An aqueous sizing modified organic fiber and its preparation method

Abstract

The present invention relates to an aqueous sizing modified organic fiber and a preparation method thereof. The aqueous sizing modified organic fiber comprises a fiber body and a sizing layer autonomously adhered to the surface of the fiber body. The fiber body comprises aramid fiber, poly(p-phenylene benzobisoxazole) (PBO) fiber, polyester fiber and polyamide fiber. The thickness of the sizing layer is 3.0 - 5.33 nm, and the interfacial shear strength between the aqueous sizing modified aromatic organic fiber and epoxy resin is 54.4 - 65.22 MPa. Preparation method: Immerse the fiber body in a sizing agent, take it out, wash with water and dry it to form a sizing layer on the surface of the fiber body, thereby obtaining the aqueous sizing modified organic fiber. In the present invention, by controlling the pH value of the sizing agent, the thickness of the sizing layer on the fiber surface is controlled to be 3.0 - 5.33 nm, so that the sized modified organic fiber and epoxy resin have excellent interfacial bonding properties.

Description

Technical Field

[0001] The present invention belongs to the technical field of surface modification of organic fibers, and relates to an aqueous sizing modified organic fiber and a preparation method thereof. Background Art

[0002] Organic fibers such as aramid fibers and PBO fibers have high specific strength and specific modulus and excellent mechanical properties. Therefore, they are widely used as reinforcing bodies in composite materials. However, while the rigid crystalline structure of the organic fiber molecular chain endows it with excellent mechanical properties, it also leads to high chemical inertness on the fiber surface, making it difficult to undergo chemical reactions with the resin matrix, resulting in poor interfacial bonding performance between the fiber and the resin. Therefore, it is necessary to perform surface modification on the organic fiber to improve the interfacial bonding strength between the fiber and the resin.

[0003] A variety of modification methods for organic fibers have been reported, including chemical grafting modification, physical modification, construction of nanostructures, etc. However, these methods are complex and cumbersome in the modification process, and the modification time is more than 20 hours, which cannot meet the requirements of continuous fiber modification. The sizing method is a commonly used fiber surface treatment method, and its modification method is fast and convenient. By using the wettability and viscosity of the sizing agent to apply the sizing, continuous in-situ modification of the fiber can be achieved. However, the sizing method for modifying fibers uses the viscosity and surface tension of the sizing agent to act on the fiber surface, and it is impossible to achieve a sizing technology at the molecular scale, which will result in a relatively large thickness of the sizing layer formed on the fiber surface, generally exceeding 10 nm. According to the different solvents, the sizing method can be divided into three categories: solvent-based sizing agents, emulsion-based sizing agents, and water-based sizing agents. Solvent-based sizing agents are prepared by dissolving resins in organic solvents to complete the preparation of the sizing agent. Literature (Proceedings of the (International Symposium on Materials Science, 2013, 34: 333-340.) The sizing agent is prepared by dissolving epoxy resin in an organic solvent, and the thickness of the sizing layer is about 100 nm. In addition, since the solvent-based sizing agent uses an organic solvent, it is volatile, which is likely to cause harm to the human body, environmental pollution and safety hazards. At the same time, the evaporation of the solvent will change the concentration of the sizing agent. In contrast, the solvents of emulsion-type and water-based sizing agents are water, which will not cause harm to the human body and the environment, and have the advantages of safety and environmental protection. The literature (Composites Part B: Engineering, 2022, 243: 110141.) uses epoxy resin emulsion nanoparticles to size and modify fibers. Since the size of the epoxy resin in the sizing agent is at the nanometer level, the thickness of the sizing layer is reduced to about 20 nm. The interfacial shear strength between the sized and modified fibers and the resin is about 50 MPa. However, the emulsion-type sizing agent is prone to demulsification during high-speed stirring, resulting in reduced stability. The water-soluble sizing agent does not require the addition of an emulsifier, and the process of modifying fibers is simple, with broader application prospects. However, the water-soluble sizing agent requires chemical grafting treatment of the resin, and the process is cumbersome. In addition, the resin will remain on the equipment, increasing the maintenance cost of the equipment. Polymers have a flexible chemical structure. Using a water-soluble polymer with a catechol structure to replace the resin can solve the above problems. This polymer structure has adhesiveness and can quickly adhere to the surface of various substrates to complete the surface modification of the substrates. Chinese Patent No. 202010275716.8 provides a surface-modified fiber and its preparation method, and discloses a method for modifying fibers with a polymer based on a catechol structure. The polymer is dissolved in deionized water to prepare a sizing agent, and then the fibers are soaked in the sizing agent to complete the sizing modification of the fibers. However, the thickness of the prepared sizing layer is relatively high (exceeding 180 nm), and the interfacial shear strength (IFSS) between the modified fibers and the resin is about 20 MPa. The thickness of the polymer sizing layer has a great influence on the interfacial shear strength between the sized and modified fibers and the resin. This is because the cohesive energy of this polymer is relatively low, and an overly thick polymer layer is prone to interface failure first, resulting in a relatively low interfacial bond between the fibers and the resin. The polymer monolayer contains a large number of catechol structures and amino groups. The catechol structure in the polymer can drive the polymer to quickly and autonomously adhere to the surface of organic fibers. At the same time, the amino groups of the polymer can undergo a ring-opening reaction with the epoxy functional groups of epoxy resin, enhancing the interfacial bond strength between the fibers and the resin. However, it is relatively difficult to reduce the thickness of the polymer sizing layer and form a monolayer on the fiber surface because the catechol polymer has adhesiveness. After it autonomously adheres to the fiber surface, more polymer may continue to adhere to the fiber surface, resulting in multiple layers of polymer on the fiber surface and increasing the thickness of the sizing layer on the fiber surface.Therefore, attempting to reduce the thickness of the polymer sizing layer and form a monomolecular polymer layer on the fiber surface is expected to further enhance the interfacial bonding strength between the organic fiber and the resin. Summary of the Invention

[0004] The object of the present invention is to solve the problems existing in the prior art and provide an aqueous sizing modified organic fiber and its preparation method.

[0005] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] An aqueous sizing modified organic fiber includes a fiber body and a sizing layer that autonomously adheres to the surface of the fiber body. The fiber body includes organic fibers such as aramid fiber, PBO fiber, polyester fiber, and nylon fiber. The sizing layer is a monomolecular polymer layer with a thickness of 3.0 - 5.33 nm, and the interfacial shear strength between the aqueous sizing modified aramid fiber and epoxy resin is 54.4 - 65.22 MPa;

[0007] The structure of the polymer in the sizing layer is as follows:

[0008]

[0009] Wherein, x and y are positive integers, and 300 ≤ x ≤ 800, 800 ≤ y ≤ 929, x:y = 1:1 - 3; this polymer has water solubility and can be dissolved in an acetate buffer solution to prepare an aqueous sizing agent, and the solvent of the sizing agent is deionized water.

[0010] As a preferred technical solution:

[0011] For the aqueous sizing modified organic fiber as described above, the fiber body and the sizing layer are connected by hydrogen bonds, cation - π, π - π stacking, and hydrophobic interactions, specifically manifested as the polymer molecules rapidly and autonomously adhering to the surface of the fiber body through the above - mentioned interactions.

[0012] The present invention also provides a preparation method of an aqueous sizing modified organic fiber. The fiber body is immersed in the sizing agent, taken out, washed with water, and dried to form a sizing layer on the surface of the fiber body, thus obtaining the aqueous sizing modified aramid fiber;

[0013] The sizing agent is prepared by dissolving the polymer in a buffer solution. The pH value of the buffer solution is 3.7 - 5.5, the solvent of the buffer solution is deionized water, and the concentration of the polymer in the sizing agent is 0.4 - 0.6 mg / mL.

[0014] As a preferred technical solution:

[0015] A preparation method of water-phase sized modified organic fibers as described above, wherein the soaking time of the fiber body in the sizing agent is 10 to 60 s. This range is set because the polymer in the sizing agent modifies aramid fibers quickly. Such a setting is conducive to in-situ and continuous modification of aramid fibers in industrial production.

[0016] A preparation method of water-phase sized modified organic fibers as described above, wherein the buffer solution is an acetic acid buffer solution, which is prepared by dissolving sodium acetate and acetic acid in deionized water.

[0017] A preparation method of water-phase sized modified organic fibers as described above, wherein the mass ratio of sodium acetate to acetic acid is 0.152 to 3.167:1.

[0018] A preparation method of water-phase sized modified organic fibers as described above, wherein after the fiber body is soaked in the sizing agent, it needs to be washed with water to remove the excess sizing agent on the surface, and the washing time is 10 to 50 s.

[0019] A preparation method of water-phase sized modified organic fibers as described above, wherein the drying temperature is 120 to 180 °C and the time is 20 to 180 s.

[0020] Principle of the invention:

[0021] In the existing preparation method of water-phase modified organic fibers, the thickness of the sizing layer on the fiber surface is usually large, more than 20 nm. This is because the existing water-phase sizing modification technology uses the adhesion and surface tension of the sizing agent to make the sizing agent act on the fiber surface, without designing modified fibers from a molecular perspective. Therefore, the thickness of the sizing layer is usually large. Through a large number of experiments, the present invention unexpectedly finds that when the thickness of the sizing layer is controlled within 3.0 to 5.33 nm, the interfacial shear strength between the sized modified organic fibers and epoxy resin can be significantly improved. In this case, the polymer monolayer adheres to the surface of the organic fiber autonomously, completing the surface modification of the fiber. When the thickness of the sizing layer on the fiber surface is higher, a large amount of polymer adheres to the surface of the organic fiber autonomously, and the inside of the sizing layer shows a layer-by-layer stacking of polymers. At this time, the interfacial strength between the fiber and the resin depends not only on the bonding strength between the fiber and the resin and the sizing polymer, but also on the interaction between the polymer chains and the polymers. When too much polymer is assembled on the fiber surface, the thickness of the sizing layer on the fiber surface increases. Due to the poor cohesive energy of the polymer, when interfacial failure occurs between the fiber and the resin, the failure first occurs in the polymer layer, resulting in a low interfacial shear strength between the fiber and the resin. On the contrary, when the thickness of the sizing layer is too low (less than 3 nm), the polymer may not completely cover the fiber surface, and the bonding strength between the sized modified organic fibers and epoxy resin cannot reach the best effect.

[0022] The interactions between catechol-structured polymers and organic fibers such as aramid fibers and PBO fibers may involve hydrogen bonding, cation-π, π-π stacking, hydrophobic interactions, etc. The change of pH will affect the ionization structure of catechol-structured polymers and the size of the hydrated particle diameter of the polymer (which can be confirmed by the data of the hydrated particle diameter measured by dynamic light scattering). After the hydrated particle diameter of the polymer increases, the hydrophobic interaction will be weakened. On the one hand, the stronger the acidity, the less likely the catechol-structured polymer is to ionize, which is beneficial to the hydrogen bonding and hydrophobic interactions between the polymer and the fiber. On the other hand, pH also affects the hydration of the polymer. When the pH value is lower, the degree of protonation of the amino groups on the polymer is higher and the hydration is stronger, thus weakening the hydrophobic interaction between the polymer and aramid. By regulating the balance of these two factors of the solution pH value, the polymer monolayer can be autonomously adhered to the surface of the organic fiber, and the thickness of the sizing layer on the aramid fiber can be controlled within 3-5 nm. The two factors compete and balance with each other, so that the polymer binds strongest to the fiber at a specific pH, and the interfacial modification effect is the best.

[0023] When the concentration of the polymer in the sizing agent is determined, the pH value of the sizing agent will affect the interaction between the polymer and the organic fiber, thereby affecting the thickness of the sizing layer. For example Figures 4 to 6As shown in the figure, according to the experimental results of quartz crystal microbalance (QCM), when the concentration of the polymer in the sizing agent is 0.5 mg / mL, after changing the pH value of the sizing agent solution, the in-situ frequency change (Δf) of the quartz crystal microbalance chip is different. This is because the adhesion force between the polymer and the fiber is different under different pH values. The forces between the polymer with catechol structure and the fiber include hydrogen bonds, cation-π, π-π stacking, hydrophobic interactions, etc. These forces are related to the pH value of the solution. When the molar feed ratio of DMA in the polymer is 25% and 35%, the force between the polymer solution and the fiber is the strongest when the pH value of the polymer solution is 4.0. When the molar feed ratio of DMA in the polymer is 50%, the force between the polymer solution and the fiber is the strongest when the pH value of the polymer solution is 4.5. When the pH value of the solution is relatively low, the protonation degree of the amino group of the polymer is stronger, more amino groups become amine ions, and the hydration degree of the polymer is higher. This will weaken the interaction between polymers and also weaken the interaction with aramid. However, after the hydration degree increases, it will enhance the hydrogen bond interaction, cation-π and hydrophobic interaction between dopamine and aramid. According to the QCM experimental results, it can also be seen that when the adhesion of the polymer on the fiber surface reaches a certain mass, when the polymer solution continues to flow over the fiber surface, the mass of the polymer on the fiber surface will not continue to increase. In this case, it is because the hydration degree of the polymer in the aqueous phase is relatively high, which will limit the interaction between polymers, making it difficult for the polymer to self-adhere so that the force between polymers is very weak. At the same time, the amino group in the polymer is protonated, and the polymer shows the same electrical property, which will increase the repulsion between polymers. The repulsion between polymers caused by polymer hydration and amino protonation makes the polymer in the solution unable to interact with the polymer on the fiber surface. This is the fundamental reason for realizing single-molecule autonomous adhesion.

[0024] Therefore, the pH value in the sizing agent will affect the thickness of the polymer sizing layer. In the present invention, by controlling the pH value of the sizing agent, the thickness of the sizing layer on the fiber surface is controlled within 3.0 - 5.33 nm, so that the sized modified organic fiber and epoxy resin have excellent interfacial bonding properties.

[0025] Beneficial effects:

[0026] (1) The preparation method of the present invention controls the concentration of the polymer in the sizing agent and the pH value of the sizing agent, and the thickness of the sizing layer on the fiber surface is controlled within 3.0 - 5.33 nm, so that the sized modified organic fiber and epoxy resin have excellent interfacial bonding properties.

[0027] (2) The aqueous-phase sized modified organic fiber prepared by the present invention greatly improves the interfacial shear strength between the sized modified organic fiber and epoxy resin. Description of the drawings

[0028] Figure 1Hydrodynamic diameters of polymer P (25% DMA-co-75% AEMA) of Examples 1-5 in acetate buffer solutions with different pH values;

[0029] Figure 2 Hydrodynamic diameters of polymer P (35% DMA-co-65% AEMA) of Examples 6-10 in acetate buffer solutions with different pH values;

[0030] Figure 3 Hydrodynamic diameters of polymer P (50% DMA-co-50% AEMA) of Examples 11-15 in acetate buffer solutions with different pH values;

[0031] Figure 4 Adhesion of P (25% DMA-co-75% AEMA) solutions with different concentrations and pH values on the surface of organic fibers;

[0032] Figure 5 Adhesion of P (35% DMA-co-65% AEMA) solutions with different concentrations and pH values on the surface of organic fibers;

[0033] Figure 6 Adhesion of P (50% DMA-co-50% AEMA) solutions with different concentrations and pH values on the surface of organic fibers. Detailed implementation manners

[0034] The present invention will be further described below in conjunction with the detailed implementation manners. 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 this application.

[0035] The test methods related to the present invention are as follows:

[0036] Interfacial shear strength: The microsphere embedding method was used to evaluate the interfacial bonding strength between the fiber and the resin. Sample preparation process: Bisphenol A epoxy resin (E-51) and amine curing agent (5784) were mixed evenly according to a mass ratio of 2.88:1 to obtain a mixture. The water-phase sized and modified aramid fiber in the example was straightened and fixed on a polytetrafluoroethylene mold. A small amount of the mixture was dipped with a 1 mL syringe and gently dropped on the water-phase sized and modified aramid fiber. The mixture would form microspheres due to surface tension. The prepared sample was placed in an oven and cured at 80 °C for 3 h to complete the preparation of the water-phase sized and modified aramid fiber-epoxy resin microsphere composite sample. Testing process: A single water-phase sized and modified aramid fiber-epoxy resin microsphere composite was fixed on a universal tensile testing machine, and an external load was applied until the water-phase sized and modified aramid fiber was separated from the epoxy resin microspheres. The loading speed was 1 mm / min, and the embedding length of the resin was 0.2 - 0.4 mm. The interfacial shear strength IFSS was calculated according to the following formula. The average value of 20 data was taken as the final value of IFSS for each group of experiments.

[0037]

[0038] Among them, F is the external load, unit: Newton; d is the fiber diameter, unit: micron; L is the resin embedding length, unit: millimeter.

[0039] In the organic fibers of the present invention, the manufacturer of the aramid fiber is Zhonglan Chenguang Research Institute of Chemical Industry Co., Ltd., and the grade is F358B; the manufacturer of the PBO fiber is Zhonglan Chenguang Research Institute of Chemical Industry Co., Ltd., and the grade is 550 dtex; the manufacturer of the polyamide fiber is BASF, and the grade is 400 dtex; the manufacturer of the polyester fiber is Jiangnan Gaoxian, and the grade is 450 dtex.

[0040] In each example, the organic fiber monofilaments selected from the organic fiber multifilaments were used for the experiment.

[0041] Quartz crystal microbalance experiment testing process:

[0042] In order to simulate the adhesion of the polymer on the surface of the organic fiber, the organic fiber was dissolved in a concentrated sulfuric acid solution and then spin-coated on the quartz crystal microbalance chip, and each polymer solution was flowed on the chip to complete the "simulated" sizing and modification process of the organic fiber. The specific process is as follows:

[0043] The specific experimental method for testing the adhesion of polymers to the surface of organic fibers using a quartz crystal microbalance is as follows: Place the QCM chip in the sample flow cell, turn on the peristaltic pump, set the flow rate to 70 μL / min, and then flow through the experimental solutions in sequence. The flow order of the specific solutions is as follows: ① Background solution: blank acetic acid buffer solution for 600 s; ② Working solution: polymer solution with a concentration of 0.5 mg / mL for 1200 s; ③ Background solution: blank acetic acid buffer solution for 600 s. Considering environmental factors, the change in the third-order frequency of the QCM chip is selected as the experimental result.

[0044] The concentrated sulfuric acid solution of organic fibers was spin-coated on the surface of the QCM chip, and the QCM was further used to investigate the interaction between the polymer and the surface of organic fibers under different pH conditions. The change in the vibration frequency of the quartz crystal is as Figures 4 to 6 shown. If the vibration frequency of the quartz crystal decreases, it indicates that the polymer adheres to the surface of the fiber. When the QCM chip was exposed to the P(25% DMA-co-75% AEMA) solution after the baseline was stable, the in-situ frequency change (Δf) was as Figure 4 shown. When the polymer solutions with pH values of 3.7, 4.0, 4.5, 5.0, and 5.5 flowed through the QCM chip, the Δf values were 18.7 Hz, 33.2 Hz, 27.7 Hz, 24.2 Hz, and 29.4 Hz, respectively. When the QCM chip was exposed to the P(35% DMA-co-65% AEMA) solutions with pH values of 3.7, 4.0, 4.5, 5.0, and 5.5, the Δf values were as Figure 5 shown, and the Δf values were 19.1 Hz, 32.4 Hz, 24.9 Hz, 22.9 Hz, and 28.5 Hz, respectively. When the QCM chip was exposed to the P(50% DMA-co-50% AEMA) solutions with pH values of 3.7, 4.0, 4.5, 5.0, and 5.5, the Δf values were 22.3 Hz, 30.4 Hz, 32.7 Hz, 25.6 Hz, and 26.8 Hz, respectively. The QCM results show that the polymer can rapidly adhere to the surface of the fiber, meeting the conditions for sizing and modifying the fiber.

[0045] Example 1

[0046] A preparation method for water-phase sized and modified aramid fibers is as follows:

[0047] (1) Dissolve sodium acetate and acetic acid in deionized water at a mass ratio of 0.152:1 to prepare an acetic acid buffer solution with a pH value of 3.7;

[0048] (2) Dissolve the polymer in the acetic acid buffer solution in step (1) to prepare a sizing agent; the concentration of the polymer in the sizing agent is 0.4 mg / mL;

[0049] The structure of polymer P (25% DMA - co - 75% AEMA) is shown as follows:

[0050]

[0051] (3) Immerse the aramid fiber body in the sizing agent for 60 s, take it out and wash it with water for 10 s, and dry it at a temperature of 120 °C for 180 s to form a sizing layer on the surface of the fiber body, thus obtaining the water - phase sized and modified aramid fiber.

[0052] The obtained water - phase sized and modified aramid fiber includes an aramid fiber body and a sizing layer with a thickness of 3 nm that adheres autonomously to the surface of the aramid fiber body; the aramid fiber body and the sizing layer are connected by hydrogen bonds, cation - π, π - π stacking, and hydrophobic interactions; the interfacial shear strength between the water - phase sized and modified aramid fiber and epoxy resin is 60.21 MPa.

[0053] Comparative Example 1

[0054] A preparation method of water - phase sized and modified aramid fiber is basically the same as that of Example 1, except that the pH value of the acetic acid buffer solution prepared in step (1) is 3.0. The thickness of the sizing layer on the surface of the obtained water - phase sized and modified aramid fiber is 0.3 nm, and the interfacial shear strength between the water - phase sized and modified aramid fiber and epoxy resin is 30.23 MPa.

[0055] Comparing Example 1 with Comparative Example 1, it can be seen that the interfacial bonding strength between the sized and modified aramid fiber in Comparative Example 1 and epoxy resin is significantly lower than that in Example 1. This is because when the pH value is lower, the degree of polymer hydration increases, which reduces the interaction between polymers and increases the repulsion between polymers with the same charge due to the increased protonation of polymer amino groups. The repulsion between polymers caused by polymer hydration and amino protonation makes the polymers in the solution unable to interact with the polymers on the fiber surface, and the polymers are difficult to adhere autonomously to the surface of the aramid fiber, resulting in a reduction in the thickness of the sizing layer on the fiber surface and poor modification effect on the fiber, so the interfacial shear strength is lower.

[0056] Comparative Example 2

[0057] A preparation method of water - phase sized and modified aramid fiber is basically the same as that of Example 1, except that the pH value of the acetic acid buffer solution prepared in step (1) is 6.0. The thickness of the sizing layer on the surface of the obtained water - phase sized and modified aramid fiber is 0.45 nm, and the interfacial shear strength between the water - phase sized and modified aramid fiber and epoxy resin is 28.5 MPa.

[0058] Comparing Example 1 with Comparative Example 2, it can be seen that the interfacial bonding strength between the sized and modified aramid fiber and epoxy resin in Comparative Example 2 is significantly lower than that in Example 1. This is because after the pH value increases, the ionization degree of phenolic hydroxyl groups is high, which seriously weakens the hydrogen bond and hydrophobic interactions between the polymer and the fiber. The driving force for the polymer to adhere to the fiber is insufficient, making it difficult for the polymer to adhere to the fiber surface, resulting in poor modification effect on the fiber. Therefore, the interfacial shear strength is relatively low.

[0059] Example 2

[0060] A preparation method of water-phase sized and modified aramid fiber is as follows:

[0061] (1) Dissolve sodium acetate and acetic acid in deionized water at a mass ratio of 0.271:1 to prepare an acetic acid buffer solution with a pH value of 4.

[0062] (2) Dissolve the polymer in the acetic acid buffer solution of step (1) to prepare a sizing agent; the concentration of the polymer in the sizing agent is 0.55 mg / mL.

[0063] The structure of the polymer is as follows:

[0064]

[0065] (3) Immerse the aramid fiber body in the sizing agent for 50 s, take it out and wash it with water for 20 s, and dry it at 130 °C for 150 s to form a sizing layer on the surface of the fiber body, thus obtaining the water-phase sized and modified aramid fiber.

[0066] The obtained water-phase sized and modified aramid fiber includes an aramid fiber body and a sizing layer with a thickness of 5.33 nm that adheres to the surface of the aramid fiber body autonomously; the aramid fiber body and the sizing layer are connected through hydrogen bonds, cation-π and π-π stacking, and hydrophobic interactions; the interfacial shear strength between the water-phase sized and modified aramid fiber and epoxy resin is 63.23 MPa.

[0067] Example 3

[0068] A preparation method of water-phase sized and modified aramid fiber is as follows:

[0069] (1) Dissolve sodium acetate and acetic acid in deionized water at a mass ratio of 0.845:1 to prepare an acetic acid buffer solution with a pH value of 4.5.

[0070] (2) Dissolve the polymer in the acetic acid buffer solution of step (1) to prepare a sizing agent; the concentration of the polymer in the sizing agent is 0.5 mg / mL.

[0071] The structure of the polymer is as follows:

[0072]

[0073] (3) Immerse the aramid fiber body in the sizing agent for 35 s, take it out and wash it with water for 30 s, and dry it at a temperature of 145 °C for 100 s to form a sizing layer on the surface of the fiber body, thus obtaining the water-phase sized and modified aramid fiber.

[0074] The obtained water-phase sized and modified aramid fiber comprises an aramid fiber body and a sizing layer with a thickness of 4.44 nm that autonomously adheres to the surface of the aramid fiber body; the aramid fiber body and the sizing layer are connected by hydrogen bonds, cation-π and π-π stacking, and hydrophobic interactions; the interfacial shear strength between the water-phase sized and modified aramid fiber and epoxy resin is 58.94 MPa.

[0075] Example 4

[0076] A preparation method of water-phase sized and modified PBO fiber, the specific steps are as follows:

[0077] (1) Dissolve sodium acetate and acetic acid in deionized water at a mass ratio of 1.824:1 to prepare an acetic acid buffer solution with a pH value of 5.

[0078] (2) Dissolve the polymer in the acetic acid buffer solution of step (1) to prepare a sizing agent; the concentration of the polymer in the sizing agent is 0.52 mg / mL.

[0079] The structure of the polymer is shown as follows:

[0080]

[0081] (3) Immerse the PBO fiber body in the sizing agent for 25 s, take it out and wash it with water for 40 s, and dry it at a temperature of 160 °C for 50 s to form a sizing layer on the surface of the fiber body, thus obtaining the water-phase sized and modified PBO fiber.

[0082] The obtained water-phase sized and modified PBO fiber comprises a PBO fiber body and a sizing layer with a thickness of 4.72 nm that autonomously adheres to the surface of the PBO fiber body; the PBO fiber body and the sizing layer are connected by hydrogen bonds, cation-π and π-π stacking, and hydrophobic interactions; the interfacial shear strength between the water-phase sized and modified PBO fiber and epoxy resin is 56.66 MPa.

[0083] Example 5

[0084] A preparation method of water-phase sized and modified PBO fiber, the specific steps are as follows:

[0085] (1) Dissolve sodium acetate and acetic acid in deionized water at a mass ratio of 3.167:1 to prepare an acetic acid buffer solution with a pH value of 5.5.

[0086] (2) Dissolve the polymer in the acetic acid buffer solution of step (1) to prepare a sizing agent; the concentration of the polymer in the sizing agent is 0.45 mg / mL;

[0087] The structure of the polymer is as follows:

[0088]

[0089] (3) Immerse the PBO fiber body in the sizing agent for 10 s, take it out and wash it with water for 50 s, and dry it at 180 °C for 30 s to form a sizing layer on the surface of the fiber body, thus obtaining the water-phase sized and modified PBO fiber.

[0090] The obtained water-phase sized and modified PBO fiber includes an aramid fiber body and a sizing layer with a thickness of 3.88 nm that adheres to the surface of the PBO fiber body by itself; the PBO fiber body and the sizing layer are connected by hydrogen bonds, cation-π and π-π stacking, and hydrophobic interactions; the interfacial shear strength between the water-phase sized and modified PBO fiber and epoxy resin is 54.4 MPa.

[0091] As Figure 1 shown, in acetic acid buffer solutions with pH values of 3.7, 4.0, 4.5, 5.0, and 5.5, the hydrodynamic diameters of P(25% DMA-co-75% AEMA) are 9.69, 15.68, 13.54, 19.61, and 18.16 nm respectively. P(25% DMA-co-75% AEMA) can be well dispersed in the acetic acid buffer solution, meeting the fiber sizing conditions.

[0092] Example 6

[0093] A preparation method of water-phase sized and modified PBO fiber, the specific steps are as follows:

[0094] (1) Dissolve sodium acetate and acetic acid in deionized water at a mass ratio of 0.152:1 to prepare an acetic acid buffer solution with a pH value of 3.7;

[0095] (2) Dissolve the polymer in the acetic acid buffer solution of step (1) to prepare a sizing agent; the concentration of the polymer in the sizing agent is 0.43 mg / mL;

[0096] The structure of the polymer P(35% DMA-co-65% AEMA) is as follows:

[0097]

[0098] (3) Immerse the PBO fiber body in the sizing agent for 60 s, take it out and wash it with water for 10 s, and dry it at 120 °C for 180 s to form a sizing layer on the surface of the fiber body, thus obtaining the water-phase sized and modified PBO fiber.

[0099] The prepared aqueous sizing modified PBO fiber comprises a PBO fiber body and a sizing layer with a thickness of 3.03 nm that adheres to the surface of the PBO fiber body autonomously; the PBO fiber body and the sizing layer are connected by hydrogen bonds, cation-π and π-π stacking, and hydrophobic interactions; the interfacial shear strength between the aqueous sizing modified PBO fiber and epoxy resin is 61.95 MPa.

[0100] Example 7

[0101] A preparation method of an aqueous sizing modified PBO fiber is as follows:

[0102] (1) Sodium acetate and acetic acid are dissolved in deionized water at a mass ratio of 0.271:1 to prepare an acetic acid buffer solution with a pH value of 4.

[0103] (2) The polymer is dissolved in the acetic acid buffer solution in step (1) to prepare a sizing agent; the concentration of the polymer in the sizing agent is 0.6 mg / mL.

[0104] The structure of the polymer is as follows:

[0105]

[0106] (3) The PBO fiber body is immersed in the sizing agent for 50 s, taken out and washed with water for 20 s, and dried at a temperature of 130 °C for 150 s to form a sizing layer on the surface of the fiber body, thus obtaining the aqueous sizing modified PBO fiber.

[0107] The prepared aqueous sizing modified PBO fiber comprises a PBO fiber body and a sizing layer with a thickness of 5.2 nm that adheres to the surface of the PBO fiber body autonomously; the PBO fiber body and the sizing layer are connected by hydrogen bonds, cation-π and π-π stacking, and hydrophobic interactions; the interfacial shear strength between the aqueous sizing modified PBO and epoxy resin is 65.22 MPa.

[0108] Example 8

[0109] A preparation method of an aqueous sizing modified PBO fiber is as follows:

[0110] (1) Sodium acetate and acetic acid are dissolved in deionized water at a mass ratio of 0.845:1 to prepare an acetic acid buffer solution with a pH value of 4.5.

[0111] (2) The polymer is dissolved in the acetic acid buffer solution in step (1) to prepare a sizing agent; the concentration of the polymer in the sizing agent is 0.48 mg / mL.

[0112] The structure of the polymer is as follows:

[0113]

[0114] (3) Immerse the PBO fiber body in the sizing agent for 35 s, take it out and wash it with water for 30 s, and dry it at a temperature of 145 °C for 100 s to form a sizing layer on the surface of the fiber body, thus obtaining the water-phase sized and modified PBO fiber.

[0115] The obtained water-phase sized and modified PBO fiber comprises a PBO fiber body and a sizing layer with a thickness of 3.99 nm that adheres autonomously to the surface of the PBO fiber body; the PBO fiber body and the sizing layer are connected by hydrogen bonds, cation-π and π-π stacking, and hydrophobic interactions; the interfacial shear strength between the water-phase sized and modified PBO fiber and epoxy resin is 63.49 MPa.

[0116] Example 9

[0117] A preparation method of water-phase sized and modified PBO fiber, the specific steps are as follows:

[0118] (1) Dissolve sodium acetate and acetic acid in deionized water at a mass ratio of 1.824:1 to prepare an acetic acid buffer solution with a pH value of 5.

[0119] (2) Dissolve the polymer in the acetic acid buffer solution of step (1) to prepare a sizing agent; the concentration of the polymer in the sizing agent is 0.45 mg / mL.

[0120] The structure of the polymer is shown as follows:

[0121]

[0122] (3) Immerse the PBO fiber body in the sizing agent for 25 s, take it out and wash it with water for 40 s, and dry it at a temperature of 160 °C for 50 s to form a sizing layer on the surface of the fiber body, thus obtaining the water-phase sized and modified PBO.

[0123] The obtained water-phase sized and modified PBO fiber comprises a PBO fiber body and a sizing layer with a thickness of 3.67 nm that adheres autonomously to the surface of the PBO fiber body; the PBO fiber body and the sizing layer are connected by hydrogen bonds, cation-π and π-π stacking, and hydrophobic interactions; the interfacial shear strength between the water-phase sized and modified PBO fiber and epoxy resin is 57.24 MPa.

[0124] Example 10

[0125] A preparation method of water-phase sized and modified aramid fiber, the specific steps are as follows:

[0126] (1) Dissolve sodium acetate and acetic acid in deionized water at a mass ratio of 3.167:1 to prepare an acetic acid buffer solution with a pH value of 5.5.

[0127] (2) Dissolve the polymer in the acetic acid buffer solution of step (1) to prepare a sizing agent; the concentration of the polymer in the sizing agent is 0.52 mg / mL;

[0128] The structure of the polymer is as follows:

[0129]

[0130] (3) Immerse the aramid fiber body in the sizing agent for 10 s, take it out and wash it with water for 50 s, and dry it at 180 °C for 30 s to form a sizing layer on the surface of the fiber body, thus obtaining the water-phase sized and modified aramid fiber.

[0131] The obtained water-phase sized and modified aramid fiber comprises an aramid fiber body and a sizing layer with a thickness of 4.57 nm that adheres to the surface of the aramid fiber body autonomously; the aramid fiber body and the sizing layer are connected by hydrogen bonds, cation-π and π-π stacking, and hydrophobic interactions; the interfacial shear strength between the water-phase sized and modified aramid fiber and epoxy resin is 55.34 MPa.

[0132] As Figure 2 shown, the hydrodynamic diameters of P(35% DMA-co-65% AEMA) in acetic acid buffer solutions with pH values of 3.7, 4.0, 4.5, 5.0, and 5.5 are 11.69, 8.72, 12.31, 15.34, and 16.88 nm respectively. P(DMA-co-AEMA) can be well dispersed in the acetic acid buffer solution, and P(DMA-co-AEMA) can be dissolved in the acetic acid buffer solution for modifying aramid fibers.

[0133] Example 11

[0134] A preparation method of a water-phase sized and modified aramid fiber, the specific steps are as follows:

[0135] (1) Dissolve sodium acetate and acetic acid in deionized water at a mass ratio of 0.152:1 to prepare an acetic acid buffer solution with a pH value of 3.7;

[0136] (2) Dissolve the polymer in the acetic acid buffer solution of step (1) to prepare a sizing agent; the concentration of the polymer in the sizing agent is 0.42 mg / mL;

[0137] The structure of the polymer P(50% DMA-co-50% AEMA) is as follows:

[0138]

[0139] (3) Immerse the aramid fiber body in the sizing agent for 60 s, take it out and wash it with water for 10 s, and dry it at 120 °C for 180 s to form a sizing layer on the surface of the fiber body, thus obtaining the water-phase sized and modified aramid fiber.

[0140] The prepared aqueous phase sized modified aramid fiber comprises an aramid fiber body and a sizing layer with a thickness of 3.58 nm that autonomously adheres to the surface of the aramid fiber body; the aramid fiber body and the sizing layer are connected by hydrogen bonds and hydrophobic interactions; the interfacial shear strength between the aqueous phase sized modified aramid fiber and epoxy resin is 62.98 MPa.

[0141] Example 12

[0142] A preparation method of an aqueous phase sized modified polyester fiber, the specific steps are as follows:

[0143] (1) Dissolve sodium acetate and acetic acid in deionized water at a mass ratio of 0.271:1 to prepare an acetic acid buffer solution with a pH value of 4.

[0144] (2) Dissolve the polymer in the acetic acid buffer solution in step (1) to prepare a sizing agent; the concentration of the polymer in the sizing agent is 0.53 mg / mL.

[0145] The structure of the polymer is as follows:

[0146]

[0147] (3) Immerse the polyester fiber body in the sizing agent for 50 s, take it out and wash it with water for 20 s, and dry it at a temperature of 130 °C for 150 s to form a sizing layer on the surface of the fiber body, thus obtaining the aqueous phase sized modified polyester fiber.

[0148] The prepared aqueous phase sized modified polyester fiber comprises a polyester fiber body and a sizing layer with a thickness of 4.88 nm that autonomously adheres to the surface of the polyester fiber body; the polyester fiber body and the sizing layer are connected by hydrogen bonds, cation-π and π-π stacking, and hydrophobic interactions; the interfacial shear strength between the aqueous phase sized modified polyester fiber and epoxy resin is 61.02 MPa.

[0149] Example 13

[0150] A preparation method of an aqueous phase sized modified polyester fiber, the specific steps are as follows:

[0151] (1) Dissolve sodium acetate and acetic acid in deionized water at a mass ratio of 0.845:1 to prepare an acetic acid buffer solution with a pH value of 4.5.

[0152] (2) Dissolve the polymer in the acetic acid buffer solution in step (1) to prepare a sizing agent; the concentration of the polymer in the sizing agent is 0.6 mg / mL.

[0153] The structure of the polymer is as follows:

[0154]

[0155] (3) Immerse the polyester fiber body in the sizing agent for 35 s, take it out and wash it with water for 30 s, and dry it at a temperature of 145 °C for 100 s to form a sizing layer on the surface of the fiber body, thus obtaining the water-phase sized modified polyester fiber.

[0156] The obtained water-phase sized modified polyester fiber comprises a polyester fiber body and a sizing layer with a thickness of 5.25 nm that autonomously adheres to the surface of the polyester fiber body; the polyester fiber body and the sizing layer are connected by hydrogen bonds, cation-π and π-π stacking, and hydrophobic interactions; the interfacial shear strength between the water-phase sized modified polyester fiber and epoxy resin is 64.12 MPa.

[0157] Example 14

[0158] A preparation method of water-phase sized modified polyamide fiber, the specific steps are as follows:

[0159] (1) Dissolve sodium acetate and acetic acid in deionized water at a mass ratio of 1.824:1 to prepare an acetic acid buffer solution with a pH value of 5.

[0160] (2) Dissolve the polymer in the acetic acid buffer solution of step (1) to prepare a sizing agent; the concentration of the polymer in the sizing agent is 0.45 mg / mL.

[0161] The structure of the polymer is as follows:

[0162]

[0163] (3) Immerse the polyamide fiber body in the sizing agent for 25 s, take it out and wash it with water for 40 s, and dry it at a temperature of 160 °C for 50 s to form a sizing layer on the surface of the fiber body, thus obtaining the water-phase sized modified polyamide fiber.

[0164] The obtained water-phase sized modified polyamide fiber comprises a polyamide fiber body and a sizing layer with a thickness of 4.11 nm that autonomously adheres to the surface of the polyamide fiber body; the polyamide fiber body and the sizing layer are connected by hydrogen bonds and hydrophobic interactions; the interfacial shear strength between the water-phase sized modified polyamide fiber and epoxy resin is 59.16 MPa.

[0165] Example 15

[0166] A preparation method of water-phase sized modified polyamide fiber, the specific steps are as follows:

[0167] (1) Dissolve sodium acetate and acetic acid in deionized water at a mass ratio of 3.167:1 to prepare an acetic acid buffer solution with a pH value of 5.5.

[0168] (2) Dissolve the polymer in the acetic acid buffer solution of step (1) to prepare a sizing agent; the concentration of the polymer in the sizing agent is 0.48 mg / mL;

[0169] The structure of the polymer is as follows:

[0170]

[0171] (3) Immerse the aramid fiber body in the sizing agent for 10 s, take it out and wash it with water for 50 s, and dry it at 180 °C for 30 s to form a sizing layer on the surface of the fiber body, thus obtaining the water-phase sized modified polyamide fiber.

[0172] The obtained water-phase sized modified polyamide fiber includes a polyamide fiber body and a sizing layer with a thickness of 4.3 nm that autonomously adheres to the surface of the polyamide fiber body; the polyamide fiber body and the sizing layer are connected by hydrogen bonds and hydrophobic interactions; the interfacial shear strength between the water-phase sized modified polyamide fiber and epoxy resin is 57.97 MPa.

[0173] As Figure 3 shown, the hydrodynamic diameters of P(50% DMA-co-50% AEMA) in acetic acid buffer solutions with pH values of 3.7, 4.0, 4.5, 5.0, and 5.5 are 24.36, 18.16, 13.544, 12.38, and 15.68 nm respectively. P(DMA-co-AEMA) can be well dispersed in the acetic acid buffer solution, and P(DMA-co-AEMA) can be dissolved in the acetic acid buffer solution for modifying aramid fibers.

Claims

1. An aqueous sizing modified organic fiber, comprising a fiber body and a sizing layer autonomously adhered to the surface of the fiber body, characterized in that: The fiber body is aramid fiber, PBO fiber, polyester fiber or polyamide fiber, the thickness of the sizing layer is 3.0 - 5.33 nm, and the interfacial shear strength between the aqueous phase sized modified organic fiber and epoxy resin is 54.4 - 65.22 MPa; The structure of the polymer in the sizing layer is as follows: wherein, x and y are positive integers, and 300 ≤ x ≤ 800, 800 ≤ y ≤ 929, and x:y = 1:1 - 3; The aqueous phase sized modified organic fiber is obtained by immersing the fiber body in the sizing agent, taking it out, washing with water and drying to form a sizing layer on the surface of the fiber body; The sizing agent is prepared by dissolving the polymer in a buffer solution. The pH value of the buffer solution is 3.7 - 5.5, the solvent of the buffer solution is deionized water, and the concentration of the polymer in the sizing agent is 0.4 - 0.6 mg / mL; The buffer solution is an acetic acid buffer solution, which is prepared by dissolving sodium acetate and acetic acid in deionized water.

2. The aqueous phase sizing modified organic fiber according to claim 1, characterized in that, The fiber body and the sizing layer are connected by hydrogen bonds, cation-π, π-π stacking and hydrophobic interactions.

3. The aqueous sizing modified organic fiber according to claim 1, characterized in that The immersion time of the fiber body in the sizing agent is 10 - 60 s.

4. The aqueous sizing modified organic fiber according to claim 1, characterized in that, The mass ratio of sodium acetate to acetic acid is 0.152 - 3.167:

1.

5. The aqueous sizing modified organic fiber according to claim 1, wherein The water washing time is 10 - 50 s.

6. The aqueous sizing modified organic fiber according to claim 1, wherein The drying temperature is 120 - 180 °C and the time is 20 - 180 s.

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