A non-silicon system heat-conducting phase change material for improving long-term reliability and a preparation method thereof

Abstract

The application belongs to the technical field of heat-conducting functional materials, and particularly relates to a non-silicon system heat-conducting phase change material for improving long-term reliability and a preparation method thereof. The non-silicon system heat-conducting phase change material for improving long-term reliability comprises the following raw materials in parts by mass: 50-70 parts of modified polyester resin, 20-30 parts of phase change wax, 1400-2000 parts of heat-conducting material, and 20-40 parts of dispersing agent; the modified polyester resin is a product of ester exchange between a polyester resin with an aromatic ring in a main chain and multi-arm polyethylene glycol. The application adopts a non-silicon system material formula, takes a high-temperature-resistant thermoplastic polyester solid resin modified by ester exchange as a main body, matches gradient particle size composite heat-conducting fillers, and realizes high heat conduction, high temperature resistance, no migration, no pumping out, and anti-shock slip through formula proportion optimization and preparation process improvement.

Description

Technical Field

[0001] This invention belongs to the field of thermally conductive functional materials technology, specifically relating to a non-silicon thermally conductive phase change material for improving long-term reliability and its preparation method. Background Technology

[0002] With the rapid development of high-end equipment such as robots, servers, and aerospace electronic equipment towards miniaturization, high integration, and high power density, the heat generation per unit volume of electronic components inside these devices is increasing dramatically. Furthermore, some equipment needs to operate for extended periods under complex and harsh conditions such as undirected vibration and high / low temperature cycling (-40℃ to 150℃), placing extremely stringent requirements on the comprehensive performance of thermal conductive materials. The heat dissipation efficiency, long-term stability, vibration and slip resistance, anti-contamination performance, and adaptability to operating conditions of thermal conductive materials directly determine the operational reliability, lifespan, and overall performance of electronic components. If heat cannot be dissipated in a timely manner, or if the thermal conductive material experiences failure phenomena such as pumping out, drying out, slippage, or silicon contamination, it will lead to overheating of components, decreased insulation performance, and even serious malfunctions such as short circuits and burnout.

[0003] Currently, the mainstream thermal conductive materials used in high-end electronic devices are mainly silicon-based, including silicone thermal conductive gels, thermal conductive greases, and silicone phase change materials. Although these materials have certain thermal conductivity, they have many inherent defects that are difficult to overcome: First, silicone gels are prone to molecular chain breakage and component migration under long-term high temperature (≥150℃) and vibration conditions, leading to pumping out, drying, and slippage, resulting in failure of the thermal interface and inability to achieve long-term stable heat dissipation; Second, the low-volatility silicon molecules contained in silicon-based materials are prone to escape during long-term service and are prone to silicon migration, forming silicon contamination. Silicon contamination will seriously damage the insulation performance and contact reliability of electronic components, and is especially unsuitable for sensitive components such as high-precision semiconductors and chips; Third, silicon-based materials generally have problems such as poor compatibility, fast thermal aging rate, and obvious low-temperature brittleness. Moreover, the phase change wax component selection is fixed and cannot be flexibly adapted to the temperature requirements of components with different heat dissipation power, further reducing the long-term service reliability of the materials.

[0004] While some existing non-silicon-based thermally conductive phase change materials can fundamentally avoid silicon contamination, they still have many technical shortcomings and cannot meet the stringent requirements of high-end equipment: insufficient temperature resistance, with long-term operating temperatures generally below 120℃; they are prone to softening, flowing, and migrating under high-temperature conditions; they dry and harden under prolonged high temperatures of 120℃, significantly increasing catalytic thermal resistance; they are prone to slippage under non-directional vibration environments, recurring some of the failure issues of organosilicon gels; the selection of thermally conductive fillers is limited, failing to construct dense thermal conductive pathways, resulting in low thermal conductivity and difficulty in meeting the heat dissipation requirements of high-power components; the selection of phase change wax lacks flexibility, not being designed as a variable component, resulting in poor adaptability; the dispersant dosage is poorly designed, easily leading to filler agglomeration in scenarios with high filler addition, resulting in decreased thermal conductivity and mechanical properties; at the same time, the material selection lacks specificity, failing to fully utilize the advantages of non-silicon materials, resulting in insufficient long-term service reliability and inability to adapt to the complex operating conditions of high-end equipment such as robots and servers. It is evident that existing silicon-based thermally conductive phase change materials suffer from core defects such as silicon contamination, silicone gel pumping out, drying, and slippage. Non-silicon-based thermally conductive phase change materials suffer from problems such as low thermal conductivity, poor temperature resistance, poor compatibility, and filler agglomeration caused by unreasonable dispersant dosage, which cannot meet the stringent requirements of high-end equipment.

[0005] Furthermore, the main resins of existing phase change materials are mainly divided into two categories: thermosetting and thermoplastic. Thermosetting resin precursors are mostly liquids, soft solids, or viscous flows, requiring irreversible curing through heating, radiation, or the addition of curing agents to avoid component leakage during the phase change process. However, the curing process is complex, time-consuming, and prone to generating byproducts, affecting material purity and component compatibility. For example, CN117987089A discloses a thermally conductive phase change interface material, which includes the following raw materials by mass percentage: 5%-18% liquid resin, 0.1%-1% thermoplastic elastomer, ≤0.1% antioxidant, ≤1.5% coupling agent, ≤0.1% dispersant, and 80%-94.6% thermally conductive filler. CN103965529A discloses a phase change thermally conductive composition comprising 2-40% liquid rubber, 2-40% phase change material, 0.5-10% reinforcing material, 0.5-5% tackifier, and 40-90% thermally conductive powder; the liquid rubber is a low molecular weight polymer that exhibits a viscous liquid state at room temperature.

[0006] Thermoplastic resins are solid at room temperature, melt upon heating to their melting point, and can be molded upon cooling without additional curing, making the process convenient. However, current thermoplastic non-silicone thermally conductive phase change materials cannot simultaneously achieve high thermal conductivity, high reliability, and adaptability to various operating conditions. Therefore, developing a non-silicone system with high thermal conductivity, high temperature resistance, vibration resistance, no silicon contamination, strong adaptability, and high long-term reliability has become an urgent need in the field of thermal conductive materials and has significant industrial application value. CN120555024A discloses a thermally conductive flexible composite phase change material, which is obtained by melt-blending maleic anhydride-grafted thermoplastic elastomer and phase change material, and adding thermally conductive fillers. CN109679535A discloses a curable phase change thermally conductive sticker for optical modules, and CN119060491A discloses a phase change thermally conductive composition. The existing technologies described above belong to thermoplastic phase change thermal conductive materials. Thermoplastic resins often employ styrene block copolymers, ethylene-vinyl acetate copolymers, polyolefin elastomers, petroleum resins, terpene resins, and rosin resins. However, these olefin-based thermoplastic resins have low melting points, generally below 150°C. Long-term use at higher temperatures easily leads to yellowing and degradation, resulting in insufficient long-term high-temperature resistance. Furthermore, polyolefin resins, due to their low polarity, generally have poor compatibility with inorganic thermally conductive fillers. Prolonged operation at high temperatures can also easily cause the thermally conductive filler to precipitate and delaminate. These combined factors result in the aforementioned phase change thermal conductive materials failing to simultaneously achieve high thermal conductivity, high temperature resistance, vibration resistance, and long-term reliability. In particular, their resistance to thermal shock and high-temperature stability are insufficient, and they are prone to slippage under non-directional vibration environments, leading to generally poor long-term reliability. Summary of the Invention

[0007] Addressing the core defects of existing silicon-based thermally conductive phase change materials, such as silicon contamination and organosilicon gel failure, as well as the problems of poor temperature resistance, weak vibration resistance, insufficient thermal conductivity, poor adaptability, and low long-term reliability of mainstream thermally conductive phase change materials, and considering the current industry situation of unreasonable main resin states, curing requirements, and dispersant dosages, this invention provides a non-silicon high-reliability thermally conductive phase change material and its preparation method. With the core objective of eliminating silicon contamination, this invention employs a non-silicon system to construct the material formulation, using high-temperature resistant thermoplastic polyester solid resin as the main component, with phase change wax as a variable component, combined with gradient particle size composite thermally conductive fillers and non-silicon functional additives. Through formulation ratio optimization and preparation process improvement, the material achieves high thermal conductivity, high temperature resistance, no migration, no pumping out, and vibration-resistant slippage. It can flexibly adapt to different heat-generating components and complex and harsh operating conditions, while simplifying the preparation process, improving industrialization feasibility, and solving the core pain points of existing technologies.

[0008] The present invention solves the above problems through the following technical solutions:

[0009] A non-silicon thermally conductive phase change material for improving long-term reliability comprises the following raw materials in parts by weight: 50-70 parts modified polyester resin, 20-30 parts phase change wax, 1400-2000 parts thermally conductive material, and 20-40 parts dispersant; wherein the modified polyester resin is a product of transesterification between a polyester resin containing an aromatic ring in its main chain and a multi-arm polyethylene glycol.

[0010] Existing thermoplastic resins based on olefin double bond polymerization (such as styrene block copolymers and polyolefin elastomers) have low melting points (generally below 150°C) and are prone to yellowing and degradation under long-term high temperatures. Polyester resins containing benzene rings have high melting points, generally between 220-230°C, which can meet the requirements for long-term heat aging resistance of phase change materials. However, phase change thermal conductive materials using PBT resin directly cannot achieve tight adhesion with heating elements under non-directional vibration conditions, easily leading to interfacial slippage and increased thermal contact resistance. Furthermore, PBT resin is a crystalline polymer, and undergoes significant volume changes during high and low temperature cycling, easily generating internal stress and deformation. Additionally, the compatibility between crystalline polymers and phase change materials such as paraffin wax is limited; when phase change occurs at higher temperatures, PBT resin's binding capacity for the phase change wax is insufficient, posing a risk of migration and / or leakage. This invention uses a modified polyester resin obtained by transesterification of multi-arm polyethylene glycol and PBT resin, which can solve the above problems. The inventors believe the possible reasons are as follows: Multiple arms of the multi-arm PEG can connect to PBT segments, constructing a three-dimensional network framework within the material. In the star-shaped structure formed by the multi-arm PEG, the dense end groups of the multiple arms can form more nucleation sites, inducing the formation of a fine and uniform microcrystalline structure, thus significantly improving the long-term reliability of the material. The introduction of the multi-arm structure significantly affects the crystallization rate and the degree of crystallization perfection, resulting in a decrease in the overall crystallinity of the material. Reduced crystallinity means a smaller volume change rate during the phase transition process, significantly improving the dimensional stability of the material under thermal cycling. Furthermore, the binding ability of this three-dimensional network structure for the phase change wax reduces the risk of migration and leakage. The inventors also found that using linear polyethylene glycol instead of multi-arm polyethylene glycol, or using small molecules such as pentaerythritol for transesterification, is not effective. Linear polyethylene glycol cannot form a three-dimensional network structure and has weak binding ability. Pentaerythritol lacks flexible segments, and the transesterification product is still a highly crystalline rigid chain, failing to solve the problem of vibration-resistant adhesion. More importantly, the PBT segments are forcibly anchored to the tiny core, reducing the free volume of the molecular chains and severely restricting the movement of the segments, which makes the material brittle and more prone to cracking due to internal stress concentration during thermal cycling.

[0011] Furthermore, the polyester resin containing aromatic rings in the main chain is selected from at least one of polybutylene terephthalate (PBT) and polyethylene terephthalate (PET), with an intrinsic viscosity of 0.7-0.9 dL / g and a melting point of 220-230℃, preferably 224-226℃.

[0012] Furthermore, the multi-arm polyethylene glycol is at least one of three-arm polyethylene glycol, four-arm polyethylene glycol, six-arm polyethylene glycol, and eight-arm polyethylene glycol, and the number-average molecular weight of the multi-arm polyethylene glycol is 2000-8000 g / mol, preferably 3000-6000 g / mol. The molecular weight of the multi-arm polyethylene glycol cannot be too low, otherwise its thermal stability will be insufficient, and it may decompose unstablely at the processing temperature, leading to a deterioration in product performance.

[0013] Further, the raw materials for the modified polyester resin include 100 parts by weight of polyester resin, 12-18 parts of multi-arm polyethylene glycol, and 0.5-1 parts of transesterification catalyst; even further, the transesterification catalyst includes at least one of zinc compound, titanium compound, tin compound, and antimony compound; specifically selected from at least one of antimony acetate, titanium acetate, zinc acetate, titanium tetrachloride, tetramethyl titanate, potassium titanate, tetraethyl titanate, tetraisopropyl titanate, tetrabutyl titanate, titanium dioxide, stannous oxide, stannous oxalate, stannous octoate, stannous chloride, stannous lactate, tributyltin acetate, dibutyltin diacetate, diphenyltin dilaurate, monobutyltin trichloride, methylstannic acid, butylstannic acid, and antimony trioxide.

[0014] Furthermore, the modified polyester resin is prepared by a method including the following steps: under an inert atmosphere, a polyester resin containing aromatic rings in the main chain, multi-arm polyethylene glycol, and an ester exchange catalyst are fed in, the temperature is raised to a temperature higher than the melting point of the polyester resin containing aromatic rings in the main chain, a vacuum is drawn, the reaction is carried out until the viscosity of the system no longer changes, an inert atmosphere is introduced to restore normal pressure, the mixture is cooled, and dried to obtain the modified polyester resin.

[0015] Furthermore, the inert atmosphere is nitrogen and / or argon, the temperature is raised to a temperature higher than the melting point of the polyester resin containing aromatic rings in the main chain, which is 230-240℃; and the vacuum is drawn to a pressure of 5-100Pa.

[0016] Furthermore, the phase change wax has a phase change temperature range of 40-70℃; specifically, it is selected from at least one of paraffin wax, microcrystalline wax, Fischer-Tropsch wax, polyethylene glycol, polyethylene wax, polypropylene wax, beeswax, and carnauba wax.

[0017] Further, the thermally conductive material includes spherical aluminum powder, boron nitride, aluminum oxide / zinc oxide, and non-silicon whisker materials. Even further, the composite thermally conductive material includes spherical aluminum powder with a D50 of 10-15 μm, boron nitride with a D50 of 2-5 μm, aluminum oxide and / or zinc oxide with a D50 of 0.2-0.5 μm, and the non-silicon whisker material is selected from at least one of calcium carbonate whiskers and aluminum borate whiskers; the non-silicon whisker material has a length of 20-60 μm, a diameter of 0.5-3 μm, and an aspect ratio of 20-30. Even further, the thermally conductive material is a mixture of spherical aluminum powder, boron nitride, aluminum oxide and / or zinc oxide, and non-silicon whisker materials in a mass ratio of 1200-1400:300-400:100-150:30-50. This invention employs a blend of various thermally conductive fillers of different sizes and in varying proportions to achieve a synergistic effect: spherical aluminum powder with larger particle sizes is inexpensive and serves as the main component of the thermally conductive filler; boron nitride with smaller particle sizes improves the uniformity of thermal conductivity; even smaller metal oxide particles fill the thermally conductive pores; and non-silicon whisker materials enhance the continuity of the thermal conductivity pathway and mechanical properties. Through the synergistic effect of fillers with different particle sizes, a significant improvement in thermal conductivity is achieved, while the mechanical properties of the material are also guaranteed to a certain extent.

[0018] Furthermore, the dispersant is selected from at least one of hydrogenated castor oil, carboxymethyl cellulose, polyvinyl alcohol, gelatin, and polycarboxylate.

[0019] Furthermore, the non-silicon thermally conductive phase change material of the present invention also includes various non-silicon functional additives, such as antioxidants and coupling agents. Their dosages and types are well known in the art. For example, the non-silicon thermally conductive phase change material also includes 1-3 parts of antioxidant and 1-10 parts of coupling agent. In one specific embodiment of the present invention, the antioxidant is selected from at least one of antioxidant 1010 and antioxidant 1076; the coupling agent is selected from at least one of aminosilane coupling agents (such as those with γ-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, γ-diethylenetriaminepropylmethyldimethoxysilane), titanate coupling agents (such as phosphate bistitanate, isopropyl dioleoyloxy(dioctylphosphoyloxy)titanate), and aluminate coupling agents (such as distearyloxyisopropylaluminate, isopropoxydistearyloxyaluminate, triisopropoxyaluminum).

[0020] The present invention also provides a method for preparing the aforementioned non-silicon thermally conductive phase change material with improved reliability, comprising the following steps:

[0021] (S1) The modified polyester resin is dried, pulverized, and added to a melting kettle. The temperature is raised until the modified polyester resin melts. Phase change wax is added to disperse the phase change wax evenly in the molten resin to form a mixed matrix.

[0022] (S2) Predispersing thermally conductive filler and dispersant yields predispersed filler;

[0023] (S3) The pre-dispersed filler is added to the mixed matrix in batches and mixed evenly under high-speed stirring. The mixed material is then added to the mold, cooled, demolded, and cut to obtain a non-silicon thermally conductive phase change material.

[0024] Further, in step (S1), drying is drying to a moisture content of ≤0.1% to remove moisture from the raw materials and avoid affecting the material properties; pulverizing is pulverizing to a particle size of 20-100μm to facilitate subsequent melting and mixing; heating to melt the modified polyester resin is heating to 230-240℃.

[0025] Furthermore, in step (S2), pre-dispersion involves initially dispersing the filler in a high-speed mixer at a speed of 2000-3000 rpm to prevent subsequent agglomeration.

[0026] Furthermore, in step (S3), the pre-dispersed filler is added to the mixed matrix in batches of 10-20% each time. After each batch is added, the filler is dispersed for 10-20 minutes under high-speed stirring and ultrasonic dispersion before adding the next batch. This batch-by-batch addition ensures that the gradient particle size thermally conductive filler is uniformly dispersed in the mixed matrix, constructing a dense thermally conductive pathway. Even further, the high-speed stirring speed is 2000-3000 rpm.

[0027] Optionally, in step (S3), after all the pre-dispersed filler is added to the mixed matrix and dispersed evenly, non-silicone functional additives, such as antioxidants and coupling agents, are added; after adding the non-silicone functional additives, the mixture is stirred at 400-1000 rpm for 0.5-1 h to ensure that the functional additives are evenly dispersed and to achieve the functional modification of the material.

[0028] The present invention has achieved the following beneficial effects:

[0029] I. The entire process of this invention adopts a non-silicon system design. All raw material components (main resin, phase change wax, composite thermally conductive filler, functional additives) do not contain any silicon elements, thus eliminating the introduction of silicon components from the source. This effectively avoids silicon contamination problems caused by the escape of low-volatility silicon molecules and silicon migration in silicon-based materials, ensuring the insulation performance and contact reliability of high-precision electronic components, and preventing component failure due to silicon contamination.

[0030] II. The main resin is a high-temperature resistant thermoplastic polyester solid resin. Through transesterification modification with multi-arm polyethylene glycol, the resulting modified polyester resin has excellent high-temperature resistance, good cohesion and compatibility. It can be used as a matrix to effectively support the uniform dispersion of thermally conductive fillers, while improving the material's temperature resistance, vibration resistance, slip resistance and long-term service stability.

[0031] III. Composite Thermal Conductive Materials: Non-silicon thermally conductive fillers are selected, employing a gradient particle size design to construct a dense thermal conductivity pathway, balancing thermal conductivity and mechanical properties. Spherical aluminum powder dominates thermal conductivity, boron nitride improves thermal conductivity uniformity, zinc oxide / alumina fills thermal conductivity gaps, and non-silicon whisker materials enhance the continuity of the thermal conductivity pathway and the mechanical properties of the materials. Through the synergistic effect of fillers with different particle sizes, a significant improvement in thermal conductivity efficiency is achieved. Attached Figure Description

[0032] Figure 1 This is an example diagram of vibration resistance performance testing.

[0033] Figure 2 These are photos of the thermally conductive patch made of phase change material in Example 1 before and after vibration resistance testing.

[0034] Figure 3 These are photos of the phase change material used in Comparative Example 1, made into a thermally conductive patch, before and after a vibration resistance test.

[0035] Figure 4 These are photos of the phase change material used in Comparative Example 3, made into a thermally conductive patch, before and after a vibration resistance test. Detailed Implementation

[0036] The present invention will be further described in detail below through specific embodiments.

[0037] The intrinsic viscosity of PBT resin is 0.82 dL / g, and the melting point is 225℃.

[0038] Preparation Example 1

[0039] Under a nitrogen atmosphere, 100 kg of PBT resin, 12 kg of tetra-arm polyethylene glycol with a number average molecular weight of 3000, and 0.5 kg of tetrabutyl titanate were added to a reactor. The temperature was raised to 230°C, and the system was evacuated to 10 Pa. The reaction was carried out for 5 hours under stirring until the viscosity of the system no longer changed. Nitrogen gas was then introduced to restore the atmospheric pressure, and the system was cooled to room temperature and dried in an oven to obtain the modified polyester resin.

[0040] Preparation Example 2

[0041] The other conditions and operations are the same as in Preparation Example 1, except that 12 kg of four-arm polyethylene glycol with a number average molecular weight of 3000 is replaced with 18 kg of six-arm polyethylene glycol with a number average molecular weight of 6000.

[0042] Comparative Preparation Example 1

[0043] The other conditions and operations are the same as in Preparation Example 1, except that 12 kg of four-arm polyethylene glycol with a number average molecular weight of 3000 is replaced with 12 kg of polyethylene glycol with a number average molecular weight of 3000.

[0044] Comparative Preparation Example 2

[0045] The other conditions and operations were the same as in Preparation Example 1, except that the PBT resin was replaced with an equal mass of PBS resin (polybutylene succinate, melting point 117°C), and the temperature was changed from 230°C to 120°C.

[0046] Example 1

[0047] (S1) Dry 5 kg of the modified polyester resin prepared in Preparation Example 1 in a vacuum drying oven until the moisture content is ≤0.1%, pulverize it to a particle size of about 50 μm, add it to a melting kettle, heat it to 230°C, add 3 kg of paraffin wax (melting point 45°C), so that the paraffin wax is evenly dispersed in the molten resin to form a mixed matrix.

[0048] (S2) 163 kg of composite thermally conductive filler (including 120 kg of spherical aluminum powder with Dv50=10μm and Dv90=21μm, 30 kg of boron nitride with Dv50=2μm, 10 kg of zinc oxide with Dv50=0.2μm, and 3 kg of calcium carbonate whiskers with a length of 30-50μm and an aspect ratio of about 20) and 2 kg of polycarboxylate XT-2000 were pre-dispersed in a high-speed mixer at 2000 rpm for 0.5 h to obtain pre-dispersed filler;

[0049] (S3) In a high-speed mixer, the pre-dispersed filler is added in 5 batches at a speed of 2000 rpm, with 20% of each batch added to the mixing matrix and mixed evenly. After each batch is added, the mixture is stirred at high speed for 15 minutes before adding the next batch. After all the pre-dispersed filler has been added and mixed, 0.1 kg of antioxidant 1010, 0.3 kg of 3-aminopropyltriethoxysilane, and 0.2 kg of phosphate bis-titanium ester are added and mixed evenly at a speed of 800 rpm. The evenly mixed material is then added to a mold, cooled, demolded, and cut to obtain a non-silicon thermally conductive phase change material.

[0050] Example 2

[0051] The other conditions and operations are the same as in Example 1, except that in step (S1), the modified polyester resin obtained in Preparation Example 1 is replaced with an equal mass of the modified polyester resin obtained in Preparation Example 2.

[0052] Example 3

[0053] The other conditions and operations are the same as in Example 1, except that in step (S1), the amount of modified polyester resin prepared in Example 1 is changed from 5 kg to 7 kg; in step (S2), the composite thermally conductive filler is changed to 200 kg of composite thermally conductive filler (including 140 kg of spherical aluminum powder with Dv50=15 μm and Dv90=27 μm, 40 kg of boron nitride with Dv50=2 μm, 15 kg of aluminum oxide with Dv50=0.2 μm, and 5 kg of aluminum borate whiskers with a length of 30-50 μm and an aspect ratio of about 30).

[0054] Example 4

[0055] The other conditions and operations are the same as in Example 1, except that calcium carbonate whiskers are not added to the composite thermally conductive filler in step (S2).

[0056] Example 5

[0057] (S1) Dry 5 kg of the modified polyester resin prepared in Example 1 in a vacuum drying oven until the moisture content is ≤0.1%, pulverize it to a particle size of about 50 μm, add it to a melting kettle, heat it to 230°C, add 3 kg of paraffin wax (melting point 45°C), so that the phase change wax is evenly dispersed in the molten resin to form a mixed matrix; that is, step (S1) is the same as in Example 1;

[0058] (S2) Weigh 163kg of composite thermally conductive filler (including 120kg of spherical aluminum powder with Dv50=10μm and Dv90=21μm, 30kg of boron nitride with Dv50=2μm, 10kg of zinc oxide with Dv50=0.2μm, and 3kg of calcium carbonate whiskers with a length of 30-50μm and an aspect ratio of about 20).

[0059] (S3) In a high-speed mixer, the composite thermally conductive filler and 3.7 kg of polycarboxylate XT-2000 are added to the mixing matrix at a speed of 2000 rpm and mixed evenly. After all the filler is added and mixed, 0.1 kg of antioxidant 1010, 0.2 kg of 3-aminopropyltriethoxysilane, and 0.3 kg of phosphate bis-titanium ester are added and mixed evenly at a speed of 800 rpm. The evenly mixed material is then added to a mold, cooled, demolded, and cut to obtain a non-silicon thermally conductive phase change material.

[0060] The difference between Example 5 and Example 1 is that the composite thermally conductive filler is not pre-dispersed with the dispersant, but is directly mixed with the dispersant and the mixed matrix. The amount of dispersant is increased from 2 kg to 3.7 kg to achieve uniform dispersion.

[0061] Comparative Example 1

[0062] The other conditions and operations are the same as in Example 1, except that in step (S1), the modified polyester resin obtained in Preparation Example 1 is replaced with an equal mass of PBT polyester resin.

[0063] Comparative Example 2

[0064] The other conditions and operations are the same as in Example 1, except that in step (S1), the modified polyester resin prepared in Preparation Example 1 is replaced with an equal mass of the modified polyester resin prepared in Comparative Preparation Example 1.

[0065] Comparative Example 3

[0066] Other conditions and operations are the same as those in Example 1, except that in step (S1), the modified polyester resin prepared in Preparation Example 1 is replaced with an equal mass of the modified polyester resin prepared in Comparative Preparation Example 2.

[0067] Application Example

[0068] The following performance tests were conducted on the thermal conductive phase change materials of the above examples and comparative examples, and the results are shown in Table 1 below.

[0069] 1. Silicon content detection: Referring to GB / T 29493.4-2013, the silicon content detection lower than 0.01% is qualified.

[0070] 2. Thermal resistance test: Refer to ASTM D5470, the test equipment is Longwin thermal resistance tester, and the test conditions are 25±2℃&50±5 RH%;

[0071] 3. Temperature resistance performance test: Keep at a constant temperature of 150℃ for 1000h, retest the thermal resistance, and calculate the thermal resistance change rate.

[0072] 4. High and low temperature cycle resistance: Cycle at -40℃ / 0.5h and 120℃ / 0.5h for 1000h, retest the thermal resistance, and calculate the thermal resistance change rate.

[0073] 5. Vibration resistance performance: Make a circular thermal conductive gasket from the thermal conductive phase change material with a size of 25mm×25mm×0.1mm. The thermal conductive gasket is attached to the test bench of the temperature, humidity and vibration three-in-one test machine. The test bench includes X and Y axes with scales. The thermal conductive gasket is attached to the center position of the X and Y axes. Under the conditions of 30Hz and an amplitude of 0.2mm, vibrate for 64 hours on the X axis + 64 hours on the Y axis, and test the slip distance of the thermal conductive gasket. If the thermal conductive gasket does not crack and the slip distance in any direction does not exceed 0.5mm, it is qualified; if cracking occurs, or the slip distance in any direction exceeds 0.5mm, it is unqualified. An example of the vibration resistance performance test is shown in Figure 1 as shown.

[0074] Figure 2 are the photos of the thermal conductive patch made of the phase change material in Example 1 before and after the vibration resistance performance test. Figure 3 are the photos of the thermal conductive patch made of the phase change material in Comparative Example 1 before and after the vibration resistance performance test. Figure 4 are the photos of the thermal conductive patch made of the phase change material in Comparative Example 3 before and after the vibration resistance performance test. It can be seen that after 128h of vibration (64 hours of X-axis vibration + 64 hours of Y-axis vibration), the sample of the phase change material in Example 1 has no slip and no cracking; the thermal conductive sheet made of the phase change material in Comparative Example 1 has serious slip after 128h of vibration; while the thermal conductive sheet made of the phase change material in Comparative Example 3 has cracking and a little slip after 128h of vibration.

[0075] Table 1 Performance Tests of Thermally Conductive Phase Change Materials

[0076]

[0077] As shown in Table 1, the thermally conductive phase change material prepared by this invention uses silicon-free raw materials throughout the entire process, completely eliminating silicon contamination. The silicon content is ≤0.01%, effectively ensuring the insulation performance and contact reliability of high-precision electronic components, avoiding short circuits and failures caused by silicon contamination. This makes it suitable for high-end applications sensitive to silicon contamination, such as servers, robots, and aerospace electronic equipment. It exhibits excellent and long-term reliable thermal conductivity. Even after long-term high-temperature aging and high-low temperature cycling, the increase in thermal resistance is minimal, allowing for long-term service at 120~150℃. Under high-low temperature cycling and vibration conditions, there is no migration, pumping out, slippage, cracking, or pulverization, resulting in a long service life.

Claims

1. A non-silicon thermally conductive phase change material for improving long-term reliability, comprising the following raw materials in parts by weight: 50-70 parts modified polyester resin, 20-30 parts phase change wax, 1400-2000 parts thermally conductive material, and 20-40 parts dispersant; characterized in that, The modified polyester resin is a product of transesterification between a polyester resin containing an aromatic ring in its main chain and a multi-arm polyethylene glycol.

2. The non-silicon thermally conductive phase change material according to claim 1, characterized in that, The polyester resin containing aromatic rings in its main chain is selected from at least one of polybutylene terephthalate (PBT) and polyethylene terephthalate (PET), with an intrinsic viscosity of 0.7-0.9 dL / g and a melting point of 220-230℃.

3. The non-silicon thermally conductive phase change material according to claim 1, characterized in that, The multi-arm polyethylene glycol is at least one of three-arm polyethylene glycol, four-arm polyethylene glycol, six-arm polyethylene glycol, and eight-arm polyethylene glycol, and the number average molecular weight of the multi-arm polyethylene glycol is 2000-8000 g / mol, preferably 3000-6000 g / mol.

4. The non-silicon thermally conductive phase change material according to claim 1, characterized in that, The modified polyester resin comprises 100 parts by weight of polyester resin, 12-18 parts of multi-arm polyethylene glycol, and 0.5-1 parts of transesterification catalyst; further, the transesterification catalyst comprises at least one of zinc compound, titanium compound, tin compound, and antimony compound; specifically selected from at least one of antimony acetate, titanium acetate, zinc acetate, titanium tetrachloride, tetramethyl titanate, potassium titanate, tetraethyl titanate, tetraisopropyl titanate, tetrabutyl titanate, titanium dioxide, stannous oxide, stannous oxalate, stannous octoate, stannous chloride, stannous lactate, tributyltin acetate, dibutyltin diacetate, diphenyltin dilaurate, monobutyltin trichloride, methylstannic acid, butylstannic acid, and antimony trioxide.

5. The non-silicon thermally conductive phase change material according to claim 1, characterized in that, The modified polyester resin is prepared by a method including the following steps: under an inert atmosphere, a polyester resin containing aromatic rings in the main chain, multi-arm polyethylene glycol, and transesterification catalyst are fed in, the temperature is raised to a temperature higher than the melting point of the polyester resin containing aromatic rings in the main chain, a vacuum is drawn, the reaction is carried out until the viscosity of the system no longer changes, an inert atmosphere is introduced to restore normal pressure, the mixture is cooled and dried to obtain the modified polyester resin. Furthermore, the inert atmosphere is nitrogen and / or argon, and the temperature is raised to a level higher than the melting point of the polyester resin containing aromatic rings in the main chain, which is 230-240°C; and the vacuum is evacuated to a pressure of 5-100 Pa.

6. The non-silicon thermally conductive phase change material according to claim 1, characterized in that, The phase change wax has a phase change temperature range of 40-70℃; specifically, it is selected from at least one of paraffin wax, microcrystalline wax, Fischer-Tropsch wax, polyethylene glycol, polyethylene wax, polypropylene wax, beeswax, and carnauba wax.

7. The non-silicon thermally conductive phase change material according to claim 1, characterized in that, The thermally conductive material includes spherical aluminum powder, boron nitride, aluminum oxide / zinc oxide, and non-silicon whisker materials; further, the composite thermally conductive material includes spherical aluminum powder with a D50 of 10-15 μm, boron nitride with a D50 of 2-5 μm, aluminum oxide and / or zinc oxide with a D50 of 0.2-0.5 μm, and the non-silicon whisker material is selected from at least one of calcium carbonate whiskers and aluminum borate whiskers; the non-silicon whisker material has a length of 20-60 μm, a diameter of 0.5-3 μm, and an aspect ratio of 20-30; and / or the dispersant is selected from at least one of hydrogenated castor oil, carboxymethyl cellulose, polyvinyl alcohol, gelatin, and polycarboxylate.

8. The non-silicon thermally conductive phase change material according to claim 1, characterized in that, The thermally conductive material is a compound of spherical aluminum powder, boron nitride, aluminum oxide and / or zinc oxide, and non-silicon whisker materials in a mass ratio of 1200-1400:300-400:100-150:30-50.

9. A method for preparing a non-silicon thermally conductive phase change material with improved reliability as described in any one of claims 1-8, characterized in that, Includes the following steps: (S1) The modified polyester resin is dried, pulverized, and added to a melting kettle. The temperature is raised until the modified polyester resin melts. Phase change wax is added to disperse the phase change wax evenly in the molten resin to form a mixed matrix. (S2) Predispersing thermally conductive filler and dispersant yields predispersed filler; (S3) The pre-dispersed filler is added to the mixed matrix in batches and mixed evenly under high-speed stirring. The mixed material is then added to the mold, cooled, demolded, and cut to obtain a non-silicon thermally conductive phase change material.

10. The preparation method according to claim 9, characterized in that, In step (S2), pre-dispersion involves initially dispersing the thermally conductive filler in a high-speed mixer at a speed of 2000-3000 rpm; and / or In step (S3), the pre-dispersed filler is added to the mixed matrix in batches of 10-20% each time. After each batch is added, the pre-dispersed filler is dispersed for 10-20 minutes by high-speed stirring and ultrasonic dispersion before the next batch of pre-dispersed filler is added. Furthermore, the high-speed stirring speed is 2000-3000 rpm.

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