose. However, as shown in Figure 4b, it can be seen that when the excessive amount of A-MWNT is added in the case of tensile strain (tensile strength) due to the decrease in the dispersibility of the A-MWNT.

In addition, FIGS. 4A to 4C are scanning electron microscopes (SEMs) photographing cross-sections of a composite film having A-MWNT contents of 0.6 wt% (FIG. 4 a), 1.0 wt% (FIG. 4 b), and 9.0 wt% (FIG. 4 c). ) Photo. At this time, the photograph of the cross section of the composite film was coated with a platinum (Platinum) on the film and measured at a voltage of 15kV. As shown in FIGS. 4A-4C, when A-MWNT is 0.6 wt% (FIG. 4 a) and 1.0 wt% (FIG. 4 b), very well dispersed A-MWNT can be seen, but 9.0 wt% (FIG. 4 c). Some of the somewhat entangled in the can be seen that, too much A-MWNT content was found to be poor dispersibility.

5A and 5B are thermal stability evaluation results of the composite film according to the content of A-MWNT. In this case, Figure 5a is a graph of a TGA thermal analysis of the measured results, Figure 5b is a first graph of Figure 5a derivative (1 ^st derivative) graph. The peak of the pure cellulose film (A-MWNT content 0.0wt%) in Figure 5b (first differential graph) is 329 ℃, the peak of the composite film having a content of 1.0wt% A-MWNT is It can be seen that it is 339 ℃, it can be seen that the peak (peak) increases as the content of A-MWNT increases. This indicates that the thermal stability increases with the amount of A-MWNT added. In addition, at 450 ° C., the residue after pyrolysis showed that the pure cellulose film (content of 0.0 wt% of A-MWNT) was 27.0 wt%, and the 1.0 wt% of A-MWNT composite film was slightly increased to 31.0 wt%.

FIG. 6 is a graph of measuring transmittance according to wavelength of each content of A-MWNT. FIG. As shown in FIG. 6, the wavelength and the transmittance of the A-MWNT were continuously decreased as the content of A-MWNT was increased. The transmittances of the composite films of 0.4 wt%, 0.8 wt% and 1.0 wt% of A-MWNT were 86%, 69% and 59% in the 550 nm wave, respectively. From the above results, as the content of A-MWNT increases, the transmittance decreases, and when it is added below 0.6wt%, it can be seen that it can be applied to a product requiring optical properties by showing transmittance of 80% or more.

Figure 7 is the result of measuring the electrical conductivity of the composite film according to the content of A-MWNT at room temperature. As shown in FIG. 7, the electrical conductivity also increased as the content of A-MWNT increased. In this case, even when A-MWNT was added in a trace amount of about 0.2 wt%, the composite film was found to have conductivity. In addition, when the content of A-MWNT is 1.0wt% or less, the conductivity level is 10 ^-5 to 10 ^-6 S / cm, and when the content of A-MWNT is 5.0wt% and 9.0wt%, 1.77 10 ^-4 and 3.07 10 ^-3 S / cm was found to have a high electrical conductivity characteristics.

From the above results, it was found that A-MWNT and cellulose were uniformly dispersed in the NMMO monohydrate solution while being combined by hydrogen bonding by acid treatment and ultrasonic grinding. In addition, the prepared composite film was improved by mechanical strength, thermal properties, etc. by A-MWNT, it can be seen that by adding a small amount of A-MWNT can have transparency simultaneously with the electrical conductivity. Accordingly, it can be seen that the reinforcement of the mechanical and thermal properties of the lyocell (cellulose), an environmentally friendly material, and the transparency and electrical conductivity can be applied to fiber products as well as optical products and electrical / electronic products. .

Meanwhile, a composite film (sample) was prepared in the same manner as in the above example, but a composite film (sample) was prepared using MWNT (multi-walled carbon nanotubes) without acid treatment (P-MWNT). . At this time, the content (wt%) of P-MWNT was added to 0.0wt%, 2.0wt%, 4.0wt%, 6.0wt%, 8.0wt% and 10.0wt% based on the mixture of P-MWNT and cellulose. . And the tensile strain (break strain) was measured in the same manner as described above for the prepared composite film (sample), the results are shown in Figure 8 attached.

As shown in Figure 8, when the MWNT is added (4.0wt% or more), it can be seen that the tensile strain is evaluated as compared to the case that is not added (0.0wt%). From these results, it can be seen that even if the MWNT is not acid treatment (functional group introduction), the addition of the MWNT alone improves the mechanical properties.

1 is a graph showing the results of FT-IR spectroscopy of acid-treated multi-walled carbon nanotubes (A-MWNT) according to an embodiment of the present invention.

2 is a photograph of a dispersion solution of NMMO and A-MWNT prepared according to an embodiment of the present invention.

Figure 3 is a graph showing the results of measuring the mechanical properties of the composite film according to an embodiment of the present invention.

Figure 4 is a SEM photograph of the cross section of the composite film according to an embodiment of the present invention.

5 is a graph showing the measurement results of the thermal properties of the composite film according to an embodiment of the present invention.

6 is a graph showing a result of measuring the transmittance of the composite film according to an embodiment of the present invention.

7 is a graph showing the results of electrical conductivity measurement of the composite film according to the embodiment of the present invention.

8 is a graph showing the measurement results of the mechanical properties of the composite film according to another embodiment of the present invention.

Claims (11)

Multi-walled carbon nanotubes; And multi-walled carbon nanotubes / cellulose composites comprising cellulose. The method of claim 1, Multi-walled carbon nanotubes, multi-walled carbon nanotubes / cellulose composites, characterized in that contained in 0.01 to 70.0% by weight based on the mixed weight of the multi-walled carbon nanotubes and cellulose. The method of claim 1, Multi-walled carbon nanotubes, multi-walled carbon nanotubes / cellulose composites, characterized in that contained in 0.2 to 5.0% by weight based on the mixed weight of the multi-walled carbon nanotubes and cellulose. The method according to any one of claims 1 to 3, Multi-walled carbon nanotubes are multi-walled carbon nanotubes / cellulose composites, characterized in that the functional group is introduced or coated with a polar compound. Preparing a multi-walled carbon nanotube; Obtaining a mixed solution containing an N-methylmorpholine-N-oxide (NMMO) solution and the multi-walled carbon nanotubes; Ultrasonically grinding the mixed solution; And Method for producing a multi-walled carbon nanotubes / cellulose composites comprising the step of mixing cellulose in the ultrasonically pulverized mixed solution. The method of claim 5, Method for producing a multi-walled carbon nanotubes / cellulose composites, characterized in that it further comprises the step of ultrasonic pulverization of a solution in which cellulose is mixed. Preparing a multi-walled carbon nanotube; Mixing an N-methylmorpholine-N-oxide (NMMO) solution, the multi-walled carbon nanotubes and cellulose; And Method for producing a multi-walled carbon nanotubes / cellulose composites comprising the step of ultrasonic grinding the mixed solution. The method according to any one of claims 5 to 7, Method for producing a multi-walled carbon nanotubes / cellulose composites further comprising the step of modifying the surface of the prepared multi-walled carbon nanotubes. The method of claim 8, The step of modifying the surface of the multi-walled carbon nanotubes, a method for producing a multi-walled carbon nanotubes / cellulose composites, characterized in that it comprises one or more processes selected from the following (1) to (7) process. (1) Acid-treatment of Multi-Walled Carbon Nanotubes (2) Ultrasonic irradiation process on multi-walled carbon nanotubes (3) Process of irradiating microwaves to multi-walled carbon nanotubes (4) A process of irradiating radiation on multi-walled carbon nanotubes (5) Corona discharge treatment of multi-walled carbon nanotubes (6) A step of irradiating ion beams to multi-walled carbon nanotubes (7) coating polar compound on the surface of multi-walled carbon nanotubes The method according to any one of claims 5 to 7, The multi-walled carbon nanotubes, the method of producing a multi-walled carbon nanotubes / cellulose composites, characterized in that the mixed to be 0.01 to 70.0% by weight based on the mixed weight of the multi-walled carbon nanotubes and cellulose. The method according to any one of claims 5 to 7, The multi-walled carbon nanotubes, the method of producing a multi-walled carbon nanotubes / cellulose composites, characterized in that the mixed to be 0.2 to 5.0% by weight based on the mixed weight of the multi-walled carbon nanotubes and cellulose.

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