CN102600778A - Nanometer composite epoxy resin self-repairing microcapsule and preparation method thereof - Google Patents

Abstract

The invention discloses a nanocomposite epoxy resin self-repairing microcapsule and a preparation method thereof. The preparation method comprises the steps of dispersing silicon dioxide nanoparticles in water, dissolving oil-soluble cross-linking agent in ethyl phenylacetate, mixing oil and water, shaking and vibrating by hand to emulsify into Pickering emulsion. The Pickering emulsion was added dropwise to the polycyanamide formaldehyde prepolymer solution, and the target product was obtained by in-situ cross-linking polymerization of the prepolymer on the emulsion droplet surface under acidic conditions. Since the prepared microcapsules use stable Pickering emulsion droplets as templates, the prepared microcapsules have a regular spherical shape, and the particle size distribution has polydispersity, and the silica particles doped in the capsule wall effectively improve The mechanical strength and thermal stability of the microcapsule are improved, and the brittleness of the microcapsule is also increased, so that the core material ethyl phenylacetate has a better release effect when the capsule is broken.

Description

A kind of nanocomposite epoxy resin self-healing microcapsule and preparation method thereof

technical field

The invention relates to the field of intelligent polymer materials, in particular to a microcapsule wrapped with an epoxy resin repair agent prepared by a Pickering emulsion droplet template method and a preparation method thereof.

Background technique

Thermosetting resins based on epoxy resins are used in a variety of fields, such as the automotive industry, aerospace, and electronics industries. However, epoxy matrix composites are brittle due to their inherent properties, and are prone to microcracks inside the matrix when subjected to sustained loading. If these cracks are allowed to grow, it will inevitably lead to structural failure of the entire material. Therefore, it is imminent to prepare a smart responsive composite material that can automatically repair cracks to maintain structural integrity and prolong service life. According to literature reports (Nature, 2001, 409: 794-797), White successfully prepared a microcapsule for epoxy resin self-repair. The microcapsules encapsulate a liquid prosthetic agent, endo-dicyclopentadiene (endo-DCPD), and the microcapsules and Gubbs' catalyst are pre-embedded in an epoxy matrix. When a crack grows in the matrix, the microcapsules rupture and release DPCD into the crack. Subsequently, DCPD undergoes ring-opening polymerization after contacting Grubbs' catalyst to form a polycyclopentadiene film, which fills the entire crack and prevents the extension of the crack, playing a repairing role. It is reported in the literature (Macromolecules , 2007, 40:8830-8832) that Caruso prepared self-healing microcapsules of pure solvent-based epoxy resin. This kind of microcapsule uses the organic good solvent of epoxy resin as the core material, such as ethyl phenylacetate, chlorobenzene, phenylacetic acid, etc. After the capsule is broken, the organic solvent siphons into the crack due to capillary action, and these solvents can swell the epoxy resin matrix at the crack, so that the remaining amine curing agent in the matrix and the epoxy monomer remaining in the matrix continue to cross-link. , played a good repair role. Many subsequent literature reports (J. Mater. Chem., 2011, 21: 9060-9065, Macromolecules 2010, 43: 1855–1859, Macromol. Rapid Commun. 2011, 32: 82–87) have successfully prepared ring Microcapsules for oxygen resin self-healing. These works have proved that the microcapsule embedding method is an effective method for preparing self-healing epoxy composites.

Most of these microcapsules encapsulating restorative agents are prepared using emulsions stabilized with emulsifiers (such as ethylene-maleic anhydride copolymers) as templates. However, this emulsifier-stabilized emulsion droplet is thermodynamically and kinetically unstable, and it cannot provide sufficient structural stability to prevent the emulsion droplets from merging, resulting in inefficient encapsulation and the prepared microcapsules are also inefficient. Irregular shapes can occur. Therefore, the stability of the emulsion is facing a huge challenge during the preparation of the capsule. The Pickering emulsion reported in the literature in recent years is an emulsion stabilized by solid nanoparticles with appropriate hydrophilicity and hydrophobicity, which has attracted the interest of many fields. Compared with emulsions stabilized by emulsifiers, Pickering emulsions have better stability due to the irreversible adsorption of nanoparticles on the oil-water interface, and the prepared Pickering emulsions can maintain sufficient stability for months or even years sex. Therefore, the preparation of epoxy resin self-repairing microcapsules by the Pickering emulsion droplet template method can maintain the encapsulation efficiency of the repairing agent to the greatest extent, ensure that the microcapsules have a regular spherical shape, and the microcapsules prepared by using the emulsifier-stabilized emulsion as a template, Due to the presence of solid nanoparticles, the microcapsules have more different properties, such as different rough surfaces, better release efficiency, and denser capsule walls, which are more suitable for self-healing systems.

Therefore, we prepared microcapsules coated with ethyl phenylacetate for self-healing system of epoxy resin by Pickering emulsion drop template method. This pure solvent-based self-healing microcapsules is based on various good properties of the self-healing microcapsules prepared when the emulsifier-stabilized emulsion is used as a template, and due to the intrinsic properties of the Pickering emulsion droplet template method, the core material is improved. Encapsulation efficiency The release efficiency of the repair agent, and endows the microcapsules with different surface morphology. the

Contents of the invention

The purpose and content of the present invention is to provide a nano-composite epoxy resin self-healing microcapsule and its preparation method in view of the defects and deficiencies of the existing epoxy resin self-healing microcapsules prepared using an emulsifier-stabilized emulsion as a template. Compared with the traditional emulsifier-stabilized emulsion droplet template method, this method not only has good stability, but also increases the mechanical strength and thermal stability of the microcapsules due to the addition of solid nanoparticles in the capsule wall. The brittleness of the capsule wall is improved, the microcapsules are more thoroughly broken under stress, and the release efficiency of the nuclear material is improved.

The epoxy resin self-healing microcapsule prepared by the present invention is based on the Pickering emulsion of water-wrapped ethyl phenylacetate stabilized by gas-phase hydrophilic random silica nanoparticles as a template, and then passed through melamine formaldehyde in the water phase The in-situ cross-linking polymerization reaction of the prepolymer forms a dense capsule wall, and the specific technical scheme is as follows.

A method for preparing nanocomposite epoxy resin self-repairing microcapsules, which comprises ultrasonically dispersing fumed silicon dioxide nanoparticles with a relative water phase mass fraction of 0.5%-5% in water to obtain a solution 1, and a relative oil phase mass fraction of 0.1%-2% of polyoxypropylene diol and diphenylmethane diisocyanate prepolymer are dissolved in ethyl phenylacetate to obtain solution 1, and solution 1 and solution 2 are mixed and emulsified into an oil-in-water Pickering emulsion; The oil Pickering emulsion is added dropwise to the melamine formaldehyde prepolymer solution, adjusted to a pH of 3-5, and at 40-60°C, the prepolymer undergoes in-situ cross-linking polymerization on the emulsion droplet surface to obtain the epoxy resin from Repair microcapsules.

In the above preparation method, the acid-base conditions in the preparation process should be properly controlled, and the pH is 3-5, otherwise more side reactions will occur, and even the melamine-formaldehyde resin capsule wall in the experimental assumption cannot be formed.

In the above preparation method, the fumed silica nanoparticles are dispersed in water by means of ultrasonic dispersion, so as to reduce the agglomeration of the silica nanoparticles and ensure uniform particle size distribution of the Pickering stable particles.

In the above-mentioned preparation method, at the temperature of 40-60° C., mechanically stirring at 200-600 rpm, and reacting for 3-5 hours, an epoxy resin self-repairing microcapsule suspension is obtained. The obtained epoxy resin self-repairing microcapsule suspension is washed with water several times, filtered, and dried at room temperature to obtain the epoxy resin self-repairing microcapsule.

In the above preparation method, the epoxy resin self-repairing microcapsule suspension prepared at last is washed with water several times, filtered, and dried to remove the melamine-formaldehyde resin particles generated during the reaction, which will affect the repairing effect of the self-repairing microcapsules.

In the above preparation method, acetic acid is used to adjust the pH. Described water adopts deionized water.

In the above preparation method, add microcapsules with a mass fraction of 5%-20% relative to the matrix into E51 liquid epoxy resin, add diethylenetriamine curing agent, then degas in vacuum for 2-5min, and cure at room temperature for 20- 30h, and then cured at 30-40°C for 20-30h to obtain an epoxy resin composite material embedded with self-repairing microcapsules. After the obtained composite material was frozen under liquid nitrogen, cracks were created with a razor blade, and then the wall thickness of the microcapsules and the release effect of the core material were observed.

Compared with existing materials and technologies, the present invention has the following advantages:

1. The preparation method of the present invention is simple, does not require special equipment, operates under normal temperature and pressure, has simple and controllable reaction, low cost, and is suitable for popularization and application;

2. The present invention prepares epoxy resin self-repairing microcapsules by the Pickering emulsion template method, and the Pickering emulsion template method improves the stability of the emulsion, so that the prepared microcapsules have a regular spherical shape; Pickering The particle size polydispersity of the emulsion makes the particle size distribution of the prepared microcapsules relatively large, so it can respond to cracks of different sizes and improve the repair efficiency.

3. The present invention uses Pickering milk droplets as a template, and introduces a solid layer of nano-silica particles on the capsule wall, which improves the mechanical strength and thermal stability of the capsule wall, and also improves the brittleness of the microcapsules, so that The microcapsules rupture more thoroughly under stress, which improves the release efficiency of the nuclear material.

4. The particle size and wall thickness of the epoxy resin self-repairing microcapsules prepared by the present invention can be adjusted and optimized by adjusting the content of nano-stabilized particles, the water-to-oil ratio and the feeding of melamine-formaldehyde prepolymer to meet the needs of different use cases. need. the

Description of drawings

Figure 1 is a scanning microscope photo of the microcapsules.

Fig. 2 is the microcapsule ethyl phenylacetate release polarized light micrograph in epoxy resin. the

Detailed ways

Below in conjunction with embodiment the present invention is described in further detail. For the epoxy resin self-repairing microcapsules obtained in the examples, adopt Wang et al. ChemPhysChem 2007, 8: 1157-1160 document disclosure method to measure the particle size and distribution of Pickering emulsion, adopt Wang et al. Colloid Polym Sci., 2009, 287: 1089-1097 to test the core material content of the microcapsules, using the method disclosed in Blaiszik et al. Materials Release effects of ethyl phenylacetate. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention.

Example 1

Ultrasonic dispersion of 50 mg of fumed silica nanoparticles in 5 ml of deionized water, shake well and dissolve 50 mg of PPG-TDI into 5 ml of ethyl phenylacetate. The oil-water phase is mixed, shaken and emulsified by hand to obtain an oil-in-water Pickering emulsion stabilized by silica nanoparticles. Add 3.35ml of 37 wt% formaldehyde solution, 2ml of triethanolamine, 10ml of water and 1.75g of melamine to a 50ml two-necked flask, and stir magnetically at 60°C for 30 minutes to obtain an aqueous solution of melamine-formaldehyde prepolymer. Add the oil-in-water Pickering emulsion obtained above dropwise into the aqueous solution of melamine-formaldehyde prepolymer, adjust the pH to 4 with acetic acid, heat to 50°C at a heating rate of 5°C/min, mechanically stir at 400 rpm, and react for 4 h . Cool down to room temperature at a rate of 2°C/min. The resulting suspension was washed three times with water, filtered, and dried at room temperature for 24 h to obtain epoxy resin self-healing microcapsules. Add 0.75 g of microcapsules to 5 g of E51 liquid epoxy resin, add 0.6 g of diethylenetriamine curing agent, then degas in vacuum for 3 minutes, cure at room temperature for 24 hours, and then cure at 35°C for 24 hours to obtain implanted self-healing Epoxy resin composites of microcapsules. The resulting composite was frozen with liquid nitrogen, cracks were created with a razor blade, and then the wall thickness of the microcapsules and the release effect of the core material were observed. The average particle size of the microcapsules is 21±5μm, and the TG test shows that the core material content is 67wt%. The scanning microscope (see Figure 1) observed that the microcapsules have a regular spherical shape, a polydisperse size distribution, and a smooth inner surface. And the rough outer surface, the wall thickness is 500-700nm, and the core material ethyl phenylacetate has a good release efficiency observed under a polarizing microscope (see Figure 2).

Example 2

37.5 mg of fumed silica nanoparticles were ultrasonically dispersed in 5 ml of deionized water, and 5 mg of PPG-TDI was shaken and dissolved in 5 ml of ethyl phenylacetate. The oil-water phase is mixed, shaken and emulsified by hand to obtain an oil-in-water Pickering emulsion stabilized by silica nanoparticles. Add 3.35ml of 37 wt% formaldehyde solution, 2ml of triethanolamine, 10ml of water and 1.75g of melamine to a 50ml two-necked flask, and stir magnetically at 60°C for 30 minutes to obtain an aqueous solution of melamine-formaldehyde prepolymer. Add the oil-in-water Pickering emulsion obtained above dropwise into the aqueous solution of melamine-formaldehyde prepolymer, adjust the pH to 3 with acetic acid, heat to 60°C at a heating rate of 5°C/min, mechanically stir at 200 rpm, and react for 3 h . Cool down to room temperature at a rate of 2°C/min. The resulting suspension was washed three times with water, filtered, and dried at room temperature for 24 h to obtain epoxy resin self-healing microcapsules. Add 0.25 g of microcapsules to 5 g of E51 liquid epoxy resin, add 0.6 g of diethylenetriamine curing agent, then degas in vacuum for 3 minutes, cure at room temperature for 20 hours, and then cure at 35°C for 30 hours to obtain implanted self-healing Epoxy resin composites of microcapsules. The resulting composite was frozen with liquid nitrogen, cracks were created with a razor blade, and then the wall thickness of the microcapsules and the release effect of the core material were observed. The average particle size of the microcapsules is 21±5μm, and the TG test shows that the core material content is 67wt%. The scanning microscope (see Figure 1) observed that the microcapsules have a regular spherical shape, a polydisperse size distribution, and a smooth inner surface. And the rough outer surface, the wall thickness is 500-700nm, under the polarizing microscope (see Figure 2), it is observed that the core material ethyl phenylacetate has good release efficiency. the

Example 3

25 mg of fumed silica nanoparticles were ultrasonically dispersed in 5 ml of deionized water, and 100 mg of PPG-TDI was shaken and dissolved in 5 ml of ethyl phenylacetate. The oil-water phase is mixed, shaken and emulsified by hand to obtain an oil-in-water Pickering emulsion stabilized by silica nanoparticles. Add 3.35ml of 37 wt% formaldehyde solution, 2ml of triethanolamine, 10ml of water and 1.75g of melamine to a 50ml two-necked flask, and stir magnetically at 60°C for 30 minutes to obtain an aqueous solution of melamine-formaldehyde prepolymer. Add the oil-in-water Pickering emulsion obtained above dropwise into the aqueous solution of melamine formaldehyde prepolymer, adjust the pH to 5 with acetic acid, heat to 40°C at a heating rate of 5°C/min, and mechanically stir at 600 rpm for 5zz h . Cool down to room temperature at a rate of 2°C/min. The resulting suspension was washed three times with water, filtered, and dried at room temperature for 24 h to obtain epoxy resin self-healing microcapsules. Add 1 g of microcapsules to 5 g of E51 liquid epoxy resin, add 0.6 g of diethylenetriamine curing agent, then degas in vacuum for 5 minutes, cure at room temperature for 30 hours, and then cure at 35°C for 204 hours to obtain implanted self-healing Epoxy resin composites of microcapsules. The resulting composite was frozen with liquid nitrogen, cracks were created with a razor blade, and then the wall thickness of the microcapsules and the release effect of the core material were observed. The average particle size of the microcapsules is 21±3μm, and the TG test shows that the core material content is 67wt%. The scanning microscope observed that the microcapsules have a regular spherical shape (see Figure 1), the size distribution is polydisperse, and it has a smooth inner surface. And the rough outer surface, the wall thickness is 500-700nm, and the core material ethyl phenylacetate has a good release efficiency observed under a polarizing microscope (see Figure 2). the

Example 4

This example is the same as Example 1 except for the following features: ultrasonically disperse 80 mg of fumed silica nanoparticles in 8 ml of deionized water, and dissolve 20 mg of PPG-TDI into 2 ml of ethyl phenylacetate. The average particle size of the microcapsules is 17±5μm, and the TG test shows that the core material content is 67wt%. The scanning microscope observes that the microcapsules have a regular spherical shape (see Figure 1), the size distribution is polydisperse, and it has a smooth inner surface. And the rough outer surface, the wall thickness is 500-700nm, and the core material ethyl phenylacetate has a good release efficiency observed under a polarizing microscope (see Figure 2).

Example 5

This example is the same as Example 1 except for the following features: ultrasonically disperse 75 mg of fumed silica nanoparticles in 7.5 ml of deionized water, shake well and dissolve 25 mg of PPG-TDI into 2.5 ml of ethyl phenylacetate. The average particle size of the microcapsules is 22±7μm, and the TG test shows that the core material content is 67wt%. The scanning microscope observed that the microcapsules have a regular spherical shape (see Figure 1), the size distribution is polydisperse, and it has a smooth inner surface. And the rough outer surface, the wall thickness is 500-700nm, and the core material ethyl phenylacetate has a good release efficiency observed under a polarizing microscope (see Figure 2).

Example 6

This example is the same as Example 1 except for the following features: ultrasonically disperse 66 mg of fumed silica nanoparticles in 6.6 ml of deionized water, and shake 33 mg of PPG-TDI into 3.3 ml of ethyl phenylacetate. The average particle size of the microcapsules is 21±5μm, and the TG test shows that the core material content is 67wt%. The scanning microscope observed that the microcapsules have a regular spherical shape (see Figure 1), the size distribution is polydisperse, and it has a smooth inner surface. And the rough outer surface, the wall thickness is 500-700nm, and the core material ethyl phenylacetate has a good release efficiency observed under a polarizing microscope (see Figure 2).

The above-mentioned embodiment is a preferred embodiment of the present invention, but the embodiment of the present invention is not limited by the above-mentioned embodiment, and any other changes, modifications, substitutions, combinations, Simplifications should be equivalent replacement methods, and all are included in the protection scope of the present invention.

Claims (7)

1. A preparation method for nanocomposite epoxy resin self-repairing microcapsules, characterized in that the relative water phase mass fraction is 0.5%-5% fumed silicon dioxide nanoparticles ultrasonically dispersed in water to obtain solution 1, the relative oil Polyoxypropylene diol and diphenylmethane diisocyanate prepolymer with a phase mass fraction of 0.1%-2% are dissolved in ethyl phenylacetate to obtain solution 1, and solution 1 and solution 2 are mixed and emulsified to form an oil-in-water Pickering emulsion Add the oil-in-water Pickering emulsion dropwise to the melamine-formaldehyde prepolymer aqueous solution, adjust the pH to 3-5, and at 40-60°C, the prepolymer undergoes in-situ cross-linking polymerization on the emulsion droplet surface to obtain the described Epoxy self-healing microcapsules. 2. The preparation method according to claim 1, characterized in that the fumed silica nanoparticles are dispersed in water by ultrasonic dispersion. 3. The preparation method according to claim 1, characterized in that acetic acid is used to adjust the pH. 4. The preparation method according to claim 3, characterized in that at said 40-60° C., mechanically stirring at 200-600 rpm, and reacting for 3-5 hours to obtain a suspension of epoxy resin self-repairing microcapsules. 5. preparation method according to claim 4 is characterized in that the epoxy resin self-repairing microcapsule suspension of gained is washed repeatedly, filters, room temperature drying, obtains epoxy resin self-repairing microcapsule. 6. preparation method according to claim 1, it is characterized in that described melamine formaldehyde prepolymer aqueous solution is prepared by following method: add successively 37 wt % formaldehyde solution of 3.35ml, 2 ml triethanolamine, 10 in 50ml two-necked flask ml of water and 1.75 g of melamine, magnetically stirred at 60°C for 30 min. 7. the self-repairing microcapsules used in epoxy resins prepared by the preparation method according to any one of claims 1 to 4.

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