Light-cured pyrimidone-terminated silicone rubber material and preparation method thereof

Abstract

The invention discloses a light-cured pyrimidone-terminated silicone rubber material and a preparation method thereof, and belongs to the technical field of silicone rubber materials. The photocuring type pyrimidone-terminated silicone rubber material is prepared from the following raw materials in parts by weight: 100 parts of pyrimidone-terminated polysiloxane, 0 to 60 parts of reinforcing filler, 0.5 to 4 parts of cross-linking agent and 0.1 to 0.5 part of photoinitiator, wherein the content of siloxane in the pyrimidinone-terminated polysiloxane is not less than 94 wt%. The pyrimidinone-terminated polysiloxane is used as a rubber matrix, so that the comprehensive mechanical property of the material is remarkably improved; the high-temperature-resistant silicone rubber material has the advantages that the high-temperature-resistant silicone rubber material is matched with the reinforcing filler, the cross-linking agent and the photoinitiator, so that synergistic balance of high strength, high elongation at break, low modulus and low hardness is realized, the high-temperature mechanical property is remarkably improved, and the comprehensive performance of the prepared silicone rubber material is outstanding.

Description

Technical Field

[0001] This application relates to a photocurable terminal pyrimidinone-based silicone rubber material and its preparation method, belonging to the technical field of silicone rubber materials. Background Technology

[0002] Polysiloxanes (PDMS), with their unique Si-O-Si inorganic backbone structure, possess excellent high and low temperature resistance, weather resistance, aging resistance, electrical insulation, and biocompatibility, making them widely used in high-end fields such as aerospace, electronic packaging, transportation, and medical care. However, compared to carbon-based polymer rubbers, the mechanical strength of PDMS is often less than ideal. This is because the Si-O bonds are relatively long and have large bond angles, giving the molecular chains extremely high flexibility; under thermodynamic equilibrium, the molecular chains tend to coil into random coil structures, resulting in weak intermolecular forces and low cohesive energy density. This inherent structural characteristic makes unreinforced silicone rubber have poor mechanical properties, greatly limiting its application in scenarios requiring high strength and toughness. Therefore, how to effectively improve the mechanical strength and toughness of silicone rubber while retaining its original excellent properties has always been a research focus in this field.

[0003] Chinese invention patent CN 119039787 A discloses a high-strength UV-curable silicone rubber and its preparation method. The raw materials, by mass fraction, include: 520 parts of hydroxyl-terminated modified silicone oil, 520 parts of alkoxy-terminated modified silicone oil, 2060 parts of acryloyloxy-terminated silicone oil, 2060 parts of silicone rubber reinforcing prepolymer, 110 parts of acryloyloxy-modified MQ silicone resin, 311 parts of silica, 38 parts of a polyamino silicone compound, 312 parts of a highly reactive diluent, 312 parts of a weakly reactive diluent, 0.55 parts of a moisture-curing catalyst, and 0.55 parts of a photoinitiator. This invention addresses the low strength of silicone rubber to some extent through multi-component synergy and high-filler reinforcement, but its technical solution has significant limitations: the preparation process is cumbersome. This method relies on the pre-preparation of a "silicone rubber reinforcing prepolymer" and involves the precise proportioning of various functional group silicone oils, resulting in complex procedures, low production efficiency, and difficulty in quality control. Therefore, developing a photocurable silicone rubber with simple components, no complicated processes, and excellent mechanical strength and toughness is a technical problem that urgently needs to be solved. Summary of the Invention

[0004] To address the aforementioned issues, a photocurable pyrimidinone-terminated silicone rubber material and its preparation method are provided. By using pyrimidinone-terminated polysiloxane as the rubber matrix, the overall mechanical properties of the material are significantly improved. Combined with reinforcing fillers, crosslinking agents, and photoinitiators, a synergistic balance is achieved between high strength, high elongation at break, and low modulus and hardness. This significantly enhances high-temperature mechanical properties. The combined hot-pressing and photocuring process results in high molding efficiency and strong process controllability, leading to a silicone rubber material with outstanding overall performance.

[0005] According to one aspect of this application, a photocurable pyrimidinone-based silicone rubber material is provided, comprising the following raw materials by weight: 100 parts of pyrimidinone-based polysiloxane, 0-60 parts of reinforcing filler, 0.5-4 parts of crosslinking agent, and 0.1-0.5 parts of photoinitiator; The siloxane content in the terminal pyrimidinone polysiloxane is not less than 94 wt%. The structural formula of the terminal pyrimidinone polysiloxane is shown in formula (1):

[0006] Equation (1); Wherein, R is one or more of methyl, phenyl, and ethyl, 0 < n / (m+n+p) ≤ 5%, 0 ≤ p / (m+p) ≤ 40%; and the molecular weight is 10,000 to 600,000.

[0007] Preferably, 0.1%≤n / (m+n+p)≤0.5%, and even more preferably, 0.15%≤n / (m+n+p)≤0.3%.

[0008] Preferably, 0 ≤ p / (m+p) ≤ 30%, and even more preferably, 0 ≤ p / (m+p) ≤ 20%.

[0009] Preferably, the molecular weight is 10,000 to 400,000, and even more preferably, the molecular weight is 60,000 to 200,000.

[0010] Specifically, the siloxane content in terminal pyrimidinone polysiloxanes is not less than 94 wt%, which means that the siloxane content in terminal pyrimidinone polysiloxanes refers to the ratio of the mass of siloxane in the main chain to the mass of the entire terminal pyrimidinone polysiloxane molecular chain, excluding the pyrimidinone ketone units on the terminal groups.

[0011] Preferably, the raw materials include the following by weight: 100 parts of terminal pyrimidinone polysiloxane, 30-55 parts of reinforcing filler, 2-4 parts of crosslinking agent, and 0.2-0.4 parts of photoinitiator.

[0012] Specifically, this application introduces pyrimidinone-based polysiloxanes, which, together with filler reinforcement and photocuring chemical crosslinking, successfully construct a dual "physical-chemical" network structure. The resulting silicone rubber elastomer, while maintaining the excellent high and low temperature resistance of polysiloxanes, overcomes the defects of low strength and poor toughness of traditional silicone rubbers, achieving a leapfrog improvement in mechanical properties.

[0013] Optionally, the siloxane content in the terminal pyrimidinone polysiloxane is not less than 98 wt%.

[0014] Optionally, the siloxane content in the terminal pyrimidinone polysiloxane is not less than 99 wt%.

[0015] Specifically, this application sets specific limits on the siloxane content in pyrimidinone-terminated polysiloxanes to ensure a high proportion of the siloxane backbone, enabling the material to possess the inherent high elasticity, low modulus, and excellent heat resistance of silicone rubber. Simultaneously, it controls the pyrimidinone end groups within a reasonable range to avoid excessive rigid units that could lead to increased hardness, decreased elongation, and high-temperature embrittlement. If the siloxane content is below the specified range, it will disrupt the balance between hydrogen bond reinforcement and the flexibility of the siloxane chain, resulting in insufficient material elasticity, decreased toughness, and degraded high-temperature performance.

[0016] Optionally, the crosslinking agent is a side-chain mercaptopropyl polydimethylsiloxane, with the structural formula shown in formula (2) or formula (3): Equation (2),

[0017] Equation (3) Among them, 10%≤a / (a+b)≤100%.

[0018] Specifically, this application makes specific limitations on the selection of crosslinking agents. The crosslinking agent is structurally compatible with the silicone rubber matrix, has good compatibility, high photocuring efficiency, and a uniform and stable crosslinking network. It can give full play to the reinforcing effect of the terminal pyrimidinone matrix and ensure that the material has both excellent mechanical properties and high temperature stability.

[0019] Preferably, the crosslinking agent is a side-chain mercaptopropyl polydimethylsiloxane, with the structural formula shown in formula (2): Equation (2).

[0020] Preferably, the crosslinking agent is a mercaptopropyl polydimethylsiloxane with a side chain of 52% mercaptopropyl chain segments, i.e., a / (a+b) is 52%.

[0021] Specifically, mercaptopropyl polydimethylsiloxane with a side chain of 52% mercaptopropyl units is used as a crosslinking agent, which can make the crosslinking efficiency of the system moderate and the crosslinking network uniform and stable. This ensures sufficient photocuring and excellent mechanical strength, while avoiding excessive crosslinking that leads to increased hardness and decreased toughness, thus achieving the best balance between high strength, high toughness and low modulus in the material.

[0022] Optionally, the photoinitiator includes one or more of 2,2-dimethylolpropionic acid, 2,2-dimethoxy-2-phenylacetophenone, 2-hydroxy-4-(2-hydroxyethoxy)-2-methylphenylacetophenone, 1-hydroxycyclohexylphenyl ketone, and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide.

[0023] Preferably, the photoinitiator is 2,2-dimethoxy-2-phenylacetophenone.

[0024] Optionally, the reinforcing filler includes one or more of the following: silica, carbon black, graphene, carbon nanotubes, gypsum fiber, carbon fiber, organic clay, and boron nitride.

[0025] Optionally, it may also include tea polyphenols.

[0026] Specifically, this application also includes tea polyphenols. The abundant highly reactive phenolic hydroxyl groups (-OH) in the tea polyphenol molecular skeleton undergo multi-site hydrogen bond self-assembly with the ureidopyrimidinone (UPy) groups at the ends of the polysiloxane chain. This "supramolecular synergistic effect" not only repairs the topological defects of a single UPy dimer but also constructs a high-density "multidentate physical cross-linking network." Simultaneously, based on the excellent redox potential characteristics of tea polyphenols, it acts as an "in-situ free radical trap" in the system. Similar to the superoxide dismutase (SOD) mechanism in living organisms, tea polyphenols can efficiently block free radical chain reactions at high temperatures, achieving a scavenging rate of over 98% for superoxide anions and hydrogen peroxide free radicals. This dual mechanism of "structural reinforcement-in-situ antioxidant" successfully overcomes the shortcomings of traditional single-function reinforcing agents and antioxidants. The synergistic effect of tea polyphenols and reinforcing fillers achieves simultaneous improvement in the mechanical properties and thermal stability of organosilicon elastomers.

[0027] Optionally, the amount of tea polyphenols used is 0.5 to 3 parts by weight.

[0028] According to another aspect of this application, a method for preparing the above-mentioned photocurable terminal pyrimidinone-based silicone rubber material is also provided, comprising the following steps: (1) Prepare each raw material according to the weight ratio, add the terminal pyrimidinone polysiloxane to the open mill, add reinforcing filler, and mix evenly to obtain the compound; (2) Place the compounded rubber in a two-roll mill, add crosslinking agent and photoinitiator, and pass through the mill several times to obtain the rubber compound. Place the rubber compound in a mold, heat press it in a vacuum vulcanizing machine, and then cure it by ultraviolet irradiation. After demolding, the pyrimidinone-based silicone rubber material is obtained.

[0029] Specifically, the temperature at which the mixture is uniformly mixed in step (1) is not higher than 60°C, and the mixed rubber is left to stand at room temperature for 24 hours after it is obtained.

[0030] Specifically, placing the rubber material in the mold involves placing the rubber material into the lower cavity of the metal mold, then attaching a layer of highly transparent polyester film to the surface of the rubber material, and finally covering it with the upper mold.

[0031] Specifically, ultraviolet irradiation curing is a double-sided curing process.

[0032] Specifically, this application employs a preparation process combining open mixing, hot pressing, and ultraviolet curing. First, the matrix and reinforcing filler are mixed at low temperature to ensure uniform filler dispersion and system stability. Then, a crosslinking agent and photoinitiator are added in a thin pass to ensure thorough mixing of all components. Subsequently, vacuum hot pressing effectively removes air bubbles, increases the density of the rubber compound, and ensures the mechanical stability of the product. Finally, ultraviolet irradiation curing is used, resulting in a rapid and controllable reaction with uniform crosslinking, eliminating the need for high-temperature, long-term vulcanization and reducing energy consumption and the risk of raw material degradation. The overall process is simple, streamlined, and highly operable, producing silicone rubber materials with few internal defects, a well-developed crosslinking network, and excellent overall performance.

[0033] Optionally, the temperature for hot pressing in step (2) is 50~180℃; the wavelength of ultraviolet irradiation is 254~400nm; and the time of ultraviolet irradiation is 0.25~4h.

[0034] Specifically, this application limits the hot pressing temperature and the wavelength and time of ultraviolet irradiation. If the hot pressing temperature is below 50°C, internal stress will exist and the material cannot be effectively fixed. If it is above 180°C, the end group hydrogen bonds will be excessively dissociated, affecting the mechanical properties. The wavelength and time of ultraviolet irradiation limited by this application can ensure that the material cross-linking is complete and will not cause photoaging.

[0035] Preferably, the hot pressing temperature in step (2) is 90~120℃; the ultraviolet irradiation wavelength is 330~365nm; and the ultraviolet irradiation time is 0.5~2h.

[0036] The beneficial effects of this application include, but are not limited to: 1. The photocurable terminal pyrimidinone-based silicone rubber material of this application uses terminal pyrimidinone-based polysiloxane as the matrix, which significantly improves tensile strength and elongation at break without significantly increasing molecular weight, achieving a combination of high strength and high toughness. It can maintain low hardness and good flexibility under high strength, and is suitable for scenarios with high requirements for elasticity and mechanical properties.

[0037] 2. According to the photocurable terminal pyrimidinone-based silicone rubber material of this application, the reinforcing filler and tea polyphenols form a synergistic reinforcing system. The introduction of tea polyphenols not only further improves tensile and tear strength, but also significantly improves mechanical decay at high temperature, so that the material still maintains high strength and elongation at 150℃, with outstanding high temperature stability, which solves the pain points of traditional silicone rubber being easy to soften and decrease in strength at high temperature.

[0038] 3. The photocurable terminal pyrimidinone-based silicone rubber material according to this application has a simple formulation, does not require blending with other high-strength rubbers to improve its mechanical properties, has a wide range of applications, and maintains the excellent high and low temperature resistance of silicone rubber while improving mechanical properties. It can bear high loads and be used for a long time under extreme conditions.

[0039] 4. The preparation method of the photocurable terminal pyrimidinone-based silicone rubber material according to this application adopts a combination of low-temperature open mixing, vacuum hot pressing and shaping and ultraviolet curing. The process is simple and highly controllable. The ultraviolet curing rate is fast and the crosslinking is uniform. There is no need for long-term high-temperature vulcanization, which reduces energy consumption and side reactions. The overall process has strong adaptability and is easy to scale up. The obtained silicone rubber has a perfect crosslinking network, few internal defects, and stable and excellent comprehensive performance, which has good industrial value. Attached Figure Description

[0040] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings: Figure 1 The 1H NMR spectrum of the pyrimidinone-terminated polysiloxane of Example 7 of this application; Figure 2 The 1H NMR spectrum of aminopropyl-terminated methyl vinyl polysiloxane in Comparative Example 3 of this application; Figure 3 This is a comparison chart of tensile strength and elongation at break between Example 4 and Comparative Example 1 of this application. Detailed Implementation

[0041] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0042] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of skill in the art. The reagents and raw materials used in this invention are readily available through conventional means, and unless otherwise specified, they shall be used in accordance with conventional methods in the art or as per the product instructions. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to the methods of this invention. The preferred embodiments and materials described in this patent are for illustrative purposes only.

[0043] Example 1: Preparation of a photocurable pyrimidinone-terminated silicone rubber material (1) Prepare each raw material according to the weight ratio. Add 1 kg of terminal pyrimidinone polysiloxane to the open mill. The molecular weight of the terminal pyrimidinone polysiloxane is 10,000. The siloxane content in the terminal pyrimidinone polysiloxane is 94 wt%. Mix at 40°C to obtain the compound. Let stand at room temperature for 24 h. (2) Place the compounded rubber in a two-roll mill, add 5g of crosslinking agent side chain mercaptopropyl polydimethylsiloxane and 1g of photoinitiator 2,2-dimethylolpropionic acid, and pass through the mill several times to obtain the rubber compound. After placing the rubber compound into the lower cavity of the metal mold, attach a layer of high-transparency polyester film to the surface of the rubber compound, cover it with the upper mold, and hot press it in a vacuum vulcanizing machine for shaping. The hot pressing temperature is 50℃, the hot pressing time is 10min, and the hot pressing pressure is 10MPa. Then, it is cured by ultraviolet irradiation. The ultraviolet irradiation wavelength is 254nm for double-sided curing, and the curing time is 0.25h. After demolding, the terminal pyrimidinone-based silicone rubber material is obtained.

[0044] Example 2: Preparation of a photocurable pyrimidinone-terminated silicone rubber material (1) Prepare each raw material according to the weight ratio. Add 1 kg of terminal pyrimidinone polysiloxane to the open mill. The molecular weight of terminal pyrimidinone polysiloxane is 190,000 and the siloxane content in terminal pyrimidinone polysiloxane is 99.1 wt%. Add 600 g of reinforcing filler graphene in three batches. Mix evenly at 40°C to obtain the compound. Let it stand at room temperature for 24 h. (2) Place the compounded rubber in a two-roll mill, add 40g of crosslinking agent side chain mercaptopropyl polydimethylsiloxane and 5g of photoinitiator 2,2-dimethoxy-2-phenylacetophenone, and pass through the mill several times to obtain the rubber compound. After placing the rubber compound into the lower cavity of the metal mold, attach a layer of high-transparency polyester film to the surface of the rubber compound, cover it with the upper mold, and hot press it in a vacuum vulcanizing machine for shaping. The hot pressing temperature is 180℃, the hot pressing time is 10min, and the hot pressing pressure is 10MPa. Then, it is cured by ultraviolet irradiation. The ultraviolet irradiation wavelength is 400nm for double-sided curing, and the curing time is 4h. After demolding, the terminal pyrimidinone-based silicone rubber material is obtained.

[0045] Example 3 Preparation of a photocurable pyrimidinone-terminated silicone rubber material (1) Prepare each raw material according to the weight ratio. Add 1 kg of terminal pyrimidinone polysiloxane to the open mill. The molecular weight of terminal pyrimidinone polysiloxane is 400,000 and the siloxane content in terminal pyrimidinone polysiloxane is 99.9 wt%. Add 300 g of reinforcing filler carbon fiber in three batches. Mix evenly at 40°C to obtain the compound. Let it stand at room temperature for 24 h. (2) Place the compounded rubber in a two-roll mill, add 20g of crosslinking agent side chain mercaptopropyl polydimethylsiloxane and 3g of photoinitiator 2-hydroxy-4-(2-hydroxyethoxy)-2-methylphenylacetone, and pass through the mill several times to obtain the rubber compound. After placing the rubber compound into the lower cavity of the metal mold, attach a layer of high-transparency polyester film to the surface of the rubber compound, cover it with the upper mold, and hot press it in a vacuum vulcanizing machine for shaping. The hot pressing temperature is 120℃, the hot pressing time is 10min, and the hot pressing pressure is 10MPa. Then, it is cured by ultraviolet irradiation. The ultraviolet irradiation wavelength is 330nm for double-sided curing, and the curing time is 2h. After demolding, the terminal pyrimidinone-based silicone rubber material is obtained.

[0046] Example 4: Preparation of a photocurable pyrimidinone-terminated silicone rubber material (1) Prepare each raw material according to the weight ratio. Add 1 kg of terminal pyrimidinone polysiloxane to the open mill. The molecular weight of terminal pyrimidinone polysiloxane is 190,000 and the siloxane content in terminal pyrimidinone polysiloxane is 99.1%. Add 500 g of reinforcing filler silica in three batches. Mix evenly at 40°C to obtain the compound. Let it stand at room temperature for 24 h. (2) Place the compounded rubber in a two-roll mill, add 30g of crosslinking agent side chain mercaptopropyl polydimethylsiloxane and 3.75g of photoinitiator 2,2-dimethoxy-2-phenylacetophenone, and pass through the mill several times to obtain the rubber compound. After placing the rubber compound into the lower cavity of the metal mold, attach a layer of high-transparency polyester film to the surface of the rubber compound, cover it with the upper mold, and hot press it in a vacuum vulcanizing machine for shaping. The hot pressing temperature is 110℃, the hot pressing time is 10min, and the hot pressing pressure is 10MPa. Then, it is cured by ultraviolet light irradiation. The ultraviolet light irradiation wavelength is 330nm, and it is cured on both sides for 30min each, with a total curing time of 1h. After demolding, the terminal pyrimidinone-based silicone rubber material is obtained.

[0047] Example 5 The difference between Example 5 and Example 4 is that the amount of silica is 450g, while the rest are the same.

[0048] Example 6 The difference between Example 6 and Example 4 is that the amount of silica is 400g, while the rest are the same.

[0049] Example 7 The difference between Example 7 and Example 4 is that the molecular weight of the terminal pyrimidinone polysiloxane is 60,000 and the siloxane content in the terminal pyrimidinone polysiloxane is 96.7%, while the rest are the same.

[0050] Example 8 The difference between Example 8 and Example 4 is that the molecular weight of the terminal pyrimidinone polysiloxane is 110,000 and the siloxane content in the terminal pyrimidinone polysiloxane is 98.8%, while the rest are the same.

[0051] Example 9 The difference between Example 9 and Example 4 is that step (1) involves preparing each raw material according to the weight ratio, adding 1 kg of terminal pyrimidinone polysiloxane and 30 g of tea polyphenols to chloroform, the molecular weight of terminal pyrimidinone polysiloxane is 190,000, and the siloxane content in terminal pyrimidinone polysiloxane is 99.1%, stirring at room temperature for 24 h to ensure uniform mixing, removing chloroform and drying to constant weight to obtain a dry mixture, adding the dry mixture to a two-roll mill, adding 500 g of reinforcing filler silica in three portions, mixing uniformly at 40°C to obtain a compound, and letting it stand at room temperature for 24 h; the rest are the same.

[0052] Example 10 The difference between Example 10 and Example 9 is that step (1) involves preparing each raw material according to the weight ratio, adding 1 kg of terminal pyrimidinone polysiloxane and 5 g of tea polyphenols to chloroform, the molecular weight of terminal pyrimidinone polysiloxane is 110,000, the siloxane content in terminal pyrimidinone polysiloxane is 98.8%, and the rest are the same.

[0053] Example 11 The difference between Example 10 and Example 9 is that step (1) involves preparing each raw material according to the weight ratio, adding 1 kg of terminal pyrimidinone polysiloxane and 10 g of tea polyphenols to chloroform, the molecular weight of terminal pyrimidinone polysiloxane is 110,000, the siloxane content in terminal pyrimidinone polysiloxane is 98.8%, and the rest are the same.

[0054] Comparative Example 1 The difference between Comparative Example 1 and Example 4 is that aminopropyl-terminated polysiloxane is used instead of pyrimidinone-terminated polysiloxane, the vinyl content is 0.3%, the molecular weight is 190,000, and the rest are the same.

[0055] Comparative Example 2 The difference between Comparative Example 2 and Example 4 is that aminopropyl-terminated polysiloxane was used instead of pyrimidinone-terminated polysiloxane, the vinyl content was 0.3%, the molecular weight was 60,000, and the rest were the same.

[0056] Comparative Example 3 The difference between Comparative Example 3 and Example 4 is that aminopropyl-terminated polysiloxane was used instead of pyrimidinone-terminated polysiloxane, the vinyl content was 0.3%, the molecular weight was 110,000, and the rest were the same.

[0057] Comparative Example 4 The difference between Comparative Example 4 and Example 4 is that methyl-terminated polymethylvinylsiloxane is used instead of pyrimidinone-based polysiloxane, the vinyl content is 0.3%, the molecular weight is 240,000, and the rest are the same.

[0058] Comparative Example 5 The difference between Comparative Example 5 and Example 10 is that aminopropyl-terminated polysiloxane is used instead of pyrimidinone-terminated polysiloxane, the vinyl content is 0.3%, the molecular weight is 110,000, and the rest are the same.

[0059] Comparative Example 6 The difference between Comparative Example 6 and Example 11 is that aminopropyl-terminated polysiloxane was used instead of pyrimidinone-terminated polysiloxane, the vinyl content was 0.3%, the molecular weight was 110,000, and the rest were the same.

[0060] The proportions of Examples 1-11 and Comparative Examples 1-6 are listed in Table 1.

[0061] Table 1. Proportioning Table

[0062] Experimental Example 1 The silicone rubber materials prepared in Examples 1-11 and Comparative Examples 1-6 were tested for performance according to the national standard GB / T-528-2009. The tests were conducted on an electronic universal testing machine at a speed of 500 mm / min. Each sample was subjected to five parallel experiments, and the average value was taken. The test results are shown in Table 2.

[0063] Table 2 Mechanical property test results

[0064] like Figures 1-2 As shown, Figure 1 The 1H NMR spectrum of the pyrimidinone-terminated polysiloxane of Example 7 of this application; Figure 2 The image shows the 1H NMR spectrum of the aminopropyl-terminated methyl vinyl polysiloxane in Comparative Example 3 of this application. Figure 1 and Figure 2 As shown, the pyrimidinone-terminated polysiloxane of this application has a different peak shape in its hydrogen nuclear magnetic resonance spectrum compared to traditional aminopropyl-terminated polysiloxanes. Figure 1 In the NMR spectrum, the peak with a chemical shift of around 8.10 ppm is a characteristic peak of -NH- on the six-membered ring of the terminal pyrimidinone group in the terminal pyrimidinone polysiloxane. Figure 2 There was no peak around 8.10 ppm. Figure 2 The NMR peak near 3.02 ppm is a characteristic peak of γ-CH2 in the aminopropyl group. Figure 1 The NMR peak near 3.87 ppm is a characteristic peak of the γ-CH2 group near Si in terminal pyrimidinone polysiloxanes. Due to the presence of the urea group and the hydrogen bonding of the terminal group, the electron cloud density around the H atom on the γ-CH2- group is reduced, thus weakening the shielding effect. Figure 2 The characteristic peak at 3.02 ppm shifts to the lower field, moving to 3.87 ppm.

[0065] As shown in Table 2, the photocurable pyrimidinone-terminated silicone rubber material provided in this application exhibits excellent comprehensive performance in terms of tensile strength, elongation at break, hardness, tear strength, and high-temperature mechanical stability, which is significantly better than the traditional aminopropyl-terminated polysiloxane and methyl-terminated polymethyl vinyl siloxane systems.

[0066] In Examples 1-3, the mechanical properties of the materials changed accordingly with variations in the molecular weight of the matrix, the siloxane content, and the type and amount of reinforcing fillers. Example 4 used a terminal pyrimidinone-based polysiloxane with a molecular weight of 190,000 and a siloxane content of 99.1%, combined with 50 parts of silica. The resulting material exhibited a tensile strength of 10.21 MPa, an elongation at break of 449%, a hardness of 44 ShA, and a tear strength of 35.29 KN / m, demonstrating excellent overall performance.

[0067] Examples 4-6 are experiments with varying amounts of silica. As the amount of silica decreases, the material hardness decreases and the elongation at break increases. At a high strength of not less than 9 MPa, the hardness can be as low as 39 ShA and as high as 45 ShA. It can be seen that by implementing an end-group functionalization strategy on the rubber matrix, high-strength, low-modulus silicone rubber materials can be obtained, achieving a balance between high strength and low hardness while maintaining high strength.

[0068] Examples 4, 7, and 8 compare different molecular weights and siloxane contents. The results show that excellent mechanical properties can be obtained when the siloxane content is not less than 96% and the molecular weight is in the range of 60,000 to 190,000. The higher the siloxane content, the more significant the reinforcing effect.

[0069] Examples 9-11 illustrate the synergistic reinforcement system of tea polyphenols. Adding 0.5-3 parts of tea polyphenols significantly improved the tear strength of the material, reaching a maximum of 46.11 KN / m, while also substantially enhancing its high-temperature mechanical stability. Example 10, at 150℃, still exhibited a tensile strength of 7.15 MPa, far superior to the sample without added tea polyphenols. This demonstrates that tea polyphenols, along with silica and the terminal pyrimidinone group structure, form a synergistic reinforcement effect, effectively suppressing the degradation of the material's mechanical properties at high temperatures and addressing the pain points of traditional silicone rubber, such as easy softening and strength reduction at high temperatures.

[0070] Compared with Comparative Examples 1-6, this application uses terminal pyrimidinone-based polysiloxanes, which significantly improve tensile strength, elongation at break, tear strength, and high-temperature retention rate under the same molecular weight, filler, and additive dosage. At 150°C, the strength retention rate of the examples in this application is much higher than that of traditional aminopropyl-terminated and methyl-terminated systems, and the high-temperature degradation is significantly reduced, fully demonstrating that the terminal pyrimidinone structure can significantly improve the overall performance and high-temperature stability of silicone rubber.

[0071] The key difference between Comparative Example 1 and Example 4 is that Comparative Example 1 uses an aminopropyl-terminated polysiloxane instead of the pyrimidinone-terminated polysiloxane of this invention. Test results show a decrease in various mechanical properties. The reason for this is that the pyrimidinone-terminated structure significantly improves the material's room-temperature mechanical properties and high-temperature stability, while the traditional aminopropyl-terminated structure cannot achieve this enhancement effect.

[0072] Compared to Example 7, Comparative Example 2 has a molecular weight of 60,000 and uses 50 parts of silica. The key difference lies in the matrix type: aminopropyl-terminated versus pyrimidinone-terminated. This demonstrates that even in a low molecular weight matrix, the pyrimidinone-terminated structure can effectively improve the material's strength and toughness, overcoming the technical bottleneck of traditional low molecular weight polysiloxanes failing to achieve high strength and toughness. Compared to Example 8, Comparative Example 3's key difference lies in the matrix end-group structure. This further confirms that the pyrimidinone-terminated structure is the core key to improving the material's overall mechanical properties.

[0073] Compared to Example 4, Comparative Example 4 used a methyl-terminated polymethylvinylsiloxane, which has a higher molecular weight than the matrix in Example 4. However, the test results showed that the tensile strength, tear strength, high-temperature tensile strength at 150°C, and high-temperature elongation at break of Comparative Example 4 were all lower. This comparison indicates that even with a higher molecular weight, the mechanical properties and high-temperature stability of conventional methyl-terminated polysiloxanes are still inferior to the pyrimidinone-based polysiloxane system of this application.

[0074] Compared with Examples 10 and 11, Comparative Examples 5 and 6 correspond to Examples 10 and 11, respectively. The core difference lies in replacing the terminal pyrimidinone polysiloxane with aminopropyl-terminated polysiloxane, and the amount of tea polyphenols used is 0.5 parts and 1 part, respectively, while other formulations remain completely the same. Test results show that the tensile strength and elongation at break of Comparative Example 5 decreased compared to Example 10; the tensile strength and elongation at break of Comparative Example 6 also decreased compared to Example 11. The reason for this is that the synergistic reinforcing effect of tea polyphenols requires the use of terminal pyrimidinone polysiloxanes. Adding tea polyphenols only to the traditional aminopropyl-terminated system cannot achieve the synergistic effect of high strength, high toughness, and high-temperature stability.

[0075] The above description is merely an embodiment of this application, and the scope of protection of this application is not limited to these specific embodiments, but is determined by the claims of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the technical concept and principles of this application should be included within the scope of protection of this application.

Claims

1. A photocurable pyrimidinone-terminated silicone rubber material, characterized in that, The product comprises, by weight, the following raw materials: 100 parts of terminal pyrimidinone polysiloxane, 0-60 parts of reinforcing filler, 0.5-4 parts of crosslinking agent, and 0.1-0.5 parts of photoinitiator; The siloxane content in the terminal pyrimidinone polysiloxane is not less than 94 wt%. The structural formula of the terminal pyrimidinone polysiloxane is shown in formula (1): Equation (1); Wherein, R is one or more of methyl, phenyl, and ethyl, 0 < n / (m+n+p) ≤ 5%, 0 ≤ p / (m+p) ≤ 40%; and the molecular weight is 10,000 to 600,000.

2. The photocurable terminal pyrimidinone-based silicone rubber material according to claim 1, characterized in that, The siloxane content in the terminal pyrimidinone-based polysiloxane is not less than 98 wt%.

3. The photocurable terminal pyrimidinone-based silicone rubber material according to claim 1, characterized in that, The siloxane content in the terminal pyrimidinone-based polysiloxane is not less than 99 wt%.

4. The photocurable terminal pyrimidinone-based silicone rubber material according to claim 1, characterized in that, The crosslinking agent is a side-chain mercaptopropyl polydimethylsiloxane, with a structural formula as shown in formula (2) or formula (3): Equation (2), Equation (3) Among them, 10%≤a / (a+b)≤100%.

5. The photocurable terminal pyrimidinone-based silicone rubber material according to claim 1, characterized in that, The photoinitiator includes one or more of 2,2-dimethylolpropionic acid, 2,2-dimethoxy-2-phenylacetophenone, 2-hydroxy-4-(2-hydroxyethoxy)-2-methylphenylacetophenone, 1-hydroxycyclohexylphenyl ketone, and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide.

6. The photocurable terminal pyrimidinone-based silicone rubber material according to claim 1, characterized in that, The reinforcing filler includes one or more of the following: silica, carbon black, graphene, carbon nanotubes, gypsum fiber, carbon fiber, organic clay, and boron nitride.

7. The photocurable terminal pyrimidinone-based silicone rubber material according to claim 6, characterized in that, It also includes tea polyphenols.

8. The photocurable terminal pyrimidinone-based silicone rubber material according to claim 7, characterized in that, The dosage of tea polyphenols is 0.5 to 3 parts by weight.

9. A method for preparing a photocurable pyrimidinone-terminated silicone rubber material according to any one of claims 1 to 8, characterized in that, Includes the following steps: (1) Prepare each raw material according to the weight ratio, add the terminal pyrimidinone polysiloxane to the open mill, add reinforcing filler, and mix evenly to obtain the compound; (2) Place the compounded rubber in a two-roll mill, add crosslinking agent and photoinitiator, and pass through the mill several times to obtain the rubber compound. Place the rubber compound in a mold, heat press it in a vacuum vulcanizing machine, and then cure it by ultraviolet irradiation. After demolding, the pyrimidinone-based silicone rubber material is obtained.

10. The method for preparing a photocurable terminal pyrimidinone-based silicone rubber material according to claim 9, characterized in that, In step (2), the hot pressing temperature is 50~180℃; the ultraviolet irradiation wavelength is 254~400nm; and the ultraviolet irradiation time is 0.25~4h.

Images