1. The application of the lignin-based hydrophilic sizing agent in the epoxy resin composite material is characterized in that: it comprises the following steps:

(1) soaking the carbon fiber cloth in 0.5-3.5 wt% lignin-based hydrophilic sizing agent aqueous solution at room temperature for 1-10min, then pulling the carbon fiber cloth out of the sizing agent aqueous solution at the speed of 1-5cm/min, and drying at 60-110 ℃ for 1-4 h to obtain the carbon fiber cloth after sizing pretreatment;

(2) and (2) arranging the carbon fiber subjected to the sizing pretreatment in the step (1) in a vacuum auxiliary forming device by adopting a vacuum auxiliary forming process, vacuumizing, injecting the epoxy resin uniformly mixed with the curing agent into the vacuum auxiliary forming device by utilizing negative pressure, vacuumizing for 20-40 minutes, and drying in a vacuum drying oven at 90-150 ℃ for 0.5-5 hours to obtain the carbon fiber reinforced epoxy resin composite material.

2. The application of the lignin-based hydrophilic sizing agent in the epoxy resin composite material according to claim 1, wherein the lignin-based hydrophilic sizing agent comprises: the epoxy resin in the step (2) is one or any combination of resorcinol epoxy resin, bisphenol A epoxy resin, bisphenol F epoxy resin, vinyl epoxy resin, hydroxymethyl bisphenol A epoxy resin or bisphenol S epoxy resin; one or any combination of ethylene diamine, hexamethylene diamine, diethylenetriamine, triethylene tetramine, diethylaminopropylamine or m-phenylenediamine serving as a curing agent; the mass ratio of the curing agent to the epoxy resin is 7-15: 90-120.

3. The application of the lignin-based hydrophilic sizing agent in the epoxy resin composite material according to claim 1, wherein the lignin-based hydrophilic sizing agent comprises: the lignin-based hydrophilic sizing agent in the step (1) is prepared by the following method steps:

(1) 4-18g of lignin is placed in an ozonization device and treated for 0.5-1.5h under the conditions that the ozone concentration is 7.5-20mg/L and the flow rate of mixed gas is 200-;

(2) dissolving the ozonized modified lignin and epoxy resin obtained in the step (1) in an organic solvent, stirring at room temperature for 3-15 minutes, then heating to 70-100 ℃, and stirring for reaction for 0.5-3 hours to obtain lignin-based epoxy resin;

(3) adding an organic solvent into the lignin-based epoxy resin obtained in the step (2), adding alcohol amine, and stirring at the temperature of 70-100 ℃ for reaction for 1-3.5h, wherein the stirring speed is 250-600rpm, so as to obtain lignin-based epoxy resin grafted with alcohol amine;

(4) adding a carboxylic acid solution into the lignin-based epoxy resin grafted with alcohol amine obtained in the step (3), stirring and reacting at 45-75 ℃ for 0.25-1.25 hours at the stirring speed of 250-600rpm, adding a silane coupling agent, reacting for 1-5 hours, and then: the mass ratio of the silane coupling agent, the epoxy resin in the step (2), the lignin in the step (1), the alcohol amine in the step (3) and the carboxylic acid is 0.1-1.2: 5-15: 0.5-2.5: 1-4: and 1-4, removing the solvent by rotary evaporation to obtain the lignin-based hydrophilic sizing agent.

4. The application of the lignin-based hydrophilic sizing agent in the epoxy resin composite material according to claim 3, wherein the lignin-based hydrophilic sizing agent comprises: the lignin in the step (1) is one or two of enzymatic hydrolysis lignin, ground wood lignin, sulfonate lignin or organic solvent lignin.

5. The application of the lignin-based hydrophilic sizing agent in the epoxy resin composite material according to claim 3, wherein the lignin-based hydrophilic sizing agent comprises: the epoxy resin in the step (2) is any one of resorcinol epoxy resin, bisphenol A epoxy resin, bisphenol F epoxy resin, vinyl epoxy resin, hydroxymethyl bisphenol A epoxy resin or bisphenol S epoxy resin; the organic solvent is N, N-dimethylformamide.

6. The application of the lignin-based hydrophilic sizing agent in the epoxy resin composite material according to claim 3, wherein the lignin-based hydrophilic sizing agent comprises: the organic solvent in the step (3) is one or any combination of methanol, ethanol, benzyl alcohol, ethylene glycol monobutyl ether or tetramethylene glycol monobutyl ether; the alcohol amine is one or any combination of ethanolamine, diethanolamine, isopropanolamine dimethylethanolamine or propylene glycol amine.

7. The application of the lignin-based hydrophilic sizing agent in the epoxy resin composite material according to claim 3, wherein the lignin-based hydrophilic sizing agent comprises: the carboxylic acid in the step (4) is one or any combination of oxalic acid, succinic acid, formic acid, acetic acid, propionic acid or phenylacetic acid; the silane coupling agent is one or any combination of vinyl triethoxysilane, methyl vinyl dioxy ethylene silane, methyl triacetoxy silane, vinyl trimethoxy silane, diethylamino methyl triethoxysilane, gamma-methacryloxypropyl-trimethoxysilane or gamma-aminopropyl triethoxysilane.

Background

Epoxy resin (Epoxyresin) has the advantages of stable chemical property, mildew resistance, simple process, no need of applying over-high pressure, good insulativity, chemical corrosion resistance, better solvent resistance and the like, thereby having wide application in composite materials. However, epoxy resin has poor wear resistance, poor impact damage resistance and poor toughness, so that the application of the epoxy resin in life is limited.

The carbon fiber is an excellent material with high specific modulus, high specific strength, low density, high temperature resistance and small thermal expansion coefficient, and is widely applied to the high-end fields of aerospace, automobile and the like. By combining the advantages of epoxy resin and carbon fiber, a high-strength and light-weight composite material can be prepared. However, carbon fibers exhibit surface chemical inertness, low surface energy and few chemical groups. The interface performance of the carbon fiber can be well improved by sizing treatment and addition of the compatilizer. By combining the epoxy resin matrix, the performance short plate of the matrix greatly reduces the overall performance of the composite material, and the composite material is brittle, easy to age, temperature-resistant and easy to damage. In addition, the materials are very difficult to combine, strict requirements on the control of the process are met, defects such as air holes, delamination and inclusion are easy to occur, and the problems of cracking and delamination are easy to occur due to overlarge local impact in the using process, so that a good sizing agent becomes an essential part.

The sizing agent has the following functions: (1) the electrostatic effect is reduced, the bundling capability of the carbon fiber is improved, and the subsequent weaving and spinning processing is facilitated; (2) air, moisture and dust are isolated, and the surface activity of the carbon fiber is kept; (3) filling the surface defects of the carbon fibers, and playing a role in assisting and reinforcing the carbon fibers to a certain extent; (4) the surface of the carbon fiber is smooth, the friction damage in subsequent processing is avoided, the burr is reduced, the service life of the carbon fiber is prolonged, and the carbon fiber is protected.

The sizing agent can be classified into a solution type sizing agent, an emulsion type sizing agent and a hydrophilic type sizing agent. The solution-type sizing agent is less used at present because a large amount of organic solvent is needed, the cost is relatively high, and the volatilization of the large amount of solvent has serious harm to the human health and the working environment. The emulsion sizing agent is a surfactant in nature because a large amount of emulsifier is needed, so that the surface of the carbon fiber is easy to absorb moisture; also, low molecular weight surfactants can affect the adhesion between the fibers and the resin. The addition of little or no emulsifier is an important direction for the development of sizing agents, the hydrophilic sizing agent is an improvement of the traditional emulsion sizing agent, hydrophilic groups are introduced into resin or functional groups are ionized to enable the resin to have self-emulsifying capacity, the resin can be self-emulsified and dispersed into emulsion in water without adding an emulsifier, and the emulsion is better dissolved in water, so that the use of the emulsifier is avoided, and the hydrophilic sizing agent has the advantages of small particle size, uniform particle size, high stability and the like. Therefore, the research on the hydrophilic environment-friendly and pollution-free sizing agent becomes the key point of the development of the sizing agent in the future.

Based on the above, the development of a hydrophilic environment-friendly sizing agent with high adhesion performance for treating carbon fibers, which improves the compatibility between the carbon fibers and epoxy resin, reduces the usage amount of a compatilizer, and meets the mechanical properties of materials, has become a technical problem to be solved urgently.

Disclosure of Invention

In order to solve the technical problem, the invention provides an application of lignin-based hydrophilic sizing agent in an epoxy resin composite material, which comprises the following steps:

(1) soaking the carbon fiber cloth in sizing agent aqueous solution with the concentration of 0.5-3.5 wt% for 1-10min at room temperature, then pulling the carbon fiber cloth out of the sizing agent aqueous solution at the speed of 1-5cm/min, and drying at the temperature of 60-110 ℃ for 1-4 hours to obtain the carbon fiber cloth subjected to sizing pretreatment;

(2) and (2) arranging the carbon fiber subjected to the sizing pretreatment in the step (1) in a vacuum auxiliary forming device by adopting a vacuum auxiliary forming process, vacuumizing, injecting the epoxy resin uniformly mixed with the curing agent into the vacuum auxiliary forming device by utilizing negative pressure, vacuumizing for 20-40 minutes, and drying in a vacuum drying oven at 90-150 ℃ for 0.5-5 hours to obtain the carbon fiber reinforced epoxy resin composite material.

Further, the epoxy resin in the step (2) is one or any combination of resorcinol epoxy resin, bisphenol A epoxy resin, bisphenol F epoxy resin, vinyl epoxy resin, hydroxymethyl bisphenol A epoxy resin or bisphenol S epoxy resin; one or any combination of ethylene diamine, hexamethylene diamine, diethylenetriamine, triethylene tetramine, diethylaminopropylamine or m-phenylenediamine serving as a curing agent; the mass ratio of the curing agent to the epoxy resin is 7-15: 90-120.

The invention also provides a sizing agent, which is prepared by the following method steps:

(1) 4-18g of lignin is placed in an ozonization device and treated for 0.5-1.5h under the conditions that the ozone concentration is 7.5-20mg/L and the flow rate of mixed gas is 200-;

(2) dissolving the ozonized modified lignin and epoxy resin obtained in the step (1) in an organic solvent, stirring at room temperature for 3-15 minutes, then heating to 70-100 ℃, and stirring for reaction for 0.5-3 hours to obtain lignin-based epoxy resin;

(3) adding an organic solvent into the lignin-based epoxy resin obtained in the step (2), adding alcohol amine, and stirring at the temperature of 70-100 ℃ for reaction for 1-3.5h, wherein the stirring speed is 250-600rpm, so as to obtain lignin-based epoxy resin grafted with alcohol amine;

(4) adding a carboxylic acid solution into the lignin-based epoxy resin grafted with alcohol amine obtained in the step (3), stirring and reacting at 45-75 ℃ for 0.25-1.25 hours at the stirring speed of 250-600rpm, adding a silane coupling agent, reacting for 1-5 hours, and then: the mass ratio of the silane coupling agent, the epoxy resin in the step (2), the lignin in the step (1), the alcohol amine and the carboxylic acid in the step (3) is 0.1-1.2: 5-15: 0.5-2.5: 1-4: and 1-4, removing the solvent by rotary evaporation to obtain the lignin-based hydrophilic sizing agent.

Further, the lignin in the step (1) is one or two of enzymatic hydrolysis lignin, ground wood lignin, sulfonate lignin or organic solvent lignin.

Further, the epoxy resin in the step (2) is any one of resorcinol epoxy resin, bisphenol A epoxy resin, bisphenol F epoxy resin, vinyl epoxy resin, hydroxymethyl bisphenol A epoxy resin or bisphenol S epoxy resin; the organic solvent is N, N-dimethylformamide.

Further, the organic solvent in the step (3) is one or any combination of methanol, ethanol, benzyl alcohol, ethylene glycol monobutyl ether or tetramethylene glycol monobutyl ether; the alcohol amine is one or any combination of ethanolamine, diethanolamine, isopropanolamine dimethylethanolamine or propylene glycol amine.

Further, the carboxylic acid in the step (4) is one or any combination of oxalic acid, succinic acid, formic acid, acetic acid, propionic acid or phenylacetic acid; the silane coupling agent is one or any combination of vinyl triethoxysilane, methyl vinyl dioxy ethylene silane, methyl triacetoxy silane, vinyl trimethoxy silane, diethylamino methyl triethoxysilane, gamma-methacryloxypropyl-trimethoxysilane or gamma-aminopropyl triethoxysilane.

The lignin-based hydrophilic sizing agent provided by the invention is a copolymer hydrophilic emulsion of lignin, a silane coupling agent, epoxy resin, alcohol amine and carboxylic acid. The adhesive has good adhesion performance, greatly shortens the dipping time, and is simple in sizing operation and easy to implement. And the good bridging effect is achieved between the carbon fiber and the epoxy resin matrix, so that the mechanical property of the composite material is further improved. The carbon fiber reinforced epoxy resin composite material prepared by pretreating the carbon fiber by adopting the sizing agent has excellent mechanical property.

Drawings

FIG. 1 is a comparison graph of IR spectra of organosolv lignin before and after ozonation in example 1;

FIG. 2 is an infrared spectrum of the lignin-based hydrophilic sizing of example 1;

FIG. 3 is a graph comparing the mechanical properties of the carbon fiber reinforced epoxy resin composite materials prepared in example 4 and comparative example 2.

Detailed Description

The following examples adopt carbon fiber cloth obtained by desizing a carbon fiber cloth of T700 to 12K, wherein the carbon fiber cloth is a carbon fiber cloth of type T700 to 12K manufactured by eastern beauty ltd, japan, and the desizing treatment is carried out before the sizing, and the desizing treatment adopts a method comprising: under the ultrasonic condition, soaking the carbon fiber cloth in a mixed solution of acetone, ethanol and water for 20-30min, then placing the soaked carbon fiber cloth in concentrated nitric acid for 24h, washing the carbon fiber cloth with deionized water, then drying the carbon fiber cloth at 85-100 ℃ to obtain the carbon fiber cloth subjected to de-sizing treatment, cutting the carbon fiber cloth into 6 x 8cm in size, cooling and placing the carbon fiber cloth in a dryer for later use. The acetone, the ethanol and the water are mixed according to the volume ratio: 1.5:1: 1.

Example 1

The preparation method of the sizing agent comprises the following steps:

(1) ozonization treatment of lignin: placing 5g of organic solvent lignin in an ozonization device, and treating for 1.5h under the conditions that the flow rate of mixed gas is 450L/h and the concentration of ozone is 13mg/L to obtain ozonized organic solvent lignin;

(2) dissolving 1.5g of ozonized organic solvent lignin obtained in the step (1) and 8.5g of bisphenol A epoxy resin in N, N-Dimethylformamide (DMF), stirring at room temperature for 15 minutes, and then heating to 95 ℃ and stirring for 1.5 hours to obtain lignin-based epoxy resin;

(3) adding absolute ethyl alcohol into the lignin-based epoxy resin obtained in the step (2), adding 3g of diethanolamine, stirring at 75 ℃ for 2h, and then stirring at the speed of 400rpm to obtain the lignin-based epoxy resin grafted with the diethanolamine;

(4) and (3) adding 1.75g of acetic acid solution into the lignin-based epoxy resin grafted with diethanolamine obtained in the step (3), stirring at 70 ℃ for 0.5 hour at the stirring speed of 400rpm, adding gamma-aminopropyltriethoxysilane (the mass ratio of the gamma-aminopropyltriethoxysilane to the bisphenol A epoxy resin in the step (2) is 1:9), reacting for 3.5 hours, and then performing rotary evaporation to remove the solvent to obtain the lignin-based hydrophilic sizing agent.

Example 2

The preparation method of the carbon fiber reinforced epoxy resin composite material (the concentration of the adopted sizing agent is 1.5 wt%):

(1) soaking the carbon fiber cloth in 1.5 wt% of the sizing agent aqueous solution obtained in the example 1 at room temperature for 6min, then pulling the carbon fiber cloth out of the sizing agent aqueous solution at the speed of 4cm/min, and drying at 90 ℃ for 2.5 hours to obtain the carbon fiber cloth after sizing pretreatment;

(2) and (2) adopting a vacuum auxiliary forming process, arranging the carbon fibers subjected to the sizing pretreatment in the step (1) in a vacuum auxiliary forming device, vacuumizing, uniformly mixing a curing agent diethylenetriamine and bisphenol A epoxy resin according to the mass ratio of 10:100 by using negative pressure, injecting into the vacuum auxiliary forming device, vacuumizing for 40 minutes, keeping vacuum, placing in a vacuum drying oven at 90 ℃ for 1 hour, and taking out after 2 hours at 120 ℃ to obtain the carbon fiber reinforced epoxy resin composite material.

Example 3

The preparation method of the carbon fiber reinforced epoxy resin composite material (the concentration of the adopted sizing agent is 2.0 wt%):

(1) soaking the carbon fiber cloth in 2.0 wt% aqueous solution of the sizing agent obtained in example 1 at room temperature for 6min, then pulling the carbon fiber cloth out of the aqueous solution of the sizing agent at the speed of 4cm/min, and drying at 90 ℃ for 2.5 hours to obtain carbon fiber cloth subjected to sizing pretreatment;

(2) and (2) adopting a vacuum auxiliary forming process, arranging the carbon fibers subjected to the sizing pretreatment in the step (1) in a vacuum auxiliary forming device, vacuumizing, uniformly mixing a curing agent diethylenetriamine and bisphenol A epoxy resin according to the mass ratio of 10:100 by using negative pressure, injecting into the vacuum auxiliary forming device, vacuumizing for 40 minutes, keeping vacuum, placing in a vacuum drying oven at 90 ℃ for 1 hour, and taking out after 2 hours at 120 ℃ to obtain the carbon fiber reinforced epoxy resin composite material.

Example 4

The preparation method of the carbon fiber reinforced epoxy resin composite material (the concentration of the adopted sizing agent is 2.5 wt%):

(1) soaking the carbon fiber cloth in 2.5 wt% aqueous solution of the sizing agent obtained in example 1 at room temperature for 6min, then pulling the carbon fiber cloth out of the aqueous solution of the sizing agent at the speed of 4cm/min, and drying at 90 ℃ for 2.5 h to obtain carbon fiber cloth subjected to sizing pretreatment;

(2) and (2) adopting a vacuum auxiliary forming process, arranging the carbon fibers subjected to the sizing pretreatment in the step (1) in a vacuum auxiliary forming device, vacuumizing, uniformly mixing a curing agent diethylenetriamine and bisphenol A epoxy resin according to the mass ratio of 10:100 by using negative pressure, injecting into the vacuum auxiliary forming device, vacuumizing for 40 minutes, keeping vacuum, placing in a vacuum drying oven at 90 ℃ for 1 hour, and taking out after 2 hours at 120 ℃ to obtain the carbon fiber reinforced epoxy resin composite material.

Example 5

The preparation method of the sizing agent comprises the following steps:

(1) ozonization treatment of lignin: placing 5g of enzymatic hydrolysis lignin in an ozonization device, and treating for 1.5h under the conditions that the flow rate of mixed gas is 450L/h and the concentration of ozone is 13mg/L to obtain ozonized enzymatic hydrolysis lignin;

(2) dissolving 1.5g of ozonized enzymatic lignin obtained in the step (1) and 8.5g of bisphenol A epoxy resin in DMF, mixing at room temperature, stirring for 15 minutes, and then heating to 95 ℃ and stirring for 1.5 hours to obtain lignin-based epoxy resin;

(3) adding absolute ethyl alcohol into the lignin-based epoxy resin obtained in the step (2), adding 3g of diethanolamine, stirring at 75 ℃ for 2h, and then stirring at the speed of 400rpm to obtain the lignin-based epoxy resin grafted with the diethanolamine;

(4) and (3) adding 3g of acetic acid solution into the lignin-based epoxy resin grafted with diethanolamine obtained in the step (3), stirring at 70 ℃ for 0.5 hour at the stirring speed of 400rpm, adding gamma-aminopropyltriethoxysilane (the mass ratio of the gamma-aminopropyltriethoxysilane to the bisphenol A epoxy resin in the step (2) is 1:9), reacting for 3.5 hours, and performing rotary evaporation to remove the solvent to obtain the lignin-based hydrophilic sizing agent.

The preparation method of the carbon fiber reinforced epoxy resin composite material (the concentration of the adopted sizing agent is 2.5 wt%):

(5) soaking the carbon fiber cloth in the sizing agent aqueous solution with the concentration of 2.5 wt% obtained in the step (4) for 6min at room temperature, then pulling the carbon fiber cloth out of the sizing agent aqueous solution at the speed of 4cm/min, and drying at 90 ℃ for 2.5 hours to obtain the carbon fiber cloth subjected to sizing pretreatment;

(6) and (3) adopting a vacuum auxiliary forming process, arranging the carbon fibers subjected to the sizing pretreatment in the step (5) in a vacuum auxiliary forming device, vacuumizing, uniformly mixing a curing agent diethylenetriamine and bisphenol A epoxy resin according to the mass ratio of 10:100 by using negative pressure, injecting into the vacuum auxiliary forming device, vacuumizing for 40 minutes, keeping vacuum, placing in a vacuum drying oven at 90 ℃ for 1 hour, and taking out after 2 hours at 120 ℃ to obtain the carbon fiber reinforced epoxy resin composite material.

Example 6

The preparation method of the sizing agent comprises the following steps:

(1) ozonization treatment of lignin: placing 5g of wood grinding lignin in an ozonization device, and treating for 1.5h under the conditions that the flow rate of mixed gas is 450L/h and the concentration of ozone is 13mg/L to obtain ozonized wood grinding lignin;

(2) dissolving 1.5g of ozonized ground wood lignin obtained in the step (1) and 8.5g of bisphenol A epoxy resin in DMF, mixing at room temperature, stirring for 15 minutes, and then heating to 95 ℃ and stirring for 1.5 hours to obtain lignin-based epoxy resin;

(3) adding absolute ethyl alcohol into the lignin-based epoxy resin obtained in the step (2), adding 3g of diethanolamine, stirring at 75 ℃ for 2h, and then stirring at the speed of 400rpm to obtain the lignin-based epoxy resin grafted with the diethanolamine;

(4) and (3) adding 3g of acetic acid solution into the lignin-based epoxy resin grafted with diethanolamine obtained in the step (3), stirring at 70 ℃ for 0.5 hour at the stirring speed of 400rpm, adding gamma-aminopropyltriethoxysilane (the mass ratio of the gamma-aminopropyltriethoxysilane to the bisphenol A epoxy resin in the step (2) is 1:9), reacting for 3.5 hours, and performing rotary evaporation to remove the solvent to obtain the lignin-based hydrophilic sizing agent.

The preparation method of the carbon fiber reinforced epoxy resin composite material (the concentration of the adopted sizing agent is 2.5 wt%):

(5) soaking the carbon fiber cloth in the sizing agent aqueous solution with the concentration of 2.5 wt% obtained in the step (4) for 6min at room temperature, then pulling the carbon fiber cloth out of the sizing agent aqueous solution at the speed of 4cm/min, and drying at 90 ℃ for 2.5 hours to obtain the carbon fiber cloth subjected to sizing pretreatment;

(6) and (3) adopting a vacuum auxiliary forming process, arranging the carbon fibers subjected to the sizing pretreatment in the step (5) in a vacuum auxiliary forming device, vacuumizing, uniformly mixing a curing agent diethylenetriamine and bisphenol A epoxy resin according to the mass ratio of 10:100 by using negative pressure, injecting into the vacuum auxiliary forming device, vacuumizing for 40 minutes, keeping vacuum, placing in a vacuum drying oven at 90 ℃ for 1 hour, and taking out after 2 hours at 120 ℃ to obtain the carbon fiber reinforced epoxy resin composite material.

Example 7

The preparation method of the sizing agent comprises the following steps:

(1) ozonization treatment of lignin: 5g of sulfonate lignin is placed in an ozonization device, and is treated for 1.5h under the conditions that the flow rate of mixed gas is 450L/h and the concentration of ozone is 13mg/L to obtain the sulfonate lignin subjected to ozonization;

(2) dissolving 1.5g of ozonized sulfonate lignin obtained in the step (1) and 8.5g of bisphenol A epoxy resin in DMF, mixing at room temperature, stirring for 15 minutes, and then heating to 95 ℃ and stirring for 1.5 hours to obtain lignin-based epoxy resin;

(3) adding absolute ethyl alcohol into the lignin-based epoxy resin obtained in the step (2), adding 3g of diethanolamine, stirring at 75 ℃ for 2h, and then stirring at the speed of 400rpm to obtain the lignin-based epoxy resin grafted with the diethanolamine;

(4) and (3) adding 3g of acetic acid solution into the lignin-based epoxy resin grafted with diethanolamine obtained in the step (3), stirring at 70 ℃ for 0.5 hour at the stirring speed of 400rpm, adding gamma-aminopropyltriethoxysilane (the mass ratio of the gamma-aminopropyltriethoxysilane to the bisphenol A epoxy resin in the step (2) is 1:9), reacting for 3.5 hours, and performing rotary evaporation to remove the solvent to obtain the lignin-based hydrophilic sizing agent.

The preparation method of the carbon fiber reinforced epoxy resin composite material (the concentration of the adopted sizing agent is 2.5 wt%):

(5) soaking the carbon fiber cloth in the sizing agent aqueous solution with the concentration of 2.5 wt% obtained in the step (4) for 6min at room temperature, then pulling the carbon fiber cloth out of the sizing agent aqueous solution at the speed of 4cm/min, and drying at 90 ℃ for 2.5 hours to obtain the carbon fiber cloth subjected to sizing pretreatment;

(6) and (3) adopting a vacuum auxiliary forming process, arranging the carbon fibers subjected to the sizing pretreatment in the step (5) in a vacuum auxiliary forming device, vacuumizing, uniformly mixing a curing agent diethylenetriamine and bisphenol A epoxy resin according to the mass ratio of 10:100 by using negative pressure, injecting into the vacuum auxiliary forming device, vacuumizing for 40 minutes, keeping vacuum, placing in a vacuum drying oven at 90 ℃ for 1 hour, and taking out after 2 hours at 120 ℃ to obtain the carbon fiber reinforced epoxy resin composite material.

Example 8

The preparation method of the carbon fiber reinforced epoxy resin composite material (the concentration of the adopted sizing agent is 2.5 wt%):

(1) soaking the carbon fiber cloth in the sizing agent aqueous solution with the concentration of 2.5 wt% obtained in the example 1 for 10min at room temperature, then pulling the carbon fiber cloth out of the sizing agent aqueous solution at the speed of 5cm/min, and drying the carbon fiber cloth for 2.5 hours at the temperature of 90 ℃ to obtain the carbon fiber cloth after sizing pretreatment;

(2) and (2) adopting a vacuum auxiliary forming process, arranging the carbon fibers subjected to the sizing pretreatment in the step (1) in a vacuum auxiliary forming device, vacuumizing, uniformly mixing a curing agent diethylenetriamine and bisphenol A epoxy resin according to the mass ratio of 9:90 by using negative pressure, injecting into the vacuum auxiliary forming device, vacuumizing for 30 minutes, keeping vacuum, placing in a vacuum drying oven at 90 ℃ for 1 hour, and taking out after 2 hours at 120 ℃ to obtain the carbon fiber reinforced epoxy resin composite material.

Example 9

The preparation method of the carbon fiber reinforced epoxy resin composite material (the concentration of the adopted sizing agent is 2.5 wt%):

(1) soaking the carbon fiber cloth in 2.5 wt% aqueous solution of the sizing agent obtained in example 1 at room temperature for 6min, then pulling the carbon fiber cloth out of the aqueous solution of the sizing agent at the speed of 4cm/min, and drying at 90 ℃ for 2 hours to obtain carbon fiber cloth subjected to sizing pretreatment;

(2) and (2) adopting a vacuum auxiliary forming process, arranging the carbon fiber subjected to the sizing pretreatment in the step (1) in a vacuum auxiliary forming device, vacuumizing, uniformly mixing a curing agent diethylenetriamine and bisphenol A epoxy resin according to the mass ratio of 13:90 by using negative pressure, injecting into the vacuum auxiliary forming device, vacuumizing for 30 minutes, keeping vacuum, placing in a vacuum drying oven at 90 ℃ for 1.5 hours, and taking out after 120 ℃ for 1.5 hours to obtain the carbon fiber reinforced epoxy resin composite material.

Example 10

The preparation method of the sizing agent comprises the following steps:

(1) ozonization treatment of lignin: putting 8g of organic solvent lignin in an ozonization device, and treating for 1.5h under the conditions that the flow rate of mixed gas is 500L/h and the concentration of ozone is 19mg/L to obtain ozonized organic solvent lignin;

(2) dissolving 2g of ozonized organic solvent lignin obtained in the step (1) and 10g of bisphenol F type epoxy resin in N, N-Dimethylformamide (DMF), stirring at room temperature for 10 minutes, then heating to 90 ℃, and stirring for 1.5 hours to obtain lignin-based epoxy resin;

(3) adding ethylene glycol into the lignin-based epoxy resin obtained in the step (2), adding 3g of isopropanolamine dimethylethanolamine, stirring at 75 ℃ for 2h, and then stirring at the speed of 400rpm to obtain lignin-based epoxy resin grafted with isopropanolamine dimethylethanolamine;

(4) and (3) adding 1.75g of propionic acid solution into the lignin-based epoxy resin grafted with isopropanolamine dimethylethanolamine obtained in the step (3), stirring at 70 ℃ for 0.5 hour at the stirring speed of 400rpm, adding diethylaminomethyl triethoxysilane (the mass ratio of the diethylaminomethyl triethoxysilane to the bisphenol F epoxy resin in the step (2) is 1:9), reacting for 3.5 hours, and performing rotary evaporation to remove the solvent to obtain the lignin-based hydrophilic sizing agent.

The preparation method of the carbon fiber reinforced epoxy resin composite material comprises the following steps:

(5) soaking the carbon fiber cloth in the sizing agent aqueous solution with the concentration of 2.5 wt% obtained in the step (4) for 6min at room temperature, then pulling the carbon fiber cloth out of the sizing agent aqueous solution at the speed of 4cm/min, and drying at 90 ℃ for 2.5 hours to obtain the carbon fiber cloth subjected to sizing pretreatment;

(6) and (3) arranging the carbon fiber subjected to the sizing pretreatment in the step (5) in a vacuum auxiliary forming device by adopting a vacuum auxiliary forming process, vacuumizing, uniformly mixing a curing agent triethylene tetramine and bisphenol F epoxy resin according to the mass ratio of 7:100 by using negative pressure, injecting into the vacuum auxiliary forming device, vacuumizing for 40 minutes, keeping the vacuum, placing in a vacuum drying oven for 1 hour at 90 ℃, and taking out after 2 hours at 120 ℃ to obtain the carbon fiber reinforced epoxy resin composite material.

Example 11

The preparation method of the sizing agent comprises the following steps:

(1) ozonization treatment of lignin: placing 5g of organic solvent lignin in an ozonization device, and treating for 1.5h under the conditions that the flow rate of mixed gas is 350L/h and the concentration of ozone is 13mg/L to obtain ozonized organic solvent lignin;

(2) dissolving 1.5g of ozonized organic solvent lignin obtained in the step (1) and 8.5g of resorcinol epoxy resin in N, N-Dimethylformamide (DMF), stirring at room temperature for 15 minutes, then heating to 95 ℃, and stirring for 1.5 hours to obtain lignin-based epoxy resin;

(3) adding absolute ethyl alcohol, methanol and ethylene glycol monobutyl ether into the lignin-based epoxy resin obtained in the step (2), adding 3.5g of ethanolamine, stirring for 2 hours at 75 ℃, and then stirring at the speed of 500rpm to obtain the lignin-based epoxy resin grafted with the ethanolamine;

(4) and (3) adding 2.0g of formic acid solution into the lignin-based epoxy resin of the grafted ethanolamine obtained in the step (3), stirring at 65 ℃ for 0.75 hour at the stirring speed of 500rpm, adding gamma methylvinyldioxyethylenesilane (the mass ratio of the gamma methylvinyldioxyethylenesilane to the resorcinol epoxy resin in the step (2) is 1:9), reacting for 3 hours, and then performing rotary evaporation to remove the solvent to obtain the lignin-based hydrophilic sizing agent.

The preparation method of the carbon fiber reinforced epoxy resin composite material (the concentration of the adopted sizing agent is 2.5 wt%):

(5) soaking the carbon fiber cloth in the sizing agent aqueous solution with the concentration of 2.5 wt% obtained in the step (4) for 6min at room temperature, then pulling the carbon fiber cloth out of the sizing agent aqueous solution at the speed of 4cm/min, and drying at 90 ℃ for 2.5 hours to obtain the carbon fiber cloth subjected to sizing pretreatment;

(6) and (3) adopting a vacuum auxiliary forming process, arranging the carbon fibers subjected to the sizing pretreatment in the step (5) in a vacuum auxiliary forming device, vacuumizing, uniformly mixing a curing agent diethylenetriamine and bisphenol A epoxy resin in a ratio of 10:100 by using negative pressure, injecting into the vacuum auxiliary forming device, vacuumizing for 40 minutes, keeping vacuum, placing in a vacuum drying oven at 90 ℃ for 1 hour, and taking out after 2 hours at 120 ℃ to obtain the carbon fiber reinforced epoxy resin composite material.

Example 12

The preparation method of the sizing agent comprises the following steps:

(1) ozonization treatment of lignin: 4g of organic solvent lignin is placed in an ozonization device, and is treated for 0.5h under the conditions that the flow rate of mixed gas is 200L/h and the concentration of ozone is 7.5mg/L, so that the ozonized organic solvent lignin is obtained;

(2) dissolving 0.5g of ozonized organic solvent lignin obtained in the step (1) and 5g of bisphenol A epoxy resin in N, N-Dimethylformamide (DMF), stirring at room temperature for 3 minutes, then heating to 70 ℃, and stirring for 0.5 hour to obtain lignin-based epoxy resin;

(3) adding absolute ethyl alcohol into the lignin-based epoxy resin obtained in the step (2), adding 1g of diethanolamine, stirring at 70 ℃ for 1h, and then stirring at the speed of 250rpm to obtain the lignin-based epoxy resin grafted with the diethanolamine;

(4) and (3) adding 1g of acetic acid solution into the lignin-based epoxy resin grafted with diethanolamine obtained in the step (3), stirring at 45 ℃ for 0.25 hour at the stirring speed of 250rpm, adding gamma-aminopropyltriethoxysilane (the mass ratio of the gamma-aminopropyltriethoxysilane to the bisphenol A epoxy resin in the step (2) is 0.1: 15), reacting for 1 hour, and performing rotary evaporation to remove the solvent to obtain the lignin-based hydrophilic sizing agent.

The preparation method of the carbon fiber reinforced epoxy resin composite material (the concentration of the adopted sizing agent is 2.5 wt%):

(5) soaking the carbon fiber cloth in the sizing agent aqueous solution with the concentration of 2.5 wt% obtained in the step (4) for 1min at room temperature, then pulling the carbon fiber cloth out of the sizing agent aqueous solution at the speed of 1cm/min, and drying at 60 ℃ for 1 hour to obtain the carbon fiber cloth subjected to sizing pretreatment;

(6) and (3) arranging the carbon fiber subjected to the sizing pretreatment in the step (5) in a vacuum auxiliary forming device by adopting a vacuum auxiliary forming process, vacuumizing, injecting the epoxy resin which is obtained by uniformly mixing the curing agent diethylenetriamine and the bisphenol A epoxy resin in a mass ratio of 7:120 into the vacuum auxiliary forming device by utilizing negative pressure, vacuumizing for 20 minutes, keeping vacuum, placing in a vacuum drying oven at 90 ℃ for 0.5 hour, and taking out to obtain the carbon fiber reinforced epoxy resin composite material.

Example 13

The preparation method of the sizing agent comprises the following steps:

(1) ozonization treatment of lignin: placing 18g of organic solvent lignin in an ozonization device, and treating for 1.5h under the conditions that the flow rate of mixed gas is 500L/h and the concentration of ozone is 20mg/L to obtain ozonized organic solvent lignin;

(2) dissolving 2.5g of ozonized organic solvent lignin obtained in the step (1) and 15g of bisphenol A epoxy resin in N, N-Dimethylformamide (DMF), stirring at room temperature for 15 minutes, then heating to 100 ℃, and stirring for 3 hours to obtain lignin-based epoxy resin;

(3) adding absolute ethyl alcohol into the lignin-based epoxy resin obtained in the step (2), adding 4g of diethanol amine, stirring at 100 ℃ for 3.5 hours, and then stirring at the speed of 600rpm to obtain the lignin-based epoxy resin grafted with diethanol amine;

(4) and (3) adding 4g of acetic acid solution into the lignin-based epoxy resin grafted with diethanolamine obtained in the step (3), stirring at 75 ℃ for 1.25 hours at the stirring speed of 600rpm, adding methylvinyldioxyethylenesilane (the mass ratio of methylvinyldioxyethylenesilane to bisphenol A epoxy resin in the step (2) is 1.2: 5), reacting for 5 hours, and performing rotary evaporation to remove the solvent to obtain the lignin-based hydrophilic sizing agent.

The preparation method of the carbon fiber reinforced epoxy resin composite material (the concentration of the adopted sizing agent is 3.5 wt%):

(5) soaking the carbon fiber cloth in the sizing agent aqueous solution with the concentration of 3.5 wt% obtained in the step (4) for 10min at room temperature, then pulling the carbon fiber cloth out of the sizing agent aqueous solution at the speed of 5cm/min, and drying at 110 ℃ for 4 hours to obtain the carbon fiber cloth subjected to sizing pretreatment;

(6) and (3) adopting a vacuum auxiliary forming process, arranging the carbon fiber subjected to the sizing pretreatment in the step (5) in a vacuum auxiliary forming device, vacuumizing, uniformly mixing a curing agent diethylenetriamine and bisphenol A epoxy resin in a mass ratio of 15:90 by using negative pressure, injecting into the vacuum auxiliary forming device, vacuumizing for 40 minutes, keeping vacuum, placing in a vacuum drying oven at 150 ℃ for 5 hours, and taking out to obtain the carbon fiber reinforced epoxy resin composite material.

Comparative example 1

The preparation method of the carbon fiber reinforced epoxy resin composite material comprises the following steps:

(1) soaking the T700-12K carbon fiber cloth in deionized water at room temperature for 6min, then pulling the carbon fiber cloth out of the deionized water at the speed of 4cm/min, and drying at 90 ℃ for 2.5 hours to obtain the pretreated carbon fiber cloth;

(2) and (2) arranging the carbon fiber pretreated in the step (1) in a vacuum auxiliary forming device by adopting a vacuum auxiliary forming process, vacuumizing, uniformly mixing a curing agent diethylenetriamine and bisphenol A epoxy resin in a quantity ratio of 10:100 by utilizing negative pressure, injecting into the vacuum auxiliary forming device, vacuumizing for 40 minutes, keeping vacuum, placing in a vacuum drying oven at 90 ℃ for 1 hour, and taking out after 2 hours at 120 ℃ to obtain the carbon fiber reinforced epoxy resin composite material.

Comparative example 2

The preparation method of the carbon fiber reinforced epoxy resin composite material comprises the following steps:

(1) soaking the carbon fiber cloth subjected to the de-sizing treatment of the T700-12K carbon fiber cloth in deionized water for 6min at room temperature, then pulling the carbon fiber cloth out of the deionized water at the speed of 4cm/min, and drying at 90 ℃ for 2.5 hours to obtain the pretreated carbon fiber cloth;

(2) and (2) arranging the carbon fiber pretreated in the step (1) in a vacuum auxiliary forming device by adopting a vacuum auxiliary forming process, vacuumizing, injecting the mixture of curing agent diethylenetriamine and bisphenol A epoxy resin with the amount ratio of 10:100 into the vacuum auxiliary forming device by utilizing negative pressure, vacuumizing for 40 minutes, keeping the vacuum, placing the mixture in a vacuum drying oven at 90 ℃ for 1 hour, and taking out the mixture after 2 hours at 120 ℃ to obtain the carbon fiber reinforced epoxy resin composite material.

FIG. 1 is a comparison spectrum of infrared spectra of organosolv lignin before and after ozonization in example 1, in which the three-dimensional network structure of benzene ring in organosolv lignin is destroyed by ozonization, and active groups such as hydroxyl groups are exposed. As can be seen from FIG. 1, 2990cm appears for both spectrograms^-1The characteristic peak is the vibration absorption peak of weak free phenolic hydroxyl group existing on the lignin, and the hydroxyl peak is obviously enhanced through ozonization, which indicates that the ozonization successfully increases the content of the hydroxyl group in the organic solvent lignin. At 1709cm^-1A strong vibration peak appears, which is attributed to the stretching vibration of C ═ O, at 1600cm^-1The peak corresponding to the aromatic benzene skeleton is reduced, which indicates that the benzene ring on the organic solvent lignin is broken to expose more active groups through ozonization.

FIG. 2 is an IR spectrum of 1043cm of lignin-based hydrophilic sizing agent obtained in example 1^-1，1118cm^-1，1385cm^-1The peak at is Si-O-CH₂CH₃All of which represent successful grafting of the sizing agent with the silane coupling agent.

The results of the stability tests of the sizing agents of examples 2 to 4 with different concentrations and the sizing agents described in the literature are shown in Table 1.

The carbon fiber fuzz amount test was performed on the carbon fiber materials after the sizing pretreatment described in examples 2 to 4 and the literature, and the results are shown in table 2.

Mechanical tests were performed on the composite materials prepared in examples 2 to 4 and comparative examples 1 to 2, and the results are shown in Table 3.

Table 1: sizing agent stability test results

Comparison of conditions	Stability (Tian)
		Example 2	240
Example 3	240
		Example 4	240
PEG4000 modified epoxy resin sizing agent	14
		Graphene oxide modified emulsion type carbon fiber sizing agent	30

The stability test period for the different concentrations of sizing agents of examples 2-4 in table 1 is 240 days, not excluding the case where the stability period is followed by a stabilization period.

In Table 1, the PEG4000 modified epoxy resin sizing agent is derived from the researches on the modification of polyethylene glycol and the performance of a water-based epoxy resin emulsion [ J ] "(the source is a novel chemical material, Yankunming, Lipeng, Chenbin, Yang Xiaoping 2019,47(07):94-98.), and the oxidized graphene modified emulsion type carbon fiber sizing agent is derived from the formula of a carbon fiber sizing agent for reinforcing polypropylene and a preparation method [ P ]" (the source is Wangting, Ma Xiao Long, Ge Mo Yi, Wan Cui, Teng Dyang, Li Yang, Shandong: CN105176008A, 2015-12-23.).

As can be seen from Table 1, the hydrophilic sizing agent prepared by the invention has better and excellent stability, thereby demonstrating that the hydrophilic lignin-based sizing agent prepared by the invention has remarkable stabilizing effect in the aspects of production, transportation, use and the like.

Table 2 shows the comparison of the amounts of broken filaments of the HS-12K carbon fiber materials in the examples 2-4 and the T700-12K carbon fiber cloth, the carbon fiber cloth after the desizing treatment of the T700-12K carbon fiber cloth and the sizing treatment.

The carbon fiber bundle is dragged between two polyurethane foams with the specification of 40mm in length, 10mm in width and 5mm in thickness at a constant speed of 15m/min, the load of the polyurethane is 200g, and the amount of the fuzz on the polyurethane foam is recorded after 50 m.

Table 2: carbon fiber broken filament quantity test result after sizing pretreatment

Comparison of conditions	Carbon fiber wool yarn amount (mg)
		Example 2	3.2±0.1
Example 3	3.1±0.1
		Example 4	3.0±0.1
T700-12K carbon fiber cloth	5.0±0.1
		Carbon fiber cloth after desizing treatment of T700-12K carbon fiber cloth	25±0.2
HS-12K carbon fiber material subjected to sizing treatment	6.0±0.5

The amount of filaments of the HS-12K carbon fiber material after the sizing treatment is also shown in Table 2. The amount of the wool of the HS-12K carbon fiber material is derived from the surface structure and the wear resistance research [ J ] of the domestic T800S-grade carbon fiber (solid rocket technology, Hui Chi Mei, Hou Wen, Chi hong, Zhang Cheng Shuang, Zhao ran. 1-7).

As can be seen from Table 2, the amount of fuzz in the sized carbon fiber is significantly reduced after the lignin-based hydrophilic sizing agent is added. Compared with the carbon fiber cloth after the desizing treatment of the T700-12K carbon fiber cloth, the carbon fiber material of the example 4 added with the sizing agent has 88 percent of reduction in the amount of carbon fiber fuzz. Therefore, the lignin-based hydrophilic sizing agent prepared by the invention has a remarkable effect in the aspect of reducing the broken filament quantity of the carbon fiber. The wear resistance of the carbon fiber is obviously improved after the sizing agent disclosed by the invention is used for sizing, and the subsequent processing of the carbon fiber is facilitated.

Table 3: comparison of mechanical properties of carbon fiber reinforced epoxy resin composites prepared in examples 2-4 and comparative examples 1-2

As can be seen from the comparison, compared with the comparative example, the carbon fiber reinforced epoxy resin composite material prepared by pretreating carbon fibers by adopting the sizing agent with the specific component has excellent mechanical properties.

Compared with the carbon fiber reinforced epoxy resin composite materials of comparative example 2 and comparative example 1, the carbon fiber reinforced epoxy resin composite material added with the sizing agent in example 2 of the invention has higher mechanical properties than those of comparative example 2 and comparative example 1, wherein compared with comparative example 2, the bending strength is improved by 67.7%, and the interlaminar shear strength is improved by 49.1%; compared with comparative example 1, the bending strength is improved by 10.1%, and the interlaminar shear strength is improved by 33.3%. Therefore, the lignin-based hydrophilic sizing agent prepared by the invention is superior to the prior art in the aspect of improving the mechanical property of the composite material.

The sizing agent reasonably utilizes lignin, and utilizes a large number of benzene rings on the lignin and carbon six-membered rings of a carbon fiber matrix to perform pi-pi conjugation, so that the interface binding force between the sizing agent and the carbon fiber is enhanced; the sizing agent contains epoxy groups, and can react with epoxy resin to perform co-curing; on the other hand, the sizing agent contains the grafted silane coupling agent, and the silane coupling agent and the epoxy resin matrix molecules generate physical entanglement to enhance the interface bonding force while keeping the hydrophilicity, so that the comprehensive mechanical property of the composite material is improved.

The above description of the embodiments is only intended to facilitate the understanding of the method of the invention and its core idea. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention.