Vinyl resin sizing agent based on bionic structure and preparation method

Abstract

The invention discloses a vinyl resin sizing agent based on a bionic structure and a preparation method, and belongs to the technical field of carbon fiber sizing agent preparation. The preparation method comprises the following steps: mixing polyethylene glycol 2000, ethylene glycol diglycidyl ether, E51 and the like for reaction to prepare modified resin; 3, 4-dihydroxyphenylpropionic acid and a double-bond structure are grafted into the modified resin; uniformly stirring and mixing with deionized water in a high-shear dispersion emulsifying machine to form a sizing agent emulsion; the vinyl resin sizing agent based on mussel bionics is prepared. The 3, 4-dihydroxyphenylpropionic acid plays a role in anchoring the carbon fibers; and the chemical copolymerization crosslinking characteristic of the double-bond structure can improve the compatibility with vinyl resin, so that the effect of enhancing the interface by the double-unit structure is achieved, and the interface performance of the composite material is obviously improved.

Description

Technical Field

[0001] This invention belongs to the field of carbon fiber sizing agent preparation technology, specifically relating to a vinyl resin sizing agent inspired by the biomimetic structure of catechol dihydroxyl group and its preparation method. Background Technology

[0002] Carbon fiber reinforced resin matrix composites (CFRPs) possess the advantages of both high specific modulus and high specific strength, and have been widely used in aerospace, high-end equipment, and new energy fields. Carbon fiber can be used to prepare carbon fiber reinforced vinyl resin composites using vinyl resin as the matrix. Vinyl resin, combining the easy molding properties of unsaturated polyester resins with the excellent corrosion resistance of epoxy resins, has become one of the important matrices suitable for this type of composite, especially in marine engineering, chemical equipment, and other scenarios requiring long-term tolerance to harsh environments. The comprehensive performance of carbon fiber reinforced vinyl resin composites depends not only on the inherent strength of the carbon fiber reinforcement and the vinyl resin matrix, but also significantly on the interface structure and bonding state between them. Good interfacial bonding can efficiently transfer stress and dissipate energy, reducing interfacial stress concentration and crack initiation, which is crucial for ensuring the overall performance of the composite material. However, the strong chemical inertness and smooth morphology of carbon fiber surfaces often make it difficult to achieve the expected interfacial adhesion between them and the resin matrix; when the composite material is used in extreme environments, the weak interfacial structure is prone to failure first, leading to a decline in the overall mechanical properties of the composite material. Therefore, strengthening the interfacial bonding through carbon fiber surface modification has always been a research hotspot in the field of CFRP. Currently, researchers have developed a variety of modification strategies, such as chemical grafting, electrophoretic deposition, chemical vapor deposition, and plasma treatment; while sizing coating method is considered one of the most promising interface control methods in recent years because it causes little damage to the carbon fiber surface, has strong process compatibility, and is easy to industrialize.

[0003] Traditional vinyl sizing agents have significant limitations in molecular design: Firstly, their main unsaturated polyester resin is polymerized from diols and diacids, lacking surface polar groups, making it difficult to form tight bonds with the hydroxyl and carboxyl groups on the carbon fiber surface through hydrogen bonds and coordination bonds. Secondly, general-purpose epoxy sizing agents have significant chemical differences from the vinyl resin matrix, failing to adapt to the free radical copolymerization characteristics of the matrix and instead forming an "interfacial barrier layer" between the fiber and matrix, hindering load transfer and resulting in low interlaminar shear strength and interfacial shear strength, among other key properties of the composite material. Moreover, current research on vinyl sizing agents largely relies on single structural units for reinforcement. Existing research indicates that single functional units cannot simultaneously achieve the integrated requirements of strong interfacial bonding and high matrix compatibility, suggesting that constructing a multifunctional synergistic system may be key to solving this problem.

[0004] Therefore, this paper innovatively proposes a sizing agent design concept based on the synergistic functionalization of catechol and double bonds, aiming to overcome the performance bottleneck of single-functional sizing agents and significantly improve the interfacial properties of carbon fiber reinforced vinyl resin matrix composites. This design concept uses vinyl resin as the matrix resin and, through molecular design and synthesis, integrates catechol and double bond structural units into the sizing agent molecular structure, forming a novel sizing agent with dual synergistic functions. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention proposes a novel vinyl resin sizing agent synthesized and prepared based on biomimetic inspiration from the dihydroxyl structure of catechol, which improves the interfacial and mechanical properties of carbon fiber reinforced vinyl resin composites.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for preparing a mussel-inspired vinyl resin sizing agent includes the following steps:

[0008] S1. Mix equimolar amounts of isophorone diisocyanate with 2-allyloxyethanol, mechanically stir at 60-80°C and reflux for 1-2 hours.

[0009] S2. Place the polyol under vacuum, heat and stir to remove moisture, then cool for later use; mix equimolar amounts of polyethylene glycol 2000, ethylene glycol diglycidyl ether (epoxy value 0.70) and E51 (epoxy value 0.51) in a double-necked flask equipped with a thermometer and a mechanical stirrer, and mechanically stir at 110-130℃ and reflux for 1-2 hours to obtain the modified resin;

[0010] S3. After cooling the modified resin, add the product obtained in S1 into a flask, then mechanically stir and reflux at 60-80℃ for 1-2 hours.

[0011] S4. After cooling the product obtained in S3, add 3,4-dihydroxyphenylpropionic acid and p-toluenesulfonic acid (add at 10% of the mass of 3,4-dihydroxyphenylpropionic acid) to the flask, immerse it in an 80°C oil bath, stir mechanically and reflux, then increase the temperature by 10°C per hour and react for 5 hours to complete the synthesis reaction.

[0012] S5. Then stabilize the temperature to 60-80℃, stir in a high shear dispersion emulsifier at a speed of 1000-2000r / min, and add deionized water dropwise evenly through a peristaltic pump until the solid content of the mixture is 30%-40%. Continue stirring for 30min, and finally dilute it with deionized water to a solid content of 0.5%-10% to obtain a vinyl resin sizing agent emulsion.

[0013] The specific preparation steps are as follows:

[0014] In S3, the mass ratio of the product obtained in S1 to the mass of the modified resin is 5%-30%, such as 10%, 15%, 20%, or 25%.

[0015] In S4, the mass ratio of the 3,4-dihydroxyphenylpropionic acid to the modified resin in S2 is 0-15% and not 0, for example, 2%, 2.8%, 5%, 5.6%, 8.3%, 10%, or 11.1%.

[0016] A mussel-inspired vinyl resin sizing agent, prepared by any one of the above preparation methods.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] 1. This invention involves reacting polyethylene glycol 2000, ethylene glycol diglycidyl ether, and E51 to prepare a modified resin. Then, 3,4-dihydroxyphenylpropionic acid and a double bond structure are grafted into the modified resin. The mixture is stirred with deionized water in a high-shear dispersion emulsifier to form a sizing agent emulsion, thus preparing a mussel-inspired vinyl resin sizing agent. Finally, the sizing agent is coated onto the surface of carbon fibers using a carbon fiber sizing device. The 3,4-dihydroxyphenylpropionic acid anchors the carbon fibers; the chemical copolymerization and crosslinking properties of the double bond structure enhance compatibility with the vinyl resin, thereby achieving a dual-unit structure that strengthens the interface and significantly improves the interfacial properties of the composite material.

[0019] 2. The carbon fibers treated with the vinyl ester resin sizing agent prepared in this invention have significantly optimized wettability and surface energy after sizing due to the introduction of a large number of active functional groups. Attached Figure Description

[0020] Figure 1 This is the overall reaction route of the present invention.

[0021] Figure 2 This is the Fourier transform infrared spectrum of the overall reaction pathway of the mussel-inspired vinyl resin sizing agent prepared according to the present invention.

[0022] Figure 3 This invention relates to a mussel-inspired vinyl resin sizing emulsion.

[0023] Figure 4 Example diagram of sizing equipment

[0024] Figure 5 Scanning electron microscope (SEM) images of fibers after sizing of samples obtained in Comparative Example 1 and Examples 1-7. Detailed Implementation

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] The present invention will be further described below through specific embodiments.

[0027] Example 1:

[0028] S1. Mix equimolar amounts of isophorone diisocyanate and 2-allyloxyethanol together in a four-necked flask, mechanically stir at 70°C and reflux for 2 hours.

[0029] S2. Place polyethylene glycol 2000 in a three-necked flask, evacuate, heat and stir to remove moisture, then cool for later use. Mix 20g polyethylene glycol, 4g ethylene glycol diglycidyl ether and 3g E51 and add to a two-necked flask equipped with a thermometer and a mechanical stirrer. Stir mechanically at 110℃ and reflux for 2 hours to complete the modification of the resin.

[0030] S3. After cooling the product obtained in (2), add the product obtained in (1) into the flask. Then, mechanically stir at 70°C and reflux for 2 hours; at this time, the mass ratio of isophorone diisocyanate and 2-allyloxyethanol to the modified resin described in S2 is 10%.

[0031] S4. After cooling the product obtained in (3), add 3,4-dihydroxyphenylpropionic acid and p-toluenesulfonic acid (added at 10% of the mass of 3,4-dihydroxyphenylpropionic acid) to the flask, immerse the mixture in an 80°C oil bath, stir mechanically and reflux, then raise the temperature by 10°C per hour and react for 5 hours to complete the synthesis reaction; at this time, the mass ratio of 3,4-dihydroxyphenylpropionic acid to the modified resin described in S2 is 2.8%, and the mass ratio of p-toluenesulfonic acid to the modified resin described in S2 is 0.28%.

[0032] S5. Then stabilize the temperature to 60℃, stir in a high shear dispersion emulsifier at a speed of 2000r / min, and add deionized water evenly dropwise through a peristaltic pump until the solid content of the mixture is 30%. Continue stirring for 30min, and finally dilute it with deionized water to a solid content of 1% to obtain a vinyl resin sizing agent emulsion.

[0033] Example 2: Example 2 differs from Example 1 only in the following way: in Example 2, the mass ratio of 3,4-dihydroxyphenylpropionic acid to the modified resin in S4 is 5.6%, and the mass ratio of p-toluenesulfonic acid to the modified resin in S2 is 0.56%.

[0034] Example 3: Example 3 differs from Example 1 only in the following way: in Example 3, the mass ratio of 3,4-dihydroxyphenylpropionic acid to the modified resin described in S2 in S4 is 8.3%, and the mass ratio of p-toluenesulfonic acid to the modified resin described in S2 is 0.83%.

[0035] Example 4: Example 4 differs from Example 1 only in the following way: in Example 4, the mass ratio of 3,4-dihydroxyphenylpropionic acid to the modified resin described in S2 is 11.1%, and the mass ratio of p-toluenesulfonic acid to the modified resin described in S2 is 1.11%.

[0036] Example 5: Example 5 differs from Example 2 only in that, in Example 5, the mass ratio of isophorone diisocyanate and 2-allyloxyethanol in S1 to the modified resin in S2 is 15%.

[0037] Example 6: Example 6 differs from Example 2 only in that, in Example 6, the mass ratio of isophorone diisocyanate and 2-allyloxyethanol in S1 to the modified resin in S2 is 20%.

[0038] Example 7: Example 7 differs from Example 2 only in that, in Example 7, the mass ratio of isophorone diisocyanate and 2-allyloxyethanol in S1 to the modified resin in S2 is 25%.

[0039] To further illustrate the key aspects of this patent, comparative examples are provided.

[0040] Comparative Example 1: Commercially available 12K, T700 high-strength fibers sized with epoxy sizing agents were degummed. The manufacturer was Toray Industries, Ltd., Japan.

[0041] Performance testing:

[0042] The stability, contact angle, sizing amount, and interlaminar shear strength of the sized carbon fibers from Examples 1-7 and Comparative Example 1 were tested respectively. The test methods are as follows:

[0043] Stability: The sizing agents prepared under different conditions were mixed with water to form a sizing agent with a solid content of 10%, and placed in centrifuge tubes. They were left to stand at room temperature for 90 days to see if any sediment was formed.

[0044] Contact angle: The contact angles of different samples of sized carbon fibers were measured using a dynamic contact angle meter (DCAT21, Data Physics). The obtained contact angle data were then used to calculate the surface energy of the samples using the Owens-Wendt method. Two liquids with significantly different polarities, deionized water and diiodomethane, were used as probes during the dynamic contact angle measurement.

[0045] Interlaminar shear strength: Carbon fiber / vinyl resin laminate composites were prepared using a hot-pressing process, with the preparation standard referencing US standards: 50 mm width and 25 mm thickness. In the laminate composite, the carbon fiber sizing amount was approximately 1%. The steps were as follows: vinyl ester resin, curing agent M-50, and accelerator cobalt isooctanoate were mixed at a mass ratio of 100:2:0.2 for 20 min to obtain a mixed matrix adhesive. The mixed matrix adhesive was uniformly applied to the surface of parallel carbon fiber bundles (volume ratio of mixed matrix adhesive to carbon fiber was 2:3), molded, and thermocured at 80℃ for 2 h to obtain the carbon fiber / vinyl resin laminate composite, which was used for interlaminar shear performance testing. Table 1 shows the relevant performance test results.

[0046] The test results are shown in Table 1.

[0047] stability Contact angle (water) Contact angle (diiodomethane) Surface energy (mN / m2) Sizing amount Interlaminar shear strength (MPa) Example 1 No sedimentation, good uniformity 74.45 63.28 34.36 0.98% 56.35 Example 2 No sedimentation, good uniformity 70.45 59.90 37.6 1.01% 64.26 Example 3 No sedimentation, good uniformity 66.88 58.83 39.9 1.05% 60.22 Example 4 No sedimentation, good uniformity 64.38 53.32 42.92 0.98% 55.43 Example 5 No sedimentation, good uniformity 61.13 51.37 45.35 0.99% 69.25 Example 6 No sedimentation, good uniformity 56.57 48.29 48.89 1.02% 59.10 Example 7 No sedimentation, good uniformity 52.92 46.80 51.46 1.01% 65.64 Comparative Example 1 / 94.51 79.49 20.55 / 51.29

[0048] The prepared sizing agent showed no precipitation and good uniformity, confirming its excellent storage stability. Comparing Examples 1-7 with Comparative Example 1, the contact angle of the examples gradually decreased, while the surface energy gradually increased, based on the contact angle, surface energy, and interlaminar shear strength test results. The improved surface wettability of the carbon fiber further enhanced the interfacial wetting efficiency with the matrix resin, thus significantly affecting the interfacial bonding strength of the composite material. The interlaminar shear strength of the carbon fiber sizing agent coated with vinyl ester resin reached a maximum of 69.25 MPa, a 35% increase compared to Comparative Example 1.

[0049] As described above, this invention effectively demonstrates that by modifying epoxy resin E51 with polyethylene glycol 2000 and ethylene glycol diglycidyl ether, and simultaneously introducing the double bond structure synthesized from 2-allyloxyethanol and IPDI, as well as 3,4-dihydroxyphenylpropionic acid, into the modified epoxy resin, and through a series of emulsification processes, a novel carbon fiber sizing agent was successfully prepared. The enhanced interfacial properties are attributed to the efficient adhesion and gripping of carbon fibers by catechol, the synergistic effect of the chemical crosslinking reaction with the double bonds and vinyl resin, and the construction of a continuous bonding interface between the carbon fiber, sizing agent, and resin matrix. This sizing agent is simple to formulate, has low requirements for production conditions, and has significant application value.

[0050] The above description is merely a preferred embodiment of the present invention and the technical principles applied thereto, and is not intended to limit the scope of protection or technical content of the present invention. For those skilled in the art, various obvious modifications, adjustments, and substitutions can be made without departing from the core concept of the present invention, and such changes should all be included within the scope of protection of the present invention. Therefore, the scope of protection of the invention should be determined by the actual claims of the patent application.

Claims

1. A method for preparing a mussel-mimetic based vinyl resin sizing agent, characterized by, The method comprises the following steps: S1. Mix isophorone diisocyanate with 2-allyloxyethanol in equal molar amounts, mechanically stir and reflux at 60-80℃ for 1-2h; S2. Place the polyol in a vacuum, heat and stir to remove moisture, then cool for use; mix equal molar amounts of polyethylene glycol 2000, ethylene glycol diglycidyl ether and E51 in a flask equipped with a thermometer and a mechanical stirrer, mechanically stir and reflux at 110-130℃ for 1-2h to obtain a modified resin; S3. After cooling the modified resin, add the product obtained in S1 to the flask, then mechanically stir and reflux at 60-80℃ for 1-2h; S4. After cooling the product obtained in S3, add 3,4-dihydroxyphenylpropionic acid and p-toluenesulfonic acid to the flask, immerse in an 80℃ oil bath, mechanically stir and reflux, then increase the temperature by 10℃ per hour, and react for 5 hours, and the synthesis reaction is complete; S5. Then stabilize the temperature to 60-80℃, stir in a high-shear dispersion emulsifier at a speed of 1000-2000r / min, and uniformly drop deionized water into the mixed system until the solid content is 30%-40%, continue stirring for 30min, and finally dilute it with deionized water to a solid content of 0.5%-10% to obtain a vinyl resin sizing agent emulsion.

2. The method of claim 1, wherein, In S3, the mass ratio of the product obtained in S1 to the modified resin is 5%-30%, specifically including 10%, 15%, 20%, 25%.

3. The method of claim 1, wherein, In S4, the mass ratio of 3,4-dihydroxyphenylpropionic acid to the modified resin in S2 is 0-15% and not 0, specifically including 2%, 2.8%, 5%, 5.6%, 8.3%, 10%, 11.1%.

4. The method of claim 1, wherein, The p-toluenesulfonic acid is 10% of the mass of 3,4-dihydroxyphenylpropionic acid.

5. A mussel-inspired vinyl resin sizing agent based on the preparation method of any one of claims 1-4.

6. The use of the mussel-inspired vinyl resin sizing agent based on claim 5 for sizing carbon fibers.

7. The use according to claim 6 for the preparation of carbon fiber / vinyl resin laminate composite materials.

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