Amphiphilic water-based polyamide acid sizing agent and preparation method thereof

Abstract

The invention discloses a carbon fiber polyimide sizing agent and a preparation method and application thereof, the carbon fiber polyimide sizing agent is suitable for a carbon fiber reinforced polyether-ether-ketone (CF / PEEK) composite material, and belongs to the field of composite materials, and the specific scheme is as follows: the amphiphilic water-based polyetherimide sizing agent comprises polyamide acid, an organic solvent, deionized water and organic weak base. The polyamide acid (PAA) is a precursor of polyetherimide (PEI), and the molecule of the polyamide acid contains two chain segments: active side group hydroxyl (-OH) is contained, so that the activity of the sizing agent is remarkably enhanced, and the surface energy of the carbon fiber is favorably increased; the sizing agent contains an ether-ether-ketone-like structure, and a fragment similar to a PEEK structure is introduced according to a similar compatibility principle, so that the compatibility of the sizing agent and a PEEK resin matrix is enhanced, the stress transfer efficiency at an interface is enhanced, and the interface performance of a composite material is improved. Meanwhile, in order to respond to the environment-friendly requirement, polyamide acid (PAA) is used as a matrix, deionized water is used as a dispersing agent, and the environment-friendly water-based sizing agent is prepared.

Description

Technical Field

[0001] This invention relates to the field of carbon fiber processing and its composite materials, specifically to the synthesis and preparation of an amphiphilic waterborne sizing agent. Background Technology

[0002] Carbon fiber reinforced thermoplastic composites combine significant advantages such as lightweight and high strength, excellent impact resistance and toughness, recyclability, and efficient rapid molding, making them a prominent representative of next-generation high-performance materials. However, the full realization of these superior properties largely depends on the "bridge" connecting the carbon fiber and the resin matrix—the thermoplastic sizing agent. And the construction of this bridge faces a series of severe challenges.

[0003] The core challenge lies in the fact that thermoplastic resins themselves lack active functional groups, making it difficult for traditional sizing agents to form strong chemical bonds with the matrix. This results in weak interfacial bonding, making it difficult for the composite material to achieve ideal key mechanical properties such as interlaminar shear strength. At the same time, to withstand the extreme processing temperatures exceeding 400°C of high-performance thermoplastic resins such as PEEK and PEKK, the sizing agent itself must possess excellent heat resistance and stability. Many existing products are prone to decomposition and failure at these high temperatures, which places enormous pressure on the development of new high-temperature resistant sizing agents.

[0004] From an industrial production perspective, sizing agents must also meet the process requirements of rapid online curing on existing production lines and transition towards environmentally friendly directions such as water-based formulations. However, this often brings new problems such as greater difficulty in reaction control and poor reproducibility. Ultimately, all these challenges boil down to a core problem: how to achieve an extremely delicate and difficult balance between molecular activity, heat resistance, process compatibility, and the overall performance of the final composite material. Only by overcoming these interfacial challenges can the enormous potential of carbon fiber reinforced thermoplastic composites be truly unleashed.

[0005] In the face of current technological bottlenecks, developing a water-based thermoplastic sizing agent that is environmentally friendly, has excellent high-temperature resistance, and high affinity has become the key to breaking through the bottlenecks in the development of carbon fiber composite materials. Summary of the Invention

[0006] The purpose of this invention is to enhance the interfacial affinity between carbon fiber and PEEK resin and avoid the serious environmental pollution caused by traditional organic solvent-based sizing agents. An amphiphilic waterborne polyamic acid sizing agent has been prepared.

[0007] The amphiphilic waterborne polyamide sizing agent of the present invention is characterized by containing both active functional groups and an "ether-ether-ketone" structure. Its components include: 1–3.5 wt% polyamic acid and 96.5–99 wt% deionized water.

[0008] Preferably, the monomer containing active functional groups has the following structural formula:

[0009]

[0010] The method for synthesizing the monomer containing the active functional group structure includes:

[0011] (1) Under ice bath conditions, 2,7-dihydroxy-9-fluorenone and aniline were added to a three-necked flask in sequence, and methanesulfonic acid was slowly added under nitrogen protection and stirring.

[0012] (2) After the material is added, keep it in an ice bath for 20 minutes, then slowly raise the temperature to 150°C and keep it at a constant temperature for 10 hours.

[0013] (3) After the reaction is complete, cool the mixture to 373 K, add a mixed solution of triethylamine and ethanol, and continue stirring for 30 min. After the system cools to room temperature, filter the mixture and wash the filter cake repeatedly with ethanol until the filtrate is clear.

[0014] (4) After drying the filter cake in an 80°C forced-air drying oven for 4 hours, it was transferred to an 80°C vacuum oven overnight to remove residual solvent, yielding a pale yellow powder. The yield was 70%.

[0015] Preferably, the monomer containing active functional groups has the following structural formula:

[0016]

[0017] The method for synthesizing monomers containing "ether-ether-ketone" structures includes:

[0018] (1) Use a 150ml two-necked round-bottom flask as the reaction apparatus. The apparatus is equipped with a nitrogen inlet, a nitrogen outlet, a Dean-Stark water separator, a condenser, a magnetic stirrer, and a heating device.

[0019] (2) Add 2.18.2g (10mmol) of 4,4'-difluorobenzophenone, 2.40g (22mmol) of 4,-aminophenol, 2.76g (20mmol) of anhydrous potassium carbonate, 30ml of N-methylpyrrolidone, and 15ml of xylene to the flask in sequence.

[0020] (3) Under nitrogen protection, the temperature is slowly increased. The moisture in the reaction apparatus is removed at 145℃ for 2 hours. The temperature is increased to 165℃ to remove the remaining xylene. The temperature is continued to be increased to 170℃ until the reaction is completed. The reaction progress is monitored by TLC (ethyl acetate: petroleum ether = 1:1). After the 4,4'-difluorobenzophenone is completely disappeared, the reaction apparatus is cooled to room temperature.

[0021] (4) Slowly pour the reaction solution into 150 ml of 10% sodium hydroxide solution and stir vigorously to precipitate the reaction product. Filter the precipitate and wash the product with a large amount of 10% sodium hydroxide solution and water.

[0022] (5) After washing, the product was transferred to a forced-air drying oven at 80°C to dry most of the moisture, and then transferred to a vacuum drying oven at 80°C overnight to dry any remaining trace moisture. The yield was 85%.

[0023] Furthermore, the synthesized monomer is polymerized with commercially available diacid anhydride 4,4'-oxydiphthalic anhydride (OPDA). The specific polymerization method includes:

[0024] (1) The diacid anhydride monomer used is commercially available 4,4'-oxydiphthalic anhydride (OPDA).

[0025] (2) The reaction requires anhydrous and oxygen-free conditions. First, 20g of 4A molecular sieve is added to the reaction vessel to remove moisture from the reaction apparatus later.

[0026] (3) Add 5.94g APBP (15mmol) and 5.70g AHF (15mmol) to a 250ml two-necked flask, purge with nitrogen three times, and then add 25ml of ultra-dry DMF to dissolve. Add 9.39g ODPA (30.3mmol) to another 50ml two-necked flask, purge with nitrogen three times, and then add 25ml of ultra-dry DMF to dissolve.

[0027] (4) Under ice-water bath conditions, the dissolved ODPA solution was slowly added to the mixed solvent of APBP and AHF while stirring vigorously to avoid excessive local heat generation. After the addition was complete, the mixture was reacted under ice bath conditions for 4 hours, and then transferred to room temperature for 8 hours to obtain a viscous PAA solution.

[0028] Furthermore, to prevent environmental pollution and other problems caused by using organic solvents as dispersion systems, this invention provides a method for preparing an aqueous sizing agent, using the obtained PAA solution as a raw material to prepare the aqueous sizing agent. The specific preparation method includes:

[0029] (1) The PAA solution was placed in a petri dish and a film was formed in the petri dish. The petri dish after film formation was placed in a forced-air drying oven at 80°C for 8 hours and then placed in a vacuum oven at 80°C for 20 hours to remove residual organic solvents. The PAA film after organic solvent removal was crushed to obtain PAA powder.

[0030] (2) Preparation of water-based sizing agent: The obtained PAA powder was added to water, and a small amount of triethylamine (TEA) was added. The mixture was then mechanically stirred to obtain a clear solution. The obtained polyamic acid solution without organic solvents was diluted with deionized water to the appropriate concentration (2 wt%) and used as a sizing agent.

[0031] An amphiphilic waterborne polyamic acid sizing agent is coated onto the surface of carbon fiber. The sized carbon fiber is then combined with PEEK to prepare a composite material, which is then applied in the aerospace field. Attached Figure Description

[0032] Figure 1 The 1H NMR spectrum of amphiphilic polyamic acid.

[0033] Figure 2 This is a picture showing the morphology of the sizing agent.

[0034] Figure 3 This is the molecular structure of polyamic acid. Detailed Implementation

[0035] The following embodiments are used to specifically illustrate the technical solutions of the present invention and should not be construed as limiting the scope of protection of the present invention. Any equivalent substitutions or improvements made by those skilled in the art based on the spirit of the present invention should be included within the scope of protection of the claims of the present invention.

[0036] Example 1

[0037] An amphiphilic waterborne polyamic acid sizing agent comprises polyamic acid, an organic weak base, and deionized water; wherein the polyimide accounts for 1% of the total mass, the deionized water accounts for 95% of the total mass, and the organic solvent accounts for 4% of the total mass; the polyimide is laboratory-synthesized polyamic acid.

[0038] The core parameters of its sizing process are: drying at 170℃ for 15 seconds. Specifically, the carbon fiber is impregnated with the sizing agent for 10 seconds and then scraped off, and then cured under these conditions to form a polyamic acid film on the surface.

[0039] Example 2

[0040] An amphiphilic waterborne polyamic acid sizing agent comprises polyamic acid, an organic weak base, and deionized water; wherein the polyimide accounts for 2% of the total mass, the deionized water accounts for 94% of the total mass, and the organic solvent accounts for 4% of the total mass; the polyimide is laboratory-synthesized polyamic acid.

[0041] The core parameters of its sizing process are: drying at 170℃ for 15 seconds. Specifically, the carbon fiber is impregnated with the sizing agent for 10 seconds and then scraped off, and then cured under these conditions to form a polyamic acid film on the surface.

Claims

1. An amphiphilic water-based sizing agent, characterized in that, It contains both active functional groups and an "ether-ether-ketone" structure. The components comprise: 1–3.5 wt% polyamic acid and 96.5–99 wt% deionized water.

2. The aqueous sizing agent according to claim 1, characterized in that... The structures of the monomers containing active functional groups and their preparation reaction equations are as follows:

3. The method for preparing the monomer containing an active functional group (AHF) according to claim 2 comprises: (1) Under ice bath conditions, 2,7-dihydroxy-9-fluorenone and aniline were added to a three-necked flask in sequence, and methanesulfonic acid was slowly added under nitrogen protection and stirring. (2) After the material is added, keep it in an ice bath for 20 minutes, then slowly raise the temperature to 150°C and keep it at a constant temperature for 10 hours. (3) After the reaction is complete, cool the mixture to 373 K, add a mixed solution of triethylamine and ethanol, and continue stirring for 30 min. After the system cools to room temperature, filter the mixture and wash the filter cake repeatedly with ethanol until the filtrate is clear. (4) After drying the filter cake in an 80°C forced-air drying oven for 4 hours, it was transferred to an 80°C vacuum oven overnight to remove residual solvent, yielding a pale yellow powder. The yield was 70%.

4. The method for preparing the monomer (APBP) with the "ether-ether-ketone" structure according to claim 1 includes: (1) Use a 150ml two-necked round-bottom flask as the reaction apparatus. The apparatus is equipped with a nitrogen inlet, a nitrogen outlet, a Dean-Stark water separator, a condenser, a magnetic stirrer, and a heating device. (2) Add 2.18.2g (10mmol) of 4,4'-difluorobenzophenone, 2.40g (22mmol) of 4,-aminophenol, 2.76g (20mmol) of anhydrous potassium carbonate, 30ml of N-methylpyrrolidone, and 15ml of xylene to the flask in sequence. (3) Under nitrogen protection, the temperature is slowly increased. The moisture in the reaction apparatus is removed at 145℃ for 2 hours. The temperature is increased to 165℃ to remove the remaining xylene. The temperature is continued to be increased to 170℃ until the reaction is completed. The reaction progress is monitored by TLC (ethyl acetate: petroleum ether = 1:1). After the 4,4'-difluorobenzophenone is completely disappeared, the reaction apparatus is cooled to room temperature. (4) Slowly pour the reaction solution into 150 ml of 10% sodium hydroxide solution and stir vigorously to precipitate the reaction product. Filter the precipitate and wash the product with a large amount of 10% sodium hydroxide solution and water. (5) After washing, the product was transferred to a forced-air drying oven at 80°C to dry most of the moisture, and then transferred to a vacuum drying oven at 80°C overnight to dry any remaining trace moisture. The yield was 85%.

5. The polymerization method of the aqueous sizing agent according to claim 1 is as follows: (1) The diacid anhydride monomer used is commercially available 4,4'-oxydiphthalic anhydride (OPDA). (2) The reaction requires anhydrous and oxygen-free conditions. First, 20g of 4A molecular sieve is added to the reaction vessel to remove moisture from the reaction apparatus later. (3) Add 5.94g APBP (15mmol) and 5.70g AHF (15mmol) to a 250ml two-necked flask and purge with nitrogen three times, then add 25ml of ultra-dry DMF to dissolve. Will 9.39 g ODPA (30.3 mmol) was added to another 50 ml two-necked flask, purged with nitrogen three times, and then dissolved in 25 ml of ultra-dry DMF. (4) Under ice-water bath conditions, the dissolved ODPA solution was slowly added to the mixed solvent of APBP and AHF while stirring vigorously to avoid excessive local heat generation. After the addition was complete, the mixture was reacted under ice bath conditions for 4 hours, and then transferred to room temperature for 8 hours to obtain a viscous PAA solution.

6. The preparation method of the water-based sizing agent according to claim 1 is as follows: (1) The PAA solution was placed in a petri dish and a film was formed in the petri dish. The petri dish after film formation was placed in a forced-air drying oven at 80°C for 8 hours and then placed in a vacuum oven at 80°C for 20 hours to remove residual organic solvents. The PAA film after organic solvent removal was crushed to obtain PAA powder. (2) Preparation of water-based sizing agent: The obtained PAA powder was added to water, and a small amount of triethylamine (TEA) was added. The mixture was then mechanically stirred to obtain a clear solution. The obtained polyamic acid solution without organic solvents was diluted with deionized water to the appropriate concentration (2 wt%) and used as a sizing agent.

7. A carbon fiber composite material, obtained by combining carbon fibers coated with the sizing agent described in claim 1 with PEEK.

8. The composite material described in claim 8 is used in the aerospace field.

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