A flexible polyurethane elastomer resistant to ionizing radiation and a method of making and using the same

Abstract

The application provides a preparation method of a flexible polyurethane elastomer resistant to ionizing radiation, comprising the following steps: S1. dissolving an isocyanate-terminated polyurethane prepolymer in an organic solvent to obtain solution A; dissolving benzophenone diamine or diol as a chain extender in an organic solvent to obtain solution B; S2. mixing solution A and solution B obtained in step S1, stirring at a certain temperature for a period of time, and removing bubbles in the reaction solution system; S3. pouring the reaction solution after the bubbles are removed in step S2 into a forming mold, removing the solvent under certain conditions to complete curing, and obtaining the polyurethane elastomer, which exhibits 3 times the ionizing radiation resistance of a conventional commercial polyurethane under high-dose gamma ray radiation, has good flexibility, and overcomes the shortcoming that the ionizing radiation resistance modification of a conventional polymer will damage the flexibility of the material.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and more specifically, to a flexible polyurethane elastomer resistant to ionizing radiation, its preparation method, and its applications. Background Technology

[0002] Polymer materials are increasingly used in nuclear energy and spacecraft manufacturing. The high levels of high-energy radiation (such as gamma rays, X-rays, and neutrons) in these environments accelerate the aging of polymer materials. Under high-energy ionizing radiation, polymer chemical bonds break, resulting in the generation of free radicals. These free radicals further damage the material, accelerating aging and severely reducing its reliability and lifespan. Polymers with a large number of aromatic ring structures in their main chain typically exhibit good resistance to ionizing radiation, such as polystyrene, polyetheretherketone, and polyimide. However, these materials generally have poor flexibility, making them unsuitable for applications requiring high flexibility. Polyurethane elastomers, due to their excellent comprehensive properties, are widely used in nuclear energy, space applications, and radiation medicine. However, long-term exposure to radiation environments leads to significant degradation and performance deterioration. Therefore, improving the ionizing radiation resistance of polyurethane elastomers is of great importance.

[0003] In existing technologies, adding radiation stabilizers to materials through blending is the most common and widely studied modification method. This method can improve the ionizing radiation resistance of materials to a certain extent, but it requires secondary processing, and the poor dispersibility of the blend can significantly affect the mechanical properties of the material. Improving the intrinsic ionizing radiation resistance of polymers can avoid the drawbacks of blending modification. Currently, the preparation of intrinsically radiation-resistant polymers mainly involves introducing aromatic ring structures into the chain structure. Aromatic structures have good radiation stability and possess large conjugated volumes and a large number of π electrons, allowing them to dissipate some of the radiation energy into light and heat energy through the movement of π electrons after receiving radiation, thus avoiding damage to the material. However, introducing a large number of rigid structures, such as benzene, acenaphthene, and anthracene, into the polymer chain will significantly increase the rigidity of the molecular chain, which is not suitable for the ionizing radiation resistance modification of flexible materials. Therefore, to improve the ionizing radiation resistance of polyurethane elastomers while maintaining good flexibility, a more rational design is required. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing a flexible polyurethane elastomer resistant to ionizing radiation. This method can significantly improve the radiation resistance of polyurethane while maintaining its flexibility, so that the material exhibits three times the ionizing radiation resistance of traditional commercial polyurethane under high-dose gamma ray radiation.

[0005] The embodiments of the present invention are achieved through the following technical solutions:

[0006] A method for preparing a flexible polyurethane elastomer resistant to ionizing radiation includes the following steps:

[0007] S1. Dissolve the isocyanate-terminated polyurethane prepolymer in an organic solvent to obtain solution A; dissolve benzophenone diamine or diol as a chain extender in an organic solvent to obtain solution B;

[0008] S2. Mix solution A and solution B obtained in step S1, stir and react at a certain temperature for a period of time, and then remove the air bubbles in the reaction solution system;

[0009] S3. After the reaction solution with bubbles removed in step S2 is poured into the molding mold, the solvent is removed under certain conditions to complete the curing, thus obtaining the polyurethane elastomer.

[0010] A flexible polyurethane elastomer resistant to ionizing radiation is prepared by the above-described method.

[0011] Application of a flexible polyurethane elastomer resistant to ionizing radiation, or a polyurethane elastomer prepared by the above method, in coatings, potting materials, or adhesives.

[0012] The technical solutions of the embodiments of the present invention have at least the following advantages and beneficial effects:

[0013] 1. This invention introduces the benzophenone structure into the hard segment chain of polyurethane, and at the same time makes the entire hard segment chain form a continuous π electron channel, realizing the characteristics of polyurethane elastomer that combine radiation resistance and flexibility. The resulting polyurethane material not only has good flexibility, but also exhibits at least 3 times the ionizing radiation resistance of traditional commercial polyurethane under high-dose gamma ray radiation.

[0014] 2. The flexible polyurethane of this invention, which is resistant to ionizing radiation, has excellent radiation resistance, good flexibility, and a wide range of applications. It can be used as an elastomer, coating material, potting material, or adhesive in various ionizing radiation environments. In particular, it is suitable for applications where both material flexibility and radiation resistance are required. It has advantages such as good flexibility and high reliability, and has excellent application prospects. Attached Figure Description

[0015] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 The infrared reflectance spectrum of the polyurethane prepared in Example 1 of this invention;

[0017] Figure 2This is a comparison of the flexibility of the polyurethane prepared in Example 1 and Comparative Example 1.

[0018] Figure 3 The changes in the hydrogen NMR spectra of the polyurethanes prepared in Example 1 and Comparative Example 1 before and after gamma irradiation.

[0019] Figure 4 The changes in infrared spectra of the polyurethanes prepared in Example 1 and Comparative Example 1 before and after gamma irradiation.

[0020] Figure 5 The stress-strain curves of polyurethane prepared in Example 1 and Comparative Example 1 under different gamma ray irradiation doses are shown below. Among them: (a) stress-strain curves of polyurethane prepared in Comparative Example 1 under different radiation doses; (b) stress-strain curves of polyurethane prepared in Example 1 under different radiation doses; (c) comparison of strength changes of polyurethane prepared in Example 1 and Comparative Example 1.

[0021] Figure 6 Stress-strain curves of polyurethanes prepared in Examples 2-4 under different gamma irradiation doses; wherein: (a) stress-strain curve of material in Example 2; (b) stress-strain curve of material in Example 3; (c) stress-strain curve of material in Example 4;

[0022] Figure 7 The changes in the paramagnetic spectrum of the polyurethanes prepared in Example 1 and Comparative Example 1 after gamma irradiation are shown.

[0023] Figure 8 The stress-strain curves of the polyurethane prepared in Comparative Example 2 under different gamma ray irradiation doses are shown. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0025] The following is a detailed description of an ionizing radiation-resistant flexible polyurethane elastomer, its preparation method, and its application, provided by embodiments of the present invention.

[0026] A flexible polyurethane elastomer resistant to ionizing radiation, comprising the following steps:

[0027] S1. Dissolve the isocyanate-terminated polyurethane prepolymer in an organic solvent, wherein the mass ratio of the isocyanate-terminated polyurethane prepolymer to the organic solvent is 1:1-3, to obtain solution A; calculate the amount of chain extender containing benzophenone according to the ratio of isocyanate to amino or hydroxyl groups of 1:1-2, and dissolve the chain extender in an organic solvent to obtain solution B.

[0028] S2. Mix solution A and solution B obtained in step S1, stir and react at 20-80℃ for 0.5-4h, and then remove the air bubbles in the reaction solution system by vacuuming.

[0029] S3. After the reaction solution with bubbles removed in step S2 is poured into the molding mold, it is placed in a forced-air drying oven and cured at 30-100℃ for 12-48 hours to remove the solvent and finally obtain a polyurethane elastomer that combines resistance to ionizing radiation and flexibility.

[0030] Further, in S1, the chain extender containing the benzophenone structure is a hydroxyl or amino group directly linked to the benzophenone molecule, and the resulting polyurethane material contains a benzophenone structure in its hard segment chain, with a continuous π-electron pathway in the hard segment chain. Specifically, the chain extender is any one or a mixture of 4,4'-diaminobenzophenone, 3,3'-diaminobenzophenone, 3,4-diaminobenzophenone, 3,4'-diaminobenzophenone, 2,4'-diaminobenzophenone, 4,4'-dihydroxybenzophenone, and 3,3'-dihydroxybenzophenone. Taking 4,4'-diaminobenzophenone chain-extended toluene-2,4-diisocyanate type polyurethane as an example, the resulting hard segment chain structure is as follows:

[0031]

[0032] This invention introduces the benzophenone structure into the hard segment chain of polyurethane, while simultaneously creating a continuous π-electron channel throughout the hard segment chain. This achieves a balance between radiation resistance and flexibility in the polyurethane elastomer. The resulting polyurethane material not only exhibits excellent flexibility but also demonstrates at least three times the ionizing radiation resistance of conventional commercial polyurethane under high-dose gamma ray radiation. Specifically: Regarding flexibility, the carbonyl structure of benzophenone can form hydrogen bonds with the amine groups in the polyurethane hard segment chain, thereby disrupting the regular arrangement of the hard segment chain and interfering with the large-area growth of the hard segment phase, thus increasing the flexibility of the polyurethane. Regarding radiation resistance, it possesses a large conjugated structure similar to other aromatic derivatives, enabling it to dissipate radiation energy. The continuous π-electron channel formed by the hard segment chain further enhances the material's dissipation of radiation energy, buffering the damage caused by high-energy rays. This significantly weakens the destructive effect of ionizing radiation on polyurethane molecules, improving the reliability of the polyurethane elastomer in ionizing radiation environments, extending the service life of the material, and overcoming the drawback that modifying polymers for ionizing radiation resistance can compromise material flexibility. The flexible polyurethane of this invention exhibits excellent radiation resistance, good flexibility, and a wide range of applications. It can be used as an elastomer, coating material, potting material, or adhesive in various ionizing radiation environments. It is especially suitable for applications where both material flexibility and radiation resistance are required. It has advantages such as excellent flexibility and high reliability, and its application prospects are excellent.

[0033] Furthermore, in S1, the organic solvent is one or a mixture of acetone, butanone, tetrahydrofuran, N,N-dimethylformamide, or dimethyl sulfoxide.

[0034] Further, in S1, the preparation method of the isocyanate-terminated polyurethane prepolymer is as follows: the polyol is stirred at 90-120℃ and under vacuum to remove water for 0.5-2h, then cooled to 50-80℃, and then diisocyanate is added and stirred for 0.5-3h to obtain the isocyanate-terminated polyurethane prepolymer, wherein the mass ratio of polyol to diisocyanate is 10-55:1-10.

[0035] Further, the polyol is any one or a mixture of polyether polyol, polyolefin polyol or polyester polyol; wherein the number average molecular weight of the polyether polyol or polyester polyol is 1000-2500.

[0036] Further, the diisocyanate is any one or a mixture of toluene-2,4-diisocyanate, hexamethylene diisocyanate, terephthalic diisocyanate, diphenylmethane-2,4'-diisocyanate or isophorone diisocyanate.

[0037] A flexible polyurethane elastomer resistant to ionizing radiation is prepared by the above-described method.

[0038] Application of a flexible polyurethane elastomer resistant to ionizing radiation, or a polyurethane elastomer prepared by the above method, in coatings, potting materials, or adhesives.

[0039] Example 1

[0040] The method for preparing the ionizing radiation-resistant flexible polyurethane elastomer in this embodiment includes the following steps:

[0041] (1) Synthesis of prepolymer: 10g of polypropylene glycol (molecular weight 1200) was placed in a three-necked flask and stirred under vacuum at 105℃ for 2h. After the temperature dropped to 40℃, 3.2g of toluene diisocyanate (TDI) was added and the reaction was continued at 80℃ for 2h to obtain polyurethane prepolymer with terminal isocyanate (TDI-PPG-TDI).

[0042] (2) Chain extension reaction: 10g of TDI-PPG-TDI was dissolved in 20g of butanone to obtain solution A; 1.3g of 4,4'-diaminobenzophenone was dissolved in 2.6ml of dimethylformamide to obtain solution B; solution A and solution B were mixed and stirred at 40℃ for 2h, and then further reacted at 60℃.

[0043] (3) Material curing: The air bubbles in the reaction solution system are removed by vacuuming. Then the reaction solution is poured into the molding mold and placed in a forced-air drying oven. The solvent is removed and the curing is completed at 80°C for 24 hours. Finally, a polyurethane elastomer (BP-PU) that combines resistance to ionizing radiation and flexibility is obtained.

[0044] Example 2

[0045] The method for preparing the ionizing radiation-resistant flexible polyurethane elastomer in this embodiment includes the following steps:

[0046] (1) Synthesis of prepolymer: 10g of polypropylene glycol (molecular weight 1200) was placed in a three-necked flask and stirred under vacuum at 105℃ for 2h. After the temperature dropped to 40℃, 3.2g of toluene diisocyanate (TDI) was added and the reaction was continued at 80℃ for 2h to obtain polyurethane prepolymer with terminal isocyanate (TDI-PPG-TDI).

[0047] (2) Chain extension reaction: 10g of TDI-PPG-TDI was dissolved in 20g of butanone to obtain solution A; 1.3g of 3,3'-diaminobenzophenone was dissolved in 3ml of dimethylformamide to obtain solution B; solution A and solution B were mixed and stirred at 40℃ for 2h, and then further reacted at 60℃.

[0048] (3) Material curing: The air bubbles in the reaction solution system are removed by vacuuming. Then the reaction solution is poured into the molding mold and placed in a forced-air drying oven. The solvent is removed and the curing is completed at 80°C for 24 hours. Finally, a polyurethane elastomer (iBP-PU) that combines resistance to ionizing radiation and flexibility is obtained.

[0049] Example 3

[0050] The method for preparing the ionizing radiation-resistant flexible polyurethane elastomer in this embodiment includes the following steps:

[0051] (1) Synthesis of prepolymer: 10g of polypropylene glycol (molecular weight 1200) was placed in a three-necked flask and stirred under vacuum at 105℃ for 2h. After the temperature dropped to 40℃, 3.2g of toluene diisocyanate (TDI) was added and the reaction was continued at 80℃ for 2h to obtain polyurethane prepolymer with terminal isocyanate (TDI-PPG-TDI).

[0052] (2) Chain extension reaction: 10g of TDI-PPG-TDI was dissolved in 12g of butanone to obtain solution A; 1.3g of 3,4-diaminobenzophenone was dissolved in 5ml of dimethylformamide to obtain solution B; solution A and solution B were mixed and stirred at 40℃ for 1h, then stirred at 60℃ for 2h, and then further reacted at 80℃.

[0053] (3) Material curing: The air bubbles in the reaction solution system are removed by vacuuming, and then the reaction solution is poured into the molding mold and placed in a forced-air drying oven. The solvent is removed and the curing is completed at 80°C for 24 hours, finally obtaining a polyurethane elastomer that combines resistance to ionizing radiation and flexibility.

[0054] Example 4

[0055] The method for preparing the ionizing radiation-resistant flexible polyurethane elastomer in this embodiment includes the following steps:

[0056] (1) Synthesis of prepolymer: 10g of polypropylene glycol (molecular weight 1200) was placed in a three-necked flask and stirred under vacuum at 105℃ for 2h. After the temperature dropped to 40℃, 3.2g of toluene diisocyanate (TDI) was added and the reaction was continued at 80℃ for 2h to obtain polyurethane prepolymer with terminal isocyanate (TDI-PPG-TDI).

[0057] (2) Chain extension reaction: 10g of TDI-PPG-TDI was dissolved in 15g of butanone to obtain solution A; 1.3g of 4,4'-dihydroxybenzophenone was dissolved in 7ml of butanone to obtain solution B; solution A and solution B were mixed and stirred at 60℃ for 2h, and then further reacted at 80℃.

[0058] (3) Material curing: The air bubbles in the reaction solution system are removed by vacuuming. Then the reaction solution is poured into the molding mold and placed in a forced-air drying oven. The solvent is removed and the curing is completed at 80°C for 24 hours. Finally, a polyurethane elastomer (eBP-PU) that combines resistance to ionizing radiation and flexibility is obtained.

[0059] Comparative Example 1

[0060] The preparation method of this comparative example of a flexible polyurethane elastomer resistant to ionizing radiation includes the following steps:

[0061] (1) Synthesis of prepolymer: 10g of polypropylene glycol (molecular weight 1200) was placed in a three-necked flask and stirred under vacuum at 105℃ for 2h. After the temperature dropped to 40℃, 3.2g of toluene diisocyanate (TDI) was added and the reaction was continued at 80℃ for 2h to obtain polyurethane prepolymer with terminal isocyanate (TDI-PPG-TDI).

[0062] (2) Chain extension reaction: 10g of TDI-PPG-TDI was dissolved in 15g of butanone to obtain solution A; 1.6g of 4,4'-methylenedi(2-chloroaniline) was dissolved in 5ml of butanone to obtain solution B; solution A and solution B were mixed and stirred at room temperature for 2h, and then further reacted at 60℃.

[0063] (3) Material curing: The air bubbles in the reaction solution system are removed by vacuuming. Then the reaction solution is poured into the molding mold and placed in a forced-air drying oven. The solvent is removed and the curing is completed at 80°C for 24 hours, and finally polyurethane elastomer (M-PU) is obtained.

[0064] Comparative Example 2

[0065] The preparation method of this comparative example of a flexible polyurethane elastomer resistant to ionizing radiation includes the following steps:

[0066] (1) Synthesis of prepolymer: 10g of polypropylene glycol (molecular weight 1200) was placed in a three-necked flask and stirred under vacuum at 105℃ for 2h. After the temperature dropped to 40℃, 3.2g of toluene diisocyanate (TDI) was added and the reaction was continued at 80℃ for 2h to obtain polyurethane prepolymer with terminal isocyanate (TDI-PPG-TDI).

[0067] (2) Chain extension reaction: 10g of TDI-PPG-TDI was dissolved in 15g of butanone to obtain solution A; 1.84g of 4,4'-bis(2-hydroxyethoxy)benzophenone was dissolved in 5ml of butanone to obtain solution B; solution A and solution B were mixed and stirred at room temperature for 2h, and then further reacted at 60℃.

[0068] (3) Material curing: Air bubbles in the reaction solution system were removed by vacuuming. The reaction solution was then poured into a molding mold and placed in a forced-air oven at 80°C for 24 hours to remove the solvent and complete curing, finally yielding polyurethane. It should be noted that, because the 4,4'-bis(2-hydroxyethoxy)benzophenone chain extender contains an unsaturated ethylene glycol chain between the benzophenone and isocyanate structures, the resulting polyurethane, although containing a benzophenone structure, was used as a control sample due to the absence of a continuous π-electron pathway in the hard segment chains.

[0069] Experimental Example 1

[0070] I. Fourier Transform Infrared Characterization

[0071] 1. Test Methods

[0072] The BP-PU prepared in Example 1 and the M-PU material prepared in Comparative Example 1 were subjected to Fourier transform infrared spectroscopy. Measurements were performed using a Nicolet IS50 infrared spectrometer manufactured by Thermo Scientific, USA, with an aperture of 4 cm⁻¹. -1 The resolution was scanned 16 times.

[0073] 2. Test Results

[0074] The peak positions of each functional group in the infrared spectrum are shown in Table 1. The infrared spectral detection results of the ionizing radiation resistant flexible polyurethane BP-PU prepared in Example 1 are shown in Table 1. Figure 1 As shown, the infrared spectral detection results of the ionizing radiation-resistant flexible polyurethane prepared in Example 1 and the polyurethane prepared in Comparative Example 1 before and after irradiation with 300 KGy gamma rays are as follows: Figure 4 As shown.

[0075] Table 1. Peak positions of various functional groups in infrared spectra.

[0076]

[0077]

[0078] in, Figure 1 The infrared spectra of BP-PU prepared in Example 1 and M-PU prepared in Comparative Example 1 are shown. Figure 1 It can be seen that the infrared spectrum shows the sample is within the range of 2850-2920 cm⁻¹. -1 There are antisymmetric and symmetric stretching vibration absorption peaks of -CH2 at 1110 cm⁻¹. -1 The presence of a tensile vibration peak of COC at this location indicates the incorporation of polyoxypropylene components into the sample. The NH bending vibration absorption peak of the sample appears at 1540 cm⁻¹. -1 At this point, the C=O absorption peak appears at 1730-1660 cm⁻¹. -1This indicates the presence of urethane or urea bonds in the structure. (950-790cm) -1 The region represents the out-of-plane vibrational band of the benzene ring, contributed by the aromatic ring structure in the material. 2254 cm⁻¹ -1 The disappearance of the N=C=O tensile vibration peak at the point indicates that the polyurethane prepolymer and chain extender have undergone a complete reaction. These results confirm the successful synthesis of M-PU and BP-PU materials.

[0079] Figure 4 The infrared spectra of BP-PU prepared in Example 1 and M-PU prepared in Comparative Example 1 are shown before and after irradiation with 300 kGy gamma rays. Figure 4 It can be seen that, comparing the M-PU prepared in Comparative Example 1 before and after irradiation, the carbonyl infrared absorption peak of M-PU significantly increased, while the infrared absorption peak of the C-H bond on the aromatic ring decreased, and the infrared absorption peak of the aryl ether bond appeared to increase. Comparing the BP-PU prepared in Example 1 before and after irradiation, the carbonyl absorption peak and the C-H bond absorption peak of the aromatic ring showed almost no change in the infrared curves before and after irradiation, exhibiting excellent resistance to ionizing radiation.

[0080] II. Characterization by 1H NMR Spectroscopy

[0081] 1. Test Methods

[0082] The BP-PU prepared in Example 1 and the M-PU prepared in Comparative Example 1 were dissolved in deuterated DMSO solvent at a concentration of 10 mg / ml and analyzed by 1H NMR spectroscopy. A Bruker NMR spectrometer (Germany) was used for the measurements at a frequency of 400 MHz.

[0083] 2. Test Results

[0084] The 1H NMR spectra of the ionizing radiation-resistant flexible polyurethane prepared in Example 1 and the polyurethane prepared in Comparative Example 1 before and after irradiation with 300KGy gamma rays are as follows: Figure 3 As shown.

[0085] Figure 3 The figures show the 1H NMR spectra of the BP-PU prepared in Example 1 and the M-PU prepared in Comparative Example 1 before and after irradiation with 300KGy gamma rays. Figure 3 It can be seen that the absorption peaks of aromatic ring hydrogen and amide hydrogen in both groups of materials changed, but the changes in both peak intensity and peak position were lower in the BP-PU group. The results of 1H NMR spectroscopy indicate that the BP-PU material exhibits low levels of chemical bond breaking and new functional group formation under irradiation, demonstrating excellent resistance to ionizing radiation.

[0086] III. Characterization of Mechanical Properties

[0087] 1. Test Methods

[0088] The radiation-resistant flexible polyurethane elastomers prepared in Examples 1-4 and the polyurethane elastomers prepared in Comparative Example 1 were subjected to gamma irradiation at 0 KGy, 100 KGy, 200 KGy, and 300 KGy, respectively, and tensile tests were performed on the materials before and after irradiation.

[0089] Tensile testing: Tensile tests were conducted using an Instron 5567 tensile testing machine manufactured by Instron Corporation, USA, with a 1kN sensor. The experiment was performed at room temperature. The specimens were cut into dumbbell shapes, measuring 35mm × 2mm × 0.6mm. All samples were tested at a strain rate of 500mm / min. Tensile strength and ultimate elongation at break were obtained from the stress-strain curves. Samples treated with different irradiation doses were tested within the same time period.

[0090] 2. Test Results

[0091] Comparison of the mechanical properties of radiation-resistant flexible polyurethane BP-PU prepared in Example 1 and polyurethane M-PU prepared in Comparative Example 1. Figure 2 As shown.

[0092] The mechanical properties of BP-PU prepared in Example 1 and M-PU prepared in Comparative Example 1 under gamma irradiation doses of 0-300 kGy are as follows: Figure 5 As shown; the changes in mechanical properties of the radiation-resistant flexible polyurethane elastomers prepared in Examples 2-4 are as follows. Figure 6 As shown.

[0093] Depend on Figure 2 It can be seen that BP-PU has a smaller Young's modulus and a larger elongation at break compared to M-PU, exhibiting better flexibility. This indicates that polyurethane prepared with a benzophenone-structured chain extender has better flexibility than commercially available chain extenders.

[0094] Figure 5 The mechanical properties of BP-PU and M-PU under different ionizing radiation doses were compared. The results showed that the tensile strength and elongation at break of M-PU material in the control group decreased significantly under ionizing radiation, while the tensile strength and elongation at break of BP-PU material were less affected by ionizing radiation. The decrease in elongation at break of BP-PU after 300 kGy irradiation was comparable to that of M-PU after 100 kGy irradiation, demonstrating radiation resistance nearly three times that of commercial polyurethane. Figure 6 The mechanical properties of other polyurethane elastomers containing benzophenone structures in Examples 2-4 were shown to change under ionizing radiation. After irradiation of 100 KGy, the strength of each group of materials was retained by more than 80%, showing excellent radiation resistance similar to BP-PU. Figure 8The mechanical properties of the polyurethane prepared in Comparative Example 2, which contains a benzophenone structure but whose hard segment chain is not a continuous π electron pathway, are shown to change under ionizing radiation. Its strength drops to 74% after 100 KGy irradiation, indicating that the radiation resistance of this group of polyurethanes is not as good as that of Examples 1-4.

[0095] The experimental results above show that the design of benzophenone structure combined with the continuous π-electron pathway of hard segment chain can significantly improve the radiation resistance of polyurethane while maintaining good flexibility.

[0096] IV. Paramagnetic Resonance Characterization

[0097] 1. Test Methods

[0098] The BP-PU material prepared in Example 1 and the M-PU material prepared in Comparative Example 1 were subjected to 90 KGy gamma irradiation treatment, and the irradiated materials were subjected to paramagnetic resonance testing.

[0099] Paramagnetic Resonance Testing: Paramagnetic resonance testing was conducted using a paramagnetic resonance spectrometer manufactured by Bruker GmbH, Germany. The test was performed at 30 dB and room temperature. The material, after being treated with ionizing radiation, was transferred under light-proof and low-temperature conditions. During the test, 40 mg of material was cut into small pieces and placed in a quartz tube for paramagnetic testing.

[0100] 2. Test Results

[0101] The paramagnetic resonance spectra of the BP-PU material prepared in Example 1 and the M-PU material prepared in Comparative Example 1 after irradiation are as follows: Figure 7 As shown.

[0102] Figure 7The free radical content in BP-PU and M-PU materials after ionizing irradiation was compared. Higher free radical content in the material resulted in a larger peak area in its paramagnetic resonance spectrum. Peak area comparisons showed that the free radical content in the M-PU group was significantly higher than that in the BP-PU group. This indicates that the BP-PU material prepared in Example 1, due to its benzophenone content and hard-segment chain structure with continuous π-electron pathways, can more efficiently dissipate radiation energy, reducing a series of free radical reactions caused by ionizing radiation in the polyurethane. With prolonged exposure, the free radical content in the M-PU group decreased rapidly, due to its higher free radical activity and faster bimolecular termination reaction. The BP-PU group showed a slower decrease in free radical content because benzophenone reacted with the active free radicals generated by radiation to produce more inert benzyl alcohol free radicals, resulting in a lower bimolecular termination rate. These results indicate that, under ionizing radiation, polyurethane molecules with a benzophenone structure and a continuous π-electron pathway in the hard segment chain can significantly improve the ionizing radiation resistance of the material by dissipating radiation energy to reduce the initiation of free radicals and by capturing already generated free radicals.

[0103] In summary, the polyurethane prepared by this invention contains a benzophenone structure while the hard segment chain forms a continuous π-electron pathway, thus achieving a balance between radiation resistance and flexibility in the polyurethane elastomer.

[0104] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for improving the resistance of flexible polyurethane elastomers to ionizing radiation, characterized in that, Includes the following steps: S1. Dissolve the isocyanate-terminated polyurethane prepolymer in an organic solvent to obtain solution A; dissolve benzophenone diamine as a chain extender in an organic solvent to obtain solution B; The isocyanate in the terminal isocyanate polyurethane prepolymer is toluene-2,4-diisocyanate; The chain extender consists of an amino group directly linked to a benzophenone molecule, resulting in a polyurethane material with a hard segment chain containing a benzophenone structure and exhibiting a continuous π-electron pathway. The structural formula of the resulting hard segment chain is as follows: ； S2. Mix solution A and solution B obtained in step S1, stir and react at a certain temperature for a period of time, and then remove the air bubbles in the reaction solution system; S3. After the reaction solution with bubbles removed in step S2 is poured into the molding mold, the solvent is removed under certain conditions to complete the curing, thus obtaining the polyurethane elastomer.

2. The method for improving the resistance of flexible polyurethane elastomers to ionizing radiation according to claim 1, characterized in that, In S1, the mass ratio of the isocyanate-terminated polyurethane prepolymer to the organic solvent is 1:1-3.

3. The method for improving the resistance of flexible polyurethane elastomers to ionizing radiation according to claim 1, characterized in that, In S1, the chain extender is added in a molar ratio of 1:1-2 between the isocyanate in the terminal isocyanate polyurethane prepolymer and the amino group in the chain extender.

4. The method for improving the resistance of flexible polyurethane elastomers to ionizing radiation according to claim 1, characterized in that, In S1, the organic solvent is one or a mixture of acetone, butanone, tetrahydrofuran, N,N-dimethylformamide, or dimethyl sulfoxide.

5. The method for improving the resistance of flexible polyurethane elastomers to ionizing radiation according to claim 1, characterized in that, In S1, the preparation method of the polyurethane prepolymer with terminal isocyanate is as follows: after stirring the polyol under certain conditions to remove water for a period of time, the temperature is lowered, and then diisocyanate is added. After stirring and reacting for a period of time, the polyurethane prepolymer with terminal isocyanate is obtained.

6. The method for improving the resistance of flexible polyurethane elastomers to ionizing radiation according to claim 5, characterized in that, The mass ratio of the polyol to the diisocyanate is 10-55:1-10.

7. The method for improving the resistance of flexible polyurethane elastomers to ionizing radiation according to claim 1, characterized in that, In S2, the reaction is carried out by stirring at 20-80℃ for 0.5-4 hours; in S3, the curing process is carried out by drying at 30-100℃ for 12-48 hours to remove the solvent and complete the curing.

8. The method for improving the resistance of flexible polyurethane elastomers to ionizing radiation according to claim 1, characterized in that, The application of the polyurethane elastomer in coatings, potting materials or adhesives.

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