CN107827770A - A kind of hexagonal nanometer boron nitride composite of aliphatic chain grafting and preparation method thereof - Google Patents

Abstract

The invention discloses a hexagonal boron nitride nanocomposite material grafted with fatty chains and a preparation method thereof. The preparation process is to pre-hydroxylate the hexagonal boron nitride nanomaterial, and then add an acid solution to react with substituted phenylamino acids. Diazonium salt reaction to obtain aniline-modified hexagonal boron nitride, and finally the aniline-modified hexagonal boron nitride is dispersed in an organic solvent under the action of an acid-binding agent to further react with acid chloride. The nano-composite material grafted with different mass fractions of fatty chains prepared by the method and the high-density polyethylene undergo blending and molding processes to prepare the nano-composite material. The invention adopts a mild and high-efficiency diazonium salt high-temperature reaction method to modify the surface of the hexagonal boron nitride, which improves the disadvantages of the traditional method, such as harsh reaction conditions, long reaction period and low grafting rate. Thus, the prepared hexagonal boron nitride nanocomposite with short branched aliphatic chains has good dispersibility in high-density polyethylene.

Description

A kind of aliphatic chain grafted hexagonal boron nitride nanocomposite material and preparation method thereof

technical field

The invention relates to a new aliphatic chain grafted hexagonal boron nitride nanocomposite material and a preparation method thereof.

Background technique

With the progress of nuclear energy development, traditional radiation protection materials can no longer meet the protection requirements of my country's nuclear power industry, such as the traditional radiation protection material - lead, which is highly toxic and has poor neutron shielding effect. Lead-containing concrete Disadvantages such as bulky and difficult to move. Therefore, in order to meet the resulting challenges, it has become an important aspect of material research and development to develop new radiation-proof materials that are non-toxic, low-density, good shielding effect, and excellent physical properties. At present, there are many types of absorbers used in neutron-absorbing materials, among which hexagonal boron nitride has a good ability to absorb neutrons because of its ¹⁰ B isotope, and nano-scale hexagonal boron nitride has a surface and The interface effect, small size effect and quantum size effect have a good effect on improving the neutron absorption effect and thermodynamic properties of the material, but because hexagonal boron nitride is a nanomaterial, its inherent easy to agglomerate effect makes it in the polymer The dispersion in the matrix is very poor, so it not only affects the neutron absorption performance, but also has certain restrictions on its mechanical properties. Therefore, it is necessary to modify the surface of boron nitride to increase its dispersion in the polymer, so that it can be uniformly dispersed in the polymer, thereby improving the neutron absorption efficiency.

At present, according to literature reports, the surface modification methods of hexagonal boron nitride mainly include plasma method, oxygen radical functionalization method, non-covalent bond adsorption and chemical deposition method. Although these methods have achieved the improvement of its different functions by grafting the surface of hexagonal boron nitride to varying degrees, the grafting rate is low (less than 10%), the modification conditions are harsh, and high temperature and pressure are required. And the reaction cycle is long, needing 48h, and other shortcomings make it limited in further application, especially when it is compounded with polymers, its dispersibility is not well improved, and the improvement in the improvement of neutron absorption performance is not obvious.

Therefore, it is necessary to adopt a high grafting rate, simple and mild modification method to modify the surface of hexagonal boron nitride, so that the surface of hexagonal boron nitride has special functionality, which can not only improve its performance in polymers The dispersibility of the modified hexagonal boron nitride and the polymer can also be improved, thereby preparing a high-performance inorganic nanoparticle composite material.

Contents of the invention

In order to solve the above problems, one of the objectives of the present invention is to provide a mild and efficient method for preparing aliphatic chain-grafted hexagonal boron nitride nanocomposites.

The second object of the present invention is to provide a polymer mixing system with good dispersibility in the polymer and its preparation method.

The modification method adopted in the present invention has the advantages of high efficiency and mildness, which makes the surface of hexagonal boron nitride have special functionality, not only can improve its dispersion in polymers, but also improve the hexagonal boron nitride after modification. Interaction forces with polymers.

The technical scheme that the present invention adopts is as follows:

The invention provides a hexagonal boron nitride nanocomposite material grafted with aliphatic chains, which has a structure as shown in formula (I):

in:

A is hexagonal boron nitride;

B is an aliphatic chain; wherein the chain length is selected from C ₁ -C ₅₀ , preferably C ₁₀ -C ₂₀ .

The "fatty chain-grafted hexagonal boron nitride nanocomposite" of the present invention has the following meanings: the hexagonal boron nitride is grafted with substituted fatty chains after surface modification, but each hexagonal boron nitride surface-grafted substitution It is not controllable whether the aliphatic chain is evenly distributed, so the number of substituted short-chain branches, molecular weight, etc. of each surface-modified hexagonal boron nitride bond are not completely uniform, so it can be called a composition or a mixture. And because the surface of the hexagonal boron nitride can't clearly explain how many substituted aliphatic chains are grafted on the surface of the hexagonal boron nitride, but the weight loss data measured by the thermogravimetric analysis (TGA) method in the present invention characterizes the grafted hexagonal nitrogen. The number of grafted aliphatic chains on the boronide surface.

According to the present invention, the hexagonal boron nitride is nanometer hexagonal boron nitride.

Among them, the technical parameters of nano-hexagonal boron nitride are shown in Table 1:

The present invention also provides a preparation method of the nanocomposite material grafted with the aliphatic chain, the method comprising the following steps:

Step 1, pre-hydroxylating the hexagonal boron nitride nanomaterial: reacting the nanomaterial with a strong base compound, and removing the unreacted strong base compound;

Step 2, add the pre-hydroxylated nanomaterials to the acid solution, and react with the substituted phenylamino acid diazonium salt to obtain aniline-modified hexagonal boron nitride, the substituted anilino sulfate diazonium salt is represented by the following structure :

wherein R ₁ is hydrogen, alkyl or alkoxy. Preferably, the above-mentioned alkyl or alkoxy group is a C ₁ -C ₁₆ , C ₁ -C ₈ or C ₁ -C ₄ alkyl or alkoxy group, and X ^- is the acid ion of the acid solution, preferably HSO ₄ ^- .

Step 3, dispersing the aniline-modified hexagonal boron nitride in an organic solvent under the action of an acid-binding agent and further reacting with acid chlorides to obtain aliphatic chain-grafted nanocomposites with the structure shown in formula (I).

The nano-composite material prepared by the above method with different mass fractions of fatty chain grafts and high-density polyethylene can be blended and formed to prepare the nano-composite material.

According to the present invention, in step 1, the method for pre-hydroxylating the hexagonal boron nitride includes: performing a solid phase reaction between the hexagonal boron nitride and a strong base; or conducting a liquid phase reaction between the hexagonal boron nitride and a strong base in a solution reaction. The solid-phase reaction or the liquid-phase reaction can be applied alone, or both can be applied. When both methods are applied, the order of implementation is not distinguished.

Preferably, the pre-hydroxylation treatment method is a solid phase reaction between the hexagonal boron nitride and a strong base.

Preferably, the reaction temperature is 100-350°C, preferably 150-250°C, more preferably 170-190°C.

According to the present invention, in step (1), preferably, the strong base compound is selected from Group I and Group II alkali metal hydroxides.

Preferably, the strong base compound is selected from one or more of sodium hydroxide, potassium hydroxide and rubidium hydroxide.

Preferably, the strong base compound is a mixture of sodium hydroxide and potassium hydroxide.

Preferably, the mass ratio of sodium hydroxide to potassium hydroxide is 1:1˜3:1.

Preferably, the method of pre-hydroxylation treatment is a high-temperature solid-state reaction between the hexagonal boron nitride and a strong base, and the mixed system of the reaction includes:

(i) sodium hydroxide (ii) potassium hydroxide (iii) hexagonal boron nitride nanosheets.

According to the present invention, in the above reaction mixture system, the mass ratio of (i) sodium hydroxide and (ii) potassium hydroxide is 1:1 to 3:1, preferably 1.5 to 2.5; and the mixture of strong base and hexagonal nitrogen The mass ratio of boron chloride is 1:1-8:1, preferably 2:1-5:1.

According to the present invention, after the reaction of step (2), the aniline-modified hexagonal boron nitride contains substituted anilines bonded to the surface. The substituted anilines are represented by the following structure:

Wherein R ₁ is hydrogen, alkyl or alkoxy, and the alkyl or alkoxy is as defined above. Preferably, wherein R ₁ is hydrogen.

According to the present invention, the mass ratio of the substituted aniline group bonded to the hexagonal boron nitride to the aniline-modified hexagonal boron nitride is 5-95%. Preferably it is 5%, 10%, 20%, 30%, 50%, 70%, 80%, 95%.

According to the present invention, in step 2, the synthesis method of the diazonium salt is: under low temperature conditions, p-phenylenediamine is reacted with excess sodium nitrite.

According to the present invention, in step 2, the acid solution is selected from one or more of hydrochloric acid, sulfuric acid, nitric acid and permanganic acid; preferably, the concentrated acid is sulfuric acid.

According to the present invention, in step 2, the acid solution has an acid concentration of at least 20%, preferably 20-80%;

According to the present invention, in step 2, the reaction temperature is above 100°C, preferably 100-300°C, more preferably 100-200°C.

According to the present invention, the mass ratio of the substituted phenylated diazonium salt to the raw material hexagonal boron nitride is 1:1-20:1. Preferably, the mass ratio is 5:1˜15:1.

According to the present invention, in step 3, the acid chloride is selected from stearoyl chloride, palmitoyl chloride, n-pentanoyl chloride, lauryl chloride, myristoyl chloride, heptanoyl chloride, octanoyl chloride, hexanoyl chloride, n-butyryl chloride and other fatty chain acid chlorides A combination of one or more; Preferably, the acid chloride is stearyl chloride.

According to the present invention, in step 3, the acid-binding agent is selected from one or more combinations of triethylamine, pyridine, diisopropylethylamine, sodium acetate, sodium carbonate, and potassium carbonate. Preferably, the acid-binding agent is pyridine.

According to the present invention, in step 3, the organic solvent includes one or more combinations of N,N-dimethylformamide, methylene chloride, carbon tetrachloride, thionyl chloride, and toluene. Preferably, the organic solvent is dichloromethane.

According to the present invention, in step 3, the reaction temperature is above 0°C, preferably 0-100°C, more preferably 0-80°C.

According to the present invention, in step 3, the reaction time is more than 12 hours, preferably 24-48 hours.

According to the present invention, in step 3, the molar ratio of the substituted anilino hexagonal boron nitride to the acid chloride is 1:1˜1:20. Preferably, the molar ratio is 1:1˜10:1.

According to the present invention, in step 3, the molar ratio of the acid chloride to the acid-binding agent is 1:1-1:20. Preferably, the molar ratio is 1:2˜1:10.

According to the present invention, in step 3, the whole reaction is carried out under anhydrous environment.

According to the present invention, in step (4), the blending method includes melt blending, emulsion blending, solution blending and powder blending, preferably melt blending.

According to the present invention, in step (4), the temperature of melt blending is 150-250°C, preferably 180-220°C.

According to the present invention, in step (4), the time for melt blending is more than 5 minutes, preferably 10-30 minutes.

According to the present invention, in step (4), the molding method includes injection molding, extrusion molding, foam molding and blow molding, preferably injection molding.

During the blending and molding process of the fatty chain-grafted nanocomposites prepared by the above method with different mass fractions and high-density polyethylene, the molding temperature is 180-300°C, preferably 200-250°C; the cooling temperature is 20-60°C, preferably 40-50°C; molding pressure 2-20MPa, preferably 5-10MPa.

In the present invention, in step 2, a mild and efficient modification method is adopted on the surface of the hexagonal boron nitride. Specifically, in a strong alkaline environment, the pre-hydroxylation treatment of the hexagonal boron nitride breaks the boron-nitrogen bond on the surface of the hexagonal boron nitride, thereby introducing a large number of boron hydroxyl groups and amino groups. The hydrogen-oxygen bond and nitrogen-hydrogen bond on the boron hydroxyl group dehydrogenate at high temperature to form oxygen free radicals and nitrogen free radicals.

Moreover, when the pre-hydroxylated hexagonal boron nitride reacts with the substituted phenyl sulfated diazonium salt in hot sulfuric acid solution, the substituted phenyl sulfated diazonium salt decomposes and loses nitrogen to form a very active aminophenyl positive ion , the aminophenyl cations further reacted with the boron hydroxyl groups on the surface of the pre-hydroxylated hexagonal boron nitride, releasing hydrogen gas. At the same time, the strongly acidic sulfuric acid solution can not only increase the temperature of the above-mentioned decomposition reaction, but also reduce the occurrence of side reactions.

A large number of aniline groups grafted on the surface of hexagonal boron nitride, among which the amino group is highly active, can further react with acid chlorides of different aliphatic chain lengths, thereby producing hexagonal boron nitride nanocomposites with a large number of short branched aliphatic chains on the surface.

According to the present invention, the modification method in step 2 is to graft aliphatic chains of different lengths on the surface of hexagonal boron nitride.

According to the present invention, the modification method in step 2 may be to generate new chemical substances on the surface of hexagonal boron nitride.

The invention also provides a polymer mixing system as a neutron shielding material, which is characterized in that the mixing system is prepared from the surface-modified hexagonal boron nitride nanocomposite material and polyethylene proposed by the invention.

The beneficial effect of the invention is that the surface modification of the hexagonal boron nitride is carried out by adopting a mild and efficient diazonium salt high-temperature reaction method, which improves the disadvantages of the traditional method such as harsh reaction conditions, long reaction period and low grafting rate. Thus, the prepared hexagonal boron nitride nanocomposite with short branched aliphatic chains has good dispersibility in high-density polyethylene.

Description of drawings

Figure 1a is a scanning electron micrograph (SEM) of hexagonal boron nitride nanosheets in the original state; b is the SEM of the hexagonal boron nitride nanocomposite material prepared according to Example 1.

Fig. 2 is the infrared spectrum of the original hexagonal boron nitride and the hexagonal boron nitride nanocomposite material prepared according to the modification method in Example 1.

Fig. 3 SEM of composites prepared with different contents of hexagonal boron nitride and HDPE.

Fig. 4 SEM of composite materials prepared by different contents of hexagonal boron nitride nanocomposites and HDPE.

Detailed ways

Below in conjunction with specific embodiment, further illustrate the present invention. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the protection scope of the present invention. In addition, it should be understood that after reading the disclosure of the present invention, those skilled in the art may make various changes or modifications to the present invention, and these equivalent forms also fall within the scope of protection defined by the present invention.

Thermogravimetric analysis: Tested under the conditions of air atmosphere and 10°C/min heating rate, thermogravimetric analysis shows that based on the weight loss between 250°C and 600°C, the samples thus prepared are based on the hexagonal nitrogen modified by the acid chloride The weight of boron chloride contains a certain percentage of acid chloride.

Infrared analysis: characterize and analyze the acid chloride branched chain on the surface of the modified hexagonal boron nitride by infrared. If the characteristic absorption peaks of aliphatic alkanes and amide groups appear, it indicates that the acid chloride has been successfully grafted onto the surface of hexagonal boron nitride.

Electron microscope analysis: Observing the surface of the modified hexagonal boron nitride through an electron microscope, if the surface or edge has a shape different from that of the hexagonal boron nitride matrix, it indicates that this part is affected by acid chloride. And comparing it with the original hexagonal boron nitride surface morphology can further verify the modification effect from the morphology.

Example 1

(1) Weigh 2.8g of sodium hydroxide and 2.2g of potassium hydroxide, add 1g of hexagonal boron nitride nanosheets, grind them into fine powder in a mortar, and mix well. The mixed powder was reacted in a crucible at 180° C. for 3 h, and cooled to room temperature. The mixed powder treated by the solid phase method was dispersed in a certain amount of water, the mixed solution was treated with an ultrasonic cell pulverizer for 2 hours, and then the supernatant was removed by centrifugation. Washing with distilled water 3 times until the pH of the solution is neutral to obtain pre-hydroxylated hexagonal boron nitride.

(2) In an ice bath, dissolve 5.4 g of p-phenylenediamine in 4 mL of 98% concentrated sulfuric acid and 32 mL of deionized water, and stir until the p-phenylenediamine is completely dissolved. Add 30% sodium nitrite solution dropwise from the liquid surface to the above solution to prepare the corresponding sulfated diazonium salt solution.

(3) Disperse the pre-hydroxylated hexagonal boron nitride in step (1) in 100 mL of deionized water and 50 mL of 98% concentrated sulfuric acid, and raise the temperature to 130°C. Under rapid stirring, the diazonium salt solution prepared in step (2) was added dropwise into the above acidic dispersion. The diazonium salt solution was added dropwise within 30 minutes. After continuing to stir for 3 h, the reaction solution was naturally cooled to room temperature, filtered, and washed with water, ammonia solution, and anhydrous methanol successively.

(4) Vacuum pump the 1000mL three-necked flask three times to create an anhydrous and oxygen-free environment. Under an ice bath, disperse the aniline hexagonal boron nitride obtained in step (3) in anhydrous N,N-dimethylformamide solvent, then add 10 mL of pyridine as an acid-binding agent, and keep stirring. Then 10 g of stearyl chloride was dissolved in 100 mL of anhydrous dichloromethane, and added dropwise to the solvent in which aniline hexagonal boron nitride was dispersed. Let the reaction system return to room temperature and continue to stir for 18 hours. After the reaction is completed, wash with anhydrous ether at least three times, and dry the washed product in a vacuum oven at 60°C for 24 hours to obtain a dry hexagonal boron nitride nanocomposite material. Figure 1a shows the SEM of the hexagonal boron nitride nanosheets in the original state; the SEM of the hexagonal boron nitride nanocomposite material prepared in Example 1 is shown in Figure 1b.

Example 2

(1) Weigh 2.8g of sodium hydroxide and 2.2g of potassium hydroxide, add 1g of hexagonal boron nitride nanosheets, grind them into fine powder in a mortar, and mix well. Transfer the mixed powder into a 100mL hydrothermal reaction kettle, add 70mL of pure water, react at 180°C for 6h, cool to room temperature, use an ultrasonic cell pulverizer to treat the mixture for 2h, and then centrifuge to remove the supernatant, the lower layer Washing with distilled water for 3 times until the pH of the solution is neutral to obtain pre-hydroxylated hexagonal boron nitride.

(2) In an ice bath, dissolve 5.4 g of p-phenylenediamine in 4 mL of 98% concentrated sulfuric acid and 32 mL of deionized water, and stir until the p-phenylenediamine is completely dissolved. Add 30% sodium nitrite solution dropwise from the liquid surface to the above solution to prepare the corresponding sulfated diazonium salt solution.

(3) Disperse the pre-hydroxylated hexagonal boron nitride in step (1) in 100 mL of deionized water and 50 mL of 98% concentrated sulfuric acid, and raise the temperature to 130°C. Under rapid stirring, the diazonium salt solution prepared in step (2) was added dropwise into the above acidic dispersion. The diazonium salt solution was added dropwise within 30 minutes. After continuing to stir for 3 h, the reaction solution was naturally cooled to room temperature, filtered, and washed with water, ammonia solution, and anhydrous methanol successively.

(4) Vacuum pump the 1000mL three-necked flask three times to create an anhydrous and oxygen-free environment. Under an ice bath, disperse the aniline hexagonal boron nitride obtained in step (3) in anhydrous N,N-dimethylformamide solvent, then add 10 mL of pyridine as an acid-binding agent, and keep stirring. Then 10 g of stearyl chloride was dissolved in 100 mL of anhydrous dichloromethane, and added dropwise to the solvent in which aniline hexagonal boron nitride was dispersed. Let the reaction system return to room temperature and continue to stir for 18 hours. After the reaction is completed, wash with anhydrous ether at least three times, and dry the washed product in a vacuum oven at 60°C for 24 hours to obtain a dry hexagonal boron nitride nanocomposite material.

Example 3

(1) Weigh 2.8g of sodium hydroxide and 2.2g of potassium hydroxide, add 1g of hexagonal boron nitride nanosheets, grind them into fine powder in a mortar, and mix well. First react the mixed powder in a crucible at 180°C for 3h, then transfer the mixed powder into a 100mL hydrothermal reaction kettle, add 70mL of pure water, and react at 180°C for 6h. After cooling to room temperature, the mixture was treated with an ultrasonic cell disruptor for 2 hours, and then the supernatant was removed by centrifugation, and the lower layer was washed with distilled water three times until the pH of the solution was neutral to obtain pre-hydroxylated hexagonal boron nitride.

(2) In an ice bath, dissolve 5.4 g of p-phenylenediamine in 4 mL of 98% concentrated sulfuric acid and 32 mL of deionized water, and stir until the p-phenylenediamine is completely dissolved. Add 30% sodium nitrite solution dropwise from the liquid surface to the above solution to prepare the corresponding sulfated diazonium salt solution.

(3) Disperse the pre-hydroxylated hexagonal boron nitride in step (1) in 100 mL of deionized water and 50 mL of 98% concentrated sulfuric acid, and raise the temperature to 130°C. Under rapid stirring, the diazonium salt solution prepared in step (2) was added dropwise into the above acidic dispersion. The diazonium salt solution was added dropwise within 30 minutes. After continuing to stir for 3 h, the reaction solution was naturally cooled to room temperature, filtered, and washed with water, ammonia solution, and anhydrous methanol successively.

(4) Vacuum pump the 1000mL three-necked flask three times to create an anhydrous and oxygen-free environment. Under an ice bath, disperse the aniline hexagonal boron nitride obtained in step (3) in anhydrous N,N-dimethylformamide solvent, then add 10 mL of pyridine as an acid-binding agent, and keep stirring. Then 10 g of stearyl chloride was dissolved in 100 mL of anhydrous dichloromethane, and added dropwise to the solvent in which aniline hexagonal boron nitride was dispersed. Let the reaction system return to room temperature and continue to stir for 18 hours. After the reaction is completed, wash with anhydrous ether at least three times, and dry the washed product in a vacuum oven at 60°C for 24 hours to obtain a dry hexagonal boron nitride nanocomposite material.

Example 4

(1) Weigh 2.8g of sodium hydroxide and 2.2g of potassium hydroxide, add 1g of hexagonal boron nitride nanosheets into a three-necked flask, add 150mL of deionized water to dissolve and disperse, stir mechanically at a high temperature of 150°C, and react for 8 hours. Cool to room temperature, centrifuge to remove the supernatant, wash the lower layer with distilled water 3 times until the pH of the solution is neutral, and obtain pre-hydroxylated hexagonal boron nitride.

(2) In an ice bath, dissolve 5.4 g of p-phenylenediamine in 4 mL of 98% concentrated sulfuric acid and 32 mL of deionized water, and stir until the p-phenylenediamine is completely dissolved. Add 30% sodium nitrite solution dropwise from the liquid surface to the above solution to prepare the corresponding sulfated diazonium salt solution.

(3) Disperse the pre-hydroxylated hexagonal boron nitride in step (1) in 100 mL of deionized water and 50 mL of 98% concentrated sulfuric acid, and raise the temperature to 130°C. Under rapid stirring, the diazonium salt solution prepared in step (2) was added dropwise into the above acidic dispersion. The diazonium salt solution was added dropwise within 30 minutes. After continuing to stir for 3 h, the reaction solution was naturally cooled to room temperature, filtered, and washed successively with water, ammonia solution (20 cc of ammonia solution in 1 liter of water), and anhydrous methanol.

(4) Vacuum pump the 1000mL three-necked flask three times to create an anhydrous and oxygen-free environment. Under an ice bath, disperse the aniline hexagonal boron nitride obtained in step (3) in anhydrous N,N-dimethylformamide solvent, then add 10 mL of pyridine as an acid-binding agent, and keep stirring. Then 10 g of stearyl chloride was dissolved in 100 mL of anhydrous dichloromethane, and added dropwise to the solvent in which aniline hexagonal boron nitride was dispersed. Let the reaction system return to room temperature and continue to stir for 18 hours. After the reaction is completed, wash with anhydrous ether at least three times, and dry the washed product in a vacuum oven at 60°C for 24 hours to obtain a dry hexagonal boron nitride nanocomposite material.

The weight loss data that embodiment 1～4 thermogravimetric analysis (TGA) (between 250～600 ℃) measure is as grafted on the hexagonal boron nitride nanosheet surface aliphatic short branch relative to hexagonal nitriding Weight fraction of boron nanocomposites. The results are shown in Table 2.

Example 5

Weigh the hexagonal boron nitride nanocomposite material prepared in Example 1 and 44.75g of high-density polyethylene (HDPE) with a mass fraction of 0.5%, add an antioxidant that accounts for 3/1000 of the mass fraction, and at 200°C Melt blend for 10 minutes. Then the mixed material was injection molded into a sample strip, and the sample strip was frozen under liquid nitrogen for 5 hours, and then brittle at low temperature to prepare a scanning electron microscope sample.

Example 6

Weigh the hexagonal boron nitride nanocomposite material prepared in Example 1 and 44.55g of high-density polyethylene (HDPE) with a mass fraction of 1%, add an antioxidant that accounts for 3/1000 of the mass fraction, and at 200°C Melt blend for 10 minutes. Then the mixed material was injection molded into a sample strip, and the sample strip was frozen under liquid nitrogen for 5 hours, and then brittle at low temperature to prepare a scanning electron microscope sample.

Example 7

Weigh the hexagonal boron nitride nanocomposite material prepared in Example 1 and 43.65g of high-density polyethylene (HDPE) with a mass fraction of 3%, add an antioxidant that accounts for 3/1000 of the mass fraction, and at 200°C Melt blend for 10 minutes. Then the mixed material was injection molded into a sample strip, and the sample strip was frozen under liquid nitrogen for 5 hours, and then brittle at low temperature to prepare a scanning electron microscope sample.

Example 8

Weigh the hexagonal boron nitride nanocomposite material prepared in Example 1 and 42.75g of high-density polyethylene (HDPE) with a mass fraction of 5%, add an antioxidant that accounts for 3/1000 of the mass fraction, and at 200°C Melt blend for 10 minutes. Then the mixed material was injection molded into a sample strip, and the sample strip was frozen under liquid nitrogen for 5 hours, and then brittle at low temperature to prepare a scanning electron microscope sample.

Example 9

Weigh the hexagonal boron nitride nanocomposite material prepared in Example 1 and 40.5 g of high-density polyethylene (HDPE) with a mass fraction of 10%, add an antioxidant that accounts for 3/1000 of the mass fraction, and at 200 ° C Melt blend for 10 minutes. Then the mixed material was injection molded into a sample strip, and the sample strip was frozen under liquid nitrogen for 5 hours, and then brittle at low temperature to prepare a scanning electron microscope sample.

Fig. 4 is the SEM image of the composite material prepared by the hexagonal boron nitride nanocomposite material and HDPE with different added mass fractions in Examples 5-9.

From the SEM images of hexagonal boron nitride nanocomposites with different added mass fractions in HDP, it can be seen intuitively that with the gradual increase in the addition of hexagonal boron nitride nanocomposites, it presents a good dispersion effect in HDPE . It can be seen from the figure that even with 10% addition of hexagonal boron nitride nanocomposites, there is still a good dispersion in the HDPE matrix, which shows that the modified hexagonal boron nitride surface has short aliphatic branched chains and HDPE has good compatibility, so the modified hexagonal boron nitride nanocomposite has good dispersion in HDPE.

The following uses unhydroxylated hexagonal boron nitride as a comparative example for comparative analysis.

Comparative example 1

In an ice bath, dissolve 5.4 g of p-phenylenediamine in 4 mL of 98% concentrated sulfuric acid and 32 mL of deionized water, and stir until the p-phenylenediamine is completely dissolved. Add 30% sodium nitrite solution dropwise from the liquid surface to the above solution to prepare the corresponding sulfated diazonium salt.

The original unhydroxylated h-BN was dispersed in 100 mL deionized water and 50 mL 98% concentrated sulfuric acid, and the temperature was raised to 130 °C. Under rapid stirring, the diazonium salt solution prepared above was added dropwise into the above acidic dispersion. The diazonium salt solution was added dropwise within 30 minutes. After continuing to stir for 3 h, the reaction solution was naturally cooled to room temperature, filtered, and washed with water, ammonia solution, and anhydrous methanol successively. The 1000mL three-necked flask was vacuum pumped three times to create an anhydrous and oxygen-free environment. Under an ice bath, disperse the aniline hexagonal boron nitride prepared in the above steps in anhydrous N,N-dimethylformamide solvent, then add 10 mL of pyridine as an acid-binding agent, and keep stirring. Then 10 g of stearyl chloride was dissolved in 100 mL of anhydrous dichloromethane, and added dropwise to the solvent in which aniline hexagonal boron nitride was dispersed. Let the reaction system return to room temperature and continue to stir for 18 hours. After the reaction is completed, wash with anhydrous ether at least three times, and dry the washed product in a vacuum oven at 60°C for 24 hours to obtain a dry hexagonal boron nitride nanocomposite material. The product was characterized by thermogravimetry and infrared. The weight loss data measured from TGA (between 250 and 600°C) were used as the weight ratio of short aliphatic branches grafted on the surface of the hexagonal boron nitride nanosheets relative to the weight of the hexagonal boron nitride nanocomposite . The results are shown in Table 3.

FIG. 2 is the infrared spectrum of the original hexagonal boron nitride and the hexagonal boron nitride nanocomposite material prepared according to the modification method in Example 1.

Comparative example 2

Take by weighing 0.5% mass fraction of the unhydroxylated original hexagonal boron nitride prepared in Comparative Example 1 and a certain amount of high-density polyethylene (HDPE) of 44.75g, add an antioxidant that accounts for 3/1000 of the mass fraction, and Melt blending at 200°C for 10 minutes. Then the mixed material was injection molded into a sample strip, and the sample strip was frozen under liquid nitrogen for 5 hours, and then brittle at low temperature to prepare a scanning electron microscope sample.

Comparative example 3

Weigh 1% mass fraction of unhydroxylated original hexagonal boron nitride and 44.5g of high-density polyethylene (HDPE) as prepared in Comparative Example 1, add an antioxidant that accounts for 3/1000 of the mass fraction, at 200 ° C Melt blend for 10 minutes. Then the mixed material was injection molded into a sample strip, and the sample strip was frozen under liquid nitrogen for 5 hours, and then brittle at low temperature to prepare a scanning electron microscope sample.

Comparative example 4

Weigh 3% mass fraction of unhydroxylated original hexagonal boron nitride and 43.65g of high-density polyethylene (HDPE) as prepared in Comparative Example 1, add an antioxidant that accounts for 3/1000 of the mass fraction, at 200 ° C Melt blend for 10 minutes. Then the mixed material was injection molded into a sample strip, and the sample strip was frozen under liquid nitrogen for 5 hours, and then brittle at low temperature to prepare a scanning electron microscope sample.

Comparative example 5

Weigh 5% mass fraction of unhydroxylated original hexagonal boron nitride and 42.75g of high-density polyethylene (HDPE) as prepared in Comparative Example 1, add an antioxidant that accounts for 3/1000 of the mass fraction, at 200 ° C Melt blend for 10 minutes. Then the mixed material was injection molded into a sample strip, and the sample strip was frozen under liquid nitrogen for 5 hours, and then brittle at low temperature to prepare a scanning electron microscope sample.

Comparative example 6

Weigh 10% mass fraction of unhydroxylated original hexagonal boron nitride and 40.5g of high-density polyethylene (HDPE) as prepared in Comparative Example 1, add an antioxidant that accounts for 3/1000 of the mass fraction, at 200 ° C Melt blend for 10 minutes. Then the mixed material was injection molded into a sample strip, and the sample strip was frozen under liquid nitrogen for 5 hours, and then brittle at low temperature to prepare a scanning electron microscope sample.

Comparative example 7

Weigh 45g of high-density polyethylene (HDPE), add 3% by mass of antioxidant, and melt blend at 200°C for 10 minutes. Then the mixed material was injection molded into a sample strip, and the sample strip was frozen under liquid nitrogen for 5 hours, and then brittle at low temperature to prepare a scanning electron microscope sample.

Fig. 3 is the SEM image of the composite material prepared by original hexagonal boron nitride and HDPE with different added mass fractions in Comparative Examples 2-7.

From the SEM images of original hexagonal boron nitride in HDP with different added mass fractions, it can be seen intuitively that as the added amount of hexagonal boron nitride gradually increases, the agglomeration phenomenon becomes more and more serious, especially from the addition of 3%. There is obvious agglomeration phenomenon. This shows that the unmodified original hexagonal boron nitride has poor compatibility with HDPE, so the dispersion of original hexagonal boron nitride in HDPE is not good.

The embodiments of the present invention have been described above. However, the present invention is not limited to the above-mentioned embodiments. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (11)

1. a kind of hexagonal nanometer boron nitride composite of aliphatic chain grafting, it is characterised in that possess the knot as shown in formula (I) Structure：

Wherein：

A is hexagonal boron nitride；

B is aliphatic chain；Its medium chain length is selected from C₁-C₅₀, it is preferably C₁₀-C₂₀。

2. a kind of preparation method of the hexagonal nanometer boron nitride composite of aliphatic chain grafting as claimed in claim 1, it is special Sign is, comprises the following steps：

Step 1, pre- hydroxylating processing is carried out to hexagonal nanometer boron nitride material：Nano material and strong alkali compound are carried out anti- Should, and remove unreacted strong alkali compound；

Step 2, pre- hydroxylated nano material is added into acid solution, is acidified diazonium reactant salt with substituted phenylamino, obtains benzene The hexagonal boron nitride that amine is modified, the substituted anilino- sulphation diazol is by following representation：

Wherein R₁For hydrogen, alkyl or alkoxy.It is preferred that abovementioned alkyl or alkoxy are C₁-C₁₆, C₁-C₈Or C₁-C₄Alkyl or alkane Epoxide, X^-For the acid ion of the acid solution, preferably HSO₄ ^-。

Step 3, aniline modified hexagonal boron nitride is scattered in the presence of acid binding agent in organic solvent further with acyl chlorides Reaction, obtain the nano composite material of the aliphatic chain grafting of the structure as shown in formula (I).

3. a kind of preparation method of the hexagonal nanometer boron nitride composite of aliphatic chain grafting as claimed in claim 2, it is special Sign is, in the step 1, the method for carrying out pre- hydroxylating processing to the hexagonal boron nitride has：Hexagonal boron nitride and highly basic Carry out solid phase reaction；Or hexagonal boron nitride carries out liquid phase reactor in the solution with highly basic；The solid phase reaction or liquid phase are anti- It should can be administered alone, or both and all to apply.

4. a kind of preparation method of the hexagonal nanometer boron nitride composite of aliphatic chain grafting as claimed in claim 2, it is special Sign is, in the step 2, it is preferable that the strong alkali compound is selected from the hydroxide of group i and group ii alkali metal.

5. a kind of preparation method of the hexagonal nanometer boron nitride composite of aliphatic chain grafting as claimed in claim 2, it is special Sign is that the method for pre- hydroxylating processing carries out high temperature solid state reaction for the hexagonal boron nitride and highly basic in the step 2, instead The mixed system answered includes：

(i) sodium hydroxide (ii) potassium hydroxide (iii) hexagonal boron nitride nanosheet.

6. a kind of preparation method of the hexagonal nanometer boron nitride composite of aliphatic chain grafting as claimed in claim 2, it is special Sign is, in the step 2, one or more of the acid solution in hydrochloric acid, sulfuric acid, nitric acid and permanganic acid；Preferably, The concentrated acid is sulfuric acid, and the acid solution has at least 20% acid concentration.

7. a kind of preparation method of the hexagonal nanometer boron nitride composite of aliphatic chain grafting as claimed in claim 2, it is special Sign is, in the step 3, the acyl chlorides is selected from stearyl chloride, palmitoyl chloride, n-amyl chloride, lauroyl chloride, myristoyl One or more combinations in the acyl chlorides of the aliphatic chains such as chlorine, oenanthyl chloro, caprylyl chloride, caproyl chloride, n-butyryl chloride.

8. a kind of preparation method of the hexagonal nanometer boron nitride composite of aliphatic chain grafting as claimed in claim 2, it is special Sign is, in the step 3, the acid binding agent is selected from triethylamine, pyridine, diisopropylethylamine, sodium acetate, sodium carbonate, carbonic acid One or more kinds of combinations in potassium.

9. a kind of preparation method of the hexagonal nanometer boron nitride composite of aliphatic chain grafting as claimed in claim 2, it is special Sign is, in the step 3, it is sub- that the organic solvent includes DMF, dichloromethane, carbon tetrachloride, dichloro One or more combinations in sulfone, toluene.

10. a kind of preparation method of the hexagonal nanometer boron nitride composite of aliphatic chain grafting as claimed in claim 2, it is special Sign is, in the step 3, reaction whole process is carried out under water-less environment.

11. a kind of mixed with polymers system as neutron shielding material, it is characterised in that the mixed system will by such as right Seek the hexagonal nanometer boron nitride composite and polyethylene preparation that the aliphatic chain described in 1 is grafted.