Composite phase change heat storage material and preparation method thereof

Abstract

The invention belongs to the technical field of phase change heat storage materials, and particularly discloses a composite phase change heat storage material and a preparation method thereof.The phase change heat storage material is prepared from, by mass, 60%-80% of an organic phase change matrix, 10%-25% of a polymer supporting body, 1%-5% of a plasticizing modifier, 3%-10% of a heat conduction reinforcing body and 0.1%-2% of a reinforcing and toughening body; the sum of the mass percentages of the components is 100%. According to the composite phase change heat storage material and the preparation method thereof, through an innovative technical route of phase change matrix compounding, heat conduction network construction and reinforced phase design, the core problems that an existing phase change heat storage material is insufficient in heat storage performance, poor in stability, low in heat conductivity and the like are solved, and the composite phase change heat storage material has outstanding substantive features and remarkable progress; the large-scale industrial application prospect is realized.

Description

Technical Field

[0001] This invention relates to the field of phase change thermal energy storage materials, and in particular to a composite phase change thermal energy storage material and its preparation method. Background Technology

[0002] With the rapid development of the global economy and the continuous growth of energy consumption, energy issues have become a global focus. Traditional fossil fuels such as coal, oil, and natural gas not only have limited reserves but also generate large amounts of pollutants during use, causing serious damage to the environment.

[0003] At the same time, clean energy sources such as solar and wind power have been widely developed due to their environmentally friendly and renewable characteristics. Therefore, high-efficiency energy storage technology has become the core support for solving the problem of clean energy consumption. It can achieve energy peak shaving and valley filling, improve energy utilization efficiency by more than 30%, and ensure supply stability.

[0004] Phase change thermal energy storage materials (PCMs) have broad application prospects in many fields due to their advantages of high energy density and near-isothermal heat storage and release. In the building sector, incorporating them into the building envelope can reduce indoor temperature fluctuations by 3-5°C and reduce air conditioning energy consumption by 20%-30%. In the solar energy utilization sector, thermal collection systems equipped with PCMs can achieve 24-hour continuous energy supply, improving utilization efficiency by more than 40%. In the industrial waste heat recovery sector, they can recover medium and low temperature waste heat below 300°C with a recovery rate of over 60%. In addition, they have important applications in electronic equipment heat dissipation and cold chain logistics.

[0005] Existing phase change thermal energy storage materials suffer from four major defects: ① Insufficient thermal storage performance: the phase change enthalpy of organic PCMs is generally below 180 J / g, while inorganic PCMs, although having higher enthalpy values, are prone to crystallization; ② Poor stability: the phase change enthalpy of organic PCMs decreases by more than 15% after 50 cycles, while inorganic PCMs are prone to phase separation; ③ Low thermal conductivity: most PCMs have a thermal conductivity of only 0.1-0.3 W / (m·K), resulting in slow heat storage and release rates; ④ Corrosion and safety issues: inorganic PCMs cause corrosion rates of 0.5-1.0 mm / year to metal containers, while organic PCMs have low flash points (some below 150℃). These defects make it difficult for existing materials to meet the needs of large-scale industrial applications, necessitating the development of new high-performance PCMs and their preparation technologies. Summary of the Invention

[0006] The purpose of this invention is to provide a composite phase change thermal storage material and its preparation method. Through an innovative technical route of phase change matrix compounding, thermally conductive network construction, and enhanced phase design, it solves the core problems of insufficient thermal storage performance, poor stability, and low thermal conductivity of existing phase change thermal storage materials. It has outstanding substantive features and significant progress, and has the prospect of large-scale industrial application.

[0007] To achieve the above objectives, the present invention provides a composite phase change thermal storage material, which, by mass percentage, is composed of the following components: 60%-80% organic phase change matrix, 10%-25% polymer support, 1%-5% plasticizer, 3%-10% thermal conductivity enhancer, and 0.1%-2% reinforcing and toughening agent; the sum of the mass percentages of each component is 100%; the phase change enthalpy of the thermal storage material is 200-250 J / g, the thermal conductivity is 1.0-2.0 W / (m·K), the phase change enthalpy retention rate after 100 phase change cycles is ≥94%, and the decomposition temperature is ≥300℃.

[0008] Preferably, the organic phase change matrix is ​​selected from one or more of C12-C24 aliphatic hydrocarbons, C8-C22 aliphatic alcohols, C8-C22 fatty acids, and polyols; when it is a mixture of aliphatic hydrocarbons and polyols, the mass ratio is 1:3-3:1.

[0009] Preferably, the polymer support is selected from one or more of ethylene-vinyl acetate copolymer, polyamide copolymer, waterborne polyurethane, and low-density polyethylene; the vinyl acetate content of the ethylene-vinyl acetate copolymer is 20%-40%.

[0010] Preferably, the plasticizer is selected from one or more of tributyl citrate, dioctyl phthalate, and dioctyl adipate, with a purity ≥99%.

[0011] Preferably, the thermal conductivity reinforcement is expanded graphite, which is obtained by expanding natural flake graphite at 700-900℃ for 30-60s, with an expansion ratio of 50-100 times and a particle size of 50-200μm.

[0012] Preferably, the reinforcing and toughening agent is alkali-free glass fiber with a single filament diameter of 0.1-30μm and a length of 1-5mm.

[0013] This invention also provides a method for preparing a composite phase change thermal storage material, comprising the following steps: Step 1, Preparation of thermally conductive reinforcement: Natural flake graphite is placed in a muffle furnace at 700-900℃ and expanded for 30-60 seconds. After cooling, expanded graphite is obtained. Step 2, Modification of the reinforcing and toughening agent: Dry the reinforcing and toughening agent, immerse it in the modification solution, and soak it at room temperature for 10-20 minutes to ensure that the fiber surface is evenly coated with the modification solution. After removing it, dry and cure it. Step 3, melting and dispersing of phase change matrix: heat the organic phase change matrix to 10-20°C above its melting point to melt it, add expanded graphite, and stir at 250-350 r / min for 25-35 min at 80-100°C; Step 4, support composite: Heat to 5-10°C above the melting temperature of the polymer support, add the polymer support, and stir at 350-450 r / min for 35-45 min; Step 5, Modification and Reinforcement: Keep the temperature constant, add plasticizer and modified reinforcement toughening agent, and stir at 450-550 r / min for 45-55 min; Step 6, Degassing and Molding: Vacuum the composite melt to -0.09~-0.095MPa, keep it at the temperature for 20-30 minutes to degas, then cast it into a mold or hot press it into a sheet, and cool it to room temperature at a rate of 5-10℃ / min to obtain the finished product.

[0014] Preferably, in step 2, the modified solution is prepared by using aminosilane or epoxysilane as a coupling agent, dissolving the coupling agent in an ethanol-water solution at a mass ratio of 1:50-1:100, with the volume ratio of ethanol to water being 3:1-5:1, and stirring for 5-10 minutes to form a uniform modified solution.

[0015] Preferably, in step 6, the hot pressing is performed using a two-roller coating machine with a roller temperature of 80-120℃ and a pressure of 5-10MPa to produce a sheet with a thickness of 0.5-5mm.

[0016] The advantages and beneficial effects of the composite phase change thermal storage material and its preparation method described above are as follows: 1. Breakthrough in Thermal Storage Performance: Through organic phase change material compounding technology, the phase change enthalpy reaches 200-250 J / g, and the melting point can be continuously controlled from 20-150℃, adapting to different application scenarios. Significantly Enhanced Stability: The polymer support and glass fiber form a dual network structure, achieving a phase change enthalpy retention rate ≥94% and a decomposition temperature ≥300℃ after 100 cycles, more than doubling the cycle life compared to traditional materials. Leapfrog Improvement in Thermal Conductivity: The thermally conductive network constructed from expanded graphite achieves a thermal conductivity of 1.0-2.0 W / (m·K), increasing the rate of heat storage and release. Enhanced Safety: The material's corrosion rate to carbon steel is ≤0.05 mm / year, and its flash point is ≥300℃, eliminating the risk of combustion.

[0017] The technical solution of the present invention will be further described in detail below through embodiments. Detailed Implementation

[0018] The technical solution of the present invention will be further described below through embodiments.

[0019] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0020] The following examples are not intended to limit the invention, but are only for illustration. Unless otherwise specified, the experimental methods used in the following examples are generally performed under conventional conditions. Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0021] Example 1 A composite phase change thermal energy storage material comprises the following components by mass percentage: stearic acid (melting point 69°C) 70%, ethylene-vinyl acetate copolymer (vinyl acetate VA content 30%, melting point 99°C) 18%, dioctyl phthalate 3%, expanded graphite (expanded at 800°C, expansion ratio 80 times) 7%, and alkali-free glass fiber (diameter 10μm, length 3mm) 2%.

[0022] A method for preparing a composite phase change thermal storage material, comprising the following steps: Step 1, Preparation of thermal conductivity reinforcement: Natural flake graphite was placed in a muffle furnace at 800℃ and expanded for 40s. After cooling, expanded graphite was obtained.

[0023] Step 2, Reinforcing and Toughening Modification: Dry the alkali-free glass fiber, immerse it in the modification solution, and soak it at room temperature for 12 minutes to ensure that the fiber surface is evenly coated with the modification solution. After removing it, dry and cure it.

[0024] The modified solution was prepared by using aminosilane as a coupling agent, dissolving the coupling agent in an ethanol-water solution at a mass ratio of 1:60, with a volume ratio of ethanol to water of 4:1, and stirring for 5 minutes to form a homogeneous modified solution.

[0025] Step 3, phase change matrix melting and dispersion: Stearic acid is heated to 80°C to melt, expanded graphite is added, and stirred at 300 r / min for 30 min at 85°C.

[0026] Step 4, support composite: Heat to 105℃, add ethylene-vinyl acetate copolymer, and stir at 400r / min for 40min.

[0027] Step 5, Modification and Reinforcement: Keep the temperature constant, add dioctyl phthalate and modified alkali-free glass fiber, and stir at 500 r / min for 50 min.

[0028] Step 6, Degassing and Molding: Vacuum the composite melt to -0.09MPa, keep it at the temperature for 25 minutes to degas, and then use a two-roller coater (roller temperature 100℃, pressure 8MPa) to make a 2mm thick sheet; cool it to room temperature at a rate of 8℃ / min.

[0029] Example 2 A composite phase change thermal storage material comprises the following components by mass percentage: 65% octadecyl alcohol (melting point 62℃), 20% polyamide 66 (melting point 260℃), 4% dioctyl adipate, 8% expanded graphite (expanded at 750℃, expansion ratio 70 times), and 3% alkali-free glass fiber (diameter 5μm, length 2mm).

[0030] A method for preparing a composite phase change thermal storage material, comprising the following steps: Step 1, Preparation of thermal conductivity reinforcement: Natural flake graphite was placed in a muffle furnace at 750℃ and expanded for 50s. After cooling, expanded graphite was obtained.

[0031] Step 2, Reinforcing and Toughening Modification: Dry the alkali-free glass fiber, immerse it in the modification solution, and soak it at room temperature for 15 minutes to ensure that the fiber surface is evenly coated with the modification solution. After removing it, dry and cure it.

[0032] The modified solution was prepared by using epoxy silane as a coupling agent, dissolving the coupling agent in an ethanol-water solution at a mass ratio of 1:70, with a volume ratio of ethanol to water of 3:1, and stirring for 10 minutes to form a homogeneous modified solution.

[0033] Step 3, phase change matrix melting and dispersion: heating octadecyl alcohol to 75°C to melt, adding expanded graphite, and stirring at 350 r / min for 35 min at 80°C.

[0034] Step 4, support composite: Heat to 265℃, add polyamide, and stir at 450r / min for 45min.

[0035] Step 5, Modification and Reinforcement: Keep the temperature constant, add dioctyl adipate and modified alkali-free glass fiber, and stir at 550 r / min for 55 min.

[0036] Step 6, Degassing and Molding: Vacuum the composite melt to -0.095MPa, hold for 25 minutes to degas, and cast into 50×50×10mm blocks; cool to room temperature at a rate of 5℃ / min.

[0037] Example 3 A composite phase change thermal energy storage material comprises the following components by mass percentage: 56.25% n-octadecane (melting point 28℃), 18.75% pentaerythritol (melting point 260℃), 15% polyurethane (melting point 170℃), 2% tributyl citrate, 6% expanded graphite (expanded at 850℃, expansion ratio 90 times), and 2% glass fiber (diameter 15μm, length 4mm).

[0038] A method for preparing a composite phase change thermal storage material, comprising the following steps: Step 1, Preparation of thermal conductivity reinforcement: Natural flake graphite was placed in a muffle furnace at 850℃ and expanded for 30s. After cooling, expanded graphite was obtained.

[0039] Step 2, Reinforcing and Toughening Modification: Dry the alkali-free glass fiber, immerse it in the modification solution, and soak it at room temperature for 20 minutes to ensure that the fiber surface is evenly coated with the modification solution. After removing it, dry and cure it.

[0040] The modified solution was prepared by using aminosilane as a coupling agent, dissolving the coupling agent in an ethanol-water solution at a mass ratio of 1:50, with a volume ratio of ethanol to water of 3:1, and stirring for 8 minutes to form a homogeneous modified solution.

[0041] Step 3, phase change matrix melting and dispersion: Mix n-octadecane and pentaerythritol and heat to 80°C to melt, add expanded graphite, and stir at 250 r / min for 25 min at 85°C.

[0042] Step 4, support composite: Heat to 175℃, add polyurethane, and stir at 350r / min for 35min.

[0043] Step 5, Modification and Reinforcement: Keep the temperature constant, add tributyl citrate and modified alkali-free glass fiber, and stir at 450 r / min for 45 min.

[0044] Step 6, Degassing and Molding: Vacuum the composite melt to -0.092MPa, keep it at the temperature for 20 minutes to degas, and then use a two-roller coater (roller temperature 90℃, pressure 8MPa) to make a 5mm thick sheet; cool it to room temperature at a rate of 10℃ / min.

[0045] Comparative Example 1 Phase change thermal energy storage material: Made of No. 58 fully refined paraffin wax (commercially available). It is directly heated to 70℃ to melt and then cast into shape, without any other additives.

[0046] Comparative Example 2 A phase change thermal storage material comprises the following components by mass percentage: 70% stearic acid (melting point 69°C), 18% ethylene-vinyl acetate copolymer (vinyl acetate VA content 30%, melting point 99°C), 3% dioctyl phthalate, 7% expanded graphite (expanded at 800°C, expansion ratio 80 times), and 2% glass fiber (diameter 10μm, length 3mm).

[0047] A method for preparing a phase change thermal storage material, comprising the following steps: Step 1, Preparation of thermal conductivity reinforcement: Natural flake graphite was placed in a muffle furnace at 800℃ and expanded for 40s. After cooling, expanded graphite was obtained.

[0048] Step 2, phase change matrix melting and dispersion: Stearic acid is heated to 80°C to melt, expanded graphite is added, and stirred at 300 r / min for 30 min at 85°C.

[0049] Step 3, support composite: Heat to 105℃, add ethylene-vinyl acetate copolymer, and stir at 400r / min for 40min.

[0050] Step 4, Modification and Reinforcement: Keep the temperature constant, add dioctyl phthalate and alkali-free glass fiber, and stir at 500 r / min for 50 min.

[0051] Step 5, Degassing and Molding: Vacuum the composite melt to -0.09MPa, keep it at the temperature for 25 minutes to degas, and then use a two-roller coater (roller temperature 100℃, pressure 8MPa) to make a 2mm thick sheet; cool it to room temperature at a rate of 8℃ / min.

[0052] Comparative Example 3 A phase change thermal storage material comprises the following components by mass percentage: 77% stearic acid (melting point 69°C), 18% ethylene-vinyl acetate copolymer (vinyl acetate VA content 30%), 3% dioctyl phthalate, and 2% alkali-free glass fiber (diameter 10 μm, length 3 mm).

[0053] A method for preparing a phase change thermal storage material, comprising the following steps: Step 1, Reinforcing and Toughening Modification: Dry the alkali-free glass fiber, immerse it in the modification solution, and soak it at room temperature for 12 minutes to ensure that the fiber surface is evenly coated with the modification solution. After removing it, dry and cure it.

[0054] The modified solution was prepared by using aminosilane as a coupling agent, dissolving the coupling agent in an ethanol-water solution at a mass ratio of 1:60, with a volume ratio of ethanol to water of 4:1, and stirring for 5 minutes to form a homogeneous modified solution.

[0055] Step 2, phase change matrix melting and dispersion: Stearic acid is heated to 80°C to melt, expanded graphite is added, and stirred at 300 r / min for 30 min at 85°C.

[0056] Step 3, support composite: Heat to 105℃, add ethylene-vinyl acetate copolymer, and stir at 400r / min for 40min.

[0057] Step 4, Modification and Reinforcement: Keep the temperature constant, add dioctyl phthalate and modified alkali-free glass fiber, and stir at 500 r / min for 50 min.

[0058] Step 5, Degassing and Molding: Vacuum the composite melt to -0.09MPa, keep it at the temperature for 25 minutes to degas, and then use a two-roller coater (roller temperature 100℃, pressure 8MPa) to make a 2mm thick sheet; cool it to room temperature at a rate of 8℃ / min.

[0059] Comparative Example 4 A phase change thermal energy storage material comprises the following components by mass percentage: 70% n-octadecane (melting point 28°C), 18% ethylene-vinyl acetate copolymer (vinyl acetate VA content 30%), 3% dioctyl phthalate, 7% expanded graphite (expanded at 800°C, expansion ratio 80 times), and 2% alkali-free glass fiber (diameter 10μm, length 3mm).

[0060] A method for preparing a phase change thermal storage material, comprising the following steps: Step 1, Preparation of thermal conductivity reinforcement: Natural flake graphite was placed in a muffle furnace at 800℃ and expanded for 40s. After cooling, expanded graphite was obtained.

[0061] Step 2, Reinforcing and Toughening Modification: Dry the alkali-free glass fiber, immerse it in the modification solution, and soak it at room temperature for 12 minutes to ensure that the fiber surface is evenly coated with the modification solution. After removing it, dry and cure it.

[0062] The modified solution was prepared by using aminosilane as a coupling agent, dissolving the coupling agent in an ethanol-water solution at a mass ratio of 1:60, with a volume ratio of ethanol to water of 4:1, and stirring for 5 minutes to form a homogeneous modified solution.

[0063] Step 3, phase change matrix melting and dispersion: Heat n-octadecane to 80°C to melt, add expanded graphite, and stir at 300 r / min for 30 min at 85°C.

[0064] Step 4, support composite: Heat to 105℃, add ethylene-vinyl acetate copolymer, and stir at 400r / min for 40min.

[0065] Step 5, Modification and Reinforcement: Keep the temperature constant, add dioctyl phthalate and modified alkali-free glass fiber, and stir at 500 r / min for 50 min.

[0066] Step 6, Degassing and Molding: Vacuum the composite melt to -0.09MPa, keep it at the temperature for 25 minutes to degas, and then use a two-roller coater (roller temperature 100℃, pressure 8MPa) to make a 2mm thick sheet; cool it to room temperature at a rate of 8℃ / min.

[0067] The performance of the thermal storage materials in Examples 1-3 and Comparative Examples 1-4 was tested.

[0068] Performance testing methods: Phase transition enthalpy and melting point were measured using differential scanning calorimetry (DSC, heating rate 10℃ / min, nitrogen atmosphere).

[0069] Thermal conductivity was tested using the hot wire method (GB / T10297-2015).

[0070] Cyclic stability was tested after 100 cycles in a high and low temperature cycling chamber (-20℃ to 80℃).

[0071] Corrosion was tested using the immersion method (GB / T10124-2021).

[0072] Performance test results: Example 1: Melting point 65℃, phase change enthalpy 205J / g, thermal conductivity 1.5W / (m·K), phase change enthalpy retention rate after 100 cycles 95%, decomposition temperature 320℃, corrosion rate to carbon steel 0.04mm / year, tensile strength 2.8MPa.

[0073] Example 2: Melting point 72℃, phase change enthalpy 210J / g, thermal conductivity 1.8W / (m·K), phase change enthalpy retention rate after 100 cycles 94%, decomposition temperature 330℃, corrosion rate to carbon steel 0.05mm / year, tensile strength 3.2MPa.

[0074] Example 3: Melting point 58℃, phase change enthalpy 220J / g, thermal conductivity 2.0W / (m·K), phase change enthalpy retention rate after 100 cycles 96%, decomposition temperature 310℃, corrosion rate to carbon steel 0.03mm / year, tensile strength 2.6MPa.

[0075] Comparative Example 1: Melting point 55℃, phase change enthalpy 150J / g, thermal conductivity 0.2W / (m·K), phase change enthalpy retention rate after 50 cycles 85%, decomposition temperature 250℃, corrosion rate to carbon steel 0.04mm / year, tensile strength 0.8MPa.

[0076] Comparative Example 2: Melting point 64℃, phase change enthalpy 202J / g, thermal conductivity 1.4W / (m·K), phase change enthalpy retention rate after 100 cycles 82%, decomposition temperature 315℃, corrosion rate to carbon steel 0.04mm / year, tensile strength 1.2MPa, elongation at break 28%.

[0077] Comparative Example 3: Melting point 65℃, phase change enthalpy 208J / g, thermal conductivity 0.35W / (m·K), phase change enthalpy retention rate after 100 cycles 93%, decomposition temperature 318℃, corrosion rate to carbon steel 0.04mm / year, tensile strength 2.6MPa, elongation at break 45%.

[0078] Comparative Example 4: Melting point 26℃, phase change enthalpy 165J / g, thermal conductivity 1.5W / (m·K), phase change enthalpy retention rate after 100 cycles 94%, decomposition temperature 280℃, corrosion rate to carbon steel 0.04mm / year, tensile strength 2.7MPa, elongation at break 48%.

[0079] Compared to Examples 1-3, Comparative Example 1 shows that traditional paraffin materials have lower phase change enthalpy, lower energy storage density, lower decomposition temperature, poorer thermal stability, extremely low thermal conductivity, and slow heat transfer rate; and exhibit significant performance degradation even with a limited number of phase change cycles. In contrast, the phase change thermal storage materials of Examples 1-3 demonstrate significant advantages in melting point, phase change enthalpy, stability, and thermal conductivity, better meeting the needs of practical applications.

[0080] Compared with Example 1, Comparative Example 2 showed that the tensile strength and cycle stability decreased after modification with the absence of silane coupling agent, indicating that the modification treatment can significantly improve the interfacial bonding force between glass fiber and organic matrix, and avoid the performance degradation caused by fiber debonding during cycling.

[0081] Compared with Example 1, Comparative Example 3 showed a decrease in thermal conductivity after removing expanded graphite, confirming that the three-dimensional thermally conductive network constructed by expanded graphite is the core to improve the thermal conductivity of the material and solves the thermal conduction bottleneck of traditional organic phase change materials.

[0082] Compared with Example 1, Comparative Example 4 shows that the single n-octadecyl body reduces the phase change enthalpy and decomposition temperature, indicating that the multi-component organic phase change matrix compounding technology used in this invention can achieve a synergistic improvement in thermal storage performance and thermal stability, breaking through the performance limitations of a single matrix.

[0083] After the modified fibers, thermal conductive network and composite matrix were missing in Comparative Examples 1-4, one or more properties were significantly degraded. However, Examples 1-3 achieved comprehensive optimization of heat storage, thermal conductivity, stability and mechanical properties through multi-component synergistic design.

[0084] Therefore, this invention employs the aforementioned composite phase change thermal storage material and its preparation method. Through innovative technical routes involving phase change matrix compounding, thermally conductive network construction, and reinforced phase design, it solves the core problems of insufficient thermal storage performance, poor stability, and low thermal conductivity of existing phase change thermal storage materials. It possesses outstanding substantive characteristics and significant progress, and has promising prospects for large-scale industrial application. Wide-range melting point control is achieved through organic phase change material compounding; the reinforced phase design ensures that the phase change enthalpy decreases by ≤6% after 100 cycles, and the decomposition temperature is ≥300℃; the thermally conductive network construction achieves a thermal conductivity ≥1.0 W / (m·K); and the material's corrosivity is reduced, with a corrosion rate of ≤0.05 mm / year for carbon steel.

[0085] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A composite phase change thermal storage material, characterized in that, By mass percentage, it consists of the following components: 60%-80% organic phase change matrix, 10%-25% polymer support, 1%-5% plasticizer, 3%-10% thermal conductivity enhancer, and 0.1%-2% reinforcing and toughening agent; the sum of the mass percentages of each component is 100%; the phase change enthalpy of the thermal storage material is 200-250 J / g, the thermal conductivity is 1.0-2.0 W / (m·K), the phase change enthalpy retention rate after 100 phase change cycles is ≥94%, and the decomposition temperature is ≥300℃.

2. The composite phase change thermal storage material according to claim 1, characterized in that: The organic phase change matrix is ​​selected from one or more of C12-C24 aliphatic hydrocarbons, C8-C22 aliphatic alcohols, C8-C22 fatty acids, and polyols; when it is a mixture of aliphatic hydrocarbons and polyols, the mass ratio is 1:3-3:

1.

3. The composite phase change thermal storage material according to claim 1, characterized in that: The polymer support is selected from one or more of ethylene-vinyl acetate copolymer, polyamide copolymer, waterborne polyurethane, and low-density polyethylene; the vinyl acetate content of the ethylene-vinyl acetate copolymer is 20%-40%.

4. The composite phase change thermal storage material according to claim 1, characterized in that: The plasticizer is selected from one or more of tributyl citrate, dioctyl phthalate, and dioctyl adipate, with a purity ≥99%.

5. The composite phase change thermal storage material according to claim 1, characterized in that: The thermal conductivity reinforcement is expanded graphite, which is made by expanding natural flake graphite at 700-900℃ for 30-60s, with an expansion ratio of 50-100 times and a particle size of 50-200μm.

6. The composite phase change thermal storage material according to claim 1, characterized in that: The reinforcing and toughening agent is alkali-free glass fiber with a single filament diameter of 0.1-30μm and a length of 1-5mm.

7. A method for preparing a composite phase change thermal storage material according to any one of claims 1-6, characterized in that, Includes the following steps: Step 1, Preparation of thermally conductive reinforcement: Natural flake graphite is placed in a muffle furnace at 700-900℃ and expanded for 30-60 seconds. After cooling, expanded graphite is obtained. Step 2, Modification of the reinforcing and toughening agent: Dry the reinforcing and toughening agent, immerse it in the modification solution, and soak it at room temperature for 10-20 minutes to ensure that the fiber surface is evenly coated with the modification solution. After removing it, dry and cure it. Step 3, melting and dispersing of phase change matrix: heat the organic phase change matrix to 10-20°C above its melting point to melt it, add expanded graphite, and stir at 250-350 r / min for 25-35 min at 80-100°C; Step 4, support composite: Heat to 5-10°C above the melting temperature of the polymer support, add the polymer support, and stir at 350-450 r / min for 35-45 min; Step 5, Modification and Reinforcement: Keep the temperature constant, add plasticizer and modified reinforcement toughening agent, and stir at 450-550 r / min for 45-55 min; Step 6, Degassing and Molding: Vacuum the composite melt to -0.09~-0.095MPa, keep it at the temperature for 20-30 minutes to degas, then cast it into a mold or hot press it into a sheet, and cool it to room temperature at a rate of 5-10℃ / min to obtain the finished product.

8. The method for preparing a composite phase change thermal storage material according to claim 7, characterized in that: In step 2, the modified solution is prepared by using aminosilane or epoxysilane as a coupling agent, dissolving the coupling agent in an ethanol-water solution at a mass ratio of 1:50-1:100, with the volume ratio of ethanol to water being 3:1-5:1, and stirring for 5-10 minutes to form a uniform modified solution.

9. The method for preparing a composite phase change thermal storage material according to claim 7, characterized in that: In step 6, hot pressing is performed using a two-roller coating machine with a roller temperature of 80-120℃ and a pressure of 5-10MPa to produce a sheet with a thickness of 0.5-5mm.