Ultraviolet crosslinking device of polycarbosilane fiber and crosslinking method thereof

Abstract

The invention discloses a polycarbosilane fiber ultraviolet crosslinking device which comprises a gas inlet system, an ultraviolet crosslinking and heat treatment system and a control system, the gas inlet system comprises a gas inlet chamber, the gas inlet chamber is communicated with a plurality of gas inlet channels, a plurality of groups of first automatic heaters are arranged in the gas inlet chamber, and the ultraviolet crosslinking and heat treatment system comprises a closed treatment chamber. An air outlet channel is communicated between the air inlet chamber and the closed treatment chamber, the closed treatment chamber comprises a first cavity and a second cavity, a treatment platform for placing polycarbosilane fiber bundles is arranged in the first cavity, a plurality of groups of second automatic heaters are arranged in the first cavity, and a plurality of ultraviolet lamps are further arranged in the closed treatment chamber. The invention also discloses a cross-linking method of the polycarbosilane fiber, the cross-linking time is shortened and the cross-linking efficiency is improved by combining ultraviolet radiation cross-linking with thermal cross-linking, and the polycarbosilane fiber treated by the cross-linking method has better thermal stability, mechanical property and chemical stability and can meet more harsh use conditions.

Description

Technical Field

[0001] The invention relates to the technical field of fiber crosslinking treatment, and in particular to an ultraviolet crosslinking device and a crosslinking method for polycarbosilane fibers. Background Art

[0002] As an important class of polymer compounds, polycarbosilane plays a core role in the preparation of high-performance ceramic materials, especially the preparation of silicon carbide (SiC) fibers. In traditional processes, polycarbosilane is converted into high-performance SiC fibers through melt spinning, infusibility treatment, pyrolysis and final calcination. Among them, infusibility treatment is a key step to ensure that the fiber maintains its shape during the subsequent high-temperature pyrolysis process.

[0003] At present, the infusibility treatment of polycarbosilane fibers mainly adopts thermal oxidation, electron beam irradiation crosslinking and chemical vapor phase infusibility, among which: 1. Thermal oxidation is a commonly used infusible treatment method, but it introduces a large amount of oxygen, which is not conducive to the high-temperature performance of the final ceramic fiber. For example, the existing silicon carbide fiber is treated with air infusibility, which introduces a certain amount (10 wt %~20 wt %), which seriously affects the high-temperature mechanical properties of the fiber; 2. Electron beam irradiation or gamma ray irradiation can achieve infusibility in an inert atmosphere and produce ceramic fibers with low oxygen content. However, this method requires huge initial investment in equipment and requires a high dose for infusibility treatment, which leads to rising costs. At the same time, conventional irradiation processing is difficult, which further increases the manufacturing cost of the fiber and reduces the production efficiency of polycarbosilane fiber. 3. Chemical vapor infusibility method, such as the oxygen-free infusibility method of polycarbosilane fiber, has the advantages of avoiding the introduction of oxygen, achieving the infusibility of polycarbosilane fiber at a lower temperature, uniform active atmosphere air flow field, and axial heating to make the fibers in different positions heated evenly. However, its reaction conditions are demanding. On the one hand, the treatment process is relatively complicated, involving the use and control of chemical gases, which increases the difficulty and complexity of the process. On the other hand, the emission of chemical gases may have adverse effects on the environment and has poor environmental protection. In addition, in the infusibility treatment of polycarbosilane and other fibers, the unsaturated hydrocarbon vapor used for chemical vapor crosslinking is toxic and harmful, and takes a long time, which is not conducive to large-scale production and application. Summary of the invention

[0004] The purpose of the present invention is to provide a UV cross-linking device and a cross-linking method for polycarbosilane fibers, which can reduce the cross-linking time and improve the cross-linking efficiency by combining UV radiation cross-linking with thermal cross-linking. The polycarbosilane fibers treated by the present invention have good thermal stability, mechanical properties and chemical stability, and can meet more stringent usage conditions.

[0005] In order to achieve the above object, the solution of the present invention is: A UV crosslinking device for polycarbosilane fiber, comprising an air intake system, a UV crosslinking and heat treatment system and a control system, wherein the air intake system comprises an air intake chamber, the air intake chamber is connected with a plurality of air intake channels, a plurality of groups of first automatic heaters are arranged in the air intake chamber, the UV crosslinking and heat treatment system comprises a closed treatment chamber, an air outlet channel is connected between the air intake chamber and the closed treatment chamber, the closed treatment chamber comprises a first cavity and a second cavity isolated from each other, the first cavity and the second cavity are arranged side by side, the first cavity and the second cavity are separated by a heat insulation board, a processing platform for placing polycarbosilane fiber bundles is arranged in the first cavity, the processing platform is provided with a rotating bracket for supporting the polycarbosilane fiber bundles and a first driving mechanism for driving the polycarbosilane fiber bundles to rotate, a plurality of groups of second automatic heaters distributed around the processing platform are arranged on the inner wall of the first cavity, a plurality of UV lamps are arranged in the closed treatment chamber, and a plurality of groups of first automatic heaters for each of the said The ultraviolet lamp moves to the second driving mechanism between the first cavity and the second cavity, each of the second driving mechanisms is located above the processing platform, a plurality of through holes for the ultraviolet lamp to pass through and for gas to flow are arranged on the insulation board, and insulation plugs for sealing the through holes are arranged at both ends of each ultraviolet lamp, a plurality of gas outlets connected to the vacuum processing system are arranged at the positions of the closed processing chamber corresponding to the first cavity and the second cavity, a three-way exhaust valve is arranged at the position of the closed processing chamber corresponding to the first cavity, one of the exhaust ports of the three-way exhaust valve is connected to the outside, and the other exhaust port of the three-way exhaust valve is connected to the second cavity, a two-way exhaust valve connected to the outside is arranged at the position of the closed processing chamber corresponding to the second cavity, and the closed processing chamber is coated with an ultraviolet shielding layer, and the control system is used to control the switches of the first driving mechanism, the second driving mechanism, the first automatic heater, the second automatic heater, the ultraviolet lamp, the vacuum processing system, the three-way exhaust valve and the two-way exhaust valve.

[0006] The air inlet chamber and the first cavity are respectively provided with temperature sensors connected to the control system, and the vacuum processing system is a vacuum pump.

[0007] A flow valve is provided on each of the air inlet passages, and the flow valve is controllably connected to the control system.

[0008] The closed processing chamber is provided with a feeding port at one end corresponding to the first cavity, and a sealing valve cover is provided at a position corresponding to the feeding port in the closed processing chamber. The inner surface of the sealing valve cover is fixedly connected to the processing platform, and the outer surface of the sealing valve cover is provided with a sliding frame. The closed processing chamber is fixed on the fixed frame, and the sliding frame is slidably connected to the fixed frame. A sliding rail that slidably cooperates with the processing platform is also provided in the first cavity.

[0009] Each of the second driving mechanisms includes a screw motor and a screw nut that cooperates with the screw of the screw motor. The bottom of each of the ultraviolet lamps is provided with a fixed base that is fixedly connected to the corresponding screw nut. Each of the screw motors is arranged at one end of the closed treatment chamber corresponding to the second cavity. One end of the screw of each of the screw motors passes between the first cavity and the second cavity and extends to one end of the closed treatment chamber corresponding to the first cavity. The heat insulation plugs at both ends of the ultraviolet lamp are respectively located on both sides of the heat insulation board.

[0010] The sliding frame is provided with a third driving mechanism for driving the sliding frame to slide, and the third driving mechanism is control-connected to the control system.

[0011] A cross-linking method for polycarbosilane fibers comprises the following steps: Step 1: first place the polycarbosilane fiber bundle on the processing platform, then send it into the first cavity of the closed processing chamber, use the vacuum processing system to evacuate the vacuum, and then pass the protective gas into the closed processing chamber through the air inlet chamber, at this time, the three-way exhaust valve is connected to the second cavity; Step 2, then controlling the second driving mechanism to work, sending each UV lamp from the second cavity into the first cavity, controlling the UV wavelength, intensity and irradiation time of the UV lamp, performing UV cross-linking treatment, and then controlling the second driving mechanism to work, sending each UV lamp from the first cavity back into the second cavity; Step 3, then controlling the heating rate, heating temperature and time of the second automatic heater to perform thermal crosslinking treatment on the polycarbosilane fiber bundle; Step 4: Finally, the heating rate, heating temperature and time of the second automatic heater are controlled to post-treat the polycarbosilane fiber bundles so as to convert the fiber molecules into an infusible mesh structure.

[0012] In step 1, the protective gas is one or a mixture of helium, argon and nitrogen, and the flow rate of the protective gas is 50-150 mL / min.

[0013] In step 2, the ultraviolet wavelength of the ultraviolet lamp is 320~400 nm, the intensity of the ultraviolet lamp is 10~30mW / cm, and the irradiation time is controlled according to the thickness of the polycarbosilane fiber bundle. In step 3, the heating rate is 1~5℃ / min, the heating temperature is 180~250℃, and the heating time is 6~8h.

[0014] In step 4, the heating rate is 1-5°C / min, the heating temperature is 330-350°C, and the heating time is 25-35 min.

[0015] After adopting the above technical solution, the UV cross-linking device and cross-linking method of polycarbosilane fiber of the present invention have the following advantages: 1. A rotating bracket is set on the processing platform. The rotation of the rotating bracket realizes all-round ultraviolet radiation of the polycarbosilane fiber, ensuring that each fiber can obtain a uniform cross-linking effect and improving product quality; the air intake system, vacuum exhaust system, three-way exhaust valve and two-way exhaust valve are used to realize the circulation of protective gas, exhaust oxygen, reduce oxidation reaction and optimize the cross-linking environment; by controlling the second automatic heater, the temperature of the cross-linking area is accurately controlled and kept within the optimal cross-linking temperature range of the fiber, which not only promotes the cross-linking reaction but also avoids fiber damage; 2. First, use an efficient and stable UV lamp that can emit UV rays of a specific wavelength to effectively excite the active groups on the surface of the polycarbosilane fiber and promote the cross-linking reaction. Then, perform thermal cross-linking treatment in an oxygen-free environment and precisely control the heating rate and insulation time. Finally, perform post-treatment in an inert atmosphere to reduce the oxygen content and consolidate the cross-linking structure. 3. Ultraviolet cross-linking is used to form a cross-linked layer on the surface of the polycarbosilane fiber, while thermal cross-linking further consolidates and improves the cross-linked structure from the inside. The combination of the two can make the polycarbosilane fiber form a more uniform and dense three-dimensional network structure, effectively improving the overall stability and performance of the fiber; 4. After the combined cross-linking treatment, the polycarbosilane fiber has good thermal stability, mechanical properties and chemical stability. Under high temperature environment, it can maintain good shape and structural integrity, withstand higher tensile stress, and its tolerance to chemical reagents is greatly improved, which can meet more demanding use conditions; 5. No chemical cross-linking agent is needed, thus avoiding the environmental pollution and influence on material properties caused by chemical cross-linking agents.

[0016] Furthermore, the present invention ensures the stability and repeatability of the process by precisely controlling various parameters (such as ultraviolet wavelength, intensity, irradiation time, thermal cross-linking temperature, insulation time and heating rate, etc.).

[0017] Furthermore, a third driving mechanism for driving the sliding frame to slide is provided on the sliding frame, so as to realize automatic auxiliary material feeding and discharging, save more labor, improve production efficiency and reduce operation difficulty. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a structural schematic diagram of a UV cross-linking device for polycarbosilane fibers of the present invention; Figure 2 It is a schematic diagram of the top view of the air intake system and the ultraviolet cross-linking and heat treatment system in the present invention; Figure 3 It is a side view structural schematic diagram of the ultraviolet cross-linking and heat treatment system in the present invention; Figure 4 This is an electron microscope image of silicon carbide fiber obtained by post-processing the polycarbosilane fiber in Example 2; Figure 5 This is an electron microscope image of the silicon carbide fiber obtained by post-processing the polycarbosilane fiber in Example 3.

[0019] In the figure: Intake chamber 1; Intake passage 11; Flow valve 12; first automatic heater 2; Sealed processing chamber 3; first cavity 31; A second automatic heater 311; a slide rail 312; Second cavity 32; Sealing valve cover 33; Ultraviolet lamp 34; heat insulation plug 341; Three-way exhaust valve 35; two-way exhaust valve 36; Processing platform 4; Rotating support 41; Rotation axis 411; crossbar 412; First driving mechanism 42; screw motor 51; Screw rod 511; screw rod nut 52; Sliding frame 6; pulley 61; The third driving mechanism 62; the fixing frame 7; Guide rail 71; Air outlet channel 8; Vacuum processing system 9; control system 10; Drum 1a. DETAILED DESCRIPTION

[0020] In order to further explain the technical solution of the present invention, the present invention is described in detail below through specific embodiments.

[0021] Embodiment 1 A UV cross-linking device for polycarbosilane fibers, such as Figure 1-Figure 3As shown, it includes an air intake system, a UV cross-linking and heat treatment system and a control system. The air intake system includes an air intake chamber 1. The air intake chamber 1 is connected to a plurality of air intake channels 11 for introducing protective gas. A flow valve 12 is provided on each air intake channel 11.

[0022] A plurality of groups of first automatic heaters 2 are arranged in the air intake chamber 1. Each group of first automatic heaters 2 is arranged axially around the inner wall of the air intake chamber 1. The first automatic heaters 2 are heating rods or heating tubes.

[0023] The UV cross-linking and heat treatment system includes a closed processing chamber 3, which includes a first cavity 31 and a second cavity 32 that are isolated from each other. The first cavity 31 and the second cavity 32 are arranged side by side, and the first cavity 31 and the second cavity 32 are separated by an insulation board. The insulation board is made of a well-known insulation material, such as a board wrapped with insulation cotton with aluminum foil.

[0024] A feeding port is provided at one end of the closed processing chamber 3 corresponding to the first cavity 31, and a sealing valve cover 33 is provided at the position of the closed processing chamber 3 corresponding to the feeding port. A processing platform 4 for placing polycarbosilane fiber bundles is provided in the first cavity 31, and a rotating bracket 41 for supporting the polycarbosilane fiber bundles and a first driving mechanism 42 for driving the polycarbosilane fiber bundles to rotate are provided on the processing platform 4. The inner surface of the sealing valve cover 33 is fixedly connected to one end of the processing platform 4. The polycarbosilane fiber bundle is usually wound on the drum 1a. The rotating bracket 41 includes a rotating shaft 411 passing through the center of the drum 1a. The rotating bracket 41 also includes a plurality of cross bars 412 mounted on the processing platform 4. The rotating shaft 411 and the cross bars 412 are on the same horizontal plane. These plurality of cross bars 412 are also passed through the drum 1a. The output end of the first driving mechanism 42 is connected to the rotating shaft 411. The first driving mechanism 42 is a driving mechanism well known in the art. For example, a driving motor is used to drive the rotating shaft 411 to rotate through the first driving mechanism 42, so that the drum 1a rotates around the rotating shaft 411.

[0025] The inner wall of the first cavity 31 is provided with several groups of second automatic heaters 311 distributed around the processing platform 4, and the second automatic heaters 311 are heating rods or heating tubes. The closed processing chamber 3 is also provided with several ultraviolet lamps 34 located above the processing platform 4, and the closed processing chamber 3 is also provided with several groups of second driving mechanisms for each ultraviolet lamp 34 to move between the first cavity 31 and the second cavity 32. The second driving mechanism is located above the processing platform 4, so that when the ultraviolet lamp 34 slides into the first cavity 31, it can be located above the processing platform 4 to perform ultraviolet cross-linking treatment on the polycarbosilane fiber bundles. Since the ultraviolet lamp 34 cannot withstand high temperatures, when the polycarbosilane fiber bundles need to be thermally cross-linked, each ultraviolet lamp 34 needs to be moved to the second cavity 33 by the second driving mechanism to avoid damage to the ultraviolet lamp 34 caused by high temperature heating.

[0026] The heat insulation board is provided with a plurality of through holes for the ultraviolet lamp 34 to pass through and for the gas to flow, so that the ultraviolet lamp 34 can move back and forth between the first cavity 31 and the second cavity 32. Preferably, there are two ultraviolet lamps 34, which are symmetrically arranged on both sides above the processing platform 4. Correspondingly, there are two second driving mechanisms and two through holes.

[0027] Both ends of each ultraviolet lamp 34 are provided with heat-insulating plugs 341 for sealing each through hole, which are respectively located on both sides of the heat-insulating plate, that is, one heat-insulating plug 341 is always located in the first cavity 31, and the other heat-insulating plug 341 is always located in the second cavity 32. When each ultraviolet lamp 34 is completely located in the second cavity 32, the heat-insulating plug 341 of the ultraviolet lamp 34 located in the first cavity 31 is stuck in the through hole to prevent hot air from entering the second cavity 32. When each ultraviolet lamp 34 is completely located in the first cavity 31, the heat-insulating plug 341 of the ultraviolet lamp 34 located in the second cavity 32 is stuck in the through hole. Preferably, when each ultraviolet lamp 34 is completely located in the second cavity 32, it is just located above the processing platform 4.

[0028] The second driving mechanism is a driving mechanism well known in the art, for example, each second driving mechanism includes a screw motor 51 and a screw nut 52 matched with a screw 511 of the screw motor 51, the bottom of each ultraviolet lamp 34 is fixedly connected to the corresponding screw nut 52, and can also be fixedly connected to the screw nut 52 through a fixing seat, each screw motor 51 is arranged outside one end of the closed treatment chamber 3 corresponding to the second cavity 32, and one end of the screw 511 of each screw motor 51 passes between the first cavity 31 and the second cavity 32 and extends to one end of the closed treatment chamber 3 corresponding to the first cavity 31. The screw nut 52 is driven to move on the screw 51 by the rotation of the screw 511 of the screw motor 51, thereby realizing the horizontal movement of each ultraviolet lamp 34.

[0029] A three-way exhaust valve 35 is provided at a position of the sealed processing chamber 3 corresponding to the first cavity 31, one of the exhaust ports of the three-way exhaust valve 35 is connected to the outside, and the other exhaust port of the three-way exhaust valve 35 is connected to the second cavity 32. A two-way exhaust valve 36 connected to the outside is provided at a position of the sealed processing chamber 3 corresponding to the second cavity 32. This arrangement can ensure that the atmosphere and air pressure in the first cavity 31 and the second cavity 32 are consistent, and ensure the normal operation of the second driving mechanism.

[0030] The outer surface of the sealing valve cover 33 is provided with a sliding frame 6, the closed processing chamber 3 is fixed on a fixed frame 7, and pulleys 61 are symmetrically provided on both sides of the lower end of the sliding frame 6, and guide rails 71 that slide with each pulley 61 are provided on both sides of the fixed frame 7, so that the sliding frame 6 is slidably connected with the fixed frame 7, and a slide rail 312 that slides with the processing platform 4 is also provided in the first cavity 31. The sliding frame 6 is symmetrically provided with a third driving mechanism 62 for driving the sliding frame 6 to slide. The third driving mechanism 62 is a driving mechanism known in the art, such as a stepping motor, and the output shaft of the third driving mechanism 62 is respectively connected to the corresponding pulley 61 in a transmission manner. This arrangement enables the processing platform 4 to automatically slide relative to the closed processing chamber 3, and the material loading and unloading is more convenient and labor-saving.

[0031] The closed processing chamber 3 is coated with an ultraviolet shielding layer, which is a well-known coating in the art that can block ultraviolet rays, such as a coating formed by coating with KINGCELA rare earth ultraviolet shielding agent.

[0032] An outlet passage 8 is connected between the air inlet chamber 1 and the closed processing chamber 3, and the outlet passage 8 is used to pass the protective gas into the closed processing chamber 3. The closed processing chamber 3 is provided with a plurality of gas outlets connected to the vacuum processing system 9 at positions corresponding to the first cavity 31 and the second cavity 32. Specifically, there are two gas outlets at the first cavity 31 and the second cavity 32. The vacuum processing system 9 is a vacuum pump.

[0033] Preferably, the position of the sealed processing chamber 3 corresponding to the second cavity 32 is provided with an inspection port ( (not shown in the figure) for easy maintenance.

[0034] The UV cross-linking device also includes a control system 10, which is used to control the switches of the flow valve 12, the first drive mechanism 42, the second drive mechanism, the third drive mechanism 62, the first automatic heater 2, the second automatic heater 311, the UV lamp 34, the vacuum pump, the three-way exhaust valve 35 and the two-way exhaust valve 36. The control system 10 is also a system well known in the art, such as a PLC control system, and the control method is also a control method well known in the art.

[0035] Temperature sensors (not shown in the figure) connected to the control system 10 are respectively provided in the air intake chamber 1 and the closed processing chamber 3, so as to achieve accurate control of the temperature in the air intake chamber 1 and the closed processing chamber 3.

[0036] Embodiment 2 A cross-linking method for polycarbosilane fibers comprises the following steps: Step 1, first place a polycarbosilane fiber bundle with a diameter of 12-13 μm on the processing platform 4, then turn on the third driving mechanism 62, send the polycarbosilane fiber bundle into the closed processing chamber 3, use a vacuum pump to evacuate, and then pass helium into the closed processing chamber 3 through the outlet channel 8 of the air inlet chamber 1, and control the flow rate of helium to 50 mL / min through the flow valve 12. At this time, the three-way exhaust valve 35 is connected to the second cavity 32 to ensure that the atmosphere and air pressure of the first cavity 31 and the second cavity 32 are the same; Step 2, then control the second driving mechanism to work, send each ultraviolet lamp 34 from the second cavity 32 into the first cavity 31, control the ultraviolet wavelength, intensity and irradiation time of the ultraviolet lamp 34, wherein the ultraviolet wavelength is 365 nm, the intensity of the ultraviolet lamp 34 is 10 mW / cm, and the irradiation time is 30 min, turn on the first driving mechanism 42, rotate the drum 1a, and perform a full range of ultraviolet cross-linking treatment, and after the treatment is completed, control the second driving mechanism to work again, so that each ultraviolet lamp 34 is sent back from the first cavity 31 to the second cavity 32; Step 3, then controlling the heating rate, heating temperature and time of the second automatic heater 311, wherein the heating rate is 2°C / min, the heating temperature is 180°C, and the heating time is 6 h, to perform thermal crosslinking treatment on the polycarbosilane fiber bundle; Step 4. Finally, the heating rate, heating temperature and time of the second automatic heater 311 are controlled, wherein the heating rate is 2°C / min, the heating temperature is 340°C, and the heating time is 30 min. The polycarbosilane fiber bundles are post-processed to convert the fiber molecules into an infusible network structure, and the gas in the closed processing chamber 3 is released through the three-way exhaust valve 35 and the two-way exhaust valve 36.

[0037] In step 1, the temperature of the protective gas can also be controlled by controlling the heating temperature of the first automatic heater 2. The heating temperature is kept consistent with the second automatic heater 311 to reduce the heat taken away by the entry of the gas and the fluctuation of the performance of the polycarbosilane fiber. Embodiment 3 A cross-linking method for polycarbosilane fibers comprises the following steps: Step 1, first place a polycarbosilane fiber bundle with a diameter of 15-16 μm on the processing platform 4, then turn on the third driving mechanism 62, send the polycarbosilane fiber bundle into the closed processing chamber 3, use a vacuum pump to evacuate, and then pass helium into the closed processing chamber 3 through the outlet channel 8 of the air inlet chamber 1, and control the flow rate of helium to 150 mL / min through the flow valve 12. At this time, the three-way exhaust valve 35 is connected to the second cavity 32 to ensure that the atmosphere and air pressure of the first cavity 31 and the second cavity 32 are the same; Step 2, then control the second driving mechanism to work, send each ultraviolet lamp 34 from the second cavity 32 into the first cavity 31, control the ultraviolet wavelength, intensity and irradiation time of the ultraviolet lamp 34, wherein the ultraviolet wavelength is 400 nm, the intensity of the ultraviolet lamp 34 is 30 mW / cm, and the irradiation time is 3 h, turn on the first driving mechanism 42, so that the drum 1a rotates, and performs a full range of ultraviolet cross-linking treatment. After the treatment is completed, control the second driving mechanism to work again, so that each ultraviolet lamp is sent back from the first cavity 31 to the second cavity 32; Step 3, then controlling the heating rate, heating temperature and time of the second automatic heater 311, wherein the heating rate is 2°C / min, the heating temperature is 250°C, and the heating time is 8h, to perform thermal crosslinking treatment on the polycarbosilane fiber bundle; Step 4. Finally, the heating rate, heating temperature and time of the second automatic heater 311 are controlled, wherein the heating rate is 2°C / min, the heating temperature is 350°C, and the heating time is 35 min. The polycarbosilane fiber bundles are post-processed to convert the fiber molecules into an infusible network structure, and the gas in the closed processing chamber 3 is released through the three-way exhaust valve 35 and the two-way exhaust valve 36.

[0038] The terms "first", "second" and the like in the description and claims of the present invention are used to distinguish different objects rather than to distinguish a specific order.

[0039] Performance Testing 1. Morphology of silicon carbide fiber The polycarbosilane cross-linked fibers obtained by cross-linking in Example 2 and Example 3 were converted into high-performance SiC fibers through steps such as hydrogen pyrolysis at 1250°C and high-temperature final calcination at 1600°C. The morphology of the silicon carbide fibers is as follows: Figure 4 and Figure 5 Its diameter is shown in Table 1.

[0040] Table 1 Single fiber diameter

[0041] The single fiber diameter of Example 2 is 10.6 μm. The relatively thin diameter gives the fiber an advantage in some specific applications. For example, when preparing high-performance composite materials, thinner fibers can be more evenly dispersed in the matrix, enhancing the overall performance of the material. At the same time, the smaller diameter may also make the fiber easier to use in some narrow spaces or in situations where there are strict requirements on material thickness. The single fiber diameter Cv is 7.25%, indicating that the consistency of the fiber diameter is good, which helps to ensure the stability and reliability of the material performance. In practical applications, the uniformity of the fiber diameter is crucial to the control of product quality.

[0042] The single fiber diameter of Example 3 is 12.5 μm. A thicker diameter may have unique advantages in certain applications. For example, in situations where greater external forces need to be withstood or higher wear resistance is required, thicker diameter fibers can provide stronger load-bearing capacity and better durability. In addition, thicker fibers may be easier to handle during processing and handling, reducing production difficulties. The single fiber diameter Cv is 7.85%, which also shows good diameter consistency. This helps to ensure the performance stability of the fiber during use and reduce quality problems caused by diameter differences.

[0043] 2. Tensile performance test Table 2 Tensile properties test results

[0044] The mechanical properties of SiC fiber are one of the important indicators to determine whether it can work for a long time in a high temperature environment. The tensile strength of the silicon carbide fiber corresponding to Example 2 is as high as 2.8 GPa, showing strong tensile resistance. This enables the silicon carbide fiber of Example 2 to withstand large external forces without breaking when used as a structural reinforcement material, providing reliable mechanical support for the product. Its tensile elastic modulus reaches 346 GPa, with high stiffness. This means that the silicon carbide fiber deforms less when subjected to force and can maintain the stability of the structure. The tensile strength of the silicon carbide fiber corresponding to Example 3 is 2.6 GPa, which is slightly lower than that of Example 2, but still at a relatively high level. This shows that the silicon carbide fiber of Example 3 has good performance in withstanding tensile loads and can meet the requirements of most structural materials.

[0045] 3. High temperature strength retention rate (1) Silicon carbide fiber obtained by processing in Example 2 Table 3 High temperature strength retention rate of silicon carbide fiber

[0046] In an air atmosphere, the silicon carbide fiber corresponding to Example 2 exhibits a high high-temperature strength retention rate at different temperatures. For example, under the conditions of air-1300℃-2000s, the high-temperature strength retention rate is 82.9%, which shows that even at relatively high temperatures and in an aerobic environment, the fiber can still maintain most of its initial strength. As the temperature rises to 1400℃ and 1500℃, although the high-temperature strength retention rate decreases, it still remains at 58.6% and 58.2%, respectively. This shows that at higher temperatures, the fiber still has a certain strength retention ability, reflecting its adaptability in a wider temperature range. For some application scenarios that may face temperature fluctuations, this feature can ensure that the material can play a certain role under different temperature conditions and reduce performance instability caused by temperature changes.

[0047] Under argon atmosphere, the high-temperature strength retention rate of the silicon carbide fiber corresponding to Example 2 is further improved. Under Ar-1300℃-2000s conditions, the high-temperature strength retention rate is as high as 87.5%, which is significantly higher than the same temperature conditions under air atmosphere. This is because the inertness of argon can effectively protect the fiber from oxidation and other chemical reactions, thereby better maintaining the strength of the fiber. When the temperature rises to 1400℃ and 1500℃, the high-temperature strength retention rates are 62.9% and 59.3%, respectively. Although they have decreased, they still remain at a high level. This shows that under the protection of argon, the fiber can still maintain good strength at higher temperatures, providing more possibilities for applications in high temperature environments.

[0048] From the test data under different temperature and atmosphere conditions, it can be seen that the high-temperature strength retention rate of the silicon carbide fiber corresponding to Example 2 is relatively stable with a small fluctuation range. This shows that the silicon carbide fiber has good performance consistency under different environments and can provide reliable performance guarantee for practical applications. Whether in air atmosphere or argon atmosphere, whether at lower or higher temperatures, the fiber can maintain a certain strength, reducing the risk caused by unstable performance.

[0049] (2) Silicon carbide fiber obtained by processing in Example 3 Table 4 High temperature strength retention rate of silicon carbide fiber

[0050] The silicon carbide fiber corresponding to Example 3 exhibits a certain high-temperature strength retention ability in both air and argon atmospheres. Under the conditions of air-1300℃-2000s, the high-temperature strength retention rate is 81.5%, which is slightly lower than that of Example 2, but still at a relatively high level. This shows that the fiber can resist the influence of high temperature to a certain extent in an air atmosphere, and is suitable for some application scenarios that require high high-temperature resistance of materials. As the temperature rises to 1400℃ and 1500℃, the high-temperature strength retention rates are 58.8% and 54.6%, respectively. Although the strength has decreased, it can still maintain a certain strength, showing the adaptability of the fiber at higher temperatures. For some industrial applications that may face high-temperature challenges, this feature can provide more possibilities for material selection.

[0051] Under argon atmosphere, the high temperature strength retention rate of the silicon carbide fiber corresponding to Example 3 is also improved. Under Ar-1300℃-2000s conditions, the high temperature strength retention rate is 84.2%, which is higher than the same temperature conditions under air atmosphere. This shows that the inert environment of argon plays a positive role in the high temperature strength retention of the fiber. When the temperature rises to 1400℃ and 1500℃, the high temperature strength retention rates are 63.5% and 58.1%, respectively. Although they have decreased, they still remain at a relatively high level. This shows that under the protection of argon, the fiber can still maintain good strength at higher temperatures, which provides a certain guarantee for its application in high temperature environments.

[0052] The above embodiments and drawings do not limit the product form and style of the present invention. Any appropriate changes or modifications made by ordinary technicians in the relevant technical field should be deemed to be within the patent scope of the present invention.

Claims

1. A UV crosslinking device for polycarbosilane fiber, comprising an air intake system, a UV crosslinking and heat treatment system and a control system, characterized in that: The air intake system includes an air intake chamber, which is connected to a plurality of air intake channels, and a plurality of groups of first automatic heaters are arranged in the air intake chamber. The ultraviolet cross-linking and heat treatment system includes a closed treatment chamber, and an air outlet channel is connected between the air intake chamber and the closed treatment chamber. The closed treatment chamber includes a first cavity and a second cavity isolated from each other, and the first cavity and the second cavity are arranged side by side, and the first cavity and the second cavity are separated by a heat insulation board. A processing platform for placing polycarbosilane fiber bundles is arranged in the first cavity, and the processing platform is provided with a rotating bracket for supporting the polycarbosilane fiber bundles and a first driving mechanism for driving the polycarbosilane fiber bundles to rotate. A plurality of groups of second automatic heaters distributed around the processing platform are arranged on the inner wall of the first cavity. A plurality of ultraviolet lamps are arranged in the closed treatment chamber, and a plurality of groups of ultraviolet lamps for each of the ultraviolet lamps to move between the first cavity and the second cavity are also arranged in the closed treatment chamber. a second driving mechanism between the two chambers, each of the second driving mechanisms is located above the processing platform, a plurality of through holes for the ultraviolet lamp to pass through and for gas to flow are arranged on the heat insulation board, and heat insulation plugs for sealing the through holes are respectively arranged at both ends of each of the ultraviolet lamps, a plurality of gas outlets connected to the vacuum processing system are respectively arranged at positions of the closed processing chamber corresponding to the first cavity and the second cavity, a three-way exhaust valve is arranged at a position of the closed processing chamber corresponding to the first cavity, one of the exhaust ports of the three-way exhaust valve is connected to the outside, and the other exhaust port of the three-way exhaust valve is connected to the second cavity, a two-way exhaust valve connected to the outside is arranged at a position of the closed processing chamber corresponding to the second cavity, and the closed processing chamber is coated with an ultraviolet shielding layer, and the control system is used to control the switches of the first driving mechanism, the second driving mechanism, the first automatic heater, the second automatic heater, the ultraviolet lamp, the vacuum processing system, the three-way exhaust valve and the two-way exhaust valve.

2. The ultraviolet cross-linking device for polycarbosilane fibers according to claim 1, characterized in that: The air inlet chamber and the first cavity are respectively provided with temperature sensors connected to the control system, and the vacuum processing system is a vacuum pump.

3. The ultraviolet cross-linking device for polycarbosilane fibers according to claim 1, characterized in that: A flow valve is provided on each of the air inlet passages, and the flow valve is controllably connected to the control system.

4. The ultraviolet cross-linking device for polycarbosilane fibers according to claim 1, characterized in that: Each of the second driving mechanisms includes a screw motor and a screw nut that cooperates with the screw of the screw motor. The bottom of each of the ultraviolet lamps is provided with a fixed base that is fixedly connected to the corresponding screw nut. Each of the screw motors is arranged at one end of the closed treatment chamber corresponding to the second cavity. One end of the screw of each of the screw motors passes between the first cavity and the second cavity and extends to one end of the closed treatment chamber corresponding to the first cavity. The heat insulation plugs at both ends of the ultraviolet lamp are respectively located on both sides of the heat insulation board.

5. The ultraviolet cross-linking device for polycarbosilane fiber according to claim 1, characterized in that: The closed processing chamber is provided with a feeding port at one end corresponding to the first cavity, and a sealing valve cover is provided at a position corresponding to the feeding port in the closed processing chamber. The inner surface of the sealing valve cover is fixedly connected to the processing platform, and the outer surface of the sealing valve cover is provided with a sliding frame. The closed processing chamber is fixed on the fixed frame, and the sliding frame is slidably connected to the fixed frame. A sliding rail that slidably cooperates with the processing platform is also provided in the first cavity.

6. The ultraviolet cross-linking device for polycarbosilane fibers according to claim 5, characterized in that: The sliding frame is provided with a third driving mechanism for driving the sliding frame to slide, and the third driving mechanism is control-connected to the control system.

7. A crosslinking method using a polycarbosilane fiber ultraviolet crosslinking device as claimed in claim 1, characterized in that: The following steps are involved: Step 1: first place the polycarbosilane fiber bundle on the processing platform, then send it into the first cavity of the closed processing chamber, use the vacuum processing system to evacuate the vacuum, and then pass the protective gas into the closed processing chamber through the air inlet chamber, at this time, the three-way exhaust valve is connected to the second cavity; Step 2, then controlling the second driving mechanism to work, sending each UV lamp from the second cavity into the first cavity, controlling the UV wavelength, intensity and irradiation time of the UV lamp, performing UV cross-linking treatment, and then controlling the second driving mechanism to work, sending each UV lamp from the first cavity back into the second cavity; Step 3, then controlling the heating rate, heating temperature and time of the second automatic heater to perform thermal crosslinking treatment on the polycarbosilane fiber bundle; Step 4: Finally, the heating rate, heating temperature and time of the second automatic heater are controlled to post-treat the polycarbosilane fiber bundles so as to convert the fiber molecules into an infusible mesh structure.

8. A method for crosslinking polycarbosilane fibers according to claim 7, characterized in that: In step 1, the protective gas is one or a mixture of helium, argon and nitrogen, and the flow rate of the protective gas is 50-150 mL / min.

9. The cross-linking method of polycarbosilane fiber according to claim 7, characterized in that: In step 2, the ultraviolet wavelength of the ultraviolet lamp is 320~400 nm, the intensity of the ultraviolet lamp is 10~30 mW / cm, and the irradiation time is controlled according to the thickness of the polycarbosilane fiber bundle. In step 3, the heating rate is 1~5℃ / min, the heating temperature is 180~250℃, and the heating time is 6~8 h.

10. The cross-linking method of polycarbosilane fiber according to claim 7, characterized in that: In step 4, the heating rate is 1-5°C / min, the heating temperature is 330-350°C, and the heating time is 25-35 min.

Images