CN106279580A - A kind of poly carboxylic acid modified graphene oxide complex and preparation method and application - Google Patents

Abstract

The invention relates to a polycarboxylic acid-modified graphene oxide compound and its preparation method and application. The preparation method of the compound is to first modify the graphene oxide so that unsaturated bonds are grafted on the surface of the graphene oxide , and then under the action of the initiator, the unsaturated bond and the carbon-carbon double bond in the polycarboxylate superplasticizer undergo a radical polymerization reaction, thereby compounding the polycarboxylate superplasticizer molecules between the graphene oxide sheets , the weight-average molecular weight of the compound is 30,000-150,000g/mol, which can improve the working performance of cement slurry and at the same time exert the strengthening and toughening effect of graphene oxide on cement-based materials, and improve the flexural and compressive strength of cement-based materials , the improvement of the early flexural strength is obvious.

Description

A kind of polycarboxylic acid-modified graphene oxide compound and its preparation method and application

technical field

The invention belongs to the technical field of concrete admixtures, and in particular relates to a polycarboxylic acid-modified graphene oxide composite, a preparation method and an application.

Background technique

In recent years, some engineers have pointed out that after the graphene oxide material is mixed into the cement-based material, its nano-sheets can regulate the hydration of the cement, making the crystal arrangement of the hydration product more regular, which is beneficial to the cement-based material. Enhance toughening effect. However, in the corresponding application and research, it was also found that the incorporation of graphene oxide reduces the fluidity of cement slurry and the dispersion of graphene oxide in cement slurry is not good. These problems will seriously affect the graphene oxide cement-based composite material. Applications.

Contents of the invention

The purpose of the present invention is to address the deficiency of graphene oxide in cement-based materials, and provide a polycarboxylic acid-modified graphene oxide composite, which is to use chemical means to combine polycarboxylic acid molecules in the form of covalent bonds Grafted on the modified graphene oxide sheet, the modified compound can improve the flexural and compressive strength of the cement-based material, and improve the workability of the slurry, especially the early flexural strength.

In order to achieve the above object, the present invention adopts the following technical solutions:

A polycarboxylic acid-modified graphene oxide compound is prepared by the following method:

(1) Preparation of modified graphene oxide: monomer c having the following structure is reacted with graphene oxide after hydrolysis reaction, and Y group is grafted on the surface of graphene oxide to obtain final product;

(2) Preparation of polycarboxylic acid-modified graphene oxide composite: with the modified graphene oxide prepared in step (1), monomer a and monomer b having the following structure as raw materials, through free radical polymerization, Composite polycarboxylic acid molecules between graphene oxide sheets to obtain;

Wherein, R ₁ is H or a group containing an unsaturated carbon-carbon bond, n is an integer of 200-500; R ₂ is H or methyl, R ₃ is H or COOM, M is an alkali metal ion, an ammonium ion or Organic amine group; X is Cl, OMe, OEt, OC ₂ H ₄ OCH ₃ , OSiMe ₃ or OAc; Y is alkenyl.

Wherein, the graphene oxide is a known substance, which is commercially available and has the following structure:

Specifically, in step (1), the X group in the monomer c is hydrolyzed into silanol, and then the hydroxyl groups on the silanol and the hydroxyl groups on the surface of graphene oxide are combined with hydrogen bonds, under the catalysis of acid and temperature The dehydration condensation reaction is completed, and the target Y group is grafted on the surface of graphene oxide to complete the modification.

Preferably, the hydrolysis of monomer c is carried out under acidic conditions, preferably in an acidic aqueous solution of pH 2-5 for 0.5-5h. In a specific embodiment, the acidic aqueous solution is an aqueous acetic acid solution.

Preferably, the weight ratio of graphene oxide to monomer c is 1:(8-25).

Preferably, before the graphene oxide reacts with the hydrolyzed monomer c, the graphene oxide is first dispersed in ethanol to form a uniformly dispersed ethanol dispersion.

Preferably, the monomer c is selected from vinyltrimethoxysilane, vinyltriethoxysilane, allyltrichlorosilane, allyltrimethylsilane, methacryloxymethyltriethylsilane One or more of oxysilane and acryloyloxymethyltrimethoxysilane.

Preferably, the reaction in step (1) is carried out at 25-80°C.

As a preferred technical solution, the operation of step (1) is as follows: first disperse graphene oxide in ethanol to make an ethanol dispersion with a concentration of 5-10g/L, for subsequent use; mix monomer c with pH 2-5 After mixing the acetic acid aqueous solution, age for 0.5-5h, then add the ethanol dispersion into the aged liquid, react at 25-80°C for 4-12h, filter the reaction liquid with suction, wash and dry the solid to obtain the modified Graphene oxide.

In step (2), the unsaturated bond grafted on the modified graphene oxide and the carbon-carbon double bond in the polycarboxylate water reducer undergo a free radical polymerization reaction under the action of an initiator, thereby reducing the polycarboxylate The water agent molecules are compounded between the graphene oxide sheets.

Preferably, the amount of modified graphene oxide is 1-30% of the weight sum of monomer a and monomer b.

Preferably, the weight ratio of monomer a to monomer b is 1: (0.05-1);

Preferably, the monomer a is selected from one or more of allyl alcohol polyoxyethylene, polyoxypropylene ether, prenyl alcohol polyoxyethylene ether, and isobutenyl alcohol polyoxyethylene ether.

Preferably, monomer b is selected from one or more of methacrylic acid, acrylic acid, methacrylic acid or monovalent metal salts of acrylic acid, ammonium salts or organic amine salts.

Preferably, the free radical polymerization reaction is carried out under the action of a free radical copolymerization initiation system, and the free radical copolymerization initiation system is a single oxidant, or a mixed system composed of an oxidant and a reducing agent.

Further preferably, the oxidizing agent is selected from one or more of persulfates, water-soluble azo compounds, and peroxides. The reducing agent is selected from one or more of alkali metal sulfites, Mohr's salts, chalk powder, L-ascorbic acid, and erythorbic acid.

Preferably, the radical polymerization reaction is also carried out under the action of a chain transfer agent, and the chain transfer agent is selected from one or both of thioglycolic acid and mercaptopropionic acid.

Preferably, the radical polymerization reaction is carried out at 25-80°C.

Preferably, the radical polymerization reaction uses water as a reaction solvent.

As a preferred technical solution, the operation of step (2) is specifically: using water as a solvent, first react the modified graphene oxide, monomer a and the oxidizing agent, and when the two react until the solid dissolves to 40-60%, Add reducing agent, monomer b, and chain transfer agent dropwise therein, react at 25-80°C for 2-10 hours, keep warm for 1-8 hours after the reaction, and finally adjust the pH value of the reaction solution to be neutral.

As the best technical scheme of the present invention, the preparation method of the complex is:

(1) Preparation of modified graphene oxide: disperse graphene oxide in ethanol to prepare an ethanol dispersion with a concentration of 5-10g/L for subsequent use; place monomer c in an aqueous acetic acid solution with a pH of 2-5 to hydrolyze for 0.5-5h, and then react with the ethanol dispersion at 25-80°C for 4-12h, after the reaction is completed, filter with suction and dry the solid to obtain the product;

(2) Preparation of polycarboxylic acid-modified graphene oxide composite: using water as a solvent, the modified graphene oxide, monomer a and oxidizing agent are first reacted. When the solid dissolves 40-60%, add the reducing agent, monomer b and chain transfer agent dropwise, react at 25-80°C, adjust the pH value of the reaction solution to be neutral after the reaction, and obtain the product.

The polycarboxylate superplasticizer-modified graphene oxide composite obtained by this method is a new type of superplasticizer whose main component is a polymer with grafted polyoxyethylene side chains, which has a higher superplasticizer And slump retention ability, can improve the workability of cement-based materials very well. In the present invention, by grafting polycarboxylate superplasticizer between graphene oxide sheets, the obtained compound can better regulate the combination of gel and crystal and the distribution of gel in the process of cement hydration, and improve the microcosmic properties of cement stone. structure, and further strengthen and toughen the cement stone. At the same time, it can also improve the flexural and compressive strength of cement-based materials, and the early flexural strength is significantly improved.

On the basis of conforming to common knowledge in the field, the above-mentioned preferred conditions can be combined with each other to obtain preferred embodiments of the present invention.

Description of drawings

Fig. 1 is the Fourier transform infrared spectrogram of embodiment 1 modified graphene oxide;

Fig. 2 is the XRD pattern of graphene oxide and modified graphene oxide;

Fig. 3 is a GPC chart of the complex of the present invention.

In the figure, "GO" stands for graphene oxide; "Mod-GO" stands for modified graphene oxide.

detailed description

The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention. The graphene oxide solid powder used in the implementation is commercial graphene oxide powder. Monomer a was produced by Liaoning Aoke Chemical Co., Ltd. Monomer b, monomer c, chain transfer agent, oxidizing agent and reducing agent are all commercial products and can be obtained commercially.

The microscopic testing instruments involved in the implementation are: X-ray diffractometer (XRD) D/max2200PC, manufactured by Rigaku Corporation of Japan; Spectrum400 Fourier Transform Infrared Spectrometer, manufactured by PE Corporation of the United States.

The preparation scheme of the "common polycarboxylate water reducer" mentioned in the "Application Effect" section is similar to the method mentioned in Example 2, specifically:

(1) Put 2 parts by mass of monomer b-2, 0.8 parts by mass of distilled water, and 0.03 parts by mass of a 1:1 mixture of thioglycolic acid and mercaptopropionic acid in a conical flask to prepare liquid A for later use; The erythorbic acid of 0.2 mass parts and the distilled water of 2.0 mass parts are placed in conical flask and made B liquid, standby;

(2) 8.5 parts by mass of monomer a-2, 7.5 parts by mass of distilled water and 0.1 parts by mass of ammonium persulfate are placed in a flask and dissolved under mechanical stirring. Pump liquid A and liquid B into the flask dropwise, react at 65°C for 4 hours, keep warm for 2.5 hours, and finally use 40% sodium hydroxide solution to neutralize to pH = 7 to obtain the product.

Table 1 lists the monomer numbers and names used in the examples.

Table 1: Monomer number and name

Example 1

A polycarboxylic acid-modified graphene oxide compound is prepared by the following steps:

(1) Preparation of modified graphene oxide: Mix 1 part by mass of graphene oxide solid powder with 320 parts by mass of absolute ethanol, and ultrasonically disperse for 1 hour to prepare a graphene oxide ethanol dispersion. 13 parts by mass of monomer c-1 were mixed with acetic acid solution at pH=3 and aged for 30 minutes. The graphene oxide ethanol dispersion and the aged monomer c-1 hydrolyzate were placed in a flask and ultrasonically dispersed for 15 minutes. The flask was placed in a shaking water bath, and the water bath shaking reaction was performed at 80°C for 8h. Suction filter the product, wash with distilled water for 3 to 5 times, and dry at 60°C for 10 hours;

(2) Preparation of the complex: 10 parts by mass of monomer b-1, 1.0 parts by mass of distilled water, and 0.1 parts by mass of thioglycolic acid were placed in a conical flask to prepare liquid A for subsequent use; 0.2 parts by mass of ascorbic acid and 2.0 parts by mass of distilled water are placed in a conical flask to make liquid B, for subsequent use;

The modified graphene oxide solid obtained in step (1) was mixed with an appropriate amount of distilled water, and ultrasonically dispersed for 30 minutes to make a graphene oxide dispersion, and the graphene oxide dispersion, 10 parts by mass of monomer a-1, and 8 parts by mass of Distilled water and 0.6 mass parts of hydrogen peroxide are placed in a flask and dissolved under mechanical stirring. When 40-60% of the solids in the flask are dissolved, use a peristaltic pump to add liquid A and liquid B to the flask dropwise, and react at 80°C 2.5h, keep warm for 1h, and finally neutralize to PH=7 with 40% sodium hydroxide solution.

Example 2

A polycarboxylic acid-modified graphene oxide compound is prepared by the following steps:

(1) Preparation of modified graphene oxide: Mix 1 part by mass of graphene oxide solid powder with 160 parts by mass of absolute ethanol, and ultrasonically disperse for 1.5 h to prepare a graphene oxide ethanol dispersion. 8 parts by mass of monomer c-2 were mixed with acetic acid solution at pH=5 and aged for 40 minutes. The graphene oxide ethanol dispersion and the aged monomer c hydrolyzate were placed in a flask, and ultrasonically dispersed for 30 minutes. The flask was placed in a shaking water bath, and the water bath shaking reaction was performed at 70°C for 6h. Filter the product with suction, wash with distilled water for 3 to 5 times, and dry at 50°C for 12 hours;

(2) Preparation of the complex: 2 parts by mass of monomer b-2, 0.8 parts by mass of distilled water and 0.03 parts by mass of a 1:1 mixture of thioglycolic acid and mercaptopropionic acid were placed in a conical flask to prepare A Liquid, standby; 0.2 mass parts of isoascorbic acid and 2.0 mass parts of distilled water are placed in conical flasks to make B liquid, standby;

Mix the modified graphene oxide solid with an appropriate amount of distilled water, and ultrasonically disperse it for 1 h to make a graphene oxide dispersion. The graphene oxide dispersion, 8.5 parts by mass of monomer a-2, 7.5 parts by mass of distilled water and 0.1 parts by mass of Ammonium persulfate is placed in a flask and dissolved under mechanical stirring. When 40-60% of the solids in the flask are dissolved, use a peristaltic pump to add liquid A and liquid B to the flask dropwise, react at 65°C for 4 hours, and keep warm for 2.5 hours. Finally, it is neutralized to PH=7 with 40% sodium hydroxide solution.

Example 3

A polycarboxylic acid-modified graphene oxide compound is prepared by the following steps:

(1) Preparation of modified graphene oxide: Mix 1 part by mass of graphene oxide solid powder with 50 parts by mass of absolute ethanol, and ultrasonically disperse for 0.5 h to prepare a graphene oxide ethanol dispersion. 3 parts by mass of monomer c-1 was mixed with acetic acid solution at pH=3 and aged for 30 minutes. The graphene oxide ethanol dispersion and the aged monomer c-1 hydrolyzate were placed in a flask and ultrasonically dispersed for 15 minutes. The flask was placed in a shaking water bath, and the water bath shaking reaction was performed at 40°C for 4h. Suction filter the product, wash with distilled water for 3 to 5 times, and dry at 60°C for 10 hours;

(2) Preparation of the complex: 2 parts by mass of monomer b-1, 0.8 parts by mass of distilled water and 0.03 parts by mass of thioglycolic acid are placed in a conical flask to prepare liquid A for subsequent use; 0.02 parts by mass of ascorbic acid and 2.0 parts by mass of distilled water are placed in a conical flask to make liquid B, for subsequent use;

Mix the modified graphene oxide solid with an appropriate amount of distilled water, and ultrasonically disperse it for 30 minutes to make a graphene oxide dispersion. The graphene oxide dispersion, 1 mass part of monomer a-1, 1 mass part of distilled water and 0.01 mass part of Put hydrogen peroxide in the flask and dissolve under mechanical stirring. When the solids in the flask are dissolved by 40-60%, use a peristaltic pump to add liquid A and liquid B to the flask dropwise, react at 80°C for 2 hours, keep warm for 1 hour, and finally Neutralize to PH=7 with 40% sodium hydroxide solution.

Example 4

A polycarboxylic acid-modified graphene oxide compound is prepared by the following steps:

(1) Preparation of modified graphene oxide: Mix 1 part by mass of graphene oxide solid powder with 500 parts by mass of absolute ethanol, and ultrasonically disperse for 5 hours to prepare a graphene oxide ethanol dispersion. 30 parts by mass of monomer c-2 was mixed with an acetic acid solution at pH=5 and aged for 5 hours. The graphene oxide ethanol dispersion and the aged monomer c hydrolyzate were placed in a flask and ultrasonically dispersed for 4 hours. The flask was placed in a shaking water bath, and the water bath shaking reaction was performed at 80°C for 12h. Suction filter the product, wash with distilled water 3 to 5 times, and dry at 50°C for 24 hours;

(2) Preparation of the complex: 10 parts by mass of monomer b-2, 5.0 parts by mass of distilled water and 1 part by mass of a 1:1 mixture of thioglycolic acid and mercaptopropionic acid were placed in a conical flask to prepare A Liquid, standby; 1 mass part of isoascorbic acid and 2.0 mass parts of distilled water are placed in a conical flask to make B liquid, standby;

Mix the modified graphene oxide solid with an appropriate amount of distilled water, and ultrasonically disperse for 1.5h to make a graphene oxide dispersion. The graphene oxide dispersion, 10 parts by mass of monomer a-2, 8 parts by mass of distilled water and 0.6 parts by mass The ammonium persulfate is placed in a flask and dissolved under mechanical stirring. When the solids in the flask are dissolved by 40-60%, use a peristaltic pump to add liquid A and liquid B to the flask dropwise, react at 80°C for 4 hours, and keep warm for 9 hours. Finally, it is neutralized to PH=7 with 40% sodium hydroxide solution.

Fig. 1 is the Fourier transform infrared spectroscopic analysis chart of the modified graphene oxide of Example 1, as can be seen from the figure, the silicon-oxygen bond characteristic peak appears on the modified graphene oxide. X-ray diffraction analysis (XRD) results are shown in Figure 2, and the results are shown in Table 2:

Table 2: Comparison of XRD results of graphene oxide and modified graphene oxide

The XRD results show that the distance between the modified graphene oxide sheets increases; the gel permeation chromatography (GPC) results of the polycarboxylate water reducer-modified graphene oxide composite are shown in Figure 3, and its weight average molecular weight is 2.026 ×104g/mol, and the number average molecular weight is 1.535×10 ⁴ g/mol.

apply effects

1. The application of improving the workability of cement paste:

1. Fluidity test of clean slurry: Standard GB/T8077-2000 "Concrete Admixture Homogeneity Test Method" is used for testing. The cement is the benchmark cement produced by Qufu Zhonglian Cement Co., Ltd., with a strength grade of 42.5. The water-to-cement ratio is 0.35, the amount of cement is 300g, the total amount of admixture is 0.8% of the cementitious material, and the admixture is the compound of Example 2, common polycarboxylate water reducer and self-configured 2g/L graphene oxide dispersion solution (using water as solvent), the results are shown in Table 3.

Table 3: Fluidity test results of clean pulp

It can be seen from Table 3 that compared with the graphene oxide dispersion, the compound of the present invention has the performance of improving the fluidity of cement slurry, and can improve the thickening effect of graphene oxide on cement.

2. Viscosity test of clean slurry: The cement is the benchmark cement produced by Qufu Zhonglian Cement Co., Ltd., with a strength grade of 42.5. The water-binder ratio of the slurry is 0.35, the amount of cement is 300g, the total amount of admixture is 0.8% of the cementitious material, and the admixtures are the compound of Example 2, common polycarboxylate water reducer and self-configured 2g/L graphite oxide olefin dispersion (with water as solvent), the results are shown in Table 4.

Table 4: Test results of pulp viscosity

Sample type Ordinary polycarboxylate superplasticizer Complex Graphene oxide dispersion Viscosity/mPa·s 2168.5 2245.5 2724.2

It can be seen from Table 4 that compared with the graphene oxide dispersion, the composite of the present invention has the ability to reduce the viscosity of cement paste, and can improve the viscosity-increasing effect of graphene oxide on cement paste.

3. Flexural and compressive strength test: The test is carried out in accordance with GB/T17617-2007 "Cement Mortar Strength Test Method", the standard sand is China ISO standard sand produced by Xiamen Aisio Standard Sand Co., Ltd., and the cement is Qufu The benchmark cement produced by China United Cement Co., Ltd. has a strength grade of 42.5. The water-binder ratio is 0.35, the amount of cement is 450g, the standard sand is 1350g, and the amount of admixture is 1.0% of the cementitious material. 2g/L graphene oxide dispersion (with water as solvent), the results are shown in Table 5.

Table 5: Flexural and compressive strength test results

It can be seen from Table 5 that compared with ordinary polycarboxylate water reducers and graphene oxide dispersions, the composite of the present invention has the performance of strengthening and toughening, and can improve the early flexural strength and compressive strength of cement stone.

Although, the present invention has been described in detail with general description, specific implementation and test above, but on the basis of the present invention, some modifications or improvements can be made to it, which will be obvious to those skilled in the art . Therefore, the modifications or improvements made on the basis of not departing from the spirit of the present invention all belong to the protection scope of the present invention.

Claims (10)

1. the preparation method of polycarboxylic acids-modified graphene oxide complex, it is characterised in that comprise the steps:

(1) prepare modified graphene oxide: there is the monomer c of following structure after hydrolysis, with graphite oxide alkene reaction, incite somebody to action Y group is grafted on the surface of graphene oxide, to obtain final product；

(2) polycarboxylic acids-modified graphene oxide complex is prepared: the modified graphene oxide for preparing with step (1), have The monomer a and monomer b of following structure are raw material, through Raolical polymerizable, polycarboxylic acids molecule are compound in graphene oxide Sheet interlayer, to obtain final product；

Wherein, R₁For H or the group containing unsaturated carbon carbon bond, n is the integer of 200-500；R₂For H or methyl, R₃For H or COOM, M are alkali metal ion, ammonium radical ion or organic amine group；X is Cl, OMe, OEt, OC₂H₄OCH₃, OSiMe₃Or OAc；Y For alkenyl.

Preparation method the most according to claim 1, it is characterised in that: the operation of step (1) is: according to graphene oxide with The weight ratio of monomer c is 1:(8-25), prior to hydrolyzed under acidic conditions monomer c, then with graphene oxide 25-80 DEG C of reaction, Obtain.

Preparation method the most according to claim 1 and 2, it is characterised in that: described monomer c is selected from vinyl trimethoxy silicon Alkane, VTES, allyltrichlorosilane, allyl trimethyl silane, methacryloxymethyl three second One or more in TMOS, acryloyloxymethyl trimethoxy silane.

Preparation method the most according to claim 1, it is characterised in that: the consumption of modified graphene oxide is monomer a and list The 1-30% of body b weight sum；The weight ratio of monomer a and monomer b is 1:(0.05～1).

5. according to the preparation method described in claim 1 or 4, it is characterised in that: described Raolical polymerizable is at 25-80 DEG C of bar Carry out under part.

Preparation method the most according to claim 5, it is characterised in that: described monomer a is selected from allyl alcohol polyethenoxy, polyoxy Propylene ether, isopentenol polyoxyethylene ether, isobutene alcohol polyoxyethylene ether one or more；And/or,

Described monomer b is selected from methacrylic acid, acrylic acid, methacrylic acid or acrylic acid monovalent metal salt, ammonium salt or organic One or more in amine salt.

Preparation method the most according to claim 1, it is characterised in that: described Raolical polymerizable draws free-radical polymerized Sending out and carry out under the effect of agent and chain-transferring agent, described free-radical polymerized initiator system is single oxidant, or oxidant and also The mixed system of former dose of composition；

Preferably, one or more in persulfate, water-soluble azo compounds, peroxide of described oxidant； And/or, described reducing agent is selected from alkali metal sulfite, Mohr's salt, rongalite, L-AA, arabo-ascorbic acid Plant or multiple；And/or, one or both in described chain-transferring agent selected from mercapto acetic acid and mercaptopropionic acid.

Preparation method the most according to claim 1, it is characterised in that: comprise the steps:

(1) prepare modified graphene oxide: be scattered in ethanol by graphene oxide, be prepared as the ethanol that concentration is 5-10g/L Dispersion liquid is standby；Monomer c is placed in the acetic acid aqueous solution of pH 2-5 hydrolysis ageing 0.5-5h, then with described alcohol dispersion liquid 25-80 DEG C of reaction, reaction terminates, and sucking filtration also dries solid, to obtain final product；

(2) prepare polycarboxylic acids-modified graphene oxide complex: with water as solvent, first make modified graphene oxide, monomer a and Oxidant reacts, and when solid dissolves 40-60%, dropping reducing agent, monomer b and chain-transferring agent, in 25-80 DEG C of reaction, reaction The pH value regulating reactant liquor after end is neutrality, to obtain final product.

9. polycarboxylic acids-modified graphene oxide complex that the method described in any one of claim 1-8 prepares；

Preferably, the weight average molecular weight of described complex is 30000～150000g/mol.

10. method described in any one of claim 1-8 prepares polycarboxylic acids-modified graphene oxide complex or right are wanted Ask the polycarboxylic acids described in 9-modified graphene oxide complex as water reducer application in cement hydration process, it is preferable that The consumption of described complex is the 0.01-5% of Binder Materials weight.