A perfluoropolyether-based polyurethane urea elastomeric seal material, and a method of making and use thereof

Abstract

The application provides a perfluoropolyether-based polyurethane urea elastic sealing material and a preparation method and application thereof, and particularly relates to the technical field of polyurethane urea elastomers. The preparation method of the perfluoropolyether-based polyurethane urea elastomer provided by the application comprises the following steps: mixing bis(1-hydroxymethyl)-terminated perfluoropolyether, isocyanate and dibutyl tin dilaurate, performing a first nucleophilic addition reaction, and obtaining a perfluoropolyether-based polyurethane elastomer; mixing the perfluoropolyether-based polyurethane elastomer, bis(3-aminopropyl)-terminated polydimethylsiloxane and an organic solvent, performing a second nucleophilic addition reaction, adding pentaerythritol, and performing a crosslinking polymerization reaction to obtain a perfluoropolyether-based polyurethane urea elastomer. The application utilizes a "flexible chain two-in-one" strategy to precisely prepare a polyurethane urea elastomer containing a PFPE segment, endows the PFPE type polymer with a structure-function integrated performance, and further expands the application form and use range of the PFPE material.

Description

Technical Field

[0001] This invention belongs to the field of polyurethane urea elastomer technology, specifically relating to a perfluoropolyether-based polyurethane urea elastic sealing material, its preparation method, and its application. Background Technology

[0002] Besides their use as sealing materials, cryogenic elastomers are also used in tires, cable sheaths, and cushioning pads, playing an irreplaceable role in extreme environments such as Antarctica and the Moon. In specific working environments such as aerospace, including at the outlet joints of liquid hydrogen and liquid oxygen devices, temperatures can drop to cryogenic ranges (below -150°C), far below the elastic temperature range of polymer materials. Therefore, developing polymer materials that exhibit good elasticity at extremely low temperatures of -80°C or even below -100°C is one of the urgent problems to be solved in the polar and aerospace technology fields.

[0003] In the extremely demanding field of sealing and vibration damping, perfluoroether elastomers, as special fluoropolymers, are highly favored due to their excellent resistance to oil and media, as well as their resistance to high and low temperatures. Although commercially available perfluoroether rubbers are widely used in high-end fields such as aerospace, they cannot meet the requirements of applications such as ultra-low temperature operating environments, high strength and toughness, repairability, and thermo-optical responsive shape memory properties. Therefore, developing novel perfluoropolyether (PFPE)-based polymer materials is the most effective way to overcome these limitations. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a perfluoropolyether-based polyurethane urea elastic sealing material, its preparation method, and its application. The perfluoropolyether-based polyurethane urea elastomer obtained by the preparation method provided by this invention has excellent tensile strength and toughness, a wide operating temperature range, and can maintain good tensile strength in environments ranging from -80℃ to 30℃.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0006] This invention provides a method for preparing a perfluoropolyether-based polyurethane urea elastomer, comprising the following steps:

[0007] A mixture of bis(1-hydroxymethyl)-terminated perfluoropolyether, isocyanate and dibutyltin dilaurate was subjected to a first nucleophilic addition reaction to obtain a perfluoropolyether-based polyurethane elastomer.

[0008] The bi(1-hydroxymethyl)-terminated perfluoropolyether has the structure shown in Formula 1:

[0009]

[0010] The perfluoropolyether-based polyurethane elastomer, bis(3-aminopropyl)-terminated polydimethylsiloxane, and organic solvent are mixed and subjected to a second nucleophilic addition reaction. Pentaerythritol is then added, and a crosslinking polymerization reaction occurs to obtain the perfluoropolyether-based polyurethane urea elastomer.

[0011] The molar ratio of the bis(1-hydroxymethyl)-terminated perfluoropolyether to isocyanate is 1:1.5 to 2.5;

[0012] The molar ratio of the bis(1-hydroxymethyl)-terminated perfluoropolyether to the bis(3-aminopropyl)-terminated polydimethylsiloxane is 1-5:1-5;

[0013] The molar ratio of pentaerythritol to bis(1-hydroxymethyl)-terminated perfluoropolyether is 0–2:1–5.

[0014] Preferably, the isocyanate includes 4,4-diisocyanate dicyclohexylmethane, isophorone diisocyanate, hexamethylene diisocyanate, or toluene diisocyanate.

[0015] Preferably, the volume ratio of dibutyltin dilaurate to the molar amount of the bis(1-hydroxymethyl)-terminated perfluoropolyether is 20–60 μL: 1–5 mmol.

[0016] Preferably, the molecular weight of the bis(1-hydroxymethyl)-terminated perfluoropolyether is 2-4 kDa;

[0017] The molecular weight of the bis(3-aminopropyl)-terminated polydimethylsiloxane is 1–5 kDa.

[0018] Preferably, the temperature of the first nucleophilic addition reaction is 70–90°C, and the time is 2–4 hours.

[0019] Preferably, the temperature of the second nucleophilic addition reaction is 20–30°C, and the time is 20–30 h.

[0020] Preferably, the crosslinking polymerization reaction is carried out at a temperature of 20–30°C for 4–8 hours.

[0021] Preferably, the organic solvent includes one or more of N,N-dimethylacetamide, chlorobenzene, fluorobenzene, tetrahydrofuran, and 1,4-dioxane.

[0022] The present invention also provides a perfluoropolyether-based polyurethane urea elastomer prepared by the preparation method described in the above technical solution.

[0023] The present invention also provides the application of the perfluoropolyether-based polyurethane urea elastomer described in the above technical solution in sealing materials.

[0024] This invention provides a method for preparing a perfluoropolyether-based polyurethane urea elastomer, comprising the following steps: mixing bis(1-hydroxymethyl)-terminated perfluoropolyether, isocyanate, and dibutyltin dilaurate, and performing a first nucleophilic addition reaction to obtain a perfluoropolyether-based polyurethane elastomer; mixing the perfluoropolyether-based polyurethane elastomer, bis(3-aminopropyl)-terminated polydimethylsiloxane, and an organic solvent, and performing a second nucleophilic addition reaction; adding pentaerythritol, and undergoing a crosslinking polymerization reaction to obtain a perfluoropolyether-based polyurethane urea elastomer; wherein the molar ratio of the bis(1-hydroxymethyl)-terminated perfluoropolyether to isocyanate is 1:1.5–2.5; the molar ratio of the bis(1-hydroxymethyl)-terminated perfluoropolyether to bis(3-aminopropyl)-terminated polydimethylsiloxane is 1–5:1–5; and the molar ratio of pentaerythritol to bis(1-hydroxymethyl)-terminated perfluoropolyether is 0–2:1–5. This invention utilizes low-temperature flexible polysiloxanes and perfluoropolyethers as soft segments, and urethane and urea bonds formed through reaction as hard segments, to prepare perfluoropolyether (PFPE)-based polyurethane urea elastomers through a "two-in-one" flexible chain strategy. The introduction of these two low-temperature flexible chains effectively lowers the glass transition temperature of polyurethane urea, while the introduction of urethane and urea bonds creates a large number of dynamic reversible hydrogen bonds in the molecular chain, thereby improving the strength and toughness of the material. The presence of pentaerythritol further increases the hydrogen bonding between polyurethane urea segments, increasing the sacrificial bond energy. From the perspective of energy dissipation mechanisms, the gradient hydrogen bond array formed by urethane and urea bonds can significantly improve the mechanical properties of PFPE-type polyurethane urea elastomers. By controlling the amount of pentaerythritol, the degree of crosslinking of PFPE-based polyurethane urea elastomers is changed, resulting in elastomers with different oil resistance properties. The method provided by this invention is simple to operate, and the obtained PFPE-based polyurethane urea elastomers maintain good sealing performance in low-temperature fuel environments.

[0025] This invention also provides a PFPE-based polyurethane urea elastomer prepared by the method described above, exhibiting a room temperature tensile strength ≥1.0 MPa, a room temperature elongation at break ≥100%, a Shore hardness D ≥55, a service temperature range of -80℃ to 30℃, a tensile strength of not less than 14 MPa at -80℃, and a toughness of not less than 18 MJ / m. 3 It possesses excellent tensile strength and toughness, as well as low-temperature resistance, and with a kerosene swelling rate ≤15%, it can be used as an extreme service material in the field of low-temperature fuel oil sealing and vibration reduction.

[0026] Meanwhile, PFPE-based polyurethane urea elastomers can possess properties such as self-healing, processability and recyclability, and thermally responsive shape memory through the synergistic effect of dynamic covalent bonds and hydrogen bonds. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 The tensile strength and elongation at break curves of the PFPE-based polyurethane urea elastomers prepared in Examples 1-5 are shown in the figure.

[0029] Figure 2 Typical room temperature tensile curves of PFPE-based polyurethane urea elastomers prepared in Examples 1-5;

[0030] Figure 3 The tensile curve of the PFPE-based polyurethane urea elastomer prepared in Example 4 at -80°C is shown.

[0031] Figure 4 The swelling rate of the PFPE-based polyurethane urea elastomers prepared in Examples 1-5 in kerosene. Detailed Implementation

[0032] This invention provides a method for preparing a perfluoropolyether-based polyurethane urea elastomer, comprising the following steps:

[0033] A mixture of bis(1-hydroxymethyl)-terminated perfluoropolyether, isocyanate and dibutyltin dilaurate was subjected to a first nucleophilic addition reaction to obtain a perfluoropolyether-based polyurethane elastomer.

[0034] The perfluoropolyether-based polyurethane elastomer, bis(3-aminopropyl)-terminated polydimethylsiloxane, and organic solvent are mixed and subjected to a second nucleophilic addition reaction. Pentaerythritol is then added, and a crosslinking polymerization reaction occurs to obtain the perfluoropolyether-based polyurethane urea elastomer.

[0035] The molar ratio of the bis(1-hydroxymethyl)-terminated perfluoropolyether to isocyanate is 1:1.5 to 2.5;

[0036] The molar ratio of the bis(1-hydroxymethyl)-terminated perfluoropolyether to the bis(3-aminopropyl)-terminated polydimethylsiloxane is 1-5:1-5;

[0037] The molar ratio of pentaerythritol to bis(1-hydroxymethyl)-terminated perfluoropolyether is 0–2:1–5.

[0038] Unless otherwise specified, all raw materials used in this invention are commercially available products well known in the art.

[0039] In this invention, before operation, it is preferable to dehumidify the bis(1-hydroxymethyl)-terminated perfluoropolyether and the bis(3-aminopropyl)-terminated polydimethylsiloxane, preferably by vacuum dehumidification at 90-95°C for 1-2 hours. Dehumidification removes moisture from the prepolymer, preventing side reactions.

[0040] This invention involves mixing a bis(1-hydroxymethyl)-terminated perfluoropolyether, an isocyanate, and dibutyltin dilaurate, and subjecting them to a first nucleophilic addition reaction to obtain a perfluoropolyether-based polyurethane elastomer.

[0041] In this invention, the molar ratio of the bis(1-hydroxymethyl)-terminated perfluoropolyether to isocyanate is preferably 1:1.5 to 2.5, more preferably 1:1.6 to 2.0, and even more preferably 1:1.7 to 1.9.

[0042] In this invention, the isocyanate preferably includes 4,4-diisocyanate dicyclohexylmethane, isophorone diisocyanate, hexamethylene diisocyanate or toluene diisocyanate, more preferably 4,4-diisocyanate dicyclohexylmethane or toluene diisocyanate, and even more preferably 4,4-diisocyanate dicyclohexylmethane.

[0043] In this invention, the molecular weight of the bis(1-hydroxymethyl)-terminated perfluoropolyether is preferably 2-4 kDa, more preferably 2.5-3 kDa. The bis(1-hydroxymethyl)-terminated perfluoropolyether of this invention has the structure shown in Formula 1:

[0044]

[0045] In this invention, the volume ratio of dibutyltin dilaurate to the molar amount of bis(1-hydroxymethyl)-terminated perfluoropolyether is preferably 20-60 μL: 1-5 mmol, more preferably 24-55 μL: 2-4 mmol, and even more preferably 45 μL: 4 mmol.

[0046] The present invention does not have special requirements for the mixing process; conventional methods in the art can be used. In a specific embodiment of the present invention, after mixing the bis(1-hydroxymethyl)-terminated perfluoropolyether with isocyanate, dibutyltin dilaurate is added dropwise.

[0047] In this invention, the temperature of the first nucleophilic addition reaction is preferably 70-90°C, more preferably 75-85°C, and the time is preferably 2-4 hours, more preferably 2.5-3.5 hours.

[0048] In this invention, the first nucleophilic addition reaction preferably includes cooling, and the cooling temperature is preferably 20-30°C, more preferably 22-28°C. During the first nucleophilic addition reaction, the isocyanate and hydroxyl group react to form an urethane bond, yielding a perfluoropolyether-based polyurethane elastomer.

[0049] After obtaining the perfluoropolyether-based polyurethane elastomer, the present invention mixes the perfluoropolyether-based polyurethane elastomer, bis(3-aminopropyl)-terminated polydimethylsiloxane and an organic solvent to undergo a second nucleophilic addition reaction, adds pentaerythritol, and undergoes a crosslinking polymerization reaction to obtain a perfluoropolyether-based polyurethane urea elastomer.

[0050] In this invention, the molar ratio of the bis(1-hydroxymethyl)-terminated perfluoropolyether to the bis(3-aminopropyl)-terminated polydimethylsiloxane is 1–5:1–5, preferably 2–4:2–4. In specific embodiments of this invention, the molar ratio of the bis(1-hydroxymethyl)-terminated perfluoropolyether to the bis(3-aminopropyl)-terminated polydimethylsiloxane is 1:1 or 2:1.

[0051] In this invention, the molecular weight of the bis(3-aminopropyl)-terminated polydimethylsiloxane is preferably 1-5 kDa, more preferably 1.5-4 kDa, and even more preferably 2-3 kDa. The bis(3-aminopropyl)-terminated polydimethylsiloxane of this invention has the structure shown in Formula 2:

[0052]

[0053] In this invention, the organic solvent preferably includes one or more of N,N-dimethylacetamide, chlorobenzene, fluorobenzene, tetrahydrofuran, and 1,4-dioxane, more preferably one or more of N,N-dimethylacetamide, chlorobenzene, fluorobenzene, and tetrahydrofuran, and even more preferably N,N-dimethylacetamide, fluorobenzene, or tetrahydrofuran. In this invention, the volume ratio of the organic solvent to the molar amount of the bis(1-hydroxymethyl)-terminated perfluoropolyether is preferably 20–50 mL: 1–5 mmol, more preferably 30–40 mL: 2–4 mmol. In specific embodiments of this invention, the volume ratio of the organic solvent to the molar amount of the bis(1-hydroxymethyl)-terminated perfluoropolyether is 30 mL: 2 mmol, 40 mL: 4 mmol, or 30 mL: 4 mmol.

[0054] The present invention does not have special requirements for the mixing process; conventional methods in the art can be used. In a specific embodiment of the present invention, after mixing the perfluoropolyether-based polyurethane elastomer and the organic solvent, bis(3-aminopropyl)-terminated polydimethylsiloxane is added.

[0055] In this invention, the temperature of the second nucleophilic addition reaction is preferably 20–30°C, more preferably 22–28°C, and the time is preferably 20–30 h, more preferably 24–26 h. During the second nucleophilic addition reaction, the amino group in the bis(3-aminopropyl)-terminated polydimethylsiloxane reacts with the isocyanate to form a urea bond.

[0056] In this invention, the molar ratio of pentaerythritol to bis(1-hydroxymethyl)-terminated perfluoropolyether is 0–2:1–5, preferably 0.2–1:2–4. In specific embodiments of this invention, the molar ratio of pentaerythritol to bis(1-hydroxymethyl)-terminated perfluoropolyether is 0:2 or 0.1:2. In this invention, pentaerythritol is preferably used in the form of a solution; the solution is preferably obtained by dissolving pentaerythritol in an organic solvent; the type of organic solvent is the same as above. The concentration of the solution is preferably 0.01–0.2 mmol / mL.

[0057] In this invention, the temperature of the crosslinking polymerization reaction is preferably 20-30°C, more preferably 22-28°C, and the time is preferably 4-8 hours, more preferably 5-6 hours.

[0058] In this invention, the preparation of the perfluoropolyether-based polyurethane urea elastomer follows the reaction described in Formula 3:

[0059]

[0060] After the crosslinking polymerization reaction is completed, the resulting perfluoropolyether-based polyurethane urea elastomer is a solution. Those skilled in the art can dry the perfluoropolyether-based polyurethane urea elastomer solution according to actual needs to obtain a solid perfluoropolyether-based polyurethane urea elastomer. In this invention, the drying temperature is preferably 40–80°C, and the drying time is preferably 24–26 hours. In a specific embodiment of this invention, a polytetrafluoroethylene mold is used, and drying is carried out in a forced-air drying oven.

[0061] The present invention also provides a perfluoropolyether-based polyurethane urea elastomer prepared by the preparation method described in the above technical solution.

[0062] Based on the polymer molecular structure design concept and taking the energy dissipation mechanism of dynamic reversible bonds as the criterion, this invention utilizes a "flexible chain two-in-one" strategy to precisely prepare perfluoropolyether (PFPE)-based polyurethane urea elastomers with polysiloxane and perfluoropolyether as soft segments and urethane and urea bonds as hard segments. The soft segments can effectively reduce the glass transition temperature of polyurethane urea, while the hard segments enable the presence of a large number of dynamic reversible hydrogen bonds in the molecular chain, which can improve the strength and toughness of the material.

[0063] The present invention also provides the application of the perfluoropolyether-based polyurethane urea elastomer described in the above technical solution in sealing materials.

[0064] In this invention, the preferred application environment temperature for the sealing material is -80℃ to 30℃.

[0065] The present invention does not impose any special limitation on the specific method of application, and any method known to those skilled in the art can be used.

[0066] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments. The described embodiments are only some embodiments of the present invention, and not all embodiments. Any modifications, equivalent substitutions, improvements, etc., made to the embodiments of the present invention based on the technical essence and general principles of the present invention without creative effort should be within the protection scope of the present invention.

[0067] Example 1

[0068] Bis(1-hydroxymethyl)-terminated perfluoropolyether and bis(3-aminopropyl)-terminated polydimethylsiloxane were placed in a 95°C oven for vacuum dehumidification for 1 h. 4.0 g (2.0 mmol) of bis(1-hydroxymethyl)-terminated perfluoropolyether and 1.05 g (4.0 mmol) of 4,4-diisocyanate dicyclohexylmethane were placed in a 100 mL three-necked flask, and 3 drops of dibutyltin dilaurate were added. The flask was placed in an oil bath preheated to 70°C and reacted for 4 h. After cooling to room temperature, 30 mL of N,N-dimethylacetamide and 5.0 g (2.0 mmol) of bis(3-aminopropyl)-terminated polydimethylsiloxane were added to the flask, and the mixture was stirred at room temperature for 24 h to obtain a PFPE-based polyurethane urea elastomer solution.

[0069] The PFPE-based urethane urea elastomer solution was placed in a polytetrafluoroethylene mold and dried in a forced-air drying oven at 80°C for 24 hours to obtain the PFPE-based polyurethane urea elastomer.

[0070] Example 2

[0071] Bis(1-hydroxymethyl)-terminated perfluoropolyether and bis(3-aminopropyl)-terminated polydimethylsiloxane were placed in a 95°C oven for vacuum dehumidification for 1 h. 8.0 g (4.0 mmol) of bis(1-hydroxymethyl)-terminated perfluoropolyether and 1.68 g (6.4 mmol) of 4,4-diisocyanate dicyclohexylmethane were placed in a 100 mL three-necked flask, and 3 drops of dibutyltin dilaurate were added. The flask was placed in an oil bath preheated to 70°C and reacted for 4 h. After cooling to room temperature, 40 mL of tetrahydrofuran and 5.0 g (2.0 mmol) of bis(3-aminopropyl)-terminated polydimethylsiloxane were added to the flask. The mixture was stirred at room temperature for 24 h, and then 10 mL of N,N-dimethylacetamide, which included 27.23 mg (0.2 mmol) pentaerythritol, was added. The mixture was reacted at room temperature for 4 h to obtain a PFPE-based polyurethane urea elastomer solution.

[0072] The PFPE-based urethane urea elastomer solution was placed in a polytetrafluoroethylene mold and dried in a forced-air drying oven at 40°C for 24 hours to obtain the PFPE-based polyurethane urea elastomer.

[0073] Example 3

[0074] Bis(1-hydroxymethyl)-terminated perfluoropolyether and bis(3-aminopropyl)-terminated polydimethylsiloxane were placed in a 95°C oven under vacuum for 1 hour to dehumidify. 8.0 g (4.0 mmol) of bis(1-hydroxymethyl)-terminated perfluoropolyether and 1.78 g (6.8 mmol) of 4,4-diisocyanate dicyclohexylmethane were placed in a 100 mL three-necked flask, and 3 drops of dibutyltin dilaurate were added. The flask was placed in an oil bath preheated to 70°C and reacted for 4 hours. After cooling to room temperature, 40 mL of fluorobenzene and 5.0 g (2.0 mmol) of bis(3-aminopropyl)-terminated polydimethylsiloxane were added to the flask. The mixture was stirred at room temperature for 24 hours, and then 10 mL of N,N-dimethylacetamide, which included 54.46 mg (0.4 mmol) of pentaerythritol, was added. The mixture was reacted at room temperature for 4 hours to obtain a PFPE-based polyurethane urea elastomer solution.

[0075] The PFPE-based urethane urea elastomer solution was placed in a polytetrafluoroethylene mold and dried in a forced-air drying oven at 50°C for 24 hours to obtain the PFPE-based polyurethane urea elastomer.

[0076] Example 4

[0077] Bis(1-hydroxymethyl)-terminated perfluoropolyether and bis(3-aminopropyl)-terminated polydimethylsiloxane were placed in an oven at 95°C and dehumidified under vacuum for 1 hour. Take 8.0 g (4.0 mmol) of bis(1-hydroxymethyl)-terminated perfluoropolyether and 1.994 g (7.6 mmol) of 4,4-diisocyanate dicyclohexylmethane into a 100 mL three-necked flask, add 3 drops of dibutyltin dilaurate, place the three-necked flask in an oil bath preheated to 70 °C, react for 4 h, cool to room temperature, add 30 mL of N,N-dimethylacetamide and 5.0 g (2.0 mmol) of bis(3-aminopropyl)-terminated polydimethylsiloxane to the three-necked flask, stir at room temperature for 24 h, add 10 mL of N,N-dimethylacetamide, which includes 108.92 mg (0.8 mmol) pentaerythritol, react at room temperature for 4 h to obtain a PFPE-based polyurethane urea elastomer solution.

[0078] The PFPE-based urethane urea elastomer solution was placed in a polytetrafluoroethylene mold and dried in a forced-air drying oven at 80°C for 24 hours to obtain the PFPE-based polyurethane urea elastomer.

[0079] Example 5

[0080] Bis(1-hydroxymethyl)-terminated perfluoropolyether and bis(3-aminopropyl)-terminated polydimethylsiloxane were placed in an oven at 95°C and dehumidified under vacuum for 1 hour. Take 8.0 g (4.0 mmol) of bis(1-hydroxymethyl)-terminated perfluoropolyether and 2.2 g (8.4 mmol) of 4,4-diisocyanate dicyclohexylmethane into a 100 mL three-necked flask, add 3 drops of dibutyltin dilaurate, place the three-necked flask in an oil bath preheated to 70 °C, react for 4 h, cool to room temperature, add 30 mL of N,N-dimethylacetamide and 5.0 g (2.0 mmol) of bis(3-aminopropyl)-terminated polydimethylsiloxane to the three-necked flask, stir at room temperature for 24 h, add 10 mL of N,N-dimethylacetamide, which includes 163.38 mg (1.2 mmol) pentaerythritol, react at room temperature for 4 h to obtain a PFPE-based polyurethane urea elastomer solution.

[0081] The PFPE-based urethane urea elastomer solution was placed in a polytetrafluoroethylene mold and dried in a forced-air drying oven at 80°C for 24 hours to obtain the PFPE-based polyurethane urea elastomer.

[0082] According to GB / T 528-2009 Determination of Tensile Stress-Strain Properties of Vulcanized Rubber or Thermoplastic Rubber, the room temperature tensile strength and elongation at break were measured on a universal tensile testing machine. The specimen shape was dumbbell-shaped, with an effective test size of 2.0 mm width, 0.5 mm thickness, and 150 mm length. The tensile speed was 10 mm / min. The swelling rate was determined according to GB / T 1690-2010 Test Method for Liquid Resistance of Vulcanized Rubber or Thermoplastic Rubber. The Shore hardness (D) was measured according to GB / T 2411-2008 Plastics and Hard Rubbers using a Hardness Tester. The relevant test data of the PFPE-based polyurethane urea prepared in Examples 1-5 are plotted in Table 1.

[0083] Table 1. Test results of PFPE-based polyurethane urea elastomers prepared in Examples 1-5

[0084] Example 1 Example 2 Example 3 Example 4 Example 5 Tensile strength at room temperature (25℃) / MPa 1.6 1.8 2.8 4.8 5.1 Elongation at break at room temperature (25℃) / % 114.6 248.6 525.7 512.7 224.5 Tensile strength at -80℃ / MPa / / / 14.7 / Elongation at break (%) at -80℃ / / / 191.2 / <![CDATA[-80℃ toughness / MJ / m 3 > / / / 18 / Swelling rate in kerosene / % 14.3 13.1 10.7 8.3 6.7 Shore hardness D 55 57 59 61 67

[0085] Figure 1 The graphs show the tensile strength and elongation at break of the PFPE-based polyurethane urea elastomers prepared in Examples 1-5. Figure 2 Typical room temperature tensile curves of PFPE-based polyurethane urea elastomers prepared in Examples 1-5 are shown, where samples 1-5 correspond to Examples 1-5 respectively. Figure 3 The tensile curve of the PFPE-based polyurethane urea elastomer prepared in Example 4 at -80°C is shown in Table 1. Figures 1-3As can be seen, the PFPE-based polyurethane urea elastomer obtained by this invention has a tensile strength ≥1.0 MPa, elongation at break ≥100%, kerosene swelling rate ≤15%, Shore hardness D ≥55, and an operating temperature range of -80℃ to 30℃. In an environment of -80℃, it exhibits excellent tensile strength and toughness. This indicates that the PFPE-based polyurethane urea elastomer obtained by this invention has good sealing performance in low-temperature fuel environments.

[0086] Figure 4 The swelling ratios of the PFPE-based polyurethane urea elastomers prepared in Examples 1-5 in kerosene are shown. Samples 1-5 correspond sequentially to Examples 1-5. Figure 4 As can be seen from the results, the PFPE-based polyurethane urea elastomers prepared in Examples 1-5 have a swelling rate of <15% in kerosene, indicating that the elastomers have good kerosene resistance; and with the increase of crosslinking degree, the swelling rate decreases and the oil resistance of the elastomers increases.

[0087] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a perfluoropolyether-based polyurethane urea elastomer, characterized in that, Includes the following steps: A mixture of bis(1-hydroxymethyl)-terminated perfluoropolyether, isocyanate and dibutyltin dilaurate was subjected to a first nucleophilic addition reaction to obtain a perfluoropolyether-based polyurethane elastomer. The bi(1-hydroxymethyl)-terminated perfluoropolyether has the structure shown in Formula 1: Formula 1; The perfluoropolyether-based polyurethane elastomer, bis(3-aminopropyl)-terminated polydimethylsiloxane, and organic solvent are mixed and subjected to a second nucleophilic addition reaction. Pentaerythritol is then added, and a crosslinking polymerization reaction occurs to obtain the perfluoropolyether-based polyurethane urea elastomer. The molar ratio of the bis(1-hydroxymethyl)-terminated perfluoropolyether to isocyanate is 1:1.5~2.5; the molar ratio of the bis(1-hydroxymethyl)-terminated perfluoropolyether to bis(3-aminopropyl)-terminated polydimethylsiloxane is 1~5:1~5. The molar ratio of pentaerythritol to bis(1-hydroxymethyl)-terminated perfluoropolyether is 0.2~2:1~5; The isocyanate is 4,4-diisocyanate dicyclohexylmethane; The molecular weight of the bis(1-hydroxymethyl)-terminated perfluoropolyether is 2~3 kDa; The molecular weight of the bis(3-aminopropyl)-terminated polydimethylsiloxane is 1~3 kDa; The cross-linking polymerization reaction is carried out at a temperature of 20-30°C for 4-8 hours.

2. The preparation method according to claim 1, characterized in that, The volume ratio of the dibutyltin dilaurate to the molar amount of the bis(1-hydroxymethyl)-terminated perfluoropolyether is 20~60 μL: 1~5 mmol.

3. The preparation method according to claim 1, characterized in that, The temperature of the first nucleophilic addition reaction is 70~90℃, and the time is 2~4h.

4. The preparation method according to claim 1, characterized in that, The second nucleophilic addition reaction is carried out at a temperature of 20-30°C for 20-30 hours.

5. The preparation method according to claim 1, characterized in that, The organic solvent includes one or more of N,N-dimethylacetamide, chlorobenzene, fluorobenzene, tetrahydrofuran, and 1,4-dioxane.

6. The perfluoropolyether-based polyurethane urea elastomer prepared by the preparation method according to any one of claims 1 to 5.

7. The application of the perfluoropolyether-based polyurethane urea elastomer of claim 6 in sealing materials.

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