CN111410759B

CN111410759B - CF/PEEK composite material with excellent high-temperature mechanical property and preparation method thereof

Info

Publication number: CN111410759B
Application number: CN202010420353.2A
Authority: CN
Inventors: 朱姝; 周剑锋; 韩克清; 史如静; 钱盈; 任毅
Original assignee: Donghua University
Current assignee: Changzhou junhang high performance composite material Co.,Ltd.
Priority date: 2020-05-18
Filing date: 2020-05-18
Publication date: 2020-12-22
Anticipated expiration: 2040-05-18
Also published as: CN111410759A

Abstract

The invention relates to a CF/PEEK composite material with excellent high-temperature mechanical properties and a preparation method thereof, wherein the preparation method comprises the following steps: (1) carrying out pyrolysis on the original sizing agent on the CF surface; (2) in a saturated water vapor environment, simultaneously carrying out microwave radiation and ultraviolet radiation on CF, and recording a product as ACF; (3) immersing the ACF into the polyamic acid/N-methyl-2-pyrrolidone/carbon nano tube suspension, taking out and drying, and then carrying out two-stage heat treatment to obtain sizing modified carbon fiber MCF; (4) hot-pressing the MCF and PEEK material lamination; the CF/PEEK composite material with excellent high-temperature mechanical properties is obtained, and has the bending strength of 780-950MPa at 25 ℃, the bending modulus of 55-65GPa and the interlaminar shear strength of 80-93 MPa; the bending strength at 200 ℃ is 550-650MPa, the bending modulus is 40-50GPa, and the interlaminar shear strength is 60-75 MPa. The method has the characteristics of high efficiency, environmental protection and large-scale production realization, and the prepared composite material can replace metal and be used in the fields of aerospace, medical treatment, machinery, automobiles and the like.

Description

CF/PEEK composite material with excellent high-temperature mechanical property and preparation method thereof

Technical Field

The invention belongs to the technical field of carbon fiber reinforced polyether ether ketone (CF/PEEK) composite materials, and relates to a CF/PEEK composite material with excellent high-temperature mechanical properties and a preparation method thereof.

Background

In recent years, thermoplastic composite materials have attracted much attention because of their advantages such as good recyclability, secondary processability, high impact toughness, high specific strength, and high specific modulus. Among various thermoplastic composite materials, CF/PEEK has excellent performances such as high rigidity, high thermal stability, chemical corrosion resistance, wear resistance, biocompatibility and the like, is expected to be used as a structural material to replace metal or thermosetting composite materials with mature processes, and is widely applied to the fields of aerospace, medical treatment, machinery, automobile and rail transit, petroleum transportation and the like.

However, the practical application of CF/PEEK thermoplastic composites is not optimistic. The main problem is that the interlaminar shear strength (ILSS) is low, resulting in low flexural strength, and especially when used under high temperature conditions, the material is prone to damage and failure when subjected to moments normal to the panel. The main reasons for this performance defect are that the interface interaction between the carbon fiber and the PEEK matrix is weak, the wettability is poor, and pores are easily generated during the molding process of the composite material. The fundamental reason is that CF is in a stable six-membered ring structure, the surface of the CF is composed of a nonpolar and highly ordered graphite basal plane, so that the surface of the fiber contains less active functional groups, and the melt viscosity of PEEK is high, so that the wettability between carbon fiber and PEEK resin is poor, and the interface bonding strength is weak. As a tie of load transmission between the fiber and the resin matrix, the bonding strength of the interface layer greatly influences the mechanical property of the whole composite material, when the composite material with low interface strength is damaged, cracks are expanded along the interface, the reinforcing effect of the fiber cannot be well exerted, and the strength of the composite material is far lower than the theoretical value.

The CF is subjected to surface modification treatment, so that the problems can be solved, and the properties such as the interlaminar shear strength of the composite material are improved. There are two types of known techniques, namely "activation (sometimes also referred to as oxidation)" and "sizing". Can be used singly or in combination and superposition. The principle of activation modification is to introduce active functional groups on the surface of the fiber, increase the number of chemical bonds or hydrogen bonds between the fiber and the polymer matrix, and improve the interface bonding strength of the composite material through strong chemical action. The principle of sizing modification is that a polymer (which can be different from a matrix) thin layer is attached to the surface of a fiber through a solution or emulsion coating, and a bridge is erected between the fiber and the matrix which originally have weak interaction by utilizing the characteristic that the polymer thin layer can generate strong interaction with the fiber and the matrix, so that the relevance of the fiber and the matrix is enhanced.

The prior activation techniques include plasma treatment, anodic electrolysis or electrodeposition treatment, strong acid treatment, ozone treatment, microwave ultrasonic co-treatment, and the like. The activation process may reduce the strength of the CF filaments by finding a balance between the number of reactive groups and the strength of the CF filaments, allowing the CF surface to generate as many hydroxyl and carboxyl groups as possible, creating as many grooves as possible to increase the contact area with the substrate, but at the same time losing as little strength as possible.

The existing sizing technology comprises a reaction type sizing agent, a coating type sizing agent and the like.

The prior art has effects in some aspects, but has various defects or shortcomings, so that the industrial production is difficult to realize when the PEEK substrate is used for a substrate which needs to be molded and processed at a high temperature of 400 ℃.

For example, when CF is treated by plasma, the effect difference between the outer layer and the inner layer of the filament bundle is obvious, and when the active groups of the outer layer are more and the strength of the monofilament is greatly damaged, the activity of the CF of the inner layer is not improved. Therefore, the stability is poor, the dispersion is large, and the method is not suitable for industrial production.

The anodic electrolysis or electrodeposition treatment process is effective in treating tows, but is difficult to treat the fabric, and the strength of the monofilaments is greatly reduced.

In the strong acid treatment, a large amount of waste acid and waste liquid is generated, so that the environmental pollution is large; the method is mostly operated intermittently, the required treatment time is long, and the method is difficult to match with a CF production line; and the corrosion resistance of equipment is high, and the operation risk coefficient is high, so the method is hardly considered in industrial production.

Ozone treatment can produce a large amount of ozone harmful to human body, the treatment of ozone-containing exhaust gas can greatly increase the cost, and the mode which is not environment-friendly is being abandoned gradually.

The strength of the CF monofilaments is greatly damaged by microwave ultrasonic co-treatment, and the damage degree is difficult to control.

The reactive sizing agents (surface grafts, coupling agents, etc.) have a low reaction rate and need to be used in conjunction with the several activation techniques previously described.

Coating-type sizing agents (relying on van der waals forces) can improve the wettability of the matrix to the fibers, but have limited effect on enhancing interfacial interactions.

The CF/PEEK composite material prepared by the known technology is generally ILSS lower than 85MPa at normal temperature, and a few technologies exceed 90MPa, but the industrial production is difficult to realize by using strong acid or plasma treatment in the preparation process. The oxygen/carbon (O/C) content ratio after the CF surface activation is improved by about 40%.

On the other hand, when the CF/PEEK composite material prepared by most of the known high-temperature-resistant sizing agents is used in an environment of 200 ℃, the performances such as the interlaminar shear strength, the bending strength and the like are greatly reduced, and the reduction range is usually more than 50%. This is due to the glass transition temperature of the sizing agent itself and the PEEK matrix being below 200 c, although the thermal decomposition temperature of these high temperature resistant sizing agents is near or above 400 c.

Disclosure of Invention

The invention aims to provide a method for preparing a CF/PEEK composite material in an acid-free environment, and the prepared composite material has the advantages of excellent high-temperature mechanical property and the like.

The invention aims to provide a CF/PEEK composite material with excellent high-temperature mechanical properties.

The invention also aims to provide a preparation method of the CF/PEEK composite material with excellent high-temperature mechanical property, which is a preparation method under completely acid-free environmental conditions, is environment-friendly and can realize large-scale production; the adopted sizing agent PAA for the PEEK substrate has good solubility, is converted into Polyimide (PI) after heat treatment, has good heat resistance, and is stable at the high temperature of 400 ℃ below zero when the CF/PEEK composite material is molded; the glass transition temperature of the PI is about 243 ℃, so that the CF/PEEK composite material has high retention rate of strength and modulus when used in an environment of 200 ℃, and has excellent high-temperature mechanical properties; the carboxylated CNT with moderate content and good dispersion is added into the sizing agent, and the interface interaction can be further enhanced through the pinning effect of the carboxylated CNT and PEEK matrix.

The preparation method of the CF/PEEK composite material with excellent high-temperature mechanical properties comprises the following steps:

(1) carrying out pyrolysis on the original sizing agent on the CF surface;

(2) subjecting CF to simultaneous microwave irradiation and ultraviolet irradiation in a saturated water vapor environment, and marking the product as activated-CF (ACF); the step carries out acid-free activation modification treatment on the CF, so that the method is environment-friendly and has the possibility of industrial mass production;

(3) immersing ACF into a polyamic acid (PAA)/N-methyl-2-pyrrolidone (NMP)/Carbon Nanotube (CNT) suspension, taking out, drying, and performing two-stage heat treatment to obtain sizing Modified Carbon Fiber (MCF);

(4) hot-pressing the MCF and PEEK material lamination; the PEEK matrix is changed from solid to melt and flows in a shearing mode under pressure to infiltrate into the inner portion of the MCF tows;

cooling to room temperature, and demoulding to obtain the CF/PEEK composite material with excellent high-temperature mechanical properties.

As a preferred technical scheme:

with the above-described preparation method, the CF is in the form of satin fabric, and when the CF is in other forms, such as chopped fiber, long fiber, fiber mat, continuous fiber tow, or plain, twill, and non-crimp fabric, the composite material can also be compounded with PEEK by using the method of the present invention, but the performance of the prepared composite material is relatively poor.

In the preparation method, the pyrolysis refers to sintering at 300-420 ℃ for 5-180 min. The original sizing agent is removed by pyrolysis. These sizing agents adhere to the surface of commercial-grade carbon fibers, are generally epoxy resin-based in composition, and must be sized before fiber winding can be achieved, otherwise fuzz can be generated and fiber breakage can even result. However, these sizing agents are not good for the combination of CF and PEEK, because these sizing agents will decompose at the high temperature (400 ℃) of PEEK molding, form pores in the composite material, and reduce the mechanical properties such as material strength. Deviations from the recommended parameter intervals would be detrimental to an efficient control of the pyrolysis process. For example, if the pyrolysis temperature is too low or the pyrolysis time is too short, the original sizing agent cannot be completely removed, and the residual part still decomposes at the high temperature of the molding processing of the CF/PEEK composite material, so that various mechanical properties of the composite material are influenced; if the pyrolysis temperature is too high or the pyrolysis time is too long, part of the surface structure of the CF is damaged by oxidation reaction, the CF surface has ravines, the strength of the monofilament is reduced by more than a certain extent (e.g. 10%), and the mechanical performance indexes of the composite material are also greatly reduced. In the pyrolysis process, if a vacuum environment or an inert gas atmosphere such as nitrogen, helium and the like can be established, the effect is better, the oxidation reaction of the CF can be inhibited, and the strength retention rate of the CF monofilament is higher.

The preparation method is characterized in that the relative humidity of saturated water vapor is more than 95 percent; the microwave radiation time is 3-30min, and the microwave frequency is 300MHz-10 GHz; the wavelength of the irradiated ultraviolet light is 290-340nm, and the ultraviolet irradiance is 20-50W/m². This step has three functions: 1) the microwave irradiation can promote the graphitization of the carbon fiber surface and make up/offset the loss of the strength of the monofilament; 2) ultraviolet irradiation is carried out, the original sizing agent residue which is not high in temperature resistance in the groove on the surface of the carbon fiber is further cleaned, and the ultraviolet can break the double bonds of the residual organic matters on the surface of the CF through oxidation reaction; 3) the ultraviolet light and the water vapor jointly act to excite the hydroxyl, carboxyl and other groups on the surface of the CF.

It is particularly emphasized that the simultaneous addition of microwave action with the action of ultraviolet and saturated water vapor is necessary because microwave irradiation can heat CF uniformly during oxidation to promote hydroxylation and carboxylation. Comparing the samples with and without microwaves, it can be seen that the O/C ratio is higher in the samples with microwaves, suggesting that the content of oxygen-containing groups is higher. Moreover, the microwave irradiation can promote the graphitization of the carbon fiber surface and make up/offset the loss of the strength of the monofilament.

If the humidity is too low, the microwave radiation time is too short, the microwave frequency is too low, the ultraviolet wavelength is too long or the irradiance is too low, the excited number of hydroxyl and carboxyl is less, the activation degree of CF is lower, the number of hydrogen bonds capable of being formed with a sizing agent is also less, and the interaction between the ACF and the sizing agent is smaller; if the microwave radiation time is too long, the microwave frequency is too high, the ultraviolet wavelength is too short or the irradiance is too high, the six-membered ring structure on the CF surface can be damaged too much, the strength of the CF monofilament is reduced too much, and thus various mechanical properties of the composite material are reduced.

The same activation modification method (generating hydroxyl groups and carboxyl groups on the surface and affecting the internal structure of the carbon nanotube-based carbon fiber as little as possible) can be applied to carbon materials such as Carbon Nanotubes (CNTs), Graphene Oxide (GO), Carbon Black (CB), and Carbon Nanofibers (CNF).

In the preparation method described above, in the polyamic acid/N-methyl-2-pyrrolidone/carbon nanotube suspension, PAA is completely dissolved and has a concentration of 0.2 to 2 wt.%, and CNT content of 0.01 to 0.1 wt.%, and a stable suspension is prepared by ultrasonic dispersion for 5 to 60 min; the CNT is a carboxyl modified single-wall or multi-wall CNT, and the weight average molecular weight of PAA is more than 55000; soaking for 5-120 min; drying to a water content of less than 0.5 wt.%; the two-stage heat treatment condition is that the PAA is continuously heated for 5-30min at 180-220 ℃, then the temperature is raised to 260-310 ℃ at the speed of 1-50 ℃/min and is kept for 10-60min, and the heat treatment process can convert the PAA into the Polyimide (PI).

The reaction equation for conversion of PAA to PI is as follows:

the PAA has good solubility, and a large amount of hydrogen bonds can be formed between carbonyl groups on the PAA and hydroxyl and carboxyl groups on the ACF, so that the PAA solution can be effectively coated on the surface of the ACF; since the carboxyl group on the CNT and the carbonyl group on the PAA can also undergo hydrogen bonding, the CNT can be stably dispersed in the PAA solution; PAA can be converted into PI under two-stage heat treatment, the PI is similar to the chemical structure of a PEEK substrate, the absolute value of the difference of surface energy is small, and the wettability of the PI and the PEEK is good; after PAA is converted into PI, the carbonyl group is not changed and can still keep a large amount of hydrogen bonding with hydroxyl and carboxyl on the surface of the ACF; the existence of CNT can increase the surface roughness of MCF on one hand, the CNT can be pricked in a PEEK matrix like a plurality of nails, the total sum of friction force is increased through a large amount of contact area, and on the other hand, the CNT also enhances the strength of a PI/CNT interface layer; the interaction of PEEK and MCF is greatly enhanced under the action of the above actions, and the interlaminar shear strength and the bending strength of the CF/PEEK composite material at normal temperature are enhanced; the PI has excellent temperature resistance, and the decomposition temperature is far higher than-400 ℃ of the CF/PEEK composite material molding processing; the glass transition temperature of the PI is about 243 ℃, so that the strength and modulus retention rate of the PI layer in the environment of 200 ℃ is high, the strength and modulus retention rate of the CF/PEEK composite material is also high when the CF/PEEK composite material is used in the environment of 200 ℃, and the high-temperature mechanical property is excellent.

If the concentration of the PAA solution is too low or the immersion time is too short, a sufficient amount of the sizing agent cannot be applied to the ACF surface; if the concentration of the PAA solution is too high, the sizing agent wrapped on the surface of the ACF is too much, the PAA layer is too thick, when the PAA layer is converted into PI under the action of heat treatment, the PAA layer which is too thick shrinks, the shrinkage rate of the PAA layer is large, large internal stress is formed, and the mechanical property of the prepared CF/PEEK composite material is not as good as that of the PAA layer with proper thickness; if the immersion time is too long, the production efficiency is affected and the cost is increased. If the molecular weight of the PAA is too low, the converted PI layer has too low strength, the interface layer is easy to break when the composite material is stressed, and the overall mechanical property of the composite material is reduced. If the content of the CNT is too low, the number of the CNT which can generate the pinning effect between the CNT and the PEEK substrate is too small, the pinning effect is not obvious, and the interaction force between the MCF and the PEEK is not large enough; if the content of the CNT is too high or the ultrasonic dispersion time is too short, the CNT is insufficiently dispersed and agglomerated, so that the wetting of PEEK on MCF is influenced; if the ultrasound time is too long, not only is energy wasted, efficiency is reduced, but the structural integrity of the CNTs may also be compromised. If the water content after drying is too large, pores are formed in the forming process of the composite material due to water vapor volatilization, and the mechanical property of the composite material is influenced. In the two-stage heat treatment, if the temperature of the first-stage heat treatment is too low or too high, the heating time is too short, the heating rate between the first stage and the second stage is too high or the temperature of the second-stage heat treatment is too high, the shrinkage rate of the PI layer is too high, and the internal stress is too large; if the two-stage heating time is too long, the energy consumption is wasted and the efficiency is reduced; if the temperature of the second-stage heat treatment is too low or the heat preservation time is too low, the conversion of PAA to PI is incomplete, the thermal stability of the sizing agent is reduced, and the mechanical property of the composite material at high temperature is poor; if the second stage heat treatment temperature is too high, the shrinkage rate of the PI layer is too high, and the internal stress is too large.

In the preparation method, the PEEK material is in the form of a film, a non-woven fabric felt, powder or fiber; the weight average molecular weight of the PEEK material is 30000-150000; the technological parameters of lamination hot pressing are as follows: the temperature is 370-420 ℃, the pressure is 0.5-5MPa, and the heat preservation and loading time is 3-30 min. In the process, because the interaction between the PEEK and the MCF is enhanced, the infiltration performance of the PEEK melt to the MCF is greatly improved, the possibility of forming pores in the composite material is reduced, the interface bonding strength of the PEEK and the MCF is increased when the composite material is damaged by external force, and the material failure mode is changed from fiber extraction to matrix fracture.

If the molecular weight of the PEEK material is too low, molecular chain entanglement in the matrix is less, the strength of the matrix is too low, and the overall strength of the composite material is limited; if the molecular weight is too high or the hot-pressing temperature is too low, the melt viscosity is too high, and the porosity of the composite material is increased; if the hot pressing temperature is too high or the heat preservation loading time is too long, PEEK is easy to degrade, discolor, age and the like at high temperature, and the strength of the resin is reduced; if the pressure is small or the loading time is too short, the shearing action on the melt is small, the CF infiltration is incomplete, and the porosity of the composite material is increased; if the pressure is too large, more resin flows out from the gaps of the die, and the composite material has the defects of poor adhesive and the like.

The CF/PEEK composite material with excellent high-temperature mechanical properties prepared by the preparation method has the bending strength of 780-950MPa at 25 ℃, the bending modulus of 55-65GPa and the interlaminar shear strength of 80-93 MPa; the bending strength at 200 ℃ is 550-650MPa, the bending modulus is 40-50GPa, and the interlaminar shear strength is 60-75 MPa.

Due to the adoption of the technical scheme, the invention has the following beneficial effects:

the principle of the CF/PEEK composite material with excellent high-temperature mechanical property prepared by the invention is that the original sizing agent on the CF surface is decomposed at high temperature. These sizing agents adhere to the surface of commercial grade carbon fibers to ensure that the fibers can be wound, however, these sizing agents decompose at the high temperatures (400 ℃) of PEEK molding, forming voids in the composite material, reducing mechanical properties such as material strength. Secondly, in a saturated water vapor environment, the CF is subjected to microwave radiation and ultraviolet radiation simultaneously. On one hand, the microwave irradiation can promote the graphitization of the carbon fiber surface and make up or offset the loss of the strength of the monofilament; in the second aspect, double bonds of residual organic matters on the surface of the CF can be broken through oxidation reaction by ultraviolet rays, so that the original sizing agent residue which is not high in temperature resistance in the groove on the surface of the carbon fiber can be further cleaned through ultraviolet irradiation; in the third aspect, the ultraviolet light and the water vapor jointly act to excite the hydroxyl, carboxyl and other groups on the CF surface. Therefore, active groups such as hydroxyl and carboxyl are grafted on the surface of CF through acid-free activation modification treatment, so that the method is environment-friendly and has the possibility of industrial mass production. Next, the ACF is dip-sized with a polyamic acid/N-methyl-2-pyrrolidone/carbon nanotube suspension. The PAA has good solubility, and a large amount of hydrogen bonds can be formed between carbonyl groups on the PAA and hydroxyl and carboxyl groups on the ACF, so that the PAA solution can be effectively coated on the surface of the ACF; since the carboxyl group on the CNT and the carbonyl group on the PAA can also undergo hydrogen bonding, the CNT can be stably dispersed in the PAA solution; PAA can be converted into Polyimide (PI) under two-stage heat treatment, the PI is similar to the chemical structure of a PEEK substrate, the absolute value of the difference of surface energy is small, and the wettability of the PI and the PEEK is good; after PAA is converted into PI, the carbonyl group is not changed and can still keep a large amount of hydrogen bonding with hydroxyl and carboxyl on the surface of the ACF; the existence of CNT can increase the surface roughness of MCF on one hand, the CNT can be pricked in a PEEK matrix like a plurality of nails, the total sum of friction force is increased through a large amount of contact area, and on the other hand, the CNT also enhances the strength of a PI/CNT interface layer; the interaction of PEEK and MCF is greatly enhanced under the action of the above actions, and the interlaminar shear strength and the bending strength of the CF/PEEK composite material at normal temperature are enhanced; the PI has excellent temperature resistance, and the decomposition temperature is far higher than-400 ℃ of the CF/PEEK composite material molding processing; the glass transition temperature of the PI is about 243 ℃, so that the strength and modulus retention rate of the PI layer in the environment of 200 ℃ is high, the strength and modulus retention rate of the CF/PEEK composite material is also high when the CF/PEEK composite material is used in the environment of 200 ℃, and the high-temperature mechanical property is excellent. Finally, the CF/PEEK composite material is prepared by laminating and hot pressing. The PEEK matrix changes from a solid to a melt under heat and, under pressure, flows in shear, infiltrating the interior of the MCF tow. In the process, because the interaction between the PEEK and the MCF is enhanced, the infiltration performance of the PEEK melt to the MCF is greatly improved, the possibility of forming pores in the composite material is reduced, the interface bonding strength of the PEEK and the MCF is increased when the composite material is damaged by external force, and the material failure mode is changed from fiber extraction to matrix fracture.

One of the advantages of the method of the invention is that the CF surface activation process is acid-free treatment, is environment-friendly and has industrialization possibility, and the activation effect is equivalent to the activation effect by using strong acid.

The CF/PEEK composite material with excellent high-temperature mechanical properties, which is prepared by the preparation method disclosed by the invention, has the bending strength of 780-950MPa at 25 ℃, the bending modulus of 55-65GPa and the interlaminar shear strength of 80-93 MPa; the bending strength at 200 ℃ is 550-650MPa, the bending modulus is 40-50GPa, and the interlaminar shear strength is 60-75 MPa.

Drawings

FIG. 1 is an XPS plot of untreated CF and oxygen element/carbon element (O/C) content, wherein a higher O/C content ratio indicates a higher activation efficiency;

FIG. 2 is an XPS plot of UV irradiation treated CF in a saturated water vapor environment with oxygen element/carbon element (O/C) content;

FIG. 3 is an XPS plot of CF treated with simultaneous microwave and UV irradiation in a saturated water vapor environment and oxygen element/carbon element (O/C) content.

FIG. 4 is a scanning electron micrograph of a carbon fiber obtained by simultaneous microwave and UV irradiation treatment in a saturated water vapor environment and sizing treatment with a suspension containing 0.03 wt.% CNT;

FIG. 5 is a scanning electron micrograph of a carbon fiber obtained by simultaneous microwave and UV irradiation treatment in a saturated water vapor environment followed by a sizing treatment of a suspension containing 0.10 wt.% CNT;

FIG. 6 is a scanning electron micrograph of the brittle fracture cross section of a CF/PEEK composite material prepared from carbon fibers in liquid nitrogen, which is obtained by performing microwave and ultraviolet irradiation treatment simultaneously in a saturated water vapor environment and then performing sizing treatment on a suspension containing 0.10 wt.% of CNT.

Detailed Description

The invention will be further illustrated with reference to specific embodiments. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Further, it should be understood that various changes or modifications of the present invention may be made by those skilled in the art after reading the teaching of the present invention, and such equivalents may fall within the scope of the present invention as defined in the appended claims.

Example 1

The preparation method of the CF/PEEK composite material with excellent high-temperature mechanical property comprises the following steps:

(1) sintering the T300 grade 3K5 satin fabric of CF for 180min at 300 ℃ to decompose the original sizing agent on the surface at high temperature;

(2) simultaneously performing microwave radiation and ultraviolet radiation on CF in a saturated water vapor environment with the relative humidity of 95.3 percent, and marking the product as ACF; the microwave radiation time is 30min, and the microwave frequency is 300 MHz; the wavelength of the irradiated ultraviolet light is 290nm, and the ultraviolet irradiance is 20W/m²；

(3) Immersing ACF into a polyamic acid/N-methyl-2-pyrrolidone/carbon nanotube suspension for 120min, wherein the weight-average molecular weight of the polyamic acid is 55500, taking out the polyamic acid, drying the polyamic acid until the water content is 0.48 wt%, and then carrying out two-stage heat treatment to obtain sizing modified carbon fiber MCF; in the polyamic acid/N-methyl-2-pyrrolidone/carbon nanotube suspension, the concentration of polyamic acid is 0.20 wt.%, and the content of carbon nanotubes is 0.01 wt.%, stable suspension is prepared by 5min ultrasonic dispersion, and the carbon nanotubes are carboxyl-modified single-walled carbon nanotubes; two-stage heat treatment, namely, continuously heating at 180 ℃ for 5min, then heating to 260 ℃ at the speed of 1 ℃/min, and preserving heat for 10 min;

(4) laminating MCF and PEEK powder with the weight-average molecular weight of 30000 for hot pressing; the technological parameters of lamination hot pressing are as follows: the temperature is 370 ℃, the pressure is 5MPa, and the loading time is 3 min;

The finally prepared CF/PEEK composite material with excellent high-temperature mechanical properties has the bending strength of 818MPa, the bending modulus of 57GPa and the interlaminar shear strength of 84MPa at 25 ℃; the flexural strength at 200 ℃ was 580MPa, the flexural modulus was 40GPa, and the interlaminar shear strength was 60 MPa.

Comparative example 1

The preparation method of the CF/PEEK composite material is basically the same as the example 1, the steps (1) and (2) are omitted relative to the example 1, meanwhile, the material immersed in the polyamic acid/N-methyl-2-pyrrolidone/carbon nanotube suspension in the step (3) is changed into T300 grade 3K5 satin fabric of CF from ACF, and other processes and parameters are the same as the example 1.

The bending strength of the finally prepared CF/PEEK composite material at 25 ℃ is 542MPa, the bending modulus is 47GPa, and the interlaminar shear strength is 62 MPa; the flexural strength at 200 ℃ was 375MPa, the flexural modulus was 31GPa, and the interlaminar shear strength was 44 MPa.

Comparing example 1 with comparative example 1, it can be seen that the bending strength, flexural modulus, interlaminar shear strength of the CF/PEEK composite material prepared in example 1 are much higher at 25 ℃ and 200 ℃ than those of comparative example 1, the XPS curve and the oxygen element/carbon element (O/C) content of the untreated CF in comparative example 1 are shown in fig. 1, the XPS curve and the oxygen element/carbon element (O/C) content of the CF treated simultaneously with microwave and ultraviolet irradiation in saturated water vapor environment in example 1 are shown in fig. 3, and it can be seen by comparison that the O/C ratio of the untreated CF is 0.0700, in which the content of O element is not high, indicating that CF is inert, and the O/C ratio of the uv + water vapor + microwave treated CF is 0.1782, in which the content of O element is significantly increased, and the O/C ratio is increased by 155% (up to 255,original%) as compared with the untreated CF, it is important to demonstrate that the microwave treatment is applied simultaneously with the uv + water vapor, which is why CF/PEEK composites made with untreated CF are low in flexural strength, flexural modulus, interlaminar shear strength at 25 ℃ and 200 ℃.

Comparative example 2

The preparation method of the CF/PEEK composite material is basically the same as the example 1, and is adjusted relative to the step (2) of the example 1, specifically, in a saturated water vapor environment, only ultraviolet radiation is carried out on CF, microwave radiation is not carried out, and other processes and parameters are the same as the example 1.

The bending strength of the finally prepared CF/PEEK composite material at 25 ℃ is 576MPa, the bending modulus is 48GPa, and the interlaminar shear strength is 65 MPa; the flexural strength at 200 ℃ was 391MPa, the flexural modulus was 31GPa, and the interlaminar shear strength was 45 MPa.

Comparing example 1 with comparative example 2, it can be seen that the flexural strength, flexural modulus, and interlaminar shear strength of the CF/PEEK composite material prepared in example 1 at 25 ℃ and 200 ℃ are much higher than those of comparative example 2, the XPS curve and the content of oxygen element/carbon element (O/C) of the CF treated by ultraviolet irradiation in a saturated water vapor environment in comparative example 2 are shown in fig. 2, the XPS curve and the content of oxygen element/carbon element (O/C) of the CF treated by simultaneous microwave and ultraviolet irradiation in a saturated water vapor environment in example 1 are shown in fig. 3, and it can be seen by comparison that the O/C ratio of the CF treated by ultraviolet + water vapor is 0.0765, in which the increase of the content of O element is not significant, indicating that the effect is not so good using only ultraviolet + water vapor, while the O/C ratio of the CF treated by ultraviolet + water vapor + microwave is 0.1782, the content of O element is obviously increased, which shows that the microwave treatment is important at the same time of ultraviolet and water vapor, and the reason why the bending strength, the bending modulus and the interlaminar shear strength of the CF/PEEK composite material prepared by the CF treated by the ultraviolet and water vapor are lower at 25 ℃ and 200 ℃.

Example 2

(1) sintering the T300 grade 3K5 satin fabric of CF at 350 ℃ for 138min to decompose the original sizing agent on the surface at high temperature;

(2) simultaneously performing microwave radiation and ultraviolet radiation on CF in a saturated water vapor environment with the relative humidity of 95.8%, and marking the product as ACF; the microwave radiation time is 27min, and the microwave frequency is 820 MHz; the irradiation ultraviolet wavelength is 299nm, and the ultraviolet irradiance is 50W/m²；

(3) Immersing ACF into polyamic acid/N-methyl-2-pyrrolidone/carbon nanotube suspension for 115min, wherein the weight-average molecular weight of the polyamic acid is 55800, taking out, drying until the water content is 0.45 wt%, and performing two-stage heat treatment to obtain sizing modified carbon fiber MCF, wherein the scanning electron microscope photograph is shown in FIG. 4; in the polyamic acid/N-methyl-2-pyrrolidone/carbon nanotube suspension, the concentration of polyamic acid is 0.8 wt.%, and the content of carbon nanotubes is 0.03 wt.%, stable suspension is prepared by 15min ultrasonic dispersion, and the carbon nanotubes are carboxyl-modified single-walled carbon nanotubes; two-stage heat treatment, namely, continuously heating at 183 ℃ for 8min, then heating to 268 ℃ at the speed of 10 ℃/min, and keeping the temperature for 15 min;

(4) laminating MCF and PEEK powder with the weight-average molecular weight of 60000 for hot pressing; the technological parameters of lamination hot pressing are as follows: the temperature is 378 ℃, the pressure is 4.7MPa, and the loading time is 7 min;

The finally prepared CF/PEEK composite material with excellent high-temperature mechanical properties has the bending strength of 839MPa, the bending modulus of 59GPa and the interlaminar shear strength of 87MPa at 25 ℃; the flexural strength at 200 ℃ was 618MPa, the flexural modulus was 46GPa, and the interlaminar shear strength was 73 MPa.

Example 3

(1) sintering the T300 grade 3K5 satin fabric of CF at 420 ℃ for 5min to decompose the original sizing agent on the surface at high temperature;

(2) simultaneously performing microwave radiation and ultraviolet radiation on CF in a saturated water vapor environment with the relative humidity of 95.9 percent, and marking the product as ACF; the microwave radiation time is 24min, and the microwave frequency is 1 GHz; the wavelength of the irradiated ultraviolet light is 305nm, and the ultraviolet irradiance is 35W/m²；

(3) Immersing ACF into a polyamic acid/N-methyl-2-pyrrolidone/carbon nanotube suspension for 94min, taking out the polyamic acid with the weight-average molecular weight of 56100, drying until the water content is 0.42 wt%, and performing two-stage heat treatment to obtain sizing modified carbon fiber MCF; in the polyamic acid/N-methyl-2-pyrrolidone/carbon nanotube suspension, the concentration of polyamic acid is 1.1 wt.%, and the content of carbon nanotubes is 0.05 wt.%, stable suspension is prepared by 28min ultrasonic dispersion, and the carbon nanotubes are carboxyl-modified single-walled carbon nanotubes; two-stage heat treatment, namely, continuously heating at 189 ℃ for 13min, then heating to 270 ℃ at the speed of 18 ℃/min, and preserving heat for 20 min;

(4) laminating MCF and PEEK non-woven fabric felt with the weight-average molecular weight of 75000 for hot pressing; the technological parameters of lamination hot pressing are as follows: the temperature is 381 ℃, the pressure is 3.4MPa, and the loading time is 11 min;

The bending strength of the finally prepared CF/PEEK composite material with excellent high-temperature mechanical properties at 25 ℃ is 885MPa, the bending modulus is 62GPa, and the interlaminar shear strength is 88 MPa; the flexural strength at 200 ℃ was 629MPa, the flexural modulus was 50GPa, and the interlaminar shear strength was 72 MPa.

Example 4

(1) sintering the T300 grade 3K5 satin fabric of CF for 168min at 335 ℃ to decompose the original sizing agent on the surface at high temperature;

(2) simultaneously performing microwave radiation and ultraviolet radiation on CF in a saturated water vapor environment with the relative humidity of 96.3 percent, and marking the product as ACF; the microwave radiation time is 20min, and the microwave frequency is 1.5 GHz; the irradiation wavelength of ultraviolet light is 313nm, and the ultraviolet irradiance is 24W/m²；

(3) Immersing the ACF into a polyamic acid/N-methyl-2-pyrrolidone/carbon nanotube suspension for 69min, taking out the polyamic acid with the weight-average molecular weight of 56800, drying until the water content is 0.41 wt%, and performing two-stage heat treatment to obtain a sizing modified carbon fiber MCF; in the polyamic acid/N-methyl-2-pyrrolidone/carbon nanotube suspension, the concentration of polyamic acid is 1.2 wt.%, and the content of the carbon nanotube is 0.08 wt.%, stable suspension is prepared by 35min ultrasonic dispersion, and the carbon nanotube is a carboxyl modified single-walled carbon nanotube; two-stage heat treatment, namely, continuously heating at 190 ℃ for 19min, then heating to 272 ℃ at the speed of 20 ℃/min, and keeping the temperature for 25 min;

(4) laminating MCF and PEEK fiber with the weight-average molecular weight of 82000 for hot pressing; the technological parameters of lamination hot pressing are as follows: the temperature is 389 ℃, the pressure is 2.9MPa, and the loading time is 15 min;

The finally prepared CF/PEEK composite material with excellent high-temperature mechanical properties has the bending strength of 950MPa at 25 ℃, the bending modulus of 64GPa and the interlaminar shear strength of 90 MPa; the flexural strength at 200 ℃ was 650MPa, the flexural modulus was 48GPa, and the interlaminar shear strength was 75 MPa.

Example 5

(1) sintering the T300 grade 3K5 satin fabric of CF at 360 ℃ for 104min to decompose the original sizing agent on the surface at high temperature;

(2) simultaneously performing microwave radiation and ultraviolet radiation on CF in a saturated water vapor environment with the relative humidity of 96.8%, and marking the product as ACF; the microwave radiation time is 16min, and the microwave frequency is 2.3 GHz; the wavelength of the irradiated ultraviolet light is 320nm, and the ultraviolet irradiance is 31W/m²；

(3) Immersing ACF into polyamic acid/N-methyl-2-pyrrolidone/carbon nanotube suspension for 51min, wherein the weight-average molecular weight of the polyamic acid is 57310, taking out, drying until the water content is 0.38 wt%, and performing two-stage heat treatment to obtain sizing modified carbon fiber MCF; in the polyamic acid/N-methyl-2-pyrrolidone/carbon nanotube suspension, the concentration of polyamic acid is 1.3 wt.%, and the content of carbon nanotubes is 0.06 wt.%, stable suspension is prepared by 39min ultrasonic dispersion, and the carbon nanotubes are carboxyl-modified multi-wall carbon nanotubes; two-stage heat treatment, namely, continuously heating at 195 ℃ for 23min, then heating to 283 ℃ at the speed of 25 ℃/min and preserving heat for 30 min;

(4) laminating MCF and PEEK film with the weight-average molecular weight of 90000 for hot pressing; the technological parameters of lamination hot pressing are as follows: the temperature is 395 ℃, the pressure is 2.3MPa, and the loading time is 19 min;

The finally prepared CF/PEEK composite material with excellent high-temperature mechanical properties has the bending strength of 908MPa at 25 ℃, the bending modulus of 65GPa and the interlaminar shear strength of 93 MPa; the flexural strength at 200 ℃ was 638MPa, the flexural modulus was 47GPa, and the interlaminar shear strength was 73 MPa.

Example 6

(1) sintering the T300 grade 3K5 satin fabric of CF at 383 ℃ for 92min to decompose the original sizing agent on the surface at high temperature;

(2) simultaneously performing microwave radiation and ultraviolet radiation on CF in a saturated water vapor environment with the relative humidity of 97.1 percent, and marking the product as ACF; the microwave radiation time is 12min, and the microwave frequency is 3.9 GHz; the irradiation ultraviolet wavelength is 330nm, and the ultraviolet irradiance is 45W/m²；

(3) Immersing ACF into a polyamic acid/N-methyl-2-pyrrolidone/carbon nanotube suspension for 38min, taking out the polyamic acid with the weight-average molecular weight of 58140, drying until the water content is 0.35 wt%, and performing two-stage heat treatment to obtain sizing modified carbon fiber MCF; in the polyamic acid/N-methyl-2-pyrrolidone/carbon nanotube suspension, the concentration of polyamic acid is 1.5 wt.%, and the content of carbon nanotubes is 0.07 wt.%, stable suspension is prepared by 48min ultrasonic dispersion, and the carbon nanotubes are carboxyl-modified multi-wall carbon nanotubes; two-stage heat treatment, namely, continuously heating at 208 ℃ for 25min, then heating to 296 ℃ at the speed of 32 ℃/min and preserving heat for 35 min;

(4) laminating MCF and PEEK film with weight-average molecular weight of 113000 by hot pressing; the technological parameters of lamination hot pressing are as follows: the temperature is 405 ℃, the pressure is 1.2MPa, and the loading time is 23 min;

The bending strength of the finally prepared CF/PEEK composite material with excellent high-temperature mechanical properties at 25 ℃ is 891MPa, the bending modulus is 58GPa, and the interlaminar shear strength is 86 MPa; the flexural strength at 200 ℃ was 576MPa, the flexural modulus was 43GPa, and the interlaminar shear strength was 67 MPa.

Example 7

(1) sintering the T300 grade 3K5 satin fabric of CF at 412 ℃ for 20min to decompose the original sizing agent on the surface at high temperature;

(2) saturated water at 97.5% relative humidityIn a steam environment, simultaneously carrying out microwave radiation and ultraviolet radiation on CF, and marking a product as ACF; the microwave radiation time is 8min, and the microwave frequency is 6.8 GHz; the wavelength of the irradiated ultraviolet light is 336nm, and the ultraviolet irradiance is 41W/m²；

(3) Immersing ACF into a polyamic acid/N-methyl-2-pyrrolidone/carbon nanotube suspension for 20min, taking out the polyamic acid with the weight-average molecular weight of 58523, drying until the water content is 0.32 wt%, and performing two-stage heat treatment to obtain sizing modified carbon fiber MCF; in the polyamic acid/N-methyl-2-pyrrolidone/carbon nanotube suspension, the concentration of polyamic acid is 1.8 wt.%, and the content of carbon nanotubes is 0.09 wt.%, stable suspension is prepared by 53min ultrasonic dispersion, and the carbon nanotubes are carboxyl-modified multi-wall carbon nanotubes; two-stage heat treatment, namely, continuously heating at 215 ℃ for 28min, then heating to 307 ℃ at the speed of 45 ℃/min, and keeping the temperature for 50 min;

(4) laminating MCF and PEEK fiber with the weight-average molecular weight of 136000 by hot pressing; the technological parameters of lamination hot pressing are as follows: the temperature is 411 ℃, the pressure is 1MPa, and the loading time is 27 min;

The bending strength of the finally prepared CF/PEEK composite material with excellent high-temperature mechanical properties at 25 ℃ is 827MPa, the bending modulus is 60GPa, and the interlaminar shear strength is 85 MPa; the flexural strength at 200 ℃ was 602MPa, the flexural modulus was 44GPa, and the interlaminar shear strength was 70 MPa.

Example 8

(1) sintering the T300 grade 3K5 satin fabric of CF at 404 ℃ for 50min to decompose the original sizing agent on the surface at high temperature;

(2) simultaneously performing microwave radiation and ultraviolet radiation on CF in a saturated water vapor environment with the relative humidity of 98.2 percent, and marking the product as ACF; the microwave radiation time is 3min, and the microwave frequency is 10 GHz; the wavelength of the irradiated ultraviolet light is 340nm, and the ultraviolet irradiance is 39W/m²；

(3) Immersing ACF into the polyamic acid/N-methyl-2-pyrrolidone/carbon nanotube suspension for 5min, wherein the weight-average molecular weight of the polyamic acid is 59647, taking out the ACF, drying the ACF until the water content is 0.28 wt.%, and then carrying out two-stage heat treatment to obtain a sizing modified carbon fiber MCF, wherein a scanning electron micrograph is shown in figure 5, and it can be seen that the carbon nanotubes can still be uniformly dispersed and wrapped on the surface of the carbon fiber at the content without agglomeration; in the polyamic acid/N-methyl-2-pyrrolidone/carbon nanotube suspension, the concentration of polyamic acid is 2 wt.%, and the content of carbon nanotubes is 0.10 wt.%, stable suspension is prepared by ultrasonic dispersion for 60min, and the carbon nanotubes are carboxyl-modified multi-wall carbon nanotubes; two-stage heat treatment, namely, continuously heating at 220 ℃ for 30min, then heating to 310 ℃ at the speed of 50 ℃/min and preserving heat for 60 min;

(4) laminating MCF and PEEK non-woven fabric felt with the weight-average molecular weight of 150000 by hot pressing; the technological parameters of lamination hot pressing are as follows: the temperature is 420 ℃, the pressure is 0.5MPa, and the loading time is 30 min;

The finally prepared CF/PEEK composite material with excellent high-temperature mechanical properties has the bending strength of 780MPa at 25 ℃, the bending modulus of 55GPa and the interlaminar shear strength of 80 MPa; the flexural strength at 200 ℃ was 550MPa, the flexural modulus was 42GPa, and the interlaminar shear strength was 63 MPa. The scanning electron micrograph of the brittle fracture section of the finally prepared CF/PEEK composite material in liquid nitrogen is shown in FIG. 6, and it can be seen that the resin and the fiber are basically not debonded, which shows that the resin and the fiber are well infiltrated and maintain good interface bonding effect in the fracture process.

Claims

1. The preparation method of the CF/PEEK composite material with excellent high-temperature mechanical properties is characterized by comprising the following steps of:

(1) carrying out pyrolysis on the original sizing agent on the CF surface; wherein the pyrolysis refers to sintering at 300-420 deg.C for 5-180 min;

(2) in a saturated water vapor environment, simultaneously carrying out microwave radiation and ultraviolet radiation on CF, and recording a product as ACF; the relative humidity of saturated water vapor is more than 95 percent; the microwave radiation time is 3-30min, and the microwave frequency is 300MHz-10 GHz; spokeIrradiating ultraviolet with wavelength of 290-340nm and ultraviolet irradiance of 20-50W/m²；

(3) Immersing the ACF into the polyamic acid/N-methyl-2-pyrrolidone/carbon nano tube suspension, taking out and drying, and then carrying out two-stage heat treatment to obtain sizing modified carbon fiber MCF;

(4) hot-pressing the MCF and PEEK material lamination;

the CF/PEEK composite material with excellent high-temperature mechanical property is obtained.

2. The method for preparing a CF/PEEK composite material having excellent high-temperature mechanical properties as claimed in claim 1, wherein CF is in the form of satin fabric.

3. The method for preparing CF/PEEK composite material with excellent high-temperature mechanical properties according to claim 1, wherein in the polyamic acid/N-methyl-2-pyrrolidone/carbon nanotube suspension, the concentration of polyamic acid is 0.2-2 wt.%, and the content of carbon nanotubes is 0.01-0.1 wt.%, stable suspension is prepared by 5-60min ultrasonic dispersion, the carbon nanotubes are single-walled or multi-walled carbon nanotubes modified by carboxyl groups, and the weight-average molecular weight of the polyamic acid is more than 55000; soaking for 5-120 min; drying to a water content of less than 0.5 wt.%; two-stage heat treatment, namely, continuously heating at 180-220 ℃ for 5-30min, heating to 260-310 ℃ at the speed of 1-50 ℃/min, and preserving heat for 10-60 min.

4. The method for preparing CF/PEEK composite material with excellent high-temperature mechanical properties as claimed in claim 1, wherein the PEEK material is in the form of a film, a non-woven felt, powder or fiber; the weight average molecular weight of the PEEK material is 30000-150000; the technological parameters of lamination hot pressing are as follows: the temperature is 370-420 ℃, the pressure is 0.5-5MPa, and the loading time is 3-30 min.

5. The CF/PEEK composite material with excellent high-temperature mechanical properties prepared by the preparation method of the CF/PEEK composite material with excellent high-temperature mechanical properties as claimed in any one of claims 1 to 4, wherein the CF/PEEK composite material with excellent high-temperature mechanical properties is characterized in that: the bending strength at 25 ℃ is 780-950MPa, the bending modulus is 55-65GPa, and the interlaminar shear strength is 80-93 MPa; the bending strength at 200 ℃ is 550-650MPa, the bending modulus is 40-50GPa, and the interlaminar shear strength is 60-75 MPa.