Crosslinked fluorosilicone rubber with wide temperature range and strong polar solvent resistance and preparation process thereof

Abstract

The application belongs to the technical field of fluorosilicone rubber materials, and particularly relates to a crosslinked fluorosilicone rubber resistant to strong polar solvents in a wide temperature range and a preparation process thereof; aiming at the limitation problem that the current crosslinked fluorosilicone rubber is easy to swell and the mechanical property significantly decreases in a strong polar solvent environment; the application obtains a rubber sheet by thin passing vinyl-terminated polymethyl(3,3,3-trifluoropropyl)siloxane, takes the rubber sheet as a base rubber, adds white carbon black, hydroxyl fluorosilicone oil, perfluoroalkyl trialkoxysilane, a heat-resistant agent, a platinum catalyst, an inhibitor, and hydrogen-containing silicone oil crosslinking agent, and obtains the crosslinked fluorosilicone rubber through a three-stage vulcanization process treatment and cooling; the obtained crosslinked fluorosilicone rubber has excellent anti-swelling performance to strong polar solvents in a wide temperature range, and has high mechanical property, and is widely applied to sealing and protection materials in the fields of aerospace, chemical industry, automobiles and the like.

Description

Technical Field

[0001] This invention belongs to the field of fluorosilicone rubber material technology, specifically relating to a cross-linked fluorosilicone rubber with a wide temperature range and strong polar solvent resistance, and its preparation process. Background Technology

[0002] Fluorosilicone rubber is an elastomer formed by introducing fluorinated organic side groups into the main chain of polysiloxane. It combines the high and low temperature resistance of silicone rubber with the oil and fuel resistance brought by the fluorinated side groups, and is commonly used in aerospace, automotive, chemical equipment, electronic packaging, and special seals.

[0003] However, existing fluorosilicone rubbers still have a problem in practical applications: they are severely inadequate in resisting highly polar solvents. The trifluoropropyl groups on the side chains of fluorosilicone rubber molecules are nonpolar fluorinated groups, possessing a natural shielding and repulsion effect against nonpolar or weakly polar media such as fuel oil and mineral oil. Therefore, fluorosilicone rubber exhibits excellent swelling resistance in these media. However, when exposed to highly polar solvents, strong dipole-dipole interactions occur between the trifluoropropyl side chains and the highly polar solvent molecules, causing a large amount of solvent molecules to penetrate into the rubber crosslinking network, resulting in swelling of the rubber molecules, a sharp decline in mechanical properties, and even structural damage.

[0004] In the prior art, publication number CN111849172B discloses a solvent-resistant fluorosilicone rubber sealing strip and its preparation method. The raw materials include 50-70 parts silicone rubber, 15-30 parts fluorosilicone rubber, 15-30 parts silica, 0.2-1 parts structure control agent, and 0.5-3 parts vulcanizing agent. The sealing strip is prepared by extrusion and two-stage vulcanization. This method improves general solvent resistance by compounding silicone rubber with fluorosilicone rubber, but it still contains a relatively large amount of ordinary silicone rubber components and does not construct a perfluoroalkyl layer at the silica / fluorosilicone rubber interface, resulting in insufficient control over swelling and extraction under long-term immersion in highly polar solvents.

[0005] In summary, there is an urgent need for a new type of crosslinked fluorosilicone rubber that can maintain its elasticity over a wide temperature range, reduce the intrusion of highly polar solvents into the rubber network and filler interface, and improve its processing and storage stability, film-forming properties, and vulcanization completeness. Summary of the Invention

[0006] This invention provides a cross-linked fluorosilicone rubber with a wide temperature range and strong polar solvent resistance, as well as its preparation process, aiming to solve the technical problems of insufficient solvent resistance and significant degradation of mechanical properties of existing fluorosilicone rubber in strong polar solvent environments.

[0007] The specific technical solution is as follows: This invention provides a crosslinked fluorosilicone rubber with a wide temperature range and resistance to strong polar solvents, and its preparation process, as detailed below: S1: Raw material pretreatment: Vinyl-terminated polymethyl (3,3,3-trifluoropropyl)siloxane is subjected to thin-pass treatment to obtain pretreated raw rubber.

[0008] S2: Mixing. The pretreated raw rubber prepared in S1 is rolled, then some silica is added and mixed. Then hydroxyl fluorosilicone oil, heat resistant agent and perfluoroalkyltrialkoxysilane are added, left to stand for treatment, and mixed. Then the remaining silica, inhibitor, platinum catalyst and hydrogen-containing silicone oil crosslinking agent are added in sequence and mixed in sequence. The mixture is dispersed in a thin stream and cooled to room temperature to obtain the compound rubber.

[0009] S3: Vulcanization molding. The compound prepared in S2 is vulcanized, cooled to room temperature, and then vulcanized again and cooled to room temperature to obtain cross-linked fluorosilicone rubber.

[0010] Furthermore, the vinyl-terminated polymethyl (3,3,3-trifluoropropyl)siloxane described in S1 has a vinyl molar content of 0.10% to 0.50%.

[0011] The thin-pass processing described in S1 has the following parameter settings: 12 to 18 passes, 0.5 to 1.5 mm roller gap, and 20 to 40°C temperature.

[0012] Furthermore, the portion of silica described in S2 comprises one-third of all silica.

[0013] The mixing parameters described in S2 are set as follows: temperature 30-50℃.

[0014] The hydroxyl fluorosilicone oil described in S2 is hydroxyl-terminated polymethyltrifluoropropylsiloxane with a hydroxyl mass fraction of 0.5% to 5.0%.

[0015] The heat-resistant agent described in S2 is one or more of cerium oxide, iron oxide, magnesium oxide, and zirconium oxide.

[0016] The perfluoroalkyltrialkoxysilane described in S2 is one of perfluorooctyltriethoxysilane, 1H,1H,2H,2H-perfluorodecyltriethoxysilane, and perfluorododecyltriethoxysilane.

[0017] The parking process described in S2 has the following parameter settings: temperature 20-30℃, duration 24-48h.

[0018] The hydrogen-containing silicone oil crosslinking agent described in S2 has a Si-H mass fraction of 0.05% to 0.30% and a Si-H to vinyl molar ratio of 1.4:1 to 2.0:1.

[0019] The compound rubber described in S2 is based on 100 parts of pretreated raw rubber, and its raw material composition is as follows: 30-50 parts of silica, 4-12 parts of hydroxyl fluorosilicone oil, 2-6 parts of perfluoroalkyltrialkoxysilane, 1-3 parts of heat resistant agent, 0.1-0.3 parts of platinum catalyst, 0.08-0.25 parts of inhibitor, and 2-4 parts of hydrogen-containing silicone oil crosslinking agent.

[0020] Furthermore, the vulcanization treatment described in S3 is divided into pre-vulcanization and main vulcanization, with the following parameter settings: pre-vulcanization temperature 90-110℃, pressure 10-15MPa, duration 12-18min; main vulcanization temperature 155-165℃, pressure 10-15MPa, duration 25-35min.

[0021] The secondary vulcanization described in S3 has the following parameter settings: heating rate 1-3℃ / min, temperature 120℃, holding time 1h, then heating to 180-200℃, holding time 2-4h.

[0022] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention reduces the adsorption of strongly polar solvents on the polar surface of silica by reacting perfluoroalkyltrialkoxysilane with the hydroxyl groups on the surface of silica and forming a perfluoroalkyl-containing interface layer together with hydroxyl fluorosilicone oil.

[0023] 2. This invention employs pre-vulcanization, main vulcanization, and two-stage vulcanization to gradually release or react solvents, trace amounts of low-boiling substances, and unreacted active groups, thereby reducing bubbles and uneven cross-linking. Attached Figure Description

[0024] Figure 1 These are the XPS full spectra of the crosslinked fluorosilicone rubbers prepared in Example 1, Comparative Example 1, and Comparative Example 4.

[0025] Figure 2 These are the C1s high-resolution peak spectra of the crosslinked fluorosilicone rubbers prepared in Example 1, Comparative Example 1, and Comparative Example 4.

[0026] Figure 3 These are the F1s high-resolution spectra of the crosslinked fluorosilicone rubbers prepared in Example 1, Comparative Example 1, and Comparative Example 4.

[0027] Figure 4 This is an angle-resolved XPS surface enrichment trend diagram of the cross-linked fluorosilicone rubber prepared in Example 1, Comparative Example 1, and Comparative Example 4. Detailed Implementation

[0028] The terms "implementation," "an implementation," "another implementation," or "certain implementations" used in this specification refer to specific features, structures, or characteristics described in relation to said implementation that are included in at least one implementation. Therefore, "implementation," "an implementation," "another implementation," or "certain implementations" do not necessarily all refer to the same implementation. Furthermore, specific features, structures, or characteristics can be combined in any way within one or more implementations. Each feature disclosed in this specification can be replaced by any alternative feature that provides the same, equivalent, or similar purpose. Therefore, unless otherwise specified, the disclosed features are merely general examples of equivalent or similar features.

[0029] This invention proposes a cross-linked fluorosilicone rubber with a wide temperature range and resistance to strong polar solvents, and its preparation process. The detailed technical solution is as follows: 1. Raw material pretreatment Vinyl-terminated polymethyl (3,3,3-trifluoropropyl)siloxane was subjected to thin-pass treatment to obtain a pretreated film.

[0030] In the initial state before thinning, the vinyl end groups of the raw rubber are partially "hidden" within the molecular chain due to chain coiling, making it difficult for them to effectively participate in the subsequent hydrosilylation crosslinking reaction. Thinning treatment subjectes the polymer chain to both stretching and shearing forces, transforming the chain from a random coiled state to a state of oriented extension. This exposes the vinyl end groups at the chain ends, making them highly efficient reactive sites in the subsequent platinum-catalyzed hydrosilylation crosslinking system. The vinyl end groups play a role in chain growth during crosslinking, increasing the crosslinking density and physical and mechanical properties of the vulcanizate. Low-temperature thinning and roller temperature control ensure that the shearing action is primarily mechanical chain breaking, suppressing oxidative degradation and side reactions of the fluorosilicone raw rubber at high temperatures.

[0031] 2. Mixing The pretreated raw rubber is rolled, then some silica is added and mixed. Then hydroxyl fluorosilicone oil, heat resistant agent, and perfluoroalkyl trialkoxysilane are added and mixed. After resting, the remaining silica, inhibitor, platinum catalyst, and hydrogen-containing silicone oil crosslinking agent are added in sequence and mixed separately. The mixture is then dispersed in a thin stream and cooled to room temperature to obtain the compound rubber.

[0032] During the compounding stage, perfluoroalkyltrialkoxysilanes undergo chemical coupling with hydroxyl groups present in the system via the hydrolysis and condensation reaction of silanoxy groups. Triethoxysilanes are triggered by trace amounts of moisture in the rubber compound during compounding, resulting in hydrolysis to generate silanols. These silanols then undergo dehydration condensation reactions with the silanol groups on the surface of silica (filler surface) and the terminal hydroxyl groups of hydroxyl fluorosilicone oil, forming covalent bonds. This process anchors the long perfluoroalkyl chains to the silica surface and the fluorosilicone rubber molecular chains via covalent bonds, forming a fluorocarbon chain-like reinforcing network. Hydroxyl fluorosilicone oil reacts with the silanol groups on the silica surface through its hydroxyl groups, consuming some of the highly reactive silanol groups on the silica surface, thus partially passivating the silica surface and slowing down the structuring process. Hydroxyl fluorosilicone oil acts as a structuring control agent, consuming some of the hydroxyl groups in silica to prevent over-structuring, while simultaneously retaining a sufficient number of hydroxyl groups for covalent bonding by perfluoroalkyltrialkoxysilanes. The two processes complement each other.

[0033] This invention employs a platinum-catalyzed hydrosilylation reaction to construct a crosslinked network. Zero-valent platinum atoms in the platinum catalyst coordinate with Si-H bonds in the crosslinking agent to form a platinum-hydrogen complex intermediate. This active intermediate undergoes an insertion reaction with vinyl groups to form a platinum-carbon bond intermediate, which subsequently undergoes a reductive elimination reaction with another Si-H bond to generate a Si-C bond and regenerated platinum catalyst, completing one catalytic cycle.

[0034] 3. Preparation and vulcanization molding of ternary mixtures The compound rubber is vulcanized, cooled to room temperature, and then vulcanized again and cooled to room temperature to obtain cross-linked fluorosilicone rubber.

[0035] During pre-curing and main curing, the rubber compound temperature rises to 90–165°C. The incompletely grafted perfluoroalkyltrialkoxysilane molecules possess a strong thermodynamic surface migration driving force due to the extremely low surface energy of their long fluorocarbon chains. Driven by the perfluorination effect, perfluoroalkyltrialkoxysilane molecules spontaneously diffuse from the interior of the rubber compound to the rubber surface and align themselves, forming a solvent-phobic monolayer structure with the fluorocarbon chains facing outwards. At this point, the excess uncondensed siloxy groups can be further condensed and anchored under the subsequent high-temperature conditions of the second-stage curing. During the stepped temperature increase in the second-stage curing, the perfluoroalkyltrialkoxysilanes spread uniformly on the rubber surface and undergo condensation reactions between silanols, forming a dense fluorocarbon cross-linked network, ultimately constructing a protective layer of a certain thickness on the rubber surface. This surface protective layer shields against the penetration and swelling effects of highly polar solvent molecules.

[0036] The three-stage vulcanization process of this invention includes a pre-vulcanization stage at a lower temperature, which initially sets the rubber compound, transforming it from a plastic to an elastic state. During this stage, the inhibitor still has a certain inhibitory effect on the platinum catalyst, and the crosslinking reaction proceeds at a moderate rate, avoiding premature curing of the compound before it fully fills the mold cavity due to excessively rapid crosslinking. The main vulcanization temperature rises to 155–165°C, where the inhibitor completely loses its inhibitory effect, the platinum catalytic activity reaches its maximum, and vinyl groups undergo a highly efficient addition reaction with Si-H to form a primary crosslinking network, achieving a crosslinking degree of 80%–90%. During the second-stage vulcanization, the remaining unreacted vinyl groups continue to react with Si-H at high temperatures, gradually perfecting the crosslinking network to a high-density state, resulting in optimal mechanical properties. Two-stage vulcanization effectively removes residual low-molecular-weight substances from the vulcanization process, preventing them from catalyzing product aging. It also stabilizes the product's basic physical properties, such as hardness, tensile strength, and elongation at break, improving compression set performance. Holding at 120℃ for 1 hour is a crucial step in two-stage vulcanization. At this temperature, low-molecular-weight substances fully volatilize from the product's interior, while the perfluoro long chains undergo micro-Brownian motion, causing a uniform redistribution of perfluoroalkyltrialkoxysilanes on the rubber surface. Subsequently, the temperature is gradually increased to 180–200℃. Under these high-temperature conditions, dehydration condensation reactions occur between the silanols of the perfluoroalkyltrialkoxysilanes and between the silanols and the silanols on the rubber surface, forming covalent chemical anchors. This ultimately forms a dense and stable perfluoroalkyl solvent-repellent protective layer on the rubber surface. If a single-stage vulcanization or ordinary two-stage vulcanization is used, the surface migration and anchoring depth of the perfluoroalkyltrialkoxysilanes are insufficient, and the resistance to strong polar solvents is weakened. If the initial temperature of the two-stage vulcanization is too high, the perfluoroalkyltrialkoxysilanes will rapidly hydrolyze and condense locally to form aggregates, resulting in an uneven fluorocarbon protective layer and decreased mechanical properties. The three-stage vulcanization process gradually densifies the cross-linked network while simultaneously achieving complete control over the chemical grafting of perfluoroalkyltrialkoxysilane molecules from the rubber's interior to their enrichment and anchoring on the surface. When a highly polar solvent comes into contact with the product, it first encounters a dense surface protective layer; the surface's supersolvent-repellent properties prevent the wetting and penetration of the polar solvent. Even if the surface layer experiences localized wear during service, the fluorocarbon network constructed within the rubber through the chemical grafting of perfluoroalkyltrialkoxysilanes can still provide a second solvent-repellent barrier, further delaying the diffusion and penetration of solvent molecules.

[0037] Example 1 A preparation process for a cross-linked fluorosilicone rubber with a wide temperature range and resistance to strong polar solvents is as follows: Table 1 Main Raw Materials ; S1: Raw material pretreatment: 100g of vinyl-terminated polymethyl (3,3,3-trifluoropropyl)siloxane is subjected to thin-pass treatment (15 times, roller gap 1mm, temperature 30℃) to obtain pretreated raw rubber.

[0038] S2: Mixing. Roller-coated 100g of pretreated raw rubber prepared in S1 is rolled, and then 13.3g of silica is added. The mixture is mixed at 40℃ until homogeneous. Then, 8g of hydroxyl fluorosilicone oil (hydroxyl-terminated polymethyltrifluoropropylsiloxane) and 2g of heat resistant agent (nano-cerium oxide) are added and mixed. The mixture is then left to stand at 25℃ for 36h. Next, 4g of perfluoroalkyltrialkoxysilane (1H,1H,2H,2H-perfluorodecyltriethoxysilane), 26.7g of silica, 0.15g of inhibitor (ethynylcyclohexanol), 0.2g of platinum catalyst (Karstedt catalyst), and 3g of hydrogen-containing silicone oil crosslinking agent (methyl hydrogen-containing silicone oil) are added sequentially and mixed until homogeneous before adding the next addition. The mixture is then dispersed in a thin stream and cooled to room temperature to obtain the compound.

[0039] S3: Vulcanization molding. The compound prepared in S2 is vulcanized, cooled to room temperature, and then subjected to secondary vulcanization and cooled to room temperature to obtain cross-linked fluorosilicone rubber. The vulcanization process is divided into pre-vulcanization and main vulcanization, with the following parameters: pre-vulcanization temperature 100℃, pressure 12.5MPa, duration 15min; main vulcanization temperature 160℃, pressure 12.5MPa, duration 30min; secondary vulcanization parameters: heating rate 2℃ / min, temperature 120℃, holding time 1h, then heating to 190℃ and holding time 3h.

[0040] Example 2 The composition and preparation process are the same as in Example 1, except that: The parameters for the thin-pass treatment in step S1 of the preparation process are set as follows: 12 passes, 0.5 mm roller gap, 20 °C temperature, and the other steps are the same.

[0041] In step S2 of the preparation process, the mixing temperature is 30℃, and the storage treatment parameters are set as follows: temperature 20℃, duration 24h, and other steps are the same.

[0042] In the preparation process S2, the perfluoroalkyltrialkoxysilane is perfluorooctyltriethoxysilane, the heat resistant agent is iron oxide, and the other components are the same.

[0043] Example 3 The composition and preparation process are the same as in Example 1, except that: The parameters for the thin-pass treatment in step S1 of the preparation process are set as follows: 18 passes, 1.5 mm roller gap, 40 °C temperature, and the other steps are the same.

[0044] In step S2 of the preparation process, the mixing temperature is 50℃, and the storage treatment parameters are set as follows: temperature 30℃, duration 48h, and other steps are the same.

[0045] In the preparation process S2, the perfluoroalkyltrialkoxysilane is perfluorododecyltriethoxysilane, and the heat resistant agents are cerium oxide and iron oxide in a mass ratio of 1:1. Other components are the same.

[0046] Example 4 The composition and preparation process are the same as in Example 1, except that: In the S2 preparation process, the heat resistant agent is iron oxide, magnesium oxide, and zirconium oxide, with a mass ratio of 1:2:2. The compound is based on 100 parts of pretreated raw rubber, and the composition of each raw material is as follows: 30 parts of silica, 4 parts of hydroxyl fluorosilicone oil, 2 parts of perfluoroalkyltrialkoxysilane, 1 part of heat resistant agent, 0.1 parts of platinum catalyst, 0.08 parts of inhibitor, 2 parts of hydrogen-containing silicone oil crosslinking agent, and the other components are the same.

[0047] The vulcanization parameters in S3 of the preparation process are set as follows: pre-vulcanization temperature 90℃, pressure 10MPa, duration 12min, main vulcanization temperature 155℃, pressure 10MPa, duration 25min, secondary vulcanization parameters are set as follows: heating rate 1℃ / min, temperature 120℃, holding time 1h, then heating to 180℃, holding time 2h, and other steps are the same.

[0048] Example 5 The composition and preparation process are the same as in Example 1, except that: In the S2 preparation process, the compound rubber is based on 100 parts of pretreated raw rubber, and the composition of each raw material is as follows: 50 parts of silica, 12 parts of hydroxyl fluorosilicone oil, 6 parts of perfluoroalkyltrialkoxysilane, 3 parts of heat resistant agent, 0.3 parts of platinum catalyst, 0.25 parts of inhibitor, 4 parts of hydrogen-containing silicone oil crosslinking agent, and the other components are the same.

[0049] The vulcanization parameters in S3 of the preparation process are set as follows: pre-vulcanization temperature 110℃, pressure 15MPa, duration 18min, main vulcanization temperature 165℃, pressure 15MPa, duration 35min, secondary vulcanization parameters are set as follows: heating rate 3℃ / min, temperature 120℃, holding time 1h, then heating to 200℃, holding time 4h, and other steps are the same.

[0050] Example 6 The composition and preparation process are the same as in Example 1, except that: In the S2 preparation process, the heat resistant agent is zirconium oxide. The compound is based on 100 parts of pretreated raw rubber, and the composition of each raw material is as follows: 45 parts of silica, 5 parts of hydroxyl fluorosilicone oil, 5 parts of perfluoroalkyltrialkoxysilane, 1.5 parts of heat resistant agent, 0.1 parts of platinum catalyst, 0.2 parts of inhibitor, 3.5 parts of hydrogen-containing silicone oil crosslinking agent, and the other components are the same.

[0051] The vulcanization parameters in S3 of the preparation process are set as follows: pre-vulcanization temperature 105℃, pressure 13MPa, duration 17min; main vulcanization temperature 161℃, pressure 14MPa, duration 32min; secondary vulcanization parameters are set as follows: heating rate 1.5℃ / min, temperature 120℃, holding time 1h, then heating to 195℃, holding time 2.5h, and other steps are the same.

[0052] Comparative Example 1 The composition and preparation process are the same as in Example 1, except that: In step S2 of the preparation process, no perfluoroalkyltrialkoxysilane is added; the other steps are the same.

[0053] Comparative Example 2 The composition and preparation process are the same as in Example 1, except that: In step S2 of the preparation process, a traditional peroxide (diisopropylbenzene peroxide) is used instead of a platinum catalyst, while the other steps are the same.

[0054] Comparative Example 3 The composition and preparation process are the same as in Example 1, except that: In the preparation process S3, only one stage of vulcanization is used, without pre-vulcanization and two-stage vulcanization, while the other steps are the same.

[0055] Comparative Example 4 The composition and preparation process are the same as in Example 1, except that: In the S3 stage of the preparation process, the temperature of the two-stage vulcanization is directly raised to 190℃, omitting the intermediate 120℃ holding stage, while the other steps are the same.

[0056] Comparative Example 5 The composition and preparation process are the same as in Example 1, except that: In step S2 of the preparation process, the perfluoroalkyltrialkoxysilane is replaced by an equal mass of hydroxyl silicone oil, and the other steps are the same.

[0057] Samples of the crosslinked fluorosilicone rubber prepared in Example 1, Comparative Example 1, and Comparative Example 4 were taken and cut into 8mm × 8mm specimens. The surface was gently blown with high-purity nitrogen to remove dust. If visible contamination was present, it was quickly wiped with anhydrous ethanol (5–10 seconds). The specimens were then dried in an environment of 23°C and approximately 50% relative humidity for 30 minutes, fixed with mechanical clamps, and subjected to XPS testing. Figure 1 , Figure 2 , Figure 3 , Figure 4 As shown, where, Figure 1 This is the XPS full spectrum. Figure 2 This is a high-resolution peak-fraction spectrum of C 1s. Figure 3 This is a high-resolution spectrum of F 1s. Figure 4Angle-resolved XPS surface enrichment trend diagram, A1 corresponds to Example 1, C1 corresponds to Example 1, C4 corresponds to Example 4, in Figure 1 In the samples, A1, C4, and C1 all exhibited C 1s, O 1s, Si 2p, and F 1s signals. The F 1s peak intensity was A1 > C4 > C1. Although C1 did not contain perfluoroalkyltrialkoxysilane, polymethyl (3,3,3-trifluoropropyl)siloxane itself contains trifluoropropyl groups, thus still exhibiting an F1s signal. A1, due to the introduction of perfluorodecylsilane and complete two-stage sulfurization migration / anchoring, showed the strongest surface F signal. C4 contained perfluorosilane but omitted the 120℃ insulation, resulting in insufficient surface rearrangement and spreading; therefore, its F signal was between that of A1 and C1. Figure 2 In the C1 / C / CH / Si-C component near 286.2 eV, the matrix consists of organic carbon and silicon-carbon structures; near 288.9 eV, the CF / C-CF component is a fluorinated carbon transition component; near 291.7 eV, CF2 and near 293.8 eV, CF3 correspond to high-binding-energy fluorinated carbon structures in perfluoroalkyl segments. The CF2 and CF3 of A1 are stronger than those of C1 and C4 because A1 uses 1H,1H,2H,2H-perfluorodecyltriethoxysilane, which contains multiple -CF2- units in its long perfluoro chain. C1 does not contain perfluoroalkylsilane, and its main fluorine source is trifluoropropyl. C4, due to the omission of the 120℃ insulation, although containing perfluorosilane, suffers from insufficient uniform surface migration and subsequent anchoring, resulting in lower CF2 / CF3 strength compared to A1. Figure 3 In the figure, the F 1s main peak is located around 687.8 eV and belongs to the CF bond. The F 1s peak of A1 is the highest and more concentrated, indicating that its surface contains more fluorine structures and the chemical environment is relatively consistent. The F 1s peak of C1 is weaker, indicating that only the matrix trifluoropropyl contributes. C4 is in between, indicating that although perfluorosilane components are present after omitting the 120℃ holding temperature, the surface enrichment layer is not fully formed. Figure 4 Among them, when the sampling angle is 15°, A1 has the highest F / Si ratio, which decreases as the angle increases, indicating that its outermost layer is enriched with fluorine-containing segments, while the internal F / Si ratio is lower. C1 has a lower F / Si value and a weaker angle dependence, indicating that no significant perfluorinated chain surface enrichment layer has been formed. C4 is between A1 and C1, indicating that the perfluorosilane itself brings a certain fluorine-containing surface signal, but the omission of 120℃ heat preservation makes its migration, spreading and anchoring insufficient, and the surface enrichment layer is not as complete as A1.

[0058] Based on Examples 1-6 and Comparative Examples 1-5, samples of the finally prepared cross-linked fluorosilicone rubber were taken for volume swelling rate testing: The cross-linked fluorosilicone rubber was cut into cubes (20mm × 20mm × 2mm), the sample surface was wiped with anhydrous ethanol, then blotted dry with lint-free paper, dried at room temperature for 30 minutes, and its mass (m1) was measured. Then, it was placed in water and weighed again (m2). The initial volume (V1) was calculated. The sample was then placed in acetone and immersed in a sealed container at a constant temperature (25℃, 72h). The mass in air and in water were then measured using the same method to obtain the volume after immersion (V2). The volume swelling rate was calculated. Five groups were tested, and the average value was taken. The calculation formula is as follows: .

[0059] Based on Examples 1-6 and Comparative Examples 1-5, samples of the finally prepared cross-linked fluorosilicone rubber were taken for tensile strength retention rate testing: The cross-linked fluorosilicone rubber was cut into dumbbell-shaped samples, the sample surface was wiped with anhydrous ethanol, then blotted dry with lint-free paper, dried at room temperature for 30 min, and conditioned at 23℃ for 24 h. The samples were divided into initial group, immersion group, low temperature group, and high temperature group. The thickness of the narrow working area of ​​the dumbbell-shaped samples was measured, and the average value was taken from three points. The immersion group was treated with acetone (25℃, 72 h), the low temperature group samples were treated at -40℃ for 30 min, and the high temperature group samples were treated at 150℃ for 15 min. Then, the initial group, immersion group, low temperature group, and high temperature group were tested using a universal testing machine (tensile rate 500 mm / min, clamp spacing 75 mm). The tensile strength retention rate was calculated. Ten groups were tested, and the average value was taken. The calculation formula is as follows: , where R σ σ0 represents the tensile strength retention rate, σ0 represents the initial tensile strength, and σ1 represents the tensile strength after treatment.

[0060] Based on Examples 1-6 and Comparative Examples 1-5, samples of the finally prepared cross-linked fluorosilicone rubber were taken for surface contact angle testing: the cross-linked fluorosilicone rubber was cut into squares (20mm×20mm×2mm), the sample surface was wiped with anhydrous ethanol, then dried with lint-free paper, and placed in an environment of 23°C and 50% relative humidity for 24 hours. Hexadecane was drawn with a microsyringe for testing. Three different positions were selected on each sample surface, and the measurement was repeated once at each position. The values ​​were calculated and averaged.

[0061] The specific test results are shown in Table 2. Figure 1 , Figure 2 , Figure 3 , Figure 4 As shown: Table 2 Comparison of core performance of Examples 1-6 and Comparative Examples 1-5 ; The comparison results above show that Example 1 exhibits the best overall performance. Thin-pass processing moderately untangles the raw rubber molecular chains, facilitating filler dispersion and forming a stable network structure. The stepwise addition of silica during compounding, combined with hydroxyl fluorosilicone oil, improves compatibility. Perfluoroalkyltrialkoxysilane introduces a high-fluorine-content, low-surface-energy layer at the filler / rubber interface through hydrolysis and condensation, effectively resisting the penetration of highly polar molecules. Platinum-catalyzed addition vulcanization combined with vulcanization treatment forms a uniform and complete three-dimensional cross-linked network, further inhibiting solvent intrusion. Examples 2 to 6 show slightly lower overall performance than Example 1 but still maintain a high level, indicating that even with a wide range of parameter variations, they still achieve good results. The first example showed excellent resistance to strong polar solvents; Comparative Example 1, without the addition of perfluoroalkyltrialkoxysilane, did not show a decrease in surface energy, and polar solvents easily penetrated it; Comparative Example 2 used peroxide instead of platinum catalysis, and the thermal and chemical stability of the cross-linked C-C bonds was lower than that of the Si-CH2-CH2-Si bonds in the addition sulfide, resulting in decreased resistance to media; Comparative Example 3 only underwent one-stage sulfide treatment, resulting in insufficient cross-linking, numerous network defects, and solvents almost caused the material to disintegrate; Comparative Example 4 underwent two-stage sulfide treatment with excessively rapid heating, leading to uneven cross-linking and significant differences between the surface and internal structures; Comparative Example 5 used an equal mass of hydroxyl silicone oil instead of perfluoroalkyltrialkoxysilane, and its resistance to strong polar solvents decreased.

[0062] In summary, it can be clearly seen from the above embodiments and comparative examples that the cross-linked fluorosilicone rubber with a wide temperature range and strong polar solvent resistance provided by the present invention has a significant improvement in resistance to strong polar solvents, and solves the technical problem of cross-linked fluorosilicone rubber in terms of resistance to strong polar solvents.

Claims

1. A cross-linked fluorosilicone rubber with a wide temperature range and resistance to strong polar solvents, characterized in that: The crosslinked fluorosilicone rubber, based on 100 parts of pretreated raw rubber, has the following raw material composition: 30-50 parts of silica, 4-12 parts of hydroxyl fluorosilicone oil, 2-6 parts of perfluoroalkyltrialkoxysilane, 1-3 parts of heat resistant agent, 0.1-0.3 parts of platinum catalyst, 0.08-0.25 parts of inhibitor, and 2-4 parts of hydrogen-containing silicone oil crosslinking agent; wherein, the molar ratio of Si-H to vinyl is 1.4:1-2.0:1, and the platinum element in the platinum catalyst is 2000-4000 ppm.

2. The cross-linked fluorosilicone rubber with a wide temperature range and resistance to strong polar solvents according to claim 1, characterized in that: The pretreated raw rubber is vinyl-terminated polymethyl (3,3,3-trifluoropropyl)siloxane, with a vinyl molar content of 0.10% to 0.50%.

3. The cross-linked fluorosilicone rubber with a wide temperature range and resistance to strong polar solvents according to claim 1, characterized in that: The hydroxyl fluorosilicone oil is hydroxyl-terminated polymethyltrifluoropropylsiloxane with a hydroxyl mass fraction of 0.5% to 5.0%.

4. The cross-linked fluorosilicone rubber with a wide temperature range and resistance to strong polar solvents according to claim 1, characterized in that: The perfluoroalkyltrialkoxysilane is one of perfluorooctyltriethoxysilane, 1H,1H,2H,2H-perfluorodecyltriethoxysilane, and perfluorododecyltriethoxysilane.

5. The cross-linked fluorosilicone rubber with a wide temperature range and resistance to strong polar solvents according to claim 1, characterized in that: The heat-resistant agent is one or more of cerium oxide, iron oxide, magnesium oxide, and zirconium oxide; the hydrogen-containing silicone oil crosslinking agent has a Si-H mass fraction of 0.05% to 0.30%.

6. A method for preparing a cross-linked fluorosilicone rubber with a wide temperature range and resistance to strong polar solvents as described in any one of claims 1-5, characterized in that, Includes the following steps: S1: Raw material pretreatment, vinyl-terminated polymethyl(3,3,3-trifluoropropyl)siloxane is subjected to thin-pass treatment to obtain pretreated raw rubber; S2: Mixing. The pretreated raw rubber prepared in S1 is rolled, then some silica is added and mixed. Then hydroxyl fluorosilicone oil, heat resistant agent and perfluoroalkyltrialkoxysilane are added and mixed. After resting, the remaining silica, inhibitor, platinum catalyst and hydrogen-containing silicone oil crosslinking agent are added in sequence and mixed in sequence. The mixture is then dispersed in a thin stream and cooled to room temperature to obtain the mixed rubber. S3: Vulcanization molding. The compound prepared in S2 is vulcanized, cooled to room temperature, and then vulcanized again and cooled to room temperature to obtain cross-linked fluorosilicone rubber.

7. The method for preparing a cross-linked fluorosilicone rubber with a wide temperature range and resistance to strong polar solvents according to claim 6, characterized in that: The thin-pass processing described in S1 has the following parameter settings: 12 to 18 passes, 0.5 to 1.5 mm roller gap, and 20 to 40°C temperature.

8. The method for preparing a cross-linked fluorosilicone rubber with a wide temperature range and resistance to strong polar solvents according to claim 6, characterized in that: The portion of silica mentioned in S2 accounts for one-third of all silica. The mixing parameters described in S2 are set as follows: temperature 30-50℃; The parking process described in S2 has the following parameter settings: temperature 20-30℃, duration 24-48h.

9. The method for preparing a cross-linked fluorosilicone rubber with a wide temperature range and resistance to strong polar solvents according to claim 6, characterized in that: The vulcanization process described in S3 is divided into pre-vulcanization and main vulcanization. The parameters are set as follows: pre-vulcanization temperature 90-110℃, pressure 10-15MPa, duration 12-18min; main vulcanization temperature 155-165℃, pressure 10-15MPa, duration 25-35min.

10. The method for preparing a cross-linked fluorosilicone rubber with a wide temperature range and resistance to strong polar solvents according to claim 6, characterized in that: The secondary vulcanization described in S3 has the following parameter settings: heating rate 1-3℃ / min, temperature 120℃, holding time 1h, then heating to 180-200℃, holding time 2-4h.

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