Composite heat-conducting silica gel applied to liquid cooling plate and preparation method of composite heat-conducting silica gel

Abstract

The invention discloses composite heat-conducting silica gel applied to a liquid cooling plate and a preparation method of the composite heat-conducting silica gel, and relates to the technical field of high-molecular compound composition organosilicon compounds. The composite heat-conducting silica gel applied to the liquid cooling plate is prepared from the following raw materials in parts by mass: 80 to 100 parts of organic silicon rubber matrix, 40 to 60 parts of composite heat-conducting filler, 3 to 8 parts of flame retardant, 2 to 5 parts of cross-linking agent, 0.5 to 2 parts of catalyst and 1 to 3 parts of anti-aging agent. Through the synergistic effect of the composite heat-conducting filler, a more efficient heat-conducting network is constructed, the performance bottleneck of a single filler system is broken through, and the heat-conducting performance is obviously superior to that of traditional heat-conducting silica gel. According to the composite heat-conducting silica gel applied to the liquid cooling plate, flame retardance, processability and long-term stability are guaranteed, meanwhile, the contradictions of brittleness increase, viscosity increase and the like caused by high filler filling are overcome, and unification of high heat conductivity and durability is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer compound compositions and organic silicon compounds, and in particular to a composite thermally conductive silica gel used in liquid cooling plates and a preparation method thereof. Background Art

[0002] As electronic equipment performance continues to improve and integration levels increase dramatically, the heat generated by electronic components during operation is also increasing. Effective heat dissipation has become a key factor in ensuring the stable operation of electronic equipment. Liquid cold plates, as highly efficient heat dissipation components, are widely used in new energy vehicles, 5G communication base stations, industrial cooling systems, and many other fields. Thermally conductive silicone, the core thermal medium of liquid cold plates, has a direct impact on the heat dissipation efficiency of the liquid cold plate and the stability of electronic equipment operation.

[0003] Current thermally conductive silicone products on the market face several pressing challenges. For one thing, the use of a single thermally conductive filler limits further improvements in thermal conductivity. For example, while using only alumina as a filler can improve thermal conductivity, high filler levels can significantly increase the material's viscosity, making processing and molding difficult. It also negatively impacts the mechanical properties of the substrate, such as brittleness and reduced tensile strength and elongation at break, making it difficult to meet the demands of liquid cold plate applications under complex operating conditions. Furthermore, the high-temperature and aging resistance of existing thermally conductive silicones needs to be improved. Under high-temperature conditions, some thermally conductive silicones experience performance degradation, with their thermal conductivity gradually decreasing over time. This is primarily due to a certain degree of dissociation of the cross-linked structure within the material at high temperatures, as well as a weakening of the interaction between the filler and the substrate. Furthermore, over long-term use, thermally conductive silicones are susceptible to aging due to factors such as oxygen and ultraviolet light, resulting in surface cracking and increased hardness. This not only affects their appearance but, more importantly, deteriorates their thermal conductivity and sealing properties, impacting the lifespan and reliability of liquid cold plates, increasing maintenance costs and the risk of failure for electronic equipment. Therefore, the development of a composite thermally conductive silicone with excellent thermal conductivity, high temperature resistance and aging resistance is of great practical significance for promoting the development of liquid cooling plate technology and improving the overall performance of electronic equipment. Summary of the Invention

[0004] The present invention addresses the challenges of existing technologies by providing a composite thermally conductive silicone rubber for liquid cold plates. By optimizing its formulation and preparation process, using graphene fibers and alumina as composite thermally conductive fillers, combined with a novel anti-aging agent, this silicone rubber achieves high thermal conductivity, excellent high-temperature resistance, and excellent aging resistance, effectively addressing the performance deficiencies of conventional thermally conductive silicone rubber in liquid cold plate applications.

[0005] To achieve the above object, the technical scheme adopted by the present application is: a composite heat-conducting silica gel applied to a liquid cooling plate, comprising the following raw materials by mass fraction: silicone rubber matrix 80-100 parts, composite heat-conducting filler 40-60 parts, flame retardant 3-8 parts, crosslinking agent 2-5 parts, catalyst 0.5-2 parts, and anti-aging agent 1-3 parts.

[0006] The anti-aging agent is a structure shown in Formula 1:

[0007]

[0008] The R1 is selected from methyl, ethyl, propyl, tert-butyl, and methoxy.

[0009] Further, the silicone rubber matrix is a mixture of vinyl silicone oil and hydrogen-based silicone oil, and the mass fraction ratio of the two is 3-5:1.

[0010] Further, the composite heat-conducting filler is composed of graphene fibers and aluminum oxide in a mass fraction ratio of 1:2-3.

[0011] Further, the flame retardant is aluminum hydroxide.

[0012] Further, the crosslinking agent is polydimethylsiloxane.

[0013] Further, the catalyst is dibutyltin dilaurate.

[0014] Further, the anti-aging agent is any one of the compounds shown in the following structures:

[0015]

[0016] A preparation method of a composite heat-conducting silica gel applied to a liquid cooling plate, comprising the following steps:

[0017] S1. The silicone rubber matrix, composite heat-conducting filler, flame retardant, and anti-aging agent are added to a mixing container and stirred and mixed under a nitrogen atmosphere;

[0018] S2. The crosslinking agent and catalyst are added, and vacuum stirring is continued until uniform dispersion is achieved, and the product is cured to obtain a composite heat-conducting silica gel applied to a liquid cooling plate.

[0019] Further, the stirring speed is 800-1200 rpm, the mixing temperature is 60-80°C, and the mixing time is 1-2 hours.

[0020] Further, the curing temperature is 120-150°C, and the curing time is 45-75 minutes.

[0021] A composite heat-conducting structure, comprising: a silica gel layer formed by a composite heat-conducting silica gel applied to a liquid cooling plate;

[0022] a non-peelable polyimide (PI) film compounded with one side of the silica gel layer;

[0023] a peelable polyethylene terephthalate (PET) film compounded with another side of the silica gel layer;

[0024] The composite structure is suitable for liquid cooling plate applications.

[0025] Further, the PI film and PET film are configured to enhance the overall puncture strength.

[0026] Further, the non-peelable PI film has a thickness of 0.1-0.5mm, the peelable PET film has a thickness of 0.05-0.2mm, and the silica gel layer is compounded with the films by hot pressing or adhesive.

[0027] Further, the puncture strength of the composite heat-conductive structure is at least 50% higher than that of a single silica gel layer.

[0028] A preparation method of a composite heat-conductive structure, comprising the following steps:

[0029] S1. applying the composite heat-conductive silica gel for liquid cooling plate applications to the surface of a non-peelable PI film, and pre-curing at 60-100℃ for 10-20 minutes;

[0030] S2. laminating a peelable PET film on the other side of the composite heat-conductive silica gel for liquid cooling plate applications, and hot pressing to compound at a pressure of 1-5MPa and a temperature of 120-150℃ for 30-60 minutes to form the composite heat-conductive structure.

[0031] The anti-aging agent contains a large number of hydroxyl groups and has strong hydrogen-donating ability, which can actively combine with free radicals generated in the aging process to generate stable phenolic oxygen free radicals. The free radicals are stabilized by conjugation effect and cannot continue to participate in chain reaction, thereby blocking the chain reaction of material oxidative degradation. The anti-aging agent can effectively inhibit the free radical oxidation reaction caused by high temperature or ultraviolet light, and delay the molecular chain rupture of the organic silicone rubber matrix. The tertiary amine and phenolic hydroxyl group form a "hindered phenol-amine" complex system: the phenolic hydroxyl group captures primary free radicals, and the tertiary amine group decomposes secondary peroxide, double blocking the oxidation path. The alkyl chain R1 has the effect of adjusting compatibility and steric hindrance, and short-chain alkyl groups such as methyl and ethyl enhance the compatibility of the anti-aging agent with the organic silicone rubber matrix, ensuring uniform dispersion. The large steric hindrance group such as tert-butyl protects the phenolic hydroxyl group and tertiary amine group through steric effect, reduces the side reaction with fillers or matrix, and reduces high-temperature volatilization loss. The methoxy group stabilizes the phenolic oxygen free radical through electron-donating effect, prolonging the anti-aging durability.

[0032] The silicone rubber matrix provides basic flexibility and reaction sites; the hydrogen-based silicone oil as a crosslinking agent and the vinyl silicone oil form a three-dimensional network structure through a silicon hydrogen addition reaction; the mass ratio of 3-5:1 balances the fluidity (processability) and elasticity after curing. The composite thermal conductive filler improves the thermal conductivity, the aluminum oxide fills the voids, and the graphene fiber builds a thermal conduction path. The flame retardant aluminum hydroxide decomposes and absorbs heat to form a flame retardant barrier, and the particle surface and the aluminum oxide / graphene form complementary filling, further reducing the interfacial thermal resistance. The crosslinking agent (polydimethylsiloxane) + catalyst (dibutyltin dilaurate) catalyzes the silicon hydrogen addition reaction and promotes curing; at a mixing temperature of 60-80℃, the catalyst delays the start time of the crosslinking reaction → ensures uniform dispersion of the filler; the curing stage (120-150℃) quickly completes the crosslinking → avoids filler sedimentation.

[0033] Compared with the prior art, the beneficial effects of the present application are:

[0034] 1. The thermal conductivity is significantly improved: through the synergistic effect of the composite thermal conductive filler, a more efficient thermal conduction network is constructed, breaking through the performance bottleneck of a single filler system, and the thermal conductivity is significantly better than that of traditional thermal conductive silicone.

[0035] 2. The high temperature aging resistance is enhanced: the new anti-aging agent effectively inhibits molecular chain rupture in high temperature environment through a synergistic mechanism of phenolic hydroxyl group / tertiary amine group, significantly slows down the performance degradation rate of the material, and solves the problem of performance degradation of traditional products after long-term high temperature use.

[0036] 3. The comprehensive performance is balanced and optimized: while ensuring flame retardancy (V-0 level), processability and long-term stability, the brittleness increase and viscosity rise caused by high filler filling are overcome, and the unification of high thermal conductivity and durability is achieved. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 The anti-aging agent 1 described in the present application is 1 HNMR chart. DETAILED DESCRIPTION

[0038] The technical solutions of the present application will be described clearly and completely below in combination with the drawings in the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor belong to the scope of protection of the present application.

[0039] Synthesis Example 1

[0040] Synthesis of anti-aging agent 1:

[0041]

[0042] First step: under nitrogen atmosphere, 20 g of raw material 1, 71.40 g of potassium phosphate tribasic, 0.16 g of pyridine-2-carboxylic acid, 1.28 g of CuI and 150 g of DMSO were sequentially added into the reaction system, stirred uniformly, 120 g of DMSO solution containing 19.79 g of raw material 2 was slowly added dropwise, stirred uniformly, heated to 85°C for 16 h; after cooling, the obtained reaction mixture was extracted with ammonia solution and methyl tert-butyl ether, the organic phase was washed with water five times, and then washed with saturated NaCl solution twice; finally, the combined organic phase was dried with anhydrous magnesium sulfate, filtered to retain the organic phase, rotary evaporated, and subjected to silica gel column chromatography with a mixture of petroleum ether and ethyl acetate as eluent, rotary evaporated to obtain 21.13 g of intermediate 1.

[0043] Second step: under nitrogen atmosphere, 21.13 g of intermediate 1, 32.49 g of raw material 3, 30.53 g of potassium carbonate, 3.03 g of tris(dibenzylideneacetone)dipalladium, 1.12 g of tri-tert-butylphosphine and 250 g of toluene were sequentially added into the reaction system, stirred uniformly, heated to 120°C and refluxed for 12 h; after the reaction was completed, the temperature was slightly lowered, diatomite was used for filtration, the filtrate was cooled to room temperature, washed with water three times, the organic phase was retained, and then the aqueous phase was extracted with ethyl acetate; after the combined organic phase was dried with anhydrous magnesium sulfate, filtered to retain the organic phase, rotary evaporated, and subjected to silica gel column chromatography with a mixture of petroleum ether and ethyl acetate as eluent, rotary evaporated to obtain 31.25 g of anti-aging agent 1.

[0044] Product structure identification:

[0045] MS (m / z) of intermediate 1: [M+H] + = 192;

[0046] MS (m / z) of anti-aging agent 1: [M+H] + = 356;

[0047] HNMR (CDCI3) of anti-aging agent 1: 1 = δ 6.76 (dd, 1H), 6.65 (d, 1H), 6.45 (m, 1H), 4.69 (d, 1H), 4.43-4.30 (m, 1H), 4.30-4.18 (m, 1H), 4.13-4.03 (m, 1H), 4.03-3.85 (m, 4H), 3.84-3.70 (m, 2H), 3.65-3.50 (m, 5H), 3.56-3.33 (m, 2H), 2.79 (m 2H), 1.99-1.74 (m, 4H), 1.12 (t, 3H).

[0048] Synthesis examples 2-5

[0049] In Synthesis Examples 2 to 5, Antiaging Agents 2 to 5 were synthesized sequentially, referring to the synthesis method of Synthesis Example 1, replacing Raw Material 2 therein, and remaining the same as Synthesis Example 1. The specific structures of Raw Material 2, Antiaging Agents 2 to 5, and MS (m / z) data are shown in Table 1.

[0050] Table 1. Structure of raw material 2, anti-aging agent 2-anti-aging agent 5, and MS (m / z) data involved in Synthesis Examples 2-5.

[0051]

[0052] Example 1

[0053] This embodiment provides a composite thermally conductive silicone rubber for use in a liquid cooling plate, the raw material composition and weight parts of which are as follows: organic silicone rubber matrix: 90 parts (composed of a mixture of vinyl silicone oil and hydrogen silicone oil in a weight ratio of 4:1), composite thermally conductive filler: 50 parts (composed of graphene fiber and alumina in a weight ratio of 1:2.5), flame retardant: 5 parts (aluminum hydroxide), cross-linking agent: 3 parts (polydimethylsiloxane), catalyst: 1 part (dibutyltin dilaurate), anti-aging agent: 2 parts (anti-aging agent 1 prepared in Synthesis Example 1).

[0054] A preparation method of composite thermally conductive silica gel used in liquid cooling plates:

[0055] S1. Place the silicone rubber matrix, composite thermal conductive filler, flame retardant, and anti-aging agent in a vacuum stirred reactor. Replace the air with nitrogen and maintain a nitrogen atmosphere. Stir and mix at 70°C and 1000 rpm for 1.5 hours.

[0056] S2. Add the crosslinking agent and catalyst to the reactor, maintain the temperature at 70 ° C and turn on the vacuum system (vacuum degree ≤ -0.095 MPa), and continue stirring at 1000 rpm for 30 minutes until the material is evenly dispersed to form a paste-like colloid;

[0057] S3. The obtained colloid is injected into a mold and placed in an oven at 135°C for curing for 60 minutes to obtain a cured composite thermally conductive silicone rubber for use in a liquid cooling plate.

[0058] Example 2-Example 5

[0059] A composite thermally conductive silica gel for liquid cooling plates was prepared by referring to the preparation method of Example 1, wherein the anti-aging agent was replaced with anti-aging agent 2 to anti-aging agent 5 prepared in Synthesis Examples 2 to 5, respectively, and the rest remained the same as Example 1.

[0060] Comparative Example 1

[0061] A kind of preparation of composite heat-conducting silica gel applied to liquid cooling plate, with reference to the preparation method of example 1, without adding the anti-aging agent therein, the rest remains the same as example 1.

[0062] Comparative example 2

[0063] A kind of preparation of composite heat-conducting silica gel applied to liquid cooling plate, with reference to the preparation method of example 1, the mass fraction of composite heat-conducting filler therein is replaced by 20 parts, the rest remains the same as example 1.

[0064] Performance test:

[0065] 1. With reference to ASTM D 5470 standard, the thermal conductivity of a kind of composite heat-conducting silica gel applied to liquid cooling plate prepared in example and comparative example is tested, and the data is shown in table 2.

[0066] 2. With reference to UL 94, the flame retardant grade of a kind of composite heat-conducting silica gel applied to liquid cooling plate prepared in example and comparative example is tested, and the data is shown in table 2.

[0067] 3. With reference to ASTM D 412 standard, the tensile strength of a kind of composite heat-conducting silica gel applied to liquid cooling plate prepared in example and comparative example after aging at 150 DEG C for 100 h is tested, and the data is shown in table 2.

[0068] Table 2. Performance test of a kind of composite heat-conducting silica gel applied to liquid cooling plate prepared in example and comparative example.

[0069] Thermal conductivity W / m-k Flame retardant rating Tensile strength Mpa after 150°C aging for 100h Example 1 8.85 V-0 0.38 Example 2 8.82 V-0 0.41 Example 3 8.80 V-0 0.35 Example 4 8.83 V-0 0.33 Example 5 8.81 V-0 0.40 Comparative Example 1 8.30 V-0 0.28 Comparative Example 2 7.20 V-0 0.30

[0070] The thermal conductivity of example is significantly higher than that of comparative example, which proves that the synergistic effect of composite heat-conducting filler and anti-aging agent can effectively build a stable heat-conducting network. The thermal conductivity of comparative example 1 decreases due to the decrease of filler dispersibility, and the thermal conductivity of comparative example 2 is the weakest due to the incomplete heat-conducting path. The flame retardant grade of all samples is V-0 grade, which indicates that the aluminum hydroxide flame retardant can play a high-efficiency flame-retardant role in different formulations and is not affected by the amount of anti-aging agent or filler. The tensile strength of example after high-temperature aging is much higher than that of comparative example, especially higher than that of comparative example 1 without adding anti-aging agent, which highlights the effect of new anti-aging agent on inhibiting molecular chain rupture.

[0071] Application example 1

[0072] Preparation of a composite heat-conducting structure:

[0073] Raw materials and equipment:

[0074] Silica gel layer: the composite heat-conducting silica gel prepared in example 1 is used;

[0075] Non-peeling polyimide (PI) film: the thickness is 0.3 mm;

[0076] Peelable polyethylene terephthalate (PET) film: thickness 0.1 mm;

[0077] Equipment: Coater, hot press (pressure range 1-5 MPa, temperature range 120-150 °C), oven.

[0078] Preparation steps:

[0079] S1. The composite heat-conducting silica gel prepared in Example 1 was uniformly coated on the surface of the non-peelable PI film, with the coating thickness controlled at 0.5 mm. The coated assembly was placed in an oven for pre-curing at 80 °C for 15 minutes.

[0080] S2. The peelable PET film was laminated on the other side of the silica gel layer, ensuring that the PET film was tightly attached to the silica gel layer. The assembly was transferred to a hot press for hot pressing at a pressure of 3 MPa and a temperature of 140 °C for 45 minutes. During the hot pressing process, the silica gel was completely cured and formed a firm interface with the PI / PET film, finally obtaining the composite heat-conducting structure.

[0081] Puncture strength test: The puncture strength of the composite heat-conducting structure was tested according to the ASTM D4833 standard. The results showed that the puncture strength of the structure was 15.2 MPa, which was 60% higher than that of a single silica gel layer (the puncture strength of the silica gel layer in Example 1 was 9.5 MPa).

[0082] Although embodiments of the present application have been shown and described, it is to be understood that various modifications, substitutions, replacements and variations can be made to these embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A composite thermally conductive silica gel used in a liquid cooling plate, characterized in that: The invention comprises the following raw materials in parts by weight: 80-100 parts of organic silicone rubber matrix, 40-60 parts of composite thermal conductive filler, 3-8 parts of flame retardant, 2-5 parts of cross-linking agent, 0.5-2 parts of catalyst, and 1-3 parts of anti-aging agent; The anti-aging agent has a structure shown in Formula 1: The R1 is selected from the group consisting of: methyl, ethyl, propyl, tert-butyl, and methoxy.

2. The composite thermally conductive silica gel for liquid cooling plate according to claim 1, characterized in that: The organic silicone rubber matrix is ​​a mixture of vinyl silicone oil and hydrogen silicone oil, with the mass ratio of the two being 3-5:

1.

3. The composite thermally conductive silica gel for liquid cooling plate according to claim 1, characterized in that: The composite thermal conductive filler is composed of graphene fiber and aluminum oxide in a mass ratio of 1:2-3.

4. The composite thermally conductive silica gel for liquid cooling plate according to claim 1, characterized in that: The flame retardant is aluminum hydroxide.

5. The composite thermally conductive silica gel for liquid cooling plate according to claim 1, characterized in that: The crosslinking agent is polydimethylsiloxane.

6. The composite thermally conductive silica gel for liquid cooling plate according to claim 1, characterized in that: The catalyst is dibutyltin dilaurate.

7. The composite thermally conductive silica gel for liquid cooling plate according to claim 1, characterized in that: The anti-aging agent is any one of the compounds shown in the following structures:

8. A method for preparing a composite thermally conductive silica gel for use in a liquid cooling plate according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1. The silicone rubber matrix, composite thermally conductive filler, flame retardant, anti-aging agent were added to a mixing container and stirred under a nitrogen atmosphere; S2. Add the cross-linking agent and catalyst, continue vacuum stirring until uniformly dispersed, and solidify to obtain a composite thermally conductive silicone for liquid cooling plates.

9. The method for preparing a composite thermally conductive silica gel for a liquid cooling plate according to claim 8, characterized in that: The stirring speed is 800-1200 rpm, the mixing temperature is 60-80°C, and the mixing time is 1-2 hours; The curing temperature is 120-150° C., and the curing time is 45-75 minutes.

10. A composite heat-conducting structure, characterized in that: include: Claims: A silicone layer formed by a composite thermally conductive silicone applied to a liquid cooling plate as described in any one of claims 1 to 7; a non-peelable polyimide film composited with one side of the silicone layer; a peelable polyethylene terephthalate film laminated to the other side of the silicone layer; The composite structure is suitable for liquid cold plate applications.

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