A foamed thermally conductive liquid silicone rubber, its preparation method and application

Abstract

This invention discloses a foamed thermally conductive liquid silicone rubber, its preparation method, and its application. The foamed thermally conductive liquid silicone rubber is composed of component A and component B. Component A includes the following raw materials by weight: 100 parts vinyl silicone oil, 5-10 parts hydroxyl silicone oil, 0.3-0.5 parts platinum catalyst, 10-15 parts modified silica, 40-45 parts fluffy thermally conductive powder, and 10-15 parts aluminum hydroxide flame retardant. Component B includes the following raw materials by weight: 100 parts vinyl silicone oil, 20-25 parts hydrogen-containing silicone oil, 0.2-0.3 parts inhibitor, and 10-15 parts modified silica; wherein the hydrogen-containing silicone oil is a blend of end-hydrogen-containing silicone oil and side-hydrogen-containing silicone oil. This invention assembles the thermally conductive powder with fibrous inorganic materials to form a large-size, flocculent, fluffy thermally conductive powder. During the foaming of the liquid silicone rubber, the flocculent, fluffy thermally conductive powder penetrates the foam micropores, reducing the thermal resistance of the foam pores and significantly improving the thermal conductivity of the foamed liquid silicone rubber.

Description

Technical Field

[0001] This invention belongs to the field of liquid silicone rubber technology, and particularly relates to a foamed thermally conductive liquid silicone rubber, its preparation method and application. Background Technology

[0002] Silicone rubber, a high-performance material with resistance to high and low temperatures, shock absorption, damping, and sealing properties, has been widely used in defense, aerospace, and new energy vehicles. Liquid silicone rubber, in particular, offers advantages beyond its general silicone rubber properties. It is convenient to use, requiring no mixing equipment, and can be directly cast in molds to prepare various cushioning pads or irregularly shaped parts. It can also be directly used for potting electronic and electrical components, and for sealing automotive parts and batteries. Furthermore, it can crosslink and cure at room temperature or under heating conditions to form an elastomer, greatly expanding its application scenarios.

[0003] Silicone rubber foam prepared from foamed liquid silicone rubber exhibits excellent elastic characteristics. Its micropores promote the superior compressibility and elastic recovery of silicone rubber, effectively absorbing impact energy and showing great application potential in fields such as precision instruments, new energy vehicles, and aerospace controllers. For example, patent document CN113831738B discloses an addition-type liquid silicone rubber foam material and its preparation method, which separates the foaming component from the crosslinking component, resulting in better matching between foaming and crosslinking. The foam produced has uniform cell structure, high expansion ratio, low density, and low compression set.

[0004] Thermally conductive liquid silicone rubber possesses excellent thermal conductivity, electrical insulation, and temperature resistance. It can be prefabricated into silicone sheets to meet the heat dissipation requirements of electronic devices and is widely used in high-power LED heat dissipation modules, electric vehicle battery components, 5G communication equipment, and avionics. For example, patent document CN113969060B discloses a high thermal conductivity and flame-retardant liquid silicone rubber for use as an insulating material. By adding a three-dimensional skeleton formed by adding four-needle-shaped zinc oxide thermally conductive filler, the surface heat is dispersed, improving the thermal conductivity of the silicone rubber material. Patent document CN114276686B discloses a high mechanical strength and high thermal conductivity heat dissipation silicone rubber pad and its preparation method. It uses hydrophobic silica to modify one of alumina, aluminum nitride, boron nitride, magnesium oxide, zinc oxide, and silicon carbide to obtain a composite thermally conductive filler, which increases the thermal conductivity of the silicone rubber to above 0.6 W / (m·K).

[0005] However, in some applications requiring vibration damping and heat dissipation, liquid silicone rubber must possess both low-density foaming and excellent thermal conductivity and heat dissipation. For example, the thermal pads for lithium battery cell modules require silicone foam with good insulation properties, high resilience, and thermal conductivity and heat dissipation. Resilience effectively prevents damage from vibration and friction between cells, while high thermal conductivity quickly transfers heat from the cells to the liquid cooling pipes.

[0006] Based on the existing technology, a large amount of thermally conductive filler needs to be added to liquid silicone rubber to form a thermally conductive network. However, in foamed liquid silicone rubber, the air gaps in the micropores create thermal resistance, preventing the thermally conductive filler from effectively linking together to form a thermally conductive path. Increasing the amount of thermally conductive filler leads to increased material costs and decreased strength. Therefore, obtaining liquid silicone rubber that combines foaming and thermal conductivity has become a technical challenge in this field. Summary of the Invention

[0007] The micropores of foamed liquid silicone rubber endow the material with good elasticity, cushioning, and sealing properties; however, the high thermal resistance during foaming weakens the thermal conductivity pathways and reduces heat dissipation. To address this deficiency in the thermal conductivity pathways of current foamed liquid silicone rubber, and to balance foam elasticity and thermal conductivity, this invention provides a foamed thermally conductive liquid silicone rubber and its preparation method. By pre-forming the thermally conductive powder material into a large, fluffy form, it is easier to construct excellent thermal conductivity pathways during the foaming and vulcanization molding of liquid silicone rubber.

[0008] To achieve the above-mentioned technical objectives, the present invention provides the following technical solution:

[0009] A foamed thermally conductive liquid silicone rubber, wherein the foamed thermally conductive liquid silicone rubber is composed of component A and component B in a mass ratio of 1:1; wherein:

[0010] Component A comprises the following raw materials in parts by weight: 100 parts vinyl silicone oil, 5-10 parts hydroxyl silicone oil, 0.3-0.5 parts platinum catalyst, 10-15 parts modified silica, 40-45 parts fluffy thermal conductive powder, and 10-15 parts aluminum hydroxide flame retardant.

[0011] Component B comprises the following raw materials in parts by weight: 100 parts vinyl silicone oil, 20-25 parts hydrogen-containing silicone oil, 0.2-0.3 parts inhibitor, and 10-15 parts modified silica.

[0012] The hydrogen-containing silicone oil is a compound of end-hydrogen-containing silicone oil and side-hydrogen-containing silicone oil in a mass ratio of 3:1.

[0013] The modified silica is prepared by the following method:

[0014] Add silica to a drying mixer and dry at 100 °C. Then add silane coupling agent at a mass ratio of silica to silane coupling agent of 100:(3-4) and stir for 15-25 minutes to obtain modified silica. Seal and store for later use.

[0015] The fluffy thermally conductive powder is pre-prepared by the following method:

[0016] Weigh out 100 parts by weight of thermally conductive powder, 10-15 parts by weight of fibrous inorganic material, 5-10 parts by weight of methyl vinyl MQ silicone resin, 0.5-1 parts by weight of hydrogen-terminated silicone oil, and 0.02-0.05 parts by weight of platinum catalyst. Mix the thermally conductive powder and fibrous inorganic material at high speed in a mixer at 80-100°C. Add the methyl vinyl MQ silicone resin, hydrogen-terminated silicone oil, and platinum catalyst to the mixer after premixing. Shear and stir at high speed for 45-60 minutes. Then grind and pass through a 50-mesh sieve to obtain a fluffy, flocculated thermally conductive powder.

[0017] Preferably, the vinyl silicone oil is a vinyl-terminated polysiloxane, which improves tear resistance during crosslinking, such as polydimethylsiloxane containing vinyl-terminated groups. More preferably, the viscosity of the vinyl silicone oil is 1000–10000 mPa·s; the mass content of the vinyl groups in the vinyl silicone oil is 0.25–0.45%. Controlling the vinyl content within a reasonable range yields silicone foam with moderate softness. Too low a vinyl content results in low crosslinking density and poor foam mechanical properties; too high a crosslinking density makes the foam brittle.

[0018] Preferably, the hydroxyl content of the hydroxyl silicone oil is 5-10% by mass; more preferably, the hydroxyl silicone oil is a hydroxyl-terminated polydimethylsiloxane.

[0019] Preferably, the platinum catalyst is a siloxane-based platinum catalyst, such as Castel platinum catalyst (platinum-divinyltetramethyldisiloxane complex); more preferably, the platinum concentration of the platinum catalyst is 500-1000 ppm.

[0020] Preferably, the active hydrogen content of the hydrogen-containing silicone oil is 0.2-1.6% by mass. When the active hydrogen in the hydrogen-containing silicone oil is terminal hydrogen, the reactivity is too high, which competes with the hydroxyl silicone oil for reaction, causing foam to form too early and affecting the strength of the silicone rubber. Therefore, the hydrogen-containing silicone oil is mainly terminal hydrogen-containing silicone oil, and the use of a small amount of side hydrogen-containing silicone oil helps to stabilize the foaming and improve the strength of the foamed material.

[0021] Preferably, the inhibitor is an alkynyl alcohol inhibitor; more preferably, the alkynyl alcohol inhibitor is at least one selected from 1-ethynyl-1-cyclohexanol, 2-methyl-3-butyn-ol, and 3,5-dimethyl-1-hexyn-3-ol. By using a suitable inhibitor, when component A and component B are mixed, the inhibitor coordinates with the platinum catalyst, avoiding a violent addition reaction and providing an operational time window for casting and molding.

[0022] Preferably, the silica is silica prepared by a gas-phase method; more preferably, the specific surface area of ​​the silica is 200–500 m² / g. 2 / g; the water content of the silica is <0.5%. By treating silica with a coupling agent, oleophilic and hydrophobic groups are increased, improving the adhesion and dispersion uniformity of the interface between silica and vinyl silicone oil. After the silica is uniformly dispersed, the hydroxyl groups on its surface can form hydrogen bonds with the siloxane segments, thereby increasing the tensile strength of the liquid silicone rubber and showing a significant reinforcing effect.

[0023] Preferably, the silane coupling agent is at least one of KH-550, KH-560, and KH-570; more preferably, the coupling agent is KH570.

[0024] Preferably, the thermally conductive powder is at least one of boron nitride, aluminum oxide, silicon carbide, aluminum nitride, and tetraneedle zinc oxide; more preferably, the particle size of the thermally conductive powder is 5-10µm.

[0025] Preferably, the fibrous inorganic material is selected from at least one of sepiolite fiber, brucite fiber, calcium sulfate whiskers, and chopped glass fiber; the length of the fibrous inorganic material is 100-1000µm.

[0026] If thermally conductive powder is directly dispersed in liquid silicone rubber, the powder exists within the foam walls during foaming, limiting its thermal conductivity and causing the pores to easily impede heat transfer. By combining the thermally conductive powder with fibrous inorganic materials, and using methyl vinyl MQ silicone resin and hydrogen-terminated silicone oil for addition curing, the thermally conductive powder and fibrous inorganic materials can be improved. The methyl vinyl MQ silicone resin itself has a three-dimensional network structure, which is further enhanced after reacting with the hydrogen-terminated silicone oil, giving the assembly better elasticity. Under grinding action, the thermally conductive powder and fibrous inorganic material composite becomes flocculent, forming large-sized, elastic, and fluffy thermally conductive powder. This powder easily constructs low-thermal-resistance thermally conductive channels in foamed liquid silicone rubber. Furthermore, the larger size of the fluffy thermally conductive powder allows it to penetrate the micropores during foaming, forming multi-level thermally conductive channels, reducing the interfacial thermal resistance, and significantly improving heat dissipation efficiency. Moreover, the fibrous inorganic materials in the fluffy thermally conductive powder can form a tight bond with the silicone rubber, effectively improving the mechanical properties after foaming.

[0027] Another object of the present invention is to provide a method for preparing a foamed thermally conductive liquid silicone rubber, characterized by comprising the following steps:

[0028] S1. Preparation of modified silica: Add silica to a drying mixer and dry at 100 °C. Then add silane coupling agent at a mass ratio of silica to silane coupling agent of 100:(3-4) and stir for 15-25 min to obtain modified silica. Seal and store for later use.

[0029] S2. Preparation of fluffy thermal conductive powder: Weigh 100 parts of thermal conductive powder, 10-15 parts of fibrous inorganic material, 5-10 parts of methyl vinyl MQ silicone resin, 0.5-1 parts of hydrogen-terminated silicone oil, and 0.02-0.05 parts of platinum catalyst according to the following weight proportions: Mix the thermal conductive powder and fibrous inorganic material at high speed in a mixer at 80-100℃; add the methyl vinyl MQ silicone resin, hydrogen-terminated silicone oil, and platinum catalyst after premixing to the mixer; shear and stir at high speed for 45-60 minutes to solidify; then grind and pass through a 50-mesh sieve to obtain fluffy thermal conductive powder in the form of flocculent material.

[0030] S3. Preparation of Component A: Vinyl silicone oil, hydroxyl silicone oil, platinum catalyst, modified silica, and aluminum hydroxide flame retardant are ground and dispersed on a three-roll mill, and then mixed evenly with fluffy thermally conductive powder to obtain Component A;

[0031] S4. Preparation of Component B: Vinyl silicone oil, hydrogen-containing silicone oil, inhibitor, and modified silica are ground and dispersed in a three-roll mill to obtain Component B;

[0032] S5. A and B component allocation: When using, mix component A and component B in a mixer at a mass ratio of 1:1 until homogeneous, and then feed the mixture into the calendering production line for calendering, vulcanization, and foaming via a feeder.

[0033] This invention also provides the application of the above-mentioned foamed thermally conductive liquid silicone rubber in the heat dissipation pads of lithium battery cell modules. In use, component A and component B are mixed evenly in a mixer at a mass ratio of 1:1, fed into a calendering production line for coating, calendered into sheets, and subjected to primary vulcanization and foaming at 80-100℃. After cooling, the sheets are peeled off and wound up. Then, a secondary vulcanization is performed at 120-150℃, followed by cooling and winding to obtain a heat dissipation pad suitable for lithium battery cell modules.

[0034] The advantages and beneficial effects of this invention are as follows:

[0035] 1) This invention combines thermally conductive powder with fibrous inorganic materials in an addition bonding and curing process with methyl vinyl MQ silicone resin and hydrogen-containing silicone oil, and then grinds the powder to form large-sized flocculated and fluffy thermally conductive powder. The flocculated and fluffy thermally conductive powder has elasticity and continuous thermal conductive pathways. When liquid silicone rubber is foamed, the flocculated and fluffy thermally conductive powder penetrates the foam micropores, reducing the thermal resistance of the foam pores and forming multi-level thermal conductive channels, which significantly improves heat dissipation efficiency.

[0036] 2) When components A and B of this invention are mixed, under the catalysis of platinum, the vinyl (Vi) of vinyl silicone oil and the Si-H bond of hydrogen-containing silicone oil undergo an addition reaction to achieve cross-linking and curing to generate Si-C bonds and form an elastomer. At the same time, the gas generated by the reaction of hydrogen-containing silicone oil and a small amount of hydroxyl silicone oil foams the liquid silicone rubber in situ. By using end-hydrogen-containing silicone oil and side-hydrogen-containing silicone oil in combination, the active end hydrogen and hydroxyl silicone oil are prevented from competing violently for reaction, so that the liquid silicone rubber can be stably foamed to form through micropores and ensure the strength of the foamed silicone rubber.

[0037] 3) This invention endows foamed liquid silicone rubber with excellent elasticity, resistance to compression set, and thermal conductivity. The preparation process is simple and can be achieved using existing mixing equipment, ball mills, and three-roll mills. The foamed gaskets can be mass-produced using a calendering foaming production line. Attached Figure Description

[0038] The accompanying drawings are provided for a more intuitive comparison and understanding of the technical solutions of the present invention. Due to experimental limitations, there may be certain defects, but they do not constitute a limitation on the technical solutions of the present invention.

[0039] Figure 1 Example 1: Microscopic image of a heat dissipation pad formed by foaming thermally conductive liquid silicone rubber.

[0040] Figure 2 Comparative Example 1: Microscopic image of a heat dissipation pad formed by foaming thermally conductive liquid silicone rubber. Detailed Implementation

[0041] The preferred embodiments of the present invention are described in detail below to make the advantages of the present invention more readily understood by those skilled in the art. The following embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. All other embodiments obtained by those skilled in the art based on the described embodiments without inventive effort are within the scope of protection of the present invention.

[0042] Unless otherwise specified, all raw materials used are those commonly used in this field and commercially available. The following are some of the raw material parameters:

[0043] Vinyl silicone oil: Vinyl-terminated polydimethylsiloxane, brand name ADL-V2A, viscosity approximately 2000 mPa·s, vinyl content 0.26%, Jiangxi Andeli High-tech Technology Co., Ltd.

[0044] Hydroxyl silicone oil: Hydroxyl-terminated polydimethylsiloxane, hydroxyl content 6%, Zhejiang Runhe Organosilicon Co., Ltd.

[0045] Hydrogen-containing silicone oil: 1-200-20, hydrogen content 0.2%, Zhejiang Chuangji Organosilicon Materials Co., Ltd.

[0046] Hydrogen-containing silicone oil: RH202-20, hydrogen content 1.55%, Zhejiang Runhe Organosilicon Co., Ltd.

[0047] Methyl vinyl MQ silicone resin: QY-3065, vinyl content 1.8%, Hangzhou Qianyang Technology Co., Ltd.

[0048] Platinum catalyst: Castells platinum catalyst (platinum-divinyltetramethyldisiloxane complex), platinum concentration 1000 ppm.

[0049] Alumina: 10µm particle size, Shandong Zhonglv.

[0050] Aluminum nitride: 10µm particle size, Great Wall Aluminum Co., Ltd.

[0051] Example 1

[0052] S1. Preparation of modified silica: Fumed silica (specific surface area 200m²) is prepared by... 2 / g) is added to a drying mixer and dried at 100℃ until the moisture content is <0.5%; then, according to the mass ratio of fumed silica to coupling agent KH570 of 100:3, coupling agent KH570 is added and stirred for 25 minutes to obtain modified silica, which is then sealed and stored for later use.

[0053] S2. Preparation of fluffy thermal conductive powder: Weigh out 50 parts by weight of alumina, 50 parts by weight of aluminum nitride, 15 parts by weight of calcium sulfate whiskers with a length of 200µm, 8 parts by weight of methyl vinyl MQ silicone resin, 0.5 parts by weight of hydrogen-terminated silicone oil, and 0.03 parts by weight of platinum catalyst; mix alumina, aluminum nitride, and calcium sulfate whiskers at 100℃ in a mixer at high speed; add methyl vinyl MQ silicone resin, hydrogen-terminated silicone oil, and platinum catalyst to the mixer after premixing; shear and stir at 800rpm for 45min to prevent agglomeration into large particles; then grind the powder through a 50-mesh sieve in a ball mill to obtain fluffy thermal conductive powder in the form of flocculent particles;

[0054] S3. Preparation of Component A: 100 parts of vinyl silicone oil, 6 parts of hydroxyl silicone oil, 0.3 parts of platinum catalyst, 12 parts of modified silica, and 15 parts of aluminum hydroxide flame retardant are ground and dispersed on a three-roll mill, and then mixed evenly with 45 parts of fluffy thermal conductive powder to obtain Component A;

[0055] S4. Preparation of Component B: 100 parts of vinyl silicone oil, 20 parts of hydrogen-containing silicone oil, 0.3 parts of inhibitor 1-ethynyl-1-cyclohexanol, and 12 parts of modified silica are ground and dispersed in a three-roll mill to obtain Component B; the hydrogen-containing silicone oil is a compound of end-hydrogen-containing silicone oil and side-hydrogen-containing silicone oil in a mass ratio of 3:1.

[0056] S5. A and B component preparation: When using, mix component A and component B in a mixer at a mass ratio of 1:1 to obtain foamed thermally conductive liquid silicone rubber.

[0057] Example 2

[0058] S1. Preparation of modified silica: Fumed silica (specific surface area 200m²) is prepared by... 2 / g) is added to a drying mixer and dried at 100℃ until the moisture content is <0.5%; then, according to the mass ratio of fumed silica to coupling agent KH570 of 100:4, coupling agent KH570 is added and stirred for 25 minutes to obtain modified silica, which is then sealed and stored for later use.

[0059] S2. Preparation of fluffy thermal conductive powder: Weigh out 70 parts by weight of alumina, 30 parts by weight of aluminum nitride, 15 parts by weight of sepiolite fiber with a length of 1000µm, 10 parts by weight of methyl vinyl MQ silicone resin, 1 part by weight of hydrogen-terminated silicone oil, and 0.04 parts by weight of platinum catalyst; mix alumina, aluminum nitride, and sepiolite fiber at 100℃ in a mixer at high speed; add methyl vinyl MQ silicone resin, hydrogen-terminated silicone oil, and platinum catalyst after premixing to the mixer; shear and stir at 800rpm for 60min to prevent agglomeration into large particles; then grind through a 50-mesh sieve in a ball mill to obtain fluffy thermal conductive powder in the form of flocculent particles;

[0060] S3. Preparation of Component A: 100 parts of vinyl silicone oil, 10 parts of hydroxyl silicone oil, 0.5 parts of platinum catalyst, 10 parts of modified silica, and 10 parts of aluminum hydroxide flame retardant are ground and dispersed on a three-roll mill, and then mixed evenly with 40 parts of fluffy thermal conductive powder to obtain Component A;

[0061] S4. Preparation of Component B: 100 parts of vinyl silicone oil, 25 parts of hydrogen-containing silicone oil, 0.2 parts of inhibitor 1-ethynyl-1-cyclohexanol, and 10 parts of modified silica are ground and dispersed in a three-roll mill to obtain Component B; the hydrogen-containing silicone oil is a mixture of end-hydrogen-containing silicone oil and side-hydrogen-containing silicone oil in a mass ratio of 3:1.

[0062] S5. A and B component preparation: When using, mix component A and component B in a mixer at a mass ratio of 1:1 to obtain foamed thermally conductive liquid silicone rubber.

[0063] Example 3

[0064] S1. Preparation of modified silica: Fumed silica (specific surface area 200m²) is prepared by... 2 / g) is added to a drying mixer and dried at 100℃ until the moisture content is <0.5%; then, according to the mass ratio of fumed silica to coupling agent KH570 of 100:3, coupling agent KH550 is added and stirred for 25 minutes to obtain modified silica, which is then sealed and stored for later use.

[0065] S2. Preparation of fluffy thermal conductive powder: Weigh out 100 parts by weight of alumina, 15 parts by weight of calcium sulfate whiskers with a length of 200µm, 10 parts by weight of methyl vinyl MQ silicone resin, 1 part by weight of hydrogen-terminated silicone oil, and 0.04 parts by weight of platinum catalyst; mix the alumina and calcium sulfate whiskers at 100℃ in a mixer at high speed; add the methyl vinyl MQ silicone resin, hydrogen-terminated silicone oil, and platinum catalyst to the mixer after premixing; shear and stir at 800rpm for 45min to prevent agglomeration into large particles; then grind the powder through a 50-mesh sieve in a ball mill to obtain fluffy thermal conductive powder in the form of flocculent particles;

[0066] S3. Preparation of Component A: 100 parts of vinyl silicone oil, 5 parts of hydroxyl silicone oil, 0.3 parts of platinum catalyst, 15 parts of modified silica, and 15 parts of aluminum hydroxide flame retardant are ground and dispersed on a three-roll mill, and then mixed evenly with 45 parts of fluffy thermal conductive powder to obtain Component A;

[0067] S4. Preparation of Component B: 100 parts of vinyl silicone oil, 20 parts of hydrogen-containing silicone oil, 0.2 parts of inhibitor 2-methyl-3-butynediol, and 15 parts of modified silica are ground and dispersed in a three-roll mill to obtain Component B; the hydrogen-containing silicone oil is a mixture of end-hydrogen-containing silicone oil and side-hydrogen-containing silicone oil in a mass ratio of 3:1.

[0068] S5. A and B component preparation: When using, mix component A and component B in a mixer at a mass ratio of 1:1 to obtain foamed thermally conductive liquid silicone rubber.

[0069] Comparative Example 1

[0070] The difference from Example 1 is that 45 parts of fluffy thermal conductive powder are replaced with 22.5 parts of alumina and 22.5 parts of aluminum nitride.

[0071] Comparative Example 2

[0072] The difference from Example 1 is that all hydrogen-containing silicone oils used are end-to-end hydrogen-containing silicone oils.

[0073] Comparative Example 3

[0074] The difference from Example 1 is that the three-roll milling dispersion was omitted when preparing components A and B, and conventional mixing was used instead.

[0075] Comparative Example 4

[0076] The difference from Example 1 is that fluffy thermal conductive powder is not used.

[0077] The foamed thermally conductive liquid silicone rubbers of Examples 1-3 and Comparative Examples 1-4 were mixed evenly in a mixer at a mass ratio of component A to component B of 1:1. The mixture was then fed into a calendering production line for coating, calendering into sheets, and subjected to primary vulcanization and foaming in a 100°C drying tunnel. After cooling, a secondary vulcanization was performed in a 140°C drying tunnel to obtain foamed silicone rubber samples. The tensile strength, elongation at break, compression set, flame retardancy, and thermal conductivity of the samples were tested. The test results are shown in Table 1. The specific test methods are as follows:

[0078] (1) Tensile strength and elongation at break were tested in accordance with GB / T 528-2009.

[0079] (2) The compression set performance is in accordance with GB / T 6669-2008. The material is compressed to 50% deformation at 70℃ and held for 22 hours. The thickness change rate after recovery is measured.

[0080] (3) Flame retardancy is in accordance with UL94-2013 (R-2021), using vertical burning test.

[0081] (4) The thermal conductivity was determined by the steady-state hot plate method and tested in accordance with GB / T 10294-2008.

[0082] Table 1:

[0083]

[0084] As shown in Table 1, this invention, by combining thermally conductive powder with fibrous inorganic materials, flocculating and fluffing the mixture, and then applying it to liquid silicone rubber, constructs a good thermal conductivity pathway, significantly improving the thermal conductivity of the silicone foam. (Appendix) Figure 1 The image shown is a microscopic image of the liquid silicone rubber foamed heat dissipation pad from Example 1. It clearly shows that the large-sized, flocculated, and loose thermally conductive powder penetrates the micropores during the foaming process of the liquid silicone rubber, avoiding thermal resistance from the air bubbles. Furthermore, the combination of end- and side-containing hydrogen-containing silicone oils ensures stable foaming of the liquid silicone rubber, forming interconnected micropores and guaranteeing good tensile strength. In addition, the large-sized, flocculated, and loose thermally conductive powder is obtained by treating methyl vinyl MQ silicone resin with a certain degree of flexibility and elasticity, which ensures a low compression set. A lower compression set indicates better material resilience.

[0085] For Comparative Example 1, the thermally conductive material was added directly as an ultrafine powder. A microscopic image of the resulting liquid silicone rubber foamed heat dissipation pad is attached. Figure 2 It is evident that the foamed micropores are relatively intact, and the thermal resistance effect of the bubble gaps results in limited improvement in thermal conductivity.

[0086] For Comparative Example 2, all hydrogen-containing silicone oil used was end-capped hydrogen-containing silicone oil, which caused severe foaming, affecting the strength of the final material and resulting in large compression set.

[0087] For Comparative Example 3, the three-roll milling dispersion of components A and B was omitted, which resulted in the silica reinforcing agent, inhibitor, and catalyst not being fully dispersed with the base adhesive, affecting the foaming uniformity and stability, and ultimately the strength of the final material.

[0088] It should be noted that those skilled in the art can make various improvements and modifications to this invention without departing from its principles, and all such improvements and modifications fall within the scope of protection of this invention.

Claims

1. A foamed thermally conductive liquid silicone rubber, characterized by, The foaming type heat-conducting liquid silicone rubber is composed of A component and B component with a mass ratio of 1:1; wherein: The A component comprises the following raw materials in parts by weight: vinyl silicone oil 100 parts, hydroxyl silicone oil 5-10 parts, platinum catalyst 0.3-0.5 parts, modified white carbon black 10-15 parts, fluffy heat-conducting powder 40-45 parts, and aluminum hydroxide flame retardant 10-15 parts; The B component comprises the following raw materials in parts by weight: vinyl silicone oil 100 parts, hydrogen-containing silicone oil 20-25 parts, inhibitor 0.2-0.3 parts, and modified white carbon black 10-15 parts; The hydrogen-containing silicone oil is a compound of end hydrogen-containing silicone oil and side hydrogen-containing silicone oil with a mass ratio of 3:1; The modified white carbon black is prepared by the following method: The white carbon black is added into a dry mixer, dried at 100 ℃, then a silane coupling agent is added according to a mass ratio of white carbon black to silane coupling agent of 100: (3-4), stirred for 15-25 min, to obtain the modified white carbon black, which is sealed and stored for later use; The fluffy heat-conducting powder is prepared by the following method: According to the weight, 100 parts of heat-conducting powder, 10-15 parts of fibrous inorganic matter, 5-10 parts of methyl vinyl MQ silicone resin, 0.5-1 part of end hydrogen-containing silicone oil, and 0.02-0.05 part of platinum catalyst are weighed; the heat-conducting powder and fibrous inorganic matter are mixed uniformly at a high speed in a mixer at 80-100 ℃, the methyl vinyl MQ silicone resin, end hydrogen-containing silicone oil and platinum catalyst are premixed and then added into the mixer, and high-speed shearing stirring is conducted for 45-60 min, and then the mixture is ground through a 50-mesh sieve to obtain fluffy heat-conducting powder in a flocculent form.

2. The foamed thermally conductive liquid silicone rubber according to claim 1, characterized in that, The vinyl silicone oil is a polysiloxane with a terminal group of vinyl; the viscosity of the vinyl silicone oil is 1000-10000 mPa·s; and the mass content of vinyl groups of the vinyl silicone oil is 0.25-0.45%.

3. The foamed thermally conductive liquid silicone rubber according to claim 1, wherein The mass content of hydroxyl groups of the hydroxyl silicone oil is 5-10%; and the hydroxyl silicone oil is a hydroxyl-terminated polydimethylsiloxane.

4. The foamed thermally conductive liquid silicone rubber of claim 1, wherein, The platinum catalyst is selected from a Kast platinum catalyst; and the platinum concentration of the platinum catalyst is 500-1000 ppm.

5. The foamed thermally conductive liquid silicone rubber of claim 1, wherein, The mass content of active hydrogen of the hydrogen-containing silicone oil is 0.2-1.6%.

6. The foamed thermally conductive liquid silicone rubber of claim 1, wherein, The inhibitor is selected from an alkyne alcohol inhibitor.

7. The foamed thermally conductive liquid silicone rubber of claim 1, wherein, The heat-conducting powder is at least one of boron nitride, aluminum oxide, silicon carbide, aluminum nitride and four acicular zinc oxide; and the particle size of the heat-conducting powder is 5-10 µm.

8. The foamed thermally conductive liquid silicone rubber of claim 1, wherein, The fibrous inorganic matter is at least one of sepiolite fiber, brucite fiber, calcium sulfate whisker and chopped glass fiber; and the length of the fibrous inorganic matter is 100-1000 µm.

9. A process for the preparation of the foamed thermally conductive liquid silicone rubber according to any one of claims 1 to 8, characterized in that The method comprises the following steps: S1. Preparation of modified white carbon black: white carbon black is added into a dry mixer, dried at 100 ℃, then a silane coupling agent is added according to a mass ratio of white carbon black to silane coupling agent of 100: (3-4), stirred for 15-25 min, to obtain the modified white carbon black, which is sealed and stored for later use; S2. Preparation of fluffy heat-conducting powder: heat-conducting powder 100 parts, fibrous inorganic matter 10-15 parts, methyl vinyl MQ silicone resin 5-10 parts, end hydrogen-containing silicone oil 0.5-1 part, platinum catalyst 0.02-0.05 parts are weighed according to weight parts; the heat-conducting powder and fibrous inorganic matter are mixed uniformly at high speed in a blender at 80-100℃, the methyl vinyl MQ silicone resin, end hydrogen-containing silicone oil and platinum catalyst are premixed and then added to the blender, and high-speed shearing stirring is carried out for 45-60 min, then the mixture is ground through a 50-mesh sieve to obtain fluffy heat-conducting powder in flocculent form; S3. Preparation of A component: the vinyl silicone oil, hydroxyl silicone oil, platinum catalyst, modified white carbon black and aluminum hydroxide flame retardant are ground and dispersed on a three-roll grinder, then mixed uniformly with the fluffy heat-conducting powder to obtain the A component; S4. Preparation of B component: the vinyl silicone oil, hydrogen-containing silicone oil, inhibitor and modified white carbon black are ground and dispersed on a three-roll grinder to obtain the B component; S5. Preparation of A component and B component: when used, the A component and B component are mixed uniformly in a mass ratio of 1:1 in a blender, and then supplied into a calender production line for calendering, vulcanization and foaming.

10. Use of the foamed heat-conducting liquid silicone rubber according to any one of claims 1-8 in a lithium battery cell module heat dissipation pad.

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