Epoxy resin wave-absorbing prepreg with strong low-frequency wave-absorbing performance and preparation method of epoxy resin wave-absorbing prepreg

Abstract

The invention belongs to the technical field of preparation of wave-absorbing materials, and particularly relates to an epoxy resin wave-absorbing prepreg with strong low-frequency wave-absorbing performance and a preparation method of the epoxy resin wave-absorbing prepreg. The method comprises the following steps: mixing an epoxy resin matrix and a flexibilizer to obtain an epoxy resin system; the preparation method comprises the following steps: putting an epoxy resin system and flaky absorbents with different particle sizes into an internal mixer for internal mixing and coarse mixing, performing fine mixing by using an open mill after coarse mixing, and adding a curing agent in the fine mixing process to obtain a low-frequency wave-absorbing resin blank; putting the low-frequency wave-absorbing resin blank into a precision calender, and carrying out wave-absorbing adhesive film calendering, so as to obtain a wave-absorbing resin film after calendering; and thermally compounding the wave-absorbing resin film and the wave-transparent fiber prepreg to obtain the epoxy resin-based wave-absorbing prepreg. The wave-absorbing prepreg prepared by the invention is excellent in mechanical property after being cured, high in low-frequency wave-absorbing property and relatively high in reliability.

Description

Technical Field

[0001] This invention belongs to the field of microwave absorbing material preparation technology, and particularly relates to an epoxy resin microwave absorbing prepreg with strong low-frequency microwave absorption performance and its preparation method. Background Art

[0002] Microwave-absorbing materials are materials that can absorb and attenuate incident electromagnetic waves, converting their electromagnetic energy into heat energy for dissipation or causing the electromagnetic waves to disappear due to interference. With the development of science and technology, microwave-absorbing materials have found wide applications in various fields, such as electromagnetic protection, microwave anechoic chambers, mobile communications, and military stealth. Due to their advantages such as high designability and the ability to be molded in large areas, resin-based microwave-absorbing composite materials have become one of the most important application materials in the aerospace stealth field.

[0003] Microwave-absorbing prepreg is an intermediate material used in the preparation of resin-based microwave-absorbing composite materials. It mainly consists of electromagnetic wave absorbers, a resin matrix, and reinforcing fibers. The prepreg is prepared by a thermal composite process using a magnetic absorbing film for the functional layer and a microwave-transparent fiber prepreg for the reinforcing layer. The magnetic absorbing film for the functional layer is prepared by mixing the absorber and the matrix resin and then calendering it. After the prepreg is laid up and cured, a laminate material with both load-bearing and microwave-absorbing functions can be prepared. With the gradual development of radar technology, microwave-absorbing materials are required to have wide-band absorption performance. For wide-band absorption, especially in the low-frequency band, it is often necessary to add a large amount of large-scale absorber powder to the microwave-absorbing material. However, the large addition of low-frequency absorber powder will increase the steric hindrance inside the material, creating porosity within the composite material, thereby reducing the material's low-frequency absorption performance.

[0004] Although relevant patents such as CN201510147702.7, CN201610539281.7, and CN201911362140.2 all describe the preparation methods of microwave absorbing prepregs, they do not mention the preparation of low-frequency large-scale absorber prepregs. For microwave absorbing prepregs with strong low-frequency microwave absorption performance, the preparation process still faces challenges. Summary of the Invention

[0005] To further improve the low-frequency absorbing performance of low-frequency absorbing prepregs, this invention provides an epoxy resin absorbing prepreg with strong low-frequency absorbing performance and its preparation method.

[0006] To address the challenges in preparing high-frequency absorbing prepregs, this patent employs a method of compounding absorbers of different scales to increase the packing density of absorbers within the prepreg, effectively improving the low-frequency electromagnetic loss of the prepreg and giving the absorbing layer material excellent low-frequency absorption performance.

[0007] To achieve the above objectives, the present invention provides, in a first aspect, a method for preparing an epoxy resin-based microwave absorbing prepreg with strong low-frequency microwave absorption properties, the method comprising the following steps:

[0008] (1) Mix the epoxy resin matrix and toughening agent to form a compound epoxy resin system;

[0009] (2) The epoxy resin system obtained in step (1) and the flake absorbents with different particle sizes are put into a resin mixer for coarse mixing. After coarse mixing, a two-roll mill is used for fine mixing. A curing agent is added during the fine mixing process to obtain a low-frequency absorbing resin blank.

[0010] (3) The low-frequency absorbing resin blank obtained in step (2) is placed into a precision calender for calendering the absorbing film, and the calendered resin film is obtained.

[0011] (4) The microwave absorbing resin film obtained in step (3) is thermally composited with the microwave transparent fiber prepreg to obtain epoxy resin-based microwave absorbing prepreg.

[0012] Preferably, in step (1), the epoxy resin matrix and toughening agent are mixed using a vertical kneader to form a compound epoxy resin system; the mixing temperature of the vertical kneader is 20-300℃, the mixing time is 10-120min, and the stirring speed is 10-250r / min.

[0013] Preferably, in step (2), the flake absorbents of different particle sizes and the epoxy resin system are mixed using an internal mixer. The mixing temperature is 20–300°C, the mixing time is 10–120 min, and the internal mixer rotor speed is 10–250 r / min.

[0014] Preferably, in step (2), a two-roll mill is used for fine mixing, with a mixing temperature of 20-300℃, a mixing time of 10-80 min, and a mixing roller speed of 2-17 m / min. After the absorbent and resin are mixed evenly, the curing agent is added and mixing continues for 2-10 min.

[0015] Preferably, in step (3), the calendering temperature is 20-300℃, the calendering thickness is 0.02-0.1mm, the calendering pressure is 1-200 tons, and the calendering speed is 0.25-8m / s.

[0016] Preferably, the microwave absorbing resin film in step (3) is composed of the following components, with the following mass fractions: absorbent: 5-85 wt%; epoxy resin matrix: 10-45 wt%; toughening agent: 2-30 wt%; curing agent: 1-30 wt%.

[0017] Preferably, the thermal bonding temperature in step (4) is 20-300℃ and the thermal bonding rate is 0.25-8m / s.

[0018] Preferably, the epoxy resin matrix is ​​at least one selected from the group consisting of E-51 type epoxy resin, E-44 type epoxy resin, E-20 type epoxy resin, F-44 type epoxy resin, and F-51 type epoxy resin.

[0019] Preferably, the toughening agent is at least one selected from the group consisting of soluble polyetherketone, polyethersulfone, and polyetherimide.

[0020] Preferably, the absorbent is at least one selected from the group consisting of carbonyl iron, iron-silicon-aluminum, and ferrite.

[0021] Preferably, the curing agent is at least one selected from the group consisting of aliphatic amines, polyamides, aromatic amines, polyether amines, dicyandiamides, and acid anhydride curing agents.

[0022] Preferably, the particle size range of the different particle size scales of the flake absorbent is in the range of 20μm-1000μm.

[0023] Preferably, the microwave-transparent fiber prepreg is at least one of the group consisting of glass fiber prepreg, quartz fiber prepreg, and aramid fiber prepreg.

[0024] In a second aspect, the present invention provides an epoxy resin-based microwave absorbing prepreg with strong low-frequency microwave absorption properties prepared by the preparation method described in the first aspect of the present invention.

[0025] Compared with existing epoxy-based microwave absorbing prepregs, the present invention has at least the following beneficial effects:

[0026] (1) The microwave absorbing prepreg prepared by the present invention has good microwave absorption performance in the low frequency band after curing. It has the ability to absorb electromagnetic waves in the low frequency band while also having excellent load-bearing characteristics.

[0027] (2) The epoxy resin-based microwave absorbing prepreg prepared by the present invention has good flexibility, viscosity and other process characteristics. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with the embodiments thereof. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0029] Example 1:

[0030] In this embodiment, the preparation method of the epoxy resin microwave absorbing prepreg with strong low-frequency microwave absorption properties includes the following steps:

[0031] (1) The epoxy resin matrix, toughening agent, etc., are mixed using a vertical kneader to form a compound epoxy resin system; the mixing temperature of the vertical kneader is 100℃, the mixing time is 60min, and the stirring paddle speed is 100r / min. The epoxy resin matrix is ​​a group composed of E-51 type epoxy resin, E-44 type epoxy resin, E-20 type epoxy resin, F-44 type epoxy resin, and F-51 type epoxy resin. The toughening agent is soluble polyetherketone.

[0032] (2) The epoxy resin system obtained in step (1) and the flake absorbent with particle sizes of 100 μm and 20 μm are placed in a resin internal mixer at a 1:1 ratio for rough mixing. After rough mixing, a two-roll mill is used for fine mixing. During the fine mixing process, a curing agent is added to obtain a low-frequency absorbing resin preform. In this step, the mixing temperature is 100℃, the mixing time is 60 min, and the internal mixer rotor speed is 100 r / min. In this step, the two-roll mill temperature is 100℃, the mixing time is 40 min, and the mixing roller speed is 7 m / min. After the absorbent and resin are mixed, a curing agent is added and mixing continues for 5 min. The amount of absorbent is 60 wt%, the amount of curing agent is 5 wt%, the amount of epoxy resin is 25 wt%, and the amount of toughening agent is 10%. The curing agent is a fatty amine.

[0033] (3) The low-frequency absorbing resin blank obtained in step (2) is placed into a precision calender for ultra-thin calendering of the absorbing film, and the calendering process yields a calendering resin film; the calendering temperature in the step is 100℃, the calendering thickness is 0.06mm, the calendering pressure is 100 tons, and the calendering speed is 4m / s.

[0034] (4) The microwave absorbing resin film obtained in step (3) is thermally bonded with the microwave transparent fiber prepreg to complete the preparation of epoxy microwave absorbing prepreg; the microwave transparent fiber prepreg is glass fiber prepreg; the thermal bonding temperature is 100℃ and the thermal bonding speed is 2m / s.

[0035] Example 2:

[0036] In this embodiment, the preparation method of the epoxy resin microwave absorbing prepreg with strong low-frequency microwave absorption properties includes the following steps:

[0037] (1) The epoxy resin matrix, toughening agent, etc., are mixed using a vertical kneader to form a compound epoxy resin system; the mixing temperature of the vertical kneader is 20℃, the mixing time is 10min, and the stirring paddle speed is 10r / min. The epoxy resin matrix is ​​a combination of E-51 type epoxy resin, E-44 type epoxy resin, and E-20 type epoxy resin. The toughening agent is polyethersulfone.

[0038] (2) The epoxy resin system obtained in step (1) and flake absorbents with particle sizes of 100 μm and 20 μm are placed in a resin internal mixer at a ratio of 0.5:1 for rough mixing. After rough mixing, fine mixing is performed using an open mill. During the fine mixing process, a curing agent is added to obtain a low-frequency absorbing resin preform. In this step, the internal mixing temperature is 20℃, the mixing time is 10 min, and the internal mixing rotor speed is 10 r / min; the open mill temperature is 20℃, the mixing time is 10 min, and the mixing roller speed is 2 m / min. After the absorbent and resin are mixed, the curing agent is added and mixing continues for 2 min. The amount of absorbent is 5 wt%, the amount of curing agent is 1 wt%, the amount of resin matrix is ​​90 wt%, and the amount of toughening agent is 4%. The curing agent is polyamide.

[0039] (3) The low-frequency absorbing resin blank obtained in step (2) is placed into a precision calender for ultra-thin calendering of the absorbing film, and the calendered film is obtained. The calendering temperature in this step is 20℃, the calendering thickness is 0.02mm, the calendering pressure is 1 ton, and the calendering speed is 0.25m / s.

[0040] (4) The microwave absorbing resin film obtained in step (3) is thermally bonded with the microwave transparent fiber prepreg to complete the preparation of epoxy microwave absorbing prepreg; the microwave transparent fiber prepreg is quartz fiber prepreg; the thermal bonding temperature is 20℃ and the thermal bonding speed is 0.25m / s.

[0041] Example 3:

[0042] In this embodiment, the preparation method of the epoxy resin microwave absorbing prepreg with strong low-frequency microwave absorption properties includes the following steps:

[0043] (1) The epoxy resin matrix, toughening agent, etc., are mixed using a vertical kneader to form a compound epoxy resin system; the mixing temperature of the vertical kneader is 300℃, the mixing time is 120min, and the stirring paddle speed is 250r / min. The epoxy resin matrix is ​​a combination of E-51 type epoxy resin, E-44 type epoxy resin, and F-51 type epoxy resin. The toughening agent is polyetherimide.

[0044] (2) The epoxy resin system obtained in step (1) and the flake absorbent with particle sizes of 100 μm and 20 μm are placed in a resin internal mixer at a ratio of 4:1 for rough mixing. After rough mixing, a two-roll mill is used for fine mixing. During the fine mixing process, a curing agent is added to obtain a low-frequency absorbing resin blank. The mixing temperature in this step is 300℃, the mixing time is 120 min, and the internal mixer rotor speed is 250 r / min. The two-roll mill temperature in this step is 300℃, the mixing time is 80 min, and the mixing roller speed is 17 m / min. After the absorbent and resin are mixed, a curing agent is added and mixing continues for 10 min. The amount of absorbent is 55 wt%, the amount of curing agent is 5 wt%, the amount of resin matrix is ​​10 wt%, and the amount of toughening agent is 30%. The curing agent is polyetheramine.

[0045] (3) The low-frequency absorbing resin blank obtained in step (2) is placed into a precision calender for ultra-thin calendering of the absorbing film, and the calendered film is obtained. The calendering temperature in this step is 300℃, the calendering thickness is 0.1mm, the calendering pressure is 200 tons, and the calendering speed is 8m / s.

[0046] (4) The microwave absorbing resin film obtained in step (3) is thermally bonded with the microwave transparent fiber prepreg to complete the preparation of epoxy microwave absorbing prepreg; the microwave transparent fiber prepreg is aramid fiber prepreg; the thermal bonding temperature is 300℃ and the thermal bonding speed is 8m / s.

[0047] Comparative Example 1:

[0048] In this comparative example, a single-component absorbent is used, without the step of compounding absorbents of different scales. The preparation method of the epoxy resin microwave absorbing prepreg in this comparative example includes the following steps:

[0049] (1) The epoxy resin matrix, toughening agent, etc., are mixed using a vertical kneader to form a compound epoxy resin system; the mixing temperature of the vertical kneader is 100℃, the mixing time is 60min, and the stirring paddle speed is 100r / min. The epoxy resin matrix is ​​selected from the group consisting of E-51 type epoxy resin, E-44 type epoxy resin, and E-20 type epoxy resin. The toughening agent is soluble polyetherketone.

[0050] (2) The epoxy resin system obtained in step (1) and the flake absorbent with a particle size of 100 μm are placed in a resin internal mixer for rough mixing. After rough mixing, a two-roll mill is used for fine mixing. During the fine mixing process, a curing agent is added to obtain a low-frequency absorbing resin preform. In this step, the mixing temperature is 100℃, the mixing time is 60 min, and the internal mixer rotor speed is 100 r / min; the two-roll mill temperature is 100℃, the mixing time is 40 min, and the mixing roller speed is 7 m / min. After the absorbent and resin are mixed, a curing agent is added and mixing continues for 5 min. The amount of absorbent is 45 wt%, the amount of curing agent is 5 wt%, the amount of epoxy resin is 35 wt%, and the amount of toughening agent is 15%. The curing agent is a fatty amine.

[0051] (3) The low-frequency absorbing resin blank obtained in step (2) is placed into a precision calender for ultra-thin calendering of the absorbing film, and the calendering process yields a calendering resin film; the calendering temperature in the step is 100℃, the calendering thickness is 0.06mm, the calendering pressure is 100 tons, and the calendering speed is 4m / s.

[0052] (4) The microwave absorbing resin film obtained in step (3) is thermally bonded with the microwave transparent fiber prepreg to complete the preparation of epoxy microwave absorbing prepreg; the microwave transparent fiber prepreg is glass fiber prepreg; the thermal bonding temperature is 100℃ and the thermal bonding speed is 2m / s.

[0053] The reflectivity test results of the microwave absorbing prepregs prepared after curing the above embodiments and comparative examples are shown in Table 1.

[0054] Table 1. Reflectivity Test Results of Absorbing Layer

[0055]

[0056] The specific embodiments of the present invention disclosed above are intended to help understand the content of the present invention and to implement it accordingly. Those skilled in the art will understand that various substitutions, changes, and modifications are possible without departing from the spirit and scope of the present invention. The present invention should not be limited to the content disclosed in the embodiments of this specification; the scope of protection of the present invention is defined by the claims.

Claims

1. An epoxy resin absorbing prepreg with strong low-frequency absorbing performance and a preparation method thereof, characterized in that: The following steps are involved: Mixing an epoxy resin matrix and a toughening agent to obtain an epoxy resin system; The epoxy resin system and the flake absorbers with different particle sizes are put into an internal mixer for rough mixing, and then fine mixing is performed using an open mixer. During the fine mixing process, a curing agent is added to obtain a low-frequency absorbing resin blank; Putting the low-frequency absorbing resin blank into a precision calender to calender the absorbing film, and obtaining the absorbing resin film after calendering; The microwave-absorbing resin film and the microwave-transmitting fiber prepreg are thermally compounded to obtain the epoxy resin-based microwave-absorbing prepreg.

2. The method according to claim 1, characterized in that The epoxy resin matrix and the toughening agent are mixed by using a vertical kneader; the mixing temperature of the vertical kneader is 20-300° C., the mixing time is 10-120 minutes, and the stirring blade speed is 10-250 r / min.

3. The method according to claim 1, characterized in that The internal mixer has a mixing temperature of 20-300°C, a mixing time of 10-120 minutes, and a mixing rotor speed of 10-250 r / min; the open mixer has an open mixing temperature of 20-300°C, a mixing time of 10-80 minutes, and a mixing roller speed of 2-17 m / min; after the absorbent and the resin are evenly mixed, the curing agent is added and the mixing is continued for 2-10 minutes.

4. The method according to claim 1, characterized in that The calendering temperature of the wave-absorbing film is 20-300° C., the calendering thickness is 0.02-0.1 mm, the calendering pressure is 1-200 tons, and the calendering speed is 0.25-8 m / s.

5. The method according to claim 1, characterized in that The mass fractions of the substances in the wave-absorbing resin film are as follows: absorbent: 5-85wt%; epoxy resin matrix: 10-45wt%; toughening agent: 2-30wt%; curing agent: 1-30wt%.

6. The method according to claim 1, characterized in that The temperature of the thermal composite is 20-300° C., and the thermal composite speed is 0.25-8 m / s.

7. The method according to claim 1, characterized in that The epoxy resin matrix is ​​at least one selected from the group consisting of E-51 epoxy resin, E-44 epoxy resin, E-20 epoxy resin, F-44 epoxy resin, and F-51 epoxy resin; the toughening agent is at least one selected from the group consisting of soluble polyether ketone, polyether sulfone, and polyether imide; the absorbent is at least one selected from the group consisting of carbonyl iron, sendust, and ferrite; the curing agent is at least one selected from the group consisting of fatty amines, polyamides, aromatic amines, polyether amines, dicyandiamide, and acid anhydride curing agents.

8. The method according to claim 1, characterized in that The particle size of the sheet-like absorbents with different particle sizes ranges from 20 μm to 1000 μm.

9. The method according to claim 1, characterized in that: The wave-transmitting fiber prepreg is at least one of the group consisting of glass fiber prepreg, quartz fiber prepreg, and aramid fiber prepreg.

10. An epoxy resin microwave absorbing prepreg having strong low-frequency microwave absorbing performance prepared according to the method of any one of claims 1 to 9.

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