A glass fiber sizing agent containing carbon nanotubes, and its preparation method and application

Abstract

The present invention relates to a glass fiber sizing containing carbon nanotubes, as well as its preparation method and application. The glass fiber sizing comprises an active ingredient and water; the active ingredient comprises, by weight, 20% to 52% of a low-molecular-weight epoxy resin emulsion containing an epoxy resin with a molecular weight of 400 to 800, 4% to 20% of a high-molecular-weight epoxy resin emulsion containing an epoxy resin with a molecular weight of 1200 to 1800, 2% to 10% of a low-molecular-weight aqueous epoxy resin solution containing an aqueous epoxy resin with a molecular weight of 300 to 400, 8% to 24% of an organosilicon lubricant, 0% to 15% of a nonionic lubricant, 6.5% to 20% of an amino silane coupling agent, 0% to 6% of an epoxy-functionalized silane coupling agent, and 0.1% to 0.6% of carbon nanotubes. The glass fiber sizing of the present invention can impart excellent microwave absorption and mechanical properties to glass fiber-reinforced composite materials.

Description

Technical Field

[0001] The present invention relates to the technical field of glass fiber sizing agents, and in particular to a glass fiber sizing agent added with carbon nanotubes and a preparation method thereof. Background Art

[0002] Glass fiber is a reinforcing material that comes in a wide variety and is an inorganic non-metallic material with excellent properties, including heat resistance, high tensile strength, good insulation, and corrosion resistance. Compared to ordinary glass fiber, high-performance glass fiber has higher mechanical properties, stronger corrosion resistance, higher heat resistance, and excellent dielectric and electrical insulation properties. As a reinforcing matrix for high-performance composite materials, it is primarily used in defense fields such as aviation, aerospace, weapons, and the nuclear industry. However, glass fiber also has disadvantages such as brittleness, poor wear resistance, static electricity after friction, and poor processing properties. One of the key technologies for glass fiber-reinforced composites is the wetting agent technology, which determines the material processing and composite interface properties.

[0003] A sizing is a surface treatment agent for glass fibers. After exiting the sluice plate, glass fibers are typically treated with a water-based sizing to impart good textile processing properties, the mechanical properties required for composite materials, and other customized properties. Different sizings impart varying properties to glass fibers. Yarns used in textiles and weaving must exhibit excellent textile properties and good compatibility with the base resin to meet diverse product requirements. Therefore, developing suitable sizings for glass fibers and their composite materials is crucial.

[0004] The traditional glass fiber sizing components mainly include one or more resin film-forming agents, coupling agents and lubricants, as well as a small amount of auxiliary additives. The film-forming agent component is generally a polymer or resin that has good compatibility with the glass fiber reinforced matrix resin, and epoxy resin film-forming agents are widely used in the sizing component of various fiber-reinforced resin systems.

[0005] Carbon nanotubes (CNTs) are crystalline forms of carbon, classified as multi-walled and single-walled. They typically have diameters of a few nanometers and lengths of several micrometers, resulting in high aspect ratios and specific surface areas. Their unique structural properties not only provide excellent mechanical properties, such as high tensile strength, a high Young's modulus, and a high aspect ratio, but are now widely used in a wide range of industries, including aerospace and automotive. Furthermore, CNTs possess high electrical conductivity and have been reported to be useful as absorbers. However, due to their large specific surface area, CNTs are prone to self-aggregation during application. To prevent this self-aggregation, composite materials are typically prepared by simply dispersing the CNTs and combining them with epoxy resin to improve their mechanical properties. While glass fiber, as a reinforcing matrix, can provide composite materials with high mechanical properties, the introduction of CNTs into glass fiber-based composites significantly limits their application in resins and other polymers due to their self-aggregation, hindering the development of CNTs in the composite material field. To expand the application prospects of carbon nanotubes in composite materials, there are reports in the prior art of adding carbon nanotubes to wetting agents. For example, Chinese patent application CN201210553280.X discloses a wetting agent for glass fibers containing added carbon nanotubes and a preparation method thereof. However, this patent application requires the carbon nanotubes to be modified first, which is a cumbersome operation process. The components of the prepared wetting agent for glass fibers containing added carbon nanotubes are mostly highly polar components. Those skilled in the art are aware that highly polar components often have polar groups or functional groups that can physically or chemically interact with the surface of carbon nanotubes. Such interactions often change the charge distribution, conductivity, and dielectric properties of the carbon nanotubes, change the impedance of the system, and make the surface magnetic state mismatched with the fiber system, thereby affecting its absorbing performance and making it unable to achieve electromagnetic stealth effect. Therefore, this patent application relies on polarity to ensure the stable adsorption of carbon nanotubes on the glass fiber surface. Although it improves the mechanical properties of the yarn, it significantly hinders its absorbing performance. The glass fiber treated with it does not have absorbing properties when made into a composite material.

[0006] In summary, it is very necessary to provide a glass fiber sizing, a preparation method and application thereof, which can impart excellent wave absorbing properties and mechanical properties to glass fiber reinforced composite materials. Summary of the Invention

[0007] To address one or more technical problems existing in the prior art, the present invention provides a carbon nanotube-added glass fiber sizing, its preparation method, and its application. The carbon nanotube-added glass fiber sizing imparts excellent microwave absorption and mechanical properties to glass fiber-reinforced composites, achieving negative reflectivity within the 3-18 GHz band and effectively improving the tensile modulus and tensile strength of the glass fiber-reinforced composites.

[0008] In a first aspect, the present invention provides a glass fiber sizing with added carbon nanotubes. The glass fiber sizing comprises effective components and water. The effective components comprise the following components in percentage by mass: 20% to 52% of a main film-forming agent, 4% to 20% of an auxiliary film-forming agent, 2% to 10% of an auxiliary dispersant, 8% to 24% of an organic silicon lubricant, 0% to 15% of a non-ionic lubricant, 6.5% to 20% of an amino silane coupling agent, 0% to 6% of an epoxy functionalized silane coupling agent, and 0. 1 to 0.6%; the main film-forming agent is a low molecular weight epoxy resin emulsion, and the molecular weight of the epoxy resin in the low molecular weight epoxy resin emulsion is 400 to 800; the auxiliary film-forming agent is a high molecular weight epoxy resin emulsion, and the molecular weight of the epoxy resin in the high molecular weight epoxy resin emulsion is 1200 to 1800; the auxiliary dispersant is a low molecular weight water-based epoxy resin solution, and the molecular weight of the water-based epoxy resin in the low molecular weight water-based epoxy resin solution is 300 to 400.

[0009] Preferably, the effective components include the following components in percentage by mass: 40% to 52% of a main film-forming agent, 5% to 15% of an auxiliary film-forming agent, 5% to 6% of an auxiliary dispersant, 12% to 20% of an organosilicon lubricant, 0% to 8% of a non-ionic lubricant, 12% to 18% of an amino silane coupling agent, 0% to 6% of an epoxy-functionalized silane coupling agent, and 0.1% to 0.3% of carbon nanotubes.

[0010] Preferably, the glass fiber sizing agent further comprises a pH regulator, the pH value of the glass fiber sizing agent is 4 to 6, the pH regulator is an organic acid, preferably, the pH regulator is one or more of acetic acid, formic acid, succinic acid, boric acid, and citric acid; the solid content of the glass fiber sizing agent is 3 to 8%.

[0011] Preferably, the epoxy resin in the low molecular weight epoxy resin emulsion and the high molecular weight epoxy resin emulsion is bisphenol A epoxy resin; and the carbon nanotube is a multi-walled carbon nanotube or a single-walled carbon nanotube.

[0012] Preferably, the glass fiber sizing agent further comprises sodium dodecylbenzenesulfonate in an amount of 0.01 to 0.1% by mass of the effective component; the amino silane coupling agent is A-1100; and the epoxy functionalized silane coupling agent is A-187.

[0013] In a second aspect, the present invention provides a method for preparing the glass fiber sizing containing carbon nanotubes as described in the first aspect of the present invention, the method comprising the following steps:

[0014] (1) adding a formulated amount of an auxiliary film-forming agent and sodium dodecylbenzene sulfonate to water for pre-emulsification to obtain a pre-emulsified liquid; the mass ratio of the water to the auxiliary film-forming agent is (3-5):1;

[0015] (2) adding a formulated amount of carbon nanotubes to water for ultrasonic dispersion, and then sequentially adding a formulated amount of an auxiliary dispersant and one-third of a formulated amount of an organosilicon lubricant dropwise to obtain a dispersion; the mass ratio of the carbon nanotubes to the water is 1:(15-25);

[0016] (3) adding the dispersion to the pre-emulsion and emulsifying at a rotation speed of 3000 to 8000 rpm to obtain a carbon nanotube dispersion;

[0017] (4) adding a formulated amount of an amino silane coupling agent and a formulated amount of an epoxy functionalized silane coupling agent to water and stirring to obtain a coupling agent aqueous dispersion, then adding a pH adjuster to the coupling agent aqueous dispersion to adjust the pH to 5 to 7 and continuing to stir to obtain a coupling agent solution; the mass ratio of the sum of the mass of the amino silane coupling agent and the epoxy functionalized silane coupling agent to the mass of the water is 1:(4 to 6);

[0018] (5) diluting the formulated amount of the main film-forming agent with water, and then sequentially adding the coupling agent solution, the remaining two-thirds of the formulated amount of the silicone lubricant, the formulated amount of the non-ionic lubricant and the carbon nanotube dispersion and stirring evenly, and then adding water to obtain the glass fiber impregnating agent with added carbon nanotubes having a preset solid content; the mass ratio of the dilution water to the main film-forming agent is (4 to 6): 1; optionally, adding a pH regulator to obtain the glass fiber impregnating agent with added carbon nanotubes having a preset pH value.

[0019] Preferably, in step (1), the pre-emulsification temperature is 25-40° C., the pre-emulsification time is 10-30 min, and the pre-emulsification is carried out at a rotation speed of 100-300 rpm; in step (2), the ultrasonic dispersion power is 50-100 W, the ultrasonic dispersion temperature is 25-40° C., and the ultrasonic dispersion time is 30-60 min.

[0020] Preferably, in step (3), the emulsification temperature is 40-60°C, and the emulsification time is 5-30 min; in step (5), the stirring temperature is 25-40°C, the stirring time is 5-15 min, and the stirring speed is 100-300 rpm.

[0021] In a third aspect, the present invention provides a glass fiber sizing with added carbon nanotubes, which is prepared by the preparation method described in the second aspect of the present invention.

[0022] In a fourth aspect, the present invention provides the use of the glass fiber impregnating agent with added carbon nanotubes as described in the first aspect of the present invention or the glass fiber impregnating agent with added carbon nanotubes prepared by the preparation method described in the second aspect of the present invention in the preparation of glass fiber for stealth material or glass fiber reinforced composite material for stealth material.

[0023] Compared with the prior art, the present invention has at least the following beneficial effects:

[0024] (1) The glass fiber impregnation agent with added carbon nanotubes in the present invention adopts low molecular weight epoxy resin emulsion as the main film-forming agent, which can be quickly and evenly spread on the surface of the glass fiber to form a uniform soft film, thereby improving the folding resistance and wear resistance of the fiber and improving the processability of the fiber; high molecular weight epoxy resin emulsion is adopted as the auxiliary film-forming agent, which can effectively coat the glass fiber and carbon nanotubes to form a dense protective layer, protecting the glass fiber and carbon nanotubes from the influence of the external environment, and effectively preventing the carbon nanotubes from self-aggregating into clusters or aggregates. The coating film formed by the low molecular weight epoxy resin emulsion is a soft film, which can reduce the hardness of the formed surface film after being compounded with the high molecular weight epoxy resin emulsion, improve the elasticity of the film, and thus improve the fatigue strength of the glass fiber; at the same time, the two film-forming agents can also cross-link and entangle with each other to form a relatively dense network structure, which can improve the While improving the performance of glass fiber, it also facilitates the orderly dispersion of carbon nanotubes; the present invention adopts a low molecular weight aqueous epoxy resin solution as an auxiliary dispersant, which is weakly electrically conductive and, like the surfactant SDBS, can enhance dispersibility, better adsorb carbon nanotubes, reduce the free movement of carbon nanotubes in the emulsification dispersion and impregnation process, reduce the self-aggregation of carbon nanotubes, ensure that the carbon nanotubes are uniformly dispersed in the glass fiber impregnation agent, and improve the overall film-forming performance of the impregnation agent while improving the compatibility between the substrate and the resin. The glass fiber impregnation agent with added carbon nanotubes in the present invention can be directly used to manufacture composite materials using a variety of processes, has high adaptability, and effectively improves the tensile modulus and tensile strength of glass fiber reinforced composite materials. When preparing glass fiber reinforced composite materials, the operation is easy to control, the production cost is low, the raw material utilization rate is high, and the product quality is excellent.

[0025] (2) The glass fiber impregnating agent with added carbon nanotubes in the present invention has all effective components that are non-polar substances. Compared with the use of polar substances as lubricants or coupling agents, the present invention does not require modification of the carbon nanotubes. Instead, the carbon nanotubes are added to water for ultrasonic dispersion, and then a low molecular weight aqueous epoxy resin solution and one-third of the organic silicon lubricant are added dropwise by a peristaltic pump to obtain a dispersion, which is then added to a pre-emulsion for emulsification. This can evenly disperse the carbon nanotubes and reduce the aggregation of the carbon nanotubes, thereby obtaining a glass fiber impregnating agent with evenly dispersed carbon nanotubes. By using polar substances or directly adding carbon nanotubes, the glass fiber sizing obtained in the present invention basically does not have the phenomenon of carbon nanotubes agglomerating into clusters or aggregates, which will not affect the display of the carbon nanotubes' wave absorbing performance. The glass fiber sizing with added carbon nanotubes in the present invention can give the glass fiber reinforced composite material excellent wave absorbing performance, thereby greatly improving the wave transmission performance of the glass fiber reinforced composite material, making its reflectivity value in the band of 3 to 18 GHz all negative, having excellent wave absorbing performance, and even the reflectivity peak can reach -7dB to -10dB.

[0026] (3) Compared with the prior art, the glass fiber sizing agent formula with added carbon nanotubes described in the present invention does not introduce too many components for auxiliary dispersion due to the addition of carbon nanotubes. It only improves the preparation process by introducing epoxy resin emulsions of different molecular weights for emulsification, coating and dispersion. The formula gives the glass fiber good processing performance, improves the mechanical properties of the glass fiber reinforced composite material, and also has good dry yarn strength and modulus. At the same time, it improves the wave transmission performance of the composite material, greatly enhancing the application prospects of carbon nanotubes in the field of composite materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 These are SEM images of glass fibers treated with a glass fiber sizing containing carbon nanotubes prepared in Example 1 of the present invention at different magnifications;

[0028] Figure 2 is a SEM image of the glass fiber sizing with added carbon nanotubes prepared in Example 1 of the present invention;

[0029] Figure 3 is a SEM image of the glass fiber sizing with added carbon nanotubes prepared in Comparative Example 3 of the present invention;

[0030] Figure 4 This is a graph showing the wave transmission performance of a glass fiber reinforced composite material made of glass fiber treated with a glass fiber sizing agent containing carbon nanotubes prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0031] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the embodiments described are part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0032] In a first aspect, the present invention provides a glass fiber sizing containing carbon nanotubes (referred to as a glass fiber sizing), wherein the glass fiber sizing comprises an active ingredient and water; in the present invention, the water may be, for example, deionized water; and the active ingredient comprises the following components, expressed in percentage by mass:

[0033] Main film-forming agent 20% to 52% (e.g., 20%, 25%, 30%, 35%, 40%, 45%, 50% or 52%), auxiliary film-forming agent 4 to 20% (e.g., 4%, 5%, 8%, 10%, 12%, 15%, 18% or 20%), auxiliary dispersant 2 to 10% (e.g., 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%), silicone lubricant 8 to 24% (e.g., 8%, 10%, 12%, 15%, 18%, 20% or 24%), non-ionic lubricant 0 to 15% % (e.g. 0%, 1%, 5%, 8%, 10%, 12% or 15%), preferably 1-12%, amino silane coupling agent 6.5-20% (e.g. 6.5%, 8%, 10%, 12%, 15%, 18% or 20%), epoxy functional silane coupling agent 0-6% (e.g. 0%, 1%, 2%, 3%, 4%, 5% or 6%), preferably 4-6%, carbon nanotubes 0.1-0.6% (e.g. 0.1%, 0.2%, 0.3%, 0.4%, 0.5% or 0.6%); the main film-forming agent is a low molecular weight The auxiliary film-forming agent is a high molecular weight epoxy resin emulsion, the molecular weight (average molecular weight) of the epoxy resin in the low molecular weight epoxy resin emulsion is 400 to 800 (for example, 400, 500, 600, 700 or 800), and preferably, the effective content (solid content) is 40 to 60 wt %; the auxiliary film-forming agent is a high molecular weight epoxy resin emulsion, the molecular weight (average molecular weight) of the epoxy resin in the high molecular weight epoxy resin emulsion is 1200 to 1800 (for example, 1200, 1300, 1400, 1500, 1600, 1700 or 1800), preferably, the effective content (solid content) is 40-60wt%; the auxiliary dispersant is a low molecular weight water-based epoxy resin solution, the molecular weight (average molecular weight) of the water-based epoxy resin in the low molecular weight water-based epoxy resin solution is 300-400 (for example, 300, 350 or 400), preferably, the effective content (solid content) is 40-60wt%; in the present invention, molecular weight refers to the number average relative molecular mass; in the present invention, the auxiliary dispersant is a low molecular weight and low polarity water-based epoxy resin solution.

[0034] The present invention does not specifically limit the sources of low molecular weight epoxy resin emulsion, high molecular weight epoxy resin emulsion, low molecular weight water-based epoxy resin solution, silicone lubricant, nonionic lubricant, amino silane coupling agent, epoxy functionalized silane coupling agent, etc., and any product that can be directly purchased on the market or synthesized by existing methods can be used. Taking the low molecular weight epoxy resin emulsion, high molecular weight epoxy resin emulsion and low molecular weight water-based epoxy resin solution as an example, as long as the molecular weight of the epoxy resin contained is within the corresponding range, it is sufficient. Preferably, the molecular weight and effective content of the epoxy resin contained are both within the corresponding range.

[0035] The glass fiber impregnating agent with added carbon nanotubes in the present invention adopts low molecular weight epoxy resin emulsion as the main film-forming agent, which can be quickly and evenly spread on the surface of the glass fiber to form a uniform soft film, thereby improving the folding resistance and wear resistance of the fiber and improving the processability of the fiber; adopting high molecular weight epoxy resin emulsion as the auxiliary film-forming agent can effectively coat the glass fiber and carbon nanotubes to form a dense protective layer, thereby protecting the glass fiber and carbon nanotubes from the influence of the external environment and effectively preventing the carbon nanotubes from self-aggregating into clusters or aggregates. The coating film formed by the low molecular weight epoxy resin emulsion is a soft film, which can reduce the hardness of the formed surface film and improve the elasticity of the film after being compounded with the high molecular weight epoxy resin emulsion, thereby improving the fatigue strength of the glass fiber; at the same time, the two film-forming agents can also cross-link and entangle with each other to form a relatively dense network structure, which not only improves the performance of the glass fiber but also facilitates the carbon nanotubes. Sequential dispersion; the present invention adopts a low molecular weight aqueous epoxy resin solution as an auxiliary dispersant, which is weakly electrically conductive and, like the surfactant sodium dodecylbenzene sulfonate SDBS, can enhance dispersibility, better adsorb carbon nanotubes, reduce the free movement of carbon nanotubes during the emulsification dispersion and wetting agent preparation and intercalation process, reduce the occurrence of self-aggregation of carbon nanotubes, ensure that the carbon nanotubes are uniformly dispersed in the glass fiber wetting agent, and while improving the overall film-forming performance of the wetting agent, can improve the compatibility of the substrate and the resin. The glass fiber wetting agent with added carbon nanotubes in the present invention can be directly used to manufacture composite materials using a variety of processes, has high adaptability, and effectively improves the tensile modulus and tensile strength of the glass fiber reinforced composite material. For example, the tensile modulus can be increased by more than 5%, and the tensile strength can be increased by more than 10%. When preparing glass fiber reinforced composite materials, the operation is easy to control, the production cost is low, the raw material utilization rate is high, and the product quality is excellent.

[0036] In the present invention, it is preferred that the glass fiber sizing include two lubricants, which lubricate the glass fiber surface and reduce wear in the wet state (during the drawing process) and the dry state (during the unwinding and textile processing of the raw yarn); the non-ionic lubricant can reduce the generation of fuzz, while improving the wear resistance of the fiber and reducing the aggregation of carbon nanotubes. In the present invention, it is preferred that the glass fiber sizing include two lubricants, including an amino silane coupling agent and an epoxy functionalized silane coupling agent. The function of the silane coupling agent is to enhance the adhesion between the film-forming agent and the glass fiber, which can reduce the amount of fuzz and breakage of the fiber during processing; give the glass fiber surface good compatibility with the matrix resin and improve the performance of the composite material. The silane coupling agent is mainly an amino silane coupling agent, such as A-1100, etc., according to the needs of the resin. In addition, it is also preferred to add an auxiliary coupling agent, which is an epoxy functionalized silane coupling agent, such as A-187, etc. When the main coupling agent forms a connection between the glass fiber and the resin, the auxiliary system forms a network connection, which is beneficial to improving the mechanical properties of the composite material.

[0037] The glass fiber sizing agent with added carbon nanotubes in the present invention has all its effective components as non-polar substances. Compared with using polar substances as lubricants or coupling agents, the present invention does not require modification of the carbon nanotubes. Instead, the carbon nanotubes are added to water for ultrasonic dispersion, and then a low molecular weight aqueous epoxy resin solution and one-third of the organic silicon lubricant are added dropwise through a peristaltic pump to obtain a dispersion liquid, which is then added to a pre-emulsion liquid for emulsification. This can evenly disperse the carbon nanotubes and reduce the aggregation of the carbon nanotubes, thereby obtaining a glass fiber sizing with evenly dispersed carbon nanotubes. Compared with using Polar substances or the direct addition of carbon nanotubes, the glass fiber sizing obtained in the present invention basically does not have the phenomenon of carbon nanotubes agglomerating into clusters or aggregates, which will not affect the display of the carbon nanotubes' wave absorbing performance. The glass fiber sizing with added carbon nanotubes in the present invention can give the glass fiber reinforced composite material excellent wave absorbing performance, so that the wave transmission performance of the glass fiber reinforced composite material is greatly improved, so that its reflectivity value in the band of 3 to 18 GHz is negative, with excellent wave absorbing performance, and even the reflectivity peak can reach -7dB to -10dB.

[0038] According to some preferred embodiments, the effective component comprises the following components in percentage by mass:

[0039] The main film-forming agent is 40% to 52% (for example, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51% or 52%), the auxiliary film-forming agent is 5 to 15% (for example, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14% or 15%), the auxiliary dispersant is 5 to 6% (for example, 5%, 5.5% or 6%), the silicone lubricant is 12 to 20% (for example, 12%, 13%, 14%, 15%, 16%, 17%, 18%). 8%, 19% or 20%), non-ionic lubricant 0-8% (for example, 0%, 1%, 2%, 3%, 4%, 5%, 6%, 7% or 8%), preferably 1-8%, amino silane coupling agent 12-18% (for example, 12%, 13%, 14%, 15%, 16%, 17% or 18%), epoxy functional silane coupling agent 0-6% (for example, 0%, 1%, 2%, 3%, 4%, 5% or 6%), preferably 4-6%, carbon nanotubes 0.1-0.3% (for example, 0.1%, 0.2% or 0.3%).

[0040] According to some preferred embodiments, the glass fiber sizing further comprises a pH adjuster, and the pH value of the glass fiber sizing is 4 to 6; the pH adjuster is an organic acid, preferably one or more of acetic acid, formic acid, succinic acid, boric acid, and citric acid, and more preferably citric acid or acetic acid. In the present invention, the glass fiber sizing preferably further comprises a pH adjuster, and the prepared glass fiber sizing is preferably stored and applied under certain pH conditions, generally preferably in an acidic environment with a pH value of 4 to 6; the present invention does not specifically limit the amount of the pH adjuster, and it is sufficient to adjust the pH of the glass fiber sizing system to 4 to 6.

[0041] According to some preferred embodiments, the solid content of the glass fiber sizing agent is 3-8% (e.g., 3%, 4%, 5%, 6%, 7% or 8%), preferably 5-6% (e.g., 5%, 5.1%, 5.2%, 5.3%, 5.4%, 5.5%, 5.6%, 5.7%, 5.8%, 5.9% or 6%).

[0042] According to some preferred embodiments, the epoxy resin in the low molecular weight epoxy resin emulsion and the high molecular weight epoxy resin emulsion is bisphenol A epoxy resin; and the carbon nanotube is a multi-walled carbon nanotube or a single-walled carbon nanotube.

[0043] According to some preferred embodiments, the glass fiber sizing further comprises sodium dodecylbenzene sulfonate, measured in percentage by mass, and the amount of sodium dodecylbenzene sulfonate is 0.01-0.1% (e.g., 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09% or 0.1%) of the mass of the effective component.

[0044] According to some preferred embodiments, the amino-based silane coupling agent is A-1100; and / or the epoxy-functional silane coupling agent is A-187.

[0045] According to some preferred embodiments, the low molecular weight epoxy resin emulsion is a low molecular weight epoxy resin emulsion NBR-210-50G, that is, the low molecular weight epoxy resin emulsion is a commercially available product provided by Nanjing Fiberglass Research and Design Institute Co., Ltd. under the name NBR-210-50G, with a molecular weight of 500 and an effective content of 50 wt% of a low molecular weight bisphenol A type epoxy resin emulsion NBR-210-50G; the high molecular weight epoxy resin emulsion is a high molecular weight epoxy resin emulsion NBR-230G, that is, the high molecular weight epoxy resin emulsion is a commercially available product provided by Nanjing Fiberglass Research and Design Institute Co., Ltd. under the name NBR-230G, with a molecular weight of 1500 and an effective content of 50 wt% of a high molecular weight bisphenol A type epoxy resin emulsion NBR-230G; the low molecular weight aqueous epoxy resin solution is a low molecular weight and low polarity aqueous epoxy resin solution, for example, it can be a low molecular weight aqueous epoxy resin solution NBR-290, a low molecular weight aqueous epoxy resin solution NBR-290. The low molecular weight aqueous epoxy resin solution NBR-290 has low polarity, that is, the low molecular weight aqueous epoxy resin solution is a commercially available low molecular weight aqueous epoxy resin solution NBR-290 provided by Nanjing Fiberglass Research and Design Institute Co., Ltd., with a trade name of NBR-290, a molecular weight of 350, and an effective content of 60 wt %; the organic silicone lubricant is organic silicone lubricant JW-020 or organic silicone lubricant SE-2175, and the organic silicone lubricant is, for example, organic silicone lubricant SE-2175 provided by Shanghai Fluoropolymer Chemical Products Co., Ltd., with an effective content of 42 wt %; the non-ionic lubricant is an ester, amide or mineral oil lubricant, for example, an ester non-ionic lubricant, specifically a polyol ester lubricant, with a model number of G70S, or the non-ionic lubricant is non-ionic lubricant 7440, that is, the non-ionic lubricant is, for example, a polyol ester lubricant provided by Shanghai Kekai Chemical Co., Ltd. Chemicals) with a trade name of 7440 and an effective content of 40 wt% of non-ionic lubricant 7440; the carbon nanotubes are, for example, single-walled carbon nanotubes, such as those provided by OCSiAl, such as single-walled carbon nanotubes Coat ENIS.

[0046] Carbon nanotubes have poor shear resistance, and glass fiber sizings require constant stirring during use. Consequently, in glass fiber sizings containing carbon nanotubes as reported in prior art, the carbon nanotubes demulsify over time and aggregate within the glass fiber sizing, preventing their uniform dispersion and defeating their intended purpose. Consequently, prior art methods typically require the carbon nanotubes to be modified or dispersed by adding various auxiliary components (such as highly polar components). However, glass fiber sizing systems are sensitive and require a high level of component type. The presence of these auxiliary components, such as highly polar components, can easily affect the performance of the glass fiber sizing or the wave absorption properties of the carbon nanotubes.

[0047] To this end, the present invention provides, in a second aspect, a method for preparing the glass fiber sizing containing carbon nanotubes as described in the first aspect of the present invention, the method comprising the following steps:

[0048] (1) adding a formulated amount of an auxiliary film-forming agent and a formulated amount of sodium dodecylbenzenesulfonate (SDBS) to water for pre-emulsification to obtain a pre-emulsion; in step (1), the mass ratio of the water to the auxiliary film-forming agent (high molecular weight epoxy resin emulsion) is (3-5):1 (e.g., 3:1, 3.5:1, 4:1, 4.5:1 or 5:1), preferably 4:1;

[0049] (2) adding a formulated amount of carbon nanotubes into water and ultrasonically dispersing the carbon nanotubes to obtain a carbon nanotube-water mixture, and then sequentially adding a formulated amount of an auxiliary dispersant and one-third of a formulated amount of an organosilicon lubricant to the carbon nanotube-water mixture to obtain a dispersion; in step (2), the mass ratio of the carbon nanotubes to the water is 1:(15-25) (e.g., 1:15, 1:16, 1:17, 1:18, 1:19, 1:20, 1:21, 1:22, 1:23, 1:24, or 1:25), preferably 1:20; In the present invention, for example, under the condition of maintaining ultrasonic dispersion of the carbon nanotube-water mixture, a peristaltic pump can be used to slowly and continuously dropwise add the auxiliary dispersant in the formula amount and 1 / 3 of the organic silicone lubricant in the formula amount until the auxiliary dispersant and 1 / 3 of the organic silicone lubricant are completely added to obtain a dispersion liquid; the present invention does not specifically limit the speed of the peristaltic pump for dropping the auxiliary dispersant in the formula amount and the organic silicone lubricant in the formula amount, and those skilled in the art can select it as needed, for example, it can be 8 to 12 g / min;

[0050] (3) adding the dispersion to the pre-emulsion and emulsifying at a rotation speed of 3000 to 8000 rpm (e.g., 3000, 3500, 4000, 4500, 5000, 5500, 6000, 6500, 7000, 7500 or 8000 rpm) to obtain a carbon nanotube dispersion;

[0051] (4) adding a formulated amount of amino silane coupling agent and a formulated amount of epoxy functionalized silane coupling agent to water and stirring to obtain a coupling agent aqueous dispersion, then adding a pH adjuster to the coupling agent aqueous dispersion to adjust the pH to 5-7 and continuing to stir to obtain a coupling agent solution; in step (4), the mass ratio of the sum of the mass of the amino silane coupling agent and the epoxy functionalized silane coupling agent to the mass of the water is 1:(4-6) (for example, 1:4, 1:4.5, 1:5, 1:5.5 or 1:6), preferably 1:5; specifically, adding a formulated amount of amino silane coupling agent and a formulated amount of epoxy functionalized silane coupling agent to water and stirring at a temperature of 25-40°C and a rotation speed of 100-30 0r / min for 5-15min to obtain a coupling agent aqueous dispersion, then adding a pH adjuster to the coupling agent aqueous dispersion to adjust the pH to 5-7 and continuing to stir at a temperature of 15-40°C and a speed of 100-300r / min, and continuing to stir until the liquid surface is clear to obtain a coupling agent solution; in this step, the pH adjuster is an organic acid, preferably, the pH adjuster is one or more of acetic acid, formic acid, succinic acid, boric acid, and citric acid, more preferably, the pH adjuster is citric acid, and the amount of the pH adjuster used in this step is not specifically limited, as long as the pH of the coupling agent aqueous dispersion is adjusted to 5-7;

[0052] (5) diluting the formulated amount of the main film-forming agent with water, then sequentially adding the coupling agent solution, the remaining two-thirds of the formulated amount of the silicone lubricant, the formulated amount of the non-ionic lubricant and the carbon nanotube dispersion and stirring evenly, and then adding water (the remaining formulated amount of water) to obtain the glass fiber sizing agent with added carbon nanotubes having a preset solid content; in step (5), the mass ratio of the dilution water to the main film-forming agent is (4-6):1 (for example, 4:1, 4.5:1, 5:1, 5.5:1 or 6:1); optionally, adding a pH regulator to obtain the glass fiber sizing agent with added carbon nanotubes having a preset pH value; in step (5), the dilution can be, for example, as follows: stirring the formulated amount of the main film-forming agent with water at a room temperature of 25-40°C and a rotation speed of 100-300 rpm for 5-15 minutes, and the mass ratio of the water to the main film-forming agent is (4-6):1.

[0053] The preparation method of the present invention uses a pre-emulsification method to enable the high molecular weight epoxy resin emulsion and sodium dodecylbenzene sulfonate to be fully mixed, thereby improving the emulsification effect of the subsequent components added with the pre-emulsion liquid, and is beneficial to ensuring the quality of the glass fiber sizing finally prepared; the present invention adopts an ultrasonic dispersion method, which is beneficial to uniformly dispersing carbon nanotubes in the low molecular weight epoxy resin emulsion, which is beneficial to subsequently increase the bonding force between the carbon nanotubes and the glass fiber, and is beneficial to improving the performance of the glass fiber sizing; when performing step (3), the present invention contains a low molecular weight water-based epoxy resin. The dispersion of the fat solution and part of the organic silicon lubricant is added to the pre-emulsion for emulsification. The addition of the low molecular weight water-based epoxy resin solution can better adsorb the carbon nanotubes, reduce the free movement of the carbon nanotubes during the emulsification dispersion and the preparation and intercalation of the wetting agent, reduce the self-aggregation of the carbon nanotubes, ensure that the carbon nanotubes are evenly dispersed in the glass fiber wetting agent, and improve the overall film-forming performance of the wetting agent while improving the compatibility of the substrate and the resin. The addition of the organic silicon lubricant helps to protect the carbon nanotubes from damage and can help the carbon nanotubes to be better dispersed. In the liquid phase, thereby preventing it from re-aggregating and precipitating in the subsequent processing process; the present invention adopts the method of slowly adding silicone lubricant and low molecular weight aqueous epoxy resin solution, which can better control the uniformity of carbon nanotube dispersion and improve the application effect of the prepared glass fiber sizing; the present invention also adds amino silane coupling agent and epoxy functionalized silane coupling agent, which is also beneficial to improve the bonding strength between the prepared glass fiber sizing and the glass fiber and increase the adhesion of the glass fiber sizing; the above steps (1) to (5) of the present invention can prepare a glass fiber sizing with moderate viscosity and The glass fiber sizing has good dispersibility and strong adhesion, and can ensure that the additive carbon nanotubes are evenly dispersed in the sizing. The glass fiber sizing obtained in the present invention basically does not have the phenomenon of carbon nanotubes agglomerating into clusters or aggregates, which will not affect the display of the carbon nanotubes' wave absorbing performance. The glass fiber sizing with added carbon nanotubes in the present invention can give glass fiber reinforced composite materials excellent wave absorbing properties, thereby greatly improving the wave transmission performance of glass fiber reinforced composite materials. In addition, the addition of carbon nanotubes in the present invention will not affect other performance properties of the glass fiber sizing.

[0054] According to some preferred embodiments, in step (1), the pre-emulsification temperature is 25-40° C. (e.g., 25, 30, 35, or 40° C.), the pre-emulsification time is 10-30 min (e.g., 10, 20, or 30 min), and the pre-emulsification is carried out at a rotation speed of 100-300 rpm (e.g., 100, 150, 200, 250, or 300 rpm); and / or in step (2), the ultrasonic dispersion power is 50-100 W (e.g., 50, 60, 70, 80, 90, or 100 W), and the ultrasonic The dispersion temperature is 25 to 40° C. (e.g., 25, 30, 35, or 40° C.), and the ultrasonic dispersion time is 30 to 60 min (e.g., 30, 40, 50, or 60 min). In the present invention, preferably, the ultrasonic dispersion time is 30 to 60 min, and the peristaltic pump drop acceleration rate is 8 to 12 g / min. If the ultrasonic dispersion time is too short, the drop addition rate of the silicone lubricant and the low molecular weight aqueous epoxy resin solution is too fast, and the carbon nanotubes may not be fully dispersed. If the ultrasonic dispersion time is too long, the molecular weight of the epoxy resin may be reduced.

[0055] According to some preferred embodiments, in step (3), the emulsification temperature is 40-60°C (e.g., 40, 45, 50, 55 or 60°C), and the emulsification time is 5-30 min (e.g., 5, 10, 15, 20, 25 or 30 min); in step (5), the stirring temperature is 25-40°C (e.g., 25, 30, 35 or 40°C), the stirring time is 5-15 min (e.g., 5, 10 or 15 min), and the stirring speed is 100-300 rpm (e.g., 100, 150, 200, 250 or 300 rpm).

[0056] In a third aspect, the present invention provides a glass fiber sizing with added carbon nanotubes, which is prepared by the preparation method described in the second aspect of the present invention.

[0057] In a fourth aspect, the present invention provides the use of the glass fiber impregnating agent with added carbon nanotubes as described in the first aspect of the present invention or the glass fiber impregnating agent with added carbon nanotubes prepared by the preparation method described in the second aspect of the present invention in the preparation of glass fiber for stealth material or glass fiber reinforced composite material for stealth material. The glass fiber for stealth material prepared by the present invention, the glass fiber precursor is dried in a drying room after being coated with the glass fiber sizing agent added with carbon nanotubes, which is beneficial to improving the coating degree and ductility of the film-forming agent, increasing the bundling property of the glass precursor, and improving the wear resistance of the glass fiber yarn for stealth material obtained; the drying of the glass fiber precursor is divided into four stages, which is placed in a dry environment at room temperature of 15-35°C for 24 hours, dried at 80°C for 90 minutes, dried at 105°C for 180 minutes, and dried at 120°C for 180 minutes; storage in a dry environment at room temperature and pre-drying at a low temperature stage are beneficial to preventing small molecules such as carbon nanotubes from escaping with water, forming aggregations on the outer layer of the precursor, and reducing the uniformity of the glass fiber sizing agent on the surface of the glass fiber; SEM images of the glass fiber treated with the glass fiber sizing agent added with carbon nanotubes prepared by the present invention at different magnifications, for example, as shown Figure 1 As shown; it can be seen from the figure that the glass fiber sizing completely covers the glass fiber precursor, the surface is smooth and flat, and there are no protrusions of carbon nanotube self-aggregated particles.

[0058] The present invention will be further described below by way of examples, but the protection scope of the present invention is not limited to these examples.

[0059] Example 1

[0060] This embodiment provides a glass fiber sizing with added carbon nanotubes and a preparation method thereof, wherein the glass fiber sizing comprises an effective component, water, a pH regulator (citric acid) and sodium dodecylbenzene sulfonate, wherein the total solid content of the glass fiber sizing is 5%, the amount of the sodium dodecylbenzene sulfonate used is 0.1% of the weight of the effective component, and the pH of the glass fiber sizing is 5.3; the effective component comprises the following components in percentage by weight: 41.9% of a main film-forming agent (a low molecular weight bisphenol A epoxy resin emulsion NBR-210-50G with a molecular weight of 500 and an effective content of 50 wt%), an auxiliary film-forming agent (a water-soluble citric acid), a water-soluble citric acid, ... The active ingredients of this embodiment are as shown in Table 1.

[0061] The preparation method of the glass fiber sizing with added carbon nanotubes in this embodiment includes the following steps:

[0062] ① Add the formulated amount of auxiliary film-forming agent and the formulated amount of sodium dodecylbenzenesulfonate to water and pre-emulsify at a temperature of 25° C. and a rotation speed of 200 rpm for 30 minutes to obtain a pre-emulsion; in step ①, the mass ratio of the water to the auxiliary film-forming agent is 4:1.

[0063] ② Add the formulated amount of carbon nanotubes to water and ultrasonically disperse them for 40 minutes to obtain a carbon nanotube-water mixture, and then use a peristaltic pump to slowly and continuously add the formulated amount of auxiliary dispersant and 1 / 3 of the formulated amount of silicone lubricant to the carbon nanotube-water mixture while maintaining the ultrasonic dispersion of the carbon nanotube-water mixture, until the auxiliary dispersant and 1 / 3 of the formulated amount of silicone lubricant are added to obtain a dispersion; the power of the ultrasonic dispersion is 100 W, the temperature of the ultrasonic dispersion is 25°C; the peristaltic pump dropping speed is 10 g / min; in step ②, the mass ratio of the carbon nanotubes to the water is 1:20.

[0064] ③ The dispersion obtained in step ② was added to the pre-emulsion obtained in step ① and emulsified at a medium temperature of 50° C. and a rotation speed of 6000 rpm for 20 min to obtain a carbon nanotube dispersion.

[0065] ④ Add the formulated amount of amino silane coupling agent and the formulated amount of epoxy functionalized silane coupling agent to water and stir at a temperature of 25 ° C. and a speed of 200 r / min for 10 minutes to obtain a coupling agent aqueous dispersion, and then add a pH adjuster (citric acid) to the coupling agent aqueous dispersion to adjust the pH to 5.3 and continue stirring at a temperature of 25 ° C. and a speed of 200 r / min. Continue stirring until the liquid surface is clear to obtain a coupling agent solution; in step ④, the mass ratio of the sum of the mass of the amino silane coupling agent and the epoxy functionalized silane coupling agent to the mass of the water is 1:5.

[0066] ⑤ Stir the formulated main film-forming agent with water at room temperature of 25°C and a rotation speed of 200 rpm for 10 minutes. The mass ratio of the water to the main film-forming agent is 5:1, so that the water dilutes the formulated low molecular weight epoxy resin emulsion, and then add the coupling agent solution, the remaining two-thirds of the formulated silicone lubricant, the formulated non-ionic lubricant and the carbon nanotube dispersion in sequence and stir at a temperature of 25°C and a rotation speed of 200 rpm for 10 minutes, and then add the remaining formulated water and pH adjuster (citric acid) to obtain a glass fiber impregnating agent with added carbon nanotubes having a pH of 5.3 and a solid content of 5%.

[0067] The SEM image of the glass fiber sizing with added carbon nanotubes prepared in Example 1 is as follows: Figure 2 As shown, from Figure 2 It can be seen that the glass fiber sizing obtained in this embodiment does not have the phenomenon of carbon nanotubes agglomerating into clusters or aggregates. The carbon nanotubes are evenly dispersed in the glass fiber sizing system, the diameter of the carbon nanotubes is small, and no cross-linking, entanglement or aggregation occurs.

[0068] Example 2

[0069] Example 2 is basically the same as Example 1, except that:

[0070] The addition amounts of carbon nanotubes and the main film-forming agent are different, and the pH value of the glass fiber sizing agent with added carbon nanotubes in this embodiment is 5.4. The specific formula of the effective components is shown in Table 1.

[0071] Example 3

[0072] Example 3 is basically the same as Example 1, except that:

[0073] The dosage of the main film-forming agent and the auxiliary film-forming agent is different. The formula of the effective components of the glass fiber sizing with added carbon nanotubes in this embodiment is specifically shown in Table 1.

[0074] Example 4

[0075] Example 4 is basically the same as Example 1, except that:

[0076] All lubricants used were silicone lubricants, and no non-ionic lubricant was added in step ⑤. The formula of the effective components of the glass fiber sizing with added carbon nanotubes in this embodiment is specifically shown in Table 1.

[0077] Example 5

[0078] Example 5 is basically the same as Example 1, except that: amino silane coupling agents are used as coupling agents, no epoxy-functional silane coupling agent is added in step ④, and the pH value of the glass fiber sizing with added carbon nanotubes in this example is 5.2. The specific formula of the effective components of the glass fiber sizing with added carbon nanotubes in this example is shown in Table 1.

[0079] Comparative Example 1

[0080] Comparative Example 1 is substantially the same as Example 1, except that:

[0081] No carbon nanotubes were added, and the amount of carbon nanotubes was replaced by the main film-forming agent; step ② was: keeping the water under ultrasonic dispersion conditions, using a peristaltic pump to slowly and continuously add the formulated amount of auxiliary dispersant and 1 / 3 of the formulated amount of silicone lubricant to the water in sequence, until the auxiliary dispersant and 1 / 3 of the formulated amount of silicone lubricant were added, to obtain a dispersion; the power of the ultrasonic dispersion was 100 W, the temperature of the ultrasonic dispersion was 25° C. The peristaltic pump dropping speed was 10 g / min; in step ②, the amount of water used was 20 times the mass of the carbon nanotubes used in Example 1. The specific formula of the effective components of the glass fiber sizing in this comparative example is shown in Table 2.

[0082] Comparative Example 2

[0083] Comparative Example 2 is basically the same as Example 1, except that: no auxiliary dispersant is added, and its addition amount is replaced by the main film-forming agent and the auxiliary film-forming agent. Step ② is: adding the formulated amount of carbon nanotubes to water and ultrasonically dispersing for 40 minutes to obtain a carbon nanotube-water mixture, and then using a peristaltic pump to slowly and continuously add 1 / 3 of the formulated amount of silicone lubricant to the carbon nanotube-water mixture while maintaining the ultrasonic dispersion of the carbon nanotube-water mixture, until 1 / 3 of the formulated amount of silicone lubricant is added to obtain a dispersion; the power of the ultrasonic dispersion is 100 W, the temperature of the ultrasonic dispersion is 25°C; the peristaltic pump dropping rate is 10 g / min; in step ②, the mass ratio of the carbon nanotubes to the water is 1:20. The specific formula of the effective components of the glass fiber sizing with added carbon nanotubes in this comparative example is shown in Table 2.

[0084] Comparative Example 3

[0085] This comparative example provides a glass fiber sizing with added carbon nanotubes and a preparation method thereof, wherein the glass fiber sizing comprises an effective component, water, a pH regulator (citric acid) and sodium dodecylbenzenesulfonate, wherein the total solid content of the glass fiber sizing is 5%, the amount of the sodium dodecylbenzenesulfonate used is 0.1% of the mass of the effective component, and the pH of the glass fiber sizing is 5.3; the effective component comprises the following components in percentage by mass: 41.9% of a main film-forming agent (a low molecular weight bisphenol A epoxy resin emulsion NBR-210-50G with a molecular weight of 500 and an effective content of 50 wt%), an auxiliary film-forming agent The following ingredients were added: (high molecular weight bisphenol A epoxy resin emulsion NBR-230G with a molecular weight of 1500 and an effective content of 50 wt%) 15%, auxiliary dispersant (low molecular weight water-based epoxy resin solution NBR-290 with a molecular weight of 350 and an effective content of 60 wt%) 5%, silicone lubricant (silicone lubricant SE-2175) 12%, non-ionic lubricant (ionic lubricant 7440) 8%, amino silane coupling agent (A-1100) 12%, epoxy-functional silane coupling agent (A-187) 6%, and single-walled carbon nanotubes 0.1%. The specific formula of the effective components of this comparative example is shown in Table 2.

[0086] The preparation method of the glass fiber sizing with added carbon nanotubes in this comparative example comprises the following steps:

[0087] ① Add the formulated amount of amino silane coupling agent and the formulated amount of epoxy functionalized silane coupling agent to water and stir for 10 minutes at a temperature of 25°C and a speed of 200 r / min to obtain a coupling agent aqueous dispersion, then add a pH adjuster (citric acid) to the coupling agent aqueous dispersion to adjust the pH to 5.3 and continue stirring at a temperature of 25°C and a speed of 200 r / min until the liquid surface becomes clear to obtain a coupling agent solution; in step ①, the mass ratio of the sum of the mass of the amino silane coupling agent and the epoxy functionalized silane coupling agent to the mass of the water is 1:5.

[0088] ② Add the formulated amount of carbon nanotubes into water and ultrasonically disperse them for 40 minutes to obtain a carbon nanotube solution; the power of the ultrasonic dispersion is 100 W, and the temperature of the ultrasonic dispersion is 25° C. In step ②, the mass ratio of the carbon nanotubes to the water is 1:20.

[0089] ③ Stir the formulated amount of the main film-forming agent with water at room temperature of 25°C and a rotation speed of 200 rpm for 10 minutes. The mass ratio of the water to the main film-forming agent is 5:1, so that the water dilutes the formulated amount of the main film-forming agent. Then, add the coupling agent solution, the formulated amount of the silicone lubricant, the formulated amount of the non-ionic lubricant, the carbon nanotube solution, the formulated amount of the auxiliary film-forming agent and the formulated amount of the auxiliary dispersant in sequence and stir at a temperature of 25°C and a rotation speed of 200 rpm for 10 minutes. Then, add the remaining formulated amount of water and pH adjuster (citric acid) to obtain a glass fiber impregnating agent with added carbon nanotubes having a pH of 5.3 and a solid content of 5%.

[0090] The SEM image of the glass fiber sizing with added carbon nanotubes prepared in this comparative example is as follows: Figure 3 As shown, from Figure 3 It can be seen that in the comparative example, the carbon nanotubes are added to the glass fiber sizing system for dispersion, the carbon nanotubes cannot be uniformly dispersed in the glass fiber sizing system, and the carbon nanotubes self-aggregate seriously, which is different from the SEM image of the glass fiber sizing with carbon nanotubes prepared in Example 1 of the present invention ( Figure 2 ), the diameter of the carbon nanotubes becomes larger, indicating that some carbon nanotubes are cross-linked and entangled.

[0091] Comparative Example 4

[0092] Comparative Example 4 is substantially the same as Example 1, except that:

[0093] In this comparative example, a cationic lubricant (fatty amine polyoxyethylene ether cationic lubricant AC-1801) was used instead of the organosilicon lubricant in Example 1 to form a glass fiber sizing with added carbon nanotubes.

[0094] Comparative Example 5

[0095] Comparative Example 5 is substantially the same as Example 1, except that:

[0096] No silicone lubricant is added in step ②, and the entire amount of silicone lubricant is added in step ⑤. The formula of the effective components of the glass fiber sizing with added carbon nanotubes in this comparative example is specifically shown in Table 2.

[0097] Comparative Example 6

[0098] Comparative Example 6 is substantially the same as Example 1, except that:

[0099] The preparation method of the glass fiber sizing with added carbon nanotubes in this comparative example is different from that in Example 1. Specifically, the preparation method of this comparative example includes the following steps:

[0100] ① Add the formulated amount of auxiliary film-forming agent, the formulated amount of sodium dodecylbenzenesulfonate, the formulated amount of auxiliary dispersant, and the formulated amount of carbon nanotubes to water and pre-emulsify at a temperature of 25°C and a rotation speed of 200 rpm for 30 minutes to obtain a pre-emulsion; the mass ratio of the water to the auxiliary film-forming agent is 4:1.

[0101] ② The pre-emulsion obtained in step ① was emulsified at a temperature of 50° C. and a rotation speed of 6000 rpm for 20 minutes to obtain a carbon nanotube dispersion.

[0102] ③ Add the formulated amount of amino silane coupling agent and the formulated amount of epoxy functionalized silane coupling agent to water and stir at a temperature of 25 ° C. and a speed of 200 r / min for 10 minutes to obtain a coupling agent aqueous dispersion, and then add a pH adjuster (citric acid) to the coupling agent aqueous dispersion to adjust the pH to 5.3 and continue stirring at a temperature of 25 ° C. and a speed of 200 r / min. Continue stirring until the liquid surface is clear to obtain a coupling agent solution; in step ③, the mass ratio of the sum of the mass of the amino silane coupling agent and the epoxy functionalized silane coupling agent to the mass of the water is 1:5.

[0103] ④ Stir the formulated amount of the main film-forming agent with water at room temperature of 25°C and a rotation speed of 200 rpm for 10 minutes. The mass ratio of the water to the main film-forming agent is 5:1, so that the water dilutes the formulated amount of the main film-forming agent. Then, add the coupling agent solution, the formulated amount of the silicone lubricant, the formulated amount of the non-ionic lubricant and the carbon nanotube dispersion in sequence and stir at a temperature of 25°C and a rotation speed of 200 rpm for 10 minutes. Then, add the remaining formulated amount of water and pH adjuster (citric acid) to obtain a glass fiber impregnating agent with added carbon nanotubes having a pH of 5.3 and a solid content of 5%.

[0104] The glass fiber sizings of the embodiments and comparative examples of the present invention were used to produce glass fiber yarns according to conventional glass fiber production processes in the art. The resulting glass fiber yarns were then subjected to the following tests, with the results shown in Tables 1 and 2. The glass fiber precursors of the yarns prepared in the present invention, after being coated with the carbon nanotube-added glass fiber sizing, were then dried in a drying oven. The drying of the glass fiber precursors was performed in four stages: 24 hours at room temperature (25°C), 90 minutes at 80°C, 180 minutes at 105°C, and 180 minutes at 120°C.

[0105] Test method:

[0106] (1) Combustible content: in accordance with GB / T9914.2 Test methods for reinforced products Part 2: Determination of combustible content of glass fiber.

[0107] (2) Dry yarn tensile strength: in accordance with GB / T7690.3 Test methods for reinforcing material yarns Part 3: Determination of breaking strength and elongation of glass fiber.

[0108] (3) Hairiness: This refers to the weight of all hairs generated during the friction between the unwound and doubling twisted yarn (twisted yarn after unwinding and doubling) and the wear-resistant device. The unit is milligrams. The sample is destroyed at a constant winding rate by using multiple points, multiple friction materials, and multiple friction angles. The collected hairiness is measured after the process is completed.

[0109] (4) Stiffness test method: The national standard GB / T7690.4-2013 was used to test the stiffness of twisted yarn after unbend.

[0110] The present invention treats the glass fiber with the glass fiber sizing in each embodiment and each comparative example, and then prepares a glass fiber reinforced composite material according to conventional techniques in the art, wherein the resin is an epoxy resin, and the resin accounts for 40wt%. The tensile properties and wave absorption properties of the prepared glass fiber reinforced composite material are tested; the results are shown in Tables 1 and 2; the testing method is: the tensile properties and elastic modulus of the composite material are tested according to the national standard GB / T1447-2005 fiber reinforced plastic tensile performance test method; the wave absorption performance of the composite material is tested according to the national standard GJB5239-2004 radio frequency absorbing material absorption performance test method; the wave transmission performance graph of the glass fiber reinforced composite material made of glass fiber treated with the glass fiber sizing added with carbon nanotubes prepared in Example 1 of the present invention is as shown in the figure. Figure 4 As shown in the figure, it can be seen that the reflectivity values ​​of the composite materials made of glass fibers coated with the sizing agent are all negative in the band of 3 to 18 GHz, which shows excellent wave absorbing performance.

[0111] Table 1

[0112]

[0113]

[0114]

[0115]

[0116] It can be seen from the data in Tables 1 and 2 that the glass fiber sizing with added carbon nanotubes in the present invention can give the glass fiber reinforced composite material excellent wave absorbing properties, thereby greatly improving the wave transmission performance of the glass fiber reinforced composite material, so that its reflectivity values ​​in the band of 3 to 18 GHz are all negative, with excellent wave absorbing performance, and even the reflectivity peak can reach -7 dB to -10 dB. At the same time, it can effectively improve the tensile modulus and tensile strength of the glass fiber reinforced composite material. The glass fiber sizing with added carbon nanotubes prepared in some preferred embodiments of the present invention can give the glass fiber reinforced composite material excellent wave absorbing properties while enabling the tensile strength of the glass fiber reinforced composite material to be not less than 692 MPa and the tensile modulus to be not less than 27.4 GPa.

[0117] Parts of the present invention that are not described in detail are well known to those skilled in the art.

[0118] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for preparing a glass fiber sizing containing carbon nanotubes, characterized in that: The glass fiber sizing agent comprises an effective component and water, wherein the effective component comprises the following components in percentage by mass: 20% to 52% of a main film-forming agent, 4% to 20% of an auxiliary film-forming agent, 2% to 10% of an auxiliary dispersant, 8% to 24% of an organosilicon lubricant, 0% to 15% of a nonionic lubricant, 6.5% to 20% of an amino silane coupling agent, 0% to 6% of an epoxy-functionalized silane coupling agent, and 0.1% to 0.6% of carbon nanotubes; the main film-forming agent is a low molecular weight epoxy resin emulsion, wherein the molecular weight of the epoxy resin in the low molecular weight epoxy resin emulsion is 400 to 800; the auxiliary film-forming agent is a high molecular weight epoxy resin emulsion, wherein the molecular weight of the epoxy resin in the high molecular weight epoxy resin emulsion is 1200 to 1800; the auxiliary dispersant is a low molecular weight water-based epoxy resin solution, wherein the molecular weight of the water-based epoxy resin in the low molecular weight water-based epoxy resin solution is 300 to 400; The glass fiber sizing agent further comprises sodium dodecylbenzenesulfonate, wherein the amount of the sodium dodecylbenzenesulfonate is 0.01 to 0.1% of the mass of the effective component; The method comprises the following steps: (1) adding a formulated amount of an auxiliary film-forming agent and sodium dodecylbenzene sulfonate to water for pre-emulsification to obtain a pre-emulsified liquid; the mass ratio of the water to the auxiliary film-forming agent is (3-5):1; (2) adding a formulated amount of carbon nanotubes to water for ultrasonic dispersion, and then sequentially adding a formulated amount of an auxiliary dispersant and one-third of a formulated amount of an organosilicon lubricant to obtain a dispersion; the mass ratio of the carbon nanotubes to the water is 1:(15-25); (3) adding the dispersion liquid to the pre-emulsion liquid and emulsifying the mixture at a rotation speed of 3000 to 8000 rpm to obtain a carbon nanotube dispersion liquid; (4) adding a formulated amount of an amino silane coupling agent and a formulated amount of an epoxy functionalized silane coupling agent to water and stirring to obtain a coupling agent aqueous dispersion, then adding a pH adjuster to the coupling agent aqueous dispersion to adjust the pH to 5-7 and continuing to stir to obtain a coupling agent solution; the mass ratio of the sum of the mass of the amino silane coupling agent and the epoxy functionalized silane coupling agent to the mass of the water is 1:(4-6); (5) Dilute the formulated amount of the main film-forming agent with water, then add the coupling agent solution, the remaining two-thirds of the formulated amount of the silicone lubricant, the formulated amount of the non-ionic lubricant and the carbon nanotube dispersion in sequence and stir evenly, then add water to obtain the glass fiber impregnating agent with added carbon nanotubes with a preset solid content; the mass ratio of the dilution water to the main film-forming agent is (4~6):

1.

2. The preparation method according to claim 1, wherein: The active ingredients include the following components in percentage by mass: Main film-forming agent 40%~52%, auxiliary film-forming agent 5~15%, auxiliary dispersant 5~6%, silicone lubricant 12~20%, non-ionic lubricant 0~8%, amino silane coupling agent 12~18%, epoxy functionalized silane coupling agent 0~6%, carbon nanotubes 0.1~0.3%.

3. The preparation method according to claim 1, wherein: The solid content of the glass fiber sizing agent is 3-8%.

4. The preparation method according to claim 1, wherein: In step (5), a pH regulator is added to obtain the glass fiber sizing with added carbon nanotubes at a preset pH value; The preset pH value of the glass fiber sizing agent is 4-6, and the pH adjuster is an organic acid.

5. The preparation method according to claim 4, characterized in that: The pH adjuster is one or more of acetic acid, formic acid, succinic acid, and citric acid.

6. The preparation method according to claim 1, wherein: The epoxy resin in the low molecular weight epoxy resin emulsion and the high molecular weight epoxy resin emulsion is bisphenol A type epoxy resin; The carbon nanotubes are multi-walled carbon nanotubes or single-walled carbon nanotubes.

7. The preparation method according to claim 1, wherein: The amino silane coupling agent is A-1100; The epoxy functional silane coupling agent is A-187.

8. The preparation method according to claim 1, wherein: In step (1): the pre-emulsification temperature is 25-40°C, the pre-emulsification time is 10-30 minutes, and the pre-emulsification is carried out at a rotation speed of 100-300 rpm; In step (2), the power of the ultrasonic dispersion is 50-100 W, the temperature of the ultrasonic dispersion is 25-40° C., and the time of the ultrasonic dispersion is 30-60 min.

9. The preparation method according to claim 1, wherein: In step (3), the emulsification temperature is 40-60°C, and the emulsification time is 5-30 minutes; In step (5), the stirring temperature is 25-40° C., the stirring time is 5-15 min, and the stirring speed is 100-300 rpm.

10. A glass fiber sizing containing added carbon nanotubes, prepared by the method according to any one of claims 1 to 9.

11. Use of the glass fiber sizing with added carbon nanotubes prepared by the preparation method according to any one of claims 1 to 9 in the preparation of glass fiber for stealth material or glass fiber reinforced composite material for stealth material.

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