A method for preparing high-thermal-conductivity heat-conducting pouring sealant from exfoliated boron nitride nanosheets
By using spherical alumina-assisted grinding to exfoliate boron nitride nanosheets and construct a three-dimensional thermally conductive network, the problem of complex boron nitride nanosheet exfoliation process was solved, and a thermally conductive potting compound with high thermal conductivity and high flowability was prepared.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHANDONG UNIV
- Filing Date
- 2023-08-10
- Publication Date
- 2026-05-29
AI Technical Summary
The boron nitride nanosheet exfoliation process in the existing technology is complex and cannot simultaneously achieve high thermal conductivity and high flowability, resulting in low thermal conductivity and poor potting effect of silicone rubber composite materials.
Through a specific mixing process, spherical alumina is used to assist in grinding and exfoliating boron nitride, and boron nitride nanosheets are exfoliated in situ. Combined with phenyl silicone oil and silane coupling agent, a three-dimensional thermally conductive network is constructed to achieve uniform dispersion and high thermal conductivity of boron nitride nanosheets.
With a low boron nitride filling ratio, the thermal conductivity and flowability of silicone rubber were significantly improved, ensuring the potting effect and realizing the preparation of a high thermal conductivity thermally conductive potting compound.
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Abstract
Description
Technical Field
[0001] This invention relates to a method for preparing a high thermal conductivity thermally conductive potting compound by peeling off boron nitride nanosheets, belonging to the field of thermally conductive encapsulation technology for power battery thermal management systems. Background Technology
[0002] With the development of new energy electric vehicles, the energy density and power of lithium-ion batteries in power battery systems are increasing, and the accompanying heat accumulation problem urgently needs to be solved. Traditional heat dissipation methods such as air cooling and water cooling can no longer meet the current heat dissipation requirements of power batteries. Therefore, the development of new heat-dissipating composite materials has become a research hotspot. Silicone rubber, due to its good encapsulation performance, low density, and good flowability, has become a widely used thermally conductive potting polymer matrix. However, the thermal conductivity of silicone rubber is currently relatively low and cannot meet the heat dissipation requirements of new energy battery packs. Thermally conductive fillers are usually used to improve thermal conductivity. To prevent short circuits and other problems inside the power battery pack, high thermal conductivity insulating inorganic fillers, such as Al2O3, BN, and SiN, are often added. Among them, boron nitride, due to its graphene-like structure, has a high in-plane thermal conductivity and has become a popular choice for thermally conductive insulating fillers. However, due to its sheet-like structure and difficulty in peeling, boron nitride cannot be evenly dispersed in the composite material. On the other hand, adding a high proportion of boron nitride will cause the viscosity of silicone rubber to rise rapidly, resulting in poor flowability and poor potting effect. Even with the addition of more thermally conductive fillers, the thermal conductivity is still low, and it is impossible to obtain a thermally conductive potting compound with high thermal conductivity.
[0003] For example, Chinese patent document CN110055020A discloses a high thermal conductivity epoxy potting compound and its preparation method. This method involves adding two types of micron-sized boron nitride ceramic particles with high thermal conductivity and different particle sizes to the raw material components of epoxy resin, along with micron-sized MgO particles that have a gelling effect. Under the combined action of a silane coupling agent, a titanate coupling agent, a fumed silica anti-settling agent, and an isophorone diisocyanate curing agent, the components undergo a cross-linking and curing reaction to prepare the epoxy potting compound. Although this patent improves the thermal conductivity of the epoxy potting compound to some extent, an excessively high proportion of boron nitride can easily lead to excessively high viscosity, affecting the potting effect. Furthermore, even with a large amount of thermally conductive filler, the thermal conductivity remains relatively low.
[0004] Therefore, it is of great significance to develop a low-cost and simple process for preparing thermally conductive and highly fluid thermally conductive potting silicone rubber composite materials. Summary of the Invention
[0005] To address the challenge of complex boron nitride nanosheet exfoliation processes that prevent the simultaneous achievement of high thermal conductivity and high flowability, this invention provides a method for preparing a high thermal conductivity thermally conductive potting compound by exfoliating boron nitride nanosheets.
[0006] This invention utilizes a specific mixing process to grind and exfoliate boron nitride with spherical alumina, generating boron nitride nanosheets through in-situ exfoliation. The spherical alumina and the in-situ generated boron nitride nanosheets synergistically construct a three-dimensional thermally conductive network, resulting in a high thermal conductivity potting silicone rubber with suitable viscosity at a low boron nitride filling ratio.
[0007] This invention is achieved through the following technical solution:
[0008] A method for preparing a high thermal conductivity thermally conductive potting compound by exfoliating boron nitride nanosheets includes the following steps:
[0009] 1) Boron nitride nanosheet powder, spherical alumina, phenyl silicone oil, silane coupling agent, and inhibitor are mixed in a three-roll mill with a roller spacing of 10-300 μm and a mixing time of 2-48 h. Reducing the roller spacing and extending the mixing time allows the boron nitride to peel off inside the composite material under the shearing force of the rollers and the rolling shearing of the spherical alumina, resulting in component A.
[0010] 2) The hydrogen-containing silicone oil and catalyst are mixed evenly in a three-roll mill to obtain component B.
[0011] 3) Degas components A and B in a vacuum degassing mixer to obtain thermally conductive potting silicone rubber.
[0012] According to a preferred embodiment of the present invention, in step 1), the mass fractions of component A are as follows:
[0013] 80-120 parts of spherical alumina, 2-15 parts of boron nitride nanosheet powder, 1-7 parts of silane coupling agent, 50-150 parts of phenyl silicone oil, and 0.1-5 parts of inhibitor.
[0014] More preferably, in step 1), the mass fractions of component A are as follows:
[0015] 50-200 parts of spherical alumina, 5-15 parts of boron nitride nanosheet powder, 1-7 parts of silane coupling agent, 100-120 parts of phenyl silicone oil, and 0.1-2 parts of inhibitor.
[0016] According to a preferred embodiment of the present invention, in step 1), the spherical alumina D50 is 0.5~100μm.
[0017] According to a preferred embodiment of the present invention, in step 1), the boron nitride nanosheet powder is hexagonal boron nitride nanosheet powder with an average sheet diameter of 1~30μm.
[0018] According to a preferred embodiment of the present invention, in step 1), the viscosity of the phenyl silicone oil is 500-2000 mPa·s, and the phenyl molar content is 5 mol%-20 mol.
[0019] According to a preferred embodiment of the present invention, in step 1), the silane coupling agent is KH550, DMDPS, or BTMOS.
[0020] Most preferably, in step 1), the coupling agent is DMDPS.
[0021] According to a preferred embodiment of the present invention, in step 1), the inhibitor is acetylenol or methylbutynol.
[0022] According to a preferred embodiment of the present invention, in step 1), the roller spacing is 30-60 μm.
[0023] According to a preferred embodiment of the present invention, in step 1), the roller speed is 10-500 rpm, preferably 30-100 rpm.
[0024] According to a preferred embodiment of the present invention, in step 1), the mixing time is 24-36 hours.
[0025] According to a preferred embodiment of the present invention, in step 2), the raw materials of component B are as follows by mass: 1-10 parts of hydrogen-containing silicone oil and 0.5-5 parts of catalyst.
[0026] According to a preferred embodiment of the present invention, in step 2), the viscosity of the hydrogen-containing silicone oil is 500-1000 mPa·s.
[0027] According to a preferred embodiment of the present invention, in step 2), the catalyst is a platinum catalyst.
[0028] According to a preferred embodiment of the present invention, in step 2), the mixing time is 20 min to 1 h and the roller spacing is 350 to 600 μm.
[0029] According to a preferred embodiment of the present invention, in step 3), the vacuum degassing time is 1-5 min and the vacuum degassing speed is 1000-3000 rpm.
[0030] Because hexagonal boron nitride nanosheets have a large number of layers and are relatively thick, the more layers there are, the more phonon scattering occurs, thus reducing thermal conductivity and preventing the full realization of its high thermal conductivity. Furthermore, hexagonal boron nitride with a large number of layers has poor dispersibility, making it difficult to integrate with the desired additives. Existing technologies include adding low-modulus boron nitride nanosheets and modifying them through grafting groups to improve dispersion and thermal conductivity, but the improvement in thermal conductivity is not ideal, and the number of hexagonal boron nitride nanosheets remains large. The process is complex, but the mixing process of component A in the preparation method provided by the present invention is different from the existing technology. The existing mixing time is usually within 1.5 hours and the roller gap is greater than 300 μm. The present invention reduces the roller gap and extends the mixing time, so that the boron nitride nanosheets are peeled off layer by layer. This peeling of boron nitride allows the thermal conductivity of the extremely high thermal conductivity BN nanosheets to be maximized in the composite material, giving full play to the advantages of the high thermal conductivity of boron nitride nanosheets. On the other hand, it makes the boron nitride nanosheets uniformly dispersed.
[0031] Furthermore, the addition of spherical alumina serves two main purposes: as a thermally conductive filler and, more importantly, as an aid in the grinding and exfoliation of boron nitride. In-situ exfoliation of boron nitride produces boron nitride nanosheets. The spherical alumina and the in-situ generated boron nitride nanosheets synergistically construct a three-dimensional thermally conductive network, further enhancing thermal conductivity. This invention improves the thermal conductivity of potting silicone rubber with a low boron nitride filling ratio while maintaining its viscosity. Moreover, the exfoliated boron nitride flakes exhibit good compatibility with the polymer, which is beneficial for the dispersion of the thermally conductive filler in the composite material. Therefore, the method of this invention can significantly improve the thermal conductivity of the potting compound while also possessing excellent flowability.
[0032] Technical features and advantages of the present invention:
[0033] 1. This invention uses phenyl silicone oil as a medium and matrix, and uses spherical alumina-assisted grinding to peel off boron nitride. By reducing the roller gap and extending the mixing time, boron nitride nanosheets are peeled off layer by layer, and boron nitride nanosheets are generated in situ. On the one hand, the thermal conductivity of the extremely high thermal conductivity BN nanosheets is maximized in the composite material, giving full play to the advantages of the high thermal conductivity of boron nitride nanosheets. On the other hand, the boron nitride nanosheets are uniformly dispersed, and a high thermal conductivity thermal potting compound is obtained with low boron nitride filler content.
[0034] 2. This invention uses spherical alumina and in-situ generated boron nitride nanosheets to synergistically construct a three-dimensional thermally conductive network, which can obtain a high thermal conductivity potting silicone rubber with suitable viscosity.
[0035] 3. The preparation method of the present invention is simple, low in cost, and can be mass-produced on a large scale. Detailed Implementation
[0036] The specific embodiments of the present invention will be described below with reference to examples in order to better understand the present invention, but the scope of protection of the present invention is not limited thereto.
[0037] All materials used in the examples are commercially available products.
[0038] Example 1
[0039] The method for preparing a high thermal conductivity thermally conductive potting compound by exfoliating boron nitride nanosheets includes the following steps:
[0040] The raw materials for thermally conductive potting compound, by weight, are as follows:
[0041] 100 parts of 20μm spherical alumina, 10 parts of 20μm boron nitride nanosheet powder, 3 parts of silane coupling agent, 100 parts of vinyl-terminated phenyl silicone oil with a phenyl molar content of 20mol%, 5 parts of hydrogen-containing silicone oil, 5 parts of acetylene cyclohexanol, and 2 parts of platinum catalyst.
[0042] 1) According to the formula, boron nitride nanosheet powder, spherical alumina, phenyl silicone oil, silane coupling agent, and acetylene cyclohexanol were placed in a three-roll mill and mixed. The roller spacing of the three-roll mill was 50 μm, the mixing time was 4 h, and the roller speed was 100 rpm. Reducing the roller spacing and extending the mixing time caused the boron nitride to peel off inside the composite material under the shearing force of the rollers and the rolling shearing of the spherical alumina, thus obtaining component A.
[0043] 2) The hydrogen-containing silicone oil and catalyst were placed in a three-roll mill and mixed evenly for 20 minutes with a roll gap of 400 μm to obtain component B.
[0044] 3) Place components A and B in a vacuum degassing mixer and degas at 2000 rpm for 2 minutes to obtain a thermally conductive potting compound. Remove the mixture and place it in a metal mold, then vulcanize at 80°C for 10 minutes to obtain a test sample sheet.
[0045] Example 2
[0046] The method described in the same way as in Example 1 differs in that:
[0047] In step 1), the mixing time is 24 hours.
[0048] Example 3
[0049] The method described in the same way as in Example 1 differs in that:
[0050] In step 1), the mixing time is 48 hours.
[0051] Example 4
[0052] The method described in the same way as in Example 3 differs in that:
[0053] In step 1), the number of spherical alumina parts is 120.
[0054] Example 5
[0055] The method described in the same way as in Example 3 differs in that:
[0056] In step 1), the number of spherical alumina parts is 150.
[0057] Example 6
[0058] The method described in the same way as in Example 5 differs in that:
[0059] In step 1), the boron nitride nanosheet powder is in the form of 8 parts.
[0060] Example 7
[0061] The method described in the same way as in Example 1 differs in that:
[0062] In step 1), the roller spacing of the three-roll mixer is 30 μm.
[0063] Example 8
[0064] The method described in the same way as in Example 1 differs in that:
[0065] In step 1), the roller spacing of the three-roll mixer is 60 μm.
[0066] Comparative Example 1
[0067] The method described in the same way as in Example 3 differs in that:
[0068] In step 2), the mixing time is 0.5 hours.
[0069] Comparative Example 2
[0070] The method described in the same way as in Example 3 differs in that:
[0071] In step 2), the mixing time is 96 hours.
[0072] Comparative Example 3
[0073] The method described in the same way as in Example 1 differs in that:
[0074] In step 2), the roller spacing is 4μm.
[0075] Comparative Example 4
[0076] The method described in the same way as in Example 1 differs in that:
[0077] In step 2), the roller spacing is 400 μm.
[0078] Comparative Example 5
[0079] The method described in the same way as in Example 1 differs in that:
[0080] Boron nitride nanosheet powder without addition.
[0081] Comparative Example 6
[0082] The method described in the same way as in Example 1 differs in that:
[0083] No spherical alumina was added.
[0084] Comparative Example 7
[0085] The method described in the same way as in Example 1 differs in that:
[0086] The amount of 20μm boron nitride nanosheet powder used is 50 parts.
[0087] Experimental Example 1
[0088] The viscosity, thermal conductivity, and thermal diffusivity of Examples 1, 3, and Comparative Examples 1-4 were tested, and the results are shown in Table 1.
[0089] Table 1 Performance parameters of potting compound materials
[0090]
[0091] As can be seen from Table 1, the viscosity of Comparative Examples 1-4 is similar to that of Examples 1 and 3 of the present invention, with good flowability, meeting the requirements for potting. However, their thermal conductivity is significantly lower than that of the present invention. The mixing time of Comparative Example 1 is significantly shorter than that of the present invention, and the mixing time of Comparative Example 2 is significantly longer than that of the present invention, both of which lead to a decrease in thermal conductivity. The roller spacing of Comparative Example 3 is significantly smaller than that of the present invention, and the roller spacing of Comparative Example 4 is significantly larger than that of the present invention, both of which lead to a decrease in thermal conductivity. It can be seen that the present invention, by appropriately reducing the roller spacing and extending the mixing time, allows the boron nitride nanosheets to be peeled off layer by layer, thus peeling the boron nitride. On the one hand, this allows the thermal conductivity of the extremely high thermal conductivity BN nanosheets to be maximized in the composite material, giving full play to the advantages of the high thermal conductivity of boron nitride nanosheets. On the other hand, it makes the boron nitride nanosheets uniformly dispersed.
[0092] Experiment Example 2
[0093] The viscosity, thermal conductivity, and thermal diffusivity of Examples 1, 3, and Comparative Examples 5-7 were tested, and the results are shown in Table 2.
[0094] Table 2 Performance parameters of potting compound materials
[0095]
[0096] As can be seen from Table 2, Comparative Example 6, without the addition of spherical alumina, has the lowest thermal conductivity, which indirectly reflects that spherical alumina is not only a thermally conductive filler, but also an aid in grinding and exfoliating boron nitride. Comparative Example 7, by increasing the proportion of boron nitride nanosheet powder, although it will improve the thermal conductivity to some extent, it is easy to cause the potting adhesive to be too viscous, which will affect the potting effect. The thermal conductivity is still low even with the addition of more thermally conductive filler, and the improvement in thermal conductivity is not significant.
[0097] In summary, this invention utilizes a specific mixing process to assisted in the grinding and exfoliation of boron nitride with spherical alumina, thereby generating boron nitride nanosheets through in-situ exfoliation. The spherical alumina and the in-situ generated boron nitride nanosheets synergistically construct a three-dimensional thermally conductive network, resulting in a high thermal conductivity potting silicone rubber with suitable viscosity at a low boron nitride filling ratio.
[0098] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A method for preparing a high thermal conductivity thermally conductive potting compound by exfoliating boron nitride nanosheets, comprising the following steps: 1) Boron nitride nanosheet powder, spherical alumina, phenyl silicone oil, silane coupling agent, and inhibitor are mixed in a three-roll mill with a roller spacing of 10-300 μm and a mixing time of 2-48 h. Reducing the roller spacing and extending the mixing time allows the boron nitride to peel off inside the composite material under the shearing force of the rollers and the rolling shearing of the spherical alumina, resulting in component A. The mass fractions of component A raw materials are as follows: 80-120 parts of spherical alumina, 5-15 parts of boron nitride nanosheet powder, 1-7 parts of silane coupling agent, 50-150 parts of phenyl silicone oil, and 0.1-5 parts of inhibitor; 2) The hydrogen-containing silicone oil and catalyst were mixed evenly in a three-roll mill to obtain component B. 3) Degas components A and B in a vacuum degassing mixer to obtain thermally conductive potting silicone rubber.
2. The method according to claim 1, characterized in that, In step 1), the spherical alumina D50 is 0.5-100 μm, and the boron nitride nanosheet powder is hexagonal boron nitride nanosheet powder with an average sheet diameter of 1-30 μm.
3. The method according to claim 1, characterized in that, In step 1), the viscosity of the phenyl silicone oil is 500-2000 mPa·s, and the phenyl molar content is 5 mol%-20 mol%.
4. The method according to claim 1, characterized in that, In step 1), the silane coupling agent is KH550, and the inhibitor is acetylenecyclohexanol or methylbutynol.
5. The method according to claim 1, characterized in that, In step 1), the roller spacing is 30-60μm.
6. The method according to claim 1, characterized in that, In step 1), the roller speed is 10-500 rpm and the mixing time is 24-36 h.
7. The method according to claim 1, characterized in that, In step 2), the raw materials of component B are as follows by mass: 1-10 parts of hydrogen-containing silicone oil and 0.5-5 parts of catalyst.
8. The method according to claim 1, characterized in that, In step 2), the viscosity of the hydrogen-containing silicone oil is 500-1000 mPa·s, the catalyst is a platinum catalyst, the mixing time is 20 min-1 h, and the roller gap is 350-600 μm.
9. The method according to claim 1, characterized in that, In step 3), the vacuum degassing time is 1-5 minutes and the vacuum degassing speed is 1000-3000 rpm.