Interface self-healing heat-conducting composite material and preparation method thereof

Abstract

The invention discloses an interface self-healing heat-conducting composite material and a preparation method thereof. The material comprises an interface functional layer and a bulk phase bearing layer which are attached to each other, the interface functional layer comprises a dynamic siloxane-based adhesive phase and a heat-conducting filler, the dynamic siloxane-based adhesive phase is formed by carboxyl-terminated or carboxyl-side-chain-containing polydimethylsiloxane and amino-terminated polydimethylsiloxane, and a dynamic network with reversible ionic bond and / or hydrogen bond interaction is constructed; the volume-phase bearing layer comprises a permanent cross-linked network formed by condensation curing of hydroxyl-terminated polydimethylsiloxane, a cross-linking agent and a condensation catalyst, and a heat-conducting filler. According to the technical scheme, self-healing of interface micro-gaps or micro-cracks can be achieved under the thermal triggering condition, interface heat conduction contact is recovered, meanwhile, material migration is inhibited, long-term stability of heat conduction performance is kept, and the heat dissipation material is suitable for heat dissipation application of high-reliability electronic devices.

Description

Technical Field

[0001] This invention relates to the field of thermally conductive composite materials technology, and in particular to an interface self-healing thermally conductive composite material and its preparation method. Background Technology

[0002] Self-healing materials are a class of functional materials capable of partially or completely recovering their performance after being damaged by external forces, developing cracks, or suffering structural defects, under external stimuli or their own intrinsic effects. These materials typically achieve their repair effect through reversible chemical bonds, physical interactions, or rearrangement of migratable components, playing a significant role in extending material lifespan and improving system reliability. As electronic devices evolve towards higher power, higher integration, and miniaturization, materials inevitably undergo thermal cycling, mechanical stress, and long-term aging during service. Self-healing materials, due to their potential failure mitigation capabilities, have gradually gained attention and have been introduced into various fields such as structural materials, coatings, and functional composite materials.

[0003] In the field of thermally conductive materials, especially thermally conductive composite materials and thermal interface materials used for heat dissipation in electronic devices, existing technologies have attempted to combine the concept of self-healing with thermally conductive filler systems. By introducing reversible reactive structures or reconfigurable networks into the polymer matrix, the material can restore its continuity under certain conditions after cracking or damage. Simultaneously, to meet heat dissipation requirements, existing technologies typically employ high-filler-volume inorganic thermally conductive fillers to construct heat conduction pathways, supplemented with silicone rubber or similar polymers as the matrix to achieve a certain degree of flexibility and processing adaptability. These approaches improve the overall durability and thermal conductivity of the material to some extent, enabling the recovery of the material's intrinsic properties under laboratory conditions or specific operating conditions.

[0004] However, in practical applications, the failure of thermally conductive composite materials often occurs first at the interface between the composite material and the component being cooled, rather than within the bulk material. On the one hand, thermal cycling and assembly stress can easily introduce microvoids or microcracks at the interface, leading to a decrease in effective contact area and a rapid increase in interfacial thermal resistance. On the other hand, highly filled thermally conductive systems may also experience component migration or deformation during long-term use, further weakening interfacial stability. Existing technologies mostly focus on the overall self-healing capability of the material, emphasizing the healing of bulk cracks or the restoration of macroscopic properties. However, for the critical failure mode of interfacial contact degradation, there is a lack of targeted structural design and functional regulation, making it difficult to achieve stable maintenance of interfacial thermal conductivity without introducing new reliability risks. This situation limits the further application of self-healing thermally conductive materials in high-reliability electronic heat dissipation scenarios. Summary of the Invention

[0005] This application provides an interface self-healing thermally conductive composite material, aiming to solve the technical problem that existing thermally conductive composite materials are prone to micro-voids or micro-cracks at the interface during service, leading to increased interface thermal resistance and difficulty in long-term stable recovery.

[0006] The present invention is achieved as follows: a self-healing thermally conductive composite material, the self-healing thermally conductive composite material comprising an interface functional layer and a bulk support layer that are bonded together, the interface functional layer constituting the contact interface of the self-healing thermally conductive composite material. The interface functional layer comprises the following raw materials in parts by weight: 20-55 parts of dynamic siloxane adhesive phase; 45-80 parts of thermally conductive filler; The dynamic siloxane adhesive phase is formed by the reaction or association of carboxyl-terminated or carboxyl-containing polydimethylsiloxane with amino-terminated polydimethylsiloxane to form a dynamic network with reversible ionic and / or hydrogen bond interactions; the thermally conductive filler of the interface functional layer is selected from alumina, boron nitride or a combination thereof. The bulk support layer comprises the following raw materials in parts by weight: 10-35 copies of permanent network substrate; 65-90 parts of thermally conductive filler; The permanent network matrix is ​​formed by a condensation curing reaction of hydroxyl-terminated polydimethylsiloxane, a crosslinking agent and a condensation catalyst to form a permanent crosslinked network. The crosslinking agent is selected from silicates, alkoxysilanes or combinations thereof. The thermally conductive filler of the bulk phase support layer is selected from alumina, boron nitride or combinations thereof.

[0007] Optionally, in the dynamic siloxane adhesive phase, the molar ratio of carboxyl to amino functional groups n(COOH):n(NH2) is 0.85~1.15.

[0008] Optionally, the interface functional layer further includes 1 to 10 parts of a siloxane thickening component containing urea groups and / or urethane groups.

[0009] Optionally, the thermally conductive filler of the interface functional layer includes spherical alumina and boron nitride, wherein the spherical alumina is 30-50 parts and the boron nitride is 15-30 parts, and the boron nitride includes spherical boron nitride and / or plate-shaped boron nitride.

[0010] Optionally, the boron nitride includes plate-shaped boron nitride, wherein the average particle size D50 of the plate-shaped boron nitride is 5~30μm and the thickness is less than 1μm.

[0011] Optionally, at least a portion of the thermally conductive filler in the interface functional layer is surface modified with a silane coupling agent, wherein the silane coupling agent is selected from aminopropyltriethoxysilane, glycidyltrimethoxysilane or a combination thereof, and the amount of the silane coupling agent is 0.1 to 2.0 wt% of the mass of the modified filler.

[0012] Optionally, the permanent network matrix comprises 9 to 29 parts of hydroxyl-terminated polydimethylsiloxane, 1 to 5.5 parts of crosslinking agent, and 0.02 to 0.5 parts of condensation catalyst; the crosslinking agent comprises tetraethoxysilane and / or methyltriethoxysilane.

[0013] Optionally, the thickness of the interface functional layer is 5~80μm, and the thickness of the bulk phase carrier layer is 50~2000μm.

[0014] This invention also provides a method for preparing a self-healing thermally conductive composite material, comprising the following steps: S1. Premix carboxyl-terminated or carboxyl-containing polydimethylsiloxane with amino-terminated polydimethylsiloxane at 40~80℃ for 10~40min to form a dynamic network composed of ionic bonds and / or hydrogen bonds. Then add the thermally conductive filler for the interface functional layer in batches. After each batch is added, disperse it by alternating low-shear and high-shear mixing until the slurry is uniform. Then perform vacuum degassing to obtain the interface functional layer slurry. S2. Hydroxyl-terminated polydimethylsiloxane is premixed with a crosslinking agent, then added to the thermally conductive filler for the bulk support layer. After mixing evenly and vacuum degassing, a condensation catalyst is added and rapidly mixed to obtain the bulk support layer slurry. S3. The interface functional layer slurry is coated on the surface of the substrate or release film to form an interface functional layer. When the interface functional layer reaches a semi-gel state, the bulk carrier layer slurry is laid on the interface functional layer. The two layers are tightly bonded by rolling or lamination, and then cured at room temperature for 4~24h. During the curing process, interpenetration or gradient transition is formed in the interface area. At the same time, the dynamic network of the interface functional layer is further stabilized, and the condensation curing reaction of the bulk carrier layer forms a permanent cross-linked network. Then, it is cured at 60~120℃ for 1~4h to enhance the stability of the filler network and obtain an interface self-healing thermally conductive composite material. The semi-gel state refers to the state in which the dynamic network in the interface functional layer is formed until the ratio of the energy storage modulus G' to the loss modulus G'' is 0.8 to 1.2, and the material surface is not sticky but still has rearrangement properties; The alternating low-shear and high-shear mixing refers to the process of first mixing at a low shear rate to slowly disperse the packing in the dynamic network during the packing dispersion process, and then mixing at a high shear rate to break up the packing agglomerates. This alternation is carried out to maintain the integrity of the dynamic network while ensuring uniform dispersion of the packing.

[0015] Optionally, before adding the thermally conductive filler in S1 and / or S2, the thermally conductive filler is pretreated, the pretreatment including: The thermally conductive filler is dried under vacuum at 110-140℃ for 2-6 hours to remove adsorbed water; and / or, the thermally conductive filler is subjected to surface modification treatment with a silane coupling agent, wherein the surface modification treatment with the silane coupling agent includes dispersing the thermally conductive filler in anhydrous ethanol or isopropanol, adding 0.1-2.0 wt% of a silane coupling agent, stirring and reacting for 0.5-2 hours, then filtering, washing and drying, wherein the silane coupling agent is selected from aminopropyltriethoxysilane, glycidyltrimethoxysilane or a combination thereof, and wt% is relative to the mass of the filler being modified.

[0016] The technical solution provided in this application constructs a thermally conductive composite material into a two-layer structure that adheres to each other, each layer undertaking different functions: maintaining interfacial contact and supporting the overall shape. The interfacial functional layer is composed of a dynamic siloxane adhesive phase and thermally conductive fillers of alumina and / or boron nitride. The dynamic siloxane adhesive phase is formed by the reaction or association of carboxyl-terminated or carboxyl-containing polydimethylsiloxane with amino-terminated polydimethylsiloxane, creating a dynamic network of reversible ionic and / or hydrogen bond interactions within this layer. This dynamic network exhibits segment rearrangement characteristics in the service thermal environment. When microscale voids or microcracks appear at the contact interface due to thermal cycling and assembly stress, the interfacial layer can undergo bond dissociation and reassociation under local stress-driven and thermally activated conditions. This promotes deformation coordination and interface rewetting around the defects, causing the gaps that originally led to a decrease in contact area to tend to close. The interface functional layer also contains a high proportion of thermally conductive fillers. During the closing process, the continuity of contact between fillers and between fillers and the matrix is ​​restored, thereby turning the heat conduction path from a discontinuous state back into a continuous state. The tendency of thermal resistance to increase at the interface is suppressed and is recoverable.

[0017] The bulk support layer consists of a permanent network matrix and a thermally conductive filler. The permanent network matrix is ​​formed by the condensation and curing of hydroxyl-terminated polydimethylsiloxane under the action of silicate ester and / or alkoxysilane crosslinking agents and condensation catalysts to form a permanent crosslinked network. This permanent crosslinked structure provides high dimensional stability and creep resistance, constraining and supporting the rearrangement deformation of the interfacial functional layers. This prevents excessive flow or deformation accumulation in the thermally conductive composite material under long-term compression and thermal cycling conditions, thereby reducing interfacial contact degradation caused by material migration. The composite structure formed by the two layers allows the rearrangement capability of the interfacial layer to focus on reducing contact interface defects, while the bulk layer maintains the overall shape and continuity of the thermally conductive filler skeleton as a stable network. The complementary function of the two layers enables the thermally conductive composite material to maintain a stable contact state and continuity of the thermal conduction path after thermal cycling and mechanical loading, thus achieving the goal of long-term stable interfacial thermal resistance. Detailed Implementation

[0018] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0019] In this invention, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Furthermore, the term "and / or" throughout the text includes three solutions; taking A and / or B as an example, it includes technical solution A, technical solution B, and a technical solution that simultaneously satisfies A and B. Additionally, the technical solutions of various embodiments can be combined with each other, provided that they are feasible for those skilled in the art. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0020] The raw materials used in the following examples and comparative examples, and their sources, are as follows: Raw materials for the interface functional layer: carboxyl-terminated polydimethylsiloxane (PDMS-COOH, carboxyl content 0.3 mmol / g, molecular weight approximately 5000, purchased from Gelest Corporation, product DMS-C31); amino-terminated polydimethylsiloxane (PDMS-NH2, amino content 0.35 mmol / g, molecular weight approximately 4500, purchased from Gelest Corporation, product DMS-A12); urea-containing siloxane thickening component (prepared by reacting hydroxyl-terminated PDMS with hexamethylene diisocyanate at 70°C for 3 hours, molecular weight approximately 10000); spherical alumina (average particle size D50 = 12 μm, purity 99.6%, purchased from Showa Denko Corporation, product Alunabeads). CB-A20); spherical boron nitride (average particle size D50=8μm, purity 99.2%, purchased from Dandong Chemical Research Institute product DH-BN05); plate-shaped boron nitride (average particle size D50=15μm, thickness approximately 0.5μm, purchased from Momentive product PT620); aminopropyltriethoxysilane (APTES, purity 98%, purchased from Sigma-Aldrich product A3648); glycidyltrimethoxysilane (GPTMS, purity 97%, purchased from Sigma-Aldrich product 440167); anhydrous ethanol (analytical grade, purity 99.7%, purchased from Sinopharm Chemical Reagent Co., Ltd.).

[0021] Raw materials for the bulk support layer: hydroxyl-terminated polydimethylsiloxane (PDMS-OH, hydroxyl content 0.2 mmol / g, molecular weight approximately 18000, viscosity approximately 10000 mPa·s, purchased from Dow Corning DC-3481 or Shin-Etsu Chemical Co., Ltd. KE-45RTV); tetraethoxysilane (TEOS, purity 98%, purchased from Sinopharm Chemical Reagent Co., Ltd.); methyltriethoxysilane (MTES, purity 97%, purchased from Gelest SIM6476.0); dibutyltin dilaurate (DBTDL, tin content 19%, purchased from Sigma-Aldrich); spherical alumina and spherical boron nitride (specifications same as fillers for the interface layer); hydrophobic fumed silica (specific surface area 200 m² / g, purchased from Evonik Aerosil R972).

[0022] Auxiliary materials: silicone release paper (silicone-coated release paper, 100μm thick, purchased from commercial products); PET release film (double-sided release, 50μm thick, purchased from commercial products).

[0023] The trade names and manufacturers of the above raw materials are merely examples. Those skilled in the art can use other commercially available products or self-made raw materials that meet the same or similar specifications as substitutes. All raw materials should be stored in a dry environment before use. Raw materials that are sensitive to moisture (such as crosslinking agents and catalysts) should be stored in sealed containers. The filler should be vacuum dried before use to remove adsorbed water. The formulation ratios in the following examples are preferred ranges, and those skilled in the art can make appropriate adjustments within the scope defined by this invention.

[0024] Example 1 Formulation of Example 1: The self-healing thermally conductive composite material prepared in this example includes an interface functional layer and a bulk support layer. The interface functional layer, by weight, comprises: 18 parts PDMS-COOH, 17 parts PDMS-NH2, 2 parts urea-containing siloxane thickening component, 35 parts spherical alumina, and 15 parts spherical boron nitride, including 3 parts lamellar boron nitride and 12 parts spherical boron nitride. The bulk support layer, by weight, comprises: 18 parts PDMS-OH, 2.5 parts TEOS, 1.2 parts MTES, 0.08 parts DBTDL, 50 parts spherical alumina, 25 parts spherical boron nitride, and 0.8 parts hydrophobic fumed silica. The molar ratio of carboxyl to amino functional groups (n(COOH):n(NH2)) of PDMS-COOH to PDMS-NH2 in the interface layer is approximately 1.03:1. The permanent network matrix in the bulk layer totals 21.78 parts, including 18 parts of PDMS-OH, 3.7 parts of crosslinking agent (2.5 parts of TEOS + 1.2 parts of MTES), and 0.08 parts of catalyst.

[0025] Filler pretreatment: The required spherical alumina and spherical boron nitride, including plate-like boron nitride, were placed separately in enamel trays and dried in a vacuum drying oven at 120℃ and 50 Pa for 4 hours. After cooling to room temperature, they were sealed for later use. 50g of the dried spherical alumina was then subjected to surface modification: The filler was dispersed in 200 mL of anhydrous ethanol, and 0.7g of APTES (1.4 wt% relative to the filler mass) was added. The mixture was magnetically stirred at room temperature for 1 hour, with ultrasonic treatment for 5 minutes every 15 minutes to promote dispersion. After the reaction was complete, the mixture was filtered through a Buchner funnel, washed twice with 50 mL of anhydrous ethanol, and the filter cake was dried in a vacuum drying oven at 80℃ for 3 hours to obtain surface-modified spherical alumina.

[0026] Preparation of the interfacial functional layer slurry: 18g of PDMS-COOH and 17g of PDMS-NH2 were added to the mixing cup of a planetary mixer (500 mL capacity) and premixed at 150 rpm for 25 min under a constant temperature water bath at 60℃. During the premixing process, the slurry color gradually changed from transparent to slightly milky white, and the viscosity increased significantly. Short filaments could be drawn when lifted with a glass rod, indicating that the carboxyl and amino groups formed a dynamic network through ionic interactions and hydrogen bonding. 2g of urea-containing siloxane thickening component was added, and stirring was continued at 150 rpm for 10 min to ensure uniform mixing. The mixer was cooled to room temperature, and then the dried and modified filler was added in three batches: The first batch consisted of 20g of spherical alumina (containing some modified filler) and 5g of spherical boron nitride. Mixing was performed at a low shear rate of 80 rpm for 15 minutes to slowly disperse the filler in the dynamic network, followed by high shear mixing at 600 rpm for 8 minutes to break up agglomerates. The second batch consisted of 15g of spherical alumina and 5g of spherical boron nitride (both spherical), and the low-shear-high-shear alternating mixing process was repeated. The third batch consisted of the remaining spherical alumina and 3g of flake boron nitride, and was similarly mixed alternately until the slurry was homogeneous and free of significant agglomeration. The slurry was transferred to a vacuum degassing machine at a vacuum of -0.09 MPa for 12 minutes. During degassing, bubbles on the slurry surface gradually broke and disappeared, resulting in a uniform and fine interfacial functional layer slurry. This slurry was then sealed and stored at room temperature.

[0027] Preparation of the bulk carrier layer slurry: 18g of PDMS-OH and the mixed crosslinking agent, namely 2.5g of TEOS and 1.2g of MTES, were pre-mixed evenly and added to another mixing cup. The mixture was stirred at 200 rpm for 15 min to ensure thorough mixing. Then, the bulk layer filler was added in two batches: the first batch consisted of 30g of spherical alumina and 15g of spherical boron nitride, mixed at 100 rpm under low shear for 10 min, followed by mixing at 500 rpm under high shear for 8 min; the second batch consisted of the remaining 20g of spherical alumina, 10g of spherical boron nitride, and 0.8g of hydrophobic fumed silica. This alternating mixing process was repeated until the slurry was homogeneous. The slurry was then degassed under vacuum for 10 min. Approximately 5 min before the coating operation, after degassed, 0.08g of DBTDL catalyst was added to the slurry and rapidly stirred at 300 rpm for 3 min to ensure uniform catalyst dispersion, thus obtaining the bulk carrier layer slurry. Note that the slurry should be used as soon as possible to prevent the condensation reaction triggered by the catalyst from causing the slurry viscosity to rise rapidly.

[0028] Layered lamination and curing: Pre-cut silicone paper (80 mm × 80 mm) was laid flat on a clean glass plate. The interface functional layer slurry was evenly coated onto the silicone paper surface using a scraper. The wet film thickness was controlled to approximately 45 μm by adjusting the scraper gap. Considering shrinkage after curing, the final dry film thickness was approximately 30 μm. After coating, the sample was placed in a room temperature environment (25°C) and allowed to stand. To determine whether the interface layer had reached a semi-gel state, an appearance test was performed every 5 minutes during the standing process: the surface of the interface layer was lightly touched with a powder-free glove. When the surface was not sticky and had no residue, but the material could still slowly flow when the edge was gently pushed with a scraper, it was considered to be in a semi-gel state. In this embodiment, the interface layer reached a semi-gel state after approximately 18 minutes of standing at room temperature. Meanwhile, a small amount of the interface layer slurry was taken and subjected to dynamic rheological testing using a TA Instruments Discovery HR-2 rheometer at 25°C, 1 Hz frequency, and 1% strain. The storage modulus G' was measured to be approximately 1850 Pa, the loss modulus G'' was approximately 1720 Pa, and the calculated G' / G'' ratio was approximately 1.08. The material exhibited a viscoelastic equilibrium state, verifying the accuracy of the semi-gel state assessment.

[0029] After the interface layer reaches a semi-gel state, the bulk carrier layer slurry is immediately applied to the interface layer surface using a scraper, controlling the wet film thickness to be approximately 650 μm, and the cured thickness to be approximately 500 μm. After application, the composite material is rolled once using a manual roller press at a pressure of 0.3 MPa and a speed of approximately 1 m / min to ensure tight adhesion between the two layers and remove any air bubbles that may be trapped between the interfaces. After rolling, the sample is kept at room temperature (25°C) for 12 hours of curing. During this period, the dynamic network of the interface functional layer further stabilizes, the condensation curing reaction of the bulk carrier layer gradually proceeds, and PDMS-OH undergoes a condensation reaction with the hydrolyzed crosslinking agent to form a permanent crosslinked network. Simultaneously, in the interface region between the two layers, the dynamic network of the interface layer and the permanent network of the bulk layer interpenetrate each other, forming an interpenetrating or gradient transition structure. After room temperature curing, the sample is transferred to an oven for post-curing at 80°C for 2 hours to enhance the stability of the filler network and further increase the crosslinking density. After post-curing, the sample was allowed to cool naturally to room temperature. The silicone paper was then carefully removed to obtain a self-healing thermally conductive composite material with a thickness of approximately 530 μm, of which the interface functional layer was approximately 30 μm thick and the bulk support layer was approximately 500 μm thick.

[0030] Sample preparation and storage: The prepared materials were cut into samples of different sizes for subsequent performance testing. Samples for thermal conductivity and interfacial thermal resistance testing were cut into 25.4 mm diameter discs; samples for interlaminar peel strength testing were cut into 25 mm × 100 mm strips; and samples for SEM cross-sectional observation were cut into 10 mm × 10 mm pieces. All samples were stored in a desiccator before testing to prevent moisture absorption.

[0031] Example 2 The formulation composition of Example 2: The interface functional layer, by weight, includes: 20 parts PDMS-COOH, 23 parts PDMS-NH2, 45 parts spherical alumina, and 25 parts spherical boron nitride (all spherical, excluding flakes). In this example, the molar ratio of carboxyl to amino functional groups, n(COOH):n(NH2), is approximately 0.87:1. The bulk phase support layer, by weight, includes: 9 parts PDMS-OH, 0.9 parts TEOS, 0.4 parts MTES, 0.02 parts DBTDL, 60 parts spherical alumina, and 30 parts spherical boron nitride. The total permanent network matrix in the bulk phase layer is 10.32 parts, including 9 parts PDMS-OH, 1.3 parts crosslinking agent, and 0.02 parts catalyst.

[0032] Preparation Method: The preparation method of Example 2 is basically the same as that of Example 1, with the following specific differences. In the filler pretreatment stage, all fillers were only vacuum dried at 125℃ and 80 Pa for 3 hours, without surface modification. In the preparation of the interface functional layer slurry, 20g of PDMS-COOH and 23g of PDMS-NH2 were premixed at 50℃ for 15 minutes without adding any thickening components. The filler was added directly in two batches, alternating between low-shear mixing at 100 rpm for 12 minutes and high-shear mixing at 550 rpm for 6 minutes after each batch was added, followed by vacuum degassing for 10 minutes. In the preparation of the bulk carrier layer slurry, 9g of PDMS-OH and 1.3g of mixed crosslinking agent (0.9 parts TEOS + 0.4 parts MTES) were premixed for 20 minutes, then added to the filler in two batches and mixed alternately. Vacuum degassing was performed for 8 minutes, and immediately after degassing, 0.02g of DBTDL catalyst was added and rapidly stirred for 2 minutes.

[0033] Layered lamination and curing: The interfacial functional layer slurry was coated onto silicone paper, with a wet film thickness of approximately 60 μm and a cured thickness of approximately 40 μm. After standing at room temperature for approximately 25 min, the interfacial layer reached a semi-gel state, at which point rheological testing showed a G' / G'' ratio of approximately 0.92. The bulk carrier layer slurry was immediately applied, with a wet film thickness of approximately 80 μm and a cured thickness of approximately 60 μm. After rolling under a pressure of 0.2 MPa, it was cured at room temperature for 18 h, and then at 100 °C for 1.5 h. This yielded an interfacial self-healing thermally conductive composite material with a total thickness of approximately 100 μm, of which the interfacial functional layer was approximately 40 μm thick and the bulk carrier layer was approximately 60 μm thick.

[0034] Example 3 The formulation composition of Example 3: The interface functional layer, by weight, includes: 24 parts PDMS-COOH, 21 parts PDMS-NH2, 5 parts urea-containing siloxane thickening component, 30 parts spherical alumina, and 20 parts spherical boron nitride, of which 6 parts are plate-like boron nitride and 14 parts are spherical boron nitride. In this example, the molar ratio of carboxyl to amino functional groups, n(COOH):n(NH2), is approximately 1.14:1. The bulk phase support layer, by weight, includes: 28 parts PDMS-OH, 4.0 parts TEOS, 1.2 parts MTES, 0.3 parts DBTDL, 55 parts spherical alumina, 20 parts spherical boron nitride, and 1.5 parts hydrophobic fumed silica. The permanent network matrix in the bulk phase layer totals 33.5 parts, including 28 parts PDMS-OH, 5.2 parts crosslinking agent, and 0.3 parts catalyst.

[0035] Preparation method: The preparation method of Example 3 is basically the same as that of Example 1, with the following specific differences. In the filler pretreatment stage, all spherical alumina and all plate-like boron nitride used in the interface layer underwent surface modification treatment: 30g of spherical alumina and 6g of plate-like boron nitride were dispersed separately in their respective anhydrous ethanol solutions. 0.6g of GPTMS was added to the spherical alumina, which is 2.0 wt% relative to the filler mass; 0.06g of APTES was added to the plate-like boron nitride, which is 1.0 wt% relative to the filler mass. Both were stirred and reacted at room temperature for 1.5h, then filtered, washed, and dried for later use. For the preparation of the interface layer slurry, 24g of PDMS-COOH and 21g of PDMS-NH2 were premixed at 75℃ for 35min. A more significant increase in slurry viscosity was observed. After adding 5g of urea-containing siloxane thickening component, mixing was continued for 15min. Then, the filler was added in three batches. During the alternating shear mixing process, the low shear stage was carried out at 60rpm for 20min, and the high shear stage at 650rpm for 10min. Vacuum degassing was performed for 15min. For the preparation of the bulk phase support layer slurry, 28g of PDMS-OH and 5.2g of mixed crosslinking agent were premixed for 10min. The filler was added in two batches, and vacuum degassing was performed for 12min. Within 3min after degassing, 0.3g of DBTDL catalyst was added and rapidly stirred for 4min.

[0036] Layered lamination and curing: The interfacial functional layer slurry was coated onto a PET release film, with a wet film thickness of approximately 110 μm and a cured thickness of approximately 75 μm. After standing at room temperature for approximately 12 minutes, it reached a semi-gel state, and rheological testing showed that G' / G'' was approximately 1.15. The bulk carrier layer slurry was immediately applied, with a wet film thickness of approximately 2700 μm and a cured thickness of approximately 1900 μm. After rolling under a pressure of 0.5 MPa, it was cured at room temperature for 8 hours, and then cured at 60°C for 4 hours. A self-healing thermally conductive interfacial composite material with a total thickness of approximately 1975 μm was obtained, of which the interfacial functional layer thickness was approximately 75 μm and the bulk carrier layer thickness was approximately 1900 μm.

[0037] Comparative Example 1 The formulation composition of Comparative Example 1: This comparative example does not employ a layered structure. Instead, the formulations of the interface functional layer and the bulk support layer are mixed into a single homogeneous formulation to verify the necessity of the layered structure design. The single formulation, by weight, includes: 9 parts PDMS-COOH, 8.5 parts PDMS-NH2, 9 parts PDMS-OH, 1.25 parts TEOS, 0.6 parts MTES, 0.04 parts DBTDL, 42.5 parts spherical alumina, and 20 parts spherical boron nitride. This formulation is obtained by normalizing the mass ratio of the interface layer and bulk layer formulations from Example 1. The dynamic siloxane adhesive phase (PDMS-COOH and PDMS-NH2) accounts for approximately 17.5 parts, the permanent network matrix (PDMS-OH, crosslinking agent, catalyst) accounts for approximately 10.89 parts, and the thermally conductive filler totals 62.5 parts.

[0038] Preparation method: 9g PDMS-COOH, 8.5g PDMS-NH2, and 9g PDMS-OH were added to the mixing cup of a planetary mixer and premixed at 150 rpm for 20 min at 60℃ to ensure thorough mixing of the carboxyl-amino dynamic network with the hydroxyl silicone oil. After cooling to room temperature, 1.85g of mixed crosslinking agent (1.25 parts TEOS + 0.6 parts MTES) was added and stirred at 200 rpm for 10 min. Then, vacuum-dried fillers were added in two batches: the first batch consisted of 30g spherical alumina and 10g spherical boron nitride, and the second batch consisted of 12.5g spherical alumina and 10g spherical boron nitride. After each batch, low-shear and high-shear alternating mixing was performed, followed by vacuum degassing for 10 min. After degassing, 0.04g DBTDL catalyst was added and rapidly stirred for 3 min to obtain a homogeneous slurry.

[0039] Molding and Curing: The slurry was coated onto silicone paper, and the wet film thickness was controlled to be approximately 700 μm using a doctor blade. After curing, the thickness was approximately 530 μm, similar to the total thickness in Example 1. The sample was cured at room temperature for 12 h, and then cured at 80 °C for 2 h. After curing, the silicone paper was removed, yielding a single-layer uniform thermally conductive composite material with a thickness of approximately 530 μm.

[0040] Comparative Example 2 Comparative Example 2 Formulation: This comparative example uses the exact same layered formulation as Example 1, but the interlayer composite process is changed; the composite is not performed in a semi-gel state to compare and verify the importance of the semi-gel state composite process. The interface functional layer, by weight, includes: 18 parts PDMS-COOH, 17 parts PDMS-NH2, 2 parts urea-containing siloxane thickening component, 35 parts spherical alumina, and 15 parts spherical boron nitride, of which 3 parts are plate-like boron nitride. The bulk carrier layer, by weight, includes: 18 parts PDMS-OH, 2.5 parts TEOS, 1.2 parts MTES, 0.08 parts DBTDL, 50 parts spherical alumina, 25 parts spherical boron nitride, and 0.8 parts hydrophobic fumed silica. The formulation is completely identical to that of Example 1.

[0041] Preparation method: The preparation process of the interface functional layer slurry and the bulk carrier layer slurry is exactly the same as in Example 1, except for the layered composite process. The interface functional layer slurry is coated onto silicone paper, and the wet film thickness is controlled to be approximately 45 μm. After coating, without waiting for the interface layer to reach a semi-gel state, the bulk carrier layer slurry is directly applied while the interface layer is still in a liquid flow state, i.e., within about 2 minutes after coating, resulting in a wet film thickness of approximately 650 μm. Since both slurries are in a liquid flow state during composite, significant mutual mixing and diffusion occur between the two slurries during the rolling process, resulting in mixing at the boundary area. The sample is cured at room temperature for 12 h, and then cured at 80 °C for 2 h. After curing, the silicone paper is removed, yielding a material with a thickness of approximately 530 μm.

[0042] Performance testing methods Thermal conductivity testing: The thermal conductivity of the samples was tested using the steady-state heat flow method according to ASTM D5470 standard. The samples were cut into circular pieces with a diameter of 25.4 mm, and the sample thickness was measured to an accuracy of 0.01 mm. The samples were placed between two aluminum hot blocks in the thermal conductivity tester, with a surface roughness Ra of 1.0 μm. Under a contact pressure of 0.2 MPa, the hot-end temperature was set to 50°C and the cold-end temperature to 30°C. After the system reached thermal equilibrium, the heat flux density q passing through the sample was measured using a heat flow sensor, and the temperature difference ΔT across the sample was measured using a thermocouple. The thermal conductivity λ = q·d / ΔT was calculated according to Fourier's law of thermal conductivity, where d is the sample thickness. Each sample was tested in triplicate, and the average value was taken as the test result.

[0043] Interfacial thermal resistance test: The interfacial thermal resistance of the samples was tested using a steady-state method. The sample was placed between two aluminum blocks with a surface roughness Ra of 1.0 μm. Under a contact pressure of 0.2 MPa, the hot end temperature was set to 50℃ and the cold end temperature to 30℃, and the total thermal resistance Rtotal of the system was measured. The interfacial thermal resistance on one side was calculated using the formula Rinterface = (Rtotal - d / λ - Rref) / 2, where d is the sample thickness, λ is the thermal conductivity, and Rref is the inherent thermal resistance of the reference aluminum block, which was pre-calibrated to be 0.05 K·cm² / W. Since the sample is in contact with the aluminum blocks on both sides, there are two interfaces; the interfacial thermal resistance on one side is half of the total interfacial thermal resistance. Each sample was tested in parallel three times, and the average value was taken. The unit of interfacial thermal resistance is K·cm² / W.

[0044] Interfacial thermal resistance self-healing performance test: This test is used to evaluate the material's ability to recover interfacial thermal resistance after thermal cycling. First, the initial interfacial thermal resistance of the sample is tested according to the method described above, denoted as R0. Then, the sample is assembled with an aluminum block into a test assembly and placed in a thermal cycling chamber for thermal cycling tests from -40℃ to 150℃. Each cycle includes holding at -40℃ for 30 min, a heating process of 10 min, holding at 150℃ for 30 min, and a cooling process of 10 min, totaling 80 min as one cycle. After 50 thermal cycles, the assembly is removed, allowed to cool naturally at room temperature for 2 h, and the interfacial thermal resistance is retested, denoted as R1. The increase rate of thermal resistance after thermal cycling is calculated as ΔR1 = (R1 - R0) / R0 × 100%. Subsequently, the sample undergoes thermally triggered repair: the assembly is heated to 80℃ and a pressure of 0.1 MPa is applied, held for 1 h, simulating the material's self-healing process at operating temperature. After repair, the assembly is cooled to room temperature, and the interfacial thermal resistance is tested again, denoted as R2. Calculate the thermal resistance recovery rate after repair, η = (R1-R2) / (R1-R0) × 100%. If η is greater than 70%, the material is considered to have good interface self-healing ability. Repeat the above thermal cycling-repair process 3 times to evaluate the material's repeatability for repair.

[0045] Oil penetration performance test: The sample was cut into a 50 mm × 50 mm square with a thickness of approximately 0.5 mm, and the initial mass m0 was accurately weighed. The sample was sandwiched between two 60 mm × 60 mm quantitative filter papers, placed between two glass plates, and a 500 g weight was applied to the upper glass plate, corresponding to a pressure of approximately 0.02 MPa. The entire assembly was placed in a 150℃ oven for 100 h. After removal and cooling to room temperature, the oil stains on the filter paper were observed and photographed, and the oil stain area S was measured using image analysis software. At the same time, the sample mass m1 was weighed, and the mass loss rate Δm = (m0 - m1) / m0 × 100% was calculated. The oil penetration rate is defined as the ratio of the oil stain area to the sample area, i.e., oil penetration rate = S / 2500 mm² × 100%. The lower the oil penetration rate, the better the oil penetration resistance of the material.

[0046] Interlayer peel strength test: Following ASTM D1876, the T-peel method was used to test the peel strength between the interface functional layer and the bulk support layer. The sample was cut into strips of 25 mm × 100 mm. At one end of the sample, the interface layer and the bulk layer were carefully separated by approximately 25 mm using a sharp blade, taking care not to damage either layer. The separated ends were clamped in the upper and lower fixtures of a universal tensile testing machine, and tension was applied at a constant speed of 50 mm / min. The force-displacement curve during the peeling process was recorded. The average force F during the stable peeling phase was taken, and the peel strength P = F / W was calculated, where W is the sample width of 25 mm. Five parallel samples were tested for each type of sample. After removing the maximum and minimum values, the average of the remaining three values ​​was taken as the test result, expressed in N / mm.

[0047] SEM cross-sectional morphology observation: The sample was cut into 10 mm × 10 mm pieces, immersed in liquid nitrogen for 5 min to allow it to cool and become brittle, and then rapidly fractured to obtain the cross-section. The fractured sample was fixed on the SEM sample stage with the cross-section facing upwards, and a gold film of approximately 10 nm thickness was sprayed onto the sample surface to enhance conductivity. The cross-sectional morphology was observed using a scanning electron microscope (FEIQuanta 250 FEG) at an accelerating voltage of 10 kV and a working distance of 10 mm. The interface region between the functional layer and the bulk carrier layer was observed in detail, and the presence of obvious boundary lines, cracks, or gaps at the interface, as well as the distribution of fillers in the two layers, were recorded. SEM images of typical areas were taken at magnifications of 500×, 2000×, and 5000× to analyze the formation of interpenetrating or gradient transition structures at the interface.

[0048] Rheological characterization of the semi-gel state: To verify the accuracy of the semi-gel state determination, during the preparation of the examples, a small amount of interfacial functional layer slurry, approximately 2 mL, was taken and subjected to dynamic rheological testing using a rotational rheometer. The slurry was coated onto the parallel plate fixture of the rheometer, with a plate spacing of 1 mm. The test temperature was 25°C, the frequency was 1 Hz, and the strain was controlled within the linear viscoelastic region, typically 1%. The changes in storage modulus G' and loss modulus G'' over time were monitored, and the time corresponding to the intersection of G' and G'' was recorded. At this point, G' / G'' is approximately equal to 1, indicating that the material has entered the semi-gel state. This test data is used to guide the control of the time window in the composite process during actual production.

[0049] Test results and data The performance of the samples prepared in Examples 1 to 3 and Comparative Examples 1 to 2 was tested according to the above test method, and the test results are as follows.

[0050] Table 1: Summary of Formulation Parameters for Examples and Comparative Examples Note: Comparative Example 1 uses a single-layer uniform formulation with no layered structure; Comparative Example 2 uses the same layered formulation as Example 1, but the interface layer is in a liquid state rather than a semi-gel state.

[0051] Table 2: Performance test data of examples and comparative examples Note: Comparative Example 1 is a single-layer structure with no interlayer interface, therefore interlayer peel strength is not tested. Thermal resistance recovery rate η = (R1-R2) / (R1-R0) × 100%.

[0052] SEM Cross-sectional Morphology Observation Results: The cross-sectional morphology of Example 1 and Comparative Example 2 was observed using a scanning electron microscope, revealing significant differences. The SEM image of Example 1, at 5000× magnification, shows no obvious boundary line or cracks at the interface between the functional layer and the bulk support layer, instead exhibiting a transition zone approximately 15 to 20 μm wide. Within this transition zone, the filler distribution of the two layers shows a continuous gradient change. The lamellar boron nitride portion of the interface layer extends into the transition zone, and a small amount of spherical filler from the bulk layer is also distributed in the transition zone, indicating that interpenetration occurred between the two layers during curing. At 2000× magnification, a continuous network of polymer matrix was observed between the two layers, without obvious breaks or gaps, confirming the formation of an interpenetrating or gradient transition structure in the interface region. In contrast, the SEM image of Comparative Example 2 shows a clear boundary line in the interface region, with locally visible gaps approximately 2 to 5 μm wide. The bonding between the two layers relies mainly on physical contact, lacking an effective interpenetrating structure. Near the boundary, uneven distribution and aggregation of fillers were observed in some areas, indicating disordered miscibility of the two slurry layers during the liquid composite process, which disrupted the expected functional zoning. SEM observations in Examples 2 and 3 were similar to those in Example 1, showing the formation of a continuous transition structure in the interface region, verifying the repeatability of the semi-gel composite process.

[0053] Rheological characterization data: During the preparation of Examples 1, 2, and 3, dynamic rheological tests were performed on the interfacial functional layer slurries to monitor the changes in storage modulus G' and loss modulus G'' over time. The results showed that in Example 1, approximately 18 minutes after coating, G' increased from approximately 500 Pa to 1850 Pa, and G'' increased from approximately 800 Pa to 1720 Pa. The intersection of these two values ​​corresponded to a G' / G'' ratio of approximately 1.08, at which point the material entered a semi-gel state. In Example 2, due to the different ratio of PDMS-COOH to PDMS-NH2, the dynamic network formation rate was slightly slower, reaching a semi-gel state at approximately 25 minutes, with a G' / G'' ratio of approximately 0.92. In Example 3, due to the addition of a larger amount of thickening components, the dynamic network formation rate was faster, reaching a semi-gel state at approximately 12 minutes, with a G' / G'' ratio of approximately 1.15. The G' / G'' values ​​of the three embodiments all fell within the range of 0.8 to 1.2, verifying the rationality and operability of the semi-gel state definition. Meanwhile, rheological testing also showed that the semi-gel state could maintain a relatively stable time window. In Example 1, within 30 minutes of reaching the semi-gel state, G' / G'' fluctuated within the range of 0.95 to 1.15, providing sufficient time for interlayer composite operations in actual production.

[0054] Evaluation of Repeatable Repair Performance: Three thermal cycle-repair cycle tests were conducted on Examples 1, 2, and 3. The results showed that all examples maintained a high thermal resistance recovery rate after three repairs. Example 1 showed a thermal resistance recovery rate of 83.3% after the first repair, 78.9% after the second, and 74.1% after the third, indicating good repeatability of the material's interface self-healing ability. Although the recovery rate decreased slightly with increasing repair cycles, this was due to the accumulation of some irreversible oxidative degradation or permanent deformation of the dynamic network during multiple thermal cycles and repairs, but it still remained above 70% after the third repair, meeting the requirements for multiple thermal cycle-repair in practical applications. Examples 2 and 3 also showed a similar trend, with thermal resistance recovery rates of 70.5% and 73.2% after the third repair, respectively, both higher than the 70% criterion. Although Example 2 had a high filler content of 70 parts in the interface layer, it still achieved effective interface self-healing under high-filling conditions due to sufficient dynamic network components. The higher content of the thickening component (5 parts) in Example 3 enhanced the density and strength of the dynamic network, thus maintaining good repeatable repair performance even under thick sample conditions. In contrast, the thermal resistance recovery rates of Comparative Examples 1 and 2 were only 14.6% and 23.8% respectively after the first repair, far lower than those of the Example. After multiple repairs, they further decreased to around 10% or even lower, indicating a lack of effective repeatable repair capability. Comparative Example 1, lacking an enriched dynamic bond design in its interfacial functional layers, relied primarily on the overall dynamic network of the material for its repair capability. However, the dynamic components, dispersed throughout the material, could not preferentially function at the contact interface, resulting in poor repair performance. Although Comparative Example 2 had a layered formulation, the liquid composite resulted in miscibility at the interface, unclear functional zoning, and a lack of effective interpenetrating structures. The interlayer bonding relied mainly on physical adhesion, making it prone to microcracks and debonding at the interface after thermal cycling, hindering the effective closure of these defects during the repair process.

[0055] Results Analysis and Conclusions 1. Comparative Analysis of Examples: As can be seen from the test data in Table 2, Examples 1, 2, and 3 all exhibited good overall performance under different formulation parameters and thickness designs. The thermal conductivity of the three examples was 4.6, 4.8, and 4.3 W / m·K, respectively, all within the range of 4.3 to 4.8 W / m·K, meeting the basic performance requirements of thermally conductive materials. Example 2, due to its higher filler content (70 parts of interface layer filler and 90 parts of bulk layer filler), had a slightly higher thermal conductivity, but its total thickness was only 100 μm, making it suitable for thin-film applications with limited space. Example 3, with a total thickness of 1975 μm, is a thick thermal pad suitable for the heat dissipation needs of high-power devices. Although its thermal conductivity was relatively low, it still maintained a good level of 4.3 W / m·K. Regarding the interface self-healing performance, the thermal resistance recovery rates after the first repair in all three embodiments exceeded 80%, specifically 83.3%, 80.8%, and 81.5%, respectively. After the third repair, the rates remained above 70%, at 74.1%, 70.5%, and 73.2%, respectively, fully demonstrating the repeatable repair capability of the technical solution within different parameter ranges. Example 1, as the preferred embodiment, employs a medium-thickness design with an interface layer thickness of 30 μm and a bulk layer thickness of 500 μm, a functional group molar ratio close to 1:1, and surface modification of some fillers. It exhibits the most balanced overall performance, the highest thermal resistance recovery rate, and a low oil seepage rate. Although Example 2 did not include any thickening components or undergo filler surface modification, the sufficient content of dynamic siloxane adhesive phase in the interface layer and the functional group molar ratio of 0.87:1, still within the effective range, still achieve a good interface self-healing effect. Example 3 incorporated a significant amount of thickening components (5 parts), enhancing the density and strength of the dynamic network. Furthermore, surface modification was performed on all spherical alumina and lamellar boron nitride in the interface layer, forming more reconfigurable weak bonds. Therefore, even with thick samples, it maintained excellent repair performance and oil resistance, with an oil penetration rate of only 2.5%. Data from the three examples demonstrate that the technical solution of this invention exhibits good parameter range adaptability and process stability. The formulation and thickness can be adjusted according to different application requirements to achieve satisfactory performance.

[0056] 2. Comparative Analysis of Examples and Comparative Examples: Comparing the data in Table 2, it can be seen that the examples and comparative examples show little difference in thermal conductivity and initial interfacial thermal resistance, indicating that the baseline conditions of the comparative experiment were fair and the initial performance of each sample was similar. However, after 50 thermal cycles, significant differences in performance between the examples and comparative examples became apparent. The interfacial thermal resistance R1 of Examples 1, 2, and 3 after thermal cycles were 0.52, 0.61, and 0.57 K·cm² / W, respectively, with an increase rate of 74.3% to 85.7%. In contrast, the interfacial thermal resistance of Comparative Examples 1 and 2 after thermal cycles were as high as 0.78 and 0.73 K·cm² / W, respectively, with an increase rate of 160.0% and 135.5%, which are 1.6 to 2.2 times that of the examples. More importantly, after thermally triggered repair at 80°C, 0.1 MPa, and 1 hour, the interfacial thermal resistance of the embodiment was significantly reduced, with a thermal resistance recovery rate of 80.8% to 83.3%, while the thermal resistance recovery rates of Comparative Examples 1 and 2 were only 14.6% and 23.8%, respectively, indicating extremely limited repair effects. This significant difference fully demonstrates the crucial role of layered structure design and semi-gel state composite process in achieving interfacial self-healing function. Comparative Example 1 uses a single-layer uniform formulation, with dynamic network components and permanent network components uniformly distributed throughout the material. Although the material as a whole has a certain self-healing ability, due to the lack of enriched dynamic bond design in the interfacial functional layer, the dynamic components cannot preferentially play a role at the contact interface, resulting in difficulty in effectively repairing cracks and defects in the interfacial region, with a thermal resistance recovery rate of only 14.6%. Although Comparative Example 2 used the same layered formulation as Example 1, the two slurries were compounded while the interface layer was still liquid, resulting in disordered miscibility at the contact interface and disrupting the intended functional zoning. SEM observations also confirmed the presence of a clear boundary line and local gaps in the interface region, lacking an effective interpenetrating or gradient transition structure. The interlayer bonding relied mainly on physical adhesion rather than chemical interpenetration, resulting in an interlayer peel strength of only 2.1 N / mm, far lower than the 5.9 to 7.2 N / mm of the Example. During thermal cycling, microcracks and partial debonding easily occurred at the interface of Comparative Example 2, and the repair process was difficult to effectively close these defects, with a thermal resistance recovery rate of only 23.8%. In contrast, the embodiment was composited in a semi-gel state. The dynamic network of the interface layer had been initially formed but still had fluidity and rearrangement. After the liquid slurry of the bulk layer was laid, the two slurries underwent limited interpenetration in the interface region. Subsequently, a continuous interpenetrating or gradient transition structure was formed during the curing process. SEM observation showed that the width of the transition zone was about 15 to 20 μm. There was no obvious boundary line or gap between the two layers, and the polymer matrix formed a continuous network. This structure ensured a strong bond between the two layers while maintaining the clarity of the functional partitions. This allowed the dynamic bonds of the interface layer to effectively close cracks and restore interfacial contact during the repair process after thermal cycling, thereby achieving a high thermal resistance recovery rate.

[0057] 3. Regarding oil seepage resistance and pumpability, the differences between the examples and the comparative examples are also significant. The oil seepage rates of Examples 1, 2, and 3 were 3.2%, 2.8%, and 2.5%, respectively, with mass loss rates of 1.8%, 1.5%, and 1.3%, respectively. In contrast, the oil seepage rates of Comparative Examples 1 and 2 were as high as 18.6% and 12.4%, with mass loss rates of 9.2% and 6.7%, respectively, which are 4 to 7 times higher than those of the examples. This difference mainly stems from the design of the bulk carrier layer. The bulk layer of the examples uses hydroxyl-terminated PDMS and a crosslinking agent to form a permanent crosslinked network through a condensation curing reaction. This results in a high crosslinking density and a dense network structure, effectively limiting the migration of low-molecular-weight silicone oil segments. Even under harsh testing conditions of 150°C, 0.02 MPa, and 100 hours, the oil seepage rate can still be controlled below 3.2%. In the single-layer structure of Comparative Example 1, dynamic and permanent networks coexist. The reversibility of dynamic bonds makes the material prone to creep and flow under high temperature and pressure. Low molecular weight chain segments are more likely to migrate to the surface and seep out, resulting in an oil seepage rate as high as 18.6%. Although Comparative Example 2 has a bulk phase support layer, due to the miscibility of the interface region during the liquid composite process, some low cross-linking density components of the interface layer diffuse into the bulk phase layer, reducing the overall cross-linking density of the bulk phase layer and weakening its oil seepage resistance. The oil seepage rate is 12.4%, which is higher than that of the example but lower than that of Comparative Example 1. Examples 2 and 3 showed even lower oil penetration rates, at 2.8% and 2.5%, respectively. This is related to their bulk layer design: Example 2 had a bulk layer filler content as high as 90 parts, and the high filler content further restricted the movement of polymer chain segments; Example 3 had a bulk layer permanent network matrix content as high as 33.5 parts and a crosslinking agent content of 5.2 parts, resulting in a higher crosslinking density. At the same time, 1.5 parts of hydrophobic fumed silica were added, which further improved the anti-pumping performance. Therefore, it was able to maintain the lowest oil penetration rate even under thick sample conditions.

[0058] 4. The comparison of interlayer peel strength further verifies the superiority of the semi-gel composite process. The interlayer peel strengths of Examples 1, 2, and 3 are 6.8, 5.9, and 7.2 N / mm, respectively, indicating that a strong chemical interpenetrating bond is formed between the two layers. The interlayer peel strength of Comparative Example 2 is only 2.1 N / mm, about 30% to 36% of that of Examples 2. This is because although the interfacial miscibility caused by liquid composite appears to be macroscopically close, it lacks an ordered interpenetrating network structure at the microscopic level. The interlayer bonding mainly relies on physical contact and limited molecular chain entanglement, making it prone to peeling under external force. The high peel strength of Examples 2 not only ensures that the material will not delaminate during processing and use, but is also an important guarantee for the interface self-healing function. This is because only when the two layers are tightly bonded and the interfacial region has a continuous network structure can the dynamic bonds of the interfacial layer effectively cross the interface, close cracks, and restore thermal contact during the thermally triggered repair process. The peel strength of Example 3 reached a maximum of 7.2 N / mm, which is attributed to the comprehensive surface modification of the filler in both the interfacial layer and the bulk layer. The GPTMS and APTES modified filler surfaces contain epoxy and amino functional groups. These functional groups can react or interact with the carboxyl and amino groups in the dynamic siloxane adhesive phase and the hydroxyl groups in the bulk layer, forming reconfigurable weak bond bridges around the filler. This enhances the interaction between the filler-polymer-filler and also promotes the interpenetration and entanglement of the two-layer network in the interfacial region, thereby significantly improving the interlayer bonding strength.

[0059] In summary, this invention achieves a synergistic effect of preferential repair of the interface region and anti-pumping in the bulk region through the functional zoning design of the interface functional layer and the bulk support layer. The interface functional layer is rich in dynamic ionic and hydrogen bond networks, which can reassociate and rearrange under thermal triggering conditions, effectively repairing interface cracks and defects caused by thermal cycling, resulting in an interface thermal resistance recovery rate of over 80%, which remains above 70% after three repair cycles, demonstrating excellent repeatable repair capability. The bulk support layer adopts a high-crosslink density permanent network and a high filler content design, effectively inhibiting the migration and pumping out of low-molecular-weight silicone oil, with an oil seepage rate of less than 3.2% and a mass loss rate of less than 1.8%, ensuring the long-term stability of the material. The layered composite process in a semi-gel state is key to achieving the aforementioned technical effects. This process utilizes the unique state formed by the dynamic network of the interfacial layer, where the ratio of storage modulus to loss modulus approaches 1. In this state, the surface is non-sticky but still possesses fluidity and rearrangement. The bulk phase slurry is then laid and rolled together, allowing limited interpenetration between the two layers at the interface. Subsequently, during room temperature and post-curing, an interpenetrating or gradient transition structure is formed, ensuring strong interlayer bonding (peel strength 5.9 to 7.2 N / mm) while maintaining clear functional zones, avoiding the disordered miscibility and functional zone destruction caused by liquid composites. Furthermore, the surface modification treatment of the filler introduces functional groups that can interact with the dynamic and permanent networks, forming reconfigurable filler-polymer-filler weak bond bridges, further enhancing the interface self-healing ability and interlayer bonding strength. The technical solution provided by this invention solves the technical problems of increased interfacial thermal resistance, performance degradation due to silicone oil seepage, and environmental pollution caused by long-term thermal cycling of existing thermally conductive materials. It has significant practical value for improving the heat dissipation reliability and extending the service life of electronic devices.

[0060] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A self-healing thermally conductive composite material, characterized in that, The self-healing thermally conductive composite material includes an interface functional layer and a bulk support layer that are bonded together, and the interface functional layer constitutes the contact interface of the self-healing thermally conductive composite material. The interface functional layer comprises the following raw materials in parts by weight: 20-55 parts of dynamic siloxane adhesive phase; 45-80 parts of thermally conductive filler; The dynamic siloxane adhesive phase is formed by the reaction or association of carboxyl-terminated or carboxyl-containing polydimethylsiloxane with amino-terminated polydimethylsiloxane to form a dynamic network with reversible ionic and / or hydrogen bond interactions; the thermally conductive filler of the interface functional layer is selected from alumina, boron nitride or a combination thereof. The bulk support layer comprises the following raw materials in parts by weight: 10-35 copies of permanent network substrate; 65-90 parts of thermally conductive filler; The permanent network matrix is ​​formed by a condensation curing reaction of hydroxyl-terminated polydimethylsiloxane, a crosslinking agent and a condensation catalyst to form a permanent crosslinked network. The crosslinking agent is selected from silicates, alkoxysilanes or combinations thereof. The thermally conductive filler of the bulk phase support layer is selected from alumina, boron nitride or combinations thereof.

2. The interface self-healing thermally conductive composite material according to claim 1, characterized in that, In the dynamic siloxane adhesive phase, the molar ratio of carboxyl to amino functional groups, n(COOH):n(NH2), is 0.85~1.

15.

3. The interface self-healing thermally conductive composite material according to claim 1, characterized in that, The interface functional layer also includes 1 to 10 parts of a siloxane thickening component containing urea groups and / or urethane groups.

4. The interface self-healing thermally conductive composite material according to claim 1, characterized in that, The thermally conductive filler of the interface functional layer includes spherical alumina and boron nitride, wherein the spherical alumina is 30-50 parts and the boron nitride is 15-30 parts, and the boron nitride includes spherical boron nitride and / or plate-shaped boron nitride.

5. The interface self-healing thermally conductive composite material according to claim 4, characterized in that, The boron nitride includes plate-shaped boron nitride, wherein the average particle size D50 of the plate-shaped boron nitride is 5~30μm and the thickness is less than 1μm.

6. The interface self-healing thermally conductive composite material according to claim 1, characterized in that, At least a portion of the thermally conductive filler in the interface functional layer is surface modified with a silane coupling agent, wherein the silane coupling agent is selected from aminopropyltriethoxysilane, glycidyltrimethoxysilane or a combination thereof, and the amount of the silane coupling agent is 0.1 to 2.0 wt% of the mass of the modified filler.

7. The interface self-healing thermally conductive composite material according to claim 1, characterized in that, The permanent network matrix comprises 9-29 parts of hydroxyl-terminated polydimethylsiloxane, 1-5.5 parts of crosslinking agent, and 0.02-0.5 parts of condensation catalyst; the crosslinking agent comprises tetraethoxysilane and / or methyltriethoxysilane.

8. The interface self-healing thermally conductive composite material according to claim 1, characterized in that, The thickness of the interface functional layer is 5~80μm, and the thickness of the bulk phase carrier layer is 50~2000μm.

9. A method for preparing the interface self-healing thermally conductive composite material according to any one of claims 1 to 8, characterized in that, Includes the following steps: S1. Premix carboxyl-terminated or carboxyl-containing polydimethylsiloxane with amino-terminated polydimethylsiloxane at 40~80℃ for 10~40min to form a dynamic network composed of ionic bonds and / or hydrogen bonds. Then add the thermally conductive filler for the interface functional layer in batches. After each batch is added, disperse it by alternating low-shear and high-shear mixing until the slurry is uniform. Then perform vacuum degassing to obtain the interface functional layer slurry. S2. Hydroxyl-terminated polydimethylsiloxane is premixed with a crosslinking agent, then added to the thermally conductive filler for the bulk support layer. After mixing evenly and vacuum degassing, a condensation catalyst is added and rapidly mixed to obtain the bulk support layer slurry. S3. The interface functional layer slurry is coated on the surface of the substrate or release film to form an interface functional layer. When the interface functional layer reaches a semi-gel state, the bulk carrier layer slurry is laid on the interface functional layer. The two layers are tightly bonded by rolling or lamination, and then cured at room temperature for 4~24h. During the curing process, interpenetration or gradient transition is formed in the interface area. At the same time, the dynamic network of the interface functional layer is further stabilized, and the condensation curing reaction of the bulk carrier layer forms a permanent cross-linked network. Then, it is cured at 60~120℃ for 1~4h to enhance the stability of the filler network and obtain an interface self-healing thermally conductive composite material. The semi-gel state refers to the state in which the dynamic network in the interface functional layer is formed until the ratio of the energy storage modulus G' to the loss modulus G'' is 0.8 to 1.2, and the material surface is not sticky but still has rearrangement properties; The alternating low-shear and high-shear mixing refers to the process of first mixing at a low shear rate to slowly disperse the packing in the dynamic network during the packing dispersion process, and then mixing at a high shear rate to break up the packing agglomerates. This alternation is carried out to maintain the integrity of the dynamic network while ensuring uniform dispersion of the packing.

10. The preparation method according to claim 9, characterized in that, Before adding the thermally conductive filler to S1 and / or S2, the thermally conductive filler is pretreated, the pretreatment including: The thermally conductive filler is dried under vacuum at 110-140℃ for 2-6 hours to remove adsorbed water; and / or, the thermally conductive filler is subjected to surface modification treatment with a silane coupling agent, wherein the surface modification treatment with the silane coupling agent includes dispersing the thermally conductive filler in anhydrous ethanol or isopropanol, adding 0.1-2.0 wt% of a silane coupling agent, stirring and reacting for 0.5-2 hours, then filtering, washing and drying, wherein the silane coupling agent is selected from aminopropyltriethoxysilane, glycidyltrimethoxysilane or a combination thereof, and wt% is relative to the mass of the filler being modified.

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