A thermally conductive phase change coating and its preparation method

Abstract

This invention discloses a thermally conductive phase change coating, comprising a binder, solvent, initiator, thermally conductive filler, phase change material, and wetting and dispersing agent. Through research on thermochromic materials, thermally conductive fillers, and binders, this invention achieves a thermally conductive phase change coating with high thermal conductivity, high enthalpy, and high polymer strength. Specifically, even at continuously high operating temperatures, the phase change material maintains good polymer strength, the components do not separate, the phase change coating does not dry out or harden, does not increase thermal resistance, and can quickly conduct and dissipate heat, extending its service life. Furthermore, this invention's coating is convenient to use; the material can be coated at high temperatures and then encapsulated with different materials. It is used in a solid state, is easy to install and handle, and can be widely applied in many fields such as electronics and aerospace.

Description

Technical fields:

[0001] This invention belongs to the field of phase change materials, specifically relating to a thermally conductive phase change coating and its preparation method. Background technology:

[0002] Thermally conductive phase change materials (PCMs) are materials whose physical state changes with temperature. They are primarily used to reduce the thermal resistance between electronic devices and heat sinks, thereby improving heat dissipation efficiency. These materials are solid at room temperature, making them easy to handle and install. When electronic devices operate and their temperature rises, the PCM absorbs heat, changing from a solid to a liquid or soft state. This fills the tiny gaps between the device and the heat sink, effectively expelling air from the interface and significantly reducing the thermal resistance between the contact surfaces. This phase change process involves the absorption or release of latent heat, giving it a significant advantage in electronic heat dissipation.

[0003] Due to their excellent thermal conductivity, phase change materials (PCMs) are widely used in high-performance modules of computers / laptops, high-frequency microprocessors, memory modules, DC / DC converters, and power modules for efficient heat dissipation. However, when devices operate at consistently high temperatures, the cohesive strength of PCMs may weaken due to temperature variations, leading to separation between components and increased thermal resistance. Furthermore, existing PCMs often suffer from slow thermal conductivity, hindering timely heat dissipation, and have a low enthalpy of absorbed heat.

[0004] Chinese patent CN112048221A discloses a method for preparing a phase change energy-saving material, which achieves temperature regulation by preparing a phase change material from expanded graphite and mixed acid. Chinese patent CN108531024A discloses a method for preparing a high thermal conductivity coating, which improves the material's high thermal conductivity by preparing a modified boron nitride nanosheet / nano titanium oxide composite material.

[0005] In contrast, this invention, through research on thermochromic materials, adhesives, and thermally conductive fillers, yields a phase change coating with high thermal conductivity, high heat absorption, and good material stability. The thermally conductive phase change material of this invention can be widely used in many fields such as electronics and aerospace, and can maintain excellent thermal conductivity and heat dissipation performance under complex environmental conditions such as continuous high-temperature changes and high-frequency vibrations. Summary of the Invention:

[0006] To address the shortcomings of the existing technologies, this invention provides a thermally conductive phase change coating and its preparation method.

[0007] The first objective of this invention is to provide a thermally conductive phase change coating.

[0008] The components of a thermally conductive phase change coating of the present invention include a binder, a solvent, an initiator, a thermally conductive filler, a phase change material, and a wetting and dispersing agent.

[0009] The adhesive composition is selected from a mixture of isooctyl acrylate, vinyl acetate, and acrylic acid. More specifically, it includes 12%–14% isooctyl acrylate, 4%–6% vinyl acetate, and 2%–4% acrylic acid. In some embodiments, the ratio of isooctyl acrylate: vinyl acetate: acrylic acid is 8.7:3.3:2. The inventors have discovered that selecting a multi-combination material composition for the adhesive is beneficial for improving the cohesive strength of the coating structure; that is, even at continuously high operating temperatures, the phase change material maintains good cohesive strength, the components do not separate, the phase change coating does not dry out or harden, and there is no increase in thermal resistance.

[0010] The initiator is selected as benzoyl peroxide, with a proportion of 0.1% to 0.5%. Further, the ratio of initiator to binder is 0.2:14 to 0.2:21; in some embodiments, the initiator formulation proportion is selected as 0.2%.

[0011] The solvent is selected from organic solvents. Specifically, toluene is selected as the organic solvent in this invention, accounting for 8% to 10%.

[0012] The preferred thermally conductive filler is an inert material with abundant pore structure. Specifically, expanded graphite is selected as the thermally conductive material in this invention, accounting for 2% to 5%. Further, the expanded graphite has a density of 1.5 to 2.1 g / cm³. 3 With a crystal grain size of 0.15–0.3 mm, expanded graphite within this density and grain size range can effectively utilize its thermal conductivity. Clearly, the abundant porosity of expanded graphite can effectively improve energy storage and release efficiency, solving the problem of poor thermal conductivity in traditional phase change thermal storage materials.

[0013] The phase change material described in this invention is a mixture of short-chain hydrocarbons extracted from petroleum. Specifically, the phase change material selected in this invention is paraffin wax, white petrolatum, etc. This type of mixture has a large melting range and can effectively absorb ambient heat. In some embodiments, paraffin wax is preferred, accounting for 50%–70%, and more preferably 60%–70%. Further, the phase change paraffin wax is a straight-chain alkane with 26 carbon atoms. This invention has found that this proportion of phase change material can effectively improve the phase change enthalpy of the coating.

[0014] The wetting and dispersing agent can be selected from polyamino cationic perylene imide graphene dispersants, accounting for 1% to 5%; further, 2% to 4%. In some embodiments, the wetting and dispersing agent accounts for 2%. The ratio of the wetting and dispersing agent to expanded graphite is in the range of 2:3 to 2:8. Within this ratio range, it can effectively promote the dispersion of expanded graphite, thereby allowing the small-particle-size, low-density expanded graphite to be uniformly dispersed in the coating, avoiding agglomeration, and thus improving the thermal conductivity of the material.

[0015] Specifically, a more preferred embodiment of the present invention may be as follows:

[0016] The weight percentage content of each component of the raw material is as follows:

[0017] Isooctyl acrylate: 12%–14%

[0018] Vinyl acetate: 4%–6%

[0019] Acrylic acid: 2%–4%

[0020] Toluene: 8%–10%

[0021] Benzoyl peroxide: 0.2%

[0022] Expanded graphite: 2%–5%

[0023] Phase change paraffin: 60%–70%

[0024] Wetting and dispersing agent: 2%.

[0025] The second objective of this invention is to provide a method for preparing a thermally conductive phase change coating.

[0026] Its preparation process steps are as follows:

[0027] (1) Add isooctyl acrylate, isooctyl acetate, acrylic acid, and some toluene into a 4-necked reaction flask, and set the external temperature to above 82°C.

[0028] (2) When the temperature of the material in the bottle rises to 79°C, the BPO solution dissolved in the remaining toluene is added dropwise into the reaction bottle evenly over 2 hours.

[0029] (3) Keep warm for 2 hours.

[0030] (4) Add phase change paraffin and wetting and dispersing agent into the reaction flask and stir rapidly for 30 minutes.

[0031] (5) Slowly add the expanded graphite to the reaction flask in batches.

[0032] (6) After stirring and dispersing for 120 minutes, apply the coating while maintaining the temperature.

[0033] This invention is a phase change coating with high thermal conductivity, high heat absorption and good material stability. It can be applied alone or in combination in many fields such as electronics and aerospace. It has good thermal conductivity, non-conductivity, good reliability and long-term stability, and can maintain stable performance under harsh temperature conditions.

[0034] Beneficial effects of this invention:

[0035] 1. The phase change coating of the present invention has a high enthalpy value for thermally conductive phase change. The enthalpy values ​​of the samples in the specific embodiments of the present invention are all above 130 J / g, indicating that the present invention absorbs more heat during thermal change, which is more conducive to dissipating more heat and reducing the accumulation of heat between devices.

[0036] 2. The thermally conductive filler of this invention is expanded graphite with a rich porous structure and a density of 1.5–2.1 g / cm³. 3 With a crystal grain size of 0.15–0.3 mm, it can effectively improve energy storage and release efficiency, increase thermal conductivity, dissipate heat in a timely manner, and extend the service life of the device.

[0037] 3. The coating of this invention exhibits high cohesive strength. The peel force remained unchanged before and after a double 85-degree resting period (85°C and 85% humidity), indicating that the adhesion strength between the coating and the release film remained unchanged, further demonstrating that the cohesive strength of the coating did not change. That is, even at continuously high operating temperatures, the phase change material maintains good cohesive strength, the components do not separate, the phase change coating does not dry out or harden, and there is no increase in thermal resistance.

[0038] 4. The present invention is convenient to prepare and use. The material can be coated with different materials and then encapsulated in a solid state when the material is in a high temperature state, which is convenient for installation and handling. Attached image description:

[0039] Figure 1 The DSC diagram for Example 1;

[0040] Figure 2 The DSC diagram for Example 2;

[0041] Figure 3 This is the DSC diagram for Example 3. Detailed implementation method:

[0042] The embodiments of this application are described in detail below. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0043] Example 1

[0044] Weigh each component of the raw material as follows:

[0045] Isooctyl acrylate: 13g

[0046] Vinyl acetate: 5g

[0047] Acrylic acid: 3g

[0048] Toluene: 9g

[0049] Benzoyl peroxide: 0.2g

[0050] Expanded graphite: 7.8g

[0051] Phase change paraffin: 60g

[0052] Polyamino cationic perylene imide graphene dispersant: 2g

[0053] A. Among them, expanded graphite has a density of 1.5-2.1 g / cm³. 3 The crystal grain size is 0.15-0.3 mm.

[0054] B. Among them, phase change paraffin is a straight-chain alkane with 26 carbon atoms.

[0055] C. The purity of isooctyl acrylate, vinyl acetate, acrylic acid, toluene, and benzoyl peroxide is >99.9%.

[0056] The above methods for preparing phase change coatings are as follows:

[0057] ① Add isooctyl acrylate, isooctyl acetate, acrylic acid, and a portion of toluene into a 4-necked reaction flask, and set the external temperature to 82℃.

[0058] ②When the temperature of the material inside the bottle rises to 79°C, add the BPO solution dissolved in the remaining toluene into the reaction bottle evenly over 2 hours.

[0059] ③ Keep the reaction at a constant temperature for 2 hours.

[0060] ④ Add the phase change paraffin and wetting and dispersing agent into the reaction flask and stir rapidly for 30 minutes.

[0061] ⑤ Slowly add the expanded graphite to the reaction flask in batches.

[0062] ⑥ After stirring and dispersing for 120 minutes, apply the coating while maintaining the temperature.

[0063] Example 2

[0064] Weigh each component of the raw material as follows:

[0065] Isooctyl acrylate: 10g

[0066] Vinyl acetate: 5g

[0067] Acrylic acid: 3g

[0068] Toluene: 9g

[0069] Benzoyl peroxide: 0.2g

[0070] Expanded graphite: 3.8g

[0071] Phase change paraffin: 67g

[0072] Polyamino cationic perylene imide graphene dispersant: 2g

[0073] A. Among them, expanded graphite has a density of 1.5-2.1 g / cm³. 3 The crystal grain size is 0.15-0.3 mm.

[0074] B. Among them, phase change paraffin is a straight-chain alkane with 26 carbon atoms.

[0075] C. The purity of isooctyl acrylate, vinyl acetate, acrylic acid, toluene, and benzoyl peroxide is >99.9%.

[0076] The above methods for preparing phase change coatings are as follows:

[0077] ① Add isooctyl acrylate, isooctyl acetate, acrylic acid, and a portion of toluene into a 4-necked reaction flask, and set the external temperature to 82℃.

[0078] ②When the temperature of the material inside the bottle rises to 79°C, add the BPO solution dissolved in the remaining toluene into the reaction bottle evenly over 2 hours.

[0079] ③ Keep the reaction at a constant temperature for 2 hours.

[0080] ④ Add the phase change paraffin and wetting and dispersing agent into the reaction flask and stir rapidly for 30 minutes.

[0081] ⑤ Slowly add the expanded graphite to the reaction flask in batches.

[0082] ⑥ After stirring and dispersing for 120 minutes, apply the coating while maintaining the temperature.

[0083] Example 3

[0084] Weigh each component of the raw material as follows:

[0085] Isooctyl acrylate: 8.7g

[0086] Vinyl acetate: 3.3g

[0087] Acrylic acid: 2g

[0088] Toluene: 6g

[0089] Benzoyl peroxide: 0.2g

[0090] Expanded graphite: 7.8g

[0091] Phase change paraffin: 70g

[0092] Polyamino cationic perylene imide graphene dispersant: 2g

[0093] A. Among them, expanded graphite has a density of 1.5-2.1 g / cm³. 3 The crystal grain size is 0.15-0.3 mm.

[0094] B. Among them, phase change paraffin is a straight-chain alkane with 26 carbon atoms.

[0095] C. The purity of isooctyl acrylate, vinyl acetate, acrylic acid, toluene, and benzoyl peroxide is >99.9%.

[0096] The above methods for preparing phase change coatings are as follows:

[0097] ① Add isooctyl acrylate, isooctyl acetate, acrylic acid, and a portion of toluene into a 4-necked reaction flask, and set the external temperature to 82℃.

[0098] ②When the temperature of the material inside the bottle rises to 79°C, add the BPO solution dissolved in the remaining toluene into the reaction bottle evenly over 2 hours.

[0099] ③ Keep the reaction at a constant temperature for 2 hours.

[0100] ④ Add the phase change paraffin and wetting and dispersing agent into the reaction flask and stir rapidly for 30 minutes.

[0101] ⑤ Slowly add the expanded graphite to the reaction flask in batches.

[0102] ⑥ After stirring and dispersing for 120 minutes, apply the coating while maintaining the temperature.

[0103] Experimental results

[0104] (1) Thermal phase change performance test

[0105] Equipment: Differential scanning calorimeter

[0106] Manufacturer and Model: German Nexos DSC 3500 Sirius

[0107] The finished products of Examples 1, 2, and 3 were tested for various performance indicators according to the corresponding experimental standards, and the test results are shown in the table below.

[0108]

[0109]

[0110] The results show that Embodiments 1, 2, and 3 of the present invention have the characteristics of high phase change enthalpy and high thermal conductivity, indicating that the present invention can effectively improve energy storage and release efficiency, increase thermal conductivity, dissipate heat in a timely manner, and improve the service life of the device.

[0111] (2) Cohesive strength test

[0112] Phase change coatings from Examples 1, 2, and 3 were applied to PET films, with a coating thickness of 50 μm. After coating, both the top and bottom surfaces of the phase change coating were covered with a 20 μm thick PET film. Cohesive strength tests were then conducted before and after a 1000-hour double 85-degree resting period (85°C and 85% humidity).

[0113] The specific testing method is as follows: use a tensile testing machine clamp to clamp two layers of 20um PET film and perform a 180° peel force test.

[0114] The test data is as follows:

[0115]

[0116] The results show that the peel force of the phase change coating of the present invention did not change before and after being subjected to a double 85-degree resting period (85°C and 85% humidity), indicating that the adhesion strength between the coating and the release film remained unchanged, and further demonstrating that the cohesive strength of the coating did not change. Therefore, the phase change coating structure of the present invention remains stable under high temperature and high humidity conditions. That is, even at continuously high operating temperatures, the phase change material of the present invention maintains good cohesive strength, the components do not separate, the phase change coating does not dry out or harden, does not increase thermal resistance, and can effectively maintain high thermal conductivity.

Claims

1. A thermally conductive phase change coating, characterized in that, Components including the following weight fractions: Isooctyl acrylate: 12%–14% Vinyl acetate: 4%~6% Acrylic acid: 2%~4% Expanded graphite: 2%~5% Phase change materials: 50%~70% Initiator: 0.1%~0.5% Solvent: 8%~10% Wetting and dispersing agent: 1%~5% The phase change material is paraffin wax; The mixture of isooctyl acrylate, vinyl acetate and acrylic acid constitutes an adhesive material; The initiator is benzoyl peroxide, and the ratio of the initiator to the adhesive material is 0.2:14 to 0.2:21; The ratio of the wetting and dispersing agent to the expanded graphite is in the range of 2:3 to 2:

8. The wetting and dispersing agent is selected from polyamino cationic perylene imide graphene dispersants, and the solvent is toluene.

2. The thermally conductive phase change coating according to claim 1, characterized in that, The expanded graphite has a density of 1.5~2.1 g / cm³ and a crystal grain size of 0.15~0.3 mm.

3. The thermally conductive phase change coating according to claim 2, characterized in that, Phase change paraffin is a straight-chain alkane with 26 carbon atoms, accounting for 60% to 70% of the formulation.

4. A method for preparing a thermally conductive phase change coating according to claim 1, 2, or 3, characterized in that, Includes the following steps: (1) Add isooctyl acrylate, vinyl acetate, acrylic acid, and some toluene into a 4-necked reaction flask and set the external temperature to above 82°C. (2) When the temperature of the material in the bottle rises to 79°C, the BPO solution dissolved in the remaining toluene is added dropwise into the reaction bottle evenly over 2 hours. (3) Keep the reaction warm for 2-4 hours; (4) Add the phase change paraffin and wetting and dispersing agent into the reaction flask and stir rapidly for 30-60 minutes; (5) Slowly add the expanded graphite to the reaction flask in batches; (6) After stirring and dispersing for 120 minutes, apply the coating while maintaining the temperature.

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