CN113214738B - Polydopamine-modified graphene oxide-modified silane emulsion and preparation method and application thereof - Google Patents
Polydopamine-modified graphene oxide-modified silane emulsion and preparation method and application thereof Download PDFInfo
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Abstract
The invention provides a polydopamine modified graphene oxide modified silane emulsion, and a preparation method and application thereof, and belongs to the technical field of silane coatings. The polydopamine modified graphene oxide modified silane emulsion provided by the invention comprises the following components in percentage by mass: 50-60% of silane monomer, 0.05-0.5% of polydopamine modified graphene oxide, 1-5% of water phase emulsifier, 0.1-0.5% of dispersant, 1-5% of oil phase emulsifier and 35-45% of water. The polydopamine modified graphene oxide modified silane emulsion provided by the invention has excellent bonding, anti-stripping performance, waterproof capability, chloride and sulfate corrosion and penetration resistance and steel bar corrosion resistance; moreover, the poly-dopamine functionalization of the graphene oxide can improve the utilization rate of the graphene oxide and greatly reduce the using amount of graphene oxide materials, so that the cost of the graphene oxide modified silane emulsion is greatly reduced.
Description
Technical Field
The invention relates to the technical field of silane emulsion, and particularly relates to polydopamine modified graphene oxide modified silane emulsion and a preparation method and application thereof.
Background
The durability of cement-based materials such as concrete is a key factor influencing the safety and reliability of a concrete structure, and the protection treatment of the surface of the concrete material by using the polymer coating is an important measure for improving the durability and the adaptability to severe environments of the concrete. The silane polymer coating is a commonly used permeable organic polymer coating in the engineering field, can form a waterproof and breathable protective layer on the surface and inside of a concrete material, and has good durability. The silane coating is subjected to nano modification, so that the physical and chemical properties of the silane coating can be improved, the waterproof property and the anti-permeability property of the silane coating are further improved, and the bonding property between the silane coating and the surface of a concrete material is enhanced.
Graphene oxide, as a two-dimensional carbon nanomaterial with an oxygen-containing functional group on the surface, can be well dispersed in water and covalently bonded with polymer molecules. The graphene oxide can functionally modify the polymer coating through an in-situ polymerization method, a sol-gel method, an intercalation method and a physical blending method, and can construct an ideal molecular configuration for polymer molecules and endow the polymer molecules with stable protective performance. The graphene oxide sheet layer can fully exert the waterproof performance and the anti-permeability performance of the polymer coating, and effectively improve the surface protection of porous heterogeneous materials such as concrete and the like. However, since the cost of graphene oxide is too high, the surface oxygen-containing functional groups are relatively limited and easy to agglomerate, the graphene oxide is easily insufficiently used when the graphene oxide is directly used for modifying the polymer coating, and the modification effect of the composite coating on the aspects of water resistance, permeability resistance and erosion resistance is not ideal.
Disclosure of Invention
In view of the above, the invention aims to provide a polydopamine modified graphene oxide modified silane emulsion, and a preparation method and an application thereof.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a modified silane emulsion which comprises the following components in percentage by mass: 50-60% of silane monomer, 0.05-0.5% of polydopamine modified graphene oxide, 1-5% of water phase emulsifier, 0.1-0.5% of dispersant, 1-5% of oil phase emulsifier and 35-45% of water.
Preferably, the preparation method of the polydopamine modified graphene oxide comprises the following steps:
pre-dispersing graphene oxide in water to obtain a graphene oxide dispersion liquid;
mixing the graphene oxide dispersion liquid with a buffer solution, adjusting the pH value to 8-8.5, and then performing ultrasonic dispersion to obtain a mixed dispersion liquid;
and carrying out secondary ultrasonic dispersion on the mixed dispersion liquid and dopamine hydrochloride to obtain the polydopamine modified graphene oxide.
Preferably, the buffer solution includes one or more of tris buffer solution, barbiturate buffer solution, ammonia-ammonium chloride buffer solution, potassium dihydrogen phosphate buffer solution, and sodium dihydrogen phosphate buffer solution.
Preferably, the particle size of the polydopamine modified graphene oxide is 200-800 meshes.
Preferably, the silane monomer comprises a substituted oxysilane.
Preferably, the water-phase emulsifier comprises one or more of vinyl ether emulsifiers, alkyl organic salt emulsifiers and ester emulsifiers.
Preferably, the dispersant comprises one or more of alkyl organic salt, polyvinyl alcohol, polyvinylpyrrolidone, polyethylene glycol and glycerol.
Preferably, the oil phase emulsifier comprises a fatty acid ester emulsifier.
The invention provides a preparation method of polydopamine modified graphene oxide modified silane emulsion, which comprises the following steps:
(1) mixing a water-phase emulsifier, a dispersant, polydopamine modified graphene oxide and water to obtain a water phase;
(2) mixing an oil phase emulsifier and a silane monomer to obtain an oil phase;
(3) dropwise adding the oil phase into the water phase and mixing to obtain polydopamine modified graphene oxide modified silane emulsion;
the step (1) and the step (2) have no chronological order.
The invention provides application of the polydopamine modified graphene oxide modified silane emulsion in the technical scheme or the polydopamine modified graphene oxide modified silane emulsion prepared by the preparation method in the technical scheme in protection of cement-based materials, rocks, metals, plastic products, wood or textiles.
The invention provides a polydopamine modified graphene oxide modified silane emulsion which comprises the following components in percentage by mass: 50-60% of silane monomer, 0.05-0.5% of polydopamine modified graphene oxide, 1-5% of water phase emulsifier, 0.1-0.5% of dispersant, 1-5% of oil phase emulsifier and 35-45% of water. The polydopamine modified graphene oxide can improve the molecular configuration of siloxane, fully exert the hydrophobic property of the polydopamine modified graphene oxide modified silane emulsion, improve the crosslinking degree of a silane system, and enable the surface of a substrate such as concrete to form a stable and compact hydrophobic film. Moreover, the polydopamine modified graphene oxide can promote a secondary hydration reaction between siloxane molecules and concrete hydration products (such as calcium silicate hydrate and calcium hydroxide), so that the compactness of concrete is improved, and external water is inhibited from entering cracks and capillary channels in the concrete. The polydopamine can convert most of graphene oxide into a reduced state, so that the number of oxygen-containing functional groups with hydrophilic properties on the surface of the graphene oxide is reduced, and the waterproof performance of the emulsion is further improved. Therefore, the polydopamine modified graphene oxide modified silane emulsion provided by the invention has excellent waterproof capability.
The polydopamine enhances the ion permeation resistance of the graphene oxide sheet layer, improves the blocking effect of graphene oxide in capillary channels of the substrate on erosion type ions, blocks and prolongs the transmission path of the erosion ions, and the polydopamine modified graphene oxide can improve the crosslinking degree of the silane emulsion and weaken the diffusion and transmission of water molecules, chloride ions and sulfate ions on the surface of the substrate and in the capillary channels, so that the polydopamine modified graphene oxide modified silane emulsion provided by the invention has excellent chloride and sulfate erosion permeation resistance.
In the invention, the polydopamine modified graphene oxide is connected with the graphene oxide sheet layer and polydopamine molecules through-NH-bonds and-CO-NH-bonds, the surface of the polydopamine modified graphene oxide contains more active functional groups (including hydroxyl, carboxyl and epoxy groups), and then the polydopamine on the graphene oxide sheet layer can be grafted with more silane molecules. Therefore, the polydopamine modified graphene oxide modified silane emulsion provided by the invention has excellent bonding and anti-stripping performances.
On one hand, the polydopamine modified graphene oxide modified silane emulsion provided by the invention can inhibit CO2The dispersion in the capillary pores of the metal substrate can maintain an alkaline environment and protect a passive film on the surface of the metal, and on the other hand, the dispersion and transmission of chloride ions in concrete can be effectively inhibited, and the corrosion of the chloride ions to the metal is reduced, so that the polydopamine modified graphene oxide modified silane emulsion provided by the invention has excellent metal corrosion resistance.
The polydopamine modified graphene oxide can improve the stability of the silane emulsion in various complex and severe working environments such as ion erosion, freeze thawing, high temperature, acid-base corrosion and the like, prolong the service life of the silane emulsion and reduce the maintenance cost; moreover, the poly-dopamine functionalization of the graphene oxide can improve the utilization rate of the graphene oxide and greatly reduce the using amount of graphene oxide materials, so that the cost of the graphene oxide modified silane emulsion is reduced by more than 70%, and the engineering application cost is low.
The invention provides a preparation method of polydopamine modified graphene oxide modified silane emulsion, which comprises the following steps: (1) mixing a water-phase emulsifier, a dispersant, polydopamine modified graphene oxide and water to obtain a water phase; (2) mixing an oil phase emulsifier and a silane monomer to obtain an oil phase; (3) dropwise adding the oil phase into the water phase and mixing to obtain polydopamine modified graphene oxide modified silane emulsion; the step (1) and the step (2) have no chronological order. The preparation method provided by the invention can effectively improve the molecular connection effect and the utilization rate of the graphene oxide in the modification process of the silane emulsion, improve the waterproof performance and the anti-ion permeation and erosion performance of the modified silane emulsion, and generate a stable bonding effect between the modified silane emulsion and the cement-based material and other base materials; moreover, the process is simple and suitable for industrial production.
Drawings
FIG. 1 is a graph showing the results of a surface water contact angle test of a cement paste test piece coated with emulsions prepared in examples 1 to 3 and comparative examples 1 to 2, respectively;
FIG. 2 is a schematic diagram of an experimental device for a concrete static capillary water absorption test;
FIG. 3 is a graph showing the results of the static capillary water absorption of concrete samples coated with the silane emulsions prepared in examples 1 to 3 and comparative examples 1 to 2;
FIG. 4 is a graph showing the results of chlorine ion etching of concrete samples coated with the silane emulsions prepared in examples 1 to 3 and comparative examples 1 to 2;
FIG. 5 is a graph showing the results of sulfate ion etching of concrete samples coated with the silane emulsions prepared in examples 1 to 3 and comparative examples 1 to 2;
FIG. 6 is a calculated fit graph of chloride ion erosion rates for concrete samples coated with the silane emulsions prepared in examples 1-3 and comparative examples 1-2;
FIG. 7 is a calculated fit graph of sulfate ion erosion rates for concrete samples coated with the silane emulsions prepared in examples 1-3 and comparative examples 1-2;
FIG. 8 is a graph showing the results of the depth of chloride ion attack of concrete samples coated with the silane emulsions prepared in examples 1 to 3 and comparative examples 1 to 2;
FIG. 9 is an SEM image of a blank cement paste test piece;
FIG. 10 is an SEM image of a specimen coated with a conventional silane emulsion;
FIG. 11 is an SEM image of a specimen coated with a graphene oxide-modified silane emulsion;
fig. 12 is an SEM image of a test piece coated with the polydopamine-modified graphene oxide-modified silane emulsion prepared in example 1;
fig. 13 is an SEM image of a test piece coated with the polydopamine-modified graphene oxide-modified silane emulsion prepared in example 2;
fig. 14 is an SEM image of a test piece coated with the polydopamine-modified graphene oxide-modified silane emulsion prepared in example 3.
Detailed Description
The invention provides a polydopamine modified graphene oxide modified silane emulsion which comprises the following components in percentage by mass: 50-60% of silane monomer, 0.05-0.5% of polydopamine modified graphene oxide, 1-5% of water phase emulsifier, 0.1-0.5% of dispersant, 1-5% of oil phase emulsifier and 35-45% of water.
In the present invention, all the raw material components are commercially available products well known to those skilled in the art unless otherwise specified.
The polydopamine modified graphene oxide modified silane emulsion provided by the invention comprises 50-60% by mass of silane monomers, preferably 52-58%, more preferably 54-56%, and most preferably 55%. In the present invention, the silane monomer preferably includes a substituted oxysilane; the compound comprises substituted triethoxysilane and/or substituted trimethoxysilane; the substituted triethoxysilane preferably comprises alkenyl triethoxysilane and/or alkyl triethoxysilane; the alkenyltriethoxysilane preferably comprises vinyltriethoxysilane; the alkyl triethoxysilane preferably comprises one or more of methyl triethoxysilane, isobutyl triethoxysilane, hexyl triethoxysilane and octyl triethoxysilane; the substituted trimethoxysilane preferably comprises hexadecyl trimethoxysilane.
The components of the polydopamine modified graphene oxide modified silane emulsion provided by the invention comprise 0.05-0.5% of polydopamine modified graphene oxide by mass, preferably 0.1-0.4%, more preferably 0.2-0.3%, and most preferably 0.25% of silane monomer by mass. In the present invention, the preparation method of the polydopamine-modified graphene oxide preferably includes the following steps:
pre-dispersing graphene oxide in water to obtain a graphene oxide dispersion liquid;
mixing the graphene oxide dispersion liquid with a buffer solution, adjusting the pH value to 8-8.5, and then performing ultrasonic dispersion to obtain a mixed dispersion liquid;
and carrying out secondary ultrasonic dispersion on the mixed dispersion liquid and dopamine hydrochloride to obtain the polydopamine modified graphene oxide.
According to the invention, graphene oxide is pre-dispersed in water to obtain a graphene oxide dispersion liquid. In the invention, the concentration of the graphene oxide dispersion liquid is preferably 0.5-5 mg/mL, more preferably 1-4 mg/mL, and most preferably 2-3 mg/mL; the pre-dispersion temperature is preferably 20-40 ℃, more preferably 25-35 ℃, and more preferably 25-30 ℃; the pre-dispersion time is preferably 10-60 min, more preferably 20-50 min, and most preferably 30-40 min; the pre-dispersion is preferably carried out in a high-speed homogenizer or an ultrasonic disperser.
After the graphene oxide dispersion liquid is obtained, the graphene oxide dispersion liquid and a buffer solution are mixed, the pH value is adjusted to 8-8.5, and then ultrasonic dispersion is carried out to obtain a mixed dispersion liquid. In the present invention, the buffer solution preferably includes one or more of a tris buffer solution, a barbiturate buffer solution, an ammonia-ammonium chloride buffer solution, a potassium dihydrogen phosphate buffer solution, and a sodium dihydrogen phosphate buffer solution; the pH value of the tris buffer solution is preferably 8.8-10.5; the pH value of the barbital buffer solution is preferably 7.2-7.6; the pH value of the ammonia-ammonium chloride buffer solution is preferably 9.5-11; the pH value of the potassium dihydrogen phosphate buffer solution is preferably 4-5; the pH value of the sodium dihydrogen phosphate buffer solution is preferably 4-5. In the invention, the mass ratio of the graphene oxide to the dopamine hydrochloride to the buffer solution is preferably (10-25): (20-60): (10-50), more preferably (12-22): (30-50): (20-40), most preferably (15-20): (40-45): (30-35). In the present invention, the pH adjusting agent used for adjusting the pH value preferably includes an acidic agent or an alkaline agent; the acidic reagent preferably comprises one or more of hydrochloric acid, nitric acid, sulfuric acid, citric acid and oxalic acid; the acidic reagent is preferably used in the form of an acidic reagent aqueous solution, and the concentration of the acidic reagent aqueous solution is preferably 0.01-10 mol/L, and more preferably 0.1-1 mol/L; the alkaline reagent preferably comprises one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate and ammonia water; the alkaline reagent is preferably used in the form of an alkaline reagent aqueous solution, and the concentration of the alkaline reagent aqueous solution is preferably 0.01-0.1 mol/L, and more preferably 0.05-0.08 mol/L; the pH value is more preferably 8.1 to 8.4, and more preferably 8.2 to 8.3. In the invention, the temperature of ultrasonic dispersion is preferably 20-40 ℃, more preferably 25-35 ℃, and most preferably 25-30 ℃; the ultrasonic dispersion time is preferably 10-60 min, more preferably 20-50 min, and most preferably 30-40 min; the power of the ultrasonic dispersion is preferably 100-5000W, more preferably 500-3000W, and most preferably 1000-2000W.
After the mixed dispersion liquid is obtained, the mixed dispersion liquid and dopamine hydrochloride are subjected to secondary ultrasonic dispersion and then are subjected to modification treatment, and the poly-dopamine modified graphene oxide is obtained. In the invention, the temperature of the secondary ultrasonic dispersion is preferably 20-40 ℃, more preferably 25-35 ℃, and more preferably 25-30 ℃; the time for the secondary ultrasonic dispersion is preferably 10-60 min, more preferably 20-50 min, and most preferably 30-40 min; the power of the secondary ultrasonic dispersion is preferably 100-5000W, more preferably 500-3000W, and most preferably 1000-2000W; in the secondary ultrasonic dispersion process, dopamine molecules can be polymerized into polydopamine molecular chains through condensation reaction between hydroxyl and amino, the polydopamine molecular chains are continuously adsorbed on the surface of a graphene oxide sheet layer, and the polydopamine molecular chains are grafted on the surface of the graphene oxide through-NH-bonds and-CO-NH-bonds.
After the secondary ultrasonic dispersion, the invention preferably further comprises the steps of carrying out centrifugal separation on the system subjected to the secondary ultrasonic dispersion, and sequentially washing, drying, grinding and sieving the obtained solid product to obtain the polydopamine modified graphene oxide. In the invention, the rotation speed of the centrifugal separation is preferably 8000-20000 r/min, more preferably 10000-18000 r/min, and most preferably 12000-15000 r/min; the time for centrifugal separation is preferably 40-70 min, more preferably 45-65 min, and most preferably 50-60 min. In the invention, the washing is preferably ethanol water washing, and the volume concentration of the ethanol water is preferably 50-100%, more preferably 60-90%, and most preferably 70-80%; the number of washing is preferably 4 to 8, more preferably 5 to 7, and most preferably 5 to 6. In the invention, the drying temperature is preferably 40-80 ℃, more preferably 50-70 ℃, and most preferably 60-65 ℃; in the present invention, the drying time is not particularly limited, and the drying time may be set to a constant weight. The grinding and sieving are not particularly limited, the particle size of the poly-dopamine modified graphene oxide can be controlled to be 200-800 meshes, the particle size of the poly-dopamine modified graphene oxide is further preferably 300-700 meshes, more preferably 400-600 meshes, and most preferably 500-600 meshes.
Based on the mass percentage of the silane monomer, the components of the polydopamine modified graphene oxide modified silane emulsion provided by the invention comprise 1-5% of a water phase emulsifier by mass, preferably 1.5-4.5%, more preferably 2-4%, and most preferably 2.5-3%. In the invention, the water-phase emulsifier preferably comprises one or more of vinyl ether emulsifiers, alkyl organic salt emulsifiers and ester emulsifiers; the vinyl ether emulsifier preferably comprises fatty alcohol-polyoxyethylene ether; the fatty alcohol-polyoxyethylene ether preferably comprises one or more of peregal O-20, peregal O-25 and peregal O-30; the ester emulsifier preferably comprises polyoxyethylene sorbitan fatty acid ester and/or monopalmitate; the polyoxyethylene sorbitan fatty acid ester preferably comprises one or more of tween 20, tween 40, tween 60 and tween 80; the alkyl organic salt emulsifier preferably comprises one or more of dodecyl sulfate, dodecyl sulfonate and dodecyl benzene sulfonate; the lauryl sulfate preferably comprises sodium lauryl sulfate; the dodecyl sulfonate preferably comprises sodium dodecyl sulfate; the dodecylbenzene sulfonate salt preferably comprises sodium dodecylbenzene sulfonate.
Based on the mass percentage of the silane monomer, the components of the polydopamine modified graphene oxide modified silane emulsion provided by the invention comprise 0.1-0.5% of a dispersing agent, preferably 0.15-0.45%, more preferably 0.2-0.4%, and most preferably 2.5-3%. In the present invention, the dispersant preferably includes one or more of alkyl organic salt, polyvinyl alcohol, polyvinyl pyrrolidone, polyethylene glycol and glycerin; the alkyl organic salt preferably comprises one or more of sodium dodecyl sulfate, sodium dodecyl sulfate and sodium dodecyl benzene sulfonate.
Based on the mass percentage of the silane monomer, the components of the polydopamine modified graphene oxide modified silane emulsion provided by the invention comprise 1-5% by mass of an oil phase emulsifier, preferably 1.5-4.5%, more preferably 2-4%, and most preferably 2.5-3%. In the present invention, the oil phase emulsifier preferably includes a fatty acid ester type emulsifier; the fatty acid ester emulsifier preferably comprises sorbitan fatty acid ester and/or polyoxyethylene sorbitan fatty acid ester; the sorbitan fatty acid ester preferably comprises span 60 and/or span 80; the polyoxyethylene sorbitan fatty acid ester preferably comprises one or more of tween 40, tween 60 and tween 80.
Based on the mass percentage of the silane monomer, the components of the polydopamine modified graphene oxide modified silane emulsion provided by the invention comprise 35-45% by mass of water, preferably 37-43%, more preferably 39-42%, and most preferably 40-41%. In the present invention, the water is preferably distilled water or deionized water.
The invention provides a preparation method of polydopamine modified graphene oxide modified silane emulsion, which comprises the following steps:
(1) mixing a water-phase emulsifier, a dispersant, polydopamine modified graphene oxide and water to obtain a water phase;
(2) mixing an oil phase emulsifier and a silane monomer to obtain an oil phase;
(3) dropwise adding the oil phase into the water phase and mixing to obtain polydopamine modified graphene oxide modified silane emulsion;
the step (1) and the step (2) have no chronological order.
According to the invention, a water phase emulsifier, a dispersant, polydopamine modified graphene oxide and water are mixed to obtain a water phase. In the invention, the mixing mode is preferably stirring mixing, and the stirring mixing speed is preferably 10000-25000 r/min, more preferably 12000-22000 r/min, and most preferably 15000-20000 r/min; the mixing time is preferably 2-10 min, more preferably 3-8 min, and most preferably 5-6 min.
The oil phase emulsifier and the silane monomer are mixed to obtain the oil phase. In the invention, the mixing mode is preferably stirring mixing, and the stirring mixing speed is preferably 10000-25000 r/min, more preferably 12000-22000 r/min, and most preferably 15000-20000 r/min; the mixing time is preferably 2-10 min, more preferably 3-8 min, and most preferably 5-6 min.
After a water phase and an oil phase are obtained, the oil phase is dripped into the water phase and mixed to obtain the polydopamine modified graphene oxide modified silane emulsion. The dropping speed is not specially limited, and the dropping can be carried out at a constant speed; the mixing mode is preferably stirring mixing; the mixing temperature is preferably 30-60 ℃, more preferably 35-55 ℃, and most preferably 40-50 ℃; the stirring and mixing speed is preferably 1200-1400 r/min, more preferably 1250-1350 r/min, and most preferably 1300 r/min; the stirring and mixing time is preferably 5-7 h, more preferably 5.5-6.5 h, and most preferably 6 h; and the time for stirring and mixing is counted by the completion of the dropwise addition of the oil phase.
The invention provides application of the polydopamine modified graphene oxide modified silane emulsion or the polydopamine modified graphene oxide modified silane emulsion prepared by the preparation method in the technical scheme in cement-based material, rock, metal, plastic product, wood or textile protection.
In the invention, the polydopamine modified graphene oxide modified silane emulsion is preferably applied to cement-based material waterproofing, rock toughening protection, metal corrosion prevention, plastic product aging resistance, wood corrosion prevention or textile waterproof breathable function modification.
In the invention, the surface of the polydopamine modified graphene oxide contains a large number of active functional groups, so that more silane molecules can be grafted, and the polydopamine molecules enhance the steric hindrance effect of the surface of the graphene oxide, so that the silane molecules can be fully hydrolyzed to generate silicon hydroxyl groups in the preparation process of the polydopamine modified graphene oxide modified silane emulsion, and a large number of orderly arranged silicon-oxygen chemical bonds can be formed between the polydopamine modified graphene oxide modified silane emulsion and a cement-based material in the application process of the polydopamine modified graphene oxide modified silane emulsion, so that the base material and the coating have good bonding performance and anti-stripping performance.
In the invention, the polydopamine modified graphene oxide can improve the molecular configuration of siloxane, fully exert the hydrophobic property of the polydopamine modified graphene oxide modified silane emulsion, and improve the crosslinking degree of a silane system, so that a stable and compact hydrophobic film is formed on the surface of concrete; moreover, the polydopamine modified graphene oxide can promote a secondary hydration reaction between siloxane molecules and concrete hydration products (hydrated calcium silicate and calcium hydroxide), improve the compactness of concrete, and inhibit external water from entering cracks and capillary channels in the concrete; in addition, polydopamine enhances the ion permeation resistance of the graphene oxide sheet layer, improves the blocking effect of graphene oxide on erosion type ions in a concrete capillary channel, blocks and prolongs the transmission path of the erosion ions, can improve the crosslinking degree of silane emulsion, weakens the diffusion and transmission of water molecules, chloride ions and sulfate ions on the surface of a base material and in the capillary channel, and has excellent chloride and sulfate erosion permeation resistance; on one hand, the polydopamine modified graphene oxide modified silane emulsion provided by the invention can inhibit CO2The diffusion in the capillary pores of the concrete maintains the alkaline environment in the concrete and protects the passive film on the surface of the reinforcing steel bar, and the concrete has excellent reinforcing steel bar corrosion resistance.
In the invention, the polydopamine modified graphene oxide can enhance the crosslinking degree of silane molecules in the silane emulsion coating on the surfaces of rocks, metals, plastic products and wood, so that a complete and compact protective film is formed on the surface of a base material. The polydopamine modified graphene oxide improves the molecular configuration of a silane system, so that more orderly arranged Si-O-Si bonds or Si-O-C bonds can be formed between the silane emulsion and rocks, metal, plastic and wood, and the silane emulsion and a base material are guaranteed to have excellent bonding performance. In addition, the polydopamine modified graphene oxide can permeate into rock cracks and wood pores along with silane molecules, and diffusion and transmission of water and aggressive ions are inhibited. Meanwhile, the polydopamine modified graphene oxide can promote the mutual crosslinking of silane molecules and textile fibers and form a complete hydrophobic protective film, so that the good air permeability is kept under the condition that the net structure of the textile is not changed, and the waterproof performance of the textile is fully improved.
The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
Placing 10g of graphene oxide aqueous dispersion with the concentration of 1% wt in 100mL of deionized water, and pre-dispersing for 1h at 25 ℃ by using an ultrasonic disperser to obtain the graphene oxide dispersion with the concentration of 1 mg/mL; adding 0.2g of barbital buffer solution (with the pH value of 8.8-10.5) into the graphene oxide dispersion liquid, uniformly stirring and mixing, adjusting the pH value to 8.3 by using 0.1mol/L sodium bicarbonate, then performing ultrasonic dispersion for 20min at the conditions of 25 ℃ and 2000r/min, adding 0.15g of dopamine hydrochloride, performing ultrasonic dispersion for 2h at the conditions of 30 ℃ and 2000r/min, performing centrifugal separation for 60min at the rotating speed of 10000r/min, washing the obtained solid product for 2 times by using absolute ethyl alcohol, washing for 2 times by using 40% ethanol water solution, drying for 8h at the temperature of 70 ℃, grinding the solid product into powder by using a mortar, and screening by using a 200-mesh fine screen, wherein the part under the screen is the polydopamine modified graphene oxide;
placing 3g of fatty alcohol-polyoxyethylene ether, 0.3g of polyvinyl alcohol, 40g of distilled water and 0.1g of polydopamine modified graphene oxide in a homogenizer, and uniformly dispersing at the speed of 15000r/min to obtain a water phase;
3g of Tween 60 and 50g of propyl trimethoxy silane are uniformly dispersed in a homogenizer at the speed of 15000r/min to obtain an oil phase;
and (3) placing the water phase in a three-neck flask, dropwise adding the oil phase at 40 ℃ at 300r/min, and stirring at a high speed of 1300r/min for 6h after the oil phase is dropwise added to obtain the polydopamine modified graphene oxide modified silane emulsion.
Example 2
Placing 20g of graphene oxide aqueous dispersion with the concentration of 1% wt in 200mL of deionized water, and pre-dispersing for 1h at 25 ℃ by using an ultrasonic disperser to obtain the graphene oxide aqueous dispersion with the concentration of 1 mg/mL; adding 0.4g of ammonia-ammonium chloride buffer solution (with the pH value of 8.8-10.5) into the graphene oxide dispersion liquid, uniformly stirring and mixing, adjusting the pH value to 8.3 by using oxalic acid with the concentration of 0.1mol/L, then ultrasonically dispersing for 20min at the conditions of 25 ℃ and 2000r/min, adding 0.3g of dopamine hydrochloride, ultrasonically dispersing for 2h at the conditions of 30 ℃ and 2000r/min, centrifugally separating for 60min at the rotating speed of 10000r/min, washing the obtained solid product for 2 times by using absolute ethyl alcohol, washing for 2 times by using an ethanol aqueous solution with the volume concentration of 50%, drying for 8h at the temperature of 70 ℃, then grinding to be powdery by using a mortar, and screening by using a fine sieve of 200 meshes, wherein the part under the sieve is the dopamine modified graphene oxide;
placing 3g of sodium dodecyl sulfate, 0.3g of glycerol, 40g of distilled water and 0.2g of polydopamine modified graphene oxide in a homogenizer, and uniformly dispersing at the speed of 15000r/min to obtain a water phase;
3g of Tween 80 and 50g of n-butyltrimethoxysilane are uniformly dispersed in a homogenizer at the speed of 15000r/min to obtain an oil phase;
and (3) placing the water phase in a three-neck flask, dropwise adding the oil phase at 40 ℃ at 300r/min, and stirring at a high speed of 1300r/min for 6h after the oil phase is dropwise added to obtain the polydopamine modified graphene oxide modified silane emulsion.
Example 3
Placing 30% wt graphene oxide aqueous dispersion liquid into 300mL deionized water, and pre-dispersing for 1h at 25 ℃ by using an ultrasonic disperser to obtain 1mg/mL graphene oxide dispersion liquid; adding 0.6g of tris (hydroxymethyl) aminomethane buffer solution (with the pH value of 8.8-10.5) into the graphene oxide dispersion liquid, stirring and mixing uniformly, adjusting the pH value to 8.3 by using hydrochloric acid with the concentration of 0.1mol/L, then performing ultrasonic dispersion for 20min at the conditions of 25 ℃ and 2000r/min, adding 0.45g of dopamine hydrochloride, performing ultrasonic dispersion for 2h at the conditions of 30 ℃ and 2000r/min, performing centrifugal separation for 60min at the rotating speed of 10000r/min, washing the obtained solid product with absolute ethyl alcohol for 2 times, washing the solid product with an ethanol aqueous solution with the volume concentration of 70% for 2 times, drying the solid product for 8h at the temperature of 70 ℃, grinding the solid product into powder by using a mortar, and screening the powder by using a fine sieve of 200 meshes, wherein the part under the sieve is the dopamine modified graphene oxide;
3g of peregal O-25, 0.3g of polyvinylidene, 40g of distilled water and 0.3g of polydopamine modified graphene oxide are placed in a homogenizer to be uniformly dispersed at the speed of 15000r/min to obtain a water phase;
3g of span 80 and 50g of isobutyl triethoxy silane are put into a homogenizer to be uniformly dispersed at the speed of 15000r/min to obtain an oil phase;
and (3) placing the water phase in a three-neck flask, dropwise adding the oil phase at 40 ℃ at 300r/min, and stirring at a high speed of 1300r/min for 6h after the oil phase is dropwise added to obtain the polydopamine modified graphene oxide modified silane emulsion.
Comparative example 1
An emulsion was prepared according to the method of example 3, except that the polydopamine-modified graphene oxide was not added to obtain a general silane emulsion, from example 3.
Comparative example 2
An emulsion was prepared according to the method of example 3, except that graphene oxide was used instead of polydopamine-modified graphene oxide to obtain a graphene oxide-modified silane emulsion from example 3.
Test example
1. Surface water contact Angle test
The emulsions prepared in examples 1 to 3 and comparative examples 1 to 2 were mixed at a ratio of 600g/m2The dosage of the test piece is coated on the surface of the cement paste test piece, the coating is carried out twice at an interval of 7 hours, and the test piece to be tested is obtained after drying.
The surface water contact angle of each test piece to be tested is measured by using a static contact angle meter, and the test results are shown in table 1 and fig. 1:
TABLE 1 surface Water contact Angle results for emulsion coated test pieces prepared in examples 1-3 and comparative examples 1-2
As can be seen from fig. 1 and table 1, the contact angle of the blank test piece without surface treatment is 52.73 °, showing a distinct hydrophilic property; the waterproof performance of the cement paste material is poor; the contact angle of a cement paste test piece subjected to surface treatment by using the common silane emulsion is 106.13 degrees; the contact angle of the surface of the test piece coated with the graphene oxide modified silane is increased to 119.29 degrees; the contact angle of a cement paste test piece treated by the polydopamine modified graphene oxide modified silane emulsion is 127.93-138.89 degrees, and the contact angle is greatly improved, so that the polydopamine modified graphene oxide modified silane emulsion prepared by the invention endows the cement paste test piece with excellent hydrophobic property, and the waterproof performance of the cement paste test piece is greatly improved.
2. Static capillary water absorption test of concrete
The test was carried out using the schematic drawing of the experimental apparatus shown in FIG. 2, one of the unfired surfaces of the dry concrete test piece was selected as the coating surface, and the silane emulsions prepared in examples 1 to 3 and comparative examples 1 to 2 were prepared at 600g/m2The dosage of the concrete sample is coated on the surface of a cement paste sample twice (at an interval of 7 hours) and then dried, four side surfaces are sealed by paraffin wax, the concrete sample is placed in a container filled with distilled water with the coated surface facing downwards, the lower part of the sample is supported by a bracket, the distance from the water surface to the bottom surface of the concrete sample is 5mm, and the measurement is carried out for 0 hour, 0.5 hour, 1 hour, 1.5 hour, 2 hour, 3 hour, 4 hour, 5 hour, 6 hour, 8 hour, 10 hour, 12 hour, 24 hour,Static capillary water absorption of 36h, 48h, 60h, 72h, 84h and 96h, which is calculated according to the formula (1), and the test results are shown in fig. 3 and table 2.
In the formula (1), A is the capillary water absorption coefficient (g.m)-2h-0.5) Δ W is the water absorption capacity (g.m) of the test piece in time t-2) And t is the static water absorption time (h).
TABLE 2 static capillary Water absorption results for emulsion coated test pieces prepared in examples 1-3 and comparative examples 1-2
As can be seen from fig. 3 and table 2, the static capillary water absorption of the concrete test piece treated by the poly-dopamine-modified graphene oxide-modified silane emulsion prepared in examples 1 to 3 is respectively reduced by 89.84%, 92.58% and 91.40% compared with the concrete blank test piece without surface treatment; compared with the concrete test piece treated by the common silane emulsion, the static capillary water absorption is respectively reduced by 57.66%, 69.10% and 64.19%, and the static capillary water absorption of the concrete treated by the polydopamine modified graphene oxide modified silane emulsion prepared in the embodiments 1 to 3 is greatly reduced. The polydopamine modified graphene oxide modified silane emulsion provided by the invention endows a concrete test piece with excellent waterproof performance, can effectively inhibit the diffusion and transmission of water in the concrete, and in addition, compared with the test piece treated by the polydopamine modified graphene oxide modified silane emulsion, the polydopamine modified graphene oxide modified silane emulsion has the advantages that the diffusion and transmission of water in the concrete are respectively reduced by 14.61%, 38.26% and 27.96%, and the static capillary water absorption is further reduced, so that the polydopamine functionalization effectively improves the modification effect of the graphene oxide on the silane emulsion.
3. Chloride and sulfate solution penetration test
One of the unfired faces of the dry concrete test piece was selected as the coating face, and example 1 was conducted separatelyAbout 3 and comparative examples 1 to 2 at 600g/m2The dosage of the sodium chloride-sodium salt is coated on the surface of a cement paste test piece twice (at an interval of 7 hours) and then dried, four sides and the opposite surface of the coated surface are sealed by paraffin wax, and the test piece is respectively soaked in 10 wt% NaCl aqueous solution and 10 wt% Na aqueous solution2SO4In the water solution, the penetration of chloride ions and sulfate ions is tested for the test pieces 0d, 1d, 3d, 5d, 7d, 10d, 15d, 20d, 25d, 30d, 40d and 50d, the concrete test piece eroded by 50d chloride ions is split along the central line by using a universal tester, and 0.1mol/LAgNO is added3The solution was sprayed on the cleaved surface of the test piece, the depth of the discolored region was measured with a vernier caliper, and the average of 5 points was taken, and the test results are shown in table 3 and fig. 4 to 5, where fig. 4 is a result of chloride ion etching and fig. 5 is a result of sulfate ion etching.
TABLE 3 results of the amount of chloride ion attack of emulsion coated test pieces prepared in examples 1 to 3 and comparative examples 1 to 2
As can be seen from fig. 4 and table 3, compared with the test piece without surface treatment and the test piece treated with the common silane emulsion, the chloride ion erosion amount of the concrete test piece treated with the poly-dopamine-modified graphene oxide-modified silane emulsion is greatly reduced, and the chloride ion erosion amount of the concrete test pieces of examples 1 to 3 is respectively reduced by 79.34%, 87.67% and 92.48% compared with the blank test piece; the polydopamine modified graphene oxide modified silane emulsion prepared by the invention endows a concrete sample with excellent chlorine salt corrosion resistance, and can effectively inhibit the diffusion and transmission of chloride ions in the concrete. Compared with a test piece treated by the graphene oxide modified silane emulsion, the chloride ion erosion amount of the test pieces in the embodiments 1 to 3 is respectively reduced by 17.52%, 50.77% and 69.90%, and the chloride ion erosion amount is further reduced, which indicates that the modification effect of graphene oxide on the chlorine salt erosion resistance of the silane emulsion is effectively improved by the poly-dopamine functionalization.
As can be seen from fig. 5 and table 3, compared with the concrete specimen without surface treatment and the specimen treated with the ordinary silane emulsion, the sulfate ion erosion amount of the concrete specimen treated with the poly-dopamine-modified graphene oxide-modified silane emulsion is greatly reduced, and the sulfate ion erosion amount of examples 1 to 3 is respectively reduced by 82.77%, 89.35% and 92.77% compared with that of the blank specimen; the polydopamine modified graphene oxide modified silane emulsion prepared by the invention endows a concrete sample with excellent sulfate erosion resistance, and can effectively inhibit the diffusion and transmission of sulfate ions in the concrete. Compared with the test piece treated by the graphene oxide modified silane emulsion, the sulfate ion erosion amount of the test pieces in the embodiments 1 to 3 is respectively reduced by 15.88%, 48.02% and 64.68%, and the sulfate ion erosion amount is further reduced, which indicates that the modification effect of the graphene oxide on the sulfate erosion resistance of the silane emulsion is effectively improved by the poly-dopamine functionalization.
The calculated fitting graph of the chloride ion erosion rate of each concrete sample is shown in fig. 6, the calculated fitting graph of the sulfate ion erosion rate is shown in fig. 7, and as can be seen from fig. 6 to 7, compared with the concrete sample without surface treatment and the sample treated by the common silane emulsion, the erosion rate of the chloride ions and the sulfate ions of the concrete sample treated by the polydopamine modified graphene oxide modified silane emulsion is greatly reduced, and the erosion rate of the chloride ions and the sulfate ions is only about 1/7 and 1/8 of the blank sample respectively; in the whole erosion process, the erosion rate of chloride ions and sulfate ions is relatively stable, which shows that the polydopamine modified graphene oxide can effectively inhibit the diffusion and transmission of erosion ions in a concrete capillary channel, block or prolong the transmission path of the erosion ions, and reduce the osmotic pressure of ions in the capillary channel.
The results of the chloride ion erosion depth test for each concrete specimen are shown in table 4 and fig. 8:
TABLE 4 chloride ion etch depth test results for emulsion coated test pieces prepared in examples 1-3 and comparative examples 1-2
As can be seen from fig. 8 and table 4, the chloride ion erosion depth of the concrete sample treated with the poly-dopamine-modified graphene oxide-modified silane emulsion was significantly reduced compared to the concrete sample without surface treatment. In examples 1 to 3, the penetration depth of chloride ions was reduced from 7.61cm to 0.67cm, 0.54cm and 0.41cm, respectively, and the reduction widths reached 91.20%, 92.90% and 94.61%, respectively. Compared with the test piece treated by the common silane emulsion and the graphene oxide modified silane, the chloride ion penetration depth of the test piece of the embodiment 1-3 is also reduced, which shows that the poly-dopamine functionalization effectively improves the modification effect of the graphene oxide on the chloride ion corrosion resistance of the silane emulsion.
4. SEM microscopic examination test
The internal morphology of each test piece to be tested (cement paste test piece) prepared by a scanning electron microscope surface water contact angle test is shown in fig. 9-14, wherein fig. 9 is an SEM image of a blank cement paste test piece, fig. 10 is an SEM image of a test piece coated with a normal silane emulsion, fig. 11 is an SEM image of a test piece coated with a graphene oxide modified silane emulsion, fig. 12 is an SEM image of a test piece coated with a polydopamine-modified graphene oxide modified silane emulsion prepared in example 1, fig. 13 is an SEM image of a test piece coated with a polydopamine-modified graphene oxide modified silane emulsion prepared in example 2, and fig. 14 is an SEM image of a test piece coated with a polydopamine-modified graphene oxide modified silane emulsion prepared in example 3.
As can be seen from fig. 9, there are more microscopic particles on the inner surface of the cement paste blank test piece, which is the morphology of the cement hydration product. As can be seen from fig. 10 to 11, the inner surface of the cement test piece treated by the common silane emulsion and the graphene oxide modified silane emulsion is covered with a flocculent structure with a certain thickness, which is a continuous and compact protective film with hydrophobic property formed on the surface of the cement hydration product after the composite emulsion permeates into the cement matrix. By observing fig. 12-14, it can be found that after the surface treatment of the polydopamine modified graphene oxide modified silane emulsion, the hydrophobic flocculation structure in the cement test piece can be further developed and subjected to intersection and connection to form a thicker and more complete cluster structure; gradually takes on a plate shape along with the increase of the content of the polydopamine modified graphene oxide, and a more compact secondary hydration product settled layer is formed on the surface of a cement hydration product.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (8)
1. The polydopamine modified graphene oxide modified silane emulsion comprises the following components in percentage by mass: 50-60% of silane monomer, 0.05-0.5% of polydopamine modified graphene oxide, 1-5% of water phase emulsifier, 0.1-0.5% of dispersant, 1-5% of oil phase emulsifier and 35-45% of water;
the preparation method of the polydopamine modified graphene oxide comprises the following steps:
pre-dispersing graphene oxide in water to obtain a graphene oxide dispersion liquid;
mixing the graphene oxide dispersion liquid with a buffer solution, adjusting the pH value to 8-8.5, and then performing ultrasonic dispersion to obtain a mixed dispersion liquid;
performing secondary ultrasonic dispersion on the mixed dispersion liquid and dopamine hydrochloride to obtain polydopamine modified graphene oxide;
the preparation method of the polydopamine modified graphene oxide modified silane emulsion comprises the following steps:
(1) mixing a water-phase emulsifier, a dispersant, polydopamine modified graphene oxide and water to obtain a water phase;
(2) mixing an oil phase emulsifier and a silane monomer to obtain an oil phase;
(3) dropwise adding the oil phase into the water phase and mixing to obtain polydopamine modified graphene oxide modified silane emulsion;
the step (1) and the step (2) have no chronological order.
2. The polydopamine-modified graphene oxide-modified silane emulsion according to claim 1, wherein the buffer solution comprises one or more of tris buffer solution, barbiturate buffer solution, ammonia-ammonium chloride buffer solution, potassium dihydrogen phosphate buffer solution, and sodium dihydrogen phosphate buffer solution.
3. The polydopamine-modified graphene oxide-modified silane emulsion according to any one of claims 1 to 2, wherein the particle size of the polydopamine-modified graphene oxide is 200 to 800 meshes.
4. The polydopamine-modified graphene oxide-modified silane emulsion of claim 1, wherein the silane monomer comprises a substituted oxysilane.
5. The polydopamine-modified graphene oxide-modified silane emulsion according to claim 1, wherein the aqueous phase emulsifier comprises one or more of an alkylether emulsifier, an alkyl organic salt emulsifier and an ester emulsifier.
6. The polydopamine-modified graphene oxide-modified silane emulsion of claim 1, wherein the dispersant comprises one or more of an alkyl organic salt, polyvinyl alcohol, polyvinylpyrrolidone, polyethylene glycol, and glycerol.
7. The polydopamine-modified graphene oxide-modified silane emulsion according to claim 1, wherein the oil-phase emulsifier comprises a fatty acid ester emulsifier.
8. Use of the polydopamine-modified graphene oxide-modified silane emulsion according to any one of claims 1 to 7 in protection of cement-based materials, rocks, metals, plastic products, wood or textiles.
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