Room-temperature self-repairing polyurethane adhesive for propellant and preparation method thereof

Abstract

The invention discloses a room-temperature self-repairing polyurethane adhesive for a propellant and a preparation method of the room-temperature self-repairing polyurethane adhesive for the propellant, and the molecular structural formula of the room-temperature self-repairing polyurethane adhesive for the propellant is shown in the specification, n is an integer ranging from 25 to 35, and the wavy lines at the two ends represent a plurality of repetitive units; and the molecular weight range is 20000 to 50000 Da. The adhesive can realize self-repairing at room temperature, has high mechanical properties, tensile strength of 14.9 MPa and elongation at break of 1710%, can recover to 90.6% of the original mechanical properties after being repaired again after being cut off and placed at room temperature for 24 hours, and has wide application prospects in the field of propellants.

Description

Technical Field

[0001] This invention relates to a room temperature self-healing polyurethane adhesive for propellants, applicable to the field of propellants. Background Technology

[0002] During the molding and storage stages of solid propellants, microcracks that are difficult to detect may develop inside the propellant grain due to thermal, mechanical, and chemical factors. These microcracks can compromise the integrity of the propellant charge structure, adversely affecting the mechanical properties and service life of the propellant grain. Traditional adhesives lack the ability to repair microcracks, thus damaged propellant grains pose significant safety hazards during use and reduce the quality of mission completion. Therefore, developing novel adhesives to address the problem of microcrack damage repair has become one of the key cutting-edge directions in solid propellant technology development.

[0003] Self-healing adhesives developed based on self-healing materials are currently the main method for repairing microcracks in solid propellant grains. The introduction of self-healing adhesives can effectively improve the safety of propellant use and extend its service life. However, currently reported self-healing materials generally require heating to achieve healing. During heating, solid propellant grains are prone to stimulating the solid filler to generate activated molecules, thereby accelerating thermal decomposition reactions and increasing the risk of combustion and explosion. Therefore, research on room-temperature self-healing adhesives suitable for solid propellant systems is urgently needed. Summary of the Invention

[0004] The purpose of this invention is to provide a room temperature self-healing polyurethane adhesive for solid propellants and its preparation method. This adhesive can achieve self-healing at room temperature and also has high mechanical properties, with a tensile strength of 14.9 MPa and an elongation at break of 1710%. After being cut and repaired, its mechanical properties can be restored to 90.6% of the original mechanical properties after being placed at room temperature for 24 hours.

[0005] The present invention achieves the above objectives through the following technical solutions: A room-temperature self-healing polyurethane adhesive for propellants, the molecular structure of which is shown below: ; The value of n is an integer ranging from 25 to 35, and the wavy lines at both ends represent several repeating units. The molecular weight range is 20,000 to 50,000 Da.

[0006] The preparation method of the room temperature self-healing polyurethane adhesive for propellants according to the present invention includes the following steps: Step 1: After drying polytetrahydrofuran, isophorone diisocyanate and dibutyltin dilaurate are mixed in an organic solvent and added to the dried polytetrahydrofuran. The prepolymer is prepared by reacting under a nitrogen protective atmosphere. Step 2: Mix 4,4'-dithiodiphenylamine and 4,4'-bis(hydroxymethyl)-2,2'-bipyridine in an organic solvent, add the mixture to the prepolymer, and react at 70°C for 3 hours. The reacted system is then cured and molded to obtain the final product.

[0007] Optionally, in step one, the molar ratio of polytetrahydrofuran, isophorone diisocyanate, and dibutyltin dilaurate is 1:2:0.01.

[0008] Optionally, in step two, the molar ratio between the prepolymer, 4,4'-dithiodiphenylamine, and 4,4'-bis(hydroxymethyl)-2,2'-bipyridine is 1:x:y, where 0 <x<1,y=1-x。

[0009] Optionally, in step one, the number-average molecular weight of the polytetrahydrofuran is 2000.

[0010] Optionally, the organic solvent is tetrahydrofuran or N,N-dimethylacetamide.

[0011] Optionally, in step one, the polytetrahydrofuran is dried by vacuum dehydration at 100°C for 2 hours, followed by cooling to 70°C.

[0012] Optionally, in step one, the reaction time in a nitrogen protective atmosphere is 3 hours.

[0013] The room temperature self-healing polyurethane adhesive for propellants described in this invention is used in the preparation of PBX explosive adhesives.

[0014] Advantages of this invention: Microcracks and the resulting decrease in product stability are a major challenge in the field of solid propellants. Existing self-healing adhesives generally require heating to achieve material self-healing, which limits their application in solid propellants. This invention utilizes a combination of disulfide and hydrogen bonds—two dynamic chemical bonds—to achieve room-temperature self-healing while maintaining good mechanical properties, making it suitable for solid propellant formulations. Attached Figure Description

[0015] The accompanying drawings are provided to further illustrate the present disclosure and form part of the specification. They are used together with the following detailed description to explain the present disclosure, but do not constitute a limitation thereof. In the drawings: Figure 1 This is a sample image of the room temperature self-healing polyurethane adhesive obtained in Example 1; Figure 2 The infrared absorption spectrum of the room-temperature self-healing polyurethane adhesive obtained in Example 1 is shown. Figure 3 This is the Raman spectrum of the room-temperature self-healing polyurethane adhesive obtained in Example 1; Figure 4 This is a stress-strain test diagram of the room temperature self-healing polyurethane adhesive obtained in Example 1. Detailed Implementation

[0016] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the invention are still within the scope of protection of the present invention.

[0017] This invention relates to a room-temperature self-healing polyurethane adhesive for propellants and its preparation method, thereby addressing the problem that traditional propellant adhesives lack room-temperature self-healing functionality. The molecular structure of the involved room-temperature self-healing polyurethane adhesive for propellants is as follows: ; The adhesive molecular structure consists of a polytetrahydrofuran molecular chain in the middle (n ranges from 25 to 35, an integer, such as 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, or 35), and two wavy lines representing several repeating units (the wavy lines represent an uncertain number of molecules). The molecular weight ranges from 20,000 to 50,000 Da. The method includes the following steps: Step 1: After drying the polytetrahydrofuran, isophorone diisocyanate and dibutyltin dilaurate are mixed in an organic solvent and added to the dried polytetrahydrofuran. The reaction is carried out under a nitrogen atmosphere to prepare a prepolymer. Step 2: 4,4'-dithiodiphenylamine and 4,4'-bis(hydroxymethyl)-2,2'-bipyridine are mixed in an organic solvent and added to the prepolymer. The reaction is carried out at 70°C for 3 hours. The system after the reaction is cured and molded to obtain the final product. This adhesive can self-heal at room temperature while also possessing high mechanical properties, with a tensile strength of 14.9 MPa and an elongation at break of 1710%. After being left at room temperature for 24 hours, its mechanical properties can recover to 90.6% of the original mechanical properties, making it a promising candidate for application in the field of propellants.

[0018] The specific steps include: Step 1: Dehydrate polytetrahydrofuran under vacuum at 100°C for 2 hours, cool to 70°C, mix isophorone diisocyanate and dibutyltin dilaurate catalyst in an organic solvent, add to the dried polytetrahydrofuran, and react in a nitrogen atmosphere for 3 hours to prepare the prepolymer.

[0019] Step 2: Mix 4,4'-dithiodiphenylamine and 4,4'-bis(hydroxymethyl)-2,2'-bipyridine in an organic solvent, add the mixture to the prepolymer solution, heat to 70°C and keep warm for 3 hours to carry out the reaction. After the reaction, the system is cured and molded to obtain the room temperature self-healing polyurethane adhesive for propellant.

[0020] In step one, the number average molecular weight of polytetrahydrofuran is 2000.

[0021] The organic solvent is either tetrahydrofuran or N,N-dimethylacetamide.

[0022] In step one, the molar ratio between polytetrahydrofuran, isophorone diisocyanate and dibutyltin dilaurate is 1:2:0.01.

[0023] In step two, the molar ratio between the prepolymer, 4,4'-dithiodiphenylamine, and 4,4'-bis(hydroxymethyl)-2,2'-bipyridine is 1:x:y, where 0 <x<1,y=1-x。

[0024] Example 1: This embodiment provides a room-temperature self-healing polyurethane adhesive for propellants, the preparation steps of which include: ; Synthesis route diagram of room temperature self-healing polyurethane adhesive; Step 1: In a 100 mL three-necked flask equipped with a mechanical stirrer, thermometer, and reflux device, 20 g (10 mmol) of polytetrahydrofuran was dehydrated under vacuum at 100 °C for 2 h, and then cooled to 70 °C. 4.4 g (20 mmol) of isophorone diisocyanate and 0.06 g (0.1 mmol) of dibutyltin dilaurate catalyst were mixed in 40 mL of N,N-dimethylacetamide and added to the dried polytetrahydrofuran. The mixture was reacted under a nitrogen atmosphere for 3 h to prepare the prepolymer.

[0025] Step 2: Mix 2g (8mmol) of 4,4'-dithiodiphenylamine and 0.4g (2mmol) of 4,4'-bis(hydroxymethyl)-2,2'-bipyridine in 10mL of N,N-dimethylacetamide, add the mixture to the prepolymer solution, heat to 70℃ and hold for 3 hours to react. Transfer the reacted solution to a polytetrafluoroethylene mold and place it in a vacuum oven at 90℃ for 24 hours for curing and molding, thus obtaining the room temperature self-healing polyurethane adhesive for the propellant. Figure 1 As shown, the cured room temperature self-healing adhesive was made into standard samples for subsequent testing.

[0026] Taking Example 1 as an example, its structure and performance are studied: Combination Figure 2As shown, analysis of the infrared absorption spectrum reveals that at 3340 cm⁻¹... -1 1701cm -1 The two infrared absorption peaks at 1099 cm⁻¹ correspond to the stretching vibrations of NH and C=O in the polyurethane adhesive, respectively, confirming the presence of urethane groups. -1 The infrared absorption peak at that location corresponds to the stretching vibration of the COC bond in the polyurethane adhesive and can be attributed to the presence of polytetrahydrofuran.

[0027] Combination Figure 3 As shown, analysis of the Raman spectrum reveals that at 486 cm⁻¹ -1 The absorption peak at that point proves the presence of disulfide bonds in the polyurethane adhesive.

[0028] Combination Figure 4 As shown, the room temperature self-healing polyurethane adhesive for propellant prepared in this embodiment has a tensile strength of 14.9 MPa and an elongation at break of 1710%.

[0029] The test results of the mechanical properties and self-healing properties of Example 1 are shown in Table 1: Table 1. Test results of mechanical properties and self-healing properties of Example 1

[0030] As shown in Table 1, the room temperature self-healing polyurethane adhesive for propellants prepared in this embodiment has a room temperature self-healing function. After being cut and repaired, its mechanical properties can be restored to 90.6% of the original mechanical properties after being placed at room temperature for 24 hours.

[0031] Example 2: This embodiment provides a room-temperature self-healing polyurethane adhesive for propellants, prepared according to the following method: Step 1: In a 100 mL three-necked flask equipped with a mechanical stirrer, thermometer, and reflux device, 20 g (10 mmol) of polytetrahydrofuran was dehydrated under vacuum at 100 °C for 2 h, and then cooled to 70 °C. 4.4 g (20 mmol) of isophorone diisocyanate and 0.06 g (0.1 mmol) of dibutyltin dilaurate catalyst were mixed in 40 mL of N,N-dimethylacetamide and added to the dried polytetrahydrofuran. The mixture was reacted under a nitrogen atmosphere for 3 h to prepare the prepolymer.

[0032] Step 2: Mix 1.5 g (6 mmol) of 4,4'-dithiodiphenylamine and 0.9 g (4 mmol) of 4,4'-bis(hydroxymethyl)-2,2'-bipyridine in 10 mL of N,N-dimethylacetamide, add the mixture to the prepolymer solution, heat to 70°C and keep warm for 3 h to react. Transfer the reacted solution to a polytetrafluoroethylene mold and place it in a vacuum oven at 90°C for 24 h to cure and shape, thus obtaining the room temperature self-healing polyurethane adhesive for propellants.

[0033] Example 3: This embodiment provides a room-temperature self-healing polyurethane adhesive for propellants, prepared according to the following method: Step 1: In a 100 mL three-necked flask equipped with a mechanical stirrer, thermometer, and reflux device, 20 g (10 mmol) of polytetrahydrofuran was dehydrated under vacuum at 100 °C for 2 h, and then cooled to 70 °C. 4.4 g (20 mmol) of isophorone diisocyanate and 0.06 g (0.1 mmol) of dibutyltin dilaurate catalyst were mixed in 40 mL of N,N-dimethylacetamide and added to the dried polytetrahydrofuran. The mixture was reacted under a nitrogen atmosphere for 3 h to prepare the prepolymer.

[0034] Step 2: Mix 1.0 g (4 mmol) of 4,4'-dithiodiphenylamine and 1.3 g (6 mmol) of 4,4'-bis(hydroxymethyl)-2,2'-bipyridine in 10 mL of N,N-dimethylacetamide, add the mixture to the prepolymer solution, heat to 70°C and keep warm for 3 h to react. Transfer the reacted solution to a polytetrafluoroethylene mold and place it in a vacuum oven at 90°C for 24 h to cure and shape, thus obtaining the room temperature self-healing polyurethane adhesive for propellants.

[0035] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A room-temperature self-healing polyurethane adhesive for propellants, characterized in that, Its molecular structure is shown below: ； The value of n is an integer ranging from 25 to 35, and the wavy lines at both ends represent several repeating units. The molecular weight range is 20,000 to 50,000 Da.

2. The preparation method of the room temperature self-healing polyurethane adhesive for propellants according to claim 1, characterized in that the steps are as follows: include: Step 1: After drying polytetrahydrofuran, isophorone diisocyanate and dibutyltin dilaurate are mixed in an organic solvent and added to the dried polytetrahydrofuran. The prepolymer is prepared by reacting under a nitrogen protective atmosphere. Step 2: Mix 4,4'-dithiodiphenylamine and 4,4'-bis(hydroxymethyl)-2,2'-bipyridine in an organic solvent, add the mixture to the prepolymer, and react at 70°C for 3 hours. The reacted system is then cured and molded to obtain the final product.

3. The method for preparing room temperature self-healing polyurethane adhesive for propellants according to claim 2, characterized in that, In step one, the molar ratio of polytetrahydrofuran, isophorone diisocyanate and dibutyltin dilaurate is 1:2:0.

01.

4. The method for preparing a room-temperature self-healing polyurethane adhesive for propellants according to claim 2 or 3, characterized in that, In step two, the molar ratio of the prepolymer, 4,4'-dithiodiphenylamine, and 4,4'-bis(hydroxymethyl)-2,2'-bipyridine is 1:x:y, wherein... 0 <x<1,y=1-x。 5. The method for preparing a room-temperature self-healing polyurethane adhesive for propellants according to claim 2 or 3, characterized in that, In step one, the number-average molecular weight of polytetrahydrofuran is 2000.

6. The method for preparing a room-temperature self-healing polyurethane adhesive for propellants according to claim 2 or 3, characterized in that, The organic solvent is tetrahydrofuran or N,N-dimethylacetamide.

7. The method for preparing a room-temperature self-healing polyurethane adhesive for propellants according to claim 2 or 3, characterized in that, In step one, the polytetrahydrofuran is dried by vacuum dehydration at 100°C for 2 hours, followed by cooling to 70°C.

8. The method for preparing a room-temperature self-healing polyurethane adhesive for propellants according to claim 2 or 3, characterized in that, In step one, the reaction time in a nitrogen protective atmosphere is 3 hours.

9. The application of the room temperature self-healing polyurethane adhesive for propellants as described in claim 1 in the preparation of PBX explosive adhesives.

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