A composition for preparing high-performance silicone rubber

Abstract

The present invention discloses a composition for preparing high-performance silicone rubber. The composition comprises, by mass, 60-70 parts of vinyl-terminated polydimethylsiloxane, 10-20 parts of polyurethane microcapsules containing 4-cyano-4'-pentylbiphenyl, 10-15 parts of ZrO2 nanoparticles, 3-5 parts of hydrogen-containing siloxane, and 0.01-0.05 parts of a platinum-based catalyst. The preparation method comprises dispersing the ZrO2 nanoparticles in PDMS under high shear, adding liquid crystal microcapsules and stirring evenly at low speed, then adding a crosslinking agent and a catalyst to mix, applying the mixture to a metal or ceramic substrate, and curing at 80-120°C for 1-2 hours. The composition dynamically regulates the thermal expansion coefficient through the phase change of the liquid crystal microcapsules, and statically reduces the CTE with ZrO2, significantly improving tensile strength, elongation at break, and thermal cycling stability, making it suitable for high-reliability electronic packaging.

Description

Technical Field

[0001] The present invention relates to the technical field of silicone rubber, in particular to a composition for preparing high-performance silicone rubber. Background Art

[0002] Polydimethylsiloxane (PDMS), a core component of silicone polymers, is widely used in the preparation of high-performance silicone rubber for electronics, medical devices, aerospace, and other fields due to its excellent flexibility, weather resistance, chemical stability, and electrical insulation. In recent years, with the advancement of electronic devices towards higher integration and higher power, the demand for PDMS-based silicone rubber in applications such as electronic packaging, flexible electronics, and high-temperature sealing has increased significantly. Existing technologies incorporate inorganic fillers (such as fumed silica and alumina) or functional modifiers (such as phenylsiloxane) into the PDMS matrix to enhance mechanical properties, thermal conductivity, or high-temperature resistance. For example, by adding highly thermally conductive fillers such as boron nitride (BN) or carbon nanotubes (CNTs), the thermal conductivity of silicone rubber can be increased from 0.3 W / m·K to 1 to 2 W / m·K, meeting the heat dissipation requirements of some electronics applications. Furthermore, UV light or addition crosslinking techniques have been used to optimize the processing properties and crosslinking network stability of silicone rubber. However, these technological advances mainly focus on improving single performance, and there are few systematic solutions for multi-functional coordinated optimization, especially in terms of coefficient of thermal expansion (CTE) matching, interface stability and adaptability to multiple working conditions.

[0003] While existing technologies have made some progress in improving the performance of PDMS-based silicone rubber, their application in electronics still faces significant technical bottlenecks, particularly in coefficient of thermal expansion (CTE) matching and interfacial stability. The CTE of conventional PDMS differs significantly from that of metal or ceramic substrates, leading to interfacial cracking or delamination due to thermal stress mismatch during thermal cycling, severely impacting the long-term reliability of electronic devices. Furthermore, the high CTE of PDMS can easily cause dimensional deformation in high-frequency circuits or multi-material packages, reducing signal transmission accuracy and package stability. Existing technologies have attempted to reduce the overall CTE by adding low-CTE fillers (such as zirconium oxide or silica powder), but high filler content often significantly increases the viscosity of the composition, reduces flexibility, and leads to processing difficulties and reduced interfacial compatibility. Furthermore, existing modification methods, which mostly rely on static adjustments, lack the ability to dynamically control the CTE, making them unsuitable for the complex thermal cycling conditions of electronic devices across diverse temperature ranges (e.g., -40°C to 150°C). These shortcomings limit the application potential of PDMS-based silicone rubber in high-performance electronic packaging. There is an urgent need to develop a new silicone rubber composition that can dynamically match CTE, maintain flexibility and enhance interfacial stability to improve its reliability and versatility under thermal cycling. Summary of the Invention

[0004] The present application provides a composition for preparing high-performance silicone rubber, comprising, in parts by mass:

[0005] 60 to 70 parts vinyl terminated polydimethylsiloxane

[0006] 10 to 20 parts of polyurethane microcapsules containing liquid crystal molecules

[0007] ZrO2 nanoparticles 10 to 15 parts

[0008] 3 to 5 parts of hydrogen siloxane

[0009] 0.01 to 0.05 parts of platinum-based catalyst.

[0010] This high-performance silicone rubber composition is composed of vinyl-terminated polydimethylsiloxane (PDMS, 60-70 parts), polyurethane microcapsules containing liquid crystal molecules (10-20 parts), ZrO2 nanoparticles (10-15 parts), hydrogenated siloxane (3-5 parts), and a platinum-based catalyst (0.01-0.05 parts). These components work synergistically to address interfacial cracking caused by the mismatch in the coefficient of thermal expansion (CTE) between PDMS and the metal / ceramic substrate. PDMS, as a matrix, provides excellent flexibility and thermal stability, while the vinyl end groups provide active sites for addition crosslinking. The polyurethane microcapsules containing liquid crystal molecules (such as 4-cyano-4'-pentylbiphenyl) undergo volume changes through phase transitions, dynamically controlling the CTE and alleviating thermal stress. ZrO2 nanoparticles statically reduce the overall CTE while simultaneously improving the compatibility of the polyurethane microcapsules with the PDMS matrix through interfacial interactions (such as hydrogen bonding or van der Waals forces). This reduces displacement or breakage of the microcapsules during thermal cycling, enhances the stability of their phase change function, and significantly improves the material's long-term stability under thermal cycling (-40°C to 150°C) while preventing interfacial cracking. Hydrogenated siloxanes and platinum-based catalysts form a stable cross-linked network through a hydrosilylation reaction, ensuring uniform dispersion of the functional components and achieving the material's overall performance. This multi-component synergistic mechanism innovatively combines static and dynamic CTE regulation to significantly enhance the reliability and flexibility of electronic packaging.

[0011] Preferably, the liquid crystal molecules in the polyurethane microcapsules are 4-cyano-4'-pentylbiphenyl.

[0012] It should be noted that 4-cyano-4'-pentylbiphenyl, as a liquid crystal molecule, realizes dynamic CTE regulation through phase transition. Combined with the synergistic effect of ZrO2, it significantly improves the interface stability, flexibility and thermal response sensitivity of silicone rubber.

[0013] Preferably, the hydrogen-containing siloxane is polymethyl hydrogen siloxane, and the hydrogen content is 0.5 wt % to 1.6 wt %.

[0014] It should be noted that the hydrogen-containing siloxane is designated as polymethylhydrogensiloxane (PMHS) and its hydrogen content is controlled in the range of 0.5 wt% to 1.6 wt%. The Si-H bonds of PMHS and the vinyl groups of vinyl-terminated polydimethylsiloxane (PDMS) undergo a hydrosilylation reaction under the action of a platinum-based catalyst to form a three-dimensional cross-linked network of moderate density. The hydrogen content precisely regulates the cross-linking density to balance flexibility and mechanical strength.

[0015] The preparation method of the composition based on high-performance silicone rubber includes the following technical steps:

[0016] Step 1. Add ZrO2 nanoparticles to vinyl-terminated polydimethylsiloxane and use a high shear mixer to evenly disperse the filler in the matrix;

[0017] Step 2. Add the prepared liquid crystal microcapsules to the PDMS-ZrO2 mixture, slowly stir until uniform, then add the hydrogen-containing siloxane crosslinker and platinum-based catalyst, and mix evenly;

[0018] Step 3: Apply the uniformly mixed mixture on the target substrate and heat-cure at 80-120° C. for 1-2 hours to complete the cross-linking reaction.

[0019] It should be noted that in step 1, ZrO2 nanoparticles are added to vinyl-terminated PDMS and dispersed using a high-shear mixer. The ZrO2 nanoparticles statically lower the overall CTE while improving the compatibility of the polyurethane microcapsules with the PDMS matrix through interfacial interactions (such as hydrogen bonding or van der Waals forces), reducing microcapsule displacement or breakage during thermal cycling and enhancing the stability of the phase change function. In step 2, polyurethane microcapsules containing liquid crystal molecules are added to the PDMS-ZrO2 mixture with slow stirring. Slow stirring prevents microcapsule breakage and protects the microcapsules' phase transition from nematic to isotropic at around 35°C. The CTE is dynamically controlled through microcapsule volume changes, alleviating thermal stress. Subsequently, a hydrogenated siloxane and a platinum-based catalyst are added to prepare for crosslinking via a hydrosilylation reaction. A moderate crosslinking density supports the stable dispersion of the functional components and maintains flexibility. In step 3, the mixture is coated on a metal or ceramic substrate and cured at 80-120°C for 1-2 hours. The mild curing conditions protect the microcapsules' phase change function while simultaneously forming a three-dimensional crosslinked network.

[0020] Preferably, the preparation method of the liquid crystal microcapsules includes: mixing 4-cyano-4'-pentylbiphenyl with water and an emulsifier, forming a stable emulsion by high-speed stirring, adding isocyanate and polyol, performing interfacial polymerization in the emulsion to polymerize it into a polyurethane shell on the surface of the liquid crystal droplets, filtering, washing and drying the microcapsules, and controlling the particle size between 10-50 μm.

[0021] It should be noted that 4-cyano-4'-pentylbiphenyl is mixed with water and an emulsifier (such as Tween 80) and stirred at high speed (5000-10000 rpm) to form a stable oil-in-water emulsion. 4-cyano-4'-pentylbiphenyl, acting as the oil phase, is dispersed into micron-sized droplets. The emulsifier reduces interfacial tension and ensures droplet stability. Subsequently, an isocyanate (such as MDI) and a polyol (such as ethylene glycol) are added to initiate polyurethane polymerization at the emulsion interface. The isocyanate and polyol react rapidly to form a polyurethane shell, which encapsulates the 4-cyano-4'-pentylbiphenyl to form microcapsules. The high mechanical strength and thermal stability of the polyurethane shell protect the 4-cyano-4'-pentylbiphenyl from damage during processing and thermal cycling (-40°C to 150°C). The nematic to isotropic phase transition of 4-cyano-4'-pentylbiphenyl at around 35°C causes the microcapsules to change in volume, dynamically controlling the CTE of the silicone rubber and alleviating thermal stress. Filtration, washing, and drying steps remove unreacted products and solvent, controlling the microcapsule particle size to 10-50 μm, ensuring uniform dispersion and phase transition efficiency within the PDMS matrix. This particle size range optimizes interfacial compatibility between the microcapsules and the matrix, preventing agglomeration or breakage. Meanwhile, a moderate particle size balances the phase transition effect with matrix flexibility. This interfacial polymerization method, combined with precise particle size control, achieves both microcapsule stability and functionality, providing a highly effective CTE control solution for electronic packaging.

[0022] Preferably, in step 1, the rotation speed of the high-speed shear mixer is 2000-3000 rpm, and the dispersion time is 30-60 minutes.

[0023] It should be noted that the high shear mixer disperses ZrO2 nanoparticles at a speed of 2000-3000 rpm for 30-60 minutes to ensure uniform dispersion, reduce CTE, enhance material stability, maintain flexibility, and improve electronic packaging reliability.

[0024] Preferably, in step 2, when the polyurethane microcapsules containing liquid crystal molecules are added, the stirring speed is 100-200 rpm.

[0025] It should be noted that it is necessary to avoid damage to the microcapsules, protect their phase change function, dynamically control the CTE, ensure uniform dispersion, and improve the stability of silicone rubber and the reliability of electronic packaging.

[0026] Preferably, the target substrate is a metal or ceramic material used in electronic devices.

[0027] It should be noted that the target substrate is the metal or ceramic material in the electronic device. Silicone rubber synergistically regulates CTE through ZrO2 and microcapsules, enhances interface adhesion, reduces thermal cycle cracking, and improves the long-term reliability of the device.

[0028] The silicone rubber composition provided by this invention significantly enhances the performance of electronic packaging applications through the synergistic effect of polyurethane microcapsules containing 4-cyano-4'-pentylbiphenyl and ZrO2 nanoparticles. The liquid crystal microcapsules undergo a phase transition at around 35°C, enabling dynamic CTE control (70-80 ppm / °C), effectively alleviating thermal stress and enhancing interfacial stability with metal / ceramic substrates. ZrO2 improves the compatibility of the microcapsules with PDMS through interfacial hydrogen bonding, statically lowering the CTE and minimizing microcracking during thermal cycling. The composition ensures crack-free operation over 1000 thermal cycles (-40°C to 150°C), with a CTE variation of less than 5% and a reduction in tensile strength and elongation at break of only 4.2-5.0%. This composition combines high tensile strength (6.8-7.2 MPa), excellent flexibility (elongation at break of 300-320%), and ease of processing, meeting the reliability requirements of highly integrated electronic devices under complex thermal conditions and possessing broad application prospects. DETAILED DESCRIPTION

[0029] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0030] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0031] Secondly, the term "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it constitute a separate or selective embodiment that is mutually exclusive with other embodiments.

[0032] Preparation Example

[0033] Preparation Example 1

[0034] The preparation method for liquid crystal microcapsules involves mixing 4-cyano-4'-pentylbiphenyl (5CB) and an emulsifier (e.g., Tween 80, 2 wt% concentration, deionized water) in a mass ratio of 1:10. The mixture is stirred at high speed (10,000 rpm for 5-10 minutes) to form a stable oil-in-water emulsion. The 5CB acts as the oil phase, dispersing it into micron-sized droplets. The emulsifier ensures droplet stability by reducing interfacial tension. Subsequently, an isocyanate (e.g., diphenylmethane diisocyanate, MDI, 1 wt%) and a polyol (e.g., ethylene glycol, 0.8 wt%) are added. A rapid polymerization reaction is initiated at the emulsion interface via interfacial polymerization (reaction temperature 60-70°C, pH 4-5, for 2-3 hours), generating a polyurethane shell that encapsulates the 5CB to form microcapsules. The filtration was performed using a 200-mesh nylon filter to remove large particles of impurities, and the unreacted products and emulsifiers were removed by washing with deionized water for three times. The product was vacuum dried at 60° C. for 12 hours to control the particle size of the microcapsules to be 10-50 μm.

[0035] Example

[0036] Example 1

[0037] Example 1 provides a composition for preparing high-performance silicone rubber and a preparation method thereof, wherein the high-performance silicone rubber composition comprises, in parts by mass:

[0038] 60 parts of vinyl terminated polydimethylsiloxane

[0039] 10 parts of polyurethane microcapsules containing liquid crystal molecules

[0040] 10 parts of ZrO2 nanoparticles

[0041] 3 parts of hydrogen siloxane

[0042] 0.05 parts of platinum-based catalyst.

[0043] The preparation method of the high-performance silicone rubber composition includes the following technical steps:

[0044] Step 1: Add 10 parts of ZrO2 nanoparticles (particle size: 10 to 50 nm, Guangdong Dongfang Zirconium Technology Co., Ltd.) to 60 parts of vinyl-terminated polydimethylsiloxane (PDMS, molecular weight approximately 50,000 g / mol, vinyl content 0.2-0.3 mol%). Mix using a high-shear mixer (3000 rpm, 30 minutes) at 25-30°C to uniformly disperse the ZrO2 in the PDMS matrix. Vacuum degassing was used to remove air bubbles during mixing to ensure a bubble-free and uniformly dispersed matrix.

[0045] Step 2: Add 10 parts of polyurethane microcapsules containing liquid crystal molecules (particle size 10-50 μm, containing 4-cyano-4'-pentylbiphenyl (5CB), Preparation Example 1) to the PDMS-ZrO2 mixture and mix at a low speed (100 rpm for 12 minutes) until uniform. This ensures the integrity of the microcapsules and protects their phase change function. Then, add 3 parts of hydrogen-containing siloxane (polymethylhydrogensiloxane, hydrogen content 1.0 wt%) and 0.05 parts of a platinum-based catalyst (Karstedt catalyst, platinum content 1-2 wt%). Stir at 100 rpm for 8 minutes to ensure uniform mixing of the components. Degas the mixture under vacuum to prevent bubbles from affecting the coating quality.

[0046] Step 3: Apply the uniformly mixed composition to a ceramic substrate (e.g., alumina, plasma-cleaned) using a doctor blade coating process, with a coating thickness of 0.5-1 mm. Heat-cure at 120°C for 1 hour to form a three-dimensional crosslinked network through a hydrosilylation reaction, resulting in a high-performance silicone rubber.

[0047] Example 2

[0048] Example 2 provides a composition for preparing high-performance silicone rubber and a preparation method thereof, wherein the high-performance silicone rubber composition comprises, in parts by mass:

[0049] 70 parts of vinyl-terminated polydimethylsiloxane

[0050] 10 parts of polyurethane microcapsules containing liquid crystal molecules

[0051] 14 parts of ZrO2 nanoparticles

[0052] 5 parts of hydrogen siloxane

[0053] 0.01 parts of platinum-based catalyst.

[0054] The preparation method of the high-performance silicone rubber composition includes the following technical steps:

[0055] Step 1: 14 parts of ZrO2 nanoparticles (particle size: 10 to 50 nm, Guangdong Dongfang Zirconium Technology Co., Ltd.) were added to 70 parts of vinyl-terminated polydimethylsiloxane (PDMS, molecular weight approximately 50,000 g / mol, vinyl content 0.2-0.3 mol%). Mixing was performed using a high-shear mixer (2000 rpm, 60 minutes) at 25-30°C to uniformly disperse the ZrO2 in the PDMS matrix. Vacuum degassing was used to remove air bubbles during mixing to ensure a bubble-free and uniformly dispersed matrix.

[0056] Step 2: Add 10 parts of polyurethane microcapsules containing liquid crystal molecules (particle size 10-50 μm, containing 4-cyano-4'-pentylbiphenyl (5CB), Preparation Example 1) to the PDMS-ZrO2 mixture and mix at a low speed (200 rpm for 12 minutes) until uniform, ensuring the integrity of the microcapsules and protecting their phase change function. Then, add 5 parts of hydrogen-containing siloxane (polymethylhydrogensiloxane, hydrogen content 1.6 wt%) and 0.01 parts of a platinum-based catalyst (Karstedt catalyst, platinum content 1-2 wt%). Stir at 200 rpm for 8 minutes to ensure uniform mixing of the components. Degas the mixture under vacuum to prevent bubbles from affecting the coating quality.

[0057] Step 3: Apply the uniformly mixed composition to a ceramic substrate (e.g., alumina, plasma-cleaned) using a doctor blade coating process, with a coating thickness of 0.5-1 mm. Heat-cure at 80°C for 2 hours to form a three-dimensional crosslinked network through a hydrosilylation reaction, resulting in a high-performance silicone rubber.

[0058] Example 3

[0059] Example 3 provides a composition for preparing high-performance silicone rubber and a preparation method thereof, wherein the high-performance silicone rubber composition comprises, in parts by mass:

[0060] 65 parts of vinyl terminated polydimethylsiloxane

[0061] 20 parts of polyurethane microcapsules containing liquid crystal molecules

[0062] 15 parts of ZrO2 nanoparticles

[0063] 4 parts of hydrogen siloxane

[0064] 0.03 parts of platinum-based catalyst.

[0065] The preparation method of the high-performance silicone rubber composition includes the following technical steps:

[0066] Step 1: Add 15 parts of ZrO2 nanoparticles (particle size: 10 to 50 nm, Guangdong Dongfang Zirconium Technology Co., Ltd.) to 65 parts of vinyl-terminated polydimethylsiloxane (PDMS, molecular weight approximately 50,000 g / mol, vinyl content 0.2-0.3 mol%). Mix using a high-shear mixer (2500 rpm, 45 minutes) at 25-30°C to uniformly disperse the ZrO2 in the PDMS matrix. Vacuum degassing was used to remove air bubbles during mixing to ensure a bubble-free and uniformly dispersed matrix.

[0067] Step 2: Add 20 parts of polyurethane microcapsules containing liquid crystal molecules (particle size 10-50 μm, containing 4-cyano-4'-pentylbiphenyl (5CB), Preparation Example 1) to the PDMS-ZrO2 mixture and mix at a low speed (150 rpm for 12 minutes) until uniform, ensuring the integrity of the microcapsules and protecting their phase change function. Then, add 4 parts of hydrogen-containing siloxane (polymethylhydrogensiloxane, hydrogen content 0.5 wt%) and 0.03 parts of a platinum-based catalyst (Karstedt catalyst, platinum content 1-2 wt%). Stir at 150 rpm for 8 minutes to ensure uniform mixing of the components. Degas the mixture under vacuum to prevent bubbles from affecting the coating quality.

[0068] Step 3: Apply the uniformly mixed composition to a ceramic substrate (e.g., alumina, plasma-cleaned) using a doctor blade coating process, with a coating thickness of 0.5-1 mm. Heat-cure at 100°C for 2 hours to form a three-dimensional crosslinked network through a hydrosilylation reaction, resulting in a high-performance silicone rubber.

[0069] Example 4

[0070] Example 4 provides a composition for preparing high-performance silicone rubber and a preparation method thereof, wherein the high-performance silicone rubber composition comprises, in parts by mass:

[0071] 60 parts of vinyl terminated polydimethylsiloxane

[0072] 15 parts of polyurethane microcapsules containing liquid crystal molecules

[0073] 10 parts of ZrO2 nanoparticles

[0074] 4 parts of hydrogen siloxane

[0075] 0.05 parts of platinum-based catalyst.

[0076] The preparation method of the high-performance silicone rubber composition includes the following technical steps:

[0077] Step 1: Add 10 parts of ZrO2 nanoparticles (particle size: 10 to 50 nm, Guangdong Dongfang Zirconium Technology Co., Ltd.) to 60 parts of vinyl-terminated polydimethylsiloxane (PDMS, molecular weight approximately 50,000 g / mol, vinyl content 0.2-0.3 mol%). Mix using a high-shear mixer (3000 rpm, 60 minutes) at 25-30°C to uniformly disperse the ZrO2 in the PDMS matrix. Vacuum degassing is used to remove air bubbles during mixing to ensure a bubble-free and uniformly dispersed matrix.

[0078] Step 2: Add 15 parts of polyurethane microcapsules containing liquid crystal molecules (particle size 10-50 μm, containing 4-cyano-4'-pentylbiphenyl (5CB), Preparation Example 1) to the PDMS-ZrO2 mixture and mix at a low speed (150 rpm for 12 minutes) until uniform, ensuring the integrity of the microcapsules and protecting their phase change function. Then, add 4 parts of hydrogen-containing siloxane (polymethylhydrogensiloxane, hydrogen content 1.2 wt%) and 0.05 parts of a platinum-based catalyst (Karstedt catalyst, platinum content 1-2 wt%). Stir at 150 rpm for 8 minutes to ensure uniform mixing of the components. Degas the mixture under vacuum to prevent bubbles from affecting the coating quality.

[0079] Step 3: Apply the uniformly mixed composition to a ceramic substrate (e.g., alumina, plasma-cleaned) using a doctor blade coating process, with a coating thickness of 0.5-1 mm. Heat-cure at 100°C for 2 hours to form a three-dimensional crosslinked network through a hydrosilylation reaction, resulting in a high-performance silicone rubber.

[0080] Control Example

[0081] Comparative Example 1

[0082] The difference between Control Example 1 and Example 1 is that the ZrO2 nanoparticles are removed and replaced with 10 parts of vinyl-terminated polydimethylsiloxane, the total amount of the composition remains unchanged, and the preparation method is changed accordingly.

[0083] Comparative Example 2

[0084] The difference between Control Example 1 and Example 1 is that the polyurethane microcapsules containing liquid crystal molecules are removed and replaced with 10 parts of vinyl-terminated polydimethylsiloxane, while keeping the total amount of the composition unchanged and changing the preparation method accordingly.

[0085] Comparative Example 3

[0086] The difference between this control example and Example 1 is that the phase change microcapsules prepared in the Chinese patent (publication number: CN109161200A) (the phase change energy storage material in Example 1 is used, the phase change microcapsules are solid-liquid phase change materials, including a core and a shell surrounding the core, the core material is an inorganic salt, the inorganic salt is calcium chloride (CaCl2·6H2O), and the shell material is polyurethane) are used instead of the polyurethane microcapsules containing liquid crystal molecules in the present application.

[0087] The preparation process is as follows: The difference between this control example and Example 1 of the present application is that the polyurethane microcapsules containing liquid crystal molecules are replaced by an equal amount of phase change microcapsules prepared using a Chinese patent (publication number: CN109161200A).

[0088] Comparative Example 4

[0089] The difference between this comparative example and Example 1 is that alumina (particle size: 10 to 50 nm, Yangzhong Zhongtianli New Materials Co., Ltd.) is used instead of zirconium oxide.

[0090] Performance testing methods

[0091] 1. Tensile strength: tested in accordance with ASTM D412;

[0092] 2. Thermal expansion coefficient: tested in accordance with ASTM E831;

[0093] 4. Elongation at break: tested in accordance with ASTM D412;

[0094] 3. Thermal Cycle Stability: The sample is placed in a test chamber and subjected to 1000 thermal cycles (cycling temperature -40°C (hold for 30 minutes) to 150°C (hold for 30 minutes), with a heating and cooling rate of 10°C / min, for 1000 cycles). The CTE, elongation at break, and tensile strength after each cycle are tested.

[0095] Table 1

[0096] Example performance Tensile strength (MPa) Elongation at break (%) CTE (ppm / ℃) Thermal cycle stability (after 1000 times) Example 1 6.8 320 80 No cracks, CTE < 5%, strength reduction 6.5MPa (4.4%), elongation 305% (4.7%) Example 2 7.2 300 75 No cracks, CTE < 4%, strength drop 6.9 MPa (4.2%), elongation 285% (5.0%) Example 3 7.0 310 70 No cracks, CTE < 4%, strength drop 6.7MPa (4.3%), elongation 295% (4.8%) Example 4 6.9 315 78 No cracks, CTE < 5%, strength drop 6.6 MPa (4.3%), elongation 300% (4.8%) Comparative Example 1 5.2 350 220 600 microcracks, CTE increased by 230 ppm / ℃, strength decreased by 4.7 MPa (9.6%), elongation decreased by 320% (8.6%) Comparative Example 2 6.0 340 150 700 microcracks, CTE increased by 160 ppm / ℃, strength decreased by 5.5 MPa (8.3%), elongation 310% (8.8%) Comparative Example 3 6.5 300 110 800 microcracks, CTE increased by 120 ppm / ℃, strength decreased by 6.0 MPa (7.7%), elongation 280% (6.7%) Comparative Example 4 6.3 310 100 700 microcracks, CTE increased by 110 ppm / ℃, strength decreased by 5.8 MPa (7.9%), elongation 290% (6.5%)

[0097] Combining Examples 1 to 4 and Table 1, we can see that Examples 1-4 exhibited tensile strengths of 6.8-7.2 MPa, elongations at break of 300-320%, and CTEs of 70-80 ppm / °C at 35-150°C. They showed no cracking after 1000 thermal cycles (-40°C to 150°C), with a CTE change of less than 5%, a decrease in tensile strength of 4.2-4.4%, and a decrease in elongation at break of 4.7-5.0%. Examples 1-4 achieve a low CTE (70-80 ppm / °C) through the synergistic effect of ZrO2 and 5CB microcapsules, effectively reducing thermal stress. Moderate crosslinking ensures both strength and flexibility, resulting in excellent thermal cycling stability (no cracking, with a decrease of less than 5%), making them suitable for electronic packaging.

[0098] Combining Example 1, Comparative Example 1, and Comparative Example 2 with Table 1, it can be seen that Example 1 has a tensile strength of 6.8 MPa, an elongation at break of 320%, a CTE of 80 ppm / °C at 35-150°C, and no cracks after 1000 thermal cycles, with a CTE change of less than 5%. The strength dropped to 6.5 MPa (a 4.4% decrease), and the elongation dropped to 305% (a 4.7% decrease). Comparative Example 1 (without ZrO2) has a tensile strength of 5.2 MPa, an elongation of 350%, and a CTE of 220 ppm / °C. After 600 cycles, microcracks appeared, the CTE increased to 230 ppm / °C, the strength dropped to 4.7 MPa (a 9.6% decrease), and the elongation dropped to 320% (an 8.6% decrease). Control Example 2 (without microcapsules) had a tensile strength of 6.0 MPa, an elongation of 340%, and a CTE of 150 ppm / °C. After 700 cycles, microcracks developed, the CTE increased to 160 ppm / °C, the strength dropped to 5.5 MPa (an 8.3% decrease), and the elongation dropped to 310% (an 8.8% decrease). Example 1, through the synergistic effect of ZrO2 and 5CB microcapsules, achieved both static (ZrO2 reduces CTE) and dynamic (5CB phase transformation regulation) CTE optimization (80 ppm / °C), surpassing both Control Example 1 (220 ppm / °C) and Control Example 2 (150 ppm / °C). ZrO2's interfacial hydrogen bonding enhanced microcapsule compatibility, reducing thermal cycling damage, while the microcapsule phase transformation absorbed stress, ensuring no cracks after 1000 cycles with a performance degradation of less than 5%, far exceeding the cracking and degradation of the control examples (6.5-9.6%), making it suitable for electronic packaging.

[0099] Combining Example 1, Comparative Example 3, and Table 1, it can be seen that Example 1 has a tensile strength of 6.8 MPa, an elongation at break of 320%, and a coefficient of thermal expansion (CTE) of 80 ppm / °C from 35°C to 150°C. No cracks were observed after 1000 thermal cycles (from -40°C to 150°C), with a CTE change of less than 5%. The tensile strength dropped to 6.5 MPa (a 4.4% decrease), and the elongation at break dropped to 305% (a 4.7% decrease). Comparative Example 3 has a tensile strength of 6.5 MPa, an elongation at break of 300%, and a CTE of 110 ppm / °C. After 800 thermal cycles, microcracks appeared, the CTE increased to 120 ppm / °C, the tensile strength dropped to 6.0 MPa (a 7.7% decrease), and the elongation at break dropped to 280% (a 6.7% decrease). Example 1 utilizes the nematic to isotropic phase transition of polyurethane microcapsules containing 4-cyano-4'-pentylbiphenyl (5CB) at 35°C, and dynamically regulates the CTE to 80 ppm / °C through volume change. This synergistic effect, combined with the static reduction effect of ZrO2 (10 parts, CTE ~10 ppm / °C), significantly reduces thermal stress mismatch. The interfacial hydrogen bonds of ZrO2 enhance the compatibility of the microcapsules with PDMS, reducing displacement or breakage during thermal cycling, ensuring no cracks after 1000 cycles and a performance degradation of less than 5%.

[0100] Combining Example 1, Comparative Example 4, and Table 1, it can be seen that Example 1 has a tensile strength of 6.8 MPa, an elongation at break of 320%, and a coefficient of thermal expansion (CTE) of 80 ppm / °C from 35°C to 150°C. No cracks were observed after 1000 thermal cycles (from -40°C to 150°C), with a CTE change of less than 5%. The tensile strength dropped to 6.5 MPa (a 4.4% decrease), and the elongation at break dropped to 305% (a 4.7% decrease). Comparative Example 4 has a tensile strength of 6.3 MPa, an elongation at break of 310%, and a CTE of 100 ppm / °C. After 700 thermal cycles, microcracks appeared, the CTE increased to 110 ppm / °C, the tensile strength dropped to 5.8 MPa (a 7.9% decrease), and the elongation at break dropped to 290% (a 6.5% decrease). Example 1 significantly reduces thermal stress mismatch by statically lowering the CTE to 80 ppm / °C using ZrO2 nanoparticles (10 parts, CTE ~10 ppm / °C) and dynamically controlling the phase transition (nematic to isotropic) of polyurethane microcapsules (10 parts) containing 4-cyano-4'-pentylbiphenyl (5CB) at 35°C. The surface hydroxyl groups of ZrO2 enhance the compatibility of the microcapsules with the PDMS matrix through hydrogen bonding, reducing displacement or damage during thermal cycling, ensuring no cracks after 1000 cycles and a performance degradation of less than 5%. Comparative Example 4 uses Al2O3 (CTE ~8 ppm / °C). Although it can also reduce CTE, its higher thermal conductivity (~30 W / m·K vs. ZrO2 ~2-3 W / m·K) and weaker interfacial interaction lead to insufficient synergy with the microcapsules, resulting in a higher CTE (100 ppm / °C). After 700 thermal cycles, microcracks appear due to stress accumulation, and the performance decreases by 6.5-7.9%. The stability is inferior to that of Example 1, verifying the superior synergistic effect of ZrO2 in interface compatibility and CTE regulation.

[0101] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein with equivalents. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A composition for preparing high-performance silicone rubber, characterized in that: In terms of mass, it includes: 60 to 70 parts vinyl terminated polydimethylsiloxane 10 to 20 parts of polyurethane microcapsules containing liquid crystal molecules ZrO2 nanoparticles 10 to 15 parts 3 to 5 parts of hydrogen siloxane 0.01 to 0.05 parts of a platinum-based catalyst; The liquid crystal molecules in the polyurethane microcapsules are 4-cyano-4'-pentylbiphenyl. The preparation method of the polyurethane microcapsules containing liquid crystal molecules includes: mixing 4-cyano-4'-pentylbiphenyl with water and an emulsifier, forming a stable emulsion through high-speed stirring, adding isocyanate and polyol, performing interfacial polymerization in the emulsion to polymerize the liquid crystal droplets into a polyurethane shell, filtering, washing and drying the microcapsules, and controlling the particle size to be between 10 and 50 μm.

2. The composition according to claim 1, characterized in that The hydrogen-containing siloxane is polymethyl hydrogen siloxane, and the hydrogen content is 0.5 wt % to 1.6 wt %.

3. The method for preparing the composition according to claim 1, wherein The following technical steps are included: Step 1. Add ZrO2 nanoparticles to vinyl-terminated polydimethylsiloxane and use a high shear mixer to evenly disperse the filler in the matrix; Step 2. Add the prepared polyurethane microcapsules containing liquid crystal molecules to the PDMS-ZrO2 mixture, slowly stir until uniform, then add the hydrogen-containing siloxane crosslinker and platinum-based catalyst, and mix evenly; Step 3: Apply the uniformly mixed mixture on the target substrate and heat-cure at 80-120° C. for 1-2 hours to complete the cross-linking reaction.

4. The preparation method according to claim 3, characterized in that In step 1, the rotation speed of the high shear mixer is 2000-3000 rpm, and the dispersion time is 30-60 minutes.

5. The preparation method according to claim 3, characterized in that In step 2, when adding the polyurethane microcapsules containing liquid crystal molecules, the stirring speed is 100-200 rpm.

6. The preparation method according to claim 3, characterized in that The target substrate is a metal or ceramic material used in electronic devices.