CN103881137A - Melamine flame retardant graft modified carbon nanotube and manufacturing method thereof - Google Patents

Abstract

The invention relates to a melamine flame retardant graft modified carbon nanotube and a preparation method thereof, belonging to the field of carbon nanotube modification. First, by acidifying the purified carbon nanotubes, active carboxyl groups are introduced on the surface; the carboxyl groups can directly condense with melamine through a condensing agent, so that the melamine flame retardant is grafted to the surface of carbon nanotubes through chemical bonds. The purpose of the present invention is to graft high-nitrogen flame retardant melamine onto the surface of carbon nanotubes through chemical bonds to obtain a new type of carbon nanotubes modified by surface grafting of flame retardants, which can be co-existed with various resin matrices. Mixed, while comprehensively improving the flame retardancy of carbon nanotubes, it can also improve their dispersion and compatibility in the resin matrix.

Description

A kind of melamine flame retardant graft modified carbon nanotube and preparation method thereof

technical field

The invention relates to the field of modification of carbon nanotubes, in particular to a surface graft modified carbon nanotube of a melamine flame retardant and a preparation method thereof.

Background technique

Since the discovery of carbon nanotubes, carbon nanotubes have been widely used because of their high strength, high aspect ratio, high specific surface area, high thermal stability, excellent electrical conductivity, excellent thermal conductivity and unique one-dimensional tubular structure. It is used in the research of drug carriers, catalysts, biosensors, etc.

The Japanese scholar Fujiwara first applied for a patent on nano-clay flame-retardant nylon in 1976, which opened up another research hotspot of nano-flame retardant materials. Studies have found that adding a very small amount (<5%) of carbon nanotubes to the resin matrix will not only improve the mechanical properties of the composite material to varying degrees, but also significantly reduce the peak heat release rate of the composite material during combustion, and delay its Combustion process (Song Pingan. Research on intumescent flame retardant, nano flame retardant and their synergistic flame retardant polypropylene [D]. Zhejiang University, 2009). Although nano-flame retardant technology can significantly reduce the heat release rate and mass loss rate of materials in the cone calorimetry test, it is not effective in traditional flame retardant tests such as limiting oxygen index test (LOI) and vertical combustion test (UL-94). But not as expected. In order to enhance the flame retardant properties of carbon nanotubes, in recent years, researchers at home and abroad have tried to graft flame retardants to the surface of carbon nanotubes, such as Ma (Advanced Functional Materials, 2008, 18, 414-421) and Song (Journal of Materials Chemistry 2008, 18, 5083) and others grafted a single-substance intumescent flame retardant PDSPB/PDBPP synthesized in the laboratory to the surface of carbon nanotubes to obtain surface-modified carbon nanotubes, and applied them to ABS/PP resin A good flame retardant effect was achieved. MWNT-PDSPB can achieve the flame retardant effect when the original MWNT content is 1% at the content of 0.2%. Chinese invention patents (CN1O2585291A, CN1O244266O A) introduce the grafting of hyperbranched polysiloxane containing phosphaphenanthrene structure and epoxy group and hyperbranched polysiloxane containing phosphaphenanthrene structure and amino group to carbon in the form of chemical bonds. The nanotube surface, because it contains active reactive groups, can achieve good dispersion in the thermosetting resin; at the same time, it can endow the thermosetting resin with good flame retardancy and toughness on the basis of maintaining the heat resistance and rigidity of the resin.

However, the preparation method of the above-mentioned modified carbon nanotubes has more or less complicated reaction process, involves thionyl chloride chlorination, and has disadvantages such as high cost, and has certain limitations in practical application. The invention adopts a two-step process and simplifies the modification process through the direct condensation reaction of carboxyl groups; meanwhile, introducing a flame retardant with high nitrogen content on the surface of the carbon nanotube can effectively improve the flame retardancy of the carbon nanotube.

Contents of the invention

The purpose of the present invention is to prepare a novel flame retardant surface-grafted modified carbon nanotube, by grafting a flame retardant with high nitrogen content to the surface of the carbon nanotube through a chemical bond, and comprehensively improving the carbon nanotube surface. Flame retardant properties, especially oxygen index and vertical burning test results.

To achieve the above object, the present invention adopts the following technical solutions:

A preparation method of melamine flame retardant grafted modified carbon nanotubes, characterized in that it comprises the steps:

(1) Preparation of acidified carbon nanotubes: the original carbon nanotubes are purified and ultrasonically treated to fully disperse them in strong acid; then continue ultrasonication for 3h-5h under heating conditions at 40°C-70°C to fully acidify them; The obtained product is repeatedly washed with a large amount of deionized water to neutrality, vacuum-filtered with a microporous filter membrane or filter paper, and completely dried in a vacuum state to obtain acidified carbon nanotubes.

(2) Preparation of carbon nanotubes grafted with melamine flame retardant: fully mix the acidified carbon nanotubes with melamine, condensing agent, and solvent in a certain proportion, and ultrasonically treat them for a certain period of time to fully dissolve and disperse them. After purging nitrogen for 20-60 minutes, react at 60°C-125°C with strong magnetic stirring for 24h-72h. After the reaction, vacuum filter the obtained product with a microporous filter membrane or filter paper, and wash it with solvent and acetone several times, then dry the product completely under vacuum at 40°C-140°C to obtain a melamine flame retardant grafted modified carbon nanotube.

The original carbon nanotubes used in the step (1) of the present invention are single-wall or multi-wall carbon nanotubes prepared by arc discharge, catalytic pyrolysis and laser evaporation methods, etc., with a diameter of 8-20 nanometers, an average length of 1-10 microns, and high purity at 95%.

The step of purifying carbon nanotubes used in step (1) of the present invention is as follows: soak 10-50 parts by mass of carbon nanotubes with 100-500 parts by volume of concentrated nitric acid for 36h-72h, then repeatedly wash the resulting product with a large amount of deionized water until Neutral, after vacuum filtration with microporous filter membrane or filter paper, completely dry under vacuum to obtain purified carbon nanotubes.

The strong acid used in the step (1) of the present invention is a mixed acid obtained by concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 1:1 to 3:1, and the amount of mixed acid used is 10-20 parts by mass for carbon nanotubes of 100-500 parts by volume.

The microporous filter membrane used in step (1) and step (2) of the present invention has a pore size of 0.3-0.6 μm, and the filter paper is conventional filter paper.

The vacuum drying time of step (1) and step (2) of the present invention is 10h-30h, and the purpose is to dry to constant weight.

The melamine used in step (2) of the present invention is a chemically pure or industrial-grade white powdery crystal product with a purity of more than 99%.

The condensing agent used in step (2) of the present invention is dicyclohexylcarbodiimide (DCC) or diisopropylcarbodiimide (DIC), and the solvent is pyridine.

The amount of acidified carbon nanotubes in step (2) of the present invention is 30-60 parts by mass, the amount of melamine is 30-60 parts by mass, the amount of condensing agent is 3-6 parts by mass, and the amount of solvent is 300-500 parts by volume.

The invention prepares a brand-new surface-modified carbon nanotube, and grafts high-nitrogen flame retardant melamine onto the surface of the carbon nanotube. The process is simple, the raw material is easy to obtain, the preparation amount is large, and the conversion rate is high. A new polymer flame retardant additive.

In practical applications, the melamine flame retardant grafted modified carbon nanotubes prepared by the present invention can be blended with various resin matrices to obtain nanocomposites; the modified carbon nanotubes can well improve the flame retardancy of the matrix resin materials properties and mechanical properties. .

Description of drawings

1 is a schematic flow diagram of a surface-modified carbon nanotube provided by an embodiment of the present invention;

Fig. 2 is an infrared comparison diagram of a surface-modified carbon nanotube provided by an embodiment of the present invention and an original carbon nanotube;

Detailed ways

The technical solutions of the present invention will be described in more detail below in conjunction with the accompanying drawings and embodiments.

Example 1:

(1) Add 2 g of purified carbon nanotubes into a conical flask filled with 45 ml of concentrated sulfuric acid and concentrated nitric acid (volume ratio 3:1), and ultrasonicate at 50°C for 3 hours. After sonication, pour a large amount of deionized water to dilute, vacuum filter and continuously wash with deionized water until neutral. The solid was dried in a vacuum oven at 80° C. for 12 h to constant weight to obtain acidified carbon nanotubes.

(2) Take 2g of acidified carbon nanotubes, 2g of melamine, 0.2g of dicyclohexylcarbodiimide, and 80ml of pyridine, pour them into a three-necked flask and mix them thoroughly, and ultrasonicate for 30 minutes to fully dissolve and disperse them. After deoxygenation by nitrogen for 20 minutes, the reaction was refluxed for 48 hours at 120° C. under strong magnetic stirring. After the reaction, the obtained product was vacuum filtered, washed with pyridine and acetone for several times, and dried at 80° C. for 12 hours to constant weight to obtain melamine flame retardant grafted modified carbon nanotubes.

Infrared analysis was carried out on the modified carbon nanotubes and the original carbon nanotubes. Compared with the unmodified carbon nanotubes, the modified carbon nanotubes appeared -NH ₂ absorption peaks at 3469cm ^-1 and 3418.4cm ^-1 , 3334cm ^-1 is the absorption peak of -NH, 1551.7cm ^-1 is the characteristic peak of C=N, and 1651.57cm ^-1 is the characteristic peak of C=O bond, which indicates that melamine is grafted to the surface of carbon tubes.

Example 2:

(1) Add 2 g of purified carbon nanotubes into a conical flask filled with 45 ml of concentrated sulfuric acid and concentrated nitric acid (volume ratio 3:1), and sonicate at 50°C for 4 hours. After sonication, pour a large amount of deionized water to dilute, vacuum filter and continuously wash with deionized water until neutral. The solid was dried in a vacuum oven at 80° C. for 12 h to constant weight to obtain acidified carbon nanotubes.

(2) Take 2g of acidified carbon nanotubes, 2g of melamine, 0.2g of dicyclohexylcarbodiimide, and 80ml of pyridine, pour them into a three-necked flask and mix them thoroughly, and ultrasonicate for 30 minutes to fully dissolve and disperse them. After deoxygenation by nitrogen for 20 minutes, the reaction was refluxed for 48 hours at 110° C. under strong magnetic stirring. After the reaction, the obtained product was vacuum filtered, washed with pyridine and acetone for several times, and dried at 80° C. for 12 hours to constant weight to obtain melamine flame retardant grafted modified carbon nanotubes.

Example 3:

(1) Add 2 g of purified carbon nanotubes into a conical flask filled with 45 ml of concentrated sulfuric acid and concentrated nitric acid (volume ratio 3:1), and ultrasonicate at 50°C for 5 hours. After sonication, pour a large amount of deionized water to dilute, vacuum filter and continuously wash with deionized water until neutral. The solid was dried in a vacuum oven at 80° C. for 12 h to constant weight to obtain acidified carbon nanotubes.

(2) Take 2g of acidified carbon nanotubes, 2g of melamine, 0.2g of dicyclohexylcarbodiimide, and 80ml of pyridine, pour them into a three-necked flask and mix them thoroughly, and ultrasonicate for 30 minutes to fully dissolve and disperse them. After deoxygenation by nitrogen for 20 minutes, the reaction was refluxed for 48 hours at 110° C. under strong magnetic stirring. After the reaction, the obtained product was vacuum filtered, washed with pyridine and acetone for several times, and dried at 80° C. for 12 hours to constant weight to obtain melamine flame retardant grafted modified carbon nanotubes.

Example 4:

(1) Add 2 g of purified carbon nanotubes into a conical flask filled with 45 ml of concentrated sulfuric acid and concentrated nitric acid (volume ratio 3:1), and ultrasonicate at 50°C for 3 hours. After sonication, pour a large amount of deionized water to dilute, vacuum filter and continuously wash with deionized water until neutral. The solid was dried in a vacuum oven at 80° C. for 12 h to constant weight to obtain acidified carbon nanotubes.

(2) Take 2g of acidified carbon nanotubes, 2g of melamine, 0.2g of dicyclohexylcarbodiimide, and 80ml of pyridine, pour them into a three-necked flask and mix them thoroughly, and ultrasonicate for 40 minutes to fully dissolve and disperse them. After deoxygenation by nitrogen for 20 minutes, the reaction was refluxed for 60 hours at 100° C. under strong magnetic stirring. After the reaction, the obtained product was vacuum filtered, washed with pyridine and acetone for several times, and dried at 80° C. for 12 hours to constant weight to obtain melamine flame retardant grafted modified carbon nanotubes.

Example 5:

(1) Add 2 g of purified carbon nanotubes into a conical flask filled with 45 ml of concentrated sulfuric acid and concentrated nitric acid (volume ratio 3:1), and ultrasonicate at 50°C for 3 hours. After sonication, pour a large amount of deionized water to dilute, vacuum filter and continuously wash with deionized water until neutral. The solid was dried in a vacuum oven at 80° C. for 12 h to constant weight to obtain acidified carbon nanotubes.

(2) Take 2g of acidified carbon nanotubes, 2g of melamine, 0.2g of dicyclohexylcarbodiimide, and 80ml of pyridine, pour them into a three-necked flask and mix them thoroughly, and ultrasonicate for 40 minutes to fully dissolve and disperse them. After purging nitrogen for 20 minutes to remove oxygen, the mixture was refluxed for 72 hours at 90° C. under strong magnetic stirring. After the reaction, the obtained product was vacuum filtered, washed with pyridine and acetone for several times, and dried at 80° C. for 12 hours to constant weight to obtain melamine flame retardant grafted modified carbon nanotubes.

Embodiment 6:

(1) Add 2 g of purified carbon nanotubes into a conical flask filled with 45 ml of concentrated sulfuric acid and concentrated nitric acid (volume ratio 3:1), and ultrasonicate at 50°C for 3 hours. After sonication, pour a large amount of deionized water to dilute, vacuum filter and continuously wash with deionized water until neutral. The solid was dried in a vacuum oven at 80° C. for 12 h to constant weight to obtain acidified carbon nanotubes.

(2) Take 2g of acidified carbon nanotubes, 2g of melamine, 0.2g of diisopropylcarbodiimide, and 80ml of pyridine, pour them into a three-necked flask and mix them thoroughly, and ultrasonicate for 40 minutes to fully dissolve and disperse them. After purging nitrogen for 20 minutes to remove oxygen, the mixture was refluxed for 72 hours at 90° C. under strong magnetic stirring. After the reaction, the obtained product was vacuum filtered, washed with pyridine and acetone for several times, and dried at 80° C. for 12 hours to constant weight to obtain melamine flame retardant grafted modified carbon nanotubes.

Embodiment 7:

(1) Add 2 g of purified carbon nanotubes into a conical flask filled with 45 ml of concentrated sulfuric acid and concentrated nitric acid (volume ratio 3:1), and ultrasonicate at 50°C for 3 hours. After sonication, pour a large amount of deionized water to dilute, vacuum filter and continuously wash with deionized water until neutral. The solid was dried in a vacuum oven at 80° C. for 12 h to constant weight to obtain acidified carbon nanotubes.

(2) Take 2g of acidified carbon nanotubes, 2g of melamine, 0.2g of diisopropylcarbodiimide, and 80ml of pyridine, pour them into a three-necked flask and mix them thoroughly, and ultrasonicate for 40 minutes to fully dissolve and disperse them. After purging nitrogen for 20 minutes to remove oxygen, the mixture was refluxed for 72 hours at 90° C. under strong magnetic stirring. After the reaction, the obtained product was vacuum filtered, washed with pyridine and acetone for several times, and dried at 80° C. for 12 hours to constant weight to obtain melamine flame retardant grafted modified carbon nanotubes.

Embodiment 8:

(1) Add 2 g of purified carbon nanotubes into a conical flask filled with 45 ml of concentrated sulfuric acid and concentrated nitric acid (volume ratio 3:1), and sonicate at 50°C for 4 hours. After sonication, pour a large amount of deionized water to dilute, vacuum filter and continuously wash with deionized water until neutral. The solid was dried in a vacuum oven at 80° C. for 12 h to constant weight to obtain acidified carbon nanotubes.

(2) Take 2g of acidified carbon nanotubes, 2g of melamine, 0.2g of dicyclohexylcarbodiimide, and 80ml of pyridine, pour them into a three-necked flask and mix them thoroughly, and ultrasonicate for 40 minutes to fully dissolve and disperse them. After deoxygenation by nitrogen for 20 minutes, the reaction was refluxed for 72 hours at 120° C. under strong magnetic stirring. After the reaction, the obtained product was vacuum filtered, washed with pyridine and acetone several times, and dried at 80° C. for 24 hours to constant weight to obtain melamine flame retardant grafted modified carbon nanotubes.

Claims (10)

1. a trimeric cyanamide fire retardant grafted modified carbon nano tube, is characterized in that: fire retardant trimeric cyanamide is arrived to carbon nano tube surface by chemical bond grafting.

2. a preparation method for trimeric cyanamide fire retardant grafted modified carbon nano tube, is characterized in that comprising the steps:

(1) produce acidifying carbon nanotube: by purified original carbon nanotube rear ultrasonication, it is well dispersed in strong acid; Under 40 DEG C of-70 DEG C of heating conditions, continue ultrasonic 3h-5h afterwards, make its complete acidifying; Products therefrom is extremely neutral with a large amount of deionized water repetitive scrubbings, and with after millipore filtration or filter paper vacuum filtration, complete drying under vacuum state, obtains acidifying carbon nanotube.

(2) produce trimeric cyanamide fire retardant grafted modified carbon nano tube: described acidifying carbon nanotube is fully mixed by a certain percentage with trimeric cyanamide, condensing agent, solvent, and supersound process certain hour makes it fully dissolve dispersion.Logical nitrogen deoxygenation is after 20-60 minute, under 60 DEG C-115 DEG C and strong magnetic agitation, and reaction 24h-72h.After reaction finishes, by millipore filtration or filter paper vacuum filtration for products therefrom, and after repeatedly washing with solvent and acetone, product is complete drying under 40 DEG C of-140 DEG C of vacuum states, obtains trimeric cyanamide fire retardant grafted modified carbon nano tube.

3. the preparation method of trimeric cyanamide fire retardant grafted modified carbon nano tube according to claim 2, is characterized in that step (1) original carbon nanotube used is single wall or the multi-walled carbon nano-tubes of the preparations such as arc-over, catalyse pyrolysis and laser evaporation method.

4. the preparation method of trimeric cyanamide fire retardant grafted modified carbon nano tube according to claim 2, it is characterized in that step (1) purifying carbon nano-tube purification step used is: the concentrated nitric acid of the carbon nanotube of 10-50 mass parts 100-500 parts by volume is soaked after 36h-72h, products therefrom is extremely neutral with a large amount of deionized water repetitive scrubbings, with after millipore filtration or filter paper vacuum filtration, complete drying under vacuum state, obtains purifying carbon nano-tube.

5. the preparation method of trimeric cyanamide fire retardant grafted modified carbon nano tube according to claim 2, it is characterized in that step (1) strong acid used is the vitriol oil and concentrated nitric acid 1:1～3:1 gained mixing acid by volume, 100-500 parts by volume mixing acid for the carbon nanotube of 10-20 mass parts.

6. the preparation method of trimeric cyanamide fire retardant grafted modified carbon nano tube according to claim 2, is characterized in that step (1) and step (2) millipore filtration used aperture are 0.3-0.6 μ m, and filter paper is conventional filter paper.

7. the preparation method of trimeric cyanamide fire retardant grafted modified carbon nano tube according to claim 2, is characterized in that step (1) and step (2) vacuum-drying time are 10h-30h.

8. the preparation method of trimeric cyanamide fire retardant grafted modified carbon nano tube according to claim 2, is characterized in that step (2) trimeric cyanamide used is chemical pure or technical grade white powder crystal product.

9. the preparation method of trimeric cyanamide fire retardant grafted modified carbon nano tube according to claim 2, it is characterized in that step (2) condensing agent used is dicyclohexylcarbodiimide (DCC) or DIC (DIC), solvent is pyridine.

10. the preparation method of trimeric cyanamide fire retardant grafted modified carbon nano tube according to claim 2, it is characterized in that the described acidifying carbon nanotube of step (2) consumption is 30-60 mass parts, trimeric cyanamide consumption is 30-60 mass parts, and condensing agent consumption is 3-6 mass parts, solvent 300-500 parts by volume.

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