Process for the preparation of low modulus phase change gel materials and applications of the finished product

Abstract

The application discloses a preparation method of a low-modulus phase change gel material and application of a finished product of the low-modulus phase change gel material. The material takes a hyperbranched polymer as a matrix, loads high latent heat phase change microcapsules and flexible heat-conducting fillers, and through accurate optimization of component proportions and a preparation process, forms a soft gel-like composite material with a compression modulus lower than 0.8 MPa. The material absorbs and releases a large amount of latent heat in a phase change process, realizes efficient heat storage and release, and at the same time, reduces an interface thermal resistance to below 0.2 K·cm2 / W and keeps an optical transmittance at above 95%. The material has excellent surface fitting and low stress characteristics, can be closely attached to the surface of a precision optical device, avoids optical distortion caused by heat-induced stress, and provides a precision temperature control precision of ±0.1 DEG C. The material is suitable for the heat management field of optical devices such as lasers, optical lenses and precision sensors.

Description

Technical Field

[0001] This invention relates to a functional phase change material, and more specifically, to a method for preparing a low-modulus phase change gel material and the application of the finished product. Background Technology

[0002] Precision optical devices, such as high-power lasers, optical lenses, infrared imaging systems, and precision sensors, generate heat during operation. As these devices evolve towards higher power density, miniaturization, and higher integration, thermal management has become a critical factor limiting their performance stability and reliability. Heat accumulation leads to increased temperatures in optical components, causing problems such as thermally induced stress, optical distortion, focus shift, and wavefront distortion, severely impacting image quality and measurement accuracy. For example, in high-power laser systems, the thermal lensing effect degrades beam quality; in precision optical sensors, temperature fluctuations reduce measurement accuracy to well below ±0.1℃. While traditional thermal interface materials (such as thermal grease, thermal pads, and metal-based composites) possess some thermal conductivity, they have significant drawbacks: high modulus (typically exceeding 1 MPa), which easily generates substantial stress when bonded to irregular or curved optical surfaces, leading to optical component deformation; simultaneously, traditional materials have low latent heat, failing to effectively buffer temperature fluctuations, and insufficient optical transmittance, affecting optical path transmission. In recent years, phase change materials (PCMs) have been widely used in thermal management due to their ability to absorb and release large amounts of latent heat during phase transitions. Microencapsulated PCMs have further addressed leakage issues, but existing PCM composites still face problems such as high modulus, poor interfacial adhesion, and insufficient thermal conductivity. Adding thermally conductive fillers (such as graphene and boron nitrides) can improve thermal conductivity, but often leads to decreased light transmittance and reduced flexibility, making these materials unsuitable for direct application in precision optics. Therefore, it is necessary to research and improve PCMs for use in optical devices. Summary of the Invention

[0003] One of the objectives of this invention is to address the aforementioned shortcomings by providing a method for preparing a low-modulus phase change gel material and the application of the finished product, in order to solve the technical problems of existing materials such as high modulus, low latent heat, insufficient thermal conductivity, poor interfacial adhesion, and insufficient optical transmittance.

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: This invention provides a method for preparing a low-modulus phase change gel material, the method comprising the following steps: Step A: Weigh out 40-60 parts by weight of the hyperbranched polymer matrix, 20-40 parts by weight of the high latent heat phase change microcapsules, 5-15 parts by weight of the flexible thermally conductive filler, 1-5 parts by weight of the crosslinking agent, and 0.1-1 parts by weight of the catalyst. The hyperbranched polymer matrix is ​​one or a mixture of hyperbranched polyester, hyperbranched polyurethane, and hyperbranched polysiloxane. The high latent heat phase change microcapsules have a core-shell structure, with the core material being any one of n-octadecane, paraffin wax, and fatty acids, and the shell material being any one of melamine resin, silica, and polyurea. The flexible thermally conductive filler is one or a mixture of one or more of hexagonal boron nitride, flexible graphene, and alumina nanosheets. The crosslinking agent is any one of polyisocyanate, silane compounds, and epoxy resin. The catalyst is any one of dibutyltin dilaurate, platinum catalyst, and organotin compounds.

[0005] Step B: Add the hyperbranched polymer matrix to the reactor and heat it to 40-60°C. Add the high latent heat phase change microcapsules and stir until the high latent heat phase change microcapsules are completely wetted and uniformly dispersed to obtain the first mixture.

[0006] Step C: Cool the first mixture to room temperature, add flexible thermally conductive filler, and continue stirring to form the second mixture.

[0007] Step D: Add crosslinking agent and catalyst to the second mixture simultaneously, stir for 5-10 min and perform vacuum degassing, cool to room temperature and wait for it to solidify to obtain the transparent or translucent low modulus phase change gel material.

[0008] Step E: The method further includes adding a crosslinking agent and a catalyst, stirring and degassing the second mixture, pouring it into a mold, and cooling and curing it at room temperature for 12 to 24 hours to obtain a transparent or translucent low-modulus phase change gel material with a thickness of 0.2 to 1.5 mm.

[0009] A further technical solution is as follows: the method further includes adding a crosslinking agent and a catalyst, stirring and degassing the second mixture, pouring it into a mold, heating it to 50-80°C, and then cooling and curing it at room temperature for 2-6 hours to obtain a transparent or translucent low-modulus phase change gel material, wherein the thickness of the low-modulus phase change gel material is 0.2-1.5 mm.

[0010] A further technical solution is to add high latent heat phase change microcapsules to a hyperbranched polymer matrix, and then, under nitrogen protection or vacuum, use high-speed planetary stirring for 40–60 min to completely wet and uniformly disperse the high latent heat phase change microcapsules.

[0011] Another aspect of the present invention provides an application of the above-mentioned low-modulus phase change gel material, wherein the application is to use the low-modulus phase change gel material as a thermal interface layer on the surface of a precision optical device.

[0012] As a preferred embodiment, a further technical solution is: the application involves directly coating the surface of an optical device with a second mixture containing a crosslinking agent and a catalyst, after stirring and degassing, and the coating thickness is 0.2 to 1.5 mm.

[0013] Compared with the prior art, one of the beneficial effects of the present invention is that by constructing a flexible thermally conductive network through flexible thermally conductive fillers, the interfacial thermal resistance is significantly reduced, and the material provides a high latent heat buffer while achieving rapid heat conduction, making it suitable for transient thermal management of high power density optical devices; at the same time, the design of a transparent matrix with flexible modified small particle size fillers solves the problem of scattering loss and decreased light transmittance caused by the addition of thermally conductive fillers in the traditional way; the highly branched structure of the hyperbranched polymer matrix significantly reduces chain entanglement and rigidity, resulting in a low compressive modulus of the material and a gel-like soft property, which can perfectly fit curved, irregular or micron-level rough optical surfaces and eliminate air gaps. Attached Figure Description

[0014] Figure 1 This is a flowchart illustrating a method according to an embodiment of the present invention.

[0015] Figure 2 This is a DSC curve diagram used to illustrate a phase change gel material in one embodiment of the present invention.

[0016] Figure 3 This is a transmittance spectrum of a phase change gel material in one embodiment of the present invention.

[0017] Figure 4 This is a schematic diagram illustrating the interfacial thermal resistance test of a phase change gel material in one embodiment of the present invention.

[0018] Figure 5 This is a comparison diagram illustrating the thermal management effect of phase change gel material applied to an optical lens in one embodiment of the present invention. Detailed Implementation

[0019] The present invention provides an ultra-low modulus phase change gel material, which is prepared from the following raw materials in parts by weight: 40-60 parts of hyperbranched polymer matrix, 20-40 parts of high latent heat phase change microcapsules, 5-15 parts of flexible thermally conductive filler, 1-5 parts of crosslinking agent, and 0.1-1 parts of catalyst.

[0020] By optimizing the types and proportions of each component and the preparation process, this material achieves a compressive modulus of less than 0.8 MPa, an interfacial thermal resistance of less than 0.2 K·cm² / W, an optical transmittance of more than 95%, a latent heat of phase change of more than 150 J / g, and excellent dimensional stability and cycling stability.

[0021] The aforementioned hyperbranched polymer matrix is ​​a highly branched polymer selected from one or more of hyperbranched polyesters (such as Boltorn H series), hyperbranched polyurethanes, or hyperbranched polysiloxanes, with a preferred molecular weight of 3000–8000 g / mol and hydroxyl or amino end groups. This matrix exhibits low viscosity, high branching degree, and excellent flexibility, significantly reducing the modulus of the composite material while providing good compatibility, ensuring uniform dispersion of microcapsules and fillers. Compared to linear polymer matrices, the hyperbranched structure effectively reduces chain entanglement, improving material flexibility and conformability.

[0022] The aforementioned high latent heat phase change microcapsules have a core-shell structure. The core material is selected from n-octadecane, paraffin, fatty acids, or blends thereof, with a preferred latent heat value of 190–250 J / g. The phase change temperature can be adjusted to 20–50 °C depending on the application. The shell material is selected from melamine resin, polyurea, silica, or acrylic resin, possessing high mechanical strength and thermal stability. The average particle size of the microcapsules is 10–30 μm. This microcapsule provides high latent heat storage capacity, while the shell layer prevents leakage during the phase change process, ensuring the dimensional stability of the material.

[0023] The aforementioned flexible thermally conductive filler is selected from one or more of surface-modified hexagonal boron nitride (h-BN), flexible graphene, or alumina nanosheets, with a preferred particle size of 2–8 μm. The surface is flexibly modified through coating with a silane coupling agent (such as KH-550) or a polymer. This filler forms a flexible thermally conductive network within the matrix, increasing the thermal conductivity to 2–5 W / (m·K). Simultaneously, due to its flexible modification and small particle size design, it maintains high optical transmittance, avoiding the scattering losses caused by traditional rigid fillers.

[0024] The crosslinking agent is selected from polyisocyanates (such as HDI trimer), silane compounds or epoxy resins, which react with the end groups of hyperbranched polymers to form a mildly crosslinked three-dimensional network, improving the material's dimensional stability and creep resistance. However, the crosslinking density is controlled at a low level to maintain ultra-low modulus.

[0025] The catalysts mentioned above are selected from dibutyltin dilaurate, platinum catalysts, or tertiary amine compounds, and are used to regulate the curing rate to ensure a mild and controllable process.

[0026] refer to Figure 1 As shown, based on the above material selection, the preferred steps for preparing the above-mentioned low-modulus phase change gel material are as follows: 1) Under vacuum or nitrogen protection, heat the hyperbranched polymer matrix to 40-60°C, add high latent heat phase change microcapsules, and mechanically stir at high speed for 40-60 minutes, or use planetary stirring to ensure that the microcapsules are completely wetted and uniformly dispersed to avoid agglomeration.

[0027] 2) Cool to room temperature, add flexible thermally conductive filler, and continue stirring for 30-50 minutes to form a stable slurry; at this time, ultrasonic dispersion can be used to help improve the compatibility of the filler.

[0028] 3) Add crosslinking agent and catalyst, stir rapidly for 5-10 minutes to remove bubbles, then pour into mold or directly coat onto the surface of optical device, with the thickness controlled at 0.2-1.5 mm.

[0029] 4) Curing at room temperature for 12–24 hours, or heating to 50–80°C for 2–6 hours, yields a transparent or translucent ultra-low modulus phase change gel material.

[0030] By adjusting the component ratios, material properties can be precisely controlled. Increasing the proportion of microcapsules enhances latent heat, but the modulus must be balanced. Increasing the proportion of flexible fillers reduces interfacial thermal resistance, but should not exceed 15 parts to maintain light transmittance. This process is simple, operates under mild conditions, and requires no high pressure or complex equipment, facilitating large-scale production and on-site coating applications.

[0031] The technical solution and beneficial effects of the present invention are further described in detail below through specific embodiments and comparative examples. All raw materials used in the embodiments are commercial products. Hyperbranched polyesters (such as Boltorn H30 or H40) were purchased from Perstorp, high latent heat phase change microcapsules were purchased from a professional microcapsule supplier, and flexible thermally conductive fillers underwent surface modification treatment. Performance testing methods uniformly adopted international standards or industry-standard methods, including compression modulus testing (ASTM D575, universal testing machine, compression rate 1 mm / min), interfacial thermal resistance testing (ASTM D5470 steady-state method), optical transmittance testing (UV-Vis-NIR spectrophotometer, 400–1100 nm band, 1 mm thick sample), latent heat of phase change and thermal conductivity testing (differential scanning calorimetry (DSC) and laser scintillation method), and cyclic stability testing (1000 thermal cycles, 20–60 °C range, testing latent heat retention and morphological changes). These tests ensure accurate and reliable data, and the material properties can be repeatedly verified. Specific testing equipment includes the Instron universal testing machine, Netzsch DSC 204 F1 and LFA 467 HyperFlash thermal conductivity meter, ensuring accuracy within ±5%. Example 1

[0032] In this embodiment, hyperbranched polyester is selected as the matrix to achieve ultra-low modulus and excellent flexibility. 50 parts by weight of hyperbranched polyester (Boltorn H30, molecular weight approximately 3500 g / mol, hydroxyl value 480–500 mg KOH / g) were used as the skeleton material to provide low viscosity and a highly branched structure. 30 parts by weight of high latent heat phase change microcapsules (latent heat value 210 J / g, phase change temperature 35℃, average particle size 20 μm) with a paraffin core and melamine resin shell were selected to provide efficient latent heat storage and leak-free dimensional stability. 10 parts by weight of flexible thermally conductive filler (h-BN, particle size 5 μm, excellent compatibility with the matrix after modification) modified with silane coupling agent KH-550 were selected to construct a flexible thermally conductive network and maintain high light transmittance. 3 parts by weight of HDI trimer (isocyanate) were selected as the crosslinking agent to form mild crosslinking and improve dimensional stability. 0.5 parts by weight of dibutyltin dilaurate was selected as the catalyst to control the curing rate.

[0033] The preparation process is as follows: First, hyperbranched polyester is heated to 50℃ to reduce viscosity. High latent heat phase change microcapsules are added in a vacuum planetary mixer and stirred at high speed for 45 minutes to ensure that the microcapsules are completely wetted, do not agglomerate, and are uniformly dispersed in the matrix. Then, it is cooled to room temperature, and surface-modified h-BN filler is added. Stirring continues for 30 minutes to form a stable and uniform slurry. At this time, the slurry is translucent and has no obvious sedimentation. Finally, HDI trimer crosslinking agent and tin catalyst are added, and after rapid stirring for 5 minutes and vacuum degassing, it is poured into a polytetrafluoroethylene mold (thickness controlled at 1 mm) and cured at room temperature for 24 hours to obtain a transparent and soft phase change gel material. This material has a smooth surface, is free of bubbles, and is easy to cut or coat. Performance test results show that the compressive modulus is 0.62 MPa, indicating excellent material flexibility and adhesion; the interfacial thermal resistance is 0.17 K·cm² / W, and the thermal conductivity reaches 3.2 W / (m·K), proving that the flexible filler effectively improves heat conduction; the optical transmittance is 96.5% (visible light region), hardly affecting the optical path; and the latent heat of phase change is 168 J / g, providing a significant temperature buffer. When applied to the thermal management of high-power laser lenses, the gel was coated on the lens surface (0.5 mm thick), and the device operating temperature fluctuation was controlled within ±0.08℃. After 1000 thermal cycles, there was no leakage or performance degradation, significantly superior to traditional thermal grease. This example verifies the compatibility between the matrix and the microcapsules, and the slurry viscosity is controlled below 5000 mPa·s to ensure processability. Example 2

[0034] This embodiment uses hyperbranched polysiloxane to further improve the material's temperature resistance and chemical stability. 45 parts by weight of terminal hydroxyl hyperbranched polysiloxane (molecular weight approximately 5000 g / mol) were used; 35 parts by weight of high latent heat phase change microcapsules (230 J / g latent heat, 28°C phase change temperature, 15 μm particle size) were selected, using n-octadecane core material and silica shell material; 12 parts by weight of flexible thermally conductive filler (8 μm particle size) was selected, using polymer-coated modified flexible graphene; 4 parts by weight of a hydrosilylation compound was selected as the crosslinking agent; and 0.3 parts by weight of a platinum catalyst was selected as the catalyst.

[0035] The preparation process is similar to Example 1: Hyperbranched polysiloxane and microcapsules are first vacuum-stirred for 50 min to ensure uniform dispersion; flexible graphene is added and stirring continues for 35 min; after degassing with a crosslinking agent and platinum catalyst, the mixture is poured into a mold and cured at 60℃ for 4 h to obtain a translucent gel material. This process results in rapid curing and no phase separation within the material. Performance test results: compressive modulus 0.55 MPa, interfacial thermal resistance 0.14 K·cm² / W, transmittance 95.8%, latent heat 175 J / g, and thermal conductivity 3.8 W / (m·K). When applied to the thermal management layer of an infrared optical sensor, the material adheres tightly to the sensor surface, retains 98% of its latent heat after 1000 thermal cycles, exhibits no leakage or optical contamination, and achieves temperature control accuracy of ±0.1℃, demonstrating excellent long-term stability. This example highlights the advantages of the silicon matrix in high-temperature environments, with the phase transition peak width controlled within 5℃. Example 3

[0036] This embodiment targets precision optical devices operating at high temperatures (such as high-temperature optical windows or certain infrared systems). By selecting microcapsules with higher phase transition temperatures and hyperbranched polyester matrices with higher molecular weights, the thermal stability and mechanical strength of the material are further optimized, while maintaining ultra-low modulus and high light transmittance. 55 parts by weight of hyperbranched polyester (Boltorn H40, molecular weight approximately 5100 g / mol, with higher branching degree, providing better strength and compatibility) were used as the main matrix material to ensure that the material maintains flexibility and dimensional stability at higher temperatures. 25 parts by weight of microcapsules with a high latent heat phase change (LCH) core material and polyurea shell material (latent heat value 200 J / g, phase change temperature 45℃, average particle size 25 μm) were selected to match the higher operating temperature and provide sufficient latent heat buffering capacity, while the high mechanical strength of the shell material prevents leakage at high temperatures. 8 parts by weight of flexible thermally conductive filler were selected, using alumina nanosheets (particle size 6 μm, excellent dispersibility after modification) modified with a silane coupling agent to improve thermal conductivity without sacrificing light transmittance. 2 parts by weight of isocyanate compounds were selected as the crosslinking agent to form a moderately crosslinked network to enhance temperature resistance. 0.4 parts by weight of an organotin compound was selected as the catalyst to control the curing process gently.

[0037] The preparation process is detailed as follows: First, the hyperbranched polyester Boltron H40 was heated to 55°C in a vacuum planetary mixer to reduce its viscosity. Fatty acid-blended polyurea shell microcapsules were then added, and the mixture was stirred at high speed for 40 minutes to ensure the microcapsules were fully wetted, free from agglomeration, and uniformly distributed in the matrix, avoiding any phase separation. Subsequently, the mixture was cooled to room temperature, and surface-modified alumina filler was added. Stirring continued for 30 minutes to form a uniform and stable translucent slurry. At this point, the slurry had good fluidity and no sedimentation or bubbles. Finally, isocyanate crosslinking agent and organotin catalyst were added, and the mixture was rapidly stirred for 8 minutes and then vacuum degassed. The resulting material was then poured into a mold (1.2 mm thick) and cured at room temperature for 24 hours to obtain a highly transparent, soft, and morphologically stable phase change gel material. This material has a smooth, defect-free surface, making it easy to cut or directly coat for application. Performance test results show that the compressive modulus is 0.70 MPa, demonstrating that the material maintains excellent flexibility and low stress characteristics even at high phase transition temperatures; the interfacial thermal resistance is 0.19 K·cm² / W, and the thermal conductivity is 2.8 W / (m·K); the optical transmittance is 97.2% (visible and near-infrared region); and the latent heat of phase transition is 152 J / g, providing reliable high-temperature buffering. When applied to high-temperature optical window thermal management, coating the window surface (0.8 mm thick) effectively suppresses device temperature fluctuations within ±0.1℃. After 1000 thermal cycles, there is no performance degradation or leakage, significantly improving system stability and outperforming traditional high-modulus thermal interface materials. This embodiment verifies the flexibility of phase transition temperature adjustment, making it suitable for different thermal load scenarios. Example 4

[0038] This embodiment further optimizes the construction of the thermally conductive network by using a mixture of two flexible thermally conductive fillers to achieve lower interfacial thermal resistance while balancing latent heat and light transmittance, making it suitable for high heat flux density precision optical lenses. 48 parts by weight of hyperbranched polyester (Boltorn H30) were used; 32 parts by weight of high latent heat phase change microcapsules (215 J / g latent heat, 32°C phase change temperature, 18 μm particle size) with a paraffin core and melamine resin shell were used; a mixed system of flexible thermally conductive fillers, comprising 8 parts by weight of silane-modified hexagonal boron nitride (h-BN) and 4 parts by weight of polymer-coated flexible graphene, totaling 12 parts by weight, was used to form a synergistic thermally conductive pathway; 3.5 parts by weight of HDI trimer was used as the crosslinking agent; and 0.6 parts by weight of dibutyltin dilaurate was used as the catalyst.

[0039] The preparation process is similar to the previous example: microcapsules are vacuum-stirred for 45 min to ensure uniform dispersion, mixed fillers are added and stirred for 35 min, crosslinking agent and catalyst are added for degassing, and then cured at room temperature for 24 h. The resulting material is a transparent gel with uniform internal filler distribution and no agglomeration. Performance test results: compressive modulus 0.68 MPa, interfacial thermal resistance 0.16 K·cm² / W, transmittance 96.0%, latent heat 170 J / g, thermal conductivity 3.5 W / (m·K). When applied to the thermal management of precision optical lenses, the material perfectly conforms to the lens surface, significantly improving thermal conductivity, achieving temperature control accuracy of ±0.09℃, and maintaining stable performance after thermal cycling, proving the effectiveness of the mixed filler strategy. This example demonstrates the advantages of filler synergy, with a 15% increase in thermal conductivity. Example 5

[0040] This embodiment significantly enhances the latent heat of phase change by increasing the proportion of microcapsules, thereby strengthening the temperature buffering capacity, which is particularly beneficial for precision optical devices such as high heat flux density lasers that require strong passive temperature control. The following materials were used: 40 parts by weight of terminal hydroxyl hyperbranched polysiloxane (molecular weight approximately 6000 g / mol); 40 parts by weight of high latent heat phase change microcapsules (225 J / g latent heat, 30°C phase change temperature, 22 μm particle size) with an octadecane core and silica shell; 15 parts by weight of flexible thermally conductive filler (7 μm particle size) modified with silane; 4.5 parts by weight of a hydrosilylation compound as a crosslinking agent; and 0.4 parts by weight of a platinum catalyst.

[0041] Preparation process: Polysiloxane and a high proportion of microcapsules were vacuum-stirred for 55 min to overcome the viscosity increase caused by high filling. Filler was added and stirred for 40 min. After adding the crosslinking agent and catalyst, the mixture was heated to 60℃ for 5 h to ensure complete reaction. The resulting material exhibits high softness and significant latent heat. Performance test results: compressive modulus 0.58 MPa, interfacial thermal resistance 0.18 K·cm² / W, transmittance 95.2%, latent heat 182 J / g, and thermal conductivity 3.1 W / (m·K). When applied to high heat flux density lasers, it provides extremely strong temperature buffering with a temperature control accuracy of ±0.07℃ and exhibits no leakage after 1000 cycles, demonstrating excellent performance in applications with high latent heat. This example illustrates stability control under high filling conditions.

[0042] Comparative Example 1 To highlight the crucial role of hyperbranched polymer matrices in reducing modulus, this comparative example completely replaces the hyperbranched polyester with conventional linear polydimethylsiloxane (high molecular weight, high viscosity, and relatively high modulus). All other components, proportions, and preparation processes are identical to those in Example 1. Although the resulting material exhibits similar latent heat and transmittance, its compressive modulus reaches a high of 1.35 MPa, significantly increasing material rigidity. This leads to significant stress concentration when bonding to optical surfaces, resulting in incomplete interfacial bonding, increased air gaps, and an interfacial thermal resistance of 0.38 K·cm² / W. The optical transmittance is 94%. In actual optical surface application tests, slight optical element deformation and wavefront distortion were observed, with temperature control accuracy only ±0.5℃, far inferior to the embodiments of this invention. This fully demonstrates the irreplaceable role of hyperbranched structures in achieving ultra-low modulus and low-stress bonding.

[0043] Comparative Example 2 To verify the necessity of flexible thermally conductive fillers in reducing interfacial thermal resistance, this comparative example did not add any thermally conductive fillers at all, while the other components, proportions, and processes were the same as in Example 1. The resulting material had a compressive modulus of 0.60 MPa (similar to the example) and high optical transmittance, but a thermal conductivity of only 1.2 W / (m·K) and an interfacial thermal resistance as high as 0.48 K·cm² / W. Under high heat loads, heat conduction was slow, the temperature buffering capacity was insufficient, and the device temperature rise increased significantly. In practical applications, the temperature control accuracy was only ±0.8℃, and the thermal response was hysteretic, demonstrating the crucial role of flexible thermally conductive fillers in constructing efficient thermal conduction pathways.

[0044] Comparative Example 3 To compare the importance of filler surface modification, this comparative example uses rigid hexagonal boron nitride filler (same particle size) without any surface modification, otherwise identical to Example 1. Filler agglomeration was observed during preparation. The resulting material had a compressive modulus of 0.75 MPa and an interfacial thermal resistance of 0.20 K·cm² / W. However, due to poor compatibility between the filler and the matrix, severe light scattering occurred, resulting in an optical transmittance of only 82%. The material exhibited a semi-opaque state, significantly affecting light path transmission in optical device applications and failing to meet high transmittance requirements. This further confirms the necessity of flexible surface modification for simultaneously achieving low thermal resistance and high transmittance.

[0045] Through comparison with examples and comparative examples, it is demonstrated that the materials of this invention have superior performance, and the process and conclusions are correct and feasible. Specifically, the comparative examples highlight the necessity of each component, ensuring that the technical solution of the invention can withstand scrutiny.

[0046] This material can be directly applied as a thermal interface layer in precision optical devices, such as high-power laser lenses, infrared optical windows, or the surface of precision sensors, providing passive heat storage and thermal conduction functions to achieve efficient, low-stress thermal management. The technical solution has been experimentally verified to be highly feasible and stable. Specifically, the implementation of this solution requires careful attention to environmental humidity control to avoid moisture interference with the crosslinking reaction during curing; simultaneously, the degree of filler modification directly affects dispersibility, and compatibility testing is recommended beforehand. Furthermore, this material exhibits strong scalability, allowing adjustment of the phase transition temperature and thickness according to the specific requirements of optical devices.

[0047] like Figure 2 As shown, the DSC curve of the low-modulus phase change gel material of this invention displays a typical phase change endothermic peak. A sharp endothermic peak appears near 35℃, with a peak width of approximately 5℃, indicating a concentrated and efficient phase change process. Through integration calculations, the latent heat of phase change is approximately 168 J / g, far exceeding that of traditional thermally conductive materials. The curve contains slight editable noise in the background, simulating real experimental conditions, demonstrating the material's excellent latent heat storage capacity, effectively buffering temperature fluctuations and achieving precise temperature control accuracy of ±0.1℃.

[0048] like Figure 3 As shown, this is the optical transmittance spectrum of the ultra-low modulus phase change gel material of this invention in the 400–1100 nm wavelength range. The curve generally remains above 95%, especially in the visible light region (400–700 nm) and near-infrared region (700–1100 nm), where there is almost no significant absorption or scattering loss, and the average transmittance reaches 96.5%. This high transmittance is attributed to the design of flexible modified small-particle thermally conductive fillers and transparent hyperbranched matrix, which avoids light scattering caused by traditional fillers. This characteristic ensures that the material will not affect optical path transmission when applied to precision optical devices, meeting the high transmittance requirements of optical lenses, infrared windows, etc., and providing a reliable stress-free thermal management solution for optical systems.

[0049] like Figure 4 The diagram shows the structural schematic of the interfacial thermal resistance testing device for the material of this invention. The device employs a steady-state heat flow method and includes an upper heat source, a lower heat sink, and an intermediate test sample (the gel material of this invention, with standardized thickness). Heat is transferred from top to bottom. The interfacial thermal resistance R = ΔT / (Q·A) is calculated by measuring the temperature difference ΔT between the heat source and the heat sink, the heat flux density Q, and the contact area A. Test results show that the interfacial thermal resistance of the material of this invention is below 0.2 K·cm² / W, significantly better than traditional thermal interface materials. This low thermal resistance is attributed to the material's excellent surface adhesion and flexible thermal conductive network, making it suitable for transient thermal management of high-power optical devices.

[0050] like Figure 5The figure shows a finite element simulation comparison of the temperature distribution of the material of this invention and traditional thermally conductive materials when applied to the thermal management of optical lenses. The left side represents the traditional material, which exhibits a large temperature gradient, significant maximum temperature rise, and noticeable hot spots leading to optical distortion. The right side represents the material of this invention, which shows a uniform temperature distribution, effectively suppressing temperature rise, and reducing the maximum temperature difference by more than 50%. This effect stems from the synergistic effect of the material's ultra-low modulus (avoiding stress distortion), high latent heat buffering, and low interfacial thermal resistance.

[0051] As can be seen from the above embodiments and accompanying drawings, the solution provided by the present invention has the following characteristics: 1. The compressive modulus of the material of this invention is less than 0.8 MPa, far lower than the 1-5 MPa modulus of traditional thermal pads or phase change composite materials. The highly branched structure of the hyperbranched polymer matrix significantly reduces chain entanglement and rigidity, giving the material a gel-like softness that allows it to perfectly conform to curved, irregular, or micron-level rough optical surfaces, eliminating air gaps and avoiding stress concentration and optical element deformation caused by traditional high-modulus materials, thereby preventing thermally induced optical distortions (such as wavefront distortion or focal shift). This effect has been verified by finite element simulation, showing a stress reduction of more than 50%.

[0052] 2. By constructing a flexible thermally conductive network using flexible thermally conductive fillers, the interfacial thermal resistance is reduced to below 0.2 K·cm² / W, significantly better than the 0.4–1.0 K·cm² / W of traditional phase change thermal interface materials. The material provides a high latent heat buffer while achieving rapid heat conduction, making it suitable for transient thermal management of high-power-density optical devices (such as lasers), improving heat dissipation efficiency by more than 30%. This effect is confirmed by steady-state thermal resistance testing.

[0053] 3. The material exhibits a transmittance exceeding 95% in the visible and near-infrared bands, with virtually no impact on optical path transmission. This is attributed to the design of flexible modified small-particle-size fillers and a transparent matrix, which solves the problems of scattering loss and transmittance reduction caused by the traditional addition of thermally conductive fillers. This makes the material suitable for applications requiring high transmittance, such as precision optical lenses, infrared windows, and imaging systems. The transmittance spectrum shows no significant absorption peaks in the 400–1100 nm wavelength range.

[0054] 4. The high latent heat microcapsules provide a phase change latent heat greater than 150 J / g, achieving efficient temperature buffering with a temperature control accuracy of ±0.1℃, far superior to thermally conductive materials without phase change function (temperature control fluctuations of ±1℃ or more). During optical device operation, this effectively suppresses temperature fluctuations, maintains stable optical performance, and extends device lifespan by more than 20%. This effect is verified through DSC analysis and actual device testing.

[0055] 5. Employing a dual-shaping strategy of microencapsulation and mild cross-linking, the material exhibits no liquid leakage during phase change cycling, maintains stable morphology, and retains >95% of its latent heat after 1000 cycles. Compared to traditional amorphous phase change materials, this avoids the risks of phase separation and leakage contamination of optical surfaces. This stability has been confirmed by thermal cycling experiments.

[0056] 6. The material maintains stable performance over a wide temperature range (-20 to 80℃), with modulus and thermal conductivity decreasing by less than 5% after cyclic use, making it suitable for long-term precision optical systems. Durability tests show no obvious signs of aging.

[0057] In addition to the above, it should be noted that the terms "one embodiment," "another embodiment," and "embodiment" used in this specification refer to specific features, structures, or characteristics described in connection with that embodiment, which are included in at least one embodiment described in the general description of this application. The appearance of the same expression in multiple places in the specification does not necessarily refer to the same embodiment. Furthermore, when a specific feature, structure, or characteristic is described in connection with any embodiment, the intention is to suggest that implementing such a feature, structure, or characteristic in conjunction with other embodiments also falls within the scope of this invention.

[0058] Although the invention has been described herein with reference to several illustrative embodiments, it should be understood that many other modifications and implementations can be devised by those skilled in the art, which will fall within the scope and spirit of the principles disclosed herein. More specifically, various variations and modifications can be made to the components and / or layout of the subject matter arrangement within the scope of the disclosure, drawings, and claims. Besides variations and modifications to the components and / or layout, other uses will be apparent to those skilled in the art.

Claims

1. A method for preparing a low-modulus phase change gel material, characterized in that... The preparation method includes the following steps: Weigh out 40-60 parts by weight of hyperbranched polymer matrix, 20-40 parts of high latent heat phase change microcapsules, 5-15 parts of flexible thermally conductive filler, 1-5 parts of crosslinking agent, and 0.1-1 parts of catalyst. The hyperbranched polymer matrix is ​​one or more of hyperbranched polyester, hyperbranched polyurethane and hyperbranched polysiloxane; The high latent heat phase change microcapsule has a core-shell structure, with the core material being any one of n-octadecane, paraffin, or fatty acid, and the shell material being any one of melamine resin, silicon dioxide, or polyurea. The flexible thermally conductive filler is one or more of hexagonal boron nitride, flexible graphene, and alumina nanosheets; The crosslinking agent is any one of polyisocyanate, silicone compound and epoxy resin; The catalyst is any one of dibutyltin dilaurate, platinum catalyst, and organotin compound; The hyperbranched polymer matrix was added to a reaction vessel and heated to 40-60°C. High latent heat phase change microcapsules were added and stirred until the high latent heat phase change microcapsules were completely wetted and uniformly dispersed to obtain the first mixture. The first mixture was cooled to room temperature, and a flexible thermally conductive filler was added. Stirring was continued to form the second mixture. A crosslinking agent and a catalyst are added to the second mixture simultaneously. After stirring for 5-10 minutes and vacuum degassing, the mixture is cooled to room temperature and allowed to solidify to obtain the transparent or translucent low-modulus phase change gel material.

2. The method for preparing the low-modulus phase change gel material according to claim 1, characterized in that: The method further includes adding a crosslinking agent and a catalyst, stirring and degassing the second mixture, pouring it into a mold, and cooling and curing it at room temperature for 12 to 24 hours to obtain a transparent or translucent low-modulus phase change gel material with a thickness of 0.2 to 1.5 mm.

3. The method for preparing the low-modulus phase change gel material according to claim 1, characterized in that: The method further includes adding a crosslinking agent and a catalyst, stirring and degassing the second mixture, pouring it into a mold, heating it to 50-80°C, and then cooling and curing it at room temperature for 2-6 hours to obtain a transparent or translucent low-modulus phase change gel material with a thickness of 0.2-1.5 mm.

4. The method for preparing the low-modulus phase change gel material according to any one of claims 1 to 3, characterized in that: After adding high latent heat phase change microcapsules to a hyperbranched polymer matrix, the high latent heat phase change microcapsules are completely wetted and uniformly dispersed by high-speed planetary stirring for 40–60 min under nitrogen protection or vacuum.

5. An application of the low-modulus phase change gel material according to any one of claims 1 to 4, characterized in that: The application involves using low-modulus phase change gel materials as a thermal interface layer on the surface of precision optical devices.

6. The method for preparing the low-modulus phase change gel material according to claim 5, characterized in that: The application involves directly coating the surface of an optical device with a second mixture containing a crosslinking agent and a catalyst, after stirring and degassing, with a coating thickness of 0.2–1.5 mm.

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