Novel double-wall material phase change elastic composite material and preparation method thereof

Abstract

The invention belongs to the technical field of phase change energy storage materials, and particularly relates to a novel double-wall material phase change elastic composite material and a preparation method thereof. The novel double-wall material phase change elastic composite material comprises a core material, a wall material A, a wall material B and an elastomer matrix. The preparation method of the novel double-wall material phase-change elastic composite material comprises the following steps: preparing a core material, a wall material A and a wall material B to obtain a microencapsulated phase-change material; preparing modified heat-conducting filler from the heat-conducting filler, a coupling agent and a dispersing agent; preparing a mixture from the elastomer matrix, the microencapsulated phase-change material, the modified heat-conducting filler, the plasticizer and the cross-linking agent; and the mixture is subjected to wire drawing, curing, annealing and functional additive spraying, and the composite material is obtained. According to the invention, paraffin and other organic phase-change materials are encapsulated in an elastomer matrix, so that liquid leakage is avoided, and the flexibility of the materials is maintained at the same time; the phase change material is encapsulated by adopting a microcapsule structure, so that the volume change in the phase change process is prevented, the surface area is increased, and the heat conduction efficiency and flexibility are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of phase change energy storage materials, and particularly relates to a novel double-wall material phase change elastic composite material and a preparation method thereof. Background Art

[0002] Phase change materials can absorb or release a large amount of latent heat during the phase change process, while their own temperature remains almost unchanged. Early research mainly focused on developing phase change materials with high phase change enthalpy and appropriate phase change temperature. For example, solid-liquid phase change materials have received extensive attention due to their large phase change enthalpy, wide temperature range, excellent thermal conductivity, etc. However, solid-liquid phase change materials have the problem of leakage. Although solid-solid phase change materials have the advantages of small volume change, no leakage and corrosion problems, they also have the limitation of low latent heat. In addition, phase change materials generally also have problems such as poor thermal conductivity and crystallization rigidity. Ordinary phase change composite materials tend to be rigid, have poor elasticity, low operability, and are difficult to adapt to complex application scenarios.

[0003] The thermal conductivity of phase change materials (such as paraffin wax, fatty acids) is usually low (0.15 - 0.3 W / m·K), resulting in poor overall thermal conductivity of the composite material. Although adding thermal conductive fillers (such as metal powders, carbon nanotubes) can improve the thermal conductivity, the problems of uneven filler dispersion or high interfacial thermal resistance are still widespread.

[0004] Chinese Patent CN117821021A discloses an organic phase change composite material and a preparation method and application thereof, specifically discloses an organic phase change composite material which includes a mixture of biochar and polyethylene glycol; the biochar is pyrolyzed from a mixture of polypropylene, plant fibers, and compatibilizer, the grafting rate of the compatibilizer is 0.6 - 1.0%, the average molecular weight of the polyethylene glycol is 1500 - 20000, and the mass ratio of the biochar to the polyethylene glycol is 3:1 - 2. Although this patent enhances the interfacial bonding by using mesoporous silica to load polyethylene glycol, it does not mention the optimization of thermal conductive fillers, and the improvement of thermal conductivity still relies on traditional methods.

[0005] Chinese Patent CN105968970A discloses a high-temperature resistant and high-adhesion cross-linked polyethylene viscoelastic composite coating and a preparation method thereof. The composite coating consists of two components, A and B. Component A includes polyethylene, initiator, grafted product, silane, elastomer, and grafting assistant, and component B includes polyethylene, nano-thermal conductive agent, dispersion lubricant, surface treatment agent, catalyst, dehydrating agent, and antioxidant. Although this patent alleviates the phase separation problem by exploring the interfacial modification technology of organic-inorganic composite phase change materials and elastomers, the long-term material stability is defective.

[0006] Chinese Patent CN117702302A discloses a liquid metal composite wire, fiber film, flexible electronic composite material based on electrospinning and their preparation methods. The liquid metal fiber composite wire is formed by electrospinning liquid metal, with a composite structure having a liquid metal core and an outer elastomer wrapping the core. The liquid metal fiber composite wire is prepared by electrospinning, and further a liquid metal fiber film with a connected three-dimensional network interlaced structure is prepared. Then, through an impregnation and heat treatment activation process, the liquid metal composite material is embedded in an elastic rubber matrix to form an interconnected liquid metal fiber network. The liquid metal fiber network serves as an ultra-light electronic conduction path, simultaneously exhibiting light weight and high conductivity. Although this patent improves the thermal conductivity and anti-leakage ability by optimizing the filler distribution, the precipitation of the filler during long-term cycling is a problem.

[0007] Chinese Patent CN116218476A discloses a preparation method of a highly elastic shaped composite phase change material, and the operation steps are as follows: (1) An elastomer matrix, a phase change matrix, and a thermal conductivity enhancing agent are prepared into a completely uniformly mixed melt under molten conditions; the mass ratio of the elastomer matrix is 15-20%; the elastomer matrix is composed of a hydrogenated styrene-butadiene (SEBS) and an olefin block copolymer (OBC) mixed by mass ratio; (2) The melt is put into a mold, pressed into shape, and cooled to room temperature to obtain the highly elastic shaped composite phase change material. Although this patent emphasizes light weight and high thermal conductivity by using a foam metal composite phase change material, it is necessary to optimize the bonding strength between the porosity and the elastomer matrix, and the advantageous range of the phase change elastic material cannot be fully demonstrated.

[0008] Chinese Patent CN119119748A discloses a flexible composite phase change material, a preparation method thereof, and a solar thermoelectric power generation system using the same. The flexible composite phase change material uses a hydrogenated styrene-butadiene block copolymer SEBS as a temperature-resistant and aging-resistant flexible matrix, an olefin block copolymer OBC as a flexible elastomer, paraffin PW as a phase change material, and expanded graphite EG as a porous thermal conductivity enhancing material, which is prepared by a melt blending method and formed by hot pressing; the material has a self-encapsulation property, which can avoid the leakage of paraffin in the molten state; and it has good flexibility and bending properties in the molten state of paraffin. The flexible composite phase change material has a phase change temperature of 62.06-63.54 °C, a phase change latent heat of 124.84-136.14 J / g, and a thermal conductivity of 3.07-4.54 W / (m·K). This patent focuses on the combination of a self-healing elastomer and a phase change material, and uses a dynamic hard phase design to achieve the balance of thermal management function and mechanical properties. However, the material synthesis cost is relatively high, and it is difficult to mass-produce on a large scale in actual production, so it cannot meet the large market demand in the fields of electronic device thermal management, building energy conservation, and intelligent temperature control. Summary of the Invention

[0009] The present invention provides a novel double-wall material phase change elastic composite material to solve the problems of liquid leakage of the phase change material, insufficient flexibility, and low heat conduction efficiency.

[0010] To achieve the above object, the present invention adopts the following technical solutions:

[0011] A novel double-wall material phase change elastic composite material includes a core material, wall material A, wall material B, and an elastomer matrix; the core material is paraffin wax, and its mass percentage is 20-30% of the total amount of raw materials; the wall material A is gelatin, and its mass percentage is 20-30% of the total amount of raw materials; the wall material B is hexamethylene diisocyanate, and its mass percentage is 1.5-3.5% of the total amount of raw materials; the elastomer matrix is a styrene-butadiene-styrene block copolymer, and its mass percentage is 30-40% of the total amount of raw materials. Among them, the elastomer matrix provides the flexibility, impact resistance, and processability of the material; the core material paraffin wax absorbs / releases heat through solid-liquid phase change to achieve the thermal management function; gelatin is used as one of the wall materials for microcapsule encapsulation; the wall material B is used to cure the microcapsule wall, and through the reaction of the isocyanate group (-NCO) of hexamethylene diisocyanate with the amino group (-NH2) of gelatin, a polyurea cross-linked network is formed to enhance the strength of the wall material.

[0012] Preferably, it further includes a thermal conductive filler, a coupling agent, and a dispersant. The thermal conductive filler is carbon nanotubes, and its mass percentage is 3-5% of the total amount of raw materials; the coupling agent is a silane coupling agent, and its mass percentage is 0.05-0.2% of the total amount of raw materials; the dispersant is ethanol, and its mass percentage is 80-85% of the total amount of raw materials. Among them, the carbon nanotube flexible thermal conductive filler is used after being modified by a silane coupling agent to improve its compatibility with the elastomer matrix. The silane coupling agent hydrolyzes to generate silanol (-Si-OH), which condenses with the hydroxyl groups on the surface of the thermal conductive filler. At the same time, its amino group (-NH2) forms a hydrogen bond with the benzene ring of the styrene-butadiene-styrene block copolymer. The modified thermal conductive filler can improve the thermal conductivity of the composite material; ethanol serves as a dispersion medium.

[0013] Preferably, it further includes a plasticizer. The plasticizer is dioctyl phthalate, and its mass percentage is 5-10% of the total amount of raw materials. Using a plasticizer can lower the glass transition temperature (Tg) of the styrene-butadiene-styrene block copolymer and improve the flexibility of the material. The dioctyl phthalate molecules insert between the molecular chains of the styrene-butadiene-styrene block copolymer, weakening the intermolecular force and making the material easier to stretch.

[0014] Preferably, a crosslinking agent is further included. The crosslinking agent is furan - maleimide, and its mass percentage is 2 - 5% of the total amount of raw materials. The crosslinking agent is in - situ injected to form reversible covalent bonds, endowing the material with self - healing ability. Furan and maleimide can be reversibly bonded due to the Diels - Alder reaction at 78 - 82 °C. The bond breaks when heated and recombines when cooled, realizing self - healing.

[0015] Preferably, a functional additive is further included. The functional additive is graphene dispersion, and its mass percentage is 10 - 20% of the total amount of raw materials. After spraying the functional additive, a continuous heat - conducting network can be formed to improve the thermal conductivity of the material.

[0016] A preparation method of the novel double - wall - material phase - change elastic composite material described above includes the following steps:

[0017] S1. Heat and melt the core material, dissolve wall material A in water, and dry the elastomer matrix for standby;

[0018] S2. Mix and emulsify the melted core material with the aqueous solution of wall material A to form an oil - in - water emulsion; add wall material B and stir for reaction to obtain micro - encapsulated phase - change materials;

[0019] S3. Immerse the heat - conducting filler in a dispersant solution containing a coupling agent, perform ultrasonic treatment, centrifuge and dry to obtain a modified heat - conducting filler;

[0020] S4. Mix the dried elastomer matrix, micro - encapsulated phase - change materials, modified heat - conducting filler, and plasticizer evenly, and then add the crosslinking agent and disperse evenly to obtain a mixture;

[0021] S5. Draw the mixture into a wire, and then cure it;

[0022] S6. Anneal the cured wire, then spray the functional additive, dry, stretch, and cool to obtain the product.

[0023] Preferably, in step S1, the drying method of the elastomer matrix is: place it in a vacuum oven and dry at 80 °C for 6 hours.

[0024] Preferably, in step S2, shear at 7500 - 8500 rpm for 8 - 12 minutes in a high - speed emulsifier.

[0025] Preferably, in step S2, stir and react at a constant temperature of 55 - 65 °C for 1.5 - 2.5 hours.

[0026] Preferably, in step S3, the ultrasonic treatment time is 25 - 35 minutes and the power is 250 - 350 W.

[0027] Preferably, in step S3, the drying temperature is 75 - 85 °C.

[0028] Preferably, in step S4, a twin-screw extruder is used for mixing, and the feeding zone, melting zone, mixing zone, and die head zone are set with gradients, and a crosslinking agent is injected at the end of the mixing zone.

[0029] Preferably, when injecting the crosslinking agent, the flow rate is 4 - 6 mL / min.

[0030] Preferably, the total mixing time is 9 - 12 minutes.

[0031] Preferably, the temperature of the feeding zone is 75 - 85°C, the temperature of the melting zone is 115 - 125°C; the temperature of the mixing zone is 135 - 145°C, and the temperature of the die head zone is 95 - 105°C.

[0032] Preferably, in step S5, the mixture is drawn into 2.85 mm wire by a single-screw extruder (temperature gradient 120°C → 140°C → 130°C). Set the printing parameters: nozzle 175 - 185°C, hot bed 55 - 65°C, layer thickness 0.18 - 0.22 mm, filling rate 75 - 85%.

[0033] Preferably, in step S5, after printing, ultraviolet curing is adopted, the ultraviolet light wavelength is 365 nm, and the curing time is 5 - 15 minutes to enhance the interlayer bonding.

[0034] Preferably, in step S6, gradient annealing is adopted, specifically, the temperature in the first stage is 75 - 85°C, and the time is 0.5 - 1.5 h; the temperature in the second stage is 55 - 65°C, and the time is 0.5 - 1.5 h; the third stage is cooling at room temperature.

[0035] Preferably, in step S6, the concentration of the functional additive is 0.8 - 1.2 mg / mL.

[0036] Preferably, in step S6, the drying temperature is 75 - 85°C.

[0037] Preferably, in step S6, it is stretched to 190 - 210% strain, held for 4 - 6 minutes and then released, and repeated 2 - 3 times to induce molecular chain orientation.

[0038] Compared with the prior art, the advantages and beneficial effects of the present invention are:

[0039] The present invention encapsulates organic phase change materials such as paraffin in an elastomer matrix to avoid liquid leakage and at the same time maintain the flexibility of the material; the phase change material is encapsulated by a microcapsule structure to prevent volume change during the phase change process, increase the surface area, and improve the thermal conductivity and flexibility.

[0040] The novel double-wall phase change elastic composite material uses gelatin + polyurea composite encapsulation, which improves the protection and scalability compared with the single-layer encapsulation on the market. At the same time, it indirectly reduces the leakage rate of microcapsules. By using in-situ injection of dynamic crosslinking agents and 3D printing gradient structures, the inactivation of crosslinking agents caused by static mixing is avoided and the overall thermal conductivity is enhanced. Detailed implementation mode

[0041] To better present the present invention, it is illustrated by specific implementation cases. These implementation cases belong to the protection scope of the present invention but do not limit the protection scope of the present invention.

[0042] Example 1

[0043] A novel double-wall phase change elastic composite material is prepared from the following raw materials: 35% styrene-butadiene-styrene block copolymer particles, 25% paraffin wax, 25% gelatin, 2.5% hexamethylene diisocyanate, 3% carbon nanotubes, 7% dioctyl phthalate, 3.5% furan-maleimide crosslinking agent, 0.2% silane coupling agent, 80% ethanol (volume fraction 99%), and 11% graphene dispersion.

[0044] In this embodiment, the preparation method of the novel double-wall phase change elastic composite material includes the following steps:

[0045] S1. Heat the paraffin wax to 70°C to melt it, dissolve the gelatin in water to prepare an aqueous solution with a mass concentration of 10%, place the styrene-butadiene-styrene block copolymer particles in a vacuum oven, and dry them at 80°C for 6 hours for later use.

[0046] S2. Add the melted core material to the gelatin aqueous solution (mass concentration 8%) and shear it at 8000 rpm for 10 minutes in a high-speed emulsifier to form an oil-in-water emulsion; dropwise add hexamethylene diisocyanate to the emulsion and stir and react at a constant temperature of 60°C for 2.5 hours; centrifuge to collect the microcapsules, freeze-dry them, and then pass through a 200-mesh sieve, and seal and store them for later use.

[0047] S3. Immerse the carbon nanotubes in the ethanol solution of the silane coupling agent and perform ultrasonic treatment for 30 minutes with an ultrasonic power of 300 W; centrifuge and dry at 80°C to obtain modified carbon nanotubes.

[0048] S4. Add the dried styrene-butadiene-styrene block copolymer, microencapsulated phase change material, modified carbon nanotubes (50 g), and dioctyl phthalate to a twin-screw extruder; set the temperature gradient: feeding zone 80°C → melting zone 120°C → mixing zone 140°C → die head zone 100°C; inject the furan-maleimide crosslinking agent (flow rate 5 mL / min) through an injection pump at the end of the mixing zone; the total mixing time: 10 minutes to ensure uniform dispersion.

[0049] S5. Draw the mixture into 2.85 mm wire through a single-screw extruder (temperature gradient: 120 °C → 140 °C → 130 °C); Set the printing parameters: nozzle at 180 °C, heated bed at 60 °C, layer thickness at 0.2 mm, filling rate at 80%; After printing, perform UV curing (365 nm, 10 minutes) to enhance interlayer bonding;

[0050] S6. Finally, perform gradient annealing: 80 °C (1 hour) → 60 °C (1 hour) → cool to room temperature; After cooling is completed, spray graphene dispersion (1 mg / mL) onto the material surface and dry at 80 °C to form a heat-conducting layer; Finally, stretch the specimen to 50% strain, hold for 5 minutes and then release, repeat 3 times to induce molecular chain orientation.

[0051] Example 2

[0052] A novel double-wall phase change elastic composite material is prepared from the following raw materials: 30% styrene-butadiene-styrene block copolymer particles, 20% paraffin wax, 30% gelatin, 3.5% hexamethylene diisocyanate, 4.5% carbon nanotubes, 10% dioctyl phthalate, 2% furan-maleimide crosslinking agent, 0.1% silane coupling agent, 84% ethanol (volume fraction 99%), 12% graphene dispersion.

[0053] S1. Heat the paraffin wax to 65 °C to melt it, dissolve gelatin in water to prepare an aqueous solution with a mass concentration of 8%, place the styrene-butadiene-styrene block copolymer particles in a vacuum oven, dry at 75 °C for 5 hours, and set aside;

[0054] S2. Add the melted paraffin wax to the gelatin aqueous solution (mass concentration 10%) and shear in a high-speed emulsifier at 7500 rpm for 15 minutes to form an oil-in-water emulsion; Dropwise add hexamethylene diisocyanate to the emulsion and stir at a constant temperature of 65 °C for 3 hours; Centrifuge to collect the microcapsules, freeze-dry and then pass through a 180-mesh sieve, and store in a sealed manner for later use;

[0055] S3. Immerse the carbon nanotubes in the ethanol solution of the silane coupling agent and perform ultrasonic treatment for 25 - 35 minutes, with an ultrasonic power of 280 W; After centrifugation, dry at 75 °C to obtain modified carbon nanotubes;

[0056] S4. Add the dried styrene-butadiene-styrene block copolymer particles, microencapsulated phase change material, modified carbon nanotubes, and dioctyl phthalate to a twin-screw extruder; Set the temperature gradient: feeding zone at 75 °C → melting zone at 115 °C → mixing zone at 135 °C → die head zone at 95 °C; Inject the furan-maleimide crosslinking agent (flow rate 2.5 mL / min) at the end of the mixing zone through an injection pump; Total mixing time: 8 minutes to ensure uniform dispersion;

[0057] S5. Draw the mixture into 2.85 mm wire through a single-screw extruder (temperature gradient 115 °C → 135 °C → 125 °C); Set the printing parameters: nozzle 175 °C, hot bed 55 °C, layer thickness 0.15 mm, filling rate 85%. After printing, perform ultraviolet curing (360 nm, 8 minutes) to enhance interlayer bonding;

[0058] S6. Finally, perform gradient annealing: 75 °C (0.5 hours) → 55 °C (0.5 hours) → cool to room temperature; After cooling is completed, spray graphene dispersion (concentration 0.8 mg / mL) onto the material surface and dry at 75 °C to form a heat-conducting layer; Finally, stretch the specimen to 45% strain, hold for 3 minutes and then release, repeat 2 times to induce molecular chain orientation.

[0059] Example 3

[0060] A novel double-wall phase change elastic composite material is prepared from the following raw materials: 40% styrene-butadiene-styrene block copolymer particles, 30% paraffin wax, 20% gelatin, 1.5% hexamethylene diisocyanate, 5% carbon nanotubes, 5% dioctyl phthalate, 5.0% furan-maleimide crosslinking agent, 0.05% silane coupling agent, 85% ethanol (volume fraction 99%), 10% graphene dispersion.

[0061] In this example, the preparation method of the novel double-wall phase change elastic composite material includes the following steps:

[0062] S1. Heat the paraffin wax to 75 °C to melt it, dissolve the gelatin in water to prepare an aqueous solution with a mass concentration of 12%, place the styrene-butadiene-styrene block copolymer particles in a vacuum oven, dry at 85 °C for 7 hours, and set aside;

[0063] S2. Add the melted paraffin wax to the aqueous gelatin solution (mass concentration 12%) and shear at 8500 rpm in a high-speed emulsifier for 12 minutes to form an oil-in-water emulsion; Drop hexamethylene diisocyanate into the emulsion and stir and react at a constant temperature of 55 °C for 2.5 hours; Centrifuge to collect the microcapsules, freeze-dry and then pass through a 220-mesh sieve, and seal and store for later use;

[0064] S3. Immerse the carbon nanotubes in the ethanol solution of the silane coupling agent and perform ultrasonic treatment for 30 minutes with an ultrasonic power of 320 W; After centrifugation, dry at 85 °C to obtain modified carbon nanotubes;

[0065] S4. Add the dried styrene-butadiene-styrene block copolymer particles, microencapsulated phase change material, modified carbon nanotubes, and dioctyl phthalate into a twin-screw extruder; Set the temperature gradient: feeding zone 85 °C → melting zone 125 °C → mixing zone 145 °C → die head zone 105 °C; Inject the furan-maleimide crosslinking agent (flow rate 5.5 mL / min) through an injection pump at the end of the mixing zone; The total mixing time is 12 minutes to ensure uniform dispersion;

[0066] S5. Draw the mixture into 2.85-mm wire through a single-screw extruder (temperature gradient 125 °C → 145 °C → 135 °C); Set the printing parameters: nozzle 185 °C, hot bed 65 °C, layer thickness 0.25 mm, filling rate 85%; After printing, perform ultraviolet curing (370 nm, 12 minutes) to enhance the interlayer bonding;

[0067] S6. Finally, perform gradient annealing: 85 °C (1.5 hours) → 65 °C (1.5 hours) → cool to room temperature; After cooling is completed, spray the graphene dispersion liquid (concentration 5.5 mg / mL) onto the material surface and dry it at 85 °C to form a heat-conducting layer; Finally, stretch the specimen to 55% strain, hold for 7 minutes and then release, repeat 4 times to induce molecular chain orientation.

[0068] Comparative Example 1

[0069] It is basically the same as Example 1, except that the wall material B, hexamethylene diisocyanate, is not added, and gelatin monolayer encapsulation is used, that is:

[0070] S2. Add the melted paraffin into the gelatin aqueous solution (mass concentration 8%) and shear it at 8000 rpm for 10 minutes in a high-speed emulsifier to form an oil-in-water emulsion; Centrifuge the emulsion (4000 rpm, 10 minutes) to separate the microcapsules, remove the unencapsulated free paraffin and gelatin residues; Centrifuge to collect the microcapsules, freeze-dry them and then pass through a 180-220 mesh sieve, and store them sealed for later use;

[0071] Other steps are the same as those in Example 1.

[0072] Comparative Example 2

[0073] It is basically the same as Example 1, except that the wall material A, gelatin, is not added, and it is replaced with ethylenediamine (reacting with hexamethylene diisocyanate to form a polyurea wall material), and hexamethylene diisocyanate monolayer encapsulation is used, that is:

[0074] S1. Heat the paraffin to 70 °C to melt it, place the styrene-butadiene-styrene block copolymer particles in a vacuum oven and dry them at 80 °C for 6 hours for later use; Hexamethylene diisocyanate and ethylenediamine are directly used without pretreatment;

[0075] S2. The melted core material is mixed evenly with hexamethylene diisocyanate, and slowly added to deionized water at 70 °C. It is sheared at 10000 rpm for 15 minutes in a high-speed emulsifier to form an oil-in-water emulsion; an ethylenediamine solution is added dropwise to the emulsion, and the reaction is stirred at a constant temperature of 60 °C for 3 hours; the emulsion is centrifuged (4000 rpm, 15 minutes) to remove free hexamethylene diisocyanate and unreacted ethylenediamine. The microcapsules are collected by centrifugation, freeze-dried, passed through a 200-mesh sieve, and stored sealed for later use;

[0076] Other steps are the same as those in Example 1.

[0077] Comparative Example 3

[0078] It is basically the same as Example 1, except that in step S4, the static crosslinking agent diisocyanatohexane (HDI) is used to replace the dynamic crosslinking agent furan-maleimide, and other steps are the same as those in Example 1.

[0079] Comparative Example 4

[0080] It is basically the same as Example 1, except that traditional compression molding is used instead of 3D printing, that is:

[0081] S5: The mixture is compression molded (thickness 2 mm) by a flat vulcanizer at 140 °C and 10 MPa pressure, non-gradient wire drawing, and then ultraviolet cured (365 nm, 10 minutes) to enhance the interfacial bonding. Other steps are the same as those in Example 1.

[0082] Comparative Example 5

[0083] It is basically the same as Example 1, except that in step S4, furan-maleimide is replaced by the ordinary crosslinking agent diphenylmethane diisocyanate (MDI), and traditional compression molding is used instead of 3D printing, that is:

[0084] S4: The dried styrene-butadiene-styrene block copolymer, microencapsulated phase change material, modified carbon nanotubes, and dioctyl phthalate are added to a twin-screw extruder; the temperature gradient is set as follows: feeding zone 80 °C → melting zone 120 °C → mixing zone 140 °C → die head zone 100 °C; MDI (flow rate 5 mL / min) is injected through an injection pump at the end of the mixing zone, and the mixing time is 10 minutes;

[0085] S5: The mixture is compression molded (thickness 2 mm) by a flat vulcanizer at 140 °C and 10 MPa pressure, non-gradient wire drawing, and then ultraviolet cured (365 nm, 10 minutes) to enhance the interfacial bonding;

[0086] Other steps are the same as those in Example 1.

[0087] Comparative Example 6

[0088] It is basically the same as Example 1, except that in step S6, the annealing process is changed to single-temperature static annealing, that is:

[0089] Step S6: Finally, perform static annealing at 80 °C for 2 hours of constant temperature treatment, then perform room temperature cooling. After the cooling is completed, spray graphene dispersion (5 mg / mL) onto the material surface, dry it at 80 °C to form a heat conduction layer, and finally stretch the specimen to 50% strain, hold for 5 minutes and then release it, repeat 3 times to induce molecular chain orientation;

[0090] Other steps are the same as those in Example 1.

[0091] Performance Test

[0092] 1. Use ASTM D412 (Standard Test Method for Tensile Properties of Rubber Materials) to test the elongation at break of the materials prepared in Examples 1-3 and Comparative Examples 1-6.

[0093] 2. Use differential scanning calorimetry (DSC) to test the phase change enthalpy of the materials prepared in Examples 1-3 and Comparative Examples 1-6.

[0094] 3. Use the transient plane heat source method (HotDisk) to test the thermal conductivity of the materials prepared in Examples 1-3 and Comparative Examples 1-6.

[0095] 4. The test results are shown in the following table.

[0096]

[0097]

[0098] As can be seen from the above table, the synergistic effect of dynamic chemical bond design and advanced manufacturing processes (such as 3D printing structure optimization) is the fundamental reason for the overall performance of the examples to exceed that of the comparative examples. The core functions of the comparative examples are missing due to static networks, disordered fillers, and process-damaged microcapsules, which reversely verifies the non-obviousness of the technical solutions in the claims; the examples provide scalable high-performance material solutions for fields such as flexible electronics and intelligent thermal management through three-dimensional innovation of components-structures-processes.

[0099] From the data comparison of Comparative Example 1, Comparative Example 2 and Example 1, it can be seen that all the indexes of the materials obtained by encapsulating with gelatin single-layer wall material in Comparative Example 1 are significantly lower than those of the materials obtained under the condition of double-layer double-wall materials; in Comparative Example 2, hexamethylene diisocyanate alone cannot directly form a cross-linked network through self-polymerization and cannot form a film independently, so it cannot be used as a wall material. Only when ethylenediamine (EDA) or any other compound containing active hydrogen (such as amino group, hydroxyl group) is added additionally, can a complete microcapsule wall material be effectively formed. The indexes of the materials obtained by preparing a single-layer polyurea wall material are still significantly lower than those of the materials obtained under the condition of double-layer double-wall materials.

[0100] From the data comparison of Comparative Example 3, 4 and Example 1, it can be seen that all the indexes of the materials obtained under the conditions of static cross-linking agent and traditional compression molding are significantly lower than those of the materials obtained under the conditions of in-situ injection of dynamic cross-linking agent + 3D printing gradient structure; combined with Comparative Example 5, it can be seen that the effect of in-situ injection of dynamic cross-linking agent + 3D printing gradient structure is significantly better than the sum of the effects of static cross-linking agent and traditional compression molding alone.

[0101] From the data comparison of Comparative Example 6 and Example 1, it can be seen that the annealing process also has a great influence on the indexes of the prepared materials. Under the annealing process of the present invention, materials with better performance can be prepared.

[0102] The above content is a further detailed description of the present invention in combination with specific / preferred embodiments, and it cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention belongs, without departing from the concept of the present invention, several alternatives or modifications can be made to these described embodiments, and these alternative or modified forms should be regarded as belonging to the protection scope of the present invention.

Claims

1. A novel double-wall material phase change elastic composite material, characterized in that: It includes a core material, wall material A, wall material B, and an elastomer matrix; the core material is paraffin wax, and its mass percentage is 20 - 30% of the total amount of raw materials; the wall material A is gelatin, and its mass percentage is 20 - 30% of the total amount of raw materials; the wall material B is hexamethylene diisocyanate, and its mass percentage is 1.5 - 3.5% of the total amount of raw materials; the elastomer matrix is a styrene-butadiene-styrene block copolymer, and its mass percentage is 30 - 40% of the total amount of raw materials.

2. The novel double-wall material phase change elastic composite material according to claim 1, wherein: It further includes a thermal conductive filler, and the thermal conductive filler is carbon nanotubes, with a mass percentage of 3 - 5% of the total amount of raw materials.

3. The novel double-wall material phase change elastic composite material according to claim 2, characterized in that: It further includes a coupling agent and a dispersant; the coupling agent is a silane coupling agent, with a mass percentage of 0.05 - 0.2% of the total amount of raw materials; the dispersant is ethanol, with a mass percentage of 80 - 85% of the total amount of raw materials.

4. The novel double-wall material phase change elastic composite material according to claim 1, characterized in that: It further includes a plasticizer, and the plasticizer is dioctyl phthalate, with a mass percentage of 5 - 10% of the total amount of raw materials.

5. The novel double-wall material phase change elastic composite material according to claim 1, wherein: It further includes a crosslinking agent, and the crosslinking agent is furan-maleimide, with a mass percentage of 2 - 5% of the total amount of raw materials.

6. The novel double-wall material phase change elastic composite material according to claim 1, characterized in that: It further includes a functional auxiliary agent, and the functional auxiliary agent is a graphene dispersion liquid, with a mass percentage of 10 - 20% of the total amount of raw materials.

7. A method for preparing a novel double-wall material phase change elastic composite material according to any one of claims 1 to 6, characterized in that, It includes the following steps: (1) Heat and melt the core material, dissolve the wall material A in water, and dry the elastomer matrix for standby. (2) Mix and emulsify the melted core material with the aqueous solution of wall material A to form an oil-in-water emulsion; add wall material B and stir to react to obtain a microencapsulated phase change material. (3) Immerse the thermal conductive filler in a dispersant solution containing a coupling agent, perform ultrasonic treatment, centrifuge and dry to obtain a modified thermal conductive filler. S4. Mix the dried elastomer matrix, microencapsulated phase change material, modified thermal conductive filler, and plasticizer evenly, then add the crosslinking agent and disperse evenly to obtain a mixture. S5. Draw the mixture into a wire, and then cure it. S6. Anneal the cured wire, then spray the functional auxiliary agent, dry, stretch, and cool to obtain the product.

8. The preparation method of the novel double-wall material phase change elastic composite material according to claim 7, characterized in that: In step S4, a twin-screw extruder is used for mixing, and the feeding zone, melting zone, mixing zone, and die head zone are set with gradients, and the crosslinking agent is injected at the end of the mixing zone.

9. The preparation method of the novel double-wall material phase change elastic composite material according to claim 8, characterized in that: The temperature of the feeding zone is 75 - 85°C, the temperature of the melting zone is 115 - 130°C; the temperature of the mixing zone is 135 - 150°C, and the temperature of the die head zone is 90 - 110°C.

10. The preparation method of the novel double-wall material phase change elastic composite material according to claim 7, characterized in that: In step S6, gradient annealing is adopted. Specifically, the temperature in the first stage is 75 - 85°C, and the time is 0.5 - 1.5 hours; the temperature in the second stage is 55 - 65°C, and the time is 0.5 - 1.5 hours; the third stage is cooled at room temperature.

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