Preparation method of graphene-based surface protective coating

Abstract

The invention relates to the technical field of protective coatings, in particular to a preparation method of a graphene-based surface protective coating. The specific preparation method comprises the following steps: carrying out surface modification on graphene oxide by adopting an amino silane coupling agent to prepare aminated graphene; the preparation method comprises the following steps: under the protection of nitrogen, carrying out polymerization reaction on glycidyl methacrylate and a silane coupling agent under the action of an initiator to prepare a PGMA-co-PMPS polymer; the PGMA-co-PMPS polymer and aminated graphene are subjected to a stirring reaction, so that a multi-crosslinking system with C-O-C and Si-O-Si bonds is formed, and the graphene-based surface protection coating is prepared. The invention solves the problems that the graphene is non-uniformly dispersed in a polymer matrix and the overall performance and durability of the coating are influenced by the compatibility difference between the graphene and the polymer matrix in the existing high-durability surface protective coating.

Description

Technical Field

[0001] The present invention relates to the technical field of protective coatings, and in particular to a method for preparing a graphene-based surface protective coating. Background Art

[0002] In the context of exploring the current technological development trends and the application of new materials, high-durability surface protective coatings are increasingly valued due to their irreplaceable nature in multiple key industries. With their unique physical and chemical properties, these coatings play a vital role in the fields of automotive manufacturing, pipeline engineering, construction engineering, aerospace, and cultural heritage protection. However, in actual applications, these coatings are exposed to complex and changeable natural environments for a long time and face multiple challenges such as corrosion, wear, and aging. These natural factors significantly shorten the service life of the coatings and reduce their effectiveness. Therefore, it is necessary to develop new high-durability surface protective coatings.

[0003] Graphene, a carbon atom in the form of sp 2 The two-dimensional carbon nanomaterials formed by hybrid orbital arrangement have become an ideal choice for the preparation of high-performance protective coatings due to their excellent physical and chemical properties, such as extremely thin thickness, extremely high hardness, rich functional groups and unique lamellar structure. The functional groups of graphene make it easy to modify the surface, so that it can react chemically with various polymer monomers to form stable chemical bonds. Its special lamellar structure can build a tight network structure in the material, effectively hindering molecular diffusion, forming a "maze effect", and significantly enhancing the aging resistance and anti-permeability of the material. In addition, the high toughness and hydrophobicity and oleophobicity of graphene also make it possible to prepare highly transparent and highly hydrophobic protective coatings.

[0004] At present, high-durability surface protection coatings are mainly prepared with graphene and epoxy resin as raw materials. However, due to its unique lamellar structure and high specific surface area, graphene is prone to agglomeration in the polymer matrix, resulting in uneven dispersion. This uneven dispersion will affect the performance of the coating, such as reducing the transparency and adhesion of the coating. In addition, the difference in compatibility between graphene and the resin matrix may lead to phase separation, affecting the overall performance and durability of the coating. Summary of the invention

[0005] In order to solve the problems of uneven dispersion of graphene in the polymer matrix in existing high-durability surface protective coatings, which affects the transparency and adhesion of the coating, and the compatibility difference between graphene and the polymer matrix, which affects the overall performance and durability of the coating, the purpose of the present invention is to provide a method for preparing a graphene-based surface protective coating.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows.

[0007] The present invention provides a method for preparing a graphene-based surface protective coating, comprising the following steps:

[0008] Under the action of a catalyst, a graphene oxide dispersion is mixed with an aminosilane coupling agent to modify the surface of the graphene oxide using the aminosilane coupling agent to obtain amino graphene; under nitrogen protection, glycidyl methacrylate and 3-(methacryloyloxy)propyltrimethoxysilane are polymerized under the action of an initiator to obtain a PGMA-co-PMPS polymer; the amino graphene is prepared into an amino graphene dispersion, and the amino graphene dispersion and the PGMA-co-PMPS polymer are stirred to react to form a multi-crosslinked system with COC bonds and Si-O-Si bonds to obtain a graphene-based surface protective coating.

[0009] The present invention firstly utilizes an aminosilane coupling agent to perform surface modification on graphene oxide to prepare amino graphene; at the same time, utilizes common solution free radical polymerization to prepare PGMA-co-PMPS polymer; through the reaction of PGMA-co-PMPS polymer with amino graphene, the amino graphene can catalyze the ring opening and hydrolysis of epoxy groups and siloxanes in copolymer segments, form strong COC bonds and Si-O-Si bonds inside the coating, and combine with graphene oxide to form a cross-linked network, thereby enhancing the dispersion of graphene at a microscopic level in a polymer matrix, greatly reducing the possibility of graphene aggregation, and being able to better avoid stress concentration inside the film, and the bonding effect of chemical bonds can also greatly reduce the occurrence of phase separation, and can also provide long-term durability of the coating while enhancing the coating structure.

[0010] Preferably, the aminosilane coupling agent is aminopropyltrimethoxysilane or [3-(6-aminohexylamino)propyl]; and the catalyst is 4-dimethylaminopyridine.

[0011] Specifically, in the present invention, the aminosilane coupling agent, such as aminopropyltrimethoxysilane or [3-(6-aminohexylamino)propyl], can react with the surface functional groups of graphene oxide, such as carboxyl, hydroxyl and epoxy groups, after hydrolysis, and be grafted to the graphene surface to form an amino graphene material, so as to improve the dispersibility of the amino graphene material. At the same time, the amino graphene catalyzes the ring opening and hydrolysis of the epoxy groups and siloxanes in the polymer, forming COC and Si-O-Si bonds inside the coating, providing a multi-crosslinking system, enhancing the coating structure, and providing the coating with long-term durability.

[0012] Preferably, the mass ratio of the catalyst to the graphene oxide is 1:1-5; the mass ratio of the catalyst to the aminosilane coupling agent is 1:1-3.

[0013] Preferably, the initiator is azobisisobutyronitrile; the molar ratio of glycidyl methacrylate, 3-(methacryloyloxy)propyltrimethoxysilane to the initiator is 100:50 to 200:1.

[0014] Preferably, the molar ratio of PGMA-co-PMPS polymer to amino graphene is 2:0.01-0.05.

[0015] Preferably, the solvent for the polymerization reaction is butanone, toluene or N,N-dimethylformamide; and the temperature for the polymerization reaction is 60°C to 80°C.

[0016] In the present invention, the reaction temperature range for preparing PGMA-co-PMPS polymer is usually between 60°C and 80°C. This temperature range is the best working temperature range for azobisisobutyronitrile as an initiator. It can decompose evenly in this range and only form one free radical without other side reactions, showing good stability and safety. Azobisisobutyronitrile has good performance in the temperature range of 60°C to 80°C. However, at higher temperatures, such as 80°C to 90°C and above, azobisisobutyronitrile will decompose rapidly, which may produce toxic gases and cause explosions and other dangerous situations. Therefore, the reaction temperature needs to be strictly controlled during the reaction.

[0017] Preferably, the temperature for stirring the reaction between the amination graphene dispersion and the PGMA-co-PMPS polymer is 40° C. to 50° C.

[0018] Preferably, the graphene oxide dispersion is obtained by dispersing graphene oxide in a dispersion solvent; the amination graphene dispersion is obtained by dispersing amination graphene in a dispersion solvent; and the dispersion solvent is at least one of tetrahydrofuran, N,N-dimethylformamide and dimethyl sulfoxide.

[0019] The dispersion of the present invention is mainly obtained by ultrasonic dispersion, and the ultrasonic time is 10 minutes to 30 minutes. The specific ultrasonic time can be determined according to the dispersion situation.

[0020] The process of preparing amino graphene includes washing, centrifugation and drying steps after the reaction is completed. During washing, the washing solvents are ethanol and distilled water, which are repeated 1 to 2 times respectively; during centrifugation, the rotation speed is 8000 r / min to 10000 r / min, and the centrifugation time is 10 min to 30 min; the drying method is vacuum drying at room temperature for 2 to 3 days.

[0021] Preferably, the concentration of the graphene oxide dispersion is 0.1 mg / mL to 1 mg / mL; the concentration of the amination graphene dispersion is 0.2 mg / mL to 1 mg / mL.

[0022] Preferably, the polymerization reaction needs to be vacuumed and nitrogen-filled for 3 to 5 cycles, and the reaction is carried out under a nitrogen atmosphere for 0.5 to 6 hours. After the reaction is completed, the following steps are further included: precipitation, reduced pressure filtration and drying. The precipitation solvent is methanol; during drying, the drying method is vacuum drying, the drying temperature is room temperature, and the drying time is 1 to 3 days.

[0023] Preferably, the stirring reaction time of the amination graphene dispersion and the PGMA-co-PMPS polymer is 1 h to 3 h.

[0024] Beneficial effects of the present invention:

[0025] 1. The present invention firstly utilizes an aminosilane coupling agent to perform surface modification on graphene oxide to prepare amino graphene; at the same time, ordinary solution free radical polymerization is utilized to form a PGMA-co-PMPS polymer; through the reaction of the PGMA-co-PMPS polymer with the amino graphene, the amino graphene can catalyze the ring opening and hydrolysis of the epoxy group and the siloxane in the copolymer chain segment, form strong COC and Si-O-Si bonds inside the coating, and combine with the graphene oxide to form a cross-linked network, thereby enhancing the dispersion of graphene at the microscopic level in the polymer matrix, greatly reducing the possibility of graphene aggregation, and being able to better avoid the stress concentration phenomenon inside the film, and the bonding effect of chemical bonds can also greatly reduce the occurrence of phase separation, and can also provide the coating with long-term durability while enhancing the coating structure; and solves the problem of poor weather resistance of the current high-durability surface protective coating.

[0026] 2. The amino graphene in the present invention can catalyze the ring opening and hydrolysis of the epoxy and siloxane groups in the copolymer chain segments, forming strong COC and Si-O-Si bonds inside the coating, providing a multi-crosslinking system; and the presence of epoxy and siloxane functional groups also provides the coating with excellent substrate bonding properties; graphene is a good physical barrier inside the coating, increasing the tortuosity of the molecular diffusion path, thereby achieving weather resistance to acids, alkalis, salts and ultraviolet light.

[0027] 3. The present invention reacts PGMA-co-PMPS polymer with amino graphene to obtain a long-term weather-resistant protective material with high transparency, high hydrophobicity and high adhesion. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a reaction equation for preparing amination graphene in one embodiment of the present invention.

[0029] Figure 2The transmission electron microscope images of graphene oxide and amination graphene in Example 1. Among them, (a) is a transmission electron microscope image of graphene oxide at 2.0 μm; (b) is a transmission electron microscope image of graphene oxide at 1.0 μm; (c) is a transmission electron microscope image of amination graphene at 5.0 μm; (d) is a transmission electron microscope image of amination graphene at 1.0 μm. The scale of (a) is 2.0 μm; the scale of (b) is 1.0 μm; the scale of (c) is 5.0 μm; the scale of (d) is 1.0 μm.

[0030] Figure 3 This is the infrared spectra of the PGMA-co-PMPS copolymer and the graphene-based copolymer PGMA-co-PMPS / GO in Example 1.

[0031] Figure 4 This is a comparison chart of water contact angles tested after the graphene-based surface protective coatings prepared in Example 1, Example 5-Example 6, and Comparative Examples 2-Example 3 and the PGMA-co-PMPS copolymer prepared in Comparative Example 4 were applied as protective coatings to the surfaces of three substrates: glass, steel, and sandstone.

[0032] Figure 5 This is a comparison chart of the adhesion strength of the graphene-based surface protective coatings prepared in Example 1, Example 5-Example 6, and Comparative Examples 2-3, and the PGMA-co-PMPS copolymer prepared in Comparative Example 4, after being applied as protective coatings to glass surfaces. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0034] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without making any creative work shall fall within the scope of protection of the present invention.

[0035] The present invention aims at the problem of poor weather resistance of the current high-durability surface protective coating, and performs surface modification on a single layer or a few layers of ultra-thin graphene oxide to successfully prepare amino graphene. Among them, multi-layer graphene has poor dispersibility and the modification effect is not ideal.

[0036] Graphene is a carbon atom in the form of sp 2The two-dimensional carbon nanomaterial composed of a hexagonal honeycomb lattice of hybrid orbitals is the thinnest and hardest material discovered so far. The surface and edges of graphene have a large number of functional groups such as hydroxyl and carboxyl, which are very easy to react with polar substances, which makes its surface modification and grafting polymer monomers possible. Graphene has a special two-dimensional flake structure, which can form a tight network in the material, hinder the diffusion of molecules, and form a "maze effect". It can serve as an excellent physical barrier to hinder the penetration of oxygen and corrosive substances and improve the aging resistance of the material. Graphene has high toughness and can be stretched infinitely. When subjected to external forces, carbon atoms bend and deform, so graphene has high stability. In addition, graphene itself is hydrophobic and oleophobic, and has good gloss.

[0037] 3-(Methacryloyloxy)propyltrimethoxysilane and glycidyl methacrylate are bifunctional monomers that can provide a continuous phase and bonding properties, can be combined with a substrate through hydrolysis to form a cross-linked network, have good adhesion, better bonding with the substrate, and strong stability. Aminated graphene can catalyze the ring opening and hydrolysis of epoxy and siloxane in the copolymer segment, form strong COC and Si-O-Si bonds inside the coating, provide a multi-cross-linked system, enhance the coating structure, and provide long-term durability of the coating. The presence of epoxy and siloxane functional groups also provides the coating with excellent substrate bonding properties; in addition, graphene is a good physical barrier inside the coating, which increases the tortuosity of the molecular diffusion path, thereby achieving weather resistance to acids, alkalis, salts, and ultraviolet light. The present invention is intended to obtain a long-term weather-resistant protective material with high transparency, high hydrophobicity, and high adhesion.

[0038] The present invention first modifies the surface of graphene, and then uses amination graphene to modify the polymer. This strategy will enhance the dispersion of graphene at the microscopic level in the polymer matrix, greatly reduce the possibility of graphene aggregation, and can better avoid the stress concentration phenomenon inside the film. In addition, the bonding action of chemical bonds can also greatly reduce the occurrence of phase separation. At the same time, amination graphene can catalyze the ring opening and hydrolysis of epoxy groups and siloxanes in the copolymer segments, forming strong COC and Si-O-Si bonds inside the coating, providing a multi-crosslinking system, enhancing the coating structure, and providing long-term durability of the coating. The presence of epoxy and siloxane functional groups also provides the coating with excellent substrate bonding properties; in addition, graphene is a good physical barrier inside the coating, increasing the tortuosity of the molecular diffusion path, thereby achieving weather resistance to acids, alkalis, salts, and ultraviolet light.

[0039] The technical solution of the present invention is further described below through specific embodiments.

[0040] In the following examples, the methods described are conventional methods unless otherwise specified; the reagents and materials described are commercially available unless otherwise specified.

[0041] In the following embodiments, graphene oxide can be purchased from the market or prepared in the laboratory. The preparation method of graphene oxide is a prior art. For example, graphene oxide is prepared by the Hummers method, with reference to the method of CN105347334B. The specific method is as follows:

[0042] Graphite powder, sodium nitrate and an appropriate amount of concentrated sulfuric acid with a mass concentration of 98wt% are placed in a three-necked flask, the amount ratio of graphite powder, sodium nitrate and concentrated sulfuric acid is 1g:100mg:23mL; after stirring and mixing evenly, mix in an ice water bath, and slowly add potassium permanganate under magnetic stirring, the amount ratio of graphite powder and potassium permanganate is 1g:1.5g; stir for 30min to 48h; slowly add hydrogen peroxide and deionized water, after complete oxidation, filter, wash with hydrochloric acid, and wash with distilled water until neutral; dry in a vacuum drying oven at 60℃ to obtain graphene oxide; store for later use.

[0043] In the following embodiments, the graphene oxide is a single layer or a few layers of ultra-thin graphene oxide with a size of 1 micron to 10 microns.

[0044] In the following embodiments, graphene oxide is denoted as GO; aminopropyltrimethoxysilane is denoted as APS; aminated graphene is denoted as GO-g-NH2; glycidyl methacrylate is denoted as GMA; 3-(methacryloyloxy)propyltrimethoxysilane is denoted as MPS; the polymer of glycidyl methacrylate and 3-(methacryloyloxy)propyltrimethoxysilane is denoted as PGMA-co-PMPS; azobisisobutyronitrile is denoted as AIBN; tetrahydrofuran is denoted as THF; and 4-dimethylaminopyridine is denoted as DMAP.

[0045] Example 1

[0046] A method for preparing a graphene-based surface protective coating comprises the following steps:

[0047] Step 1, preparation of amination graphene:

[0048] Graphene oxide and tetrahydrofuran were placed in a round-bottom flask, and ultrasonicated for 10 minutes until the graphene oxide was evenly dispersed to obtain a graphene oxide dispersion; the concentration of the graphene oxide dispersion was 0.5 mg / mL.

[0049] Under magnetic stirring, 4-dimethylaminopyridine was added to the graphene oxide dispersion, and then aminopropyltrimethoxysilane was slowly added dropwise with a syringe, and the mass ratio of 4-dimethylaminopyridine to aminopropyltrimethoxysilane was controlled to be 1:2; the mass ratio of 4-dimethylaminopyridine to graphene oxide was 1:3. The reaction was carried out at room temperature for 24 hours. After the reaction was completed, the product was washed twice with ethanol and twice with distilled water, centrifuged at a speed of 8000r / min for 15 minutes, and vacuum dried at room temperature for 2 days to constant weight to obtain amination graphene, recorded as GO-g-NH2.

[0050] Step 2, preparation of PGMA-co-PMPS copolymer:

[0051] Weigh azobisisobutylene in a reaction bottle, evacuate and pass nitrogen at room temperature, repeat 4 times, add butanone, glycidyl methacrylate and 3-(methacryloyloxy)propyltrimethoxysilane in nitrogen atmosphere, control the molar ratio of glycidyl methacrylate, 3-(methacryloyloxy)propyltrimethoxysilane and azobisisobutylene to be 100:100:1; the dosage ratio of azobisisobutylene to butanone is 1mmol:20mL. Keep the reaction in a 70℃ oil bath for 6h. After the reaction is completed, add the product dropwise to excess methanol for precipitation, filter under reduced pressure, and vacuum dry at room temperature for 3 days to obtain a white solid, which is PGMA-co-PMPS copolymer.

[0052] Step 3, preparation of graphene-based surface protective coating:

[0053] Add the aminated graphene and tetrahydrofuran into a reaction bottle, and perform ultrasonication for 30 minutes until the aminated graphene is evenly dispersed to obtain an aminated graphene dispersion having a concentration of 0.2 mg / mL.

[0054] PGMA-co-PMPS copolymer was added to the amino graphene dispersion, and the molar ratio of PGMA-co-PMPS copolymer to amino graphene was 100: 1. Then, the reaction was continued under stirring at 50°C for 3 hours to obtain a graphene-based surface protective coating, which was recorded as PGMA-co-PMPS / GO2.

[0055] Embodiment 2:

[0056] A method for preparing a graphene-based surface protective coating, which differs from Example 1 in that the aminosilane coupling agent uses 3-(6-aminohexylamino)propyltrimethoxysilane; the specific method comprises the following steps:

[0057] Step 1, preparation of amination graphene:

[0058] Graphene oxide and tetrahydrofuran were placed in a round-bottom flask, and ultrasonicated for 10 minutes until the graphene oxide was evenly dispersed to obtain a graphene oxide dispersion; the concentration of the graphene oxide dispersion was 0.5 mg / mL.

[0059] Under magnetic stirring, 4-dimethylaminopyridine was added to the graphene oxide dispersion, and then 3-(6-aminohexylamino)propyltrimethoxysilane was slowly added dropwise with a syringe, and the mass ratio of 4-dimethylaminopyridine and 3-(6-aminohexylamino)propyltrimethoxysilane was controlled to be 1:2; the mass ratio of 4-dimethylaminopyridine and graphene oxide was 1:3. The reaction was carried out at room temperature for 24 hours. After the reaction was completed, the product was washed twice with ethanol and twice with distilled water, centrifuged at a speed of 8000r / min for 15 minutes, and vacuum dried at room temperature for 2 days to constant weight to obtain amination graphene, recorded as GO-g-NH2.

[0060] Step 2, preparation of PGMA-co-PMPS copolymer:

[0061] Weigh azobisisobutylene in a reaction bottle, evacuate and pass nitrogen at room temperature, repeat 4 times, add butanone, glycidyl methacrylate and 3-(methacryloyloxy)propyltrimethoxysilane in nitrogen atmosphere, control the molar ratio of glycidyl methacrylate, 3-(methacryloyloxy)propyltrimethoxysilane and azobisisobutylene to be 100:100:1; the dosage ratio of azobisisobutylene to butanone is 1mmol:20mL. Keep the reaction in a 70℃ oil bath for 6h. After the reaction is completed, add the product dropwise to excess methanol for precipitation, filter under reduced pressure, and vacuum dry at room temperature for 3 days to obtain a white solid, which is PGMA-co-PMPS copolymer.

[0062] Step 3, preparation of graphene-based surface protective coating:

[0063] Add the aminated graphene and tetrahydrofuran into a reaction bottle, and perform ultrasonication for 30 minutes until the aminated graphene is evenly dispersed to obtain an aminated graphene dispersion having a concentration of 0.2 mg / mL.

[0064] PGMA-co-PMPS copolymer was added to the aminated graphene dispersion, and the molar ratio of PGMA-co-PMPS copolymer to aminated graphene was 100: 1. Then, the reaction was continued under stirring at 50° C. for 3 h to obtain a graphene-based surface protective coating.

[0065] Example 3

[0066] A method for preparing a graphene-based surface protective coating, which is different from Example 1 in that the molar ratio of glycidyl methacrylate, 3-(methacryloyloxy)propyltrimethoxysilane and azobisisobutyl is 100:50:1; the specific method comprises the following steps:

[0067] Step 1, preparation of amination graphene:

[0068] Graphene oxide and tetrahydrofuran were placed in a round-bottom flask, and ultrasonicated for 10 minutes until the graphene oxide was evenly dispersed to obtain a graphene oxide dispersion; the concentration of the graphene oxide dispersion was 0.5 mg / mL.

[0069] Under magnetic stirring, 4-dimethylaminopyridine was added to the graphene oxide dispersion, and then aminopropyltrimethoxysilane was slowly added dropwise with a syringe, and the mass ratio of 4-dimethylaminopyridine to aminopropyltrimethoxysilane was controlled to be 1:2; the mass ratio of 4-dimethylaminopyridine to graphene oxide was 1:3. The reaction was carried out at room temperature for 24 hours. After the reaction was completed, the product was washed twice with ethanol and twice with distilled water, centrifuged at a speed of 8000r / min for 15 minutes, and vacuum dried at room temperature for 2 days to constant weight to obtain amination graphene, recorded as GO-g-NH2.

[0070] Step 2, preparation of PGMA-co-PMPS copolymer:

[0071] Weigh azobisisobutylene in a reaction bottle, evacuate and pass nitrogen at room temperature, repeat 4 times, add butanone, glycidyl methacrylate and 3-(methacryloyloxy)propyltrimethoxysilane in nitrogen atmosphere, control the molar ratio of glycidyl methacrylate, 3-(methacryloyloxy)propyltrimethoxysilane and azobisisobutylene to be 100:50:1; the dosage ratio of azobisisobutylene to butanone is 1mmol:20mL. Keep the reaction in a 70℃ oil bath for 6h. After the reaction is completed, add the product dropwise to excess methanol for precipitation, filter under reduced pressure, and vacuum dry at room temperature for 3 days to obtain a white solid, which is PGMA-co-PMPS copolymer.

[0072] Step 3, preparation of graphene-based surface protective coating:

[0073] Add the aminated graphene and tetrahydrofuran into a reaction bottle, and perform ultrasonication for 30 minutes until the aminated graphene is evenly dispersed to obtain an aminated graphene dispersion having a concentration of 0.2 mg / mL.

[0074] PGMA-co-PMPS copolymer was added to the aminated graphene dispersion, and the molar ratio of PGMA-co-PMPS copolymer to aminated graphene was 100: 1. Then, the reaction was continued under stirring at 50° C. for 3 h to obtain a graphene-based surface protective coating.

[0075] Example 4

[0076] A method for preparing a graphene-based surface protective coating, which is different from Example 1 in that the molar ratio of glycidyl methacrylate, 3-(methacryloyloxy)propyltrimethoxysilane and azobisisobutyl is 100:200:1; the specific method comprises the following steps:

[0077] Step 1, preparation of amination graphene:

[0078] Graphene oxide and tetrahydrofuran were placed in a round-bottom flask, and ultrasonicated for 10 minutes until the graphene oxide was evenly dispersed to obtain a graphene oxide dispersion; the concentration of the graphene oxide dispersion was 0.5 mg / mL.

[0079] Under magnetic stirring, 4-dimethylaminopyridine was added to the graphene oxide dispersion, and then aminopropyltrimethoxysilane was slowly added dropwise with a syringe, and the mass ratio of 4-dimethylaminopyridine to aminopropyltrimethoxysilane was controlled to be 1:2; the mass ratio of 4-dimethylaminopyridine to graphene oxide was 1:3. The reaction was carried out at room temperature for 24 hours. After the reaction was completed, the product was washed twice with ethanol and twice with distilled water, centrifuged at a speed of 8000r / min for 15 minutes, and vacuum dried at room temperature for 2 days to constant weight to obtain amination graphene, recorded as GO-g-NH2.

[0080] Step 2, preparation of PGMA-co-PMPS copolymer:

[0081] Weigh azobisisobutylene in a reaction bottle, evacuate and pass nitrogen at room temperature, repeat 4 times, add butanone, glycidyl methacrylate and 3-(methacryloyloxy)propyltrimethoxysilane in nitrogen atmosphere, control the molar ratio of glycidyl methacrylate, 3-(methacryloyloxy)propyltrimethoxysilane and azobisisobutylene to be 100:200:1; the dosage ratio of azobisisobutylene to butanone is 1mmol:20mL. Keep the reaction in a 70℃ oil bath for 6h. After the reaction is completed, add the product dropwise to excess methanol for precipitation, filter under reduced pressure, and vacuum dry at room temperature for 3 days to obtain a white solid, which is PGMA-co-PMPS copolymer.

[0082] Step 3, preparation of graphene-based surface protective coating:

[0083] Add the aminated graphene and tetrahydrofuran into a reaction bottle, and perform ultrasonication for 30 minutes until the aminated graphene is evenly dispersed to obtain an aminated graphene dispersion having a concentration of 0.2 mg / mL.

[0084] PGMA-co-PMPS copolymer was added to the aminated graphene dispersion, and the molar ratio of PGMA-co-PMPS copolymer to aminated graphene was 100: 1. Then, the reaction was continued under stirring at 50° C. for 3 h to obtain a graphene-based surface protective coating.

[0085] Example 5

[0086] A method for preparing a graphene-based surface protective coating, which differs from Example 1 in that the molar ratio of the PGMA-co-PMPS copolymer to the amino graphene is 200:1; the specific method comprises the following steps:

[0087] Step 1, preparation of amination graphene:

[0088] Graphene oxide and tetrahydrofuran were placed in a round-bottom flask, and ultrasonicated for 10 minutes until the graphene oxide was evenly dispersed to obtain a graphene oxide dispersion; the concentration of the graphene oxide dispersion was 0.5 mg / mL.

[0089] Under magnetic stirring, 4-dimethylaminopyridine was added to the graphene oxide dispersion, and then aminopropyltrimethoxysilane was slowly added dropwise with a syringe, and the mass ratio of 4-dimethylaminopyridine to aminopropyltrimethoxysilane was controlled to be 1:2; the mass ratio of 4-dimethylaminopyridine to graphene oxide was 1:3. The reaction was carried out at room temperature for 24 hours. After the reaction was completed, the product was washed twice with ethanol and twice with distilled water, centrifuged at a speed of 8000r / min for 15 minutes, and vacuum dried at room temperature for 2 days to constant weight to obtain amination graphene, recorded as GO-g-NH2.

[0090] Step 2, preparation of PGMA-co-PMPS copolymer:

[0091] Weigh azobisisobutylene in a reaction bottle, evacuate and pass nitrogen at room temperature, repeat 4 times, add butanone, glycidyl methacrylate and 3-(methacryloyloxy)propyltrimethoxysilane in nitrogen atmosphere, control the molar ratio of glycidyl methacrylate, 3-(methacryloyloxy)propyltrimethoxysilane and azobisisobutylene to be 100:100:1; the dosage ratio of azobisisobutylene to butanone is 1mmol:20mL. Keep the reaction in a 70℃ oil bath for 6h. After the reaction is completed, add the product dropwise to excess methanol for precipitation, filter under reduced pressure, and vacuum dry at room temperature for 3 days to obtain a white solid, which is PGMA-co-PMPS copolymer.

[0092] Step 3, preparation of graphene-based surface protective coating:

[0093] Add the aminated graphene and tetrahydrofuran into a reaction bottle, and perform ultrasonication for 30 minutes until the aminated graphene is evenly dispersed to obtain an aminated graphene dispersion having a concentration of 0.2 mg / mL.

[0094] PGMA-co-PMPS copolymer was added to the amino graphene dispersion, and the molar ratio of PGMA-co-PMPS copolymer to amino graphene was 200: 1. Then, the reaction was continued under stirring at 50°C for 3 hours to obtain a graphene-based surface protective coating, which was recorded as PGMA-co-PMPS / GO1.

[0095] Example 6

[0096] A method for preparing a graphene-based surface protective coating, which differs from Example 1 in that the molar ratio of the PGMA-co-PMPS copolymer to the amino graphene is 200:5; the specific method comprises the following steps:

[0097] Step 1, preparation of amination graphene:

[0098] Graphene oxide and tetrahydrofuran were placed in a round-bottom flask, and ultrasonicated for 10 minutes until the graphene oxide was evenly dispersed to obtain a graphene oxide dispersion; the concentration of the graphene oxide dispersion was 0.5 mg / mL.

[0099] Under magnetic stirring, 4-dimethylaminopyridine was added to the graphene oxide dispersion, and then aminopropyltrimethoxysilane was slowly added dropwise with a syringe, and the mass ratio of 4-dimethylaminopyridine to aminopropyltrimethoxysilane was controlled to be 1:2; the mass ratio of 4-dimethylaminopyridine to graphene oxide was 1:3. The reaction was carried out at room temperature for 24 hours. After the reaction was completed, the product was washed twice with ethanol and twice with distilled water, centrifuged at a speed of 8000r / min for 15 minutes, and vacuum dried at room temperature for 2 days to constant weight to obtain amination graphene, recorded as GO-g-NH2.

[0100] Step 2, preparation of PGMA-co-PMPS copolymer:

[0101] Weigh azobisisobutylene in a reaction bottle, evacuate and pass nitrogen at room temperature, repeat 4 times, add butanone, glycidyl methacrylate and 3-(methacryloyloxy)propyltrimethoxysilane in nitrogen atmosphere, control the molar ratio of glycidyl methacrylate, 3-(methacryloyloxy)propyltrimethoxysilane and azobisisobutylene to be 100:100:1; the dosage ratio of azobisisobutylene to butanone is 1mmol:20mL. Keep the reaction in a 70℃ oil bath for 6h. After the reaction is completed, add the product dropwise to excess methanol for precipitation, filter under reduced pressure, and vacuum dry at room temperature for 3 days to obtain a white solid, which is PGMA-co-PMPS copolymer.

[0102] Step 3, preparation of graphene-based surface protective coating:

[0103] Add the aminated graphene and tetrahydrofuran into a reaction bottle, and perform ultrasonication for 30 minutes until the aminated graphene is evenly dispersed to obtain an aminated graphene dispersion having a concentration of 0.2 mg / mL.

[0104] PGMA-co-PMPS copolymer was added to the amino graphene dispersion, and the molar ratio of PGMA-co-PMPS copolymer to amino graphene was 200:5. Then, the reaction was continued under stirring at 50°C for 3 hours to obtain a graphene-based surface protective coating, which was recorded as PGMA-co-PMPS / GO3.

[0105] Comparative Example 1

[0106] A method for preparing a graphene-based surface protective coating, which differs from Example 1 in that no surface modifier is added, that is, the graphene oxide is not surface modified; the specific method comprises the following steps:

[0107] Step 1, preparation of PGMA-co-PMPS copolymer:

[0108] Weigh azobisisobutylene in a reaction bottle, evacuate and pass nitrogen at room temperature, repeat 4 times, add butanone, glycidyl methacrylate and 3-(methacryloyloxy)propyltrimethoxysilane in nitrogen atmosphere, control the molar ratio of glycidyl methacrylate, 3-(methacryloyloxy)propyltrimethoxysilane and azobisisobutylene to be 100:100:1; the dosage ratio of azobisisobutylene to butanone is 1mmol:20mL. Keep the reaction in a 70℃ oil bath for 6h. After the reaction is completed, add the product dropwise to excess methanol for precipitation, filter under reduced pressure, and vacuum dry at room temperature for 3 days to obtain a white solid, which is PGMA-co-PMPS copolymer.

[0109] Step 2, preparation of graphene-based surface protective coating:

[0110] Graphene oxide and tetrahydrofuran were added to a reaction bottle, and ultrasonicated for 30 minutes until the graphene oxide was evenly dispersed to obtain a graphene oxide dispersion having a concentration of 0.2 mg / mL.

[0111] PGMA-co-PMPS copolymer was added to the graphene oxide dispersion, and the molar ratio of PGMA-co-PMPS copolymer to graphene oxide was 100: 1. Then, the reaction was continued under stirring at 50° C. for 3 h to obtain a graphene-based surface protective coating.

[0112] Comparative Example 2

[0113] A method for preparing a graphene-based surface protective coating, which differs from Example 1 in that 3-(methacryloyloxy)propyltrimethoxysilane is not added; the specific method comprises the following steps:

[0114] Step 1, preparation of amination graphene:

[0115] Graphene oxide and tetrahydrofuran were placed in a round-bottom flask, and ultrasonicated for 10 minutes until the graphene oxide was evenly dispersed to obtain a graphene oxide dispersion; the concentration of the graphene oxide dispersion was 0.5 mg / mL.

[0116] Under magnetic stirring, 4-dimethylaminopyridine was added to the graphene oxide dispersion, and then aminopropyltrimethoxysilane was slowly added dropwise with a syringe, and the mass ratio of 4-dimethylaminopyridine to aminopropyltrimethoxysilane was controlled to be 1:2; the mass ratio of 4-dimethylaminopyridine to graphene oxide was 1:3. The reaction was carried out at room temperature for 24 hours. After the reaction was completed, the product was washed twice with ethanol and twice with distilled water, centrifuged at a speed of 8000r / min for 15 minutes, and vacuum dried at room temperature for 2 days to constant weight to obtain amination graphene, recorded as GO-g-NH2.

[0117] Step 2, preparation of PGMA polymer:

[0118] Weigh azobisisobutylene into a reaction bottle, evacuate and pass nitrogen at room temperature, repeat 4 times, add butanone and glycidyl methacrylate in a nitrogen atmosphere, control the molar ratio of glycidyl methacrylate to azobisisobutylene to be 100:1; the dosage ratio of azobisisobutylene to butanone is 1mmol:20mL. Keep the reaction in a 70℃ oil bath for 6h. After the reaction is completed, add the product dropwise to excess methanol for precipitation, filter under reduced pressure, and vacuum dry at room temperature for 3 days to obtain a white solid, which is PGMA-co-PMPS copolymer.

[0119] Step 3, preparation of graphene-based surface protective coating:

[0120] Add the aminated graphene and tetrahydrofuran into a reaction bottle, and perform ultrasonication for 30 minutes until the aminated graphene is evenly dispersed to obtain an aminated graphene dispersion having a concentration of 0.2 mg / mL.

[0121] PGMA polymer was added to the amino graphene dispersion, and the molar ratio of PGMA polymer to amino graphene was 100: 1. Then, the reaction was continued at 50°C with stirring for 3 hours to obtain a graphene-based surface protective coating, which was recorded as PGMA / GO2.

[0122] Comparative Example 3

[0123] A method for preparing a graphene-based surface protective coating, which differs from Example 1 in that glycidyl methacrylate is not added; the specific method comprises the following steps:

[0124] Step 1, preparation of amination graphene:

[0125] Graphene oxide and tetrahydrofuran were placed in a round-bottom flask, and ultrasonicated for 10 minutes until the graphene oxide was evenly dispersed to obtain a graphene oxide dispersion; the concentration of the graphene oxide dispersion was 0.5 mg / mL.

[0126] Under magnetic stirring, 4-dimethylaminopyridine was added to the graphene oxide dispersion, and then aminopropyltrimethoxysilane was slowly added dropwise with a syringe, and the mass ratio of 4-dimethylaminopyridine to aminopropyltrimethoxysilane was controlled to be 1:2; the mass ratio of 4-dimethylaminopyridine to graphene oxide was 1:3. The reaction was carried out at room temperature for 24 hours. After the reaction was completed, the product was washed twice with ethanol and twice with distilled water, centrifuged at a speed of 8000r / min for 15 minutes, and vacuum dried at room temperature for 2 days to constant weight to obtain amination graphene, recorded as GO-g-NH2.

[0127] Step 2, preparation of PMPS polymer:

[0128] Weigh azobisisobutylene in a reaction bottle, evacuate and pass nitrogen at room temperature, repeat 4 times, add butanone and 3-(methacryloyloxy)propyltrimethoxysilane in a nitrogen atmosphere, control the molar ratio of 3-(methacryloyloxy)propyltrimethoxysilane to azobisisobutylene to be 100:1; the dosage ratio of azobisisobutylene to butanone is 1mmol:20mL. Keep the reaction in a 70℃ oil bath for 6h. After the reaction is completed, add the product dropwise to excess methanol for precipitation, filter under reduced pressure, and vacuum dry at room temperature for 3 days to obtain a white solid, which is PMPS polymer.

[0129] Step 3, preparation of graphene-based surface protective coating:

[0130] Add the aminated graphene and tetrahydrofuran into a reaction bottle, and perform ultrasonication for 30 minutes until the aminated graphene is evenly dispersed to obtain an aminated graphene dispersion having a concentration of 0.2 mg / mL.

[0131] PMPS polymer was added to the amino graphene dispersion, and the molar ratio of PMPS polymer to amino graphene was 100: 1. Then, the reaction was continued under stirring at 50°C for 3 hours to obtain a graphene-based surface protective coating, which was recorded as PMPS / GO2.

[0132] Comparative Example 4

[0133] A method for preparing a PGMA-co-PMPS copolymer, wherein the PGMA-co-PMPS copolymer is prepared according to the method of Example 1, and the specific method comprises the following steps:

[0134] Weigh azobisisobutylene in a reaction bottle, evacuate and pass nitrogen at room temperature, repeat 4 times, add butanone, glycidyl methacrylate and 3-(methacryloyloxy)propyltrimethoxysilane in nitrogen atmosphere, control the molar ratio of glycidyl methacrylate, 3-(methacryloyloxy)propyltrimethoxysilane and azobisisobutylene to be 100:100:1; the dosage ratio of azobisisobutylene to butanone is 1mmol:20mL. Keep the reaction in a 70℃ oil bath for 6h. After the reaction is completed, add the product dropwise to excess methanol for precipitation, filter under reduced pressure, and vacuum dry at room temperature for 3 days to obtain a white solid, which is PGMA-co-PMPS copolymer.

[0135] Test 1: Transmission electron microscopy image analysis.

[0136] The reaction equation for preparing amination graphene in Example 1 is as follows: Figure 1 The transmission electron microscopy images of graphene oxide and amino-treated graphene in Example 1 are shown in FIG. Figure 2 shown.

[0137] Depend on Figure 2 It can be seen that graphene oxide has a single-layer or few-layer ultra-thin flaky structure with a size of 1 micron to 10 microns, and the flaky structure is relatively clear, with obvious interlayer spacing. Aminated graphene also has a flaky structure, but compared with graphene oxide, there are spot-like substances on its surface. These spot-like substances are reaction products or residual amino groups during the amination process. From the transmission electron microscopy image, it can be seen that both the aminated graphene flakes and graphene oxide are evenly distributed, with clear flakes and no obvious agglomeration.

[0138] Test 2: Infrared spectroscopy.

[0139] The structures of the PGMA-co-PMPS copolymer and the graphene-based copolymer PGMA-co-PMPS / GO in Example 1 were characterized by infrared spectroscopy analysis. The infrared spectra of the PGMA-co-PMPS copolymer and the graphene-based copolymer PGMA-co-PMPS / GO in Example 1 are shown in FIG. Figure 3 shown.

[0140] Depend on Figure 3 It can be seen that PGMA-co-PMPS and PGMA-co-PMPS / GO have -1 、1725cm -1 The characteristic peaks at 1080 cm-1 and 1090 cm-2 belong to the stretching vibration peaks of -CH3 / CH2 and -C=O, respectively. The characteristic peaks of -CO / Si-O of PGMA-co-PMPS / GO shifted significantly from 1080 cm-1 to 1090 cm-2. -1 The shift to 1152cm -1 At 1660cm -1 A new NH2 / -NH stretching vibration peak appears at 3200cm -1 and 1400cm -1 ~1600cm -1 New characteristic peaks of benzene ring C=CH and benzene ring skeleton vibration peaks appeared. Infrared spectrum showed that PGMA-co-PMPS / GO was successfully synthesized.

[0141] Test 3: Effect of surface modifiers.

[0142] In order to explore the effects of different surface modifiers and dosages on the modification of graphene oxide and the performance of the product, experiments were conducted using different surface modifiers or no surface modifiers to prepare different graphene-based surface protective coatings, and the performance of different graphene-based surface protective coatings was characterized. The comparison of experimental conditions is shown in Table 1.

[0143] Table 1 Comparison of experimental conditions of different surface modifiers and dosages

[0144]

[0145] Note: “-” indicates that no surface modifier was added, that is, the graphene oxide was not amino-modified.

[0146] a represents the molar ratio of PGMA-co-PMPS copolymer and graphene oxide.

[0147] The graphene-based surface protective coatings prepared with different surface modifiers and dosages were coated on different substrates to form protective films. The substrates used were glass, steel and sandstone. The results are shown in Table 2.

[0148] Table 2 Effects of different surface modifiers and dosage on product performance (on glass surface)

[0149]

[0150] From Table 2 and Figure 4 and Figure 5 It can be seen that compared with Comparative Example 1, Examples 1 and 2 of the present invention show that after the surface of graphene oxide is modified, the dispersion of graphene at the microscopic level in the polymer matrix is ​​significantly enhanced, the aggregation of graphene is greatly reduced, and the stress concentration phenomenon inside the membrane can be better avoided. The bonding effect of chemical bonds can also greatly reduce the occurrence of phase separation, and can also provide the coating with better hydrophobicity and adhesion while enhancing the coating structure.

[0151] Test 4: The effect of different dosage ratios of polymer monomers.

[0152] In order to explore the effect of different dosage ratios of polymer monomers on product performance, different graphene-based surface protective coatings were prepared using different dosage ratios of polymer monomers, and the performance of different graphene-based surface protective coatings was characterized. The comparison of experimental conditions is shown in Table 3.

[0153] Table 3 Comparison of experimental conditions for different dosage ratios of polymer monomers

[0154]

[0155]

[0156] The graphene-based surface protective coatings prepared based on different dosage ratios of polymer monomers were coated on different substrates to form protective films. The substrates used were glass, steel and sandstone. The results are shown in Table 4.

[0157] Table 4 Effect of different dosage ratios of polymer monomers on product properties (on glass surface)

[0158]

[0159] From the results in Table 4, it can be seen that with the increase in the amount of MPS, the contact angle of the protective film on the glass surface is significantly increased. This is mainly because the higher the MPS content, the more Si-O-Si bonds will be formed after the excessive silane functional groups are hydrolyzed, the surface roughness will increase, and the hydrophobicity will be improved. However, the higher the MPS content, the more silane functional groups will be hydrolyzed, which will cause the film to turn white, and the excessive Si-O-Si bonds and excessive cross-linking stress will easily cause the film to crack.

[0160] Test 5: Effect of different polymer monomers.

[0161] In order to explore the effect of different polymer monomers on product performance, different graphene-based surface protective coatings were prepared using different polymer monomers, and the performance of different graphene-based surface protective coatings was characterized. The comparison of experimental conditions is shown in Table 5.

[0162] Table 5 Comparison of experimental conditions of different polymer monomers

[0163]

[0164] Note: 100:0 means no MPS added; 0:100 means no GMA added.

[0165] The graphene-based surface protective coatings prepared based on different polymer monomers were coated on different substrates to form protective films. The substrates used were glass, steel and sandstone. The results are shown in Table 6.

[0166] Table 6 Effect of different polymer monomers on product properties (on glass surface)

[0167]

[0168] From the results in Table 6, we can see that compared with PMPS / GO2, the films formed by PGMA / GO2 and PGMA-co-PMPS / GO2 on the glass surface have better uniformity and continuity, which is mainly because the PGMA component in the polymer can greatly improve the continuity and compatibility of the film layer. However, the presence of PGMA will reduce the hydrophobicity of the film surface.

[0169] Test 5: Effect of different dosage ratios of copolymer and amino graphene.

[0170] In order to explore the effect of different dosage ratios of copolymer and amino graphene on the product performance, different graphene-based surface protective coatings were prepared by using different dosage ratios of copolymer and amino graphene, and the performance of different graphene-based surface protective coatings was characterized. The comparison of experimental conditions is shown in Table 7.

[0171] Table 7 Comparison of experimental conditions of different polymer monomers

[0172]

[0173] Note: 100:0 in Table 7 means no amino-modified graphene was added.

[0174] The graphene-based surface protective coatings prepared based on different dosage ratios of copolymer and amino graphene were coated on different substrates to form protective films. The substrates used were glass, steel and sandstone. The results are shown in Table 8.

[0175] Table 8 Effect of different dosage ratios of copolymer and amino graphene on product properties (on glass surface)

[0176]

[0177] From the results in Table 8, it can be seen that with the introduction and increase of the content of modified graphene, the contact angle of the film on the surface of the glass sheet gradually increases, and the surface hydrophobicity is improved. This is mainly due to the fact that the introduction of graphene can greatly improve the surface roughness of the film, thereby increasing the surface contact angle. However, the introduction and content of graphene have little effect on the bonding performance.

[0178] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a graphene-based surface protective coating, characterized in that: The following steps are involved: Under the action of a catalyst, a graphene oxide dispersion is mixed with an aminosilane coupling agent to modify the surface of the graphene oxide using the aminosilane coupling agent to obtain amino-modified graphene; Under nitrogen protection, glycidyl methacrylate and 3-(methacryloyloxy)propyltrimethoxysilane were polymerized with an initiator to prepare PGMA-co-PMPS polymer. The aminated graphene is prepared into an aminated graphene dispersion, and the aminated graphene dispersion is stirred and reacted with a PGMA-co-PMPS polymer to form a multi-crosslinking system with COC bonds and Si-O-Si bonds, thereby preparing a graphene-based surface protective coating.

2. The method for preparing the graphene-based surface protective coating according to claim 1, characterized in that: The aminosilane coupling agent is aminopropyltrimethoxysilane or [3-(6-aminohexylamino)propyl]; and the catalyst is 4-dimethylaminopyridine.

3. The method for preparing the graphene-based surface protective coating according to claim 2, characterized in that: The mass ratio of catalyst to graphene oxide is 1:1 to 5; The mass ratio of the catalyst to the aminosilane coupling agent is 1:1-3.

4. The method for preparing the graphene-based surface protective coating according to claim 1, characterized in that: The initiator is azobisisobutyronitrile; The molar ratio of glycidyl methacrylate, 3-(methacryloyloxy)propyltrimethoxysilane and the initiator is 100:50 to 200:

1.

5. The method for preparing the graphene-based surface protective coating according to claim 1, characterized in that: The molar ratio of PGMA-co-PMPS polymer to amino graphene is 2:0.01-0.

05.

6. The method for preparing the graphene-based surface protective coating according to claim 1, characterized in that: The solvent of the polymerization reaction is butanone, toluene or N,N-dimethylformamide; the temperature of the polymerization reaction is 60°C to 80°C.

7. The method for preparing the graphene-based surface protective coating according to claim 1, characterized in that: The temperature for stirring the reaction between the amination graphene dispersion and the PGMA-co-PMPS polymer is 40°C to 50°C.

8. The method for preparing the graphene-based surface protective coating according to claim 1, characterized in that: The graphene oxide dispersion is obtained by dispersing graphene oxide in a dispersion solvent; The aminated graphene dispersion is obtained by dispersing the aminated graphene in a dispersion solvent; The dispersing solvent is at least one of tetrahydrofuran, N,N-dimethylformamide and dimethyl sulfoxide.

9. The method for preparing the graphene-based surface protective coating according to claim 1, characterized in that: The concentration of the graphene oxide dispersion is 0.1 mg / mL to 1 mg / mL; the concentration of the amination graphene dispersion is 0.2 mg / mL to 1 mg / mL.

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