A high tear strength methylvinyl silicone rubber and a method for producing the same

Abstract

This application discloses a high tear strength methyl vinyl silicone rubber and its preparation method. The silicone rubber uses vinyl-containing methyl vinyl silicone rubber as raw material, compounded with a special methyl vinyl silicone rubber containing non-vinyl cyclic olefin structures, and is obtained through blending and compounding. The raw rubber and the special rubber are compounded in an appropriate mass ratio. This application constructs a spatial heterogeneous crosslinked network of "flexible matrix encapsulating rigid nodes" by controlling the difference in the content of crosslinking functional groups and the vulcanization rate between the two. This breakthrough in molecular structure design overcomes the limitations of traditional raw rubber modification, improving the material's mechanical properties while ensuring processing fluidity and avoiding pre-crosslinking during processing. It also takes into account the inherent properties of silicone rubber, such as high and low temperature resistance and aging resistance. The preparation process is simple and compatible with existing production equipment, meeting the application requirements under harsh working conditions.

Description

Technical Field

[0001] This application relates to the field of organosilicon polymer materials, specifically to a high tear strength methyl vinyl silicone rubber and its preparation method. Background Technology

[0002] Silicone rubber is an organosilicon polymer material with polysiloxane as its main chain. Its unique Si-O alternating bonding structure endows the material with a series of outstanding properties, including biocompatibility, long-term stability under high temperature and oxidative environments, resistance to ultraviolet radiation and extreme weathering, extremely low surface tension, and unique high gas permeability. Leveraging these advantages, silicone rubber has become a core raw material for key components such as high-performance seals, thermal insulation materials, precision shock-absorbing pads, stamped gaskets, and weather-resistant protective coatings. It is widely used in leather processing, plastic molding, automotive manufacturing, mold industry, electronic packaging, and medical devices, making it an indispensable special polymer material in modern industrial systems.

[0003] However, the relatively long Si-O bond length and the outward spiral arrangement of the side alkyl groups in silicone rubber result in weak van der Waals forces between the molecular chains. These intermolecular forces are significantly weaker than those in carbon-chain polymers. This structural characteristic leads to relatively low mechanical strength, especially tear strength, in silicone rubber, becoming a key bottleneck restricting its application under harsh conditions. For example, in the automotive industry, silicone rubber parts are highly susceptible to tearing failure due to stress concentration during hot mold opening or long-term dynamic stress. Therefore, improving the tear strength of silicone rubber under harsh conditions has become an important research direction in the industry.

[0004] Current research on improving the tear strength of silicone rubber mainly focuses on formulation optimization. Using general-purpose methyl vinyl silicone rubber as a base, performance improvements are achieved through compounding, blending, reinforcing fillers, structure control agents, crosslinking agents, and other additives. Related studies cover the types, amounts, and surface modifications of reinforcing fillers; the compounding and dosage control of structure control agents; optimization of crosslinking system parameters; and analysis of the structure-property relationship of crosslinking networks. However, research on improving the tear strength of methyl vinyl silicone rubber raw rubber, the core component of silicone rubber, by optimizing its molecular chain structure design and changing the type and content distribution of crosslinking functional groups is rarely reported.

[0005] Current research on modifying raw rubber to improve the tear strength of silicone rubber still focuses on the basic parameter control of traditional commercial raw rubber. Existing studies have only compared the performance differences between vinyl-terminated and methyl-terminated raw rubber, or systematically studied the effect of single vinyl content on the tear resistance of silicone rubber. Although it has been found that compounding traditional raw rubber with different vinyl contents can improve tear strength to a certain extent, the overall research has not broken through the structural framework of traditional raw rubber. It has only remained at the level of optimizing basic parameters and lacks innovative design of raw rubber molecular structure, thus failing to fundamentally solve the technical problem of insufficient tear strength of silicone rubber. Summary of the Invention

[0006] The purpose of this application is to provide a methyl vinyl silicone rubber with a novel molecular structure and high tear strength.

[0007] To achieve the above objectives, the technical solution adopted in this application is as follows: A high tear strength methyl vinyl silicone rubber is provided, the raw materials for which include raw rubber and a special rubber, wherein the special rubber contains... and / or The structure of the methyl vinyl silicone rubber, wherein the raw rubber is a methyl vinyl silicone rubber containing vinyl groups.

[0008] As a preferred embodiment, the special adhesive is methyl vinyl silicone rubber disclosed in patent number CN202310085845.4.

[0009] As a preferred embodiment, the special adhesive has the following general structural formula: Wherein, R is selected from vinyl; R' is selected from... or x and y are positive integers, and x+y is an integer between 8000 and 10000.

[0010] As a preferred embodiment, the molar fraction of crosslinking functional groups Vi* / Si in the special adhesive is 0.15%~0.5%.

[0011] As a preferred embodiment, the vinyl molar fraction Vi / Si in the raw rubber is 0.03~0.15%.

[0012] As a preferred embodiment, the difference between the molar fraction of crosslinking functional groups Vi* / Si in the special adhesive and the molar fraction of vinyl groups Vi / Si in the raw rubber is greater than 0.1%, i.e., Vi* / Si - Vi / Si > 0.1%.

[0013] As a preferred embodiment, the special adhesive has an average molecular weight of 600,000 to 800,000 g / mol, the raw rubber has an average molecular weight of 600,000 to 800,000 g / mol, and the raw rubber has a degree of polymerization of 8,000 to 10,000.

[0014] As a preferred embodiment, the molar fraction of crosslinking functional groups Vi* / Si in the special adhesive ranges from 0.16 to 0.3%, and the molar fraction of vinyl groups Vi / Si in the raw rubber ranges from 0.04 to 0.10%.

[0015] This application also provides a method for preparing high tear strength methyl vinyl silicone rubber, wherein raw rubber and special rubber are mixed and kneaded in a kneader to obtain the high tear strength methyl vinyl silicone rubber, wherein the special rubber is methyl vinyl silicone rubber prepared by the method disclosed in patent number CN202310085845.4, and the raw rubber is methyl vinyl silicone rubber containing vinyl groups.

[0016] Further preferably, the mass ratio of the raw rubber to the special rubber is 2:3 to 4:1.

[0017] Compared with the prior art, the beneficial effects of this application are as follows: (1) The high tear strength methyl vinyl silicone rubber of this application can efficiently disperse stress and hinder crack propagation by constructing a spatial heterogeneous cross-linking network. Compared with traditional methyl vinyl silicone rubber, its core mechanical properties such as tear strength and tensile strength are significantly improved, which effectively solves the technical pain point of insufficient mechanical properties of traditional silicone rubber. (2) The high tear strength methyl vinyl silicone rubber of this application relies on the differentiated design of crosslinking functional group content and vulcanization speed to avoid the pre-crosslinking problem that is easy to occur in traditional modification methods, while ensuring excellent processing fluidity. It can be directly adapted to existing silicone rubber processing equipment and production process without additional modification of process equipment, thus reducing the modification cost of production application. (3) The high tear strength methyl vinyl silicone rubber of this application breaks through the limitations of traditional raw rubber modification at the molecular structure design level. While achieving a leap in mechanical properties, it also takes into account the inherent excellent properties of silicone rubber such as high and low temperature resistance and aging resistance. It can better adapt to the application needs under harsh working conditions in the fields of chemical, mechanical and electronic industries, and greatly expand the application scenarios of the product. Attached Figure Description

[0018] Figure 1 This is a schematic diagram showing the crosslinking of traditional raw rubber with the high tear strength methyl vinyl silicone rubber of this application. Detailed Implementation

[0019] The present application will be further described below with reference to specific embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0020] The terms “comprising” and “having”, and any variations thereof, in the specification and claims of this application are intended to cover non-exclusive inclusion, for example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product, or device.

[0021] The raw materials for preparing the high tear strength methyl vinyl silicone rubber of this application include raw rubber and specialty rubber, wherein the specialty rubber contains... and / or The structure is methyl vinyl silicone rubber, and the raw rubber is methyl vinyl silicone rubber containing vinyl groups.

[0022] In some embodiments, the raw rubber is conventional commercially available methyl vinyl silicone rubber containing vinyl groups, and the specialty rubber is the methyl vinyl silicone rubber disclosed in patent number CN202310085845.4. The raw rubber accounts for 40% to 80% of the total mass, with the remainder being specialty rubber.

[0023] The general structural formula of specialty adhesives is: Wherein, R is selected from vinyl; R' is selected from... or x and y are positive integers, and x+y is an integer between 8000 and 10000.

[0024] like Figure 1 As shown, traditional raw rubber undergoes cross-linking reactions through a single functional group. This application's high tear strength methyl vinyl silicone rubber, starting with molecular structure design, introduces cyclic olefins to replace vinyl cross-linking and utilizes a special rubber compounded with raw rubber to regulate the spatial distribution of functional groups, constructing a spatial heterogeneous cross-linking network, significantly improving the tear resistance of the raw rubber. This design retains the good processing flowability of traditional raw rubber while utilizing the slow vulcanization characteristics of the special rubber to avoid pre-cross-linking problems during processing, and simultaneously provides the possibility for precise control of material properties.

[0025] This application's high tear strength methyl vinyl silicone rubber, through the compounding of specialty rubber and raw rubber, utilizes the difference in vulcanization rates between the non-vinyl cyclic olefins in the specialty rubber and the vinyl groups in the raw rubber to form a layered structure of rigid anchors and a tough skeleton. Its network structure undergoes an orderly evolution in three stages: the initial stage involves the construction of a uniform flexible skeleton. After vulcanization begins, traditional vinyl units form linear cross-links, constructing a continuous, uniform, flexible skeleton. This stage of the network has three core characteristics: moderate cross-link density, ensuring both basic elasticity and good processing fluidity; large free volume of chain segments, providing ample space for subsequent diffusion and reaction of non-vinyl cyclic olefins; and a highly uniform network structure, effectively avoiding early localized stress concentrations that could lead to vulcanization defects. Then, the rigid node formation stage begins. Due to their low reactivity, non-vinyl cyclic olefins gradually participate in the cross-linking reaction after the flexible skeleton is initially formed. Their unique cyclic structure produces two key effects: the cyclic structure with greater steric hindrance tends to aggregate in local areas rather than be uniformly dispersed in the "flexible skeleton"; the rigid bicyclic cross-linking bonds formed after the reaction can significantly increase the local modulus, thereby forming local high-density cross-linked microregions, i.e., "rigid anchor points".

[0026] The preparation method of the special adhesive has also been disclosed in patent number CN202310085845.4, and will not be repeated here.

[0027] The molar fraction of crosslinking functional groups in a molecular structure is defined as the ratio of the number of moles of crosslinking functional groups (Vi*) to the number of moles of silicon atoms (Si). Therefore, the preferred special adhesive of this application has an average molecular weight of 600,000 to 800,000 g / mol, and the range of the molar fraction of crosslinking functional groups Vi* / Si = (y+2) / (x+y+2) in its molecular structure is 0.15% to 0.5%.

[0028] The vinyl molar fraction in the molecular structure is defined as the ratio of the number of vinyl moles (Vi) to the number of silicon atoms (Si). Therefore, the degree of polymerization of the raw rubber in this application is 8,000 to 10,000, the average molecular weight is 600,000 to 800,000 g / mol, and the vinyl molar fraction Vi / Si in the molecular structure ranges from 0.03 to 0.15%.

[0029] In a preferred embodiment, the molar fraction of crosslinking functional groups Vi* / Si in the special adhesive ranges from 0.16 to 0.3%, and the molar fraction of vinyl groups Vi / Si in the raw rubber ranges from 0.04 to 0.10%.

[0030] In a preferred embodiment, the difference between the molar fraction of crosslinking functional groups Vi* / Si in the special adhesive and the molar fraction of vinyl groups Vi / Si in the raw rubber is greater than 0.1%, i.e., Vi* / Si - Vi / Si > 0.1%.

[0031] This application regulates the content of crosslinking functional groups in specialty rubbers and raw rubbers, and then utilizes the difference in vulcanization rates between non-vinyl cyclic olefins and vinyl groups, such as... Figure 1 As shown, special adhesive molecules with high functional group content first become "concentrated crosslinking points" during vulcanization, forming local crosslinking hotspots, or "high-concentration crosslinking domains." These crosslinking domains promote the further expansion of local high-density crosslinked microregions, ultimately forming nanoscale rigid nodes with a size of 5-10 nm, uniformly dispersed in the flexible continuous phase composed of traditional raw rubber, forming a heterogeneous topological structure of "flexible matrix encapsulating rigid nodes." The mechanical advantages of this structure are: the rigid nodes can act as stress concentration diffusers, effectively hindering crack propagation; the flexible matrix acts as an energy absorption buffer, absorbing energy through the stretching and slippage of molecular chains. The synergistic effect of the two can significantly improve the tear resistance and fatigue resistance of the material.

[0032] In some embodiments, specialty rubber and raw rubber with similar molecular weights can be compounded to prepare the high tear strength methyl vinyl silicone rubber of this application. If products with different molecular weight grades are to be prepared, specialty rubber and raw rubber with corresponding molecular weights can be compounded separately.

[0033] This application also provides a method for preparing high tear strength methyl vinyl silicone rubber: preparing a special rubber by mixing raw rubber and the special rubber together in a kneader at a temperature not exceeding 80 ℃ to obtain the high tear strength methyl vinyl silicone rubber of this application.

[0034] The high tear strength methyl vinyl silicone rubber of this application has the following advantages: First, by compounding a special rubber containing special crosslinking functional groups with traditional vinyl raw rubber, this application utilizes the difference in vulcanization speed between non-vinyl cyclic olefins and vinyls, as well as the difference in the content of crosslinking functional groups between the two, to construct a spatial heterogeneous crosslinking network, forming a heterogeneous topological crosslinking structure of "flexible matrix wrapping rigid nodes", which significantly improves the tear resistance of methyl vinyl silicone rubber.

[0035] Secondly, unlike existing technologies that regulate end-capping groups or vinyl content, the high tear strength methyl vinyl silicone rubber of this application redesigns the molecular structure, introduces non-vinyl cyclic olefins to crosslink with vinyl groups, regulates the spatial distribution of crosslinking functional groups, and constructs a spatial heterogeneous crosslinking network. The resulting high tear strength methyl vinyl silicone rubber possesses both good processing fluidity and avoids the problem of pre-crosslinking during processing, providing a possibility for precise control of silicone rubber material properties.

[0036] Finally, the design incorporates a special adhesive and raw rubber to form a uniform, flexible skeleton during the rapid crosslinking stage. This skeleton possesses a moderate crosslinking density and a large free volume of chain segments, ensuring good processing flowability and adaptability to the molding requirements of complex-shaped products. The subsequently formed rigid nodes impart excellent mechanical properties to the material. This "molding first, strengthening later" vulcanization characteristic solves the problem of decreased processability of traditional methyl vinyl silicone rubber after its mechanical properties are improved.

[0037] Example 1-1 Special adhesives were prepared according to the method disclosed in patent number CN202310085845.4. The molar fraction of crosslinking functional groups Vi* / Si in the special adhesives was 0.22%, and the average molecular weight was 650,000 g / mol.

[0038] Specialty rubber and raw rubber are mixed and kneaded in a kneader at a mass ratio of 1:9 to obtain the high tear strength methyl vinyl silicone rubber of this application. The raw rubber is sourced from Zhejiang Hesheng Silicon Industry Co., Ltd., with a vinyl molar fraction Vi / Si of 0.06% and an average molecular weight of 650,000 g / mol.

[0039] In Examples 1-2 to 1-9, the mass ratio of raw rubber to special rubber was adjusted to 1:4, 3:7, 2:3, 1:1, 3:2, 7:3, 4:1, and 9:1, respectively, while other preparation conditions remained the same as those in Example 1-1.

[0040] Comparative Examples 1-1 and 1-2 used only special adhesives and only raw rubber, respectively, with other preparation conditions remaining the same as those in Example 1.

[0041] Comparative Examples 1-3 used a single conventional commercial methyl vinyl silicone rubber with a vinyl molar fraction Vi / Si of 0.15% and an average molecular weight of 650,000 g / mol.

[0042] In Example 2-1, the vinyl molar fraction Vi / Si of the raw rubber was adjusted to 0.04%, and the average molecular weight was 650,000 g / mol. The crosslinking functional group molar fraction Vi* / Si of the specialty rubber was 0.3%, and the average molecular weight was 650,000 g / mol. The mass ratio of raw rubber to specialty rubber was 1:9. Other preparation conditions were the same as those in Example 1-1.

[0043] Examples 2-2 to 2-9 were prepared by adjusting the mass ratio of raw rubber to special rubber to 1:4, 3:7, 2:3, 1:1, 3:2, 7:3, 4:1, and 9:1, respectively, while keeping other preparation conditions consistent with those in Example 2-1.

[0044] Comparative Examples 2-1 and 2-2 use only special adhesives and only raw rubber, respectively, with other preparation conditions remaining consistent with those in Example 2-1.

[0045] In Example 3-1, the vinyl molar fraction Vi / Si of the raw rubber was adjusted to 0.1%, and the average molecular weight was 650,000 g / mol. The crosslinking functional group molar fraction Vi* / Si of the specialty rubber was 0.16%, and the average molecular weight was 650,000 g / mol. The mass ratio of raw rubber to specialty rubber was 1:9. Other preparation conditions were the same as those in Example 1-1.

[0046] Examples 3-2 to 3-9 were prepared by adjusting the mass ratio of raw rubber to special rubber to 1:4, 3:7, 2:3, 1:1, 3:2, 7:3, 4:1, and 9:1, respectively, while keeping other preparation conditions consistent with those in Example 3-1.

[0047] Comparative Examples 3-1 and 3-2 used only special adhesives and only raw rubber, respectively, with other preparation conditions remaining consistent with those in Example 3-1.

[0048] Comparative Example 4-1 uses two types of raw rubber for compounding. The first raw rubber has a vinyl molar fraction Vi / Si of 0.04% and an average molecular weight of 650,000 g / mol, while the second raw rubber has a vinyl molar fraction Vi / Si of 0.03% and an average molecular weight of 650,000 g / mol. The mass ratio of the first raw rubber to the second raw rubber is 1:9, and other preparation conditions are consistent with those in Example 1-1.

[0049] Comparative Examples 4-2 to 4-9 were adjusted to have a mass ratio of first raw rubber to second raw rubber of 1:4, 3:7, 2:3, 1:1, 3:2, 7:3, 4:1, and 9:1, respectively, while other preparation conditions remained the same as those in Comparative Example 4-1.

[0050] Comparative Examples 4-10 and 4-11 used only the first raw rubber and only the second raw rubber, respectively, with other preparation conditions remaining the same as those in Comparative Example 4-1.

[0051] The silicone rubber samples prepared according to the above embodiments and comparative examples were prepared as follows: 100 parts by mass of silicone rubber prepared according to each embodiment or comparative example were taken, and 40 parts by mass of fumed silica and 5 parts by mass of hydroxyl silicone oil were added and mixed evenly in a kneader. One part of vulcanizing agent DBPMH was added to a double-roll open mill, and the mixture was then uniformly sheeted. Vulcanization was performed using a hot flat vulcanizing machine at a vulcanization temperature of 175 °C. The vulcanization time was determined by the positive vulcanization time (T90) measured by a vulcanizing instrument. Subsequently, a two-stage vulcanization was performed in an electrically heated blast drying oven at 200 °C for 4 hours. The samples were allowed to mature at room temperature for 24 hours before testing.

[0052] The fumed silica is from Zhejiang Hesheng Silicon Oil Co., Ltd., product grade HS-200, with a specific surface area of ​​200 m². 2 / g; the hydroxyl silicone oil is a product of Guangdong Biaomei Silicon and Fluorine Fine Chemical Research Institute Co., Ltd., with a hydroxyl molar fraction of 6%; the vulcanizing agent is a product of Shin-Etsu Chemical Co., Ltd. of Japan, with the brand name HM-18.

[0053] Performance testing: Shore A hardness: determined according to GB / T531—1999; tensile strength and elongation at break: determined according to GB / T528—1998; tear strength: determined according to GB / T529—1999; crosslinking density: characterized by the average molar mass Mc between crosslinking points, and determined by the equilibrium swelling method.

[0054] The calculation method for the molar fraction of cross-linking functional groups in the compound system is: (0.06% × A glue amount + 0.22% × B glue amount) / (A glue amount + B glue amount).

[0055] The performance test results of Examples 1-1 to 1-9, Comparative Examples 1-1 and 1-3 are recorded in Table 1 below.

[0056] Table 1 Performance test results of Examples 1-1 to 1-9, Comparative Examples 1-1 and 1-3

[0057] As shown in Table 1, the tear strength of the vulcanized silicone rubber product first increases and then decreases as the molar fraction of crosslinking functional groups in the raw rubber increases from 0.06% to 0.22%. When the mass ratio of raw rubber to specialty rubber is in the range of 2:3 to 4:1, the silicone rubber product exhibits a high tear strength, with a maximum value of 55.7 kN / m, corresponding to a tensile strength of 11.3 MPa and an elongation at break of 787%, indicating that the silicone rubber has excellent comprehensive mechanical properties within this compounding ratio range.

[0058] The tensile strength of the silicone rubber prepared in this application does not change significantly with the increase of the molar fraction of crosslinking functional groups; the hardness shows an increasing trend; the crosslinking density Mc gradually decreases, with a gradual decrease in the early stage, and a rapid decrease after the molar fraction of crosslinking functional groups exceeds the critical value; the elongation at break does not decrease significantly in the early stage, and even shows a slight increase in the range of 2:3 to 4:1 when the mass ratio of raw rubber to special rubber is 2:3 to 4:1, and then decreases rapidly.

[0059] Examples 1-4 and Comparative Examples 1-3 show that, although the molar fractions of crosslinking functional groups are similar (0.156% vs 0.15%), Examples 1-4 exhibit significantly better tear strength and elongation at break than Comparative Examples 1-3, and also have a higher crosslinking density Mc, meaning a larger average molar mass between crosslinking points. This is because the vinyl groups in the monomethyl vinyl silicone rubber are uniformly distributed and, after curing, form a dispersed crosslinked network structure, such as... Figure 1 As shown in (a), when subjected to external force, its crosslinking bonds will break one by one, so the mechanical properties of cured silicone rubber, especially its tear resistance, are poor.

[0060] When raw rubber and specialty adhesives with different crosslinking functional group contents are compounded, the distribution of crosslinking groups becomes uneven. Specialty adhesive molecules with high crosslinking functional group content become "concentrated crosslinking points" during the curing process, forming local crosslinking hotspots, i.e., "high-concentration crosslinking domains," which are uniformly dispersed in the flexible continuous phase composed of raw rubber, forming a heterogeneous topological structure of "flexible matrix encapsulating rigid nodes," such as... Figure 1 As shown in (b). The mechanical advantages of this structure are: the rigid nodes can act as stress concentration diffusers, effectively hindering crack propagation; the flexible matrix acts as a buffer zone for energy absorption, absorbing energy through the stretching and slippage of molecular chains. The synergistic effect of the two can significantly improve the tear resistance and fatigue resistance of the material.

[0061] However, when the amount of special rubber with high crosslinking functional group content is too large, the distance between the crosslinking points will decrease due to the excessive number of concentrated crosslinking points, which will shorten the chain segments between them and lead to a decrease in the tear strength of the silicone rubber product. Therefore, in the high tear strength methyl vinyl silicone rubber of this application, the mass ratio of raw rubber to special rubber is preferably in the range of 2:3 to 4:1.

[0062] The performance test results of Examples 2-1 to 2-9, Comparative Examples 2-1 and 2-2 are recorded in Table 2 below.

[0063] Table 2 Performance test results of Examples 2-1 to 2-9, Comparative Examples 2-1 and 2-2

[0064] As shown in Table 2, the tear strength of the vulcanized silicone rubber first increased and then decreased as the molar fraction of the crosslinking functional groups in the raw rubber increased from 0.04% to 0.3%. When the mass ratio of raw rubber to specialty rubber was in the range of 2:3 to 4:1, the tear strength of the silicone rubber was at a relatively high level, with a maximum value of 55.9 kN / m, corresponding to a tensile strength of 11.4 MPa and an elongation at break of 827%. This indicates that the silicone rubber product has excellent comprehensive mechanical properties within this compounding ratio range, and the overall trend is consistent with the results of Example 1.

[0065] The performance test results of Examples 3-1 to 3-9, Comparative Examples 3-1 and 3-2 are recorded in Table 3 below.

[0066] Table 3 Performance test results of Examples 3-1 to 3-9, Comparative Examples 3-1 and 3-2

[0067] As shown in Table 3, as the molar fraction of crosslinking functional groups in the raw rubber increases from 0.1% to 0.16%, the tear strength of the vulcanized silicone rubber product first increases and then decreases, with a maximum value of only 37.8 kN / m, corresponding to a tensile strength of 9.0 MPa and an elongation at break of 720%. This is presumably because when the molar fractions of crosslinking functional groups in the two blended raw rubbers are relatively close, a relatively homogeneous crosslinking network is formed, lacking high-density crosslinked microregions that can effectively disperse stress. The resulting heterogeneous crosslinking topology is not obvious, inhibiting the heterogeneous reinforcement mechanism. Therefore, when blending, the difference between the molar fraction of crosslinking functional groups Vi* / Si of the special methyl vinyl silicone rubber and the molar fraction of vinyl groups Vi / Si of the traditional commercial methyl vinyl silicone rubber should be greater than 0.1%, i.e., Vi* / Si - Vi / Si > 0.1%.

[0068] The performance test results of Comparative Examples 4-1 to 4-11 are recorded in Table 4 below.

[0069] Table 4 Performance test results of Comparative Examples 4-1 to 4-11

[0070] As shown in Table 4, the tear strength of the vulcanized silicone rubber first increases and then decreases as the molar fraction of crosslinking functional groups in the raw rubber increases from 0.04% to 0.3%. When the mass ratio of the first raw rubber to the second raw rubber is in the range of 2:3 to 4:1, the silicone rubber exhibits a high tear strength, with a maximum value of 45.3 kN / m, corresponding to a tensile strength of 9.8 MPa and an elongation at break of 789%. This indicates that the silicone rubber has excellent comprehensive mechanical properties within this compounding ratio range, and the overall trend is consistent with that of the examples.

[0071] Analyzing the performance test results in Tables 2 and 4, the maximum tear strength of Examples 2-7 is significantly higher than that of Comparative Examples 4-7. This is because Examples 2-7 utilize the difference in vulcanization rates between non-vinyl cyclic olefins and vinyl groups to construct a spatial heterogeneous crosslinking network, forming a layered structure of "rigid anchor points + tough skeleton". Its network structure undergoes an orderly evolution in three stages: the initial stage is the construction of a uniform flexible skeleton. After vulcanization begins, traditional vinyl units form linear crosslinks, constructing a continuous, uniform flexible skeleton. This stage of the network has three core characteristics: moderate crosslink density, ensuring both basic elasticity and good processing fluidity; large free volume of chain segments, providing ample space for subsequent diffusion and reaction of non-vinyl cyclic olefins; and highly uniform network structure, effectively avoiding early local stress concentration and vulcanization defects. Then, the rigid node formation stage begins. Due to their low reactivity, non-vinyl cyclic olefins gradually participate in the cross-linking reaction after the flexible framework is initially formed. Their unique cyclic structure produces two key effects: the cyclic structure with greater steric hindrance tends to aggregate in local areas rather than be uniformly dispersed in the flexible framework; the rigid bicyclic cross-linking bonds formed after the reaction can significantly increase the local modulus, thereby forming local high-density cross-linked microregions, i.e., "rigid anchor points".

[0072] In Comparative Examples 4-1 to 4-11, both types of raw rubber are vinyl crosslinking systems with similar vulcanization rates. In the initial stage of vulcanization, rigid crosslinks begin competing for reaction sites, leading to disordered competition in the construction of the crosslinking network. This prevents the formation of the ordered crosslinking process described in this application, where "flexible skeleton precedes rigid nodes." While this synchronous competitive vulcanization mode does form the expected "concentrated crosslinking domains" to some extent, it also results in over-crosslinking in some areas due to excessive crosslinking agent, or crosslinking defects due to excessive binding of molecular chain segments, generating internal stress and ultimately limiting the improvement of the material's tear strength.

[0073] The above embodiments of the present invention focus on the differences between the embodiments. The optimization features in each embodiment that do not contradict each other can be combined to form a better implementation scheme. For the sake of brevity, they will not be described in detail here.

[0074] In summary, the high tear strength methyl vinyl silicone rubber of this application, through the compounding of a special rubber containing non-vinyl cyclic olefins with traditional methyl vinyl silicone rubber raw rubber, utilizes the differences in the content of crosslinking functional groups and the vulcanization rate of the two to construct a spatial heterogeneous crosslinking network of "flexible matrix encapsulating rigid nodes." This network can efficiently disperse stress, hinder crack propagation, and significantly improve the mechanical properties of the material, such as tear strength and tensile strength. This solution breaks through the limitations of traditional raw rubber modification at the molecular structure design level, ensuring excellent processing fluidity while avoiding pre-crosslinking during processing. It resolves the contradiction between improving the mechanical properties and decreasing the processability of traditional silicone rubber, resulting in superior overall performance compared to traditional raw rubber compounding solutions, and better adapting to the application requirements under harsh working conditions.

[0075] The basic principles, main features, and advantages of this application have been described above. Those skilled in the art should understand that this application is not limited to the above embodiments. The embodiments and descriptions in the specification are merely the principles of this application. Various changes and modifications can be made to this application without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claims. The scope of protection claimed by this application is defined by the appended claims and their equivalents.

Claims

1. A high tear strength methyl vinyl silicone rubber, characterized in that, The raw materials for preparation include raw rubber and specialty rubber, wherein the specialty rubber contains... and / or The structure of the methyl vinyl silicone rubber, wherein the raw rubber is a methyl vinyl silicone rubber containing vinyl groups.

2. The high tear strength methyl vinyl silicone rubber as described in claim 1, characterized in that, The special adhesive is the methyl vinyl silicone rubber disclosed in patent number CN202310085845.

4.

3. The high tear strength methyl vinyl silicone rubber as described in claim 2, characterized in that, The general structural formula of the special adhesive is: Wherein, R is selected from vinyl; R' is selected from... or x and y are positive integers, and x+y is an integer between 8000 and 10000.

4. The high tear strength methyl vinyl silicone rubber as described in claim 1, characterized in that, The molar fraction of crosslinking functional groups Vi* / Si in the special adhesive is 0.15%~0.5%.

5. The high tear strength methyl vinyl silicone rubber as described in claim 4, characterized in that, The vinyl molar fraction Vi / Si in the raw rubber is 0.03~0.15%.

6. The high tear strength methyl vinyl silicone rubber as described in claim 5, characterized in that, The difference between the molar fraction of crosslinking functional groups Vi* / Si in the special adhesive and the molar fraction of vinyl groups Vi / Si in the raw rubber is greater than 0.1%, i.e., Vi* / Si - Vi / Si > 0.1%.

7. The high tear strength methyl vinyl silicone rubber as described in claim 6, characterized in that, The special adhesive has an average molecular weight of 600,000 to 800,000 g / mol, the raw rubber has an average molecular weight of 600,000 to 800,000 g / mol, and the degree of polymerization of the raw rubber is 8,000 to 10,000.

8. The high tear strength methyl vinyl silicone rubber as described in claim 5, characterized in that, The crosslinking functional group molar fraction Vi* / Si in the special adhesive ranges from 0.16 to 0.3%, and the vinyl group molar fraction Vi / Si in the raw rubber ranges from 0.04 to 0.10%.

9. A method for preparing high tear strength methyl vinyl silicone rubber, characterized in that, The high tear strength methyl vinyl silicone rubber is prepared by mixing raw rubber and special rubber in a kneader. The special rubber is methyl vinyl silicone rubber prepared by the method disclosed in patent number CN202310085845.4, and the raw rubber is methyl vinyl silicone rubber containing vinyl groups.

10. The preparation method according to claim 9, characterized in that, The mass ratio of the raw rubber to the special rubber is 2:3 to 4:1.

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