1. A preparation method of a high-temperature-resistant carbon fiber thermoplastic sizing agent is characterized in that the preparation method of the high-temperature-resistant carbon fiber thermoplastic sizing agent is completed according to the following steps:

firstly, preparing sulfonated polyether ether ketone:

adding concentrated sulfuric acid into the polyether-ether-ketone for multiple times, and uniformly stirring to obtain a polyether-ether-ketone/concentrated sulfuric acid mixture; placing the polyether-ether-ketone/concentrated sulfuric acid mixture in a water bath for sulfonation to obtain a reaction product; dropwise adding the reaction product into deionized water, and cleaning the reaction product by using the deionized water until the pH value of the cleaning liquid is neutral to obtain a white spherical substance, namely sulfonated polyether ether ketone;

secondly, putting the sulfonated polyether-ether-ketone into an oven for drying to obtain a bright yellow spherical substance, namely the dried sulfonated polyether-ether-ketone; adding the dried sulfonated polyether ether ketone into N-methyl pyrrolidone, and then carrying out ultrasonic stirring to obtain a stable SPEEK NMP sizing agent solution;

adding the carboxylated carbon nano tubes into the stable SPEEK NMP sizing agent solution, and stirring by using an ultrasonic cell disruptor to obtain the sulfonated polyether-ether-ketone-carbon nano tube sizing agent solution, namely the high-temperature-resistant carbon fiber thermoplastic sizing agent.

2. The method for preparing the high temperature resistant carbon fiber thermoplastic sizing agent according to claim 1, wherein the volume ratio of the mass of the polyetheretherketone to the concentrated sulfuric acid in the polyetheretherketone/concentrated sulfuric acid mixture in the step one is (1 g-3 g) to (20 mL-80 mL).

3. The method for preparing the high temperature resistant carbon fiber thermoplastic sizing agent according to claim 2, wherein the volume ratio of the mass of the polyetheretherketone in the polyetheretherketone/concentrated sulfuric acid mixture in the step one to the volume of the concentrated sulfuric acid is 2.5g:50 mL.

4. The method for preparing the high-temperature-resistant carbon fiber thermoplastic sizing agent according to claim 1, wherein the sulfonation temperature in the step one is 30-80 ℃, and the sulfonation time is 1-5 h.

5. The method for preparing the high temperature resistant carbon fiber thermoplastic sizing agent according to claim 4, wherein the sulfonation temperature in the step one is 50 ℃ and the sulfonation time is 2h to 3 h.

6. The method for preparing the high temperature resistant carbon fiber thermoplastic sizing agent according to claim 5, wherein the sulfonation degree of the sulfonated polyether ether ketone in the step one is 10.97-64.76%.

7. The method for preparing the high-temperature-resistant carbon fiber thermoplastic sizing agent according to claim 5, wherein the mass fraction of the concentrated sulfuric acid in the step one is 98%.

8. The method for preparing the high temperature resistant carbon fiber thermoplastic sizing agent according to claim 1, wherein the concentration of the sulfonated polyether ether ketone in the sulfonated polyether ether ketone-carbon nanotube sizing agent solution in the step three is 0.05g/L to 1g/L, and the mass fraction of the carboxylated carbon nanotubes is 0.25 percent to 1 percent.

9. The method for preparing the high temperature resistant carbon fiber thermoplastic sizing agent according to claim 8, wherein the concentration of the sulfonated polyether ether ketone in the sulfonated polyether ether ketone-carbon nanotube sizing agent solution in the step three is 0.5g/L, and the mass fraction of the carboxylated carbon nanotubes is 0.5%.

10. The preparation method of the high-temperature-resistant carbon fiber thermoplastic sizing agent according to claim 1, wherein the ultrasonic stirring time in the second step is 0.5-2 h; in the second step, the sulfonated polyether-ether-ketone is put into an oven with the temperature of 80-120 ℃ for drying for 20-24 h; in the third step, the stirring time by using an ultrasonic cell crusher is 0.5-2 h.

Background

The thermoplastic resin matrix composite material is compounded by thermoplastic resin and reinforced fibers, so the material has the advantages of the thermoplastic resin, such as recyclable leftover materials, good high temperature resistance, high mechanical properties, particularly high impact strength, no toxic gas release in the molding process and convenience for connection between structural members. The thermoplastic composite material not only has excellent performance, but also completely omits the investment of traditional manufacturing equipment (such as a high-temperature high-pressure autoclave and the like) and the use of high-temperature resistant auxiliary materials compared with the thermosetting resin-based composite material, and can reduce the manufacturing cost by more than 30 percent. This will revolutionize the manufacturing industry of composite materials, and boeing, air passengers, etc. are all actively developing related technologies.

Thermoplastic resins are widely available, and polyetheretherketone is an ideal matrix material for fiber-reinforced thermoplastic composites due to its stable chemical properties and outstanding balance of properties. The polyetheretherketone is a linear crystalline thermoplastic resin containing benzene rings, ether bonds and ketone bonds, and the benzene rings contained in the main chain ensure that the PEEK has better chemical stability and high strength and rigidity; the ether bond on the main chain can rotate flexibly, so that the PEEK has certain flexibility and processability and can be melted and crystallized. PEEK has excellent mechanical properties, and the tensile strength of the PEEK can reach 90 MPa; can work for a long time at the temperature of 250 ℃, and can keep the mechanical property for a short time at the temperature close to the melting point of the alloy; has excellent impact resistance and can still provide good strength and toughness under different environmental conditions. The CF/PEEK composite material prepared by compounding PEEK and CF can be applied to components with higher requirements on heat resistance and impact strength, and becomes a hotspot of research and application in recent years. At present, the surface of the common CF is provided with a layer of sizing agent which prevents fiber damage and is beneficial to spinning when the CF is delivered from a factory, but the sizing agent is usually produced aiming at the common thermosetting resin and has a plurality of problems when the CF is used for molding PEEK. Because the high melting point of the PEEK and the molding temperature of the PEEK are both more than 350 ℃, the sizing agent on the surface of the commercial carbon fiber can be decomposed at high temperature at the temperature, bubbles can be generated to form defects on an interface, and the PEEK molecular chain is rigid and nonpolar and can not form better infiltration with the CF with inert surface, so that the preparation of the heat-resistant thermoplastic sizing agent is very important for improving the mechanical property of the CF/PEEK composite material.

Disclosure of Invention

The invention aims to solve the problems that sizing agents prepared by the existing method are suitable for thermosetting resin and coated on the surface of carbon fibers, the sizing agents can be decomposed at high temperature when a carbon fiber/polyether-ether-ketone composite material is prepared, bubbles are generated at an interface, and polyether-ether-ketone molecular chains are rigid and nonpolar and cannot be well infiltrated with carbon fibers inert to the surface, so that the mechanical property of the carbon fiber/polyether-ether-ketone composite material is poor, and provides a preparation method of a high-temperature-resistant carbon fiber thermoplastic sizing agent.

A preparation method of a high-temperature-resistant carbon fiber thermoplastic sizing agent comprises the following steps:

firstly, preparing sulfonated polyether ether ketone:

adding concentrated sulfuric acid into the polyether-ether-ketone for multiple times, and uniformly stirring to obtain a polyether-ether-ketone/concentrated sulfuric acid mixture; placing the polyether-ether-ketone/concentrated sulfuric acid mixture in a water bath for sulfonation to obtain a reaction product; dropwise adding the reaction product into deionized water, and cleaning the reaction product by using the deionized water until the pH value of the cleaning liquid is neutral to obtain a white spherical substance, namely sulfonated polyether ether ketone;

secondly, putting the sulfonated polyether-ether-ketone into an oven for drying to obtain a bright yellow spherical substance, namely the dried sulfonated polyether-ether-ketone; adding the dried sulfonated polyether ether ketone into N-methyl pyrrolidone, and then carrying out ultrasonic stirring to obtain a stable SPEEK NMP sizing agent solution;

adding the carboxylated carbon nano tubes into the stable SPEEK NMP sizing agent solution, and stirring by using an ultrasonic cell disruptor to obtain the sulfonated polyether-ether-ketone-carbon nano tube sizing agent solution, namely the high-temperature-resistant carbon fiber thermoplastic sizing agent.

The invention has the advantages that:

firstly, sulfonating polyether-ether-ketone by using concentrated sulfuric acid, then dissolving sulfonated polyether-ether-ketone (SPEEK) in NMP (N-methyl pyrrolidone), and finally dispersing a certain proportion of carboxylated carbon nanotubes in the NMP solution of SPEEK to obtain the high-temperature-resistant carbon fiber thermoplastic sizing agent. The high-temperature-resistant carbon fiber thermoplastic sizing agent disclosed by the invention is simple in preparation process and good in sizing effect;

and secondly, the CF/PEEK composite material prepared by using the high-temperature-resistant carbon fiber thermoplastic sizing agent prepared by the invention has the bending strength which is 31.4 percent higher than that of the original T300 reinforced PEEK composite material, and the interlaminar shear strength which is 72.5 percent higher than that of the original T300 reinforced PEEK composite material.

The invention can obtain the high-temperature-resistant carbon fiber thermoplastic sizing agent.

Drawings

FIG. 1 is a digital photograph of a product prepared in the first example, in which a) PEEK is dissolved in concentrated sulfuric acid, b) white spherical material obtained in the first example is sulfonated PEEK, and c) dried sulfonated PEEK obtained in the second example is obtained;

FIG. 2 is a thermogravimetric plot of PEEK at 1, sulfonated PEEK at 2, sulfonated PEEK at 3, sulfonated PEEK at 4, sulfonated PEEK at 5, sulfonated PEEK at 6, and sulfonated PEEK at 6, respectively;

FIG. 3 is a graph showing an infrared spectrum in which 1 is PEEK, SPEEK-1 is sulfonated PEEK prepared in one step one of the examples, SPEEK-2 is sulfonated PEEK prepared in one step one of the examples, SPEEK-3 is sulfonated PEEK prepared in one step three of the examples, SPEEK-4 is sulfonated PEEK prepared in one step four of the examples, and SPEEK-5 is sulfonated PEEK prepared in one step five of the examples;

FIG. 4 is an SEM photograph of carbon fiber bundles before and after sizing, in which a is an unsized carbon fiber bundle and b is a carbon fiber bundle treated by sizing;

FIG. 5 is a graph showing stiffness tests, in which 1 is an unsized carbon fiber bundle, 2 is a sizing agent-treated carbon fiber bundle SPEEK-CF prepared in comparative example two, and 3 is a sizing agent-treated carbon fiber bundle prepared in example two;

FIG. 6 is a test chart of bundling properties of carbon fibers, in which a is T300 carbon fibers, b is carbon fibers which are not sized, and c is carbon fibers which are treated with a sizing agent prepared in example two;

FIG. 7 is a bending strength test chart;

FIG. 8 is a graph showing interlaminar shear strength testing;

FIG. 9 is a graph of the mechanical loss factor tan delta of the composite material as a function of temperature, wherein 1 is ECF/PEEK composite material and 2 is SPEEK-CNTS-CF/PEEK composite material.

Detailed Description

The following examples further illustrate the present invention but are not to be construed as limiting the invention. Modifications and substitutions to methods, procedures, or conditions of the invention may be made without departing from the spirit of the invention.

The first embodiment is as follows: the preparation method of the high-temperature-resistant carbon fiber thermoplastic sizing agent of the embodiment is completed according to the following steps:

firstly, preparing sulfonated polyether ether ketone:

adding concentrated sulfuric acid into the polyether-ether-ketone for multiple times, and uniformly stirring to obtain a polyether-ether-ketone/concentrated sulfuric acid mixture; placing the polyether-ether-ketone/concentrated sulfuric acid mixture in a water bath for sulfonation to obtain a reaction product; dropwise adding the reaction product into deionized water, and cleaning the reaction product by using the deionized water until the pH value of the cleaning liquid is neutral to obtain a white spherical substance, namely sulfonated polyether ether ketone;

secondly, putting the sulfonated polyether-ether-ketone into an oven for drying to obtain a bright yellow spherical substance, namely the dried sulfonated polyether-ether-ketone; adding the dried sulfonated polyether ether ketone into N-methyl pyrrolidone, and then carrying out ultrasonic stirring to obtain a stable SPEEK NMP sizing agent solution;

adding the carboxylated carbon nano tubes into the stable SPEEK NMP sizing agent solution, and stirring by using an ultrasonic cell disruptor to obtain the sulfonated polyether-ether-ketone-carbon nano tube sizing agent solution, namely the high-temperature-resistant carbon fiber thermoplastic sizing agent.

The second embodiment is as follows: the present embodiment differs from the present embodiment in that: the ratio of the mass of the polyether-ether-ketone in the polyether-ether-ketone/concentrated sulfuric acid mixture in the step one to the volume of the concentrated sulfuric acid is (1 g-3 g): 20 mL-80 mL. Other steps are the same as in the first embodiment.

The third concrete implementation mode: the present embodiment differs from the first or second embodiment in that: the volume ratio of the mass of the polyether-ether-ketone in the polyether-ether-ketone/concentrated sulfuric acid mixture in the step one to the volume of the concentrated sulfuric acid is 2.5g:50 mL. The other steps are the same as in the first or second embodiment.

The fourth concrete implementation mode: the difference between this embodiment and one of the first to third embodiments is as follows: the sulfonation temperature in the step one is 30-80 ℃, and the sulfonation time is 1-5 h. The other steps are the same as those in the first to third embodiments.

The fifth concrete implementation mode: the difference between this embodiment and one of the first to fourth embodiments is: the temperature of sulfonation in the step one is 50 ℃, and the time of sulfonation is 2-3 h. The other steps are the same as those in the first to fourth embodiments.

The sixth specific implementation mode: the difference between this embodiment and one of the first to fifth embodiments is as follows: the sulfonation degree of the sulfonated polyether ether ketone in the step one is 10.97-64.76%. The other steps are the same as those in the first to fifth embodiments.

The seventh embodiment: the difference between this embodiment and one of the first to sixth embodiments is: the mass fraction of the concentrated sulfuric acid in the step one is 98%. The other steps are the same as those in the first to sixth embodiments.

The specific implementation mode is eight: the difference between this embodiment and one of the first to seventh embodiments is: the concentration of the sulfonated polyether ether ketone in the sulfonated polyether ether ketone-carbon nano tube sizing agent solution in the step three is 0.05 g/L-1 g/L, and the mass fraction of the carboxylated carbon nano tubes is 0.25-1%. The other steps are the same as those in the first to seventh embodiments.

The specific implementation method nine: the difference between this embodiment and the first to eighth embodiments is: the concentration of the sulfonated polyether ether ketone in the sulfonated polyether ether ketone-carbon nano tube sizing agent solution in the step three is 0.5g/L, and the mass fraction of the carboxylated carbon nano tubes is 0.5 percent. The other steps are the same as those in the first to eighth embodiments.

The detailed implementation mode is ten: the difference between this embodiment and one of the first to ninth embodiments is as follows: the ultrasonic stirring time in the step two is 0.5 to 2 hours; in the second step, the sulfonated polyether-ether-ketone is put into an oven with the temperature of 80-120 ℃ for drying for 20-24 h; in the third step, the stirring time by using an ultrasonic cell crusher is 0.5-2 h. The other steps are the same as those in the first to ninth embodiments.

The present invention will be described in detail below with reference to the accompanying drawings and examples.

The first embodiment is as follows: a preparation method of a high-temperature-resistant carbon fiber thermoplastic sizing agent comprises the following steps:

firstly, preparing sulfonated polyether ether ketone:

adding concentrated sulfuric acid into the polyether-ether-ketone for 20 times, and uniformly stirring to obtain a polyether-ether-ketone/concentrated sulfuric acid mixture; placing the polyether-ether-ketone/concentrated sulfuric acid mixture in a water bath kettle at the temperature of 50 ℃ for sulfonation for 1h to obtain a reaction product; dropwise adding the reaction product into deionized water, and cleaning the reaction product by using the deionized water until the pH value of the cleaning liquid is neutral to obtain a white spherical substance, namely sulfonated polyether ether ketone;

the mass fraction of the concentrated sulfuric acid in the step one is 98%;

the volume ratio of the mass of the polyether-ether-ketone in the polyether-ether-ketone/concentrated sulfuric acid mixture in the step one to the volume of the concentrated sulfuric acid is 2.5g:50 mL;

the sulfonation degree of the sulfonated polyether ether ketone in the step one is 10.97 percent;

secondly, drying the sulfonated polyether-ether-ketone in an oven at the temperature of 110 ℃ for 24 hours to obtain a bright yellow spherical substance, namely the dried sulfonated polyether-ether-ketone; adding the dried sulfonated polyether ether ketone into N-methyl pyrrolidone, and then ultrasonically stirring for 1h to obtain a stable SPEEK NMP sizing agent solution;

adding a carboxylated carbon nano tube into the stable SPEEK NMP sizing agent solution, and stirring for 1h by using an ultrasonic cell disruption instrument to obtain a sulfonated polyether-ether-ketone-carbon nano tube sizing agent solution, namely the high-temperature-resistant carbon fiber thermoplastic sizing agent;

the concentration of the sulfonated polyether ether ketone in the sulfonated polyether ether ketone-carbon nano tube sizing agent solution in the step three is 0.5g/L, and the mass fraction of the carboxylated carbon nano tubes is 0.5 percent.

Example two: the present embodiment is different from the first embodiment in that: in the first step, the mixture of polyether-ether-ketone and concentrated sulfuric acid is placed in a water bath kettle at the temperature of 50 ℃ for sulfonation for 2 hours to obtain a reaction product. Other steps and parameters are the same as those in the first embodiment.

The degree of sulfonation of the sulfonated polyetheretherketone described in example step one is 16.67%.

Comparative example two: the preparation method of the sulfonated polyether-ether-ketone sizing agent solution is completed according to the following steps:

firstly, preparing sulfonated polyether ether ketone:

adding concentrated sulfuric acid into the polyether-ether-ketone for 20 times, and uniformly stirring to obtain a polyether-ether-ketone/concentrated sulfuric acid mixture; placing the polyether-ether-ketone/concentrated sulfuric acid mixture in a water bath kettle at the temperature of 50 ℃ for sulfonation for 2 hours to obtain a reaction product; dropwise adding the reaction product into deionized water, and cleaning the reaction product by using the deionized water until the pH value of the cleaning liquid is neutral to obtain a white spherical substance, namely sulfonated polyether ether ketone;

the mass fraction of the concentrated sulfuric acid in the step one is 98%;

the volume ratio of the mass of the polyether-ether-ketone in the polyether-ether-ketone/concentrated sulfuric acid mixture in the step one to the volume of the concentrated sulfuric acid is 2.5g:50 mL;

the sulfonation degree of the sulfonated polyether ether ketone in the step one is 16.67 percent;

secondly, drying the sulfonated polyether-ether-ketone in an oven at the temperature of 110 ℃ for 24 hours to obtain a bright yellow spherical substance, namely the dried sulfonated polyether-ether-ketone; adding dried sulfonated polyether ether ketone into N-methyl pyrrolidone, and ultrasonically stirring for 1h to obtain a sulfonated polyether ether ketone sizing agent solution;

and the concentration of the sulfonated polyether-ether-ketone in the sulfonated polyether-ether-ketone sizing agent solution in the second step is 0.5 g/L.

Example three: the present embodiment is different from the first embodiment in that: in the first step, the mixture of polyether-ether-ketone and concentrated sulfuric acid is placed in a water bath kettle at the temperature of 50 ℃ for sulfonation for 3 hours to obtain a reaction product. Other steps and parameters are the same as those in the first embodiment.

The degree of sulfonation of the sulfonated polyetheretherketone described in the first three steps of the example was 39.35%.

Example four: the present embodiment is different from the first embodiment in that: in the first step, the mixture of polyether-ether-ketone and concentrated sulfuric acid is placed in a water bath kettle at the temperature of 50 ℃ for sulfonation for 4 hours to obtain a reaction product. Other steps and parameters are the same as those in the first embodiment.

The sulfonation degree of the sulfonated polyether ether ketone in the fourth step one of the example is 53.07%.

Example five: the present embodiment is different from the first embodiment in that: in the first step, the mixture of polyether-ether-ketone and concentrated sulfuric acid is placed in a water bath kettle at the temperature of 50 ℃ for sulfonation for 5 hours to obtain a reaction product. Other steps and parameters are the same as those in the first embodiment.

The sulfonation degree of sulfonated polyetheretherketone described in example five step one is 64.76%.

FIG. 1 is a digital photograph of a product prepared in the first example, in which a) PEEK is dissolved in concentrated sulfuric acid, b) white spherical material obtained in the first example is sulfonated PEEK, and c) dried sulfonated PEEK obtained in the second example is obtained;

FIG. 2 is a thermogravimetric plot of PEEK at 1, sulfonated PEEK at 2, sulfonated PEEK at 3, sulfonated PEEK at 4, sulfonated PEEK at 5, sulfonated PEEK at 6, and sulfonated PEEK at 6, respectively;

as can be seen from fig. 2, the Polyetheretherketone (PEEK) resin powder starts to suffer a significant mass loss at high temperatures. The initial temperature was 550 ℃ and when the temperature was further raised to 600 ℃ the mass loss reached 40%, which was due to pyrolysis of the main chain, thus showing a higher thermal stability of PEEK.

The sulfonated polyether ether ketone (SPEEK) with different sulfonation degrees obtained by sulfonation treatment has obviously reduced thermal stability, obvious mass loss occurs before 400 ℃, and when the sulfonation time is prolonged, the initial temperature of the mass loss is gradually reduced, the mass loss percentage at the same temperature is increased, and the thermal stability is poorer. At 400 ℃, the mass loss of the sulfonated polyether ether ketone prepared in the first step of the example, the sulfonated polyether ether ketone prepared in the first step of the example and the sulfonated polyether ether ketone prepared in the first step of the three steps of the example is below 15%, compared with the mass loss of the sulfonated polyether ether ketone prepared in the first step of the four steps of the example and the sulfonated polyether ether ketone prepared in the first step of the five steps of the example, which is large, and the heat resistance is poor. The heat loss occurring at this stage is due to thermal decomposition of the sulfonic acid group contained in the sulfonated polyetheretherketone. The higher the degree of sulfonation, the higher the proportion of sulfonic acid groups contained in SPEEK, the poorer the regularity of the macromolecular chain modified with concentrated sulfuric acid, the more likely thermal decomposition occurs, and the poorer the heat resistance of SPEEK. After a temperature rise of 500 ℃, a further considerable loss of mass of SPEEK occurs. The mass loss at this stage is synchronized with the mass loss of PEEK at this stage, also due to degradation of the polymer backbone, and the initial temperature of heat loss gradually decreases as the sulfonation time increases. The main chain structure of the polymer is unchanged before and after sulfonation, so the influence of sulfonation treatment on the thermal stability at this stage is small. The sulfonated polyether ether ketone prepared in the first step of the embodiment has a small sulfonation degree, and the sulfonated polyether ether ketone prepared in the first step of the embodiment and the sulfonated polyether ether ketone prepared in the first step of the fifth step of the embodiment have a large sulfonation degree, so that the sulfonated polyether ether ketone prepared in the first step of the second step of the embodiment and the sulfonated polyether ether ketone prepared in the first step of the third step of the embodiment, which have moderate sulfonation degree and good heat resistance, are selected as solutes of the sulfonated polyether ether ketone sizing agent, and further research is subsequently conducted to compare the modification of carbon fibers by two sulfonated polyether ether ketone sizing agents with different sulfonation degrees and the influence of the two sulfonated polyether ether ketone sizing agents on the performance of a carbon fiber/polyether ether ketone composite (CF/PEEK composite) laminated plate.

FIG. 3 is a graph showing an infrared spectrum in which 1 is PEEK, SPEEK-1 is sulfonated PEEK prepared in one step one of the examples, SPEEK-2 is sulfonated PEEK prepared in one step one of the examples, SPEEK-3 is sulfonated PEEK prepared in one step three of the examples, SPEEK-4 is sulfonated PEEK prepared in one step four of the examples, and SPEEK-5 is sulfonated PEEK prepared in one step five of the examples;

comparing PEEK with sulfonated SPEEK in FIG. 3, it can be seen that the six samples are at 1647cm^-1The characteristic absorption peak of the C ═ O carbonyl function, 1225cm, appeared^-1The characteristic peak of the Ar-O functional group is found at 650-900cm^-1And more than one bending vibration characteristic peak corresponding to the outside of the C-H bond surface in the benzene ring exists in the stage. SPEEK obtained after reaction treatment is respectively 1024cm^-1And 1087cm^-1The method finds characteristic peaks which do not exist on a polyether-ether-ketone infrared spectrum curve, and the characteristic peaks are new functional groups grafted on a main chain structure when concentrated sulfuric acid modifies polyether-ether-ketone. After comparison with the standard infrared group characteristic peak, the method can confirm that the peak is 1024cm-1 and 1087cm^-1The characteristic peaks are two absorption characteristic peaks of O ═ S ═ O respectively. The infrared spectrum curves of five sulfonated PEEK with different sulfonation degrees have overall consistent characteristic absorption peaks, and the overall curves have small differences, which indicates that the sulfonation time has no influence on the chemical structure of SPEEK. Therefore, the modification treatment of the PEEK by the concentrated sulfuric acid does not damage the main structure of the PEEK, and the sulfonic acid group-SO is successfully grafted in the main molecular chain₃H。

Example six:

the carbon fiber woven cloth used for preparing the CF/PEEK composite material in the embodiment is carbon fiber (T300 carbon fiber) produced by Dongli corporation in Japan, and the surface of the carbon fiber woven cloth is uniformly coated with a layer of epoxy resin sizing agent, so that the carbon fiber woven cloth needs to be desized before the modification treatment of the carbon fiber woven cloth, the desizing method is to arrange the carbon fiber woven cloth with the size of 150mm multiplied by 100mm into a soxhlet extractor, extract the carbon fiber woven cloth with acetone for 24h in a water bath at 80 ℃, then clean the surface of the carbon fiber with deionized water, and finally arrange the carbon fiber woven cloth in an electrothermal constant temperature drying oven at 100 ℃ for 24h to obtain carbon fiber bundles without sizing.

And (3) immersing the carbon fiber bundles which are not subjected to sizing into the high-temperature-resistant carbon fiber thermoplastic sizing agent prepared in the second embodiment for 2 hours, taking out the carbon fiber bundles, putting the carbon fiber bundles into an electrothermal constant-temperature drying oven set to be 100 ℃, and drying the carbon fiber bundles for 1 hour to obtain sized carbon fiber bundles (SPEEK-CNTS-CF). SEM photographs of the carbon fiber bundles treated with the sizing agent and carbon fiber bundles without sizing are shown in fig. 4.

FIG. 4 is an SEM photograph of carbon fiber bundles before and after sizing, in which a is an unsized carbon fiber bundle and b is a carbon fiber bundle treated by sizing;

as shown in fig. 4, the unsized carbon fiber bundle surface has grooves arranged in parallel along the axial direction due to the carbon fiber production process, and the existence of the grooves increases the roughness of the carbon fiber surface to some extent, which is beneficial to the deposition and adhesion of carbon nanotubes on the carbon fiber surface during the sizing process. The carbon fiber bundle after sizing (carbon fiber bundle after sizing) has obviously and uniformly adhered coating, reduced gully and obvious carbon nanotube adsorption on the surface, thereby proving successful sizing.

Comparative example six:

the carbon fiber woven cloth used for preparing the CF/PEEK composite material in the embodiment is carbon fiber (T300 carbon fiber) produced by Dongli corporation in Japan, and the surface of the carbon fiber woven cloth is uniformly coated with a layer of epoxy resin sizing agent, so that the carbon fiber woven cloth needs to be desized before the modification treatment of the carbon fiber woven cloth, the desizing method is to arrange the carbon fiber woven cloth with the size of 150mm multiplied by 100mm into a soxhlet extractor, extract the carbon fiber woven cloth with acetone for 24h in a water bath at 80 ℃, then clean the surface of the carbon fiber with deionized water, and finally arrange the carbon fiber woven cloth in an electrothermal constant temperature drying oven at 100 ℃ for 24h to obtain carbon fiber bundles without sizing.

The carbon fiber bundle which is not sized is immersed into the sulfonated polyetheretherketone sizing agent prepared in the second comparative example for 2 hours, taken out and put into an electrothermal constant temperature drying oven set at 100 ℃ to be dried for 1 hour, and sized carbon fiber bundle (SPEEK-CF) is obtained.

The stiffness of a carbon fiber is a measure of how much the CF of a certain length hangs at the midpoint, the fiber splays. The CF was first rapidly wound up three times on top, i.e. unwound, with a stainless steel wheel. The CF with the radius of 10mm is weighed and hung on a wheel with the radius of 500mm to serve as a hanging point, a steel plate ruler is placed 60mm below the hanging point, and the distance between two ends of the CF is measured. The study on the stiffness of the carbon fiber is very important, because the bending angle of the CF on a weaving machine is very large in weaving, the CF needs to have certain softness to ensure that the CF is not damaged in the processing on the weaving machine, and the stiffness is an important index for measuring the softness of the CF, so the influence of sizing modification of a sizing agent on the processing performance of the carbon fiber is studied in an experiment. The hardness of the carbon fiber after the sizing treatment by the sizing agent added with the reinforcing and toughening auxiliary agent carboxylated carbon nanotube is compared with the hardness of the carbon fiber after the sizing treatment by the sizing agent not added with the reinforcing and toughening auxiliary agent carboxylated carbon nanotube, and the comparison is shown in figure 5;

FIG. 5 is a graph showing stiffness tests, in which 1 is an unsized carbon fiber bundle, 2 is a sizing agent-treated carbon fiber bundle SPEEK-CF prepared in comparative example two, and 3 is a sizing agent-treated carbon fiber bundle prepared in example two;

as can be seen from fig. 5, the carbon fiber treated by the sizing agent without the carboxylated carbon nanotube has a very high stiffness of 83mm and a poor softness, and after the addition of the carboxylated carbon nanotube for toughening and modification, the softness of the carbon fiber is moderate, which is obviously improved.

FIG. 6 is a test chart of bundling properties of carbon fibers, in which a is T300 carbon fibers, b is carbon fibers which are not sized, and c is carbon fibers which are treated with a sizing agent prepared in example two;

as can be seen in fig. 6, the unsized CF had poor inter-filament bonding after being pulled apart by force and had a longer recovery time after the force was removed. The sized modified CF has improved network properties between filaments and improved overall bundling properties compared to the unsized CF and T300CF after being pulled apart under force.

Example seven:

weighing PEEK powder with corresponding amount according to the volume fraction ratio of carbon fiber to PEEK resin of 6:4 by using T300 carbon fiber woven fabric (ECF for short), unsized carbon fiber bundle (DCF for short) obtained in the sixth embodiment and sized carbon fiber bundle (SPEEK-CNTS-CF) obtained in the sixth embodiment, sequentially laying eight layers, and performing compression molding by using a small-sized flat vulcanizing machine to prepare the CF/PEEK composite laminated plate. The molding temperature is 370 ℃ in the molding process, and the molding pressure is 5 MPa. In order to ensure the melting of the resin in the prefabricated member and reduce the defects in the process, gradient temperature rise is adopted, the temperature is firstly heated to 200 ℃ from room temperature and then is preserved for 30min, then the temperature is heated to 370 ℃ for preserving heat, maintaining pressure and melting for 30min, finally the temperature is reduced to 300 ℃ for preserving heat, maintaining pressure and crystallizing for 30min, and finally the prepared composite material laminated plate is obtained by slow natural cooling in the air.

The bending performance of the composite material is tested by adopting a universal testing machine, the testing process refers to the standard ASTM D7264, the testing loading speed is 1mm/min, the size of a test sample is 50mm 13mm 1.5mm, the test is carried out by adopting a three-point bending mode, and the span is set to be 40 mm. And respectively carrying out five times of bending tests on the T300 carbon fiber composite material, the carbon fiber composite material after desizing and the carbon fiber composite material sample treated by the SPEEK-CNTS sizing agent, and averaging the bending strength obtained by the tests to record the final bending strength. The calculated flexural strength of the different laminates is shown in fig. 7.

FIG. 7 is a bending strength test chart;

as can be seen from fig. 7, with the carbon fiber composite material after desizing (the carbon fiber bundle obtained in example six without sizing) as a reference standard, the bending strength of the laminate prepared from the T300 woven carbon fiber fabric and PEEK was improved by 32.6% compared with the carbon fiber composite material after desizing, while the bending strength of the laminate prepared from the carbon fiber bundle obtained in example six after sizing treatment could reach 902.886MPa, which is improved by 74.2% compared with the bending strength of the carbon fiber composite material after desizing. The reason is that the addition of the sulfonated polyether ether ketone increases the wettability between the surface of the carbon fiber and the PEEK, so that the interface bonding capability is enhanced, and the bending performance is obviously improved. On the other hand, the nano-particle carboxylated carbon nano-tube has larger specific surface area, so that the roughness of the carbon fiber is obviously improved after the surface of the carbon fiber is introduced, and the interface bonding force between the fiber and PEEK resin is enhanced, thereby obviously improving the bending performance.

The interlaminar shear strength of the composite material is tested by using a universal testing machine, the test process refers to a standard ASTM D2344, the test loading speed is 1mm/min, the size of a test sample is 12mm 4mm 1.5mm, the test is carried out by adopting a three-point bending mode, and the span-thickness ratio is set to be 5: 1. And (3) respectively carrying out five interlaminar shear strength tests on samples of the ECF/PEEK composite material, the DCF/PEEK composite material and the SPEEK-CNTS-CF/PEEK composite material, and taking an average value of the interlaminar shear strengths obtained by the tests to record the interlaminar shear strength as the final interlaminar shear strength. The calculated interlaminar shear strengths of the different laminates are shown in fig. 8.

FIG. 8 is a graph showing interlaminar shear strength testing;

as can be seen from fig. 8, with the carbon fiber composite material after desizing as a reference standard, the interlaminar shear strength of the laminate prepared from the T300 carbon fiber woven cloth and PEEK is only increased by 6.8% compared with that of the carbon fiber composite material after desizing, while the interlaminar shear strength of the laminate prepared from the carbon fiber prepared by the sizing treatment with the high-temperature-resistant carbon fiber thermoplastic sizing agent prepared in the fifth embodiment is significantly increased, which can reach 79.776MPa, and is increased by 84.2% compared with that of the carbon fiber composite material after desizing. The failure of the interlayer of the composite material laminate is mainly caused by the failure of the interface of the fiber and the resin, namely, the interlayer shear strength of the composite material is related to the bonding strength of the interface. The wetting property between the carbon fiber surface and the PEEK is improved and the interface bonding capability is enhanced due to the addition of the sulfonated polyether-ether-ketone, and on the other hand, the roughness of the carbon fiber surface is obviously improved after the carbon fiber surface is introduced due to the large specific surface area of the nano particle carboxylated carbon nano tube, and the interface bonding force between the fiber and the PEEK resin is enhanced. After sizing modification, the wettability between matrix resin and reinforcing fibers becomes good, the interface bonding is tighter, and the interlaminar shear strength of the composite material is obviously improved. Therefore, the SPEEK sizing agent added with the carboxylated carbon nanotubes can obviously improve the bending strength and the interlaminar shear strength between the carbon fibers and the resin matrix, so that the composite material has excellent mechanical properties.

The ECF/PEEK composite material and the SPEEK-CNTS-CF/PEEK composite material are made into a standard required by a test, the size is 50mm multiplied by 10mm multiplied by 1.5mm, the frequency is 1Hz, the temperature is from room temperature to 200 ℃, a single-arm suspension mode is set to be adopted, the dynamic thermal mechanical property analysis is carried out on the composite material, and a change curve of dynamic mechanical parameters of the composite material along with the temperature is obtained through the test and is shown in figure 9;

FIG. 9 is a graph of the mechanical loss factor tan delta of the composite material as a function of temperature, wherein 1 is ECF/PEEK composite material and 2 is SPEEK-CNTS-CF/PEEK composite material;

the mechanical loss factor tan delta represents the ratio of energy dissipated in the form of heat to stored energy, and represents the ability of the material to lose energy itself during deformation. The peak of each curve represents the glass transition temperature Tg of the composite ECF/PEEK and SPEEK-CNTS-CF/PEEK. Since the glass transition temperature Tg of PEEK is 143 ℃, the glass transition temperature of the composite material is higher than that of pure polyetheretherketone, which may be due to the fact that carbon fibers in the composite material act as a barrier during the segmental motion of polyetheretherketone. When the temperature is lower than the glass transition temperature Tg, the loss change of the composite material is not large at the temperature far lower than the Tg, namely the composite material generates small deformation under the action of external force, the deformation rate is fast, the loss factor is small, namely the internal consumption is small, and the deformation of the material is basically consistent with the change of stress. The temperature is increased, the chain segment starts to move and is subjected to great frictional resistance, so that the deformation speed of the material is lower than the stress change, the internal loss is increased, and the glass transition temperature Tg is reached. When the temperature continues to rise, although the deformation increases, the segments of polyetheretherketone move more freely, so that the internal friction begins to decrease again. The composite material prepared from the carbon fiber after sizing modification has larger loss factor than the T300 carbon fiber composite material, and needs more consumed energy, so that the obtained interface combination is better.