阅读说明：本技术 一种碳纤维用二氧化硅改性环氧树脂上浆剂及其制备方法和应用 (Silicon dioxide modified epoxy resin sizing agent for carbon fibers and preparation method and application thereof ) 是由 王傲峰 雷彩红 崔泽君 徐睿杰 张笑晴 于 2021-08-17 设计创作，主要内容包括：本发明属于上浆剂技术领域,公开了一种碳纤维用二氧化硅改性环氧树脂上浆剂及其制备方法和应用。该上浆剂的制备原料包括以下按重量份数计的组分：不同分子量酰胺低聚物20-40份,环氧树脂10-30份,改性二氧化硅5-30份,催化剂0.1-3份,溶剂30-60份；和一般的上浆剂相比,本发明制备的上浆剂中含有经改性的二氧化硅且经不同低分子量的酰胺固化,上浆后的碳纤维表面极性力显著增加,表面能提高,大大增加了碳纤维的集束性,碳纤维与基体间的界面强度得到提高,也提高了制备成型的复合材料的各项力学性能。(The invention belongs to the technical field of sizing agents, and discloses a silicon dioxide modified epoxy resin sizing agent for carbon fibers, and a preparation method and application thereof. The sizing agent is prepared from the following raw materials in parts by weight: 20-40 parts of amide oligomer with different molecular weights, 10-30 parts of epoxy resin, 5-30 parts of modified silicon dioxide, 0.1-3 parts of catalyst and 30-60 parts of solvent; compared with the common sizing agent, the sizing agent prepared by the invention contains modified silicon dioxide and is solidified by amides with different low molecular weights, the polarity force of the surface of the sized carbon fiber is obviously increased, the surface energy is improved, the bundling property of the carbon fiber is greatly increased, the interface strength between the carbon fiber and a matrix is improved, and various mechanical properties of the prepared and molded composite material are also improved.)

1. A silicon dioxide modified epoxy resin sizing agent for carbon fibers is characterized in that: the sizing agent is prepared from the following raw materials in parts by weight: 20-40 parts of amide oligomer with different molecular weights, 10-30 parts of epoxy resin, 5-30 parts of modified silicon dioxide, 0.1-3 parts of catalyst and 30-60 parts of solvent.

2. The silica-modified epoxy resin sizing agent for carbon fibers according to claim 1, wherein: the sizing agent is prepared from the following raw materials in parts by weight: 20-30 parts of amide oligomer with different molecular weights, 10-20 parts of epoxy resin, 10-20 parts of modified silicon dioxide, 0.1-2 parts of catalyst and 30-50 parts of solvent.

3. The silica-modified epoxy resin sizing agent for carbon fibers according to claim 1, wherein: the amide oligomers with different molecular weights are more than one of caprolactam, acetamide, 2, 4-dihydroxy benzamide, valeramide and dimethylformamide; the epoxy resin is more than one of glycidyl ester type epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, alicyclic epoxy resin, glycidyl amine type epoxy resin and linear aliphatic epoxy resin; the catalyst is more than one of N-N dimethylformamide, triphenylphosphine and potassium hydrogen phthalate; the solvent is more than one of n-butanol, ethanol, acetone, isopropanol, chloroform, dichloromethane, ethyl acetate, methanol, diethyl ether and butyl acetate.

4. The silica-modified epoxy resin sizing agent for carbon fibers according to claim 1, wherein: the particle size of the modified silicon dioxide is 5-100nm, and the modified silicon dioxide is prepared by the following preparation steps: dissolving silicon dioxide in ethanol-water solution to obtain a solution with the mass fraction of 20%, adding a KH550 coupling agent with the mass fraction of 0.1-5%, performing ultrasonic dispersion for 10 minutes, stirring and dispersing at 80 ℃ for 2 hours, performing high-speed centrifugation on the mixed solution, removing supernatant, performing reduced pressure suction filtration, repeatedly moistening with ethanol, and drying in vacuum for 10 hours to obtain the modified silicon dioxide.

5. The method of claim 1, comprising the steps of:

heating and dissolving amide oligomers with different molecular weights and epoxy resin in a solvent, adding a catalyst to react to obtain an epoxy sizing agent, stirring and mixing the epoxy sizing agent with deionized water to prepare an emulsion, and mixing and reacting the emulsion with modified silicon dioxide under the heating and stirring conditions to obtain the silicon dioxide modified epoxy resin sizing agent.

6. The preparation method according to claim 5, wherein the temperature for heating and dissolving is 60-100 ℃; the heating and stirring temperature is 60-120 ℃; the time for adding the catalyst to react is 2-24 h; the mixing reaction time is 1-24 h.

7. The use of the silica-modified epoxy resin sizing agent for carbon fibers according to claim 1 for the preparation of polyamide composites, characterized in that: the polyamide composite material comprises a polyamide 6, polyamide 66 or polyamide 46 composite material.

8. Use according to claim 7, characterized in that: the polyamide composite material is polyamide 6, and the polyamide 6 is prepared from the following raw materials in parts by weight: 5-45 parts of reinforcing agent, 650-80 parts of polyamide and 1-5 parts of sizing agent.

9. Use according to claim 7, characterized in that: the polyamide composite material is polyamide 66, and the polyamide 66 is prepared from the following raw materials in parts by weight: 5-40 parts of reinforcing agent, 6660-95 parts of polyamide and 1-8 parts of sizing agent.

10. Use according to claim 7, characterized in that: the polyamide composite material is polyamide 46, and the polyamide 46 is prepared from the following raw materials in parts by weight: 5-50 parts of reinforcing agent, 4660-90 parts of polyamide and 1-10 parts of sizing agent.

Technical Field

The invention belongs to the technical field of sizing agents, and particularly relates to a silicon dioxide modified epoxy resin sizing agent for carbon fibers, and a preparation method and application thereof.

Background

Carbon fiber is one of the advanced novel materials with high strength and high modulus, can resist high temperature and friction, and has the properties of heat conduction and electric conduction. Carbon fibers are usually used in combination with other substrates as a reinforcement to provide reinforcement. The method is mainly applied to the military industry and civil fields, such as aerospace, machinery, light textile, automobile, electronics and other industries.

However, carbon fibers have many defects, especially poor quality of precursor and more fiber impurities, which cause the carbon fibers to have poor performance, large dispersion coefficient, poor compatibility with other base materials, large bottleneck in downstream markets, difficult processing and high production cost, and therefore need to be subjected to sizing treatment. The sizing treatment is to soak the carbon fiber in sizing agent to form a layer of film on the surface of the carbon fiber, which can protect the surface of the carbon fiber and improve the interface acting force, so as to improve the surface activity of the carbon fiber and combine the carbon fiber with polymer well. Therefore, the preparation of sizing agents is highly demanding, the difference of the base materials causes the difference of the interface performance, and the selected sizing agents are also different. In industry, different special sizing agents are mostly prepared for different materials, however, the preparation method of the sizing agent is rarely published and becomes a confidential technology, so that the problem of solving the carbon fiber sizing agent is urgent, and the development of a novel sizing agent which has stable performance and can greatly improve the bonding strength of the carbon fiber and a matrix is urgently needed.

The emulsion type sizing agent disclosed in the Chinese patent CN201210398172.X has the advantages that more additives need to be added, the process is complex, the cost is high, and the mechanical strength of the prepared composite material is not greatly improved.

Disclosure of Invention

In order to overcome the defects and shortcomings of the prior art and solve the problems that the compatibility and the interface performance of the existing carbon fiber reinforced material and the plastic matrix material are poor, so that the reinforcing effect of the plastic matrix material is poor, the invention mainly aims to provide the silicon dioxide modified epoxy resin sizing agent for carbon fibers.

The invention also aims to provide a preparation method of the silicon dioxide modified epoxy resin sizing agent for the carbon fibers.

The invention also aims to provide application of the silicon dioxide modified epoxy resin sizing agent for the carbon fibers.

The purpose of the invention is realized by the following technical scheme:

a silicon dioxide modified epoxy resin sizing agent for carbon fibers is prepared from the following raw materials in parts by weight: 20-40 parts of amide oligomer with different molecular weights, 10-30 parts of epoxy resin, 5-30 parts of modified silicon dioxide, 0.1-3 parts of catalyst and 30-60 parts of solvent.

Preferably, the preparation raw materials of the sizing agent comprise the following components in parts by weight: 20-30 parts of amide oligomer with different molecular weights, 10-20 parts of epoxy resin, 10-20 parts of modified silicon dioxide, 0.1-2 parts of catalyst and 30-50 parts of solvent.

Preferably, the amide oligomers with different molecular weights are more than one of caprolactam, acetamide, 2, 4-dihydroxybenzamide, valeramide and dimethylformamide; the epoxy resin is more than one of glycidyl ester type epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, alicyclic epoxy resin, glycidyl amine type epoxy resin and linear aliphatic epoxy resin; the catalyst is more than one of N-N dimethylformamide, triphenylphosphine and potassium hydrogen phthalate; the solvent is more than one of n-butanol, ethanol, acetone, isopropanol, chloroform, dichloromethane, ethyl acetate, methanol, diethyl ether and butyl acetate.

Preferably, the particle size of the modified silica is 5-100nm, and the modified silica is prepared by the following preparation steps: dissolving silicon dioxide in ethanol-water solution to obtain a solution with the mass fraction of 20%, adding a KH550 coupling agent with the mass fraction of 0.1-5%, performing ultrasonic dispersion for 10 minutes, stirring and dispersing at 80 ℃ for 2 hours, performing high-speed centrifugation on the mixed solution, removing supernatant, performing reduced pressure suction filtration, repeatedly moistening with ethanol, and drying in vacuum for 10 hours to obtain the modified silicon dioxide.

The preparation method of the silicon dioxide modified epoxy resin sizing agent for the carbon fibers comprises the following steps:

heating and dissolving amide oligomers with different molecular weights and epoxy resin in a solvent, adding a catalyst to react to obtain an epoxy sizing agent, stirring and mixing the epoxy sizing agent with deionized water to prepare an emulsion, and mixing and reacting the emulsion with modified silicon dioxide under the heating and stirring conditions to obtain the silicon dioxide modified epoxy resin sizing agent.

The temperature for heating and dissolving is 60-100 ℃, more preferably 60 ℃, 65 ℃, 70 ℃, 80 ℃, 90 ℃ and 100 ℃;

the heating and stirring temperature is 60-120 ℃, more preferably 60 ℃, 65 ℃, 70 ℃ or 80 ℃;

the time for adding the catalyst for reaction is 2-24 h, and more preferably 2h, 4h, 6h, 8h, 11h, 20h, 24h and 13 h;

the time of the mixing reaction is 1 to 24 hours, and more preferably 1 hour, 5 hours, 7 hours, 10 hours, 11 hours, 20 hours, 24 hours and 14 hours.

The application of the silica modified epoxy resin sizing agent for the carbon fibers in preparing the polyamide composite material comprises polyamide 6, polyamide 66 or polyamide 46 composite material.

The polyamide composite material is polyamide 6, and the polyamide 6 is prepared from the following raw materials in parts by weight: 5-45 parts of reinforcing agent, 650-80 parts of polyamide and 1-5 parts of sizing agent.

The polyamide composite material is polyamide 66, and the polyamide 66 is prepared from the following raw materials in parts by weight: 5-40 parts of reinforcing agent, 6660-95 parts of polyamide and 1-8 parts of sizing agent.

The polyamide composite material is polyamide 46, and the polyamide 46 is prepared from the following raw materials in parts by weight: 5-50 parts of reinforcing agent, 4660-90 parts of polyamide and 1-10 parts of sizing agent.

The epoxy resin sizing agent has the advantages of small pollution, simplicity and easy obtainment, and has a reinforcing effect because the epoxy resin sizing agent has low molecular weight, small viscosity and strong fluidity and is easy to disperse between a matrix and a reinforcing body. The nano-silica is a modified reinforcing material with low price and strong surface activity, the surface polarity, the surface energy and the dispersibility of the sizing carbon fiber are obviously improved after the nano-silica is modified by adding a coupling agent, and the nano-silica can fill gaps between the carbon fiber and a matrix material, so that the reinforcing effect of the carbon fiber on the matrix material is further improved.

The sizing agent can improve the polarity of the carbon fiber reinforced material, thereby improving the compatibility of the carbon fiber reinforced material and a polyamide matrix, promoting the uniform dispersion of the reinforced material in the polyamide matrix and improving the mechanical property of the composite material.

Compared with the prior art, the invention has the following advantages and effects:

the sizing agent has the advantages of simple and easily obtained raw materials, low price and small pollution; by adjusting the proportion of the epoxy resin sizing agent and the modified nano-silica in the sizing agent, the sizing agent can promote the carbon fiber reinforced material to be uniformly dispersed in the polyamide matrix, improve the compatibility of the carbon fiber in the plastic matrix, reduce the tendency of the carbon fiber to be condensed in the polyamide matrix, improve the interface performance of the carbon fiber reinforced material and the matrix, and meet the mechanical property of the material, thereby effectively improving the reinforcing effect of the carbon fiber on the polyamide matrix.

Detailed Description

The present invention will be described in further detail with reference to examples, but the embodiments of the present invention are not limited thereto.

Example 1

A silicon dioxide modified epoxy resin sizing agent for carbon fibers is prepared by the following specific steps:

taking 15 parts by weight of bisphenol F type epoxy resin (F51), adding 60 parts by weight of ethanol, stirring and ultrasonically dissolving, adding 25 parts by weight of low molecular weight acetamide powder and 0.1 part by weight of triphenylphosphine catalyst, stirring and dispersing, raising the temperature of the system to 140 ℃, reacting for 9 hours, taking out the system product, shaking up, carrying out vacuum filtration, repeatedly moistening with ethanol, and drying to obtain the epoxy resin sizing agent.

Dissolving silica in 70: forming a solution with the mass fraction of 20% in 10 mass percent of ethanol-water solution, adding 0.1-5 mass percent of KH550 coupling agent, performing ultrasonic dispersion for 10 minutes, stirring and dispersing at 80 ℃ for 2 hours, performing high-speed centrifugation on the mixed solution, removing supernatant, performing reduced pressure suction filtration, repeatedly moistening with ethanol, and drying in vacuum for 10 hours to obtain the modified silicon dioxide.

Then stirring and mixing the epoxy resin sizing agent with deionized water to prepare an emulsion with the mass fraction of 2%, adding modified silicon dioxide, wherein the modified silicon dioxide accounts for 10% of the mass of the epoxy resin sizing agent, and stirring for 2 hours at 80 ℃ to obtain the silicon dioxide modified epoxy resin sizing agent.

Example 2

A silicon dioxide modified epoxy resin sizing agent for carbon fibers is prepared by the following specific steps:

taking 30 parts by weight of bisphenol A type epoxy resin (E44), adding 40 parts by weight of N-butanol, stirring and ultrasonically dissolving, adding 30 parts by weight of low molecular weight polycaprolactam powder and 0.1 part by weight of N-N dimethylformamide catalyst, stirring and dispersing, raising the temperature of a system to 130 ℃, reacting for 8 hours, taking out a system product, uniformly shaking, carrying out reduced pressure suction filtration, repeatedly moistening with ethanol, and drying to obtain the epoxy resin sizing agent.

Dissolving silica in 65: adding 0.1-5% of KH550 coupling agent in mass fraction into 15 mass percent of ethanol-water solution, performing ultrasonic dispersion for 10 minutes, stirring and dispersing at 80 ℃ for 2 hours, performing high-speed centrifugation on the mixed solution, removing supernatant, performing vacuum filtration, repeatedly moistening and washing with ethanol, and performing vacuum drying for 10 hours to obtain the modified silicon dioxide.

And stirring and mixing the epoxy resin sizing agent with deionized water to prepare an emulsion with the mass fraction of 2%, respectively adding modified silicon dioxide with the mass fraction of 10% of solute, and stirring for 2 hours at the temperature of 80 ℃ to obtain the silicon dioxide modified epoxy resin sizing agent.

Example 3

A silicon dioxide modified epoxy resin sizing agent for carbon fibers is prepared by the following specific steps:

taking 20 parts by weight of bisphenol A type epoxy resin (E51), adding 55 parts by weight of ethanol, stirring and ultrasonically dissolving, adding 25 parts by weight of low molecular weight 2, 4-dihydroxybenzamide powder and 0.1 part by weight of triphenylphosphine catalyst, stirring and dispersing, raising the temperature of a system to 140 ℃, reacting for 9 hours, taking out a system product, uniformly shaking, carrying out vacuum filtration, repeatedly moistening with ethanol, and drying to obtain the epoxy resin sizing agent.

Dissolving 20% of silicon dioxide in a mass fraction of 72: adding 0.1-5% KH550 coupling agent into 8 mass percent ethanol-water solution, performing ultrasonic dispersion for 10 minutes, stirring and dispersing at 80 ℃ for 2 hours, performing high-speed centrifugation on the mixed solution, removing supernatant, performing vacuum filtration, repeatedly rinsing with ethanol, and performing vacuum drying for 10 hours to obtain the modified silicon dioxide.

And stirring and mixing the epoxy resin sizing agent with deionized water to prepare an emulsion with the mass fraction of 2%, respectively adding modified silicon dioxide with the mass fraction of 10% of solute, and stirring for 2 hours at the temperature of 80 ℃ to obtain the silicon dioxide modified epoxy resin sizing agent.

Example 4

A silicon dioxide modified epoxy resin sizing agent for carbon fibers is prepared by the following specific steps:

taking 20 parts by weight of JF-45 epoxy resin, adding 50 parts by weight of acetone, stirring and ultrasonically dissolving, then adding 30 parts by weight of low molecular weight polyamide powder and 0.1 part by weight of potassium hydrogen phthalate catalyst, stirring and dispersing, raising the temperature of the system to 140 ℃, reacting for 9 hours, taking out a system product, shaking up, carrying out reduced pressure suction filtration, repeatedly moistening with ethanol, and drying to obtain the epoxy resin sizing agent.

Dissolving 20 mass percent of silicon dioxide in 68: adding 0.1-5% of KH550 coupling agent in mass fraction into 12 mass percent of ethanol-water solution, performing ultrasonic dispersion for 10 minutes, stirring and dispersing at 80 ℃ for 2 hours, performing high-speed centrifugation on the mixed solution, removing supernatant, performing vacuum filtration, repeatedly moistening and washing with ethanol, and performing vacuum drying for 10 hours to obtain the modified silicon dioxide.

And stirring and mixing the epoxy resin sizing agent with deionized water to prepare an emulsion with the mass fraction of 2%, respectively adding modified silicon dioxide with the mass fraction of 10% of solute, and stirring for 2 hours at the temperature of 80 ℃ to obtain the silicon dioxide modified epoxy resin sizing agent.

Example 5

A silicon dioxide modified epoxy resin sizing agent for carbon fibers is prepared by the following specific steps:

taking 15 parts by weight of bisphenol A type epoxy resin (E51), adding 55 parts by weight of chloroform for stirring and ultrasonic dissolution, adding 30 parts by weight of low molecular weight dimethyl formamide powder and 0.1 part by weight of N-N dimethyl formamide catalyst for stirring and dispersion, raising the temperature of a system to 140 ℃, reacting for 9 hours, taking out a system product, shaking uniformly, carrying out vacuum filtration, repeatedly moistening with ethanol, and drying to obtain the epoxy resin sizing agent.

20% silica was dissolved in 72: adding 0.1-5% of KH550 coupling agent in mass fraction into the ethanol-water solution of 8, performing ultrasonic dispersion for 10 minutes, stirring and dispersing at 80 ℃ for 2 hours, performing high-speed centrifugation on the mixed solution, removing supernatant, performing vacuum filtration, repeatedly rinsing with ethanol, and performing vacuum drying for 10 hours to obtain the modified silicon dioxide.

And then stirring and mixing the epoxy resin sizing agent with deionized water to prepare an emulsion with the mass fraction of 2%, respectively adding modified silicon dioxide with the mass fraction of 10% of solute, and stirring for 2 hours at the temperature of 80 ℃ to obtain the silicon dioxide modified epoxy resin sizing agent.

Example 6

A silicon dioxide modified epoxy resin sizing agent for carbon fibers is prepared by the following specific steps:

taking 25 parts by weight of JF-45 epoxy resin, adding 45 parts by weight of N-butyl alcohol, stirring and ultrasonically dissolving, then adding 30 parts by weight of low molecular weight polycaprolactam powder and 0.1 part by weight of N-N dimethylformamide catalyst, stirring and dispersing, raising the temperature of the system to 140 ℃, reacting for 9 hours, taking out a system product, shaking up, carrying out reduced pressure suction filtration, repeatedly moistening with ethanol, and drying to obtain the epoxy resin sizing agent.

Dissolving 20 mass percent of silicon dioxide in 68: 12, adding 0.1-5% of KH550 coupling agent in mass fraction into the ethanol-water solution, performing ultrasonic dispersion for 10 minutes, stirring and dispersing at 80 ℃ for 2 hours, performing high-speed centrifugation on the mixed solution, removing supernatant, performing vacuum filtration, repeatedly rinsing with ethanol, and performing vacuum drying for 10 hours to obtain the modified silicon dioxide.

And stirring and mixing the epoxy resin sizing agent with deionized water to prepare an emulsion with the mass fraction of 2%, respectively adding modified silicon dioxide with the mass fraction of 10% of solute, and stirring for 2 hours at the temperature of 80 ℃ to obtain the silicon dioxide modified epoxy resin sizing agent.

Example 7

A silicon dioxide modified epoxy resin sizing agent for carbon fibers is prepared by the following specific steps:

taking 15 parts by weight of JF-45 epoxy resin, adding 55 parts by weight of acetone, stirring and ultrasonically dissolving, then adding 20 parts by weight of low molecular weight polyamide powder and 0.1 part by weight of potassium hydrogen phthalate catalyst, stirring and dispersing, raising the temperature of the system to 140 ℃, reacting for 9 hours, taking out a system product, shaking up, carrying out reduced pressure suction filtration, repeatedly moistening with ethanol, and drying to obtain the epoxy resin sizing agent.

Dissolving 20 mass percent of silicon dioxide in 68: 12, adding 0.1-5% of KH550 coupling agent in mass fraction into the ethanol-water solution, performing ultrasonic dispersion for 10 minutes, stirring and dispersing at 80 ℃ for 2 hours, performing high-speed centrifugation on the mixed solution, removing supernatant, performing vacuum filtration, repeatedly rinsing with ethanol, and performing vacuum drying for 10 hours to obtain the modified silicon dioxide.

And stirring and mixing the epoxy resin sizing agent with deionized water to prepare an emulsion with the mass fraction of 2%, respectively adding modified silicon dioxide with the mass fraction of 10% of solute, and stirring for 2 hours at the temperature of 80 ℃ to obtain the silicon dioxide modified epoxy resin sizing agent.

Comparative example 1

The reinforcing agent (carbon fibers) was soaked with n-butanol solution (analytical grade) to obtain treated carbon fibers.

Comparative example 2

The epoxy resin sizing agents (without adding modified silica) prepared in example 1 are respectively prepared into emulsions with mass concentration of 2%, reinforcing agent carbon fibers are continuously soaked for 15s by a sizing machine and then dried and cured to obtain the treated carbon fibers.

Example 8

The silica-modified epoxy resin sizing agents prepared in the embodiments 1 to 7 are respectively prepared into emulsions with mass concentration of 2%, and the carbon fiber reinforcing agent is continuously soaked for 15 seconds by a sizing machine and then dried and cured to obtain the treated carbon fiber.

Example 9

The treated carbon fiber of example 8 and the treated carbon fibers of comparative examples 1 and 2 were examined for sizing rate, surface energy, and polar force.

TABLE 1 sizing percentage, surface energy and polar force of carbon fibers treated in examples 1 to 7 and comparative examples 1 and 2

Example 10

The treated carbon fibers of examples 1 to 7 and comparative examples 1 and 2 were used to prepare polyamide 6 composite materials.

Example 11

The carbon fibers treated in examples 1 to 7 and comparative examples 1 and 2 were used to prepare polyamide 66 composite materials.

Example 12

The carbon fibers treated in examples 1 to 7 and comparative examples 1 and 2 were used to prepare polyamide 46 composite materials.

Example 13

In this example, a twin-screw extruder is used to prepare a polyamide 6 composite material, and the carbon fibers prepared in example 8 and comparative examples 1 and 2 are added into polyamide 6 respectively, and the specific steps are as follows:

adopting a double-screw extruder, wherein the temperatures are respectively 180 ℃, 190 ℃, 195 ℃, 200 ℃, 210 ℃, 215 ℃ and 220 ℃; because the carbon fiber is easy to break in the processing process, in order to reduce the abrasion in the processing process, the side feeding opening is selected for feeding the carbon fiber, so that the friction between the fiber and the screw rod is reduced; and considering the problem of the dispersibility of the carbon fiber in the processing process, the position of the side feeding is selected as the middle position five area. Respectively blending different carbon fibers with polyamide 6 by the content of 20%, granulating, drying, and performing injection molding at the injection temperature of 250 ℃, 240 ℃ and 220 ℃; the remaining parameters were in accordance with the injection parameters of PA6, after which injection moulding gave a polyamide 6 composite material.

TABLE 2 mechanical Strength of carbon fibers treated in examples 1-7 and comparative examples 1 and 2 in different polyamide 6 composites

	Tensile strength	Bending strength	Unnotched impact strength
				Example 1	139	230	57.86
Example 2	145	238	60.41
				Example 3	138	231	58.95
Example 4	135	227	57.28
				Example 5	140	229	58.86
Example 6	143	235	59.12
				Example 7	139	234	57.56
Comparative example 1	113	175	46.48
				Comparative example 2	133	213	56.22

Example 14

In this example, a twin-screw extruder is used to prepare a polyamide 66 composite material, and the carbon fibers prepared in example 8 and comparative examples 1 and 2 are added into the polyamide 66 respectively, and the specific steps are as follows:

adopting a double-screw extruder at the temperature of 240 ℃, 245 ℃, 250 ℃, 255 ℃, 260 ℃, 270 ℃ and 275 ℃ respectively; because the carbon fiber is easy to break in the processing process, in order to reduce the abrasion in the processing process, the side feeding opening is selected for feeding the carbon fiber, so that the friction between the fiber and the screw rod is reduced; and considering the problem of the dispersibility of the carbon fiber in the processing process, the position of the side feeding is selected as the middle position five area. Respectively blending different carbon fibers with polyamide 66 by the content of 20%, granulating, drying, and performing injection molding at 275 ℃, 260 ℃ and 240 ℃; the remaining parameters were in accordance with the injection parameters of PA66, after which injection moulding gave a polyamide 66 composite.

TABLE 3 mechanical Strength of carbon fibers treated in examples 1-7 and comparative examples 1 and 2 in different polyamide 66 composites

	Tensile strength	Bending strength	Unnotched impact strength
				Example 1	112	194	45.79
Example 2	115	189	46.72
				Example 3	113	196	45.67
Example 4	108	198	43.29
				Example 5	116	192	44.36
Example 6	112	187	46.38
				Example 7	117	195	46.94
Comparative example 1	98	148	37.45
				Comparative example 2	108	176	46.37

Example 15

In this example, a twin-screw extruder is used to prepare a polyamide 46 composite material, and the carbon fibers prepared in example 8 and comparative examples 1 and 2 are added into the polyamide 46 respectively, and the specific steps are as follows:

adopting a double-screw extruder, wherein the temperatures are 270 ℃, 275 ℃, 280 ℃, 285 ℃, 290 ℃, 300 ℃, 305 ℃, 310 ℃ and 315 ℃ respectively; because the carbon fiber is easy to break in the processing process, in order to reduce the abrasion in the processing process, the side feeding opening is selected for feeding the carbon fiber, so that the friction between the fiber and the screw rod is reduced; and considering the problem of the dispersibility of the carbon fiber in the processing process, the position of the side feeding is selected as the middle position five area. Respectively blending different carbon fibers with polyamide 46 by the content of 20%, granulating, drying, and performing injection molding at the injection temperature of 310 ℃, 305 ℃ and 295 ℃; the remaining parameters were in accordance with the injection parameters of PA46, after which injection moulding gave a polyamide 46 composite material.

TABLE 4 mechanical Strength of carbon fibers treated in examples 1-7 and comparative examples 1 and 2 in different polyamide 46 composites

	Tensile strength	Bending strength	Unnotched impact strength
				Example 1	127	201	51.32
Example 2	124	203	52.51
				Example 3	131	198	51.69
Example 4	128	206	51.38
				Example 5	126	197	50.69
Example 6	130	198	50.18
				Example 7	129	204	52.37
Comparative example 1	106	175	42.13
				Comparative example 2	125	187	51.38

The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.