Continuous fiber-reinforced prepreg tape and method of making same

Abstract

The application belongs to the technical field of prepreg tape production, and particularly relates to a continuous fiber reinforced prepreg tape and a preparation method thereof. The method comprises the following steps: 1) pretreating base fibers to obtain pretreated fibers; 2) performing spread yarn treatment on the pretreated fibers by using an air flow spread yarn method to obtain a continuous fiber thin layer tape; and 3) performing segmented impregnation reinforcement treatment on the continuous fiber thin layer tape, and then cooling and setting to obtain the continuous fiber reinforced prepreg tape. The application combines the air flow spread yarn method and the impregnation technology, enhances the Y-axis bonding strength of the prepreg tape from the micro level, improves the fiber distribution form, significantly improves and optimizes the overall mechanical properties of the prepreg tape, and significantly improves the weather resistance of the prepreg tape through the treatment of the impregnated material.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of prepreg tape production, and particularly relates to a continuous fiber reinforced prepreg tape and a preparation method thereof. BACKGROUND

[0002] Fiber reinforced resin matrix composites can be divided into two categories according to the properties of the resin matrix: thermosetting resin matrix composites and thermoplastic resin matrix composites. Thermosetting resin matrix composites have some inherent disadvantages, such as low fracture toughness, low damage tolerance, poor moisture absorption, poor environmental adaptability, long processing cycle, and difficult recycling, which limit their development and application. Thermoplastic resin matrix composites have the following advantages: 1. good toughness, high fatigue strength, and high impact damage tolerance; 2. unlimited storage period of fiber prepreg and sheet-shaped mold; 3. good thermoforming process, short forming cycle, and high production efficiency; 4. edge or waste materials can be remelted and formed or recycled, which is environmentally friendly. Therefore, thermoplastic composites are increasingly attracting attention and have become a research and development hotspot in the field of composites.

[0003] In the production process of traditional prepreg tapes, a series of technical bottleneck problems need to be solved: first, uneven fiber spreading is a major problem. During the fiber tow spreading stage, due to the difficulty in accurately controlling the tension distribution, local accumulation or loosening often occurs. This phenomenon directly negatively affects the subsequent impregnation uniformity, threatening the quality of the final product. Second, low resin impregnation efficiency is also a major challenge. The existing impregnation mold flow channel structure is relatively simple, which makes it difficult for the molten resin to fully penetrate the fiber tow due to various obstacles. As a result, dry spots often appear on the prepreg tape, or the glue content fluctuates, seriously affecting the performance and quality stability of the product. Third, the coupling relationship between process parameters is extremely complex. Traction speed, resin viscosity, and temperature are all key parameters that are related and influenced by each other. If these parameters are not accurately controlled, the performance stability of the prepreg tape will be poor, making it difficult to meet the requirements of high-quality production.

[0004] To address this, there are currently studies that combine airflow spreading technology to improve the uniformity of fiber spreading in prepreg tapes. However, in such studies, it is found that this method can effectively improve the main performance of the product, i.e., the tensile strength in the X-axis (long fiber axial direction), and significantly optimize the impregnation uniformity and impregnation efficiency, but the Y-axis (perpendicular to the long fiber axial direction) strength of the prepreg tape product is limited, and the weather resistance of the prepreg tape is still limited. SUMMARY

[0005] The technical scheme of the present application aims at the problems in the traditional fiber reinforcing scheme, such as uneven fiber development, low impregnation efficiency of resin, complex coupling of process parameters, and the defects of poor performance of the new yarn development and impregnation technology, and provides a continuous fiber reinforced prepreg tape and a preparation method thereof.

[0006] The main purpose of the present application is to: 1. Achieve efficient and uniform development of fiber filaments in the prepreg tape.

[0007] 2. Improve the impregnation efficiency and uniformity of molten resin.

[0008] 3. Accurately control the stability of resin content and prepreg tape size.

[0009] 4. Effectively improve the comprehensive mechanical properties and weather resistance of the prepreg tape.

[0010] To achieve the above purpose, the present application adopts the following technical scheme.

[0011] A preparation method of a continuous fiber reinforced prepreg tape, the method comprising: 1) pretreating the base fibers to obtain pretreated fibers.

[0012] 2) developing the pretreated fibers by airflow development to obtain a continuous fiber thin layer tape.

[0013] 3) segmentally impregnating and reinforcing the continuous fiber thin layer tape, and then cooling and setting to obtain a continuous fiber reinforced prepreg tape.

[0014] As a preferred, the base fibers in step 1) are carbon fibers; the carbon fibers are mixed fibers of continuous long fibers and chopped fibers; the continuous long fibers are ≥200 m; the length of the chopped fibers is 5-15 mm.

[0015] As a preferred, the proportion of the chopped fibers in the base fibers is 12-18 wt%.

[0016] As a preferred, the pretreatment process in step 1) is: dissolving the modified impregnation into a concentrated sulfuric acid solution to prepare a pretreatment liquid, uniformly atomizing and spraying the pretreatment liquid on the base fibers, washing with deionized water after standing for 5-10 min and drying; the concentrated sulfuric acid is industrial concentrated sulfuric acid with a sulfuric acid degree ≥70 wt%; the concentration of the modified impregnation in the pretreatment liquid is 5-8 wt%; the amount of the pretreatment liquid is 8-10 wt% of the base fibers.

[0017] As a preferred, the airflow temperature is controlled to be 350-380 ℃ and the airflow velocity is controlled to be 3-5 m / s in the yarn development process in step 2).

[0018] As preferred, the segmental impregnation process in step 3) is all carried out under the condition of impregnating the continuous fiber thin layer strip in the molten modified impregnation material in a protective atmosphere; the segmental impregnation is divided into initial segmental movement impregnation and final segmental penetration impregnation; the initial segmental movement impregnation controls the pulling speed of the continuous fiber thin layer strip in the molten modified impregnation material to be 3-5 m / min, and an intermediate prepreg strip is obtained after impregnation, the mass content of the matrix fiber in the intermediate prepreg strip being 92-95 wt%; the final segmental penetration impregnation controls the pulling speed of the intermediate prepreg strip in the molten modified impregnation material to be 1.5-2.5 m / min, and a semi-finished prepreg strip is obtained after impregnation, the mass content of the matrix fiber in the semi-finished prepreg strip being 68-72 wt%.

[0019] As preferred, the modified impregnation material is composed of modified polyether ether ketone, maleic anhydride grafted compatilizer, antioxidant B215 and N,N-ethylene bis stearamide in a mass ratio of 50:1.5:1.5:0.1, and the modified polyether ether ketone is heated to just melt, then the other components are added and uniformly mixed to obtain the modified impregnation material; the modified polyether ether ketone is prepared by the following method: uniformly mixing polyether ether ketone and 95-98 wt% concentrated sulfuric acid in a mass ratio of 1:(0.8-1.2), reacting under the condition of a temperature of 55-65 ℃ for 1.75-2.25 h, using ion water to dialyze to pH 6.8-7.2, and vacuum drying to prepare sulfonated polyether ether ketone; uniformly mixing the sulfonated polyether ether ketone and the modifier in a mass ratio of 1:(0.4-0.6), and using a twin-screw extruder to melt blend under the condition of a temperature of 340-360 ℃ and a screw rotation speed of 80-90 rpm to prepare the modified polyether ether ketone.

[0020] The modifier is furan and N,N'-(4,4'-methylene diphenyl) bismaleimide uniformly mixed in a mass ratio of 1:(1.75-1.95).

[0021] As preferred, in the cooling and shaping process in step 3), the relative humidity of the environment is controlled to be ≤30 %.

[0022] A continuous fiber reinforced prepreg strip.

[0023] For the technical scheme of the present application, the core lies in the organic combination of air flow spreading technology and impregnation technology.

[0024] In the air flow spreading link, the present application discards the traditional mechanical roller pressing or tension control mode, and instead uses high-pressure air flow to implement non-contact spreading on the fiber tows, which can effectively avoid the problems of fiber damage and local stress concentration caused by the traditional method, and provide better fiber basis conditions for the subsequent process flow.

[0025] But in the early research and development process, it is also found that simply using the combination of air flow spreading and dipping technology will lead to great distribution difference of the mechanical properties of the prepreg tape, which performs well in the X-axis and performs poorly in the Y-axis, mainly because air flow spreading can indeed greatly improve the uniformity of fiber distribution, but its distribution axis is too single, and after combining with the dipping technology to prepare the prepreg tape, the Y-axis performance is mainly provided by the cured impregnated material, resulting in a more significant distribution of mechanical properties.

[0026] Therefore, the present application uses a special processing method to make the air flow spreading technology and the dipping technology in the preparation process more effectively combined. In this process, the first and foremost important thing is the pretreatment of the base fiber, i.e. the carbon fiber used in the present application. Generally speaking, air flow spreading prepreg tape usually only uses continuous long fibers, because short fibers are easy to gather together in the air flow, and are difficult to disperse evenly like long fibers, resulting in poor spreading effect and unable to form a uniform fiber thin layer, at the same time, short fibers are easy to entangle and knot with each other in the air flow, forming a mass, affecting the uniformity and continuity of the spreading. On the other hand, due to the short length of the short fibers, they are more easily impacted and rubbed by the air flow in the air flow, which can easily cause fiber breakage, increase the number of loose fibers, reduce the strength and quality of the fibers, and may also repeatedly fold and bend, further exacerbating the damage to the fibers and affecting the mechanical properties.

[0027] But in the present application, after dissolving part of the present application impregnated material with commercially available 70 wt% industrial concentrated sulfuric acid before air flow spreading, a pretreatment liquid with better flowability is formed and uniformly wetted on the surface of the base fiber by atomizing spraying for pretreatment, which can produce "distributed point treatment" on the fiber. Because in addition to the impregnated material treatment, the concentrated acid in the pretreatment liquid can actually change the surface properties of the base carbon fiber to some extent, especially in terms of polarity.

[0028] The carbon fiber is one of the preferred fibers for the air flow spreading technology, and the non-polar or weakly polar fiber is more suitable for the air flow spreading technology and is not easy to agglomerate and form a group. After the pretreatment, the polarity of the carbon fiber surface can be changed to a certain extent, and under the condition of appropriate concentration of concentrated sulfuric acid and appropriate treatment conditions, some polar functional groups such as carbonyl and carboxyl can be introduced on the surface of the carbon fiber, so that the surface energy and wettability of the carbon fiber are improved. In this way, the bonding strength of the carbon fiber and the modified impregnated material can be further improved, and a uniform "polar point" can be formed, which can be used as a linking point to realize the linking of long and short fibers and the movement characteristics of the linking point as the "axle" and the short fibers in the air flow spreading process. The distribution form of the matrix fiber is changed, the Y-axis linking effect is enhanced, and the preliminary fixation of the modified impregnated material is realized. The fixation is not to solidify and coat on the surface of the fiber, but to protect the polar linking point in situ while the matrix carbon fiber is pretreated by the oxidizing concentrated acid to generate the polar linking point, so as to realize the preliminary Y-axis reinforcement.

[0029] Of course, this process also needs to be improved in cooperation with the air flow spreading process. In the air flow spreading process, the hot air pre-spreading method is used as the spreading air flow. In this way, the axial nature of the long fiber spreading can be better, the local fiber enrichment can be reduced, the stress concentration can be reduced, the short fibers can be effectively and naturally distributed, and the yield and average performance of the product can be improved.

[0030] Then, the impregnation process is adjusted. The segmented impregnation treatment is adopted, and different pulling rates (note: the pulling direction is along the axial direction of the long fiber) are adopted in the segmented impregnation treatment process. This is also because the pretreatment process and the preceding air flow spreading can make the short fibers in the continuous fiber thin layer show a certain degree of oblique distribution characteristics. In the initial stage of movement and impregnation, the Y-axis distribution trend of the short fibers can be further enhanced, and the distribution of the long and short fibers by the impregnated material can be preliminarily coated and fixed. Then, the final stage of permeation and impregnation similar to the conventional impregnation is adopted, the effective and complete coating and fixation of the impregnated material are realized, and the finished product pre-impregnated tape is obtained.

[0031] The application also has another core point, that is, the prepreg is also improved and optimized. That is, the thermoplastic resin is treated by organic modification, the polar functional groups are introduced by sulfonation modification, and a reversible network and a guiding effect are constructed by a dynamic crosslinking agent, so that the resin material can be effectively enhanced in performance. The organic functional groups and the polar groups on the fiber surface form a crosslinked network, thereby effectively strengthening the mechanical properties of the resin material. The organic treatment of polyether ether ketone realizes the strong constraint and uniform distribution of the fiber at the molecular level. The synergistic effect of chemical bonds (hydrogen bond, covalent bond and dynamic bond) significantly improves the interfacial strength, moisture resistance and functional properties of the prepreg, and ensures the high performance of the prepreg in extreme environment.

[0032] Polyether ether ketone is a semi-crystalline high-performance thermoplastic polymer, and the main chain is composed of benzene ring, ether bond and ketone group, which endows it with excellent high-temperature resistance, chemical stability and mechanical strength. However, the unmodified polyether ether ketone has low polarity, and the interface between the unmodified polyether ether ketone and the non-polar or weakly polar fiber (such as carbon fiber) is weak, which leads to insufficient interlaminar shear strength of the composite material. The application introduces specific functional groups and chemical bonds by organic treatment, which can significantly enhance the interfacial bonding and optimize the fiber distribution.

[0033] In the application, the polyether ether ketone is dissolved in concentrated sulfuric acid, the sulfonic acid group is introduced on the benzene ring through electrophilic substitution reaction, and the wettability of the resin and the fiber surface is significantly improved by the strong polarity of the sulfonic acid group. The protons of the sulfonic acid group in the resin matrix after sulfonation can form hydrogen bonds with the hydroxyl groups on the fiber surface, and can bond the connection strength between the matrix and the fiber through electrostatic action in alkaline environment. And the polar groups reduce the adsorption of water on the interface through chemical bonding, so that the material still has high strength retention after wet heat aging.

[0034] The modified polyether ether ketone matrix and the fiber interface in the application play the effect of transferring load, effectively connecting groups and reinforcing bodies. In the conventional technology, the interface between the matrix and the fiber is the weak link in the fracture process of the fiber prepreg, and in the application, the maleimide and furan can construct a cycloalkene skeleton in a low temperature environment, the conjugated diene can construct a cycloalkene skeleton with a dienophile, the connection strength of the modified polyether ether ketone matrix to the continuous fiber is strengthened, and in a high temperature use environment, the resin viscosity in the prepreg is reduced, the fiber produces a large displacement, the cycloalkene skeleton can be opened to form an effective carbon chain, allowing the fiber to be stretched and arranged under shear force, ensuring the chemical linkage of the matrix to the fiber, improving the tensile strength of the prepreg in extreme environment, and restoring the cycloalkene skeleton to form a crosslinked network to fix the fiber position after cooling.

[0035] The present application has the beneficial effects that: the present application enhances the Y-axis bonding strength of the prepreg tape and improves the fiber distribution form from the micro level through the organic combination of airflow spreading and dip coating technology, so that the overall mechanical properties of the prepreg tape are significantly improved and optimized, and the weather resistance of the prepreg tape is also significantly improved through the treatment improvement of the impregnated material. DETAILED DESCRIPTION

[0036] The present application will be further clarified by the following specific examples. Those skilled in the art will be able to implement the present application based on these descriptions. In addition, the embodiments of the present application involved in the following description are generally only a part of the embodiments of the present application, not all the embodiments. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments in the present application without creative labor should be within the scope of protection of the present application.

[0037] Unless otherwise specified, the raw materials used in the embodiments of the present application are commercially available or can be obtained by those skilled in the art; unless otherwise specified, the methods used in the embodiments of the present application are methods mastered by those skilled in the art.

[0038] Unless otherwise specified, the carbon fiber continuous long fiber length used in the embodiments of the present application is 220-250 m, the carbon fiber short cut fiber length is 5-15 mm, and the tensile strength of the high-quality carbon fiber is 3600-3800 MPa.

[0039] Embodiment 1: A method for preparing a continuous fiber reinforced prepreg tape, the method comprising: 1) preparing a modified impregnated material, the modified impregnated material being composed of modified polyether ether ketone, maleic anhydride grafted compatibilizer, antioxidant B215 and N,N-aziridine bis-hydroxystearic acid amide in a mass ratio of 50:1.5:1.5:0.1, the modified polyether ether ketone is heated to just melt and then the other ingredients are mixed uniformly to obtain the modified impregnated material.

[0040] The modified polyether ether ketone is prepared by the following method: mixing polyether ether ketone and 96 wt% concentrated sulfuric acid in a mass ratio of 1:1 uniformly, reacting for 2 h under the condition of a temperature of 62 ℃, using ion water to dialyze to pH 7, and vacuum drying to prepare sulfonated polyether ether ketone.

[0041] Mixing sulfonated polyether ether ketone and modifier uniformly in a mass ratio of 1:0.5, melt blending in a twin-screw extruder under the condition of a temperature of 350 ℃ and a screw speed of 85 rpm to prepare modified polyether ether ketone.

[0042] The modifier is furan and N,N'-(4,4'-methylene diphenyl) bismaleimide mixed uniformly in a mass ratio of 1:1.8.

[0043] 2) The carbon fiber continuous long fiber and the carbon fiber short fiber with a mass ratio of 85:15 are used as the matrix fiber, the continuous long fiber is spread and the short fiber is uniformly spread on the surface of the continuous long fiber, then the pretreatment is carried out, in the pretreatment process, the modified polyether ether ketone is dissolved in a 70 wt% sulfuric acid solution to prepare a pretreatment solution with a modified polyether ether ketone concentration of 6.5 wt%, the pretreatment solution is uniformly sprayed on the matrix fiber, the amount of the pretreatment solution is 8 wt% of the matrix fiber, after standing for 10 min, the pretreatment fiber is washed with deionized water and dried.

[0044] 3) The pretreatment fiber is subjected to yarn spreading treatment by air flow yarn spreading method, the air flow temperature is controlled to be 355 ℃ and the air flow speed is controlled to be 4 m / s in the air flow yarn spreading treatment process, and a continuous fiber thin layer belt is obtained.

[0045] 4) The continuous fiber thin layer belt is subjected to segmented impregnation reinforcement treatment; the segmented impregnation is divided into initial segment motion impregnation and final segment penetration impregnation; the continuous fiber thin layer belt is controlled to have a pulling speed of 4.5 m / min in the modified melting impregnation material at 355-360 ℃ in the initial segment motion impregnation process, and an intermediate pre-impregnated belt is obtained after impregnation, the mass content of the matrix fiber in the intermediate pre-impregnated belt is 93.1 wt%; the intermediate pre-impregnated belt is controlled to have a pulling speed of 2 m / min in the modified melting impregnation material at 355-360 ℃ in the final segment penetration impregnation process, and a semi-finished product pre-impregnated belt is obtained after impregnation, the mass content of the matrix fiber in the semi-finished product pre-impregnated belt is 69.6 wt%; then the continuous fiber reinforced pre-impregnated belt is obtained by natural cooling and setting in an environment with a relative humidity of ≤30%.

[0046] The fiber reinforced pre-impregnated belt prepared in this example is subjected to performance detection, and the specific characterization results are as follows.

[0047] Air flow yarn spreading uniformity detection: the fiber layer after yarn spreading in step (1) is subjected to cross-section slicing, a scanning electron microscope (SEM) is used to observe the distribution of the filaments, 10 points are randomly selected along the axis of the continuous long fiber, the standard deviation (σ) and the average value (z) of the yarn spreading width of the continuous long fiber are measured, and the coefficient of variation (c.v.%) of the continuous long fiber is calculated by combining the standard deviation of the yarn spreading width with the average value of the yarn spreading width, and the specific calculation formula is as follows: .

[0048] Resin impregnation efficiency: the pre-impregnated belt is subjected to three-dimensional imaging, the penetration rate of the resin in the fiber bundle is analyzed, 1 m of the pre-impregnated belt is randomly cut, and the area ratio of the dry spots (the area without resin coverage) is counted.

[0049] Mechanical property detection: the tensile strength of the X-axis and the Y-axis of the pre-impregnated belt is respectively characterized and detected.

[0050] Durability test in hot and humid environment: the fiber reinforced prepreg tape prepared in this example was aged for 500 h under the environmental conditions of 85 ℃ and 85% humidity, and the mechanical property retention rate was tested.

[0051] The performance test results are shown in Table 1 below.

[0052] Table 1: Performance test results of the sample of Example 1:

[0053] From the above Table 1 characterization results, it can be seen that the prepreg tape of the present application has very significant performance superiority. In terms of coefficient of variation, it shows very small coefficient of variation, indicating that the uniformity of continuous long fiber distribution is very high, and the unfolding is very smooth, and the connection points formed by pretreatment can maintain very good axial unfolding and transverse arrangement under the process cooperation of hot air flow spreading, which is mainly because under the temperature condition of hot air flow spreading, a small amount of impregnated material of the connection points softens or even melts to form droplets, and under the cooperation of the tension of the droplets and the polarity connection between the fibers, the long fiber connection points can slide along the axial direction to realize straightening, reduce bending and the like, while avoiding the influence of the original uniform connection of short fibers to produce enrichment, but a too high hot air temperature should not be used, because a too high hot air temperature will lead to the agglomeration and clumping of short fibers, thereby increasing the coefficient of variation and reducing the mechanical properties. On the other hand, the mechanical properties are extremely excellent. Generally, the resin matrix in the prepreg tape will form a certain structure after curing, which has an important influence on the strength of the composite material. Although the resin can enhance the mechanical properties of the fiber, improve the toughness, impact resistance and environmental stress cracking resistance of the composite material, etc., compared with the high strength of the carbon fiber itself, the strength of the resin matrix is relatively low, which will reduce the overall axial tensile strength to a certain extent. For example, the UD unidirectional tape prepreg tape prepared from commercially available IMS65 carbon fiber has a fiber tensile strength of about 5800 MPa, and the X-axis tensile strength of its product is about 2900 MPa, and the Y-axis tensile strength is only about 90-102 MPa, and the X-axis tensile strength is only about 50% of the original carbon fiber, while the present application is as high as 73.4-77.5%, which indicates that the modified impregnated material used in the present application is much better than the commercially available impregnated material, and the combination effect is better, which can better form the load transfer effect and thus show higher performance retention rate. In theory, the use of higher quality carbon fiber can show extremely superior tensile strength performance. The most significant optimization is the Y-axis tensile strength, which is generally only 90-110 MPa for the existing carbon fiber prepreg tape, while the present application reaches more than ten times the performance. This is because the present application realizes the special distribution of short fibers through the cooperation of pretreatment-hot air spreading-segmented impregnation, which significantly enhances the Y-axis tensile strength, and the tensile strength can reach about 28.7-30.3% of the original fiber tensile strength, which is much higher than the tensile strength of modified polyether ether ketone, indicating that the short fibers play a role in enhancing the tensile strength in the Y-axis direction, indicating the effectiveness of the scheme. In addition to optimizing the mechanical properties of the modified polyether ether ketone, it also shows excellent weather resistance, and the overall strength retention rate can reach more than 95% after aging test.

[0054] Example 2: A method for preparing a continuous fiber reinforced prepreg tape, the method comprising: 1) preparing a modified impregnation material, the modified impregnation material being composed of modified polyether ether ketone, maleic anhydride grafted compatibilizer, antioxidant B215 and N, N-azepane bisstearamide in a mass ratio of 50:1.5:1.5:0.1, the modified polyether ether ketone being heated to just melt and then mixed with other ingredients to obtain the modified impregnation material.

[0055] The modified polyether ether ketone is prepared by the following method: mixing polyether ether ketone and 98 wt% concentrated sulfuric acid in a mass ratio of 1:0.8, reacting for 2.25 h at a temperature of 55 ℃, dialyzing with ionized water until the pH is 6.8, and vacuum drying to obtain sulfonated polyether ether ketone.

[0056] Mixing the sulfonated polyether ether ketone and the modifier in a mass ratio of 1:0.4, melt blending in a twin-screw extruder at a temperature of 340 ℃ and a screw speed of 80 rpm to obtain the modified polyether ether ketone.

[0057] The modifier is furan and N, N'-(4, 4'-methylene diphenyl) bismaleimide mixed in a mass ratio of 1:1.75.

[0058] 2) Using carbon fiber continuous long fibers and carbon fiber short fibers in a mass ratio of 82:18 as base fibers, the continuous long fibers are spread out and the short fibers are evenly spread on the surface of the continuous long fibers, then pre-treating, during the pre-treating process, dissolving the modified polyether ether ketone in a 70 wt% concentrated sulfuric acid solution to prepare a pre-treating solution with a modified polyether ether ketone concentration of 8.0 wt%, evenly spraying the pre-treating solution on the base fibers, the amount of pre-treating solution being 10.0 wt% of the base fibers, washing with deionized water after standing for 5 min and drying to obtain pre-treated fibers.

[0059] 3) Air flow spreading yarn method is used to spread the pre-treated fibers, the air flow temperature is controlled at 350 ℃ and the air flow speed is 3 m / s during the air flow spreading yarn process to obtain a continuous fiber thin layer tape.

[0060] 4) segmentally impregnating the continuous fiber thin layer tape; the segmental impregnation is divided into an initial stage of moving impregnation and a final stage of permeation impregnation; the initial stage of moving impregnation controls the pulling rate of the continuous fiber thin layer tape in the molten modified impregnating material at 355-360 ℃ to be 3 m / min, and an intermediate prepreg tape is obtained after impregnation, the mass content of the matrix fiber in the intermediate prepreg tape being 92.6 wt%; the final stage of permeation impregnation controls the pulling rate of the intermediate prepreg tape in the molten modified impregnating material at 355-360 ℃ to be 1.5 m / min, and a semi-finished prepreg tape is obtained after impregnation, the mass content of the matrix fiber in the semi-finished prepreg tape being 70.2 wt%; and then natural cooling and setting in an environment with a relative humidity of ≤30 % to obtain a continuous fiber reinforced prepreg tape.

[0061] The fiber reinforced prepreg tape prepared in this example was subjected to performance detection, and the specific characterization results are as follows.

[0062] Air flow spreading uniformity detection: the fiber layer after spreading in step (1) of the example was cross-sectioned, a scanning electron microscope (SEM) was used to observe the filament distribution, 10 points were randomly selected along the axis of the continuous long fiber, the standard deviation (σ) and the average value (z) of the spread width of the continuous long fiber were measured, and the coefficient of variation (c.v.%) of the continuous long fiber was calculated by combining the standard deviation of the spread width with the average value of the spread width, the specific calculation formula being: .

[0063] Resin impregnation efficiency: three-dimensional imaging was performed on the prepreg tape to analyze the penetration rate of the resin in the fiber bundle, 1 m of the prepreg tape was randomly cut off, and the dry spot area ratio (resin-free coverage area) was counted.

[0064] Mechanical property detection: the tensile strength of the X-axis and Y-axis of the prepreg tape was respectively characterized and detected.

[0065] Durability detection in a humid heat environment: the fiber reinforced prepreg tape prepared in this example was aged for 500 h under the environmental conditions of a temperature of 85 ℃ and an environmental humidity of 85 %, and the mechanical property retention rate was tested.

[0066] The performance test results are shown in Table 2 below.

[0067] Table 2: Performance test results of the sample of Example 2

[0068] From the above table 2 characterization results, the application uses more modified prepreg in the pretreatment process, further enhances the preliminary linking effect, which makes the tensile strength of Y axis further optimized, but the X axis strength produces a more significant decline, and the coefficient of variation and dry spot rate also increase, which shows that the pretreatment process has a significant impact on the uniformity and mechanical properties of the continuous long fiber of the product.

[0069] Example 3: A method for preparing a continuous fiber reinforced prepreg tape, the method comprising: 1) adjusting the modified prepreg, the modified prepreg being composed of modified polyether ether ketone, maleic anhydride grafted compatibilizer, antioxidant B215 and N, N-ethylene bis stearamide in a mass ratio of 50:1.5:1.5:0.1, the modified polyether ether ketone is heated to just melt and then the other ingredients are mixed uniformly to obtain the modified prepreg.

[0070] The modified polyether ether ketone is prepared by the following method: mixing polyether ether ketone and 95 wt% concentrated sulfuric acid in a mass ratio of 1:1.2, uniformly, reacting at a temperature of 65 ℃ for 1.75 h, using ion water dialysis to pH 7.2, vacuum drying, to prepare sulfonated polyether ether ketone.

[0071] Mixing sulfonated polyether ether ketone and modifier in a mass ratio of 1:0.6, melt blending in a twin-screw extruder at a temperature of 360 ℃ and a screw speed of 90 rpm, to prepare modified polyether ether ketone.

[0072] The modifier is furan and N, N'-(4, 4'-methylene diphenyl) bismaleimide mixed in a mass ratio of 1:1.95.

[0073] 2) Using carbon fiber continuous long fiber and carbon fiber short fiber as base fiber in a mass ratio of 88:12, the continuous long fiber is spread and the short fiber is evenly spread on the surface of the continuous long fiber, then pretreated, the modified polyether ether ketone is dissolved in 70 wt% concentrated sulfuric acid solution to prepare a pretreatment solution with a modified polyether ether ketone concentration of 5.0 wt%, the pretreatment solution is evenly sprayed on the base fiber, the amount of pretreatment solution is 8 wt% of the base fiber, after standing for 10 min, it is washed with deionized water and dried to obtain pretreated fiber.

[0074] 3) Air flow yarn spreading method is used to spread the pretreated fiber, the air flow temperature is controlled at 360 ℃ and the air flow speed is 5 m / s during the air flow yarn spreading process, to obtain a continuous fiber thin layer tape.

[0075] 4) segmentally impregnating the continuous fiber thin layer tape; the segmental impregnation is divided into an initial stage of moving impregnation and a final stage of permeation impregnation; the initial stage of moving impregnation controls the pulling rate of the continuous fiber thin layer tape in the molten modified impregnation material at 355-360 ℃ to be 4.5 m / min, and an intermediate prepreg tape is obtained after impregnation, the mass content of the matrix fiber in the intermediate prepreg tape being 92.9 wt%; the final stage of permeation impregnation controls the pulling rate of the intermediate prepreg tape in the molten modified impregnation material at 355-360 ℃ to be 2 m / min, and a semi-finished prepreg tape is obtained after impregnation, the mass content of the matrix fiber in the semi-finished prepreg tape being 69.9 wt%; and then natural cooling and setting in an environment with a relative humidity of ≤30 % to obtain the continuous fiber reinforced prepreg tape.

[0076] The fiber reinforced prepreg tape prepared in this example was subjected to performance detection, and the specific characterization results are as follows.

[0077] Air flow spreading uniformity detection: the fiber layer after spreading in step (1) of the example was cross-sectioned, a scanning electron microscope (SEM) was used to observe the filament distribution, 10 points were randomly selected along the axis of the continuous long fiber, the standard deviation (σ) and the average value (z) of the spread width of the continuous long fiber were measured, and the coefficient of variation (c.v.%) of the continuous long fiber was calculated based on the standard deviation of the spread width combined with the average value of the spread width, and the specific calculation formula was: .

[0078] Resin impregnation efficiency: three-dimensional imaging was performed on the prepreg tape to analyze the penetration rate of the resin in the fiber bundle, 1 m of the prepreg tape was randomly cut off, and the area ratio of the dry spots (resin-free coverage area) was counted.

[0079] Mechanical property detection: the tensile strength of the X-axis and Y-axis of the prepreg tape was respectively characterized and detected.

[0080] Durability detection in a humid heat environment: the fiber reinforced prepreg tape prepared in this example was aged for 500 h under the environmental conditions of a temperature of 85 ℃ and an environmental humidity of 85 %, and the mechanical property retention rate was tested.

[0081] The performance test results are shown in Table 3 below.

[0082] Table 3: Performance test results of the sample of Example 3

[0083] From the characterization results in Table 3 above, the modified impregnation material used in the pretreatment process is relatively reduced in this example, which does not have a significant impact on the variation coefficient, the dry spot rate and the X-axis tensile strength of the product, but has a very significant impact on the Y-axis tensile strength. It can be seen that the pretreatment process is extremely critical for the construction of the product with good Y-axis tensile performance.

[0084] Comparative Example 1: Based on Example 1, this example does not perform the pretreatment described in step 2), and is compared with Example 1 in the transverse direction. The following comparison groups are specifically set.

[0085] Table 4: Comparison of the preparation processes of Comparative Example 1 and Example 1 in the transverse direction:

[0086] The products of each group are subjected to the same experimental characterization, specifically including: airflow spreading uniformity detection: after the fiber layer is spread by the step (1) of the example, a cross-section slice is cut, a scanning electron microscope (SEM) is used to observe the filament distribution, 10 points are randomly selected along the axis of the continuous long fiber, the standard deviation (σ) of the spread width of the continuous long fiber and the average value (z) of the spread width of the continuous long fiber are measured, and the coefficient of variation (c.v.%) of the continuous long fiber is calculated by combining the standard deviation of the spread width with the average value of the spread width. The specific calculation formula is: .

[0087] Resin impregnation efficiency: three-dimensional imaging is performed on the prepreg tape to analyze the penetration rate of the resin in the fiber bundle. A 1 m prepreg tape is randomly cut, and the dry spot area ratio (resin-free coverage area) is counted.

[0088] Mechanical property detection: the tensile strength of the X-axis and Y-axis of the prepreg tape is respectively characterized and detected.

[0089] Durability detection in a humid heat environment: the fiber reinforced prepreg tape prepared in this example is aged for 500 h under the environmental conditions of a temperature of 85 ℃ and an environmental humidity of 85 %, and the mechanical property retention rate is tested.

[0090] The performance test results are shown in Table 5 below.

[0091] Table 5: Performance test results of the sample of Comparative Example 1:

[0092] From the characterization results in Table 5 above, it can be clearly seen that the pretreatment process of the present application has a very significant effect on the preliminary distribution and fixation of long and short fibers. If effective pretreatment is not performed, the subsequent steps are the same as Example 1, and a very large performance difference will also be produced. Although the X-axis difference is relatively small, the Y-axis performance difference is as high as several times.

[0093] Comparative Example 2: Based on Example 1, the airflow spreading process in step 3) is controlled in this example, and is compared in the transverse direction. The following comparison groups are specifically set.

[0094] Table 6: Comparison of the preparation processes of Comparative Example 2 and Example 1 in the transverse direction:

[0095] The same experimental characterization was performed on the products of each group, specifically including: airflow spreading uniformity detection: after the fiber layer was spread by the step (1) of the example, a cross-section slice was made, a scanning electron microscope (SEM) was used to observe the filament distribution, 10 points were randomly selected along the axis of the continuous long fiber, the standard deviation (σ) of the spread width of the continuous long fiber and the average value (z) of the spread width were measured, and the coefficient of variation (c.v.%) of the continuous long fiber was calculated by combining the standard deviation of the spread width with the average value of the spread width, and the specific calculation formula was: .

[0096] Resin impregnation efficiency: three-dimensional imaging was performed on the prepreg tape to analyze the penetration rate of the resin in the fiber bundle, 1 m of the prepreg tape was randomly cut, and the area ratio of the dry spots (resin-free coverage area) was counted.

[0097] Mechanical property detection: the tensile strength of the X-axis and Y-axis of the prepreg tape was respectively characterized and detected.

[0098] Durability detection in a humid heat environment: the fiber reinforced prepreg tape prepared in this example was aged for 500 h under the environmental conditions of a temperature of 85 ℃ and an environmental humidity of 85 %, and the mechanical property retention rate was tested.

[0099] The performance test results are shown in Table 7 below.

[0100] Table 7: Performance test results of the sample of Comparative Example 2:

[0101] From the above characterization results in Table 7, it can be clearly seen that using room temperature airflow for airflow spreading will significantly increase the coefficient of variation of the product distribution uniformity, increase the dry spot rate, and dramatically decrease the X-axis tensile strength. However, due to the possible generation of more obliquely distributed fibers or the entanglement and twisting of the continuous long fibers, the Y-axis supporting tensile effect is generated, but the comprehensive performance obviously does not meet the expected performance of the present application. Using slightly lower temperature hot air airflow spreading also has similar problems, but the relative degree is reduced. Using excessively high temperature hot air airflow spreading significantly affects the distribution of short fibers, possibly generating less agglomeration and bunching, resulting in a slight increase in the coefficient of variation, and although the X-axis tensile strength decreases at a smaller rate, it is still at a relatively optimal level, but the Y-axis tensile strength decreases at a very large rate, indicating that the temperature during the airflow spreading process has a significant effect.

[0102] Comparative Example 3: based on Example 1, the impregnation process in step 4) was controlled, and the following comparative groups were set up for horizontal comparison.

[0103] Table 8: Horizontal comparison table of the preparation processes of Comparative Example 3 and Example 1:

[0104] The same experimental characterization was performed on the products of each group, specifically including: airflow spreading uniformity detection: after the fiber layer was spread by the step (1) of the example, a cross-section slice was made, a scanning electron microscope (SEM) was used to observe the filament distribution, 10 points were randomly selected along the axis of the continuous long fibers, the standard deviation (σ) of the spread width of the continuous long fibers and the average value (z) of the spread width were measured, and the coefficient of variation (c.v.%) of the continuous long fibers was calculated by combining the standard deviation of the spread width with the average value of the spread width, and the specific calculation formula was: .

[0105] Resin impregnation efficiency: three-dimensional imaging was performed on the prepreg tape to analyze the penetration rate of the resin in the fiber bundle, 1 m of the prepreg tape was randomly cut, and the dry spot area ratio (resin-free coverage area) was counted.

[0106] Mechanical property detection: the tensile strength of the X-axis and Y-axis of the prepreg tape was respectively characterized and detected.

[0107] Durability detection in a humid heat environment: the fiber reinforced prepreg tape prepared in this example was aged for 500 h under the environmental conditions of a temperature of 85 ℃ and an environmental humidity of 85 %, and the mechanical property retention rate was tested.

[0108] The performance test results are shown in Table 9 below.

[0109] Table 9: Performance test results of the sample of Comparative Example 3:

[0110] As can be clearly seen from the characterization results in Table 9 above, the dipping process, as a core process of the technical solution of the present application, also has a major impact on the performance of the product. The segmented dipping is a key process for controlling the distribution of long and short fibers. Using too small an initial segment pulling speed will cause the distribution form and axis direction of the short fibers to deviate from the expected target after the initial coating and fixation of the short fibers, but too large a pulling speed may cause the continuous long fibers to curl or even stage. For a conventional continuous fiber thin layer tape, the impact of too large a pulling speed is not significant, but for the continuous fiber thin layer tape of the present application, due to the formation of link points in the pretreatment process, too large a pulling speed will likely cause the link points to be close together, and the fibers between the link points to bend, resulting in a significant decrease in performance.

[0111] Comparative Example 4: based on Example 1, only the impregnated material was adjusted in this example.

[0112] Table 10: horizontal comparison table of the preparation processes of Comparative Example 4 and Example 1:

[0113] The products of each group are subjected to the same experimental characterization, specifically including: airflow spreading uniformity detection: after the fiber layer is spread by the step (1) of the example, a cross-section slice is made, a scanning electron microscope (SEM) is used to observe the filament distribution, 10 points are randomly selected along the axis of the continuous long fiber, the standard deviation (σ) of the spread width of the continuous long fiber and the average value (z) of the spread width of the continuous long fiber are measured, and the coefficient of variation (c.v.%) of the continuous long fiber is calculated by combining the standard deviation of the spread width with the average value of the spread width, and the specific calculation formula is: .

[0114] Resin impregnation efficiency: three-dimensional imaging is performed on the prepreg tape to analyze the penetration rate of the resin in the fiber bundle, 1 m of the prepreg tape is randomly cut, and the dry spot area ratio (resin-free coverage area) is counted.

[0115] Mechanical property detection: the tensile strength of the X-axis and Y-axis of the prepreg tape is respectively characterized and detected.

[0116] Durability detection in a humid heat environment: the fiber reinforced prepreg tape prepared in this example is aged for 500 h under the environmental conditions of a temperature of 85 ℃ and an environmental humidity of 85 %, and the mechanical property retention rate is tested.

[0117] The performance test results are shown in Table 11 below.

[0118] Table 11: Performance test results of the sample of Comparative Example 4:

[0119] From the characterization results in Table 11 above, it can be clearly seen that the modified polyether ether ketone of the application has a significant effect on the performance of the product. Because the bonding strength of polyether ether ketone itself with carbon fiber is limited, it is difficult to play a good load transfer and reinforcement role, and the weather resistance is also much weaker than the modified polyether ether ketone constructed by the application, which leads to a sharp decline in strength retention rate after humid heat aging.

[0120] In summary, it can be clearly seen that for the technical solution of the application, to prepare high-quality products is the effective optimization formed by the synergistic cooperation of pretreatment, hot air airflow spreading and segmented immersion plating.

Claims

1. A method for preparing a continuous fiber-reinforced prepreg tape, characterized in that, The method includes: 1) The matrix fibers are pretreated to obtain pretreated fibers; 2) The pretreated fibers are spread using the air-flow spreading method to obtain a continuous fiber thin strip; 3) The continuous fiber thin-layer tape is subjected to segmented impregnation reinforcement treatment, followed by cooling and shaping to obtain a continuous fiber reinforced prepreg tape; Step 1) The preprocessing process is as follows: The modified impregnating material was dissolved in concentrated sulfuric acid solution to prepare a pretreatment solution. The pretreatment solution was evenly atomized and sprayed onto the matrix fiber. After standing for 5 to 10 minutes, it was washed with deionized water and dried. Step 3) The segmented impregnation process involves placing the continuous fiber thin strip in a protective atmosphere and impregnating it with melt-modified impregnating material. The modified impregnating material includes modified polyetheretherketone; Step 1) The matrix fiber is carbon fiber; The carbon fiber is a mixture of continuous long fibers and chopped fibers; The continuous long fiber is ≥200 m; The length of the chopped fibers is 5–15 mm; In step 2), the airflow temperature is controlled at 350–380 °C and the airflow velocity is controlled at 3–5 m / s during the yarn unfolding process. Step 3) The segmented impregnation is divided into initial motion impregnation and final penetration impregnation; The initial impregnation process controls the traction speed of the continuous fiber thin film in the melt-modified impregnating material to be 3–5 m / min, resulting in an intermediate prepreg tape with a matrix fiber content of 92–95 wt% after impregnation. The final stage of the impregnation process controls the traction rate of the intermediate prepreg tape in the melt-modified impregnating material to be 1.5–2.5 m / min. After impregnation, a semi-finished prepreg tape is obtained, in which the matrix fiber content is 68–72 wt%. The modified impregnating material is prepared by the following method: Polyether ether ketone and 95–98 wt% concentrated sulfuric acid were mixed evenly at a mass ratio of 1:(0.8–1.2) and reacted at an environment of 55–65 °C for 1.75–2.25 h. The mixture was then dialyzed with deionized water until the pH reached 6.8–7.2 and dried under vacuum to prepare sulfonated polyether ether ketone. Sulfonated polyether ether ketone and modifier are mixed evenly at a mass ratio of 1:(0.4-0.6), and melt-blended in a twin-screw extruder under environmental conditions of 340-360 ℃ and screw speed of 80-90 rpm to prepare modified polyether ether ketone; The modifier is a mixture of furan and N,N'-(4,4'-methylenediphenyl)bismaleimide in a mass ratio of 1:(1.75-1.95).

2. The method for preparing a continuous fiber reinforced prepreg tape according to claim 1, characterized in that, The proportion of short-cut fibers in the matrix fibers is 12-18 wt%.

3. The method for preparing a continuous fiber reinforced prepreg tape according to claim 1, characterized in that, In the preprocessing process described in step 1): The concentrated sulfuric acid is industrial concentrated sulfuric acid with a sulfuric acid content ≥ 70 wt%; The concentration of the modified impregnating agent in the pretreatment solution is 5–8 wt%; The amount of the pretreatment solution used is 8-10 wt% of the matrix fiber.

4. The method for preparing a continuous fiber reinforced prepreg tape according to claim 1, characterized in that, During the cooling and shaping process described in step 3), the relative humidity of the environment is controlled to be ≤30%.

5. A continuous fiber-reinforced prepreg tape prepared by any one of claims 1 to 4.

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