CN104624132B - Epoxy resin self-repairing microcapsule and preparation method thereof - Google Patents

Abstract

The invention provides an epoxy resin self-repairing microcapsule and a preparation method thereof. The method comprises: mixing an aqueous phase comprising nano-inorganic particles and water with an oil phase comprising epoxy resin, monoolefinic monomer, multiolefinic crosslinking agent and initiator to form a stable oil-in-water emulsion; and heating the emulsion to carry out emulsion polymerization to form the self-healing epoxy resin microcapsules. According to the method of the present invention, inorganic nanoparticles are used as emulsifiers and epoxy resin self-repairing microcapsules are prepared by emulsion polymerization; compared with the method using molecular emulsifiers, the method does not require subsequent emulsifier removal processes, so the method The process of the method is simple and has no pollution to the environment, and the prepared epoxy resin self-repairing microcapsules have excellent stability and airtightness and a high covering rate.

Description

Epoxy resin self-healing microcapsules and preparation method thereof

technical field

The invention relates to the technical field of composite materials with self-healing function, more specifically, the invention relates to epoxy resin self-healing microcapsules synthesized by emulsion polymerization and a preparation method thereof.

Background technique

The concept of self-healing composite materials was first proposed by the US military in the mid-1980s. The earliest self-healing system was a simple simulation of the animal vascular network. Hollow glass fibers were embedded in concrete, and acetal polymer solution was injected into the fibers as an adhesive. Due to the difficulties in the manufacturing method of the hollow fiber network system, this technology is difficult to realize automatic preparation, so it is difficult to enter into industrial application.

At present, the most researched self-healing microcapsules at home and abroad are microcapsule systems synthesized by coating DCPD (dicyclopentadiene) monomer with polyurea formaldehyde. J.S.Moore and Scottos N.R. of the University of Illinois in the United States (see literature 1-3) have been working on the research of self-repair technology since the mid-1990s. This technology uses metal ruthenium complex Grubbs as a catalyst to cause micron-sized microcapsules (capsule wall material is urea-formaldehyde resin) to rupture in the defect area of the epoxy matrix to release DCPD, which undergoes active ring-opening polymerization to achieve self-healing effect . However, the above-mentioned self-healing system with DCPD microcapsules as the key component has the following disadvantages: the price of Grubbs catalyst is high; it is unstable and easy to decompose when it is higher than 120 ° C, and it is susceptible to epoxy resin curing agent amines during the synthesis process. The influence of DCPD weakens the catalytic efficiency; although DCPD microcapsules have achieved good results in the repair of polymer matrix composites formed at room temperature, there are two isomers of α and β in DCPD (condensation points are 19.5°C and 33°C, respectively ℃), so DCPD is not suitable for self-healing of composite materials used at low temperatures; the mechanical properties of DCPD polymerization reaction products are low; in the traditional process of preparing urea-formaldehyde resin wall materials, the main raw material is formaldehyde, and the teratogenicity of the latter Sexuality and toxicity have been confirmed, so it is very necessary to prepare low-formaldehyde or formaldehyde-free phase-change microcapsules. In addition, Professor Hirozo Mihashi of Tohoku University in Japan (document 4) mixed hollow capsules containing adhesives into concrete materials. Once the concrete cracked under the action of external force, part of the capsules ruptured, and the adhesive liquid flowed into the cracks. The bonding fluid can re-heal concrete cracks. However, the size of the hollow capsule is large (2-35mm) and uneven, which is not conducive to the combination of the capsule and the matrix, which has a great impact on the mechanical strength of the matrix.

Reference materials:

Non-patent literature 1: Jones A.S.Rule J.D. and Moore J.S. et al., CatalystMorphology and Dissolution Kinetics of Self-Healing Polymers, Chem.Mater.2006; 18:1312-1317

Non-patent literature 2: Keller M.W., White S.R. and Sottos N.R., etc., A Self-healingPoly(Dimethyl Siloxane) Elastomer, Adv.Funct.Mater., 2007; 17:2399-2404

Non-patent literature 3: Rule J.D., Brown E.N. and Sottos N.R., Wax-protected Catalyst Microspheres for Efficient Self-healing Materials, Adv. Mater., 2005; 17:205-208

Non-patent literature 4: Zhang Xiong, Xi Zhizhen, Wang Shengxian and Yao Wu, etc., Research Progress of Biomimetic Self-healing Concrete, Concrete, 2001; 137:10-13

Contents of the invention

The purpose of the present invention is to provide a preparation method of epoxy resin self-healing microcapsules, which can control the particle size of self-healing microcapsules through shear emulsification, so as to obtain uniformly distributed microcapsules with a size from a few microns to nearly a hundred microns. Epoxy resin microcapsules, so that the mechanical composite between the self-healing microcapsules and the matrix material is stable.

A further object of the present invention is to provide a preparation method of epoxy resin self-repairing microcapsules, which uses inorganic nanoparticles as emulsifier and prepares epoxy resin self-repairing microcapsules by emulsion polymerization; and adopts molecular type emulsifier Compared with the method, this method does not need the subsequent process of removing the emulsifier, so the method has simple process, low cost and no pollution to the environment.

A further object of the present invention is to provide a micron-sized epoxy resin self-healing microcapsule with excellent stability and airtightness and high coverage.

Above-mentioned invention purpose is realized by following technical scheme:

According to one aspect of the present invention, there is provided a method for preparing epoxy resin self-repairing microcapsules, comprising:

a) adding the nano-inorganic particles into water and dispersing them, so that the obtained dispersion is used as an aqueous phase;

b) Mix the epoxy resin, monoolefinic monomer, polyolefinic crosslinking agent and initiator uniformly, so that the obtained mixed solution is used as the oil phase;

c) mixing the water and oil phases and stirring to form a stable oil-in-water emulsion; and

d) heating the emulsion to carry out emulsion polymerization to form self-healing epoxy resin microcapsules with epoxy resin as the core material and polymers copolymerized with monoolefin monomers and polyolefin crosslinking agents as wall materials.

Further, the method preferably includes e) spray-drying the liquid containing epoxy resin self-healing microcapsules obtained in step d), so as to obtain a dry powder of epoxy resin self-healing microcapsules.

According to another aspect of the present invention, there is provided an epoxy resin self-healing microcapsule, the microcapsule uses epoxy resin as a core material, is polymerized with one or more monoolefin monomers and is crosslinked by multiolefins The polymer cross-linked by the agent is the shell part, wherein the epoxy resin self-healing microcapsules are prepared by the above method.

The preparation method of the epoxy resin self-healing microcapsules according to the present invention has universality, can prepare a series of self-healing microcapsules with different core materials and wall materials, and the composition and shell layer of the self-healing microcapsules are controllable. For example, this method can be used for a variety of epoxy resins as core materials, such as bisphenol A type resin E51 and novolak epoxy resin F44, etc., with various polymers as wall materials, such as polyacrylonitrile and polymethacrylic acid Methyl ester, etc., so as to obtain self-healing microcapsules with different compositions and properties. In addition, the method of the invention has a simple process and can be synthesized in one step, and the prepared microcapsules have excellent stability and airtightness, and are green and pollution-free. The shear emulsification of the method of the present invention can control the particle diameter of the self-healing microcapsules, thereby producing epoxy resin microcapsules with a size from a few microns to nearly a hundred microns and uniform distribution, and the capsules can be better compounded with the matrix material without Brittle cracking has little effect on the mechanical properties of the matrix.

Description of drawings

Fig. 1 is the scanning electron microscope (SEM) picture of the epoxy resin self-healing microcapsule prepared in embodiment 1;

Fig. 2 is the transmission electron microscope (TEM) picture of the epoxy resin self-healing microcapsule prepared in embodiment 1;

Fig. 3 is the infrared spectrum (IR) figure of the epoxy resin self-healing microcapsule prepared in embodiment 1;

Fig. 4 is the thermal weight loss (TGA) curve diagram of the epoxy resin self-healing microcapsule prepared in embodiment 1;

Fig. 5 is a process flow diagram of the method for preparing epoxy resin self-healing microcapsules according to the present invention.

detailed description

Specific embodiments of the present invention are described in detail below.

According to one aspect of the present invention, there is provided a method for preparing epoxy resin self-healing microcapsules, which includes: a) adding nano-inorganic particles into water and dispersing them, so that the obtained dispersion is used as the water phase; b) Mix the epoxy resin, monoolefinic monomer, multiolefinic crosslinking agent and initiator uniformly to obtain the mixed solution as the oil phase; c) mix the water phase and the oil phase and stir to form a stable water an oil-in-emulsion; and d) heating the emulsion to carry out emulsion polymerization to form a self-healing ring with epoxy resin as the core material and a polymer copolymerized with monoolefin monomer and polyolefin crosslinking agent as the wall material Oxygen resin microcapsules.

Further, the method further includes e) spray-drying the liquid containing epoxy resin self-healing microcapsules obtained in step d), so as to obtain dry powder of epoxy resin self-healing microcapsules. Preferably, the drying step can be performed by other common drying methods, as long as the drying method does not destroy the structure and composition of the microcapsules. For example, low-temperature drying or natural drying may be used.

The nano-inorganic used in the method of the present invention can be any chemically stable inorganic particle. For example, the emulsifier of nano inorganic particles can be montmorillonite, lithium algae, silicon carbide, silicon dioxide, barium sulfate, calcium carbonate, iron oxide or titanium dioxide, one or more of which can be used. It is preferable to use at least one of lithium celite and silicon carbide.

Further, preferably, the average particle size of the nano-inorganic particle emulsifier is 1 nm to 1000 nm, preferably 20 nm to 800 μm, more preferably 80-700 nm, most preferably 100-600 nm.

Further, it is preferred that the monoolefinic monomer is selected from the group consisting of styrene, methylstyrene, methyl methacrylate, ethyl methacrylate, butyl methacrylate, tert-butyl methacrylate, methyl acrylate, One or more of ethyl acrylate, butyl acrylate, tert-butyl acrylate and isooctyl acrylate. Preferably, the amount of the monoolefinic monomer is 20-80% by weight relative to the epoxy resin material.

Further, the multiolefin crosslinking agent is preferably selected from divinylbenzene, ethylene glycol dimethacrylate, propylene glycol dimethacrylate, butylene glycol dimethacrylate and dimethacrylic acid One or more of hexanediol esters. The amount of the polyene-based crosslinking agent is preferably 5 to 80% by weight relative to the epoxy resin material.

Further, the initiator is azobisisobutyronitrile, azobisisoheptanonitrile, benzoyl peroxide or potassium persulfate. More preferred is azobisisobutyronitrile.

Further, before the oil phase is mixed with the water phase, the components of the oil phase are heated to a temperature of 60° C., so that the components of the oil phase are mixed evenly. Preferably, after mixing the oil phase and the water phase, a high-speed mixer is used for shearing and stirring, thereby forming a stable oil-in-water emulsion.

Further, the mixture of the oil phase and the water phase is heated to above 70° C. to carry out the polymerization reaction.

Further, the monoolefinic monomer is styrene, the polyolefinic crosslinking agent is divinylbenzene, and the crosslinking agent is azobisisobutyronitrile.

Further, the epoxy resin is at least one of bisphenol A resin E51 and novolak epoxy resin F44.

According to another aspect of the present invention, an epoxy resin self-healing microcapsule is provided, the microcapsule uses epoxy resin as a core material, is polymerized with one or more monoolefin monomers and is crosslinked by multiolefins The polymer cross-linked by the agent is the shell part, wherein the epoxy resin self-healing microcapsules are prepared by the above method.

Further, the prepared epoxy resin self-healing microcapsules have a particle size of 0.1-1000 μm, preferably 1-50 μm.

The preparation method of the epoxy resin self-healing microcapsules according to the present invention has universality, can prepare a series of self-healing microcapsules with different core materials and wall materials, and the composition and shell layer of the self-healing microcapsules are controllable. For example, this method can be used for a variety of epoxy resins as core materials, such as bisphenol A type resin E51 and novolak epoxy resin F44, etc., with various polymers as wall materials, such as polyacrylonitrile and polymethacrylic acid Methyl ester, etc., so as to obtain self-healing microcapsules with different compositions and properties. In addition, the method of the invention has a simple process and can be synthesized in one step, and the prepared microcapsules have excellent stability and airtightness, and are green and pollution-free. The shear emulsification of the method of the present invention can control the particle diameter of the self-healing microcapsules, thereby producing micron-sized and evenly distributed epoxy resin microcapsules, which can be better compounded with the matrix material without embrittlement, and have no impact on the matrix. The mechanical properties are less affected.

Example

Below in conjunction with specific embodiment, further illustrate the present invention. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the protection scope of the present invention. In addition, after reading the content disclosed or taught in the present invention, those skilled in the art can make various modifications and/or improvements to the present invention, and these modifications or improved forms all fall within the scope of the claims of the present invention. within range. Again, the experimental methods used in the following examples are conventional methods unless otherwise specified; the materials and reagents used in the following examples can be obtained from commercial sources unless otherwise specified.

Example 1

Add 0.5 g of hectorite particles (purchased from Rockwood, with an average particle size of 105 nm, a maximum particle size of 500 nm, and a minimum particle size of 20 nm) into 100 g of water to obtain a dispersion as the water phase. Mix 1.0g of bisphenol A type epoxy resin E51 (purchased from Bluestar New Material Company), 0.5g of oil-soluble monomer styrene (St), 0.5g of oil-soluble crosslinking agent divinylbenzene (DVB), 0.5g Styrene and 0.002 g of initiator azobisisobutyronitrile (AIBN) were mixed, and the mixed liquid was used as an oil phase. Put the water phase and the oil phase into a 70°C oven to heat for 20 minutes and 3 minutes respectively for preheating, and stir to mix the components of the oil phase evenly (the total mass of epoxy resin E51 and monomer and crosslinking agent The mass ratio is 1:1, the mass ratio of divinylbenzene to styrene is 1:1). The water phase and the oil phase are mixed, and a stable oil-in-water emulsion is obtained by high-speed shearing at a speed of 12,000 rpm for 30 seconds.

The emulsion system was transferred to a reaction kettle preheated to 70°C in advance, an inert gas nitrogen was introduced, mechanical stirring was performed at a rotation speed of 300 rpm, and polymerization was carried out at 70°C for 12 hours. As the polymerization reaction proceeds, divinylbenzene and styrene begin to undergo copolymerization reaction, and under the action of phase separation, monomers and low molecular prepolymers migrate from the interior of the epoxy resin to the oil-water interface for further polymerization to form a core-shell self-healing microcapsules. The specific process can be referred to as shown in FIG. 5 . The dry powder of the self-healing microcapsules is obtained by spray drying.

The self-healing microcapsules prepared above were observed by scanning electron microscope, as shown in FIG. 1 . It can be seen from Figure 1 that the size of the epoxy resin self-healing microcapsules is uniform, and the average particle size is about 10.0 μm. The results of infrared spectroscopy analysis are shown in Figure 2. Figure 2 is a transmission electron microscope picture of the prepared microcapsules, it can be seen that the prepared epoxy resin self-repairing microcapsules have excellent airtightness. Further, it can be seen from Figure 3: the -COC- stretching vibration peak of epoxy resin (1250-780cm ^-1 ) and the benzene ring skeleton vibration peak in the copolymer of DVB and St (1600-1450cm ^-1 three spectrum band) is clearly visible. Further thermogravimetric analysis (TGA) test results are shown in Figure 4. It can be seen from Figure 4 that the complete decomposition temperature of the core material bisphenol A epoxy resin E51 is about 330°C, and the complete decomposition temperature of the wall material DVB and St copolymer The temperature is about 450°C.

In addition, it can be seen from Figure 5 that the coating rate of the prepared epoxy resin self-healing microcapsules is as high as 87%.

After the microcapsule dry powder obtained after spray drying was placed for 30 days, the amount of bisphenol A epoxy resin E51 existing on the outer surface of the microcapsule was detected, and it was found that its content did not change substantially, which reflected that the epoxy resin E51 prepared in this example The resin self-healing microcapsules have excellent airtightness and stability.

Example 2

An aqueous solution of 0.5 g of silicon carbide particles (purchased from Sinopharm Chemical Reagent Co., Ltd., with an average particle size of 80 nm, a minimum particle size of 5 nm, and a maximum particle size of 230 nm) and 0.2 g of potassium persulfate (1% KPS) was added to 100 g In water, a dispersion was obtained as an aqueous phase. Mix 0.1g oil-soluble crosslinking agent ethylene glycol di(methacrylate) ester (EGDMA), 0.1g oil-soluble monomer methyl methacrylate (MMA), and 1.0g bisphenol A epoxy resin E51, This mixed solution was used as the oil phase. Put the water phase and the oil phase into a 70°C oven to heat for 20 minutes and 3 minutes respectively for preheating, and stir to mix the components of the oil phase evenly (the total mass of epoxy resin E51 and monomer and crosslinking agent The mass ratio is 5:1, and the mass ratio of methyl methacrylate to ethylene glycol di(methacrylate) ester is 1:1). The water phase and the oil phase are mixed, and a stable oil-in-water emulsion is obtained by high-speed shearing at 1200 rpm for 30 seconds.

The emulsion system was transferred to a reaction kettle preheated to 70°C in advance, an inert gas nitrogen was introduced, mechanical stirring was performed at a rotation speed of 300 rpm, and polymerization was carried out at 70°C for 12 hours. As the polymerization reaction proceeds, methyl methacrylate and ethylene glycol di(methacrylate) start to undergo a copolymerization reaction, and under the action of phase separation, monomers and low-molecular prepolymers migrate from the interior of the epoxy resin to The oil-water interface is further aggregated to form core-shell self-healing microcapsules. The specific process can be referred to as shown in FIG. 5 . The microcapsule emulsion can be dried by a spray drying method to obtain a dry powder of the self-repairing microcapsule.

The self-healing microcapsules prepared above were observed by scanning electron microscope and transmission electron microscope, infrared spectrum analysis and thermogravimetric analysis. The test results showed that the epoxy resin self-healing microcapsules were uniform in size, and the average particle size was about 20.30 μm. The results of infrared spectroscopic analysis and thermogravimetric analysis are similar to the test results described in Example 1.

In addition, the coating rate of the epoxy resin self-healing microcapsules prepared in this example is as high as 89%, and the test results of airtightness and stability are the same as those in Example 1, which are also excellent.

Example 3

Add 0.5 g of lithium diatomaceous earth particles (purchased from Rockwood (Rockwood) company, with an average particle size of 105 nm, a maximum particle size of 500 nm, and a minimum particle size of 20 nm) and 0.2 g of initiator azobisisobutyronitrile (AIBN) into the 100 g of water to obtain a dispersion as an aqueous phase. Mix 1.0g bisphenol A type epoxy resin F44 (purchased from Blue Star New Material Company) from Shanghai Resin Factory, 0.1g oil-soluble crosslinking agent divinylbenzene (DVB) and 0.1g styrene (St), This mixed solution was used as an oil phase. Put the water phase and the oil phase into a 70°C oven to heat for 20 minutes and 5 minutes respectively for preheating, and stir to mix the components of the oil phase evenly (wherein the mass ratio of epoxy resin F44 to the total mass of monomers is 5: 1. The mass ratio of divinylbenzene to styrene is 1:1). The water phase and oil phase prepared above were mixed, and the temperature was raised to 70° C., and a high-speed mixer was used to stir and emulsify at a speed of 9000 rpm for 30 seconds to obtain an oil-in-water emulsion.

The emulsion system was transferred to a reaction kettle preheated to 70°C in advance, an inert gas nitrogen was introduced, mechanical stirring was performed at a rotation speed of 300 rpm, and polymerization was carried out at 70°C for 12 hours. As the polymerization reaction proceeds, divinylbenzene and styrene begin to undergo copolymerization reaction, and under the action of phase separation, monomers and low molecular prepolymers migrate from the interior of the epoxy resin to the oil-water interface for further polymerization to form a core-shell self-healing microcapsules, the specific process can be referred to as shown in Figure 5. . The dry powder of the self-healing microcapsules is obtained by spray drying.

Scanning electron microscope photo observation, infrared spectrum analysis and thermogravimetric analysis were carried out on the self-healing microcapsules prepared above, and the test results showed that the epoxy resin self-healing microcapsules were uniform in size, with an average particle size of about 25.1 μm. The results of infrared spectroscopic analysis and thermogravimetric analysis are similar to the test results described in Example 1.

In addition, the coverage rate of the epoxy resin self-healing microcapsules prepared in this example is as high as 87.5%, and the test results of airtightness and stability are the same as the test results of Example 1, which are also excellent.

Claims (16)

1. A method for preparing epoxy resin self-repairing microcapsules, comprising: a) adding the nano-inorganic particles into water and dispersing it, so that the obtained dispersion is used as the water phase; b) uniformly mixing the epoxy resin, monoolefinic monomer, multiolefinic crosslinking agent and initiator, so that the obtained mixed solution is used as the oil phase; c) mixing the water and oil phases and stirring to form a stable oil-in-water emulsion; and d) heating the emulsion to carry out emulsion polymerization to form self-healing epoxy resin microcapsules with epoxy resin as the core material and polymers copolymerized with monoolefin monomers and polyolefin crosslinking agents as wall materials. 2. The method of claim 1, wherein the method further comprises: e) spray-drying the liquid containing epoxy resin self-healing microcapsules obtained in step d), to obtain dry powder of epoxy resin self-healing microcapsules. 3. The method according to claim 1, wherein the nano-inorganic particles are selected from at least A sort of. 4. The method according to any one of claims 1-3, wherein the average particle size of the nano-inorganic particles is 1 nm to 600 nm. 5. The method according to any one of claims 1-3, wherein the monoolefinic monomer is selected from the group consisting of styrene, methylstyrene, methyl methacrylate, ethyl methacrylate, methyl One or more of butyl acrylate, tert-butyl methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, tert-butyl acrylate and isooctyl acrylate. 6. The method according to any one of claims 1-3, wherein the amount of the monoolefinic monomer is 20-80% by weight relative to the epoxy resin material. 7. The method according to any one of claims 1-3, wherein the multiolefin crosslinking agent is selected from divinylbenzene, ethylene glycol dimethacrylate, propylene glycol dimethacrylate One or more of esters, butanediol dimethacrylate and hexanediol dimethacrylate. 8. The method according to any one of claims 1-3, wherein the amount of the polyene-based crosslinking agent is 5-80% by weight relative to the epoxy resin material. 9. The method according to any one of claims 1-3, wherein the initiator is azobisisobutyronitrile, azobisisoheptanonitrile, benzoyl peroxide or potassium persulfate. 10. The method according to any one of claims 1-3, wherein the components of the oil phase are heated to a temperature of 60° C. before the oil phase is mixed with the water phase, so that the components of the oil phase are uniformly mixed. 11. The method according to any one of claims 1-3, wherein, after mixing the oil phase and the water phase, a high-speed mixer is used for shearing and stirring, thereby forming a stable oil-in-water emulsion. 12. The method according to any one of claims 1-3, wherein the mixture of the oil phase and the water phase is heated above 70° C. to carry out the polymerization reaction. 13. The method according to any one of claims 1-3, wherein the monoolefinic monomer is styrene, the multiolefinic crosslinking agent is divinylbenzene, and the crosslinking agent is Azobisisobutyronitrile. 14. The method according to any one of claims 1-3, wherein the epoxy resin is at least one of bisphenol A type resin E51 and epoxy novolac resin F44. 15. An epoxy resin self-repairing microcapsule, the microcapsule uses epoxy resin as the core material, polymerized with one or more monoolefin monomers and crosslinked by a multiolefin crosslinking agent The object is a shell part, wherein the epoxy resin self-healing microcapsules are prepared by the method according to any one of claims 1-14. 16. The epoxy resin self-healing microcapsule according to claim 15, wherein the particle diameter of the epoxy resin self-healing microcapsule is 1-50 μm.