CN111423695A

CN111423695A - CF/PEEK with high interlaminar shear strength and bending strength and preparation method thereof

Info

Publication number: CN111423695A
Application number: CN202010420351.3A
Authority: CN
Inventors: 朱姝; 周剑锋; 史如静; 马禹; 王文翰; 张玥
Original assignee: Donghua University
Current assignee: Donghua University; National Dong Hwa University
Priority date: 2020-05-18
Filing date: 2020-05-18
Publication date: 2020-07-17
Anticipated expiration: 2040-05-18
Also published as: CN111423695B

Abstract

The invention relates to a CF/PEEK with high interlaminar shear strength and bending strength 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 sulfonated polyether ether ketone/dimethyl sulfoxide/carbon nanotube suspension, taking out and drying to obtain sizing modified carbon fiber MCF; (4) hot-pressing the MCF and PEEK material lamination; thus obtaining the CF/PEEK with high interlayer shear strength and bending strength. The bending strength of the finally prepared product is 850-1100MPa, the bending modulus is 55-65GPa, the interlaminar shear strength is 95-110MPa, and the residual compressive strength after impact is 220-260 MPa. The method has the characteristics of high efficiency, environmental protection and large-scale production realization, and the prepared product can replace metal and be used in the fields of aerospace, medical treatment, machinery, automobile and rail transportation, petroleum transportation and the like.

Description

CF/PEEK with high interlaminar shear strength and bending strength 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 with high interlaminar shear strength and bending strength 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.

The main reason for this performance deficiency is that the interface between the carbon fibers and the PEEK matrix is weak in interaction and wettability, and is prone to voids during the molding process of the composite material, the CF is a relatively stable six-membered ring structure, the surface is composed of non-polar and highly ordered graphite basal planes, so that the fiber surface contains few active functional groups, and the PEEK melt viscosity is high, so that the wettability between the carbon fibers and the PEEK resin is poor, and the interfacial bonding strength is weak.

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 I L SS lower than 85MPa, the bending strength is generally not more than 700MPa, and the bending strength is more than 90MPa and more than 700MPa in a few technologies I L SS, but the industrial production is difficult to realize by using strong acid or plasma treatment in the preparation process, and the content ratio of oxygen to carbon (O/C) after the CF surface activation is improved by about 40 percent.

Disclosure of Invention

The invention aims to provide a method for preparing a CF/PEEK composite material in an acid-free environment, wherein the composite material has the advantages of high interlaminar shear strength, high bending strength and the like.

It is an object of the present invention to provide a CF/PEEK with high interlaminar shear strength and flexural strength.

The invention also aims to provide a preparation method of CF/PEEK with high interlaminar shear strength and bending strength, which is a preparation method under completely acid-free environmental conditions, is environment-friendly and can realize large-scale production; the active groups carboxyl and hydroxyl on the CF surface are stable at the high temperature of 400 ℃; the adopted sizing agent SPEEK aiming at the PEEK matrix has good solubility and heat resistance, and is stable at the high temperature of 400 ℃ below zero of the molding of the CF/PEEK composite material; the SPEEK and PEEK have highly similar chemical structures and excellent wettability and compatibility; a large number of sulfonic acid groups on SPEEK and carboxyl and hydroxyl on CF can form a large number of hydrogen bonds, and the interaction is strong; the interface interaction can be further enhanced by the pinning effect of the carboxylated CNTs with a moderate content and good dispersion in SPEEK.

The preparation method of CF/PEEK with high interlayer shear strength and bending strength comprises the following steps:

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

(2) simultaneously subjecting CF to microwave radiation and ultraviolet radiation 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 SPEEK/DMSO/CNT suspension, taking out and drying to obtain sizing Modified Carbon Fiber (MCF); since the sulfonic acid group on SPEEK can form a double hydrogen bond with the carboxyl group on ACF, the interface interaction is greatly enhanced;

(4) hot-pressing the MCF and PEEK material lamination; the PEEK matrix changes from a solid to a melt and under pressure, shear flows, infiltrating the interior of the MCF tow.

Cooling to room temperature, and demolding to obtain the CF/PEEK with high interlayer shear strength and bending strength.

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 the temperature of 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 SPEEK/DMSO/CNT suspension, SPEEK is completely dissolved and has a concentration of 0.2-3 wt.%, and CNT content of 0.01-0.1 wt.%, stable suspension is prepared by ultrasonic dispersion for 5-60min, and CNT is carboxyl modified single-wall or multi-wall CNT; SPEEK is prepared by the sulfonation of PEEK with concentrated sulfuric acid by the process of: slowly adding dried PEEK powder into 98% concentrated sulfuric acid (the proportion is 0.01-0.3g/ml) at room temperature, stirring until the powder is completely dissolved, heating the solution to 50-55 ℃, stirring for 1-5h, cooling to room temperature, slowly adding the cooled solution into excessive ice water under stirring, separating out a precipitate, washing the precipitate with deionized water until the pH value is 7, and completely drying in a vacuum oven to obtain a product SPEEK; immersing the ACF into the suspension for 5-120 min; drying to a water content of less than 0.5 wt.%.

The reaction equation for PEEK to react with concentrated sulfuric acid to form SPEEK is as follows:

the sulfonic acid group on the SPEEK and the carboxyl and hydroxyl on the CF can form a large number of double hydrogen bonds, the interaction of the hydrogen bonds is far stronger than the single hydrogen bond of the carboxyl/hydroxyl on the surface of PEI or PI and the action force of the former is almost twice that of the latter, so the SPEEK solution can be effectively coated on the surface of the ACF and forms an interface with the ACF, the interface bonding strength of the SPEEK solution is greatly higher than that of the PEI or PI sizing agent and the ACF; SPEEK is produced by reacting PEEK with concentrated sulfuric acid, and has a chemical structure highly similar to PEEK, except that part of hydrogen on a benzene ring is substituted with a sulfonic acid group, and wettability and compatibility are excellent because they are similarly compatible; the polarity introduced by the sulfonic acid group makes the SPEEK soluble; since the carboxyl group on the CNT and the sulfonic acid group on the SPEEK can also undergo hydrogen bonding, the CNT can be stably dispersed in the SPEEK solution; the SPEEK has good heat resistance, and does not degrade at high temperature (400 ℃) of CF/PEEK composite material molding processing; the presence of CNTs on the one hand increases the surface roughness of the MCF, which CNTs can stick like many nails in the PEEK matrix, increasing the sum of the friction forces by a large contact area, and on the other hand it also increases the strength of the SPEEK/CNT interface layer itself; the combined actions greatly enhance the interaction between PEEK and MCF, and the interlayer shear strength and the bending strength of the CF/PEEK composite material are obviously increased.

If the SPEEK solution concentration 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 SPEEK solution is too high, the sizing agent wrapped on the surface of the ACF is too much, the strength of the composite material is reduced, and the SPEEK has lower crystallinity and lower strength because the chemical structure symmetry is reduced and the steric hindrance is increased compared with the PEEK; if the immersion time is too long, the production efficiency is affected and the cost is increased. 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. In the process of preparing the SPEEK, if the proportion of the PEEK and concentrated sulfuric acid is too small or the stirring time is too long, the sulfonation degree is too high (the content of sulfonic acid groups is too large), and the strength of the SPEEK is reduced; if the mixture ratio is too large, the reaction temperature is too low or the stirring time is too short, the sulfonation degree is too low (the content of sulfonic acid groups is too small); if the reaction temperature is too high, the reaction is too vigorous and difficult to control. 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 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 ℃ and 420 ℃, the pressure is 0.5-5MPa, and the 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 with high interlaminar shear strength and bending strength prepared by the preparation method has the bending strength of 850-1100MPa, the bending modulus of 55-65GPa, the interlaminar shear strength (I L SS) of 95-110MPa and the residual compressive strength (CAI) after impact of 220-260 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 high interlaminar shear strength and bending strength 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 was dip-sized with a SPEEK/DMSO/CNT suspension. The sulfonic acid group on the SPEEK and the carboxyl and hydroxyl on the CF can form a large number of double hydrogen bonds, the interaction of the hydrogen bonds is far stronger than the single hydrogen bond of the carboxyl/hydroxyl on the surface of PEI or PI and the action force of the former is almost twice that of the latter, so the SPEEK solution can be effectively coated on the surface of the ACF and forms an interface with the ACF, the interface bonding strength of the SPEEK solution is greatly higher than that of the PEI or PI sizing agent and the ACF; SPEEK is produced by reacting PEEK with concentrated sulfuric acid, and has a chemical structure highly similar to PEEK, except that part of hydrogen on a benzene ring is substituted with a sulfonic acid group, and wettability and compatibility are excellent because they are similarly compatible; the polarity introduced by the sulfonic acid group makes the SPEEK soluble; since the carboxyl group on the CNT and the sulfonic acid group on the SPEEK can also undergo hydrogen bonding, the CNT can be stably dispersed in the SPEEK solution; the SPEEK has good heat resistance, and does not degrade at high temperature (400 ℃) of CF/PEEK composite material molding processing; the presence of CNTs on the one hand increases the surface roughness of the MCF, which CNTs can stick like many nails in the PEEK matrix, increasing the sum of the friction forces by a large contact area, and on the other hand it also increases the strength of the SPEEK/CNT interface layer itself; the combined actions greatly enhance the interaction between PEEK and MCF, and the interlayer shear strength and the bending strength of the CF/PEEK composite material are obviously increased.

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 with high interlaminar shear strength and bending strength prepared by the preparation method has the bending strength of 850-1100MPa, the bending modulus of 55-65GPa, the interlaminar shear strength (I L SS) of 95-110MPa and the residual compressive strength (CAI) after impact of 220-260MPa, wherein the interlaminar shear strength and the bending strength are greatly higher than those of other known technologies which are environment-friendly and have industrialized conditions.

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 0.09 wt.% CNT;

fig. 5 is a scanning electron micrograph of a carbon fiber obtained by performing microwave and ultraviolet irradiation treatment simultaneously in a saturated water vapor environment and then performing sizing treatment on a suspension containing 0.5 wt.% of CNTs.

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

(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 the ACF into the sulfonated polyether ether ketone/dimethyl sulfoxide/carbon nanotube suspension for 120min, taking out, and drying until the water content is 0.48 wt.% to obtain sizing modified carbon fiber MCF;

in the sulfonated polyether ether ketone/dimethyl sulfoxide/carbon nano tube suspension, the sulfonated polyether ether ketone is completely dissolved and the content is 0.2 wt.%, and the content of the carbon nano tube is 0.01 wt.%, and stable suspension is prepared by 5min ultrasonic dispersion, wherein the carbon nano tube is a carboxyl modified single-walled carbon nano tube;

the sulfonated polyether ether ketone is prepared by the sulfonation reaction of PEEK and concentrated sulfuric acid, and the process comprises the following steps: slowly adding dried PEEK powder into 98 wt.% concentrated sulfuric acid at room temperature according to the proportion of 0.01g/ml, stirring until the powder is completely dissolved, heating the solution to 50 ℃, stirring for 1h, cooling to room temperature, slowly adding the cooled solution into excessive ice water under stirring, separating out a precipitate, washing the precipitate with deionized water until the pH value is 7, and completely drying in a vacuum oven to obtain a sulfonated polyether ether ketone product;

(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 bending strength of the finally prepared CF/PEEK with high interlaminar shear strength and bending strength is 909MPa, the bending modulus is 59GPa, the interlaminar shear strength is 98MPa, and the residual compressive strength after impact is 229 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 sulfonated polyether ether ketone/dimethyl sulfoxide/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 is 561MPa, the bending modulus is 49GPa, the interlaminar shear strength is 66MPa, and the residual compressive strength after impact is 198 MPa.

Comparing example 1 with comparative example 1, it can be seen that the bending strength, flexural modulus, interlaminar shear strength, and residual compressive strength after impact of the CF/PEEK composite material prepared in example 1 are much higher than those of comparative example 1, the XPS curve and the content of oxygen element/carbon element (O/C) of the untreated CF in comparative example 1 are shown in fig. 1, the XPS curve and the content of oxygen element/carbon element (O/C) 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 the 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, the O/C ratio is increased by 155% (up to 255% of the original one%) as compared with the untreated CF, it is important to demonstrate that the use of microwave treatment in combination with uv + water vapor is why CF/PEEK composites made with untreated CF have low flexural strength, flexural modulus, interlaminar shear strength, and residual compressive strength after impact.

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 is 587MPa, the bending modulus is 49GPa, the interlaminar shear strength is 67MPa, and the residual compressive strength after impact is 207 MPa.

Comparing example 1 with comparative example 2, it can be seen that the flexural strength, flexural modulus, interlaminar shear strength, and residual compressive strength after impact of the CF/PEEK composite material prepared in example 1 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 insignificant, 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 the O element is obviously increased, which shows that the microwave treatment is important at the same time of ultraviolet and water vapor, and the reasons why the bending strength, the bending modulus, the interlaminar shear strength and the residual compression strength after impact of the CF/PEEK composite material prepared by the CF treated by the ultraviolet and water vapor are all lower are the same.

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 the ACF into the sulfonated polyether ether ketone/dimethyl sulfoxide/carbon nano tube suspension for 115min, taking out, and drying until the water content is 0.45 wt.%, thereby obtaining sizing modified carbon fiber MCF;

in the sulfonated polyether ether ketone/dimethyl sulfoxide/carbon nano tube suspension, the sulfonated polyether ether ketone is completely dissolved and the content is 0.5 wt.%, and the content of the carbon nano tube is 0.02 wt.%, and the stable suspension is prepared by 18min ultrasonic dispersion, wherein the carbon nano tube is a carboxyl modified single-walled carbon nano tube;

the sulfonated polyether ether ketone is prepared by the sulfonation reaction of PEEK and concentrated sulfuric acid, and the process comprises the following steps: slowly adding dried PEEK powder into 98 wt.% concentrated sulfuric acid at room temperature according to the proportion of 0.03g/ml, stirring until the powder is completely dissolved, heating the solution to 54 ℃, stirring for 2.5h, cooling to room temperature, slowly adding the cooled solution into excessive ice water under stirring, separating out a precipitate, washing the precipitate with deionized water until the pH value is 7, and completely drying in a vacuum oven to obtain a product of sulfonated polyether ether ketone;

(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 final CF/PEEK with high interlaminar shear strength and bending strength has the bending strength of 938MPa, the bending modulus of 61GPa, the interlaminar shear strength of 102MPa and the residual compressive strength after impact of 243 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 the ACF into the sulfonated polyether ether ketone/dimethyl sulfoxide/carbon nanotube suspension for 94min, taking out, and drying until the water content is 0.42 wt.%, thereby obtaining sizing modified carbon fiber MCF;

in the sulfonated polyether ether ketone/dimethyl sulfoxide/carbon nano tube suspension, the sulfonated polyether ether ketone is completely dissolved and the content is 0.8 wt.%, and the content of the carbon nano tube is 0.03 wt.%, and the stable suspension is prepared by 22min ultrasonic dispersion, wherein the carbon nano tube is a carboxyl modified single-walled carbon nano tube;

the sulfonated polyether ether ketone is prepared by the sulfonation reaction of PEEK and concentrated sulfuric acid, and the process comprises the following steps: slowly adding dried PEEK powder into 98 wt.% concentrated sulfuric acid at room temperature according to the proportion of 0.1g/ml, stirring until the powder is completely dissolved, heating the solution to 52 ℃, stirring for 3.5h, cooling to room temperature, slowly adding the cooled solution into excessive ice water under stirring, separating out a precipitate, washing the precipitate with deionized water until the pH value is 7, and completely drying in a vacuum oven to obtain a product of sulfonated polyether ether ketone;

(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 with high interlaminar shear strength and bending strength is 925MPa, the bending modulus is 62GPa, the interlaminar shear strength is 105MPa, and the residual compressive strength after impact is 260 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 the sulfonated polyether ether ketone/dimethyl sulfoxide/carbon nanotube suspension for 69min, taking out, and drying until the water content is 0.41 wt.%, thereby obtaining sizing modified carbon fiber MCF;

in the sulfonated polyether ether ketone/dimethyl sulfoxide/carbon nano tube suspension, the sulfonated polyether ether ketone is completely dissolved and the content is 1.2 wt.%, and the content of the carbon nano tube is 0.04 wt.%, and stable suspension is prepared by 35min ultrasonic dispersion, wherein the carbon nano tube is a carboxyl modified single-walled carbon nano tube;

the sulfonated polyether ether ketone is prepared by the sulfonation reaction of PEEK and concentrated sulfuric acid, and the process comprises the following steps: slowly adding dried PEEK powder into 98 wt.% concentrated sulfuric acid at room temperature according to the proportion of 0.15g/ml, stirring until the powder is completely dissolved, heating the solution to 51 ℃, stirring for 4h, cooling to room temperature, slowly adding the cooled solution into excessive ice water under stirring, separating out a precipitate, washing the precipitate with deionized water until the pH value is 7, and completely drying in a vacuum oven to obtain a sulfonated polyether ether ketone product;

(4) laminating MCF and PEEK non-woven fabric felt with the weight-average molecular weight of 82000 by 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 bending strength of the finally prepared CF/PEEK with high interlaminar shear strength and bending strength is 978MPa, the bending modulus is 64GPa, the interlaminar shear strength is 108MPa, and the residual compressive strength after impact is 255 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 the ACF into the sulfonated polyether ether ketone/dimethyl sulfoxide/carbon nano tube suspension for 51min, taking out, and drying until the water content is 0.38 wt.% to obtain sizing modified carbon fiber MCF;

in the sulfonated polyether ether ketone/dimethyl sulfoxide/carbon nano tube suspension, the sulfonated polyether ether ketone is completely dissolved and the content is 1.8 wt.%, and the content of the carbon nano tube is 0.06 wt.%, and the stable suspension is prepared by 40min ultrasonic dispersion, wherein the carbon nano tube is a carboxyl modified multi-wall carbon nano tube;

the sulfonated polyether ether ketone is prepared by the sulfonation reaction of PEEK and concentrated sulfuric acid, and the process comprises the following steps: slowly adding dried PEEK powder into 98 wt.% concentrated sulfuric acid at room temperature according to the proportion of 0.19g/ml, stirring until the powder is completely dissolved, heating the solution to 55 ℃, stirring for 5 hours, cooling to room temperature, slowly adding the cooled solution into excessive ice water under stirring, separating out a precipitate, washing the precipitate with deionized water until the pH value is 7, and completely drying in a vacuum oven to obtain a sulfonated polyether ether ketone product;

(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 bending strength of the finally prepared CF/PEEK with high interlaminar shear strength and bending strength is 1100MPa, the bending modulus is 65GPa, the interlaminar shear strength is 110MPa, and the residual compressive strength after impact is 252 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 wavelength of the irradiated ultraviolet light is 330nm,ultraviolet irradiance of 45W/m²；

(3) Immersing the ACF into the sulfonated polyether ether ketone/dimethyl sulfoxide/carbon nano tube suspension for 38min, taking out, and drying until the water content is 0.35 wt.% to obtain sizing modified carbon fiber MCF;

in the sulfonated polyether ether ketone/dimethyl sulfoxide/carbon nano tube suspension, the sulfonated polyether ether ketone is completely dissolved and the content is 2.2 wt.%, and the content of the carbon nano tube is 0.07 wt.%, and the stable suspension is prepared by 48min ultrasonic dispersion, wherein the carbon nano tube is a carboxyl modified multi-wall carbon nano tube;

the sulfonated polyether ether ketone is prepared by the sulfonation reaction of PEEK and concentrated sulfuric acid, and the process comprises the following steps: slowly adding dried PEEK powder into 98 wt.% concentrated sulfuric acid at room temperature according to the proportion of 0.21g/ml, stirring until the powder is completely dissolved, heating the solution to 50 ℃, stirring for 5 hours, cooling to room temperature, slowly adding the cooled solution into excessive ice water under stirring, separating out a precipitate, washing the precipitate with deionized water until the pH value is 7, and completely drying in a vacuum oven to obtain a sulfonated polyether ether ketone product;

(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 with high interlaminar shear strength and bending strength is 1004MPa, the bending modulus is 63GPa, the interlaminar shear strength is 103MPa, and the residual compressive strength after impact is 244 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) simultaneously performing microwave radiation and ultraviolet radiation on CF in a saturated water vapor environment with the relative humidity of 97.5 percent, and marking the product as ACF; the microwave radiation time is 8min, and the microwave frequency is 6.8GHz; the wavelength of the irradiated ultraviolet light is 336nm, and the ultraviolet irradiance is 41W/m²；

(3) Immersing the ACF into the sulfonated polyether ether ketone/dimethyl sulfoxide/carbon nanotube suspension for 20min, taking out, and drying until the water content is 0.32 wt.% to obtain sizing modified carbon fiber MCF, wherein a scanning electron microscope photograph is shown in FIG. 4;

in the sulfonated polyether ether ketone/dimethyl sulfoxide/carbon nano tube suspension, the sulfonated polyether ether ketone is completely dissolved and the content is 2.7 wt.%, and the content of the carbon nano tube is 0.09 wt.%, and the stable suspension is prepared by 54min ultrasonic dispersion, wherein the carbon nano tube is a carboxyl modified multi-wall carbon nano tube;

the sulfonated polyether ether ketone is prepared by the sulfonation reaction of PEEK and concentrated sulfuric acid, and the process comprises the following steps: slowly adding dried PEEK powder into 98 wt.% concentrated sulfuric acid at room temperature according to the proportion of 0.26g/ml, stirring until the powder is completely dissolved, heating the solution to 54 ℃, stirring for 4.2h, cooling to room temperature, slowly adding the cooled solution into excessive ice water under stirring, separating out a precipitate, washing the precipitate with deionized water until the pH value is 7, and completely drying in a vacuum oven to obtain a product of sulfonated polyether ether ketone;

(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 with high interlaminar shear strength and bending strength is 927MPa, the bending modulus is 58GPa, the interlaminar shear strength is 97MPa, and the residual compression strength after impact is 239 MPa.

Comparative example 3

The preparation method of the CF/PEEK composite material is basically the same as that in example 7, and is adjusted relative to the step (3) in example 7, specifically, the content of the Carbon Nanotubes (CNTs) is changed to 0.5 wt.%, and other processes and parameters are the same as those in example 7.

The bending strength of the finally prepared CF/PEEK composite material is 621MPa, the bending modulus is 55GPa, the interlaminar shear strength is 72MPa, and the residual compression strength after impact is 211 MPa. Wherein, the scanning electron micrograph of the intermediate product (i.e. the modified carbon fiber) obtained after the steps (1), (2) and (3) is shown in fig. 5.

Comparing example 7 with comparative example 3, it can be seen that the bending strength, bending modulus, interlaminar shear strength and residual compressive strength after impact of the CF/PEEK composite material prepared in example 7 are much higher than those of comparative example 3, the content of the carbon nanotubes in comparative example 3 is 0.5 wt.%, the carbon nanotube agglomeration due to the excessively high content (compare fig. 4 and fig. 5), and the effect of improving the interfacial interaction between the carbon fiber and the PEEK matrix resin is not very good, which indicates that the content of the carbon nanotubes is a key process parameter, which is why the bending strength, bending modulus, interlaminar shear strength and residual compressive strength after impact of the CF/PEEK composite material prepared by sizing the carbon fiber with the carbon nanotube suspension with the content of 0.5 wt.% are all lower.

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 the ACF into the sulfonated polyether ether ketone/dimethyl sulfoxide/carbon nano tube suspension for 5min, taking out and drying until the water content is 0.28 wt.%, thereby obtaining sizing modified carbon fiber MCF;

in the sulfonated polyether ether ketone/dimethyl sulfoxide/carbon nano tube suspension, the sulfonated polyether ether ketone is completely dissolved and the content is 3 wt.%, and the content of the carbon nano tube is 0.1 wt.%, and the stable suspension is prepared by ultrasonic dispersion for 60min, wherein the carbon nano tube is a carboxyl modified multi-wall carbon nano tube;

the sulfonated polyether ether ketone is prepared by the sulfonation reaction of PEEK and concentrated sulfuric acid, and the process comprises the following steps: slowly adding dried PEEK powder into 98 wt.% concentrated sulfuric acid at room temperature according to the proportion of 0.3g/ml, stirring until the powder is completely dissolved, heating the solution to 53 ℃, stirring for 2.8h, cooling to room temperature, slowly adding the cooled solution into excessive ice water under stirring, separating out a precipitate, washing the precipitate with deionized water until the pH value is 7, and completely drying in a vacuum oven to obtain a product of sulfonated polyether ether ketone;

(4) laminating MCF and PEEK fiber with the weight-average molecular weight of 150000 for 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 bending strength of the finally prepared CF/PEEK with high interlaminar shear strength and bending strength is 850MPa, the bending modulus is 55GPa, the interlaminar shear strength is 95MPa, and the residual compressive strength after impact is 220 MPa.

Claims

1. The preparation method of CF/PEEK with high interlayer shear strength and bending strength is characterized by comprising 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 sulfonated polyether ether ketone/dimethyl sulfoxide/carbon nanotube suspension, taking out and drying to obtain sizing modified carbon fiber MCF;

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

thus obtaining the CF/PEEK with high interlayer shear strength and bending strength.

2. The method of claim 1, wherein the CF is in the form of a satin weave.

3. The method for preparing CF/PEEK having high interlaminar shear strength and bending strength as claimed in claim 1, wherein the pyrolysis is sintering at 300-420 ℃ for 5-180 min.

4. The method of claim 1 wherein the saturated water vapor has a relative humidity of greater than 95%; 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。

5. The method for preparing CF/PEEK having high interlaminar shear strength and bending strength as claimed in claim 1, wherein in the sulfonated polyetheretherketone/dimethylsulfoxide/carbon nanotube suspension, the sulfonated polyetheretherketone is completely dissolved and contained in an amount of 0.2-3 wt.%, and the carbon nanotubes are contained in an amount of 0.01-0.1 wt.%, and the stable suspension is prepared by ultrasonic dispersion for 5-60min, wherein the carbon nanotubes are carboxyl-modified single-walled or multi-walled carbon nanotubes;

the sulfonated polyether ether ketone is prepared by the sulfonation reaction of PEEK and concentrated sulfuric acid, and the process comprises the following steps: slowly adding dried PEEK powder into 98 wt.% concentrated sulfuric acid at room temperature according to the proportion of 0.01-0.3g/ml, stirring until the powder is completely dissolved, heating the solution to 50-55 ℃, stirring for 1-5h, cooling to room temperature, slowly adding the cooled solution into excessive ice water under stirring, separating out a precipitate, washing the precipitate with deionized water until the pH value is 7, and completely drying in a vacuum oven to obtain a product of sulfonated polyether ether ketone;

immersing the ACF into the suspension for 5-120 min;

drying to a water content of less than 0.5 wt.%.

6. The method of claim 1, wherein the PEEK material is in the form of a film, a non-woven felt, a powder, or a 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 ℃ and 420 ℃, the pressure is 0.5-5MPa, and the loading time is 3-30 min.

7. The method for preparing CF/PEEK having high interlaminar shear strength and flexural strength according to any one of claims 1 to 6, wherein the CF/PEEK having high interlaminar shear strength and flexural strength is prepared by: the bending strength is 850-1100MPa, the bending modulus is 55-65GPa, the interlaminar shear strength is 95-110MPa, and the residual compressive strength after impact is 220-260 MPa.