CN103483516A - Preparation method of graphene oxide-boron-modified phenolic resin - Google Patents

Abstract

A preparation method of graphene oxide-boron modified phenolic resin relates to phenolic resin. Firstly, graphene oxide was prepared by the improved Hummers method; then the obtained graphene oxide was ultrasonically dispersed in a mixture of phenol and formaldehyde; then sodium hydroxide was added as a catalyst to utilize the active groups of graphene oxide itself and phenol , formaldehyde, so that the small molecules of phenolic resin can be smoothly inserted into the middle of the graphene oxide layer; finally, boric acid is introduced, and by changing the reaction conditions, the small molecules in the phenolic resin in the graphene oxide and boric acid initiate a polymerization reaction, thereby preparing a high Performance graphene oxide-boron modified phenolic resin. It not only maintains the structure and performance of graphene, but also retains some oxygen-containing functional groups, which can well solve the problems of poor dispersion, solubility and processability of graphene.

Description

A kind of preparation method of graphene oxide-boron modified phenolic resin

technical field

The invention relates to phenolic resins, in particular to a preparation method of graphene oxide-boron modified phenolic resins.

Background technique

As one of the three synthetic thermosetting resins, phenolic resin has experienced a history of more than one hundred years and has been widely used in adhesives, molding compounds, coatings, foam plastics, etc. Although the amount used is less than that of unsaturated polyester resin and epoxy resin, it has also played a huge role in the military industry, construction industry, automobile industry, etc., not only in the form of resin, but also in the form of composite materials. In order to make the phenolic resin available in a wider range of applications, it is necessary to add various substances to the phenolic resin for modification to improve its comprehensive performance. Widely used modification techniques include adding inorganic nanomaterials (nano-SiO ₂ , nano-TiO ₂ , nano-montmorillonite (MMT), etc.), organic compounds (organosilicon, organoboron, cashew nut shell oil, etc.), inorganic Compounds (borides, molybdenum, etc.) etc. However, many modifications can only improve the thermal or mechanical properties of phenolic resins alone, but cannot improve their thermal and mechanical properties at the same time. In addition, inorganic particles cannot be sufficiently dispersed in organic polymers, which affects the performance of materials. At present, methods to improve the dispersion of inorganic particles in organic polymers include ultrasonic methods, mechanical methods, and surface modification methods, but it is still difficult to realize the composite of polymers and inorganic particles.

Studies on boride-modified phenolic resins show that boron plays a significant role in improving the heat resistance and ablation resistance of phenolic resins. Regardless of the introduction of inorganic borides or organic borides into the molecular structure, it can significantly improve the heat resistance and carbon residue rate of phenolic resins ([1] Xu Peijun, Liu Yuhong, Jing Xinli. Research progress on boride-modified phenolic resins[J] .Aerospace Materials Technology, 2009(6):1-5), but the defects of inorganic boride modified phenolic resin are still obvious in terms of processability and mechanical properties. Therefore, it is necessary to add other compounds for modification, so as to improve the mechanical properties of the modified phenolic resin.

Graphene is the thinnest known material, its thickness is only one atom, but because of its special structure, it has very high hardness, 300 times harder than steel. In addition, graphene also has many peculiar properties in terms of electrical and magnetic properties, such as room temperature quantum Hall effect, bipolar electric field effect, ferromagnetism, superconductivity and high electron mobility, especially its thermal conductivity can be Up to 5300W/(m·K), more than 10 times the thermal conductivity of copper. Therefore, graphene has quite broad application prospects. The application of graphene to polymer materials is one of its applications. Although graphene has a huge market space, its industrial production and market demand are both in its infancy due to its special structure, and many researches are still in the research and development stage. At the end of 2012, the Future Emerging Technologies of the European Union gave Nokia a research grant of US$1.35 billion for research on graphene materials (Graphene). The special hexagonal structure of graphene makes it contain many peculiar physical and chemical properties that are superior to most of today's materials, such as high specific surface area and excellent thermal conductivity, mechanical properties and electron transfer capabilities. At present, the main methods for preparing graphene are: mechanical exfoliation method, chemical vapor deposition method, epitaxial growth method, redox method ([2] Chen Ruican, Wang Haiyan, Han Yonggang, etc. Preparation of graphene by redox method and its characterization[J] . Materials Bulletin B: Research, 26(6):114-117).

One of the ways to apply the excellent properties of graphene is to combine graphene sheets with polymers to prepare composite materials. Producing such composites requires graphene to be evenly distributed on the substrate. However, the structural stability of graphene itself and the strong van der Waals force between layers prevent it from being well composited with other matrix materials, thus limiting the further development and utilization of graphene. Therefore, generally by chemically modifying graphene, the commonly used method is the Hummers method. The principle is similar to the above-mentioned redox method. Graphene is oxidized by intercalation with strong acid at low temperature to obtain oxygen-rich oxygen-containing groups. Graphite, and then obtained graphene oxide with nitrogen atomic layer thickness by ultrasound to obtain graphene oxide, and introduced active groups to improve its compatibility with polymer monomers or polymers ([3] Deng Yao, Huang Xiaorong , Wu Xiaoling. Research progress of graphene oxide composites[J]. Materials Herald A: Review, 2012,26(8):84-87).

Contents of the invention

The object of the present invention is to provide a kind of preparation method of graphene oxide-boron modified phenolic resin.

The present invention comprises the following steps:

1) Add concentrated sulfuric acid to a three-neck round bottom flask, then place it in an ice-water bath, add graphite and sodium nitrate, then add solid potassium permanganate, keep the temperature of the ice-water bath not exceeding 5°C, and then add deionized water , keep the temperature between 32 and 38°C for reaction, when the reaction is close to the end, place it at room temperature, then dilute with warm water, then add H ₂ O ₂ to reduce the remaining high-valent manganese ions until the solution turns bright yellow, then centrifuge Wash until the solution is neutral and detect that there is no SO ₄ ^2- in the supernatant with barium salt, then wash with absolute ethanol, and dry to obtain graphene oxide;

2) Add phenol and formaldehyde into a three-necked flask equipped with a stirrer, a thermometer, and a condenser, then add graphene oxide, add flake sodium hydroxide after ultrasonic dispersion, heat up and reflux for reaction, and dehydrate under reduced pressure to obtain graphene oxide Phenolic resin emulsion;

3) Boric acid was added to the graphene oxide phenolic resin emulsion obtained in step 2), and after heating and reflux reaction, the dark green viscous material was poured out, cooled to room temperature, and the graphene oxide-boron modified phenolic resin was obtained after vacuum drying.

In step 1), the mass ratio of graphite, concentrated sulfuric acid, sodium nitrate, solid potassium permanganate, deionized water, and _H2O2 can be 1: (35-45): ₍ 0.3-0.6): ( 2.5～3.5): (40～60): (15～20); the reaction time can be 30～60min; the time of standing at room temperature can be 72～96h; the temperature of the warm water can be 50 ~60°C; the conditions for the centrifugal washing can be 10000-12000 rpm and 10-20 minutes.

In step 2), the mass ratio of phenol, formaldehyde, graphene oxide, and flaky sodium hydroxide may be 1: (0.97-1.14): (0.005-0.01): (0.01-0.03); the ultrasonic dispersion The conditions for the reaction may be a temperature of 50-60° C. and a time of 20-30 minutes; the conditions for the temperature-rising reflux reaction may be a temperature of 60-65° C. and a time of 1-2 hours.

In step 3), the mass ratio of the amount of boric acid added to the phenol in step 1) can be 1: (0.13-0.27); the conditions for the temperature-raising reflux reaction can be a temperature of 90-100°C and a time of 1- 2h; the vacuum drying conditions may be a temperature of 50-60°C and a time of 24-36h.

The principle of the present invention is: firstly, graphene oxide is prepared by the improved Hummers method; then the obtained graphene oxide is ultrasonically dispersed in a mixture of phenol and formaldehyde; then sodium hydroxide is added as a catalyst to utilize graphene oxide itself The reaction between the active groups of the phenolic resin and phenol and formaldehyde allows the small molecules of the phenolic resin to be smoothly inserted into the middle of the graphene oxide layer; finally, boric acid is introduced, and by changing the reaction conditions, the small molecules of the phenolic resin in the graphene oxide and boric acid initiate polymerization reaction, thereby preparing a high-performance graphene oxide-boron modified phenolic resin.

The main features of the present invention are: the controllable reduction of graphene oxide not only maintains the structure and properties of graphene (such as excellent thermal stability and mechanical properties), but also endows it with some new properties: the retained part contains oxygen Functional groups can well solve the problems of poor dispersion, solubility and processability of graphene. The carbon residue rate of this method is 70.41%, which is 2.1% higher than that of ordinary boron-modified phenolic resin. Moreover, its bending strength is 96.5MPa, tensile strength is 48.3MPa, and impact strength is 9.7kJ/m ² , which is 46% higher in bending strength, 38% higher in tensile strength, and 53% higher in impact strength than ordinary boron-modified phenolic resin. %.

Description of drawings

Fig. 1 is the residual char ratio of graphene and graphene oxide in embodiment 2. In Fig. 1, the marks ■ represent graphene oxide; ● represent graphene.

为硼改性酚醛树脂。Fig. 2 is the thermal degradation curve of the carbon residue rate of graphene oxide-boron modified phenolic resin, graphene-boron modified phenolic resin and common boron modified phenolic resin in embodiment 2. In Fig. 2, mark ■ is graphene-boron modified phenolic resin; ● is graphene oxide-boron modified phenolic resin;

It is boron modified phenolic resin.

Fig. 3 is the impact strength comparison of graphene oxide-boron modified phenolic resin and common boron modified phenolic resin in embodiment 2. In Figure 3, a is graphene oxide-boron modified phenolic resin, and b is common boron modified phenolic resin.

Fig. 4 is the tensile strength comparison of graphene oxide-boron modified phenolic resin and common boron modified phenolic resin in Example 2. In Figure 4, a is graphene oxide-boron modified phenolic resin, and b is common boron modified phenolic resin.

Fig. 5 is the bending strength comparison of graphene oxide-boron modified phenolic resin and common boron modified phenolic resin in Example 2. In Figure 5, a is graphene oxide-boron modified phenolic resin, and b is ordinary boron modified phenolic resin.

Detailed ways

Example 1

The first step, the preparation of graphene oxide;

Add 75ml of 98% concentrated sulfuric acid to a three-neck round bottom flask, then place it in an ice-water bath, then add 3.5g of graphite and 1.6g of sodium nitrate, stir well, slowly add solid potassium permanganate, and keep stirring for 2h , keep the temperature of the ice-water bath not exceeding 5°C; then, slowly add deionized water, during which there will be a strong exotherm accompanied by a small amount of bubbles, keep the temperature at 32-38°C for 45 minutes, when the reaction is close to the end, black The suspension turned into a taupe viscous substance, and then placed at room temperature for 72h. Finally, dilute with 500ml of warm water at a temperature of 60°C, and then dropwise add 60ml of _{H 2} O ₂ to reduce the remaining high-valent manganese ions (because excessive permanganate ions will pollute the environment) until the solution turns bright yellow. Wash by centrifugation (11000rpm, 20min) until the solution is neutral and there is no SO ₄ ^2- in the supernatant detected by barium salt, then wash twice with absolute ethanol, and the washed product is dried in a vacuum oven. After drying, graphene oxide is obtained.

Second step, the preparation of graphene oxide phenolic resin liquid;

First add 47g of phenol and 56.8g of formaldehyde into a three-necked flask equipped with a stirrer, thermometer, and condenser, then add 0.47g of graphene oxide with 1% phenol mass, ultrasonically disperse at 60°C for 30min, and then add 1.4g of flake sodium hydroxide (catalyst), continue to slowly raise the temperature to 65°C, continue to reflux for 1.5 hours, and dehydrate under reduced pressure for 15 minutes.

The third step, the preparation of graphene oxide-boron modified phenolic resin;

Add 9.3g of boric acid to the reaction vessel of the previous stage, raise the temperature to 95°C, reflux for 2 hours, pour out the dark green viscous substance while it is hot, and cool to room temperature to obtain graphene oxide-boron modified phenolic resin, at 60°C Vacuum dried for 24h.

Example 2

The first step, the preparation of graphene oxide;

Add about 75ml of 98% concentrated sulfuric acid to the three-necked round-bottomed flask, then place it in an ice-water bath, then add 3.5g of graphite and 1.6g of sodium nitrate, stir well, then slowly add solid potassium permanganate, and keep stirring for 2h. Keep the temperature of the ice-water bath not exceeding 5°C; then, slowly add deionized water, during which there will be a strong exotherm accompanied by a small amount of bubbles, keep the temperature between 32 and 38°C for 45 minutes, when the reaction is close to the end, black The suspension turned into a gray-brown viscous substance, and then left at room temperature for 72h. Finally, dilute with 500ml of warm water at a temperature of 60°C, and then dropwise add 60ml of _{H 2} O ₂ to reduce the remaining high-valent manganese ions (because excessive permanganate ions will pollute the environment) until the solution turns bright yellow. Wash by centrifugation (10000rpm, 15min) until the solution is neutral and there is no SO ₄ ^2- in the supernatant detected by barium salt, then wash twice with absolute ethanol, and the washed product is dried in a vacuum oven. After drying, graphene oxide is obtained.

Second step, the preparation of graphene oxide phenolic resin liquid;

First add 47g of phenol and 56.8g of formaldehyde into a three-necked flask equipped with a stirrer, thermometer, and condenser, then add 0.235g of graphene oxide with 0.5% phenol mass, ultrasonically disperse at 60°C for 30min, and then add 1.4g of flake sodium hydroxide (catalyst), continue to slowly raise the temperature to 65°C, continue to reflux for 1.5 hours, and dehydrate under reduced pressure for 15 minutes.

The third step, the preparation of graphene oxide-boron modified phenolic resin;

Add 9.3g of boric acid to the reaction vessel of the previous stage, raise the temperature to 95°C, reflux for 2 hours, pour out the dark green viscous substance while it is hot, and cool to room temperature to obtain graphene oxide-boron modified phenolic resin, at 60°C Vacuum dried for 24h.

It can be seen from Figure 1 that the residual rate of graphene is 85.44%. The reason for the weight loss may be that graphene still has a small part of unreduced oxygen-containing groups and interlayer moisture, which makes graphene produce a weightlessness. The carbon residue rate of graphene oxide is 44.49%, and its thermal decomposition is divided into two stages: the mass loss at 0-100°C is mainly due to the loss of water contained in graphene oxide; the mass loss at 150-240°C is The loss may be caused by the thermal decomposition of oxygen-containing groups in graphene oxide to produce CO, CO ₂ and H ₂ O.

It can be seen from Figure 2 that the graphene oxide-boron modified phenolic resin is gentler than the other two groups, and its carbon residue rate is 70.41%. Obviously better than graphene modified phenolic resin 53.08% and common boron modified phenolic resin 68.31%.

It can be seen from Figures 3 to 5 that when a small amount of graphene oxide is doped, the bending strength of graphene oxide-boron modified phenolic resin is _96.5MPa , the tensile strength is _48.3MPa , and the impact strength is 9.7MPa. kJ/m ² , the flexural strength increased by 46%, the tensile strength increased by 38%, and the impact strength was 53% higher than that of ordinary boron-modified phenolic resin.

Claims (10)

1. the preparation method of a graphene oxide-boron modified phenolic resin is characterized in that comprising the following steps:

1) add the vitriol oil in three mouthfuls of round-bottomed flasks, then be placed in ice-water bath, add graphite and SODIUMNITRATE, then add solid potassium permanganate, keep the temperature of ice-water bath to be no more than 5 ℃, then add deionized water, holding temperature is reacted between 32～38 ℃, when reaction approaches terminal, at room temperature places, with the warm water dilution, then add H again ₂o ₂reduce remaining value Mn ion, till becoming glassy yellow to solution, then centrifuge washing to solution is neutral and detects in supernatant liquor without SO with barium salt ₄ ^2-till, then use absolute ethanol washing, obtain graphene oxide after drying;

2) phenol and formaldehyde are added in the there-necked flask that agitator, thermometer, prolong are housed, then add graphene oxide, after ultrasonic dispersion, add flaky sodium hydrate, after the temperature rising reflux reaction, decompression dehydration, obtain graphene oxide resol emulsion;

3) to step 2) add boric acid in the graphene oxide resol emulsion of gained, after the temperature rising reflux reaction, pour out blackish green dope, be cooled to room temperature, obtain graphene oxide-boron modified phenolic resin after vacuum-drying.

2. a kind of preparation method of graphene oxide-boron modified phenolic resin as claimed in claim 1, is characterized in that in step 1) described graphite, the vitriol oil, SODIUMNITRATE, solid potassium permanganate, deionized water, H ₂o ₂mass ratio be 1: (35～45): (0.3～0.6): (2.5～3.5): (40～60): (15～20).

3. a kind of preparation method of graphene oxide-boron modified phenolic resin as claimed in claim 1, is characterized in that in step 1), and the time of described reaction is 30～60min.

4. a kind of preparation method of graphene oxide-boron modified phenolic resin as claimed in claim 1, is characterized in that in step 1), and the described time of at room temperature placing is 72～96h.

5. a kind of preparation method of graphene oxide-boron modified phenolic resin as claimed in claim 1, is characterized in that in step 1), and the temperature of described warm water is 50～60 ℃.

6. a kind of preparation method of graphene oxide-boron modified phenolic resin as claimed in claim 1, is characterized in that in step 1), and the condition of described centrifuge washing is speed 10000～12000rpm, time 10～20min.

7. a kind of preparation method of graphene oxide-boron modified phenolic resin as claimed in claim 1, it is characterized in that in step 2) in, the mass ratio of described phenol, formaldehyde, graphene oxide, flaky sodium hydrate is 1: (0.97～1.14): (0.005～0.01): (0.01～0.03).

8. a kind of preparation method of graphene oxide-boron modified phenolic resin as claimed in claim 1, is characterized in that in step 2) in, the condition of described ultrasonic dispersion is 50～60 ℃ of temperature, time 20～30min.

9. a kind of preparation method of graphene oxide-boron modified phenolic resin as claimed in claim 1, is characterized in that in step 2) in, the condition of described temperature rising reflux reaction is 60～65 ℃ of temperature, time 1～2h.

10. a kind of preparation method of graphene oxide-boron modified phenolic resin as claimed in claim 1, is characterized in that in step 3), and the add-on of described boric acid and the mass ratio of the phenol in step 1) are 1: (0.13～0.27); The condition of described temperature rising reflux reaction can be 90～100 ℃ of temperature, time 1～2h; Described vacuum drying condition can be 50～60 ℃ of temperature, time 24～36h.

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