Low-shrinkage temperature-resistant organic silicon pouring sealant and preparation method thereof

Abstract

The invention discloses a low-shrinkage temperature-resistant organic silicon pouring sealant and a preparation method thereof.The organic silicon pouring sealant comprises a component A and a component B. The component A is prepared from, by mass, 80-120 parts of sulfenyl modified polydimethylsiloxane, 30-50 parts of heat conduction filler, 2-5 parts of coupling agent and 5-10 parts of basalt whisker; the component B comprises the following components in parts by weight: 8-16 parts of a cross-linking agent, 0.1-1 part of a catalyst and 10-20 parts of a plasticizer. According to the invention, sulfur groups are introduced into polydimethylsiloxane, and the sulfur group modified polydimethylsiloxane and a silane cross-linking agent are subjected to a cross-linking reaction to form a three-dimensional cross-linked network structure. Meanwhile, the basalt whiskers serve as a fiber material with a high length-diameter ratio and can be embedded into a three-dimensional cross-linked network structure in a crossed mode, the basalt whiskers can form an elastic supporting structure in a cross-linked network, in the pouring sealant curing process, the whiskers can play a certain limiting role in shrinkage of molecular chains, and through the synergistic effect of the whiskers and the cross-linked network, the shrinkage of the molecular chains can be limited to a certain extent; the shrinkage resistance of the pouring sealant is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of potting adhesives, and in particular relates to a low-shrinkage, heat-resistant organic silicon potting adhesive and a preparation method thereof. Background Art

[0002] In the fields of electronics, electrical engineering, new energy, etc., the potting protection of electronic components is crucial, and the shrinkage performance of potting glue is one of the key factors affecting its protection effect.

[0003] Traditional silicone potting compounds often experience a certain degree of volume shrinkage during the curing process due to chemical reactions and physical changes. In the initial stages of the curing reaction, as the crosslinking density of the system gradually increases, the mobility of the molecular chains is restricted, and the volume begins to shrink. This shrinkage not only creates gaps between the potting compound and the components, reducing the sealing and reliability of the potting, but also can damage electronic components due to the internal stress generated by shrinkage. Especially in some precision electronic assemblies, shrinkage of the potting compound can cause component displacement or deformation, affecting their electrical performance and mechanical stability.

[0004] After curing, traditional potting compounds, due to the characteristics of their polymer network structure, will shrink to varying degrees when affected by external factors such as temperature fluctuations. When the temperature rises, the movement of the polymer chains intensifies, causing volume expansion; when the temperature drops, the chain movement is restricted, causing volume contraction. This mismatch in thermal expansion coefficients and shrinkage can easily weaken the bonding between the potting compound and components, affecting the long-term stability and service life of electronic devices.

[0005] In order to meet the high performance requirements of the modern electronics industry for potting compounds and solve the problems caused by the poor shrinkage performance of traditional silicone potting compounds, it is of great practical significance to develop a low-shrinkage and heat-resistant silicone potting compound. Summary of the Invention

[0006] Based on the above-mentioned prior art, the present invention provides a low-shrinkage, heat-resistant silicone potting compound and a preparation method thereof. The silicone potting compound of the present invention has excellent heat resistance and thermal conductivity, especially low shrinkage, which greatly improves the long-term stability and service life of electronic equipment.

[0007] The technical solution adopted to achieve the above-mentioned purpose of the present invention is:

[0008] A low-shrinkage, heat-resistant silicone potting compound comprises a component A and a component B. Component A comprises, by weight, 80-120 parts of sulfur-modified polydimethylsiloxane, 30-50 parts of thermally conductive filler, 2-5 parts of coupling agent, and 5-10 parts of basalt whiskers; and component B comprises 8-16 parts of a cross-linking agent, 0.1-1 part of a catalyst, and 10-20 parts of a plasticizer.

[0009] Furthermore, the preparation method of the sulfur-modified polydimethylsiloxane is as follows:

[0010] 1. Under nitrogen protection, vinyl-terminated polydimethylsiloxane, free radical initiator and mercaptosilane were added to toluene and mixed thoroughly until completely dissolved to obtain a mixed solution;

[0011] The molar ratio of vinyl terminated polydimethylsiloxane, free radical initiator and mercapto monomer is 1:0.05-3:1-1.2;

[0012] 2. Under nitrogen protection, heat the mixed solution to 60-120°C and stir the reaction at 60-120°C for 2-12 hours;

[0013] 3. After the reaction is completed, cool to room temperature, add the obtained mixed product into acetone, start precipitation, let it stand until the precipitation is complete, centrifuge, wash the obtained precipitate with acetone, and dry it to obtain sulfur-modified polydimethylsiloxane.

[0014] Furthermore, the free radical initiator is selected from at least one of azobisisobutyronitrile, benzoyl peroxide, and dicumyl oxide.

[0015] Furthermore, the thermally conductive filler is selected from at least one of alumina, silicon dioxide, and boron nitride.

[0016] Furthermore, the coupling agent is selected from at least one of γ-mercaptopropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, propyl dioleate acyloxy (dioctyl phosphate acyloxy) titanate and isopropyl tris (dioctyl pyrophosphate acyloxy) titanate.

[0017] Furthermore, the crosslinking agent is selected from at least one of hydrogen silicone oil, vinyltrimethoxysilane, vinyltrimethoxysilane and γ-glycidyloxypropyltrimethoxysilane.

[0018] Furthermore, the catalyst is at least one of triethylamine, dimethylethanolamine, dibutyltin dilaurate, chloroplatinic acid and isopropyl tris(dioctyl pyrophosphate) titanate.

[0019] Furthermore, the plasticizer is selected from at least one of tricresyl phosphate, triphenyl phosphate, diphenyl octyl phosphate and triethyl phosphate.

[0020] A method for preparing a low-shrinkage, heat-resistant silicone potting compound comprises the following steps:

[0021] S1. Add sulfur-modified polydimethylsiloxane to a reaction kettle, gradually add thermal conductive filler and basalt whiskers while stirring, stir evenly, then slowly add coupling agent, continue stirring to evenly disperse the coupling agent, and then perform degassing to obtain component A;

[0022] S2. Add the crosslinking agent and plasticizer to the reactor under stirring, mix them evenly, then slowly add the catalyst, continue stirring to evenly disperse the catalyst, and then perform degassing to obtain component B;

[0023] S3. Mixing component A and component B uniformly, and then performing a degassing treatment to obtain the low-shrinkage and heat-resistant organic silicone potting adhesive.

[0024] Compared with the prior art, the advantages and beneficial effects of the present invention are:

[0025] 1. The present invention introduces sulfur groups into polydimethylsiloxane, and the sulfur-modified polydimethylsiloxane undergoes a cross-linking reaction with a silane cross-linking agent to form a three-dimensional cross-linked network structure. This cross-linked network limits the free movement and shrinkage tendency of the polydimethylsiloxane molecular chain. During the curing process of the potting compound, the mobility of the molecular chain is reduced, thereby effectively reducing the volume shrinkage caused by the curling and shrinkage of the molecular chain. At the same time, basalt whiskers, as a fiber material with a high aspect ratio, can be cross-embedded in the three-dimensional cross-linked network structure. The basalt whiskers can form an elastic support structure in the cross-linked network. During the curing process of the potting compound, the presence of the whiskers can play a certain limiting role in the shrinkage of the molecular chain. Through the synergistic effect with the cross-linked network, the material's anti-shrinkage ability is improved, so that the potting compound maintains a more stable volume after curing.

[0026] 2. The present invention introduces sulfur groups into polydimethylsiloxane, and the cross-linking reaction improves the heat resistance of the potting compound, making it less likely to decompose or denature in a high-temperature environment, and can better maintain the stability of its molecular structure and performance.

[0027] 3. The present invention adds basalt whiskers, which can improve the weather resistance and anti-aging performance of the potting compound, making it more resistant to erosion by environmental factors such as ultraviolet rays and ozone during long-term use, and maintaining good performance stability.

[0028] 4. The present invention incorporates basalt whiskers, which inherently have high thermal conductivity. Their dispersion within the matrix helps form thermal pathways, thereby improving the overall thermal conductivity of the potting compound and reducing the amount of thermally conductive filler required. Furthermore, basalt whiskers, inherently flame retardant, can enhance the potting compound's flame retardancy and reduce the material's flammability and flame propagation speed during combustion. DETAILED DESCRIPTION

[0029] In order to facilitate those skilled in the art to understand and implement the present invention, the present invention is further described in detail below in conjunction with embodiments. It should be understood that the embodiments described herein are only used to illustrate and explain the present invention and are not used to limit the present invention.

[0030] Example 1

[0031] 1. Preparation of sulfur-modified polydimethylsiloxane

[0032] ①. Under nitrogen protection, add 25.000g vinyl-terminated polydimethylsiloxane, 0.164g AIBN and 0.281g mercaptopropyltriethoxysilane into a 250mL three-necked flask containing 50mL toluene. Use a magnetic stirrer to stir at 400rpm for 30 minutes. After complete dissolution, a uniform and transparent mixed solution is formed.

[0033] ②. Under nitrogen protection, place the three-necked flask in an oil bath at 80°C and continue stirring at 400 rpm for 6 hours;

[0034] ③ After the reaction is completed, cool naturally to room temperature (about 1 hour), slowly pour the resulting mixed product into 150 mL of acetone to start precipitation, stir for 10 minutes to ensure complete precipitation, then let it stand for 2 hours to allow precipitation to complete. Use a centrifuge to centrifuge at 4000 rpm for 10 minutes to separate the precipitate, collect the precipitate, and wash it twice with 30 mL of acetone, centrifuging at 4000 rpm for 5 minutes after each wash. Place the washed precipitate in a vacuum drying oven at 50°C and dry it for 12 hours to obtain sulfur-modified polydimethylsiloxane.

[0035] 2. Preparation of component A:

[0036] 100 kg of sulfur-modified polydimethylsiloxane, 40 kg of aluminum oxide, 3.5 kg of γ-methacryloxypropyltrimethoxysilane (CAS No.: 2530-85-0), and 3.5 kg of basalt whiskers were mixed and stirred at 1000 rpm until uniformly mixed. The uniformly mixed mixture was transferred to a vacuum mixer and stirred at a vacuum degree of -0.1 MPa and a speed of 500 rpm for degassing for about 40 minutes to obtain component A.

[0037] 3. Preparation of component B:

[0038] 12 kg of vinyl trimethoxysilane and 15 kg of tricresyl phosphate were mixed and stirred at 700 rpm until uniformly mixed. Then, 0.5 kg of chloroplatinic acid was slowly added while stirring and dispersing at a speed of 1000 rpm. After uniform dispersion, degassing was carried out at a vacuum degree of -0.1 MPa and a speed of 400 r / min for about 20 minutes to obtain component B;

[0039] When in use, component A and component B are mixed evenly in a certain ratio (such as the common A:B=1-10:1, volume ratio), and then the potting operation can be carried out.

[0040] Example 2

[0041] The preparation method of the low-shrinkage, heat-resistant silicone potting compound of this embodiment is the same as that of Example 1, except that the formula ratio of this embodiment is different.

[0042] The low-shrinkage, heat-resistant silicone potting compound of this embodiment comprises component A of 80 kg of sulfur-modified polydimethylsiloxane, 50 kg of aluminum oxide, 2 kg of γ-methacryloxypropyltrimethoxysilane (CAS No. 2530-85-0), and 10 kg of basalt whiskers; and component B of 16 kg of vinyltrimethoxysilane, 10 kg of tricresyl phosphate, and 0.1 kg of chloroplatinic acid.

[0043] Example 3

[0044] The preparation method of the low-shrinkage, heat-resistant silicone potting compound of this embodiment is the same as that of Example 1, except that the formula ratio of this embodiment is different.

[0045] The low-shrinkage, heat-resistant silicone potting compound of this embodiment comprises component A of 120 kg of sulfur-modified polydimethylsiloxane, 30 kg of aluminum oxide, 5 kg of γ-methacryloxypropyltrimethoxysilane (CAS No. 2530-85-0), and 5 kg of basalt whiskers; and component B comprises 8 kg of vinyltrimethoxysilane, 20 kg of tricresyl phosphate, and 1 kg of chloroplatinic acid.

[0046] Comparative Example 1

[0047] The preparation method of the organosilicon potting compound in this comparative example is the same as that in Example 1, except that the formula ratio of this comparative example is different.

[0048] The silicone potting compound of this embodiment comprises component A of 100 kg of sulfur-modified polydimethylsiloxane, 40 kg of aluminum oxide, and 3.5 kg of γ-methacryloxypropyltrimethoxysilane (CAS No. 2530-85-0); and component B comprises 12 kg of vinyltrimethoxysilane, 15 kg of tricresyl phosphate, and 0.5 kg of chloroplatinic acid.

[0049] Comparative Example 2

[0050] The preparation method of the organosilicon potting compound in this comparative example is the same as that in Example 1, except that the formula ratio of this comparative example is different.

[0051] The silicone potting compound of this embodiment comprises component A of 100 kg polydimethylsiloxane, 40 kg alumina, 3.5 kg γ-methacryloxypropyltrimethoxysilane (CAS No. 2530-85-0), and 3.5 kg basalt whiskers; and component B comprises 12 kg vinyltrimethoxysilane, 15 kg tricresyl phosphate, and 0.5 kg chloroplatinic acid.

[0052] Comparative Example 3

[0053] The preparation method of the organosilicon potting compound in this comparative example is the same as that in Example 1, except that the formula ratio of this comparative example is different.

[0054] The silicone potting compound of this embodiment comprises component A of 100 kg polydimethylsiloxane, 40 kg alumina, and 3.5 kg γ-methacryloxypropyltrimethoxysilane (CAS No. 2530-85-0); and component B comprises 12 kg vinyltrimethoxysilane, 15 kg tricresyl phosphate, and 0.5 kg chloroplatinic acid.

[0055] Comparative Example 4

[0056] The preparation method of the organosilicon potting compound in this comparative example is the same as that in Example 1, except that the formula ratio of this comparative example is different.

[0057] The silicone potting compound of this embodiment comprises component A of 100 kg of sulfur-modified polydimethylsiloxane, 40 kg of aluminum oxide, 3.5 kg of γ-methacryloxypropyltrimethoxysilane (CAS No. 2530-85-0), and 3.5 kg of basalt whiskers; and component B comprises 12 kg of ethyl orthosilicate, 15 kg of tricresyl phosphate, and 0.5 kg of chloroplatinic acid.

[0058] The silicone potting adhesives prepared in Examples 1-3 and Comparative Examples 1-3 were subjected to the following performance tests:

[0059] Thermal conductivity: thermal conductivity is measured according to GB / T 10297;

[0060] Volume shrinkage: measured by volume method;

[0061] High temperature aging resistance: Refer to HG / T 5053-2016, test conditions: blast drying oven 180℃, 24h.

[0062] The test results are shown in Table 1 below:

[0063]

[0064] As shown in Table 1, the present invention introduces sulfur groups into polydimethylsiloxane and adds basalt whiskers. The sulfur groups form a three-dimensional cross-linked network structure and the basalt whiskers provide elastic support. The two produce a synergistic effect, significantly improving the high-temperature aging resistance and shrinkage performance of the silicone potting compound.

Claims

1. A low-shrinkage, heat-resistant silicone potting compound, characterized by: The invention comprises component A and component B. Component A comprises, by weight, 80-120 parts of sulfur-modified polydimethylsiloxane, 30-50 parts of thermally conductive filler, 2-5 parts of coupling agent, and 5-10 parts of basalt whiskers; and component B comprises 8-16 parts of cross-linking agent, 0.1-1 part of catalyst, and 10-20 parts of plasticizer.

2. The low-shrinkage, heat-resistant silicone potting compound according to claim 1, characterized in that The preparation method of the sulfur-modified polydimethylsiloxane is as follows: 2.

1. Under nitrogen protection, vinyl-terminated polydimethylsiloxane, free radical initiator, and mercaptosilane were added to toluene and mixed thoroughly until completely dissolved to obtain a mixed solution; The molar ratio of vinyl terminated polydimethylsiloxane, free radical initiator and mercapto monomer is 1:0.05-3:1-1.2; 2.

2. Under nitrogen protection, heat the mixed solution to 60-120°C and stir the reaction at 60-120°C for 2-12 hours; 3.

3. After the reaction is completed, cool to room temperature, add the obtained mixed product into acetone, start precipitation, let it stand until the precipitation is complete, centrifuge, wash the obtained precipitate with acetone, and dry it to obtain sulfur-modified polydimethylsiloxane.

3. The low-shrinkage, heat-resistant silicone potting compound according to claim 2, characterized in that: The free radical initiator is selected from at least one of azobisisobutyronitrile, benzoyl peroxide, and dicumyl oxide.

4. The low-shrinkage, heat-resistant silicone potting compound according to claim 1, characterized in that: The thermally conductive filler is selected from at least one of aluminum oxide, silicon dioxide, and boron nitride.

5. The low-shrinkage, heat-resistant silicone potting compound according to claim 1, characterized in that: The coupling agent is selected from at least one of γ-mercaptopropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, propyl dioleate acyloxy (dioctyl phosphate acyloxy) titanate and isopropyl tris (dioctyl pyrophosphate acyloxy) titanate.

6. The low-shrinkage, heat-resistant silicone potting compound according to claim 1, characterized in that: The crosslinking agent is selected from at least one of hydrogen silicone oil, vinyl trimethoxy silane, vinyl trimethoxy silane and γ-glycidyl ether oxypropyl trimethoxy silane.

7. The low-shrinkage, heat-resistant silicone potting compound according to claim 1, characterized in that: The catalyst is at least one of triethylamine, dimethylethanolamine, dibutyltin dilaurate, chloroplatinic acid and isopropyl tris(dioctyl pyrophosphate acyloxy) titanate.

8. The low-shrinkage, heat-resistant silicone potting compound according to claim 1, characterized in that: The plasticizer is selected from at least one of tricresyl phosphate, triphenyl phosphate, diphenyl octyl phosphate and triethyl phosphate.

9. A method for preparing the low-shrinkage, heat-resistant silicone potting compound according to claim 1, characterized in that The steps include: S1. Add sulfur-modified polydimethylsiloxane to a reaction kettle, gradually add thermal conductive filler and basalt whiskers while stirring, stir evenly, then slowly add coupling agent, continue stirring to evenly disperse the coupling agent, and then perform degassing to obtain component A; S2. Add the crosslinking agent and plasticizer into the reactor under stirring, mix them evenly, then slowly add the catalyst, continue stirring to make the catalyst evenly dispersed, and then perform degassing treatment to obtain component B.

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