Preparation and application of a gamma ray radiation resistant hetero-element modified polyimide resin coating

Abstract

The application discloses a preparation and application of a gamma-ray radiation resistant hetero-element modified polyimide resin coating and belongs to surface protection in a nuclear radiation environment. The hetero-element modified polyimide resin coating is obtained by in-situ introduction of fluorine or boron element monomers with neutron absorption into a polyimide precursor to form a hetero-element modified polyimide resin, and then through compounding of a lubricating functional filler to obtain a bonding solid protective coating material with excellent nuclear radiation resistance. The hetero-element modified polyimide coating has good comprehensive mechanical properties and lubricating protective properties, and still has excellent comprehensive mechanical properties and lubricating protective properties after irradiation of a large dose of gamma rays (cumulative irradiation dose 1000 kGy), and the modified polyimide material can be used for surface protection of related moving parts in a long-term nuclear radiation environment.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of radiation protection, and particularly relates to preparation and application of a heteroelement-modified polyimide resin resistant to gamma ray radiation. BACKGROUND

[0002] Polyimide materials have good thermal stability, mechanical properties, light weight, flexibility, easy molding and processing, and radiation resistance, and are widely used in extreme working conditions such as aerospace and nuclear energy. However, under long-term, high-dose nuclear radiation environment, polyimide materials will still undergo radiation degradation, resulting in material aging, hardness and brittleness, serious decline in mechanical properties, and reduction in service life, and failure in a short period (J. Nucl. Mater., 1987, 148, 53-60; J. Phys.: Conf. Ser., 2020, 1622, 012026; New Chem Mater, 2023, 51(10): 156-160). Therefore, it is of great scientific significance and engineering value to further improve the mechanical properties and radiation resistance of polyimide by molecular structure design and modification. Chinese patent (CN202111067932.4) discloses a sandwich structure radiation-resistant polyimide and its preparation method and application, which achieves the purpose of improving radiation resistance through multi-layer structure design. Chinese patent (CN201910744025.5) discloses a method for improving the radiation resistance of polyimide composite film by using modified boron nitride; similarly, Chinese patent (CN201910489096.5) discloses a neutron radiation-resistant polyimide coating and its preparation method and application, which mainly reacts cyanoborane triamine and acid anhydride-terminated polyimide oligomers to obtain hyperbranched polyimide, and then obtains it by ball milling and blending with functional slow neutron adsorption compounds and silane coupling agents. It can be seen that the existing technology improves the radiation resistance of the composite material by multi-layer structure design and the introduction of functional fillers, but does not essentially improve the nuclear radiation resistance of the polyimide base resin. SUMMARY

[0003] The present application aims to provide a preparation method of a heteroelement-containing gamma ray radiation-resistant modified polyimide resin, which mainly uses host-guest condensation reaction strategy to introduce fluorine or boron element-containing monomers with neutron absorption effect into polyimide prepolymer in situ from the molecular level, essentially improving the nuclear radiation stability of the polyimide base resin, and obtaining a modified polyimide prepolymer with excellent mechanical properties and good anti-radiation performance. And by compounding different lubricating functional fillers, a radiation-resistant lubricating material with excellent mechanical properties and lubrication protection performance is obtained.

[0004] The preparation method of the gamma-ray radiation-resistant heteroelement-modified polyimide resin coating described in the present invention is based on a host-guest condensation reaction strategy, in which a heteroelement-containing monomer is in situ introduced into a polyimide precursor to obtain a heteroelement-modified polyimide resin with good radiation resistance; and the heteroelement-modified polyimide resin is used as a base resin binder, and a radiation-resistant lubricating coating with excellent comprehensive mechanical properties and lubrication and protective properties is obtained by compounding functional fillers.

[0005] The heteroelement-containing monomer is one or two of 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane, 4-aminoformylphenylboronic acid, and 4-aminophenylboronic acid pinacol ester.

[0006] The polyimide precursor is a mixture of a diamine monomer 4,4-diaminodiphenyl ether and a dianhydride monomer 3,3'4,4'-diphenyl ether tetracarboxylic dianhydride.

[0007] The in-situ introduction process involves dissolving the diamine monomer 4,4-diaminodiphenyl ether and the heteroelement-containing monomer in an organic solvent and stirring to mix them evenly. Subsequently, under nitrogen protection, the dianhydride monomer 3,3'-4,4'-diphenyl ether tetracarboxylic dianhydride is added in batches. The mixture is stirred and reacted at -20-15°C for 20-30 hours. The molar ratio of the diamine monomer to the heteroelement-containing monomer is 2:1-18:1, and the molar ratio of the dianhydride monomer to the diamine monomer is 1:1-1.5:1. The organic solvent is dehydrated N,N-dimethylformamide or N,N-dimethylacetamide.

[0008] The specific preparation process of the radiation-resistant lubricating coating is as follows: using a polyimide resin modified with heteroelement as the base resin binder, a mixture of molybdenum disulfide and lanthanum trifluoride, previously ground two to three times on a conical mill, as the functional filler, and a mixed solvent of N,N-dimethylformamide and N-methylpyrrolidone as the diluent. After high-speed shearing, the radiation-resistant lubricating coating with a solid content of 30% to 40% is obtained. The molar ratio of molybdenum disulfide to lanthanum trifluoride is 3:1 to 5:1, and the volume ratio of N,N-dimethylformamide to N-methylpyrrolidone is 1:2 to 2:1.

[0009] Another object of the present invention is to disclose the application of the gamma-ray radiation-resistant mixed element-containing modified polyimide resin coating in radiation-resistant coatings.

[0010] The specific preparation process of the radiation-resistant coating is as follows: after spraying the coating on the metal substrate using a spray gun, the coating is kept at 130-150°C for 1-2 hours, and then heated and cured at 270-290°C for 1-2 hours.

[0011] The radiation-resistant coating obtained by the present invention was subjected to a gamma-ray irradiation test with a total irradiation dose of 300 kGy and 1000 kGy, respectively. The mechanical properties and tribological properties before and after irradiation were tested, and the surface micromorphology changes of the coating before and after irradiation were observed using a scanning electron microscope.

[0012] The specific test method is as follows:

[0013] Mechanical properties test: tested in accordance with ISO 527:2019;

[0014] Tribological properties: The atmospheric friction and wear properties of the coatings before and after irradiation were tested using a CSM tribometer. The test conditions were a rotation mode with a rotation radius of 0.5 cm, a linear speed of 5 cm / s, a load of 5 N, and a Φ6 mm GCr15 steel ball as the dual ball.

[0015] The test results show that the heteroelement modified polyimide film prepared by the present invention has good resistance to gamma ray radiation ( Figure 1-2 ), after the unmodified polyimide film was irradiated with a dose of 1000kGy, the surface color became darker and the aging phenomenon was serious, while the color of the modified film remained unchanged after irradiation. At the same time, the tensile test showed that the tensile strength and elongation at break of the modified film did not change significantly after γ-ray irradiation; the comparison of the tribological properties under different radiation doses showed that the modified polyimide composite coating not only had a lower friction coefficient and wear rate ( Figure 3-5 ), and γ-ray irradiation has no obvious effect on its tribological properties.

[0016] In summary, the present invention has the following beneficial effects:

[0017] The modified polyimide lubricating composite coating of the present invention utilizes fluorine- or boron-containing polymer monomers introduced azimuthally through chemical polycondensation to form a highly cross-linked macromolecular network structure. This improves the tensile strength and elongation at break of the polyimide material, while reducing the coefficient of friction and wear rate. Furthermore, the fluorine, boron, and phenolic hydroxyl groups in the molecular structure exhibit excellent radiation suppression, effectively blocking external radiation and enhancing the polyimide's resistance to nuclear radiation. This ensures that the modified polyimide composite coating maintains excellent comprehensive mechanical and tribological properties even under long-term nuclear radiation exposure. Furthermore, the modified polyimide lubricating composite coating of the present invention is readily available, simple to prepare, and has a short production cycle, making it suitable for industrial production and large-scale engineering applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The macroscopic surface morphologies of the modified polyimide (BPI15) and pure polyimide film (PI) prepared in Example 1 and Comparative Example 1 before and after irradiation.

[0019] Figure 2 Microstructure morphology of modified polyimide (BPI15) and pure polyimide film (PI) prepared in Example 1 and Comparative Example 1 before and after irradiation.

[0020] Figure 3 Friction coefficient change curve of coating material prepared in Example 1 before and after irradiation.

[0021] Figure 4 Friction coefficient change curve of coating material prepared in Comparative Example 1 before and after irradiation.

[0022] Figure 5 Wear rate change of coating material prepared in Example 1 and Comparative Example 1 under different irradiation doses. DETAILED DESCRIPTION

[0023] The technical solutions of the present application will be further described in detail below in combination with several embodiments and the accompanying drawings, but are not limited to the following embodiments.

[0024] Example 1

[0025] The diamine monomer 4,4-diaminodiphenyl ether (5.41 g, 0.027 mol) and 2,2-bis(3-amino-4-hydroxyphenyl) hexafluoropropane (1.10 g, 0.003 mol) were added to a dehydrated N,N-dimethylformamide solvent, transferred to a three-necked flask, protected by nitrogen, and mechanically stirred uniformly, then the dianhydride monomer 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride (9.31 g, 0.03 mol) was slowly added in batches, and the total molar ratio of dianhydride to diamine monomer was controlled to be 1.01:1. Before the addition of the acid anhydride monomer was completed, the solution was kept in an ice water bath environment, and after the acid anhydride monomer was completely added to the solution, the ice water bath was removed, and the reaction was mechanically stirred at room temperature for 24 h to obtain a light yellow viscous solution. According to the requirements for the size of the test piece in the ISO 527:2019 test standard, the modified polyimide film after curing at 140°C for 1 h and 280°C for 1 h was cut into standard tensile test pieces for subsequent tensile testing.

[0026] Meanwhile, based on the obtained light yellow viscous liquid as the base resin binder, the mixture of molybdenum disulfide and lanthanum trifluoride (molar ratio of molybdenum disulfide to lanthanum trifluoride is 4:1) which was previously ground and dispersed was compounded as the functional filler, and the total mass ratio of the modified resin binder to the functional filler was controlled to be about 3:8. Then, the total solid content of the coating was adjusted to 35% by using a mixed solvent of N,N-dimethylformamide and N-methylpyrrolidone with a volume ratio of 1:1, and a liquid lubricating composite coating was obtained. After the coating was sprayed on the metal substrate by using a spray gun, and then heated and cured at 140°C for 1 h and 280°C for 1 h, a coating material was obtained.

[0027] Example 2

[0028] The diamine monomer 4,4-diaminodiphenyl ether (5.41 g, 0.027 mol) and 4-carbamoylphenylboronic acid (0.49 g, 0.003 mol) were added to the dehydrated N,N-dimethylformamide solvent, transferred to a three-necked flask, and nitrogen was introduced. After mechanical stirring, the dianhydride monomer 3,3'4,4'-diphenyl ether tetracarboxylic dianhydride (9.31 g, 0.03 mol) was slowly added in batches to control the total molar ratio of dianhydride to diamine monomer to be 1.01:1. Before the anhydride monomer is added, ensure that the solution is in an ice-water bath environment. After the anhydride monomer is completely added to the solution, remove the ice-water bath and mechanically stir the reaction at room temperature for 24 hours to obtain a light yellow viscous solution. According to the requirements for test piece size in the ISO 527:2019 test standard, the modified polyimide film after curing at 140°C for 1 hour and at 280°C for 1 hour is cut into standard tensile test pieces for subsequent tensile tests.

[0029] At the same time, the obtained light yellow viscous liquid was used as the base resin binder, and a mixture of molybdenum disulfide and lanthanum trifluoride (the molar ratio of molybdenum disulfide to lanthanum trifluoride was 4:1) that had been ground and dispersed in advance was compounded as a functional filler. The total mass ratio of the modified resin binder to the functional filler was controlled to be approximately 3:8. Then, a mixed solvent of N,N-dimethylformamide and N-methylpyrrolidone with a volume ratio of 1:1 was used to adjust the total solid content of the coating to 35%, thereby obtaining a liquid lubricating composite coating. The coating was sprayed on a metal substrate using a spray gun, and then heated and cured at 140°C for 1 hour and at 280°C for 1 hour to obtain a coating material.

[0030] Example 3

[0031] The diamine monomer 4,4-diaminodiphenyl ether (5.41 g, 0.027 mol) and 4-aminophenylboronic acid pinacol ester (0.66 g, 0.003 mol) were added to the dehydrated N,N-dimethylformamide solvent, transferred to a three-necked flask, and nitrogen was introduced. After mechanical stirring, the dianhydride monomer 3,3'4,4'-diphenyl ether tetracarboxylic dianhydride (9.31 g, 0.03 mol) was slowly added in batches to control the total molar ratio of dianhydride to diamine monomer to be 1.01:1. Before the anhydride monomer is added, ensure that the solution is in an ice-water bath environment. After the anhydride monomer is completely added to the solution, remove the ice-water bath and mechanically stir the reaction at room temperature for 24 hours to obtain a light yellow viscous solution. According to the requirements for test piece size in the ISO 527:2019 test standard, the modified polyimide film after curing at 140°C for 1 hour and at 280°C for 1 hour is cut into standard tensile test pieces for subsequent tensile tests.

[0032] At the same time, the obtained light yellow viscous liquid was used as the base resin binder, and a mixture of molybdenum disulfide and lanthanum trifluoride (the molar ratio of molybdenum disulfide to lanthanum trifluoride was 4:1) that had been ground and dispersed in advance was compounded as a functional filler. The total mass ratio of the modified resin binder to the functional filler was controlled to be approximately 3:8. Then, a mixed solvent of N,N-dimethylformamide and N-methylpyrrolidone with a volume ratio of 1:1 was used to adjust the total solid content of the coating to 35%, thereby obtaining a liquid lubricating composite coating. The coating was sprayed on a metal substrate using a spray gun, and then heated and cured at 140°C for 1 hour and at 280°C for 1 hour to obtain a coating material.

[0033] Example 4

[0034] The diamine monomer 4,4-diaminodiphenyl ether (9.42 g, 0.047 mol) and 4-aminophenylboronic acid pinacol ester (0.66 g, 0.003 mol) were added to the dehydrated N,N-dimethylformamide solvent, transferred to a three-necked flask, and nitrogen was introduced for protection. After mechanical stirring, the dianhydride monomer 3,3'4,4'-diphenyl ether tetracarboxylic dianhydride (15.52 g, 0.05 mol) was slowly added in batches to control the total molar ratio of dianhydride to diamine monomer to be 1.01:1. Before the anhydride monomer is added, ensure that the solution is in an ice-water bath environment. After the anhydride monomer is completely added to the solution, remove the ice-water bath and mechanically stir the reaction at room temperature for 24 hours to obtain a light yellow viscous solution. According to the requirements for test piece size in the ISO 527:2019 test standard, the modified polyimide film after curing at 140°C for 1 hour and at 280°C for 1 hour is cut into standard tensile test pieces for subsequent tensile tests.

[0035] At the same time, the obtained light yellow viscous liquid was used as the base resin binder, and a mixture of molybdenum disulfide and lanthanum trifluoride (the molar ratio of molybdenum disulfide to lanthanum trifluoride was 4:1) that had been ground and dispersed in advance was compounded as a functional filler. The total mass ratio of the modified resin binder to the functional filler was controlled to be approximately 3:8. Then, a mixed solvent of N,N-dimethylformamide and N-methylpyrrolidone with a volume ratio of 1:1 was used to adjust the total solid content of the coating to 35%, thereby obtaining a liquid lubricating composite coating. The coating was sprayed on a metal substrate using a spray gun, and then heated and cured at 140°C for 1 hour and at 280°C for 1 hour to obtain a coating material.

[0036] Comparative Example 1

[0037] The diamine monomer, 4,4-diaminodiphenyl ether (6.01 g, 0.03 mol), was added to a dehydrated N,N-dimethylformamide solvent. The mixture was transferred to a three-necked flask, purged with nitrogen, and mechanically stirred until uniform. The dianhydride monomer, 3,3'-4,4'-diphenylether tetracarboxylic dianhydride (9.31 g, 0.03 mol), was then slowly added in batches, maintaining a total molar ratio of dianhydride to diamine of 1.01:1. Prior to the complete addition of the anhydride monomer, the solution was placed in an ice-water bath. After complete addition of the anhydride monomer, the ice-water bath was removed. The solution was mechanically stirred at room temperature for 24 hours to yield a pale yellow viscous solution. Following curing at 140°C for 1 hour and then at 280°C for 1 hour, the modified polyimide film was cut into standard tensile test pieces according to the test piece size requirements of ISO 527:2019 for subsequent tensile testing.

[0038] At the same time, the obtained light yellow viscous liquid was used as the base resin binder, and a mixture of molybdenum disulfide and lanthanum trifluoride (the molar ratio of molybdenum disulfide to lanthanum trifluoride was 4:1) that had been ground and dispersed in advance was compounded as a functional filler. The total mass ratio of the modified resin binder to the functional filler was controlled to be approximately 3:8. Then, a mixed solvent of N,N-dimethylformamide and N-methylpyrrolidone with a volume ratio of 1:1 was used to adjust the total solid content of the coating to 35%, thereby obtaining a liquid lubricating composite coating. The coating was sprayed on a metal substrate using a spray gun, and then heated and cured at 140°C for 1 hour and at 280°C for 1 hour to obtain a coating material.

[0039] Comparative Example 2

[0040] The diamine monomer, 4,4-diaminodiphenyl ether (10.02 g, 0.05 mol), was added to a dehydrated N,N-dimethylformamide solvent. The mixture was transferred to a three-necked flask, purged with nitrogen, and mechanically stirred until uniform. The dianhydride monomer, 3,3'-4,4'-diphenylether tetracarboxylic dianhydride (15.52 g, 0.05 mol), was then slowly added in batches, maintaining a total molar ratio of dianhydride to diamine of 1.01:1. Prior to the complete addition of the anhydride monomer, the solution was placed in an ice-water bath. After complete addition of the anhydride monomer, the ice-water bath was removed. The solution was mechanically stirred at room temperature for 24 hours to yield a pale yellow viscous solution. Following curing at 140°C for 1 hour and then at 280°C for 1 hour, the modified polyimide film was fabricated into standard tensile test specimens according to the test specimen size requirements of ISO 527:2019 for subsequent tensile testing.

[0041] At the same time, the obtained light yellow viscous liquid was used as the base resin binder, and a mixture of molybdenum disulfide and lanthanum trifluoride (the molar ratio of molybdenum disulfide to lanthanum trifluoride was 4:1) that had been ground and dispersed in advance was compounded as a functional filler. The total mass ratio of the modified resin binder to the functional filler was controlled to be approximately 3:8. Then, a mixed solvent of N,N-dimethylformamide and N-methylpyrrolidone with a volume ratio of 1:1 was used to adjust the total solid content of the coating to 35%, thereby obtaining a liquid lubricating composite coating. The coating was sprayed on a metal substrate using a spray gun, and then heated and cured at 140°C for 1 hour and at 280°C for 1 hour to obtain a coating material.

[0042] The mechanical and tribological properties of the coatings prepared in Examples 1-4 and Comparative Examples 1-2 were compared before and after irradiation. The specific results are as follows:

[0043] Table 1 Mechanical properties of the coating films prepared in Examples 1-4 and Comparative Examples 1-2 without irradiation

[0044]

[0045] It can be seen from Table 1 that the tensile strength and elongation at break of the modified polyimide films prepared in Examples 1 to 4 are significantly higher than those of the polyimide films prepared in Comparative Examples 1 and 2. The introduction of fluorine- or boron-containing heteroelement monomers achieves both reinforcement and toughening, which is mainly due to the bridging effect of multiple active reaction points in the fluorine- or boron-containing monomers, thereby increasing the crosslinking density of the polyimide polymer and improving the overall density of the film after curing.

[0046] Table 2 Mechanical properties of the coating films prepared in Examples 1-4 and Comparative Examples 1-2 after 300 and 1000 kGy γ irradiation

[0047]

[0048] Table 2 shows the changes in tensile strength and elongation at break of the polyimide films prepared in Examples 1-4 and Comparative Examples 1-2 after static γ-ray irradiation at 300 kGy and 1000 kGy, respectively. The modified polyimide films prepared in Examples 1-4 showed an overall increase in tensile strength and a decrease in elongation at break after low-dose γ-ray irradiation. After high-dose irradiation, both tensile strength and elongation at break decreased, but the degree of decrease was not significant. This is primarily due to the excellent absorption and annihilation of radiation energy by fluorine-, boron-, and hydroxyl-containing groups in the modified polyimide films. Furthermore, low-dose γ-ray irradiation disrupts the long organic chains in the polyimide films, leading to secondary crosslinking and polymerization of the resulting small molecular chain free radicals, which hardens the films, increases tensile strength, and decreases elongation at break. In contrast, the polyimide films prepared in Comparative Examples 1 and 2 showed a significant decrease in tensile strength and elongation at break after high-dose γ-ray irradiation. This is primarily due to severe radiation degradation of the polymer chains in the films, with the degradation rate far exceeding the crosslinking rate. This shows that the introduction of heteroelements can significantly improve the radiation resistance of polyimide films under high doses.

[0049] Figure 3-5 The following chart compares the tribological properties of the coating films prepared in Examples 1-4 and Comparative Examples 1-2 after 300 and 1000 kGy γ-ray irradiation. As shown, the friction coefficients of the modified polyimide films prepared in Examples 1-4 remained below 0.15 before and after γ-ray irradiation, exceeding those of polyimide films (0.2-0.25). Their wear rates also remained between 7 and 8, also exceeding those of polyimide films (above 10). This demonstrates that the introduction of heterogeneous elements can improve the tribological properties of polyimide films.

Claims

1. A method for preparing a gamma-ray radiation-resistant heteroelement-modified polyimide resin coating, characterized in that: This method is based on the host-guest condensation reaction strategy, in which heteroelement-containing monomers are in situ introduced into the polyimide precursor to obtain heteroelement-modified polyimide resin with good radiation resistance. A radiation-resistant lubricating coating with excellent comprehensive mechanical properties and lubrication protection properties is obtained by using hetero-element modified polyimide resin as the base resin binder and compounding functional fillers. The heteroelement-containing monomer is one or both of 4-aminoformylphenylboronic acid and 4-aminophenylboronic acid pinacol ester; The in-situ introduction process is as follows: the diamine monomer 4,4-diaminodiphenyl ether and the monomer containing heteroelements are dissolved in an organic solvent and stirred to mix uniformly, and then the dianhydride monomer 3,3'4,4'-diphenyl ether tetracarboxylic dianhydride is added in batches under nitrogen protection, and the mixture is stirred and reacted at -20-15°C for 20-30 hours; The molar ratio of the diamine monomer to the heteroelement-containing monomer is 2:1 to 18:1, and the molar ratio of the dianhydride monomer to the diamine monomer is 1:1 to 1.5:1; The functional filler is a mixture of molybdenum disulfide and lanthanum trifluoride.

2. The method for preparing a gamma-ray radiation-resistant heteroelement-modified polyimide resin coating according to claim 1, wherein: The organic solvent is N,N-dimethylformamide or N,N-dimethylacetamide that has been dehydrated.

3. The method for preparing a gamma-ray radiation-resistant heteroelement-modified polyimide resin coating according to claim 1, wherein: The specific preparation process of the radiation-resistant lubricating coating is as follows: using heteroelement-modified polyimide resin as a base resin binder, a mixture of molybdenum disulfide and lanthanum trifluoride previously ground 2 to 3 times on a conical mill as a functional filler, and a mixed solvent of N,N-dimethylformamide and N-methylpyrrolidone as a diluent, and obtaining a radiation-resistant lubricating coating with a solid content of 30% to 40% after high-speed shearing.

4. The method for preparing a gamma-ray radiation-resistant heteroelement-modified polyimide resin coating according to claim 3, wherein: The molar ratio of molybdenum disulfide to lanthanum trifluoride is 3:1-5:1, and the volume ratio of N,N-dimethylformamide to N-methylpyrrolidone is 1:2-2:

1.

5. Use of the heteroelement-modified polyimide resin coating resistant to gamma-ray radiation prepared by the method of claim 1 in radiation-resistant coating.

6. Use of the heteroelement-modified polyimide resin coating resistant to gamma ray radiation as claimed in claim 5 in an anti-radiation coating, characterized in that: The specific preparation process of the radiation-resistant coating is as follows: after spraying the coating on the metal substrate using a spray gun, the coating is kept at 130-150°C for 1-2 hours, and then heated and cured at 270-290°C for 1-2 hours.

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