Lightweight low-viscosity heat-conducting gel and preparation process thereof

Abstract

The application relates to a light-weight low-viscosity heat-conducting gel and a preparation process thereof, and relates to the technical field of heat-conducting gels. The preparation raw materials comprise the following components in mass fractions: 7-10 parts of organic silicon vinyl resin, 0.15-0.25 parts of tackifier, 0.6-1.0 parts of methyl hydrogen-containing silicone oil, 0.08-0.12 parts of platinum gold catalyst, 0.05-0.15 parts of inhibitor and 85-88 parts of boron nitride-aluminum oxide core-shell structure filler. The organic silicon vinyl resin comprises end-vinyl polydimethylsiloxane and asymmetric monovinyl terminated polydimethylsiloxane. In the application, the viscoelasticity of the organic silicon vinyl resin is regulated, the interface combination of the tackifier is strengthened, the low-resistance dispersion of the core-shell filler is matched with the heat and humidity barrier, so that the construction fluidity, the bonding strength and the heat-conducting performance retention rate after aging are synergistically improved.

Description

Technical Field

[0001] This application relates to the field of thermally conductive gel technology, and in particular to a lightweight, low-viscosity thermally conductive gel and its preparation process. Background Technology

[0002] As audio equipment evolves towards miniaturization, lightweight design, high integration, and high sound quality, its core components such as speakers, amplifiers, and motherboards generate heat during operation. Furthermore, these devices are susceptible to vibration during use, leading to issues such as loosening of components, abnormal noise, and performance degradation. Therefore, the industry urgently needs an adaptable material that can simultaneously meet multiple functional requirements, including heat dissipation, shockproof bonding, lightweight design, and easy disassembly and maintenance.

[0003] Currently, mainstream thermally conductive adhesives on the market have significant performance shortcomings. Traditional polyurethane thermally conductive adhesives have high application viscosity, poor flowability, and excessive bonding strength after curing, making it impossible to disassemble the bonded components. Forced disassembly easily causes damage, making them completely unsuitable for the maintainability requirements of audio equipment. While ordinary vinyl silicone oil thermally conductive gels have good flowability, their bonding strength after curing is low, resulting in poor shock absorption and fixation. Components are prone to loosening and shifting under long-term vibration, failing to meet the shock resistance and reliability requirements of audio equipment. Furthermore, existing conventional thermally conductive adhesives generally suffer from insufficient long-term reliability of thermal conductivity. Under the coupled effects of thermal-mechanical stress and environmental humidity generated during the long-term operation of audio equipment, the thermal conduction pathway is prone to deterioration due to substrate aging, interface debonding, or filler sedimentation, leading to a continuous increase in thermal resistance and a significant decrease in thermal conductivity over time. This thermal instability easily causes problems such as heat accumulation in components, sound quality distortion, and shortened lifespan, making it difficult to meet the core requirement of long-term stable thermal management for audio equipment. Summary of the Invention

[0004] To address the aforementioned issues, this application provides a lightweight, low-viscosity thermally conductive gel and its preparation process.

[0005] This application provides a lightweight, low-viscosity thermally conductive gel and its preparation process, which adopts the following technical solution: In a first aspect, this application provides a lightweight, low-viscosity thermally conductive gel, employing the following technical solution: A lightweight, low-viscosity thermally conductive gel is prepared from raw materials comprising the following components in parts by weight: 7-10 parts of silicone vinyl resin 0.15-0.25 parts of tackifier 0.6-1.0 parts of methyl hydrogen silicone oil Platinum catalyst 0.08-0.12 parts Inhibitor 0.05-0.15 parts 85-88 parts of boron nitride-alumina core-shell structured filler; The organosilicon vinyl resin includes vinyl-terminated polydimethylsiloxane and asymmetric monovinyl-terminated polydimethylsiloxane.

[0006] Organosilicon vinyl resin serves as the base polymer of the system. Its main chain is a compliant polysiloxane structure, with side chains or end groups containing vinyl functional groups capable of participating in hydrosilylation crosslinking reactions. After curing, it forms an elastic network with excellent flexibility, resistance to high and low temperatures, and low crosslinking density. The tackifier forms a strong chemical bridge through hydrolytic condensation of silanoxy groups with the filler surface and covalent bonding of epoxy groups with the resin matrix. Methyl hydrogen silicone oil, platinum catalyst, and inhibitor constitute an addition-curing system, ensuring controllable room-temperature operating time and heat curing.

[0007] In traditional thermally conductive gels, using alumina filler alone results in high density and limited thermal conductivity improvement, while using boron nitride alone leads to weak interfacial bonding and poor dispersibility due to its strong surface inertness. Physical mixing of these two materials results in high internal friction and severe agglomeration due to significant differences in interfacial properties, leading to high application viscosity, low thermal conductivity, and severe performance degradation in humid and hot environments. Therefore, this application uses low-density, high-thermal-conductivity spherical boron nitride as the core, with a continuous and dense nano-alumina shell in situ coating its surface to form a core-shell integrated structure. This reduces density from the source to achieve lightweighting, and the chemical bonding between the shell and the matrix unifies the interface, completely eliminating interfacial incompatibility and agglomeration problems associated with physical blending. This allows the gel to maintain low viscosity even with high filler content. Simultaneously, the dense alumina shell effectively blocks moisture, inhibits interface debonding during humid and hot aging, and prevents the collapse of thermal conductivity pathways. Thus, the overall performance is synergistically improved from multiple perspectives: lightweighting, interface strengthening, improved dispersion, and enhanced humid and hot stability.

[0008] In traditional thermally conductive gels, using vinyl-terminated polydimethylsiloxane as the base polymer results in uncontrollable crosslinking density of the cured network. This leads to excessively high cohesive strength, making the bonded devices impossible to disassemble, and the rigid network is prone to stress cracking during humid and heat aging, causing a significant decrease in thermal conductivity, thus failing to achieve satisfactory results. Therefore, this application employs a combination of vinyl-terminated polydimethylsiloxane and asymmetric monovinyl-terminated polydimethylsiloxane. The former constructs the crosslinking framework and reaction sites, while the latter introduces an end-inert suspension chain to precisely control the crosslinking density. From a shock-absorbing and fixing perspective, this combination maintains sufficient cohesive strength to resist device loosening caused by long-term vibration of audio equipment. From a disassembly and maintenance perspective, the suspension chain dissipates energy through sliding under large peeling forces, providing reversible separation capability at the interface. From a humid and heat stability perspective, the moderately reduced crosslinking density effectively alleviates stress concentration and cracking tendency of the rigid network during aging, significantly improving thermal conductivity retention. Thus, the overall performance of the gel is synergistically improved from multiple perspectives, including network structure control, energy dissipation and disassembly, and anti-aging degradation.

[0009] In this application, the viscoelasticity regulated by organosilicon vinyl resin, the interfacial bonding strengthened by tackifier, and the low-resistance dispersion of core-shell filler, combined with the humid heat barrier, synergistically improve construction fluidity, bond strength, and thermal conductivity retention after aging.

[0010] Preferably, the boron nitride-alumina core-shell structured filler is prepared using the following steps: Spherical boron nitride was dispersed in ethanol, and aluminum isopropoxide solution was added under heating and stirring conditions to adjust the pH of the system to alkaline. After hydrolysis by heating and stirring, the boron nitride-alumina core-shell structured filler was separated, washed, dried, and calcined to obtain the boron nitride-alumina core-shell structured filler.

[0011] An alumina shell is formed by in-situ hydrolysis of aluminum isopropoxide on the surface of spherical boron nitride using a sol-gel method, followed by calcination to densify the shell. This step ensures that the alumina uniformly coats the boron nitride surface. Compared to simple blending, this core-shell structure reduces the polarity difference between the filler and the silicone matrix during subsequent gel formulation, decreasing the tendency for filler agglomeration. This further improves the dispersion uniformity on top of the existing workability, resulting in a more stable thermal network.

[0012] Preferably, the D50 particle size of the spherical boron nitride is 10-20 μm.

[0013] By limiting the median particle size of spherical boron nitride to 10-20 μm, this size range avoids both excessively small particle size leading to an excessively large specific surface area and increased oil absorption value, which would impair application flowability, and excessively large particle size causing sedimentation or insufficient packing density. Within this particle size range, spherical particles can achieve relatively close packing in the organosilicon matrix. Combined with the core-shell structure, this helps to build a continuous thermal conductivity pathway while maintaining good application flowability, thus improving thermal conductivity stability.

[0014] Preferably, the mass ratio of the spherical boron nitride to aluminum isopropoxide is (5-10):1.

[0015] The thickness of the alumina shell was controlled by adjusting the mass ratio of boron nitride to aluminum isopropoxide within (5-10):1. If the ratio is too low, the surface coating is discontinuous, and the exposed boron nitride has poor compatibility with the matrix, leading to interface deterioration after hygrothermal aging. If the ratio is too high, the filler density and polarity increase, resulting in higher application viscosity. This preferred range achieves a moderate shell thickness, effectively shielding the moisture absorption of boron nitride without significantly increasing internal friction, thereby further improving the thermal conductivity retention rate after hygrothermal aging while maintaining the original flowability and adhesion properties.

[0016] Preferably, the boron nitride-alumina core-shell structure filler is modified and prepared using the following steps: Boron nitride-alumina core-shell structured filler and octaepoxy cage-type polysilsesquioxane were added to ethanol, ultrasonicated, heated and stirred to react. After the reaction was completed, the ethanol was recovered and dried to obtain the modified boron nitride-alumina core-shell structured filler.

[0017] Unmodified core-shell fillers retain some hydroxyl groups on their surface, which differ in polarity from the silicone matrix. These hydroxyl groups are chemically bonded to the hydroxyl groups on the filler surface via the epoxy groups of octa-epoxy cage-type polysilsesquioxane (POSS), forming an organic-inorganic hybrid layer. This modified layer reduces the surface energy of the filler, improving its wetting and dispersion within the silicone matrix, thus helping to maintain a lower viscosity in the composite slurry and enhancing its flowability during application. In the cured system, the epoxy groups on the POSS surface form a hydrogen bond network with the silanol groups generated by the hydrolysis of the tackifier. Simultaneously, the rigid cage-like structure of POSS itself acts as physical nodes at the interface, collectively strengthening the interfacial bonding between the filler and the matrix. Furthermore, the hydrophobic POSS layer and the alumina shell layer synergistically construct a moisture barrier, and work in conjunction with the flexible suspension chains formed by the asymmetric monovinyl-terminated polydimethylsiloxane in the compound resin, allowing for more effective stress dissipation during humid heat aging, thereby improving the long-term retention rate of thermal conductivity. Thus, the POSS modification, together with the tackifier, compound resin and core-shell structure in this system, forms multiple synergies, further optimizing the construction fluidity, bonding performance and thermal conductivity stability on the basis of the original balance.

[0018] Preferably, the mass ratio of the boron nitride-alumina core-shell structure filler to the octaepoxy cage-type polysilsesquioxane is 1:(0.08-0.12).

[0019] The aforementioned range ensures that POSS forms a complete monolayer covering on the filler surface without excessive accumulation. Below this range, the modification effect is insufficient, and the filler dispersion and interfacial reinforcement effects are limited; above this range, excess POSS may remain free in the matrix, interfering with the crosslinking network. At this preferred ratio, POSS achieves the highest modification efficiency, simultaneously improving three properties: application flowability, bond strength, and thermal conductivity.

[0020] Preferably, the mass ratio of the vinyl-terminated polydimethylsiloxane to the asymmetric monovinyl-terminated polydimethylsiloxane is 1:(0.15-0.2).

[0021] The mass ratio of the compounded resin is 1:(0.15-0.2), which is a key window for controlling the crosslinking density and the proportion of suspended chains. If the proportion of asymmetric silicone oil is too low, there will be insufficient suspended chains, resulting in excessive network rigidity. This will cause the bond strength to exceed the disassembly range and make it prone to microcracks after humid heat aging. If the proportion is too high, the crosslinking points will be sparse, the cohesive strength will be insufficient, and the vibration resistance will decrease. This preferred range balances the crosslinking density and the number of suspended chains, ensuring adequate bond strength while maintaining sufficient cohesive damping. This further improves the vibration resistance and thermal conductivity stability after humid heat aging, based on the original construction fluidity.

[0022] Preferably, the tackifier comprises γ-glycidoxypropyltrimethoxysilane.

[0023] γ-glycidoxypropyltrimethoxysilane was selected as the tackifier. Its epoxypropoxy group can react with the hydroxyl groups on the surface of the metal substrate to form chemical bonds, while the methoxysilane portion is compatible with silicone resin. This tackifier, in synergy with silicone vinyl resin, boron nitride-alumina core-shell structure filler, and POSS modified layer, constructs a continuous chemical bonding network between filler, matrix, and substrate. This overcomes the weakness of simple silicone oil gels in adhering to substrates such as aluminum alloys, improving adhesion performance without sacrificing removability.

[0024] Secondly, this application provides a preparation process for a lightweight, low-viscosity thermally conductive gel, employing the following technical solution: A process for preparing a lightweight, low-viscosity thermally conductive gel includes the following steps: Organosilicon vinyl resin and tackifier are mixed and stirred to obtain matrix premix; boron nitride-alumina core-shell structure filler is added to matrix premix in batches, and stirred under heating and vacuum conditions to obtain composite slurry; methyl hydrogen silicone oil and inhibitor are added and stirred; platinum catalyst is added and stirred; after stirring is stopped, the mixture is filtered and degassed to obtain lightweight low-viscosity thermally conductive gel.

[0025] The above-described preparation process, through its orderly feeding and temperature control design, further ensures the synergistic effect of each component: first, the resin and tackifier are mixed to ensure the tackifier is uniformly dispersed in the matrix; fillers are added in batches, accompanied by high-speed stirring under vacuum and heating, which avoids local agglomeration and removes moisture and air bubbles, preventing poisoning of the platinum catalyst; after cooling, hydrogen-containing silicone oil, inhibitors, and catalysts are added sequentially to ensure room temperature operation. Finally, filtration and vacuum degassing eliminate mechanically introduced air bubbles and potential gel particles. This process allows the performance advantages of the above components to be fully transformed into the low viscosity, stable bonding strength, and resistance to damp heat aging of the finished gel, thus effectively implementing the synergistic effect at the formulation level at the product level.

[0026] In summary, this application includes at least one of the following beneficial technical effects: 1. This application precisely controls the crosslinking density by compounding terminal vinyl groups with asymmetric monovinyl silicone oil. This maintains sufficient cohesive strength to resist vibration while endowing the suspension chain with the ability to dissipate energy during slippage, achieving a balance between detachability and shock resistance, and mitigating stress cracking during humid heat aging. Tackifiers strengthen the interfacial bonding between the filler and the substrate, compensating for insufficient silicone oil adhesion. The boron nitride-alumina core-shell structure filler uses low-density boron nitride as the core to achieve lightweighting, while the alumina shell improves dispersion, reduces viscosity under high filler conditions, and constructs a moisture barrier to enhance humid heat stability. The synergistic effect of these three components comprehensively improves the gel's application flowability, detachable bond strength, and thermal conductivity retention after aging.

[0027] 2. Through POSS modification, the epoxy groups chemically bond with the hydroxyl groups on the filler surface to form an organic-inorganic hybrid layer, reducing surface energy and improving the wetting and dispersion of the filler in the organosilicon matrix. This maintains the composite slurry at a lower viscosity and improves its workability. After curing, the epoxy groups on the POSS surface can form a hydrogen bond network with the silanol groups generated by the hydrolysis of the tackifier. Simultaneously, the rigid cage structure of POSS itself acts as physical nodes distributed at the interface, enhancing interfacial bonding and increasing tensile shear strength. Furthermore, the hydrophobic layer of POSS and the alumina shell synergistically construct a moisture barrier, and work in conjunction with the flexible suspension chain formed by the asymmetric monovinyl silicone oil to effectively dissipate heat and moisture aging stress, improving long-term thermal conductivity retention. Thus, POSS modification, along with the tackifier, compound resin, and core-shell structure, creates multiple synergies, further optimizing workability, adhesion, and thermal conductivity stability. Detailed Implementation

[0028] This application discloses a lightweight, low-viscosity thermally conductive gel and its preparation process. Unless otherwise specified, all raw materials used in this application are commercially available. The following detailed description, in conjunction with embodiments, further illustrates this application: Raw material specifications: Spherical boron nitride was purchased from Yumu (Ningbo) New Materials Co., Ltd.; aluminum isopropoxide (CAS No.: 555-31-7); vinyl-terminated polydimethylsiloxane was purchased from Wuhan Kemike Biomedical Technology Co., Ltd.; asymmetric monovinyl-terminated polydimethylsiloxane (CAS No.: 68951-99-5) was purchased from Shanghai Huayuan Century Trading Co., Ltd.; γ-glycidyl etheroxypropyltrimethoxysilane (CAS No.: 2530-83-8); methyl hydrogen silicone oil JZH-202 was purchased from Jiangsu Zhonghe Silicon-based New Materials Co., Ltd.; platinum catalyst TJ-PL-5000 was purchased from Guangzhou Tianjiang High-tech Materials Co., Ltd.; inhibitor CX-5002H was purchased from Guangdong Chenxi New Materials Technology Co., Ltd.; octa-epoxy cage-type polysilsesquioxane was purchased from Angxing New Carbon Materials Changzhou Co., Ltd.; and spherical alumina was purchased from Jiangsu Shengtian New Materials Co., Ltd. Example 1

[0029] Preparation of boron nitride-alumina core-shell structured fillers The D50 particle size of the spherical boron nitride is 10 μm, and the mass ratio of spherical boron nitride to aluminum isopropoxide is 10:1.

[0030] Spherical boron nitride was ultrasonically dispersed in anhydrous ethanol (solid-liquid ratio 1:15 g / mL). A 0.1 g / mL aluminum isopropoxide ethanol solution was added dropwise while stirring at 60°C. After the addition was complete, the pH of the system was adjusted to 9 with 0.1 mol / L dilute ammonia. The mixture was kept at a constant temperature of 60°C and stirred at 500 rpm for 4 hours for hydrolysis. The mixture was then centrifuged and washed with deionized water until neutral. The resulting powder was dried at 120°C for 2 hours and then calcined in a tube furnace at 600°C for 3 hours under a nitrogen atmosphere with a heating rate of 5°C / min to obtain the boron nitride-alumina core-shell structured filler.

[0031] Preparation of lightweight, low-viscosity thermally conductive gel Weigh the following components in parts by mass: 7 parts silicone vinyl resin, 0.15 parts tackifier, 0.6 parts methyl hydrogen silicone oil, 0.08 parts platinum catalyst, 0.05 parts inhibitor, and 85 parts boron nitride-alumina core-shell structure filler; the silicone vinyl resin is composed of terminal vinyl polydimethylsiloxane and asymmetric monovinyl-terminated polydimethylsiloxane in a mass ratio of 1:0.15, the tackifier is γ-glycidoxypropyltrimethoxysilane, the methyl hydrogen silicone oil is JZH-202, the platinum catalyst is TJ-PL-5000, and the inhibitor is CX-5002H.

[0032] Organosilicon vinyl resin and tackifier were mixed and stirred at 500 rpm for 10 min to obtain a matrix premix. Boron nitride-alumina core-shell structure filler (pre-dried under vacuum at 120℃ for 2 h) was added to the matrix premix in 3 batches. After each batch was added, it was first wetted at 300 rpm for 5 min, heated to 50℃, and stirred at 1000 rpm for 30 min under vacuum of -0.1 MPa to obtain a composite slurry. The vacuum was maintained and the material temperature was lowered to 25℃. Methyl hydrogen silicone oil and inhibitor were added in sequence and stirred at 600 rpm for 10 min. Finally, platinum catalyst was added and stirred at 300 rpm for 8 min. After stopping stirring, the mixture was filtered through a 200-mesh stainless steel filter and allowed to stand under vacuum of -0.09 MPa for 20 min to degas. The mixture was then dispensed into light-proof sealed containers to obtain a lightweight, low-viscosity thermally conductive gel. Example 2

[0033] Preparation of boron nitride-alumina core-shell structured fillers The D50 particle size of the spherical boron nitride is 20 μm, and the mass ratio of spherical boron nitride to aluminum isopropoxide is 5:1.

[0034] Spherical boron nitride was ultrasonically dispersed in anhydrous ethanol (solid-liquid ratio 1:15 g / mL). A 0.1 g / mL aluminum isopropoxide ethanol solution was added dropwise while stirring at 60°C. After the addition was complete, the pH of the system was adjusted to 9 with 0.1 mol / L dilute ammonia. The mixture was kept at a constant temperature of 60°C and stirred at 500 rpm for 4 hours for hydrolysis. The mixture was then centrifuged and washed with deionized water until neutral. The resulting powder was dried at 120°C for 2 hours and then calcined in a tube furnace at 600°C for 3 hours under a nitrogen atmosphere with a heating rate of 5°C / min to obtain the boron nitride-alumina core-shell structured filler.

[0035] Preparation of lightweight, low-viscosity thermally conductive gel Weigh the following components in parts by mass: 10 parts silicone vinyl resin, 0.25 parts tackifier, 1 part methyl hydrogen silicone oil, 0.12 parts platinum catalyst, 0.15 parts inhibitor, and 88 parts boron nitride-alumina core-shell structure filler; the silicone vinyl resin is composed of terminal vinyl polydimethylsiloxane and asymmetric monovinyl-terminated polydimethylsiloxane in a mass ratio of 1:0.2, the tackifier is γ-glycidyl etheroxypropyltrimethoxysilane, the methyl hydrogen silicone oil is JZH-202, the platinum catalyst is TJ-PL-5000, and the inhibitor is CX-5002H.

[0036] Organosilicon vinyl resin and tackifier were mixed and stirred at 500 rpm for 10 min to obtain a matrix premix. Boron nitride-alumina core-shell structure filler (pre-dried under vacuum at 120℃ for 2 h) was added to the matrix premix in 3 batches. After each batch was added, it was first wetted at 300 rpm for 5 min, heated to 50℃, and stirred at 1000 rpm for 30 min under vacuum of -0.1 MPa to obtain a composite slurry. The vacuum was maintained and the material temperature was lowered to 25℃. Methyl hydrogen silicone oil and inhibitor were added in sequence and stirred at 600 rpm for 10 min. Finally, platinum catalyst was added and stirred at 300 rpm for 8 min. After stopping stirring, the mixture was filtered through a 200-mesh stainless steel filter and allowed to stand under vacuum of -0.09 MPa for 20 min to degas. The mixture was then dispensed into light-proof sealed containers to obtain a lightweight, low-viscosity thermally conductive gel. Example 3

[0037] Preparation of boron nitride-alumina core-shell structured fillers The D50 particle size of the spherical boron nitride is 15 μm, and the mass ratio of spherical boron nitride to aluminum isopropoxide is 7.5:1.

[0038] Spherical boron nitride was ultrasonically dispersed in anhydrous ethanol (solid-liquid ratio 1:15 g / mL). A 0.1 g / mL aluminum isopropoxide ethanol solution was added dropwise while stirring at 60°C. After the addition was complete, the pH of the system was adjusted to 9 with 0.1 mol / L dilute ammonia. The mixture was kept at a constant temperature of 60°C and stirred at 500 rpm for 4 hours for hydrolysis. The mixture was then centrifuged and washed with deionized water until neutral. The resulting powder was dried at 120°C for 2 hours and then calcined in a tube furnace at 600°C for 3 hours under a nitrogen atmosphere with a heating rate of 5°C / min to obtain the boron nitride-alumina core-shell structured filler.

[0039] Preparation of lightweight, low-viscosity thermally conductive gel Weigh the following components in parts by mass: 8.5 parts silicone vinyl resin, 0.2 parts tackifier, 0.8 parts methyl hydrogen silicone oil, 0.1 parts platinum catalyst, 0.1 parts inhibitor, and 86.5 parts boron nitride-alumina core-shell structure filler; the silicone vinyl resin is composed of terminal vinyl polydimethylsiloxane and asymmetric monovinyl-terminated polydimethylsiloxane in a mass ratio of 1:0.175, the tackifier is γ-glycidyl etheroxypropyltrimethoxysilane, the methyl hydrogen silicone oil is JZH-202, the platinum catalyst is TJ-PL-5000, and the inhibitor is CX-5002H.

[0040] Organosilicon vinyl resin and tackifier were mixed and stirred at 500 rpm for 10 min to obtain a matrix premix. Boron nitride-alumina core-shell structure filler (pre-dried under vacuum at 120℃ for 2 h) was added to the matrix premix in 3 batches. After each batch was added, it was first wetted at 300 rpm for 5 min, heated to 50℃, and stirred at 1000 rpm for 30 min under vacuum of -0.1 MPa to obtain a composite slurry. The vacuum was maintained and the material temperature was lowered to 25℃. Methyl hydrogen silicone oil and inhibitor were added in sequence and stirred at 600 rpm for 10 min. Finally, platinum catalyst was added and stirred at 300 rpm for 8 min. After stopping stirring, the mixture was filtered through a 200-mesh stainless steel filter and allowed to stand under vacuum of -0.09 MPa for 20 min to degas. The mixture was then dispensed into light-proof sealed containers to obtain a lightweight, low-viscosity thermally conductive gel. Example 4

[0041] Example 4 is based on Example 3. The only difference between Example 4 and Example 3 is that the mass ratio of spherical boron nitride to aluminum isopropoxide is 12:1 when preparing the boron nitride-alumina core-shell structure packing in Example 4. Example 5

[0042] Example 5 is based on Example 3. The only difference between Example 5 and Example 3 is that in Example 5, the mass ratio of spherical boron nitride to aluminum isopropoxide is 3:1 when preparing the boron nitride-alumina core-shell structure packing. Example 6

[0043] Example 6 is based on Example 3. The only difference between Example 6 and Example 3 is that the boron nitride-alumina core-shell structure filler in Example 6 has been modified and prepared using the following steps: The mass ratio of boron nitride-alumina core-shell structured filler to octaepoxy cage-type polysilsesquioxane is 1:0.08.

[0044] Boron nitride-alumina core-shell structured filler and octacyclic cage-type polysilsesquioxane were added to anhydrous ethanol (the solid-liquid ratio of boron nitride-alumina core-shell structured filler to anhydrous ethanol was 1:4 g / mL), ultrasonically dispersed for 30 min, and reacted at a constant temperature of 60℃ and 400 rpm for 3 h. After the reaction was completed, the ethanol was recovered by vacuum distillation, and the filler was vacuum dried at 80℃ for 4 h to obtain the modified boron nitride-alumina core-shell structured filler. Example 7

[0045] Example 7 is based on Example 6. The only difference between Example 7 and Example 6 is that in Example 7, the mass ratio of boron nitride-alumina core-shell structured filler to octaepoxy cage-type polysilsesquioxane is 1:0.12 when preparing the modified boron nitride-alumina core-shell structured filler. Example 8

[0046] Example 8 is based on Example 6. The only difference between Example 8 and Example 6 is that in Example 8, the mass ratio of boron nitride-alumina core-shell structured filler to octaepoxy cage-type polysilsesquioxane is 1:0.1 when preparing the modified boron nitride-alumina core-shell structured filler. Example 9

[0047] Example 9 is based on Example 6. The only difference between Example 9 and Example 6 is that in Example 9, the mass ratio of boron nitride-alumina core-shell structured filler to octaepoxy cage-type polysilsesquioxane is 1:0.05 when preparing the modified boron nitride-alumina core-shell structured filler. Example 10

[0048] Example 10 is based on Example 6. The only difference between Example 10 and Example 6 is that in Example 10, the mass ratio of boron nitride-alumina core-shell structured filler to octaepoxy cage-type polysilsesquioxane is 1:0.15 when preparing the modified boron nitride-alumina core-shell structured filler. Example 11

[0049] Example 11 is based on Example 3. The only difference between Example 11 and Example 3 is that in Example 11, the mass ratio of terminal vinyl polydimethylsiloxane to asymmetric monovinyl-terminated polydimethylsiloxane in the organosilicon vinyl resin is 1:0.05. Example 12

[0050] Example 12 is based on Example 3. The only difference between Example 12 and Example 3 is that in Example 12, the mass ratio of terminal vinyl polydimethylsiloxane to asymmetric monovinyl-terminated polydimethylsiloxane in the organosilicon vinyl resin is 1:0.25.

[0051] Comparative Example 1 Comparative Example 1 is based on Example 3. The only difference between Comparative Example 1 and Example 3 is that Comparative Example 1 adds only terminal vinyl polydimethylsiloxane to the silicone vinyl resin.

[0052] Comparative Example 2 Comparative Example 2 is based on Example 3. The only difference between Comparative Example 2 and Example 3 is that the boron nitride-alumina core-shell structure packing in Comparative Example 2 is replaced with an equal mass of packing composed of spherical boron nitride and spherical alumina in a mass ratio of 9:1. The D50 particle size of the spherical boron nitride is 15 μm, and the D50 particle size of the spherical alumina is 2 μm. Performance testing experiment

[0053] (1) GB / T 2794-2022 "Determination of viscosity of adhesives" was selected as the standard. The single-cylinder rotational viscometer method was used. The test temperature was 25℃. The rotor was No. 4 and the rotation speed was 20rpm. The sample was placed in the test cup. After the temperature was balanced, the viscometer was started to read the stable reading. Each sample was tested three times. The average value was taken after measurement and the results were recorded in Table 1.

[0054] (2) GB / T 7124-2008 "Determination of tensile shear strength of adhesives (rigid material to rigid material)" was selected as the standard. The substrate was aluminum alloy (2024-T3). The specimen size was 100mm×25mm×2mm, the single-sided overlap length was 12.5mm, and the adhesive layer thickness was 0.2mm. After curing at 25℃×48h+80℃×2h, it was loaded at a rate of 5mm / min on a universal testing machine until failure. The maximum load was recorded and the tensile shear strength was calculated. Three samples were prepared for each specimen. The average value was taken after measurement and the results were recorded in Table 1.

[0055] (3) ASTM D5470-17 was selected as the standard. The initial thermal conductivity was tested at 25℃ and 50kPa. The sample was then aged in a constant temperature and humidity chamber at 85℃ and 85% humidity for 500h. After being taken out, it was placed at 25℃ for 24h to recover to the equilibrium state. The thermal conductivity after aging was tested again under the same conditions. The retention rate (%) was calculated as: thermal conductivity after aging / initial thermal conductivity × 100%. Three samples were prepared for each sample. The average value was taken after measurement and the results were recorded in Table 1.

[0056] Table 1. Test results of construction fluidity, bond strength and thermal conductivity. Example 1 23.5 0.21 91.2 Example 2 24.3 0.24 90.8 Example 3 23.9 0.22 91.0 Example 4 25.1 0.17 80.5 Example 5 29.5 0.19 92.1 Example 6 21.0 0.27 94.2 Example 7 20.5 0.29 94.8 Example 8 20.0 0.30 95.5 Example 9 22.5 0.25 92.1 Example 10 21.8 0.28 93.5 Example 11 28.5 0.40 85.2 Example 12 18.3 0.15 88.7 Comparative Example 1 32.4 0.55 83.8 Comparative Example 2 40.0 0.11 55.8 As shown in Table 1, the dynamic viscosity of Examples 1-3 is above 23.5 Pa·s, the tensile shear strength is above 0.21 MPa, and the thermal conductivity retention rate is above 90.8%, which shows that the thermally conductive gel prepared in this application has good construction fluidity, bonding performance and thermal conductivity stability.

[0057] As shown in Table 1, the only difference between Examples 4 and 5 and Example 3 is that the specific ratio of spherical boron nitride and aluminum isopropoxide was changed in Example 4. A low amount of aluminum isopropoxide will result in discontinuous alumina shell, poor compatibility between exposed boron nitride and the matrix, and weak interfacial bonding. If the amount is too high, the alumina layer will be too thick, increasing the filler density and surface polarity, increasing the friction within the system, and affecting the performance.

[0058] As shown in Table 1, the only difference between Examples 6-10 and Example 3 is that in Examples 6-8, the boron nitride-alumina core-shell structure filler was modified according to the specified ratio, and the performance was improved; in Examples 9 and 10, the specified ratio was changed, and the performance improvement effect was reduced.

[0059] As shown in Table 1, the only difference between Examples 11 and 12 and Example 3 is that the limited ratio of organosilicon vinyl resin was changed in Example 11. If the amount of asymmetric monovinyl-terminated polydimethylsiloxane is too low, there will be too few suspended chains, too high crosslinking density, and large network rigidity. If the amount is too high, there will be too many suspended chains, insufficient crosslinking density, too loose network, and decreased overall performance.

[0060] As shown in Table 1, the only difference between Comparative Example 1 and Example 3 is that Comparative Example 1 only used vinyl-terminated polydimethylsiloxane, without adding asymmetric monovinyl-terminated polydimethylsiloxane, and without the suspension chain to adjust the crosslinking density, resulting in excessive crosslinking of the network and deterioration of performance.

[0061] As shown in Table 1, the only difference between Comparative Example 2 and Example 3 is that in Comparative Example 2, the boron nitride-alumina core-shell structure filler was replaced with a physically mixed spherical boron nitride and spherical alumina. The two fillers have no chemical bonding, resulting in high internal friction, numerous interface defects, and deteriorated performance.

[0062] This specific embodiment is merely an explanation of this application and is not intended to limit it. Based on the above description, those skilled in the art can make various changes and modifications without departing from the technical concept of this application. The technical scope of this application is not limited to the contents of the specification but must be determined according to the scope of the claims.

Claims

1. A lightweight, low-viscosity thermally conductive gel, characterized in that: The raw materials for preparation include the following components in parts by weight: 7-10 parts of silicone vinyl resin 0.15-0.25 parts of tackifier 0.6-1.0 parts of methyl hydrogen silicone oil Platinum catalyst 0.08-0.12 parts Inhibitor 0.05-0.15 parts 85-88 parts of boron nitride-alumina core-shell structured filler; The organosilicon vinyl resin includes vinyl-terminated polydimethylsiloxane and asymmetric monovinyl-terminated polydimethylsiloxane.

2. The lightweight, low-viscosity thermally conductive gel according to claim 1, characterized in that: The boron nitride-alumina core-shell structured filler was prepared using the following steps: Spherical boron nitride was dispersed in ethanol, and aluminum isopropoxide solution was added under heating and stirring conditions to adjust the pH of the system to alkaline. After hydrolysis by heating and stirring, the boron nitride-alumina core-shell structured filler was separated, washed, dried, and calcined to obtain the boron nitride-alumina core-shell structured filler.

3. The lightweight, low-viscosity thermally conductive gel according to claim 2, characterized in that: The D50 particle size of the spherical boron nitride is 10-20 μm.

4. The lightweight, low-viscosity thermally conductive gel according to claim 2, characterized in that: The mass ratio of the spherical boron nitride to aluminum isopropoxide is (5-10):

1.

5. The lightweight, low-viscosity thermally conductive gel according to claim 1, characterized in that: The boron nitride-alumina core-shell structured filler was modified and prepared using the following steps: Boron nitride-alumina core-shell structured filler and octaepoxy cage-type polysilsesquioxane were added to ethanol, ultrasonicated, heated and stirred to react. After the reaction was completed, the ethanol was recovered and dried to obtain the modified boron nitride-alumina core-shell structured filler.

6. The lightweight, low-viscosity thermally conductive gel according to claim 5, characterized in that: The mass ratio of the boron nitride-alumina core-shell structure filler to the octacyclic cage-type polysilsesquioxane is 1:(0.08-0.12).

7. The lightweight, low-viscosity thermally conductive gel according to claim 1, characterized in that: The mass ratio of the terminal vinyl polydimethylsiloxane to the asymmetric monovinyl-terminated polydimethylsiloxane is 1:(0.15-0.2).

8. The lightweight, low-viscosity thermally conductive gel according to claim 1, characterized in that: The thickener includes γ-glycidoxypropyltrimethoxysilane.

9. A preparation process for a lightweight, low-viscosity thermally conductive gel as described in any one of claims 1-8, characterized in that: Includes the following steps: Organosilicon vinyl resin and tackifier are mixed and stirred to obtain matrix premix; boron nitride-alumina core-shell structure filler is added to matrix premix in batches, and stirred under heating and vacuum conditions to obtain composite slurry; methyl hydrogen silicone oil and inhibitor are added and stirred; platinum catalyst is added and stirred; after stirring is stopped, the mixture is filtered and degassed to obtain lightweight low-viscosity thermally conductive gel.