Bismaleimide resin-based composite material surface film capable of being cured at low temperature and preparation method thereof

Abstract

The invention discloses a low-temperature curable bismaleimide resin-based composite material surface film and a preparation method thereof, relates to the field of bismaleimide resin composite material surface films, and aims at solving the problem that the curing temperature of an existing bismaleimide resin composite material surface film is too high. The surface film is composed of bismaleimide resin, an allyl compound, thermoplastic resin, a catalyst and a fluidity control agent. The preparation method comprises the following steps: adding the allyl compound into a reaction kettle, heating and stirring, adding the thermoplastic resin, cooling, adding the bismaleimide resin, continuously heating and stirring, and carrying out double-roller hot rolling film forming on the bismaleimide resin and a carrier for manufacturing an adhesive film through an adhesive film machine to prepare the low-temperature curable bismaleimide resin surface film.

Description

Technical Field

[0001] This invention relates to the field of bismaleimide resin composite material surface films, specifically to a method for preparing low-temperature curable bismaleimide resin-based composite material surface films using bismaleimide resin, thermoplastic resin, allyl compound, catalyst, and flow control agent. Background Technology

[0002] With the rapid development of the aviation industry, bismaleimide composite materials are increasingly used in aircraft structural components, especially in high-temperature resistant parts. Consequently, bismaleimide composite surface films, used in conjunction with bismaleimide composites to improve the surface quality of composite materials, have also seen rapid development and are currently in use. However, the biggest problem in molding bismaleimide composite materials is the excessively high curing temperature, with post-processing temperatures reaching 230℃ or even 260℃. Such excessively high curing temperatures can cause thermal damage to the bismaleimide composite material and other components, and also result in significant energy consumption. Therefore, bismaleimide composite materials will inevitably develop towards lower curing temperatures and higher heat resistance, which will also drive the development of bismaleimide composite surface films in this direction. Currently, the curing and post-processing temperatures of commercially available bismaleimide composite surface films are too high to be compatible with existing bismaleimide composite materials. Therefore, inventing a low-temperature curable bismaleimide resin-based composite surface film is imperative. Summary of the Invention

[0003] This invention aims to solve the problem of excessively high curing temperatures in existing bismaleimide resin composite surface films. The curing temperature of existing bismaleimide composite surface films is above 200°C, with post-treatment temperatures reaching 230°C or even higher. Bismaleimide resin surface films are generally co-cured with bismaleimide prepreg; excessively high curing temperatures can cause thermal damage to the bismaleimide composite and other components, and also result in energy waste.

[0004] The present invention discloses a low-temperature curable bismaleimide resin-based composite material surface film, which is composed of 85-110 parts of bismaleimide resin, 65-80 parts of allyl compound, 15-20 parts of thermoplastic resin, 1-4 parts of catalyst and 5-8 parts of flow control agent by weight; wherein the catalyst is 2-ethyl-4-methylimidazole.

[0005] Furthermore, the low-temperature curable bismaleimide resin-based composite material surface film is composed of 90-100 parts of bismaleimide resin, 70-80 parts of allyl compound, 18-20 parts of thermoplastic resin, 2-4 parts of catalyst, and 6-8 parts of flow control agent by weight.

[0006] Furthermore, the low-temperature curable bismaleimide resin-based composite material surface film is composed of 95-105 parts of bismaleimide resin, 70-80 parts of allyl compound, 17-19 parts of thermoplastic resin, 2-4 parts of catalyst, and 5-7 parts of flow control agent by weight.

[0007] Furthermore, the low-temperature curable bismaleimide resin-based composite material surface film is composed of 100 parts bismaleimide resin, 70 parts allyl compound, 18 parts thermoplastic resin, 3 parts catalyst, and 6 parts flow control agent by weight.

[0008] Furthermore, the low-temperature curable bismaleimide resin-based composite material surface film is composed of 105 parts bismaleimide resin, 80 parts allyl compound, 20 parts thermoplastic resin, 4 parts catalyst, and 8 parts flow control agent by weight.

[0009] Furthermore, the bismaleimide resin is composed of diphenylmethane-type bismaleimide resin, bismaleimide resin containing ether ketone structure, and bismaleimide resin containing ether sulfone structure in a mass ratio of (2~4):(1~3):1.

[0010] Furthermore, the allyl compound is composed of allyl bisphenol A, allyl phenolic resin and allyl ether compound in a weight ratio of (3~5):(2~4):1.

[0011] Furthermore, the thermoplastic resin is a mixture of polyether acetone, polyetherimide and polyarylether sulfone in equal mass ratios.

[0012] The present invention discloses a method for preparing a low-temperature curable bismaleimide resin-based composite material surface film, which is prepared according to the following method: Step 1: Weigh out 85-110 parts of bismaleimide resin, 65-80 parts of allyl compound, 15-20 parts of thermoplastic resin, 1-4 parts of catalyst, and 5-8 parts of flow control agent according to the weight proportions. Step 2: Add the allyl compound weighed in Step 1 to the reaction vessel, heat to 210℃~220℃, add the thermoplastic resin at one time while stirring, and keep at 205℃~210℃ for 8-10 minutes to obtain a homogeneous blended resin. Step 3: Cool the blended resin obtained in Step 2 to 80℃-90℃, add bismaleimide resin all at once, and heat to 130℃-140℃ for prepolymerization for 25min~30min. Step 4: Cool the mixed resin prepared in Step 3 to 70℃-80℃, add the catalyst, stir for 5min-8min, then add the flow control agent and stir for 5min-8min, then cool and set aside for use. Step 5: The adhesive material obtained in Step 4 and the carrier used for film manufacturing are hot-pressed into a film by a double-roller hot pressing machine to obtain a bismaleimide resin surface film that can be cured at low temperature.

[0013] Further, in step two, the allyl compound weighed in step one is added to the reactor, heated to 215°C, and the thermoplastic resin is added all at once while stirring. The mixture is then kept at 210°C for 8-10 minutes.

[0014] Furthermore, in step three, the blended resin obtained in step two is cooled to 85°C, bismaleimide resin is added at once, and the temperature is raised to 135°C for prepolymerization for 25-30 minutes.

[0015] The bismaleimide resin of this invention is a compound of diphenylmethane-type bismaleimide resin, ether-ketone-containing bismaleimide resin (EK-BMI), and ether-sulfone-containing bismaleimide resin in a specific ratio. The ether bond structure enhances intermolecular forces, increases the activity of carbon-carbon double bonds, and lowers the curing reaction temperature. The use of imidazole compounds (such as 2-ethyl-4-methylimidazolium, 2-methylimidazolium, and 1,1'-methylenediimidazole) achieves the formation of a conjugated structure between the methyl and ethyl groups, activating the lone pair electrons of the nitrogen atom and significantly reducing the curing temperature. The compounding of silica and kaolin (in equal mass or a 2:1 ratio) controls the resin's flowability and viscosity.

[0016] This invention's surface film, through the synergistic effect of a compounded bismaleimide resin, imidazole catalyst, enhanced ether bond activity, and flowability control, can be fully cured at 180℃ for 3 hours, achieving shear strengths of 18.4 MPa at room temperature and 16.1 MPa at high temperature. This contrasts sharply with typical bismaleimide resins (such as XU292), which require post-treatment at 250℃, and aerospace-grade 802 bismaleimide resin, which, after curing, has a Tg of 325℃ but requires curing at 200℃. This invention's surface film achieves equivalent performance at 180℃, solving the problem of excessively high curing temperatures (>200℃) in traditional bismaleimide surface films. Its preparation process is highly controllable; this surface film not only lowers the curing temperature but also maintains excellent mechanical properties. In aerospace composite applications, its good shear strength ensures the reliability of structural component connections, while its low-temperature curing characteristics reduce the impact of thermal stress on the composite matrix, extending product lifespan. Furthermore, through precise control of the preparation process, this surface film exhibits excellent processing performance, meeting the surface protection requirements of complex-shaped composite components. The bismaleimide resin-based composite material surface film of the present invention provides a more efficient and environmentally friendly solution for the aerospace industry. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the spirit of the contents disclosed in the present invention will be described in detail below. After understanding the embodiments of the present invention, any person skilled in the art can make changes and modifications based on the technology taught in the present invention without departing from the spirit and scope of the present invention.

[0018] The illustrative embodiments and descriptions of the present invention are used to explain the present invention, but are not intended to limit the present invention.

[0019] Example 1 The following is a method for preparing a low-temperature curable bismaleimide resin-based composite material surface film in this embodiment: Step 1: Weigh out 90 parts of bismaleimide resin, 70 parts of allyl compound, 20 parts of thermoplastic resin, 2 parts of catalyst, and 6 parts of flow control agent by weight. The bismaleimide resin is composed of diphenylmethane-type bismaleimide resin, bismaleimide resin containing ether ketone structure (EK-BMI), and bismaleimide resin containing ether sulfone structure in a mass ratio of 3:2:1. The allyl compound is composed of allyl bisphenol A, allyl phenolic resin and allyl ether compound in a weight ratio of 4:3:1; The thermoplastic resin is a mixture of poly(phenylene ether nitrile ketone) (PPENK), polyetherimide (PEI), and polyarylether sulfone (PES) in equal mass ratios. The catalyst is 2-methylimidazole; The flow control agent is a mixture of silica and kaolin in equal mass ratios. Step 2: Add the allyl compound weighed in Step 1 to the reaction vessel, heat to 210°C, add the thermoplastic resin at once while stirring, and keep at 210°C for 8-10 minutes to obtain a homogeneous blended resin. Step 2: Cool the blended resin obtained in Step 2 to 80-90℃, add bismaleimide resin all at once, and heat to 130℃ for prepolymerization for 25-30 minutes. Step 4: Cool the mixed resin prepared in Step 3 to 80℃, add the catalyst, stir for 5-8 minutes, then add the flow control agent and stir for 5-8 minutes. Cool and set aside for use. Step 5: The adhesive material obtained in Step 4 and the carrier used for film manufacturing are hot-pressed into a film by a double-roller hot pressing machine to obtain a bismaleimide resin surface film that can be cured at low temperature.

[0020] The chemical structural formula of the 2-ethyl-4-methylimidazolium is as follows:

[0021] The 2-ethyl-4-methylimidazolium selected in this embodiment contains methyl and ethyl groups, which can form a conjugated structure and strongly activate the lone pair electrons on the nitrogen atom, significantly reducing the curing reaction temperature of the bismaleimide resin. Furthermore, both bismaleimide resins selected in this invention contain ether bonds. Due to intermolecular forces, the carbon-carbon double bond activity is enhanced, increasing the reactivity of the bismaleimide resin and thus lowering its curing reaction temperature. This is a unique feature of the three materials selected in this invention.

[0022] The structural formula of the diphenylmethane-type bismaleimide resin is as follows:

[0023] The structural formula of the bismaleimide resin (EK-BMI) containing an ether ketone structure is as follows:

[0024] The structural formula of the bismaleimide resin containing the ether sulfone structure is as follows:

[0025] Example 2 The difference between this embodiment and Embodiment 1 is that the bismaleimide resin consists of 100 parts, allyl compound 80 parts, thermoplastic resin 18 parts, catalyst 3 parts, and flow control agent 7 parts. Everything else is the same as in Embodiment 1.

[0026] Example 3 The difference between this embodiment and Embodiment 1 is that the bismaleimide resin consists of 110 parts, allyl compound 80 parts, thermoplastic resin 20 parts, catalyst 4 parts, and flow control agent 8 parts.

[0027] The bismaleimide resin is composed of diphenylmethane-type bismaleimide resin, bismaleimide resin containing ether ketone structure (EK-BMI), and bismaleimide resin containing ether sulfone structure in a weight ratio of 3:1:1.

[0028] The thermoplastic resin is composed of poly(phenylene ether nitrile ketone) (PPENK) and polyether imide (PEI) in a weight ratio of 1:1.

[0029] Everything else is the same as in Example 1.

[0030] This embodiment presents a low-temperature curable bismaleimide resin-based composite material surface film, highlighting its low-temperature curing characteristics, achieving curing at 180℃. When the curing process is 180℃ / 3h, the room temperature shear strength of the aluminum alloy specimen bonded with the bismaleimide surface film reaches 18.4MPa, and the shear strength at 230℃ reaches 16.1MPa, demonstrating the high strength and high-temperature resistance of this surface film. When the curing process is 200℃ / 3h, the room temperature shear strength of the aluminum alloy specimen bonded with the bismaleimide surface film reaches 18.9MPa, and the shear strength at 230℃ reaches 16.4MPa. Data comparison shows that the mechanical properties of the bismaleimide surface film of this invention are similar when cured at 180℃ and 200℃, indicating that the surface film can be completely cured at 180℃, a feature not found in other bismaleimide surface films.

[0031] Example 4 The difference between this embodiment and Embodiment 1 is that the bismaleimide resin consists of 100 parts, allyl compound 75 parts, thermoplastic resin 18 parts, catalyst 3 parts, and flow control agent 6 parts.

[0032] The bismaleimide resin is composed of diphenylmethane-type bismaleimide resin, bismaleimide resin containing ether ketone structure (EK-BMI), and bismaleimide resin containing ether sulfone structure in a weight ratio of 2:2:1.

[0033] The allyl compound is composed of allyl bisphenol A, allyl phenolic resin and allyl ether compound in a weight ratio of 3:2:1.

[0034] The thermoplastic resin is composed of poly(phenylene ether nitrile ketone) (PPENK) and polyether imide (PEI) in a weight ratio of 1:1.

[0035] The flowability control agent is composed of silica and kaolin in a weight ratio of 2:1.

[0036] Everything else is the same as in Example 1.

[0037] Example 5 The difference between this embodiment and Embodiment 1 is that the bismaleimide resin consists of 100 parts, allyl compound 75 parts, thermoplastic resin 18 parts, catalyst 3 parts, and flow control agent 6 parts.

[0038] The bismaleimide resin is composed of diphenylmethane-type bismaleimide resin, bismaleimide resin containing ether ketone structure (EK-BMI), and bismaleimide resin containing ether sulfone structure in a weight ratio of 2:2:1.

[0039] The allyl compound is composed of allyl bisphenol A, allyl phenolic resin and allyl ether compound in a weight ratio of 3:2:1.

[0040] The thermoplastic resin is composed of poly(phenylene ether nitrile ketone) (PPENK) and polyether imide (PEI) in a weight ratio of 1:1.

[0041] The flowability control agent is composed of silica and kaolin in a weight ratio of 2:1.

[0042] Everything else is the same as in Example 1.

[0043] Example 6 The difference between this embodiment and Embodiment 1 is that the bismaleimide resin consists of 85 parts, allyl compound 65 parts, thermoplastic resin 15 parts, catalyst 2 parts, and flow control agent 5 parts.

[0044] The bismaleimide resin is composed of diphenylmethane-type bismaleimide resin, bismaleimide resin containing ether ketone structure (EK-BMI), and bismaleimide resin containing ether sulfone structure in a weight ratio of 2:2:1.

[0045] The allyl compound is composed of allyl bisphenol A, allyl phenolic resin and allyl ether compound in a weight ratio of 2:3:1.

[0046] The thermoplastic resin is composed of polyarylether sulfone (PES) and poly(phenylene ether nitrile ketone) (PPENK) in a weight ratio of 1:1.

[0047] Everything else is the same as in Example 1.

[0048] Example 7 The difference between this embodiment and Example 3 is that the catalyst in Example 3 is 2-methylimidazole and 1,1'-methylenediimidazole (1:1), while the other components remain unchanged.

[0049] When the curing process was 180℃ / 3h, the room temperature shear strength of the bismaleimide surface film bonded aluminum alloy specimen was 12.5MPa, and the 230℃ shear strength was 10.2MPa; when the curing process was 200℃ / 3h, the room temperature shear strength of the bismaleimide surface film bonded aluminum alloy specimen was 13.8MPa, and the 230℃ shear strength was 11.3MPa. The room temperature and 230℃ shear strengths of this embodiment are significantly lower than those of Example 3.

[0050] Example 8 The difference between this embodiment and Embodiment 3 is that the bismaleimide resin in Embodiment 3 is diphenylmethane type bismaleimide resin, while other components remain unchanged.

[0051] When the curing process was 180℃ / 3h, the room temperature shear strength of the bismaleimide surface film bonded aluminum alloy specimen was 15.3 MPa, and the 230℃ shear strength was 13.5 MPa. When the curing process was 200℃ / 3h, the room temperature shear strength of the bismaleimide surface film bonded aluminum alloy specimen was 15.9 MPa, and the 230℃ shear strength was 14.0 MPa. When the bismaleimide resin was replaced with a single diphenylmethane type, the room temperature and 230℃ shear strengths were both lower than in Example 3.

Claims

1. A low-temperature curable bismaleimide resin-based composite material surface film, characterized in that... It is composed of 85-110 parts by weight of bismaleimide resin, 65-80 parts of allyl compound, 15-20 parts of thermoplastic resin, 1-4 parts of catalyst and 5-8 parts of flow control agent; the catalyst is 2-ethyl-4-methylimidazole.

2. The low-temperature curable bismaleimide resin-based composite material surface film according to claim 1, characterized in that... The low-temperature curable bismaleimide resin-based composite material surface film is composed of 90-100 parts of bismaleimide resin, 70-80 parts of allyl compound, 18-20 parts of thermoplastic resin, 2-4 parts of catalyst, and 6-8 parts of flow control agent by weight.

3. The low-temperature curable bismaleimide resin-based composite material surface film according to claim 1, characterized in that... The low-temperature curable bismaleimide resin-based composite material surface film is composed of 100 parts bismaleimide resin, 70 parts allyl compound, 18 parts thermoplastic resin, 3 parts catalyst, and 6 parts flow control agent by weight.

4. The low-temperature curable bismaleimide resin-based composite material surface film according to claim 1, characterized in that... The low-temperature curable bismaleimide resin-based composite material surface film is composed of 105 parts bismaleimide resin, 80 parts allyl compound, 20 parts thermoplastic resin, 4 parts catalyst, and 8 parts flow control agent by weight.

5. A low-temperature curable bismaleimide resin-based composite material surface film according to any one of claims 1 to 4, characterized in that... The bismaleimide resin is composed of diphenylmethane-type bismaleimide resin, bismaleimide resin containing ether ketone structure, and bismaleimide resin containing ether sulfone structure in a mass ratio of (2~4):(1~3):

1.

6. A low-temperature curable bismaleimide resin-based composite material surface film according to any one of claims 1 to 4, characterized in that... The allyl compound is composed of allyl bisphenol A, allyl phenolic resin and allyl ether compound in a weight ratio of (3~5):(2~4):

1.

7. A low-temperature curable bismaleimide resin-based composite material surface film according to any one of claims 1 to 6, characterized in that... The thermoplastic resin is a mixture of polyether ketone, polyetherimide and polyarylether sulfone in equal mass ratios.

8. A method for preparing a low-temperature curable bismaleimide resin-based composite material surface film as described in claim 1, characterized in that... The preparation method is as follows: Step 1: Weigh out 85-110 parts of bismaleimide resin, 65-80 parts of allyl compound, 15-20 parts of thermoplastic resin, 1-4 parts of catalyst, and 5-8 parts of flow control agent according to the weight proportions. Step 2: Add the allyl compound weighed in Step 1 to the reaction vessel, heat to 210℃~220℃, add the thermoplastic resin at one time while stirring, and keep at 205℃~210℃ for 8-10 minutes to obtain a homogeneous blended resin. Step 3: Cool the blended resin obtained in Step 2 to 80℃-90℃, add bismaleimide resin all at once, and heat to 130℃-140℃ for prepolymerization for 25min~30min. Step 4: Cool the mixed resin prepared in Step 3 to 70℃-80℃, add the catalyst, stir for 5min-8min, then add the flow control agent and stir for 5min-8min, then cool and set aside for use. Step 5: The adhesive material obtained in Step 4 and the carrier used for film manufacturing are hot-pressed into a film by a double-roller hot pressing machine to obtain a bismaleimide resin surface film that can be cured at low temperature.

9. The method according to claim 8, characterized in that... In step two, the allyl compound weighed in step one is added to the reaction vessel, heated to 215°C, and the thermoplastic resin is added all at once while stirring. The mixture is then kept at 210°C for 8-10 minutes.

10. The method according to claim 8, characterized in that... In step three, the blended resin obtained in step two is cooled to 85°C, bismaleimide resin is added at once, and the temperature is raised to 135°C for prepolymerization for 25-30 minutes.

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