Sealing cement gum for marine environment based on fluorescence monitoring and triggering type self-repairing and preparation method of sealing cement gum

Abstract

The invention relates to the technical field of high polymer materials, and particularly discloses a sealing mortar for a marine environment based on fluorescence monitoring and trigger type self-repairing and a preparation method of the sealing mortar. The sealing mortar comprises the following raw materials in parts by weight: 50-70 parts of modified silicone rubber; 0.1 to 1 part of environment response type fluorescent dye; 3-8 parts of superficial layer repairing microcapsules; 5-12 parts of a deep repairing microcapsule; 1-3 parts of an ultraviolet light absorber; 2-5 parts of a salt mist corrosion resistant agent; 15 to 25 parts of nano silicon dioxide; wherein the shallow-layer repairing microcapsules and the deep-layer repairing microcapsules are filled with repairing agents with different properties respectively, and the repairing function can be triggered according to the crack depth gradient. Ocean engineering facilities are sealed by using the prepared sealing cement gum, the aging degree and crack development condition of the sealing cement gum are evaluated by monitoring fluorescence intensity change through ultraviolet irradiation, when the fluorescence intensity reaches a preset threshold value, cracks are developed to a critical depth, a deep repair mechanism is triggered, and the crack development condition is evaluated. And the optimal configuration of the restoration resources is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high polymer materials, in particular to a sealing mastic for marine environment based on fluorescence monitoring and triggered self-repairing and a preparation method thereof, which can visually monitor the distribution of aging cracks through fluorescent dyes and trigger the self-repairing function when the cracks develop to a critical degree. BACKGROUND

[0002] As an important sealing material, sealing mastic is widely used in the sealing protection of marine engineering facilities such as ships, offshore platforms and submarine pipelines. However, the harsh conditions in the marine environment, such as high salt mist, high humidity, strong ultraviolet radiation and drastic temperature changes, can easily cause the aging and cracking of traditional sealing mastics, and thus the loss of sealing performance. The sealing mastic products on the market mainly have the following technical defects:

[0003] 1. Lack of aging monitoring means: the aging process of traditional sealing mastic is difficult to monitor directly, and the cracks often expand internally to a serious degree before being discovered, at which time irreversible sealing failure has already occurred.

[0004] 2. Passive self-repairing mechanism: existing self-repairing sealing materials mostly use the method of uniformly dispersing repair agents, and the repair behavior is unrelated to the damage degree, which can easily cause waste of repair materials or untimely repair.

[0005] 3. Poor adaptability to marine environment: ordinary sealing mastic is prone to problems such as molecular chain rupture and filler shedding under the action of ultraviolet light and salt mist, resulting in decreased elasticity and sealing failure.

[0006] 4. Low repair efficiency: existing self-repairing materials mostly need external heating or the addition of catalysts to realize repair, which limits their application in marine engineering sites.

[0007] In view of the above problems, the present application proposes an intelligent sealing mastic system based on fluorescence monitoring and crack-triggered repair, which can visually monitor the aging degree through fluorescent dyes and design a crack depth-sensitive microcapsule repair system to realize precise self-repairing. SUMMARY

[0008] In order to overcome the problems of difficult aging monitoring, inaccurate repair and poor adaptability to marine environment in the prior art, the present application aims to provide a sealing mastic for marine environment based on fluorescence monitoring and triggered self-repairing, which can realize real-time visual monitoring of the distribution of aging cracks and automatically trigger the repair function when the cracks develop to a critical degree.

[0009] Another object of the present application is to provide a preparation method of the sealant for marine environment based on fluorescence monitoring and triggered self-repair, which provides real-time aging data through fluorescence monitoring, automatically triggers repair when reaching the aging threshold, and realizes real-time and non-destructive evaluation of aging and cracks.

[0010] In order to achieve the above object, the present application adopts the following technical solutions:

[0011] The sealant for marine environment based on fluorescence monitoring and triggered self-repair comprises the following components and raw materials in weight percentage: modified silicone rubber 50-70 parts; environment-responsive fluorescent dye 0.1-1 part; shallow repair microcapsule 3-8 parts; deep repair microcapsule 5-12 parts; ultraviolet absorber 1-3 parts; salt mist corrosion inhibitor 2-5 parts; nano-silicon dioxide 15-25 parts; wherein the shallow repair microcapsule and the deep repair microcapsule are filled with different properties of repair agents, which can trigger the repair function according to the crack depth gradient.

[0012] Optionally, the modified silicone rubber is hydroxyl-terminated polydimethylsiloxane containing cyclosiloxane branches, and the content of the cyclosiloxane branches is 5-15 mol%.

[0013] Optionally, the environment-responsive fluorescent dye is fluorescein or rhodamine B or their derivatives, which are uniformly distributed in the sealant, and the relationship between the fluorescence intensity I at the crack and the crack depth d satisfies the formula: I=I0×e^(k*d), wherein I0 is the initial fluorescence intensity, and k is a material constant.

[0014] Optionally, the particle size of the shallow repair microcapsule is 10-50 μm, the wall material is polyurethane urea with a thickness of 1-2 μm and a breaking stress of 0.5-1.5 MPa, and the core material is room temperature curing silane-terminated polyether repair liquid; the particle size of the deep repair microcapsule is 80-150 μm, the wall material is melamine resin with a thickness of 3-5 μm and a breaking stress of 3-5 MPa, and the core material is alkali catalyzed siloxane repair liquid.

[0015] Further, the alkali catalyzed siloxane repair liquid comprises a cyclic siloxane monomer, a silane coupling agent and a latent alkali catalyst, and the latent alkali catalyst is microencapsulated tetramethylammonium hydroxide which is released when pH>9.

[0016] Optionally, the ultraviolet absorber is 2-hydroxy-4-methoxybenzophenone, and the salt mist corrosion inhibitor is a rare earth organic compound.

[0017] A preparation method of the aforementioned sealant for marine environment based on fluorescence monitoring and triggered self-repair, comprising the following steps:

[0018] (1) Modified silicone rubber preparation: the hydroxyl-terminated polydimethylsiloxane and cyclosiloxane are balanced under the action of a catalyst to introduce cyclosiloxane branches, thereby obtaining modified silicone rubber containing 5-15 mol% cyclosiloxane branches;

[0019] (2) Fluorescent dye treatment: the environment-responsive fluorescent dye is surface treated with a silane coupling agent at a mass ratio of 1:0.2-0.5;

[0020] (3) Repair microcapsule preparation:

[0021] Shallow repair microcapsule: a microcapsule with a particle size of 10-50 μm is prepared by using an interfacial polymerization method, using room temperature curing silane-terminated polyether as a core material and polyurethane urea as a wall material;

[0022] Deep repair microcapsule: a microcapsule with a particle size of 80-150 μm is prepared by using an in-situ polymerization method, using an alkali catalyzed siloxane repair liquid as a core material and melamine resin as a wall material;

[0023] (4) Compound mixing: the modified silicone rubber, the treated fluorescent dye, the two types of repair microcapsules, the ultraviolet light absorber, the anti-salt mist corrosion agent and the nano silicon dioxide are uniformly mixed on a two-roll open mill, the mixing temperature is controlled at 40-60°C, and the mixing time is 20-40 minutes;

[0024] (5) Molding and curing: the mixed rubber is placed in a mold, and is vulcanized and molded under the conditions of a pressure of 5-10 MPa, a temperature of 80-120°C and a time of 0.5-2 hours, thereby obtaining a final product, a sealant.

[0025] Optionally, the microcapsule with a particle size of 10-50 μm is prepared by using an interfacial polymerization method, using room temperature curing silane-terminated polyether as a core material and polyurethane urea as a wall material, and the preparation process specifically includes:

[0026] Step 1, raw material preparation:

[0027] Oil phase, core material solution: the room temperature curing silane-terminated polyether and the polyisocyanate monomer are mixed and dissolved in an organic solvent;

[0028] Water phase, wall material reaction solution: a water solution containing a protective colloid and an emulsifier is prepared;

[0029] Step 2, emulsification and dispersion: the oil phase is slowly added to the water phase, and is sheared and emulsified at a speed of 6000-18,000 rpm for 3-5 minutes, thereby forming an oil-in-water emulsion;

[0030] Step 3, interfacial polymerization reaction: the isocyanate in the oil phase and the amine / water in the water phase continuously undergo condensation polymerization at room temperature under continuous stirring, thereby generating the polyurethane urea wall material on the surface of the core material droplets:

[0031] Step 4: Curing:

[0032] Heating and curing: Raise the temperature of the reaction system to 60-80°C and continue stirring for 2-6 hours to crosslink and densify the wall material; continue curing at 60°C for 1 hour to enhance the stability of the capsule wall;

[0033] Step 5, separation and drying: After cooling, filter, remove unreacted monomers with acid washing, and dry to obtain shallow repair microcapsule powder.

[0034] Optionally, the in-situ polymerization method is used to prepare microcapsules with a particle size of 80-150 μm using base-catalyzed silicone repair liquid as the core material and melamine resin as the wall material. The preparation process specifically includes:

[0035] Step 1: Preparation of melamine prepolymer:

[0036] Raw material ratio: Mix melamine and formaldehyde solution in a molar ratio of 1:3-1:5, add distilled water, use an alkaline regulator, stir in a water bath at 65-70℃ for 5-10 minutes until the system becomes transparent, and continue the reaction for 20-50 minutes to obtain a transparent water-soluble melamine prepolymer;

[0037] Step 2: Emulsify and disperse the core material, emulsify at low temperature:

[0038] Prepolymer treatment: Mix the prepolymer and emulsifier in a mass ratio of 100:20~100:30, and stir to dissolve at room temperature;

[0039] Core material addition: Add base-catalyzed silicone repair liquid with a core material to prepolymer mass ratio of 1:1 to 2.5:1; emulsify in an ice bath using a high shear emulsifier at 1500-2500 r / min for 20-50 minutes to form an O / W emulsion; adjust the pH to 4-5;

[0040] Step 3: Step-by-step temperature control and in-situ polymerization coating:

[0041] Polycondensation reaction: Raise the temperature to 40-50℃, stir with turbulent stirring paddle, and react for 2-3 hours to make the melamine prepolymer condense and deposit on the surface of the core material to form a dense capsule wall;

[0042] Step 4, termination of reaction and post-treatment: adjusting pH ≥ 6 to terminate the reaction, filtering and washing, and vacuum drying at 50° C. to obtain white spherical deep repair microcapsules.

[0043] A method for sealing marine engineering facilities uses the aforementioned sealing putty for sealing, and monitors the changes in fluorescence intensity through ultraviolet irradiation to evaluate the aging degree and crack development of the sealing putty. When the fluorescence intensity reaches a preset threshold, it indicates that the crack has developed to a critical depth, triggering a deep repair mechanism.

[0044] Compared with the prior art, the present application has the following beneficial effects:

[0045] 1. Visual aging monitoring: the visual monitoring of the aging cracks of the sealing cement is realized by the environmental response type fluorescent dye, the aging degree of the material can be intuitively evaluated, and timely maintenance is facilitated.

[0046] 2. Intelligent gradient repair: the designed gradient repair system can intelligently trigger different repair mechanisms according to the crack depth, shallow microcracks are processed by the shallow repair system, and deep cracks are processed by the deep repair system, so that the accurate allocation of repair resources is realized.

[0047] 3. Marine environment adaptability: the special marine environment stabilizer combination and modified silicone rubber matrix endow the material with excellent ultraviolet resistance and salt spray corrosion resistance, and the material is particularly suitable for marine environment application.

[0048] 4. Long-acting self-repairing ability: the chemical repair mechanism based on the cyclosiloxane branch can provide multiple repair capabilities, which is different from the single repair limitation of traditional physical repair mechanism.

[0049] 5. Simple operation: the repair process does not require external energy input or complex operation, and is completely completed by the automatic response of the functional components designed inside the material, which is suitable for marine engineering site application.

[0050] 6. The method improves the intelligent level and maintenance efficiency of the sealing cement, is suitable for long-term unattended environment of marine engineering facilities, reduces downtime and labor cost. BRIEF DESCRIPTION OF DRAWINGS

[0051] Figure 1 The figure is a schematic diagram of the composition structure of the sealing cement.

[0052] Explanation of reference signs: 1: modified silicone rubber; 2: fluorescent dye; 3: crack; 4: fluorescent enhancement zone; 5: shallow repair microcapsule; 6: deep repair microcapsule. DETAILED DESCRIPTION

[0053] The technical solutions in the embodiments of the present application will be described below in a clear and complete manner. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments.

[0054] A sealing cement for marine environment based on fluorescent monitoring and trigger type self-repairing, comprising the following components and weight fractions of raw materials:

[0055] Base material: modified silicone rubber 50-70 parts;

[0056] Fluorescent indication system: environmental response type fluorescent dye 0.1-1 parts;

[0057] Gradient repair system: 3-8 parts of shallow repair microcapsules (particle size 10-50 μm); 5-12 parts of deep repair microcapsules (particle size 80-150 μm);

[0058] Marine environment stabilizer: 1-3 parts of ultraviolet absorber; 2-5 parts of anti-salt mist corrosion agent;

[0059] Reinforcing filler: 15-25 parts of nano-silicon dioxide.

[0060] In the present application, the modified silicone rubber is a hydroxyl-terminated polydimethylsiloxane containing cyclosiloxane branches, the content of the cyclosiloxane branches being 5-15 mol%, which can undergo ring-opening polymerization under alkaline conditions to achieve self-repair.

[0061] In the present application, the environment-responsive fluorescent dye is selected from fluorescein, rhodamine B or derivatives thereof, and is more preferably a fluorescein derivative modified by a silane coupling agent, which can form a chemical bond with the silicone rubber matrix to avoid loss in the marine environment.

[0062] The environment-responsive fluorescent dye is uniformly distributed in the sealant, and when a crack occurs on the surface of the material, the dye concentration at the crack increases due to stress concentration, and under ultraviolet irradiation, a significant fluorescence enhancement effect is exhibited, and the fluorescence intensity I is exponentially related to the crack depth d:

[0063] I=I0×e^(k*d)

[0064] Wherein, I is the fluorescence intensity, I0 is the initial fluorescence intensity, k is the material constant, and d is the crack depth.

[0065] In the present application, the shallow repair microcapsules and the deep repair microcapsules respectively fill different properties of repair agents:

[0066] Shallow repair microcapsules: the particle size of the shallow repair microcapsules is 10-50 μm, the wall material is polyurethane urea, the thickness is 1-2 μm, the breaking stress is 0.5-1.5 MPa, and the core material is a room temperature curing silane-terminated polyether repair liquid, which can be released and quickly cured in the early stage of the crack (depth < 50 μm);

[0067] Deep repair microcapsules: the particle size of the deep repair microcapsules is 80-150 μm, the wall material is melamine resin, the thickness is 3-5 μm, the breaking stress is 3-5 MPa, and the core material is an alkali catalyzed siloxane repair liquid, which is released when the crack expands to the critical depth (> 80 μm), and realizes deep repair under the action of the catalyst.

[0068] In the present application, the alkali catalyzed siloxane repair liquid comprises a cyclic siloxane monomer, a silane coupling agent and a latent alkali catalyst, and the latent alkali catalyst is a microencapsulated tetramethylammonium hydroxide, which is released at pH> 9.

[0069] In the present application, the ultraviolet absorber is 2-hydroxy-4-methoxybenzophenone; the anti-salt mist corrosion agent is a rare earth complex of dibenzoylmethane (HDBM). The rare earth mainly includes complexes of europium (Eu³⁺), gadolinium (Gd³⁺), samarium (Sm³⁺), and lanthanum (La³⁺), such as Eu(DBM)3phen: dibenzoylmethane (DBM) as the first ligand, phenanthroline (phen) as the second ligand, the emission wavelength is about 614 nm (the excitation wavelength is 352 nm), and it has high fluorescence purity and intensity. It is a rare earth agricultural film light conversion material, and the specific product name is: tris(dibenzoylmethane root)-(o-phenanthroline) europium (III).

[0070] A preparation method of the aforementioned fluorescent monitoring and trigger type self-repairing sealant for marine environment, referring to Figure 1 , comprising the following steps:

[0071] Step 1, preparation of modified silicone rubber 1: hydroxyl-terminated polydimethylsiloxane and cyclotetrasiloxane (D4) are subjected to equilibration reaction under the action of a catalyst to introduce cyclotetrasiloxane branches, thereby obtaining modified silicone rubber containing 5-15 mol% cyclotetrasiloxane branches. The preparation process specifically includes:

[0072] Step 1.1, feeding: hydroxyl-terminated polydimethylsiloxane and cyclotetrasiloxane (D4) are added to a reaction kettle in a molar ratio of 1:5-1:10. At the same time, a catalyst is added, which is generally selected to be tetramethylammonium hydroxide (a mature product on the market) and the amount is 0.004-0.05% of the mass of the raw materials (hydroxyl-terminated polydimethylsiloxane and cyclotetrasiloxane).

[0073] Step 1.2, dehydration: under reduced pressure (about 0.06 MPa vacuum degree) and N2 flow, the temperature is raised to 50°C and maintained for 30 minutes to remove water.

[0074] Step 1.3, equilibration reaction: the temperature is raised to 100-110°C and maintained for 2-3 hours to perform ring-opening polymerization and branch introduction. Stirring is performed during the period to ensure uniformity.

[0075] Step 1.4, post-treatment: the temperature is raised to 170-180°C to destroy the catalyst under reduced pressure (0.5-1 hour to decompose the catalyst into low-boiling substances). The low-boiling substances are removed under vacuum (vacuum degree-0.098 MPa) to obtain modified silicone rubber.

[0076] Step 2, treatment of fluorescent dye 2: the environment-responsive fluorescent dye is subjected to surface treatment with a silane coupling agent in a mass ratio of 1:0.2-0.5 to enhance the compatibility with the rubber matrix. The preparation process specifically includes:

[0077] Step 2.1, Solvent preparation: Dissolve silane coupling agent in organic solvent (such as ethanol, isopropanol, toluene, etc.) or water-alcohol mixed solution, and prepare a dilute solution with a concentration of 0.5% to 2.0%.

[0078] Step 2.2, Surface treatment operation (spraying / immersion method): immerse the environmentally responsive fluorescent dye in the silane solution, or evenly cover the silane solution on the surface of the fluorescent dye by spraying. Treatment time: 20-30 minutes.

[0079] Step 2.3, Drying and curing: The treated dye needs to be cured at 110-120°C for 20-30 minutes, or use dynamic drying method (such as fluidized bed drying) to remove the solvent. After curing, a hydrophobic silane layer should be formed on the surface of the dye, reducing the number of hydroxyl groups and enhancing the compatibility with rubber.

[0080] Step 3, Preparation of repair microcapsules:

[0081] Shallow repair microcapsules 5: using interfacial polymerization, room temperature curing silane-terminated polyether as core material, polyurethane urea as wall material to prepare microcapsules with particle size of 10-50 μm; the preparation process specifically includes:

[0082] Step 3.1.1, Raw material preparation:

[0083] Core material solution (oil phase): mix room temperature curing silane-terminated polyether with polyisocyanate monomer (such as isophorone diisocyanate / IPDI) and dissolve in organic solvent (such as cyclohexane or dichloromethane).

[0084] Wall material reaction solution (aqueous phase): prepare an aqueous solution containing protective colloid (such as 1-4% polyvinyl alcohol / PVA aqueous solution) and emulsifier (such as 0.5-2% Tween 80 or sodium dodecyl sulfate).

[0085] Step 3.1.2, Emulsification and dispersion: slowly add the oil phase to the water phase, shear emulsify at a speed of 6000-18,000 rpm for 3-5 minutes to form an oil-in-water (O / W) emulsion. Among them, the shear rate determines the size of the generated microcapsule particle size.

[0086] Step 3.1.3, Interfacial polymerization reaction: continue stirring (50-300 rpm) at room temperature, isocyanate (-NCO) in the oil phase and amine / water in the aqueous phase undergo polycondensation reaction to form polyurethane urea wall material on the surface of the core material droplets:

[0087] Step 3.1.4, Curing:

[0088] Temperature curing: increase the temperature of the reaction system to 60-80°C, continue stirring for 2-6 hours to make the wall material crosslink and densify; continue to cure at 60°C for 1 hour to enhance the stability of the capsule wall.

[0089] Step 3.1.5, Isolation and drying: After cooling, filtration, washing with acid (such as dilute hydrochloric acid) to remove unreacted monomers, and drying to obtain a light layer repair microcapsule powder.

[0090] Deep repair microcapsule 6: A microcapsule with a particle size of 80-150 μm is prepared by in-situ polymerization, using an alkali-catalyzed silicone repair liquid as the core material and a melamine resin as the wall material. The preparation process specifically includes:

[0091] Step 3.2.1, Preparation of melamine prepolymer (basic conditions)

[0092] Raw material ratio: melamine and formaldehyde solution are mixed at a molar ratio of 1:3-1:5 (formaldehyde mass concentration 15-36%), and distilled water (1-3 times the mass of formaldehyde) is added. Reaction conditions: adjust with an alkaline adjuster (pH 8-9) such as sodium hydroxide, 65-70°C water bath stirring for 5-10 min until the system is transparent, continue to react for 20-50 min, and obtain a transparent water-soluble melamine prepolymer.

[0093] Step 3.2.2, Emulsification and dispersion of core material (low-temperature emulsification)

[0094] Prepolymer treatment: Mix the prepolymer with an emulsifier (such as sodium dodecyl benzene sulfonate or xanthan gum) at a mass ratio of 100:20-100:30, and stir and dissolve at room temperature.

[0095] Core material addition: Add an alkali-catalyzed silicone repair liquid (core material to prepolymer mass ratio 1:1-2.5:1). Under ice bath conditions, emulsify with a high-shear emulsifier at a speed of 1500-2500 r / min for 20-50 min to form an O / W type emulsion (control the droplet size to be 80-150 μm); adjust the pH to 4-5 with weak acids such as oxalic acid and acetic acid (avoid strong acids that can damage the activity of the silicone).

[0096] Step 3.2.3, In-situ polymerization coating (step-by-step temperature control)

[0097] Polycondensation reaction: Increase the temperature to 40-50°C (avoid high temperature to cause the inactivation of the core material), and stir with a turbulent stirring paddle (400-600 r / min). React for 2-3 h to allow the melamine prepolymer to condense and deposit on the surface of the core material, forming a dense capsule wall.

[0098] Step 3.2.4, Reaction termination and post-treatment: terminate the reaction by adjusting the pH to ≥6 with a sodium hydroxide solution; after filtration and washing (remove residual reagents with petroleum ether or deionized water), perform vacuum drying at 50°C to obtain white spherical deep repair microcapsules.

[0099] Step 4, compound mixing: the modified silicone rubber, treated fluorescent dye, two kinds of repair microcapsules, marine environment stabilizer and reinforcing filler are mixed uniformly on a two-roll open mill, the mixing temperature is controlled at 40-60℃, and the time is 20-40 minutes.

[0100] In the step 4 compound mixing process, referring to Figure 1 The fluorescent dye 2 and the two kinds of microcapsules can be ensured to be uniformly distributed in the modified silicone rubber matrix 1, and due to the light weight of the shallow repair microcapsules 5, the shallow repair microcapsules 5 float to the upper part during the mixing process, and the deep repair microcapsules 6 sink to the lower part.

[0101] Step 5, forming and curing: the mixed rubber is placed in a mold, and is vulcanized and formed under the conditions of a pressure of 5-10 MPa, a temperature of 80-120℃ and a time of 0.5-2 hours to obtain a final product.

[0102] The working principle of the sealing cement is as follows:

[0103] 1. Aging monitoring mechanism: the environment-responsive fluorescent dye uniformly dispersed in the cement emits fluorescence under ultraviolet irradiation. When the microcracks 3 are generated on the surface of the material, the stress concentration at the crack tip causes the dye molecules to aggregate, and the intensity of the fluorescence enhancement zone 4 is significantly enhanced. By quantitatively measuring the change of the fluorescence intensity, an empirical relationship between the crack depth d and the fluorescence intensity I can be established: I=I0×e^(k*d), and the visual monitoring of the crack development is realized.

[0104] 2. Gradient repair mechanism:

[0105] Shallow repair: when the surface microcracks (depth < 50 μm) are generated, the shallow repair microcapsules (particle size 10-50 μm) are broken due to stress concentration, and release room temperature curing silane-terminated polyether repair liquid to quickly fill and repair the microcracks;

[0106] Deep repair: when the crack extends to the critical depth (> 80 μm), the deep repair microcapsules (particle size 80-150 μm) are broken, and release the alkali catalyzed siloxane repair liquid and catalyst to initiate the ring-opening polymerization of the branched siloxane, and realize the deep repair.

[0107] 3. Marine environment stability: the synergistic effect of the ultraviolet absorber and the salt mist corrosion inhibitor effectively resists the ultraviolet radiation and salt mist corrosion in the marine environment, and prolongs the service life of the material.

[0108] The application will be further described in detail in combination with specific examples.

[0109] Example 1:

[0110] A kind of sealing cement for marine environment based on fluorescence monitoring and triggered self-repair, comprising the following raw materials by weight:

[0111] Modified silicone rubber (10 mol% cyclosiloxane branch) 60 parts:

[0112] Silane coupling agent modified fluorescein derivative 0.5 parts:

[0113] Shallow repair microcapsule (particle size 30 ± 10 μm) 5 parts;

[0114] Deep repair microcapsule (particle size 100 ± 20 μm) 8 parts;

[0115] Ultraviolet absorber (2-hydroxy-4-methoxybenzophenone) 2 parts;

[0116] Salt fog corrosion resistant agent (dibenzoylmethane (HDBM) rare earth complex) 3 parts;

[0117] Nano-silicon dioxide 20 parts.

[0118] The preparation method is the same as above, wherein the test parameters such as temperature, stirring time, etc. are averaged, and the reaction time is taken as the maximum value.

[0119] Example 2:

[0120] The same as example 1, except that:

[0121] The content of cyclosiloxane branch in the modified silicone rubber is 15 mol%;

[0122] The particle size of the deep repair microcapsule is adjusted to 120 ± 20 μm;

[0123] 1 part of carbon nanotube is added to enhance the electrical conductivity, which is convenient for electrical monitoring.

[0124] The preparation method is the same as example 1.

[0125] Comparative example 1:

[0126] A common silicone rubber sealant, comprising the following raw materials by weight:

[0127] Hydroxyl-terminated polydimethylsiloxane 60 parts; Rohn reagent (500 g package, viscosity 40 cSt);

[0128] Precipitated white carbon black 20 parts; JF-225M (specific surface area 160-180 m² / g);

[0129] Silane coupling agent 1 part;

[0130] Vulcanizing agent 2 parts; such as: bis-ditetravulcanizing agent (bis(2,4-dichlorobenzoyl) peroxide);

[0131] The preparation method thereof comprises the following steps:

[0132] 1. Preliminary mixing and dehydration:

[0133] Add hydroxyl terminated polydimethylsiloxane into a mixer, and heat to 70-80℃. Add fumed silica in batches: add in 3-4 times, and stir to uniformity after each addition (avoid clumping). Dehydrate under vacuum (-0.1 MPa) for 2 hours to remove moisture and volatiles.

[0134] 2. Coupling agent addition:

[0135] Cool to 40℃, and add silane coupling agent (1 part), and continue stirring for 20-30 minutes.

[0136] 3. Curing agent mixing:

[0137] Further cool to 30℃ (avoid premature reaction of curing agent), and add bis-dinitrosulphuric acid curing agent (2 parts). Stir under vacuum (-0.1 MPa) until no air bubbles (about 15-30 minutes).

[0138] 4. Discharge and storage:

[0139] Extrude the sealant from the equipment, and seal and package to avoid contact with air moisture to cause curing.

[0140] The sealant prepared in Example 1, 2 and Comparative Example 1 was subjected to performance testing, and the results are shown in Table 1.

[0141] Table 1. Performance testing results of the sealant

[0142] Test item Example 1 Example 2 Comparative Example 1 Initial tensile strength (MPa) 2.5 2.6 2.3 Initial elongation at break (%) 450 440 400 Tensile strength retention rate (%) after artificial aging for 500 h 85 88 45 Elongation at break retention rate (%) after artificial aging for 500 h 80 82 35 Mass change rate (%) after salt spray test for 30 days +1.2 +1.0 +8.5 Self-repairing efficiency (%) 92 90 Crack detection sensitivity (μm) 10 10

[0143] *Note: The self-repairing efficiency is defined as the percentage of the recovered value of the mechanical property after repair to the initial value.

[0144] As can be seen from Table 1, the sealant prepared in Example 1 and Example 2 of the present application has excellent initial mechanical properties, and the performance retention rate after artificial accelerated aging and salt spray test is significantly higher than that of Comparative Example 1, showing good adaptability to marine environment. In addition, the product of the present application also has significant self-repairing ability and crack detection sensitivity.

[0145] Establishment of the relationship between crack depth and fluorescence intensity:

[0146] Through microscope observation and fluorescence intensity measurement, the empirical relationship between the crack depth d (μm) and the fluorescence intensity I (relative unit) of the sealant of Example 1 was established:

[0147] I = 15.0 × e^(0.03d) (R²=0.95)

[0148] The relationship can be used to quantitatively evaluate the aging degree and crack development of the sealing cement in actual use.

[0149] Repair trigger mechanism verification:

[0150] The trigger mechanism of the gradient repair system is verified through a crack propagation experiment:

[0151] 1. When the crack depth is < 50 μm, only the shallow repair microcapsules (particle size 10-50 μm) in examples 1 and 2 are observed to break, repairing the shallow cracks;

[0152] 2. When the crack depth is > 80 μm, the deep repair microcapsules (particle size 80-150 μm) in examples 1 and 2 are observed to start breaking, releasing the repair agent to achieve deep repair;

[0153] 3. When the crack depth is between 50-80 μm, the two kinds of microcapsules work together to complete the repair.

[0154] The experimental results show that the designed gradient repair system can intelligently trigger the corresponding repair mechanism according to the crack depth, realizing the optimal allocation of repair resources.

[0155] The above is only a specific implementation in the present application, and the protection scope of the present application is not limited thereto. Any person skilled in the art can understand and think of changes or substitutions within the technical scope disclosed by the present application, which should be covered within the scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. Sealing putty for marine environment based on fluorescence monitoring and triggered self-repair, characterized by: The raw materials include the following components and weight proportions: 50-70 parts of modified silicone rubber; 0.1-1 parts of environmental responsive fluorescent dye; 3-8 parts of shallow repair microcapsules; 5-12 parts of deep repair microcapsules; 1-3 parts of ultraviolet absorber; 2-5 parts of salt spray corrosion inhibitor; 15-25 parts of nano-silicon dioxide; wherein the shallow repair microcapsules and deep repair microcapsules are respectively filled with repair agents of different properties, which can trigger the repair function according to the crack depth gradient.

2. The sealing putty for marine environment based on fluorescence monitoring and triggered self-repair according to claim 1, characterized in that: The modified silicone rubber is a hydroxyl-terminated polydimethylsiloxane containing cyclosiloxane side chains, and the cyclosiloxane side chain content is 5-15 mol%.

3. The sealing putty for marine environment based on fluorescence monitoring and triggered self-repair according to claim 1, characterized in that: The environmentally responsive fluorescent dye is fluorescein or rhodamine B or their derivatives, which are uniformly distributed in the sealing putty. The fluorescence intensity I at the crack and the crack depth d satisfy the relationship: I=I0×e^(k*d), where I0 is the initial fluorescence intensity and k is the material constant.

4. The sealing putty for marine environment based on fluorescence monitoring and triggered self-repair according to claim 1, characterized in that: The particle size of the shallow repair microcapsules is 10-50 μm, the wall material is polyurethane urea, the thickness is 1-2 μm, the rupture stress is 0.5-1.5 MPa, and the core material is room temperature curing silane-terminated polyether repair liquid; the particle size of the deep repair microcapsules is 80-150 μm, the wall material is melamine resin, the thickness is 3-5 μm, the rupture stress is 3-5 MPa, and the core material is base-catalyzed silicone repair liquid.

5. The sealing putty for marine environment based on fluorescence monitoring and triggered self-repair according to claim 4 is characterized in that: The base-catalyzed silicone repair liquid comprises a cyclic silicone monomer, a silane coupling agent and a latent base catalyst. The latent base catalyst is microencapsulated tetramethylammonium hydroxide, which is released when the pH is greater than 9.

6. The sealing putty for marine environment based on fluorescence monitoring and triggered self-repair according to claim 1, characterized in that: The ultraviolet absorber is 2-hydroxy-4-methoxybenzophenone, and the anti-salt spray corrosion agent is a rare earth organic compound.

7. A method for preparing a sealing putty for marine environment based on fluorescence monitoring and triggered self-repair according to any one of claims 1 to 6, characterized in that: The following steps are involved: (1) Preparation of modified silicone rubber: Hydroxyl-terminated polydimethylsiloxane and cyclosiloxane are subjected to equilibrium reaction under the action of a catalyst to introduce cyclosiloxane side chains to obtain a modified silicone rubber containing 5-15 mol% cyclosiloxane side chains; (2) Fluorescent dye treatment: Surface treatment is performed with an environmentally responsive fluorescent dye and a silane coupling agent at a mass ratio of 1:0.2-0.5; (3) Preparation of repair microcapsules: Shallow repair microcapsules: Using interfacial polymerization, room temperature curing silane-terminated polyether is used as the core material and polyurethane urea is used as the wall material to prepare microcapsules with a particle size of 10-50μm; Deep repair microcapsules: Using in-situ polymerization, base-catalyzed silicone repair liquid is used as the core material and melamine resin is used as the wall material to prepare microcapsules with a particle size of 80-150μm; (4) Compound mixing: the modified silicone rubber, the treated fluorescent dye, the two repair microcapsules, the ultraviolet absorber, the anti-salt spray corrosion agent and the nano-silica are mixed evenly on a double-roll mill, the mixing temperature is controlled at 40-60°C, and the mixing time is 20-40 minutes; (5) Molding and curing: The mixed rubber material is placed in a mold and vulcanized under the conditions of a pressure of 5-10 MPa, a temperature of 80-120°C, and a time of 0.5-2 hours to obtain the final product, the sealing putty.

8. The method for preparing sealing putty for marine environment based on fluorescence monitoring and triggered self-repair according to claim 7, characterized in that: The interfacial polymerization method is used to prepare microcapsules with a particle size of 10-50 μm using room temperature curing silane-terminated polyether as the core material and polyurethane urea as the wall material. The preparation process specifically includes: Step 1: Raw material preparation: Oil phase, core material solution: room temperature curing silane-terminated polyether and polyisocyanate monomer are mixed and dissolved in an organic solvent; Water phase, wall material reaction solution: prepare an aqueous solution containing protective colloid and emulsifier; Step 2: Emulsification and dispersion: Slowly add the oil phase to the water phase and shear emulsify at 6000-18,000 rpm for 3-5 minutes to form an oil-in-water emulsion; Step 3, interfacial polymerization reaction: Under continuous stirring at room temperature, the isocyanate in the oil phase undergoes a condensation reaction with the amines / water in the aqueous phase, forming a polyurethane urea wall material on the surface of the core material droplet: Step 4: Curing: Heating and curing: Raise the temperature of the reaction system to 60-80°C and continue stirring for 2-6 hours to crosslink and densify the wall material; continue curing at 60°C for 1 hour to enhance the stability of the capsule wall; Step 5, separation and drying: After cooling, filter, remove unreacted monomers with acid washing, and dry to obtain shallow repair microcapsule powder.

9. The method for preparing sealing putty for marine environment based on fluorescence monitoring and triggered self-repair according to claim 7, characterized in that: The in-situ polymerization method is used to prepare microcapsules with a particle size of 80-150 μm using base-catalyzed silicone repair liquid as the core material and melamine resin as the wall material. The preparation process specifically includes: Step 1: Preparation of melamine prepolymer: Raw material ratio: Mix melamine and formaldehyde solution in a molar ratio of 1:3-1:5, add distilled water, use an alkaline regulator, stir in a water bath at 65-70℃ for 5-10 minutes until the system becomes transparent, and continue the reaction for 20-50 minutes to obtain a transparent water-soluble melamine prepolymer; Step 2: Emulsify and disperse the core material, emulsify at low temperature: Prepolymer treatment: Mix the prepolymer and emulsifier in a mass ratio of 100:20~100:30, and stir to dissolve at room temperature; Core material addition: Add base-catalyzed silicone repair liquid with a core material to prepolymer mass ratio of 1:1 to 2.5:1; emulsify in an ice bath using a high shear emulsifier at 1500-2500 r / min for 20-50 minutes to form an O / W emulsion; adjust the pH to 4-5; Step 3: Step-by-step temperature control and in-situ polymerization coating: Polycondensation reaction: Raise the temperature to 40-50℃, stir with turbulent stirring paddle, and react for 2-3 hours to make the melamine prepolymer condense and deposit on the surface of the core material to form a dense capsule wall; Step 4, termination of reaction and post-treatment: adjusting pH ≥ 6 to terminate the reaction, filtering and washing, and vacuum drying at 50° C. to obtain white spherical deep repair microcapsules.

10. A method for sealing marine engineering facilities, characterized in that: The sealing putty according to any one of claims 1 to 9 is used for sealing, and the aging degree and crack development of the sealing putty are evaluated by monitoring the change in fluorescence intensity through ultraviolet irradiation. When the fluorescence intensity reaches a preset threshold, it indicates that the crack has developed to a critical depth, triggering a deep repair mechanism.

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