High performance quartz fiber reinforced polyimide radome forming process

Abstract

This invention belongs to the field of composite material technology, specifically relating to a high-performance quartz fiber reinforced polyimide radome molding process. The high-performance quartz fiber reinforced polyimide radome molding process of this invention includes the following steps: S1, preparing intermediate A using 4-(chloromethyl)phenyltrimethoxysilane and thiourea as raw materials, then mixing it with diethylamine for a neutralization reaction to obtain a mercaptosilane coupling agent; pretreating 2.5D quartz fiber braid, then impregnating and modifying it with the mercaptosilane coupling agent to obtain a silane-modified 2.5D quartz fiber braid; S2, using an RTM molding process to mold the silane-modified 2.5D quartz fiber braid and polyimide into a composite material, heating and curing to obtain a high-performance quartz fiber reinforced polyimide radome. This invention achieves excellent comprehensive performance through the synergistic effect between components, realizing high load-bearing capacity and high temperature resistance of the radome composite material.

Description

Technical Field

[0001] This invention belongs to the field of composite material technology, specifically relating to a high-performance quartz fiber reinforced polyimide radome molding process. Background Technology

[0002] The radome is a crucial component of a missile, needing to protect it from damage, withstand various harsh environments encountered during flight, and meet guidance requirements. The higher the missile's speed, the more intense the friction with the air during flight, generating aerodynamic heating and causing the missile's surface temperature to rise continuously. This results in a very high rate of temperature increase on the radome walls. Hypersonic missiles experience enormous shear forces, axial forces, and bending moments due to overloads in different directions during flight, thus placing extremely high demands on the mechanical properties of the radome materials. Furthermore, they must possess excellent wave transmission capabilities.

[0003] The main molding processes for radomes include wet hand lay-up molding, dry prepreg molding, and closed-mold molding. Wet hand lay-up molding is an open-mold process with low-cost molds and equipment, and strong process applicability, making it widely used in low- to mid-range civilian products. However, its application is increasingly limited due to factors such as excessive volatile organic compound emissions, significant health impacts on operators, low product performance, and poor quality consistency. Dry prepreg molding is generally used in weaponry and aerospace applications with high performance requirements. Its high mold and equipment costs, relatively complex processes, and high raw material prices make it difficult to commercialize. Closed-mold molding utilizes positive and negative pressure to inject resin into pre-laid fiber reinforcement material within a closed mold until complete impregnation and curing. This process offers advantages such as excellent product performance, stable quality, high production efficiency, low cost, and environmental friendliness, and has also found widespread application in radome products.

[0004] Chinese Patent (Announcement No. CN115925435B) discloses a rapid composite molding method for a 2.5D quartz composite ceramic radome, comprising the following steps: boiling the braided body in boiling high-purity water and then drying it; calcining it; mixing epichlorohydrin-dimethylamine polymer cationic modifier with high-purity water to prepare a solution with a concentration of 0.5%~1%; heating the braided body in the solution in a water bath, removing it and drying it to constant weight; placing the braided body in an RTM injection fixture; injecting anionic silica sol with a solid content of 40%~45% into the braided body, and after filling it, placing it together with the RTM injection fixture in an oven and drying it to constant weight; immersing the braided body in anionic silica sol with a solid content of 40%~45%, heating it in a water bath under a vacuum of -0.09MPa~-0.1MPa, removing it and drying it in an oven to constant weight; heat treatment; and processing it into a quartz composite ceramic radome product. This technology mainly uses silica sol RTM injection, but it lacks research on the load-bearing capacity and thermal stability of the radome.

[0005] Therefore, how to use 2.5D quartz fiber braid as the matrix material, polyimide as the injection component, and prepare quartz fiber reinforced polyimide radomes through RTM molding process, and improve the mechanical properties and thermogravimetric temperature of the composite material by introducing modified components to achieve high load-bearing capacity and high temperature resistance, has become a direction that needs to be studied. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a high-performance quartz fiber reinforced polyimide radome molding process. This invention uses a mercaptosilane coupling agent for surface modification to obtain a silane-modified 2.5D quartz fiber braid, and prepares a sulfonated hyperbranched polyimide with an amino hyperbranched polysiloxane core, rigid benzene ring polyimide segments as arms, and containing sulfonic acid groups. By controlling the parameters of the RTM molding process, a high-performance quartz fiber reinforced polyimide radome composite material is prepared. Through the synergistic effect between components, excellent comprehensive performance is achieved, realizing high load-bearing capacity and high temperature resistance of the radome composite material.

[0007] The present invention provides a high-performance quartz fiber reinforced polyimide radome molding process, comprising the following steps:

[0008] S1. Intermediate A is prepared from 4-(chloromethyl)phenyltrimethoxysilane and thiourea. Intermediate A is mixed with diethylamine and neutralized to obtain a mercaptosilane coupling agent. The 2.5D quartz fiber braid is pretreated first, and then the pretreated 2.5D quartz fiber braid is impregnated and modified with the mercaptosilane coupling agent to obtain a silane-modified 2.5D quartz fiber braid.

[0009] S2. The silane-modified 2.5D quartz fiber braid and polyimide are molded into a composite material using the RTM molding process and then cured by heating to obtain a high-performance quartz fiber reinforced polyimide radome.

[0010] As a preferred technical solution of the present invention, the preparation steps of intermediate A are as follows: 100-140 parts by weight of 4-(chloromethyl)phenyltrimethoxysilane, 40-50 parts by weight of thiourea and 2.2-2.4 parts by weight of potassium iodide are mixed and heated to 105-115°C under a nitrogen atmosphere and refluxed for 12-16 hours to obtain intermediate A.

[0011] As a preferred technical solution of the present invention, the neutralization reaction step is as follows: by weight, 30-40 parts of diethylamine are added to 100-140 parts of intermediate A at 40-50°C, the temperature is raised to 55-65°C for neutralization reaction for 2-4 hours, after the reaction is completed, 100-140 parts of petroleum ether are added and stirred for 2-4 hours, the filtrate is obtained by filtration, the filtrate is distilled and dried to obtain a mercaptosilane coupling agent.

[0012] This invention uses 4-(chloromethyl)phenyltrimethoxysilane as a starting material, reacts with thiourea under the catalysis of potassium iodide to obtain intermediate A. Diethylamine, as a strong organic base, provides an alkaline environment, and reacts with intermediate A through a neutralization reaction to obtain a mercaptosilane-containing coupling agent.

[0013] As a preferred technical solution of the present invention, the pretreatment step is as follows: immersing the 2.5D quartz fiber braid in a 1mol / L hydrochloric acid solution, sonicating at 50~60℃ for 50~60min, washing with deionized water, and drying to obtain the pretreated 2.5D quartz fiber braid.

[0014] The pretreatment of this invention can effectively remove residual organic sizing agents, grease, and dust from the fibers during production and weaving. At the same time, dilute hydrochloric acid soaking and ultrasonic-assisted treatment can achieve surface activation of the 2.5D quartz fiber braid, significantly improving its surface activity and enhancing the effect of subsequent impregnation modification.

[0015] As a preferred technical solution of the present invention, the impregnation modification step is as follows: by weight, 900-950 parts of anhydrous ethanol and 50-100 parts of deionized water are mixed, the pH is adjusted to 4-5, and then 10-20 parts of the mercaptosilane coupling agent are added and stirred for 20-30 minutes to obtain a silane impregnation solution. The pretreated 2.5D quartz fiber braid is immersed in the silane impregnation solution for 8-12 hours. After impregnation, it is washed with acetone and vacuum dried to obtain a silane-modified 2.5D quartz fiber braid.

[0016] The present invention first pre-treats the 2.5D quartz fiber braid with acid to remove oil or contaminants, and then impregnates it in a silane impregnation solution made of mercaptosilane coupling agent for impregnation modification, finally obtaining a silane-modified 2.5D quartz fiber braid containing mercapto and benzene rings.

[0017] The 2.5D quartz fiber braid of this invention reduces surface energy through silane treatment, making it easier for organic resin to wet and penetrate into the dense 2.5D braid, thereby reducing defects such as porosity. At the same time, the introduced benzene rings provide rigid support, increase the interfacial layer modulus, and prevent premature interface yielding. The synergistic effect results in good flexural strength and tensile strength, ensuring high load-bearing capacity of the composite material. In addition, the densification of the fiber-matrix interface between the silane-modified 2.5D quartz fiber braid and polyimide reduces thermal oxygen permeation channels, the rigid structure of the benzene rings inhibits the thermal motion of chain segments, and the mercapto groups and resins combine to achieve local cross-linking in the interfacial region, increasing the material's 5% thermal weight loss temperature and obtaining high-temperature resistance.

[0018] As a preferred embodiment of the present invention, the polyimide is a sulfonated hyperbranched polyimide.

[0019] As a preferred embodiment of the present invention, the preparation method of the sulfonated hyperbranched polyimide is as follows: amino hyperbranched molecules are prepared by using methyltrimethoxysilane and 3-aminopropyl(diethoxy)methylsilane as raw materials, and 4,4'-diaminostilbene-2,2'-disulfonic acid, 2,3,3',4'-biphenyltetracarboxylic dianhydride, 3-aminophenylacetylene and the amino hyperbranched molecules are mixed and subjected to polymerization reaction to obtain sulfonated hyperbranched polyimide.

[0020] The hyperbranched polysiloxane core of the sulfonated hyperbranched polyimide of this invention, as a multifunctional core, can form a three-dimensional extended topological structure. This structure can more effectively transfer and disperse stress and avoid stress concentration. At the same time, rigid segments such as benzene rings provide the material with high modulus and strength. The combined effect improves the flexural strength and tensile strength of the composite material and achieves high load-bearing capacity. In addition, the rigid benzene ring structure in the sulfonated hyperbranched polyimide can improve thermal stability, while the Si-O bond of the polysiloxane core can delay further thermal decomposition through high bond energy, effectively improving the high-temperature resistance of the material.

[0021] As a preferred technical solution of the present invention, the preparation steps of the amino hyperbranched molecule are as follows: by weight, 18-20 parts of methyltrimethoxysilane and 10-12 parts of 3-aminopropyl(diethoxy)methylsilane are mixed, then 150-160 parts of anhydrous ethanol and 4-6 parts of deionized water are added and stirred at room temperature for 50-60 min, heated to 65-75°C for 12-16 h, and rotary evaporated to obtain the amino hyperbranched molecule.

[0022] As a preferred embodiment of the present invention, the polymerization reaction steps are as follows: 20-24 parts by weight of 4,4'-diaminostilbene-2,2'-disulfonic acid are added to 130-140 parts of N-methylpyrrolidone, and stirred under a nitrogen atmosphere for 20-30 minutes. Then, 18-20 parts by weight of 2,3,3',4'-biphenyltetracarboxylic dianhydride and 30-40 parts by weight of N-methylpyrrolidone are added and stirred for 100-120 minutes. Next, 0.4-0.6 parts by weight of 3-aminophenylacetylene are added for end-capping treatment for 2-3 hours. Finally, 0.8-1.2 parts by weight of the amino hyperbranched molecules are added and stirred for 3-4 hours. Animation treatment is performed using a mixture of 24-26 parts by weight of acetic anhydride and 24-26 parts by weight of triethylamine for 3-4 hours. After the reaction is completed, 250-300 parts by weight of anhydrous ethanol are added to precipitate a solid, which is washed with anhydrous ethanol and dried under vacuum to obtain sulfonated hyperbranched polyimide.

[0023] This invention first uses methyltrimethoxysilane and 3-aminopropyl(diethoxy)methylsilane as raw materials to form an amino hyperbranched molecule with a Si-O-Si backbone through a hydrolysis-condensation reaction of silane; then, 4,4'-diaminostilbene-2,2'-disulfonic acid, 2,3,3',4'-biphenyltetracarboxylic dianhydride, 3-aminophenylacetylene and the amino hyperbranched molecule are mixed and polymerized to obtain sulfonated hyperbranched polyimide; the sulfonated hyperbranched polyimide has an amino hyperbranched polysiloxane as the core, rigid benzene ring polyimide segments as arms, and sulfonic acid groups suspended on the side chains.

[0024] As a preferred embodiment of the present invention, the flow rate of polyimide injected into the mold in the RTM molding process is 1~2L / min and the pressure is 0.2~0.4MPa.

[0025] As a preferred technical solution of the present invention, the heating curing step is as follows: first, cure at 150~160℃ for 100~120min, then cure at 180~190℃ for 100~120min, then cure at 200~210℃ for 120~140min, and finally cure at 240~250℃ for 120~140min.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) In this invention, a mercaptosilane coupling agent is first prepared, and then the agent is used to modify the surface of 2.5D quartz fiber braid to obtain silane-modified 2.5D quartz fiber braid. Then, sulfonated hyperbranched polyimide is compounded with the fiber braid using RTM molding process to obtain quartz fiber reinforced polyimide radome composite material. Through the synergistic effect between the materials, the composite material can achieve high load-bearing capacity and high temperature resistance, and has good application prospects.

[0028] (2) The silane-modified 2.5D quartz fiber braid of the present invention contains mercapto groups, which can undergo thiol-ene click crosslinking with the unsaturated bonds in sulfonated hyperbranched polyimide during high-temperature curing, thereby obtaining a chemical crosslinking network; at the same time, the benzene rings introduced on the fiber surface by silane modification can undergo π-π stacking and physical entanglement with the benzene rings carried by the synthetic raw materials in sulfonated hyperbranched polyimide, thereby constructing a physical interpenetrating reinforcement layer; through the combined effect of the chemical crosslinking network and the physical interpenetrating reinforcement layer, the comprehensive performance of the quartz fiber reinforced polyimide composite material is effectively improved, thereby obtaining a high-performance radome. Attached Figure Description

[0029] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is the FTIR spectrum of the mercaptosilane coupling agent in Example 1 of the present invention.

[0031] Figure 2 The image shows the XRD pattern of the sulfonated hyperbranched polyimide in Example 1 of this invention. Detailed Implementation

[0032] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0033] The sources of some components in the examples and comparative examples are as follows:

[0034] 4-(chloromethyl)phenyltrimethoxysilane, CAS No. 24413-04-5, was purchased from Hubei Fangde New Materials Co., Ltd.

[0035] Thiourea, CAS No. 62-56-6, purchased from Sinopharm Chemical Reagent Co., Ltd.

[0036] Potassium iodide, CAS No. 7681-11-0, was purchased from Sinopharm Chemical Reagent Co., Ltd.

[0037] Diethylamine, CAS No. 109-89-7, was purchased from Sinopharm Chemical Reagent Co., Ltd.

[0038] Methyltrimethoxysilane, CAS No. 1185-55-3, was purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0039] 3-Aminopropyl(diethoxy)methylsilane, CAS No. 3179-76-8, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0040] 4,4'-Diaminostilbene-2,2'-disulfonic acid, CAS No. 81-11-8, was purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0041] 2,3,3',4'-Biphenyltetracarboxylic dianhydride, CAS No. 36978-41-3, was purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0042] 3-Aminophenylacetylene, CAS No. 54060-30-9, purchased from Sinopharm Chemical Reagent Co., Ltd.;

[0043] Acetic anhydride, CAS No. 108-24-7, was purchased from Sinopharm Chemical Reagent Co., Ltd.

[0044] Triethylamine, CAS No. 121-44-8, was purchased from Sinopharm Chemical Reagent Co., Ltd.

[0045] Polyimide resin, item number P406634, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0046] Example 1

[0047] This embodiment provides a high-performance quartz fiber reinforced polyimide radome molding process, including the following steps:

[0048] S1. By weight, 140 parts of 4-(chloromethyl)phenyltrimethoxysilane, 50 parts of thiourea, and 2.4 parts of potassium iodide were mixed and heated to 115°C under a nitrogen atmosphere and refluxed for 12 hours to obtain intermediate A. 40 parts of diethylamine were added to 140 parts of intermediate A at 50°C, and the mixture was heated to 65°C for a neutralization reaction for 2 hours. After the reaction was complete, 140 parts of petroleum ether were added and stirred for 4 hours. The mixture was filtered to obtain a filtrate, which was then distilled and dried to obtain a mercaptosilane-containing coupling agent. A 2.5D quartz fiber braid was then immersed in... The 2.5D quartz fiber braid was pretreated by sonication at 60°C for 50 min in a 1 mol / L hydrochloric acid solution, followed by washing with deionized water and drying. 950 parts of anhydrous ethanol and 50 parts of deionized water were mixed, the pH was adjusted to 5, and 20 parts of the mercaptosilane coupling agent were added and stirred for 30 min to obtain a silane impregnation solution. The pretreated 2.5D quartz fiber braid was immersed in the silane impregnation solution for 12 h. After impregnation, it was washed with acetone and vacuum dried to obtain a silane-modified 2.5D quartz fiber braid.

[0049] S2. The silane-modified 2.5D quartz fiber braid and sulfonated hyperbranched polyimide are molded into a composite material using an RTM molding process (the flow rate of polyimide injected into the mold is 2L / min, and the pressure is 0.4MPa). The material is first cured at 160℃ for 100min, then cured at 190℃ for 1000min, then cured at 210℃ for 120min, and finally cured at 250℃ for 120min to obtain a high-performance quartz fiber reinforced polyimide radome.

[0050] Preparation of sulfonated hyperbranched polyimide: By weight, 20 parts of methyltrimethoxysilane and 12 parts of 3-aminopropyl(diethoxy)methylsilane were mixed, then 160 parts of anhydrous ethanol and 6 parts of deionized water were added and stirred at room temperature for 60 min. The mixture was then heated to 75 °C and reacted for 12 h. The mixture was then rotary evaporated to obtain amino hyperbranched molecules. 24 parts of 4,4'-diaminostilbene-2,2'-disulfonic acid were added to 140 parts of N-methylpyrrolidone and stirred under a nitrogen atmosphere for 30 min. Then, 20 parts of 2,3,3',4'-biphenyltetracarboxylic dianhydride and 40 parts of N-methylpyrrolidone were added and stirred for 120 min. Finally, 0.6 parts of 3- The aminophenylacetylene was end-capped for 3 hours, and then 1.2 parts of the amino hyperbranched molecule were added and stirred for 4 hours. The mixture of 26 parts of acetic anhydride and 26 parts of triethylamine was used for imidization for 4 hours. After the reaction was completed, 300 parts of anhydrous ethanol were added to precipitate the solid. The solid was washed with anhydrous ethanol and dried under vacuum to obtain sulfonated hyperbranched polyimide.

[0051] The FTIR spectrum of the mercaptosilane coupling agent in Example 1 is as follows: Figure 1 As shown, 2576cm -1 The absorption peak for SH is at 1386 cm⁻¹. -1 The peak at this location represents the deformation vibration of S-CH2; the XRD pattern of the sulfonated hyperbranched polyimide in Example 1 is shown below. Figure 2 As shown.

[0052] Example 2

[0053] This embodiment provides a high-performance quartz fiber reinforced polyimide radome molding process, including the following steps:

[0054] S1. By weight, 100 parts of 4-(chloromethyl)phenyltrimethoxysilane, 40 parts of thiourea, and 2.2 parts of potassium iodide are mixed and heated to 105°C under a nitrogen atmosphere and refluxed for 16 hours to obtain intermediate A; 30 parts of diethylamine are added to 100 parts of intermediate A at 40°C, and the mixture is heated to 55°C for a neutralization reaction for 4 hours. After the reaction is complete, 100 parts of petroleum ether are added and stirred for 2 hours. The mixture is filtered to obtain a filtrate, which is then distilled and dried to obtain a mercaptosilane-containing coupling agent; 2.5D quartz fiber braids are then immersed in... The 2.5D quartz fiber braid was pretreated by sonication at 50°C for 60 min in a 1 mol / L hydrochloric acid solution, followed by washing with deionized water and drying. 900 parts of anhydrous ethanol and 100 parts of deionized water were mixed, the pH was adjusted to 4, and 10 parts of the mercaptosilane coupling agent were added and stirred for 20 min to obtain a silane impregnation solution. The pretreated 2.5D quartz fiber braid was immersed in the silane impregnation solution for 8 h. After impregnation, it was washed with acetone and vacuum dried to obtain a silane-modified 2.5D quartz fiber braid.

[0055] S2. The silane-modified 2.5D quartz fiber braid and sulfonated hyperbranched polyimide are molded into a composite material using an RTM molding process (the flow rate of polyimide injected into the mold is 1L / min, and the pressure is 0.2MPa). The material is first cured at 150℃ for 120min, then cured at 180℃ for 120min, then cured at 200℃ for 140min, and finally cured at 240℃ for 140min to obtain a high-performance quartz fiber reinforced polyimide radome.

[0056] Preparation of sulfonated hyperbranched polyimide: By weight, 18 parts of methyltrimethoxysilane and 10 parts of 3-aminopropyl(diethoxy)methylsilane were mixed, then 150 parts of anhydrous ethanol and 4 parts of deionized water were added and stirred at room temperature for 50 min. The mixture was then heated to 65°C and reacted for 16 h. The mixture was then rotary evaporated to obtain amino hyperbranched molecules. 20 parts of 4,4'-diaminostilbene-2,2'-disulfonic acid were added to 130 parts of N-methylpyrrolidone and stirred under a nitrogen atmosphere for 20 min. Then, 18 parts of 2,3,3',4'-biphenyltetracarboxylic dianhydride and 30 parts of N-methylpyrrolidone were added and stirred for 100 min. Finally, 0.4 parts of 3- The aminophenylacetylene was end-capped for 2 hours, and then 0.8 parts of the amino hyperbranched molecule were added and stirred for 3 hours. The mixture of 24 parts of acetic anhydride and 24 parts of triethylamine was used for imidization for 3 hours. After the reaction was completed, 250 parts of anhydrous ethanol were added to precipitate the solid. The solid was washed with anhydrous ethanol and dried under vacuum to obtain sulfonated hyperbranched polyimide.

[0057] Example 3

[0058] This embodiment provides a high-performance quartz fiber reinforced polyimide radome molding process, including the following steps:

[0059] S1. By weight, 120 parts of 4-(chloromethyl)phenyltrimethoxysilane, 45 parts of thiourea, and 2.3 parts of potassium iodide were mixed and heated to 110°C under a nitrogen atmosphere and refluxed for 14 hours to obtain intermediate A; 35 parts of diethylamine were added to 120 parts of intermediate A at 45°C, and the mixture was heated to 60°C for a neutralization reaction for 3 hours. After the reaction was completed, 120 parts of petroleum ether were added and stirred for 3 hours. The mixture was filtered to obtain a filtrate, which was then distilled and dried to obtain a mercaptosilane-containing coupling agent; 2.5D quartz fiber braids were immersed in 1... The 2.5D quartz fiber braid was pretreated by sonicating in a mol / L hydrochloric acid solution at 55°C for 55 min, washing with deionized water, and drying. 920 parts of anhydrous ethanol and 80 parts of deionized water were mixed, the pH was adjusted to 4.5, and 15 parts of the mercaptosilane coupling agent were added and stirred for 25 min to obtain a silane impregnation solution. The pretreated 2.5D quartz fiber braid was immersed in the silane impregnation solution for 10 h. After impregnation, it was washed with acetone and vacuum dried to obtain a silane-modified 2.5D quartz fiber braid.

[0060] S2. The silane-modified 2.5D quartz fiber braid and sulfonated hyperbranched polyimide are molded into a composite material using an RTM molding process (the flow rate of polyimide injected into the mold is 1.5 L / min, and the pressure is 0.3 MPa). The mixture is first cured at 155℃ for 110 min, then at 185℃ for 110 min, then at 205℃ for 130 min, and finally at 245℃ for 130 min to obtain a high-performance quartz fiber reinforced polyimide radome.

[0061] Preparation of sulfonated hyperbranched polyimide: By weight, 19 parts of methyltrimethoxysilane and 11 parts of 3-aminopropyl(diethoxy)methylsilane were mixed, then 155 parts of anhydrous ethanol and 4-6 parts of deionized water were added and stirred at room temperature for 55 min. The mixture was then heated to 70°C and reacted for 14 h. The mixture was then rotary evaporated to obtain amino hyperbranched molecules. 22 parts of 4,4'-diaminostilbene-2,2'-disulfonic acid were added to 135 parts of N-methylpyrrolidone and stirred under a nitrogen atmosphere for 25 min. Then, 19 parts of 2,3,3',4'-biphenyltetracarboxylic dianhydride and 35 parts of N-methylpyrrolidone were added and stirred for 110 min. Finally, 0.5 parts of 3- The aminophenylacetylene was end-capped for 2.5 h, and then 1.0 part of the amino hyperbranched molecule was added and stirred for 3.5 h. The mixture of 25 parts of acetic anhydride and 25 parts of triethylamine was used for imidization for 3.5 h. After the reaction was completed, 280 parts of anhydrous ethanol were added to precipitate the solid. The solid was washed with anhydrous ethanol and dried under vacuum to obtain sulfonated hyperbranched polyimide.

[0062] Comparative Example 1

[0063] The difference between this comparative example and Example 1 is that a commercially available 2.5D quartz fiber braid is used instead of the silane-modified 2.5D quartz fiber braid.

[0064] Comparative Example 2

[0065] The difference between this comparative example and Example 1 is that no pretreatment is performed during the preparation of the silane-modified 2.5D quartz fiber braid.

[0066] Comparative Example 3

[0067] The difference between this comparative example and Example 1 is that a commercially available polyimide resin (product number P406634) was used instead of sulfonated hyperbranched polyimide.

[0068] The properties of the composite materials provided in the above embodiments and comparative examples were tested using the following methods:

[0069] (1) Load-bearing capacity test: The bending strength test is carried out with reference to GB / T 1449-2005 Test method for bending properties of fiber reinforced plastics, and the tensile strength test is carried out with reference to GB / T 1447-2005 Test method for tensile properties of fiber reinforced plastics. The load-bearing capacity of the material is evaluated using the bending strength and tensile strength.

[0070] (2) Temperature resistance test: Thermogravimetric analysis was performed on the examples and comparative examples using a thermogravimetric analyzer (TGA, model Q50, TA Instruments, USA). The test temperature range was 30~800℃, the heating rate was 20℃ / min, the gas atmosphere was nitrogen, and the sample mass was 5mg. The temperature resistance of the materials was evaluated using the 5% thermogravimetric temperature.

[0071] The performance test data above are shown in Table 1.

[0072] Table 1 Performance Test Results

[0073]

[0074] As can be seen from the above, the present invention uses a mercaptosilane coupling agent to perform surface modification to obtain a silane-modified 2.5D quartz fiber braid, and prepares a sulfonated hyperbranched polyimide with an amino hyperbranched polysiloxane core, rigid benzene ring polyimide segments as arms, and containing sulfonic acid groups. By controlling the parameters of the RTM molding process, a high-performance quartz fiber reinforced polyimide radome composite material (Examples 1 to 3) is obtained, which has the best comprehensive performance.

[0075] Compared to Example 1, the use of commercially available 2.5D quartz fiber braid instead of silane-modified 2.5D quartz fiber braid resulted in a lack of modification with a mercaptosilane coupling agent, leading to lower flexural and tensile strengths and a lower 5% thermogravimetric temperature (Comparative Example 1). Compared to Example 1, the lack of pretreatment during the preparation of the silane-modified 2.5D quartz fiber braid resulted in poor impregnation modification, leading to lower flexural and tensile strengths and a lower 5% thermogravimetric temperature (Comparative Example 2). Compared to Example 1, the use of commercially available polyimide resin (product number P406634) instead of sulfonated hyperbranched polyimide resulted in a lack of the effect of sulfonated hyperbranched polyimide, leading to lower flexural and tensile strengths and a lower 5% thermogravimetric temperature (Comparative Example 3).

Claims

1. A molding process for a quartz fiber reinforced polyimide radome, characterized in that, Includes the following steps: S1. Intermediate A is prepared from 4-(chloromethyl)phenyltrimethoxysilane and thiourea. Intermediate A is mixed with diethylamine and neutralized to obtain a mercaptosilane coupling agent. The 2.5D quartz fiber braid is pretreated first, and then the pretreated 2.5D quartz fiber braid is impregnated and modified with the mercaptosilane coupling agent to obtain a silane-modified 2.5D quartz fiber braid. The preparation steps of intermediate A are as follows: 100-140 parts by weight of 4-(chloromethyl)phenyltrimethoxysilane, 40-50 parts by weight of thiourea and 2.2-2.4 parts by weight of potassium iodide are mixed and heated to 105-115°C under a nitrogen atmosphere and refluxed for 12-16 hours to obtain intermediate A. The neutralization reaction steps are as follows: by weight, 30-40 parts of diethylamine are added to 100-140 parts of intermediate A at 40-50°C, the temperature is raised to 55-65°C for a neutralization reaction for 2-4 hours, after the reaction is completed, 100-140 parts of petroleum ether are added and stirred for 2-4 hours, the filtrate is obtained by filtration, the filtrate is distilled and dried to obtain a mercaptosilane coupling agent; The pretreatment steps are as follows: immerse the 2.5D quartz fiber braid in a 1mol / L hydrochloric acid solution, sonicate at 50~60℃ for 50~60min, wash with deionized water, and dry to obtain the pretreated 2.5D quartz fiber braid. The impregnation modification step is as follows: by weight, 900-950 parts of anhydrous ethanol and 50-100 parts of deionized water are mixed, the pH is adjusted to 4-5, and then 10-20 parts of the mercaptosilane coupling agent are added and stirred for 20-30 minutes to obtain a silane impregnation solution. The pretreated 2.5D quartz fiber braid is immersed in the silane impregnation solution for 8-12 hours. After impregnation, it is washed with acetone and vacuum dried to obtain a silane-modified 2.5D quartz fiber braid. S2. The silane-modified 2.5D quartz fiber braid and sulfonated hyperbranched polyimide are molded into a composite material using RTM molding process, and then heated and cured to obtain a quartz fiber reinforced polyimide radome. The preparation method of the sulfonated hyperbranched polyimide is as follows: amino hyperbranched molecules are prepared using methyltrimethoxysilane and 3-aminopropyl(diethoxy)methylsilane as raw materials, and 4,4'-diaminostilbene-2,2'-disulfonic acid, 2,3,3',4'-biphenyltetracarboxylic dianhydride, 3-aminophenylacetylene and the amino hyperbranched molecules are mixed and subjected to polymerization reaction to obtain sulfonated hyperbranched polyimide; The preparation steps of the amino hyperbranched molecule are as follows: by weight, 18-20 parts of methyltrimethoxysilane and 10-12 parts of 3-aminopropyl(diethoxy)methylsilane are mixed, then 150-160 parts of anhydrous ethanol and 4-6 parts of deionized water are added and stirred at room temperature for 50-60 min, heated to 65-75℃ for 12-16 h, and rotary evaporated to obtain the amino hyperbranched molecule; The polymerization reaction steps are as follows: 20-24 parts by weight of 4,4'-diaminostilbene-2,2'-disulfonic acid are added to 130-140 parts of N-methylpyrrolidone, and the mixture is stirred under a nitrogen atmosphere for 20-30 minutes. Then, 18-20 parts of 2,3,3',4'-biphenyltetracarboxylic dianhydride and 30-40 parts of N-methylpyrrolidone are added and stirred for 100-120 minutes. Next, 0.4-0.6 parts of 3-aminophenylacetylene are added for end-capping treatment for 2-3 hours. Finally, 0.8-1.2 parts of the amino hyperbranched molecules are added and the mixture is stirred for 3-4 hours. Animation treatment is performed using a mixture of 24-26 parts of acetic anhydride and 24-26 parts of triethylamine for 3-4 hours. After the reaction is complete, 250-300 parts of anhydrous ethanol are added to precipitate a solid. The solid is washed with anhydrous ethanol and dried under vacuum to obtain sulfonated hyperbranched polyimide.

2. The quartz fiber reinforced polyimide radome molding process according to claim 1, characterized in that, In the RTM molding process, the flow rate of polyimide injected into the mold is 1~2L / min, and the pressure is 0.2~0.4MPa.

3. The quartz fiber reinforced polyimide radome molding process according to claim 1, characterized in that, The heating and curing steps are as follows: first, cure at 150~160℃ for 100~120min, then cure at 180~190℃ for 100~120min, then cure at 200~210℃ for 120~140min, and finally cure at 240~250℃ for 120~140min.

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