KR101102848B1 - Polypropylene-graft-maleic anhydride/Carbon Nanotube Nanocomposites with Excellent Thermal Stability and Electrical Conductivity - Google Patents

Abstract

The present invention relates to the preparation of polypropylene-graft-maleic anhydride / carbon nanotube nanocomposites having excellent heat resistance and electrical conductivity. In the present invention, after the acid-treated multi-walled carbon nanotubes to prepare a multi-walled carbon nanotubes (MWCNT-COOH) introduced with a carboxyl group (-COOH), it is polypropylene-graft-maleic anhydride (PP-g- It relates to a method for producing polypropylene-graft-maleic anhydride / carbon nanotube nanocomposites by melt mixing with MA). From the polypropylene-graft-maleic anhydride / carbon nanotube nanocomposite of the present invention, it can be prepared into various products such as films, fibers, plastics, etc. having heat resistance and antistatic function.

Polypropylene-Graft-Maleic Anhydride, Carbon Nanotubes, Acid Treated Carbon Nanotubes, Melt Blends, Films, Fibers, Plastics

Description

Polypropylene-graft-maleic anhydride / Carbon Nanotube Nanocomposites with Excellent Thermal Stability and Electrical Conductivity}

According to the present invention, carbon nanotubes are acid-treated with carbon nanotubes to form carbon nanotubes having a carboxyl group (-COOH) introduced therein, and then melt-mixed with polypropylene-graft-maleic anhydride polymer to have a polypropylene- having excellent heat resistance and electrical conductivity. A graft-maleic anhydride / carbon nanotube nanocomposite is provided.

As the industrial society is highly developed and many products are produced from petroleum, polymers have become closely related to our lives and become one of our necessities. Polymers have been developed into plastics, films, and fibers that are light and have various uses, properties, and properties, and are widely used in human life. Among them, polypropylene (PP), a polymer that is commonly found in our surroundings and easily found, is widely used in plastics, films and fibers. Polypropylene has a low specific gravity and is used for various purposes as a plastic product, and its general properties are similar to polyethylene, but its stress crushing properties, transparency, and tensile strength are superior to that of polyethylene, and it is lightweight. Has a hinge characteristic. It is a very good material for food hygiene and it has good durability against external stress and has a good surface appearance.

Polypropyelen-graft-maleic anhydride (PP-g-MA) is a polypropylene made by adding maleic anhydride (MA) as an anhydride to polypropylene. It has high adhesiveness.

Carbon nanotube (CNT) is a material that is spotlighted as an almost perfect new material without defects among existing materials, and its electrical conductivity is similar to that of copper, the thermal conductivity is the most excellent diamond in nature, and the strength is steel. 100 times better. Carbon fiber breaks with only 1% strain while CNTs withstand 15% strain and are very stable. CNTs have a graphite sheet rounded off to a nano-sized diameter, and exhibit the characteristics of a metal or a semiconductor depending on the angle and structure of the graphite sheet being dried. In addition, single-walled carbon nanotubes (SWCNTs), double-walled carbon nanotubes (DWCNTs), and multi-walled carbon nanotubes (SWCNTs), depending on the number of bonds forming a wall. MWCNT), and bundle carbon nanotubes (Rope Carbon Nanotube, RCNT). Carbon nanotubes, like nano-scale fillers, have a very strong tendency to bundle together by van der Waals forces. Therefore, a lot of researches are being made to supplement the methods and weaknesses to improve the dispersibility and the functional groups that can interact with other compounds by acid treatment of carbon nanotubes.

In the present invention, after the acid treatment of MWCNT used as a reinforcing material to increase the interaction with the PP-g-MA and carbon nanotube matrix to prepare a multi-walled carbon nanotube (MWCNT-COOH) with a carboxyl group (-COOH), The purpose of the present invention is to provide a method and properties for producing PP-g-MA / MWCNT and PP-g-MA / MWCNT-COOH nanocomposites with excellent thermal stability and electrical conductivity by melt mixing with PP-g-MA.

In order to achieve the above object, according to a preferred embodiment of the present invention, the carbon nanotubes are acid-treated with a carboxyl group-attached carbon nanotubes and polypropylene-graft-maleic anhydride to melt-mix the polypropylene-graft It provides a method for preparing maleic anhydride / carbon nanotube nanocomposites.

According to another suitable embodiment of the present invention, the nanocomposite comprises 0.01 to 50 wt% of carboxyl group attached carbon nanotubes and 50 to 99.99 wt% of polypropylene-graft-maleic acid based on the total weight of the composite. It is characterized by producing an anhydride by melt mixing.

According to another suitable embodiment of the present invention, the acid treated carbon nanotubes are characterized by having 1 to 5 × 10 ²² carboxyl groups per gram of carbon nanotubes.

According to another suitable embodiment of the invention, the polypropylene-graft-maleic anhydride is characterized in that it comprises 0.01 to 10 wt% maleic anhydride.

According to another suitable embodiment of the present invention, there is provided a polypropylene-graft-maleic anhydride / carbon nanotube nanocomposite prepared by the above method.

In the present invention, the acid treatment of MWCNT, MWCNT-COOH to give a carboxyl group on the surface of the carbon nanotube is a polymer matrix by chemical reaction and / or physical interaction (polar bond including hydrogen bond) with MA of the polymer PP-g-MA There is an effect with improved dispersibility within. In addition, the PP-g-MA / MWCNT-COOH nanocomposite prepared in the present invention has the effect of improving the thermal stability than PP-g-MA.

The preparation method of the PP-g-MA / MWCNT-COOH nanocomposite of the present invention improves the electrical conductivity of the PP-g-MA single polymer. In addition, the PP-g-MA / MWCNT nanocomposite and PP-g-MA / MWCNT-COOH nanocomposite having excellent heat resistance and electrical conductivity of the present invention are applied to fibers, films, plastics, etc. requiring excellent thermal properties and antistatic function. Can be.

In the present invention, a multi-walled carbon nanotube (hereinafter referred to as "MWCNT") is a multi-walled carbon nanotube (hereinafter referred to as "MWCNT-) in which a carboxyl group (-COOH) is introduced by acid treatment using sulfuric acid and nitric acid. COOH "), which is then melt mixed with a polypropylene-graft-maleicanhydride (hereinafter referred to as" PP-g-MA ") polymer to provide excellent heat and electrical conductivity. A polypropylene-graft-maleic anhydride / carbon nanotube nanocomposite having the same is prepared.

Definitions of terms used in the present specification are as follows. "PP-g-MA" refers to polypropylene-graft-maleic anhydride, and refers to a polymer to which polypropylene is grafted with maleic anhydride. PP-g-MA in the present invention is preferably a content of 0.01 to 10 wt% maleic anhydride, more preferably 0.1 to 1wt%.

"MWCNT" stands for Multi-walled Carbon Nanotube. MWCNT used in the present invention is a CM-95 product of Iljin Nanotech. As used herein, the term "MWCNT-COOH" is a material modified by MWCNT by acid treatment using nitric acid and sulfuric acid, and has a carboxyl group (-COOH) on its surface, and has excellent electrical conductivity and heat resistance. MWCNT-COOH herein has from 1 to 5 × 10 ²² carboxyl groups (—COOH) per gram of MWCNT.

"PP-g-MA / MWCNT-COOH" used in the present invention refers to a material prepared by melt-mixing MWCNT-COOH and polymer PP-g-MA.

"PP-g-MA / MWCNT" used in the present invention refers to a material prepared by melt-mixing MWCNT and polymer PP-g-MA.

In the present invention, the acid treatment of carbon nanotubes using a strong acid, the carbon nanotubes are not particularly limited, single-walled carbon nanotubes, multi-walled carbon nanotubes, multiple carbon nanotubes can be used. Hereinafter, the case of using the multi-walled carbon nanotubes (MWCNT) will be described as an example of the present invention.

First, the carbon nanotube (MWCNT-COOH) having a carboxyl group (-COOH) attached to the surface is prepared by acid treatment of the multi-walled carbon nanotube (MWCNT). The acid treatment may be performed using an acid mixed solution composed of various strong acid combinations. In the present invention, a strong acid solution in which nitric acid and sulfuric acid are mixed at a molar ratio of 3: 1 is used. The multi-walled carbon nanotubes were added to the nitric acid / sulfuric acid solution, and then treated with ultrasonic waves and refluxed again for 2 to 3 hours. After the reflux is completed, the suspension solution is cooled to room temperature, precipitated with excess distilled water, and washed with water to pH 7. Thereafter, the filter process is followed by vacuum drying at 70 ~ 90 ℃ to produce a multi-walled carbon nanotubes (MWCNT-COOH) attached to a carboxyl group.

The carboxyl group (-COOH) attached multi-walled carbon nanotubes prepared by the above method is one per 1 g of MWCNT To 5 × 10 ²² carboxyl groups (—COOH).

PP-g-MA / MWCNT-COOH nanocomposites are prepared by melt-mixing the MWCNT-COOH and PP-g-MA prepared above. Specifically, MWCNT-COOH and PP-g-MA homopolymers are melt-mixed at 160 to 240 ° C. using a melt kneader (mixer or extruder) to prepare PP-g-MA / MWCNT-COOH nanocomposites.

The PP-g-MA / MWCNT-COOH nanocomposites prepared in the present invention have better heat resistance than PP-g-MA homopolymers or PP-g-MA / MWCNT nanocomposites. In addition, the PP-g-MA / MWCNT-COOH nanocomposite of the present invention has better electrical conductivity than the PP-g-MA single polymer.

Preparation Example 1 ( Preparation of MWCNT-COOH by Acid Treatment)

First, a method for preparing a multiwall carbon nanotube (MWCNT-COOH) in which a carboxyl group is introduced by acid treatment will be described. Pure MWCNTs are added to a mixed solution of nitric acid / sulfuric acid (3/1, molar ratio) and sonicated for 1 hour to form a suspension solution. The suspension solution is refluxed for 2 hours while maintaining 120 ℃ in the reflux device. After reflux, the suspension solution is cooled to room temperature, precipitated in excess distilled water, and washed with water until pH reaches 7. Subsequently, MWCNT-COOH can be obtained by vacuum drying at 80 ° C. through a filter process. In the MWCNT-COOH, the carboxyl group (-COOH) has 1 to 5 × 10 ²² per g of MWCNT.

Preparation Example 2 ( Preparation of PP-g-MA / MWCNT-COOH by Melt Mixing)

MWCNT-COOH (COOH 5 × 10 ²² pieces / MWCNT 1g) and PP-g-MA (MA content 0.8wt%) single polymer prepared in Preparation Example 1 were 160 using a melt kneader (mixer or extruder). Melt mixing at ˜240 ° C. can yield the PP-g-MA / MWCNT-COOH nanocomposite. For comparison, PP-g-MA / MWCNT nanocomposites are prepared by the same melt mixing method using MWCNT which is not treated with PP-g-MA.

Preparation Example 3 ( Preparation of PP-g-MA / MWCNT-COOH nanocomposite film)

PP-g-MA homopolymer, PP-g-MA / MWCNT-COOH nanocomposite prepared in Preparation Example 2 and PP-g-MA / MWCNT nanocomposite were sufficiently dried in a vacuum at 80 ℃, heating press at 180 ℃ It can be obtained in the form of a film by compressing to a thickness of 0.2 mm.

The present invention will be described in detail with reference to the following examples, but the scope of the present invention is not limited by the examples.

Example 1 (manufactured by MWCNT-COOH)

In silicon oil, 630 mL of sulfuric acid and 186 mL of nitric acid are added first, and 7g of MWCNTs are added while stirring slowly. Acid treated MWCNTs are diluted with water and filtered through filtration and washed with water to adjust the pH to 7 or higher. MWCNT-COOH obtained by the above method is dried by vacuum drying for 24 hours before melt mixing.

Example 2 ( Preparation of PP-g-MA / MWCNT-COOH by Melt Mixing)

PP-g-MA / CNT-COOH nanocomposites were prepared by melt mixing various weights of MWCNT-COOH with polymer PP-g-MA as shown in Table 1. First, MWCNT-COOH and PP-g-MA polymer prepared in the ratios shown in Table 1 were sufficiently mixed in a solid state with a mechanical mixer, melt mixed at a temperature range of 170 to 200 ° C. through a melt kneader, and extruded after 0.1 mmHg. It was dried at room temperature for 24 hours under high vacuum. PP-g-MA / CNT-COOH nanocomposite powder samples obtained by drying were melted at 190 ° C. for 3 minutes using a heating press, and then quenched to 0 ° C. and then PP-g-MA / MWCNT having a uniform thickness of 0.2 mm. Prepared with -COOH nanocomposite film.

Comparative Example 1

PP-g-MA / MWCNT nanocomposite films were prepared in the same manner as described in Example 2 with MWCNTs of the same weight in place of MWCNT-COOH described in Table 1.

Test Example 1 (Measurement of Thermal Stability of PP-g-MA / MWCNT and PP-g-MA / MWCNT-COOH)

Thermogravimetric analyzer (TGA) was used to measure the thermal stability of PP-g-MA / MWCNT-COOH and PP-g-MA / MWCNT nanocomposites. As shown in FIG. 1, the PP-g-MA homopolymer showed a 5 wt% thermal weight loss at 355 ° C. and the PP-g-MA / MWCNT nanocomposite was at a much higher temperature than the PP-g-MA homopolymer. Pyrolysis behavior is shown. Even when the content of MWCNT is 10 wt% it can be seen that the pyrolysis behavior at a temperature higher than 80 ℃ higher than the PP-g-MA single polymer. By adding MWCNT to the PP-g-MA homopolymer, it can be seen that it exhibits high heat resistance.

On the other hand, as shown in FIG. 2, the PP-g-MA / MWCNT-COOH nanocomposite has a thermal decomposition temperature (T _5% ) corresponding to a 5 wt% weight loss despite the MWCNT-COOH content of 0.1%. The temperature is higher than 20 ℃ higher than the MA single polymer.

Also, in FIG. 2, when 10 wt% of MWCNT-COOH is added to the PP-g-MA homopolymer, the thermogravimetry is reduced at a temperature of about 100 ° C. or more, which is much higher than that of MWCNT. It can be seen that thermal stability, ie, heat resistance, is improved by strong physical interactions such as chemical bonding or hydrogen bonding between the MA of PP-g-MA and the COOH of MWCNT-COOH.

Table 2 summarizes the thermal decomposition temperature of PP-g-MA homopolymer, PP-g-MA / MWCNT nanocomposite and PP-g-MA / MWCNT-COOH nanocomposite obtained from the pyrolysis curves shown in FIGS. will be.

1) T _{5 %} : Temperature at which 5 wt% weight loss of the initial weight of the sample occurs

2) T _{50 %} : Temperature at which 50 wt% weight loss of the initial weight of the sample occurs

Test Example 2 (Electric Conductivity of PP-g-MA / MWCNT and PP-g-MA / MWCNT-COOH)

A high resistance meter was used to measure the electrical resistance (inverse of the electrical conductivity) of the PP-g-MA / MWCNT and PP-g-MA / MWCNT-COOH nanocomposite films. As shown in FIG. 3, the PP-g-MA polymer film exhibits a high electrical resistance value of ˜10 ¹⁷ (μm · cm). In the PP-g-MA / MWCNT-COOH nanocomposite (b), it can be seen that the MWCNT-COOH content has an electrical resistance of about 10 ⁷ (μm · cm) at about 5 wt%. The other hand, in the PP-g-MA / MWCNT nanocomposite film (a), is the electric resistance value to the lot to 10 ⁸ in the content of 3 wt% of small CNT (Ω · cm) less than 5 wt% to 10 ⁶ (Ω · The electrical resistance value of cm) is shown. This can be said to be the result of the electrical conductivity decreased slightly as the carbon conjugated double bond of MWCNT was destroyed during MWCNT acid treatment. However, both PP-g-MA / MWCNT and PP-g-MA / MWCNT-COOH nanocomposites have low electrical resistance values of ˜10 ^{6-7 ~} · cm when the MWCNT content is above 5 wt%. The low electrical resistance values (~ 10 ^6-7 Ωcm) of PP-g-MA / MWCNT-COOH and PP-g-MA / MWCNT nanocomposites according to the present invention were almost charged when made of fiber, film or plastic. It means having excellent electrical conductivity that does not occur (electrostatic generation).

PP-g-MA / MWCNT-COOH nanocomposite prepared according to the method of the present invention, as evidenced from the results of the test example, compared with the conventional PP-g-MA homopolymer and PP-g-MA / MWCNT nanocomposite Has excellent thermal stability. The low electrical resistance values of PP-g-MA / MWCNT-COOH and PP-g-MA / MWCNT nanocomposites show excellent antistatic effects. Therefore, the PP-g-MA / MWCNT and PP-g-MA / MWCNT nanocomposites according to the present invention can be usefully applied in various fields such as films, fibers, plastics, and the present invention is not limited to these specific examples.

Figure 1 shows the weight change with temperature of the PP-g-MA / MWCNT nanocomposite.

Figure 2 shows the weight change with temperature of the PP-g-MA / MWCNT-COOH nanocomposite.

Figure 3 shows the electrical resistivity (Electrical resistivity) value according to the MWCNT or MWCNT-COOH content of the PP-g-MA / MWCNT nanocomposite (a) and PP-g-MA / MWCNT-COOH nanocomposite (b).

Claims (5)

Acid-processing the carbon nanotubes to prepare carbon nanotubes to which carboxyl groups are attached; Preparing a polypropylene-graft-maleic anhydride comprising 0.01 to 10 wt% maleic anhydride; And Including melting and mixing the carboxyl group-attached carbon nanotubes and the polypropylene-graft-maleic anhydride at a temperature of 170 to 200 ° C. A method for producing a polypropylene-graft-maleic anhydride / carbon nanotube nanocomposite, wherein the electrical resistance has a value of 10 ⁷ Ωcm or less. The method of claim 1, wherein the nanocomposite is melt-mixed carbon nanotubes having 5 to 50 wt% of carboxyl groups to the total weight of the composite and 50 to 95 wt% of polypropylene-graft-maleic anhydride relative to the total weight of the composite. Method for producing a polypropylene-graft-maleic anhydride / carbon nanotube nanocomposite, characterized in that the production. The polypropylene-graft-maleic anhydride / carbon nanotube nano according to claim 1, wherein the carbon nanotube to which the carboxyl group is attached by acid treatment has 1 to 5 × 10 ²² carboxyl groups per gram. Composite manufacturing method. delete Polypropylene-graft-maleic anhydride / carbon nanotube nanocomposite prepared by the method of claim 1.

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