High-strength tear-resistant silicone rubber composite and method of making same

Abstract

This invention discloses a high-strength tear-resistant silicone rubber composite material and its preparation method, belonging to the field of silicone rubber technology. The silicone rubber composite material comprises the following raw materials in parts by weight: 100 parts of side-chain functionalized polysiloxane, 10-30 parts of fumed silica, and 5-20 parts of multi-arm thiol crosslinking agent. The side-chain functionalized polysiloxane is prepared by a hydrosilylation reaction of 100 parts of hydrogen-containing silicone oil, 5-15 parts of allyl dimethyl sulfonate, 5-15 parts of 1-(4-vinyl-phenyl)-ethyl ketone, and 0.04-0.08 parts of a hydrosilylation catalyst, and its side chain contains both sulfonate groups and ketone groups. The silicone rubber composite material of this invention possesses excellent tear resistance, room-temperature catalyst-free self-healing function, catalyst-free multimodal reprocessability, and intrinsic antibacterial activity.

Description

Technical Field

[0001] This invention relates to the field of silicone rubber technology, specifically to a high-strength tear-resistant silicone rubber composite material and its preparation method. Background Technology

[0002] Silicone rubber is widely used in electronics, automotive, medical devices, aerospace and other fields due to its excellent resistance to high and low temperatures, electrical insulation, chemical stability and biocompatibility. However, the intermolecular forces of silicone rubber are relatively weak, and its tear strength is generally low. Low-hardness products are usually below 15 kN / m, which is difficult to meet the stringent requirements of no less than 24.5 kN / m in aerospace and other fields.

[0003] To improve the tear resistance of silicone rubber, existing technologies mainly include: (1) adding nanofillers such as fumed silica to enhance mechanical strength. However, nanofillers are prone to agglomeration and difficult to disperse. Excessive filling will lead to a sharp increase in system viscosity and a significant decrease in processing fluidity, and the reinforcing effect has a clear upper limit; (2) enhancing the network structure by adjusting the crosslinking density or introducing multifunctional crosslinking agents. Studies have shown that the crosslinking network has a more significant impact on the static tear strength of silicone rubber than the filler network. However, once the traditional covalent crosslinking network is formed, it is irreversible, and the material cannot be reprocessed or recycled; (3) introducing dynamic covalent bonds such as Diels-Alder bonds and disulfide bonds to endow the material with self-healing and recyclable properties. However, the activation of most dynamic covalent bonds depends on external conditions such as heating, ultraviolet light or catalysts, and it is difficult to achieve efficient dynamic exchange at room temperature; at the same time, the introduction of dynamic bonds often leads to a decrease in the crosslinking density of the material and a significant deterioration in mechanical properties (especially tear strength); (4) Existing antibacterial silicone rubbers mostly use surface coating or physical blending to add antibacterial agents, which have problems such as antibacterial agent precipitation, poor antibacterial durability, and damage to the mechanical properties of the matrix, making it difficult to achieve long-term stable intrinsic antibacterial properties.

[0004] In summary, existing technologies struggle to balance high-strength tear resistance with room-temperature repair or recyclability, and lack intrinsic antibacterial properties, thus hindering the sustainable development of high-performance silicone rubber in fields such as electronics, automobiles, and medicine.

[0005] In existing technologies, sulfonium salts are mainly used as cationic photoinitiators or catalysts in epoxy resin curing and silicone rubber processing. When applied to rubber, they are often used as small-molecule additives to improve resistance to thermo-oxidative aging, rather than as conventional polymer structural units. Multi-arm thiol crosslinking agents are mainly used as crosslinking agents to construct permanent crosslinked networks through thiol-ene click reactions. Currently, no publicly disclosed technical solutions have been found that introduce sulfonium salts as functional groups into polysiloxane side chains and synergistically construct dynamic crosslinked networks with multi-arm thiols.

[0006] Based on this, the present invention provides a high-strength tear-resistant silicone rubber composite material and its preparation method. By introducing hemithionyl ketal dynamic covalent bonds, sulfonium salt groups, and fumed silica, the aim is to endow the material with excellent tear resistance while achieving room temperature catalyst-free self-healing, catalyst-free multimodal reprocessing, and room temperature closed-loop chemical recycling, thus overcoming the technical bottleneck of achieving both high strength and sustainability in silicone rubber. Summary of the Invention

[0007] Therefore, the present invention provides a high-strength tear-resistant silicone rubber composite material and its preparation method to overcome the shortcomings of the prior art.

[0008] To achieve the above objectives, the present invention provides the following technical solution: According to a first aspect of the present invention, a high-strength tear-resistant silicone rubber composite material is provided, comprising the following parts by weight of raw materials: 100 parts of side-chain functionalized polysiloxane; 10-30 parts of fumed silica; 5-20 parts of multi-arm thiol crosslinking agent.

[0009] Furthermore, the side chains of the side-chain functionalized polysiloxane contain sulfonium salt groups and ketone groups.

[0010] Furthermore, the side-chain functionalized polysiloxane is composed of the following raw materials in parts by weight: 100 parts of hydrogen-containing silicone oil; Contains 5-15 parts of allyl dimethyl sulfonate; 5-15 parts of 1-(4-vinyl-phenyl)-ethyl ketone; 0.04-0.08 parts of hydrosilylation catalyst.

[0011] Furthermore, the side-chain functionalized polysiloxane is composed of the following raw materials in parts by weight: 100 parts of hydrogen-containing silicone oil; Contains 10 parts of allyl dimethyl sulfonate; 10 parts of 1-(4-vinyl-phenyl)-ethyl ketone; 0.05 parts of hydrosilylation catalyst.

[0012] Furthermore, the hydrogen-containing silicone oil is selected from side-chain type hydrogen-containing silicone oil and / or end-side composite type hydrogen-containing silicone oil.

[0013] Furthermore, the hydrogen-containing silicone oil is a side-chain type hydrogen-containing silicone oil with a Si-H bond content of 0.3wt.%-1.0wt.%.

[0014] Furthermore, the hydrosilylation catalyst is selected from at least one of zero-valent iron catalysts, iron complex catalysts, and cobalt complex catalysts.

[0015] Furthermore, the hydrosilylation catalyst is an iron complex catalyst (e.g., bis(2-ethylhexanooxy)(2-pyridyl-5-fluoro-8-diisopropylphosphoquinoline)iron(II)).

[0016] Furthermore, the multi-arm thiol crosslinking agent is selected from at least one of pentaerythritol tetra(3-mercaptopropionate), trimethylolpropane tri(3-mercaptopropionate), and dipentaerythritol hexa(3-mercaptopropionate).

[0017] According to a second aspect of the present invention, a method for preparing a high-strength tear-resistant silicone rubber composite material is provided, comprising the following steps: (1) Preparation of allyl dimethyl sulfonium salt; (2) Preparation of side-chain functionalized polysiloxanes; (3) Mix and stir the side-chain functionalized polysiloxane, multi-arm thiol crosslinking agent and fumed silica at 25-35℃ for 0.5-1h; after vacuum degassing, pour into the mold; let stand at room temperature for 12-48h to obtain silicone rubber composite material.

[0018] Furthermore, the method for preparing the allyl dimethyl sulfonium salt in step (1) is as follows: Dimethyl sulfide and allyl bromide were dissolved in anhydrous acetonitrile at a molar ratio of 1:(1-1.1) and reacted at 40-60℃ for 24-48 h. After being concentrated to 1 / 4-1 / 3 of the original volume by vacuum distillation, the mixture was washed 2-3 times with ethyl acetate, filtered, and dried under vacuum to obtain allyl dimethyl sulfonium bromide. The parameters for the vacuum distillation are as follows: temperature 30-45℃; vacuum degree -0.095MPa to -0.1MPa; The parameters for vacuum drying are as follows: temperature 50-60℃; vacuum degree -0.095MPa to -0.1MPa.

[0019] Furthermore, the method for preparing the side-chain functionalized polysiloxane in step (2) is as follows: Hydrogen-containing silicone oil, allyl dimethyl sulfonate, and 1-(4-vinyl-phenyl)-ethyl ketone were dissolved in anhydrous toluene. The system was heated to 90-100°C under a nitrogen atmosphere. A hydrosilylation catalyst was added, and the reaction was stirred for 6-10 hours. The side-chain functionalized polysiloxane was obtained by vacuum distillation. The parameters for vacuum distillation are as follows: temperature 60-70℃; vacuum degree -0.095MPa to -0.1MPa.

[0020] Furthermore, the vacuum degree of vacuum degassing in step (3) is -0.095MPa to -0.1MPa.

[0021] According to a third aspect of the present invention, the application of the silicone rubber composite material prepared by the said preparation method in electronics, automotive and medical fields is provided.

[0022] Compared with the prior art, the present invention has the following advantages: (1) The silicone rubber composite material of the present invention achieves a significant improvement in tear strength by constructing a triple network synergistic toughening mechanism of hemithionyl dynamic covalent bonds, sulfonium salt ion-dipole interactions, and fumed silica reinforcement. The mechanism is as follows: the ion-dipole interaction between the sulfonium salt cation and the polysiloxane backbone acts as a low-bond-energy non-covalent bond, which preferentially breaks during tearing and acts as a sacrificial bond to efficiently dissipate energy, forming the first line of defense; the hemithionyl dynamic covalent bonds act as dynamic covalent cross-linking points, which achieve network topological rearrangement and disperse stress concentration through reversible fracture and recombination under stress, forming the second line of defense; fumed silica, as a nano-reinforcing filler, forces crack deflection or bifurcation during crack propagation through the strong interfacial bonding between its surface silanol groups and the matrix, increasing the fracture path length, forming the third line of defense. The three lines of defense work together to form a cascade toughening effect, and the mechanisms work synergistically to enhance each other.

[0023] (2) The silicone rubber composite material of the present invention utilizes the characteristic that its hemithioketal bonds can undergo rapid dynamic exchange at room temperature without a catalyst, endowing the material with intrinsic self-healing ability. After the material is damaged, the fracture surface can be bonded at room temperature to achieve crack healing, and it still maintains a high efficiency of self-healing ability after multiple cutting and repair cycles. The mechanism is as follows: after the fracture, the sulfonium salt ion-dipole interaction on both sides of the fracture surface preferentially recombines, anchoring the molecular chain end within the effective reaction distance, significantly increasing the effective collision frequency of the hemithioketal bond exchange reaction; at the same time, the polar environment of the sulfonium salt group lowers the kinetic energy barrier of the dynamic exchange reaction, and accelerates the repair process synergistically from both physical guidance and chemical promotion levels, so that the material can achieve efficient and sustainable crack healing without any external stimulation after damage.

[0024] (3) Based on the characteristic that the hemithioketal bond in the silicone rubber composite material of the present invention can undergo quantitative solvation in chloroform at room temperature, the material of the present invention can achieve quantitative depolymerization and monomer recovery at room temperature without consuming any additional chemical reagents. The recovered monomer can be reused for material synthesis, realizing atom-economic closed-loop recycling, fundamentally solving the industry problem of the difficulty in recycling thermosetting silicone rubber.

[0025] (4) The silicone rubber composite material of the present invention can be reprocessed by various conventional industrial technologies such as compression molding, injection molding, and extrusion molding without the addition of any catalyst, and still maintains excellent mechanical properties after multiple cycles of reprocessing. The mechanism is as follows: the hemithionyl bond undergoes thermally induced reversible breakage and recombination under hot pressing conditions, enabling the cross-linked network to achieve topological rearrangement; the sulfonium salt group enhances the mobility of molecular chain segments through ion-dipole interaction, reducing the kinetic resistance of network rearrangement. The two work together to enable the material to maintain stable mechanical properties in multiple hot pressing cycles.

[0026] (5) The sulfonium salt groups on the side chains of the matrix in the silicone rubber composite material of the present invention endow the material with intrinsic antibacterial activity, eliminating the need for additional antibacterial agents and avoiding the inherent defects of traditional physically added antibacterial agents, such as easy precipitation, poor durability, and damage to the mechanical properties of the matrix. The mechanism lies in: the sulfonium salt cation (S... + Through electrostatic adsorption, it tightly binds to the negatively charged bacterial cell membrane, inserts into the phospholipid bilayer, disrupts the cell membrane potential balance and ion gradient, leading to irreversible leakage of key intracellular substances and ultimately causing bacterial death.

[0027] (6) The silicone rubber composite material of the present invention embodies the concept of green sustainability throughout its entire life cycle from synthesis to disposal: the semithioketal bonding does not require a catalyst and can be operated without solvents, avoiding the use of toxic catalysts and organic solvents in traditional silicone rubber synthesis; the room temperature self-healing function extends the service life of the material and reduces waste generation; the room temperature closed-loop chemical recycling realizes the recovery of monomers with zero chemical consumption, so that the performance of the material does not significantly decline after multiple cycles.

[0028] In summary, the silicone rubber composite material of this invention possesses excellent tear resistance, room temperature catalyst-free self-healing function, catalyst-free multimodal reprocessability, and intrinsic antibacterial activity. It breaks through the technical bottleneck of traditional silicone rubber, which makes it difficult to achieve both high performance and sustainability, and provides a new approach for the development of high-performance multifunctional silicone rubber materials. Detailed Implementation

[0029] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] According to a first aspect of the present invention, a high-strength tear-resistant silicone rubber composite material is provided, comprising the following parts by weight of raw materials: 100 parts of side-chain functionalized polysiloxane; 10-30 parts of fumed silica; 5-20 parts of multi-arm thiol crosslinking agent.

[0031] Furthermore, the side chains of the side-chain functionalized polysiloxane contain sulfonium salt groups and ketone groups.

[0032] Furthermore, the side-chain functionalized polysiloxane is composed of the following raw materials in parts by weight: 100 parts of hydrogen-containing silicone oil; Contains 5-15 parts of allyl dimethyl sulfonate; 5-15 parts of 1-(4-vinyl-phenyl)-ethyl ketone; 0.04-0.08 parts of hydrosilylation catalyst.

[0033] Furthermore, the side-chain functionalized polysiloxane is composed of the following raw materials in parts by weight: 100 parts of hydrogen-containing silicone oil; Contains 10 parts of allyl dimethyl sulfonate; 10 parts of 1-(4-vinyl-phenyl)-ethyl ketone; 0.05 parts of hydrosilylation catalyst.

[0034] Furthermore, the hydrogen-containing silicone oil is selected from side-chain type hydrogen-containing silicone oil and / or end-side composite type hydrogen-containing silicone oil.

[0035] Furthermore, the hydrogen-containing silicone oil is a side-chain type hydrogen-containing silicone oil with a Si-H bond content of 0.3wt.%-1.0wt.%.

[0036] Furthermore, the hydrosilylation catalyst is selected from at least one of zero-valent iron catalysts, iron complex catalysts, and cobalt complex catalysts.

[0037] Furthermore, the hydrosilylation catalyst is an iron complex catalyst (e.g., bis(2-ethylhexanooxy)(2-pyridyl-5-fluoro-8-diisopropylphosphoquinoline)iron(II)).

[0038] Furthermore, the multi-arm thiol crosslinking agent is selected from at least one of pentaerythritol tetra(3-mercaptopropionate), trimethylolpropane tri(3-mercaptopropionate), and dipentaerythritol hexa(3-mercaptopropionate).

[0039] According to a second aspect of the present invention, a method for preparing a high-strength tear-resistant silicone rubber composite material is provided, comprising the following steps: (1) Preparation of allyl dimethyl sulfonium salt; (2) Preparation of side-chain functionalized polysiloxanes; (3) Mix and stir the side-chain functionalized polysiloxane, multi-arm thiol crosslinking agent and fumed silica at 25-35℃ for 0.5-1h; after vacuum degassing, pour into the mold; let stand at room temperature for 12-48h to obtain silicone rubber composite material.

[0040] Furthermore, the method for preparing the allyl dimethyl sulfonium salt in step (1) is as follows: Dimethyl sulfide and allyl bromide were dissolved in anhydrous acetonitrile at a molar ratio of 1:(1-1.1) and reacted at 40-60℃ for 24-48 h. After being concentrated to 1 / 4-1 / 3 of the original volume by vacuum distillation, the mixture was washed 2-3 times with ethyl acetate, filtered, and dried under vacuum to obtain allyl dimethyl sulfonium bromide. The parameters for vacuum distillation are as follows: temperature 30-45℃; vacuum degree -0.095MPa to -0.1MPa; The parameters for vacuum drying are as follows: temperature 50-60℃; vacuum degree -0.095MPa to -0.1MPa.

[0041] Furthermore, the method for preparing the side-chain functionalized polysiloxane in step (2) is as follows: Hydrogen-containing silicone oil, allyl dimethyl sulfonate, and 1-(4-vinyl-phenyl)-ethyl ketone were dissolved in anhydrous toluene. The system was heated to 90-100°C under a nitrogen atmosphere. A hydrosilylation catalyst was added, and the reaction was stirred for 6-10 hours. The side-chain functionalized polysiloxane was obtained by vacuum distillation. The parameters for vacuum distillation are as follows: temperature 60-70℃; vacuum degree -0.095MPa to -0.1MPa.

[0042] Furthermore, the vacuum degree of vacuum degassing in step (3) is -0.095MPa to -0.1MPa.

[0043] According to a third aspect of the present invention, the application of a silicone rubber composite material prepared by the preparation method is provided in electronics, automotive and medical fields.

[0044] To better illustrate the technical effects of this invention, the following embodiments are provided.

[0045] Preparation Example 1 Preparation of allyl dimethyl sulfonium salts (1) Take a 10L three-necked flask and connect it in sequence to a reflux condenser (with a drying tube filled with CaCl2 at the top), a constant pressure dropping funnel, and a nitrogen inlet tube. Connect the outlet to a tail gas absorption bottle device (containing 2L of 10% NaOH solution); introduce nitrogen to replace the air.

[0046] (2) Under a nitrogen atmosphere, add 6L of anhydrous acetonitrile and 1243g of dimethyl sulfide to the 10L three-necked flask of step (1), and stir at 400rpm to obtain a mixture; under an ice-water bath (4℃) for cooling, slowly add 2541g of allyl bromide to the mixture through a constant pressure dropping funnel, controlling the dropping rate to 1 drop / 2s, and complete the dropping within 1.5h, with the system temperature not exceeding 30℃; after the dropping is completed, remove the ice bath and continue stirring for 30min.

[0047] (3) Heat the reaction system in step (2) to 50°C and keep it at a constant temperature for 36 hours to obtain the reaction mixture. If the system is too thick during the process, add 0.5-1L of anhydrous acetonitrile. Monitor the reaction progress by thin-layer chromatography (TLC) using a mixed solvent of petroleum ether and ethyl acetate in a volume ratio of 4:1 as the developing solvent. When the raw material spot (dimethyl sulfide) completely disappears and no new impurity spot appears, it is considered the reaction endpoint.

[0048] (4) After the reaction is completed, the reaction mixture obtained in step (3) is transferred to a rotary evaporator and distilled under reduced pressure at 35°C and -0.1 MPa to concentrate to 1 / 3 of the original volume to obtain a concentrate. Add 3 L of ethyl acetate to the concentrate, stir for 12 min, filter with a Buchner funnel, and wash the filter cake three times with ethyl acetate (2.5 L each time) until the filtrate is colorless. If the product is pale yellow, it can be recrystallized with a pre-cooled ethyl acetate-ethanol mixed solvent with a volume ratio of 5:1.

[0049] The washed concentrate was transferred to a vacuum drying oven and dried at 55°C and -0.1 MPa for 10 hours until constant weight. It was then sealed and stored in the dark to obtain allyl dimethyl sulfonium bromide, which appeared as white crystals.

[0050] Preparation Example 2 Side-chain functionalized polysiloxanes 10 kg of LY-207 hydrogen-containing silicone oil (Si-H bond content of 0.5 wt.%, purchased from Jiande Lianying Organosilicon Materials Co., Ltd.), 1 kg of allyl dimethyl sulfonate obtained in Preparation Example 1, and 1 kg of 1-(4-vinyl-phenyl)-ethyl ketone were dissolved in 25 L of anhydrous toluene. The system was heated to 95 °C under a nitrogen atmosphere. 5 g of bis(2-ethylhexanooxy)(2-pyridyl-5-fluoro-8-diisopropylphosphoquinoline)iron(II) (product number: B6618, purchased from Shanghai TCI Chemical Industry Development Co., Ltd.) was added, and the mixture was stirred for 8 h. The reaction progress was judged by monitoring the decrease of the Si-H bond peak by Fourier transform infrared spectroscopy (FTIR). After the reaction was completed, the mixture was distilled under reduced pressure at 65 °C and -0.1 MPa to obtain side-chain functionalized polysiloxane.

[0051] Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance spectroscopy (FTIR) 1 Characterization results (H NMR): FTIR: 2160cm -1 The characteristic peak of the Si-H bond at 1700 cm⁻¹ significantly decreased, indicating that the hydrosilylation reaction had proceeded fully; -1 The appearance of a new C=O bond characteristic absorption peak indicates that the ketone group has been successfully introduced into the polysiloxane side chain.

[0052] 1 ¹H NMR: The Si-H bond signal disappears at 4.7 ppm; the characteristic signal of sulfonium salt methyl appears at 3.0-3.5 ppm; the characteristic signal of ketone group adjacent methylene appears at 2.5-3.0 ppm; and the aromatic hydrogen signal of benzene ring appears at 7.2-8.0 ppm.

[0053] Quantitative determination of residual Si-H bonds: Calculate the conversion rate (%) using the following formula: ; in, A 产物 This indicates that the 2160 cm⁻¹ in the FTIR before the reaction... -1 The area ratio of the characteristic absorption peaks of the Si-H bond. A 原料 This indicates that the 2160 cm⁻¹ in the FTIR after the reaction -1 The area ratio of the characteristic absorption peaks of the Si-H bond. The results showed that the Si-H bond conversion rate was 97.8%, indicating that the grafting reaction was complete.

[0054] Preparation Example 3 Preparation of sulfonium salt-containing polysiloxanes 10 kg of LY-207 hydrogen-containing silicone oil (Si-H bond content of 0.5 wt.%, purchased from Jiande Lianying Organosilicon Materials Co., Ltd.) and 1 kg of the allyl dimethyl sulfonium salt obtained in Preparation Example 1 were dissolved in 25 L of anhydrous toluene. The system was heated to 95 °C under a nitrogen atmosphere. 5 g of bis(2-ethylhexanooxy)(2-pyridyl-5-fluoro-8-diisopropylphosphoquinoline)iron(II) (product number: B6618, purchased from Shanghai TCI Chemical Industry Development Co., Ltd.) was added, and the mixture was stirred for 8 h. The reaction progress was judged by monitoring the decrease of the Si-H bond peak by Fourier transform infrared spectroscopy (FTIR). After the reaction was completed, the mixture was distilled under reduced pressure at 65 °C and -0.1 MPa to obtain the sulfonium salt-containing polysiloxane.

[0055] Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance spectroscopy (FTIR) 1 Characterization results (H NMR): FTIR: 2160cm -1 The Si-H bond characteristic peak was significantly weakened, indicating that the hydrosilylation reaction had proceeded fully; no obvious C=O bond characteristic absorption peak was detected.

[0056] 1 ¹H NMR: The Si-H bond signal disappears at 4.7 ppm; the characteristic signal of sulfonium salt methyl appears at 3.0-3.5 ppm; no characteristic signal of methylene adjacent to ketone group appears at 2.5-3.0 ppm; and no aromatic hydrogen signal of benzene ring appears at 7.2-8.0 ppm.

[0057] Quantitative determination of residual Si-H bonds: The conversion rate (%) calculated according to the formula in Preparation Example 2 shows that the Si-H bond conversion rate is 96.9%, indicating that the grafting reaction is sufficient.

[0058] Preparation Example 4 Preparation of ketone-containing polysiloxanes 10 kg of LY-207 hydrogen-containing silicone oil (Si-H bond content of 0.5 wt.%, purchased from Jiande Lianying Organosilicon Materials Co., Ltd.) and 1 kg of 1-(4-vinyl-phenyl)-ethyl ketone were dissolved in 25 L of anhydrous toluene. The system was heated to 95 °C under a nitrogen atmosphere. 5 g of bis(2-ethylhexanooxy)(2-pyridyl-5-fluoro-8-diisopropylphosphoquinoline)iron(II) (item number: B6618, purchased from Shanghai TCI Chemical Industry Development Co., Ltd.) was added, and the mixture was stirred for 8 h. The reaction progress was judged by monitoring the decrease of the Si-H bond peak by Fourier transform infrared spectroscopy (FTIR). After the reaction was completed, the mixture was distilled under reduced pressure at 65 °C and -0.1 MPa to obtain ketone-containing polysiloxane.

[0059] Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance spectroscopy (FTIR) 1 Characterization results (H NMR): FTIR: 2160cm -1 The characteristic peak of the Si-H bond at 1700 cm⁻¹ significantly decreased, indicating that the hydrosilylation reaction had proceeded fully; -1 The appearance of a new C=O bond characteristic absorption peak indicates that the ketone group has been successfully introduced into the polysiloxane side chain.

[0060] 1 ¹H NMR: The Si-H bond signal disappears at 4.7 ppm; a characteristic signal of methylene adjacent to the ketone group appears at 2.5-3.0 ppm; an aromatic hydrogen signal of the benzene ring appears at 7.2-8.0 ppm; no characteristic signal of methyl sulfonate is found at 3.0-3.5 ppm.

[0061] Quantitative determination of residual Si-H bonds: The conversion rate (%) calculated according to the formula in Preparation Example 2 shows that the Si-H bond conversion rate is 96.3%, indicating that the grafting reaction is sufficient.

[0062] Note: The side-chain functionalized polysiloxane obtained in Preparation Example 2, the sulfonium salt-containing polysiloxane obtained in Preparation Example 3, and the ketone-containing polysiloxane obtained in Preparation Example 4 all had Si-H bond conversion rates in the range of 96.3%-97.8%, and their residual Si-H bonds were in the range of 2.2%-3.7% (approximately 0.011wt.%-0.0185wt.% of the total Si-H bonds in the raw materials). This content is lower than the quantitative detection limit of conventional infrared spectroscopy (0.071wt.%) and far lower than the minimum hydrogen content benchmark for effective crosslinking agents in addition-type silicone rubber (0.1wt.%). Therefore, in the presence of the multi-arm thiol crosslinking agent (pentaerythritol tetra(3-mercaptopropionate)), this residual amount of Si-H bonds is insufficient to initiate a detectable crosslinking reaction.

[0063] Example 1 1 kg of the side-chain functionalized polysiloxane obtained in Preparation Example 2, 200 g of fumed silica, and 100 g of pentaerythritol tetra(3-mercaptopropionate) were mixed and stirred in a planetary mixer at 30 °C for 1 h. After degassing under vacuum at -0.1 MPa, the mixture was poured into a mold and allowed to stand at room temperature for 24 h to obtain a silicone rubber composite material.

[0064] Example 2 1 kg of the side-chain functionalized polysiloxane obtained in Preparation Example 2, 150 g of fumed silica, and 200 g of pentaerythritol tetra(3-mercaptopropionate) were mixed and stirred in a planetary mixer at 30 °C for 1 h. After degassing under vacuum at -0.1 MPa, the mixture was poured into a mold and allowed to stand at room temperature for 24 h to obtain a silicone rubber composite material.

[0065] Example 3 1 kg of the side-chain functionalized polysiloxane obtained in Preparation Example 2, 300 g of fumed silica, and 50 g of pentaerythritol tetra(3-mercaptopropionate) were mixed and stirred in a planetary mixer at 30 °C for 1 h. After degassing under vacuum at -0.1 MPa, the mixture was poured into a mold and allowed to stand at room temperature for 24 h to obtain a silicone rubber composite material.

[0066] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the side-chain functionalized polysiloxane was replaced with an equal amount of the sulfonium salt-containing polysiloxane obtained in Example 3.

[0067] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the side-chain functionalized polysiloxane was replaced with an equal amount of the ketone-containing polysiloxane obtained in Example 4.

[0068] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that an equal amount of n-butanethiol (a monofunctional thiol) was used instead of pentaerythritol tetra(3-mercaptopropionate).

[0069] Test Example 1 Mechanical property testing To evaluate the mechanical properties of the silicone rubber composite material of the present invention, the tear strength and tensile strength of the silicone rubber composite materials in Examples 1-3 and Comparative Examples 1-3 were tested. The specific test methods are as follows (test environment: 23±2℃, 50±10%RH): (1) Tear strength test According to GB / T 529-2008 "Determination of Tear Strength of Vulcanized Rubber or Thermoplastic Rubber (Pants-shaped, Right-angled and Crescent-shaped Specimens)", each group of silicone rubber composite materials was cut into right-angled specimens with a thickness of (2±0.2) mm. A pre-cut notch was made at the inner corner apex of the specimen using a sharp blade, with a depth of (1±0.2) mm. The specimen was installed in the upper and lower clamps of a universal tensile testing machine, ensuring the specimen was centered and perpendicular. The specimen was stretched at a constant speed of 500 mm / min until it completely tore. The maximum tear force (N) was recorded, and the tear strength was calculated using the following formula: ( T s (kN / m) ; in, F This indicates the maximum tearing force (N). d Indicates the sample thickness (mm).

[0070] Five parallel samples were set up for each group, and the results are expressed as mean ± standard deviation.

[0071] Evaluation criteria: tear strength ≥ 35 kN / m.

[0072] (2) Tensile strength test According to GB / T 528-2009 "Determination of Tensile Stress-Strain Properties of Vulcanized Rubber or Thermoplastic Rubber", each group of silicone rubber composite materials was cut into dumbbell-shaped (Type 2) specimens with an effective tensile zone width of (6±0.5) mm and a thickness of (2±0.2) mm. The dumbbell-shaped specimens were installed in the upper and lower clamps of a universal tensile testing machine, and the clamp spacing was adjusted. The specimens were stretched at a constant speed of 500 mm / min until fracture. The maximum tensile force (N) and the change in gauge length at fracture were recorded. The tensile strength (MPa) and elongation at break (%) were calculated using the following formulas: ; in, F max This indicates the maximum tensile force (N). A Indicates the initial cross-sectional area of ​​the sample (mm²) 2 ).

[0073] ; in,L 0 indicates the initial gauge length (mm). L b Indicates the gauge length (mm) at the time of breakage.

[0074] Five parallel samples were set up for each group, and the results are expressed as mean ± standard deviation.

[0075] Evaluation criteria: tensile strength ≥ 8 MPa, 300% ≤ elongation at break ≤ 600%.

[0076] The test results are shown in Table 1 below: Table 1. Mechanical property test results of each group of silicone rubber composite materials (n=5):

[0077] Note: The silicone rubber composite material in Comparative Example 1 was not cured and therefore no tear strength or tensile strength tests were performed. Compared with Examples 1-3, the tear strength and tensile strength of the silicone rubber composite materials in Comparative Example 2 and Comparative Example 3 were significantly different. p <0.01).

[0078] It can be seen from Table 1 above: In Examples 1-3, the tear strength of the silicone rubber composite materials ranged from 37-50 kN / m, the tensile strength from 8.4-10.2 MPa, and the elongation at break from 425.8%-565.5%, all meeting the evaluation criteria. This indicates that the silicone rubber composite material of the present invention has excellent tear resistance. The mechanism is as follows: the sulfonium salt ion-dipole interaction, as a low-bond-energy non-covalent bond, preferentially breaks and dissipates energy under tear stress, forming the first line of defense; the hemithioketal dynamic covalent bond achieves network topological rearrangement through reversible fracture-reorganization, dispersing stress concentration, forming the second line of defense; the fumed silica, through the strong interfacial bonding between the surface silanol groups and the matrix, forces crack deflection and bifurcation during crack propagation, increasing the fracture path length, forming the third line of defense. The three lines of defense work together to form cascade toughening, significantly improving tear resistance through a multi-level mechanism of sacrificial bond energy dissipation, dynamic bond rearrangement, and crack deflection.

[0079] Compared to Examples 1-3, the silicone rubber composite material in Comparative Example 1, which replaced the side-chain functionalized polysiloxane with an equal amount of sulfonium-containing polysiloxane, failed to form a hemithioketal dynamic covalent crosslinking network with the thiol in the multi-arm thiol crosslinking agent because the sulfonium-containing polysiloxane only contained sulfonium groups and lacked ketone groups. Although fumed silica provided some physical reinforcement, the lack of a chemical crosslinking network resulted in a paste-like material that could not be cut into standard samples for mechanical property testing. This result confirms that ketone groups are a necessary prerequisite for constructing a hemithioketal crosslinking network.

[0080] In Comparative Example 2, where an equal amount of ketone-containing polysiloxane replaced the side-chain functionalized polysiloxane, the tear strength of the silicone rubber composite material was (26±2) kN / m, the tensile strength was (5.8±0.4) MPa, and the elongation at break was (602.0±16.6)%, all of which failed to meet the evaluation criteria. This is because the ketone-containing polysiloxane only contains ketone groups and lacks sulfonate groups. Although it can form a dynamic covalent crosslinking network of hemithioketal, it cannot construct sulfonate ion-dipole interactions. The material loses the sacrificial bond energy dissipation mechanism and cannot absorb energy through the preferential breakage of non-covalent bonds during tearing, resulting in a significantly lower tear strength than in Examples 1-3. p <0.01); Simultaneously, the lack of contribution from ion-dipole interactions to the physical cross-linking between molecular chains resulted in significantly lower tensile strength compared to groups 1-3 of Examples ( p <0.01). Its elongation at break exceeds the upper limit of the evaluation standard (600%), indicating that the low crosslinking density leads to excessive orientation and slippage of the molecular chains during stretching. This is directly related to the reduction of physical crosslinking points formed by ion-dipole interactions after the absence of sulfonate groups. Although fumed silica provides some physical reinforcement, the lack of sacrificial bond energy dissipation mechanism and physical crosslinking enhancement effect of sulfonate groups means that the material cannot effectively dissipate energy during tearing and stretching, resulting in a significant decrease in mechanical properties.

[0081] In Comparative Example 3, where pentaerythritol tetra(3-mercaptopropionate) was replaced with an equal amount of n-butanethiol, the elongation at break of the silicone rubber composite material was (497.7±14.3)%, which met the evaluation criteria. However, its tear strength was (20±2) kN / m and its tensile strength was (6.1±0.3) MPa, both of which failed to meet the evaluation criteria. This is because, during the crosslinking process, the four thiol groups of the tetrafunctional pentaerythritol tetra(3-mercaptopropionate) can react with ketone groups on different polymer chains to form multiple hemithioketal bonds, bridging the linear molecular chains into a complete three-dimensional crosslinked network. While the monofunctional n-butanethiol can react with the side-chain ketone groups to form hemithioketal bonds, it can only end-cap the polysiloxane side chains and cannot form a bridging structure between polymer chains, thus failing to construct an effective three-dimensional crosslinked network. Although fumed silica provides some physical reinforcement, the lack of a chemical crosslinking network results in a material with extremely low crosslinking density and an incomplete network structure, leading to a significantly lower tear strength compared to groups 1-3 of Examples. p <0.01). This result confirms that the multifunctional structure of the multi-arm thiol crosslinker is key to constructing a complete three-dimensional crosslinking network by forming multiple hemithioketal bonds, and that this crosslinking network is the structural basis for achieving excellent mechanical properties.

[0082] In summary, the silicone rubber composite material of this invention, through the construction of a triple network synergistic toughening system of hemithionyl ketal dynamic covalent bonds, sulfonium salt ion-dipole interactions, and fumed silica reinforcement, not only achieves a significant improvement in tear strength (≥37kN / m), but also possesses excellent tensile strength (≥8.4MPa) and elongation at break (425.8%-565.5%), providing a solid mechanical foundation for subsequent self-healing and processability performance.

[0083] Test Example 2 Room temperature self-healing performance test To evaluate the self-healing ability of the silicone rubber composite material of the present invention under room temperature conditions, the silicone rubber composite materials in Examples 1-3 and Comparative Examples 1-3 were subjected to the following tests (test environment: 23±2℃, 50±10% RH): (1) Room temperature self-healing efficiency test According to GB / T 528-2009 standard, each group of silicone rubber composite materials was cut into dumbbell-shaped (Type 2) specimens with an effective tensile zone width of (6±0.5) mm and a thickness of (2±0.2) mm. The dumbbell-shaped specimens were installed in the upper and lower clamps of a universal tensile testing machine, and the clamp spacing was adjusted. The specimens were stretched at a constant speed of 500 mm / min until fracture. The maximum tensile force (N) and the change in gauge length at fracture were recorded. The initial tensile strength was calculated using the formula corresponding to Test Example 1. s 0, MPa) and initial elongation at break ( e 0, %).

[0084] Cut the specimen completely in the middle with a clean scalpel blade, ensuring a clean and smooth cut. Place the cut surfaces of the specimen tightly together and leave it at room temperature (25±2℃) for 24 hours without applying any external pressure or heating. Calculate the tensile strength of the repaired specimen according to the formula in GB / T 528-2009 standard and Test Example 1. s h (MPa) and elongation at break ( e h The initial tensile strength repair efficiency (%) and elongation at break repair efficiency (%) after room temperature (25±2℃) repair are calculated using the following formulas: ; in, s 0 represents the initial tensile strength of the specimen (MPa). s h The tensile strength (MPa) of the sample after repair at room temperature (25±2℃) is indicated.

[0085] ; in, e0 represents the initial elongation at break of the specimen (%). e h The percentage of elongation at break after the sample was repaired at room temperature (25±2℃) is expressed as %.

[0086] Five parallel samples were set up for each group, and the results are expressed as mean ± standard deviation.

[0087] Evaluation criteria: tensile strength repair efficiency ≥80%, elongation at break repair efficiency ≥75%.

[0088] The test results are shown in Table 2 below: Table 2. Test results of the initial tensile strength repair efficiency and elongation at break repair efficiency of each group of silicone rubber composite materials after room temperature (25±2℃) repair (n=5):

[0089] Note: In Comparative Example 1, the silicone rubber composite material was not cured and therefore no room temperature self-healing efficiency test was performed. Comparative Example 3 used n-butanethiol (a monofunctional thiol), which did not form an effective three-dimensional cross-linked network and therefore lacked room temperature self-healing capability. Compared to Examples 1-3, the initial tensile strength repair efficiency and initial elongation at break repair efficiency of the silicone rubber composite material in Comparative Example 2 showed significant differences. p <0.001).

[0090] It can be seen from Table 2 above: In Examples 1-3, the initial tensile strength repair efficiency of the silicone rubber composite material after room temperature (25±2℃) repair was in the range of 82.6%-90.6%, and the initial elongation at break repair efficiency after room temperature (25±2℃) repair was in the range of 76.3%-85.9%, both meeting the evaluation criteria. This indicates that the silicone rubber composite material of the present invention, by constructing a dynamic covalent bond of hemithionyl ketal, can achieve efficient network recombination and crack overlap under room temperature and catalyst-free conditions, endowing the material with intrinsic self-healing ability.

[0091] Compared with Examples 1-3, the silicone rubber composite material in Comparative Example 2, which replaced the side-chain functionalized polysiloxane with an equal amount of ketone-containing polysiloxane, showed a first tensile strength repair efficiency of (73.9±3.0)% and a first elongation at break repair efficiency of (64.9±3.0)% after room temperature (25±2℃) repair, both failing to meet the evaluation criteria. This is because the ketone-containing polysiloxane only contains ketone groups and lacks sulfonate groups. Although it can form a hemithioketal dynamic covalent crosslinking network, it cannot construct sulfonate ion-dipole interactions, resulting in significantly lower tensile strength and elongation at break repair efficiencies compared to Examples 1-3. p<0.001). The mechanism is as follows: after fracture, the sulfonium salt ion-dipole interaction on both sides of the fracture surface preferentially and rapidly recombines as a non-covalent sacrificial bond (kinetically faster than the exchange reaction of covalent bonds), anchoring the molecular chain within the effective reaction distance and increasing the effective collision frequency of the hemithioketal bond exchange reaction; at the same time, the polar environment of the sulfonium salt group lowers the kinetic energy barrier of the dynamic exchange reaction of the hemithioketal bond, making the network recombination more complete and efficient. The two work synergistically to accelerate the repair process from both physical guidance and chemical promotion levels, significantly improving the integrity and mechanical property recovery rate of the repaired network. Although fumed silica provides a certain physical reinforcement, the self-repair function depends on the synergistic mechanism of molecular guidance and kinetic promotion of the sulfonium salt group. Without the sulfonium salt group, it is impossible to effectively guide the broken molecular chain to achieve precise docking and efficient recombination at the fracture surface, resulting in a significant decrease in repair efficiency.

[0092] In Comparative Example 3, where pentaerythritol tetra(3-mercaptopropionate) was replaced with an equal amount of n-butanethiol, the initial tensile strength and elongation at break repair efficiencies of the silicone rubber composites after room temperature (25±2℃) repair were both (0.0±0.0)%. This is because n-butanethiol is a monofunctional thiol, which, although it can form hemithioketal bonds with side-chain ketone groups, can only end-cap the polysiloxane side chains and cannot construct an effective three-dimensional cross-linked network. Therefore, the material lacks a complete network structure capable of bearing stress, and its room temperature self-healing function cannot be realized. Although fumed silica provides some physical reinforcement, physical reinforcement cannot replace the core function of the chemical cross-linked network in achieving network recombination through dynamic bond exchange during the self-healing process. This result confirms that the complete hemithioketal dynamic covalent cross-linked network constructed by the multi-arm thiol cross-linking agent is the structural basis for realizing the room temperature self-healing function.

[0093] (2) Repeated cut-off and repair cycle test Following the test method in step (1) above, the same sample was repeatedly cut, repaired, and tested 5 times. The tensile strength repair efficiency (%) and elongation at break repair efficiency (%) after the fifth cycle were calculated according to the corresponding formula in step (1).

[0094] Evaluation criteria: Tensile strength repair efficiency ≥75% after the fifth cycle of repair, and elongation at break repair efficiency ≥70% after the fifth cycle of repair.

[0095] The test results are shown in Table 3 below: Table 3. Test results of tensile strength repair efficiency and elongation at break repair efficiency of each group of silicone rubber composite materials after the fifth repair cycle (n=5):

[0096] Note: In Comparative Example 1, the silicone rubber composite material was not cured and therefore no multiple cut-and-repair cycle tests were performed. Comparative Example 3 used n-butanethiol (a monofunctional thiol), which did not form an effective three-dimensional cross-linked network and lacked room-temperature self-healing ability; therefore, no multiple cut-and-repair cycle tests were performed. Compared with Examples 1-3, the tensile strength repair efficiency and elongation at break repair efficiency of the silicone rubber composite material in Comparative Example 2 showed significant differences. p <0.001).

[0097] It can be seen from Table 3 above: In Examples 1-3, the tensile strength repair efficiency of the silicone rubber composite material after the fifth cycle of repair was within the range of 77.0%-83.2%, and the elongation at break repair efficiency was within the range of 73.9%-81.0%, both meeting the evaluation criteria. This indicates that the silicone rubber composite material of the present invention can still maintain a high level of dynamic crosslinking ability during multiple cutting and repair processes. The mechanism is that the dynamic exchange process of hemithioketal bonds does not consume any chemical reagents, and no by-products are generated during the exchange process. Therefore, the chemical integrity of the crosslinked network can be maintained in multiple cycles.

[0098] Compared with Examples 1-3, the tensile strength repair efficiency of the silicone rubber composite material in Comparative Example 2, which replaced the side-chain functionalized polysiloxane with an equal amount of ketone-containing polysiloxane, was (63.8±3.5)% and the elongation at break repair efficiency was (54.5±3.0)% after the fifth cycle of repair, both failing to meet the evaluation criteria. This is because, without the sulfonate ion-dipole interaction, the repair process relies solely on the slow exchange reaction of the hemithioketal bond, lacking the guidance and traction assistance of the ionic bond. Therefore, the tensile strength repair efficiency and elongation at break repair efficiency after the fifth cycle were significantly lower than those in Examples 1-3. p <0.001). The mechanism is as follows: after each break, the molecular chains on both sides of the fracture surface undergo random thermal motion due to the lack of ionic bond guidance and traction, making it difficult for the corresponding reaction sites to accurately dock within a finite time. After multiple cycles, this misalignment accumulation leads to a gradual decrease in the recombination efficiency of the cross-linked network, and the repair efficiency decays rapidly. This result further confirms that sulfonate groups, as self-repair guiding units, guide the fractured network to achieve efficient and precise repair through synergy with dynamic covalent bonds.

[0099] In summary, the hemithionyl ketal dynamic covalent bonds in the silicone rubber composite material of this invention provide a reversible cross-linked network, which is the chemical basis for its self-healing function. Network recombination is achieved through dynamic exchange at room temperature without a catalyst. The sulfonium salt ion-dipole interaction acts as a sacrificial bond, playing a dual synergistic role of molecular guidance and kinetic promotion during the repair process, accelerating and guiding the efficient recombination of dynamic bonds. The fumed silica reinforcement improves the load-bearing capacity of the repaired fracture surface through physical reinforcement, ensuring the mechanical reliability of the repair interface. The synergistic effect of these three factors enables the material to achieve excellent self-healing performance with an initial repair efficiency of ≥80% and ≥75% after 5 cycles under catalyst-free conditions at room temperature, breaking through the technical bottleneck of the traditional silicone rubber's inability to simultaneously achieve high strength and self-healing.

[0100] Test Example 3 Reprocessability test To evaluate the reprocessability of the silicone rubber composite material of the present invention under room temperature conditions, the silicone rubber composite materials in Examples 1-3 and Comparative Examples 1-3 were subjected to the following tests (test environment: temperature 23±2℃, relative humidity 50±10%): (1) Initial performance measurement According to GB / T 528-2009 standard, each group of silicone rubber composite materials was cut into dumbbell-shaped (Type 2) specimens with an effective tensile zone width of (6±0.5) mm and a thickness of (2±0.2) mm. The dumbbell-shaped specimens were installed in the upper and lower clamps of a universal tensile testing machine, and the clamp spacing was adjusted. The specimens were stretched at a constant speed of 500 mm / min until fracture. The maximum tensile force (N) and the change in gauge length at fracture were recorded. The initial tensile strength was calculated using the formula corresponding to Test Example 1. s 0, MPa) and initial elongation at break ( e 0, %) is used as the baseline value.

[0101] (2) First reprocessing test Each group of silicone rubber composite materials was cut into 5mm × 5mm (length × width) fragments. The fragments were placed into a metal mold and hot-pressed at 120℃ and 8MPa for 20 minutes on a flat vulcanizing machine. After naturally cooling to room temperature, the fragments were removed to obtain the reprocessed samples. The tensile strength of the reprocessed samples was calculated according to the formula in GB / T 528-2009 standard and Test Example 1. s 1, MPa) and elongation at break ( e 1%, %). Calculate the tensile strength retention rate (%) and elongation at break retention rate (%) after reprocessing using the following formulas: ; in, s 0 represents the initial tensile strength of the specimen (MPa). s1 represents the tensile strength (MPa) of the sample after the first reprocessing.

[0102] ; in, e 0 represents the initial elongation at break of the specimen (%). e 1 represents the elongation at break (%) after the first reprocessing of the sample.

[0103] Five parallel samples were set up for each group, and the results are expressed as mean ± standard deviation.

[0104] The test results are shown in Table 4 below: Table 4. Test results of tensile strength retention and elongation at break retention of each group of silicone rubber composite materials after the first reprocessing (n=5):

[0105] Note: In Comparative Example 1, the silicone rubber composite material was not cured and therefore no first reprocessing test was performed. Comparative Example 3 used n-butanethiol (a monofunctional thiol), which did not form an effective three-dimensional cross-linked network and therefore lacked reprocessability. Compared to Examples 1-3, the tensile strength retention and elongation at break retention of the silicone rubber composite material in Comparative Example 2 after the first reprocessing were significantly different. p <0.001).

[0106] It can be seen from Table 4 above: In Examples 1-3, the tensile strength retention rate of the silicone rubber composite materials after the first reprocessing was within the range of 84.7%-91.0%, and the elongation at break retention rate was within the range of 78.2%-84.4%, both meeting the evaluation criteria. This indicates that the hemithioketal dynamic covalent bonds constructed in the silicone rubber composite materials of the present invention can achieve network structure recombination through topological rearrangement under heating conditions (120℃), endowing the material with excellent processability.

[0107] Compared with Examples 1-3, the tensile strength retention rate and elongation at break retention rate of the silicone rubber composite material in Comparative Example 2, which replaced the side-chain functionalized polysiloxane with an equal amount of ketone-containing polysiloxane, were (72.0±2.9)% and (65.4±3.5)% respectively after the first reprocessing, both failing to meet the evaluation criteria. This is because the lack of sulfonate ion-dipole interaction resulted in a lack of lubrication and promotion of molecular chain segment movement by ionic bonds during hot pressing, leading to a lower efficiency of the hemithioketal bond exchange reaction and insufficient network rearrangement, thus affecting the recovery of performance after reprocessing. Therefore, the tensile strength retention rate and elongation at break retention rate after the first reprocessing were significantly lower than those in Examples 1-3. p<0.001). The mechanism is as follows: sulfonium salt groups enhance the mobility of molecular chain segments through ion-dipole interactions, reducing the kinetic resistance of topological rearrangement and enabling efficient thermally induced reversible exchange of hemithionyl bonds; the reversible cross-linked network constructed by hemithionyl bonds provides a mechanically supportive environment for the sulfonium salt groups, ensuring the full realization of their lubrication-promoting effect. Although fumed silica provides a certain physical reinforcement, its reprocessability depends on the reduction of the kinetic resistance of network rearrangement by sulfonium salt groups during hot pressing. The lack of sulfonium salt groups reduces the efficiency of network topological rearrangement, leading to a significant decrease in performance retention after reprocessing.

[0108] In Comparative Example 3, where pentaerythritol tetra(3-mercaptopropionate) was replaced with an equal amount of n-butanethiol, the tensile strength and elongation at break of the silicone rubber composites after the first reprocessing were both (0.0±0.0)%. This is because n-butanethiol is a monofunctional thiol, which, although it can form hemithioketal bonds with ketone groups, can only end-cap and cannot construct a three-dimensional cross-linked network, thus the material lacks reprocessability. Although fumed silica provides some physical reinforcement, the reprocessability depends on the topological rearrangement ability of hemithioketal bonds under hot-pressing conditions; physical reinforcement cannot replace the reversible cross-linked network constructed by dynamic covalent bonds. This result confirms that the complete hemithioketal dynamic covalent cross-linked network constructed by multi-arm thiol cross-linking agents is the structural basis for achieving reprocessability.

[0109] (3) Repeated reprocessing test The sample after the first reprocessing was cut into smaller pieces again, and the operation in step (2) above was repeated for the second, third, fourth, and fifth reprocessing. The tensile strength after the nth reprocessing was calculated according to the formula in GB / T 528-2009 standard and test example 1. s n (MPa) and elongation at break ( e n , %). Calculate the tensile strength retention rate (%) and elongation at break retention rate (%) after the nth reprocessing using the following formulas: ; in, s 0 represents the initial tensile strength of the specimen (MPa). s n This represents the tensile strength (MPa) of the specimen after the nth reprocessing, where n represents the number of reprocessing cycles (n = two, three, four, five).

[0110] ; in, e 0 represents the initial elongation at break of the specimen (%). e nThe value represents the elongation at break (%) after the nth reprocessing of the sample, where n represents the number of reprocessing operations (n ​​= two, three, four, five).

[0111] Five parallel samples were set up for each group, and the results are expressed as mean ± standard deviation.

[0112] The test results are shown in Table 5 below: Table 5. Test results of tensile strength retention and elongation at break retention of each group of silicone rubber composites after the fifth reprocessing (n=5):

[0113] Note: In Comparative Example 1, the silicone rubber composite material was not cured and therefore no reprocessing test was performed. Comparative Example 3 used n-butanethiol (a monofunctional thiol), which did not form an effective three-dimensional cross-linked network and therefore lacked reprocessing capability; therefore, no reprocessing test was performed. Compared to Examples 1-3, the tensile strength retention and elongation at break retention of the silicone rubber composite material in Comparative Example 2 after the fifth reprocessing were significantly different. p <0.001).

[0114] It can be seen from Table 5 above: In Examples 1-3, the tensile strength retention rate of the silicone rubber composite materials after the fifth reprocessing was within the range of 78.0%-85.4%, and the elongation at break retention rate was within the range of 72.0%-81.5%, both meeting the evaluation criteria. This indicates that the hemithionyl ketal dynamic covalent bonds constructed by the silicone rubber composite materials of the present invention can still maintain efficient topological rearrangement ability during multiple hot-pressing cycles. The mechanism is as follows: under hot-pressing conditions at 120°C, the hemithionyl ketal bonds undergo reversible breakage and recombination after absorbing heat energy, enabling the crosslinked network to rearrange its topological structure; simultaneously, the exchange reaction of the hemithionyl ketal bonds does not consume chemical reagents and produces no byproducts, thus maintaining the chemical integrity of the crosslinked network during multiple reprocessing cycles.

[0115] Compared with Examples 1-3, the tensile strength retention rate of the silicone rubber composite material in Comparative Example 2, which replaced the side-chain functionalized polysiloxane with an equal amount of ketone-containing polysiloxane, was (67.2±3.1)% and the elongation at break retention rate was (54.6±3.5)% after the fifth reprocessing, both failing to meet the evaluation criteria. This is because, without the sulfonate ion-dipole interaction, the reprocessing process relies solely on the thermally induced exchange reaction of the hemithioketal bond, lacking the lubrication and promoting effect of the ionic bond. This leads to a gradual decrease in network rearrangement efficiency and an accelerated decay in retention rate. Therefore, the tensile strength retention rate and elongation at break retention rate after the fifth reprocessing are significantly lower than those in Examples 1-3. p<0.001). The mechanism is as follows: sulfonium salt groups enhance the mobility of molecular chain segments through ion-dipole interactions, reducing the viscous flow activation energy of network rearrangement, thus enabling efficient thermally induced topological rearrangement of hemithionyl bonds; the reversible cross-linked network constructed by hemithionyl bonds provides a stable mechanical support environment for sulfonium salt groups, ensuring the full realization of their lubrication-promoting effect. The two synergistically constitute a positive feedback loop of ionic bond lubrication promotion and efficient dynamic bond rearrangement, significantly improving the integrity of the network structure and the recovery rate of mechanical properties after reprocessing.

[0116] In summary, in the silicone rubber composite material of this invention, the dynamic covalent bonds of hemithionyl groups provide a thermo-induced reversible cross-linking network, which is the chemical basis for reprocessing functionality. Network topological rearrangement is achieved by activating the dynamic exchange reaction through heating (120°C). The sulfonium salt ion-dipole interaction provides ion-dipole interactions; its polar groups increase the mobility of molecular chain segments during hot pressing, reduce the viscosity resistance of the hemithionyl group exchange reaction, and improve the network rearrangement efficiency, resulting in a significant improvement in performance retention after reprocessing. The fumed silica reinforcement enhances the mechanical load-bearing capacity of the reprocessed material through physical reinforcement, ensuring performance stability after multiple reprocessing cycles. The synergistic effect of these three factors results in a mechanical property retention rate of ≥76.3% after the first reprocessing and ≥73.9% after five reprocessing cycles. This fully demonstrates the sustainability of the thermo-induced topological rearrangement of the hemithionyl group dynamic covalent bonds and the synergistic enhancement mechanism of the sulfonium salt ion-dipole interaction on reprocessing efficiency, enabling the material to maintain stable mechanical properties during multiple hot pressing cycles. This provides a new approach for the development of recyclable silicone rubber materials.

[0117] Test Example 4 Intrinsic antibacterial performance test To evaluate the intrinsic antibacterial activity of the silicone rubber composite material of the present invention at room temperature, the silicone rubber composite materials in Examples 1-3 and Comparative Examples 1-3 were subjected to the following tests (test environment: 23±2℃, 50±10% RH): Referring to GB / T 31402-2023 "Determination of antibacterial activity of plastics and other non-porous materials", the following bacterial strains were selected: Gram-positive bacteria: Staphylococcus aureus ( Staphylococcus aureus subsp. aureus Rosenbach) (ATCC 6538); Gram-negative bacteria: Escherichia coli ( Escherichia coli (ATCC 8739); All were purchased from the American Type Culture Collection (ATCC, USA).

[0118] (1) Preparation of bacterial culture Staphylococcus aureus and Escherichia coli were separately inoculated onto nutrient agar slant medium and activated by incubation at 37°C for 20 h. Single colonies of the activated bacteria were picked up using an inoculation loop and inoculated into nutrient broth medium, then cultured at 37°C with shaking at 150 rpm for 16 h until the logarithmic growth phase. The bacterial suspension was diluted to 1×10⁻⁶ with phosphate buffer. 6 CFU / mL available for use.

[0119] (2) Sample preparation The silicone rubber composite materials from Examples 1-3 and Comparative Examples 1-3 were cut into 50mm × 50mm (length × width) square specimens with a thickness of approximately (2 ± 0.2) mm. Three parallel specimens were prepared for each group. A high-density polyethylene (PE) sheet of the same size was used as a blank control. All specimens and control samples were immersed in 70% ethanol solution for 1 min, rinsed three times with sterile water, and sterilized under ultraviolet light for 30 min before use.

[0120] (3) Shaking flask method test Place the prepared samples into 250 mL Erlenmeyer flasks, with three replicates per group. Add 70 mL of phosphate buffer and 1 mL of the prepared bacterial culture to each flask to achieve an inoculum concentration of approximately 1 × 10⁻⁶. 6 CFU / mL. Place the Erlenmeyer flask in a constant temperature shaking incubator and incubate at 37℃ and 150 rpm for 24 h.

[0121] (4) Colony count After incubation, remove the Erlenmeyer flasks and perform 10-fold serial dilutions of the culture medium using sterile phosphate buffer. Select 2-3 suitable dilutions, and spread 100 μL onto nutrient agar plates, with 3 parallel plates per group. Incubate the plates upside down in a 37°C incubator for 20 hours, and count the colonies. Select plates with colony counts between 30-300 CFU for counting, and calculate the antibacterial rate (%) using the following formula: ; in, N 0 represents the average viable bacteria count (CFU / mL) in the blank control group. N 1 represents the average viable count (CFU / mL) of the sample group.

[0122] Results are expressed as mean ± standard deviation.

[0123] Evaluation criteria: Antibacterial rate against Staphylococcus aureus ≥85%, antibacterial rate against Escherichia coli ≥75%.

[0124] The test results are shown in Table 6 below: Table 6. Antibacterial rate test results of silicone rubber composite materials in each group (n=3):

[0125] Note: In Comparative Example 2, the silicone rubber composite material lacked sulfonate groups in its matrix side chains, resulting in no significant antibacterial activity against Staphylococcus aureus and Escherichia coli. Compared with Examples 1-3, the antibacterial rates against Staphylococcus aureus and Escherichia coli in Comparative Example 1 and Comparative Example 3 were significantly different. p <0.001).

[0126] It can be seen from Table 6 above: In Examples 1-3, the antibacterial rates of the silicone rubber composite materials against Staphylococcus aureus ranged from 92.8% to 96.4%, and against Escherichia coli ranged from 88.7% to 93.5%, both meeting the evaluation criteria. This result fully demonstrates that the silicone rubber composite material of this invention achieves intrinsic antibacterial function through side-chain sulfonium salt groups without adding any external antibacterial agents, avoiding the inherent defects of traditional physically added antibacterial agents such as easy precipitation, poor durability, and damage to the mechanical properties of the matrix. The mechanism lies in: sulfonium salt cations (S... + By electrostatically adsorbing onto the negatively charged bacterial cell membrane, it inserts into the phospholipid bilayer, disrupting the cell membrane's potential balance and ion gradient, leading to irreversible leakage of key intracellular substances (such as potassium ions, ATP, and amino acids), ultimately causing bacterial death.

[0127] Compared with Examples 1-3, the antibacterial rate of Staphylococcus aureus and the antibacterial rate of Escherichia coli in the silicone rubber composite material of Comparative Example 1, which replaced the side-chain functionalized polysiloxane with an equal amount of sulfonium salt-containing polysiloxane, were (80.0±3.8)% and (70.9±3.4)% respectively. Although they possessed some antibacterial activity, both were significantly lower than those of Examples 1-3. p <0.001), and did not meet the evaluation criteria. This is because sulfonium-containing polysiloxanes only contain sulfonium groups and lack ketone groups, making it impossible to form a hemithioketal crosslinking network with multi-arm thiol crosslinking agents. The material is paste-like, and the sulfonium groups cannot be effectively exposed and uniformly distributed on a regular surface, thus limiting antibacterial activity. Although fumed silica provides some physical reinforcement, it lacks a regular three-dimensional network structure, and its surface reinforcement effect cannot be effectively exerted.

[0128] In comparative example two groups, where equal amounts of ketone-containing polysiloxane were used to replace side-chain functionalized polysiloxane, the antibacterial rates against Staphylococcus aureus and Escherichia coli in the silicone rubber composites were both (0.0±0.0)%. This is because the matrix side chains lack sulfonium salt groups, thus failing to provide a source of antibacterial activity. Furthermore, the hemithioketal crosslinking network itself does not possess antibacterial function; therefore, the material showed no significant antibacterial activity against either of the tested bacterial species. Although fumed silica provided some physical reinforcement, its lack of a regular three-dimensional network structure prevented its surface reinforcement effect from being effectively utilized. This result confirms that the hemithioketal crosslinking network itself does not possess antibacterial activity, and the sulfonium salt groups are the sole source of the material's intrinsic antibacterial function.

[0129] In Comparative Example 3, where pentaerythritol tetra(3-mercaptopropionate) was replaced with an equal amount of n-butanethiol, the antibacterial rate of the silicone rubber composite material against Staphylococcus aureus was (79.7±3.0)% and the antibacterial rate against Escherichia coli was (68.5±3.2)%. Although it possessed some antibacterial activity, both were significantly lower than those in Examples 1-3. p The value was <0.001), and the evaluation criteria were not met. This is because n-butanethiol is a monofunctional thiol. Although it can form hemithionyl ketal bonds with side-chain ketone groups, it can only end-cap the polysiloxane side chains and cannot construct a regular three-dimensional cross-linked network. This results in limited orderly arrangement and effective exposure of sulfonate groups on the material surface, thus hindering the full realization of antibacterial activity. Although fumed silica provides some physical reinforcement and surface support, a regular network structure is key to achieving orderly arrangement and effective exposure of sulfonate groups. Physical reinforcement alone cannot replace the structural guiding role of the chemical cross-linked network. This result further confirms that the complete hemithionyl ketal dynamic covalent cross-linked network constructed by multi-arm thiol cross-linking agents not only endows the material with excellent mechanical properties and dynamic functions, but also promotes the effective arrangement and exposure of sulfonate antibacterial groups by constructing a regular network structure, which is the structural guarantee for realizing intrinsic antibacterial function.

[0130] In summary, in the silicone rubber composite material of this invention, the dynamic covalent bonds of hemithionyl ketones construct a well-ordered three-dimensional cross-linked network, providing a structural basis for the orderly arrangement and uniform dispersion of sulfonium salt groups on the material surface; the sulfonium salt cations (S... +As the antibacterial active center, it exerts its bactericidal function. Its dynamic non-covalent cross-linking characteristics allow the sulfonate groups to maintain a certain degree of migration on the material surface, which is conducive to effective contact with bacterial cell membranes. The fumed silica reinforcement improves the surface regularity and density of the material through nano-reinforcement, further promoting the uniform distribution of sulfonate groups on the surface. The synergistic effect of these three factors enables the material to achieve excellent mechanical properties while simultaneously realizing highly efficient intrinsic antibacterial function (antibacterial rate of Staphylococcus aureus ≥92.8%, antibacterial rate of Escherichia coli ≥88.7%). This breakthrough overcomes the technical bottleneck of the difficulty in synergizing the structural performance and functional characteristics of traditional silicone rubber, and provides a new approach for the development of high-performance multifunctional silicone rubber materials.

[0131] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A high-strength tear-resistant silicone rubber composite material, characterized in that, Including the following parts by weight of raw materials: 100 parts of side-chain functionalized polysiloxane; 10-30 parts of fumed silica; 5-20 parts of multi-arm thiol crosslinking agent.

2. The high-strength tear-resistant silicone rubber composite material as described in claim 1, characterized in that, The side chains of the functionalized polysiloxane contain sulfonate groups and ketone groups.

3. The high-strength tear-resistant silicone rubber composite material as described in claim 2, characterized in that, The side-chain functionalized polysiloxane is composed of the following raw materials in parts by weight: 100 parts of hydrogen-containing silicone oil; Contains 5-15 parts of allyl dimethyl sulfonate; 5-15 parts of 1-(4-vinyl-phenyl)-ethyl ketone; 0.04-0.08 parts of hydrosilylation catalyst.

4. The high-strength tear-resistant silicone rubber composite material as described in claim 3, characterized in that, The hydrogen-containing silicone oil is selected from side-chain type hydrogen-containing silicone oil and / or end-side composite type hydrogen-containing silicone oil.

5. The high-strength tear-resistant silicone rubber composite material as described in claim 3, characterized in that, The hydrosilylation catalyst is selected from at least one of zero-valent iron catalysts, iron complex catalysts, and cobalt complex catalysts.

6. The high-strength tear-resistant silicone rubber composite material as described in claim 1, characterized in that, The multi-arm thiol crosslinking agent is selected from at least one of pentaerythritol tetra(3-mercaptopropionate), trimethylolpropane tri(3-mercaptopropionate), and dipentaerythritol hexa(3-mercaptopropionate).

7. A method for preparing a high-strength tear-resistant silicone rubber composite material, used to prepare the high-strength tear-resistant silicone rubber composite material as described in any one of claims 1-6, characterized in that, Includes the following steps: (1) Preparation of allyl dimethyl sulfonium salt; (2) Preparation of side-chain functionalized polysiloxanes; (3) Mix and stir the side-chain functionalized polysiloxane, multi-arm thiol crosslinking agent and fumed silica at 25-35℃ for 0.5-1h; after vacuum degassing, pour into the mold; let stand at room temperature for 12-48h to obtain silicone rubber composite material.

8. The preparation method according to claim 7, characterized in that, The method for preparing the allyl dimethyl sulfonium salt in step (1) is as follows: Dimethyl sulfide and allyl bromide were dissolved in anhydrous acetonitrile at a molar ratio of 1:(1-1.1) and reacted at 40-60℃ for 24-48 h. The product was then subjected to vacuum distillation, washing with ethyl acetate, filtration, and vacuum drying to obtain allyl dimethyl sulfonium bromide.

9. The preparation method according to claim 7, characterized in that, The method for preparing side-chain functionalized polysiloxanes in step (2) is as follows: Hydrogen-containing silicone oil, allyl dimethyl sulfonate, and 1-(4-vinyl-phenyl)-ethyl ketone were dissolved in anhydrous toluene. The system was heated to 90-100°C under a nitrogen atmosphere. A hydrosilylation catalyst was added, and the reaction was stirred for 6-10 hours. The side-chain functionalized polysiloxane was obtained by vacuum distillation.

10. The application of the silicone rubber composite material prepared by the preparation method according to any one of claims 7-9 in electronics, automobiles and medical fields.

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