Polyurethane-based rotary blowout preventer rubber core material and preparation method thereof

Abstract

The invention relates to the technical field of high-performance polymer materials, and discloses a rotary blowout preventer rubber core material based on polyurethane and a preparation method, the material has an interpenetrating polymer network structure, and is composed of a main bearing network I providing high mechanical strength and a functional network II formed by in-situ polymerization in the main bearing network I. A dynamic disulfide bond is introduced into the functional network II, so that the material is endowed with thermally-induced self-repairing capability; the visual early warning of the damage is realized by introducing a work-induced discoloration additive; by integrating a cascade type catalytic system containing a low-temperature catalyst and a latent high-energy catalyst, temperature control grading response in the repairing process is achieved, and daily maintenance and efficient repairing are both considered. The coating is prepared by a method of first permeating and then in-situ curing. The prepared rubber core material not only has excellent comprehensive mechanical properties and ultra-long anti-fatigue life, but also integrates damage self-repairing and visual indication functions, and effectively solves the technical problems that the traditional material is irreversible in damage and lacks state monitoring means.

Description

Technical Field

[0001] This invention relates to the field of high-performance polymer materials technology, specifically to a polyurethane-based rotary blowout preventer core material and its preparation method. Background Technology

[0002] Rotary blowout preventers (BOPs) are critical safety devices for controlling wellhead pressure during oil and gas drilling and workover operations. Their core sealing component—the rubber core—endures intense friction from the drill string, scouring from high-pressure fluids, and complex alternating stresses during pressurized rotary drilling, operating in an extremely harsh environment. Therefore, the comprehensive mechanical properties of the rubber core material, such as high strength, high toughness, wear resistance, and fatigue resistance, are subject to very high requirements. Currently, high-performance polyurethane elastomers are the mainstream material for manufacturing these rubber cores.

[0003] However, traditional polyurethane core materials have inherent technical drawbacks in practical applications. First, the chemical structure of these materials is based on a permanent covalent cross-linked network. Once microcracks or other damage occur during service due to stress concentration or fatigue accumulation, this damage is irreversible. These micro-damages will continue to expand and merge, eventually leading to a decline in the macroscopic mechanical properties of the material and even overall failure. This not only limits the service life of the core but also poses safety hazards.

[0004] Secondly, the occurrence and accumulation of the aforementioned damage are "silent" within the material, lacking effective real-time monitoring methods. Operators cannot visually assess the health status of the core and typically rely on experience or fixed time cycles for preventative replacement. This can lead to waste due to premature replacement or catastrophic accidents due to failure to detect potential problems in time. Therefore, traditional materials cannot provide visual early warning of their own damage status.

[0005] Furthermore, to overcome the aforementioned shortcomings, researchers have attempted to introduce functional components such as repair and sensing agents into the polyurethane matrix. However, through traditional one-step blending or simple copolymerization methods, the introduction of these functional additives often interferes with the perfect formation of the main load-bearing network, easily leading to phase separation or structural defects, thus significantly sacrificing the material's essential high strength, high toughness, and other fundamental mechanical properties. How to successfully and effectively integrate multiple functions without reducing the material's mechanical properties, while ensuring the integrity and controllability of each network structure, remains a major challenge for current technology. Summary of the Invention

[0006] The technical problem to be solved by the present invention is that the damage generated inside the existing rotary blowout preventer core material during its service life is difficult to be assessed in real time, which poses a potential safety risk. At the same time, it does not have the ability to repair itself after damage, resulting in a limited service life.

[0007] To address the aforementioned technical problems, this invention provides a polyurethane-based rotary blowout preventer core material and its preparation method, which integrates damage indication function and self-healing capability.

[0008] The first aspect of this invention provides a polyurethane-based rotary blowout preventer core material, which is made from raw materials comprising the following components: The raw material I of the main load-bearing network I includes polyol, diisocyanate and chain extender; Raw material II, which is formed by infiltration polymerization in the main load-bearing network I to form functional network II, comprises diisocyanate and diol containing dynamic disulfide bonds; Color-changing additives; cascaded catalytic system.

[0009] Through the above technical solution, this invention constructs an interpenetrating polymer network structure. The main load-bearing network I serves as the macroscopic framework of the material, providing fundamental mechanical support. Functional network II permeates and fills the interior of the main load-bearing network I, physically interpenetrating with it.

[0010] In this invention, dynamic disulfide bonds are introduced into the polymer segments of functional network II. Under specific thermodynamic conditions, these disulfide bonds can undergo reversible bond exchange reactions. When microcracks form within the material, an external thermal field is applied, causing the disulfide bonds at the crack interface to break and recombine, allowing the polymer segments to reconnect across the crack interface, thus repairing the internal damage. A color-changing additive, acting as a molecular probe, is dispersed within the polymer matrix. When subjected to external mechanical stress, the additive's internal chemical bonds (such as carbon-oxygen bonds) break, causing the molecular configuration to change from a stable closed-ring state to an open-ring state with a large conjugated system. This change in the molecular conjugated system causes a change in its visible light absorption spectrum, macroscopically manifesting as a color change in the stress concentration or damaged areas, thus providing a visual indication of damage.

[0011] A cascaded catalytic system is used to precisely control the polymerization reaction timing of functional network II. This system contains two catalysts activated at different temperatures, ensuring that the permeate containing functional network II raw materials maintains low viscosity and high fluidity during the low-temperature permeation stage. After sufficient permeation of the main load-bearing network I, the highly active catalyst is activated by raising the temperature, initiating rapid in-situ polymerization and solidification of functional network II within the main load-bearing network I, ultimately forming a structurally complete and functionally integrated interpenetrating network.

[0012] In a specific technical solution, the raw material I of the main load-bearing network I includes: The polyol is a mixture of polytetrahydrofuran ether diol and polycaprolactone diol; The diisocyanate is a modified liquefied diphenylmethane diisocyanate; The chain extender is 1,4-butanediol.

[0013] In a specific technical solution: the diol containing dynamic disulfide bonds in the raw material II of the functional network II is a bis(2-hydroxyethyl) disulfide; The color-changing additive is 1',3'-dihydro-8-hydroxymethyl-1',3',3'-trimethyl-6-nitrospiro[2H-1-benzopyran-2,2'-indole]; The cascaded catalytic system comprises diisopropylethylamine as a low-temperature catalyst A and a DBU-carbonate adduct as a latent high-energy catalyst B.

[0014] In a specific technical solution, the proportions of the raw materials satisfy the following conditions: In the raw material I of the main load-bearing network I, the weight ratio of polytetrahydrofuran ether diol to polycaprolactone diol is 7:3, and the molar ratio of isocyanate groups to hydroxyl groups used to prepare the prepolymer is 2.0-2.5. The total molar ratio of isocyanate groups to hydroxyl groups in the entire network I reaction system is 0.95-0.98. In the raw material II of the functional network II, the molar ratio of isocyanate groups to hydroxyl groups is 1.0-1.05; Based on 100 parts by weight of the total mass of diisocyanate and bis(2-hydroxyethyl) disulfide in raw material II of the functional network II: The amount of the color-changing additive is 0.05-0.20 parts by weight; The amount of the low-temperature catalyst A is 0.01-0.05 parts by weight; The amount of the latent high-energy catalyst B is 0.10-0.30 parts by weight.

[0015] In one specific technical solution, the bis(2-hydroxyethyl) disulfide is prepared by oxidative coupling of 2-mercaptoethanol under the action of hydrogen peroxide; the DBU-carbonate adduct is prepared by reacting 1,8-diazabicyclo[5.4.0]undec-7-ene with carbon dioxide.

[0016] A second aspect of the present invention provides a method for preparing the above-mentioned polyurethane-based rotary blowout preventer core material, comprising the following steps: a) A prepolymer with NCO-terminated end groups was prepared by reacting polyol with diisocyanate, and then a chain extender was added to carry out a chain extension reaction. After that, it was cast and cured in the first stage to obtain the preform of the main load-bearing network I. b) A multifunctional permeate was prepared by mixing diisocyanate, diol containing dynamic disulfide bonds, chromogenic additives and a cascade catalytic system. c) The preform is immersed in the multifunctional permeation liquid and permeated by alternating vacuum and atmospheric pressure treatment. Then it is taken out and cured in the second stage. Functional network II is formed by in-situ polymerization inside the preform, thereby obtaining the polyurethane-based rotary blowout preventer core material.

[0017] In a specific technical solution, in step a), the reaction temperature for preparing the prepolymer is 75-85℃, the reaction time is 2.0-2.5 hours, the curing temperature for the first stage is 100-110℃, and the curing time is 8-10 hours.

[0018] In one specific technical solution, in step b), the mixing is carried out at 40-50°C and the mixture is mixed for 0.5-1.5 hours to form a multifunctional permeate.

[0019] In one specific technical solution, the vacuum-atmospheric pressure alternation process in step c) is carried out at 55-65°C, including evacuating to below 1000Pa and maintaining it for 20-30 minutes, then restoring to atmospheric pressure and maintaining it for 30-40 minutes, and repeating the process 5 times.

[0020] In a specific technical solution, the curing temperature in the second stage of step c) is 110-115℃, and the curing time is 16-24 hours.

[0021] This invention provides a polyurethane-based rotary blowout preventer core material and its preparation method. It has the following beneficial effects: 1. This invention introduces a color-changing additive into polyurethane materials, enabling the material to display damage. When the core material is subjected to excessive mechanical stress or develops internal microcracks, the molecular structure of the additive reversibly transforms from a colorless closed-ring state to a colored open-ring large conjugated structure, thus macroscopically producing a color change in the stress concentration or damage area. This design allows the health status of the core to be assessed intuitively and in real time, providing a reliable basis for preventive maintenance and replacement, and significantly improving the operational safety of the equipment.

[0022] 2. This invention endows materials with thermo-induced self-healing capabilities by constructing a functional network II containing dynamic disulfide bonds. The disulfide bonds in this network can undergo reversible breakage and recombination exchange reactions under thermal action. When damage occurs inside the material (such as microcracks), heating the core can promote the re-formation of chemical bonds across the crack interface by polymer segments, thereby achieving structural repair of the material. This function effectively extends the service life of the core and reduces its total lifespan cost.

[0023] 3. The preparation method employed in this invention, particularly the use of a cascaded catalytic system, enables precise control over the formation of the interpenetrating network structure. This system ensures that the raw materials of functional network II, in a low-viscosity liquid form, fully penetrate into the interior of the main load-bearing network I at low temperatures. After penetration, the latent high-energy catalyst is activated by heating, initiating rapid in-situ polymerization. This stepwise, controllable curing process guarantees the formation of a uniform and complete physically interpenetrating structure between the two networks, thus providing a structural foundation for the material's excellent comprehensive mechanical properties and the stable realization of the aforementioned functionalities. Detailed Implementation

[0024] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the preparation examples, comparative examples, and test examples. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] The main raw materials and reagents used in the following examples and comparative examples have the following sources and specifications. Reagents not specifically mentioned are all commercially available analytical grade or higher grade products.

[0026] Polytetrahydrofuran ether diol, average molecular weight 2000 g / mol, CAS No.: 25190-06-1; Polycaprolactone diol, average molecular weight 2000 g / mol, CAS No.: 36890-68-3; Bis(2-hydroxyethyl) disulfide, prepared according to Preparation Example 1; The color-changing additive (SP-OH) was prepared according to Preparation Example 2; Latent high-energy catalyst B (DBU-carbonate adduct) was prepared according to preparation example 3.

[0027] Preparation Examples 1-3: Preparation Example 1: Preparation of bis(2-hydroxyethyl) disulfide (HEDS) In a 1000 mL three-necked flask equipped with a magnetic stirrer, thermometer, and dropping funnel, add 156.2 g (2.0 mol) of 2-mercaptoethanol and 400 mL of deionized water. Cool the mixture to below 10 °C in an ice-water bath.

[0028] 249.6 g (2.2 mol) of a 30% (w / w) hydrogen peroxide aqueous solution was slowly added dropwise through a dropping funnel under vigorous stirring. The dropping rate was strictly controlled to ensure that the internal temperature of the reaction system was maintained below 30°C. The dropping process lasted approximately 2 hours.

[0029] After the addition is complete, remove the ice-water bath and continue stirring the reaction system at room temperature (20-25℃) for 5 hours to ensure the reaction is complete.

[0030] After the reaction was complete, sodium chloride solid was added to the reaction mixture in portions until the solution was saturated. The mixture was then transferred to a separatory funnel. Extraction was performed three times using 200 mL of ethyl acetate each time.

[0031] Combine all organic extract phases, wash once with 100 mL of saturated sodium bicarbonate aqueous solution, and then wash once with 100 mL of saturated saline solution. Dry the washed organic phases with anhydrous magnesium sulfate, let stand for 30 minutes, and then filter.

[0032] The filtrate was transferred to a rotary evaporator, and the solvent ethyl acetate was removed by evaporation under vacuum at a water bath temperature of 45°C, finally yielding 152.5g of a colorless to pale yellow oily liquid, which is the target product bis(2-hydroxyethyl) disulfide (HEDS).

[0033] Preparation Example 2: Preparation of a color-changing additive (SP-OH) This preparation example includes two steps: Step A: Preparation of intermediate 1-(3-hydroxypropyl)-2,3,3-trimethyl-3H-indole quaternary ammonium bromide In a 500 mL round-bottom flask, 31.8 g (0.2 mol) of 2,3,3-trimethyl-3H-indole and 30.6 g (0.22 mol) of 3-bromo-1-propanol were added, along with 200 mL of acetonitrile as solvent. The mixture was heated to 80–85 °C and refluxed at this temperature for 24 hours. After the reaction was complete, the reaction solution was cooled to room temperature and then refrigerated for 4 hours, resulting in the precipitation of a large amount of solid. The solid was collected by filtration, washed with a small amount of ice-cold acetonitrile, and dried under vacuum to obtain a pink solid quaternary ammonium salt intermediate.

[0034] Step B: Synthesis of the final product 1',3'-dihydro-8-hydroxymethyl-1',3',3'-trimethyl-6-nitrospiro[2H-1-benzopyran-2,2'-indole] (SP-OH) The quaternary ammonium salt intermediate (0.2 mol) obtained in step A and 33.4 g (0.2 mol) of 3-hydroxy-4-nitrobenzaldehyde were added to 500 mL of anhydrous ethanol. 22.2 g (0.22 mol) of triethylamine was added as an acid-binding agent. The mixture was heated to reflux and reacted for 7 hours. The reaction progress was monitored using thin-layer chromatography (TLC).

[0035] After the reaction was complete, the reaction solution was cooled to room temperature, and a solid product precipitated. The crude product was collected by filtration and washed with a small amount of ice-cold ethanol. The collected crude product was dissolved in a minimal amount of dichloromethane, and then n-hexane was slowly added. Purification was carried out by recrystallization. The recrystallization operation was repeated twice. Finally, the product was filtered, collected, and dried under vacuum at 40°C for 6 hours to obtain 25.1 g of the final product SP-OH, which was a light yellow powder.

[0036] Preparation Example 3: Preparation of Latent High-Energy Catalyst B (DBU-Carbonate Adduct) In a 500 mL three-necked flask that has been thoroughly dried and equipped with a gas inlet tube, a gas outlet tube, and a powerful magnetic stirrer, 30.4 g (0.2 mol) of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) was added, and 200 mL of anhydrous tetrahydrofuran (THF) was added via syringe.

[0037] At room temperature (20-25℃), start magnetic stirring and slowly introduce carbon dioxide gas, dried in a silica gel drying tower, into the DBU THF solution at a flow rate of approximately 100 mL / min through the gas inlet tube. Connect the gas outlet tube to a paraffin oil bubble meter to monitor the gas flow rate.

[0038] As carbon dioxide was introduced, a large amount of white precipitate quickly appeared and formed in the solution. Aeration continued for 2 hours to ensure the DBU reaction was complete.

[0039] Stop the carbon dioxide flow and continue stirring for 30 minutes. Then, under nitrogen protection, rapidly transfer the reaction suspension through a dry tubing to a dry filter for vacuum filtration. Wash the filter cake twice with 50 mL of anhydrous THF.

[0040] The collected white solid filter cake was placed in a vacuum drying oven and dried under vacuum at 35°C for 8 hours to obtain 38.5g of white powdery product, which is the DBU-carbonate adduct. It was sealed and stored in a desiccator before use.

[0041] Examples 1-3: Example 1: Step 1: Preparation of the main load-bearing network (Network I) preform Raw material preparation and dehydration: In a clean, dry 10L reactor, accurately weigh 7.00 kg of polytetrahydrofuran ether glycol (PTMG, average molecular weight 2000 g / mol) and 3.00 kg of polycaprolactone glycol (PCL, average molecular weight 2000 g / mol). Start stirring and heat the mixed polyols to 105°C. Simultaneously turn on the vacuum pump and continue stirring and dehydrating for 2 hours under a vacuum of less than 500 Pa.

[0042] Prepolymer preparation: After dehydration, heating was stopped and dry nitrogen was introduced to break the vacuum. The temperature of the mixed polyol was lowered to 75°C and stabilized. At this temperature, preheated modified liquefied diphenylmethane diisocyanate (Modified MDI) was rapidly added. The amount added was precisely calculated based on the molar ratio (NCO / OH) of isocyanate groups (-NCO) to hydroxyl groups (-OH) in the prepolymer reaction system being 2.0:1. After the addition was complete, high-speed stirring (500 rpm) was immediately started, and the reaction was carried out at 75°C for 2.5 hours to obtain a prepolymer with -NCO-terminated groups.

[0043] Chain extension and casting: After the prepolymerization reaction, the reactor temperature is raised to 80℃, and the prepolymer is subjected to vacuum degassing for 15 minutes at this temperature, with a vacuum degree below 500 Pa. After degassing, dry nitrogen is introduced to break the vacuum. 1,4-Butanediol (BDO) is added as a chain extender, and its amount is calculated based on the principle that the final molar ratio (R value) of total -NCO to total -OH in the entire reaction system is 0.95. After adding BDO, the stirring speed is immediately increased to 2500 rpm, and vigorous mixing is performed for 45 seconds.

[0044] Initial Curing and Molding: After thorough mixing, the viscous reactant material is quickly poured from the bottom outlet of the reactor into a preheated metal core mold coated with a release agent at 100°C. The filled mold is then smoothly transferred into a large programmed oven for the first stage of curing at 100°C for 10 hours. After curing, the mold is opened, the fully formed polyurethane core preform is removed, and it is allowed to cool naturally at room temperature for later use.

[0045] Step 2: Preparation of multifunctional permeate Raw material ratio: In a separate, clean, dry 5L stainless steel light-proof reaction vessel, prepare the following ratio based on 100 parts by weight of the total mass of modified MDI and HEDS in the final permeate: Modified liquefied diphenylmethane diisocyanate (Modified MDI) and bis(2-hydroxyethyl) disulfide (HEDS) prepared in Preparation Example 1: The amounts of both were calculated based on the principle that the molar ratio of -NCO to -OH in their reaction system is 1.0:1.

[0046] Color-changing additive (SP-OH): 0.05 parts by weight were added, which is the product obtained in Preparation Example 2.

[0047] Low-temperature catalyst A (DIPEA): 0.01 parts by weight added.

[0048] Latent high-energy catalyst B: 0.10 parts by weight of the DBU-carbonate adduct prepared in Example 3 was added.

[0049] Mixing process: First, metered amounts of modified MDI and HEDS are added to the reaction vessel and stirred at low speed at 40°C to achieve initial mixing. Subsequently, metered amounts of SP-OH, DIPEA, and latent high-energy catalyst B are added to the mixture sequentially. The temperature inside the vessel is maintained at 40°C, and stirring is continued at low speed for 0.5 hours until all solid components are completely dissolved or uniformly dispersed, forming a clear, homogeneous, pale yellow transparent permeate free of visible particles.

[0050] Step 3: Penetration, Saturation, and Final Curing Infiltration and Saturation: The preformed core obtained in step 1 and cooled to room temperature is completely immersed in the multifunctional infiltration solution prepared in step 2, ensuring that the liquid completely covers the core. The entire immersion system is placed in a large vacuum impregnation tank. Alternating vacuum and atmospheric pressure treatments are performed at 55°C. First, evacuate to a pressure below 1000 Pa and maintain this pressure for 20 minutes. Then, introduce dry nitrogen to restore the pressure to atmospheric pressure and maintain this pressure for 30 minutes. This completes one cycle. Perform five cycles in total, with a total permeation time of four hours.

[0051] Final Curing and Functional Integration: After the infiltration process, the core is removed from the infiltration solution. Excess liquid adhering to the surface is gently scraped off with a special PTFE scraper, and then wiped clean with a non-woven cloth. The treated core is immediately transferred to a programmed oven equipped with a light filter (filtering out light with wavelengths less than 450nm). Second-stage curing is performed at 115°C for 24 hours.

[0052] Cooling and Finished Product: After the curing process is complete, turn off the oven power and allow the core to cool slowly to room temperature in the sealed oven for 12 hours. The final product of this embodiment is then obtained.

[0053] Example 2: Step 1: Preparation of the main load-bearing network (Network I) preform Raw material preparation and dehydration: In a clean, dry 10L reactor, accurately weigh 7.00 kg of polytetrahydrofuran ether glycol (PTMG, average molecular weight 2000 g / mol) and 3.00 kg of polycaprolactone glycol (PCL, average molecular weight 2000 g / mol). Start stirring and heat the mixed polyols to 110°C. Simultaneously turn on the vacuum pump and continue stirring and dehydrating for 2 hours under a vacuum of less than 500 Pa.

[0054] Prepolymer Preparation: After dehydration, heating was stopped and dry nitrogen was introduced to break the vacuum. The temperature of the mixed polyol was lowered to 80°C and stabilized. At this temperature, preheated modified liquefied diphenylmethane diisocyanate (Modified MDI) was rapidly added. The amount added was precisely calculated based on the molar ratio (NCO / OH) of isocyanate groups (-NCO) to hydroxyl groups (-OH) in the prepolymer reaction system being 2.2:1. After the addition was complete, high-speed stirring (650 rpm) was immediately started, and the reaction was carried out at 80°C for 2.0 hours to obtain a prepolymer with -NCO-terminated groups.

[0055] Chain extension and casting: After the prepolymerization reaction, the reactor temperature is raised to 85℃, and the prepolymer is subjected to vacuum degassing for 12 minutes at this temperature, with a vacuum degree below 500 Pa. After degassing, dry nitrogen is introduced to break the vacuum. 1,4-Butanediol (BDO) is added as a chain extender, and its amount is calculated based on the principle that the final molar ratio (R value) of total -NCO to total -OH in the entire reaction system is 0.965. After adding BDO, the stirring speed is immediately increased to 2800 rpm, and vigorous mixing is performed for 50 seconds.

[0056] Initial Curing and Molding: After thorough mixing, the viscous reactant material is quickly poured from the bottom outlet of the reactor into a preheated metal core mold coated with a release agent at 105°C. The filled mold is then smoothly transferred into a large programmed oven for the first stage of curing at 105°C for 9 hours. After curing, the mold is opened, the fully formed polyurethane core preform is removed, and it is allowed to cool naturally at room temperature for later use.

[0057] Step 2: Preparation of multifunctional permeate Raw material ratio: In a separate, clean, dry 5L stainless steel light-proof reaction vessel, prepare the following ratio based on 100 parts by weight of the total mass of modified MDI and HEDS in the final permeate: Modified liquefied diphenylmethane diisocyanate (Modified MDI) and bis(2-hydroxyethyl) disulfide (HEDS) prepared in Preparation Example 1: The amounts of both were calculated based on the principle that the molar ratio of -NCO to -OH in their reaction system is 1.02:1.

[0058] Color-changing additive (SP-OH): 0.12 parts by weight were added, which is the product obtained in Preparation Example 2.

[0059] Low-temperature catalyst A (DIPEA): 0.03 parts by weight added.

[0060] Latent high-energy catalyst B: 0.20 parts by weight of the DBU-carbonate adduct prepared in Example 3 was added.

[0061] Mixing process: First, add measured amounts of modified MDI and HEDS to the reaction vessel and stir at low speed at 45°C to achieve initial mixing. Then, sequentially add measured amounts of SP-OH, DIPEA, and latent high-energy catalyst B to the mixture. Maintain the vessel temperature at 45°C and continue stirring at low speed for 1 hour until all solid components are completely dissolved or uniformly dispersed, forming a clear, homogeneous, pale yellow transparent permeate free of visible particles.

[0062] Step 3: Penetration, Saturation, and Final Curing Infiltration and Saturation: The preformed core obtained in step 1 and cooled to room temperature is completely immersed in the multifunctional infiltration solution prepared in step 2, ensuring that the liquid completely covers the core. The entire immersion system is placed in a large vacuum impregnation tank. Alternating vacuum and atmospheric pressure treatment is performed at 60°C. First, evacuate to a pressure below 1000 Pa and maintain this pressure for 25 minutes. Then, introduce dry nitrogen to restore the pressure to atmospheric pressure and maintain this pressure for 35 minutes. This completes one cycle. Perform five cycles in total, with a total permeation time of five hours.

[0063] Final Curing and Functional Integration: After the infiltration process, the core is removed from the infiltration solution. Excess liquid adhering to the surface is gently scraped off with a special PTFE scraper, and then wiped clean with a non-woven cloth. The treated core is immediately transferred to a programmed oven equipped with a light filter (filtering out light with wavelengths less than 450nm). Second-stage curing is performed at 110°C for 20 hours.

[0064] Cooling and Finished Product: After the curing process is complete, turn off the oven power and allow the core to cool slowly to room temperature in the sealed oven for 12 hours. The final product of this embodiment is then obtained.

[0065] Example 3: Step 1: Preparation of the main load-bearing network (Network I) preform Raw material preparation and dehydration: In a clean, dry 10L reactor, accurately weigh 7.00 kg of polytetrahydrofuran ether glycol (PTMG, average molecular weight 2000 g / mol) and 3.00 kg of polycaprolactone glycol (PCL, average molecular weight 2000 g / mol). Start stirring and heat the mixed polyols to 115°C. Simultaneously turn on the vacuum pump and continue stirring and dehydrating for 2 hours under a vacuum of less than 500 Pa.

[0066] Prepolymer Preparation: After dehydration, heating was stopped and dry nitrogen was introduced to break the vacuum. The temperature of the mixed polyol was lowered to 85°C and stabilized. At this temperature, preheated modified liquefied diphenylmethane diisocyanate (Modified MDI) was rapidly added. The amount added was precisely calculated based on the molar ratio (NCO / OH) of isocyanate groups (-NCO) to hydroxyl groups (-OH) in the prepolymer reaction system being 2.5:1. After the addition was complete, high-speed stirring (800 rpm) was immediately started, and the reaction was carried out at 85°C for 2.0 hours to obtain a prepolymer with -NCO-terminated groups.

[0067] Chain extension and casting: After the prepolymerization reaction, the reactor temperature is raised to 90℃, and the prepolymer is subjected to vacuum degassing for 10 minutes at this temperature, with a vacuum degree below 500 Pa. After degassing, dry nitrogen is introduced to break the vacuum. 1,4-Butanediol (BDO) is added as a chain extender, and its amount is calculated based on the principle that the final molar ratio (R value) of total -NCO to total -OH in the entire reaction system is 0.98. After adding BDO, the stirring speed is immediately increased to 3000 rpm, and vigorous mixing is performed for 60 seconds.

[0068] Preliminary Curing and Molding: After thorough mixing, the viscous reactant material is quickly poured from the bottom outlet of the reactor into a preheated metal core mold coated with a release agent at 110°C. The filled mold is then smoothly transferred into a large programmed oven for the first stage of curing at 110°C for 8 hours. After curing, the mold is opened, the fully formed polyurethane core preform is removed, and it is allowed to cool naturally at room temperature for later use.

[0069] Step 2: Preparation of multifunctional permeate Raw material ratio: In a separate, clean, dry 5L stainless steel light-proof reaction vessel, prepare the following ratio based on 100 parts by weight of the total mass of modified MDI and HEDS in the final permeate: Modified liquefied diphenylmethane diisocyanate (Modified MDI) and bis(2-hydroxyethyl) disulfide (HEDS) prepared in Preparation Example 1: The amounts of both were calculated based on the principle that the molar ratio of -NCO to -OH in their reaction system is 1.05:1.

[0070] Color-changing additive (SP-OH): 0.20 parts by weight were added, which is the product obtained in Preparation Example 2.

[0071] Low-temperature catalyst A (DIPEA): Add 0.05 parts by weight.

[0072] Latent high-energy catalyst B: 0.30 parts by weight of the DBU-carbonate adduct prepared in Example 3 was added.

[0073] Mixing process: First, metered amounts of modified MDI and HEDS are added to the reaction vessel and stirred at low speed at 50°C to achieve initial mixing. Subsequently, metered amounts of SP-OH, DIPEA, and latent high-energy catalyst B are added to the mixture sequentially. The temperature inside the vessel is maintained at 50°C, and stirring is continued at low speed for 1.5 hours until all solid components are completely dissolved or uniformly dispersed, forming a clear, homogeneous, pale yellow transparent permeate free of visible particles.

[0074] Step 3: Penetration, Saturation, and Final Curing Infiltration and Saturation: The preformed core obtained in Step 1 and cooled to room temperature was completely immersed in the multifunctional infiltration solution prepared in Step 2, ensuring that the liquid completely covered the core. The entire immersion system was placed in a large vacuum impregnation tank. Vacuum-atmospheric pressure alternating treatment was performed at 65°C: first, a vacuum was drawn to a pressure below 1000 Pa and maintained for 30 minutes, then dry nitrogen was introduced to restore the pressure to atmospheric pressure and maintained for 40 minutes; this constituted one cycle. A total of 5 cycles were performed, with a total infiltration time of 6 hours.

[0075] Final Curing and Functional Integration: After the infiltration process, the core is removed from the infiltration solution. Excess liquid adhering to the surface is gently scraped off with a special PTFE scraper, and then wiped clean with a non-woven cloth. The treated core is immediately transferred to a programmed oven equipped with a light filter (filtering out light with wavelengths less than 450nm). Second-stage curing is performed at 115°C for 16 hours.

[0076] Cooling and Finished Product: After the curing process is complete, turn off the oven power and allow the core to cool slowly to room temperature in the sealed oven for 12 hours. The final product of this embodiment is then obtained.

[0077] Comparative Examples 1-6: Comparative Example 1: Traditional High-Performance Polyurethane Materials Compared to Example 2, the difference lies in the preparation method and chemical composition. This comparative example was prepared using a conventional one-step casting method, rather than the stepwise infiltration and in-situ curing method employed in this invention. Its chemical composition does not contain bis(2-hydroxyethyl) disulfide (HEDS), chromogenic additive (SP-OH), low-temperature catalyst A (DIPEA), or latent high-energy catalyst B. This formulation is a typical non-repairing, non-intelligent high-performance polyurethane, with a molar ratio R of 1.05 between the total isocyanate groups and the total hydroxyl groups. All other raw material ratios and curing conditions followed conventional high-performance polyurethane processes.

[0078] Comparative Example 2: Functional polyurethane prepared by simple blending method The difference between Example 2 and Example 3 is that a one-step blending method is used for preparation. That is, all chemical components used to constitute Network I and Network II in Example 2 (including PTMG, PCL, MDI, BDO, HEDS, SP-OH, catalyst A, and catalyst B) are mixed uniformly in one step after the prepolymerization reaction, and then directly cast and cured, without forming the interpenetrating network structure of this invention. The total amount of the remaining components and the curing process parameters are the same as in Example 2.

[0079] Comparative Example 3: Interpenetrating network materials without dynamic repair networks The difference from Example 2 is that, in preparing the multifunctional permeate, instead of using bis(2-hydroxyethyl) disulfide (HEDS) containing dynamic disulfide bonds, it is replaced with an equimolar amount of 1,4-butanediol (BDO), thereby forming a permanent cross-linked network II that does not possess dynamic repair capabilities. All other steps, raw materials, and process parameters are exactly the same as in Example 2.

[0080] Comparative Example 4: Repairable materials without color-changing properties The difference between Example 2 and Example 3 is that no chromogenic additive (SP-OH) is added when preparing the multifunctional permeate. All other steps, raw materials, and process parameters are exactly the same as in Example 2.

[0081] Comparative Example 5: Dynamic Repair Material Without Any Catalyst The difference between Example 2 and Example 3 is that neither low-temperature catalyst A (DIPEA) nor latent high-energy catalyst B is added when preparing the multifunctional permeate. All other steps, raw materials, and process parameters are exactly the same as in Example 2.

[0082] Comparative Example 6: Dynamic Repair Material Containing Only a Single Low-Temperature Catalyst The difference between Example 2 and Example 3 is that no latent high-energy catalyst B is added when preparing the multifunctional permeate. This material contains only a low-temperature catalyst A (DIPEA) for routine maintenance. All other steps, raw materials, and process parameters are exactly the same as in Example 2.

[0083] Test Examples 1-6: Test Example 1: Mechanical Force-Induced Color Change Function Verification Test Experimental Description: This test is used to verify the color change function of the polyurethane material prepared by this invention under a preset mechanical force.

[0084] Experimental steps: Sample preparation: Two square samples with dimensions of 50mm × 50mm × 10mm were cut from the core materials prepared in Examples 1, 2, 3, Comparative Example 1, and Comparative Example 4, for a total of 10 samples. All samples were ensured to have a smooth surface free of initial scratches or defects. Each sample was numbered, and its initial surface color was recorded.

[0085] Test equipment and parameter settings: A Brinell hardness tester was used as the loading device. A standard steel ball indenter with a diameter of 5mm was selected. The loading load was set to 500N, and the holding time was set to 30 seconds.

[0086] Loading Operation: Place the numbered samples one by one onto the testing platform of the Brinell hardness tester. Start the equipment, causing the steel ball indenter to press vertically towards the geometric center of the sample at the set rate. After reaching a load of 500N, the equipment automatically holds the load for 30 seconds. After the load holding period ends, the indenter automatically unloads and returns to its initial position.

[0087] Results Observation and Recording: Within one minute of the load being completely removed, the specimen was immediately removed from the test platform and placed in an observation box equipped with a standard D65 light source. The color of the indentation area and its surrounding area was visually observed and compared with the color of the unstressed area of ​​the specimen. The color change was recorded in detail.

[0088] Experimental data: Table 1. Test results of mechanically induced color-changing function

[0089] Conclusion: The test results recorded in Table 1 show that the materials prepared in Examples 1, 2, and 3 exhibited a visible color change in their stressed areas after being subjected to a preset local mechanical force, transforming from an initial pale yellow to varying degrees of pink or purplish-red. In contrast, the samples in Comparative Examples 1 and 4, which did not contain the color-changing additive, did not show any visible color change after being subjected to the same load. This result confirms the function of the material described in this invention in generating a color response to mechanical force.

[0090] This phenomenon corresponds to the molecular structure response mechanism of the chromogenic additive (SP-OH) contained in the polyurethane matrix. When the local stress of the material exceeds a certain threshold, mechanical energy is absorbed by the molecules, thereby initiating a reversible isomerization transformation of the closed-ring structure of the spiropyran molecule into the open-ring colored cyanine structure. This open-ring conjugated structure changes the light absorption characteristics of the molecule, thus causing the material to exhibit a color different from its initial state on a macroscopic scale.

[0091] Therefore, this color transformation provides a direct visual representation of stress concentration areas or potential damage areas within the material. This function enables the recording and location of the material's history of exceeding the threshold stress, allowing for the identification of potential weak points or areas where high stress events have occurred through visual inspection, providing direct physical evidence for assessing the material's condition.

[0092] Test Example 2: Basic Self-Healing Function Verification Test Experimental Description: This test is used to quantitatively evaluate the degree of recovery of the mechanical properties of the polyurethane material prepared in this invention after undergoing macroscopic notch damage under the specified heat treatment conditions.

[0093] Experimental steps: Sample grouping: Six dumbbell-shaped tensile specimens conforming to GB / T528-2009 were cut from the materials prepared in Example 2, Comparative Example 1, and Comparative Example 3, respectively. The six specimens of each material were randomly divided into two groups: the original control group (3 specimens) and the damage repair group (3 specimens), and were assigned corresponding numbers.

[0094] Initial strength test: Using a universal testing machine, all original control group specimens were subjected to tensile tests at an ambient temperature of (23±2)℃ and a tensile rate of 500 mm / min until they fractured. The maximum tensile strength of each specimen was recorded, and the initial average tensile strength (P0) of each material was calculated.

[0095] Damage application: For all damaged test specimens, at the geometric center of their narrowest point, use a new, sharp blade to make a cut perpendicular to the specimen length. Use a micrometer to control and ensure the cut depth is (50 ± 2)% of the specimen thickness.

[0096] Repair treatment: The two cut surfaces of each notched specimen were tightly fitted together, and slight pressure was applied using a clamp to maintain contact. Subsequently, all the fixed damage repair group specimens were placed horizontally in a forced-air oven and heat-treated at 80°C for 6 hours.

[0097] Post-repair strength test: After heat treatment, all specimens were removed, the clamps were released, and the specimens were allowed to cool at room temperature for 2 hours. Then, using the same equipment, parameters, and environmental conditions as in step 2, tensile tests were performed on all repaired specimens. The maximum tensile strength at fracture was recorded, and the average tensile strength (P1) of each material after repair was calculated.

[0098] Repair efficiency calculation: The repair efficiency of each material is calculated according to the following formula: Repair efficiency (%) = (P1 / P0) × 100%.

[0099] Experimental data: Table 2. Basic self-healing function test data

[0100] Conclusion: The test data shown in Table 2 indicate that the tensile strength of the specimen prepared in Example 2 was significantly restored after undergoing notch damage and subsequent heat treatment, with a repair efficiency exceeding 74%. In contrast, the specimens prepared in Comparative Example 1 (without a dynamic repair network) and Comparative Example 3 (without dynamic chemical bonds in the repair network) showed a tensile strength recovery rate of less than 5% after undergoing the same damage and repair process, indicating that effective structural connections were not formed at their notch interfaces.

[0101] This strength recovery phenomenon is directly related to the dynamic chemical mechanism integrated within the material. In the polyurethane interpenetrating network of Example 2, network II contains a large number of disulfide bonds. Under heat treatment conditions of 80°C, these disulfide bonds undergo a reversible exchange reaction in the presence of low-temperature catalyst A. When the damaged interface is reattached, the disulfide bonds on the polymer chains on both sides of the interface cross the original crack interface through this dynamic exchange, reforming new covalent bonds. This allows the two separated surfaces to rebond at the molecular scale, ultimately manifesting macroscopically as crack healing and restoration of the material's mechanical properties.

[0102] Therefore, the test results confirm that constructing a dynamic interpenetrating network containing disulfide bonds in polyurethane materials can endow the materials with self-repair capabilities after macroscopic damage. The test results of Comparative Examples 1 and 3 further confirm that the realization of this repair function depends on the presence of dynamic chemical bonds (disulfide bonds), rather than simply the interpenetrating network structure or the thermoplastic behavior of the material. This function enables the material to actively repair damage generated during service and prevent damage accumulation, thus distinguishing it from traditional polyurethane materials where damage is irreversible.

[0103] Test Example 3: Cascaded Catalytic Remediation Efficiency Verification Test Experimental Description: This test is used to verify and compare the differences in the repair behavior of the polyurethane material prepared in this invention at different heat treatment temperatures, aiming to confirm the function of latent catalysts in the material being activated at higher temperatures and affecting the repair process.

[0104] Experimental steps: Sample Grouping: Nine dumbbell-shaped tensile specimens conforming to GB / T528-2009 were cut from the material prepared in Example 2. The specimens were randomly divided into three groups: the original control group (Group A, 3 specimens), the low-temperature repair group (Group B, 3 specimens), and the high-temperature repair group (Group C, 3 specimens), and were assigned corresponding numbers.

[0105] Original strength test: Using a universal testing machine, tensile tests were performed on all specimens in group A at an ambient temperature of (23±2)℃ and a tensile rate of 500 mm / min. The maximum tensile strength was recorded and the initial average tensile strength (P0) of the material was calculated.

[0106] Damage application: For all specimens in groups B and C, a notch with a depth of (50±2)% of the specimen thickness was applied at the center of the specimen, in accordance with the method and standard described in step 3 of test example B.

[0107] Group repair processing: Group B (Low Temperature Repair): The cut surfaces of the Group B samples are attached together and fixed with clamps, and then placed in an 80°C forced-air oven for heat treatment for 6 hours.

[0108] Group C (High Temperature Repair): The cut surfaces of the Group C samples are attached together and fixed with clamps, and then placed in a 140℃ forced-air oven for heat treatment for 1 hour.

[0109] Post-repair strength testing: After each group of repair treatments was completed, the specimens were removed, the clamps were released, and the specimens were allowed to cool at room temperature for 2 hours. Then, using the same equipment, parameters, and environmental conditions as in step 2, tensile tests were performed on all repaired specimens in groups B and C, respectively. The maximum tensile strength at fracture was recorded, and the average tensile strength (P) after repair was calculated. B ) and (P C ).

[0110] Repair efficiency calculation: According to the formula "Repair efficiency (%) = (P... B " / P0)×100%" and "Repair efficiency (%)=( ... C Calculate and record the repair efficiency of groups B and C using " / P0)×100%".

[0111] Experimental data: Table 3. Test data on the efficiency of cascaded catalytic remediation

[0112] Conclusion: The test data in Table 3 clearly show that the material in Example 2 exhibits strength recovery capability under both different repair conditions. After 6 hours of repair at 80°C, the tensile strength of the material recovered to more than 76% of its original strength. When the repair conditions were changed to 140°C and 1 hour, the tensile strength recovery rate of the material exceeded 92%. This result indicates that at higher temperatures, even with a significantly shorter repair time, the material can achieve a higher degree of repair.

[0113] This temperature-dependent difference in repair behavior corresponds to the mechanism of the cascaded catalytic system integrated within the material. At a low temperature of 80°C, the low-temperature catalyst A (DIPEA) in the system is active, catalyzing the dynamic exchange reaction of disulfide bonds, thus achieving the material's basic repair function. When the temperature rises to 140°C, the latent high-energy catalyst B (DBU-carbonate adduct) undergoes thermal decomposition, releasing DBU with catalytic activity far exceeding that of DPEA. This highly active DBU significantly accelerates the disulfide bond exchange reaction rate, enabling polymer segments to complete interfacial reconstruction and chemical bonding in a shorter time, thus macroscopically manifesting as a simultaneous increase in both repair speed and repair extent.

[0114] Therefore, this test confirms the effectiveness of the cascaded catalytic system in the present invention. This system enables the material to possess two response modes: conventional repair over a long period at lower temperatures, and deep repair at higher temperatures through activation of a high-energy catalyst for short-term, high-efficiency repair. This dual repair mechanism provides a tiered repair strategy for the material to cope with damage scenarios of different degrees or urgency, distinguishing it from materials with only a single repair mode.

[0115] Test Example 4: Comparative Test of Basic Mechanical Properties Experimental Description: This test is used to quantitatively measure and compare the basic mechanical properties of the materials prepared by the embodiments of the present invention and the comparative examples, including hardness, tensile strength, elongation at break and tear strength.

[0116] Experimental steps: Sample preparation: Samples conforming to the various test standards were cut from the materials prepared in Examples 1, 2, 3, and Comparative Examples 1 to 6. All samples were placed at (23±2)℃ and (50±5)% relative humidity for more than 24 hours before testing.

[0117] Hardness testing: Each material was tested using a Shore A hardness tester according to GB / T531.1-2008 standard. Five measurements were taken at different locations on each material sample, and the arithmetic mean was taken as the hardness value of the material.

[0118] Tensile property testing: According to GB / T528-2009 standard, dumbbell-shaped specimens are clamped on a universal testing machine. A constant tensile load is applied to the specimen at a tensile rate of 500 mm / min until fracture. The maximum tensile strength and elongation at fracture are recorded. Three valid specimens are tested for each material, and the results are taken as the arithmetic mean.

[0119] Tear strength test: According to GB / T529-2008 standard, a right-angled specimen is used for testing. The specimen is clamped on a universal testing machine and torn at a constant rate of 500 mm / min, and the force values ​​during the tearing process are recorded. The tear strength of the material is calculated and recorded. Three valid specimens are tested for each material, and the results are taken as the arithmetic mean.

[0120] Experimental data: Table 4. Comparative Test Data of Basic Mechanical Properties

[0121] Conclusion: The experimental data in Table 4 show that the materials prepared in Examples 1, 2, and 3 all exhibit high Shore A hardness, tensile strength, elongation at break, and tear strength. Compared to Comparative Example 1 (conventional high-performance polyurethane), the basic mechanical properties of the materials in these examples are similar, indicating that the preparation method and formulation of this invention do not weaken the basic mechanical load-bearing capacity required for the materials as structural components. Compared to Comparative Example 2 (prepared by simple blending), the tensile strength, elongation at break, and tear strength of the materials in these examples are significantly improved, confirming the decisive role of the interpenetrating network structure in the mechanical properties of the materials.

[0122] The mechanical properties of a material are directly related to its microstructure. The interpenetrating polymer network structure formed by the stepwise infiltration-in-situ curing method used in the examples is the basis for its high mechanical properties. The main load-bearing network I, formed by the prepolymer method, provides the material's stiffness and strength, while network II, formed by subsequent infiltration and curing, interweaves within the gaps of network I. The two networks, through physical entanglement and topological interlocking of chain segments, construct a synergistic load-bearing overall structure. This structure can effectively transfer and disperse external stress, inhibiting the initiation and propagation of cracks, thereby endowing the material with high strength and high toughness. Comparative Example 2, lacking this interpenetrating structure, experiences phase separation among its components, failing to form an effective synergistic load-bearing mechanism, resulting in a significant decrease in its mechanical properties.

[0123] The test results confirm that the technical solution of this invention successfully constructs an interpenetrating network structure in a polyurethane matrix. Furthermore, comparing the data from Example 2 with those from Comparative Examples 3, 4, 5, and 6 shows that introducing chemical components (such as HEDS, SP-OH, and catalysts) to achieve repair and color-changing functions based on the interpenetrating network structure did not negatively impact the material's fundamental mechanical properties. This indicates that the technical solution of this invention effectively combines a high-mechanical-performance matrix with multiple functional components, ultimately yielding a polyurethane material possessing high strength, high toughness, and specific responsive functions. Its comprehensive performance differs from traditional single-function or poorly mechanically-performing functional materials.

[0124] Test Example 5: Comparative Test of Fatigue Resistance Experimental Description: This test is used to measure and compare the total number of cycles that the materials prepared by the embodiments of the present invention and the comparative examples undergo under a preset cyclic tensile load until complete fracture occurs, i.e., fatigue life.

[0125] Experimental steps: Sample preparation: Dumbbell-shaped samples conforming to GB / T528-2009 standard were cut from the materials prepared in Example 2, Comparative Example 1, Comparative Example 2, and Comparative Example 3, respectively. Three valid samples were prepared for each material. All samples were placed at (23±2)℃ and (50±5)% relative humidity for more than 24 hours before testing.

[0126] Test equipment and parameter settings: An electro-hydraulic servo fatigue testing machine was used. The specimen was clamped in the tensile fixture of the testing machine. The cyclic tensile program was set: a sinusoidal waveform was used, and the specimen was subjected to cyclic tensile testing at a test frequency of 1 Hz within the strain range of 0% to 150%.

[0127] Test Execution and Result Recording: The test program is initiated, and the equipment begins applying cyclic loads to the specimen, automatically recording the number of cycles. The test continues until the specimen completely fractures, at which point the equipment automatically stops. The total number of cycles at fracture for each specimen is recorded as its fatigue life. The average fatigue life of three specimens for each material is calculated.

[0128] Experimental data: Table 5. Comparison Test Data of Fatigue Resistance Performance

[0129] Conclusion: The experimental data recorded in Table 5 show that, under the same cyclic tensile testing conditions, the material prepared in Example 2 can withstand a significantly higher number of cycles than the materials prepared in Comparative Examples 1, 2, and 3. The average fatigue life of the material in Example 2 is more than four times that of the materials in Comparative Examples 1 and 3, and more than 29 times that of the material in Comparative Example 2.

[0130] This difference in fatigue life is directly related to the dynamic repair mechanism designed within the material to cope with the accumulation of micro-damage. Under cyclic loading, microcracks continuously form and propagate within the material. In the material of Example 2, the disulfide bonds contained in its interpenetrating network II can undergo dynamic fracture and recombination under the localized energy dissipation induced by cyclic stress. This in-situ chemical bond exchange can repair emerging microcracks or passivate stress concentration at the crack tip, thereby delaying the process of damage accumulating from the microscopic to macroscopic fracture.

[0131] In contrast, the material in Comparative Example 1 is a traditional permanently cross-linked polyurethane, whose internal chemical bonds are static. Micro-damage generated can only accumulate and cannot be repaired, thus limiting its fatigue life. Although the material in Comparative Example 3 also has an interpenetrating network structure, its network II lacks dynamic disulfide bonds and therefore also lacks damage repair capabilities; its fatigue life is on the same order of magnitude as Comparative Example 1. The material in Comparative Example 2, lacking an interpenetrating network structure, has lower basic mechanical properties and structural integrity, leading to premature failure under cyclic loading. Therefore, the test results confirm that introducing network II containing dynamic disulfide bonds into the interpenetrating network structure is the direct reason for achieving the technical effect of increased fatigue life.

[0132] Test Example 6: Comparative Test of Mechanical Property Retention Rate After Damage Experimental Description: This test is used to quantitatively compare the degree of tensile strength recovery of materials prepared by the embodiments of the present invention and each comparative example under simulated severe damage conditions after undergoing uniform high-temperature repair treatment.

[0133] Experimental steps: Sample grouping: Six dumbbell-shaped tensile specimens conforming to GB / T528-2009 were cut from the materials prepared in Examples 1, 2, 3, and Comparative Examples 1 to 6. The six specimens of each material were randomly divided into two groups: the original control group (3 specimens) and the damage repair group (3 specimens), and were assigned corresponding numbers.

[0134] Original strength test: Using a universal testing machine, tensile tests were performed on all original control group specimens at an ambient temperature of (23±2)℃ and a tensile rate of 500 mm / min. The maximum tensile strength was recorded and the initial average tensile strength (P0) of each material was calculated.

[0135] Damage application: For all damaged test specimens, at the geometric center of their narrowest point, use a new, sharp blade to make a cut perpendicular to the specimen length. Use a micrometer to control and ensure the cut depth is (50 ± 2)% of the specimen thickness.

[0136] Repair treatment: The two cut surfaces of each incision specimen were tightly fitted together, and slight pressure was applied using a clamp to maintain contact. Subsequently, all the fixed damage repair group specimens were placed horizontally in a forced-air oven and heat-treated uniformly at 140°C for 1 hour.

[0137] Post-repair strength test: After heat treatment, all specimens were removed, the clamps were released, and the specimens were allowed to cool at room temperature for 2 hours. Then, using the same equipment, parameters, and environmental conditions as in step 2, tensile tests were performed on all repaired specimens. The maximum tensile strength at fracture was recorded, and the average tensile strength (P1) of each material after repair was calculated.

[0138] Strength recovery rate calculation: The strength recovery rate of each material is calculated according to the following formula: Strength recovery efficiency (%) = (P1 / P0) × 100%.

[0139] Experimental data: Table 6. Comparison of Mechanical Property Retention Rate After Damage Test Data

[0140] Conclusion: The test results in Table 6 show that, under the high-temperature repair condition of 140℃, the tensile strength recovery rates of the materials prepared by Examples 1, 2, 3, and Comparative Example 4 all reached over 89%. In contrast, the strength recovery rates of Comparative Examples 1, 2, and 3 were less than 5%, indicating that their damage was irreversible. Comparative Examples 5 and 6 showed a certain degree of strength recovery, but their recovery rates were significantly lower than those of Examples 1, 2, and 3.

[0141] This difference in strength recovery rate directly reflects the synergistic effect of the material's internal chemical structure and catalytic system. The high recovery rate of the material in the example is due to the inclusion of dynamic disulfide bonds in Network II of its interpenetrating network structure. Under heat treatment conditions of 140°C, the latent high-energy catalyst B undergoes thermal decomposition, releasing a highly active catalyst. This catalyst significantly promotes the dynamic exchange reaction rate of disulfide bonds on both sides of the cut interface, enabling the broken polymer chains to re-bond across the interface in a short time, thereby achieving the restoration of structural integrity and mechanical strength. Comparative Examples 1 and 3, lacking dynamic disulfide bonds, and Comparative Example 2, lacking an interpenetrating network structure, were unable to achieve effective repair.

[0142] The test results of Comparative Example 5 (without any catalyst) and Comparative Example 6 (containing only a low-temperature catalyst) further confirmed the necessity of the cascaded catalytic system. Although the material in Comparative Example 5 contains disulfide bonds, its intrinsic exchange reaction efficiency is very low within 1 hour due to the lack of a catalyst, resulting in limited strength recovery. The material in Comparative Example 6 contains a low-temperature catalyst, which exhibits certain catalytic activity at 140°C, but its catalytic efficiency is insufficient compared to the activated high-energy catalyst in the examples, thus resulting in a lower strength recovery rate. These tests demonstrate that the present invention, through the combination of interpenetrating networks, dynamic chemical bonds, and a cascaded catalytic system, achieves rapid and high-level repair of macroscopic damage—a function not possessed by traditional materials or other incomplete systems.

Claims

1. A polyurethane-based rotary blowout preventer core material, characterized in that, Made from raw materials containing the following components: The raw material I of the main load-bearing network I includes polyol, diisocyanate and chain extender; Raw material II, which is formed by infiltration polymerization in the main load-bearing network I to form functional network II, comprises diisocyanate and diol containing dynamic disulfide bonds; Color-changing additives; Cascaded catalytic system.

2. The polyurethane-based rotary blowout preventer core material according to claim 1, characterized in that, In the raw material I of the main load-bearing network I: The polyol is a mixture of polytetrahydrofuran ether diol and polycaprolactone diol; The diisocyanate is a modified liquefied diphenylmethane diisocyanate; The chain extender is 1,4-butanediol.

3. The polyurethane-based rotary blowout preventer core material according to claim 1, characterized in that, The diol containing dynamic disulfide bonds in the raw material II of the functional network II is a bis(2-hydroxyethyl) disulfide; The color-changing additive is 1',3'-dihydro-8-hydroxymethyl-1',3',3'-trimethyl-6-nitrospiro[2H-1-benzopyran-2,2'-indole], and the cascade catalytic system includes diisopropylethylamine as low-temperature catalyst A and DBU-carbonate adduct as latent high-energy catalyst B.

4. The polyurethane-based rotary blowout preventer core material according to claim 1, characterized in that, The proportions of the raw materials must meet the following conditions: In the raw material I of the main load-bearing network I, the weight ratio of polytetrahydrofuran ether diol to polycaprolactone diol is 7:3, and the molar ratio of isocyanate groups to hydroxyl groups used to prepare the prepolymer is 2.0-2.

5. The total molar ratio of isocyanate groups to hydroxyl groups in the entire network I reaction system is 0.95-0.

98. In the raw material II of the functional network II, the molar ratio of isocyanate groups to hydroxyl groups is 1.0-1.5; Based on 100 parts by weight of the total mass of diisocyanate and bis(2-hydroxyethyl) disulfide in raw material II of the functional network II: The amount of the color-changing additive is 0.05-0.20 parts by weight; The amount of the low-temperature catalyst A is 0.01-0.05 parts by weight; The amount of the latent high-energy catalyst B is 0.10-0.30 parts by weight.

5. The polyurethane-based rotary blowout preventer core material according to claim 1, characterized in that, The bis(2-hydroxyethyl) disulfide was prepared by oxidative coupling of 2-mercaptoethanol under the action of hydrogen peroxide. The DBU-carbonate adduct was prepared by reacting 1,8-diazabicyclo[5.4.0]undec-7-ene with carbon dioxide.

6. A method for preparing a polyurethane-based rotary blowout preventer core material according to any one of claims 1-5, characterized in that, Includes the following steps: a) A prepolymer with NCO-terminated end groups was prepared by reacting polyol with diisocyanate, and then a chain extender was added to carry out a chain extension reaction. After that, it was cast and cured in the first stage to obtain the preform of the main load-bearing network I. b) A multifunctional permeate was prepared by mixing diisocyanate, diol containing dynamic disulfide bonds, chromogenic additives and a cascade catalytic system. c) The preform is immersed in the multifunctional permeation liquid and permeated by alternating vacuum and atmospheric pressure treatment. Then it is taken out and cured in the second stage. Functional network II is formed by in-situ polymerization inside the preform, thereby obtaining the polyurethane-based rotary blowout preventer core material.

7. The method for preparing the polyurethane-based rotary blowout preventer core material according to claim 6, characterized in that, In step a), the reaction temperature for preparing the prepolymer is 75-85℃, the reaction time is 2.0-2.5 hours, the curing temperature for the first stage is 100-110℃, and the curing time is 8-10 hours.

8. The method for preparing the polyurethane-based rotary blowout preventer core material according to claim 6, characterized in that, In step b), mixing is carried out at 40-50°C and the mixture is mixed for 0.5-1.5 hours to form a multifunctional permeate.

9. The method for preparing the polyurethane-based rotary blowout preventer core material according to claim 6, characterized in that, The vacuum-atmospheric pressure alternation process in step c) is carried out at 55-65°C, including evacuating to below 1000Pa and holding for 20-30 minutes, then restoring to atmospheric pressure and holding for 30-40 minutes, and repeating 5 cycles.

10. The method for preparing the polyurethane-based rotary blowout preventer core material according to claim 6, characterized in that, The curing temperature in the second stage of step c) is 110-115℃, and the curing time is 16-24 hours.

Images