CN106832783B - Toughening modification method of epoxy resin - Google Patents
Toughening modification method of epoxy resin Download PDFInfo
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- CN106832783B CN106832783B CN201710095628.8A CN201710095628A CN106832783B CN 106832783 B CN106832783 B CN 106832783B CN 201710095628 A CN201710095628 A CN 201710095628A CN 106832783 B CN106832783 B CN 106832783B
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Abstract
The invention provides a method for toughening and modifying epoxy resin, which comprises the following steps: grafting a polymer long chain on a hydroxyl position of graphene by using Atom Transfer Radical Polymerization (ATRP) to prepare functionalized graphene; and uniformly mixing the functionalized graphene and the epoxy resin to obtain the modified epoxy resin. The application of the invention can effectively improve the impact toughness of the epoxy resin, and simultaneously can not generate the problems of influencing the inherent characteristics of the epoxy resin, such as two-phase structure, uneven dispersion and the like.
Description
Technical Field
The application relates to the technical field of organic polymer compound preparation, in particular to a method for toughening and modifying epoxy resin.
Background
Epoxy resins have been widely used in the fields of coatings, composites, high performance adhesives, electrical insulation materials, aviation, aerospace, etc. because of their excellent physical and mechanical properties, thermal stability, superior electrical properties, and outstanding chemical resistance. However, epoxy resins contain a large number of epoxy groups, and the cured products have a high crosslinking density, which causes problems such as brittleness and poor impact resistance. In recent years, toughening and modification of epoxy resins have been the hot topic of domestic and foreign research.
The modification of the traditional epoxy resin is mainly physical modification, and the main idea is to blend a modifier and the epoxy resin, and the two-phase structure is formed after blending. The traditional approaches for modifying epoxy resins are mainly as follows: rubber elastomer modification, thermoplastic resin modification, rigid particle modification, and the like. The modifier generally has better toughness and higher modulus. The modified epoxy resin is indeed improved in impact toughness, but the disadvantages and problems caused by the modified epoxy resin are also obvious: the glass transition temperature elastic modulus, viscosity and the like of the modified epoxy resin are influenced to a certain degree, and the application and field operability of the epoxy resin are limited.
Disclosure of Invention
In view of the above, the present invention provides a method for toughening and modifying an epoxy resin, so that the impact toughness of the epoxy resin can be effectively improved, and meanwhile, the problems that the intrinsic properties of the epoxy resin are affected by a two-phase structure, uneven dispersion, and the like do not occur.
The technical scheme of the invention is realized as follows:
a method of toughening modification of an epoxy resin, the method comprising:
grafting a polymer long chain on a hydroxyl position of graphene by using Atom Transfer Radical Polymerization (ATRP) to prepare functionalized graphene;
and uniformly mixing the functionalized graphene and the epoxy resin to obtain the modified epoxy resin.
Preferably, the step of grafting a polymer long chain on a hydroxyl position of graphene by using ATRP to prepare functionalized graphene comprises:
introducing a side group with ATRP active halogen atoms into a hydroxyl position of graphene oxide to synthesize a graphene oxide macromolecular initiator;
ATRP is adopted to initiate monomer polymerization, and polymer long chains are grafted to graphene oxide to prepare the functionalized graphene.
Preferably, the step of introducing a side group with an ATRP active halogen atom at a hydroxyl position of graphene oxide comprises:
adding the graphene oxide, the halogenated nucleophilic reagent and the catalyst into a flask with stirring according to the molar ratio of the hydroxyl functional group of the graphene oxide to the halogenated nucleophilic reagent of 0.6-2.1: 1 or 0.5-2.0: 1 and the weight ratio of the hydroxyl functional group of the graphene oxide to the catalyst of 5.0-20.0: 1, and placing the flask in an oil bath for reaction under the protection of inert gas to obtain the graphene oxide macromolecular initiator.
Preferably, the halogenated nucleophile is a halocarboxylic nucleophile having an active substituent on the α -carbon or a halocarboxylic nucleophile having a weak R-X bond on the α -carbon;
wherein R is N, S or O, and X is Cl or Br.
Preferably, the reactive substituent is aryl, carbonyl or allyl.
Preferably, the catalyst is a basic compound having a catalytic effect on a reaction between a hydroxyl group of graphene oxide and a carboxylic acid nucleophile.
Preferably, the catalyst is NaOH, KOH or tetramethylammonium salt.
Preferably, the state of the graphene oxide is a solution state.
Preferably, the graphene oxide is graphene oxide with an oxidation degree of 1% -60%.
Preferably, the graphene oxide solution is prepared by fully dissolving graphene oxide powder and tetrahydrofuran or toluene as a first solvent.
Preferably, the method further comprises:
before the addition of the halogenated nucleophile and the catalyst, Na is used2CO3And adjusting the pH value of the graphene oxide solution to 7-10.
Preferably, the halogenated nucleophile is at least one of 2-bromoisobutyric acid, 2-bromopropionic acid, p-bromomethylbenzoic acid, and p-carboxybenzenesulfonyl chloride.
Preferably, the method further comprises:
cleaning the prepared functionalized graphene with one or more of absolute ethyl alcohol, acetone or water, and repeating for 4-8 times; and vacuum drying at 40-80 deg.C.
Preferably, the initiating a polymerization reaction of the monomer by ATRP to graft the polymer long chain onto the graphene oxide to obtain the functionalized graphene comprises:
adding the graphene oxide macroinitiator, the ATRP catalyst and the ligand into a flask with a stirrer according to the molar ratio of halogen atoms in the graphene oxide macroinitiator to the ATRP catalyst and the ligand of 1-1.5: 1-3, tightly sealing the reaction flask, vacuumizing, filling inert gas, and repeating for 2-4 times; then, adding a second solvent and a monomer by using an injector, placing the mixture in an oil bath for reaction, and carrying out ATRP reaction on the system in a solution state; after the reaction is finished, precipitating, washing and vacuum drying the polymerization product to obtain the functionalized graphene.
Preferably, the ATRP catalyst is CuX or FeX2、CuX2Or FeX3；
Wherein X is Cl or Br, and the type of X is consistent with that of a halogen atom in the halogenated nucleophile.
Preferably, the ligand is one or more N-or P-containing ligands, which are sigma-or pi-bonded to the transition metal.
Preferably, the ligand is one or more of 2,2 '-bipyridine (bpy), 4' -bis (penta-nonyl) -2,2 '-bipyridine (dNbpy), 4' -di-N-butyl-2, 2 '-bipyridine (dTbpy), N' -Pentamethyldiethylenetriamine (PMDETA), Triphenylphosphine (TPP) or Tributylphosphine (TBUP).
Preferably, the monomer is methyl methacrylate, methacrylic acid or glycidyl methacrylate.
Preferably, the second solvent is an organic solvent capable of dissolving the graphene oxide macroinitiator.
Preferably, the second solvent is toluene, tetrahydrofuran or acetone.
Preferably, the step of uniformly mixing the functionalized graphene and the epoxy resin to obtain the modified epoxy resin comprises:
dissolving functionalized graphene in one or more of tetrahydrofuran, acetone or toluene to prepare a solution; under the ice bath condition, completely dispersing the mixture by ultrasonic in ultrasonic waves; adding epoxy resin into the solution, and completely dispersing the functionalized graphene in the epoxy resin by mechanical stirring; and then placing the mixture in a vacuum drying oven for vacuum drying to obtain the modified epoxy resin.
Preferably, the state of the functionalized graphene is a solution state.
Preferably, the functionalized graphene is obtained by grafting methyl methacrylate, methacrylic acid or glycidyl methacrylate on the surface of graphene oxide.
According to the technical scheme, the reaction activity between the hydroxyl group and the nucleophilic reagent is utilized, and the side group with the ATRP active halogen atom is introduced to the hydroxyl position of the graphene oxide to synthesize the graphene oxide macromolecular initiator; then initiating a monomer to carry out polymerization reaction by adopting ATRP (atom transfer radical polymerization), and successfully grafting a polymer long chain onto graphene oxide to prepare functionalized graphene; and finally, doping the epoxy resin into the functionalized graphene solution, and uniformly mixing to prepare the modified epoxy resin. Therefore, the graphene-toughened epoxy resin provided by the invention can effectively improve the impact toughness of the epoxy resin, and meanwhile, as the long polymer chain grafted by the graphene oxide can generate a chemical bonding effect with an epoxy group, the problems of two-phase structure and uneven dispersion can not occur, the inherent characteristics of the epoxy resin are not influenced, and the defects caused by the traditional modification methods such as physical modification and the like are avoided. The invention changes the rigid chain segment of the epoxy resin into the flexible chain segment by a molecular design means, thereby fundamentally improving the toughness of the epoxy resin. For example, the impact toughness of the epoxy resin modified by the method of the invention is improved by 42-86%.
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Fig. 1 is a flowchart of a method for toughening and modifying an epoxy resin in an embodiment of the present invention.
Fig. 2 is a synthesis route diagram of synthesis of graphene oxide macromolecules and grafting of polymer long chains on graphene oxide hydroxyl positions by an ATRP method in an embodiment of the present invention.
Detailed Description
In order to make the technical scheme and advantages of the invention more apparent, the invention is further described in detail with reference to the accompanying drawings and specific embodiments.
In an embodiment of the present invention, a method for toughening modification of an epoxy resin is provided.
Fig. 1 is a flowchart of a method for toughening and modifying an epoxy resin in an embodiment of the present invention, and fig. 2 is a synthesis route diagram of a graphene oxide macro molecule and a polymer long chain grafted on a graphene oxide hydroxyl position by an ATRP method in an embodiment of the present invention. As shown in fig. 1 in combination with fig. 2, the method for toughening and modifying an epoxy resin in the embodiment of the present invention includes the following steps:
in the technical solution of the present invention, the step 11 can be implemented in various ways.
For example, in an embodiment of the present invention, the step 11 may specifically be:
step 111, introducing a side group with ATRP active halogen atoms into a hydroxyl position of graphene oxide to synthesize a graphene oxide macroinitiator;
in the step, a side group with ATRP active halogen atoms can be introduced to the hydroxyl position of the graphene oxide by utilizing the reaction activity between the hydroxyl group and the nucleophilic reagent to synthesize the graphene oxide macroinitiator.
And 112, initiating a monomer to perform a polymerization reaction by adopting ATRP, and grafting a polymer long chain onto the graphene oxide to prepare the functionalized graphene.
Through the steps 111 and 112, the functionalized graphene can be prepared.
And 12, uniformly mixing the functionalized graphene with the epoxy resin to obtain the modified epoxy resin.
The two-dimensional nano-structure graphene has excellent mechanical property, thermal stability, excellent electrical property and outstanding magnetic property, so that the two-dimensional nano-structure graphene can be used for enhancing high polymer materials.
In order to improve the performance of the graphene/polymer composite material to the maximum extent, two key factors need to be satisfied: 1) the graphene is uniformly distributed in the polymer matrix; 2) and (3) effectively transferring external load between the graphene-polymer matrix interface.
To solve these problems, graphene and its derivatives may be functionally modified. Among them, the most effective and common is the covalently modified graphene. The graphene oxide prepared by the redox method contains active functional groups such as hydroxyl, carboxyl, epoxy group and the like on the surface of a sheet layer, and the existence of the functional groups provides good conditions for realizing graphene functionalization through covalent modification.
After the research, the inventors found that graphene oxide containing functional groups such as carboxyl, hydroxyl and epoxy groups on the surface can be used to react with organic halides to form an initiator. Then, a transition metal complex can be used as a halogen atom carrier, and is matched with an initiator to use an initiation monomer to react, so that the polymer long chain is successfully grafted on the surface of the graphene oxide. Because the grafted graphene oxide shows good dispersibility, the functionalized graphene can be uniformly dispersed in a solvent, and epoxy resin is added and uniformly mixed, so that the modification of the epoxy resin is realized.
In the technical solution of the present invention, the step 111 can be implemented in various ways.
For example, in an embodiment of the present invention, the step 111 can be implemented by the following specific implementation manners:
adding the graphene oxide, the halogenated nucleophile and the catalyst into a flask with stirring according to the molar ratio of the hydroxyl functional group of the graphene oxide to the halogenated nucleophile of 0.6-2.1: 1 (or 0.5-2.0: 1) and the weight ratio of the hydroxyl functional group of the graphene oxide to the catalyst of 5.0-20.0: 1, and placing the mixture in an oil bath to react under the protection of inert gas (for example, reacting in the oil bath at 25-90 ℃ for 0.25-2.5 h) to obtain the graphene oxide macroinitiator (for example, the graphene oxide macroinitiator which contains active halogen atoms on the surface and has the halogen atom supporting capacity of 1-60%).
Further, preferably, in embodiments of the present invention, the halogenated nucleophile is a halocarboxylic nucleophile having an active substituent on the α -carbon or a halocarboxylic nucleophile having a weak R-X bond on the α -carbon; wherein R can be N, S or O, and X can be Cl or Br.
Preferably, in the embodiment of the present invention, the reactive substituent may be an aryl group, a carbonyl group or an allyl group.
Preferably, in an embodiment of the present invention, the catalyst is a basic compound having a catalytic effect on a reaction between a hydroxyl group of graphene oxide and a carboxylic acid nucleophile.
For example, in a preferred embodiment of the invention, the catalyst may be NaOH, KOH or tetramethylammonium salt.
Preferably, in an embodiment of the present invention, the state of the graphene oxide is a solution state.
Preferably, in an embodiment of the present invention, the graphene oxide may be a graphene oxide with an oxidation degree of 1% to 60%.
Preferably, in embodiments of the invention, Na is used prior to the addition of other reactants (e.g., halogenated nucleophiles and catalyst)2CO3And adjusting the pH value of the graphene oxide solution to 7-10.
Preferably, in an embodiment of the present invention, the graphene oxide solution may be prepared by sufficiently dissolving graphene oxide powder with tetrahydrofuran or toluene as the first solvent.
Preferably, in a specific embodiment of the present invention, the halogenated nucleophile is at least one of 2-bromoisobutyric acid, 2-bromopropionic acid, p-bromomethylbenzoic acid, and p-carboxybenzenesulfonyl chloride.
Preferably, in an embodiment of the present invention, the method further includes:
cleaning the prepared functionalized graphene with one or more of absolute ethyl alcohol, acetone or water, and repeating for 4-8 times; and vacuum drying at 40-80 deg.C.
In the solution of the present invention, the step 112 can also be implemented in various ways.
For example, in an embodiment of the present invention, the step 112 can be implemented by the following specific implementation manners:
adding the graphene oxide macroinitiator, the ATRP catalyst and the ligand into a flask with a stirrer according to the molar ratio of halogen atoms in the graphene oxide macroinitiator to the ATRP catalyst and the ligand of 1-1.5: 1-3, tightly sealing the reaction flask, vacuumizing, filling inert gas, and repeating for 2-4 times; then, adding a second solvent and a monomer by using an injector, placing the mixture in an oil bath (for example, an oil bath at 25-110 ℃) for reaction, and carrying out an ATRP reaction in a solution state; after the reaction is finished, precipitating, washing and vacuum drying the polymerization product to obtain the functionalized graphene.
In addition, preferably, in the embodiment of the present invention, the ATRP catalyst can be CuX or FeX2、CuX2Or FeX3(ii) a Wherein X can be Cl or Br, and the type of X is consistent with the type of halogen atom in the halogenated nucleophile.
Preferably, in embodiments of the present invention, the ligand may be one or more N-or P-containing ligands, which are sigma-or pi-bonded to the transition metal (e.g., Fe or Cu).
For example, in a preferred embodiment of the invention, the ligand may be a mixture of one or more of 2,2 '-bipyridine (bpy), 4' -di (pentanonyl) -2,2 '-bipyridine (dNbpy), 4' -di-N-butyl-2, 2 '-bipyridine (dTbpy), N' -Pentamethyldiethylenetriamine (PMDETA), Triphenylphosphine (TPP) or Tributylphosphine (TBUP).
Preferably, in the embodiment of the present invention, the monomer may be Methyl Methacrylate (MMA), Methacrylic Acid (MA) or Glycidyl Methacrylate (GMA).
Preferably, in an embodiment of the present invention, the second solvent is an organic solvent capable of dissolving the graphene oxide macroinitiator.
For example, in a preferred embodiment of the present invention, the second solvent may be toluene, tetrahydrofuran or acetone.
In the technical solution of the present invention, the step 12 can be implemented in various ways.
For example, in a preferred embodiment of the present invention, the step 12 can be implemented by the following specific implementation manners:
dissolving functionalized graphene in one or more of tetrahydrofuran, acetone or toluene to prepare a solution (for example, a solution with a concentration of 0.025-0.25 mg/mL); under the ice bath condition, fully dispersing the mixture by ultrasonic in ultrasonic waves (for example, ultrasonic in 20-65 kHZ ultrasonic waves for 2-5 hours); adding epoxy resin into the solution, and completely dispersing the functionalized graphene in the epoxy resin by mechanical stirring (for example, mechanical stirring for 1-5 hours); and then the mixture is placed in a vacuum drying oven for vacuum drying (for example, vacuum drying is carried out for 2-6 hours at the temperature of 45-75 ℃) to obtain the modified epoxy resin.
Preferably, in an embodiment of the present invention, the state of the functionalized graphene is a solution state.
Preferably, in an embodiment of the present invention, the functionalized graphene may be obtained by grafting Methyl Methacrylate (MMA), Methacrylic Acid (MA) or Glycidyl Methacrylate (GMA) on the surface of graphene oxide.
The technical solution of the present invention will be further described in detail in the following three embodiments.
The first embodiment,
In the first embodiment, the following specific implementation steps can be used to obtain the modified epoxy resin:
(1) preparing a graphene oxide macroinitiator;
specifically, 25g of graphene oxide can be sufficiently dissolved in 150mL of dichloromethane, the obtained solution, 1.734g of 2-bromopropionic acid and 0.0835g of tetramethylammonium salt of 2-bromopropionic acid are added into a flask with a stirrer, the flask is placed in an oil bath at 56 ℃ under the protection of nitrogen for reaction for 28 hours (h), and after the reaction is finished, an organic phase is separated by hydrochloric acid/water, and a solvent is evaporated; then precipitating in acetone, filtering, and drying in vacuum to constant weight to obtain the graphene oxide macromolecular initiator with active halogen atoms on the surface.
(2) Preparing functionalized graphene:
specifically, 1g of graphene oxide initiator together with 0.341g of CuBr, 0.325g N, N, N' -Pentamethyldiethylenetriamine (PMDETA) was charged into a flask equipped with stirring, the reaction flask was sealed, evacuated and charged with nitrogen gas, and the reaction was repeated 4 times; then, 25mL of toluene and 10g of Glycidyl Methacrylate (GMA) were introduced via syringe, and placed in an oil bath at 85 ℃ for reaction for 24 hours (h); after the reaction is finished, the polymerization product is subjected to acetone precipitation, distilled water washing and vacuum drying at 60 ℃ to obtain the functionalized graphene.
(3) Preparation of modified epoxy resin:
specifically, 0.3g of functionalized graphene can be dissolved in 240mL of toluene to prepare a solution with a concentration of 0.125 mg/mL; under the ice bath condition, performing ultrasonic treatment in 40kHz ultrasonic waves for 3 hours to completely disperse the functionalized graphene in the solution; pouring 300g of epoxy resin, and mechanically stirring for 2 hours to completely disperse the functionalized graphene in the epoxy resin; placing the mixture in a vacuum drying oven at 60 ℃ to remove the solvent, and cooling to room temperature; adding a curing agent, pouring into a mould for curing, and testing the mechanical property of the modified epoxy resin. When the content of the functionalized graphene is 0.1 wt.%, the tensile toughness is increased by 253.4%, and the impact toughness is increased by 120.5%; when the content of the functionalized graphene is 0.2 wt.%, the tensile toughness is increased by 168.3%, and the impact toughness is increased by 97.5%.
Example II,
In the second embodiment, the following specific implementation steps can be used to obtain the modified epoxy resin:
(1) preparing a graphene oxide macroinitiator;
specifically, the graphene oxide powder may be first dissolved in a mixed solution of acetone and tetrahydrofuran. Adding 5g of graphene oxide solution, 0.683g of p-bromomethylbenzoic acid and 0.0183g of NaOH into a flask with stirring, placing the flask in an oil bath at 55 ℃ for reaction for 24 hours under the protection of argon, repeatedly washing the flask by using distilled water and methanol after the reaction is finished, filtering the flask, and drying the flask in vacuum at 45 ℃ to constant weight to obtain the graphene oxide macroinitiator.
(2) Preparing functionalized graphene:
specifically, 1g of graphene oxide can be initially charged with 0.343g of CuCl, 0.404g N, N, N' -Pentamethyldiethylenetriamine (PMDETA) in a stirred flask, and the reaction flask tightly sealed; vacuumizing and filling argon, and repeating for 4 times; then, 35mL of tetrahydrofuran and 10g of Methyl Methacrylate (MMA) were introduced by a syringe, and placed in an oil bath at 90 ℃ for reaction for 24 hours; after the reaction is finished, the polymerization product is subjected to methanol precipitation, distilled water washing and vacuum drying at 50 ℃ to constant weight, so that the functionalized graphene is obtained.
(3) Preparation of modified epoxy resin:
specifically, 0.3g of functionalized graphene may be first dissolved in 500mL of toluene to prepare a solution with a concentration of 0.6 mg/mL. Under the ice bath condition, performing ultrasonic treatment in 40kHz ultrasonic waves for 4 hours to completely disperse the functionalized graphene in the solution; pouring 150g of epoxy resin, and mechanically stirring for 3 hours to completely disperse the functionalized graphene in the epoxy resin; the mixture was placed in a vacuum oven at 45 ℃ to remove the solvent and cooled to room temperature. Adding a curing agent, pouring into a mould for curing, and testing the mechanical property of the modified epoxy resin. When the content of the functionalized graphene is 0.1 wt.%, the tensile toughness is increased by 267.5%, and the impact toughness is increased by 102.7%; when the content of the functionalized graphene is 0.2 wt.%, the tensile toughness is increased by 173.9%, and the impact toughness is increased by 81.9%.
Example III,
In the third embodiment, the following specific implementation steps can be used to obtain the modified epoxy resin:
(1) preparing a graphene oxide macroinitiator;
specifically, 5g of graphene oxide was sufficiently dissolved in 35mL of dichloromethane, and the obtained solution was added to a flask equipped with a stirrer together with 0.609g of 2-bromoisobutyric acid and 0.0232g of tetramethylammonium salt of 2-bromoisobutyric acid, and the obtained mixture was placed in an oil bath at 75 ℃ for reaction for 24 hours under the protection of nitrogen; and after the reaction is finished, repeatedly washing the reaction product by distilled water and methanol, filtering the reaction product, and drying the reaction product in vacuum at 65 ℃ to constant weight to obtain the graphene oxide macromolecular initiator.
(2) Preparing functionalized graphene:
specifically, 0.5g of graphene oxide initiator, 0.176g of CuBr and 0.124g of 2, 2' -bipyridine (bpy) are added into a flask with stirring, the reaction flask is sealed, vacuum is pumped, nitrogen is filled, and the steps are repeated for 4 times; then, 35mL of toluene and 12g of Methyl Methacrylate (MMA) were introduced by a syringe, and placed in an oil bath at 50 ℃ to react for 24 hours; after the reaction is finished, the polymerization product is subjected to acetone precipitation, distilled water washing and vacuum drying at 60 ℃ to obtain the functionalized graphene.
(3) Preparation of modified epoxy resin:
specifically, 0.4g of functionalized graphene may be dissolved in 600mL of toluene to prepare a solution with a concentration of 0.667 mg/mL. Under the ice bath condition, performing ultrasonic treatment in 40kHz ultrasonic waves for 4 hours to completely disperse the functionalized graphene in the solution; pouring 445g of epoxy resin, and mechanically stirring for 3.5h to completely disperse the functionalized graphene in the epoxy resin; placing the mixture in a vacuum drying oven at 55 ℃ to remove the solvent, and cooling to room temperature; adding a curing agent, pouring into a mould for curing, and testing the mechanical property of the modified epoxy resin. When the content of the functionalized graphene is 0.1 wt.%, the tensile toughness is increased by 189.2%, and the impact toughness is increased by 73.8%; when the content of the functionalized graphene is 0.2 wt.%, the tensile toughness is increased by up to 158.7%, and the impact toughness is increased by up to 72.1%.
In summary, in the technical scheme of the present invention, because the reactivity between the hydroxyl group and the nucleophile is utilized, the side group with the ATRP active halogen atom is introduced to the hydroxyl position of the graphene oxide to synthesize the graphene oxide macroinitiator; then initiating a monomer to carry out polymerization reaction by adopting ATRP (atom transfer radical polymerization), and successfully grafting a polymer long chain onto graphene oxide to prepare functionalized graphene; and finally, doping the epoxy resin into the functionalized graphene solution, and uniformly mixing to prepare the modified epoxy resin. Therefore, the graphene-toughened epoxy resin provided by the invention can effectively improve the impact toughness of the epoxy resin, and meanwhile, as the long polymer chain grafted by the graphene oxide can generate a chemical bonding effect with an epoxy group, the problems of two-phase structure and uneven dispersion can not occur, the inherent characteristics of the epoxy resin are not influenced, and the defects caused by the traditional modification methods such as physical modification and the like are avoided. The invention changes the rigid chain segment of the epoxy resin into the flexible chain segment by a molecular design means, thereby fundamentally improving the toughness of the epoxy resin. For example, the impact toughness of the epoxy resin modified by the method of the invention is improved by 42-86%.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (16)
1. A method for toughening and modifying epoxy resin is characterized by comprising the following steps:
adding graphene oxide, a halogenated nucleophilic reagent and a catalyst into a flask with stirring according to the molar ratio of the hydroxyl functional group of the graphene oxide to the halogenated nucleophilic reagent of 0.6-2.1: 1 or 0.5-2.0: 1 and the weight ratio of the hydroxyl functional group of the graphene oxide to the catalyst of 5.0-20.0: 1, and placing the mixture in an oil bath for reaction under the protection of inert gas to obtain a graphene oxide macromolecular initiator;
the halogenated nucleophile is a halogenated carboxylic acid nucleophile having an active substituent on the alpha-carbon or a halogenated carboxylic acid nucleophile having a weak R-X bond on the alpha-carbon;
wherein the active substituent is aryl or allyl, R is N, S or O, and X is Cl or Br;
the catalyst is NaOH, KOH or tetramethyl ammonium salt;
adding the graphene oxide macroinitiator, the ATRP catalyst and the ligand into a flask with a stirrer according to the molar ratio of halogen atoms in the graphene oxide macroinitiator to the ATRP catalyst and the ligand of 1-1.5: 1-3, tightly sealing the reaction flask, vacuumizing, filling inert gas, and repeating for 2-4 times; then, adding a second solvent and a monomer by using an injector, placing the mixture in an oil bath for reaction, and carrying out ATRP reaction on the system in a solution state; after the reaction is finished, precipitating, washing and vacuum-drying the polymerization product to obtain functionalized graphene;
and uniformly mixing the functionalized graphene and the epoxy resin to obtain the modified epoxy resin.
2. The method of claim 1, wherein:
the state of the graphene oxide is a solution state.
3. The method of claim 1, wherein:
the graphene oxide is graphene oxide with the oxidation degree of 1% -60%.
4. A method according to claim 2 or 3, characterized in that:
the graphene oxide solution is prepared by fully dissolving graphene oxide powder and tetrahydrofuran or toluene serving as a first solvent.
5. The method of claim 1, further comprising:
before the addition of the halogenated nucleophile and the catalyst, Na is used2CO3And adjusting the pH value of the graphene oxide solution to 7-10.
6. The method of claim 1, wherein:
the halogenated nucleophile is at least one of 2-bromoisobutyric acid, 2-bromopropionic acid, p-bromomethylbenzoic acid, and p-carboxybenzenesulfonyl chloride.
7. The method of claim 1, further comprising:
cleaning the prepared functionalized graphene with one or more of absolute ethyl alcohol, acetone or water, and repeating for 4-8 times; and vacuum drying at 40-80 deg.C.
8. The method of claim 1, wherein:
the ATRP catalyst is CuX or FeX2、CuX2Or FeX3；
Wherein X is Cl or Br, and the type of X is consistent with that of a halogen atom in the halogenated nucleophile.
9. The method of claim 8, wherein:
the ligand is one or more N-or P-containing ligands, which are coordinated to the transition metal by sigma-bonds or pi-bonds.
10. The method of claim 8, wherein:
the ligand is one or more of 2,2 '-bipyridine, 4' -di (penta-nonyl) -2,2 '-bipyridine, 4' -di-N-butyl-2, 2 '-bipyridine, N, N, N' -pentamethyldiethylenetriamine, triphenylphosphine or tributylphosphine.
11. The method of claim 1, wherein:
the monomer is methyl methacrylate, methacrylic acid or glycidyl methacrylate.
12. The method of claim 1, wherein:
the second solvent is an organic solvent capable of dissolving the graphene oxide macroinitiator.
13. The method of claim 1, wherein:
the second solvent is toluene, tetrahydrofuran or acetone.
14. The method according to claim 1, wherein the step of uniformly mixing the functionalized graphene with the epoxy resin to obtain the modified epoxy resin comprises:
dissolving functionalized graphene in one or more of tetrahydrofuran, acetone or toluene to prepare a solution; under the ice bath condition, completely dispersing the mixture by ultrasonic in ultrasonic waves; adding epoxy resin into the solution, and completely dispersing the functionalized graphene in the epoxy resin by mechanical stirring; and then placing the mixture in a vacuum drying oven for vacuum drying to obtain the modified epoxy resin.
15. The method of claim 14, wherein:
the state of the functionalized graphene is a solution state.
16. The method of claim 1, wherein:
the functionalized graphene is prepared by grafting methyl methacrylate, methacrylic acid or glycidyl methacrylate on the surface of graphene oxide.
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