A UV-resistant PBOH fiber and its preparation method

Abstract

This invention relates to a UV-resistant PBOH fiber, its preparation method, and its application in aerospace or fireproof and bulletproof materials, solving the problems of PBO fiber's poor UV resistance and low compressive strength. The PBOH fiber consists of stable five-, six-, and eight-membered ring structures formed by hydrogen bonds between PBO macromolecular chains and the macromolecules, both intramolecularly and intermolecularly. These rings are adjacent to heterocyclic rings such as oxazole and imidazole rings, forming a reinforcing macrocyclic structure. This allows the PBOH fiber to maintain the high strength and modulus of PBO fiber while improving its UV resistance and compressive strength. The high-strength, radiation-resistant PBOH fiber retains 81% of its tensile strength after 480 hours of UV aging. The PBOH fiber synthesis method is simple, easy to implement, and represents a highly promising modification method for PBO fibers with significant practical value.

Description

Technical Field

[0001] This invention belongs to the field of polymer material processing technology, specifically relating to the field of high-performance fiber modification, and more specifically to a high-strength radiation-resistant PBOH fiber and its preparation method. Background Technology

[0002] PBO (poly(p-phenylenebenzobisoxazole)) fiber is a high-performance aromatic heterocyclic organic fiber with a tensile strength as high as 5.8 GPa and a modulus of 280 GPa, almost twice that of high-performance Kevlar fiber. Furthermore, under an inert atmosphere, PBO fiber has a thermal decomposition temperature as high as 650℃ and can be used for extended periods at 300℃. With a limiting oxygen index (LOI) of 68, PBO fiber boasts excellent overall performance and is hailed as the "King of Fibers." PBO fiber has broad application prospects in aerospace, fireproofing, and bulletproofing. Its superior performance mainly relies on the rigid conjugated polymer backbone between benzobisoxazole and the benzene ring. This structure generates π-electron delocalization and resonance effects, making the PBO fiber structure extremely stable.

[0003] Despite this, PBO fibers, like most aromatic heterocyclic fibers, suffer from the fatal flaw of being susceptible to ultraviolet (UV) radiation. Under UV irradiation, PBO fibers age rapidly, their mechanical properties decline sharply, and their applications are severely limited. Therefore, research on UV aging resistance modification of PBO fibers has been a hot topic. Currently, UV aging resistance modification of PBO fibers mainly focuses on methods such as in-situ blending / copolymerization and fiber surface coating modification. Improving the UV resistance of PBO fibers through in-situ blending / copolymerization has been a key research focus. For example, CN 101906677 A discloses a method for preparing UV-resistant PBO fibers: passing PBO spinning solution through a coagulation bath containing an anti-aging agent, followed by drying, winding, and heat treatment to obtain high-modulus PBO fibers containing an anti-aging agent. The fibers exhibit long-lasting anti-aging properties, but reproducibility is low. In contrast, fiber surface coating modification is simple and rapid. For example, CN 102277726 A discloses a method for resisting ultraviolet aging of poly(p-phenylene benzobisoxazole) fibers: A mixed solution containing an anti-ultraviolet agent, a coupling agent, an acidic medium, and an accelerator is prepared. Under the assistance of ultrasonic vibration, a uniform anti-ultraviolet aging gel coating of 0.02–0.05 mm is formed on the surface of the PBO fibers, achieving ultraviolet protection for the PBO fibers. This method does not change the internal structure of PBO, but the modification causes irreversible damage to the fiber surface, leading to a decrease in fiber strength. Furthermore, the coating's ultraviolet resistance is not stable enough; over time, substances such as ultraviolet absorbers are gradually lost, and the ultraviolet resistance of the PBO also decreases. In addition, CN202410497552.1 also discloses a method to directly improve the UV resistance of PBO fibers through heat treatment. The study suggests that after short-term treatment at 600-700℃, chromophores C=O and auxochromes NH conjugated with benzene rings are generated in the PBO fiber structure, resulting in a greater red shift in the UV spectrum. The original B band absorption shifts from about 400nm to nearly 500nm. However, this treatment method significantly reduces the initial strength of PBO fibers.

[0004] Meanwhile, compared with aramid fibers, PIPD fibers, graphite fibers, and aryl fibers, PBO fibers also have the weakness of low compressive strength. Analysis suggests that this performance defect is mainly caused by the "inert" structure of PBO fibers. Because the PBO molecular chain lacks polar groups such as hydroxyl and amino groups, PBO molecules cannot form intramolecular and intermolecular hydrogen bonds. The weak inter-fiber forces make PBO fibers prone to buckling and deformation under axial compressive stress, leading to microfiber peeling and failure, thus limiting the application of PBO fibers in advanced structural composite materials. Researchers typically introduce hydroxyl groups into the PBO molecular chain to form hydrogen bonds within the fiber to improve compressive strength. However, this method usually introduces a third monomer, which disrupts the regularity of the PBO fiber, resulting in a decrease in its mechanical properties.

[0005] Therefore, developing PBO fibers with improved UV resistance and compression resistance can effectively expand the application of PBO fibers in the field of advanced structural composite materials. In particular, developing a simple and effective preparation method that simultaneously improves the UV resistance and compression resistance of PBO fibers is a problem that urgently needs to be solved in the field of PBO fiber research. Summary of the Invention

[0006] The present invention aims to provide a high-strength UV-resistant PBOH fiber, and a simple and efficient method for modifying PBO fiber to prepare a high-strength UV-resistant PBOH fiber, which improves the UV resistance and compression resistance of PBO fiber while maintaining its high strength and high modulus.

[0007] The high-strength, UV-resistant PBOH fiber is characterized by having the molecular structure shown in Formula I:

[0008] (Formula I)

[0009] Where: x is 100~140, y is 5~35.

[0010] R1 is R 1-01（ ） R 1-02（ ） R 1-03（ ） R 1-04（ ） R 1-05（ ） R 1-06（ ） R 1-07（ ） One of them.

[0011] R2 is R 2-01（ ） R 2-02（ ） R 2-03（ ） R 2-04（ ） R 2-05（ ） R 2-06（ ） R2-07（ ） R 2-08（ ）， R 2-09（ ）， R 2-10（ ）, R 2-11（ ）， R 2-12（ ）， R 2-13（ ）， R 2-14（ ）， R 2-15（ ）， R 2-16（ ）， R 2-17（ ）， R 2-18（ ） One of them.

[0012] The present invention also claims protection for the use of the UV-resistant PBOH fiber in aerospace vehicles and in fireproof and bulletproof materials.

[0013] The high-strength, radiation-resistant PBOH fiber has a large number of intramolecular and intermolecular hydrogen bonds formed on the oxazole ring, which absorb and shield ultraviolet light.

[0014] The hydrogen bonds are O—H--N, O—H--F, O—H--O, N—H--F, and N—H--O on the imidazole ring and the oxazole ring.

[0015] The hydrogen bonds form relatively stable five-membered, six-membered, and eight-membered ring structures on the imidazole and oxazole rings.

[0016] The high-strength, UV-resistant PBOH fiber is prepared by copolymerization, including the following steps:

[0017] Preparation of PBO oligomer solution: Under argon protection, 4,6-diaminoresorcinol hydrochloride, R2, phosphorus pentoxide, phosphoric acid, and stannous chloride were added to a reaction vessel, controlling the phosphorus pentoxide ratio in the phosphoric acid to be 83.5 wt%. The temperature was gradually increased to 80 °C, and the mixture was stirred at a constant temperature for 2–8 h to remove hydrogen chloride. Phosphorus pentoxide was then added, and the temperature was gradually increased to 100–120 °C. The reaction was carried out for 4–10 h to obtain the PBO oligomer solution.

[0018] Preparation of R1-R2 oligomer solution: Under argon protection, R1 hydrochloride, R2, phosphorus pentoxide, phosphoric acid, and stannous chloride were added to a reaction vessel, and the proportion of phosphorus pentoxide in the phosphoric acid was controlled at 83.5 wt%. The temperature was gradually increased to 80℃ and stirred at a constant temperature for 2-8 h to remove hydrogen chloride. Phosphorus pentoxide was added, and then the temperature was gradually increased to 100-150℃ and reacted for 6-16 h to obtain R1-R2 oligomer solution.

[0019] Copolymerization of PBO with R1-R2 oligomers: Under argon protection, the PBO oligomer solution and the R1-R2 oligomer solution were mixed. Then, under argon protection, the mixture was stirred and heated to 120-150 °C for 6-16 h; then heated to 160-185 °C for 2-18 h to obtain a high-viscosity PBOH copolymer solution.

[0020] Chain extension: The high-viscosity PBOH copolymer solution was added to an argon-protected twin-screw extruder reactor for repolymerization at a temperature of 185-195 °C for 0.1-3 h to obtain a polymer solution of high molecular weight PBOH copolymer.

[0021] Spinning: The polymer solution of high molecular weight PBOH copolymer is spun, washed, and dried using a dry-jet wet spinning method to obtain PBOH nascent fibers.

[0022] Heat treatment: PBOH nascent fibers are heat-treated under certain temperature, tension and draw ratio, and the heat treatment time is controlled to obtain high-strength radiation-resistant PBOH fibers.

[0023] The high-strength, radiation-resistant PBOH fiber has a large number of intramolecular and intermolecular hydrogen bonds formed on the oxazole ring, which absorb and shield ultraviolet light.

[0024] The hydrogen bonds are O—H--N, O—H--F, O—H--O, N—H--F, and N—H--O on the imidazole ring and the oxazole ring.

[0025] The hydrogen bonds form relatively stable five-membered, six-membered, and eight-membered ring structures on the imidazole and oxazole rings.

[0026] The heat treatment temperature is 300-550℃; the heat treatment time is 5s-10min; and the axial tension is 4~16N.

[0027] The high-strength, UV-resistant PBOH fiber prepared by the above method retains a tensile strength of up to 81% after 480 hours of UV aging.

[0028] The beneficial effects of the PBO modification method and the PBOH structure proposed in this invention are as follows:

[0029] 1) In-situ copolymerization modification introduces abundant O-H-O and other hydrogen bond structures into the PBO molecular chain, making the molecular chain orientation structure of PBO microfiber more regular and stable, with higher tensile strength and greater modulus.

[0030] 2) Introducing O-H-N hydrogen bond structures on both sides of the UV-sensitive imidazole ring in the PBO molecular chain significantly improves the UV resistance of the imidazole ring and provides a long-lasting modification effect.

[0031] 3) The intermolecular forces are strengthened by the N-H-F hydrogen bonds, which significantly improves the compressive strength of PBO fibers;

[0032] 4) The modified method is simple and basically the same as the PBO fiber synthesis and preparation process. It is easy to promote and is a highly promising PBO fiber modification method with great practical value. It can be widely used in aerospace and military fields. Attached Figure Description

[0033] Figure 1 The molecular structure of PBOH-47 obtained in Example 1;

[0034] Figure 2 The hydrogen bond network structure within PBOH-47 fibers obtained in Example 1;

[0035] Figure 3 XRD comparison diagram of PBOH-47 and PBO fibers obtained in Example 1;

[0036] Figure 4 Comparison of infrared spectra of PBOH-47 and PBO obtained in Example 1;

[0037] Figure 5 Comparison of XPS spectra of PBOH-47 and PBO fibers obtained in Example 1;

[0038] Figure 6 Example 1: Strength-UV irradiation time curves of PBOH-47 and PBO fibers;

[0039] Figure 7Surface morphology of PBOH-47 fibers obtained in Example 1 after UV irradiation for different times;

[0040] Figure 8 Comparison of the compressive strength of PBOH and PBO fibers obtained in the examples;

[0041] Figure 9 Image of PBOH-47 fiber obtained in Example 1. Detailed Implementation

[0042] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only a part of the embodiments of the invention, not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially. Example

[0043] Preparation of PBO oligomer solution: Under argon protection, 21.3 g of 4,6-diaminoresorcinol hydrochloride and R... 2-09 18.26 g of phosphorus pentoxide (56.73 g), 93.43 g of phosphoric acid, and 1.1 g of stannous chloride were added to a reaction vessel, and the temperature was gradually increased to 80 °C. The mixture was stirred at a constant temperature for 8 h to remove hydrogen chloride. 23.92 g of phosphorus pentoxide was added to control the proportion of phosphorus pentoxide in the phosphoric acid to 83.5 wt%. The temperature was then gradually increased to 115 °C, and the reaction was carried out for 6 h to obtain a PBO oligomer solution.

[0044] Preparation of R1-R2 oligomer solution: Under argon protection, R 1-04 Hydrochloride (3.4 g), R 2-07 6.552 g of phosphorus pentoxide (14.27 g), 23.5 g of phosphoric acid, and 0.3 g of stannous chloride were added to a reaction vessel, and the temperature was gradually increased to 80 °C. The mixture was stirred at a constant temperature for 6 h to remove hydrogen chloride. 6.02 g of phosphorus pentoxide was then added to control the proportion of phosphorus pentoxide in the phosphoric acid to 83.5 wt%. The temperature was then gradually increased to 140 °C, and the reaction was carried out for 15 h to obtain an R1-R2 oligomer solution.

[0045] Copolymerization of PBO with R1-R2 oligomers: Under argon protection, the PBO oligomer solution was mixed with the R1-R2 oligomer solution. Then, under argon protection, the mixture was stirred and heated to 150 °C for 12 h; subsequently, the temperature was increased to 175 °C and the reaction was continued for 16 h to obtain a high-viscosity PBOH copolymer solution.

[0046] Chain extension: The high-viscosity PBOH copolymer solution was added to an argon-protected twin-screw extruder reactor for repolymerization at a reaction temperature of 190 °C for 1 h, resulting in a polymer solution of 14.5% high molecular weight PBOH copolymer.

[0047] Spinning: The polymer solution of high molecular weight PBOH copolymer is spun, washed, and dried using a dry-jet wet spinning method to obtain PBOH nascent fibers.

[0048] Heat treatment: The nascent PBOH fibers were heat-treated at 350℃ and under a tension of 10N for 2 minutes to obtain high-strength, radiation-resistant PBOH-47 fibers. These fibers exhibit a compressive strength of 0.65 GPa and a tensile strength of 5.6 GPa at room temperature, and retain 78% of their tensile strength after 480 hours of UV irradiation. Example

[0049] Preparation of PBO oligomer solution: Under argon protection, 21.3 g of 4,6-diaminoresorcinol hydrochloride and R... 2-09 18.26 g of phosphorus pentoxide (51.01 g), 79.11 g of phosphoric acid, and 0.9 g of stannous chloride were added to a reaction vessel, and the temperature was gradually increased to 80 °C. The mixture was stirred at a constant temperature for 2 h to remove hydrogen chloride. 20.36 g of phosphorus pentoxide was added to control the proportion of phosphorus pentoxide in the phosphoric acid to 83.5 wt%. The temperature was then gradually increased to 120 °C and the reaction was carried out for 4 h to obtain a PBO oligomer solution.

[0050] Preparation of R1-R2 oligomer solution: Under argon protection, R 1-01 Hydrochloride (1.88 g), R 2-01 2.178 g of phosphorus pentoxide (5.23 g), 8.11 g of phosphoric acid, and 0.11 g of stannous chloride were added to a reaction vessel, and the temperature was gradually increased to 80 °C. The mixture was stirred at a constant temperature for 8 h to remove hydrogen chloride. 2.09 g of phosphorus pentoxide was added to control the proportion of phosphorus pentoxide in the phosphoric acid to 83.5 wt%. The temperature was then gradually increased to 100 °C, and the reaction was carried out for 6 h to obtain an R1-R2 oligomer solution.

[0051] Copolymerization of PBO with R1-R2 oligomers: Under argon protection, the PBO oligomer solution was mixed with the R1-R2 oligomer solution. Then, under argon protection, the mixture was stirred and heated to 160 °C for 17 h; subsequently, the temperature was increased to 185 °C and the reaction was continued for 2 h to obtain a high-viscosity PBOH copolymer solution.

[0052] Chain extension: The high-viscosity PBOH copolymer solution was added to an argon-protected twin-screw extruder reactor for repolymerization at a reaction temperature of 185 °C for 0.1 h to obtain a polymer solution of 16% high molecular weight PBOH copolymer.

[0053] Spinning: The polymer solution of high molecular weight PBOH copolymer is spun, washed, and dried using a dry-jet wet spinning method to obtain PBOH nascent fibers.

[0054] Heat treatment: The nascent PBOH fibers were heat-treated at 550℃ and 16N tension for 5 s to obtain high-strength, radiation-resistant PBOH-11 fibers. The fibers have a room temperature compressive strength of 0.33 GPa, a tensile strength of 5.3 GPa, and retain 76% of their tensile strength after 480 h of ultraviolet irradiation. Example

[0055] Preparation of PBO oligomer solution: Under argon protection, 21.3 g of 4,6-diaminoresorcinol hydrochloride and R... 2-09 18.26 g of phosphorus pentoxide (52.47 g), 103.45 g of phosphoric acid, and 0.92 g of stannous chloride were added to a reaction vessel, and the temperature was gradually increased to 80 °C. The mixture was stirred at a constant temperature for 8 h to remove hydrogen chloride. Phosphorus pentoxide (34.76 g) was then added to control the proportion of phosphorus pentoxide in the phosphoric acid to 83.5 wt%. The temperature was then gradually increased to 120 °C, and the reaction was carried out for 10 h to obtain a PBO oligomer solution.

[0056] Preparation of R1-R2 oligomer solution: Under argon protection, R 1-02 Hydrochloride (0.7 g), R 2-04 1.012 g of phosphorus pentoxide (2.27 g), 4.48 g of phosphoric acid, and 0.24 g of stannous chloride were added to a reaction vessel, and the temperature was gradually increased to 80 °C. The mixture was stirred at a constant temperature for 4 h to remove hydrogen chloride. 1.5 g of phosphorus pentoxide was added to control the proportion of phosphorus pentoxide in the phosphoric acid to 83.5 wt%. The temperature was then gradually increased to 150 °C, and the reaction was carried out for 16 h to obtain the R1-R2 oligomer solution.

[0057] Copolymerization of PBO with R1-R2 oligomers: Under argon protection, the PBO oligomer solution was mixed with the R1-R2 oligomer solution. Then, under argon protection, the mixture was stirred and heated to 140 °C for 10 h; subsequently, the temperature was increased to 185 °C and the reaction was continued for 18 h to obtain a high-viscosity PBOH copolymer solution.

[0058] Chain extension: The high-viscosity PBOH copolymer solution was added to an argon-protected twin-screw extruder reactor for repolymerization at a reaction temperature of 195 °C for 0.1 h to obtain a polymer solution of 13% high molecular weight PBOH copolymer.

[0059] Spinning: The polymer solution of high molecular weight PBOH copolymer is spun, washed, and dried using a dry-jet wet spinning method to obtain PBOH nascent fibers.

[0060] Heat treatment: The nascent PBOH fibers were heat-treated at 300℃ and under a tension of 16N for 1 min to obtain high-strength, radiation-resistant PBOH-24 fibers. The fibers have a compressive strength of 0.45 GPa and a tensile strength of 5.2 GPa at room temperature, and retain 81% of their tensile strength after 480 h of ultraviolet irradiation. Example

[0061] Preparation of PBO oligomer solution: Under argon protection, 21.3 g of 4,6-diaminoresorcinol hydrochloride and R... 2-09 18.26 g of phosphorus pentoxide (41.88 g), 89.22 g of phosphoric acid, and 0.98 g of stannous chloride were added to a reaction vessel, and the temperature was gradually increased to 80 °C. The mixture was stirred at a constant temperature for 5 h to remove hydrogen chloride. Phosphorus pentoxide (34.71 g) was then added to control the proportion of phosphorus pentoxide in the phosphoric acid to 83.5 wt%. The temperature was then gradually increased to 110 °C, and the reaction was carried out for 7 h to obtain a PBO oligomer solution.

[0062] Preparation of R1-R2 oligomer solution: Under argon protection, R 1-03 Hydrochloride (2.76 g), R 2-06 5.236 g of phosphorus pentoxide (8.46 g), 18.03 g of phosphoric acid, and 0.22 g of stannous chloride were added to a reaction vessel, and the temperature was gradually increased to 80 °C. The mixture was stirred at a constant temperature for 5 h to remove hydrogen chloride. 7.01 g of phosphorus pentoxide was added to control the proportion of phosphorus pentoxide in the phosphoric acid to 83.5 wt%. The temperature was then gradually increased to 130 °C, and the reaction was carried out for 14 h to obtain an R1-R2 oligomer solution.

[0063] Copolymerization of PBO with R1-R2 oligomers: Under argon protection, the PBO oligomer solution was mixed with the R1-R2 oligomer solution. Then, under argon protection, the mixture was stirred and heated to 140 °C for 12 h; subsequently, the temperature was increased to 165 °C and the reaction was continued for 18 h to obtain a high-viscosity PBOH copolymer solution.

[0064] Chain extension: The high-viscosity PBOH copolymer solution was added to an argon-protected twin-screw extruder reactor for repolymerization at a reaction temperature of 185 °C for 3 h, resulting in a polymer solution with a mass fraction of 15% high molecular weight PBOH copolymer.

[0065] Spinning: The polymer solution of high molecular weight PBOH copolymer is spun, washed, and dried using a dry-jet wet spinning method to obtain PBOH nascent fibers.

[0066] Heat treatment: The nascent PBOH fibers were heat-treated at 450℃ and 4 N tension for 5 min to obtain high-strength, radiation-resistant PBOH-36 fibers. The fibers have a room temperature compressive strength of 0.39 GPa, a tensile strength of 5.1 GPa, and retain 69% of their tensile strength after 480 h of ultraviolet irradiation. Example

[0067] Preparation of PBO oligomer solution: Under argon protection, 21.3 g of 4,6-diaminoresorcinol hydrochloride and R... 2-09 18.26 g of phosphorus pentoxide (54.55 g), 87.96 g of phosphoric acid, and 0.9 g of stannous chloride were added to a reaction vessel, and the temperature was gradually increased to 80 °C. The mixture was stirred at a constant temperature for 8 h to remove hydrogen chloride. 23.23 g of phosphorus pentoxide was added to control the proportion of phosphorus pentoxide in the phosphoric acid to 83.5 wt%. The temperature was then gradually increased to 100 °C and the reaction was carried out for 4 h to obtain a PBO oligomer solution.

[0068] Preparation of R1-R2 oligomer solution: Under argon protection, R 1-05 Hydrochloride (2.09 g), R 2-02 2.376 g of phosphorus pentoxide (6.16 g), 9.93 g of phosphoric acid, and 0.21 g of stannous chloride were added to a reaction vessel, and the temperature was gradually increased to 80 °C. The mixture was stirred at a constant temperature for 8 h to remove hydrogen chloride. 2.62 g of phosphorus pentoxide was added to control the proportion of phosphorus pentoxide in the phosphoric acid to 83.5 wt%. The temperature was then gradually increased to 150 °C, and the reaction was carried out for 16 h to obtain an R1-R2 oligomer solution.

[0069] Copolymerization of PBO with R1-R2 oligomers: Under argon protection, the PBO oligomer solution was mixed with the R1-R2 oligomer solution. Then, under argon protection, the mixture was stirred and heated to 150 °C for 12 h; subsequently, the temperature was increased to 185 °C and the reaction was continued for 18 h to obtain a high-viscosity PBOH copolymer solution.

[0070] Chain extension: The high-viscosity PBOH copolymer solution was added to an argon-protected twin-screw extruder reactor for repolymerization at a reaction temperature of 195 °C for 3 h, resulting in a polymer solution with a mass fraction of 14.8% high molecular weight PBOH copolymer.

[0071] Spinning: The polymer solution of high molecular weight PBOH copolymer is spun, washed, and dried using a dry-jet wet spinning method to obtain PBOH nascent fibers.

[0072] Heat treatment: The nascent PBOH fibers were heat-treated at 550℃ and under a tension of 9 N for 0.5 min to obtain high-strength, radiation-resistant PBOH-52 fibers. The fibers have a compressive strength of 0.42 GPa and a tensile strength of 5.4 GPa at room temperature, and retain 73% of their tensile strength after 480 h of ultraviolet irradiation. Example

[0073] Preparation of PBO oligomer solution: Under argon protection, 21.3 g of 4,6-diaminoresorcinol hydrochloride and R... 2-09 18.26 g of phosphorus pentoxide (61.84 g), 102.92 g of phosphoric acid, and 1.15 g of stannous chloride were added to a reaction vessel, and the temperature was gradually increased to 80 °C. The mixture was stirred at a constant temperature for 6 h to remove hydrogen chloride. 24.13 g of phosphorus pentoxide was added to control the proportion of phosphorus pentoxide in the phosphoric acid to 83.5 wt%. The temperature was then gradually increased to 100 °C and the reaction was carried out for 4 h to obtain a PBO oligomer solution.

[0074] Preparation of R1-R2 oligomer solution: Under argon protection, R 1-07 Hydrochloride (4.75 g), R 2-08 6.048 g of phosphorus pentoxide (16.88 g), 28.09 g of phosphoric acid, and 0.27 g of stannous chloride were added to a reaction vessel, and the temperature was gradually increased to 80 °C. The mixture was stirred at a constant temperature for 8 h to remove hydrogen chloride. Phosphorus pentoxide (6.59 g) was then added to control the proportion of phosphorus pentoxide in the phosphoric acid to 83.5 wt%. The temperature was then gradually increased to 100 °C, and the reaction was carried out for 12 h to obtain an R1-R2 oligomer solution.

[0075] Copolymerization of PBO with R1-R2 oligomers: Under argon protection, the PBO oligomer solution was mixed with the R1-R2 oligomer solution. Then, under argon protection, the mixture was stirred and heated to 150 °C for 12 h; subsequently, the temperature was increased to 165 °C and the reaction was continued for 16 h to obtain a high-viscosity PBOH copolymer solution.

[0076] Chain extension: The high-viscosity PBOH copolymer solution was added to an argon-protected twin-screw extruder reactor for repolymerization at a reaction temperature of 185 °C for 2.5 h to obtain a polymer solution of high molecular weight PBOH copolymer with a mass fraction of 13.6%.

[0077] Spinning: The polymer solution of high molecular weight PBOH copolymer is spun, washed, and dried using a dry-jet wet spinning method to obtain PBOH nascent fibers.

[0078] Heat treatment: The nascent PBOH fibers were heat-treated at 300℃ and 16 N tension for 10 min to obtain high-strength, radiation-resistant PBOH-78 fibers. The fibers have a room temperature compressive strength of 0.37 GPa, a tensile strength of 5.3 GPa, and retain 54% of their tensile strength after 480 h of ultraviolet irradiation.

[0079] Preferably, R1-04 and R2-07 are used as comonomers of the PBO polymer to copolymerize and obtain the PBOH molecular structure, as shown in the attached figure. Figure 1 As shown in the attached diagram, this PBOH fiber contains a rich network of hydrogen bonds, including O—H—-N, O—H—-F, O—H—-O, N—H—-F, and N—H—O. Figure 2 As shown.

Claims

1. A UV-resistant PBOH fiber, characterized in that, It has the molecular structure shown in Formula I: Where: x is 100~140, y is 5~35.

2. The application of the UV-resistant PBOH fiber of claim 1 in aerospace vehicles or in fireproof and bulletproof materials.

3. A method for preparing UV-resistant PBOH fibers, characterized in that, The copolymerization preparation method includes the following steps: (1) Preparation of PBO oligomer solution: Under argon protection, 4,6-diaminoresorcinol hydrochloride, R 2-09 Phosphorus pentoxide, phosphoric acid, and stannous chloride are added to a reaction vessel, and the temperature is gradually increased to 80°C. The mixture is stirred at this constant temperature for 2–8 hours to remove hydrogen chloride. Phosphorus pentoxide is then added, and the temperature is gradually increased to 100–120°C. The reaction is continued for 4–10 hours to obtain a PBO oligomer solution. R... 2-09 The structure is as follows: ; (2) Preparation of R1-R2 oligomer solution: Under argon protection, R1 hydrochloride, R2, phosphorus pentoxide, phosphoric acid and stannous chloride are added to the reactor, the temperature is gradually increased to 80°C, and the mixture is stirred at a constant temperature for 2-8 h to remove hydrogen chloride; phosphorus pentoxide is added, and then the temperature is gradually increased to 100-150°C and the reaction is carried out for 6-16 h to obtain R1-R2 oligomer solution; The structure of R1 is one of the following: R 1-01 ;R 1-02 ; R 1-03 ; R 1-04 The structure is R 1-05 ;R 1-07 The structure of R2 is one of the following: R 2-01 ;R 2-02 ;R 2-04 ; R 2-06 ;R 2-07 The structure is as follows: ;R 2-08 (3) Copolymerization of PBO with R1-R2 oligomers: Under argon protection, PBO oligomer solution and R1-R2 oligomer solution are mixed; then stirred under argon protection, heated to 120~150℃, and reacted for 6~16 h; then heated to 160~185℃ and reacted for 2~18 h to obtain high viscosity PBOH copolymer solution; (4) Chain extension: The high-viscosity PBOH copolymer solution is added to an argon-protected twin-screw extruder reactor for repolymerization at a reaction temperature of 185~195℃ for 0.1~3 h to obtain a polymer solution of high molecular weight PBOH copolymer; (5) Spinning: The polymer solution of high molecular weight PBOH copolymer is spun, washed and dried by dry-jet wet spinning to obtain PBOH nascent fibers; (6) Heat treatment: PBOH nascent fibers are heat treated at a certain temperature, tension and draw ratio, and the heat treatment time is controlled to obtain radiation-resistant PBOH fibers.

4. The method for preparing UV-resistant PBOH fiber according to claim 3, characterized in that, The heat treatment temperature is 300-550℃.

5. The method for preparing UV-resistant PBOH fiber according to claim 3, characterized in that, The heat treatment time is 5 seconds to 10 minutes.

6. The method for preparing UV-resistant PBOH fiber according to claim 3, characterized in that, The tension is 4~16N.

7. The method for preparing UV-resistant PBOH fiber according to claim 3, characterized in that, In steps (1) and (2), the proportion of phosphorus pentoxide in phosphoric acid is controlled to be 83.5 wt%.

8. The UV-resistant PBOH fiber prepared by the method of claim 3, characterized in that, The radiation-resistant PBOH fiber retains up to 81% of its tensile strength after 480 hours of UV aging.

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