Underwater adhesive as well as preparation method and small molecule driven bonding method thereof

Abstract

The invention relates to an underwater adhesive as well as a preparation method and a small molecule driven bonding method thereof, and belongs to the technical field of underwater adhesives. In order to solve the problems that an existing underwater adhesive is poor in bonding performance, not resistant to water and limited in types of bonding materials, the underwater adhesive is provided and comprises perfluoropolyether glycol, isocyanate, a tin-based catalyst, degradable polyester polyol and a chain extender, and the underwater adhesive is an adhesive film with the thickness of 0.001-2 cm. The adhesive film material with hydrophobicity and biocompatibility is constructed through molecular structure design, a small molecule driven curing mechanism is provided, efficient curing in an underwater environment is achieved, and the problems that a traditional adhesive is slow in underwater curing and low in strength are solved. And the underwater bonding strength can reach up to 2.48 + / -0.38 Mpa after being driven and cured by small molecules. The underwater adhesive disclosed by the invention has good underwater durability and broad-spectrum material adaptability, and can be used for bonding dissimilar materials such as metal, plastic, rubber, ceramic and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of underwater adhesives, and in particular relates to an underwater adhesive and a preparation method thereof, and a small molecule driven bonding method. Background Art

[0002] In recent years, with the rapid development of marine resource development, underwater engineering repair, and shipbuilding, the demand for underwater adhesives has been growing. However, traditional underwater adhesives still face many technical bottlenecks in practical application.

[0003] The underwater environment is complex, and adhesives are easily affected by water flow, pressure, and temperature fluctuations during the curing process, resulting in insufficient interfacial bonding strength. Existing adhesives often have difficulty forming a stable, high-strength bonding layer underwater due to incomplete curing or poor interfacial permeability, and are particularly prone to debonding failure under dynamic loads. Water molecules will penetrate the adhesive-substrate interface, triggering hydrolysis or swelling, and reducing the durability of the bond. Some adhesives (such as epoxy resins) will experience a significant decrease in mechanical properties after long-term immersion in water, making it difficult to meet the requirements of deep-sea or long-term underwater service. Most underwater adhesives are designed for common materials such as metal and concrete, but have poor adaptability to glass, ceramics, biological tissue surfaces, or hydrophobic plastic surfaces. Summary of the Invention

[0004] In order to solve the problems of poor bonding performance, water resistance and limited types of bonding materials of existing underwater adhesives, the present invention provides an underwater adhesive and its preparation method and a small molecule driven bonding method.

[0005] The technical solution of the present invention:

[0006] An underwater adhesive comprises the following components in parts by weight: 20-30 parts of perfluoropolyether diol, 1-15 parts of isocyanate, 0.01-0.1 parts of a tin-based catalyst, 5-20 parts of a degradable polyester polyol, and 0-10 parts of a chain extender; the underwater adhesive is a film with a thickness of 0.001-2 cm.

[0007] Furthermore, the molecular weight of the perfluoropolyether diol is 500, 1000 or 2000, the degradable polyester polyol is one or a combination of polylactic acid polyol, polycaprolactone polyol, polybutylene adipate glycol or polyethylene furandicarboxylate, and the molecular weight of the degradable polyester polyol is 500, 1000 or 2000; the isocyanate is one or a combination of polymethylene polyphenyl isocyanate, toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate or lysine diisocyanate; the tin-based catalyst is dibutyltin dilaurate, stannous octoate or stannous chloride; the chain extender is one or a combination of isophthalic acid dihydrazide, sebacic acid dihydrazide, succinic acid dihydrazide and 2,5-bis(benzyloxy)terephthalic acid dihydrazide.

[0008] A method for preparing an underwater adhesive comprises the following steps:

[0009] Step 1: Preparation of isocyanate-terminated PFPE prepolymer:

[0010] 20-30 parts of perfluoropolyether diol are stirred at a first heating temperature and moisture and air in the system are extracted using a vacuum pump. Subsequently, 1-15 parts of isocyanate and 0.01-0.1 parts of a tin-based catalyst are added under the protection of a nitrogen atmosphere, and the mixture is stirred at a second heating temperature for a certain period of time to obtain an isocyanate-terminated PFPE prepolymer.

[0011] Step 2: Prepare underwater adhesive film:

[0012] 5 to 20 parts of a degradable polyester polyol are added to the isocyanate-terminated PFPE prepolymer system obtained in step 1, an anhydrous organic solvent is added to reduce the concentration of the reaction system, the reaction is carried out at a third heating temperature for a certain time, and then 0 to 10 parts of a chain extender are added after the temperature is lowered to room temperature. After reacting at room temperature for a certain time, the resulting mixed system is cast into a film, and the solvent is evaporated and removed at room temperature or under heating conditions to obtain an underwater adhesive film.

[0013] Furthermore, the molecular weight of the perfluoropolyether diol in step 1 is 500, 1000 or 2000, and the perfluoropolyether diol is dried in a vacuum oven at 90°C for 8 to 10 hours before use; the isocyanate is one or a combination of polymethylene polyphenyl isocyanate, toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate or lysine diisocyanate; and the tin-based catalyst is dibutyltin dilaurate, stannous octoate or stannous chloride.

[0014] Furthermore, in step 1, the first heating temperature is 80° C., the stirring time at the first heating temperature is 2 to 3 hours, the second heating temperature is 60 to 120° C., and the stirring time at the second heating temperature is 12 to 36 hours.

[0015] Furthermore, in step 2, the degradable polyester polyol is one or a combination of polylactic acid polyol, polycaprolactone polyol, polybutylene adipate or polyethylene furandicarboxylate, and the molecular weight of the degradable polyester polyol is 500, 1000 or 2000; the degradable polyester polyol is dried in a vacuum oven at 90°C for 8 to 10 hours before use; the anhydrous organic solvent is one of butanone, dioxane, N,N-dimethylformamide or dimethylacetamide, and the chain extender is one or a combination of isophthalic acid dihydrazide, sebacic acid dihydrazide, succinic acid dihydrazide and 2,5-bis(benzyloxy)terephthalic acid dihydrazide.

[0016] Furthermore, the amount of the anhydrous organic solvent added in step 2 is 5 to 30 parts, the third heating temperature is 60 to 120°C, the reaction time at the third heating temperature is 5 to 24 hours, the reaction time at room temperature is 12 to 24 hours, the heating temperature for volatilizing and removing the solvent is 50°C, and the thickness of the underwater adhesive film is 0.001 to 2 cm.

[0017] A small molecule-driven bonding method for underwater adhesives comprises spraying a small molecule organic compound evenly on both sides of the underwater adhesive film, laying the sprayed film between the materials to be bonded, applying a certain vertical pressure, and then placing it in fresh water or seawater to complete room-temperature bonding and curing; the small molecule organic compound is formic acid, acetic acid, methanol, or ethanol.

[0018] Furthermore, the spraying amount of the small molecule organic compound is 0.001~0.2 mL / cm 2 The volume concentration of the small molecule organic compound is 75-98%, the pressure is 0.05-0.5 MPa, and the bonding curing time is 8-24 h.

[0019] Furthermore, the material to be bonded includes wood, bamboo, stainless steel, glass, ceramic, aluminum sheet, plastic or rubber, and the plastic is polyethylene, polytetrafluoroethylene or methyl methacrylate.

[0020] Beneficial effects of the present invention:

[0021] The underwater adhesive provided by this invention utilizes perfluoropolyether diol (PFPE) and polylactic acid polyol (PLA-polyol) as the soft segment matrix and isocyanate as the hard segment crosslinker. Through molecular structural design, this adhesive film material exhibits both hydrophobicity and biocompatibility. This invention innovatively proposes a small-molecule-driven curing mechanism. By spraying small-molecule organic compounds such as formic acid, acetic acid, and methanol onto the film surface, they rapidly penetrate the film interface, triggering a rapid crosslinking reaction of the isocyanate, achieving efficient curing in underwater environments. This overcomes the challenges of slow underwater curing and low strength of traditional adhesives. After small-molecule-driven curing, a dense crosslinked network is formed, achieving underwater bond strengths as high as 2.48±0.38 MPa. The perfluoropolyether segments impart superhydrophobicity to the film, making the small-molecule-driven underwater adhesive provided by this invention compatible with a broad range of materials, including metals, plastics, rubber, and ceramics, both homogeneous and heterogeneous materials. It is particularly suitable for complex applications such as underwater equipment repair and biomedical bonding. The invention introduces polylactic acid polyol to reduce the environmental load of perfluoropolymer, and the spraying process is simple, does not require complicated equipment, and is suitable for industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a comparison chart of the underwater bonding strength of the underwater adhesive films prepared in Examples 1 to 3 and Comparative Example 1 for bonding glass, stainless steel and tetrafluoroethylene. DETAILED DESCRIPTION

[0023] The technical solution of the present invention is further described below with reference to the embodiments, but is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention shall be included in the scope of protection of the present invention. The process equipment or devices not specifically noted in the following examples are all conventional equipment or devices in the art. Unless otherwise specified, the raw materials used in the examples of the present invention can be obtained commercially; unless otherwise specified, the technical means used in the examples of the present invention are all conventional means well known to those skilled in the art.

[0024] Example 1

[0025] This embodiment provides an underwater adhesive and a preparation method thereof.

[0026] The underwater adhesive in this example includes the following components by weight: 26.5 parts perfluoropolyether diol, 5.4 parts isophorone diisocyanate, 0.6 parts dibutyltin dilaurate (tin-based catalyst), and 6.16 parts polylactic acid polyol. The perfluoropolyether diol and polylactic acid polyol used in this example have a molecular weight of 500 and 500, respectively. Both the perfluoropolyether diol and polylactic acid polyol were dried in a vacuum oven at 90°C for 8 hours before use to remove moisture from the polyols.

[0027] This embodiment also provides a method for preparing an underwater adhesive, comprising the following steps:

[0028] Step 1: Preparation of isocyanate-terminated PFPE prepolymer:

[0029] 26.5 parts of perfluoropolyether diol were added to a three-necked flask with a stirring paddle, heated to 80°C in an oil bath, and the moisture and air in the system were evacuated using a vacuum pump. Subsequently, 5.4 parts of isophorone diisocyanate and 0.6 parts of a tin-based catalyst, dibutyltin dilaurate, were added under nitrogen atmosphere, and stirred at 80°C for 36 hours to obtain an isocyanate-terminated PFPE prepolymer.

[0030] Step 2: Prepare underwater adhesive film:

[0031] 6.16 parts of polylactic acid polyol were added to the isocyanate-terminated PFPE prepolymer system obtained in step 1, 30 parts of butanone were added to reduce the concentration of the reaction system, and then the reaction was carried out at 80°C for 8 hours, and then cooled to room temperature. The resulting mixed system was cast on a clean polypropylene plate and dried in a 50°C oven for 24 hours to evaporate and remove the solvent, thereby obtaining an underwater adhesive film with a thickness of 0.002 cm.

[0032] Example 2

[0033] This embodiment provides an underwater adhesive and a preparation method thereof.

[0034] The underwater adhesive of this example comprises the following components by weight: 26.5 parts perfluoropolyether diol, 5.4 parts isophorone diisocyanate, 0.6 parts dibutyltin dilaurate (tin-based catalyst), 6.16 parts polylactic acid polyol, and 1.17 parts isophthalic acid dihydrazide (chain extender). The molecular weight of the perfluoropolyether diol and polylactic acid polyol used in this example is 500, and the molecular weight of the polylactic acid polyol is 500. Both the perfluoropolyether diol and polylactic acid polyol were dried in a vacuum oven at 90°C for 8 hours before use to remove moisture from the polyols.

[0035] This embodiment also provides a method for preparing an underwater adhesive, comprising the following steps:

[0036] Step 1: Preparation of isocyanate-terminated PFPE prepolymer:

[0037] 26.5 parts of perfluoropolyether diol were added to a three-necked flask with a stirring paddle, heated to 80°C in an oil bath, and the moisture and air in the system were evacuated using a vacuum pump. Subsequently, 5.4 parts of isophorone diisocyanate and 0.6 parts of a tin-based catalyst, dibutyltin dilaurate, were added under nitrogen atmosphere, and stirred at 80°C for 36 hours to obtain an isocyanate-terminated PFPE prepolymer.

[0038] Step 2: Prepare underwater adhesive film:

[0039] 6.16 parts of polylactic acid polyol were added to the isocyanate-terminated PFPE prepolymer system obtained in step 1, 30 parts of butanone were added to reduce the concentration of the reaction system, and then the reaction was carried out at 80°C for 8 hours. After cooling to room temperature, 1.17 parts of chain extender isophthalic acid dihydrazide were added and the reaction was carried out at room temperature for 12 hours. The resulting mixed system was cast on a clean polypropylene plate and dried in a 50°C oven for 24 hours to evaporate and remove the solvent to obtain an underwater adhesive film with a thickness of 0.0002 cm.

[0040] Example 3

[0041] This embodiment provides an underwater adhesive and a preparation method thereof.

[0042] The underwater adhesive of this example comprises the following components by weight: 26.5 parts perfluoropolyether diol, 5.4 parts isophorone diisocyanate, 0.6 parts dibutyltin dilaurate (tin-based catalyst), 6.16 parts polylactic acid polyol, and 1.17 parts isophthalic acid dihydrazide (chain extender). The molecular weight of the perfluoropolyether diol used in this example is 500, and the molecular weight of the polylactic acid polyol is 2000. Both the perfluoropolyether diol and the polylactic acid polyol were dried in a vacuum oven at 90°C for 8 hours before use to remove moisture from the polyols.

[0043] This embodiment also provides a method for preparing an underwater adhesive, comprising the following steps:

[0044] Step 1: Preparation of isocyanate-terminated PFPE prepolymer:

[0045] 26.5 parts of perfluoropolyether diol were added to a three-necked flask with a stirring paddle, heated to 80°C in an oil bath, and the moisture and air in the system were evacuated using a vacuum pump. Subsequently, 5.4 parts of isophorone diisocyanate and 0.6 parts of a tin-based catalyst, dibutyltin dilaurate, were added under nitrogen atmosphere, and stirred at 80°C for 36 hours to obtain an isocyanate-terminated PFPE prepolymer.

[0046] Step 2: Prepare underwater adhesive film:

[0047] 6.16 parts of polylactic acid polyol were added to the isocyanate-terminated PFPE prepolymer system obtained in step 1, 30 parts of butanone were added to reduce the concentration of the reaction system, and then the reaction was carried out at 80°C for 8 hours. After cooling to room temperature, 1.17 parts of chain extender isophthalic acid dihydrazide were added and the reaction was carried out at room temperature for 12 hours. The resulting mixed system was cast on a clean polypropylene plate and dried in a 50°C oven for 24 hours to evaporate and remove the solvent to obtain an underwater adhesive film with a thickness of 0.002 cm.

[0048] Example 4

[0049] This embodiment provides an underwater adhesive and a preparation method thereof.

[0050] The underwater adhesive of this example comprises the following components by weight: 26.5 parts perfluoropolyether diol, 5.4 parts isophorone diisocyanate, 0.6 parts dibutyltin dilaurate (tin-based catalyst), 6.16 parts polylactic acid polyol, and 1.17 parts isophthalic acid dihydrazide (chain extender). The molecular weight of the perfluoropolyether diol and polylactic acid polyol used in this example is 500, and the molecular weight of the polylactic acid polyol is 500. Both the perfluoropolyether diol and polylactic acid polyol were dried in a vacuum oven at 90°C for 8 hours before use to remove moisture from the polyols.

[0051] This embodiment also provides a method for preparing an underwater adhesive, comprising the following steps:

[0052] Step 1: Preparation of isocyanate-terminated PFPE prepolymer:

[0053] 26.5 parts of perfluoropolyether diol were added to a three-necked flask with a stirring paddle, heated to 80°C in an oil bath, and the moisture and air in the system were evacuated using a vacuum pump. Subsequently, 5.4 parts of isophorone diisocyanate and 0.6 parts of a tin-based catalyst, dibutyltin dilaurate, were added under nitrogen atmosphere, and stirred at 80°C for 36 hours to obtain an isocyanate-terminated PFPE prepolymer.

[0054] Step 2: Prepare underwater adhesive film:

[0055] 6.16 parts of polylactic acid polyol were added to the isocyanate-terminated PFPE prepolymer system obtained in step 1, 10 parts of butanone were added to reduce the concentration of the reaction system, and then the reaction was carried out at 80°C for 8 hours. After cooling to room temperature, 1.17 parts of chain extender isophthalic acid dihydrazide were added and the reaction was carried out at room temperature for 12 hours. The resulting mixed system was cast on a clean polypropylene plate and dried in a 50°C oven for 24 hours to evaporate and remove the solvent to obtain an underwater adhesive film with a thickness of 0.0015 cm.

[0056] Example 5

[0057] This embodiment provides an underwater adhesive and a preparation method thereof.

[0058] The underwater adhesive of this example comprises the following components by weight: 26.5 parts perfluoropolyether diol, 5.4 parts isophorone diisocyanate, 0.6 parts dibutyltin dilaurate (tin-based catalyst), 6.16 parts polylactic acid polyol, and 1.17 parts isophthalic acid dihydrazide (chain extender). The molecular weight of the perfluoropolyether diol and polylactic acid polyol used in this example is 500, and the molecular weight of the polylactic acid polyol is 500. Both the perfluoropolyether diol and polylactic acid polyol were dried in a vacuum oven at 90°C for 8 hours before use to remove moisture from the polyols.

[0059] This embodiment also provides a method for preparing an underwater adhesive, comprising the following steps:

[0060] Step 1: Preparation of isocyanate-terminated PFPE prepolymer:

[0061] 26.5 parts of perfluoropolyether diol were added to a three-necked flask with a stirring paddle, heated to 80°C in an oil bath, and the moisture and air in the system were evacuated using a vacuum pump. Subsequently, 5.4 parts of isophorone diisocyanate and 0.6 parts of a tin-based catalyst, dibutyltin dilaurate, were added under nitrogen atmosphere, and stirred at 80°C for 36 hours to obtain an isocyanate-terminated PFPE prepolymer.

[0062] Step 2: Prepare underwater adhesive film:

[0063] 6.16 parts of polylactic acid polyol were added to the isocyanate-terminated PFPE prepolymer system obtained in step 1, 10 parts of butanone were added to reduce the concentration of the reaction system, and then the reaction was carried out at 80°C for 8 hours. After cooling to room temperature, 1.17 parts of chain extender isophthalic acid dihydrazide were added and the reaction was carried out at room temperature for 12 hours. The resulting mixed system was cast on a clean polypropylene plate and dried in a 50°C oven for 24 hours to evaporate and remove the solvent to obtain an underwater adhesive film with a thickness of 0.002 cm.

[0064] Example 6

[0065] This embodiment provides an underwater adhesive and a preparation method thereof.

[0066] The underwater adhesive of this example comprises the following components by weight: 26.5 parts perfluoropolyether diol, 5.4 parts isophorone diisocyanate, 0.6 parts dibutyltin dilaurate (tin-based catalyst), 6.16 parts polylactic acid polyol, and 1.17 parts isophthalic acid dihydrazide (chain extender). The molecular weight of the perfluoropolyether diol and polylactic acid polyol used in this example is 500, and the molecular weight of the polylactic acid polyol is 500. Both the perfluoropolyether diol and polylactic acid polyol were dried in a vacuum oven at 90°C for 8 hours before use to remove moisture from the polyols.

[0067] This embodiment also provides a method for preparing an underwater adhesive, comprising the following steps:

[0068] Step 1: Preparation of isocyanate-terminated PFPE prepolymer:

[0069] 26.5 parts of perfluoropolyether diol were added to a three-necked flask with a stirring paddle, heated to 80°C in an oil bath, and the moisture and air in the system were evacuated using a vacuum pump. Subsequently, 5.4 parts of isophorone diisocyanate and 0.6 parts of a tin-based catalyst, dibutyltin dilaurate, were added under nitrogen atmosphere, and stirred at 80°C for 36 hours to obtain an isocyanate-terminated PFPE prepolymer.

[0070] Step 2: Prepare underwater adhesive film:

[0071] 6.16 parts of polylactic acid polyol were added to the isocyanate-terminated PFPE prepolymer system obtained in step 1, 10 parts of butanone were added to reduce the concentration of the reaction system, and then the reaction was carried out at 80°C for 8 hours. After cooling to room temperature, 1.17 parts of chain extender isophthalic acid dihydrazide were added and the reaction was carried out at room temperature for 12 hours. The resulting mixed system was cast on a clean polypropylene plate and dried in a 50°C oven for 24 hours to evaporate and remove the solvent to obtain an underwater adhesive film with a thickness of 0.002 cm.

[0072] Comparative Example 1

[0073] This comparative example provides a comparative adhesive and a preparation method thereof.

[0074] The adhesive in this comparative example consisted of the following components by weight: 26.5 parts perfluoropolyether diol, 2.68 parts isophorone diisocyanate, and 0.6 parts dibutyltin dilaurate (tin-based catalyst). The perfluoropolyether diol used in this comparative example had a molecular weight of 500 and was dried in a vacuum oven at 90°C for 8 hours before use to remove moisture from the polyol.

[0075] The preparation method of the adhesive in this comparative example is:

[0076] 26.5 parts of perfluoropolyether diol were added to a three-necked flask with a stirring paddle, heated to 80°C in an oil bath, and the moisture and air in the system were extracted using a vacuum pump. Subsequently, 2.68 parts of isophorone diisocyanate and 0.6 parts of tin-based catalyst dibutyltin dilaurate were added under the protection of a nitrogen atmosphere. The mixture was stirred at 80°C for 36 hours. 10 parts of butanone were added to reduce the concentration of the reaction system. The resulting mixed system was cast on a clean polypropylene plate and dried in a 50°C oven for 24 hours to evaporate and remove the solvent, obtaining a control adhesive film with a thickness of 0.002 cm.

[0077] The underwater adhesive films prepared in Comparative Example 1, Example 1, Example 2 and Example 3 were used for underwater bonding of glass to glass, stainless steel to stainless steel and polytetrafluoroethylene to polytetrafluoroethylene, respectively. The specific bonding methods were as follows:

[0078] Evenly spray 95% methanol on both sides of the underwater adhesive film at a spray volume of 0.1 mL / cm 2， The sprayed adhesive film is laid between the materials to be bonded, and a vertical pressure of 0.05 MPa is applied and then placed in fresh water or sea water to complete the bonding and curing at room temperature. The bonding and curing time is 8 hours. The underwater bonding strength of each bonding surface is tested. The results are as follows Figure 1 shown.

[0079] Depend on Figure 1 By comparison, it can be seen that the control adhesive of Comparative Example 1 can bond glass and stainless steel, but cannot bond polytetrafluoroethylene, while Examples 1, 2, and 3 can all bond glass, stainless steel, and polytetrafluoroethylene. The addition of fluorinated polyols improves the hydrophobicity of the material and the versatility of the bonding material.

[0080] The underwater adhesive film prepared in Example 2 was used for underwater bonding of glass to glass, and small molecule driven bonding was performed using formic acid, methanol, and acetic acid, respectively. The specific bonding methods were:

[0081] Formic acid drive: Spray 78% formic acid evenly on both sides of the underwater adhesive film at a spray volume of 0.1 mL / cm 2 The sprayed film is laid between the materials to be bonded, and after applying a vertical pressure of 0.1 MPa, it is placed in fresh water or sea water to complete room temperature bonding and curing. The bonding and curing time is 8 hours, and the underwater bonding strength is 0.14±0.01 Mpa.

[0082] Methanol drive: Spray 98% methanol evenly on both sides of the underwater adhesive film at a spray volume of 0.05 mL / cm 2 The sprayed film is laid between the materials to be bonded, and after applying a vertical pressure of 0.5 MPa, it is placed in fresh water or sea water to complete room temperature bonding and curing. The bonding curing time is 8 hours, and the underwater bonding strength is 1.04±0.13 Mpa.

[0083] Acetic acid drive: spray 78% acetic acid evenly on the front and back of the underwater adhesive film at a spray volume of 0.2 mL / cm 2 The sprayed film is laid between the materials to be bonded, and after applying a vertical pressure of 0.5 MPa, it is placed in fresh water or sea water to complete room temperature bonding and curing. The bonding curing time is 8 hours, and the underwater bonding strength is 2.48±0.38 Mpa.

Claims

1. An underwater adhesive, characterized in that: The underwater adhesive comprises the following components in parts by mass: 20-30 parts of perfluoropolyether diol, 1-15 parts of isocyanate, 0.01-0.1 parts of tin-based catalyst, 5-20 parts of degradable polyester polyol and 0-10 parts of chain extender; the underwater adhesive is a film with a thickness of 0.001-2 cm.

2. The underwater adhesive according to claim 1, characterized in that: The molecular weight of the perfluoropolyether diol is 500, 1000 or 2000, the degradable polyester polyol is one or a combination of polylactic acid polyol, polycaprolactone polyol, polybutylene adipate glycol or polyethylene furandicarboxylate, and the molecular weight of the degradable polyester polyol is 500, 1000 or 2000; the isocyanate is one or a combination of polymethylene polyphenyl isocyanate, toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate or lysine diisocyanate; the tin-based catalyst is dibutyltin dilaurate, stannous octoate or stannous chloride; the chain extender is one or a combination of isophthalic acid dihydrazide, sebacic acid dihydrazide, succinic acid dihydrazide and 2,5-bis(benzyloxy)terephthaloyl dihydrazide.

3. A method for preparing an underwater adhesive, characterized in that: The method comprises the following preparation steps: Step 1: Preparation of isocyanate-terminated PFPE prepolymer: 20-30 parts of perfluoropolyether diol are stirred at a first heating temperature and moisture and air in the system are extracted using a vacuum pump. Subsequently, 1-15 parts of isocyanate and 0.01-0.1 parts of a tin-based catalyst are added under the protection of a nitrogen atmosphere, and the mixture is stirred at a second heating temperature for a certain period of time to obtain an isocyanate-terminated PFPE prepolymer. Step 2: Prepare underwater adhesive film: 5 to 20 parts of a degradable polyester polyol are added to the isocyanate-terminated PFPE prepolymer system obtained in step 1, an anhydrous organic solvent is added to reduce the concentration of the reaction system, the reaction is carried out at a third heating temperature for a certain time, and then 0 to 10 parts of a chain extender are added after the temperature is lowered to room temperature. After reacting at room temperature for a certain time, the resulting mixed system is cast into a film, and the solvent is evaporated and removed at room temperature or under heating conditions to obtain an underwater adhesive film.

4. The method for preparing the underwater adhesive according to claim 3, wherein: The molecular weight of the perfluoropolyether diol in step 1 is 500, 1000 or 2000, and the perfluoropolyether diol is dried in a vacuum oven at 90°C for 8 to 10 hours before use; the isocyanate is one or a combination of polymethylene polyphenyl isocyanate, toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate or lysine diisocyanate; and the tin-based catalyst is dibutyltin dilaurate, stannous octoate or stannous chloride.

5. The method for preparing the underwater adhesive according to claim 3 or 4, characterized in that: In step 1, the first heating temperature is 80° C., the stirring time at the first heating temperature is 2 to 3 hours, the second heating temperature is 60 to 120° C., and the stirring time at the second heating temperature is 12 to 36 hours.

6. The method for preparing the underwater adhesive according to claim 5, characterized in that: In step 2, the degradable polyester polyol is one or a combination of polylactic acid polyol, polycaprolactone polyol, polybutylene adipate or polyethylene furandicarboxylate, and the molecular weight of the degradable polyester polyol is 500, 1000 or 2000; the degradable polyester polyol is dried in a vacuum oven at 90°C for 8 to 10 hours before use; the anhydrous organic solvent is one of butanone, dioxane, N,N-dimethylformamide or dimethylacetamide, and the chain extender is one or a combination of isophthalic acid dihydrazide, sebacic acid dihydrazide, succinic acid dihydrazide and 2,5-bis(benzyloxy)terephthalic acid dihydrazide.

7. The method for preparing the underwater adhesive according to claim 6, wherein: The amount of the anhydrous organic solvent added in step 2 is 5 to 30 parts, the third heating temperature is 60 to 120°C, the reaction time at the third heating temperature is 5 to 24 hours, the reaction time at room temperature is 12 to 24 hours, the heating temperature for volatilizing and removing the solvent is 50°C, and the thickness of the underwater adhesive film is 0.001 to 2 cm.

8. A small molecule driven bonding method of underwater adhesive according to claim 1 or 2, characterized in that: A small molecule organic compound is evenly sprayed on the front and back sides of the underwater adhesive film, the sprayed film is laid between the materials to be bonded, and after applying a certain vertical pressure, it is placed in fresh water or sea water to complete room temperature bonding and curing; the small molecule organic compound is formic acid, acetic acid, methanol or ethanol.

9. The small molecule driven bonding method of underwater adhesive according to claim 8, characterized in that: The spraying amount of the small molecule organic compound is 0.001~0.2 mL / cm 2 The volume concentration of the small molecule organic compound is 75-98%, the pressure is 0.05-0.5 MPa, and the bonding curing time is 8-24 h.

10. The small molecule driven bonding method of underwater adhesive according to claim 9, characterized in that: The materials to be bonded include wood, bamboo, stainless steel, glass, ceramics, aluminum sheets, plastic or rubber, and the plastic is polyethylene, polytetrafluoroethylene or methyl methacrylate.

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