A silicone foam sheet and a battery module and battery pack containing the same.

Abstract

This invention discloses a silicone foam sheet and a battery module and battery pack containing the same, belonging to the technical field of silicone foam materials. The linear expansion coefficient α of the foam sheet's pore diameter satisfies 1≤α≤8, and the linear contraction coefficient β of the foam sheet's pore wall thickness satisfies 4≤β≤9. This invention enables the silicone foam sheet to have more spatial gaps and a lower thermal conductivity under room temperature conditions; it also enables the silicone foam sheet to maintain an intact pore structure and high strength after sintering at high temperatures, thus preventing breakage. Therefore, the silicone foam sheet of this invention has good thermal insulation performance; simultaneously, the silicone foam sheet of this invention also exhibits good cushioning performance.

Description

Technical Field

[0001] This invention relates to a silicone foam sheet and a battery module and battery pack containing the same, belonging to the technical field of silicone foam materials. Background Technology

[0002] Battery modules in new energy vehicles consist of multiple cells. These cells can experience thermal runaway due to factors such as internal short circuits, overcharging and discharging, and high-temperature environments. When thermal runaway occurs, the cells release heat and gas, which can ignite under high temperature and pressure. Preventing the propagation of thermal runaway between adjacent cells is one of the key technological challenges, and various materials have already been developed and applied.

[0003] Aerogels are the most common gasket material used to prevent thermal runaway between adjacent battery cells. Aerogels have a nanoporous structure and low thermal conductivity, which can block the transfer of high temperatures to adjacent cells. However, aerogels are expensive; and their brittle texture can cause cracks or even shattering in the vibration environment of battery pack assembly or vehicle operation, leading to failure of thermal insulation performance. In addition, composite phase change materials are also widely used. They absorb a large amount of latent heat at specific temperatures and undergo a phase change, delaying the temperature rise of the battery cells. However, the heat absorption capacity of composite phase change materials depends on their latent heat value. In continuous or extreme thermal runaway scenarios, composite phase change materials may quickly reach thermal saturation, making it difficult to prevent the spread of thermal runaway for a long time; moreover, there may be a risk of leakage when composite phase change materials melt into a liquid state.

[0004] Compared to the two materials mentioned above, ceramicized silicone foam is more advanced. It is relatively soft at room temperature, but sintersects into a hard ceramic body when exposed to high-temperature flames, preventing thermal runaway from spreading between adjacent cells. However, the high-temperature resistance of existing ceramicized silicone foam is typically between 220-240℃. If exposed to temperatures of 400-1000℃ for an extended period, the foam will lose its complete cellular structure, or the cellular structure will collapse under slight force, causing the foam to shatter and lose its insulation properties, thus failing to prevent the spread of thermal runaway. Furthermore, increasing the ceramic strength of the ceramicized silicone foam often results in an excessively high thermal conductivity at room temperature, leading to poor insulation performance.

[0005] Therefore, existing silicone foam sheets often fail to balance the strength after high-temperature sintering with the thermal conductivity at room temperature, making it difficult to achieve good thermal insulation performance. Summary of the Invention

[0006] To address the aforementioned technical problems, the present invention aims to provide a silicone foam sheet and a battery module and battery pack containing the same. The present invention enables the silicone foam sheet to have more spatial gaps and a lower thermal conductivity under normal temperature conditions; it also enables the silicone foam sheet to maintain an intact cell structure and high strength after sintering at high temperatures, thus preventing breakage. Therefore, the silicone foam sheet of the present invention has good thermal insulation performance. Simultaneously, the silicone foam sheet of the present invention also exhibits good cushioning performance.

[0007] To achieve the above objectives, the first aspect of the present invention provides a silicone foam sheet, wherein the linear expansion coefficient α of the foam pore diameter of the silicone foam sheet satisfies 1≤α≤8, and the linear shrinkage coefficient β of the foam pore wall thickness of the silicone foam sheet satisfies 4≤β≤9.

[0008] The linear expansion coefficient α of the bubble diameter and the linear shrinkage coefficient β of the bubble wall thickness are calculated using the following formulas:

[0009] , ,

[0010] In the formula, α is the coefficient of linear expansion of the bubble diameter, with units of °C. -1 β is the linear shrinkage coefficient of the bubble wall thickness, in °C. -1 L0 is the average cell diameter of the silicone foam sheet at room temperature, in μm; L1 is the average cell diameter of the silicone foam sheet after heating at 1000℃ for 30 min, in μm; d0 is the average cell wall thickness of the silicone foam sheet at room temperature, in μm; d1 is the average cell wall thickness of the silicone foam sheet after heating at 1000℃ for 30 min, in μm; T is the temperature difference between room temperature and 1000℃, in °C.

[0011] According to a specific embodiment of the present invention, preferably, the ratio of α to β satisfies α / β = 0.2-1.8.

[0012] According to a specific embodiment of the present invention, preferably, the number of effective cells in the silicone foam sheet after heating at 1000°C for 30 minutes accounts for more than 90% of the total number of cells.

[0013] According to a specific embodiment of the present invention, preferably, the average pore diameter of the silicone foam sheet at room temperature is 100-1200 μm, and the average pore diameter of the silicone foam sheet after heating at 1000°C for 30 min is 110-1350 μm. More preferably, the average pore diameter of the silicone foam sheet at room temperature is 200-1000 μm, and the average pore diameter of the silicone foam sheet after heating at 1000°C for 30 min is 220-1200 μm.

[0014] According to a specific embodiment of the present invention, preferably, the average cell wall thickness of the silicone foam sheet at room temperature is 5-100 μm, and the average cell wall thickness of the silicone foam sheet after heating at 1000°C for 30 min is 3-60 μm. More preferably, the average cell wall thickness of the silicone foam sheet at room temperature is 5-90 μm, and the average cell wall thickness of the silicone foam sheet after heating at 1000°C for 30 min is 3-55 μm.

[0015] According to a specific embodiment of the present invention, preferably, the thermal insulation Q per unit area of ​​the silicone foam sheet at a T0 setting of 450°C is ≥30, and the thermal insulation Q per unit area of ​​the silicone foam sheet at a T0 setting of 650°C is ≥45; the thermal insulation Q per unit area is obtained by testing using the following method:

[0016] A heating plate and a cold plate are provided, with the cold plate positioned above the heating plate. The heating plate has a hot surface. A silicone foam sheet is placed on the hot surface of the heating plate, and then the cold plate is pressed down until it contacts the silicone foam sheet, applying a pressure of 0.3 MPa to the silicone foam sheet. The hot surface of the heating plate reaches a heating temperature T0. After maintaining the pressure and the heating temperature for 30 minutes, the highest temperature T1 of the contact surface between the cold plate and the silicone foam sheet during the 30-minute holding time is recorded. The contact surface between the cold plate and the silicone foam sheet, the hot surface of the heating plate, and the silicone foam sheet are all matched in shape and have equal areas.

[0017] The heat insulation per unit area Q is calculated using the following formula: Q = K × (T1 - T0) × A / H;

[0018] In the formula, Q represents the heat insulation per unit area, in W; K represents the thermal conductivity of the silicone foam sheet at room temperature, in W / (m·K); T0 represents the temperature of the hot surface of the heating plate (i.e., the heating temperature), in K, and the set value of T0 is 450℃ or 650℃; T1 represents the highest temperature of the contact surface between the cold plate and the silicone foam sheet during the 30-minute holding time, in K; and A represents the area of ​​the hot surface of the heating plate, in m². 2H represents the thickness of the silicone foam sheet, in meters (m).

[0019] According to a specific embodiment of the present invention, preferably, the absolute value of the difference between the Shore A hardness of the silicone foam sheet at room temperature and the Shore A hardness after heating at 1000°C for 30 minutes is 20-60°.

[0020] According to a specific embodiment of the present invention, preferably, the Shore A hardness of the silicone foam sheet at room temperature is 5-50°, and the Shore A hardness of the silicone foam sheet after heating at 1000°C for 30 minutes is 65-70°.

[0021] According to a specific embodiment of the present invention, preferably, the density of the silicone foam sheet at room temperature is 300-1100 kg / m³. 3 .

[0022] According to a specific embodiment of the present invention, preferably, the 25% compressive stress of the silicone foam sheet under normal temperature conditions is 20-500 kPa.

[0023] According to a specific embodiment of the present invention, preferably, the thermal conductivity of the silicone foam sheet at room temperature is 0.05-0.11 W / (m·K).

[0024] According to a specific embodiment of the present invention, preferably, the thickness of the silicone foam sheet at room temperature is 0.5-25 mm.

[0025] A second aspect of the present invention provides a battery module comprising: two or more battery cells and one or more of the aforementioned silicone foam sheets, wherein the silicone foam sheets are disposed between adjacent battery cells.

[0026] A third aspect of the present invention provides a battery pack comprising: a housing and the aforementioned battery module; the housing includes a frame, a top cover, a wiring harness isolation plate, and a liquid cooling plate; the battery module is disposed in the frame; the top cover is disposed on the top of the battery module; the wiring harness isolation plate is disposed between the battery module and the top cover; the wiring harness isolation plate is provided with a busbar for connecting the battery cells in the battery module; the aforementioned silicone foam sheet is disposed between the wiring harness isolation plate and the top cover for covering the top of the busbar; the liquid cooling plate is disposed around the sides and / or the bottom of the battery module.

[0027] The present invention has at least the following beneficial effects:

[0028] This invention provides silicone foam sheets with ample space between cells at room temperature, resulting in low thermal conductivity. Furthermore, it ensures that the silicone foam sheet maintains its intact pore structure after sintering at high temperatures, leading to high ceramic strength and preventing breakage. Therefore, the silicone foam sheet of this invention exhibits excellent thermal insulation properties. Simultaneously, the silicone foam sheet of this invention also provides good cushioning performance. The silicone foam sheet of this invention can be used as a thermal insulation pad in battery modules and battery packs to prevent the spread of thermal runaway. Attached Figure Description

[0029] Figure 1 This is a SEM image of the silicone foam sheet from Example 1.

[0030] Figure 2 The image shows a SEM image of the silicone foam sheet from Example 1 after heating at 1000°C for 30 minutes. Detailed Implementation

[0031] To provide a clearer understanding of the technical features, objectives, and beneficial effects of the present invention, the present invention will now be described in detail below, but this should not be construed as limiting the scope of the invention.

[0032] It should be noted that, unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0033] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0034] It should be understood that the terms “comprising,” “including,” and / or “containing” as used herein specify the presence of the stated features, integers, steps, components, or combinations thereof, but do not exclude the presence or addition of one or more other features, integers, steps, components, or combinations thereof.

[0035] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.

[0036] According to a specific embodiment of the first aspect of the present invention, the present invention provides a silicone foam sheet, wherein the linear expansion coefficient α of the cell diameter of the silicone foam sheet satisfies 1≤α≤8, for example, but not limited to α=1, 2, 3, 4, 5, 6, 7 or 8, and the linear shrinkage coefficient β of the cell wall thickness of the silicone foam sheet satisfies 4≤β≤9, for example, but not limited to β=4, 5, 6, 7, 8 or 9;

[0037] The linear expansion coefficient α of the bubble diameter and the linear shrinkage coefficient β of the bubble wall thickness are calculated using the following formulas:

[0038] , ,

[0039] In the formula, α is the coefficient of linear expansion of the bubble diameter, with units of °C. -1 β is the linear shrinkage coefficient of the bubble wall thickness, in °C. -1 L0 is the average cell diameter of the silicone foam sheet at room temperature, in μm; L1 is the average cell diameter of the silicone foam sheet after heating at 1000℃ for 30 min, in μm; d0 is the average cell wall thickness of the silicone foam sheet at room temperature, in μm; d1 is the average cell wall thickness of the silicone foam sheet after heating at 1000℃ for 30 min, in μm; T is the temperature difference between room temperature and 1000℃, in °C.

[0040] In this invention, ambient temperature refers to 23±2℃.

[0041] If the coefficient of linear expansion α of the cell diameter is less than 1, although the expansion of the cell diameter before and after high-temperature sintering is small, it will result in the silicone foam sheet having an excessively small cell diameter at room temperature, or even almost no cells, making it nearly solid. This leads to fewer gaps in the silicone foam sheet, an excessively high thermal conductivity, and poor thermal insulation performance. It also reduces the material's cushioning performance, and the thermal insulation per unit area at 450℃ and 650℃ will be difficult to meet the requirements of Q≥30 and ≥45, respectively. If the coefficient of linear expansion α of the cell diameter is greater than 8, the expansion of the cell diameter before and after high-temperature sintering is large. This results in too few cell walls in the silicone foam sheet after high-temperature sintering, making the cell structure prone to collapse, causing the foam sheet to break and lose its thermal insulation performance. At the same time, the structural stability at high temperatures is insufficient, making it difficult to meet the thermal insulation performance requirements at 450℃ and 650℃.

[0042] If the linear shrinkage coefficient β of the cell wall thickness is less than 4, the shrinkage of the cell wall thickness before and after high-temperature sintering is small. However, this results in excessively thick cell walls and an excessive number of cell structures in the silicone foam sheet at room temperature, leading to insufficient cell structure, small cell diameter, and excessively high thermal conductivity. This results in poor thermal insulation performance and weakens the material's cushioning properties. Furthermore, it is difficult to achieve the required thermal insulation per unit area of ​​Q≥30 and ≥45 at 450℃ and 650℃, respectively. If the linear shrinkage coefficient β of the cell wall thickness is greater than 10, the shrinkage of the cell wall thickness before and after high-temperature sintering is large and severe. This makes the cell structure prone to collapse, causing the foam sheet to break and lose its thermal insulation performance. At the same time, the cell support structure is lost after high-temperature sintering, making it impossible to guarantee effective thermal insulation at 450℃ and 650℃.

[0043] This invention controls the linear expansion coefficient α of the cell diameter and the linear contraction coefficient β of the cell wall thickness of the silicone foam sheet within the aforementioned range before and after sintering at 1000℃. This allows the silicone foam sheet to possess suitable cell diameter and cell wall thickness, resulting in more spatial gaps within the foam sheet, leading to a lower thermal conductivity and good buffering performance. It also ensures thermal insulation performance at 450℃ and 650℃, and maintains an intact cell structure after sintering at 1000℃, forming a ceramic body with high ceramic strength, thus preventing the foam sheet from cracking after high-temperature sintering. Therefore, the silicone foam sheet of this invention has good thermal insulation performance and can prevent the spread of thermal runaway.

[0044] In some embodiments, the ratio of α to β satisfies α / β = 0.2-1.8, such as, but not limited to, α / β = 0.2, 0.4, 0.6, 0.8, 1.0, 1.2, 1.4, 1.6, or 1.8. By controlling the value of α / β within the above range, the foam sheet can further achieve both good thermal insulation performance and good cushioning performance.

[0045] In some embodiments, the number of effective cells in the silicone foam sheet after heating at 1000°C for 30 minutes accounts for more than 90% of the total number of cells. By controlling the proportion of effective cells after high-temperature sintering at 1000°C within the above range, the foam sheet maintains an intact cell structure after high-temperature sintering, thereby achieving better thermal insulation performance.

[0046] In some embodiments, the average pore diameter of the silicone foam sheet at room temperature is 100-1200 μm, such as, but not limited to, 100 μm, 200 μm, 300 μm, 400 μm, 500 μm, 600 μm, 700 μm, 800 μm, 900 μm, 1000 μm, 1100 μm, or 1200 μm. The average pore diameter of the silicone foam sheet after heating at 1000℃ for 30 min is 110-1350 μm, such as, but not limited to, 110 μm, 200 μm, 300 μm, 400 μm, 500 μm, 600 μm, 700 μm, 800 μm, 900 μm, 1000 μm, 1100 μm, 1200 μm, 1300 μm, or 1350 μm. Preferably, the average pore diameter of the silicone foam sheet at room temperature is 200-1000 μm, and the average pore diameter of the silicone foam sheet after heating at 1000℃ for 30 min is 220-1200 μm. By controlling the average pore diameter at room temperature and after high-temperature sintering at 1000℃ to be within the above range, the foam sheet has a suitable pore diameter, more spatial gaps within the foam sheet, and maintains an intact pore structure after high-temperature sintering, thereby achieving better thermal insulation performance.

[0047] In some embodiments, the average cell wall thickness of the silicone foam sheet at room temperature is 5-100 μm, and the average cell wall thickness of the silicone foam sheet after heating at 1000°C for 30 min is 3-60 μm. Preferably, the average cell wall thickness of the silicone foam sheet at room temperature is 5-90 μm, and the average cell wall thickness of the silicone foam sheet after heating at 1000°C for 30 min is 3-55 μm. By controlling the average cell wall thickness at room temperature and after high-temperature sintering at 1000°C to be within the above range, the foam sheet further has a suitable cell wall thickness, resulting in more spatial gaps within the foam sheet. This further enhances the thermal insulation performance of the foam sheet at 450°C and 650°C, and further ensures that the foam sheet maintains an intact cell structure after high-temperature sintering, thereby achieving better thermal insulation performance.

[0048] In some embodiments, the thermal insulation Q per unit area of ​​the silicone foam sheet at a T0 setting of 450°C is ≥30, for example, but not limited to, 30, 35, 40, 45, 50, 55, 60, 65, or 70, etc.; and the thermal insulation Q per unit area of ​​the silicone foam sheet at a T0 setting of 650°C is ≥45, for example, but not limited to, 45, 50, 55, 60, 65, 70, 75, 80, 85, or 90, etc.; the thermal insulation Q per unit area is obtained by testing using the following method:

[0049] A heating plate and a cold plate are provided, with the cold plate positioned above the heating plate. The heating plate has a hot surface. A silicone foam sheet is placed on the hot surface of the heating plate, and then the cold plate is pressed down until it contacts the silicone foam sheet, applying a pressure of 0.03 MPa to the silicone foam sheet. The hot surface of the heating plate reaches a heating temperature T0. After maintaining the pressure and the heating temperature for 30 minutes, the highest temperature T1 of the contact surface between the cold plate and the silicone foam sheet during the 30-minute holding time is recorded. The contact surface between the cold plate and the silicone foam sheet, the hot surface of the heating plate, and the silicone foam sheet are all matched in shape and have equal areas.

[0050] The heat insulation per unit area Q is calculated using the following formula: Q = K × (T1 - T0) × A / H;

[0051] In the formula, Q represents the heat insulation per unit area, in W; K represents the thermal conductivity of the silicone foam sheet at room temperature, in W / (m·K); T0 represents the temperature of the hot surface of the heating plate (i.e., the heating temperature), in K, and the set value of T0 is 450℃ or 650℃; T1 represents the highest temperature of the contact surface between the cold plate and the silicone foam sheet during the 30-minute holding time, in K; and A represents the area of ​​the hot surface of the heating plate, in m². 2 H represents the thickness of the silicone foam sheet, in meters (m).

[0052] By controlling the thermal insulation capacity Q per unit area of ​​the foam sheet within the above range, it is further ensured that the foam sheet has good thermal insulation performance.

[0053] In some embodiments, the absolute value of the difference between the Shore A hardness of the silicone foam sheet at room temperature and the Shore A hardness after heating at 1000°C for 30 minutes is 20-60°, for example, but not limited to 20°, 30°, 40°, 50° or 60°.

[0054] In some embodiments, the Shore A hardness of the silicone foam sheet at room temperature is 5-50°, such as, but not limited to, 5°, 10°, 15°, 20°, 25°, 30°, 35°, 40°, 45° or 50°, etc., and the Shore A hardness of the silicone foam sheet after heating at 1000°C for 30 minutes is 65-70°, such as, but not limited to, 65°, 66°, 67°, 68°, 69° or 70°, etc.

[0055] By controlling the Shore A hardness and its variation value of the foam sheet under normal temperature conditions and after high temperature sintering at 1000℃ within the above range, it is possible to adapt to the multi-gradient compression requirements of different materials in relevant parts of the battery pack housing, from soft to hard. This facilitates its use in battery modules and battery packs for assembly, and gives the foam sheet better cushioning performance. Furthermore, after high temperature sintering, the foam sheet forms a ceramic body with high ceramic strength, thus providing better thermal insulation performance.

[0056] In some embodiments, the density of the silicone foam sheet at room temperature is 300-1100 kg / m³. 3 For example, but not limited to 300 kg / m 3 400kg / m 3 500kg / m 3 600kg / m 3 700kg / m 3 800kg / m 3 900kg / m 3 1000kg / m 3 Or 1100kg / m 3 By controlling the density of the foam sheet within the aforementioned range, the foam sheet achieves suitable compressive stress while maintaining a low thermal conductivity, thus providing appropriate support for the battery cell and exhibiting good thermal insulation performance. If the density is less than 300 kg / m³... 3 This results in excessively low compressive stress in the foam sheet, making it difficult to provide sufficient support when used between battery cells; simultaneously, the density is below 300 kg / m³. 3 The foamed sheets prepared using the process of this invention are difficult to achieve and do not have good thermal insulation effects; if the density is greater than 1100 kg / m³ 3 This results in excessive compressive stress in the foam sheet, which may cause excessive compression of the battery cells when used between them. It also does not meet the requirements for lightweight foam sheets and leads to excessively high thermal conductivity, resulting in poor thermal insulation performance.

[0057] In some embodiments, the 25% compressive stress of the silicone foam sheet under room temperature conditions is 20-500 kPa, such as, but not limited to, 20 kPa, 50 kPa, 100 kPa, 200 kPa, 300 kPa, 400 kPa, or 500 kPa. By controlling the 25% compressive stress of the foam sheet within the above range, the foam sheet has suitable flexibility, which, when used between battery cells, can provide sufficient support without causing excessive compression to the battery cells, thus exhibiting good cushioning performance.

[0058] In some embodiments, the thermal conductivity of the silicone foam sheet at room temperature is 0.05-0.11 W / (m·K), such as, but not limited to, 0.05 W / (m·K), 0.06 W / (m·K), 0.07 W / (m·K), 0.08 W / (m·K), 0.09 W / (m·K), 0.10 W / (m·K), or 0.11 W / (m·K). By controlling the thermal conductivity of the foam sheet within the above range, the foam sheet further exhibits better thermal insulation performance.

[0059] In some embodiments, the thickness of the silicone foam sheet is 0.5-25 mm at room temperature. By controlling the thickness of the foam sheet within the above range, the foam sheet can provide sufficient thermal insulation pad thickness within the space of the battery pack and battery module, thereby ensuring good thermal insulation performance while meeting the compact design requirements of the battery pack and battery module.

[0060] <Raw Materials for Silicone Foam Sheets>

[0061] According to a specific embodiment of the present invention, the silicone foam sheet of the present invention may include the following raw materials: a silicone rubber matrix, a ceramic filler, a foaming agent, a structural stabilizer, and a flux. Based on a weight of 100 parts of the silicone rubber matrix, the amount of the ceramic filler is 16-25 parts, the amount of the foaming agent is 6-11 parts, the amount of the structural stabilizer is 3-6 parts, and the amount of the flux is 8-12 parts.

[0062] In some embodiments, the silicone rubber matrix comprises an organopolysiloxane containing an alkenyl group. Examples of the alkenyl group include vinyl, allyl, and hexenyl. Vinyl is preferred. Other examples of organic groups combining silicon atoms besides the alkenyl group include alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, and hexyl; aryl groups such as phenyl, tolyl, and xylyl; aralkyl groups such as benzyl and phenethyl; and halogen-substituted alkyl groups such as 3,3,3-trifluoropropyl. Specifically, the silicone rubber matrix may comprise methyl vinyl silicone rubber and / or methyl vinyl phenyl silicone rubber. The molar content (mol%) of the vinyl group in the silicone rubber matrix may be 0.19%-0.24%, and the molecular weight of the silicone rubber matrix may be 300,000-450,000.

[0063] In some embodiments, the ceramic filler includes zinc borate, silicon nitride, and alumina, etc.; based on 100 parts by weight of the silicone rubber matrix, the amount of zinc borate is 6-10 parts, the amount of silicon nitride is 6-10 parts, and the amount of alumina is 4-5 parts. These ceramic fillers are all powders. The particle size of the zinc borate powder can be 3-15 μm, preferably 5-7 μm. The silicon nitride powder can be pretreated (i.e., purified) to have a metal impurity content of less than 200 ppm and a particle size of 5-7 μm. Silicon nitride with these physical properties can be obtained by purifying conventional silicon nitride powder through washing, grinding, and spray drying. The particle size of conventional silicon nitride powder can be 5-30 μm, preferably 7-10 μm. Washing can be performed using, for example, methanol and / or a hydrochloric acid solution with a mass concentration of approximately 10%. The particle size of alumina powder can be 0.05-5μm, preferably 50-300nm.

[0064] In some embodiments, the foaming agent includes expanded microspheres, an organic foaming agent, and an inorganic foaming agent; based on a weight ratio of 100 parts of the silicone rubber matrix, the amount of expanded microspheres is 1-2 parts, the amount of the organic foaming agent is 3-5 parts, and the amount of the inorganic foaming agent is 0.8-2 parts. It is understood that the expanded microspheres have a small particle size when unexpanded, and form a hollow structure with a larger particle size after expansion. The expansion temperature of the expanded microspheres can be 100-110℃. The particle size of the unexpanded expanded microspheres can be 5-50 μm, and the density can be 1.0-1.3 g / cm³. 3 The expanded particle size can be 20-300 μm. The expanded microspheres can be existing expanded microspheres, such as thermoplastic hollow polymer microspheres; this invention does not impose any special restrictions on their material. The organic foaming agent can include azo foaming agents and / or sulfonyl hydrazine foaming agents, such as one or more of azodicarbonamide, azobisisobutyronitrile, diisopropyl azodicarbonate, and 4,4-oxobisbenzenesulfonyl hydrazine. The inorganic foaming agent can include one or more of carbonate foaming agents, such as sodium bicarbonate, ammonium bicarbonate, and ammonium carbonate.

[0065] In some embodiments, the structural stabilizer includes organosilicon microspheres, etc. The particle size of the organosilicon microspheres can be 0.8-5 μm.

[0066] In some embodiments, the flux includes glass powder, etc. The melting temperature of the glass powder can be 400-600°C.

[0067] In some embodiments, the silicone foam sheet may further comprise the following raw material: an activator; based on a weight ratio of 100 parts of the silicone rubber matrix, the amount of the activator is 2-3 parts. The activator may include one or more of zinc oxide, zinc stearate, calcium oxide, and magnesium oxide, preferably zinc oxide. The activator is a powder. The particle size of the activator powder (preferably zinc oxide powder) may be 10-100 nm, preferably 40-60 nm.

[0068] In some embodiments, the silicone foam sheet may further comprise the following raw material: a structure modifier; based on a weight ratio of 100 parts of the silicone rubber matrix, the weight ratio of the structure modifier is 3-6 parts. The structure modifier may include compounds containing silanol groups or compounds capable of generating silanol groups. Specifically, the structure modifier may include one or more of hydroxyl silicone oil, diphenylsilanediol, and octamethylcyclotetrasiloxane. Hydroxyl silicone oil is preferred, and the hydroxyl content in the hydroxyl silicone oil may be 8.5% or more.

[0069] In some embodiments, the silicone foam sheet may further comprise the following raw materials: a reinforcing agent; based on a silicone rubber matrix content of 100 parts by weight, the amount of the reinforcing agent is 10-25 parts. The reinforcing agent may include fumed silica and / or precipitated silica, etc. The specific surface area of ​​the reinforcing agent may be 150-300 m² / g. 2 / g.

[0070] In some embodiments, the silicone foam sheet may further comprise the following raw material: a crosslinking agent; based on a weight ratio of 1-2 parts, with the amount of the silicone rubber matrix being 100 parts, the amount of the crosslinking agent is 1-2 parts. The crosslinking agent may include organic peroxides. Specifically, the crosslinking agent includes one or more of dicumyl peroxide (DCP), 2,5-dimethyl-2,5-di(tert-butylperoxide)hexane (DHBP), and benzoyl peroxide (BPO). It is understood that the crosslinking temperature of the crosslinking agent needs to be coordinated with the decomposition temperature of the foaming agent, and is generally slightly higher than the decomposition temperature of the foaming agent, so as not to restrict foaming by the crosslinking agent.

[0071] <Preparation method of silicone foam sheet>

[0072] According to a specific embodiment of the present invention, the method for preparing the silicone foam sheet of the present invention may include the following steps:

[0073] Mixing: The raw materials of the silicone foam sheet are mixed to obtain a compound;

[0074] Injection molding: The compounded rubber is injected into a mold;

[0075] Foaming and vulcanization: Under suitable temperature and pressure conditions, the compound in the mold is foamed and vulcanized to obtain the silicone foam sheet.

[0076] In some embodiments, the method for preparing the silicone foam sheet may further include the following steps: before the mixing step, the powder comprising the ceramic filler and the powder comprising the selectively added activator are co-milled. Specifically, zinc borate, silicon nitride, alumina, and the selectively added activator (preferably zinc oxide) are co-milled. More specifically, the above powder can be placed in a ball mill jar, anhydrous ethanol and ammonium polyacrylate are added to form a suspension, and then ball milling is performed, followed by ultrasonic dispersion, and then ball milling is performed again. The above steps of ball milling, ultrasonic dispersion, and ball milling are repeated several times. When the D50 particle size of the powder in the suspension no longer decreases, ball milling is stopped, and then spray drying is performed to obtain the co-milled mixed powder. The solid-liquid mass ratio of the powder and anhydrous ethanol can be 1:(1.5-2), preferably 1:2, with the liquid being twice the amount of the solid. Ammonium polyacrylate, with its low molecular weight, facilitates the formation of a uniform adsorption layer on the particle surface, generating strong electrostatic repulsion between particles and preventing agglomeration. A moderate chain length provides good electrostatic repulsion, improving the stability and flowability of the slurry. The selected molecular weight is 5000-10000, and the addition amount is 0.8%-1.2% of the powder mass. The ball milling speed can be 300-400 r / min, and the ball milling time can be 2-4 hours per cycle. The ultrasonic dispersion time can be 30-60 minutes per cycle. The inlet temperature of the spray dryer is 160-180℃, and the outlet temperature can be 60-70℃.

[0077] In some embodiments, the compounding process may include: softening the silicone rubber matrix at 40-60°C for 10-30 min; then selectively adding reinforcing agents and / or structure modifiers, and compounding at 40-60°C for 15-30 min; then adding ceramic fillers, structure stabilizers, fluxes, and selective activators, and compounding at 40-60°C for 5-10 min; then adding a foaming agent at 40-60°C and compounding for 3-5 min; and then selectively adding a crosslinking agent, and compounding at 40-60°C for 3-10 min to obtain the compound.

[0078] In some embodiments, during the injection molding process, the mold includes a lower mold and an upper mold. First, a release agent is sprayed onto the inner walls of the lower mold and the upper mold. Then, the lower mold is preheated to 80-100°C, and the compounded rubber is injected into the lower mold. Finally, the upper mold and the lower mold are closed.

[0079] In some embodiments, the foaming and vulcanization may include the following stages:

[0080] First foaming: Heat the mold to 100-110℃ and control the pressure in the mold to 1-3MPa. Maintain the temperature and pressure for 15-30 minutes to complete the first foaming.

[0081] Secondary foaming: Then heat the mold to 135-150℃ and control the pressure in the mold to 5-10MPa, keep it at the temperature and pressure for 3-10 minutes to complete the secondary foaming;

[0082] Three-stage foaming and one-stage vulcanization: The mold is then heated to 150-180℃, preferably 170-180℃, and the pressure in the mold is controlled at 5-10MPa. The temperature and pressure are maintained for 10-20 minutes to complete the three-stage foaming and one-stage vulcanization.

[0083] During the primary foaming, secondary foaming, tertiary foaming, and primary vulcanization processes, the mold can be heated to the aforementioned temperature at a rate of 5-10℃ / min.

[0084] In other embodiments, the above-described primary foaming, secondary foaming, tertiary foaming, and primary vulcanization process can be simplified as follows: The mold is heated to 170-180°C, and the pressure within the mold is controlled at 1-3 MPa, maintaining this temperature and pressure for 15-30 minutes; then, the pressure within the mold is increased to 8-10 MPa, maintaining this temperature and pressure for 10-20 minutes. Afterward, the mold can be cooled to below 80°C, the pressure released, the mold opened, the foamed and vulcanized products removed, and then dried to obtain a silicone foam sheet.

[0085] In some embodiments, the method for preparing the silicone foam sheet may further include the following steps: after the foaming and vulcanization steps, the foamed and vulcanized products are removed from the mold, and the foamed and vulcanized products are subjected to secondary vulcanization to obtain the silicone foam sheet. Specifically, the mold may be cooled to below 80°C before pressure is released and the mold is opened to remove the foamed and vulcanized products. The temperature of the secondary vulcanization may be 180°C-200°C, the pressure may be atmospheric pressure, and the time may be 1 hour-4 hours.

[0086] In some other embodiments, the above-mentioned secondary vulcanization may be omitted. In this case, during the three foaming and one vulcanization process, the temperature can be maintained at 180℃-200℃ and 5-10MPa for 1-4 hours.

[0087] <Applications of Silicone Foam Sheets>

[0088] According to a specific embodiment of the second aspect of the present invention, the present invention provides a battery module comprising: two or more battery cells and one or more of the aforementioned silicone foam sheets, wherein the silicone foam sheets are disposed between adjacent battery cells.

[0089] According to a specific embodiment of a third aspect of the present invention, the present invention provides a battery pack, comprising: a housing and the aforementioned battery module; the housing includes a frame, a top cover, a wiring harness isolation plate, and a liquid cooling plate; the battery module is disposed in the frame; the top cover is disposed on the top of the battery module; the wiring harness isolation plate is disposed between the battery module and the top cover; the wiring harness isolation plate is provided with a busbar for connecting the battery cells in the battery module; the aforementioned silicone foam sheet is disposed between the wiring harness isolation plate and the top cover for covering the top of the busbar; the liquid cooling plate is disposed around the sides and / or the bottom of the battery module.

[0090] This invention provides silicone foam sheets with ample space between cells at room temperature, resulting in low thermal conductivity. Furthermore, it ensures that the silicone foam sheet maintains its intact pore structure after sintering at high temperatures of 400-1000℃, achieving high ceramic strength and preventing cracking. Therefore, the silicone foam sheet of this invention exhibits excellent thermal insulation performance. The silicone foam sheet of this invention can be used between adjacent battery cells. Under conventional thermal runaway conditions of 450℃ and 650℃ between cells, the silicone foam sheet of this invention maintains its intact pore structure and high ceramic strength, preventing cracking. Thus, when one battery cell experiences thermal runaway, the foam sheet of this invention provides excellent thermal insulation, preventing the spread of thermal runaway and protecting adjacent cells from thermal runaway. In addition, the silicone foam sheet of this invention can also be used between the wiring harness separator and the top cover of a battery pack. It can withstand flame impact at 1000℃, maintaining its intact pore structure and high ceramic strength, preventing cracking and effectively protecting the battery module. At the same time, the silicone foam sheet of the present invention also has good cushioning performance.

[0091] <Testing Methods>

[0092] 1. Coefficient of linear expansion α of bubble diameter

[0093] The linear expansion coefficient α of the bubble diameter is calculated using the following formula:

[0094] ,

[0095] In the formula, α is the coefficient of linear expansion of the bubble diameter, with units of °C. -1 L0 is the average cell diameter of the silicone foam sheet at room temperature (e.g., 23°C), in μm; L1 is the average cell diameter of the silicone foam sheet after heating at 1000°C for 30 min, in μm; T is the temperature difference between room temperature and 1000°C (977 in the following examples), in °C.

[0096] The method for heating the silicone foam sheet at 1000℃ for 30 minutes is as follows: heat the muffle furnace to 1000℃, place the sample in the sintering vessel of the muffle furnace, maintain the temperature at 1000℃ for 30 minutes, and then remove the sample.

[0097] 2. Linear shrinkage coefficient β of bubble wall thickness

[0098] ,

[0099] The linear shrinkage coefficient β of the bubble wall thickness is calculated using the following formula:

[0100] In the formula, β is the linear shrinkage coefficient of the bubble wall thickness, with units of °C. -1 d0 is the average cell wall thickness of the silicone foam sheet at room temperature (e.g., 23°C), in μm; d1 is the average cell wall thickness of the silicone foam sheet after heating at 1000°C for 30 minutes, in μm; T is the temperature difference between room temperature and 1000°C (977 in the following examples), in °C. That is, calculating... The absolute value of.

[0101] The method of heating the silicone foam sheet at 1000℃ for 30 minutes is the same as described above, and will not be repeated here.

[0102] 3. Percentage of effective cells after heating at 1000℃ for 30 minutes

[0103] Take 5 sets of samples. The length of the samples can be about 20 mm and the thickness can be about 5 mm. After heating the samples at 1000℃ for 30 min and cooling them, take magnified photographs of the cross-section of each sample (e.g., about 20 mm × 20 mm) using a digital microscope to observe the pore state. Those pores with a complete irregular elliptical structure that can be observed and whose diameter can be measured are considered valid pores and included in the count. The total number of pores is X0, the number of valid pores is X1, and the percentage of valid pores is θ = X1 / X0 × 100%.

[0104] 4. Average bubble diameter

[0105] The average cell diameter of the silicone foam sheet at room temperature and after heating at 1000℃ for 30 minutes were tested as follows: Ten samples were taken. The sample length was approximately 20 mm and the thickness was approximately 5 mm. Five samples were untreated, and five samples were treated with high temperature. A magnified photograph of the cross-section of each sample was taken using a digital microscope. A 2 mm × 2 mm area was randomly selected on each cross-section, and the effective cell diameter was measured using the software. The cell diameter of each of the five samples was counted, and the average cell diameter was calculated.

[0106] 5. Average cell wall thickness

[0107] The average cell wall thickness of silicone foam sheets at room temperature and after heating at 1000℃ for 30 minutes were tested as follows: Ten samples were taken. The sample length was approximately 20 mm and the thickness was approximately 5 mm. Five samples were untreated, and five samples were treated. A magnified photograph of the cross-section of each sample was taken using a digital microscope. On each cross-section, a 2 mm × 2 mm area was randomly selected, and the gauge length of the effective cell wall thickness was measured in the software (the cell wall thickness was clearly visible around the effective cells). The cell wall thickness of each of the five samples was counted, and the average cell wall thickness was calculated.

[0108] 6. Insulation capacity per unit area, Q

[0109] The heat insulation capacity Q per unit area was obtained by testing using the following method:

[0110] A heating plate and a cold plate are provided, with the cold plate positioned above the heating plate. The heating plate has a hot surface. A sample is placed on the hot surface of the heating plate, and then the cold plate is pressed down until it contacts the sample, applying a pressure of 0.3 MPa to the sample. The hot surface of the heating plate reaches a heating temperature T0. After maintaining the pressure and the heating temperature for 30 minutes, the highest temperature T1 of the contact surface between the cold plate and the sample during the 30-minute holding time is recorded. The contact surface between the cold plate and the sample, the hot surface of the heating plate, and the sample are all matched in shape and have equal areas (i.e., the contact surface between the cold plate and the sample, the hot surface of the heating plate, and the sample completely overlap).

[0111] The heat insulation per unit area Q is calculated using the following formula: Q = K × (T1 - T0) × A / H;

[0112] In the formula, Q is the heat insulation per unit area, in W; K is the thermal conductivity of the sample at room temperature, in W / (m·K); T0 is the temperature of the hot surface of the heating plate (i.e., the heating temperature), in K; T1 is the temperature of the contact surface between the cold plate and the sample, in K, and the set value of T0 is 450℃ or 650℃; A is the area of ​​the hot surface of the heating plate, in m². 2 H represents the thickness of the sample, in meters (m). The area of ​​the hot surface of the heating plate can be, for example, (100±1) mm × (100±1) mm, which means the area of ​​the sample is also (100±1) mm × (100±1) mm.

[0113] 7. Shore A hardness

[0114] The Shore A hardness of the silicone foam sheet at room temperature and after heating at 1000℃ for 30 minutes were tested according to the method of the Type A Shore hardness tester in GB / T 531.1-2008.

[0115] 8. Density

[0116] The density of the silicone foam sheet at room temperature was tested according to the method in GB / T 6343-2009. The apparent total density of the sample (including the skin) was calculated using formula (1) in 7.1.

[0117] 9. 25% compressive stress

[0118] The 25% compressive stress of silicone foam sheets under normal temperature conditions is tested according to the method in GB / T 18942.1-2003. The planar dimensions of the sample can be, for example, (50±0.5) mm × (50±0.5) mm. Specifically, the thickness of the sample to be tested is 10 mm or more (for samples with a thickness of less than 10 mm, multiple samples should be stacked until the thickness is 10 mm or more); before the test begins, a prestress of (100±10) Pa is applied to the sample. After the prestress load is completed, the display value of the compression ratio on the testing machine is adjusted to zero; the sample is compressed at a rate of (50±10)% of its initial thickness per minute; the compressive stress is tested when the sample is first compressed to a compression ratio of 25% (i.e., compressed to 75% of the initial thickness of the sample).

[0119] 10. Thermal conductivity

[0120] The thermal conductivity of silicone foam sheets at room temperature is tested according to the method in GB / T 10295-2008. The sample dimensions can be, for example, 300mm × 300mm, and the thickness should be the actual sample thickness.

[0121] 11. Thickness

[0122] The thickness of the silicone foam sheet at room temperature was measured using vernier calipers. The planar dimensions of the sample could be, for example, (50±0.5) mm × (5±0.5) mm. Specifically, at least three samples were placed in an environment with a temperature of 23-27℃ and a humidity (RH) of 45-55% for 2 hours; then the thickness of each sample was measured using vernier calipers, and the average value was taken to obtain the thickness of the silicone foam sheet.

[0123] 12. Strength evaluation after high-temperature sintering

[0124] The sample (size can be 50mm×50mm×5mm) is heated at 1000℃ for 30 minutes, then removed and allowed to cool naturally to room temperature. The sample surface is then observed for cracks. If cracks appear, the strength evaluation result after high-temperature sintering is NG. For samples without cracks, a compressive strength test is performed: the sample is placed on a pressure testing machine (or a simple pressure device), and a pressure of 1MPa is applied. The sample is observed for cracking. If it does not crack, the strength evaluation result after high-temperature sintering is OK; otherwise, it is NG.

[0125] 13. Evaluation of thermal insulation performance

[0126] If the thermal conductivity at room temperature is below 0.11 W / (m·K) and the heat insulation per unit area Q is ≥30 at 450℃ and ≥45 at 650℃, then the evaluation result of the thermal insulation performance is OK; if either the thermal conductivity at room temperature or the heat insulation per unit area Q does not meet the above range, then the evaluation result of the thermal insulation performance is NG.

[0127] <Example>

[0128] The technical solutions of the present invention are specifically illustrated by the following embodiments, but the present invention is not limited to these embodiments. Of course, various modifications can be made within the scope of the key points of the present invention.

[0129] The raw materials used in the following examples and comparative examples include:

[0130] Methyl vinyl silicone rubber: The molar content (mol%) of vinyl is 0.19-0.24%, the molecular weight is 300,000-450,000, and the grade is 110-3s.

[0131] Zinc borate: Particle size is 3-15μm.

[0132] Silicon nitride: The metal impurity content is below 200 ppm, and the particle size is 5-7 μm. Silicon nitride with these physical properties is obtained by purifying commercially available silicon nitride powder through washing, grinding, and spray drying. Methanol or a hydrochloric acid solution with a mass concentration of approximately 10% is used as the washing solution.

[0133] Alumina: Particle size is 80-200nm.

[0134] Zinc oxide: Particle size is 40-60nm.

[0135] Organosilicon microspheres: particle size in the range of 0.8-5 μm.

[0136] Glass powder: melting temperature is 400-600℃.

[0137] Hydroxyl silicone oil: hydroxyl content is 8.5%.

[0138] Fumed silica: specific surface area is 200m² 2 / g.

[0139] Expanded microspheres (Nourion Chemicals, FN-78D): Unexpanded particle size 30 μm, density 1.1 g / cm³ 3 The expanded particle size is 200μm, and the expansion temperature is 100-110℃.

[0140] Azodicarbonamide: medium temperature type, foaming temperature 160-190℃, particle size 8-15μm.

[0141] Sodium bicarbonate: Particle size 6-10μm, purity ≥99%, decomposition temperature 130-150℃.

[0142] Dicumyl peroxide: purity ≥95%, decomposition temperature approximately 170℃.

[0143] Example 1

[0144] This embodiment provides a silicone foam sheet, which, by weight, is composed of the following components: 100 parts methyl vinyl silicone rubber, 10 parts zinc borate, 10 parts silicon nitride, 5 parts alumina, 2 parts zinc oxide, 5 parts organosilicon microspheres, 8 parts glass powder, 5 parts hydroxyl silicone oil, 15 parts fumed silica, 2 parts expanded microspheres, 4 parts azodicarbonamide, 1 part sodium bicarbonate, and 1.5 parts dicumyl peroxide.

[0145] The method for preparing the silicone foam sheet in this embodiment includes the following steps:

[0146] Blending and grinding: Zinc borate, silicon nitride, alumina, and zinc oxide are placed in a ball mill jar in a fixed ratio. Anhydrous ethanol and ammonium polyacrylate are added. The solid-liquid mass ratio of all powders to anhydrous ethanol is 1:2. The amount of ammonium polyacrylate added is 0.8% of the powder mass, forming a suspension. Then, the mixture is ball-milled at 300 r / min for 2 hours, followed by ultrasonic dispersion for 30 minutes, and then ball-milled at 300 r / min for 4 hours. The above ball milling-ultrasonic dispersion and ball milling steps are repeated several times. When the D50 particle size of the powder in the suspension no longer decreases, the ball milling is stopped. Then, spray drying is performed. The inlet temperature of the spray dryer is 180℃ and the outlet temperature is 60℃ to obtain the blended powder after blending and grinding.

[0147] Mixing: Soften methyl vinyl silicone rubber at 50°C for 10 min; then add fumed silica and hydroxyl silicone oil, and mix at 50°C for 15 min; then add the blended and ground powder, organosilicon microspheres and glass powder, and mix at 50°C for 8 min; then add expanded microspheres, azodicarbonamide and sodium bicarbonate at 50°C, and mix for 3-5 min; then add dicumyl peroxide, and mix at 50°C for 8 min to obtain the compound;

[0148] Molding: First, spray the release agent on the inner wall of the lower mold and the upper mold, then preheat the lower mold to 90°C, then inject the compound into the lower mold, and then close the upper mold and the lower mold.

[0149] Foaming and vulcanization:

[0150] One-stage foaming: The mold is heated to 100°C at a rate of 10°C / min, and the pressure in the mold is controlled at 2MPa. The temperature and pressure are maintained for 15 minutes to complete one-stage foaming.

[0151] Secondary foaming: Then, the mold is heated to 140°C at a rate of 5°C / min, and the pressure in the mold is controlled at 8MPa. The temperature and pressure are maintained for 5 minutes to complete the secondary foaming.

[0152] Three foaming and one vulcanization: The mold is then heated to 170°C at a rate of 10°C / min, and the pressure in the mold is controlled at 8MPa. The temperature and pressure are maintained for 15 minutes to complete the three foaming and one vulcanization.

[0153] Demolding and secondary vulcanization: First, cool the mold to below 80°C, then release the pressure and open the mold. Take out the foamed and vulcanized product and place it in an oven at 180°C for 2 hours to obtain silicone foam sheets.

[0154] Example 2

[0155] This embodiment provides a silicone foam sheet, which, by weight, is composed of the following components: 100 parts methyl vinyl silicone rubber, 10 parts zinc borate, 10 parts silicon nitride, 5 parts alumina, 2 parts zinc oxide, 5 parts organosilicon microspheres, 8 parts glass powder, 5 parts hydroxyl silicone oil, 18 parts fumed silica, 1 part expanded microspheres, 4 parts azodicarbonamide, 1 part sodium bicarbonate, and 1.5 parts dicumyl peroxide.

[0156] The method for preparing the silicone foam sheet in this embodiment includes the following steps:

[0157] Blending and grinding: Zinc borate, silicon nitride, alumina, and zinc oxide are placed in a ball mill jar in a fixed ratio. Anhydrous ethanol and ammonium polyacrylate are added. The solid-liquid mass ratio of all powders to anhydrous ethanol is 1:2. The amount of ammonium polyacrylate added is 0.8% of the powder mass, forming a suspension. Then, the mixture is ball-milled at 300 r / min for 2 hours, followed by ultrasonic dispersion for 30 minutes, and then ball-milled at 300 r / min for 4 hours. The above ball milling-ultrasonic dispersion and ball milling steps are repeated several times. When the D50 particle size of the powder in the suspension no longer decreases, the ball milling is stopped. Then, spray drying is performed. The inlet temperature of the spray dryer is 180℃ and the outlet temperature is 60℃ to obtain the blended powder after blending and grinding.

[0158] Mixing: Soften methyl vinyl silicone rubber at 50°C for 10 min; then add fumed silica and hydroxyl silicone oil, and mix at 40°C for 15 min; then add the blended and ground powder, organosilicon microspheres and glass powder, and mix at 40°C for 8 min; then add expanded microspheres, azodicarbonamide and sodium bicarbonate at 50°C, and mix for 3-5 min; then add dicumyl peroxide, and mix at 50°C for 8 min to obtain the compound;

[0159] Molding: First, spray the release agent on the inner wall of the lower mold and the upper mold, then preheat the lower mold to 90°C, then inject the compound into the lower mold, and then close the upper mold and the lower mold.

[0160] Foaming and vulcanization:

[0161] One-stage foaming: The mold is heated to 100°C at a rate of 10°C / min, and the pressure in the mold is controlled at 2MPa. The temperature and pressure are maintained for 15 minutes to complete one-stage foaming.

[0162] Secondary foaming: Then, the mold is heated to 140°C at a rate of 5°C / min, and the pressure in the mold is controlled at 8MPa. The temperature and pressure are maintained for 5 minutes to complete the secondary foaming.

[0163] Three foaming and one vulcanization: The mold is then heated to 170°C at a rate of 10°C / min, and the pressure in the mold is controlled at 10MPa. The temperature and pressure are maintained for 15 minutes to complete the three foaming and one vulcanization.

[0164] Demolding and secondary vulcanization: First, cool the mold to below 80°C, then release the pressure and open the mold. Take out the foamed and vulcanized product and place it in an oven at 180°C for 2 hours to obtain silicone foam sheets.

[0165] Example 3

[0166] This embodiment provides a silicone foam sheet, which, by weight, is composed of the following components: 100 parts methyl vinyl silicone rubber, 6 parts zinc borate, 6 parts silicon nitride, 4 parts aluminum oxide, 3 parts zinc oxide, 5 parts organosilicon microspheres, 12 parts glass powder, 5 parts hydroxyl silicone oil, 10 parts fumed silica, 2 parts expanded microspheres, 5 parts azodicarbonamide, 1.5 parts sodium bicarbonate, and 1.5 parts dicumyl peroxide.

[0167] The method for preparing the silicone foam sheet in this embodiment includes the following steps:

[0168] Blending and grinding: Zinc borate, silicon nitride, alumina, and zinc oxide are placed in a ball mill jar in a fixed ratio. Anhydrous ethanol and ammonium polyacrylate are added. The solid-liquid mass ratio of all powders to anhydrous ethanol is 1:2. The amount of ammonium polyacrylate added is 0.8% of the powder mass, forming a suspension. Then, the mixture is ball-milled at 300 r / min for 2 hours, followed by ultrasonic dispersion for 30 minutes, and then ball-milled at 300 r / min for 4 hours. The above ball milling-ultrasonic dispersion and ball milling steps are repeated several times. When the D50 particle size of the powder in the suspension no longer decreases, the ball milling is stopped. Then, spray drying is performed. The inlet temperature of the spray dryer is 180℃ and the outlet temperature is 60℃ to obtain the blended powder after blending and grinding.

[0169] Mixing: Soften methyl vinyl silicone rubber at 50°C for 10 min; then add fumed silica and hydroxyl silicone oil, and mix at 50°C for 15 min; then add the blended and ground powder, organosilicon microspheres and glass powder, and mix at 50°C for 8 min; then add expanded microspheres, azodicarbonamide and sodium bicarbonate at 50°C, and mix for 3-5 min; then add dicumyl peroxide, and mix at 50°C for 8 min to obtain the compound;

[0170] Molding: First, spray the release agent on the inner wall of the lower mold and the upper mold, then preheat the lower mold to 90°C, then inject the compound into the lower mold, and then close the upper mold and the lower mold.

[0171] Foaming and vulcanization:

[0172] One-stage foaming: The mold is heated to 110°C at a rate of 10°C / min, and the pressure in the mold is controlled at 1MPa. The temperature and pressure are maintained for 30 minutes to complete one-stage foaming.

[0173] Secondary foaming: Then, the mold is heated to 150°C at a rate of 5°C / min, and the pressure in the mold is controlled at 5MPa. The temperature and pressure are maintained for 5 minutes to complete the secondary foaming.

[0174] Three foaming and one vulcanization: The mold is then heated to 180°C at a rate of 10°C / min, and the pressure in the mold is controlled at 5MPa. The temperature and pressure are maintained for 15 minutes to complete three foaming and one vulcanization.

[0175] Demolding and secondary vulcanization: First, cool the mold to below 80°C, then release the pressure and open the mold. Take out the foamed and vulcanized product and place it in an oven at 180°C for 2 hours to obtain silicone foam sheets.

[0176] Example 4

[0177] This embodiment provides a silicone foam sheet, which, by weight, is composed of the following components: 100 parts methyl vinyl silicone rubber, 10 parts zinc borate, 10 parts silicon nitride, 5 parts alumina, 2 parts zinc oxide, 5 parts organosilicon microspheres, 10 parts glass powder, 5 parts hydroxyl silicone oil, 25 parts fumed silica, 2 parts expanded microspheres, 4 parts azodicarbonamide, 0.8 parts sodium bicarbonate, and 1.5 parts dicumyl peroxide.

[0178] The method for preparing the silicone foam sheet in this embodiment includes the following steps:

[0179] Blending and grinding: Zinc borate, silicon nitride, alumina, and zinc oxide are placed in a ball mill jar in a fixed ratio. Anhydrous ethanol and ammonium polyacrylate are added. The solid-liquid mass ratio of all powders to anhydrous ethanol is 1:2. The amount of ammonium polyacrylate added is 0.8% of the powder mass, forming a suspension. Then, the mixture is ball-milled at 300 r / min for 2 hours, followed by ultrasonic dispersion for 30 minutes, and then ball-milled at 300 r / min for 4 hours. The above ball milling-ultrasonic dispersion and ball milling steps are repeated several times. When the D50 particle size of the powder in the suspension no longer decreases, the ball milling is stopped. Then, spray drying is performed. The inlet temperature of the spray dryer is 180℃ and the outlet temperature is 70℃ to obtain the blended powder after blending and grinding.

[0180] Mixing: Soften methyl vinyl silicone rubber at 50°C for 10 min; then add fumed silica and hydroxyl silicone oil, and mix at 60°C for 15 min; then add the blended and ground powder, organosilicon microspheres and glass powder, and mix at 60°C for 10 min; then add expanded microspheres, azodicarbonamide and sodium bicarbonate at 50°C, and mix for 3-5 min; then add dicumyl peroxide, and mix at 50°C for 8 min to obtain the compound;

[0181] Molding: First, spray the release agent on the inner wall of the lower mold and the upper mold, then preheat the lower mold to 90°C, then inject the compound into the lower mold, and then close the upper mold and the lower mold.

[0182] Foaming and vulcanization:

[0183] One-stage foaming: The mold is heated to 100°C at a rate of 10°C / min, and the pressure in the mold is controlled at 3MPa. The temperature and pressure are maintained for 15 minutes to complete one-stage foaming.

[0184] Secondary foaming: Then, the mold is heated to 140℃ at a rate of 5℃ / min, and the pressure in the mold is controlled at 10MPa. The temperature and pressure are maintained for 5 minutes to complete the secondary foaming.

[0185] Three foaming and one vulcanization: The mold is then heated to 170°C at a rate of 10°C / min, and the pressure in the mold is controlled at 10MPa. The temperature and pressure are maintained for 15 minutes to complete the three foaming and one vulcanization.

[0186] Demolding and secondary vulcanization: First, cool the mold to below 80°C, then release the pressure and open the mold. Take out the foamed and vulcanized product and place it in an oven at 180°C for 2 hours to obtain silicone foam sheets.

[0187] Example 5

[0188] This embodiment provides a silicone foam sheet, which, by weight, is composed of the following components: 100 parts methyl vinyl silicone rubber, 10 parts zinc borate, 10 parts silicon nitride, 5 parts alumina, 2 parts zinc oxide, 3 parts organosilicon microspheres, 8 parts glass powder, 5 parts hydroxyl silicone oil, 18 parts fumed silica, 1 part expanded microspheres, 3 parts azodicarbonamide, 0.8 parts sodium bicarbonate, and 1.5 parts dicumyl peroxide.

[0189] The method for preparing the silicone foam sheet in this embodiment includes the following steps:

[0190] Blending and grinding: Zinc borate, silicon nitride, alumina, and zinc oxide are placed in a ball mill jar in a fixed ratio. Anhydrous ethanol and ammonium polyacrylate are added. The solid-liquid mass ratio of all powders to anhydrous ethanol is 1:2. The amount of ammonium polyacrylate added is 0.8% of the powder mass, forming a suspension. Then, the mixture is ball-milled at 300 r / min for 2 hours, followed by ultrasonic dispersion for 30 minutes, and then ball-milled at 300 r / min for 4 hours. The above ball milling-ultrasonic dispersion and ball milling steps are repeated several times. When the D50 particle size of the powder in the suspension no longer decreases, the ball milling is stopped. Then, spray drying is performed. The inlet temperature of the spray dryer is 180℃ and the outlet temperature is 60℃ to obtain the blended powder after blending and grinding.

[0191] Mixing: Soften methyl vinyl silicone rubber at 50°C for 10 min; then add fumed silica and hydroxyl silicone oil, and mix at 50°C for 15 min; then add the blended and ground powder, organosilicon microspheres and glass powder, and mix at 50°C for 8 min; then add expanded microspheres, azodicarbonamide and sodium bicarbonate at 50°C, and mix for 3-5 min; then add dicumyl peroxide, and mix at 50°C for 8 min to obtain the compound;

[0192] Molding: First, spray the release agent on the inner wall of the lower mold and the upper mold, then preheat the lower mold to 90°C, then inject the compound into the lower mold, and then close the upper mold and the lower mold.

[0193] Foaming and vulcanization:

[0194] The mold is slowly heated to 180°C at a rate of 5°C / min, and the pressure in the mold is controlled at 3MPa. The temperature and pressure are maintained for 30min. Then the pressure in the mold is increased to 10MPa and the temperature and pressure are maintained for 15min.

[0195] Then, the mold is cooled to below 80°C, the pressure is released and the mold is opened. The foamed and vulcanized products are taken out and placed in an oven at 180°C for 2 hours to obtain silicone foam sheets.

[0196] Example 6

[0197] This embodiment provides a silicone foam sheet, which, by weight, is composed of the following components: 100 parts methyl vinyl silicone rubber, 8 parts zinc borate, 8 parts silicon nitride, 5 parts aluminum oxide, 2 parts zinc oxide, 5 parts organosilicon microspheres, 10 parts glass powder, 5 parts hydroxyl silicone oil, 13 parts fumed silica, 2 parts expanded microspheres, 4 parts azodicarbonamide, 1 part sodium bicarbonate, and 2 parts dicumyl peroxide.

[0198] The method for preparing the silicone foam sheet in this embodiment includes the following steps:

[0199] Blending and grinding: Zinc borate, silicon nitride, alumina, and zinc oxide are placed in a ball mill jar in a fixed ratio. Anhydrous ethanol and ammonium polyacrylate are added. The solid-liquid mass ratio of all powders to anhydrous ethanol is 1:2. The amount of ammonium polyacrylate added is 0.8% of the powder mass, forming a suspension. Then, the mixture is ball-milled at 300 r / min for 2 hours, followed by ultrasonic dispersion for 30 minutes, and then ball-milled at 300 r / min for 4 hours. The above ball milling-ultrasonic dispersion and ball milling steps are repeated several times. When the D50 particle size of the powder in the suspension no longer decreases, the ball milling is stopped. Then, spray drying is performed. The inlet temperature of the spray dryer is 180℃ and the outlet temperature is 60℃ to obtain the blended powder after blending and grinding.

[0200] Mixing: Soften methyl vinyl silicone rubber at 50°C for 10 min; then add fumed silica and hydroxyl silicone oil, and mix at 50°C for 15 min; then add the blended and ground powder, organosilicon microspheres and glass powder, and mix at 50°C for 8 min; then add expanded microspheres, azodicarbonamide and sodium bicarbonate at 50°C, and mix for 3-5 min; then add dicumyl peroxide, and mix at 50°C for 8 min to obtain the compound;

[0201] Molding: First, spray the release agent on the inner wall of the lower mold and the upper mold, then preheat the lower mold to 90°C, then inject the compound into the lower mold, and then close the upper mold and the lower mold.

[0202] Foaming and vulcanization:

[0203] One-stage foaming: The mold is heated to 100°C at a rate of 10°C / min, and the pressure in the mold is controlled at 2MPa. The temperature and pressure are maintained for 30 minutes to complete one-stage foaming.

[0204] Secondary foaming: Then, the mold is heated to 150°C at a rate of 5°C / min, and the pressure in the mold is controlled at 5MPa. The temperature and pressure are maintained for 10 minutes to complete the secondary foaming.

[0205] Three-stage foaming and vulcanization: The mold is then heated from 150°C to 180°C at a rate of 10°C / min, and held at 180°C and 5MPa pressure for 2 hours. The mold is then cooled to below 80°C, the pressure is released, the mold is opened, and the sample is taken out to obtain a silicone foam sheet.

[0206] Example 7

[0207] This embodiment provides a silicone foam sheet, which, by weight, is composed of the following components: 100 parts methyl vinyl silicone rubber, 10 parts zinc borate, 10 parts silicon nitride, 5 parts alumina, 2 parts zinc oxide, 5 parts organosilicon microspheres, 8 parts glass powder, 3 parts diphenylsilanediol, 15 parts fumed silica, 2 parts expanded microspheres, 4 parts 4,4-oxobisbenzenesulfonyl hydrazine, 1 part sodium bicarbonate, and 1.5 parts dicumyl peroxide.

[0208] The method for preparing the silicone foam sheet in this embodiment includes the following steps:

[0209] Blending and grinding: Zinc borate, silicon nitride, alumina, and zinc oxide are placed in a ball mill jar in a fixed ratio. Anhydrous ethanol and ammonium polyacrylate are added. The solid-liquid mass ratio of all powders to anhydrous ethanol is 1:2. The amount of ammonium polyacrylate added is 0.8% of the powder mass, forming a suspension. Then, the mixture is ball-milled at 300 r / min for 2 hours, followed by ultrasonic dispersion for 30 minutes, and then ball-milled at 300 r / min for 4 hours. The above ball milling-ultrasonic dispersion and ball milling steps are repeated several times. When the D50 particle size of the powder in the suspension no longer decreases, the ball milling is stopped. Then, spray drying is performed. The inlet temperature of the spray dryer is 180℃ and the outlet temperature is 60℃ to obtain the blended powder after blending and grinding.

[0210] Mixing: Soften methyl vinyl silicone rubber at 50°C for 10 min; then add fumed silica and diphenylsilanediol, and mix at 50°C for 15 min; then add the blended and ground powder, organosilicon microspheres and glass powder, and mix at 50°C for 8 min; then add expanded microspheres, 4,4-oxobisbenzenesulfonyl hydrazine and sodium bicarbonate at 50°C, and mix for 3-5 min; then add dicumyl peroxide, and mix at 50°C for 8 min to obtain the compound;

[0211] Molding: First, spray the release agent on the inner wall of the lower mold and the upper mold, then preheat the lower mold to 90°C, then inject the compound into the lower mold, and then close the upper mold and the lower mold.

[0212] Foaming and vulcanization:

[0213] One-stage foaming: The mold is heated to 100°C at a rate of 10°C / min, and the pressure in the mold is controlled at 2MPa. The temperature and pressure are maintained for 15 minutes to complete one-stage foaming.

[0214] Secondary foaming: Then, the mold is heated to 135°C at a rate of 5°C / min, and the pressure in the mold is controlled at 5MPa. The temperature and pressure are maintained for 3 minutes to complete the secondary foaming.

[0215] Three foaming and one vulcanization: The mold is then heated to 150°C at a rate of 10°C / min, and the pressure in the mold is controlled at 8MPa. The temperature and pressure are maintained for 15 minutes to complete three foaming and one vulcanization.

[0216] Demolding and secondary vulcanization: First, cool the mold to below 80°C, then release the pressure and open the mold. Take out the foamed and vulcanized product and place it in an oven at 180°C for 2 hours to obtain silicone foam sheets.

[0217] Comparative Example 1

[0218] This comparative example provides a silicone foam sheet, which, by weight, is composed of the following components: 100 parts methyl vinyl silicone rubber, 8 parts zinc borate, 8 parts silicon nitride, 5 parts aluminum oxide, 2 parts zinc oxide, 3 parts organosilicon microspheres, 4 parts glass powder, 6 parts hydroxyl silicone oil, 8 parts fumed silica, 3 parts expanded microspheres, 6 parts azodicarbonamide, 2.2 parts sodium bicarbonate, and 1.5 parts dicumyl peroxide.

[0219] The preparation method of the silicone foam sheet in this comparative example includes the following steps:

[0220] Blending and grinding: Zinc borate, silicon nitride, alumina, and zinc oxide are placed in a ball mill jar in a fixed ratio. Anhydrous ethanol and ammonium polyacrylate are added. The solid-liquid mass ratio of all powders to anhydrous ethanol is 1:2. The amount of ammonium polyacrylate added is 0.8% of the powder mass, forming a suspension. Then, the mixture is ball-milled at 300 r / min for 2 hours, followed by ultrasonic dispersion for 30 minutes, and then ball-milled at 300 r / min for 4 hours. The above ball milling-ultrasonic dispersion and ball milling steps are repeated several times. When the D50 particle size of the powder in the suspension no longer decreases, the ball milling is stopped. Then, spray drying is performed. The inlet temperature of the spray dryer is 180℃ and the outlet temperature is 60℃ to obtain the blended powder after blending and grinding.

[0221] Mixing: Soften methyl vinyl silicone rubber at 50°C for 10 min; then add fumed silica and hydroxyl silicone oil, and mix at 50°C for 15 min; then add the blended and ground powder, organosilicon microspheres and glass powder, and mix at 50°C for 8 min; then add expanded microspheres, azodicarbonamide and sodium bicarbonate at 50°C, and mix for 3-5 min; then add dicumyl peroxide, and mix at 50°C for 8 min to obtain the compound;

[0222] Molding: First, spray the release agent on the inner wall of the lower mold and the upper mold, then preheat the lower mold to 90°C, then inject the compound into the lower mold, and then close the upper mold and the lower mold.

[0223] Foaming and vulcanization:

[0224] One-stage foaming: The mold is heated to 110°C at a rate of 10°C / min, and the pressure in the mold is controlled at 1MPa. The temperature and pressure are maintained for 30 minutes to complete one-stage foaming.

[0225] Secondary foaming: Then, the mold is heated to 150°C at a rate of 5°C / min, and the pressure in the mold is controlled at 5MPa. The temperature and pressure are maintained for 5 minutes to complete the secondary foaming.

[0226] Three foaming and one vulcanization: The mold is then heated to 180°C at a rate of 10°C / min, and the pressure in the mold is controlled at 5MPa. The temperature and pressure are maintained for 15 minutes to complete three foaming and one vulcanization.

[0227] Demolding and secondary vulcanization: First, cool the mold to below 80°C, then release the pressure and open the mold. Take out the foamed and vulcanized product and place it in an oven at 180°C for 2 hours to obtain silicone foam sheets.

[0228] Comparative Example 2

[0229] This comparative example provides a silicone foam sheet, which, by weight, is composed of the following components: 100 parts methyl vinyl silicone rubber, 5 parts zinc borate, 5 parts silicon nitride, 3 parts aluminum oxide, 1 part zinc oxide, 5 parts organosilicon microspheres, 15 parts glass powder, 5 parts hydroxyl silicone oil, 26 parts fumed silica, 2 parts expanded microspheres, 4 parts azodicarbonamide, 1 part sodium bicarbonate, and 1.5 parts dicumyl peroxide.

[0230] The preparation method of the silicone foam sheet in this comparative example includes the following steps:

[0231] Blending and grinding: Zinc borate, silicon nitride, alumina, and zinc oxide are placed in a ball mill jar in a fixed ratio. Anhydrous ethanol and ammonium polyacrylate are added. The solid-liquid mass ratio of all powders to anhydrous ethanol is 1:2. The amount of ammonium polyacrylate added is 0.8% of the powder mass, forming a suspension. Then, the mixture is ball-milled at 300 r / min for 2 hours, followed by ultrasonic dispersion for 30 minutes, and then ball-milled at 300 r / min for 4 hours. The above ball milling-ultrasonic dispersion and ball milling steps are repeated several times. When the D50 particle size of the powder in the suspension no longer decreases, the ball milling is stopped. Then, spray drying is performed. The inlet temperature of the spray dryer is 180℃ and the outlet temperature is 70℃ to obtain the blended powder after blending and grinding.

[0232] Mixing: Soften methyl vinyl silicone rubber at 50°C for 10 min; then add fumed silica and hydroxyl silicone oil, and mix at 60°C for 15 min; then add the blended and ground powder, organosilicon microspheres and glass powder, and mix at 60°C for 10 min; then add expanded microspheres, azodicarbonamide and sodium bicarbonate at 50°C, and mix for 3-5 min; then add dicumyl peroxide, and mix at 50°C for 8 min to obtain the compound;

[0233] Molding: First, spray the release agent on the inner wall of the lower mold and the upper mold, then preheat the lower mold to 90°C, then inject the compound into the lower mold, and then close the upper mold and the lower mold.

[0234] Foaming and vulcanization:

[0235] One-stage foaming: The mold is heated to 110°C at a rate of 10°C / min, and the pressure in the mold is controlled at 1MPa. The temperature and pressure are maintained for 30 minutes to complete one-stage foaming.

[0236] Secondary foaming: Then, the mold is heated to 150°C at a rate of 5°C / min, and the pressure in the mold is controlled at 5MPa. The temperature and pressure are maintained for 5 minutes to complete the secondary foaming.

[0237] Three foaming and one vulcanization: The mold is then heated to 180°C at a rate of 10°C / min, and the pressure in the mold is controlled at 5MPa. The temperature and pressure are maintained for 15 minutes to complete three foaming and one vulcanization.

[0238] Demolding and secondary vulcanization: First, cool the mold to below 80°C, then release the pressure and open the mold. Take out the foamed and vulcanized product and place it in an oven at 180°C for 2 hours to obtain silicone foam sheets.

[0239] Comparative Example 3

[0240] This comparative example provides a silicone foam sheet, which, by weight, is composed of the following components: 100 parts methyl vinyl silicone rubber, 12 parts zinc borate, 12 parts silicon nitride, 7 parts alumina, 4 parts zinc oxide, 5 parts organosilicon microspheres, 4 parts glass powder, 2 parts hydroxyl silicone oil, 10 parts fumed silica, 2 parts expanded microspheres, 5 parts azodicarbonamide, 1 part sodium bicarbonate, and 1.5 parts dicumyl peroxide.

[0241] The preparation method of the silicone foam sheet in this comparative example includes the following steps:

[0242] Blending and grinding: Zinc borate, silicon nitride, alumina, and zinc oxide are placed in a ball mill jar in a fixed ratio. Anhydrous ethanol and ammonium polyacrylate are added. The solid-liquid mass ratio of all powders to anhydrous ethanol is 1:2. The amount of ammonium polyacrylate added is 0.8% of the powder mass, forming a suspension. Then, the mixture is ball-milled at 300 r / min for 2 hours, followed by ultrasonic dispersion for 30 minutes, and then ball-milled at 300 r / min for 4 hours. The above ball milling-ultrasonic dispersion and ball milling steps are repeated several times. When the D50 particle size of the powder in the suspension no longer decreases, the ball milling is stopped. Then, spray drying is performed. The inlet temperature of the spray dryer is 180℃ and the outlet temperature is 60℃ to obtain the blended powder after blending and grinding.

[0243] Mixing: Soften methyl vinyl silicone rubber at 50°C for 10 min; then add fumed silica and hydroxyl silicone oil, and mix at 50°C for 15 min; then add the blended and ground powder, organosilicon microspheres and glass powder, and mix at 50°C for 8 min; then add expanded microspheres, azodicarbonamide and sodium bicarbonate at 50°C, and mix for 3-5 min; then add dicumyl peroxide, and mix at 50°C for 8 min to obtain the compound;

[0244] Molding: First, spray the release agent on the inner wall of the lower mold and the upper mold, then preheat the lower mold to 90°C, then inject the compound into the lower mold, and then close the upper mold and the lower mold.

[0245] Foaming and vulcanization:

[0246] One-stage foaming: The mold is heated to 110°C at a rate of 10°C / min, and the pressure in the mold is controlled at 1MPa. The temperature and pressure are maintained for 30 minutes to complete one-stage foaming.

[0247] Secondary foaming: Then, the mold is heated to 150°C at a rate of 5°C / min, and the pressure in the mold is controlled at 5MPa. The temperature and pressure are maintained for 5 minutes to complete the secondary foaming.

[0248] Three foaming and one vulcanization: The mold is then heated to 180°C at a rate of 10°C / min, and the pressure in the mold is controlled at 5MPa. The temperature and pressure are maintained for 15 minutes to complete three foaming and one vulcanization.

[0249] Demolding and secondary vulcanization: First, cool the mold to below 80°C, then release the pressure and open the mold. Take out the foamed and vulcanized product and place it in an oven at 180°C for 2 hours to obtain silicone foam sheets.

[0250] Comparative Example 4

[0251] This comparative example provides a silicone foam sheet, which, by weight, is composed of the following components: 100 parts methyl vinyl silicone rubber, 10 parts zinc borate, 10 parts silicon nitride, 5 parts alumina, 2 parts zinc oxide, 5 parts organosilicon microspheres, 8 parts glass powder, 4 parts hydroxyl silicone oil, 18 parts fumed silica, 1 part expanded microspheres, 2 parts azodicarbonamide, 0.5 parts sodium bicarbonate, and 1.5 parts dicumyl peroxide.

[0252] The preparation method of the silicone foam sheet in this comparative example includes the following steps:

[0253] Mixing: Soften methyl vinyl silicone rubber at 50°C for 10 min; then add fumed silica and hydroxyl silicone oil, and mix at 60°C for 15 min; then add zinc borate, silicon nitride, alumina, zinc oxide, organosilicon microspheres and glass powder, and mix at 60°C for 10 min; then add expanded microspheres, azodicarbonamide and sodium bicarbonate at 50°C, and mix for 3-5 min; then add dicumyl peroxide, and mix at 50°C for 8 min to obtain the compound;

[0254] Molding: First, spray the release agent on the inner wall of the lower mold and the upper mold, then preheat the lower mold to 90°C, then inject the compound into the lower mold, and then close the upper mold and the lower mold.

[0255] Foaming and vulcanization:

[0256] One-stage foaming: The mold is heated to 100°C at a rate of 10°C / min, and the pressure in the mold is controlled at 3MPa. The temperature and pressure are maintained for 15 minutes to complete one-stage foaming.

[0257] Secondary foaming: Then, the mold is heated to 140℃ at a rate of 5℃ / min, and the pressure in the mold is controlled at 10MPa. The temperature and pressure are maintained for 5 minutes to complete the secondary foaming.

[0258] Three foaming and one vulcanization: The mold is then heated to 170°C at a rate of 10°C / min, and the pressure in the mold is controlled at 10MPa. The temperature and pressure are maintained for 15 minutes to complete the three foaming and one vulcanization.

[0259] Demolding and secondary vulcanization: First, cool the mold to below 80°C, then release the pressure and open the mold. Take out the foamed and vulcanized product and place it in an oven at 180°C for 2 hours to obtain silicone foam sheets.

[0260] The characteristics of the silicone foam sheets in the above embodiments and comparative examples, as well as the evaluation results of their strength and thermal insulation performance after high-temperature sintering, are shown in Tables 1 and 2.

[0261] also, Figure 1 and Figure 2The images are SEM images of the silicone foam sheet of Example 1 before and after heating at 1000°C for 30 minutes.

[0262] Table 1

[0263]

[0264] Table 2

[0265]

[0266] As can be seen, the embodiments of the present invention control the linear expansion coefficient α of the cell diameter and the linear contraction coefficient β of the cell wall thickness of the silicone foam sheet before and after high-temperature sintering at 1000℃ to be within the range of the present invention. This allows the silicone foam sheet to have suitable cell diameter and cell wall thickness, resulting in more spatial gaps within the foam sheet and thus a lower thermal conductivity at room temperature. Furthermore, it maintains an intact cell structure after high-temperature sintering, forming a ceramic body with high ceramic strength, preventing the foam sheet from cracking after high-temperature sintering. Therefore, the silicone foam sheets of the embodiments of the present invention have good thermal insulation performance and can be used in battery modules and battery packs to prevent the spread of thermal runaway while also providing good buffering performance. In contrast, the linear expansion coefficient α of the cell diameter and / or the linear contraction coefficient β of the cell wall thickness in the comparative examples are not within the range of the present invention, making it difficult for the silicone foam sheet to simultaneously achieve both strength and thermal insulation performance after high-temperature sintering.

[0267] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A silicone foam sheet, wherein the linear expansion coefficient α of the cell diameter of the silicone foam sheet satisfies 1≤α≤8, and the linear shrinkage coefficient β of the cell wall thickness of the silicone foam sheet satisfies 4≤β≤9. in, The linear expansion coefficient α of the bubble diameter and the linear shrinkage coefficient β of the bubble wall thickness are calculated using the following formulas: ， ， In the formula, α is the coefficient of linear expansion of the bubble diameter, with units of °C. -1 β is the linear shrinkage coefficient of the bubble wall thickness, in °C. -1 L0 is the average cell diameter of the silicone foam sheet at room temperature, in μm; L1 is the average cell diameter of the silicone foam sheet after heating at 1000℃ for 30 min, in μm; d0 is the average cell wall thickness of the silicone foam sheet at room temperature, in μm; d1 is the average cell wall thickness of the silicone foam sheet after heating at 1000℃ for 30 min, in μm; T is the temperature difference between room temperature and 1000℃, in °C.

2. The silicone foam sheet according to claim 1, wherein, The ratio of α to β satisfies α / β = 0.2 - 1.

8.

3. The silicone foam sheet according to claim 1, wherein, The effective number of cells in the silicone foam sheet after heating at 1000℃ for 30 minutes accounts for more than 90% of the total number of cells.

4. The silicone foam sheet according to claim 1, wherein, The average pore diameter of the silicone foam sheet at room temperature is 100-1200 μm, and the average pore diameter of the silicone foam sheet after heating at 1000℃ for 30 min is 110-1350 μm. And / or, the average pore diameter of the silicone foam sheet at room temperature is 200-1000 μm, and the average pore diameter of the silicone foam sheet after heating at 1000℃ for 30 min is 220-1200 μm.

5. The silicone foam sheet according to claim 1, wherein, The average cell wall thickness of the silicone foam sheet at room temperature is 5-100 μm, and the average cell wall thickness of the silicone foam sheet after heating at 1000℃ for 30 min is 3-60 μm. And / or, the average cell wall thickness of the silicone foam sheet at room temperature is 5-90 μm, and the average cell wall thickness of the silicone foam sheet after heating at 1000℃ for 30 min is 3-55 μm.

6. The silicone foam sheet according to claim 1, wherein, The thermal insulation capacity Q of the silicone foam sheet at a T0 setting of 450℃ is ≥30, and the thermal insulation capacity Q of the silicone foam sheet at a T0 setting of 650℃ is ≥45; the thermal insulation capacity Q is obtained by the following method: A heating plate and a cold plate are provided, with the cold plate positioned above the heating plate. The heating plate has a hot surface. A silicone foam sheet is placed on the hot surface of the heating plate, and then the cold plate is pressed down until it contacts the silicone foam sheet, applying a pressure of 0.3 MPa to the silicone foam sheet. The hot surface of the heating plate reaches a heating temperature T0. After maintaining the pressure and the heating temperature for 30 minutes, the highest temperature T1 of the contact surface between the cold plate and the silicone foam sheet during the 30-minute holding time is recorded. The contact surface between the cold plate and the silicone foam sheet, the hot surface of the heating plate, and the silicone foam sheet are all matched in shape and have equal areas. The heat insulation per unit area Q is calculated using the following formula: Q = K × (T1 - T0) × A / H; In the formula, Q represents the heat insulation per unit area, in W; K represents the thermal conductivity of the silicone foam sheet at room temperature, in W / (m·K); T0 represents the temperature of the hot surface of the heating plate, in K, and the set value of T0 is 450℃ or 650℃; T1 represents the highest temperature of the contact surface between the cold plate and the silicone foam sheet during the 30-minute holding time, in K; and A represents the area of ​​the hot surface of the heating plate, in m². 2 H represents the thickness of the silicone foam sheet, in meters (m).

7. The silicone foam sheet according to claim 1, wherein, The absolute value of the difference between the Shore A hardness of the silicone foam sheet at room temperature and the Shore A hardness after heating at 1000℃ for 30 minutes is 20-60°.

8. The silicone foam sheet according to claim 1 or 7, wherein, The silicone foam sheet has a Shore A hardness of 5-50° at room temperature, and a Shore A hardness of 65-70° after heating at 1000°C for 30 minutes.

9. The silicone foam sheet according to claim 1, wherein, The density of the silicone foam sheet at room temperature is 300-1100 kg / m³. 3 ; And / or, the silicone foam sheet has a 25% compressive stress of 20-500 kPa under normal temperature conditions.

10. The silicone foam sheet according to claim 1, wherein, The thermal conductivity of the silicone foam sheet at room temperature is 0.05-0.11 W / (m·K).

11. The silicone foam sheet according to claim 1, wherein, The thickness of the silicone foam sheet at room temperature is 0.5-25 mm.

12. A battery module comprising: Two or more battery cells and one or more silicone foam sheets according to any one of claims 1-11, wherein the silicone foam sheets are disposed between adjacent battery cells.

13. A battery pack comprising: The housing and the battery module as described in claim 12; the housing includes a frame, a top cover, a wiring harness isolation plate, and a liquid cooling plate; the battery module is disposed in the frame; the top cover is disposed on the top of the battery module; the wiring harness isolation plate is disposed between the battery module and the top cover; the wiring harness isolation plate is provided with a busbar for connecting the battery cells in the battery module; a silicone foam sheet as described in any one of claims 1-11 is disposed between the wiring harness isolation plate and the top cover for covering the top of the busbar; the liquid cooling plate is disposed around the sides and / or the bottom of the battery module.

Images