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

Abstract

The invention relates to a CF/PEEK with inter-layer shear strength and flexural strength and a preparation method thereof. The preparation method comprises the following steps: (1) pyrolyzing the original sizing agent on the CF surface; (2) in saturated water vapor In the environment, microwave irradiation and ultraviolet light irradiation were simultaneously performed on CF, and the product was recorded as ACF; (3) ACF was immersed in the sulfonated polyether ether ketone/dimethyl sulfoxide/carbon nanotube suspension, taken out and dried to obtain Sizing modified carbon fiber MCF; (4) laminating MCF and PEEK material and hot pressing; namely, CF/PEEK with inter-layer shear strength and flexural strength is obtained. The final product has a flexural strength of 850-1100 MPa, a flexural modulus of 55-65 GPa, an interlaminar shear strength of 95-110 MPa, and a residual compressive strength after impact of 220-260 MPa. The method of the invention is characterized by high efficiency, environmental protection and large-scale production, and the prepared product can be used in the fields of aerospace, medical treatment, machinery, automobile and rail transportation, oil transportation and the like instead of metal.

Description

CF/PEEK with interlayer shear strength and flexural strength and its preparation method

technical field

The invention belongs to the technical field of carbon fiber reinforced polyetheretherketone (CF/PEEK) composite materials, and relates to a CF/PEEK with inter-layer shear strength and bending strength and a preparation method thereof.

Background technique

In recent years, thermoplastic composites have received extensive attention due to their good recyclability, secondary processability, high impact toughness, high specific strength, and high specific modulus. Among various thermoplastic composite materials, CF/PEEK has excellent properties such as high stiffness, high thermal stability, chemical corrosion resistance, wear resistance, and biocompatibility, and is expected to be used as a structural material to replace mature metal or thermoset composite materials. , widely used in aerospace, medical, machinery, automobile and rail transportation, oil transportation and other fields.

However, the practical application of CF/PEEK thermoplastic composites is not optimistic. The main problem is that its interlaminar shear strength (ILSS) is low, resulting in low bending strength. When subjected to a moment perpendicular to the panel, the material is prone to delamination or other forms of damage and destruction. The main reason for this performance defect is that the interface between carbon fiber and PEEK matrix has weak interaction and poor wettability, and pores are easily generated during the molding process of composite materials. The fundamental reason is that CF has a relatively stable six-membered ring structure, and the surface is composed of non-polar and highly ordered graphite basal planes, so that the surface of the fiber contains less active functional groups, and PEEK has a high melt viscosity, so carbon fiber. The wettability with PEEK resin is poor, and the interface bond strength is weak. As the link of load transfer between the fiber and the resin matrix, the bonding strength of the interface layer greatly affects the mechanical properties of the overall composite material. When the composite material with low interfacial strength is damaged, the crack propagates along the interface, and the reinforcement of the fiber is not effective. to perform well, so that the strength of the composite material is much lower than the theoretical value.

Surface modification treatment of CF can solve the above problems and improve the properties of composite materials such as interlaminar shear strength. There are two types of known techniques, one is "activation (sometimes called oxidation)" and the other is "sizing". Can be used alone or in combination. The principle of activation modification is to introduce active functional groups on the fiber surface, increase the number of chemical bonds or hydrogen bonds between the fiber and the polymer matrix, and improve the interfacial bonding strength of the composite material through strong chemical action. The principle of sizing modification is to attach a thin layer of polymer (which can be different from the matrix) to the surface of the fiber through solution or emulsion coating, and use its characteristic of strong interaction with the fiber and the matrix at the same time. A bridge is built between the fiber and the matrix to enhance the connection between the two.

Existing 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 monofilament. It is necessary to find a balance between the number of active groups and the strength of the CF monofilament, so that as many hydroxyl and carboxyl groups as possible are generated on the surface of the CF, and as many grooves as possible are generated to increase the distance between the CF and the substrate. contact area, but at the same time to minimize the loss of monofilament strength.

Existing sizing technologies include reactive sizing agents and coating sizing agents.

Although the prior art has achieved results in some aspects, there are various defects or deficiencies, which make it difficult to realize industrialized production when targeting PEEK, a substrate that requires high temperature forming processing at ~400°C.

For example, when CF is treated by plasma, the effect of the outer layer and inner layer of the tow is significantly different. When there are many active groups in the outer layer and the strength of the monofilament is greatly damaged, the activity of the inner layer of CF is often not improved. Therefore, the stability is poor, the dispersion is large, and it is not suitable for industrial production.

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

Due to the production of a large amount of waste acid and waste liquid, the strong acid treatment has a large environmental pollution; most of them are intermittent operations, which require a long processing time and are difficult to match with the CF production line; and the equipment has high requirements for corrosion resistance and high operational risk factor. , so it is hardly considered in industrial production.

Ozone treatment will generate a large amount of ozone that is harmful to the human body, and the treatment of ozone-containing waste gas will greatly increase the cost. This unenvironmental method is gradually being abandoned.

Microwave ultrasonic co-treatment has great damage to the strength of CF monofilament, and the damage degree is difficult to control.

The reaction rate of reactive sizing agent (surface grafting, coupling agent, etc.) is low, and it needs to be used together with the previous activation techniques.

Coating-type sizing agents (relying on van der Waals forces) can improve the wettability of the matrix to the fibers, but the effect of improving the interfacial interaction is limited.

The CF/PEEK composites prepared by the above known techniques usually have an ILSS lower than 85MPa and a bending strength of not more than 700MPa. In a few technologies, the ILSS is over 90MPa and the bending strength is over 700MPa. However, either strong acid or plasma treatment is used in the preparation process. It is difficult to realize industrial production. The oxygen/carbon (O/C) content ratio after CF surface activation was increased by about 40%.

SUMMARY OF THE INVENTION

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

One of the objects of the present invention is to provide a CF/PEEK with inter-layer shear strength and flexural strength.

The second purpose of the present invention is to provide a preparation method of CF/PEEK with inter-layer shear strength and flexural strength, which is a preparation method under completely acid-free environmental conditions, is environmentally friendly, and can realize large-scale production; CF surface The active group carboxyl and hydroxyl groups are stable at a high temperature of ~400 °C; the sizing agent SPEEK for PEEK matrix has good solubility and good heat resistance, and is stable at a high temperature of ~400 °C in the molding of CF/PEEK composite materials; SPEEK and PEEK has a highly similar chemical structure, excellent wettability and compatibility; a large number of sulfonic acid groups on SPEEK can form a large number of hydrogen bonds with carboxyl and hydroxyl groups on CF, and the interaction is strong; SPEEK is mixed with moderate content and good dispersion. Carboxylated CNTs can further enhance the interfacial interaction through their pinning effect with the PEEK matrix.

The preparation method of the CF/PEEK with interlayer shear strength and flexural strength of the present invention comprises the following steps:

(1) Decomposing the original sizing agent on the CF surface at high temperature;

(2) In a saturated water vapor environment, microwave irradiation and ultraviolet light irradiation are simultaneously performed on CF, and the product is recorded as activated-CF (ACF). The possibility of industrial scale production;

(3) Immerse ACF in SPEEK/DMSO/CNT suspension, take it out and dry to obtain sizing modified carbon fiber (MCF); because the sulfonic acid groups on SPEEK can form double hydrogen bonds with the carboxyl groups on ACF, the interface interaction is greatly enhance;

(4) The MCF and PEEK materials are laminated and hot-pressed; the PEEK matrix changes from solid to melt, and under pressure, shear flow occurs and infiltrates the interior of the MCF tow.

After cooling to room temperature, the mold is demolded to obtain CF/PEEK with inter-layer shear strength and flexural strength.

As the preferred technical solution:

The preparation method as described above, CF is in the form of satin fabric, when CF is in other forms, such as chopped fibers, long fibers, fiber mats, continuous fiber tows, or plain, twill, non-crimp fabrics, the same can also be used The method of the present invention composites it with PEEK, but the properties of the resulting composite material are relatively poor.

In the preparation method described above, the pyrolysis refers to sintering at 300-420° C. for 5-180 min. By pyrolysis, the original sizing agent is removed. These sizing agents are attached to the surface of commercial-grade carbon fibers, and the composition is usually epoxy resin. It must be sizing before leaving the factory to achieve fiber winding, otherwise it will produce filaments and even cause fiber breakage. However, if these sizing agents are not removed, it will be unfavorable for the composite of CF and PEEK, because these sizing agents will decompose at the high temperature (~400 °C) of PEEK molding, form pores in the composite material, and reduce the mechanical properties such as material strength. . Deviation from the recommended parameter range will be detrimental to the effective control of the pyrolysis process. For example, if the pyrolysis temperature is too low or the time is too short, the original sizing agent cannot be completely removed, and the remaining part will still be decomposed at the high temperature of the CF/PEEK composite molding process, affecting the mechanical properties of the composite material; If the pyrolysis temperature is too high or the time is too long, the surface structure of part of the CF will be damaged due to the oxidation reaction, the CF surface will appear gullies, and the strength of the monofilament will drop by more than a certain extent (such as 10%), and the mechanical properties of the composite material will be reduced. Performance indicators will also drop significantly with it. In the process of high temperature decomposition, if a vacuum environment or an inert gas atmosphere such as nitrogen and helium can be established, the effect will be better, the oxidation reaction of CF itself can be suppressed, and the strength retention rate of CF monofilament can be higher.

According to the above preparation method, the relative humidity of saturated water vapor is greater than 95%; the time of microwave irradiation is 3-30min, the microwave frequency is 300MHz-10 GHz; the wavelength of ultraviolet light is 290-340nm, and the ultraviolet irradiance is 20 -50W/m ² . This step has three functions: 1) microwave irradiation can promote the graphitization of the carbon fiber surface, making up/offset the loss of monofilament strength; 2) ultraviolet irradiation, further cleaning the original sizing agent residues in the grooves on the surface of carbon fibers that are not resistant to high temperature , because UV can break the double bonds of residual organics on the CF surface through oxidation reaction; 3) UV light and water vapor work together to excite groups such as hydroxyl and carboxyl groups on the CF surface.

It is particularly emphasized that it is necessary to add microwave action at the same time as the action of ultraviolet and saturated water vapor, because during the oxidation process, microwave irradiation can uniformly heat CF and promote the hydroxylation and carboxylation. Comparing the samples with and without microwaves, it can be seen that the samples with microwaves have a higher O/C ratio, implying a higher content of oxygen-containing groups. Moreover, microwave irradiation can promote the graphitization of the carbon fiber surface, which compensates/offsets the loss of monofilament strength.

If the humidity is too low, the microwave irradiation time is too short, the microwave frequency is too low, the wavelength of ultraviolet light is too long or the irradiation is too low, the number of hydroxyl and carboxyl groups to be excited is less, the activation degree of CF is low, and it can form with the sizing agent. The number of hydrogen bonds is also less, and the interaction between ACF and sizing agent is small; if the microwave irradiation time is too long, the microwave frequency is too high, the ultraviolet wavelength is too short or the irradiation is too high, it may damage the CF surface too much. Due to the ring-membered structure, the strength of the CF monofilament decreases too much, which leads to the decrease of the mechanical properties of the composite material.

The same activation modification method (generating hydroxyl and carboxyl groups on the surface, and affecting its own internal structure as little as possible) can also be applied to carbon nanotubes (CNT), graphene, graphene oxide (GO), carbon black (CB) , carbon nanofibers (CNF) and other carbon materials.

In the SPEEK/DMSO/CNT suspension, SPEEK was completely dissolved and the concentration was 0.2-3 wt.%, and the CNT content was 0.01-0.1 wt.%. A stable suspension was prepared by ultrasonic dispersion for 5-60 min. Wall or multi-wall CNT; SPEEK is prepared by the sulfonation reaction of PEEK and concentrated sulfuric acid. The process is: slowly add dry PEEK powder to 98% concentrated sulfuric acid at room temperature (the ratio is 0.01-0.3g/ml), stir When the powder is completely dissolved, the solution is heated to 50-55°C, stirred for 1-5h, cooled to room temperature, and the cooled solution is slowly added to excess ice water with stirring, the precipitate is precipitated, and the precipitate is washed with deionized water until pH The value is 7, and it is completely dried in a vacuum oven to obtain the product SPEEK; the time for ACF to be immersed in the suspension is 5-120 min; and it is dried to a water content of less than 0.5 wt.%.

The reaction equation that PEEK reacts with concentrated sulfuric acid to generate SPEEK is as follows:

The sulfonic acid group on SPEEK can form a large number of double hydrogen bonds with the carboxyl group and hydroxyl group on CF, and the interaction of such hydrogen bonds is far stronger than the single hydrogen bond between the carbonyl group on PEI or PI and the carboxyl group/hydroxyl group on the surface of CF , the force of the former is almost twice that of the latter, so the SPEEK solution can be effectively coated on the surface of ACF and form a strong interface with it, and the interface bond strength greatly exceeds the interface formed by PEI or PI sizing agent and ACF; SPEEK is formed by the reaction of PEEK and concentrated sulfuric acid. Its chemical structure is highly similar to that of PEEK. The difference is that some of the hydrogens on the benzene ring are replaced by sulfonic acid groups. Because the two are similar and compatible, they have excellent wettability and compatibility; The polarity introduced by the acid group makes SPEEK soluble; because the carboxyl group on CNT and the sulfonic acid group on SPEEK can also undergo hydrogen bonding, CNT can be stably dispersed in SPEEK solution; PEEK composites do not degrade at high temperatures (~400°C) during molding; on the one hand, the presence of CNTs increases the surface roughness of MCF, and CNTs can be stuck in the PEEK matrix like many nails, increasing the total frictional force through a large number of contact areas On the other hand, CNT also enhances the strength of the SPEEK/CNT interface layer itself; the above effects together greatly enhance the interaction between PEEK and MCF, and the interlayer shear strength and flexural strength of CF/PEEK composites increase significantly.

If the concentration of SPEEK solution is too low or the immersion time is too short, a sufficient amount of sizing agent cannot be applied to the surface of ACF; if the concentration of SPEEK solution is too high, too much sizing agent is wrapped on the surface of ACF, and the strength of the composite material decreases, which is due to Compared with PEEK, SPEEK has lower chemical structure symmetry and increased steric hindrance. Therefore, SPEEK has lower crystallinity and lower strength than PEEK; if the immersion time is too long, it will affect production efficiency and increase cost. If the CNT content is too low, the number of CNTs that can cause pinning effect between CNT and PEEK matrix is too small, the pinning effect is not obvious, and the interaction force between MCF and PEEK is not large enough; if the CNT content is too high or the ultrasonic dispersion time is too short, It will cause insufficient dispersion of CNTs and agglomeration, which will affect the infiltration of PEEK into MCF; if the ultrasonic time is too long, it will not only waste energy consumption, reduce efficiency, but also may damage the structural integrity of CNTs. In the process of preparing SPEEK, if the ratio of PEEK and concentrated sulfuric acid is too small or the stirring time is too long, the sulfonation will be too high (the content of sulfonic acid groups is too large), and the strength of SPEEK itself will decrease; if the ratio is too large, the reaction If the temperature is too low or the stirring time is too short, the sulfonation is too low (the content of sulfonic acid groups is too small); if the reaction temperature is too high, the reaction is too violent and difficult to control. If the moisture content after drying is too large, pores will be formed due to volatilization of water vapor during the molding process of the composite material, which will affect the mechanical properties of the composite material.

According to the above preparation method, the form of PEEK material is film, non-woven felt, powder or fiber; the weight average molecular weight of PEEK material is 30000-150000; the process parameters of laminated hot pressing: temperature 370-420 ℃, pressure 0.5 -5MPa, loading time 3-30min. In this process, due to the enhanced interaction between PEEK and MCF, the wettability of PEEK melt to MCF is greatly improved, the possibility of forming pores inside the composite material is reduced, and when the composite material is damaged by external force, the interface between PEEK and MCF is sticky. The knot strength increases and the material failure mode shifts from fiber pullout to matrix fracture.

If the molecular weight of the PEEK material is too low, the molecular chains in the matrix are less entangled, the strength of the matrix itself is too small, 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 large, and the composite The porosity of the material increases; if the hot pressing temperature is too high or the heat preservation loading time is too long, the PEEK is prone to degradation, discoloration, aging, etc. at high temperature, and the resin strength decreases; if the pressure is small or the loading time is too short, the melt The shearing effect is small, the infiltration of CF is incomplete, and the porosity of the composite material increases; if the pressure is too large, more resin will flow out from the mold gap, and the composite material will have defects such as poor glue.

The CF/PEEK with interlaminar shear strength and flexural strength prepared by the preparation method of the invention has a flexural strength of 850-1100 MPa, a flexural modulus of 55-65 GPa, an interlaminar shear strength (ILSS) of 95-110 MPa, and an impact of 850-1100 MPa. The residual compressive strength (CAI) after this is 220-260 MPa.

Due to adopting the above technical solutions, the present invention has the following beneficial effects:

The principle of the CF/PEEK composite material with inter-layer shear strength and flexural strength prepared by the invention is to decompose the original sizing agent on the CF surface through high temperature first. These sizing agents are attached to the surface of commercial grade carbon fibers to ensure that the fibers can be wound, however these sizing agents will decompose at the high temperature (~400°C) of PEEK molding, forming pores in the composite material, reducing mechanical properties such as material strength . Second, the CF was irradiated with microwave and UV light simultaneously in a saturated water vapor environment. On the one hand, microwave irradiation can promote the graphitization of the carbon fiber surface, making up or offsetting the loss of monofilament strength; on the other hand, ultraviolet radiation can break the double bonds of residual organics on the surface of CF through oxidation reaction, so ultraviolet irradiation can further clean the grooves on the surface of carbon fibers. The original sizing agent that is not resistant to high temperature remains; thirdly, ultraviolet light and water vapor work together to excite groups such as hydroxyl and carboxyl groups on the surface of CF. Therefore, the active groups such as hydroxyl and carboxyl groups can be grafted on the surface of CF through acid-free activation modification treatment, which is environmentally friendly and has the possibility of industrial scale production. Next, the ACF was dipped and sized with a SPEEK/DMSO/CNT suspension. The sulfonic acid group on SPEEK can form a large number of double hydrogen bonds with the carboxyl group and hydroxyl group on CF, and the interaction of such hydrogen bonds is far stronger than the single hydrogen bond between the carbonyl group on PEI or PI and the carboxyl group/hydroxyl group on the surface of CF , the force of the former is almost twice that of the latter, so the SPEEK solution can be effectively coated on the surface of ACF and form a strong interface with it, and the interface bond strength greatly exceeds the interface formed by PEI or PI sizing agent and ACF; SPEEK is formed by the reaction of PEEK and concentrated sulfuric acid. Its chemical structure is highly similar to that of PEEK. The difference is that some of the hydrogens on the benzene ring are replaced by sulfonic acid groups. Because the two are similar and compatible, they have excellent wettability and compatibility; The polarity introduced by the acid group makes SPEEK soluble; because the carboxyl group on CNT and the sulfonic acid group on SPEEK can also undergo hydrogen bonding, CNT can be stably dispersed in SPEEK solution; PEEK composites do not degrade at high temperatures (~400°C) during molding; on the one hand, the presence of CNTs increases the surface roughness of MCF, and CNTs can be stuck in the PEEK matrix like many nails, increasing the total frictional force through a large number of contact areas On the other hand, CNT also enhances the strength of the SPEEK/CNT interface layer itself; the above effects together greatly enhance the interaction between PEEK and MCF, and the interlayer shear strength and flexural strength of CF/PEEK composites increase significantly.

Finally, CF/PEEK composites were prepared by lamination hot pressing. The PEEK matrix changes from solid to melt under heating, and under pressure, undergoes shear flow, wetting the interior of the MCF tow. In this process, due to the enhanced interaction between PEEK and MCF, the wettability of PEEK melt to MCF is greatly improved, the possibility of forming pores inside the composite material is reduced, and when the composite material is damaged by external force, the interface between PEEK and MCF is sticky. The knot strength increases and the material failure mode shifts from fiber pullout to matrix fracture.

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

The CF/PEEK with interlaminar shear strength and flexural strength prepared by the preparation method of the present invention has a flexural strength of 850-1100 MPa, a flexural modulus of 55-65 GPa, an interlaminar shear strength (ILSS) of 95-110 MPa, and an impact of 95-110 MPa. The residual compressive strength (CAI) after this is 220-260 MPa. Among them, the interlaminar shear strength and bending strength are significantly higher than other known technologies with environmental protection and industrialization conditions.

Description of drawings

Figure 1 shows the XPS curve and oxygen/carbon (O/C) content of untreated CF, where the larger the O/C content ratio, the higher the activation efficiency;

Figure 2 shows the XPS curve and oxygen/carbon (O/C) content of UV-irradiated CF in a saturated water vapor environment;

Figure 3 shows the XPS curve and oxygen/carbon (O/C) content of CF treated with microwave and UV irradiation simultaneously in a saturated water vapor environment.

Fig. 4 is a scanning electron microscope photograph of carbon fibers obtained by simultaneous microwave and ultraviolet irradiation treatment in a saturated water vapor environment, followed by sizing treatment with a suspension containing 0.09 wt.% CNT;

FIG. 5 is a scanning electron microscope photograph of carbon fibers obtained by simultaneous microwave and ultraviolet irradiation treatment in a saturated water vapor environment, followed by sizing treatment with a suspension containing 0.5 wt.% CNTs.

Detailed ways

The present invention will be further described below in conjunction with specific embodiments. It should be understood that these examples are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of the present application.

Example 1

The preparation method of CF/PEEK with interlayer shear strength and flexural strength, the steps are as follows:

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

(2) In a saturated water vapor environment with a relative humidity of 95.3%, microwave irradiation and ultraviolet light irradiation were simultaneously performed on CF, and the product was recorded as ACF; the microwave irradiation time was 30 min, and the microwave frequency was 300 MHz; is 290nm, and the ultraviolet irradiance is 20W/m ² ;

(3) immersing the ACF in the sulfonated polyether ether ketone/dimethyl sulfoxide/carbon nanotube suspension for 120 min, taking out and drying to a water content of 0.48 wt.% to obtain sizing modified carbon fiber MCF;

In the sulfonated polyether ether ketone/dimethyl sulfoxide/carbon nanotube suspension, the sulfonated polyether ether ketone was completely dissolved and the content was 0.2wt.%, and the carbon nanotube content was 0.01wt.%, which was dispersed by ultrasonic for 5min A stable suspension is prepared, and the carbon nanotubes are carboxyl-modified single-walled carbon nanotubes;

The sulfonated polyether ether ketone is prepared by the sulfonation reaction of PEEK and concentrated sulfuric acid. The process is as follows: at room temperature, the dry PEEK powder is slowly added to 98wt.% concentrated sulfuric acid at a ratio of 0.01g/ml, and stirred until the powder is completely Dissolved, the solution was heated to 50 °C, stirred for 1 h, cooled to room temperature, slowly added the cooled solution to excess ice water with stirring, the precipitate was precipitated, washed with deionized water until the pH value was 7, in a vacuum oven It is completely dried to obtain the product sulfonated polyether ether ketone;

(4) Laminate hot pressing of MCF and PEEK powder with a weight average molecular weight of 30000; the process parameters of the laminated hot pressing: temperature 370°C, pressure 5MPa, loading time 3min;

After cooling to room temperature, the mold is demolded to obtain CF/PEEK with inter-layer shear strength and flexural strength.

The final CF/PEEK with interlaminar shear strength and flexural strength has a flexural strength of 909 MPa, a flexural modulus of 59 GPa, an interlaminar shear strength of 98 MPa, and a residual compressive strength of 229 MPa after impact.

Comparative Example 1

The preparation method of CF/PEEK composite material is basically the same as that of Example 1. Compared with Example 1, steps (1) and (2) are omitted. The material in the sulfone/carbon nanotube suspension was changed from ACF to CF T300 grade 3K5 satin fabric, and other processes and parameters were the same as in Example 1.

The flexural strength of the final CF/PEEK composite material was 561 MPa, the flexural modulus was 49 GPa, the interlaminar shear strength was 66 MPa, and the residual compressive strength after impact was 198 MPa.

Comparing Example 1 with Comparative Example 1, it can be seen that the flexural strength, flexural modulus, interlaminar shear strength, and residual compressive strength of the CF/PEEK composite prepared in Example 1 are much higher than those of Comparative Example 1. , the XPS curve and oxygen/carbon (O/C) content of untreated CF in Comparative Example 1 are shown in Figure 1. In Example 1, the XPS of CF was treated by microwave and ultraviolet irradiation simultaneously in a saturated water vapor environment. The curve and the oxygen/carbon (O/C) content are shown in Figure 3. It can be seen from the comparison that the O/C ratio of untreated CF is 0.0700, and the content of O is not high, indicating that CF is inert, while The O/C ratio of UV + water vapor + microwave treated CF is 0.1782, in which the content of O element is significantly increased. Compared with untreated CF, the O/C ratio is increased by 155% (up to 255% of the original) , indicating that microwave treatment at the same time as UV + water vapor is important, which is why the flexural strength, flexural modulus, interlaminar shear strength, residual compression after impact of CF/PEEK composites prepared with untreated CF The reason for the low strength.

Comparative Example 2

The preparation method of the CF/PEEK composite material is basically the same as that of Example 1, and is adjusted relative to the step (2) of Example 1. Specifically, in a saturated water vapor environment, CF is only irradiated with ultraviolet light without microwave. Radiation, other processes and parameters are the same as in Example 1.

The flexural strength of the final CF/PEEK composite material was 587 MPa, the flexural modulus was 49 GPa, the interlaminar shear strength was 67 MPa, and the residual compressive strength after impact was 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. , in Comparative Example 2, the XPS curve and oxygen/carbon (O/C) content of CF treated by ultraviolet irradiation in a saturated water vapor environment are shown in Figure 2. The XPS curves and oxygen/carbon (O/C) content of CF treated by microwave and UV irradiation are shown in Figure 3. The comparison shows that the O/C ratio of CF treated by UV + water vapor is 0.0765, where O The increase in the content of elements is not obvious, indicating that only the use of UV + water vapor is not very effective, and the O/C ratio of CF treated with UV + water vapor + microwave is 0.1782, and the content of O element is significantly increased, indicating that in Microwave treatment at the same time as UV + water vapor is important, which is why the flexural strength, flexural modulus, interlaminar shear strength, residual compression after impact of CF/PEEK composites prepared with UV + water vapor treated CF The reason for the low strength.

Example 2

The preparation method of CF/PEEK with interlayer shear strength and flexural strength, the steps are as follows:

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

(2) In a saturated water vapor environment with a relative humidity of 95.8%, microwave irradiation and ultraviolet light irradiation were simultaneously performed on CF, and the product was recorded as ACF; the microwave irradiation time was 27 min, and the microwave frequency was 820 MHz; the irradiation wavelength of ultraviolet light is 299nm, and the ultraviolet irradiance is 50W/m ² ;

(3) immersing the ACF in the sulfonated polyether ether ketone/dimethyl sulfoxide/carbon nanotube suspension for 115 min, taking out and drying to a water content of 0.45 wt.% to obtain sizing modified carbon fiber MCF;

In the sulfonated polyether ether ketone/dimethyl sulfoxide/carbon nanotube suspension, the sulfonated polyether ether ketone was completely dissolved and the content was 0.5wt.%, and the carbon nanotube content was 0.02wt.%, which was dispersed by ultrasonic for 18min A stable suspension is prepared, and the carbon nanotubes are carboxyl-modified single-walled carbon nanotubes;

Sulfonated polyether ether ketone is prepared by the sulfonation reaction of PEEK and concentrated sulfuric acid. The process is as follows: at room temperature, the dry PEEK powder is slowly added to 98wt.% concentrated sulfuric acid at a ratio of 0.03g/ml, and stirred until the powder is completely Dissolve, heat the solution to 54°C, stir for 2.5h, cool to room temperature, slowly add the cooled solution to excess ice water with stirring, the precipitate is precipitated, wash the precipitate with deionized water until the pH value is 7, in a vacuum It is completely dried in an oven to obtain the product sulfonated polyetheretherketone;

(4) Laminate hot pressing of MCF and PEEK powder with a weight average molecular weight of 60000; the process parameters of the laminated hot pressing: temperature 378°C, pressure 4.7MPa, loading time 7min;

After cooling to room temperature, the mold is demolded to obtain CF/PEEK with inter-layer shear strength and flexural strength.

The final CF/PEEK with interlaminar shear strength and flexural strength has a flexural strength of 938 MPa, a flexural modulus of 61 GPa, an interlaminar shear strength of 102 MPa, and a residual compressive strength of 243 MPa after impact.

Example 3

The preparation method of CF/PEEK with interlayer shear strength and flexural strength, the steps are as follows:

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

(2) In a saturated water vapor environment with a relative humidity of 95.9%, microwave irradiation and ultraviolet light irradiation were simultaneously performed on CF, and the product was recorded as ACF; the microwave irradiation time was 24 min, and the microwave frequency was 1 GHz; the irradiation wavelength of ultraviolet light was is 305nm, and the ultraviolet irradiance is 35W/m ² ;

(3) immersing the ACF in the sulfonated polyether ether ketone/dimethyl sulfoxide/carbon nanotube suspension for 94 min, taking out and drying to a water content of 0.42 wt.% to obtain sizing modified carbon fiber MCF;

In the sulfonated polyether ether ketone/dimethyl sulfoxide/carbon nanotube suspension, the sulfonated polyether ether ketone was completely dissolved and the content was 0.8wt.%, and the carbon nanotube content was 0.03wt.%, which was dispersed by ultrasonic for 22min A stable suspension is prepared, and the carbon nanotubes are carboxyl-modified single-walled carbon nanotubes;

The sulfonated polyether ether ketone is prepared by the sulfonation reaction of PEEK and concentrated sulfuric acid. The process is as follows: at room temperature, the dried PEEK powder is slowly added to 98 wt.% concentrated sulfuric acid at a ratio of 0.1 g/ml, and stirred until the powder is completely Dissolve, heat the solution to 52°C, stir for 3.5h, cool to room temperature, slowly add the cooled solution to excess ice water with stirring, the precipitate is precipitated, wash the precipitate with deionized water until the pH value is 7, in a vacuum It is completely dried in an oven to obtain the product sulfonated polyetheretherketone;

(4) Laminate MCF and PEEK non-woven felt with a weight-average molecular weight of 75000 and hot-press; the process parameters of the lamination hot-pressing: temperature 381°C, pressure 3.4MPa, loading time 11min;

After cooling to room temperature, the mold is demolded to obtain CF/PEEK with inter-layer shear strength and flexural strength.

The final CF/PEEK with interlaminar shear strength and flexural strength has a flexural strength of 925 MPa, a flexural modulus of 62 GPa, an interlaminar shear strength of 105 MPa, and a residual compressive strength of 260 MPa after impact.

Example 4

The preparation method of CF/PEEK with interlayer shear strength and flexural strength, the steps are as follows:

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

(2) In a saturated water vapor environment with a relative humidity of 96.3%, microwave irradiation and ultraviolet light irradiation were simultaneously performed on CF, and the product was recorded as ACF; the microwave irradiation time was 20 min, and the microwave frequency was 1.5 GHz; The wavelength is 313nm, and the ultraviolet irradiance is 24W/m ² ;

(3) immersing the ACF in the sulfonated polyether ether ketone/dimethyl sulfoxide/carbon nanotube suspension for 69 minutes, taking it out and drying to a water content of 0.41 wt.% to obtain sizing modified carbon fiber MCF;

In the sulfonated polyether ether ketone/dimethyl sulfoxide/carbon nanotube suspension, the sulfonated polyether ether ketone was completely dissolved and the content was 1.2wt.%, and the carbon nanotube content was 0.04wt.%, which was dispersed by ultrasonic for 35min A stable suspension is prepared, and the carbon nanotubes are carboxyl-modified single-walled carbon nanotubes;

The sulfonated polyether ether ketone is prepared by the sulfonation reaction of PEEK and concentrated sulfuric acid. The process is as follows: at room temperature, the dry PEEK powder is slowly added to 98wt.% concentrated sulfuric acid at a ratio of 0.15g/ml, and stirred until the powder is completely Dissolved, the solution was heated to 51 °C, stirred for 4 h, cooled to room temperature, slowly added the cooled solution to excess ice water with stirring, the precipitate was precipitated, washed with deionized water until the pH value was 7, in a vacuum oven It is completely dried to obtain the product sulfonated polyether ether ketone;

(4) MCF and PEEK non-woven felt with a weight average molecular weight of 82000 are laminated and hot-pressed; the process parameters of the laminated hot-pressing: temperature 389°C, pressure 2.9MPa, loading time 15min;

After cooling to room temperature, the mold is demolded to obtain CF/PEEK with inter-layer shear strength and flexural strength.

The final CF/PEEK with interlaminar shear strength and flexural strength has a flexural strength of 978 MPa, a flexural modulus of 64 GPa, an interlaminar shear strength of 108 MPa, and a residual compressive strength of 255 MPa after impact.

Example 5

The preparation method of CF/PEEK with interlayer shear strength and flexural strength, the steps are as follows:

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

(2) In a saturated water vapor environment with a relative humidity of 96.8%, microwave irradiation and ultraviolet light irradiation were simultaneously performed on CF, and the product was recorded as ACF; the microwave irradiation time was 16 min, and the microwave frequency was 2.3 GHz; The wavelength is 320nm, and the ultraviolet irradiance is 31W/m ² ;

(3) immersing the ACF in the sulfonated polyether ether ketone/dimethyl sulfoxide/carbon nanotube suspension for 51 min, taking out and drying to a water content of 0.38 wt.% to obtain sizing modified carbon fiber MCF;

In the sulfonated polyether ether ketone/dimethyl sulfoxide/carbon nanotube suspension, the sulfonated polyether ether ketone was completely dissolved and the content was 1.8wt.%, and the carbon nanotube content was 0.06wt.%, which was dispersed by ultrasonic for 40min A stable suspension is prepared, and the carbon nanotubes are carboxyl-modified multi-walled carbon nanotubes;

The sulfonated polyether ether ketone is prepared by the sulfonation reaction of PEEK and concentrated sulfuric acid. The process is as follows: at room temperature, the dry PEEK powder is slowly added to 98 wt.% concentrated sulfuric acid at a ratio of 0.19 g/ml, and stirred until the powder is completely Dissolved, the solution was heated to 55 °C, stirred for 5 h, cooled to room temperature, slowly added the cooled solution to excess ice water with stirring, the precipitate was precipitated, washed with deionized water until the pH value was 7, in a vacuum oven It is completely dried to obtain the product sulfonated polyether ether ketone;

(4) MCF and PEEK film with a weight average molecular weight of 90000 are laminated and hot-pressed; the process parameters of the laminated hot-pressing: temperature 395°C, pressure 2.3MPa, loading time 19min;

After cooling to room temperature, the mold is demolded to obtain CF/PEEK with inter-layer shear strength and flexural strength.

The final CF/PEEK with interlaminar shear strength and flexural strength has a flexural strength of 1100 MPa, a flexural modulus of 65 GPa, an interlaminar shear strength of 110 MPa, and a residual compressive strength of 252 MPa after impact.

Example 6

The preparation method of CF/PEEK with interlayer shear strength and flexural strength, the steps are as follows:

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

(2) In a saturated water vapor environment with a relative humidity of 97.1%, microwave irradiation and ultraviolet light irradiation were simultaneously performed on CF, and the product was recorded as ACF; the microwave irradiation time was 12 min, and the microwave frequency was 3.9 GHz; The wavelength is 330nm, and the ultraviolet irradiance is 45W/m ² ;

(3) immersing the ACF in the sulfonated polyether ether ketone/dimethyl sulfoxide/carbon nanotube suspension for 38 minutes, taking out and drying to a water content of 0.35 wt.% to obtain sizing modified carbon fiber MCF;

In the sulfonated polyether ether ketone/dimethyl sulfoxide/carbon nanotube suspension, the sulfonated polyether ether ketone was completely dissolved and the content was 2.2wt.%, and the carbon nanotube content was 0.07wt.%, which was dispersed by ultrasonic for 48min A stable suspension is prepared, and the carbon nanotubes are carboxyl-modified multi-walled carbon nanotubes;

Sulfonated polyether ether ketone is prepared by the sulfonation reaction of PEEK and concentrated sulfuric acid. The process is as follows: at room temperature, the dry PEEK powder is slowly added to 98 wt.% concentrated sulfuric acid at a ratio of 0.21 g/ml, and stirred until the powder is completely Dissolved, the solution was heated to 50 °C, stirred for 5 h, cooled to room temperature, slowly added the cooled solution to excess ice water with stirring, the precipitate was precipitated, washed with deionized water until the pH value was 7, in a vacuum oven It is completely dried to obtain the product sulfonated polyether ether ketone;

(4) MCF and PEEK film with a weight average molecular weight of 113000 are laminated and hot-pressed; the process parameters of the laminated hot-pressing: temperature 405°C, pressure 1.2MPa, loading time 23min;

After cooling to room temperature, the mold is demolded to obtain CF/PEEK with inter-layer shear strength and flexural strength.

The final CF/PEEK with interlaminar shear strength and flexural strength has a flexural strength of 1004 MPa, a flexural modulus of 63 GPa, an interlaminar shear strength of 103 MPa, and a residual compressive strength of 244 MPa after impact.

Example 7

The preparation method of CF/PEEK with interlayer shear strength and flexural strength, the steps are as follows:

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

(2) In a saturated water vapor environment with a relative humidity of 97.5%, microwave irradiation and ultraviolet light irradiation were simultaneously performed on CF, and the product was recorded as ACF; the microwave irradiation time was 8 min, and the microwave frequency was 6.8 GHz; The wavelength is 336nm, and the ultraviolet irradiance is 41W/m ² ;

(3) Immerse the ACF in the sulfonated polyether ether ketone/dimethyl sulfoxide/carbon nanotube suspension for 20 min, take it out, and dry it to a water content of 0.32 wt.% to obtain the sizing modified carbon fiber MCF. The scanning electron microscope photo is as follows As shown in Figure 4;

In the sulfonated polyether ether ketone/dimethyl sulfoxide/carbon nanotube suspension, the sulfonated polyether ether ketone was completely dissolved and the content was 2.7wt.%, and the carbon nanotube content was 0.09wt.%, which was dispersed by ultrasonic for 54min A stable suspension is prepared, and the carbon nanotubes are carboxyl-modified multi-walled carbon nanotubes;

The sulfonated polyether ether ketone is prepared by the sulfonation reaction of PEEK and concentrated sulfuric acid. The process is as follows: at room temperature, the dry PEEK powder is slowly added to 98 wt.% concentrated sulfuric acid at a ratio of 0.26 g/ml, and stirred until the powder is completely Dissolved, the solution was heated to 54 °C, stirred for 4.2 h, cooled to room temperature, slowly added the cooled solution to excess ice water with stirring, the precipitate was precipitated, washed with deionized water until the pH value was 7, in a vacuum It is completely dried in an oven to obtain the product sulfonated polyetheretherketone;

(4) MCF and PEEK fiber with a weight average molecular weight of 136000 are laminated and hot-pressed; the process parameters of the laminated hot-pressing: temperature 411°C, pressure 1MPa, loading time 27min;

After cooling to room temperature, the mold is demolded to obtain CF/PEEK with inter-layer shear strength and flexural strength.

The final CF/PEEK with interlaminar shear strength and flexural strength has a flexural strength of 927 MPa, a flexural modulus of 58 GPa, an interlaminar shear strength of 97 MPa, and a residual compressive strength of 239 MPa after impact.

Comparative Example 3

The preparation method of CF/PEEK composite material is basically the same as that of Example 7, and is adjusted relative to step (3) of Example 7, specifically, the content of carbon nanotubes (CNT) is changed to 0.5wt.%, and other processes and parameters are the same. Example 7.

The flexural strength of the final CF/PEEK composite material was 621 MPa, the flexural modulus was 55 GPa, the interlaminar shear strength was 72 MPa, and the residual compressive strength after impact was 211 MPa. Among them, the scanning electron microscope photograph of the intermediate product (namely modified carbon fiber) obtained after steps (1), (2) and (3) is shown in Figure 5.

Comparing Example 7 with Comparative Example 3, 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 7 are much higher than those of Comparative Example 3. , the carbon nanotube content in Comparative Example 3 is 0.5 wt.%, the carbon nanotubes agglomerate due to the excessively high content (compare Figure 4 and Figure 5), the effect of improving the interface interaction between the carbon fiber and the PEEK matrix resin It is not very good, indicating that the content of carbon nanotubes is a key process parameter, which is why the flexural strength, flexural modulus, The reason for the low interlaminar shear strength and residual compressive strength after impact.

Example 8

The preparation method of CF/PEEK with interlayer shear strength and flexural strength, the steps are as follows:

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

(2) In a saturated water vapor environment with a relative humidity of 98.2%, microwave irradiation and ultraviolet light irradiation were simultaneously performed on CF, and the product was recorded as ACF; the microwave irradiation time was 3 min, and the microwave frequency was 10 GHz; is 340nm, and the ultraviolet irradiance is 39W/m ² ;

(3) immersing the ACF in the sulfonated polyether ether ketone/dimethyl sulfoxide/carbon nanotube suspension for 5 min, taking it out and drying to a water content of 0.28 wt.% to obtain sizing modified carbon fiber MCF;

In the sulfonated polyether ether ketone/dimethyl sulfoxide/carbon nanotube suspension, the sulfonated polyether ether ketone is completely dissolved and the content is 3wt.%, and the carbon nanotube content is 0.1wt.%, prepared by 60min ultrasonic dispersion Stable suspension, carbon nanotubes are carboxyl-modified multi-walled carbon nanotubes;

The sulfonated polyether ether ketone is prepared by the sulfonation reaction of PEEK and concentrated sulfuric acid. The process is as follows: at room temperature, the dry PEEK powder is slowly added to 98wt.% concentrated sulfuric acid at a ratio of 0.3 g/ml, and stirred until the powder is completely Dissolve, heat the solution to 53 °C, stir for 2.8 h, cool to room temperature, slowly add the cooled solution to excess ice water with stirring, the precipitate is precipitated, wash the precipitate with deionized water until the pH value is 7, in a vacuum It is completely dried in an oven to obtain the product sulfonated polyetheretherketone;

(4) MCF and PEEK fiber with a weight average molecular weight of 150000 are laminated and hot-pressed; the process parameters of the laminated hot-pressing: temperature 420°C, pressure 0.5MPa, loading time 30min;

After cooling to room temperature, the mold is demolded to obtain CF/PEEK with inter-layer shear strength and flexural strength.

The final CF/PEEK with interlaminar shear strength and flexural strength has a flexural strength of 850 MPa, a flexural modulus of 55 GPa, an interlaminar shear strength of 95 MPa, and a residual compressive strength of 220 MPa after impact.

Claims (7)

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.

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