Bio-based epoxy emulsifier, sizing agent, carbon fiber, composite material and preparation method thereof

Abstract

The present invention provides a bio-based epoxy emulsifier, a sizing agent, a carbon fiber, a composite material, and a preparation method thereof. The raw materials of the bio-based epoxy emulsifier include the following components: polysaccharide, epoxy resin, phenolic acid, and a catalyst. The preparation method of the bio-based epoxy emulsifier includes the following steps: S101: heating the epoxy resin to 50-100°C until it is completely melted, then adding polysaccharide, and reacting at 80-110°C for 4-15 hours to obtain a polysaccharide-modified epoxy resin; S102: heating the polysaccharide-modified epoxy resin to 120-200°C, then adding phenolic acid and a catalyst, and reacting for 5-18 hours to obtain a bio-based epoxy emulsifier. When using the bio-based epoxy emulsifier provided by the present invention to prepare a sizing agent, no organic solvent is required. At the same time, the sizing agent prepared using the emulsifier can improve the performance of carbon fibers and composite materials.

Description

Technical Field

[0001] The present invention relates to the field of sizing agents, and in particular to a bio-based epoxy emulsifier, a sizing agent, a carbon fiber, a composite material and a preparation method thereof. Background Art

[0002] Carbon fiber / epoxy resin composites are widely used in a variety of fields, including aerospace, medical devices, automotive transportation, and wind power generation, due to their numerous advantages, including high temperature resistance, friction resistance, corrosion resistance, high modulus, and high strength. However, during the industrial production of carbon fiber, industrial and process issues inevitably cause irreversible damage to the fiber itself, resulting in a large number of longitudinal grooves and filaments on the fiber surface, which affects the strength of the fiber itself and reduces the mechanical properties of the carbon fiber / epoxy resin composite.

[0003] In order to improve the surface condition of carbon fiber, enhance its polarity and interfacial bonding performance with resin, a variety of methods have been proposed, including gas phase oxidation, plasma treatment and vapor deposition. However, these methods have the risk of directly or indirectly damaging the carbon fiber. In contrast, the sizing method has become an ideal choice for optimizing the surface properties of carbon fiber due to its cost-effectiveness, strong controllability and no damage to the fiber. The sizing method not only improves the wettability of the fiber surface, but also connects the fiber and the matrix through the "chain" effect, providing physical and chemical bonding properties at the interface, thereby improving the mechanical properties of the composite material.

[0004] Although the sizing method has many advantages, existing water-based epoxy emulsifiers still face some problems when preparing sizing agents. In particular, existing emulsifiers use toxic and harmful raw materials during industrial production, which poses a threat to the ecological environment and human health. In addition, existing emulsifiers can usually only achieve a single function of de-emulsifying resins and have no additional contribution to the subsequent preparation of composite materials, resulting in waste of raw materials and increased production costs. This is contrary to the principles of contemporary enterprises to pursue product efficiency and achieve raw material diversification. Take the Chinese patent publication number CN100500984C as an example, which discloses an emulsion-type sizing agent prepared by mixing polyimide resin and epoxy resin. Although this method improves the surface properties of carbon fibers to a certain extent, the prepared sizing agent contains a difficult-to-volatile organic solvent, which is difficult to remove and difficult to degrade, causing serious pollution to the environment. This defect limits its widespread application in modern industrial production.

[0005] The present invention aims to solve the above-mentioned problems. Summary of the Invention

[0006] To address the above-mentioned issues, the present invention proposes a bio-based epoxy emulsifier, a sizing agent, a carbon fiber, a composite material, and a method for preparing the same. This bio-based epoxy emulsifier avoids the use of toxic and hazardous raw materials in industrial production, enabling multiple methods for preparing the sizing agent. It simultaneously performs multiple functions, including protecting fibers, enhancing interfacial bonding, and improving the mechanical properties of composite materials. This bio-based epoxy emulsifier and the sizing agent produced using it are easily degradable, meeting the requirements of sustainable development in modern industry.

[0007] The present invention provides a bio-based epoxy emulsifier, the raw materials of which include the following components: polysaccharide, epoxy resin, phenolic acid and catalyst;

[0008] The preparation method of the bio-based epoxy emulsifier comprises the following steps:

[0009] S101: heating the epoxy resin to 50-100° C. until it is completely melted, then adding polysaccharide, and reacting at 80-110° C. for 4-15 hours to obtain a polysaccharide-modified epoxy resin;

[0010] S102: Heat the polysaccharide-modified epoxy resin to 120-200° C., then add phenolic acid and a catalyst, and react for 5-18 hours to obtain a bio-based epoxy emulsifier.

[0011] In one or more embodiments, the mass ratio of polysaccharide to epoxy resin in step S101 is 1:(3-4.5).

[0012] In one or more embodiments, in step S102, the mass ratio of the polysaccharide-modified epoxy resin to the phenolic acid is 1:(0.1-1), and the mass of the catalyst accounts for 0.001%-0.008% of the total mass of the raw materials.

[0013] In one or more embodiments, the bio-based epoxy emulsifier has one or more of the following characteristics:

[0014] The polysaccharide is selected from one or more of chitosan, chitosan derivatives and chitobiose hydrochloride, and the chitosan derivative is selected from one or more of carboxymethyl chitosan and chitosan oligosaccharides;

[0015] The epoxy resin is selected from one or more of bisphenol A epoxy resin, bisphenol F epoxy resin, diphenol propane type epoxy resin and polyphenol type glycidyl ether epoxy resin;

[0016] The phenolic acid is selected from one or more of cinnamic acid and cinnamic acid derivatives, and the cinnamic acid derivative is selected from one or more of hydroxycinnamic acid, butyl cinnamate and 4-methylcinnamic acid;

[0017] The catalyst includes tetrabutylammonium bromide.

[0018] The present invention also provides a sizing agent comprising a bisphenol A epoxy resin in a mass ratio of 1: (0.25-0.37): (3.34-4): (0.007-0.13): (0.007-0.13), the bio-based epoxy emulsifier as described above, water, a lubricant and an antistatic agent.

[0019] In one or more embodiments, the sizing agent is prepared by:

[0020] S111: heating the bisphenol A epoxy resin to a molten state, adding the bio-based epoxy emulsifier and mixing the bisphenol A epoxy resin and the bio-based epoxy emulsifier using a high-speed shearing machine;

[0021] S112: After the mixture is evenly stirred, the rotation speed is increased and water is slowly added to continue stirring and mixing;

[0022] S113: After stirring and mixing evenly, a lubricant and an antistatic agent are added to obtain a sizing agent.

[0023] The present invention also provides a sizing agent comprising the bio-based epoxy emulsifier as described above, amines, water, a lubricant and an antistatic agent in a mass ratio of 1: (0.01-0.15): (2.6-3): (0.007-0.13): (0.007-0.13).

[0024] In one or more embodiments, the sizing agent is prepared by:

[0025] S121: Cool the bio-based epoxy emulsifier to 50-70°C, then add the amine and stir to mix;

[0026] S122: Increase the stirring speed to 1000-2000 rpm, slowly add water dropwise, and continue stirring and mixing;

[0027] S123: After stirring and mixing evenly, a lubricant and an antistatic agent are added to obtain a sizing agent.

[0028] The present invention also provides a sizing-treated carbon fiber, which is prepared by sizing the carbon fiber using the sizing agent as described above.

[0029] The present invention also provides a carbon fiber / epoxy resin composite material, which is prepared by curing the sizing-treated carbon fiber as described above, epoxy resin and curing agent in a mass ratio of 1:(100-200):(10-20).

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] 1. The bio-based epoxy emulsifier provided by this invention, made from polysaccharides and phenolic acids, offers advantages such as readily available raw materials, high yield, simple operation, and high degradation efficiency. This emulsifier eliminates the need for organic solvents in the preparation of sizing agents, thus avoiding equipment damage and achieving environmentally friendly production. It has the potential for large-scale production applications.

[0032] 2. The bio-based epoxy emulsifier provided by this invention is versatile and can be used as a surfactant to emulsify epoxy resins via a phase inversion method. Furthermore, a simpler self-emulsification method can be used to directly prepare water-based sizing agents, eliminating the need for pre-preparation of the emulsifier, thus simplifying the process and saving time.

[0033] 3. The sizing-treated carbon fibers provided by this invention contain double bonds that readily undergo cycloaddition reactions under ultraviolet light, thereby shortening the curing time of the composite material. Composite materials prepared using UV-curable resins offer low energy consumption, minimal pollution, and low cost, while also exhibiting excellent mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is an infrared chromatogram characterization of the sizing agent prepared in Example 1 of the present invention.

[0035] Figure 2 This is the thermogravimetric diagram of the sizing agent prepared in Example 2 of the present invention.

[0036] Figure 3 This is a surface morphology image (SEM) of the sizing-treated carbon fiber prepared in Example 3 of the present invention.

[0037] Figure 4 This is a surface morphology (SEM) of the sizing-treated carbon fiber prepared in Example 4 of the present invention.

[0038] Figure 5 This is a surface morphology (SEM) of the carbon fiber recovered after degradation of the carbon fiber / epoxy resin composite material prepared in Example 4 of the present invention.

[0039] Figure 6 Schematic diagram showing a comparison of the interlaminar shear strength of the carbon fiber / epoxy resin composite materials prepared in Examples 1 to 4 of the present invention and Comparative Example 1. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the invention and are not intended to limit the invention.

[0041] Throughout this document, all features, such as values, amounts, amounts, and concentrations, specified in numerical ranges or percentage ranges are provided for simplicity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to encompass and specifically disclose all possible subranges and individual values ​​within those ranges (including integers and fractions).

[0042] In this document, unless otherwise specified, percentage refers to mass percentage and ratio refers to mass ratio.

[0043] Herein, when describing embodiments or examples, it should be understood that they are not intended to limit the present invention to these embodiments or examples. On the contrary, all alternatives, modifications and equivalents of the methods and materials described herein are encompassed within the scope defined by the claims.

[0044] In this document, for the sake of brevity, not all possible combinations of the various technical features in each embodiment or example are described. Therefore, as long as there are no contradictions in the combination of these technical features, the various technical features in each embodiment or example can be combined in any way, and all possible combinations should be considered to be within the scope of this specification.

[0045] Herein, “comprising,” “including,” “containing” and similar terms encompass the meanings of “consisting essentially of” and “consisting of,” for example, when “A comprises B and C” is disclosed herein, “A consists essentially of B and C” and “A consists of B and C” should be deemed to have been disclosed herein.

[0046] The invention provides a bio-based epoxy emulsifier, the raw materials of which include the following components: polysaccharide, epoxy resin, phenolic acid and catalyst.

[0047] In the present invention, the polysaccharide is selected from one or more of chitosan, chitosan derivatives and chitobiose hydrochloride. Among them, the chitosan derivative can be one or more selected from carboxymethyl chitosan and chitosan oligosaccharide.

[0048] In the present invention, the epoxy resin is selected from one or more of bisphenol A epoxy resin, bisphenol F epoxy resin, diphenol propane type epoxy resin and polyphenol type glycidyl ether epoxy resin.

[0049] In the present invention, the phenolic acid is selected from one or more of cinnamic acid and cinnamic acid derivatives, wherein the cinnamic acid derivatives can be one or more of hydroxycinnamic acid, butyl cinnamate and 4-methylcinnamic acid.

[0050] In the present invention, the catalyst includes but is not limited to tetrabutylammonium bromide catalyst.

[0051] The preparation method of the bio-based epoxy emulsifier comprises the following steps:

[0052] S101: heating the epoxy resin to 50-100° C. until it is completely melted, then adding polysaccharide, and reacting at 80-110° C. for 4-15 hours to obtain a polysaccharide-modified epoxy resin;

[0053] S102: heating the entire polysaccharide-modified epoxy resin obtained in step S101 to 120-200° C., then adding phenolic acid and a catalyst, and reacting for 5-18 hours to obtain a bio-based epoxy emulsifier.

[0054] In step S101, the mass ratio of the polysaccharide to the epoxy resin is 1:(3-4.5). In some embodiments, the mass ratio of the polysaccharide to the epoxy resin can be 1:(3.5-4.5), or 1:(3-4), or 1:(4-4.5). Preferably, the mass ratio of the polysaccharide to the epoxy resin is 1:4, or 1:3.33, or 1:4.33.

[0055] For example, the polysaccharide-modified epoxy resin is formed by the reaction of chitosan and bisphenol A epoxy resin in a mass ratio of 1:4, or by the reaction of carboxymethyl chitosan and bisphenol F epoxy resin in a mass ratio of 1:3.33, or by the reaction of chitosan oligosaccharide and diphenol propane epoxy resin in a mass ratio of 1:3.33, or by the reaction of chitobiose hydrochloride and polyphenol glycidyl ether epoxy resin in a mass ratio of 1:4.33.

[0056] In step S102, the mass ratio of the polysaccharide-modified epoxy resin to the phenolic acid is 1:(0.1-1), and the mass of the catalyst accounts for 0.001%-0.008% of the total mass of the raw materials (i.e., the total mass of the polysaccharide-modified epoxy resin, phenolic acid, and catalyst).

[0057] The bio-based epoxy emulsifier provided by the present invention is prepared based on polysaccharides and phenolic acids, and the raw materials are easy to obtain, the yield is high, the operability is strong and the degradation efficiency is high. Moreover, in the process of preparing the sizing agent using the bio-based epoxy emulsifier prepared by the present invention, no organic solvent is used, which avoids damage to the equipment and is green and environmentally friendly, and has an application prospect for large-scale production. In addition, the bio-based epoxy emulsifier provided by the present invention is multifunctional. The bio-based epoxy emulsifier can be used as a surfactant to emulsify epoxy resin through the phase inversion method, and the self-emulsification method can also be used to directly prepare the water-based sizing agent, which is simple to operate and saves time.

[0058] The present invention also provides a sizing agent, comprising a bisphenol A epoxy resin in a mass ratio of 1: (0.25-0.37): (3.34-4): (0.007-0.13): (0.007-0.13), the bio-based epoxy emulsifier as described above, water, a lubricant and an antistatic agent.

[0059] In the present invention, the lubricant is selected from one or more of polyoxyethylene ether, butyl stearate, higher fatty amines, and higher fatty alcohols. In this article, when describing the selection of lubricants, "higher fatty amines" and "higher fatty alcohols" refer to those with relatively long carbon chains. For example, higher fatty amines refer to amine compounds with relatively long carbon chains, typically fatty acids containing 12 or more carbon atoms. Higher fatty alcohols refer to alcohol compounds with relatively long carbon chains, also typically containing 12 or more carbon atoms.

[0060] In the present invention, the antistatic agent is selected from one or more of polyetheresteramide, polyetheresteracetamide, polyethylene oxide and propylene oxide copolymer.

[0061] Preferably, deionized water is used.

[0062] In some embodiments, the sizing agent comprises a bisphenol A epoxy resin, a bio-based epoxy emulsifier as described above, water, a lubricant, and an antistatic agent in a mass ratio of 1: (0.26-0.3): (3.44-3.7): (0.01-0.11): (0.04-0.08).

[0063] In some embodiments, the sizing agent comprises a bisphenol A epoxy resin, a bio-based epoxy emulsifier as described above, water, a lubricant, and an antistatic agent in a mass ratio of 1:0.28:(3.54-3.6):(0.05-0.09):0.06.

[0064] Preferably, the sizing agent comprises a bisphenol A epoxy resin, a bio-based epoxy emulsifier as described above, water, a lubricant and an antistatic agent in a mass ratio of 1:0.28:3.6:0.05:0.06, or comprises a bisphenol A epoxy resin, a bio-based epoxy emulsifier as described above, water, a lubricant and an antistatic agent in a mass ratio of 1:0.28:3.54:0.09:0.06.

[0065] The preparation method of the sizing agent is a phase inversion method, in which a bio-based epoxy emulsifier is used to emulsify bisphenol A epoxy resin. The preparation method of the sizing agent comprises the following steps:

[0066] S111: heating the bisphenol A epoxy resin to a molten state, adding the bio-based epoxy emulsifier and mixing the bisphenol A epoxy resin and the bio-based epoxy emulsifier using a high-speed shearing machine;

[0067] S112: After the mixture is evenly stirred, the rotation speed is increased and water is slowly added to continue stirring and mixing;

[0068] S113: After stirring and mixing evenly, a lubricant and an antistatic agent are added to obtain a sizing agent.

[0069] The present invention also provides a sizing agent comprising the bio-based epoxy emulsifier as described above, amines, water, a lubricant and an antistatic agent in a mass ratio of 1: (0.01-0.15): (2.6-3): (0.007-0.13): (0.007-0.13).

[0070] Similar to the sizing agent described above, in the present invention, the lubricant is selected from one or more of polyoxyethylene ether, top-grade stearic acid esters, higher fatty amines, and higher fatty alcohols. The antistatic agent is selected from one or more of polyether ester amides, polyether ester acetamides, polyethylene oxide, and propylene oxide copolymers. Preferably, deionized water is used. In addition, in the present invention, the amine includes but is not limited to triethylamine.

[0071] In some embodiments, the sizing agent comprises the bio-based epoxy emulsifier described above, amines, water, a lubricant, and an antistatic agent in a mass ratio of 1: (0.07-0.15): (2.8-3): (0.02-0.13): (0.08-0.13).

[0072] In some embodiments, the sizing agent comprises the bio-based epoxy emulsifier, amines, water, a lubricant, and an antistatic agent as described above in a mass ratio of 1: (0.09-0.13): 3: (0.08-0.13): (0.1-0.12).

[0073] Preferably, the sizing agent comprises the bio-based epoxy emulsifier, amines, water, lubricant and antistatic agent as described above in a mass ratio of 1:0.13:3:0.13:0.12, or comprises the bio-based epoxy emulsifier, amines, water, lubricant and antistatic agent as described above in a mass ratio of 1:0.09:3:0.08:0.1.

[0074] The preparation method of the sizing agent is a self-emulsification method, comprising the following steps:

[0075] S121: Cool the bio-based epoxy emulsifier to 50-70°C, then add the amine and stir to mix;

[0076] S122: Increase the stirring speed to 1000-2000 rpm, slowly add water dropwise, and continue stirring and mixing;

[0077] S123: After stirring and mixing evenly, a lubricant and an antistatic agent are added to obtain a water-based epoxy carbon fiber sizing agent.

[0078] The present invention also provides a sizing-treated carbon fiber, which is prepared by sizing the carbon fiber using the sizing agent described above. Specifically, it comprises the following steps:

[0079] The commercial carbon fiber (filament) is placed in a container filled with acetone and subjected to a desizing treatment at 50-100°C for 5-24 hours to obtain desizing carbon fiber;

[0080] Then, the carbon fiber is placed in a beaker containing the sizing agent described above and soaked for 5 to 15 minutes. The carbon fiber coated with the sizing agent is placed in an oven at 100 to 200° C. for 2 to 30 minutes to obtain sizing-treated carbon fiber.

[0081] When commercial carbon fiber cloth is used as the carbon fiber, the carbon fiber is sizing treated by using the sizing agent described above, including the following steps:

[0082] The commercial carbon fiber cloth was cut into small pieces of 80×80 mm in size and placed in a container filled with acetone, heated and soaked at 60-120°C for 10-24 hours, washed with deionized water several times, and then vacuum-dried at 105-120°C for 4-10 hours to obtain the desizing carbon fiber cloth.

[0083] Then, the desized carbon fiber cloth is placed in a beaker containing the sizing agent described above and soaked for 30 to 60 minutes. The carbon fiber cloth coated with the sizing agent is placed in an oven at 105 to 120° C. and vacuum dried for 2 to 4 hours to obtain a sizing-treated carbon fiber cloth.

[0084] The present invention also provides a carbon fiber / epoxy resin composite material, which is prepared by curing the sizing-treated carbon fiber described above, epoxy resin, and curing agent. In some embodiments, the carbon fiber / epoxy resin composite material is prepared by curing carbon fiber, epoxy resin, and curing agent in a mass ratio of 1:(100-200):(10-20). The epoxy resin and curing agent are both in excess to ensure that the carbon fiber is fully impregnated.

[0085] In one embodiment, a method for preparing a carbon fiber / epoxy resin composite material comprises the following steps:

[0086] Six layers of the sizing-treated carbon fiber cloth described above were laid out and placed in a mold. The epoxy resin and curing agent were mixed and air bubbles removed. The mixture was then vacuum-injected into the mold and cured at 105°C for 2 hours and 125°C for 2 hours to obtain a carbon fiber composite material. Different numbers of carbon fiber layers result in different mechanical properties, and the carbon fiber cloth is relatively uniform by default.

[0087] Preferably, the mass ratio of the epoxy resin to the curing agent is 100: 10. In addition, the curing agent includes but is not limited to diethylenetriamine.

[0088] In some embodiments, the curing is performed under UV light with an intensity of 25.0 J / cm -2Under UV irradiation, the sizing agent undergoes a cycloaddition reaction with the matrix, which can improve the strength of the composite material. In addition, UV-curable resins have the advantages of low energy consumption, low pollution, low cost and good performance when preparing composite materials.

[0089] Compared with the prior art, the present invention has the following beneficial effects:

[0090] 1. The bio-based epoxy emulsifier provided by this invention, made from polysaccharides and phenolic acids, offers advantages such as readily available raw materials, high yield, simple operation, and high degradation efficiency. This emulsifier eliminates the need for organic solvents in the preparation of sizing agents, thus avoiding equipment damage and achieving environmentally friendly production. It has the potential for large-scale production applications.

[0091] 2. The bio-based epoxy emulsifier provided by this invention is versatile and can be used as a surfactant to emulsify epoxy resins via a phase inversion method. Furthermore, a simpler self-emulsification method can be used to directly prepare water-based sizing agents, eliminating the need for pre-preparation of the emulsifier, thus simplifying the process and saving time.

[0092] 3. The sizing-treated carbon fibers provided by this invention contain double bonds that readily undergo cycloaddition reactions under ultraviolet light, thereby shortening the curing time of the composite material. Composite materials prepared using UV-curable resins offer low energy consumption, minimal pollution, and low cost, while also exhibiting excellent mechanical properties.

[0093] The present invention will be described below by way of specific examples. It should be understood that these examples are merely illustrative and are not intended to limit the scope of the present invention. The methods, reagents, and materials used in the examples are, unless otherwise stated, conventional methods, reagents, and materials in the art. The starting compounds in the examples can all be purchased from commercial sources.

[0094] Example 1

[0095] (1) Preparation of bio-based epoxy emulsifier:

[0096] S101: 40 g of bisphenol A epoxy resin is added to an oil bath, heated to 65° C. and stirred until completely melted, and then 10 g of chitosan is added. The oil bath is heated to 90° C. and reacted for 4 h to obtain a polysaccharide-modified epoxy resin. The polysaccharide-modified epoxy resin is now a chitosan-modified epoxy resin.

[0097] S102: Heat all the chitosan-modified epoxy resin obtained in step S101 to 120° C., then add 5 g of cinnamic acid and 0.006 g of tetrabutylammonium bromide catalyst, and react at a constant temperature for 5 hours to obtain a bio-based epoxy emulsifier.

[0098] (2) Preparation of sizing agent (phase inversion method is used in this embodiment):

[0099] S111: 100 g of bisphenol A epoxy resin is heated to a molten state, and 28 g of a bio-based epoxy emulsifier is added and mixed. The bisphenol A epoxy resin and the bio-based epoxy emulsifier are stirred and mixed using a high-speed shearing machine;

[0100] S112: Stirring at a speed of 500 rpm for 10 minutes. After the mixture is evenly mixed, the speed is increased to 2000 rpm, and 360 g of deionized water is slowly added, and the mixture is continued to be stirred and mixed.

[0101] S113: After stirring and mixing evenly, 5 g of polyoxyethylene ether and 6 g of polyether ester amide are added to obtain a sizing agent.

[0102] (3) Preparation of sizing treated carbon fiber:

[0103] The commercial carbon fiber was placed in a container filled with acetone and subjected to a desizing treatment at 50°C for 5 hours to obtain desizing carbon fiber;

[0104] Then, the carbon fiber was placed in a beaker containing the sizing agent described above and soaked for 5 minutes. The carbon fiber coated with the sizing agent was placed in an oven at 100° C. for 2 minutes to obtain sizing-treated carbon fiber.

[0105] (4) Preparation of carbon fiber / epoxy resin composite materials:

[0106] Take 6 layers of the above-mentioned sizing-treated carbon fiber cloth, lay them out and put them into the mold, mix the epoxy resin and curing agent diethylenetriamine in a mass ratio of 100:10, remove the bubbles and vacuum inject them into the mold, and cure them at 105°C for 2h and 125°C for 2h to obtain a carbon fiber / epoxy resin composite material.

[0107] The sizing agent prepared in Example 1 was characterized by infrared chromatogram. The characterization results are shown in Figure 1 In the infrared spectrum, the horizontal axis represents the wave number (wavenumbers), the unit is cm -1 .like Figure 1 As shown, at 1595 cm -1 The absorption peak of NH2 is at 915 cm -1 and 771 cm -1 The characteristic peak at 1710 cm is the end epoxy absorption peak. It can be found that the characteristic peaks of amino and epoxy groups become smaller, which indicates that bisphenol A epoxy resin reacts with chitosan. -1 The characteristic peak at 1595 cm -1 The weakening of the absorption characteristic peak indicates that the content of amino (-NH2) functional groups decreases. These phenomena indicate that an amide bond (-CONH-) is formed between the amino group (-NH2) of chitosan and the carboxyl group (-COOH) of cinnamic acid.

[0108] Example 2

[0109] (1) Preparation of bio-based epoxy emulsifier:

[0110] S101: 50 g of bisphenol F epoxy resin is added to an oil bath, heated to 60° C. and stirred until completely melted, and then 15 g of carboxymethyl chitosan is added. The oil bath is heated to 80° C. and reacted for 4 h to obtain a polysaccharide-modified epoxy resin. The polysaccharide-modified epoxy resin is a carboxymethyl chitosan-modified epoxy resin.

[0111] S102: Heat all the carboxymethyl chitosan-modified epoxy resin obtained in step S101 to 125° C., then add 10 g of hydroxycinnamic acid and 0.008 g of tetrabutylammonium bromide catalyst, and react at a constant temperature for 8 hours to obtain a bio-based epoxy emulsifier.

[0112] (2) Preparation of sizing agent (self-emulsification method is used in this embodiment):

[0113] S121: Cool 75 g of bio-based epoxy emulsifier to 60° C., slowly add 10 g of triethylamine dropwise, and stir at 500 rpm for 15 min.

[0114] S122: Increase the speed to 1500 rpm, slowly add 225 g of deionized water, and continue stirring to mix;

[0115] S123: After stirring and mixing evenly, 10 g of butyl stearate and 9 g of polyether acetamide were added to obtain a sizing agent.

[0116] (3) Preparation of sizing treated carbon fiber:

[0117] The process of preparing sizing-treated carbon fibers is the same as that in Example 1.

[0118] (4) Preparation of carbon fiber / epoxy resin composite materials:

[0119] The process of preparing the carbon fiber / epoxy resin composite material is the same as that in Example 1.

[0120] The sizing agent prepared in Example 2 was subjected to thermogravimetric analysis. The thermogravimetric test results are shown in FIG. Figure 2 .like Figure 2 As shown in the graph, at 290°C, the sizing agent experienced a small weight loss of 5%, which was attributed to the cleavage of the amide segments in the sizing agent. At 367°C, the weight loss was 87%, which was attributed to thermal decomposition. This indicates that the sizing agent has good thermal stability.

[0121] Example 3

[0122] S101: 40 g of diphenol propane epoxy resin is added to an oil bath, heated to 80° C. and stirred until completely melted, and then 12 g of chitosan oligosaccharide is added. The oil bath is heated to 95° C. and reacted for 8 h to obtain a polysaccharide-modified epoxy resin. The polysaccharide-modified epoxy resin is chitosan oligosaccharide-modified epoxy resin.

[0123] S102: The entire chitosan-modified epoxy resin obtained in step S101 is heated to 130° C., and then 6 g of butyl cinnamate and 0.006 g of tetrabutylammonium bromide catalyst are added, and the mixture is reacted at a constant temperature for 10 hours to obtain a bio-based epoxy emulsifier.

[0124] (2) Preparation of sizing agent (phase inversion method is used in this embodiment):

[0125] S111: 100 g of bisphenol A epoxy resin and 28 g of bio-based epoxy emulsifier were stirred and mixed using a high-speed shearing machine;

[0126] S112: Stirring at a speed of 650 rpm for 10 minutes. After the mixture is evenly mixed, the speed is increased to 2400 rpm, and 354 g of deionized water is slowly added, and the mixture is continued to be stirred and mixed.

[0127] S113: After stirring and mixing evenly, 9 g of higher fatty amine and 6 g of polyethylene oxide are added to obtain a sizing agent.

[0128] (3) Preparation of sizing treated carbon fiber:

[0129] The process of preparing sizing-treated carbon fibers is the same as that in Example 1.

[0130] (4) Preparation of carbon fiber / epoxy resin composite materials:

[0131] Other conditions were the same as those in the process of preparing the carbon fiber / epoxy resin composite material in Example 1, except that the curing process was carried out under ultraviolet light irradiation with a light intensity of 25.0 J / cm -2 .

[0132] The surface morphology of the sizing treated carbon fiber prepared in Example 3 was observed using a scanning electron microscope (SEM). The characterization results are as follows: Figure 3 As shown. Figure 3 It can be seen that the surface of the carbon fiber after sizing treatment is evenly covered with the sizing agent, and is smooth and flat.

[0133] Example 4

[0134] (1) Preparation of bio-based epoxy emulsifier:

[0135] S101: Add 65 g of polyphenol-type glycidyl ether epoxy resin to an oil bath, heat to 100° C. and stir until it is completely melted, then add 15 g of chitobiose hydrochloride, heat the oil bath to 110° C. and react for 8 hours to obtain a polysaccharide-modified epoxy resin. The polysaccharide-modified epoxy resin is chitobiose hydrochloride-modified epoxy resin;

[0136] S102: The entire chitobiose hydrochloride-modified epoxy resin obtained in step S101 is heated to 120° C., and then 10 g of 4-methylcinnamic acid and 0.009 g of tetrabutylammonium bromide catalyst are added, and the mixture is reacted at a constant temperature for 8 hours to obtain a bio-based epoxy emulsifier.

[0137] (2) Preparation of sizing agent (self-emulsification method is used in this embodiment):

[0138] S121: Cool 90 g of bio-based epoxy emulsifier to 60°C, slowly add 8 g of triethylamine dropwise, and stir at 500 rpm for 15 min;

[0139] S122: Increase the speed to 1500 rpm, slowly add 270 g of deionized water, and continue stirring to mix;

[0140] S123: After stirring and mixing evenly, 7 g of higher fatty alcohol and 9 g of propylene oxide copolymer are added to obtain a sizing agent.

[0141] (3) Preparation of sizing treated carbon fiber:

[0142] The process of preparing sizing-treated carbon fibers is the same as that in Example 1.

[0143] (4) Preparation of carbon fiber / epoxy resin composite materials:

[0144] The process of preparing the carbon fiber / epoxy resin composite material is the same as that in Example 1.

[0145] The surface morphology of the sizing-treated carbon fibers obtained in Example 4, i.e., the surface morphology of the carbon fibers before recycling, was observed using a scanning electron microscope (SEM). Figure 4 The surface morphology of the carbon fiber recovered from the degradation of the carbon fiber / epoxy resin composite material prepared in Example 4 was observed using a scanning electron microscope (SEM), that is, the surface morphology characteristics of the recovered carbon fiber, see Figure 5 .like Figure 4 and Figure 5 As shown, the surface of the carbon fiber before recycling is evenly wrapped by the sizing agent, while the surface of the carbon fiber after degradation has a large number of grooves, which shows that the sizing agent is degradable and does not cause any damage to the carbon fiber.

[0146] Among them, before observing the surface morphology of the recycled carbon fiber, the composite material needs to be treated as follows:

[0147] 5 g of the carbon fiber / epoxy resin composite prepared in Example 4 was placed in a glass bottle, 3 mL of acetonitrile and 9 mL of acetic acid solvent were added, and the mixture was then placed in a 90°C oil bath for degradation. After the composite material was completely degraded, it was filtered and washed with ethanol to obtain recovered carbon fiber.

[0148] Meanwhile, degradation analysis was performed on the composite material prepared in Example 4, which proved that the sizing agent provided in this example has the possibility of degradation.

[0149] Comparative Example 1

[0150] Preparation of carbon fiber / epoxy resin composites:

[0151] The carbon fiber cloth coated with a commercial sizing agent was cut into small pieces of 80×80 mm in size. Six layers of the above small pieces were laid out and placed in a mold. Epoxy resin and curing agent diethylenetriamine in a mass ratio of 100:10 were mixed and vacuum injected into the mold after removing bubbles. The mixture was cured at 105°C for 2 h and 125°C for 2 h to obtain a carbon fiber / epoxy resin composite material.

[0152] It should be noted that in the preparation process of commercial sizing agents, one or more of acetone, ethylene glycol monomethyl ether and ethylene glycol butyl ether are usually used. Other organic solvents may also be used, which are only used as examples here.

[0153] Test Case

[0154] Interlaminar shear strength test

[0155] Test method: Refer to the industry standard JC / T 773-2010 for the determination of the interlaminar shear strength (ILSS) of fiber-reinforced plastics using the short beam method, or refer to the national standard GB / T 1450.1-2005 for the test method of interlaminar shear strength of fiber-reinforced plastics.

[0156] The test results of the interlaminar shear strength of the carbon fiber / epoxy resin composite materials prepared in Examples 1 to 4 and Comparative Example 1 are shown in Tables 1 and Figure 6 As shown in Table 1 and Figure 6 It can be seen that after the sizing treatment, the carbon fibers in the present invention significantly enhance the interfacial adhesion with the matrix and significantly improve the mechanical properties of the composite material.

[0157] Table 1: Interlaminar shear strength of carbon fiber / epoxy resin composites prepared in Examples 1 to 4 and Comparative Example 1

[0158] Carbon fiber / epoxy resin composite material Interlaminar shear strength / MPa Example 1 71.14 Example 2 76.36 Example 3 72.48 Example 4 73.57 Comparative Example 1 62.54

[0159] Particle size testing

[0160] Testing method: The average particle size of the sizing agents prepared in Examples 1 to 4 and Comparative Example 1 was measured using a Zetasizer NanoZS90 dynamic laser scattering instrument produced by Malvern Instruments.

[0161] Particle size has an important influence on the stability, distribution uniformity and interaction of sizing agent with carbon fiber. As shown in Table 2 below, Example 2 and Example 4 show smaller particle size, which helps sizing agent to be more evenly distributed on the carbon fiber surface. In combination with Table 1 and Table 2, it can be seen that different particle sizes have slightly different effects on the interfacial properties of carbon fiber composite materials, and smaller particle size has a significant effect on improving the mechanical properties of carbon fiber composite materials. Specifically, sizing agent with smaller particle size can make its coating on the carbon fiber surface more uniform, thereby making the surface of carbon fiber smoother after coating, and the interface thickness is thinner, which is conducive to the full combination and reaction of carbon fiber and epoxy resin. As shown in the foregoing, the sizing agent of Example 2 and Example 4 is prepared by self-emulsification method, and the sizing agent of Example 1 and Example 3 is prepared by phase inversion method. Therefore, the interfacial properties of carbon fiber / epoxy resin composite material prepared by self-emulsification method are better than those prepared by phase inversion method. Although the interfacial properties of composite material obtained by sizing agent prepared by phase inversion method are lower, the method is simple to operate, low in cost and has a higher degree of industrialization. The present invention does not limit the preparation method of the sizing agent. Depending on the actual situation, a self-emulsification method or a phase inversion method can be adopted.

[0162] pH test

[0163] Test method: The pH value of the sizing agent was obtained by using a DELTA 320 pH meter from Mettler-Toledo, USA.

[0164] Changes in pH affect the chemical stability of the sizing agent and its interaction with the fiber, which in turn affects the fiber's dyeing properties and feel. As shown in Table 2 below, the pH values ​​of Comparative Example 1 and all Examples are mostly close to neutral, which may contribute to the product's stability and storage properties.

[0165] Viscosity test

[0166] Test method: The viscosity of the sizing agent was measured using a Brookfield DV-II Pro rotational viscometer.

[0167] Viscosity directly affects the sizing rate, the ratio of penetration to coating, and the thickness of the film. As shown in Table 2, the viscosities of the sizing agents in Examples 1 to 4 are significantly lower than the viscosity of the commercial sizing agent in Comparative Example 1. Therefore, the sizing agent prepared with a bio-based epoxy emulsifier helps improve its sizing performance, including sizing rate, penetration to coating ratio, and film thickness.

[0168] Stiffness test

[0169] Test method: The stiffness of carbon fiber is characterized according to the stiffness determination performance in Part 4 of GB / T 7690.4-2013 Test methods for reinforcing material yarns.

[0170] Stiffness testing helps us understand the effects of sizing agents on the shape and structure of textiles. Higher stiffness helps textiles maintain their shape, which may improve product performance. Figure 2 As shown, the stiffness of Examples 1 to 4 is greater than that of Comparative Example 1. Therefore, the sizing-treated carbon fibers provided by the present invention can better maintain their shape and have better performance than commercial carbon fibers. Specifically, the stiffness of Example 2 reaches 98 cm, while the stiffness of Comparative Example 1 is 92 cm, indicating that the carbon fibers prepared in Example 2 have the best performance.

[0171] Hair quantity test

[0172] Test method: The fuzz content of carbon fiber was obtained according to GB-T 41956-2022 Determination of fuzz content of carbon fiber tow.

[0173] The effectiveness of the sizing agent in reducing carbon fiber fuzz can be evaluated by measuring the amount of fuzz. As shown in Table 2 below, the amount of fuzz in the carbon fibers prepared in Examples 1 to 4 was lower than that in Comparative Example 1. This demonstrates that the sizing agent prepared using the bio-based epoxy emulsifier in the present invention is effective in reducing carbon fiber fuzz.

[0174] Comprehensive stiffness and fuzz test results show that the performance of carbon fiber / epoxy resin composites can be significantly improved by sizing carbon fiber with a sizing agent made from a bio-based epoxy emulsifier.

[0175] Table 2: Particle size, pH value and viscosity of sizing agent and stiffness and fuzz content of carbon fiber in Examples 1 to 4 and Comparative Example 1

[0176] Comparative Example 1 Example 1 Example 2 Example 3 Example 4 Particle size / nm 308 278 156 285 178 pH 6.89 7.68 7.06 7.45 7.32 Viscosity / cp 37.8 35.4 28.5 34.2 29.5 Stiffness / cm 92 95 98 93 95 Hair amount / mg 2.45 2.32 1.98 2.13 2.34

[0177] In summary, the sizing agents, carbon fibers, and composite materials made therefrom of Examples 1-4 are superior to commercial sizing agents and their corresponding products in terms of performance, stability, and cost-effectiveness.

Claims

1. A bio-based epoxy emulsifier, characterized in that The raw materials of the bio-based epoxy emulsifier include the following components: polysaccharide, epoxy resin, phenolic acid and catalyst; The preparation method of the bio-based epoxy emulsifier comprises the following steps: S101: heating the epoxy resin to 50-100° C. until it is completely melted, then adding a polysaccharide, and reacting at 80-110° C. for 4-15 hours to obtain a polysaccharide-modified epoxy resin, wherein the mass ratio of the polysaccharide to the epoxy resin is 1:(3-4.5); S102: Heat the polysaccharide-modified epoxy resin to 120-200° C., then add phenolic acid and tetrabutylammonium bromide, and react for 5-18 hours to obtain a bio-based epoxy emulsifier, wherein the mass ratio of the polysaccharide-modified epoxy resin to the phenolic acid is 1:(0.1-1), and the mass of the tetrabutylammonium bromide accounts for 0.001%-0.008% of the total mass of the raw materials.

2. The bio-based epoxy emulsifier according to claim 1, characterized in that Bio-based epoxy emulsifiers have one or more of the following characteristics: The polysaccharide is selected from one or more of chitosan, chitosan derivatives and chitobiose hydrochloride, and the chitosan derivative is selected from one or more of carboxymethyl chitosan and chitosan oligosaccharides; The epoxy resin is selected from one or more of bisphenol A epoxy resin, bisphenol F epoxy resin, diphenol propane type epoxy resin and polyphenol type glycidyl ether epoxy resin; The phenolic acid is selected from one or more of cinnamic acid and cinnamic acid derivatives, and the cinnamic acid derivative is selected from one or more of hydroxycinnamic acid, butyl cinnamate and 4-methylcinnamic acid.

3. A sizing agent, characterized in that The invention comprises a bisphenol A epoxy resin in a mass ratio of 1: (0.25-0.37): (3.34-4): (0.007-0.13): (0.007-0.13), the bio-based epoxy emulsifier according to claim 1, water, a lubricant and an antistatic agent.

4. The sizing agent according to claim 3, characterized in that The preparation method of the sizing agent is: S111: heating the bisphenol A epoxy resin to a molten state, adding the bio-based epoxy emulsifier and mixing the bisphenol A epoxy resin and the bio-based epoxy emulsifier using a high-speed shearing machine; S112: After the mixture is evenly stirred, the rotation speed is increased and water is slowly added to continue stirring and mixing; S113: After stirring and mixing evenly, a lubricant and an antistatic agent are added to obtain a sizing agent.

5. A sizing agent comprising the bio-based epoxy emulsifier according to claim 1, amines, water, a lubricant and an antistatic agent in a mass ratio of 1: (0.01-0.15): (2.6-3): (0.007-0.13): (0.007-0.13).

6. The sizing agent according to claim 5, characterized in that The preparation method of the sizing agent is: S121: Cool the bio-based epoxy emulsifier to 50-70°C, then add the amine and stir to mix; S122: Increase the stirring speed to 1000-2000 rpm, slowly add water dropwise, and continue stirring and mixing; S123: After stirring and mixing evenly, a lubricant and an antistatic agent are added to obtain a sizing agent.

7. A sizing-treated carbon fiber, characterized in that: The sizing-treated carbon fiber is produced by sizing carbon fiber using the sizing agent according to any one of claims 3 to 6.

8. A carbon fiber / epoxy resin composite material, characterized in that: The carbon fiber / epoxy resin composite material is prepared by curing the sizing-treated carbon fiber according to claim 7, epoxy resin and curing agent in a mass ratio of 1:(100-200):(10-20); The curing process is as follows: curing at 105°C for 2h and curing at 125°C for 2h; Alternatively, the curing process is carried out under UV light with an intensity of 25.0 J / cm -2 .

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