A method for improving the ultraviolet resistance of PBO fibers by doping nanoparticles

Abstract

The application belongs to the field of high-performance fiber preparation, and discloses a method for improving the ultraviolet resistance of PBO fiber by doping nanoparticles, which comprises the following steps: taking PBO as a core layer, uniformly mixing anti-ultraviolet nanoparticles and polyimide (PI) by blending, taking the polyimide (PI) doped with the anti-ultraviolet nanoparticles as an outer layer, and preparing a PBO / PI-anti-ultraviolet nanoparticle fiber with a skin-core structure; compared with untreated PBO fiber and common PBO / PI fiber with a skin-core structure, the PBO / PI-anti-ultraviolet nanoparticle fiber has good ultraviolet resistance; the above modification method is simple to operate, and is a modification method for anti-ultraviolet PBO fiber with wide application and promotion value.

Description

Technical Field

[0001] This invention relates to the field of high-performance fiber preparation, and in particular to a method for improving the UV resistance of PBO fibers by doping with nanoparticles. Background Technology

[0002] PBO (poly(p-phenylenebenzobisoxazole)) fiber is a high-performance fiber with polyaromatic heterocycles. It features high strength, high modulus, high temperature resistance, and high flame retardancy. Its strength reaches 5.4 GPa, its modulus can reach 240 GPa, and its density is only 1.56 g / cm³. 3 With a limiting oxygen index (LOI) of 68 and a maximum decomposition temperature of 650℃, PBO possesses excellent chemical resistance and impact resistance, making it the best-performing organic fiber and earning it the title of the 21st-century super fiber. PBO is widely used in key military applications such as armor protection, aerospace structures, and stealth technology, demonstrating broad application prospects.

[0003] However, the mechanical properties of PBO fibers deteriorate significantly under light exposure, particularly in terms of UV resistance, hindering their application in aerospace, personal protective equipment, and armor protection. Currently, the most common method to improve the UV resistance of PBO fibers is to coat their surface with UV-resistant nanoparticles after molding, specifically through surface coating. However, with increasing UV exposure time, these nanoparticles easily detach, significantly reducing the fiber's UV resistance. Alternatively, some researchers have utilized the excellent UV resistance of polyimide itself, combining it with PBO fibers to form core-sheath composite fibers. While this method offers some improvement in UV resistance with increasing exposure time compared to the method using UV-resistant particles adsorbed on the PBO fiber surface, its mechanical properties still show a significant decrease, failing to meet the requirements for applications in aerospace structures and armor protection.

[0004] Therefore, how to further improve the UV resistance of PBO fibers through modification has become one of the urgent problems to be solved in this field. Summary of the Invention

[0005] This invention addresses the numerous shortcomings of existing technologies by providing a method for improving the UV resistance of PBO fibers through nanoparticle doping. The method uses PBO as the core layer, employing a blending process to uniformly mix UV-resistant nanoparticles with polyimide (PI). Then, the polyimide (PI) doped with UV-resistant nanoparticles is used as the outer layer, resulting in a core-sheath structure PBO / PI-UV-resistant nanoparticle fiber. Compared to untreated PBO fibers and ordinary core-sheath structure PBO / PI fibers, the PBO / PI-UV-resistant nanoparticle fiber exhibits superior UV resistance. This modification method is simple to operate and possesses broad application and promotional value for modifying UV-resistant PBO fibers.

[0006] The main concept of this invention is as follows:

[0007] Polyimide macromolecules contain numerous stable structures such as imide rings and benzene rings, which conjugate with the C=O groups in aromatic rings, increasing molecular bond energy and strengthening intermolecular forces. Furthermore, the imide rings in the polyimide molecule have a high electron cloud density. When polyimide is coated onto the surface of PBO fibers, the surface polyimide fiber macromolecules exhibit strong resistance to external energy attacks under ultraviolet radiation, making chain breakage difficult and reducing the likelihood of internal PBO fibers breaking due to ultraviolet irradiation, thus demonstrating excellent UV resistance. Additionally, UV-resistant nanoparticles can both absorb and scatter / reflect ultraviolet light, also exhibiting good UV resistance. This invention utilizes the excellent UV resistance of nanoparticles and polyimide, blending them and coating them onto the surface of PBO fibers. This reduces nanoparticle shedding and leverages the UV resistance advantages of both, further enhancing the UV resistance of PBO fibers.

[0008] The specific technical solution of this invention is as follows:

[0009] A method for improving the UV resistance of PBO fibers by doping with nanoparticles, the specific steps of which are as follows:

[0010] (1) Preparation of polyimide spinning solution

[0011] Under nitrogen atmosphere, N-methyl-2-pyrrolidone (NMP) solvent (1 / 3 volume of the reactor) was added to the polymerization reactor. Then, 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFMB) monomer was added and stirred for 40-80 min to ensure complete dissolution. Next, 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA) was added at a molar ratio of 0.5:1 to 0.6:1 with 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl. The reaction was carried out at 20-30°C for 6 h. Finally, 6-10 g of isoquinoline was added, and the temperature was raised to 100-120°C and stirred for 4 h. The temperature was then raised to 140-160°C and stirred for 3 h. Finally, the reaction was carried out at 180-200°C for 10 h to obtain the polyimide spinning solution.

[0012] (2) PBO prepolymerization

[0013] Add polyphosphoric acid solvent to 1 / 3 of the reactor volume, then add the polymerization monomers 4,6-diamino-1,3-benzene hydrochloride (DADHB), terephthalic acid (TPA), and the antioxidant stannous chloride in sequence. The molar ratio of DADHB to TPA is 1.002:1 to 1.005:1, and the content of the antioxidant stannous chloride is 1% to 5% of the mass of TPA. Heat to 100 to 120°C and stir for 4 to 6 hours. Then add phosphorus pentoxide, with a mass ratio of phosphorus pentoxide to TPA of 2.5:1 to 1.5:1. Continue to heat to 130 to 150°C and stir for 8 to 10 hours to complete the PBO prepolymerization.

[0014] (3) Preparation of PBO spinning solution

[0015] The PBO prepolymer from step (2) is fed to a twin-screw extruder via a metering pump for further polymerization. The screw length-to-diameter ratio is 52, the screw speed is 20-60 r / min, and the temperature is set to 150-200℃ to obtain a high-polymerization-degree PBO spinning solution.

[0016] (4) Hybridization of UV-resistant nanoparticles

[0017] The polyimide spinning solution prepared in step (1) is pumped into a twin-screw extruder via a metering pump. At the same time, UV-resistant nanoparticles dispersed in N-methyl-2-pyrrolidone solvent in 1 / 3 of the reactor volume are added to the twin-screw extruder in the form of side feed. The molar ratio of UV-resistant nanoparticles to 3,3',4,4'-benzophenone tetracarboxylic dianhydride is 0.01:1 to 0.03:1. The screw length-to-diameter ratio is 52, the screw speed is 60 to 120 r / min, and the temperature is set to 150 to 200 °C. Under the strong shearing action of the twin screw, the UV-resistant nanoparticles and polyimide are completely blended to obtain a polyimide spinning solution doped with UV-resistant nanoparticles.

[0018] The UV-resistant nanoparticles mentioned above are selected from Ce 0.8 Ca 0.2 O 1.8 One of SiO2, TiO2, and ZnO, with a particle size generally selected from 20 to 60 nanometers; Ce is preferred. 0.8 Ca 0.2 O 1.8 The use of the aforementioned UV-resistant nanoparticles further enhances the UV resistance of PBO.

[0019] The Ce 0.8 Ca 0.2 O 1.8 The preparation method of (calcium oxide-doped cerium dioxide) nanoparticles is as follows:

[0020] Cerium chloride and calcium chloride were dissolved in deionized water at a molar ratio of 4:1 to form a mixed solution. Then, 5-10 g of sodium hydroxide was added to form a precipitate. A suitable amount of hydrogen peroxide was then added, and the pH of the solution was adjusted to 10-12 with NaOH. The reaction was continued at 40-50℃ for 10-16 hours. After the reaction, the product was washed with water, dried, and then calcined in a muffle furnace at 700-800℃ for 1-2 hours to obtain calcium oxide-doped cerium dioxide (Ce). 0.8 Ca 0.2 O 1.8 Nanoparticles.

[0021] (5) Preparation of UV-resistant core-sheath structure PBO fiber

[0022] The spinning solutions from steps (3) and (4) are respectively transported to the spinning metering pump through pipelines. After precise metering, they enter the core-sheath bicomponent spinning assembly. By controlling the ratio of the two components in the core-sheath spinning assembly, the PBO content is 50-90wt% and the polyimide content is 10-50wt%, resulting in bicomponent fibers with different contents of polyimide and PBO containing UV-resistant nanoparticles. After solvent removal in a coagulation bath, stretching and winding, PBO fibers with a core-sheath structure and UV resistance are obtained.

[0023] Another objective of this application is to provide a PBO fiber with a core-sheath structure that has UV resistance, obtained by using the above-mentioned method of improving the UV resistance of PBO fibers by doping with nanoparticles. The fiber has PBO as the core layer and polyimide (PI) doped with UV-resistant nanoparticles as the outer layer. The content of PBO in the core layer is 50-90 wt%, the content of polyimide in the outer layer is 10-50 wt%, and the content of UV-resistant nanoparticles is 0.1-1 wt% of the polyimide.

[0024] The main advantages of the PBO fibers with core-sheath structure and UV resistance obtained above are as follows:

[0025] Polyimide itself possesses UV resistance, and coating it onto the surface of PBO fibers can enhance its UV resistance. Similarly, UV-resistant nanoparticles are typically coated onto the surface of PBO fibers, but with increasing UV exposure time, these nanoparticles easily detach from the PBO surface, leading to a significant reduction in UV resistance. Compared to surface coating methods that simply coat the PBO fiber surface with UV-resistant nanoparticles or polyimide, this invention utilizes the excellent UV resistance of both nanoparticles and polyimide. By blending the two and employing a core-sheath spinning assembly, it directly coats the PBO fiber surface using a one-step spinning process. This reduces nanoparticle detachment and leverages the UV resistance advantages of both materials to further improve the UV resistance of the PBO fibers.

[0026] After 300 hours of UV irradiation, the modified PBO fiber showed an increase in the retention rate of monofilament tensile strength from 25.1% to 71.4%. In addition, the modified fiber strength reached 5.2 GPa, which can meet the requirements of aerospace and other special environments for material performance under UV resistance. The elongation at break and tensile modulus were basically the same as before the modification, indicating that the modification did not affect the performance of PBO fiber.

[0027] In summary, the method for preparing PBO fibers with improved UV resistance by doping nanoparticles provided by this invention is universal, simple to operate, requires low equipment conditions, is green and pollution-free, and the process is controllable. The content of the cortex polyimide and UV-resistant nanoparticles can be adjusted according to needs to obtain PBO fibers with different UV resistance properties, which can meet the performance requirements of different application scenarios. It is a very promising fiber modification method. Attached Figure Description

[0028] Figure 1 PBO / PI-Ce obtained in Example 2 0.8 Ca 0.2 O 1.8 Schematic diagram of fiber cross-section.

[0029] Figure 2 With a strength of 50w / m 2 Before and after 300 hours of ultraviolet irradiation, PBO and PBO / PI-Ce in Example 2 0.8 Ca 0.2 O 1.8 A schematic diagram of the tensile strength of a fiber. Detailed Implementation

[0030] To better understand the present invention, the following embodiments further illustrate the content of the present invention. The present invention described herein is only for explaining the present invention and is not intended to limit the present invention.

[0031] Ce in the following examples 0.8 Ca0.2 O 1.8 The preparation method of (calcium oxide-doped cerium dioxide) nanoparticles is as follows:

[0032] Cerium chloride and calcium chloride were dissolved in deionized water at a molar ratio of 4:1 to form a mixed solution. Then, 6g of sodium hydroxide was added to form a precipitate. A suitable amount of hydrogen peroxide was then added, and the pH of the solution was adjusted to 12 with NaOH. The reaction was continued at 50℃ for 12 hours. After the reaction was completed, the product was washed with water, dried, and then calcined in a muffle furnace at 800℃ for 2 hours to obtain calcium oxide-doped cerium dioxide (Ce). 0.8 Ca 0.2 O 1.8 Nanoparticles.

[0033] The following anti-UV nanoparticles Ce 0.8 Ca 0.2 O 1.8 The particle size range of SiO2, TiO2, and ZnO is 20–60 nanometers.

[0034] Example 1

[0035] A method for improving the UV resistance of PBO fibers by doping with nanoparticles, using PBO as the core layer and doping with UV-resistant Ce. 0.8 Ca 0.2 O 1.8 The nanoparticles have a polyimide (PI) outer layer, with an outer layer polyimide content of 10 wt%, and a core layer PBO content of 90 wt%, providing UV resistance (Ce). 0.8 Ca 0.2 O 1.8 The nanoparticle content is 0.5 wt% of polyimide.

[0036] The specific preparation steps are as follows:

[0037] (1) Preparation of polyimide spinning solution: N-methyl-2-pyrrolidone (NMP) solvent with a volume of 1 / 3 of the reactor was added under nitrogen atmosphere in the polymerization reactor. Then, 2,2'-bistrifluoromethyl-4,4'-diaminobiphenyl (TFMB) monomer was added and stirred for 60 min to dissolve it completely. Then, 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA) with a molar ratio of 0.6:1 to TFMB was added. The reaction was carried out at 20℃ for 6 h. Finally, 10 g of isoquinoline was added, the temperature was raised to 120℃ and stirred for 4 h, the temperature was raised to 150℃ and stirred for 3 h, and finally the reaction was carried out at 180℃ for 10 h to obtain polyimide spinning solution.

[0038] (2) PBO prepolymerization: Add polyphosphoric acid solvent to 1 / 3 of the kettle volume, and then add the polymerization monomers 4,6-diamino-1,3-benzenediol hydrochloride (DADHB), terephthalic acid (TPA), and antioxidant stannous chloride in sequence. The molar ratio of DADHB to TA is 1.002:1, and the content of antioxidant stannous chloride is 2% of the mass of TPA. The temperature is raised to 100℃ and stirred for 6 hours. Then, phosphorus pentoxide is added, and the mass ratio of phosphorus pentoxide to TPA is 2.0:1. The temperature is raised to 150℃ and stirred for 10 hours to complete the PBO prepolymerization.

[0039] (3) Preparation of PBO spinning solution: The PBO prepolymer from step (2) is transported to a twin-screw extruder for further polymerization via a metering pump. The screw length-to-diameter ratio is 52, the screw speed is 30 r / min, and the temperature is set to 180℃ to obtain a high degree of polymerization PBO spinning solution.

[0040] (4) Anti-UV Ce 0.8 Ca 0.2 O 1.8 Nanoparticle mixing: The polyimide spinning solution prepared in step (1) was pumped into a twin-screw extruder via a metering pump. Simultaneously, UV-resistant nanoparticles dispersed in N-methyl-2-pyrrolidone (NMP) solvent (1 / 3 of the reactor volume) were added to the twin-screw extruder via side feeding. The UV-resistant Ce... 0.8 Ca 0.2 O 1.8 The molar ratio of nanoparticles to 3,3',4,4'-benzophenone tetracarboxylic acid dianhydride was 0.02:1. The screw's aspect ratio was 52, screw speed was 60 r / min, and temperature was set to 180℃. Through the strong shearing action of the twin-screw extruder, the UV-resistant nanoparticles and polyimide were completely blended, resulting in a polyimide spinning solution doped with UV-resistant nanoparticles. The UV-resistant Ce... 0.8 Ca 0.2 O 1.8 The nanoparticle content is 0.5 wt% of polyimide;

[0041] (5) Preparation of UV-resistant core-sheath structure PBO fiber: The spinning solutions from steps (3) and (4) are respectively transported to the spinning metering pump through pipelines. After precise metering, they enter the core-sheath type bicomponent spinning assembly, wherein the ratio of the two components in the core-sheath type assembly is 10:90, to obtain bicomponent fibers containing 10wt% UV-resistant nanoparticles of polyimide and 90wt% PBO. After solvent removal in a coagulation bath, stretching and winding, PBO fibers with a core-sheath structure and excellent UV resistance are obtained;

[0042] Testing revealed that the unmodified PBO fiber had a tensile strength of 5.1 GPa, while the modified PBO fiber had a tensile strength of 5.0 GPa. Although this was slightly lower than the unmodified fiber, it still met the material performance requirements for aerospace engineering. (Using 50 W / m...) 2 After being irradiated with high intensity ultraviolet light for 300 hours, the tensile strengths of the unmodified PBO fiber and the modified PBO fiber were 1.1 GPa and 3.0 GPa, respectively, and the retention rate of the monofilament tensile strength increased from 21.6% to 60%.

[0043] Example 2

[0044] A method for improving the UV resistance of PBO fibers by doping with nanoparticles, using PBO as the core layer and doping with UV-resistant Ce. 0.8 Ca 0.2 O 1.8 The nanoparticles have a polyimide (PI) outer layer, with an outer layer polyimide content of 20 wt%, and a core layer PBO content of 80 wt%, providing UV resistance (Ce). 0.8 Ca 0.2 O 1.8 The nanoparticle content is 0.5 wt% of polyimide.

[0045] The specific preparation steps are as follows:

[0046] (1)-(4) Same as Example 1;

[0047] (5) Preparation of UV-resistant core-sheath structure PBO fiber: The spinning solutions from steps (3) and (4) are respectively transported to the spinning metering pump through pipelines. After precise metering, they enter the core-sheath type bicomponent spinning assembly, wherein the ratio of the two components in the core-sheath type assembly is 20:80, to obtain bicomponent fibers containing 20wt% UV-resistant nanoparticles of polyimide and 80wt% PBO. After solvent removal in a coagulation bath, stretching and winding, PBO fibers with a core-sheath structure and excellent UV resistance are obtained;

[0048] Testing revealed that the unmodified PBO fiber had a tensile strength of 5.1 GPa, while the modified PBO fiber had a tensile strength of 4.9 GPa. Although this was slightly lower than the unmodified fiber, it still met the material performance requirements for aerospace engineering. (Using 50 W / m...) 2 After being irradiated with high intensity ultraviolet light for 300 hours, the tensile strengths of the unmodified PBO fiber and the modified PBO fiber were 1.1 GPa and 3.7 GPa, respectively, and the retention rate of the monofilament tensile strength increased from 21.6% to 75.5%.

[0049] Example 3

[0050] A method for improving the UV resistance of PBO fibers by doping with nanoparticles, using PBO as the core layer and doping with UV-resistant Ce. 0.8 Ca 0.2 O 1.8 The nanoparticles have a polyimide (PI) outer layer, with an outer layer polyimide content of 50 wt%, and a core layer PBO content of 50 wt%, with UV-resistant Ce. 0.8 Ca 0.2 O 1.8 The nanoparticle content is 0.5 wt% of polyimide.

[0051] The specific preparation steps are as follows:

[0052] (1)-(4) Same as Example 1;

[0053] (5) Preparation of UV-resistant core-sheath structure PBO fiber: The spinning solutions from steps (3) and (4) are respectively transported to the spinning metering pump through pipelines. After precise metering, they enter the core-sheath type bicomponent spinning assembly, wherein the ratio of the two components in the core-sheath type assembly is 50:50, to obtain bicomponent fibers containing 50wt% UV-resistant nanoparticles of polyimide and 50wt% PBO. After solvent removal in a coagulation bath, stretching and winding, PBO fibers with a core-sheath structure and excellent UV resistance are obtained;

[0054] Testing revealed that the tensile strength of unmodified PBO fiber was 5.1 GPa, while the tensile strength of the modified PBO fiber was 4.1 GPa, indicating a certain degree of decrease in tensile strength. (Using 50w / m...) 2 After irradiating the PBO fiber with high intensity ultraviolet light for 300 hours, the tensile strengths of the unmodified PBO fiber and the modified PBO fiber were 1.1 GPa and 2.1 GPa, respectively, and the retention rate of the monofilament tensile strength increased from 21.6% to 51.2%.

[0055] Example 4

[0056] A method for improving the UV resistance of PBO fibers by doping with nanoparticles, using PBO as the core layer and doping with UV-resistant Ce. 0.8 Ca 0.2 O 1.8 The nanoparticles have a polyimide (PI) outer layer, with an outer layer polyimide content of 20 wt%, and a core layer PBO content of 80 wt%, providing UV resistance (Ce). 0.8 Ca 0.2 O 1.8 The nanoparticle content is 0.1 wt% of polyimide.

[0057] The specific preparation steps are as follows:

[0058] (1)-(3) Same as Example 1;

[0059] (4) Anti-UV Ce 0.8 Ca 0.2 O 1.8 Nanoparticle mixing: The polyimide spinning solution prepared in step (1) was fed into a twin-screw extruder via a metering pump. Simultaneously, UV-resistant nanoparticles dispersed in 1 / 3 of an N-methyl-2-pyrrolidone (NMP) solvent were added to the twin-screw extruder via side feeding. The UV-resistant Ce... 0.8 Ca 0.2 O 1.8 The molar ratio of nanoparticles to 3,3',4,4'-benzophenone tetracarboxylic acid dianhydride was 0.01:1. The screw's aspect ratio was 52, screw speed was 60 r / min, and temperature was set to 180℃. Through the strong shearing action of the twin-screw extruder, the UV-resistant nanoparticles and polyimide were completely blended, resulting in a polyimide spinning solution doped with UV-resistant nanoparticles. The UV-resistant Ce... 0.8 Ca 0.2 O 1.8 The nanoparticle content is 0.1 wt% of polyimide;

[0060] (5) Preparation of UV-resistant core-sheath structure PBO fiber: The spinning solutions from steps (3) and (4) are respectively transported to the spinning metering pump through pipelines. After precise metering, they enter the core-sheath type bicomponent spinning assembly, wherein the ratio of the two components in the core-sheath type assembly is 20:80, to obtain bicomponent fibers containing 20wt% UV-resistant nanoparticles of polyimide and 80wt% PBO. After solvent removal in a coagulation bath, stretching and winding, PBO fibers with a core-sheath structure and excellent UV resistance are obtained;

[0061] Testing revealed that the unmodified PBO fiber had a tensile strength of 5.1 GPa, while the modified PBO fiber had a tensile strength of 4.9 GPa. Although this was slightly lower than the unmodified fiber, it still met the material performance requirements for aerospace engineering. (Using 50 W / m...) 2 After irradiating the PBO fiber with high intensity ultraviolet light for 300 hours, the tensile strengths of the unmodified PBO fiber and the modified PBO fiber were 1.1 GPa and 3.2 GPa, respectively, and the retention rate of the monofilament tensile strength increased from 21.6% to 65.3%.

[0062] Example 5

[0063] A method for improving the UV resistance of PBO fibers by doping with nanoparticles, using PBO as the core layer and doping with UV-resistant Ce. 0.8 Ca 0.2 O 1.8The nanoparticles have a polyimide (PI) outer layer, with an outer layer polyimide content of 20 wt%, and a core layer PBO content of 80 wt%, providing UV resistance (Ce). 0.8 Ca 0.2 O 1.8 The nanoparticle content is 1 wt% of polyimide.

[0064] The specific preparation steps are as follows:

[0065] (1)-(3) Same as Example 1;

[0066] (4) Anti-UV Ce 0.8 Ca 0.2 O 1.8 Nanoparticle mixing: The polyimide spinning solution prepared in step (1) was fed into a twin-screw extruder via a metering pump. Simultaneously, UV-resistant nanoparticles dispersed in 1 / 3 of the N-methyl-2-pyrrolidone (NMP) solvent were added to the twin-screw extruder via side feeding. The UV-resistant Ce... 0.8 Ca 0.2 O 1.8 The molar ratio of nanoparticles to 3,3',4,4'-benzophenone tetracarboxylic acid dianhydride was 0.03:1. The screw's aspect ratio was 52, screw speed was 60 r / min, and temperature was set to 180℃. Through the strong shearing action of the twin-screw extruder, the UV-resistant nanoparticles and polyimide were completely blended, resulting in a polyimide spinning solution doped with UV-resistant nanoparticles. The UV-resistant Ce... 0.8 Ca 0.2 O 1.8 The nanoparticle content is 1 wt% of polyimide;

[0067] (5) Preparation of UV-resistant core-sheath structure PBO fiber: The spinning solutions from steps (3) and (4) are respectively transported to the spinning metering pump through pipelines. After precise metering, they enter the core-sheath type bicomponent spinning assembly, wherein the ratio of the two components in the core-sheath type assembly is 20:80, to obtain bicomponent fibers containing 20wt% UV-resistant nanoparticles of polyimide and 80wt% PBO. After solvent removal in a coagulation bath, stretching and winding, PBO fibers with a core-sheath structure and excellent UV resistance are obtained.

[0068] Testing revealed that the unmodified PBO fiber had a tensile strength of 5.1 GPa, while the modified PBO fiber had a tensile strength of 5.0 GPa. Although this was slightly lower than the unmodified fiber, it still met the material performance requirements for aerospace engineering. (Using 50 W / m...) 2 After being irradiated with high intensity ultraviolet light for 300 hours, the tensile strengths of the unmodified PBO fiber and the modified PBO fiber were 1.1 GPa and 3.5 GPa, respectively, and the retention rate of the monofilament tensile strength increased from 21.6% to 70%.

[0069] As can be seen from Examples 1-5, under the same experimental conditions, in Example 2, the outer polyimide content was 20wt%, the core layer PBO content was 80wt%, and the UV resistance Ce was [missing information]. 0.8 Ca 0.2 O 1.8 When the nanoparticle content is 0.5 wt% of polyimide, the tensile strength retention rate of its monofilament increases from 21.6% to 75.5%, exhibiting the best UV resistance.

[0070] Example 6

[0071] A method for improving the UV resistance of PBO fibers by doping with nanoparticles, wherein PBO is used as the core layer and polyimide (PI) doped with UV-resistant SiO2 nanoparticles is used as the outer layer, wherein the content of polyimide in the outer layer is 20 wt%, the content of PBO in the core layer is 80 wt%, and the content of UV-resistant SiO2 nanoparticles is 0.5 wt% of the polyimide.

[0072] The specific preparation steps are as follows:

[0073] (1)-(3) Same as Example 1;

[0074] (4) Mixing of UV-resistant SiO2 nanoparticles: The polyimide spinning solution prepared in step (1) is pumped into a twin-screw extruder via a metering pump. At the same time, UV-resistant nanoparticles dispersed in 1 / 3 of the N-methyl-2-pyrrolidone (NMP) solvent are added to the twin-screw extruder in the form of side feed. The molar ratio of UV-resistant SiO2 nanoparticles to 3,3',4,4'-benzophenone tetracarboxylic dianhydride is 0.02:1. The screw length-to-diameter ratio is 52, the screw speed is 60 r / min, and the temperature is set to 180℃. Under the strong shearing action of the twin screw, the UV-resistant nanoparticles and polyimide are completely mixed to obtain a polyimide spinning solution doped with UV-resistant nanoparticles. The content of UV-resistant SiO2 nanoparticles is 0.5 wt% of polyimide.

[0075] (5) Preparation of UV-resistant core-sheath structure PBO fiber: The spinning solutions from steps (3) and (4) are respectively transported to the spinning metering pump through pipelines. After precise metering, they enter the core-sheath type bicomponent spinning assembly, wherein the ratio of the two components in the core-sheath type assembly is 20:80, to obtain bicomponent fibers containing 20wt% UV-resistant nanoparticles of polyimide and 80wt% PBO. After solvent removal in a coagulation bath, stretching and winding, PBO fibers with a core-sheath structure and excellent UV resistance are obtained;

[0076] Testing revealed that the unmodified PBO fiber had a tensile strength of 5.1 GPa, while the modified PBO fiber had a tensile strength of 4.8 GPa. Although this was slightly lower than the unmodified fiber, it still met the material performance requirements for aerospace engineering. (Using 50 W / m...) 2 After irradiating the PBO fiber with high intensity ultraviolet light for 300 hours, the tensile strengths of the unmodified PBO fiber and the modified PBO fiber were 1.1 GPa and 3.2 GPa, respectively, and the retention rate of the monofilament tensile strength increased from 21.6% to 66.7%.

[0077] Example 7

[0078] A method for improving the UV resistance of PBO fibers by doping with nanoparticles, wherein PBO is used as the core layer and polyimide (PI) doped with UV-resistant TiO2 nanoparticles is used as the outer layer, wherein the content of polyimide in the outer layer is 20 wt%, the content of PBO in the core layer is 80 wt%, and the content of UV-resistant TiO2 nanoparticles is 0.5 wt% of the polyimide.

[0079] The specific preparation steps are as follows:

[0080] (1)-(3) Same as Example 1;

[0081] (4) Mixing of UV-resistant TiO2 nanoparticles: The polyimide spinning solution prepared in step (1) is pumped into a twin-screw extruder via a metering pump. At the same time, UV-resistant nanoparticles dispersed in 1 / 3 of the N-methyl-2-pyrrolidone (NMP) solvent are added to the twin-screw extruder in the form of side feed. The molar ratio of UV-resistant TiO2 nanoparticles to 3,3',4,4'-benzophenone tetracarboxylic dianhydride is 0.02:1. The screw length-to-diameter ratio is 52, the screw speed is 60 r / min, and the temperature is set to 180℃. Under the strong shearing action of the twin screw, the UV-resistant nanoparticles and polyimide are completely mixed to obtain a polyimide spinning solution doped with UV-resistant nanoparticles. The content of UV-resistant TiO2 nanoparticles is 0.5 wt% of polyimide.

[0082] (5) Preparation of UV-resistant core-sheath structure PBO fiber: The spinning solutions from steps (3) and (4) are respectively transported to the spinning metering pump through pipelines. After precise metering, they enter the core-sheath type bicomponent spinning assembly, wherein the ratio of the two components in the core-sheath type assembly is 20:80, to obtain bicomponent fibers containing 20wt% UV-resistant nanoparticles of polyimide and 80wt% PBO. After solvent removal in a coagulation bath, stretching and winding, PBO fibers with a core-sheath structure and excellent UV resistance are obtained;

[0083] Testing revealed that the unmodified PBO fiber had a tensile strength of 5.1 GPa, while the modified PBO fiber had a tensile strength of 4.8 GPa. Although this was slightly lower than the unmodified fiber, it still met the material performance requirements for aerospace engineering. (Using 50 W / m...) 2 After irradiating the PBO fiber with high intensity ultraviolet light for 300 hours, the tensile strengths of the unmodified PBO fiber and the modified PBO fiber were 1.1 GPa and 3.0 GPa, respectively, and the retention rate of the monofilament tensile strength increased from 21.6% to 62.5%.

[0084] Example 8

[0085] A method for improving the UV resistance of PBO fibers by doping with nanoparticles, wherein PBO is used as the core layer and polyimide (PI) doped with UV-resistant ZnO nanoparticles is used as the outer layer, wherein the content of polyimide in the outer layer is 20 wt%, the content of PBO in the core layer is 80 wt%, and the content of UV-resistant ZnO nanoparticles is 0.5 wt% of the polyimide.

[0086] The specific preparation steps are as follows:

[0087] (1)-(3) Same as Example 1;

[0088] (4) Mixing of UV-resistant ZnO nanoparticles: The polyimide spinning solution prepared in step (1) is pumped into a twin-screw extruder via a metering pump. At the same time, UV-resistant nanoparticles dispersed in 1 / 3 of the N-methyl-2-pyrrolidone (NMP) solvent are added to the twin-screw extruder in the form of side feed. The molar ratio of UV-resistant ZnO nanoparticles to 3,3',4,4'-benzophenone tetracarboxylic dianhydride is 0.02:1. The screw length-to-diameter ratio is 52, the screw speed is 60 r / min, and the temperature is set to 180℃. Under the strong shearing action of the twin screw, the UV-resistant nanoparticles and polyimide are completely mixed to obtain a polyimide spinning solution doped with UV-resistant nanoparticles. The content of UV-resistant ZnO nanoparticles is 0.5 wt% of polyimide.

[0089] (5) Preparation of UV-resistant core-sheath structure PBO fiber: The spinning solutions from steps (3) and (4) are respectively transported to the spinning metering pump through pipelines. After precise metering, they enter the core-sheath type bicomponent spinning assembly, wherein the ratio of the two components in the core-sheath type assembly is 20:80, to obtain bicomponent fibers containing 20wt% UV-resistant nanoparticles of polyimide and 80wt% PBO. After solvent removal in a coagulation bath, stretching and winding, PBO fibers with a core-sheath structure and excellent UV resistance are obtained;

[0090] Testing revealed that the unmodified PBO fiber had a tensile strength of 5.1 GPa, while the modified PBO fiber had a tensile strength of 4.8 GPa. Although this was slightly lower than the unmodified fiber, it still met the material performance requirements for aerospace engineering. (Using 50 W / m...) 2 After being irradiated with high intensity ultraviolet light for 300 hours, the tensile strengths of the unmodified PBO fiber and the modified PBO fiber were 1.1 GPa and 3.1 GPa, respectively, and the retention rate of the monofilament tensile strength increased from 21.6% to 64.6%.

[0091] Compared with Examples 6-8, Example 2 shows that under the same experimental conditions—keeping the outer polyimide content at 20 wt%, the core PBO content at 80 wt%, and the anti-UV nanoparticle content at 0.5 wt% of polyimide—the four anti-UV Ce... 0.8 Ca 0.2 O 1.8 In SiO2, TiO2, and ZnO nanoparticles, Ce 0.8 Ca 0.2 O 1.8 Nanoparticles have the best UV protection properties.

[0092] Compare with Example 1

[0093] A method for preparing PBO fibers with improved UV resistance by doping with TiO2 nanoparticles, wherein PBO fibers are used as raw materials and polydopamine doped with UV-resistant TiO2 nanoparticles is used as the outer layer, wherein the TiO2 content of the outer layer is 0.5 wt% of the PBO fibers.

[0094] The specific preparation steps are as follows:

[0095] (1) Ultrasonic cleaning of PBO fibers

[0096] PBO fibers were immersed in acetone and ultrasonically treated at 30°C for 3 hours. Then they were completely immersed in deionized water at 70°C and ultrasonically treated for 2 hours. They were then washed twice with deionized water to remove oil and impurities from the surface of the PBO fibers. Finally, they were placed in a vacuum oven and dried at 50°C for 6 hours to remove moisture from the fibers.

[0097] (2) Surface coating of TiO2 nanoparticles

[0098] 0.305-0.423 g of Tris was dissolved in 300 mL of distilled water, and the pH was adjusted to 8.5 with hydrochloric acid. Then, 0.40-0.52 g of dopamine was added and stirred thoroughly to prepare a dopamine buffer solution. Next, 0.1-0.5 g of UV-resistant TiO2 nanoparticles were added, followed by immersion of 1-5 g of ultrasonically cleaned PBO fibers in the solution. The solution was then shaken at a constant temperature of 30-40℃ for 12-48 hours. After the reaction, the PBO fibers were removed and rinsed repeatedly with deionized water four times to remove easily detachable polydopamine and TiO2 nanoparticles from the surface of the PBO fibers. The fibers were then vacuum dried at 50℃ for 12 hours to remove moisture. The TiO2 content was found to be 0.5 wt% of the PBO fibers.

[0099] Testing revealed that the tensile strength of unmodified PBO fiber was 5.1 GPa, while that of the modified PBO fiber was 4.5 GPa. (Using 50 W / m...) 2 After being irradiated with high intensity ultraviolet light for 300 hours, the tensile strengths of the unmodified PBO fiber and the modified PBO fiber were 1.1 GPa and 2.21 GPa, respectively, and the retention rate of the monofilament tensile strength increased from 21.6% to 49.1%.

[0100] As can be seen, under the same UV experimental conditions, compared with Example 2, the tensile strength of the modified PBO fiber is 3.7 GPa, while the tensile strength of the modified PBO fiber in Control Example 1 is only 2.21 GPa. The tensile strength retention rates of the monofilaments are 75.5% and 49.1%, respectively. This indicates that the method described in this invention is more beneficial to the UV resistance of PBO fibers.

[0101] Compare with Example 2

[0102] According to the method for preparing a high-temperature resistant and UV-resistant composite fiber described in patent CN 202297901 U, the outer layer polyimide content is 20wt% and the core layer PBO content is 80wt%.

[0103] The specific preparation steps are as follows:

[0104] The prepared polyimide spinning solution and PBO spinning solution were separately piped to a spinning metering pump. After precise metering, they entered a core-sheath type bicomponent spinning assembly, where the ratio of polyimide to PBO in the core-sheath type assembly was 20:80, resulting in bicomponent fibers containing 20 wt% polyimide and 80 wt% PBO. After solvent removal in a coagulation bath, drawing, and winding, bicomponent PBO fibers with a core-sheath structure and UV resistance were obtained.

[0105] Testing revealed that the tensile strength of unmodified PBO fiber was 5.1 GPa, while that of the modified PBO fiber was 4.7 GPa. (Using 50 W / m...)2 After irradiating the PBO fiber with high intensity ultraviolet light for 300 hours, the tensile strengths of the unmodified PBO fiber and the modified PBO fiber were 1.1 GPa and 2.65 GPa, respectively, and the retention rate of the monofilament tensile strength increased from 21.6% to 56.4%.

[0106] As can be seen, under the same UV experimental conditions, compared with Example 2, the tensile strength of the modified PBO fiber is 3.7 GPa, while the tensile strength of the modified PBO fiber in Control Example 2 is only 2.65 GPa. The tensile strength retention rates of the monofilaments are 75.5% and 56.4%, respectively. This indicates that the method described in this invention is more beneficial to the UV resistance of PBO fibers.

[0107] For those skilled in the art, the specific embodiments are merely illustrative descriptions of the present invention. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any non-substantial improvements made using the inventive concept and technical solution of the present invention, or the direct application of the inventive concept and technical solution to other situations without modification, are all within the protection scope of the present invention.

Claims

1. A method for improving the UV resistance of PBO fibers by doping with nanoparticles, characterized in that, The specific steps are as follows: (1) Preparation of polyimide spinning solution, the specific steps are as follows: Under nitrogen atmosphere, N-methyl-2-pyrrolidone solvent (1 / 3 volume of the reactor) was added to the polymerization reactor. Then, 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl was added and stirred for 40-80 min to ensure complete dissolution. Next, 3,3',4,4'-benzophenone tetracarboxylic dianhydride (at a molar ratio of 0.5:1-0.6:1 to 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl) was added and reacted at 20-30 °C for 6 h. Finally, 6-10 g of isoquinoline was added, and the temperature was raised to 100-120 °C and stirred for 4 h. The temperature was then raised to 140-160 °C and stirred for 3 h. Finally, the reaction was carried out at 180-200 °C for 10 h to obtain the polyimide spinning solution. (2) The specific steps of PBO prepolymerization are as follows: Add polyphosphoric acid solvent to 1 / 3 of the reactor volume, then add the polymerization monomers 4,6-diamino-1,3-benzenehydrin hydrochloride, terephthalic acid, and antioxidant stannous chloride sequentially. The molar ratio of 4,6-diamino-1,3-benzenehydrin hydrochloride to terephthalic acid is 1.002:1-1.005:1, and the content of antioxidant stannous chloride is 1-5% of the mass of terephthalic acid. Heat to 100-120℃ and stir for 4-6 h. Then add phosphorus pentoxide, with the mass ratio of phosphorus pentoxide to terephthalic acid being 2.5:1-1.5:

1. Continue to heat to 130-150℃ and stir for 8-10 h to complete the PBO prepolymerization. (3) The specific steps for preparing PBO spinning solution are as follows: The PBO prepolymer from step (2) is fed to a twin-screw extruder via a metering pump for further polymerization, wherein the screw length-to-diameter ratio is 52, the screw speed is 20-60 r / min, and the temperature is set to 150-200℃ to obtain a high degree of polymerization PBO spinning solution. (4) The specific steps for mixing the anti-UV nanoparticles are as follows: The polyimide spinning solution prepared in step (1) is pumped into a twin-screw extruder via a metering pump. Simultaneously, UV-resistant nanoparticles dispersed in N-methyl-2-pyrrolidone solvent (1 / 3 volume of the reactor) are added to the twin-screw extruder via side feeding. The molar ratio of the UV-resistant nanoparticles to 3,3',4,4'-benzophenone tetracarboxylic dianhydride is 0.01:1-0.03:

1. The screw aspect ratio is 52, the screw speed is 60-120 r / min, and the temperature is set to 150-200℃. Through the strong shearing action of the twin-screw extruder, the UV-resistant nanoparticles and polyimide are completely blended, resulting in a polyimide spinning solution doped with UV-resistant nanoparticles. The UV-resistant nanoparticles are selected from Ce... 0.8 Ca 0.2 O 1.8 One of SiO2, TiO2, and ZnO; (5) The specific steps for preparing UV-resistant core-sheath structure PBO fibers are as follows: The spinning solutions from steps (3) and (4) are respectively transported to the spinning metering pump through pipelines. After precise metering, they enter the core-sheath bicomponent spinning assembly. By controlling the ratio of the two components in the core-sheath spinning assembly, the PBO content is 50-90 wt% and the polyimide content is 10-50 wt%, resulting in bicomponent fibers with different contents of polyimide and PBO containing UV-resistant nanoparticles. After solvent removal in a coagulation bath, stretching and winding, PBO fibers with UV resistance and core-sheath structure are obtained.

2. The method for improving the UV resistance of PBO fibers by doping with nanoparticles according to claim 1, characterized in that: Anti-UV nanoparticles using Ce 0.8 Ca 0.2 O 1.8 Its preparation method is as follows: Cerium chloride and calcium chloride were dissolved in deionized water at a molar ratio of 4:1 to form a mixed solution. Then, 5-10 g of sodium hydroxide was added to form a precipitate. A suitable amount of hydrogen peroxide was then added, and the pH of the solution was adjusted to 10-12 with NaOH. The reaction was continued at 40-50℃ for 10-16 h. After the reaction, the product was washed with water, dried, and then calcined in a muffle furnace at 700-800℃ for 1-2 h to obtain Ce. 0.8 Ca 0.2 O 1.8 Nanoparticles.

3. The PBO fiber with a core-sheath structure and UV resistance obtained by the method according to claim 1 is characterized in that: It uses PBO as the core layer and polyimide doped with UV-resistant nanoparticles as the outer layer. The PBO content in the core layer is 50-90 wt%, the polyimide content in the outer layer is 10-50 wt%, and the UV-resistant nanoparticle content is 0.1-1 wt% of the polyimide.

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