Epoxy molding compound with self-repairing function and preparation method thereof

Abstract

The invention discloses an epoxy molding compound with a self-repairing function and a preparation method thereof, and belongs to the technical field of epoxy molding compound preparation, and the preparation method comprises the following steps: step a, carrying out ball milling on a silicon dioxide powder filler, and then firing the silicon dioxide powder filler into a spherical shape through a flame melting method; b, mixing the microcapsules with the repairing agent inside with the silicon dioxide powder filler, wherein the appearance and the size of the mixture are kept consistent with those of the microcapsules; and c, mixing the powder filler mixture containing the microcapsules with epoxy resin, heating, keeping the temperature for a period of time, adding a curing accelerator, and keeping a vacuum state in the curing process until the mixture is completely cooled and fixed to form the epoxy molding compound. According to the invention, not only are the problems of bubbles and layering of the filler in the epoxy molding compound solved, but also the problem that the crack strength is reduced when the epoxy molding compound is used can be solved.

Description

Technical Field

[0001] The invention relates to the technical field of epoxy molding compound preparation, in particular to an epoxy molding compound with a self-repairing function and a preparation method thereof. Background Art

[0002] Epoxy molding compound (EMC) is a commonly used polymer material, which is a composite material composed of epoxy resin and filler. Due to its excellent mechanical properties, chemical stability and electrical insulation, epoxy molding compound is widely used in electronics, electrical, aerospace and other fields. However, in the actual application process, the epoxy molding compound is prone to pores and delamination problems in the downstream packaging process, which seriously affects its performance and service life. In addition, due to external stress (such as mechanical shock or temperature change) during use, micro cracks will appear inside the epoxy molding compound, affecting subsequent use. The existing technology improves its bonding performance and anti-bubble ability by changing the formula of epoxy resin and adding some modifiers, but changing the formula of epoxy resin may affect other excellent properties, such as mechanical strength, heat resistance, etc., and the existing technology cannot automatically repair when cracks appear inside the epoxy molding compound during use, resulting in the epoxy molding compound being unable to continue to be used.

[0003] Bubbles and delamination are common problems in the production of epoxy molding compounds. They are usually caused by uneven stirring, voids in silicon powder, etc. The present invention combines the existing microcapsule technology and uses microcapsules with repair agents to propose a new solution to cracks, bubbles, sealing and other related problems. In the implementation of this solution, steps such as ball milling can help to evenly distribute the size of filler particles and improve the sphericity of particles, which also helps to improve the problem.

[0004] In addition, during the encapsulation process, since the material is not solidified but in a flowing state, the microcapsules will not break due to stress. During use, the stress generated by the rupture of electronic components will cause the microcapsules to break, and the released repair agent will enter the cracks under the capillary action and solidify after reacting with the curing accelerator in the epoxy molding compound under the use environment. This will improve the problem of reduced strength of the epoxy molding compound due to cracks, pores, delamination, etc. during use. Summary of the invention

[0005] In order to solve the technical problems mentioned in the above background technology, the present invention provides a method for preparing an epoxy molding compound with a self-repairing function, and the technical solution adopted is as follows:

[0006] Step a: prepare a certain amount of microcapsules with a repair agent inside, where the repair agent is a liquid polymer, such as one or more of liquid polyurethane, liquid epoxy resin, liquid polyethylene, liquid acrylic acid, and liquid olefin.

[0007] The originally irregular powder filler is ball-milled into a powder filler with a smaller particle size, and the powder filler is burned into a spherical shape. The appearance and size are consistent with the microcapsule. The ratio of microcapsule D50 to spherical powder D50 is 1-1.5:1. The amount of microcapsule added is 5%-10% of the silicon powder. By adjusting the particle size and filling amount of the microcapsule of the self-healing agent, its uniform dispersion in the epoxy molding compound matrix is ​​ensured;

[0008] Step b: Mix the microcapsules and powder fillers evenly. In order to ensure the uniform dispersion of the microcapsules in the epoxy molding compound, the powder fillers and microcapsules can be surface modified by a chemical coupling agent to improve the compatibility of the two with the matrix material and avoid stratification during the curing process;

[0009] Step c: Mix the powder filler containing microcapsules with the epoxy resin, then heat it, keep it warm for a period of time, and then add the curing agent. After adding the curing agent, evacuate it during the curing process until it is completely cooled and fixed to form an epoxy molding compound. During the vacuum-assisted curing process, the microcapsules of the self-healing agent should remain intact to avoid premature rupture.

[0010] Preferably, the selected filler is silicon dioxide powder with a particle size of 1-10 μm.

[0011] Preferably, the powder filler is ground and pulverized by a grinder.

[0012] Preferably, the particle size of the powder filler after ball milling is controlled within the range of 1-5 μm.

[0013] Preferably, the addition amount of the powder filler and the microcapsule mixture is 70-80% of the mass of the epoxy molding compound. This is the optimal addition ratio determined through repeated experiments. The appropriate addition amount should ensure that the basic properties of the epoxy molding compound are not affected while maximizing the self-healing effect.

[0014] Preferably, the silica powder filler containing microcapsules is mixed with the epoxy resin and heated to 30-50°C·h, then a curing accelerator is added, and the mixture is heated to 120-240°C·h, and finally cooled to room temperature. During the curing process, the mixture of microcapsules and powder fillers is evacuated to a vacuum degree of less than -0.1MPa for more than 30 minutes, and then the vacuum is gradually released and the curing is continued until it is completely cooled and cured into an epoxy molding compound.

[0015] Preferably, the surface morphology of the powder filler is burned into a spherical shape by a flame melting method.

[0016] The present invention has the following advantages:

[0017] The originally irregular powder filler is first ball-milled to reduce the particle size, and then ball-milled into a sphere with the same appearance and size as the microcapsule, so that the powder filler and the microcapsule are uniformly mixed, not only the gaps between the originally large and irregular powder fillers are reduced, the bubbles are reduced, the stratification is reduced, and the arrangement is tighter, and the microcapsules are not only mixed with the powder filler as a filler; when the epoxy ground plastic is subjected to mechanical shock or temperature changes during use and microcracks appear inside, the microcapsules are ruptured to release the repair agent, and the repair agent penetrates into the microcracks as a supplementary filling, thereby maintaining the physical strength of the epoxy molding plastic and allowing the epoxy molding plastic to be used sustainably. The present invention not only solves the problem of bubbles and stratification of fillers in the epoxy molding plastic, but also solves the problem of reduced strength of cracks when the epoxy molding plastic is used.

[0018] Porosity and stratification observation method: Prepare and slice the sample, use a microscope to observe the pore condition of the epoxy molding compound, and observe the cross-sectional stratification of the epoxy molding compound.

[0019] Tensile strength test method: Fix the epoxy molding compound on the fixture of the tensile testing machine, stretch the sample at a speed of 2mm / min until the sample breaks, and record the maximum load during the stretching process, as well as the width and thickness of the sample. Use the formula σt=F / (b×d) to calculate the tensile strength, where σt is the tensile strength (MPa), F is the maximum load (N), b is the sample width (mm), and d is the sample thickness (mm).

[0020] Bending strength test method: Place the epoxy molding compound on two supports and apply a concentrated load at the midpoint of the two supports to form a three-point bend, gradually increase the load until the specimen is bent and broken. Record the maximum load at the time of failure, as well as the span and thickness of the specimen. Use the formula R = (3F × L) / (2b × h × h) to calculate the bending modulus, where R is the bending strength (MPa), F is the breaking load (N), L is the span (mm), b is the sample width (mm), and h is the sample thickness or height (mm). DETAILED DESCRIPTION

[0021] The following will combine this observation method to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] Example 1

[0023] Step 1: 500 g of silica powder filler with a particle size of 10 μm is mechanically crushed to a D50 particle size of 5 μm after crushing, and its surface morphology is burned into a spherical shape at high temperature using a flame melting method.

[0024] Step 2: Add 5% of the mass of silica powder into liquid dicyclopentadiene (DCPD) as microcapsules of the repair agent.

[0025] Step 3: Add 100 g of epoxy resin, 70 g of phenolic resin and 500 g of silica mixed filler containing microcapsules into the mixer in sequence.

[0026] Step 4: Heat the components in step 3 to 40℃·h, then add 8g of triethylamine curing accelerator, continue heating to 120℃·h, and finally cool to room temperature. During the curing process, apply a vacuum degree of -0.1MPa for 30 minutes, then gradually release the vacuum and continue curing until completion. During the vacuum-assisted curing process, the microcapsules of the self-healing agent should remain intact to avoid premature rupture.

[0027] Example 2

[0028] Step 1: 500 g of silica powder filler with a particle size of 10 μm is mechanically crushed to a D50 particle size of 1 μm after crushing, and its surface morphology is burned into a spherical shape at high temperature using a flame melting method.

[0029] Step 2: Add 5% by mass of silica powder into liquid epoxy resin repair agent as microcapsules of the repair agent.

[0030] Step 3: Add 100 g of epoxy resin, 70 g of phenolic resin and 500 g of silica mixed filler containing microcapsules into the mixer in sequence.

[0031] Step 4: Heat the components in step 3 to 50℃·h, then add 8g of acetic anhydride curing accelerator, continue heating to 240℃·h, and finally cool to room temperature. During the curing process, apply a vacuum of -0.1MPa for 30 minutes, then gradually release the vacuum and continue curing until completion. During the vacuum-assisted curing process, the microcapsules of the self-healing agent should remain intact to avoid premature rupture.

[0032] Example 3

[0033] Step 1: 500 g of silica powder filler with a particle size of 10 μm is mechanically crushed to a D50 particle size of 3 μm after crushing, and its surface morphology is burned into a spherical shape at high temperature using a flame melting method.

[0034] Step 2: Add 5% by mass of silica powder into liquid polyethylene repair agent as microcapsules of the repair agent.

[0035] Step 3: Add 100 g of epoxy resin, 70 g of phenolic resin and 500 g of silica mixed filler containing microcapsules into the mixer in sequence.

[0036] Step 4: Heat the components in step 3 to 30℃·h, then add 8g of phenol curing accelerator, continue heating to 180℃·h, and finally cool to room temperature. During the curing process, apply a vacuum of -0.1MPa for 30 minutes, then gradually release the vacuum and continue curing until completion. During the vacuum-assisted curing process, the microcapsules of the self-healing agent should remain intact to avoid premature rupture.

[0037] Example 4

[0038] Step 1: 500 g of silica powder filler with a particle size of 10 μm is mechanically crushed to a D50 particle size of 5 μm after crushing, and its surface morphology is burned into a spherical shape at high temperature using a flame melting method.

[0039] Step 2: Add 8% silica powder by weight into liquid polyurethane as microcapsules of the repair agent.

[0040] Step 3: Add 130 g of epoxy resin, 100 g of phenolic resin and 500 g of silica mixed filler containing microcapsules into the mixer in sequence.

[0041] Step 4: Heat the components in step 3 to 40℃·h, then add 8g of imidazole salt curing accelerator, continue heating to 120℃·h, and finally cool to room temperature. During the curing process, apply a vacuum degree of -0.1MPa for 30 minutes, then gradually release the vacuum and continue curing until completion. During the vacuum-assisted curing process, the microcapsules of the self-healing agent should remain intact to avoid premature rupture.

[0042] Example 5

[0043] Step 1: 500 g of silica powder filler with a particle size of 10 μm is mechanically crushed to a D50 particle size of 5 μm after crushing, and its surface morphology is burned into a spherical shape at high temperature using a flame melting method.

[0044] Step 2: Add 10% by mass of silica powder into liquid acrylic acid as microcapsules of the repair agent.

[0045] Step 3: Add 260 g of epoxy resin, 240 g of phenolic resin and 500 g of silica mixed filler containing microcapsules into the mixer in sequence.

[0046] Step 4: Heat the components in step 3 to 40℃·h, then add 8g of triethylamine curing accelerator, continue heating to 120℃·h, and finally cool to room temperature. During the curing process, apply a vacuum degree of -0.1MPa for 30 minutes, then gradually release the vacuum and continue curing until completion. During the vacuum-assisted curing process, the microcapsules of the self-healing agent should remain intact to avoid premature rupture.

[0047] Example 6

[0048] Compared with Example 1, the only difference is that a chemical coupling agent with a powder filler mass fraction of 3% is added, and the other steps are the same as Example 1.

[0049] Example 7

[0050] Compared with Example 1, the only difference is that a chemical coupling agent with a powder filler mass fraction of 5% is added, and the other steps are the same as Example 1.

[0051] The results of Examples 1-7 are as follows:

[0052]

[0053] Note: The data and conclusions in the table are based on fixed formulation experimental conditions. The actual situation may vary depending on the specific experimental conditions and material formulation.

[0054] Example 1: Liquid dicyclopentadiene (DCPD) microcapsules can effectively repair cracks, restore most of the tensile strength and bending strength, and have no obvious pores and delamination after curing.

[0055] Example 2: The repair effect of liquid epoxy resin microcapsules is better than that of DCPD, with higher recovery of tensile strength and flexural strength, and only a very small number of micropores.

[0056] Example 3: The repair effect of the liquid polyethylene repair agent microcapsules is relatively poor, the tensile strength and bending strength recovery are low, and there are a small amount of micropores and slight stratification.

[0057] Example 4: Liquid polyurethane microcapsules showed the best repair effect, completely restored the tensile strength and bending strength, and had no pores and delamination after curing.

[0058] Example 5: The repair effect of liquid acrylic microcapsules is moderate, the tensile strength and bending strength are recovered to a reasonable level, there are trace pores but no delamination.

[0059] Example 6: Adding 3% chemical coupling agent to DCPD microcapsules can further enhance the repair effect, and the tensile strength and flexural strength are improved.

[0060] Example 7: Continuing to increase the chemical coupling agent to 5% can further improve the performance of the repair layer, indicating that the chemical coupling agent has a significant effect on enhancing the repair effect.

[0061] Comparative Example 1

[0062] It is basically the same as Example 1, except that the vacuum degree is set to 0 MPa.

[0063] Comparative Example 2

[0064] It is basically the same as Example 1, except that the filler containing the microcapsule self-healing agent is replaced by the original silica filler.

[0065] Comparative Example 3

[0066] The method is basically the same as Example 1, except that no microcapsules are added to the powder filler, and the repair agent is directly applied to the surface of the epoxy molding compound. The repaired epoxy molding compound is tested for its tensile strength, bending strength and other mechanical properties.

[0067] The results of Comparative Examples 1-3 are as follows:

[0068]

[0069] Comparative Example 1: DCPD microcapsules were used for repair under a vacuum degree of 0 MPa. The results showed that both the tensile strength and the bending strength decreased, and there were obvious pores and slight stratification, indicating that the vacuum degree has an important influence on the repair effect.

[0070] Comparative Example 2: After using the original filler to replace the microcapsule self-healing agent, the repair effect is extremely poor, the tensile strength and bending strength are extremely low, and a large number of pores and serious stratification appear, indicating that the microcapsule self-healing agent is crucial to improving the repair effect.

[0071] Comparative Example 3: The repair agent was directly applied to the surface of the epoxy molding compound without using microcapsules. Although the repair effect was better than using the original silica filler, the tensile strength and bending strength were still lower than when using microcapsules, and there were a small amount of pores and slight stratification, indicating that the microcapsule technology has better repair performance.

[0072] The present invention is simple to operate, convenient to use, and suitable for comprehensive promotion and application. Although the embodiments of the present invention have been shown and described, it is understood by those skilled in the art that various changes, modifications, substitutions and variations may be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An epoxy molding compound with self-repairing function, prepared from the following raw materials: a) epoxy resin, content is 3 to 18 parts; b) phenolic resin, content is 2 to 8 parts; c) curing accelerator, content is 0.1 to 1 part; d) filler, content is 70-80 parts; in, The filler comprises spherical silica powder with a particle size of about 1-5 μm and microcapsules containing a repairing agent; The curing accelerator is one of organic amine, acid anhydride, imidazole or phenol accelerators.

2. The epoxy molding compound with self-repairing function according to claim 1, characterized in that: The preparation method comprises the following steps: Step a: placing an irregular silica powder filler with a particle size of 1-10 μm in a grinder for grinding and pulverizing, and controlling the particle size within the range of 1-5 μm after grinding; Step b: calcining the crushed powder filler into a spherical shape by a flame melting method, and adding microcapsules containing a self-healing agent thereto after cooling; Step c: uniformly mixing the microcapsules and the powder filler, and adding a chemical coupling agent with a mass fraction of 0-5% of the powder filler to perform surface modification on the powder filler and the microcapsules; Step d: Mix the powder filler with microcapsules in step c with epoxy resin, add a curing accelerator after heating and heat preservation for a period of time, and keep the vacuum state during the curing process until it is completely cooled and fixed to form an epoxy molding compound.

3. The method for preparing an epoxy molding compound having a self-repairing function according to claim 2, characterized in that: The ratio of the microcapsules D50 to the spherical powder D50 in step b is 1-1.5:

1.

4. The method for preparing an epoxy molding compound having a self-repairing function according to claim 2, characterized in that: The repairing agent carried by the microcapsule in step b is a liquid polymer, and the liquid polymer is one or more of liquid olefin, liquid polyurethane, liquid epoxy resin, liquid polyethylene, and liquid acrylic acid.

5. The method for preparing an epoxy molding compound having a self-repairing function according to claim 2, characterized in that: In step d, the mass ratio of the powder filler with microcapsules to the resin is 3:1-3.

6. The method for preparing an epoxy molding compound having a self-repairing function according to claim 2, characterized in that: In step d, the added amount of the powder filler and the microcapsule mixture is 70-80% of the mass of the entire epoxy molding compound.

7. The method for preparing an epoxy molding compound having a self-repairing function according to claim 2, characterized in that: After mixing the silica powder filler containing microcapsules with epoxy resin, heat it to 30-50℃·h, then add the curing accelerator, continue heating to 120-240℃·h, and finally cool to room temperature. During the curing process, the mixture of microcapsules and powder fillers is evacuated to a vacuum degree of less than -0.1MPa for more than 30 minutes, and then the vacuum is gradually released and the curing is continued until it is completely cooled and cured into an epoxy molding compound.

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